DC Link Voltage Balance and Discharge in Three-Level NPC Fed PMSM-Powered EVs Using External Circuit

The paper introduces a voltage balance control algorithm designed to balance and discharge the DC link voltage in three-level neutral-point clamped (NPC) multilevel inverters feeding to permanent magnet synchronous motor (PMSM) based Electric Vehicle (EV). The paper also describes the DC bus voltage discharge on account of the emergency condition due to safety reasons. The control logic is implemented with the use of space vector pulse width modulation (SVPWM) to balance the DC link capacitors of the NPC with the help of an external circuit. In this method the NPC feeding to the PMSM operate normally with balanced dc link voltages. At a moment when suddenly the load increases or due to any emergence condition the DC link voltage gets unbalanced, then at this time the external circuit will get activated. The control logic will adjust the operation of the switches in such a way to keep the DC link in a minimum band of variations to provide system stability and balance the dc bus voltages. The scheme is performed on MATLAB simulations to verify the results in transients and emergent conditions.