Direct torque control of sparse three level inverter fed low voltage IPMSM drive

Abstract

This paper proposes a simple three-level direct torque control scheme incorporating a sparse three-level neutral point clamped inverter for the control of a low voltage interior permanent magnet synchronous machine. The main objective of the proposed scheme is to improve the torque and flux responses of the direct torque controlled interior permanent magnet machine with the minimum amount of semiconductor switches. Although the number of semiconductor switches is reduced with the usage of sparse three-level neutral point clamped inverter, the proposed scheme can utilize all voltage vectors of a conventional three-level neutral point clamped inverter so that the degree of freedom of a classical three-level direct torque control is maintained. Furthermore, the proposed algorithm is capable of minimizing the neutral point voltage imbalance. Simulation results are provided to prove the feasibility and effectiveness of the proposed method.