Search

This article presents the methodology and results developed as part of the Integration of Energy Resources through Local Electricity Markets (IREMEL) project, whose aim is to assess the capability of flexibility markets to manage eventual distribution network (DN) congestion produced by a high penetration of distributed energy resources (DERs), including photovoltaic (PV) panels, battery energy storage systems (BESSs), and electric vehicles (EVs). The distribution system simulator OpenDSS has been used to simulate three Spanish DNs under multiple DER penetration scenarios considering an urban and rural low-voltage network and an industrial medium-voltage DN. Likewise, the congestion events detected in the annual simulations have been used to measure the potential of flexibility markets under different DER penetrations and energy pricing. The results suggest that oversized distribution networks could prevent a profitable flexibility market implementation since the simulations developed in this article shows that networks with high congestion levels are prime candidates to solve this issue through a market mechanism. Likewise, the results suggest that a proper price for the energy managed through a local flexibility market (LFM) could have a bigger effect on market viability than DER penetration. [ABSTRACT FROM AUTHOR]

This article presents the methodology and results developed as part of the Integration of Energy Resources through Local Electricity Markets (IREMEL) project, whose aim is to assess the capability of flexibility markets to manage eventual distribution network (DN) congestion produced by a high penetration of distributed energy resources (DERs), including photovoltaic (PV) panels, battery energy storage systems (BESSs), and electric vehicles (EVs). The distribution system simulator OpenDSS has been used to simulate three Spanish DNs under multiple DER penetration scenarios considering an urban and rural low-voltage network and an industrial medium-voltage DN. Likewise, the congestion events detected in the annual simulations have been used to measure the potential of flexibility markets under different DER penetrations and energy pricing. The results suggest that oversized distribution networks could prevent a profitable flexibility market implementation since the simulations developed in this article shows that networks with high congestion levels are prime candidates to solve this issue through a market mechanism. Likewise, the results suggest that a proper price for the energy managed through a local flexibility market (LFM) could have a bigger effect on market viability than DER penetration.

This paper presents a distribution system operator (DSO) framework for wholesale and retail market participation of distributed energy resources (DERs) aggregators. The DSO coordinates aggregators’ energy and regulation offers as well as end-users’ energy consumption through the unbalanced retail market and submits balanced energy and regulation offers to the wholesale market on behalf of all the aggregators and end-users within its territory. Various kinds of DER aggregators including demand response aggregators (DRAGs), energy storage aggregators (ESAGs), electric vehicle (EV) charging stations (EVCSs), dispatchable distributed generation aggregators (DDGAGs), and renewable energy aggregators (REAGs) are modeled. To handle unbalanced distribution grids with single-phase aggregators, a linearized unbalanced power flow is tailored to model operating constraints of the distribution grid with various aggregators. A market settlement approach is proposed for the DSO, which coordinates with wholesale market clearing process and ensures the DSO’s non-profit characteristic. It is proved that at the wholesale-DSO coupling substation, the total payment received/compensated by the DSO under the wholesale price is identical to that under three single-phase retail prices for each phase at the substation. Case studies are performed on the modified IEEE 33-node and 240-node distribution test systems to investigate the market outcomes of the proposed DSO. [ABSTRACT FROM AUTHOR]

The two-settlement electricity markets are widely accepted. In current practice, the markets are cleared based on locational marginal prices. However, this market clearing scheme leaves arbitrage opportunities between day-ahead and real-time markets for strategic distribution system operators (DSOs). They can submit biased bids from their actual load forecasts in the day-ahead market for additional benefits. Worse still, due to the high penetration of distributed energy resources, the impact of such strategic behaviors becomes increasingly severe as the uncertainties in DSOs’ load forecasts increase. In this paper, we first identify the profitable arbitrage opportunities of DSOs and the impact of uncertainties by a simplified analytical model. We then propose a Nash bargaining solution based market clearing scheme for real-time coordination between the transmission system operator and the DSOs. This scheme guarantees the fairness of net-benefit allocation among all the operators, prevents the strategic behaviors of DSOs, and helps the consistency between day-ahead commitment and real-time operation. Finally, we validate the effectiveness of the proposed scheme on both a simplified system and a practical power system testbed. [ABSTRACT FROM AUTHOR]

