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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]

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]

The way to produce and use energy is undergoing deep changes with the fast-pace introduction of renewables and the electrification of transportation and heating systems. As a consequence, the electrical grid sees much higher power variability than in the past, challenging its frequency and voltage regulation. Energy storage systems will be fundamental for ensuring the energy supply and the voltage power quality to customers. This survey paper offers an overview on potential energy storage solutions for addressing grid challenges following a "system-component-system" approach. Starting from system challenges, the energy storage technologies and their power electronics integration in the grid are described at component level considering the last scientific trends, including the hybrid energy storage concept. The impact of the energy storage technologies on the power systems are then described by exemplary large-scale projects and realistic laboratory assessment with Power Hardware In the Loop techniques, returning at system level. Finally, this work addresses some of the most important challenges for a sustainable and safe integration of energy storage systems, such as the circular economy and the safety aspects. [ABSTRACT FROM AUTHOR]

Utilizing Distributed Generators (DGs) and Energy Storage Systems (ESSs) enhances power system reliability, drawing significant research attention. However, these systems pose challenges, compelling scientists to explore optimization methods. Our paper presents an innovative solution, Parallel Multi-Objective Multi-Verse Optimization (PMOMVO), aimed at optimizing DGs and Battery Energy Storage Systems (BESSs) allocation. This optimization addresses voltage violations and operation costs, crucial concerns for system operators and consumers. By leveraging a parallel approach, PMOMVO significantly accelerates the optimization process. We compared its results with a base case scenario, demonstrating the superior efficiency of our parallel method. It not only enhances the optimization performance but also proves its efficacy by generating optimal solutions from the Pareto front set. This research showcases the benefits of PMOMVO, offering a faster, more efficient, and reliable way to optimize power systems, benefiting both operators and consumers. • Introduces a novel bi-level optimization approach for DG and BESS allocation and operation. • Proposing a multi-objective formulation to identify Pareto optimal solutions, offering a balance between voltage stability and cost-effectiveness. • Optimizes asset operation strategies, considering both peak and off-peak load times, enhancing resource utilization. • Proposes a parallel processing method based on modified MOMVO, significantly accelerating computations for large distribution systems problems. • Achieves a substantial improvement in the speed-up index, ensuring swift and effective DG and BESS allocation and operation in complex systems. [ABSTRACT FROM AUTHOR]

Residential communities are increasingly adopting renewable energy sources (RES) to minimize energy consumption costs. However, these RES are weather-dependent and uncertain, posing challenges to ensuring reliable operations. Addressing the uncertainties in power supply management becomes a critical research question. Energy storage systems play a crucial role in providing battery-powered supply for residential loads under uncertain conditions. The operation of microgrids is directly influenced by uncertainties. This paper proposes data-driven-based net load uncertainty quantification fusion mechanisms for cloud-based energy storage management with renewable energy integration. Firstly, a fusion model is developed using SVR, LSTM, and CNN-GRU algorithms to estimate day-ahead load and PV power forecasting errors. After that, two mechanisms are proposed to determine the day-ahead net load error. In the first mechanism, the net load error is directly forecasted, while in the second mechanism, it is derived from the forecast errors of load and PV power. The net error analysis is conducted with a statistical mean and standard deviation, resulting in different uncertainty-bound confidence intervals around the forecasted value. Subsequently, the cloud energy storage system operation cost is calculated with the best uncertainty quantification mechanism for two different case studies. This approach allows for better management of uncertainties in energy storage systems and enables more informed decision-making under varying conditions. • Learning-based fusion algorithm for net load forecasting. • Develop uncertainty mechanism for uncertainty quantification. • Economic assessment of cloud energy storage. [ABSTRACT FROM AUTHOR]

