Dynamic DC-Link Over-Voltage Mitigation Method in Electrolytic Capacitor-Less Adjustable Speed Drive Systems

Due to thin film capacitor's enhanced reliability and improved input current harmonic performance, adjustable speed drives (ASDs) without using electrolytic dc-link capacitors have been researched extensively in recent years. However, because of thin film capacitor's smaller capacitance per volume, it can experience a more severe dc-link over-voltage problem. In this paper, the underlying mechanism and possible scenarios of the dc-link over-voltage phenomenon are discussed. A new mitigation method of overcoming dc-link over-voltage problem is then introduced. Adaptive controller is applied to achieve fast response while maintaining system stability. Experiments are further conducted on a 2.2kW, 380V, 50Hz ASD setup with small thin film dc-link capacitor to validate the theoretical analysis for the proposed mitigation method.