As the distributed energy resources penetration level increases, the distribution system operator faces a challenging task of unintentional islanding detection. Besides islanding detection schemes are affected due to the presence of different types of distributed generation systems and smart inverters. The presence of these devices hinders the capability of islanding detection schemes. To mitigate these issues, this study proposes a practical methodology of variational mode decomposition‐based energy index for islanding detection. It decomposes the sampled voltage signal at the point of common coupling into four modes/intrinsic mode functions (IMFs). Among these modes/IMFs, the energy index of mode two has been utilised to detect the islanding. It is an entirely intrinsic, adaptive, and variational method. The five bus and practical distribution systems have been modelled using PSCAD/EMTDC software while considering various components' practical aspects. The technique has been tested for the mixed type of distributed generation and various transient events. The test results reveal that the proposed method is capable of discriminating the islanding event from other disturbances. [ABSTRACT FROM AUTHOR]

Transport electrification is becoming the mainstream as a means to improve efficiency, performance, and sustainability of transportation systems. Electrical vehicles (EVs) can help to de‐carbonise the environment, but a downside is the technical issues presented to the low‐voltage distribution network. To quantify the stochastic nature of transport‐affected electrification, probabilistic load flow is employed. Monte Carlo‐based simulation is applied to accommodate the probabilistic uncertainties associated with variable EV charging patterns. This study considers high‐power charging (up to 11 kW) at the domestic level while monitoring power quality variations (voltage drop, voltage unbalance factor, voltage sag) standards. This work focuses on the Irish and UK, distribution system operator's–transmission system operator's perspectives, as it will help to identify the likely impacts due to high‐EV charger proliferation at household locations. The results indicate that if a 3.68 kW charger is used at the domestic level, it is possible for 40% of total household consumers to connect EVs directly to the distribution network without any power quality breaches. Furthermore, the proliferation of EV can be increased up to 100% if constrained to the start, and middle portions of the network (relative to the feeder substation transformer). For higher charger capacities (up to 11 kW), a bottleneck is presented regarding a resultant voltage unbalance factor. [ABSTRACT FROM AUTHOR]

The increased penetration of distributed energy resources (DERs) installed in distribution networks via power electronic converters reduces the overall rotating inertia of the power system, causing faster frequency dynamics after a large disturbance. However, these DERs coupled with energy storage systems (ESSs) can be managed to provide valuable grid support functions such as fast frequency response (FFR) and assist the transmission system operator (TSO) in frequency control. In this study, single‐ and three‐phase clusters of electric vehicles (EVs), acting as mobile‐ESSs, are grouped together as virtual power plants (VPPs) to centralise the provision of FFR for the distribution system operator (DSO) whilst considering network unbalance. Furthermore, the parameters of the EV clusters within each VPP are optimised to minimise the inertia‐weighed maximum frequency deviation following a disturbance whilst adhering to network security and power quality constraints. To this aim, a variant of the metaheuristic optimisation algorithm called improved harmony search is used for the optimisation process. Finally, the merits of the proposed methodology are shown with an illustrative example of an unbalanced three‐phase transmission and distribution network modelled in DIgSILENT PowerFactory. The results show that clusters of EVs grouped as VPPs effectively improve frequency support via the TSO–DSO interaction. [ABSTRACT FROM AUTHOR]

This study focuses on future distribution networks featuring the integration of extra‐high distributed energy resources (DERs). In these distribution networks, the extra‐high DER penetration and the randomness and volatility of DER outputs increase the likelihood of voltage problems. Hence, it is necessary to design efficient solutions for DER output setpoints to regulate the voltages of distribution networks. However, the existing online distributed algorithms were designed based on different linearised technologies for power flow equations, which will cause imprecise results under extra‐high DER integration. In this study, the authors propose an increment‐correction method to improve the linearised power flow model. To obtain an efficient distributed manner, they introduced an indirect function into the end‐customer (the DER owner)'s objective function, stimulating them to provide voltage‐regulating service. In particular, two price incentive signals contained in the indirect function were transmitted from the distribution system operator to drive the DER owner to regulate output increments, which is suitable for cases where the DER belongs to different end‐customers. The proposed method can not only protect the private information of end‐customers but also enhance the robustness of the distribution network for the DER integration level. Numerical test results demonstrate the merits of the proposed method. [ABSTRACT FROM AUTHOR]

