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This paper studies the impact of distributed energy resources (DER) on economic displacements or delays of power system investments. We investigate how the operational flexibility from DER controllability can influence the integrated expansion of transmission and energy storage. Given the interplay of flexibility provision from different technologies, accurately representing uncertainties is essential to avoid over- or under-estimating the flexible operational capabilities of DER. To address this challenge, we propose a multi-stage stochastic expansion planning model that can optimise transmission and storage investments, as well as DER services against long-term uncertainties and detailed operational constraints. We employ a four-stage scenario tree to represent uncertainties and a Dantzig–Wolfe decomposition within a column generation approach to tackle computational challenges. Case studies performed on real Australian National Electricity Market (NEM) scenarios demonstrate that a deterministic model overestimates the capabilities of controllable DER to displace transmission investments, particularly in early stages. Conversely, the proposed stochastic model provides a more measured assessment, maintaining a steadier estimate of transmission displacement potential by controllable DER throughout various stages. • Multi-stage model optimising DER with investments in transmission and storage. • Analysis of DER controllability's impact on investments under uncertainty. • Comparison of deterministic and stochastic approaches in real scenarios. • Stochastic model enhances investment robustness by incorporating flexible DER. • Deterministic models show increased uncertainty in resulting portfolios. [ABSTRACT FROM AUTHOR]

• A quasi-static time series simulation approach for transmission system expansion planning to capture off-peak issues and opportunities. • A quantitative study of the operation of a Hydro-Québec transmission system planning with a massive integration of distributed energy resources. • The level of penetration of distributed photovoltaics can create counterintuitive operational risk in the long term or lead to unoptimized system planning. • The use of resources to maintain a stable and secure transmission system is very sensitive to the penetration rate of electric vehicles and charging times. Due to advancements in solar cell fabrication and inverter-based technology, as well as decreasing acquisition costs, solar distributed generation systems have emerged as a promising renewable source. Furthermore, electrification of the transportation system is an alternative promoted by many governments to mitigate the dependency on fossil fuels and achieve the goals of decarbonizing the economy. However, interconnecting a large quantity of distributed energy resources (DERs) to the power system reveals technical problems affecting the entire system. Planning coordinators and grid operators need to understand the full-spectrum impact of DERs on the power system to ensure secure and reliable grid planning and operations. The operation of a Hydro-Québec transmission system planned for 2030 is simulated in quasi-static time series mode with a massive integration of 1 million of electric vehicles and 1000 – 3000 MW of distributed photovoltaics. This paper provided findings on assessment of high DER penetrations impacts on the transmission system in terms of voltage control, mitigation means used, MVAR availability and consumption margin, generating unit optimal operation, and switching actions of several equipment. [ABSTRACT FROM AUTHOR]

This paper uses convex inner approximations (CIA) of the AC power flow to tackle the optimization problem of quantifying a 3-phase distribution feeder's capacity to host distributed energy resources (DERs). This is often connoted hosting capacity (HC), but herein we consider separative bounds for each node on positive and negative DER injections, which ensures that injections within these nodal limits satisfy feeder voltage and current limits and across nodes sum up to the feeder HC. The methodology decomposes a 3-phase feeder into separate phases and applies CIA-based techniques to each phase. An analysis is developed to determine the technical condition under which this per-phase approach can still satisfy network constraints. New approaches are then presented that modify the per-phase optimization problems to overcome conservativeness inherent to CIA methods and increase overall HC, including selectively modifying the per-phase impedances and iteratively relaxing per-phase voltage bounds. Discussion is included on trade-offs and feasibility. To validate the methodology, simulation-based analysis is conducted with the IEEE 37-node test feeder and a real 534-node unbalanced radial distribution feeder. [ABSTRACT FROM AUTHOR]

This paper proposes a cooperative approach aimed at distributed energy resources sizing in a renewable energy community, with considerations of the community's optimal operation, impact on the electrical grid and an allocation of the benefits to its members. To this purpose, multiple investment modes are evaluated via a two-step procedure. In the first step, the size of renewable energy sources is determined by solving an optimization problem that maximizes community welfare, considering network and investments. In the second step, an optimization problem maximizing additional community member profit with price regularization is solved. This step shares benefits among community members. The potential of the proposed procedure is illustrated using a benchmark Dickert-LV network. This is a full y cooperative framework where the community operator is ensuring adequate grid operation, operational planning and sizing of new investments. • Energy communities are a good enabler for energy transition and prosumer empowerment. • The incentive for DER investment that they provide needs quantification. • Intra-community exchanges and co-investments have effects on the grid. • What are the benefits of an energy communities with and without co-investments? • How could these benefits and return on investments be computed? [ABSTRACT FROM AUTHOR]

Distributed Energy Resources (DERs) integration into distribution systems becomes problematic when the penetration level exceeds the system DER hosting capacity. Although several studies propose to quantify DER hosting capacity, methodologies to maximize it in distribution systems are scarce. Some approaches propose installing var compensators, incurring in costly solutions; others propose reduced cost solutions like network reconfiguration or optimized Volt–Var curve. Nevertheless, the combination of these approaches has not been proposed. Therefore, this paper proposes the simultaneous network reconfiguration and optimized setting of grid-tie inverter Volt–Var curve to maximize DER hosting capacity and minimize power losses. The uncertainties are addressed using Monte Carlo simulation, whereas Non-Dominated Sorting Genetic Algorithm II handles the multi-objective problem. The simulations are performed using Matlab and OpenDSS software, considering the IEEE 33-bus test system. Finally, the results demonstrate the superiority of the proposed approach against previous studies that performed network reconfiguration and Volt–Var optimization separately. • Network reconfiguration and Volt–Var optimization for hosting capacity maximization. • Multi-objective approach to increase DER hosting capacity and minimize power losses. • Inclusion of uncertainties related to DERs and loads in a 24-hour cycle. • Cost-effective solution by avoiding the need for additional var compensator equipment. [ABSTRACT FROM AUTHOR]

Using spatiotemporal data can increase forecasting accuracy for distributed energy resources such as wind farms, solar power plants, and electric vehicle charging stations. The underlying forecasting models assume that data are shared by the different data owners, which is not always feasible because of privacy and confidentiality constraints. Existing methods for privacy-preserving data-sharing are based mainly on linear or non-linear univariate models. This is quite limiting concerning the potential of non-linear multivariate forecasting approaches, since these models can be computationally more efficient than univariate approaches and can learn non-linear relationships. This paper introduces a new federated forecasting approach implementing a multivariate non-linear learning scheme based on decision trees while enabling fully decentralized computation. Results show higher predictive performance than existing linear or univariate energy forecasting models while preserving privacy. • New encryption for lossless and efficient federated regression trees. • We address the need for multivariate and non-linear models simultaneously. • We analyze the resilience to missing data. • The proposed method is computationally feasible for spatiotemporal applications. • Application to DER-Forecasting is more accurate than State of the Art methods. [ABSTRACT FROM AUTHOR]

