单相非隔离型光伏并网系统中共模电流抑制的研究

RESEARCH ON COMMON-MODE CURRENT REDUCTION OF NONISOLATED SINGLE-PHASE GRID-CONNECTED PHOTOVOLTAIC SYSTEMS

首先分析了无变压器的光伏并网系统中产生共模电流的原因,从单相半桥和全桥拓扑结构出发,在得出共模电流抑制基本规律的基础上,研究了几种能有效抑制共模电流的拓扑结构,并提出一种能够抑制共模电流的混合桥臂拓扑,通过仿真验证了该方案的正确性。最后,对这几种拓扑结构的损耗进行了比较研究。

Common-mode currents due to the capacitance between the photovoltaic army and earth could occur and the electromagnetic emissions and potential safety troubles could increase. So common-mode currents must be reduced in grid-connected inverters for nonisolated photovoltaic systems. In this paper, causes for common-mode currents in transformless grid-connected photovoltaic systems were analyzed firstly; several inverter topologies that could avoid these common-mode currents are analyzed on the basis of basic laws of common-mode current reduction obtained from single-phase half-bridge and full-bridge. A new transformerless inverter called hybrid-bridge inverter is proposed. This topology generates no common-mode currents and has been validated by simulation. At last, the losses of these topologies are compared.