Three phase multi-string boost front-end hybrid multilevel inverter for standalone system

The paper describes a high efficiency photovoltaic system using a hybrid multilevel inverter circuit with multi-string boost converter topology. The proposed inverter circuit is built by connecting a line-frequency three-phase bridge inverter in series with three high-frequency single-phase H-bridge inverters. The multi-string topology with separate MPPT control achieves maximum power available from the PV which maximizes the efficiency. By comparing the traditional inverter circuit, this circuit can achieve high efficiency and low harmonics and it can reduce the voltage stress on the power switches. Since the circuit is modularized and having independent voltage control, it can be controlled easily. This paper includes the study of photovoltaic system with independent MPPT control, inverter topology, principle of operation, switching states and its control circuit design. Simulation of a three phase proposed inverter with multistring boost converter photo-voltaic system is carried out using MATLAB-Simulink software and the result shows the viability of the proposed topology.