Design of a Flexible Commutation Switch Based on AC Power Frequency Converter

This study presents the design of a flexible commutation switch based on an AC power frequency converter (AFC) to control the three-phase imbalance in a distribution system. The traditional commutation switch mainly uses an interphase commutation device as the basis for the rapid commutation of the load. However, it causes a sudden change in the phase of the load voltage during commutation, which causes an inductive load to generate an in-rush current and seriously affects stable operation of the equipment. A traditional commutation switch has higher requirements for commutation time to ensuring normal power supply; also, it has the risk of causing a short circuit between phases during commutation. To solve these problems, this study proposes a new type of commutation switch based on the AFC. The switch removes the load from the power grid by providing transitional voltage with the same frequency and phase as the load voltage, and then controls the AFC output voltage so that the load can smoothly switch from one phase to another, solving the problem of sudden phase changes in the load voltage. Also, the power grid has no risk of a short circuit between the two phases during the commutation process. In this study, the feasibility of the designed commutation switch and commutation scheme based on AFC was verified through MATLAB/Simulink simulation, and the actual circuit was built.