This paper proposes a new local energy market design for distribution systems, which integrates peer-to-peer (P2P) energy trading and probabilistic locational marginal pricing. Distribution locational marginal pricing and P2P energy trading have each been proposed as potential alternatives to traditional retail pricing, to improve coordination between prosumers with distributed energy resources. Unidirectional locational pricing provides a scalable approach for coordinating demand, considering constraints and losses; while P2P energy trading allows prosumers to negotiate mutually beneficial bilateral energy transactions that increase the utilisation of their flexible energy resources. This paper proposes a market design combining the benefits of these two strategies. First, a new strategy for day-ahead locational marginal pricing is developed, which manages the uncertainty associated with local generation, demand and upstream prices by introducing a spread between the prices charged for energy imports and paid for energy exports. Then, local P2P energy trading platforms are integrated to additionally enable direct prosumer-to-prosumer trading, with transaction fees penalising energy transfers according to probabilistic differential locational marginal prices. Case studies are presented for a multi-phase low voltage distribution network, showing how the design can create value for prosumers, and the system as a whole, by reducing the curtailment of renewable generation. [ABSTRACT FROM AUTHOR]

Current feed‐in‐tariff (FIT) schemes for photovoltaic (PV) generators are set in the long term, thus they do not provide optimal dynamic price signals on the operational state of the distribution system. This work presents a transactive energy scheme to jointly optimise the operation of smart distribution networks, residential flexible loads and distributed PV‐battery systems. With this aim, a day‐ahead dynamic pricing (DADP) is proposed, which results in the economic social welfare maximisation of both distribution system operator (DSO) and prosumers in a 24 h time window, considering AC network constraints. DADP consists of distribution locational marginal prices that quantify DSO power delivery costs over time and across distribution network buses. To enable the participation of PV batteries in the DADP settlement scheme, and to consider the value of stored energy, a preference model is proposed on the willingness of prosumers to charge or discharge active power from batteries. The social welfare maximisation problem is proposed within the context of Latin American distribution networks and solved using the alternating direction method of multipliers, which is tested via simulations on a radial test feeder. Results indicate that DADP outperforms FIT scheme in terms of social welfare, and volume of exchanges among prosumers, DSO and wholesale market. [ABSTRACT FROM AUTHOR]

Power quality events associated with the occurrence of ferroresonances in medium voltage (MV) isolated‐neutral distribution power systems are well known but they still happen in nowadays grids. This work deals with the study of ferroresonance events in a distribution grid region characterised by having distributed generators and being lightly loaded. The study shows that well‐known solutions, i.e. voltage transformer damping, are difficult to apply due to the legal considerations and, alternatively, the distribution system operator can take actions to minimise their effect on the distribution system. The data provided and the obtained results correspond to a three‐year measurement campaign at a real MV isolated‐neutral distribution power system. The measurements and analysis given allow reaching general conclusions about the distribution system operation oriented to minimise the effect of ferroresonances. [ABSTRACT FROM AUTHOR]

This study presents a novel networked microgrid (MG)‐aided approach for service restoration in power distribution systems. This study considers both dispatchable and non‐dispatchable distributed generators (DGs), and energy storage systems. The uncertainty of the customer load demands and DG outputs are modelled in a scenario‐based form. A stochastic mixed‐integer linear program is formulated with the objective to maximise the served load, while satisfying the operation constraints of the distribution system and MGs. The interaction among MGs is modelled using the type 1 special ordered set. Two approaches are developed and compared: (i) a centralised approach where all MGs are controlled by a distribution system operator, and (ii) a decentralised approach where the distribution system and MGs are managed by different entities. The proposed restoration models are tested on a modified IEEE 123‐bus distribution system. The results demonstrate the advantages of leveraging networked MGs to facilitate service restoration. [ABSTRACT FROM AUTHOR]

This study develops a methodology for coordinated operation of distributed energy storage systems in distribution networks. The developed methodology considers that energy storage resources can contribute to their owners' inherent activities and to a more flexible and efficient distribution network operation. The optimisation tool based on mixed‐integer linear programming is developed to maximise the technical and economic value of distributed storage taking into account their multifunctional potential and the presence of intermittent renewable sources. The methodological developments are validated in a case study of a real medium‐voltage distribution network with two storage systems coupled with a wind park and an industrial 'prosumer' (i.e. energy consumers who are producing their own energy). Results make evident the robustness of the methodology and enable the assessment of the technical and economic impacts of the integration of distributed storage. Moreover, opportunity costs for distributed storage to perform services to the distribution system operator are demonstrated. [ABSTRACT FROM AUTHOR]