SIMULATION OF HIGH EFFICIENT HYBRID CASCADED INVERTER FOR SINGLE PHASE INDUCATION MOTOR USING RENEWABLE ENERGY SYSTEM
Voltage source inverter is commonly used as the interface to connect the renewable energy source and thepower grid. In order to improve the performance of renewableenergy system, the topology and control method of the invertersystem need to be analysed. In this paper, a single-phasehybrid cascaded inverter is proposed. It is based on two kindsof power devices - MOSFET and IGBT. The cascaded inverterconsists of three H-bridges. The DC voltage of each H-bridgemeets the proportional relationship of 1:2:4 and the threemodules are connected in series at the AC side. The low voltagebridge is composed of MOSFETs, while the medium and highvoltage bridges are composed of IGBTs. This hybrid cascadedinverter can output at most 15 voltage levels at the AC sidewith rather low switching frequency. At the same time, it canfully exhibit the advantages of different power devices andmake the inverter operation flexible. Voltage gradational andPWM carrier modulation methods are adopted in the paper. Itis shown that the conversion efficiency reaches up to 98% andthe output THD is less than 5% (meets requirement of the IEEE standards). Meanwhile, with different combination ofswitching states, the distribution of input active power in eachH-bridge can be adjusted. As a result, for renewable energysystem, larger control freedom is provided and the need ofpower balance is satisfied. The validity of the inverter system istested by simulation.