• The planning scenarios for island microgrids are categorized into three types, and selection methods are proposed for each type of scenario. • Establishing the unified GES model, which includes transferable load, reducible load, P2G-GS-MT, and energy storage. • Considering the impact of typhoons and utilizing GES, a planning model for pelagic island microgrids is developed, and a solution method for this model is presented. Stand-alone microgrid system consist of hybrid wind/photovoltaic/energy storage is one of the effective approaches to solve the problem for future pelagic island power supply. Also, the frequent typhoons have brought serious impact to the pelagic island microgrids. In this context, a multi-scenario planning model for pelagic island microgrid with generalized energy storage (GES) is proposed to address the issues of high-impact, low-probability typhoon events and insufficient flexibility in low-impact, high-probability situations. Given the impact of typhoons, the planning scenarios of island microgrids are divided into regular, typhoon and typhoon early warning scenarios. Meanwhile, the selection method for each type of scenario is given. In addition, this paper establishes the unified GES model which includes power to gas-gas storage-micro gas turbine (P2G-GS-MT), transferable loads, reducible loads, and electric energy storage. The proposed methodology has been validated on an enhanced microgrid, resulting in a cost reduction of 11.9% compared to traditional method. The results demonstrate that this approach reduces the planning capacity of equipment, cost reduction, and ensure uninterrupted power supply to important loads even during typhoon conditions. [ABSTRACT FROM AUTHOR]

The increasing applications of renewable energy resources and energy storage units (ESU) raise the necessity for reliable, efficient, and economical power systems. However, the charge/discharging power loss of ESUs cannot be ignored in the islanded microgrid. This paper focuses on the economic dispatch (ED) problem of ESUs in DC microgrids to reduce charging/discharging power loss, meet the power balance requirement, and against communication delays. Specifically, the distributed cooperative control algorithm designed in this paper forces incremental costs of all ESUs to a consistent value to minimize the sum operation loss of all ESUs in the small time scale. Meanwhile, power imbalance auxiliary variables are added to the control algorithm to satisfy the power balance constraint in the control process. Moreover, the ubiquitous time delay effect of communication links on the dispatch performance is solved by presenting an aperiodic sampled data-driven control method. The control parameters are determined by solving strict linear matrix inequalities, and the system stability analysis is also presented through the Lyapunov–Krasovskii functionals. Compared with the traditional control methods, the provided algorithm can overcome the negative effect of communication delay and save 16.94% of the sum ESUs operation loss under the given scenario. • An economic dispatch optimization algorithm for energy storage units is proposed. • The power balance constraint can be satisfied during the control process. • Develop a buffer-based waiting time strategy to avoid the effect of time delay. • The stability of the presented closed-loop system is proved. [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]

• A novel GNA optimized FOPTID+1 controller is suggested to supress the fluctuations in frequency in multi-source one and two-area multi-source power systems. • The supremacy of the controller is established over published techniques. • The effect of capacitive energy storage device is tested. • Robustness of the controller is scrutinized under extensive variation in system parameters and tie-line outages. The demand for power increases during the peak hours and the power supply can't exceed its limitations. This results into mismatch between the supplied and demanded powers causing fluctuations in the frequency. Extreme power-frequency deviations may cause power system blackouts. To maintain the constant frequency of power system, automatic generation control (AGC) should be embedded with a reliable controller. In this paper, a fractional order proportional tilt integral derivative plus one (FOPTID+1) controller is introduced in the design of AGC to retain frequency constancy. This controller has the ability to regulate the frequency hastily during load disruptions. The controller parameters are optimized by exploiting global neighbourhood algorithm (GNA). Firstly, the investigation is directed on a one-area multi-source thermal-hydro-gas generating system. To authenticate the expandability of the method, the study is then extended to multi-source interconnected two-area thermal-hydro-gas power system without/with nonlinearities. The dominance of the suggested controller is recognized over various recently published results of I/PI/PID/TID/FOTID and GNA tuned PID/FOPID controllers. Inspection of results authorizes the worthier performance of FOPTID+1 over other controllers regarding least overshoot/undershoot/settling time of frequency/tie-line power change and error criteria at disturbances. To further advance the system performance, capacitive energy storage (CES) units are incorporated to compensate the power demanded by the load disturbances. The obtained results demonstrate that CES is capable to improve system performance effectively. With CES, FOPTID+1 produces less cost function value for both one-area (9.52%) and two-area (8.97% for linear and 11.38% for nonlinear) systems. The control system stability is verified by the study of bode diagram. The resilience behaviour of the controller is confirmed by the stout conduct of controller under ±25% variation of system parameters and tie-line outages. [ABSTRACT FROM AUTHOR]

