Constant switching frequency using proposed controller with optimal DTC switching strategy for dual-inverter supplied drive

Abstract

This paper presents a simple solution to the variable switching frequency and high torque ripple which encountered by hysteresis-based Direct Torque Control (DTC) drive. To solve this two major problems, a new carried-based torque controller is introduced to replace the previous hysteresis torque controller which operate by comparing torque error with the triangular waveform. Since the dual-inverter supplied drive is implemented, an optimal switching strategy scheme is adopted for ensuring the most appropriate amplitude of voltage vectors is selected according to machine operation condition. As a result, the torque error become easier to be control inside triangular waveform since the rate change of torque or torque slope become lesser then the slope of triangular waveform. By combining this simple carrier-based torque controller with optimal switching strategy scheme, the DTC performances able to be improved further by providing constant switching frequency as well as torque ripple reduction. Then, all this improvement offered by proposed schemes are validated through the experimental results.