For network-safe coordination of distributed energy resources (DERs), many approaches impose some form of constraint set to guarantee the safe operation of a distribution network. This paper presents a comparative analysis of two distinct approaches that leverage a constraint set for network-safe coordination: nodal operating envelopes versus network-wide constraints on the action of a DER aggregator. We investigate their respective strengths and limitations by considering information and communication requirements and trade-offs in terms of flexibility and fairness. The availability of potentially private information to the aggregator or to the distribution system operator determines which of the approaches is feasible. The results of the case studies suggest that if the goal is to maximize DER flexibility, a nodal constraint approach should be used. However, if the aggregator does not have information on how the constraints map to its DERs and/or does not have the ability to send out node-specific control inputs, the nodal constraint approach is not feasible and a network-wide constraint approach is needed. We show that a network-wide constraint approach constraining the aggregator's control input provides a good balance between flexibility and fairness. • Distributed energy resources (DERs) can cause electric grid constraint violations. • DER aggregators and distribution system operators must coordinate. • Comparison of nodal and network-wide constraints for network-safe operation. • Regulatory and communication frameworks dictate which approach is feasible. • Operational outcomes differ depending on the consideration of equity. [ABSTRACT FROM AUTHOR]

During the last few decades, extensive research has been conducted to mitigate potential voltage-related problems that high penetration of Distributed Energy Resources (DERs) may cause. One of these problems is the voltage variation caused by the disconnection of the DERs due to their anti-islanding protection action after a temporary fault. This issue has not been deeply studied so far and it may pose severe voltage variations to distribution systems' consumers. In this context, this paper proposes a new formulation aiming at the preventive voltage regulation strategy for step voltage regulators considering the impacts triggered by a sudden disconnection of DERs. The voltage control is accomplished by a specialized Particle Swarm Optimization that selects control actions predicting the possibility of the DERs being disconnected. Results show that voltage violations were minimized after the disconnection of DERs, keeping the nodal voltages within statutory limits. • Centralized tap control minimizes violations after generators are disconnected. • Specialized Particle Swarm Optimization for Step Voltage Regulators was proposed. • Coordination of Voltage Regulators with generators improves voltage regulation. • Mitigation of voltage sags caused by anti-islanding protection was achieved. • A proactive approach enhances grid resilience by disruptive events. [ABSTRACT FROM AUTHOR]

This paper proposes an uncertainty modeling method for the aggregated power flexibility of DERs. Basically, both outer and inner approximated power-energy boundary models are utilized to describe the aggregated flexibility of controllable DERs. These power and energy boundary parameters are uncertain because the availability of controllable devices, such as electric vehicles and thermostatically controlled loads, cannot be precisely predicted. The optimal operation problem of the aggregator is thus formulated as chance-constrained programming (CCP). Then, a flexibility envelope searching algorithm based on the ALSO-X+ method is proposed to solve the CCP, the result of which is a conservative approximation of the original CCP but not as conservative as the Conditional Value-at-Risk approximation. After optimizing the aggregated power of the group of DERs, the decision at the aggregator level is disaggregated into the flexibility regions of individual DERs. Finally, the numerical test demonstrates the effectiveness and robustness of the proposed method. • Uncertainty modeling of the aggregated flexibility of DERs. • Chance constraint approximation based on the ALSO-X+ approach. • Comparative analysis of costs, risk levels, and feasibility with Conditional Value at Risk. • Comparison between the outer and inner approximated flexibility aggregation models. [ABSTRACT FROM AUTHOR]

Although several approaches have been proposed in the literature to utilize inverter-based distributed energy resources (DERs) in the secondary frequency control (SFC), challenges related to practically implementing SFC with inverter-based DERs have not been considered. These challenges include response time of DERs, the communication environment, and emulation of the actual Automatic Generation Control (AGC). This paper develops and implements a coordinated operation and control for below the substation resources such as inverter-based DERs and a utility-scale battery energy storage system (USBESS) to participate in the secondary frequency control. A linearized optimization problem is formulated to simultaneously determine optimal setpoints of participating resources and satisfy AGC requests in real time for the secondary frequency control. To mimic the actual process of AGC, a hardware- and software-in-the-loop-based experimental setup is developed with the integration of real-time digital simulators (RTDS), a centralized controller at the substation, and gateways as IoT devices, which are commonly used in practice to interface DERs to control and monitoring systems. The controller remains in listening mode until it receives an AGC signal. When it receives an AGC signal, it optimally dispatches the USBESS and DERs and monitors the change in power flow at the substation. The controller iteratively dispatches the participating resources considering their response time until the AGC request is satisfied. The proposed control is implemented on an actual feeder configuration located in Las Vegas, Nevada, in collaboration with NV Energy—the largest public utility in Nevada. The results illustrate that USBESS and DERs can be coordinated and dispatched to satisfy AGC requests for SFC. • Novel linearized optimization-based secondary frequency controller • High fidelity prototype for practical implementation of AGC on real system • Combined hardware-and software-in-the-loop-based real-time laboratory setup for AGC [ABSTRACT FROM AUTHOR]

Highlights • Control of parallel-connected voltage source converters. • Voltage control loop affects synchronous reference frame inverter output impedance. • Mathematical modeling of error in power sharing between parallel inverters. • Designing dq virtual resistive, inductive, and capacitive impedances. • Experiments validate resistive, inductive, and capacitive droop control in dq-RF. Abstract This paper investigates dq -reference-frame (dq -RF) self and cross-coupling output impedances of the islanded voltage source converter (VSC), by considering the controller impacts. The dq -RF impedances for the closed-loop system are designed to exhibit the desired resistive, inductive, or capacitive characteristics, and are employed in the power control of VSC. The effects of these impedances and connecting lines impedances on the power control of islanded parallel connected VSCs, for different impedance characteristics, are also studied. It is shown in this paper that the unbalanced impedance significantly affects the performance and power control of these parallel converters. Besides, virtual impedance based active and reactive power control of the parallel converters in the dq -RF, for resistive, inductive, and capacitive cases, are designed and implemented. The numerical and experimental results verify the analysis presented in this paper about the dq -output impedance and the virtual impedance based power sharing control. [ABSTRACT FROM AUTHOR]

