The increasing proportion of renewable energy introduces both long-term and short-term uncertainty to power systems, which restricts the implementation of energy management systems (EMSs) with high dependency on accurate prediction techniques. A hierarchical online EMS (HEMS) is proposed in this paper to economically operate the Hybrid hydrogen–electricity Storage System (HSS) in a residential microgrid (RMG). The HEMS dispatches an electrolyzer-fuel cell-based hydrogen energy storage (ES) unit for seasonal energy shifting and an on-site battery stack for daily energy allocation against the uncertainty from the renewable energy source (RES) and demand side. The online decision-making of the proposed HEMS is realized through two parallel fuzzy logic (FL)-based controllers which are decoupled by different operating frequencies. An original local energy estimation model (LEEM) is specifically designed for the decision process of FL controllers to comprehensively evaluate the system status and quantify the electricity price expectation for the HEMS. The proposed HEMS is independent of RES prediction or load forecasting, and gives the optimal operation for HSS in separated resolutions: the hydrogen ES unit is dispatched hourly and the battery is operated every minute. The performance of the proposed method is verified by numerical experiments fed by real-world datasets. The superiority of the HEMS in expense-saving manner is validated through comparison with PSO-based day-ahead optimization methods, fuzzy logic EMS, and rule-based online EMS.

@en

The extensive integration of distributed renewable energy resources (DRES) can lead to several issues in power grids, particularly in distribution grids, due to their inherent intermittency. This paper presents a stochastic simulation-based approach to estimate the maximum permissible penetration level of DRES and to determine the optimal capacity of centralized battery energy storage systems (BESS) in distribution networks while adhering to technical constraints. The stochastic method creates a wide range of scenarios under various conditions. For each scenario, our proposed approach calculates the maximum allowable penetration level of DRES and the required BESS capacity with different DRES control logics. The maximum allowable penetration level of DRES and the requirements of the BESS capacity are determined by an analysis of various simulation results. This paper's unique contribution lies in equipping distribution system operators (DSOs) with the ability to compare results and select the most appropriate voltage control and power smoothing methods. This aids in mitigating challenges associated with overvoltage and intermittency issues arising from DRES-generated power, thereby enhancing the overall resilience and reliability of the power grid. Case studies that include four voltage control algorithms and three power smoothing methods demonstrate the universality and effectiveness of the proposed approach.

@en

This paper deals with a systematic assessment of the power system frequency dynamics under high penetration of converter-interfaced renewable energy sources (CI-RESs). Specifically, the concept of the virtual synchronous generator (VSG) is implemented in the CI-RESs located at the transmission system (TS) side and/or the distribution network (DN) side. Dynamic RMS simulations are performed on a testbed consisting of the IEEE 9-bus TS grid and the CIGRE medium-voltage DN grid under different CI-RES penetration levels and VSG control parameters to assess the VSG impact on the power system frequency dynamics. It is shown that the decommissioning of conventional power plants coupled via synchronous generators can be safely performed in case the VSG concept is adopted correctly.@en

This paper introduces a flexible and extendable easy-to-use energy system integration development kit: the Illuminator. The Illuminator illustrates challenges arising from the energy transition. Hence, it is suitable in education and for demonstration. It also acts as a sandbox for testing new research concepts, and particularly, distributed energy coordination algorithms in real and non-real time. The Illuminator technology is primarely a modular software platform developed to run on a Raspberry Pi (RasPi) cluster. It is open-source, available at GitHub and developed in Python. The Illuminator comprises models of common energy technologies, such as photovoltaic (PV) panels, wind turbines, batteries, and hydrogen systems. The uniqueness of the Illuminator is in its modularity and flexibility to reconfigure scenarios and cases on the fly, even by non-experts in a plug-and-play fashion. This paper introduces the Illuminator and shows its performance in a simple case study.@en

As the penetration of Converter-Interfaced Dis-tributed Renewable Energy Sources (CI-DRES) increases, several problems are revealed in electric power systems, e.g., power quality issues, reverse power flows and frequency instability. A solution to tackle these issues is the mitigation of high CI-DRES active power ramp-rates (RRs) by utilizing energy storage systems (ESS). In many grid-codes at transmission system (TS) level, it is specified that the CI-DRES limit their RRs, while also the utilization of a central ESS has been proposed to limit the RRs. Nevertheless, this approach involves only large energy market players. Although various RRL methods have been proposed for CI-DRES, a remaining gap is the evaluation of the RR of a Distribution Network (DN) containing CI-DRES and loads together with the influence of distributed ESS in the DN. Towards this direction, in this paper, this evaluation is performed in order to study the RRL capability of a low-voltage (LV) DN considering both central and distributed ESS. The analysis is conducted in the LV CIGRE DN via quasi-steady-state and RMS simulations in PowerFactory considering several techno-economic parameters, e.g., ESS size, type, per unit cost. This evaluation will help towards the integration of the RRL control in the grid codes in DNs so that it can be considered as a new ancillary service to be remunerated in respective markets where also small CI-DRES owners will be able to participate.@en

