| 摘要 |
PURPOSE:To perform parallel operation by controlling the oscillation frequency of an oscillating means based on a phase difference voltage corresponding to the phase difference between AC output voltage and current so that the phase difference will be zero. CONSTITUTION:A phase detector 16 outputs a phase difference voltage corresponding to the phase difference between signals (b), (b') to a VCO 6 and controls the oscillation frequency thereof. Frequency controlled output oscillation signal from the VCO 6 is subjected to frequency division through a frequency divider and fed, as a clock signal, to a sine wave forming circuit 8. The sine wave forming circuit 8 generates a stepping sine wave signal based on the clock signal and thus generated sine wave signal is fed to an electronic volume 9. The electronic volume 9 controls blocking/passage of the sine wave and the attenuation thereof at the time of passage and thus controlled sine wave is then fed through an LPF 10 to a PWM 11 which produces a pulse subjected to PWM modulation by the sine wave signal. Consequently, no special scheme is required at the time of parallel operation. |
