Simulation study of permanent magnet synchronous machine direct drive wind power generator using three level NPC converter system

In this paper, two three-phase three-level neutral point clamped (NPC) converters connected back-to-back are used for a direct drive wind power generator. A permanent magnet synchronous generator (PMSG) is used as the generator, which is driven by the wind turbine. Main problem of voltage unbalance in each electrolyte capacitor is controlled by using a simple chopper control circuit. A simple hardware method for balancing the neutral point (NP) voltage is proposed, which allows enhanced ride-through performance. This method can effectively balance the NP voltage without the limitations of modulation methods and load conditions. It also provides increased ride-through capabilities for the inverter during input voltage sags. Because of the NP balancing, the necessary size of the DC-bus capacitors is reduced. Here, Matlab/Simulink simulation results are presented for the validity of proposed scheme.