A three level neutral point clamped inverter with buck-boost capability for renewable energy sources

As demand for renewable energy generation increases, the demand for power inverters with voltage buck-boost capability is also expected to rise. This is because the output of renewable energy sources such as solar panel, wind turbines etc are not constant due to varying climatic as well as geographic conditions. So in order to obtain an ac supply with adjustable voltage and frequency, a multi level inverter with buck boost capability is proposed. Multi-level converters are power-conversion systems composed by an array of power semiconductors and capacitive voltage sources that, when properly connected and controlled, can generate a multiple step voltage waveform with variable and controllable frequency, phase, and amplitude. In this a three level neutral point clamped inverter topology is used. Normally a neutral point clamped (NPC) inverter has a disadvantage of input capacitor voltage unbalancing. This can also be avoided by a special arrangement of input capacitors. Alternate Phase Opposition Disposition (APOD) modulation scheme is used for the modulation of NPC bridge. This inverter is used to drive a three phase induction motor. Simulation works are carried out in MATLAB/SIMULINK.