| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an electric power conversion equipment that permits to fulfill two-arm modulation and the reduction of similar average switching frequency without entailing stepped changes of output potentials, to eliminate the need for large-sized common mode filter and insulating transformer, to achieve reduced size and light weight, and to inhibit output distortions during soft starting and during output transients caused by making and breaking loads. <P>SOLUTION: In the electric power conversion equipment for converting three-phase AC voltage into DC voltage, or DC voltage to three-phase AC voltage, a pulse width modulation is performed using carrier waves with different frequencies depending on phase and instantaneous value of the AC voltage. And, in the vicinity of zero-cross of phase voltage of the AC voltage, the pulse width modulation is performed using a carrier wave with a first frequency; and in the vicinity of peak of phase voltage of the AC voltage, using a carrier wave with a second frequency having a smaller value than that of the first frequency. <P>COPYRIGHT: (C)2007,JPO&INPIT |
