Research of Off-grid Energy Storage Converter Based on Repetitive Control and PI Control

The coordinated control of photovoltaic energy storage DC power supply system is one of most important issues for ensuring the system reliable operation. An autonomous control strategy is proposed for photovoltaic-energy storage DC power supply system without communication, With this strategy, any unit in system can switch its control mode smoothly via common DC bus voltage. During transition, its droop curve can be adjusted adaptively according to current operating state. The DC bus voltage amplitude is employed as an information carrier to determine the operation mode switching. Hence, each controller operates independently without communicating each other. With this method, voltage regulation, power balance and power sharing among different sources are guaranteed. Above conclusions are verified through PSCAD simulation in a photovoltaic energy storage DC power supply system.