Improving Synchronization Reliability for Active Rectifiers with the Mains

The operation of a synchronization unit based on the principle of phase-locked frequency tuning has been considered. The classical method to measure the supply voltage implemented on the basis of phase-locked frequency tuning is more appropriate than the method of symmetric components, which is more complicated in design, operation, and commissioning. The phase-locked loop frequency method is successfully used in synchronization units for valve frequency converters if the amplitude of a reverse phase sequence is more than 20%. The dependence of the transient process time of a measured voltage variable in the synchronization device on the level of supply voltage asymmetry determined by the voltage component amplitude of a reverse phase sequence has been obtained. The area of application of a phase-locked frequency system can be enlarged due to the use of a selective Butterworth filter and a correct choice of its Q-factor.