A simplified method for protecting the power capacitor from over-voltage/over-current is proposed. The proposed method retrieves the voltageacross the power capacitor to calculate the root mean square (RMS) values of the power capacitor voltage and the power capacitor current. Thesalient point of the proposed method is this method can protect the power capacitor from over-voltage/over-current caused by harmonic or powerresonance only sensing the power capacitor voltage. The control circuit generates a trigger signal to actuate the electromagnetic switch to switchoff the power capacitor from the power system or adjust the impedance characteristic of inductor/power capacitor for protecting the powercapacitor from over-voltage/over-current if an abnormal voltage or current is detected. The proposed method has the advantages of simplifiedcontrol circuit, easy installation and low implementation cost. A prototype is implemented to verify its performance. The test results show that theproposed method has the expected performance.
Electrical Power and Energy Systems, v. 28, 2006, p. 215-220