Inventor-controlled power unit

An invertor-controlled power unit which is arranged for connection in parallel with another invertor-controlled power unit, said first-mentioned invertor-controlled power unit comprising:

• a direct current power source circuit;
• an invertor circuit for effecting switching control of an output from said direct current power source circuit in response to a control signal to thereby convert said output into an alternating current output having a predetermined frequency;
• a pair of output lines conducting said alternating current output from said invertor circuit;
• output terminals connected to said pair of output lines for parallelly connecting said first-mentioned invertor-controlled power unit to said another invertor-controlled power unit;
• voltage waveform-detecting means for detecting a waveform of voltage appearing between said output lines;
• overvoltage-detecting means for detecting an overvoltage state of said direct current power source circuit;
• reference signal-generating means for generating a target output waveform signal having said predetermined frequency, said invertor circuit effecting said switching control of said output from said direct current power source circuit based on said target output waveform signal;
• control signal-generating means for converting said target output waveform signal into said control signal and for supplying said control signal to said invertor circuit;
• inhibiting means for rendering said control signal-generating means inoperative while said overvoltage-detecting means detects said overvoltage state of said direct current power source circuit;
• and
• synchronizing means for causing said control signal-generating means to start supplying said control signal to said invertor circuit at a timing at which the waveform of the voltage between said output lines detected by said voltage waveform-detecting means crosses a substantially zero volt level, and when said overvoltage state of said direct current power source circuit is not detected, whereby said alternating current output is delivered from said invertor circuit in synchronism with said voltage waveform appearing between said output lines.