The advent of distributed energy resources (DERs) in microgrids has provided significant benefits. University campus microgrids can manage their DER efficiently to minimize consumption, energy losses, and environmental impacts. Thus, to boost the transition from a traditional university campus to a sustainable and smart campus, this paper proposes an optimal siting and sizing study of photovoltaic systems and electric vehicle charging stations for a microgrid of a Brazilian university. This problem is formulated as mixed-integer nonlinear programming and is carried out in two stages. The first stage minimizes grid losses by locating and sizing photovoltaic panels, while the second stage minimizes the grid losses and maximizes the proximity of charging stations to the load centers by optimizing the place and sizing of charging stations. In addition, this work considers load uncertainty through the Monte Carlo method with a scenario reduction technique. The results estimate that photovoltaic systems can reduce 13.48% of the monthly electricity cost. The optimal charging station location is usually nearby the photovoltaic system siting or the substation. However, the increase in the number of chargers in buses with high consumption causes an increase of around 5% in grid losses. Furthermore, this paper discusses possible scenarios for photovoltaic systems and charging station installation based on the benefits of the transition to a sustainable and smart campus, considering Brazilian electricity sector policies. • Perform a scenario reduction to deal with load and generation curves uncertainties. • Minimize electrical losses by optimizing the siting and sizing photovoltaic systems. • Perform multi-objective optimization for siting and sizing charging stations. • Sensitivity analysis for distributed energy resource installation. • Discuss the advent of distributed energy resources to university campus. [ABSTRACT FROM AUTHOR]

The management of distributed energy resources (DER) in power distribution systems and the concept of demand side management (DSM) are becoming increasingly important in recent years, provided that emerging communication technologies contribute to the formation of smart distribution networks of the future. Several methods have been proposed in the literature for the optimal operation of smart distribution networks (OOSDN) with renewables and/or non-renewable DER, DSM and energy storage systems. The main scope of this paper is to review the most significant papers in the area of OOSDN and to introduce a taxonomy of models and optimization methods that are applied to the OOSDN problem. Moreover, the basic schemes for active network management are briefly presented. The article also discusses challenges and areas for future research in the field of OOSDN. [ABSTRACT FROM AUTHOR]

• For islanded ADM, a novel supervisory control method is presented. The challenge of restoring frequency and voltage magnitude while lowering generating cost is formulated using the sensitivity matrix generated from the Jacobian matrix incorporating droop-based DGs as a multi objective function. • PV and wind units and uncertain nature of their output are considered with Monte Carlo simulation and scenario reduction technique. • The effect of the reactive power on the frequency is considered with using the frequency sensitivity. Load demand has locally met the distributed energy resources (DERs) under an infrastructure that is called microgrid. In this paper, a new supervisory control approach is presented based on MPC method, using a stochastic optimization model. The objective function (OF) of the proposed central controller consists of the combined cost-based and system-based parts. Indeed, the setpoints of DERs are updated by the supervisory control method to regulate voltage and frequency to their nominal values as well as to decrease the generation costs. The stochastic optimization formulation is conducted based on MPC structure. Moreover, the uncertain nature of DERs is considered in the optimization formulation and MPC framework using several scenarios. In addition, the effect of reactive power on frequency is considered in this paper and the results show better voltage and frequency regulations. The algorithm is implemented on a modified IEEE 33-bus test system with AC and DC parts. Furthermore, several cases and the sensitivity analysis are accomplished to show the efficiency of the proposed model. [ABSTRACT FROM AUTHOR]

This paper develops three novel methodologies for optimal reconfiguration of distribution networks in the presence of distributed energy resources (DERs). The novelty is in achieving a non-conservative and robust solution to grid reconfiguration. The optimal solution is the minimum-loss-configuration of the distribution network taking into account the cost of switching and the grid operational constraints. The methods are based on the concepts of receding horizon control (RHC) and scenario analysis (SA) which inherently optimize switching costs and losses. The salient feature of incorporating RHC and SA is that it avoids the need to pre-define the period of change of configuration. The methods vary in their degree of robustness and conservatism. A robust configuration will not violate the constraints under any of the predicted DER variations called scenarios. A non-conservative configuration exploits better benefits with respect to the objective of reconfiguration under all scenarios. Depending on the desired level of robustness and non-conservatism, one of the three methods developed in this paper can be used to find the optimal configuration. The methods can be used for planning as well as for operation of the distribution network since they indicate the most frequently open switches in the network and the time at which they are to be operated. [ABSTRACT FROM AUTHOR]

• Consensus-based distributed control methods in DC microgrids are investigated. • Recent literature on consensus-based distributed secondary control is reviewed. • Various types of consensus algorithms are compared through simulations. • Insights into future research directions are provided. Secondary control (SC) is the middle layer of the well-known hierarchical control structure, which plays an essential role in maintaining the desired operation of microgrids (MGs). Generally, SC layer is divided into three categories of decentralized, distributed, and centralized control schemes. Among them, distributed control strategy is superior to the decentralized and centralized ones in terms of effectiveness, reliability, and scalability. Accordingly, this paper presents a comprehensive overview on distributed secondary control (DSC) schemes in DC MGs, specifically focusing on consensus-based cooperative DSC schemes. In this overview, the consensus-based DSC methods are classified into five groups of dynamic consensus, leader-follower consensus, finite-time consensus, PI consensus, and event-triggered consensus. These consensus-based DSC strategies are investigated, reviewed, and assessed in detail. Furthermore, different case studies are provided to compare the performance and merits of different consensus-based cooperative DSC structures using time-domain simulations in MATLAB/Simulink environment. Key findings are provided, and finally, challenges ahead of future research are highlighted. [ABSTRACT FROM AUTHOR]

• A novel stochastic-robust approach is developed for energy communities. • Individual and collective assets are considered and analysed. • The problem is solved using a novel three-stage procedure. • Operating cost is incremented 77$ when the degree of robustness grows. • Collective storage systems help to reduce unserved demand and wasted generation. This paper presents an extended model for aggregation of operational settings of droop-controlled Distributed Energy Resources (DERs) in Microgrid (MG) planning, thus deriving in a novel problem named Optimal Siting, Sizing and Setting (OSSS) of DERs. The proposed approach precisely deals with the power flow formulation for autonomous MG as an essential constraint for accurate results. Furthermore, the proposed OSSS model considers the frequency and voltage dependence characteristic of loads. The problem casts in multi-objective formulation to consider different technical, power quality and controlling aspects. This will help the designer to provide efficient decision for allocation of DERs. The effects of realistic load model as well as power sharing error index are elaborately investigated in simulation results. The model is thus further validated and its usefulness demonstrated. Finally, the performance of multi-objective OSSS model is verified by comparing the results with the previous simplified models presented in the recently published literatures. [ABSTRACT FROM AUTHOR]

• Random-fuzzy multi-objective optimal power flow. • Transmission and distribution interaction. • Security region constraints. In order to deal with the static voltage stability region problem of the power system caused by the penetration of distributed energy resources, this paper presents an interactive random-fuzzy optimal power flow method for transmission-distribution network considering security region constraints. Firstly, based on the random-fuzzy theory, the output of wind power and multi-energy coupling energy hub connected to transmission-distribution network are obtained. On this basis, the security region model of transmission-distribution network is established. As the interaction and cooperation between multiple distribution networks and transmission network throughout the system are described, the global random-fuzzy model of transmission-distribution interaction is established. Then, the security domain opportunity constraints are incorporated into the multi-objective optimization model of transmission-distribution network. Finally, based on the improved IEEE30 bus transmission system and IEEE33 bus distribution system, the power flow of transmission-distribution interactive network under the proposed model is calculated. The simulation results validate the effectiveness of the proposed model and algorithm. The safe operation distance of the power grid system can be improved and the active power network loss and power generation cost can be reduced. [ABSTRACT FROM AUTHOR]

