Online E-Cap Condition Monitoring Method Based on State Observer

An online condition monitoring method is presented for electrolytic capacitors health condition based on state observer method. With this method, both capacitance and equivalent series resistor in an electrolytic capacitor can be estimated online without disassembly from power converter systems. The method is with high precision without any additional hardware in application. The estimated capacitance and equivalent series resistor can be used to predict the rest useful life of the electrolytic capacitors and provide the suitable time for preventive maintenance. The method was verified by both simulation analysis and prototype testing. Experiment results shown a high precision results with relative error of less than 3%