Multiple Sinusoidal Signal Integrators and Unintentional Islanding Controlled PV-BES System at Unbalanced Grid Conditions

This paper demonstrates the multiple sinusoidal signal integrators (MSSI) and unintentional islanding control for photovoltaic (PV)-battery energy storage (BES) system. The unintentional islanding event is a serious issue in the grid interactive distributed renewable energy system at failure of the distribution grid. This event causes an interruption in the supply to emergency loads. Therefore, this control and topology address the issues of power quality and provide continuous power to the emergency loads under ON/OFF scenarios of the distribution grid. The precise harmonic current tracking of nonlinear load is obtained by using the MSSI control, which is also used for the mitigation of the grid voltage pollution and gives the accurate synchronization angle at operating mode transfer under ON/OFF grid conditions. The PV-BES system comprises of a bidirectional control of BES and a DC-AC converter controlled through MSSI control in ON grid mode. However, during disappearance of the grid or OFF grid mode, a transformation-based voltage algorithm is used for islanded operation. The buck/boost controller maintains the injected current to the DC link capacitor. A hybrid seamless transfer approach is implemented utilizing rate of change of frequency over power (ROCOFOP) and the islanding/synchronization is achieved as per the IEEE 1547–2018 undated standard.