Modelling and controller design of quasi‐Z‐source cascaded multilevel inverter‐based three‐phase grid‐tie photovoltaic power system

Quasi‐Z source cascaded multilevel inverter (qZS‐CMI) is an emerging topology applied to photovoltaic (PV) power system. It can overcome disadvantages of conventional CMI‐based PV power system, because of achieving the balanced dc‐link voltage through using its boost ability, and saving one‐third modules. At present, there was not literature to disclose the modelling and controller design for qZS‐CMI‐based three‐phase grid‐tie PV power system. In this study, a control scheme for three‐phase qZS‐CMI‐based grid‐tie PV power system is proposed, where distributed maximum power point tracking (MPPT) and constant dc‐link peak voltage are achieved for all qZS H‐bridge inverter (qZS‐HBI)‐based PV modules, with grid‐injected power in unity power factor. The detailed controller parameter design is demonstrated by using Bode plots and the built models of qZS‐HBI‐based PV module and whole system. A test bench of 7‐level three‐phase qZS‐CMI‐based PV power system is built. Simulation and experimental results validate the proposed control scheme and design method.