• Novel protection technique for microgrids with inverter-based resources. • Effective both in grid-connected and islanded modes of operation unlike other relays such as differential relays. • Not affected by inverter-type and its control strategy, microgrid topology and level of generation. Due to the unavailability of a suitable relay for microgrid protection, various utilities are fitting available IEDs for the protection of microgrids. At present, microgrid protection is achieved using a combination of conventional numerical relays. These numerical relays are not suitable for all kinds of microgrid architectures and do not provide complete protection with inverter-based generators. Since these relays were designed considering the fault characteristics of synchronous generators, they fail to respond to the fault characterized by inverter-based generators. This paper proposes a new protection technique that is independent of the type of generating sources, control philosophy of inverters as well as microgrid architecture. Simulations are performed using PSCAD/EMTDC and performance of the protection scheme is also evaluated in real-time using RTDS. Pertinent results are presented which demonstrate the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

• A method to preplan segmentation of power distribution system into MGs with flexible boundaries to enhance resiliency. • A three-stage algorithm to enable resiliency of the PDS subjected to natural disasters and/or multiple faults, using MILP. • Assessed the impact of the controllable MGs with flexible boundaries on power system resiliency performance with a composite metric. With the increased frequency of adverse weather and manmade events in recent years, the issue of the power distribution system (PDS) resiliency has become drastically important. Microgrids with various types of distributed energy resources (DERs) have capabilities to enhance the PDS's resiliency against high impact low probability (HILP) events. Resiliency is defined as the ability of the system to keep supplying critical loads even during and after extreme contingencies. This paper presents a systematic method to segmentize parts of a PDS into microgrids with flexible boundaries to enhance resiliency and mitigate negative impacts from anticipated threats. The method is aimed at anticipation and preparation to HILP events in advance: alternative flexible boundaries of the microgrids must be preplanned during normal operation and dynamically changed prior to or during disturbances. The Mixed-Integer Linear Programming (MILP) is formulated and applied to select switching actions to adjust microgrids' boundaries as well as to supply critical loads, while meeting system constraints. Networked microgrids are merged and reconfigured as necessary to maximize supply to critical loads, driven by a factor-based resiliency metric, which is obtained using the Analytical Hierarchy Process (AHP). The modified IEEE 123 bus system was utilized for validation of the proposed method. Compared with the traditional fixed-boundary microgrids, this approach determines the most resilient network configuration to supply high-priority critical loads. The developed method can be employed in power system planning, operation, and in decision-making to enhance operational resiliency and invest in system upgrades appropriately. [ABSTRACT FROM AUTHOR]

• Voltage relays showed high dependability and are promising for microgrid protection. • The enhanced method efficiently improved the reliability of voltage-based protection. • The method was tested for sympathetic trips and changes in the microgrid operation. • The improvements did not imply an increase in the complexity of the protection method. • The voltages and currents were analyzed for the islanded and grid-connected microgrid. Microgrids emerged as an efficient way to integrate distributed energy resources and local loads into power distribution systems, allowing the local system operation in grid-connected and islanded modes. However, the microgrids imply several challenges for the protection systems, such as the changes in fault current path and the decrease of the fault current amplitude during islanded operation. Therefore, conventional overcurrent protection does not guarantee selectivity, coordination, reliability, and adequate trip time in AC microgrids. Under this perspective, voltage-based relays have been widely investigated as a potential protection for AC microgrids. Thus, this paper critically reviews voltage-based protection and proposes improvements to an existing technique, aiming to simplify the settings and guarantee reliability and selectivity among various voltage-based protection devices. The results showed that our modifications improved the selectivity and reliability of the voltage-based protection compared with the original technique and the traditional overcurrent protection devices for different topologies of an AC microgrid. [ABSTRACT FROM AUTHOR]

• A coordinating mechanism for aggregators in active distribution network is given. • The physical constraints of active distribution network and DERs are considered. • An iterative distributed algorithm is given based on non-cooperative game theory. • The Nash equilibrium state of the proposed non-cooperative game is studied. • Confidentiality of aggregators' information is addressed in the proposed algorithm. The support of distributed energy resources (DERs) for providing operational flexibility can be beneficial from the transmission system operators' (TSOs') viewpoint. Despite all opportunities, using DERs within an active distribution network (ADN) for providing flexibility brings operational challenges such as lines congestions and excessive voltage deviations management. Moreover, there are information asymmetries challenges for coordinating the DERs specifically when the strategic aggregators are introduced to manage them. In this paper, a local coordinating mechanism is proposed for the strategic aggregators to provide the operational flexibility. This paper furthers efforts toward proposing an iterative distributed algorithm converging to the Nash equilibrium (NE) of the non-cooperative game incorporated in the proposed mechanism. To validate the performance of the proposed mechanism, the IEEE 33 nodes radial distribution network is considered for a case study. The efficiency of the obtained NE and the proposed iterative distributed algorithm are thoroughly analyzed in the case study. [ABSTRACT FROM AUTHOR]

• Paper illustrates the effects that P2P trading can have on the network operation. • Presents OPF based tool to integrate P2P into distribution network operation. • Investigates influences of P2P on DGs under Last-In-First-Out principle of access. • Understanding unintended consequences of P2P trading on network and DGs is key. The increasing uptake of Distributed Energy Resources and advancement in blockchain technology has led to the growth in interest in the peer-to-peer (P2P) based energy trading. However, there has been a lack of consideration how these trades may affect the network operation, in particular in networks that apply Active Network Management using Last-in-First-out (LIFO) access rules, such as in the UK. This paper presents a novel application of Optimal Power Flow that manages the P2P trading whilst optimising legacy DGs under a LIFO access agreement. Analysis show that under such arrangements, and in combination with autonomous P2P trading, lower priority DGs are vulnerable to excessive curtailment levels. [ABSTRACT FROM AUTHOR]

Innovations in information, communication, forecasting, and control technologies, along with the high investments to enhance the capabilities of active neighborhoods to participate in crucial grid balancing services like fast frequency control (FFC), have gained wide attention in the research community recently. This paper aims to provide a structured and comprehensive study of the challenges, opportunities, and potentials of active neighborhood resources, e.g., distributed energy resources (DERs) and smart flexible loads, to actively participate in FFC services. Technical details, regulatory requirements, and control strategies with practices in several countries are discussed in detail. Furthermore, the challenges and opportunities for the participation of active neighborhood resources are elaborated and categorized as technical, economic, and other challenges. Finally, a model on coordinated synthetic inertia control (SIC) is demonstrated to examine the DERs like energy storage systems, small scale wind turbine generator, photovoltaic generator diesel engine generator, electric vehicle capability to provide the fast frequency response (FFR). It is observed that proposed SIC framework is potentially capable to arrest high rate of change of frequency (RoCoF) and reduce frequency nadir at different loading conditions. The observations and discussions made in this study would be demystifying for every stakeholder of the energy community. • A comprehensive study of the potentials of active neighborhood resources is presented. • Technical, regulatory, and control practices in several countries are discussed. • Challenges and opportunities are elaborated as technical, economic, and other challenges. • A model is demonstrated to examine the DERs capability to provide the FFR. [ABSTRACT FROM AUTHOR]