• A PSO-based optimization method for VRCD coordination control parameters of shipboard MVDC system is proposed. • Models of gas turbine and MVDC power system are established, leading to the quantification of evaluation indicators considering gas turbine capacity and HESS configuration. • The simulation results validate the effectiveness of the proposed control strategy and optimization method, contributing to improved transient power flow. Supplying power for large pulsed power load with shipboard MVDC system has continued to be a challenge. Due to limited grid capacity and power ramp rate of prime movers, the high-power load mutation will cause intolerable impact, which is an essential issue to be solved. In this paper, hybrid energy storage system is configured for transient power compensation, and the distributed virtual resistive capacitive droop is introduced to power coordination for MVDC sources. The transient flow evaluation function considering the speed state of the genset and the configuration cost of hybrid energy storage system is defined, models of the gas turbine and MVDC power system are established, and the optimization method of control parameters and system flow based on PSO and model simulation is proposed. The effectiveness of the proposed control strategy and optimization method is verified by MATLAB/Simulink simulations. [ABSTRACT FROM AUTHOR]

• Protection against electric shock and protection selectivity in collective prosumer electrical installations (cPEI) are investigated. • A cPEI can be easily established based on LV distribution system. • Original protective devices implemented in LV distribution system must be verified while the cPEI is planned to operate in island mode. • The case study demonstrates the whole process of protection verification to meet the requirements. • The case study prove the original protection devices and introducing molded case circuit breakers can satisfy the protection requirements. IEC 60364-8-2 introduces many safety issues concerning a new concept of integration of electricity consumers and local power generation and energy storage, i.e., prosumer's low-voltage electrical installations. A collective type of them is several consumer installations connected to the same public distribution system and sharing one common set of local power supplies and energy storage unit. The transition to island mode raises technical challenges related to ensuring the protection selectivity and the effectiveness of protection against electric shock. They result from the expected short-circuit currents, much smaller compared to other modes. In this paper, the first approach for protection verification and design concerning collective prosumers' electrical installation to be established based on an existing low-voltage distribution system in each area (group of prosumers) is proposed. It includes the following: calculation of short-circuit currents while operating in island mode, selection of the currents relying on the current limit of an energy storage unit, verification of the protection devices, and design of the additional protection. The case study confirms the approach allows for the investigation of the common protection devices in terms of meeting both the safety and selectivity requirements. Otherwise, advanced protection schemes and strategies should be considered to meet the same safety requirements. [ABSTRACT FROM AUTHOR]

The Non-Utility Distributed Energy Resources (nDERs) are those not responsible for supporting the distribution system operation. These resources are crucial for improving the Energy mix's sustainability due to their majority renewable nature. However, integrating these resources into distribution systems has become a challenge for Distribution Companies (DisCos) due to their intermittent behavior. This challenge is even more significant when a gap in distribution system modernization (smart meters and communication systems) exists. This paper proposes an approximate method to evaluate the nDERs' impact on the distribution system's steady-state voltage. The method is based on a linear approximation of voltage drop/rise and the impedance matrix. It has been validated on two distribution systems considering five scenarios. Numerical comparison with exact solution has shown good results in four scenarios with maximum absolute errors around 0.01 p.u. in low-risk and high-risk voltage violation situations. The proposed method can be used in the planning or operation stage as a first estimation where no real-time monitoring is available, or the power-flow calculation is difficult to obtain. • The method does not require running a power flow simulation for each analysis. • The nDERs' voltage impact can be easily estimated by matrix/vector operation. • The DisCo can define power limits for operation without real-time monitoring. • A first estimation of nDERs' voltage impact in common scenarios. [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]

With the continuous reform of the world's energy system, the energy microgrid built to achieve green, flexible, autonomous and sustainable development of highway is facing new challenges in energy dispatching and management due to the uncertainty from both the supply and demand sides. In this paper, an enhanced coordinated energy scheduling scheme is proposed for typical highway demand scenarios, based on the introduction of mobile energy storage system, to replace the traditional centered power scheduling. It could maintain the balance between energy supply and users demand, and minimize the cost of energy system dispatch operations. The appropriate selection and cost of the mobile energy storage system are investigated and evaluated. Utilizing the data from the designed 30% renewable energy highway service station construction project in Xinjiang, China, the effectiveness of the proposed mobile dispatching scheme is verified. The proposed scheme provides a feasible solution and forward-looking guidance for the integration of highway transportation energy nexus. [ABSTRACT FROM AUTHOR]

