Capacitor Condition Monitoring for the Low-Capacitance StatCom: An Online Approach

The cascaded H-bridge low-capacitance static compensator (LC-StatCom) uses relatively small capacitors subjected to large voltage oscillations. When a capacitor degrades, its capacitance differs from the nominal value, and this deteriorates the StatCom operation and safety. This is an important reason to monitor the capacitors condition in StatComs. This letter presents a detailed analysis of the capacitor voltage oscillations and their dependence on the capacitance values. The analysis allows monitoring the condition of the capacitors using a closed-loop approach that feedbacks the error in voltage oscillations. The proposed method is a hardware-free online solution for capacitor condition monitoring (CCM) in LC-StatComs. The letter presents simulation and experimental results that corroborate the effectiveness of the proposed CCM loop.