The increasing penetration of prosumers, residential customers equipped with distributed energy resources (DER), offers an opportunity to aggregate DER into virtual power plants (VPP) operated as a single dispatchable resource. Yet that raises the question of how to financially reward prosumers for participating in VPPs. Against this backdrop, this paper explores multi-period dynamic export tariffs based on the dual variables of the optimisation problem used for aggregation. In contrast to the existing approaches, we use a multi-period optimisation model to account for inter-temporal coupling introduced by battery storage systems. We focus on three different VPP models with different objective functions, reflecting varying levels of customer focus. Our analysis is illustrated in a case study, underlying outcome and economic benefits of each VPP model. • Dynamic export tariff has financial performance on rewarding prosumers. • Pricing of export tariff impacts the efficacy of electricity cost-saving. • Prosumer's economic profits varies with customer focus of virtual power plants. [ABSTRACT FROM AUTHOR]

The increasing penetration of distributed energy resources (DERs) brings the valuable flexibility to the system as well as challenges, which requires the coordination between transmission system operator (TSO) and distribution system operators (DSOs). This paper quantitatively models the goals and constraints of TSO and DSOs in procuring flexibility resources from DERs and proposes a flexibility market. We resolve the potential conflicts between TSO and DSOs in the flexibility market via mutual economic compensation, specified by Nash Bargaining (NB) theory. Two alternative TSO-DSOs interaction modes, i.e., the DSO-managed mode and the hybrid-managed mode, and two detailed payment schemes are discussed and compared. The hybrid-managed mode guarantees efficiency and fairness, while the DSO-managed mode is less complicated and can protect information privacy. Numerical studies further validate our findings. • Quantify the coupling effects of the respective actions of TSO and DSOs. • Analyze the TSO-DSOs interactions using the General Nash Bargaining (GNB) theory. • Compare TSO-DSOs interaction modes in terms of complexity, fairness, and efficiency. • Show implications for choosing the payment scheme to derive closed-formed solutions. [ABSTRACT FROM AUTHOR]

This paper presents probabilistic coordination of distributed energy resources (DERs) operation in an islanded microgrid with consideration of the associated uncertainties. In doing so, a comprehensive stochastic mathematical model is developed which incorporates a set of valid probabilistic scenarios for the uncertainties of load and intermittency in wind and solar generation sources. The uncertainty is addressed through a combination of a stochastic optimization model and additional reserve requirements. The model also includes hourly interruption costs for a variety of customer types as a means of determining the optimal probabilistic interruptible load whose reliability-based value is low enough to enable it to be shed if necessary. A case study is carried out using a benchmark microgrid; numerical results demonstrate that coordinated operation of DERs brings notable benefits in terms of expected operation costs and system security. This probabilistic coordination further reduces the consequences of the expected power dispatch of controllable generators and hourly unserved power. [ABSTRACT FROM AUTHOR]

• The DSO participates in the balancing market as a balance responsible party. • DSO scheduled actions are reflected on TSO balancing market clearing results. • Flexibility resources provide flexibility at distribution and/or transmission level. • Pan-European market-based coordination at distribution and transmission level. • Aligned operation of flexibility markets at distribution and transmission level. This paper proposes a framework for DSO-TSO market-based coordination in a feasible and transparent way, compatible with the European-type electricity market. The DSO participates in the balancing market as a Balance Responsible Party, by submitting price-taking offers that represent the net outcome of DSO scheduled actions at the distribution level. With this approach, the balancing market clearing results reflect the impact of scheduled actions at distribution level on system power balance. In addition, specific design aspects of the DSO market are highlighted that could align DSO and TSO market, increasing the market coordination efficiency and promoting the wider participation of distributed energy resources in both markets. The advantages of the proposed method are: (a) more accurate balancing market pricing signals while congestion management services and balancing services remain decoupled, (b) low data exchange requirements between the two Operators, (c) distributed energy resources opportunity to participate efficiently either in one or both markets, and finally (d) easy pan-European market-based coordination of TSOs-DSOs based on current balancing market development action plans. [ABSTRACT FROM AUTHOR]

• Proposing a novel resiliency-oriented DER planning model for distribution grids. • Considering both normal and event situations in the model as objectives. • Developing a procedure for obtaining components outage scenarios against earthquakes. • The proposed model leads to a plan with an acceptable resiliency and planning costs. Distribution systems are one of the most important infrastructures of each country which are exposed to numerous damages through unexpected events. The development of distributed energy resources (DERs) is one of the solutions which can bring several benefits to the operation and planning of distribution systems in both normal and event situations. This paper proposes a new multi-objective planning model for optimal siting and sizing of DERs in distribution systems to minimize the total planning costs including operation and active power loss costs, as the normal operation objective, and to minimize the expected prioritized load shedding exposed to an earthquake incident, as the resilience improvement goal. Also, a novel incident-based outage scenario determination procedure is proposed using the fragility curves of distribution components to model the impact of earthquake events in resiliency evaluation stage. Since the proposed model is a non-linear and non-convex optimization problem with two contradictory objectives, the non-dominated sorting genetic algorithm II (NSGAII) followed by fuzzy decision making are utilized to find the Pareto solutions and the final optimal plan. Finally, the numerical results based on the IEEE 33-bus and IEEE 69-bus distribution systems are reported to evaluate the effectiveness of the proposed model. [ABSTRACT FROM AUTHOR]

Abstract: This paper proposes a multi-agent system for energy resource scheduling of an islanded power system with distributed resources, which consists of integrated microgrids and lumped loads. Distributed intelligent multi-agent technology is applied to make the power system more reliable, efficient and capable of exploiting and integrating alternative sources of energy. The algorithm behind the proposed energy resource scheduling has three stages. The first stage is to schedule each microgrid individually to satisfy its internal demand. The next stage involves finding the best possible bids for exporting power to the network and compete in a whole sale energy market. The final stage is to reschedule each microgrid individually to satisfy the total demand, which is the addition of internal demand and the demand from the results of the whole sale energy market simulation. The simulation results of a power system with distributed resources comprising three microgrids and five lumped loads show that the proposed multi-agent system allows efficient management of micro-sources with minimum operational cost. The case studies demonstrate that the system is successfully monitored, controlled and operated by means of the developed multi-agent system. [ABSTRACT FROM AUTHOR]

