基于双模式逆变器的光伏-储能住宅发电系统无缝切换控制策略

With the increasing depletion of global traditional energy supply and escalating environmental problems, photovoltaic (PV)-energy storage based residential power generation systems have gained significant development. These systems, equipped with an energy storage system, can operate both in grid-connected (GC) mode and islanded (IS) mode. To ensure uninterrupted power supply (UPS) for residential loads, seamless transfer between GC and IS modes is critical. Therefore, this paper proposes a seamless transfer control strategy based on a unified control structure, which comprises a voltage outer loop and a current inner loop. In GC mode, the inverter behaves as a current source and the voltage loop effectively idle. In IS mode, the inverter serves as a voltage source and both loops are active. The mode adaptive behavior in such unified control structure avoids voltage and current surges caused by switching between different controllers. Since this control structure belongs to direct control, it has the merits of fast dynamics response and good power quality. To ensure smooth voltage reference during mode transfer, a simple voltage reference reconstruction and pre-synchronization control is proposed. Moreover, considering the safety standard in practical application, relay is usually used as the grid-side switch, its delay characteristic is also fully considered when mode switching. A step-by-step controller design is provided and a specified time sequence for mode transfer is proposed. Finally, a 5-kVA experimental platform is built and various comparative experimental results are provided to validate the superiority of the proposed strategy.