A technique for FFT harmonics compensation and leakage current suppression in 10kW PV inverter

摘要

Because of the conventional two-level topology, without isolation transformer of three-phase 380V solar inverter difficult to suppress harmonics and leakage current, this paper proposes a new low-cost, high reliability solution. Based on the same LC filter parameters of three-level topology, using an improved FFT algorithm to obtain real-time spectrum analysis of output current, and accordingly to compensate and control output voltage, achieve the purpose of output current correction and harmonic suppression. To solve the leakage current of three-phase four-wire, two-level solar inverter without isolation transformer, by using a 3FB-SC(The Three-phase Full-Bridge VSI Inverter With Split Capacitor) topology, and increasing impedance on the N line to achieve the third harmonic suppression on the N line. Verified by 10kW prototype testing, the maximum conversion efficiency is up to 97%, the output of Ithd = 3%, the normal leakage current is less than 30mA; therefore it has a strong practical value.