Statistical characteristic analysis and an adaptive control of synchronous vacuum switches

Controlled closing and opening of shunt capacitor banks by synchronous vacuum switches with three-independent-pole-operated permanent magnetic actuators can reduce energization transients and eliminate de-enrgization restrikes. The synchronous closing and opening performances of capacitor banks mainly depend on the synchronous accuracy of the reference voltage zero points and the mechanical scatters of the operating times. The principle of detection of the zero crossing points of the reference voltage an the synchronous errors caused by the drift of the actual power network frequency are discussed firstly in this paper, and a synchronous sampling algorithm and 12bit A/D are used to reduce the synchronous errors. A compensation algorithm is adopted to reduce the variations of the operating times caused by the control voltage and the ambient temperature. And the drifts of operating times that caused by the idle times and the past operations of the actuators are compensated by an adaptive feedback control. The experimental results showed that the synchronous vacuum switches can gain satisfactory performance of controlled closing and opening shunt capacitor banks.