Efficiency Evaluation of a Matrix Converter with a Boost-Up AC Chopper in an Adjustable Drive System

This paper proposes a circuit topology for a matrix converter with a boost-up AC chopper in the input stage in order to improve the voltage transfer ratio, which is defined as the ratio between the input and output voltages. The proposed system is applied in an IPMSM adjustable speed drive system where the application range of flux-weakening control is wide. In order to drive the motor at the rated speed in the high-torque region, there are three possible solutions: (i) applying flux-weakening control, (ii) boosting up the voltage by the AC chopper or (iii) a combination of both the solutions (i) and (ii). In terms of the total loss, the proposed system with the solutions (ii) or (iii) is compared with the conventional matrix converter by using solution (i). Consequently, the chopper loss in the AC chopper and the copper loss of the motor are calculated theoretically to evaluate the total loss. In addition, the proposed system is demonstrated as a 3.7-kW prototype by experiments. In this paper, the input voltage is degraded so that a larger boost-up ratio can be applied to the AC chopper. Further, the proposed system is compared to the conventional matrix converter by expanding the range of flux-weakening control, which depends on the input voltage. As a result, it is confirmed that the converter efficiency of the proposed system reaches 94.8% at the maximum point. Furthermore, it is revealed that the efficiency of the proposed system is higher when the rated motor voltage is greater than 107% of the input voltage.