A Simplified Braking Method for Direct Matrix Converter-Fed PMSM Drives with Consideration of Avoiding Regenerative Energy

This paper presents a simplified braking method for direct matrix converter (DMC) - fed permanent magnet synchronous motor (PMSM) drives with special consideration of avoiding the regenerative energy from feeding back to the grid. As a four-quadrant converter, the DMC has the bidirectional energy-flow capability, which is seen as a great benefit. However, the regenerative energy feeding back to the grid is not always needed, in some cases might be not allowed or not possible. These could happen due to the grid load status, strict quality specifications of the grid current or grid failure, where the DMC needs to be decoupled from the grid. In order to avoid the regenerative energy temporarily or completely, a three-phase diode bridge (B6) with chopper resistance on the motor side is employed together with the traditional B12-clamp circuit, which is used for overvoltage protection. Furthermore, the motor torque during braking could be controlled without large fluctuation and within the required limitation. The principle of the proposed strategy is described in detail. Simulation results are used to verify the feasibility of the proposed strategy.