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A Novel DC-Link Voltage Feedback Active Damping Control Method for IPMSM Drives With Small DC-Link Capacitors

In a small dc-link drive system, the LC resonance is a typical phenomenon caused by the negative inverter admittance related to the constant power load, which is considered an instability problem that needs to be resolved well. In this article, a novel dc-link voltage feedback active damping control method is proposed to improve system stability. First, the feedback control loop with time delay is established. Based on the inverter admittance, the feedback gain is designed to handle various operating conditions properly. Meanwhile, the inverter equivalent admittance can be changed into positive to improve the system stability. Then, the oversampling method is proposed to reduce the digital control delay time and improve the damping current precision. Therefore, the system damping performance is further enhanced. Finally, the damping current modification is applied, in which the damping current is modified to negative in the motor regenerative braking mode to improve the grid power factor. Compared with the conventional active damping method, the power factor is increased to 0.989 and the grid current harmonics are reduced to satisfy the requirements of EN61000-3-2. The effectiveness of the proposed active damping method is also verified by the experimental results.