Control strategy for the front-end DC-DC converter to reduce the second-order harmonic current in the two-stage inverter

The instantaneous output power of the two-stage single-phase inverter pulsates at twice the output voltage frequency, generating second-order harmonic current (SHC) in the front-end DC-DC converter. To reduce the SHC, this paper proposes a control strategy based on the virtual impedance. For the case that adopting a resistor as the virtual impedance, a closed-loop parameter design method is presented, indicating that this instance is not beneficial to increasing the voltage loop crossover frequency (VLCF). To overcome this problem, a control strategy with inner inductor current feedback through the band-pass filter(BPF) is put forward and a damping resistor is added into the BPF in order to improve the stability margin. The proposed control strategy can not only reduce the SHC significantly, but also improve the dynamic performance of the front-end DC/DC converter effectively while guarantee the converter working in stability. Finally, an 1kVA prototype is built and tested in the lab. The experimental results are given to verify the effectiveness of the proposed control strategy.