Comparative evaluation of inverter topologies for wind and solar applications

NPP topology is used to implement 3-level inverter for AC drives. Here 3-level inverter is used to improve output wave form and also to reduce harmonics torque. This will allow a digital controller or micro-processor based control structure to be implemented. Many inverter topologies are present to implement the 3-level inverter technique. The NPP (natural point piloted) technique, allows lesser voltage stress on switches by the series connection of two IGBT to allow for a bi-directional switching, hence 4-quadrat operation is possible. So regenerative braking can be used. Moreover the speed of drive may be controlled more effectively. Proper switching may also reduces/eliminates the need of sine-wave filters which is a big advantage over other inverter topology, the size and cost comes down and the efficiency goes up.