Stability Study of Output Voltages of Two-Stage PV System Based Three Levels Inverter

Abstract

This paper presents an algorithm of regulation of AC voltage of photovoltaic conversion system composed by PV generator-boost converter-three phases three levels inverter for stand-alone application without introduced any system to regulate the fluctuation of the DC bus. The maximum power point tracking based on the “perturb & observe” (P&O) approach as a control strategy of a boost DC-DC converter is applied. In order to get the best AC voltage waveform, the simplified space vector pulse width modulation technique is used in this paper. To maintain the two capacitors voltages of DC bus equal, the redundant vectors of space vector diagram of three levels inverter are used. Without any system to regulate the fluctuation of the DC bus and to get a stable output inverter voltage, authors in this paper propose a proportional regulator of inverter modulation index. A theoretical analysis with a complete simulation of the system with different profiles of irradiance is presented to prove the excellent performance of the proposed technique.