基于储能电路的大型发电机组灭磁方式优化

Optimization of De-excitation Mode for Large Capacity Generators based on Energy Storage Circuit

随着同步发电机组单机容量大幅提高,其额定励磁电压和励磁电流也大大增加,如何在机组故障和空载误强励等极端运行条件下实现灭磁的快速性、安全性和可靠性三者之间的协调,已成为亟待研究和解决的课题。本文受无源零开断自动灭磁技术的启发,以三峡水轮发电机组的励磁系统为研究对象,运用电力电子软开关技术实现快速灭磁,并利用储能元件存储灭磁过程中的部分磁场能量。通过对灭磁过程中的建压、换流、移能、耗能等环节进行理论分析和仿真验证发现,软开关控制电路的引入实现了磁场断路器的零电流关断,在保证器件安全性和灭磁可靠性的同时,整个灭磁过程所用时间仅为0.668s。同时,储能电路的引入有效减小了励磁绕组和励磁主回路断路器两端电压的突变尖峰,进一步提高了灭磁的安全性和可靠性。对储能电路的进一步优化表明,通过增大储能电容的电容值可以显著提高磁场能量的回收利用率,其中,3300μF的储能电容可以减少约0.1629%的磁场能量泄露。

With the significant increase of the capacity for single synchronous generator,the rated excitation voltage and current of it are also greatly increased.Therefore,how to achieve the coordination among the rapidity,safety and reliability of de-excitation under extreme operating conditions,such as system failure and no-load faulty forced excitation,has become an urgent problem that needs to be studied and solved.In this paper,the excitation system of the Three Gorges hydroelectric generator unit is taken as the research object.The power electronic soft-switching technology is used to realize rapid de-excitation,which is inspired by the passive zero-switching automatic de-excitation technology,and part of the magnetic field energy during the de-excitation process is stored by the energy storage components.Through the theoretical analysis and simulation verification of voltage establishment,current conversion,energy shifting,energy consumption and other links in the process of de-excitation,it is found that the introduction of the soft-switching control circuit realizes the zero-current shutdown of the magnetic field circuit breaker,which ensures the safety of device and the reliability of de-excitation,and the entire process of de-excitation only takes0.668 s.While at the same time,the introduction of the energy storage circuit effectively reduces the sudden peak voltage at both ends of the excitation winding and the excitation main circuit breaker,which further improves the safety and reliability of de-excitation.Further optimization of the energy storage circuit shows that the recovery utilization rate of the magnetic field energy can be significantly improved by increasing the capacitance value of the energy storage capacitor,for example,the leakage of the magnetic field energy can be reduced by approximately 0.1629%for a 3300μF energy storage capacitor.