Control apparatus, electric power conversion apparatus, and method for detecting failure of ac capacitor

A method for detecting failure of an AC capacitor in a power conversion apparatus including the AC capacitor disposed on an output side of an inverter and disconnected from a circuit when the AC capacitor malfunctions, the method comprising:

• a current component extraction step of acquiring current values of a current flowing through the AC capacitor during synchronization control that synchronizes an output voltage from the inverter with a system voltage of a system, the synchronization control performed during activation of the power conversion apparatus with an AC switch on a side facing the system open, and extracting a value of a current component having a frequency synchronized with a frequency of the output voltage from the inverter out of the current values;
• a failure evaluation step of comparing the value of the current component extracted in the current component extraction step with a predetermined evaluation value in terms of magnitude, and determining that the AC capacitor malfunctions when the value of the current component is smaller than the predetermined evaluation value;
• and
• a failure information notification step of issuing failure information representing that the AC capacitor malfunctions when the failure evaluation step determines that the AC capacitor malfunctions during the synchronization control.