| 摘要 |
PROBLEM TO BE SOLVED: To generate a reference sinusoidal wave stably with a simple configuration, by causing a detected value of a source voltage cross frequency to pass a low-pass filter to find an average power source frequency, finding a frequency increment from the phase deviation between a source voltage at the time of zero cross and a reference sinusoidal wave, and finding a reference sinusoidal wave frequency by adding these. SOLUTION: In a first means 1, the zero cross frequency value of a source voltage measured is caused to pass a low-pass filter, and an average frequency ωs is found. Besides, in a second means 2 the difference between a power source phase θcross at a zero cross point and the phase of a reference sinusoidal wave at that point of time is amplified, and the increment Δωc of the frequency of the reference sinusoidal wave is computed. And in a third means 3, the frequency ωc of the reference sinusoidal wave is computed by adding the frequency increment Δωc to the average power source frequency value ωs . Consequently, it becomes possible to constitute a reference sinusoidal wave generator stable and free from an error offset left behind. |
