Condition monitoring of a DC-link capacitor in an inverter with a front-end diode rectifier under imbalanced three-phase supply voltage

• Published in: Microelectronics and reliability Vol. 173; p. 115873
• Main Authors: Yamasoto, Takuma, Hasegawa, Kazunori
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.10.2025
• ISSN: 0026-2714
• DOI: 10.1016/j.microrel.2025.115873

DC-link capacitors in inverters have a shorter lifetime than the other devices, and thus degrade reliability of the inverters. The inverters are usually fed by three-phase supply voltages; however, the three-phase voltages are frequently imbalanced due to the connection of single-phase power sources and loads, such as renewable energy, which places additional stress on the DC-link capacitors. This paper proposes a condition monitoring method of a DC-link capacitor without an additional current sensor in an inverter system under the imbalanced three-phase supply voltage. This inverter system employs a front-end six-pulse diode rectifier with a DC reactor. The method is based on an analysis of the rectifier output ripple voltage including the uncharacteristic harmonics that result from imbalanced supply voltage, which is valid in a practical imbalance ratio around 5%. Experimental results obtained from a 200-V 1.5-kW laboratory system confirmed that both the capacitance and ESR were monitored even though the supply voltage was imbalanced. •This paper presents a condition monitoring of DC-link capacitors under imbalanced three-phase supply voltage.•The paper deals with a motor drive inverter with a front-end diode rectifier.•The method uses theoretically-analyzed current and measured voltage of the capacitor.•The harmonic components of the diode rectifier are analyzed with imbalanced three-phase supply voltage.•Experimental results confirmed that capacitance and ESR were monitored even under imbalanced supply voltage.