Abstract: Photovoltaic (PV) power systems are becoming one of the most developing investment areas in the field of Renewable Energy Sources (RES). A statement of the status quo of PV power systems in Greece, and their contribution towards the improvement of power system reliability, is the scope of the present paper. Siting and installation of PV power systems is performed according to a recent Greek law, along with environmental and geographical constraints. Meteorological data are computed, formulated and imported to appropriate software in order to simulate the PV units and generate their power output. Data for unserved loads, resulting from load shedding during peak hours, are compared to the above estimated power production. Assuming that a proportion of the eventually unsupplied power could be provided by the accessed power generation of the PV units, the reliability of both transmission and distribution system is improved. The impact on the transmission system is shown by an improvement of LOLP and LOEP indices, whereas peak shaving for the Interconnected Greek Transmission System (IGTS) is also illustrated. For the distribution system the impact is quantified using the distribution system reliability indices SAIDI, SAIFI, and CAIDI. Finally, the resulting improvement is also expressed in financial terms. [Copyright &y& Elsevier]

• A new methodology for the Steady-state security region for the security assessment of distribution systems with the presence of DER. • Consideration of the intermittent characteristic of the DER generations. • The proposed methodology can be used in online or offline environments. • The proposed tool can be used in planning studies of distribution systems. • The proposed methodology can also be used for DER Regulation and Allocation in Distribution Networks: Volt/Var optimization and Congestion Relief. Modern Electric Power Systems are evolving from a centralized generation model toward a complex infrastructure with the presence of Distributed Energy Resources (DER). The transformative changes are especially pronounced at the level of the distribution system. The emergence of new generation technologies as solar, for example, affects the customer profile, expansion planning, and operation procedures of distribution utilities. Therefore, this paper describes a new methodology based on steady-state security regions concept for the security assessment of distribution systems with the presence of DER. The main objective of the proposed methodology is to allow an effective evaluation of the operating conditions of distribution systems with high penetration of DER, focusing on the intermittence of the new generation resources. The proposed methodology has been tested using two distribution systems. The first one is a tutorial 13-bus system, which is a small tutorial feeder, and the second one is a real large-scale model of a distribution network. The results presented indicate the effectiveness of the proposed technique in the distribution system security analysis. The proposed methodology is implemented using the Python language and uses the OpenDSS software as a power flow solver. [ABSTRACT FROM AUTHOR]

• Assessment of approaches to modeling voltage measurement highlighting pros and cons. • Convergence, accuracy, difficult to implement, and computational aspects are assessed. • Relevant issues and the scenarios where they can rise are for the first time reported. • Comparative summary indicates the more suitable approaches. • Case Studies based on an actual feeder containing actual measurements and DERs confirm the findings. The adoption of Distributed Energy Resources (DER) changes the way distribution systems are managed. While DER provides flexibility, they increase operational challenges. In this context, the Active Distribution Networks (ADNs) rise, creating a suitable environment and the need for the massive adoption of the so-called Distribution System State Estimators (DSSEs). Noticeable efforts can be identified in the literature aiming at the maturation of the state estimators devoted to distribution systems, namely, the Admittance Matrix Based-State Estimator (AMB-SE) and the Branch Current Based-State Estimator (BCB-SE). For sure, one the biggest challenges faced by these state estimators is related the modeling of the voltage magnitude measurements. This paper presents a comprehensive comparison of the approaches available to modeling voltage magnitude measurements in DSSEs. Aspects regarding computational implementation, convergence, performance, and accuracy of the DSSEs in the presence of the three voltage magnitude approaches were assessed and discussed. Original findings observed due to the adequately designed simulations, assist the choice for the more suitable approach. Results clearly show that the proper choice of the approach to modeling voltage magnitude measurements makes the DSSEs as accurate and numerically robust as the widely accepted Traditional State Estimator (TSE), whereas they perform significantly better and are easier to implement. This can help to leverage these estimators and make them widely accepted. [ABSTRACT FROM AUTHOR]

Abstract: Integration of distributed energy resources (DER) into distribution systems is a new concept for improving system capacity and stability, feeder voltage, and supply quality and reliability. This paper has addressed voltage support in distribution systems by energy injection from a battery storage distributed energy system. An operation strategy for an inverter interface battery energy storage DER has been developed for maximum improvement in feeder voltage with minimum energy injection from the DER. A control strategy has been proposed for inverter based battery storage DER to regulate network voltage effectively, through operating the DER to generate real (P) and reactive (Q) power with Q priority. The implementation of the inverter interface DER with battery energy storage will save fuel cost of DER but be of much higher capital cost than using a rotary generator. The proposed technique has been evaluated by simulation on a three-phase distribution system with time varying loads. Test results indicate that DER operating with Q priority offers the best solution for maximum voltage improvement. The results also confirm that DER injecting P and Q at the ratio of maximum voltage sensitivity of line presents better solution for power loss reduction than the solution offered by the DER operating with Q priority. [Copyright &y& Elsevier]

• Developing a comprehensive method for enabling high-resilient power distribution networks. • Assessing the impact of additional DERs and tie-lines with automated switches on the resiliency performance of power distribution networks. • Proposing an algorithm, based on composite resiliency indices, to quantify the feasibility of a planning decision in terms of resiliency performance of a power system. • Evaluating the resiliency of the IEEE 123 bus system against probable contingencies and devastating natural events. Power system planning engineers aim to create a reliable, and efficient grid to meet load demand, while avoiding costly investments in advanced distribution technologies. Recent extreme weather and cyber events have exposed the vulnerability of the power grid and posed a new requirement for system resiliency, which denotes its ability to keep serving critical loads even with adverse events. Additionally, a push for integrating distributed energy resources provides multiple opportunities and challenges. The resiliency-driven planning strategies for system resources are still in their infancy, and more investigation is needed. This paper presents a systematic method for enabling highly resilient power distribution systems by suggesting strategies to utilize distributed energy resources and automated switches in efficient way. Topology-based and novel feasible-network-based scores are developed for resiliency measure and to guide selection of appropriate strategies given multiple options. Efficiency of the developed algorithm was substantiated on the modified IEEE 123 node system and provides the most resilient feasible network. The proposed algorithm can be employed by power system engineers for resiliency-driven planning and system upgrades. [ABSTRACT FROM AUTHOR]

This paper proposes a mechanism for time-frequency analysis of post-fault transient response in hybrid AC/DC microgrids. The proposed mechanism is based on the continuous wavelet transform of the electromagnetic transient (EMT) simulation data in grid-connected and islanded modes of operation. The proposed mechanism is used to evaluate the impact of fault parameters on the post-fault voltage recovery and to estimate the critical clearance time of the faults. Moreover, a simulation benchmark is developed that involves different types of distributed energy resources (DERs) including solar photovoltaic (PV), wind, and battery energy storage systems. The developed microgrid benchmark is implemented in EMTP software and extensive simulation results are analyzed to obtain insights into the voltage recovery and transient response of hybrid AC/DC microgrid subject to faults. • The interactions between the DERs and the ICs may lead to post-fault disturbances. • The voltages may not be recovered depending on the fault duration. • AC and DC dispersion parameters can indicate post-fault voltage recovery. • The nodes connected with a grid-forming exhibit small critical clearance time. • The critical clearance time may vary significantly depending on the fault location. [ABSTRACT FROM AUTHOR]

