Power capability improvement of interior permanent magnet synchronous motor drives using capacitive network

This paper proposes a method to improve the power capability of an interior PM synchronous motor by boosting its terminal voltages with a capacitive network. In the conventional drive fed by a voltage source inverter (VSI), the terminal voltages of the motor are limited to the dc voltage. Such limitations cause the torque capability to decrease at high speeds and thereby lower the maximum output power. To overcome this problem, the proposed drive introduces a capacitive network between the VSI and the motor. The series capacitors boost the motor terminal voltages beyond the inverter output voltages to increase the rated speed, resulting in improved power capability. The enhanced power capability at high speeds and the design freedom of the rated speed are particularly advantageous in fan-load applications. This paper presents a dynamic d-q axis model, operating characteristics, and operable area of the proposed IPMSM drive. Experimental results are given to verify the feasibility and effectiveness of the system.