Dynamics of a minimum DC link voltage driving method to reduce system loss for hybrid electric vehicles

In the proposed method, inverter DC link voltage is controlled in proportion to the motor terminal voltage rather than maintaining a constant value. The motor can be driven at lower voltage and driving point remains at where current is at its smallest so system losses can be reduced. In this paper, in order to realize such control method, it is studied about the transient state and the DC link voltage controller gain. A sudden change in the DC link voltage during transient state can cause the vibration to the battery current. But rapid convergence to the target voltage is required for high speed torque response. It is confirmed that there is a trade-off relationship between the torque response speed and the battery current stability depending on the proportional gain of the DC link voltage controller. And the dynamics are verified by scale down experimental system with a motor rated 1kW.