DC Bus Capacitance Identification Method Based on Frequency Domain Data Drive for EV Charging System

For an electric vehicle charging system, its control performance and reliability are affected by the health and aging of dc bus capacitor in the three-phase pulsewidth modulation (PWM) rectifier. To monitor the status of capacitor and then adjust the operation mode in time, a dc bus capacitance identification method based on the frequency domain data-driven approach is proposed. It has advantages such as high accuracy and high applicability. It uses all the data in one cycle for identification and is less affected by noise. There is no need for iterative calculation, and the identification speed is fast. Compared with the neural network identification method, the proposed method does not need to be trained under various working conditions and overcomes the disadvantage of limited application conditions. The bandpass filter is used to extract the capacitor voltage and current components, which can be used in the case of unknown loads. Transforming the time-domain model into frequency-domain model, the identification stability can be improved. In this article, the experimental platform of a three-phase PWM rectifier is built. The experiment results have verified the accuracy of the proposed method and its applicability in different loads.