| 摘要 |
PROBLEM TO BE SOLVED: To continue the operation of a power converter by detecting the phase of system voltage which is accurate and positive and controlling it stably, even if abnormality is generated in an AC system. SOLUTION: A reference phase θFi, obtained by integrating a frequency reference signal, is used for trigonometric function computing which obtains an (α) element and a (β) element of a Fourier transform for each of three phases, and an (α)-axis element and a (β)-axis element of positive-phase-sequence voltage is calculated from the (α) element and the (β) element of respective Fourier-transformed phases, and based on the (α)-axis element and the (β)-axis element, positive-phase-sequence voltage phase Δθ is obtained. By taking the phase as a phase difference between a system voltage phase θs and the reference phase, the reference phase is added to the phase difference Δθ, a positive-phase- sequence voltage absolute value is obtained, and an obtained positive-phase- sequence voltage phase difference is stored. If the positive-phase-sequence voltage absolute value exceeds a preset reference value, the value of the phase difference Δθis kept constant at a value, before exceeding the reference value, and a control phase θu which is obtained by adding the reference phase to the phase difference is taken as the phase of the trigonometric function for power control. |
