Automatic quasi-synchronization based on adaptive complex control for synchronous motor soft starting system

Stable phase slip is crucial to the grid-connection of automatic quasi-synchronizing device in the synchronous motor soft starting system. Analysis reveals that, the application of PI speed controller in the dual close-loop speed control system may cause unstable phase slip if the dynamic characteristics of current loop are nonideal. A strategy of adaptive complex speed control is thus proposed, which adopts the single rate adaptive speed control algorithm to eliminate the static offset in its speedup stage while applies the quasi-synchronization control algorithm based on phase slip to make the phase slip stable in its quasi-synchronization stage. Reliable grid-connection judgment is also presented. The experimental results demonstrate its validity and the reliable grid-connection of synchronous motor soft starting system is realized.