Design and Real-Time Simulation of an AC Voltage Regulator Based Battery Charger for Large-Scale PV-Grid Energy Storage Systems

In a conventional energy storage system in a grid-connected solar power stations, solar power is transferred to the grid through a PV-Inverter, and the battery is charged and discharged through a bi-directional converter. In this paper, a novel grid energy storage system for large-scale PV systems is discussed. With the proposed configuration, the battery charging and discharging are carried out through an AC voltage regulator which is connected in series to the line. For this system, cascaded H-bridge (CHB)-based PV-Inverter which is suitable for a high power application is selected. In case of failure in one H-Bridge of a CHB inverter, it is difficult to integrate solar inverter with the grid as the voltages of inverter and grid are not matched. Fault tolerant operation of the CHB-based PV-Inverter can also be achieved through the proposed configuration. In this paper, basic operation and control of a voltage regulator, application of the voltage regulator in grid energy storage systems, fault tolerant operation of a CHB inverter through the voltage regulator are presented. To validate the performance of the controls proposed, Real-time simulations are carried out by interfacing the simulated power circuit with the real controller card with the help of an Opal-RT make real-time simulator. Performance of the proposed system is analyzed through presented results.