采用虚拟电阻的电力电容器保护法

A Power Capacitor Protection Method Adopting Emulated Resistor

电力电容器易与系统阻抗发生谐振引起过电压和过电流,常规的谐振保护方法是在产生谐振时切除电容器组。作者分析了通过阻抗变换抑制谐振、保护电容器的机理,将瞬时无功谐波电流检测法引入到电压型逆变器,通过在电容器支路串联一个对基波有功功率和谐波分量呈正电阻性质的功率变换器实现在谐振情况下对电容器组的保护。由于该方法无需切除电容器,也保证了对系统正常的无功补偿。运用Matlab软件对某10kV配电系统中无功补偿电容器组的谐振保护进行仿真,结果表明了上述方法的正确性和有效性。

In power grids, the resonance between power capacitor banks and system impedance is easy to take place that causes overvoltage and overcurrent. Conventional protection method for the resonance is to cut off capacitor banks while resonance occurs. The mechanism that restricts resonance and protects capacitor banks by impedance conversion is proposed in this paper, that is, to implement the protection of capacitor banks under the condition of resonance, the instantaneous reactive harmonic current detection is led into voltage source inverter and a power converter,＂ which reveals itself positive resistance with regard to both harmonic and fundamental components of active power, is connected in series with the capacitor branch. When the proposed protection method is applied, the capacitor banks are not to be cut off, thus the normal reactive power compensation of pOWer grid can be ensured. By means of Matlab software, the resonance protection for capacitor bank in a certain 10kV distribution network is simulated, results show that the proposed method is correct and effective.