Virtual energy storage system for peak shaving and power balancing the generation of a MW photovoltaic plant

This article proposes a novel control of a Virtual Energy Storage System (VESS) for the correct management of non-programmable renewable sources by coordinating the loads demand and the battery storage systems operations at the residential level. The proposed novel control aims at covering two main gaps in current state-of-the-art VESSs. The first gap is considering a distributed battery storage system instead of a centralized one, the second gap is providing the electricity grid operator with two services instead of one. To this aim, the authors explore a VESS consisting of residential buildings where each apartment is equipped with an air conditioner but also with a battery storage system. The explored VESS provides the grid operator with both peak shaving and power balancing services for the generation of a megawatt photovoltaic plant located near the VESS. The goodness of the proposed coordinated control is demonstrated via numerical experiments and using real data, measured every 15 min in September 2019. The case study consists of a 1.4 MW photovoltaic plant located near a small town, 21 residential buildings with 168 apartments, each equipped with an air conditioner (continuous power is 1.5 kW) and battery energy storage systems (3 kW /2.5 kWh). The numerical results show that the battery energy storage systems are charged correctly during peak hours (the charging power is between 0.45 and 0.90 kW, and the state of charge varies from 20 % to 78 %) and that the residual photovoltaic plant generation resembles a horizontal line. Later, in the early afternoon, the reference temperature of the air conditioners and the charge/discharge of the battery storage systems are suitably adjusted by solving a mixed linear integer programming problem, to balance the reduction in photovoltaic plant generation, which lasts an hour and a half and peaks at 188 kW. Finally, the numerical results also show that the energy that remained in the batteries is entirely consumed by users in the late afternoon or evening and that the amplitude and the duration of the so-called “load rebound” are so slight that no compensation action (e.g., the bath returning or linear recovery strategy) is required for the considered case study.