Door middel van een zo representatief mogelijk rekenmodel voor het middenspanningsnet van de Amsterdamse gebieden Buiksloterham-Zuid/Overhoeks (BZOH), heeft het onderzoeksteam een detailanalyse kunnen uitvoeren naar de verwachte leveringscongestie in dit gebied zoals aangekondigd door Liander op 24 juni 2021. De detailanalyse laat een grootschalige toename in elektriciteitsverbruik in 3 jaar tijd zien, voornamelijk vanwege de stedelijke ontwikkeling in Overhoeks. Uit de beperkte beschikbare data en de resultaten uit het rekenmodel blijkt dat deze toename in vermogensvraag in het middenspanningsnet boven de normale beleidsgrenzen komt totdat de realisatie van de geplande netuitbreiding halverwege 2023 gereed is. De capaciteit is vooral ontoereikend in storings- en/of onderhoudssituaties, ook wel verschakelde toestand genoemd, in bepaalde delen van het netwerk. De studie laat zien dat het effectief verschakelen van het netwerk door Liander een groot deel van het capaciteitsprobleem vermindert. Er bestaan meerdere mogelijkheden om de configuratie van het net aan te passen om zowel in normaal bedrijf als in storings- en/of onderhoudssituaties belastingen beter in het netwerk te kunnen integreren. Een optimale netwerktopologie is daarom noodzakelijk om capaciteit vrij te spelen. In combinatie met een alternatieve reservestelling voor storing en onderhoud (t.o.v. de huidige reservecapaciteit in het netwerk) blijkt dat kritieke netsituaties voorkomen kunnen worden. Om tot een kosteneffectieve en uitvoerbare inschatting te komen voor de dimensionering en locatie van de alternatieve reservestelling, is het detailniveau van netanalyse cruciaal en is voor het toepassen van een alternatieve reservestelling in BZOH een kalibratie van deze studie door Liander noodzakelijk. Daarbij kan de detailanalyse inzichten bieden om in tijden van congestie het overschrijden van de normale beleidsgrenzen omtrent kabelbelasting tijdelijk toe te staan onder de veilige omstandigheden. Op basis van de resultaten uit deze studie zijn deze opties voor reservestelling vanuit energetisch perspectief kansrijk voor BZOH, zonder een verdere uitwerking te bieden voor implementatie.@en

As the penetration of distributed energy resources (DERs) increases significantly in the distribution networks, their integration reshapes distribution system power flows and leads to serious voltage quality problems in distribution networks. In this paper, a novel distributed cooperation voltage regulation method is proposed for future distribution networks. The proposed method can minimize the number of agents involved in the voltage regulation and it minimizes the change of required power for voltage regulation, which together minimizes the need for re-dispatching, i.e. the impact of voltage regulation on exchange of energy. Moreover, the proposed method performs online optimization, i.e the value of the decision variable is physically implemented as a controller set-point at each iteration which reduces the response time. The presented algorithm is benchmarked against ADMM and centralized optimization. The results show the voltage regulation effectiveness. Compared to the centralized method, the proposed method performs better in the case of a single agent failure, and compared to the ADMM method, the proposed method greatly reduces the action time and does not require retuning if network topology or agent participation changes.@en

The rapid growth of rooftop solar, and on the rise technologies such as electric vehicles and heat pumps, is leading to congestion problems in low voltage distribution networks. If not dealt with, the congestion will prevent the installation of further units limiting the pace of the energy transition. Energy Storage Systems (ESS) are often seen as the technology with a high potential for congestion reduction. In this paper, we propose to use Relocatable Energy Storage System (RESS) fleet, to physically move the ESS throughout the distribution grid in an effort to alleviate congestion. The proposed method consists of two parts. First, a Mixed Integer Linear Program (MILP) is created to minimise the amount of RESS used and penalise displacement. Second, an algorithm with a Minimum Cost Maximum Matching objective is used to determine the dispatch of each individual RESS. The results on a CIGRE test system show the benefits of this method compared to stationary placed ESS in the grid.@en

Rapid and large variation of photovoltaic (PV) power may incur frequency variation in a power system with high PV penetration. In such a case, much more reserve capacity of automatic generation control (AGC) for frequency regulation will be needed. In this paper, the energy storage station (ESS) is used to decrease the ramp rate of the total PV power and consequently decrease the AGC reserve capacity requirement of the power grid. However, as an expensive option, the ESS capacity should be optimally determined considering the balance between ESS cost and the equivalent benefit from the reduction of AGC payment. Therefore, an optimal sizing scheme for ESS in a power system with high PV penetration is proposed to strike a balance between the ESS cost and the reduction of the AGC payment. Firstly, a control scheme of ESS is proposed for smoothing PV power variation, during which the ramp rate of PV power can be finitely controlled with a size-limited ESS. Afterwards, an object function aiming to achieve the tradeoff between the investment cost of ESS and the reduction of AGC payment for frequency regulation is presented. Finally, case studies are conducted with actual PV power data to verify the effectiveness of the presented sizing scheme.

@en