• Joint planning of capacitor, dispatchable DG, and energy storage with renewables. • Improve technical and economic effects of Volt-VAR optimization for energy saving. • High accuracy and low computational burden through MultiGMM-based data cluster. • Adaptive to scenario-based planning problems in large-scale distribution systems. • Provide incentives for distribution companies to invest in Volt-VAR optimization. With recent installations of intermittent renewable energy generations in electric distribution systems, their impacts on classical Volt-VAR optimization (VVO) schemes, especially the energy-saving effects, are becoming one of the major issues. The optimality of VVO schemes is hard to be guaranteed due to voltage fluctuations caused by distributed renewable generations. Distributed energy resources (DERs) could be a solution to provide flexibilities to improve VVO performance if the high cost is lowered while their locations and sizes are optimized. In this paper, an optimization model is proposed for a joint planning of capacitors, dispatchable distributed generators, and energy storage to improve VVO energy-saving effects while minimizing the system operating cost. The uncertainties of renewable energy resources, electricity demand, and electricity prices are accurately modeled benefited from emerging data analysis technologies. The technical and economic effects of the proposed model are proved and tested using real data sets and compared with classical models. The high precision of the proposed model is verified using time-series simulations. [ABSTRACT FROM AUTHOR]

• Increase speed and accuracy in compensating for voltage and frequency fluctuations. • Intelligent power and energy management based on MPC and INN algorithms. • Optimal performance of primary and secondary controllers based on uncertainties. • Optimal control of power generation sources and energy storage units. This paper presents an intelligent energy management method to control the voltage and frequency at the primary and secondary control levels of micro-grids. The proposed model is based on the model predictive control (MPC) at the primary and intelligent neural network (INN) at the secondary. The purpose of this paper is to control the voltage and frequency based on the uncertainties of power generation resources and loads. In order to validate, the results of the proposed model are compared in different scenarios with other methods such as Fuzzy and PID controllers. The performance of the proposed method in primary and secondary as well as the coordination of this method with a high degree of sensitivity along with HESS and diesel generator units, in addition to increasing stability and reliability, protects the operation of the micro-grid against fluctuations based on uncertainties. The results show that this method, in addition to accuracy, has a higher operating speed than other controllers. As a result, the voltage and frequency restoration in the primary and the compensation of deviations from the reference in the secondary are associated with acceptable results. In order to validate the simulation results and experimental results are also presented. [ABSTRACT FROM AUTHOR]

Abstract: This paper discusses the design, implementation, experimental validation and performances of a fully digital fast power switch fault detection and compensation for three-phase shunt active power filters. The approach introduced in this paper minimizes the time interval between the fault occurrence and its diagnosis. This paper demonstrates the possibility to detect a faulty switch of the active filter in less than 10μs by using simultaneously a “time criterion” and a “voltage criterion”. In order to attain this fast detection time a FPGA (Field Programmable Gate Array) is used. The other feature introduced in this approach is that the control scheme used to compensate the current load harmonics and fault tolerant scheme are both programmed in only one FPGA. “FPGA in the loop” prototyping results and fully experimental results based on a real active power filter verify satisfactory performances of the proposed method. [Copyright &y& Elsevier]

The high penetration of distributed energy resources (DERs) (i.e. solar energy, wind power, photovoltaic and energy storage system) are integrated into the transmission grid (TG) and the active distribution networks (ADNs) in a centralized or decentralized manner or distributed manner, which significantly impose crucial challenges on the frequency regulation of power system. To make full use of the frequency regulation effect in dispatch and control, and considering the topology interlinked and the information sharing between TG+ADNs, in this paper, a distributional TG+ADNs two-level synergetic unit commitment (TLS-UC) considering three scheduling states is proposed. To explore the synergetic capacity of the TG+ADNs accommodating uncertainties of load and DERs, three scheduling states including the automatic synergetic state (i.e. primary frequency regulation (PFR)), the coordinated synergetic state (i.e. secondary frequency regulation (SFR)) and the controlled synergetic state (i.e. economic dispatch (ED)) of TG are defined and implemented to deal with uncertainties through the interconnection of the tie-line between TG+ADNs. A decentralized and parallel analytical target cascading (ATC) algorithm is employed to solve the proposed TLS-UC model. A modified 6-bus TG system with 2 ADNs (T6D2) and IEEE 118-bus TG system with 10 ADNs (T118D10) are used to test the proposed TLS-UC model. Test results illustrate that the proposed method is effective and efficient, and it can enhance the synergic capacity of power system to keep source power balance under uncertainties. [ABSTRACT FROM AUTHOR]

