DC-Link Voltage Stabilization Based on Complex-Coefficient Current Controller for IPMSM Drives Without Electrolytic Capacitors

The electrolytic capacitorless drive inverter uses the smaller film capacitor instead of the larger electrolytic capacitor. Due to the absence of energy storage, it results in the fluctuated dc-link voltage. However, it is difficult to control the motor current when the voltage fluctuates. As a result, the voltage is unstable since the current is out of control. Besides, there exists the voltage resonance between the grid-link inductance and the dc-link capacitor. To improve the voltage stability, it is necessary to suppress the fluctuated component in voltage through the inverter control. In this article, a capacitor power regulation (CPR) method is proposed to reduce the oscillating voltage. The capacitor power error is transformed into the compensated current in q-axis. In addition, the complex-coefficient current controller (CCT) is proposed to improve the current tracking ability under the condition of fluctuated and insufficient dc-link voltage. Compared to the conventional current control method, the proposed method has smaller phase delay when the frequency is high. Therefore, it has the stability to track the reference within a wide frequency range. Moreover, it can improve the current tracking ability by modifying the current reference trajectory. Experimental results confirm the expected performance of the proposed method.