Grid Integration of Quasi-Z Source Based PV Multilevel Inverter

This chapter presents a quasi Z-source (qZS) based cascaded H-bridge (CHB) multilevel inverter for the grid integration of photovoltaic (PV) systems. The mixed topology is characterized by high-quality staircase output voltage with low harmonic distortions, independent dc-link voltage compensation with special voltage step-up/down function in a single-stage power conversion, and independent control of power delivery with high reliability. Moreover, a model predictive control (MPC) technique is used to transfer the power to the grid with unity power factor, low THD, low voltage ride-through (LVRT) capability, and anti-islanding protection. The synchronization of the power electronics interface with the grid remains one of the most important issues in the integration of DGs into the smart grids. Islanding protection is an important safety requirement to be addressed in grid connected power electronic systems. The antiislanding protection performance was evaluated for three phase-shift based active islanding detection methods: active frequency drift, slip-mode phase shift, and Sandia frequency shift.