数字锁相环同步切换系统的设计

Design of Synchronous Switching System with Digital Phase-locked Loop

同步切换是将电动机从变频器切换到电网供电,然后使电动机脱开变频器;或者使变频器与准备脱离电网供电的电动机进行匹配,然后脱开电网,切换到由变频器控制。如果切换不当,会引起很大的冲击电流和功率倒灌。为保证电网和变频器的安全性,采用Matlab软件对高压变频器和电网之间的切换进行研究,计算各种切换情况的冲击电流和功率流向,捕捉最佳投切时刻。设计了切换顺序和各切换状态、数字锁相环系统及在FPGA中的实现,最后给出了相应的切换算法。

Synchronous switching includes two reverse processes., one is switching the power supplier of motor from high-voltage coverter to electric power grid, and shutting off the high-voltage coverter; the other is matching high-voltage coverter to motor which gets ready to be cut off from electric power grid, and then the motor is controlled by the high-voltage converter completely. It would cause large current impulsion and backward power when it switches improperly. In order to ensure the security of electric power grid and high-voltage coverter, the switching processes between high-voltage coverter and electric power grid were studied using Matlab. The current impulsion and power flow on every kind of switching occasions were measured to capture the optimal switching time. The switching sequence and the switching states were designed, and a digital phase -locked loop system was designed and implemented in FPGA. Finally the corresponding switching algorithm was presented.