Patent ID: 6556457
Filing Date: 2003-04-29
Classification: H02M

Abstract:
A method of controlling a parallel operation of two inverter power generation apparatuses each comprising an AC generator, a DC power supply section having a rectifier to rectify an output of said AC generator and a smoothing capacitor connected across DC output terminals of said smoothing capacitor to generate a DC power supply voltage across said smoothing capacitor, an inverter circuit having on-off controllable switch elements to convert said DC power supply voltage into an AC voltage by switching said switch elements, a filter circuit to remove a harmonic component from said output of said inverter circuit and load connection terminals across which an output of said filter circuit should be applied whereby said inverter circuit is controlled so as to output an AC voltage of desired frequency when no voltage is applied across said load connection terminals from an external power supply and to make a waveform, a crest value and a phase of said AC voltage output from said filter circuit coincident with those of the AC voltage applied from said external power supply, respectively, said method comprising the steps of detecting said DC power supply voltage of each of said inverter power generation apparatuses, limiting a load current of each of said inverter power generation apparatuses to a value equal to or less than the maximum rated load current allowed for outputting the AC voltage having no waveform distortion from each of said inverter power generation apparatuses when both of said DC power supply voltages of said two inverter power generation apparatuses are equal to or less than a judgment value set at a value equal to or more than a no-load output voltage of the corresponding DC power supply section and allowing said load current of one of said two inverter power generation apparatuses to exceed the value of said maximum rated load current when the DC power supply voltage of the other inverter power generation apparatus exceeds said judgment value.