Zero-Sequence Circulating Current Reduction for Three-Phase Three-Level Modular Photovoltaic Grid-Connected System

An equivalent model is established for zero-sequence circulating current (ZSCC) in three-phase three-level modular photovoltaic grid-connected system, and ZSCC is classified by frequency into high-frequency and low-frequency components. A parallel solution based on improved LCL filter is proposed to reduce high frequency component of ZSCC, and the low-frequency component of ZSCC can be reduced by using the ZSCC controller. The ZSCC model analysis and reduction methods are verified by experimental results based on a 10 kW three-phase three-level modular photovoltaic grid-connected system.