Reliability Calculation Improvement of Electrolytic Capacitor Banks Used in Energy Storage Applications Based on Internal Capacitor Faults and Degradation

Abstract

Capacitor banks (CBs) play a crucial role in energy storage and frequency control within autonomous microgrids. However, the impact of internal capacitor configurations, varying in terms of equivalent series resistance (ESR), capacitance, and rated voltage, on CB degradation, reliability, and peak current remains an understudied aspect. Moreover, the absence of a capacitance degradation coefficient in the standard MIL-HDBK-217 equations for predicting the reliability of electrolytic capacitors poses a significant challenge. To address these issues, this study examines a microgrid composed of diverse renewable energy systems, featuring nine distinct CB arrangements. The design of CBs considers both capacitance and peak output current individually. An evaluation is conducted to compare construction costs, lifetimes, and peak output currents across all layouts. Additionally, a novel formula is introduced to estimate the reliability and lifetime of CBs, while an existing formula for calculating CB peak output current is enhanced. The research explores the impact of ambient temperature and capacitor voltage on the reliability of various capacitor designs, proposing a novel framework for assessing CB reliability based on MIL-HDBK-338B, which accounts for both short-circuit and open-circuit faults. The practicality of these findings is confirmed through a comparison of experimental and simulation results. The inverter operation video, simulation, and all production data including PCB and processor codes are also attached.

Keywords

• Power electronics
• renewable energy
• capacitor bank
• degradation modeling
• equivalent series resistance
• applied mathematics