Abnormal Operation State Analysis and Control of Asymmetric Impedance Network-Based Quasi-Z-Source PV Inverter (AIN-qZSI)

Since its conception, the quasi-Z-source inverter (qZSI) has been extensively studied, especially in renewable energy applications fields due to its ability to withstand shoot-through and provide continuous current. However, research thus far has only explored symmetric qZSI/ZSI impedance network with large inductances and capacitances. By utilizing next-gen wideband-gap devices at high-switching frequency, the impedance network can be significantly reduced. However, the reduced qZS impedance network will result in abnormal operation modes, in addition to frequency resonances, in several kilohertz range. Thus, this paper first thoroughly explains the occurrence of the abnormal states, analyzes the effects of the abnormal states on the frequency resonance, and then proposes a control method to suppress the resonance that result from the reduced impedance network. A 1-kW prototype is built and experimental results verify the effectiveness of the analysis and proposed control method.