Synchronization System for Semiconductor Frequency Converters with a Power Supply Network

This article provides a detailed description of synchronization node operation based on the well-known method of a phase-locked loop. It is shown that the phase-locked loop method can be successfully applied in synchronization nodes of valve frequency converters provided that the amplitude of the reverse phase sequence does not exceed 20%. The dependence of the transient time of the measured variable voltage in the synchronization device is obtained depending on the level of asymmetry of the supply voltage, which was estimated by the amplitude of the voltage component of the reverse phase sequence. The dependence of the transition time on the amplitude of the reverse phase sequence is quadratic because of the need to reduce the uniform bandwidth of the second-order filter. The results of the refinement calculation of the metrological characteristics of the synchronization device with account for nonlinear distortions showed that, with the simultaneous presence of nonlinear distortions in the supply voltage curve and asymmetry of the supply voltage, the permissible level of the amplitude of the negative sequence voltage is limited to 10%.