风电次同步谐振对主变偏磁的影响机理

风电经串补送出系统发生次同步谐振(subsynchronousresonance, SSR)现象时,风电场和相关汇集站的主变会出现异响和振动加剧现象,给电力系统安全稳定运行带来隐患。通过分析工程现场SSR故障录波和系统的等效电路,提出超过一定量的次同步电流注入含串补的系统后,造成主变铁芯周期性正负交替偏磁饱和,从而导致主变励磁电流增大、异响和振动加剧。通过 RTDS(real time digital simulator)仿真和物理变压器低压模型实验,对上述机理和现象进行了验证。适当降低系统工频电压运行水平,可以一定程度减小谐振时主变偏磁饱和的程度和危害;而采取适当措施抑制SSR,是解决上述问题的根本方法。

Influence Mechanism of Wind Farm Subsynchronous Resonance on Magnetic Bias of Transformer

Step-up transformers vibrate abnormally and generate loud noise when subsynchronous resonance (SSR) occurs in wind farm substations. This brings potential risks to security and stability of power system. By analyzing the fault records and equivalent circuit of the system, it is proved that when certain amount of SSR current is injected into the system, the flux of transformer iron core will be periodically biased, saturated and the exciting current will increase. These characteristics lead the transformer to abnormal working status. This result is verified by tests with real time digital simulator (RTDS) and transformer physical experiments. Appropriate decrease of system voltage can reduce the saturation level and the influence of step-up transformer. Damping the SSR with appropriate measures is the ultimate solution for above problem.