| 摘要 |
PROBLEM TO BE SOLVED: To detect ripple voltage with the influence of eliminated and moreover with only small errors, regardless of whether or not phase interruption is occurring in multi-phase AC. SOLUTION: A unit sampling period length 'τ', which is continuously repeated N times is set to be a half of the multi-phase AC cycle 2T or smaller and to be 1/N of the 2T or larger. Sampling is performed plural time within each unit sampling period, and a quasi-maximum value and a quasi-minimum value are calculated for each unit sampling period. Taking the K-th unit sampling period as an example, the quasi-maximum value is a second largest sampling value VM2 ,k , and the quasi-minimum value is a second smallest sampling values Vm2 ,k . The maximum value VMM out of the quasi-maximum value VMi ,1 ,..., VMi ,N, and the minimum value Vmm out of the quasi-minimum values Vmj ,1 ,..., Vmj ,N are calculated. The minimum value Vmm is deducted from the maximum value VMM, thus providing estimation of the ripple voltage also.
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