Loss evaluation of aluminum electrolytic capacitor under power electronics converter excitation

Aluminum electrolytic capacitors used in power electronics converters are a major factor that reduce the reliability of these devices. To evaluate the lifetime and reliability of this type of capacitors, capacitor loss needs to be evaluated under the excitation conditions of power electronics converters. However, the capacitor loss data provided by manufacturers is always measured under sinusoidal excitation. The authors therefore proposed a capacitor loss evaluation method for arbitrary excitation waveforms found in power electronics converters. This method features a simple configuration, and the capacitor loss can be practically evaluated using a function generator without the need of a real power electronics converter. Therefore, the capacitor loss can be analyzed under different conditions, ranging from fundamental analysis to practical analysis, for instance, pulse-width modulated (PWM) inverter excitation. In this study, the capacitor loss was evaluated using fundamental excitation and (PWM) inverter excitation. Moreover, the capacitor loss of four different type of capacitors was assessed. Under PWM inverter excitation, nonlinear loss behaviors were observed. Nonlinear loss characteristics could be expressed using a hysteresis curve in the Q-V plane. It was found that the hysteresis curves changed when the rectangular excitation current had zero current phases and different duty ratios due to the voltage unbalance of the tunnel pit capacitance in the capacitor sheets.