• Providing a chance-constrained framework for congestion management and frequency regulation. • Evaluating the performance of the model in both normal and emergency conditions. • Investigating the effect of spinning reserve rate on congestion, LMP and frequency. • Investigating the effect of EES systems on congestion, LMP and frequency. This paper presents a chance-constrained optimization framework for transmission congestion management in the presence of wind turbines and electrical energy storage (EES) systems. In the proposed model, the uncertainties of the wind farms' output power and electricity demand are considered, and in order to model these uncertainties, the chance-constrained method is used. In order to reduce the computational burden in this problem, a filtering algorithm is proposed that detects sensitive lines and applies security constraints only on them. The results illustrate that applying the proposed algorithm has reduced the solution time by about 83%. In addition, the proposed model is implemented on a modified IEEE 30-bus test system and solved under normal and emergency conditions (N-1). The simulation results demonstrate that considering the chance constraints, by increasing the spinning reserve, leads to a decrease in the amount of energy not supplied (ENS) and consequently operating costs during the contingent events. The numerical results illustrate that considering the spinning reserves, despite a 10% increase in operating costs under normal operating conditions, has reduced the amount of ENS by about 18% during the outage of the thermal unit. In addition, the results demonstrate that EES systems keep the system frequency within the allowable range under emergency conditions due to their fast ramp rate. [ABSTRACT FROM AUTHOR]

This paper proposes a market mechanism for multi-interval electricity markets with generator and storage participants. Drawing ideas from supply function bidding, we introduce a novel bid structure for storage participation that allows storage units to communicate their cost to the market using energy-cycling functions that map prices to cycle depths. The resulting market-clearing process – implemented via convex programming – yields corresponding schedules and payments based on traditional energy prices for power supply and per-cycle prices for storage utilization. We illustrate the benefits of our solution by comparing the competitive equilibrium – assuming price-taker participants – of the resulting mechanism to that of an alternative solution that uses prosumer-based bids. Our solution shows several advantages over the standard prosumer-based approach that prices energy per slot. It does not require a priori price estimation. It also incentivizes participants to reveal their truthful cost, thus leading to an efficient, competitive equilibrium. Numerical experiments using New York Independent System Operator (NYISO) data validate our findings. • Study the effect of storage bid structure on electricity market efficiency. • Consider a competitive equilibria analysis with price-taker participants. • Storage bids based on pricing energy per slot lead to inefficiencies. • Propose a novel market mechanism for storage that relies on pricing energy cycles. • The cycle-based mechanism aligns with the social optimum. [ABSTRACT FROM AUTHOR]

This paper describes an economic dispatch formulation for a power system control area with high penetration of renewable generation and energy storage. We develop a comprehensive objective function that is unbiased to both the conventional and renewable generation sources. Operating constraints of conventional sources are considered, wind turbine generation is treated as a dispatchable source, and solar photovoltaic generation as negative load. A simulated annealing and particle swarm optimization algorithm are separately applied to minimize the objective function. The results obtained by the proposed economic dispatch formulation show that even a variable energy resource like wind can be dispatched in a manner that benefits the control area as a whole. [ABSTRACT FROM AUTHOR]