• The approach integrates the generation and storage system models into the VSC control. • Primary energy source variations are considered to modify the control references. • Functional models of converter integrated DER are developed for microgrid studies. • The balance between accuracy and simplicity of the equivalent models is obtained. • Test validates the straight forward and accurate strategy for DER model integration. Studies related to the integration of distributed energy resources (DERs) face challenges in considering models for the primary energy source, the conversion equipment, the inverters, and the microgrid. Most of the current approaches only consider some of these models, then the complete modelling is uncommon, leading to simplified system representations. As a solution, this paper presents a three-stage approach to easily integrate the generation and storage system models into the d q 0 control algorithm of a voltage source converter (VSC), useful in microgrid studies. The considered DERs, correspond to battery energy storage system (BESS), wind generation and photovoltaic (PV) generation systems; then, the model influence and the variation of the primary energy source modify the control references. This approach allows an appropriate balance between model accuracy and simplicity of steady-state and dynamic equivalent models for converter integrated DER (CIDER). The results show how this modelling facilitates the steady and dynamic state studies, as is evidenced in the tests performed in a CIGRE based microgrid. [ABSTRACT FROM AUTHOR]

• Analytical physics-based models for DER effect compensation on impedance-based fault location solutions. • Consideration in the impedance-based FL formulation, of multiple simultaneous DER technologies types connected to the MG. • Adaptive solution considering or not wide-area measurements from distributed energy resources to improve the fault location. Distributed energy resources consideration by fault location formulations is a technical challenge. Stochastic behavior complicates deterministic solutions, while probabilistic approaches are yet to be fully explored. This paper presents analytical physics-based models towards the solution to this challenge. Presented models consider information availability from distributed energy resources to improve the fault location reliability. Information considered is divided into two categories: synchronized measurements provided by intelligent electronic devices located in the substation and in each terminal of distributed energy resources; and linear analytical-based models of distributed energy resources. Distributed energy resources models are used only when remote measurements are not available. Different distributed energy resources technologies and their operation modes are modeled. The presented fault location solution is validated on the IEEE 34-nodes test feeder modified. Easy-to-implement model, without hard-to-design parameters, built on the classical impedance-based fault location solution, indicates potential for real-life applications. [ABSTRACT FROM AUTHOR]

• An intensive and systematic review covers the protection techniques of AC microgrid. • Impact of grounding and fault current nature is analyzed to perceive protection needs. • Protection challenges and successive modifications of protection schemes are elucidated. • The need for communication and relay adaptability for dynamic fault current is divulged. • This work also includes current practice and future proclivity of AC microgrid protection. The addition of distributed generation to a power system improves its performance. It makes it more sustainable and efficient. But it also poses substantial challenges for designing a protection scheme. Due to the penetration of distributed energy resources (DERs), the fault level in the microgrid changes significantly. Conventional protection philosophies are substantially affected by the nature, penetration level, location, and operation state of the DERs, and can make microgrids vulnerable to outages. Thus, for improving the resilience of the micro-grid, the conventional protection philosophy needs to be modified. The protection devices (PDs) need to alter their operational settings to accommodate the system parameter changes due to changes in an operation state or network reconfiguration. A communication assisted protection architecture, which assures continuous data exchange between PDs, can provide a fast, secure, and reliable protection. Use of real-time analysis in microgrids can help protection system to anticipate faults. This paper explores and analyses various microgrid protection techniques to find out their shortcomings and seek a viable solution for future smart microgrid. [ABSTRACT FROM AUTHOR]

• Application of IMG in EM-SBO power system of 460 MWe NPP is modeled as test setup. • Load flow and short circuit analysis carried out by using ETAP software. • A novel adoptive overcurrent protection scheme is proposed for test setup. • Response of the protection scheme is analyzed by simulating various case studies. • Finally, discussion on simulation results and possible suggestions are given. Inclusion of distributed energy resources based integrated microgrid (IMG) into emergency station blackout (SBO) (EM-SBO) power system of nuclear power plant (NPP) has complicated its existing protection scheme due to varying system fault level with bidirectional flow of power. During SBO in NPP, it is of topmost priority to safeguard the reactor through EM-SBO supply. However, if any severe fault occurs, it may lead to complete collapse of the safety power supply in the NPP. So, availability of this tiny power system is most important as compared to the tripping of reactor safety of the NPP. In this paper, a 460 MWe NPP station has been considered to implement IMG into its EM-SBO power system and focuses on its overcurrent protection coordination scheme as a case study. The combined fuse and numerical relays inter-linked with digital logic-based adaptive overcurrent protection (AOP) scheme has been proposed after load flow analysis and calculating short circuit fault level through ETAP software. The sensitivity, the selectivity and the speed of the protection scheme have been evaluated in different network configurations like on-grid, semi-islanding and islanding mode of operation of IMG. Finally, it is proposed that the protection schemes vary from case-to-case basis leading to necessity of communication among the relays. So, an advanced AOP scheme with digital logic linked through peer-to-peer Hi-speed communication (IEC 61,850 confirmed GOOSE technology) has been proposed to resolve the protection issue of the modern NPPs operated through IMG. [ABSTRACT FROM AUTHOR]

• The influence of load dynamics in the islanding transition of a microgrid is assessed. • A sensitivity analysis of exponential and rotating load parameters is presented. • Increase values of system inertia ease the islanding transition of a microgrid. • Including rotating loads is important to assess the transient stability of microgrids. Microgrids (MGs) are characterized by faster dynamics than conventional grid-connected distributions systems. This is in part due to the lack of inertia of inverter-interfaced distributed energy resources such as photovoltaic and energy storage systems. In this context, load dynamics considerably affects the transient stability performance of MGs, especially if disconnected from the main grid. The aim of the paper is to analyze the influence of the load modeling and the load composition in the transient stability assessment of a medium voltage MG during islanding transition. The MG we analyze consists of a photovoltaic power plant, two battery energy storage systems, a synchronous generator and different classes and types of load, which we consider representative for the problem of interest. The system is implemented in the EMTP-RV simulation environment. The importance of appropriate load modeling for the adequate analysis of the transient response of an islanding microgrid is also addressed and discussed. [ABSTRACT FROM AUTHOR]

