DC-Bus Capacitor Maximum Power Discharge Strategy for EV-PMSM Drive System With Small Safe Current

To prevent the passengers from electric shock, the DC-bus capacitor voltage of the high-voltage permanent magnet synchronous machine (PMSM)-based drives in electric vehicles (EVs) is required to decline to safe voltage as quickly as possible when emergency occurs. Considering that the discharge time for small safe current limit powertrain systems will be longer than required, this paper proposed a maximum power discharge strategy to accelerate the dissipating process and meanwhile avoid the voltage surge. Firstly, the PMSM discharge model as a generator is established on the basis of analyzing the discharge course. Secondly, the feasible reference current trajectory is presented by drawing the trajectories of the voltage, current, and power constraints. Then the maximum power discharge strategy is achieved by following the extreme points in the reference trajectory. Finally, simulation and experiment are conducted on a three-phase SPMSM powertrain system to validate the proposed algorithm can effectively shorten the discharge process.