| 摘要 |
Disclosed is a PWM rectifier in which switching losses in a semiconductor device are reduced without degrading the response of a control system. In a PWM overmodulation region, the modulation scheme is set to a three-phase modulation scheme. In other regions, a switchover condition such as the amplitude of an input current is acquired and compared with a switchover level. If the switchover condition equals or exceeds the switchover level, the modulation scheme is switched over to a modified two-phase modulation scheme which reduces the number of switching operations to two thirds for the same PWM frequency.
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