Comprehensive Modeling of Single-Phase Quasi-Z-Source Photovoltaic Inverter to Investigate Low-Frequency Voltage and Current Ripple

The second harmonic (2ω) power ripple of single-phase quasi-Z-source (qZS) photovoltaic (PV) inverter highly affects the whole system´s design and performance. The topology´s 2ω ripple model is very important to analyze qZS PV inverter´s 2ω voltage and current ripple. The existing models did not consider the PV-panel dynamic and terminal capacitors, which causes the theoretical results apart from the truth. In this paper, a comprehensive modeling for single-phase qZS-PV inverter is proposed, where the 2ω ripple model of the qZS-PV inverter system with a real PV source is established and discussed without and with a PV terminal capacitor. The influences from qZS inductance and capacitance, and PV-panel terminal capacitance to the 2ω voltage and current ripple are investigated using the built model. The system parameter design method is proposed to mitigate this ripple. Simulation and experimental results validate the proposed 2ω ripple model and parameter design method.