186 / 2022-03-14 17:05:03

Condition Monitoring for Capacitors in Modular Multilevel Converter Based on Bilateral CUSUM Detection Method of Sliding Window

Modular Multilevel Converter,condition monitoring,capacitor

Modular multilevel converters (MMC) are widely used in medium and high power applications due to their high modularity, availability and high power quality. As the core component of the sub-module(SM) of the MMC system, the capacitor is one of the most easily failed components due to its long-term working in the AC and high-power working environment. Therefore, in order to solve this problem, this paper proposes an online acquisition method of SM capacitance value based on bilateral cumulative sum(CUSUM) detection method of sliding window. First, use the sliding window to process the capacitance voltage signals of SM, calculate the cumulative sum of the detection window, determine the switch-on time and cut-off time of the SM and restore the switching sequence of the SM. Secondly, according to the charging period of the capacitor in this switching sequence, combined with the arm current to realize the online monitoring of the capacitance value. Finally, the accuracy and effectiveness of the method are verified by the MMC system operating condition simulation platform. The method proposed in this paper does not need to measure the switching signal, but only needs to collect the capacitor voltage and arm current signals in the control system to realize the evaluation of the capacitance value with a small amount of calculation, which greatly reduces the difficulty of online condition monitoring for capacitors in MMC system. Provide theoretical and technical support for the health management and operation and maintenance of capacitors.