Online Estimation of Output Capacitor Parameters for Boost PFC Converter With Optimized Harmonic Injection

Aluminum electrolytic capacitors (AECs) are critical components in power converters, yet they are susceptible to degradation. Consequently, real-time monitoring of capacitance (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i>) and equivalent series resistance (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ESR</i>) is essential to ensure system reliability. This article proposes an online estimation method of output capacitor parameters for boost power factor correction (PFC) converter with optimized harmonic injection (including injection form optimization and parameter optimization selection). First, the capacitor current reconstruction is realized using the harmonic information of the output voltage, and hence an ideal estimation model of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ESR</i> is constructed. Concurrently, estimation model I with global harmonic injection is proposed to address the current zero-crossing distortion caused by harmonic injection. The estimation model is further improved by optimizing harmonic injection form with zero-crossing interval removal, where the symmetrical capacitor currents are constructed to achieve a simple estimation model II. Furthermore, the appropriate parameters of harmonic injection are optimized through a comparison of various cases in simulation. Ultimately, a single-phase boost PFC converter experimental prototype is constructed for verification (48–144 W), which demonstrates that the improved harmonic injection method with zero-crossing interval removal exhibits superior performance compared to the global injection, with an estimated error of less than 5% (average across multiple tests).