Power conversion apparatus

A power conversion apparatus having a converter for converting an AC power to a DC power, an inverter for converting the DC power to an AC power controlled by an inverter controller, and an input power source fluctuation detecting and controlling circuit, the input power source fluctuation detecting and controlling circuit comprising:

• an input power source fluctuation detector;
• a converter failure detector to detect overcurrent and/or overvoltage of the converter;
• wherein, when an input power source fluctuation is detected by the input power source fluctuation detector and a converter failure is detected by the converter failure detector, the converter is gate blocked, and the inverter continues its operation, and when the DC voltage is determined to be lower than a threshold voltage while the converter is gate blocked, the input power source fluctuation detecting and controlling circuit outputs an inverter control changeover flag to the inverter controller for switching a contents of inverter control, and
• the input power fluctuation detector has a first detecting circuit, comprising:
• a voltage fluctuation detector to detect a voltage variation of input power source directly;
• an absolute value detector to compute an absolute value of the voltage variation inputted from the voltage fluctuation detector;
• an input voltage level judgment part which outputs an abnormal input voltage detection signal as it is regarded that the fluctuation of input voltage is detected, when the absolute value of voltage variation exceeds an input voltage variation detection level in comparison of them.