Analysis and application of auto-recognition algorithm of phase and phase sequence of phase-controlled rectifier

According to the limits of traditional method to get proper phase-shift control of phase-controlled rectifier, a special synchronous signal generation circuit is designed. It has two synchronous signals with a phase difference of 30 degrees. The calculating algorithm is proposed. This algorithm is used to calculate the valid synchronous signals, phase sequence of main circuit, zero-cross point of valid synchronous signals, and the natural phase-shift point of six line-voltages of main circuit. Improvements to control software of traditional rectifier are proposed. Compared with the traditional digital phase-controlled rectifier, this method does not increase cost, and it adapts to any load impedance.