• Two-timescale volt/var optimization that utilizes distributed energy resources. • Coordinating distributed energy resources along with utility-owned assets. • Engaging utility operator in the decision-making process. • Active distribution network with high distributed energy resources penetration. • Incorporate all resources and assets for enhanced network performance. The high penetrations of distributed energy resources of renewable energy sources, battery energy storage systems, and electric vehicles introduced several challenges to power networks. It can lead to high voltage variation, sudden over/under-power generation, high losses issues, and negatively impact distribution assets. Thus, there is a vital need for volt/var optimization schemes that integrate conventional volt/var devices with inverter-interfaced resources to overcome these challenges. This paper demonstrates a performance assessment of the volt/var optimization scheme utilizing different utility-owned assets and resources based on a two-timescale multi-objective algorithm. At the slow timescale, it utilizes capacitor banks and on-load tap changers to minimize system losses and maximize asset lifetime based on their conditions. The algorithm incorporates the utility operator's direct input for setting the conventional volt/var devices. The operation of these devices is optimized, in three steps, by limiting the number of switching operations based on the operator preferences. At the faster scale, it considers renewable energy sources, electric vehicle charging stations, and battery energy storage systems to be optimized to limit voltage variation and system losses further. The IEEE 33-bus distribution network is modified and used to demonstrate the effectiveness of the algorithm. [ABSTRACT FROM AUTHOR]

• Practical method to determine whether shunt/series ESS can mitigate voltage sags. • Auxiliary chart obtained easily and analytically. • The method obtains Energy Storage System capacity required to mitigate voltage sags. • The method obtains the optimum power factor for operation of Energy Storage System. Energy storage systems (ESS) have attracted significant interest and investments. Despite this interest, industry and utility engineers have not widely considered this technology as a potential solution to improve the power quality supplied for critical loads. This is in part because of the high cost and in part because of the high complexity to assess this type of solution. This paper, therefore, proposes a practical approach to determine whether shunt/series ESS can mitigate voltage sags assuming the availability of system information, as short-circuit impedance and historical voltage sags, and load information. This is done by analyzing a chart obtained analytically, which can be easily constructed based on simple information from the system and load, without resorting to computer simulations. By inspecting this chart, engineers can quickly determine not only the ESS capacity required to mitigate specific sags, but also which is the optimum power factor for operation. Sensitivity studies are provided to reveal key factors affecting ESS capability to mitigate voltage sags and to validate the proposed approach. Results outline that the requirements of shunt ESS depend on the system short-circuit level and X / R ratio, whereas requirements of series ESS depend on the load demand and power factor. [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]

• Mobile emergency generator and mobile energy storage system meets the power demand of critical loads in emergency conditions. • Traffic congestion information is adopted to the proposed scheme considering the interdependent operation of coupled distribution transportation systems. • Coordinated operation of multiple types of mobile power sources and repair crews is addressed. • Distribution system constraints are modelled according to the linearized distflow equations in mixed integer quadratic programming framework. In this paper, a mixed integer quadratic programming (MIQCP) based post-event distribution restoration framework in response to high impact low probable events is propounded to maintain the power supply continuity of critical loads particularly in emergency conditions. Mobile power sources (MPSs) including mobile energy storage system (MESS) and mobile emergency generator (MEG) are considered as grid-support services in resiliency enhancement strategy due mainly to their spatiotemporal flexibility. Power system constraints are modelled according to the linearized DistFlow equations; on the other hand, traffic congestion is also considered while directing MPSs from staging locations to damaged areas. Repair crew dispatching schedule for maximizing the objective function is provided in a deterministic fashion. Numerical results based on the conducted case studies on modified version of the 15-bus distribution system show the capabilities of the model. Hereby power demand of all critical loads is served after an optimal allocation of MPS even though the damages are not completely cleared in the branches. Further, the decisions are close to what can be realistically expected in practical implementation, that fast-responded resources are exploited depending on traffic-related constraints and economic issues. [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 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]

• 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 virtual power plant aggregates distributed resources and energy storage systems. • Proper control and stability analysis of virtual power plants are necessary. • Energy Storage is crucial for the frequency control of virtual power plants. • Communication delays for the centralized control strategy impact on stability. This paper studies the impact of coordinated and non-coordinated frequency control of Virtual Power Plants (VPPs) on power system transients. A realistic modelling of the communication system within the VPP is also taken into account. The case study considers a modified version of the WSCC 9-bus test system with inclusions of a VPP with distributed generations and, discusses the performance of the coordinated frequency controller in the VPP. All simulations are performed considering both deterministic and stochastic variations of the wind and voltage-dependent loads. [ABSTRACT FROM AUTHOR]