This paper presents a convex, multi-period, AC-feasible Optimal Power Flow (OPF) framework that robustly dispatches flexible demand-side resources in unbalanced distribution feeders against uncertainty in very-short timescale solar Photo-Voltaic (PV) forecasts. This is valuable for power systems with significant behind-the-meter solar PV generation as their operation is affected by uncertainty from forecasts of demand and solar PV generation. The aim of this work is then to ensure the feasibility and reliability of distribution system operation under high solar PV penetration. We develop and present a novel, robust OPF formulation that accounts for both the nonlinear power flow constraints and the uncertainty in forecasts. This is achieved by linearizing an optimal trajectory and using first-order methods to systematically tighten voltage bounds. Case studies on a realistic distribution feeder shows the effectiveness of a receding-horizon implementation. [ABSTRACT FROM AUTHOR]

• P2P energy trading is modeled as a prosumer coalitional game • A computationally efficient pricing mechanism is proposed to construct a stable grand coalition of prosumers • The effectiveness of the proposed mechanism is validated against state-of-the-art mechanisms using real-world system data Load balancing issues in distribution networks have emerged alongside the large-scale deployment of distributed renewable generation sources. In light of this challenge, peer-to-peer (P2P) energy trading constitutes a promising approach for delivering secure and economic supply-demand balance when faced with variable load and intermittent renewable generation through matching energy demand and supply locally. However, state-of-the-art mechanisms for governing P2P energy trading either fail to suitably incentivize prosumers to participate in P2P trading or suffer severely from the curse of dimensionality with their computational complexity increase exponentially with the number of prosumers. In this paper, a P2P energy trading mechanism based on cooperative game theory is proposed to establish a grand energy coalition of prosumers and a computationally efficient pricing algorithm is developed to suitably incentivize prosumers for their sustainable participation in the grand coalition. The performance of the proposed algorithm is demonstrated by comparing it to state-of-the-art mechanisms through numerous case studies in a real-world scenario. The superior computational performance of the proposed algorithm is also validated. [ABSTRACT FROM AUTHOR]

• A novel MI-QCQP for optimizing reactive power from domestic-scale DERs is proposed • The approach considers both inverter and network losses, and load-voltage sensitivity • Unbalanced European and North American networks are studied, with and without taps • Total demand reduction, of up to 0.5%, depends strongly on inverter loss coefficients • Control with reduced communication requirements can realize 98% of potential benefits This paper proposes a method for studying the potential benefits of reactive power control by domestic-scale inverters, considering network losses, inverter losses, and load-voltage sensitivity. The model is developed as a mixed-integer quadratically constrained quadratic program (MI-QCQP), using a linearization of the unbalanced distribution load flow equations. Networks both with and without on-load tap changers are studied, with the test cases covering both European and North American-style circuits. The use of domestic inverter control is shown to increase benefits compared to conventional tap control by 20%, reducing the total feeder power draw by as much as 0.5% of the feeder load. In contrast, the minimization of either load or losses in isolation is shown to increase the amount of power that a feeder draws in five of the seven circuits. To reduce the communications overhead of the approach, a control scheme is proposed that specifies the reactive power of all inverters on each phase identically; this approach is shown to realise up to 98% of the potential benefits of inverter reactive power control. [ABSTRACT FROM AUTHOR]

• Local energy markets enable direct energy trading among participating customers. • The interactions among electricity retailers and local energy markets are modelled. • A novel approach is employed for solving the developed bi-level optimization model. • Local energy markets are shown to enhance the competitiveness of retailers. • Local energy markets are shown to increase the economic surplus of the customers. Local energy markets (LEM) have recently attracted great interest as they enable effective coordination of small-scale distributed energy resources (DER) at the customer side, and avoidance of distribution network reinforcements. However, the introduction of LEM has also significant implications on the strategic interactions between the customers and incumbent electricity retailers. This paper explores for the first time these interactions by proposing a novel multi-period bi-level optimization model, which captures the pricing decisions of a strategic retailer in the upper level (UL) and the response of both independent customers and the LEM (both including flexible consumers, micro-generators and energy storages) in the lower level (LL). Since the LL problem representing the LEM is non-convex, a new analytical approach is employed for solving the developed bi-level problem. The examined case studies demonstrate that the introduction of an LEM reduces the customers' energy dependency on the retailer and limits the retailer's strategic potential of exploiting the customers through large differentials between buy and sell prices. As a result, the profit of the retailer is significantly reduced while the customers, primarily the LEM participants and to a lower extent non-participating customers, achieve significant economic benefits. [ABSTRACT FROM AUTHOR]

• A high-, medium-, and low-voltage test system is synthesised from limited data • Distributed energy resources and flexible loads are modelled individually • The response of distributed energy resources depends on their location in the system Future scenarios with high penetration of Distributed Energy Resources (DERs) call out for detailed network modelling at all voltage levels. The challenges of building a network model that is realistic at both the transmission and distribution levels have led to test systems that use aggregate medium-voltage (MV) loads. In this paper, we present a methodology that uses low-voltage networks with a sensible load allocation to disaggregate MV loads that were previously used in combined Transmission-Distribution (TD) network simulations. The resulting network accurately captures the interaction of transmission and distribution networks, thereby proving useful for new control schemes and stability studies that account for the participation of small and large-scale distributed energy resources. This extended network model is a convenient tool for research, training, and teaching. [ABSTRACT FROM AUTHOR]

Nowadays, the uncertainty in distribution systems rises, notably due to an increasing share of solar panels and electric vehicles whose power production and consumption are characterized by a high volatility. This poses challenges to distribution system operators to ensure stable and secure operation of their grid. Hence, an optimal integration of these distributed energy resources in real-time control schemes inevitably relies on appropriate forecasts of the near-future system state. This paper investigates the short-term probabilistic state prediction of low-voltage grids for operation purposes. The performance of two quantile forecasting algorithms is evaluated for different levels of distributed energy resources penetration and availability of measurements. Quantile forecasts are finally integrated into the framework of an optimization problem that aims at minimizing the costs associated with overvoltages by suitable solar power curtailment. The advantages of quantile forecasts considering different imbalance prices are demonstrated. [ABSTRACT FROM AUTHOR]

• A decentralised method for the management of generating and consuming DERs. • DLMPs calculated in an iterative, decentralized manner. • Convergence speed improvement using topological information. • Result show up to threefold reduction of required iterations. Dynamic pricing has been proposed for scheduling and controlling distributed energy resources (DERs) to mitigate operational problems in distribution networks. In this paper, we employ distribution locational marginal prices (DLMPs) to optimally schedule DERs, considering both line and voltage constraints. DLMPs are calculated in an iterative, decentralized manner to respect user privacy, using dual decomposition and the subgradient method. The inclusion of generating DERs in the problem formulation, and the nature of the subgradient method, may significantly increase the amount of required iterations. Recognizing the importance of convergence speed in such a mechanism, we act upon this by proposing a novel concept to identify and remove redundant constraints of the problem. The method is based on network topology observations in radial distribution networks. Redundant constraints are mapped to the respective Lagrange multipliers and are set to zero, thereby significantly increasing convergence speed. We validate our method in a 33 and a 136 bus system, showing the synergies of the co-optimization of generating and consuming DERs, and reducing the number of iterations at least threefold. [ABSTRACT FROM AUTHOR]