Power Conversion System

A power conversion system comprising:

• a power converter that is connected between an AC circuit and a DC circuit and includes at least one self-commutating type semiconductor switching element;
• an AC current detector to detect an AC output current from the power converter to the AC circuit;
• and
• a control device to generate an on/off command for the semiconductor switching element to control the power converter,
• the control device includes:
• a current command value setting unit to set an AC current command value;
• and
• an AC current control unit to generate the on/off command according to an AC voltage command value calculated to cause the AC output current detected by the AC current detector to follow the AC current command value,
• in a first operation mode in which the power converter operates as a voltage source, the current command value setting unit sets the AC current command value based on a fundamental wave component of the AC output current detected by the AC current detector, and
• in the first operation mode, the AC current control unit calculates the AC voltage command value according to the sum of a feedback component for compensating for a current difference between the AC current command value and the AC output current detected by the AC current detector and an AC component having a frequency of the fundamental wave component.