A Unique Pulse Width Modulation to Reduce Leakage Current for Cascaded H-Bridge Inverters in PV and Battery Energy Storage Applications

摘要

Cascaded H-bridge(CHB)inverters operate with isolated DC sources,which makes them a favorable topology for hybrid-interfaced applications.Parasitic capacitance of grounded photovoltaics(PV)results in leakage currents that may deteriorate the system performance and raise safety concerns.In order to address this problem,a common-mode equivalent circuit for a multilevel CHB is illustrated.The study reveals that common modulation techniques such as phase shifted pulse width modulation fail to suppress the leakage current.A unique modulation scheme,based on considering the switching states is proposed in order to ensure that the topology conforms to the transformerless inverter regulations and standards such as VDE-0126-1-1.Simulation study results for conventional and proposed modulation methods are presented and analyzed in a symmetrical grid inductance filter circuit.