Boost PFC converter is commonly utilized in rectifier circuits due to its ability to achieve a high power factor and low input current distortion. For the single-phase boost PFC converter, large-capacity and low-priced aluminum electrolytic capacitors (AECs) are typically employed to balance the instantaneous power deviation between the input and the output. However, the failure-prone nature of electrolytic capacitors may result in system instability or even collapse. Therefore, the real-time detection of electrolytic capacitor status information, assessment of its service life, and timely replacement of the soon-to-be-failed electrolytic capacitor can provide an important technical guarantee for the reliability of PFC power supply operation. This paper proposes an improved "zero-crossing removal interval" harmonic injection method for online detection of capacitance parameters to solve current zero-crossing distortion caused by harmonic injection. Additionally, based on the harmonic response of the bus voltage, the harmonic capacitor current reconstruction is achieved, and a model for calculating the C_R and R_E parameters without capacitor current sampling is constructed.

Firstly, the AC and DC input-output power action characteristics of the Boost PFC converter are fully utilized, i.e., the high harmonic current injection of the current control loop produces a high harmonic voltage splitting phenomenon on the output voltage. The two split harmonic voltage signals are employed to reconstruct the capacitor current; the capacitor's low-frequency impedance model is used to estimate C_R; a mid-frequency domain harmonic capacitor parameter computation model is established to estimate the R_E. In addition, the high harmonic current injection in the current loop inevitably results in an asymmetric zero-crossing distortion of the input current, directly affecting the accuracy of the capacitance parameter computation model. Consequently, the zero-crossing removal interval harmonic current injection method is employed to solve zero-crossing distortion caused by inter-area injection. The improved “zero-crossing removal interval” method avoids the reconstructed high-order capacitor current calculation error, enhancing C_R and R_E accuracy.

Eighteen types of capacitor conditions are selected for simulation calculation, and 48 W/72 W/144 W Boost PFC experimental prototypes are established. The proposed detection method is verified under an input voltage of 60 V, a switching frequency of 100 kHz, and an output voltage of 120 V. The results demonstrated that the method exhibits high detection accuracy under symmetrical injection conditions with a 10% zero-crossing removal interval, a 10 V injection amplitude, and a 650 Hz frequency. Furthermore, the improved “zero-crossing removal interval” method can achieve parameter detection error within 5% under different loads (100 Ω, 200 Ω, and 300 Ω) and capacitor conditions (196 mΩ/412 μF and 216 mΩ/617 μF), regardless of light or heavy loads.

This paper presents the following conclusions. (1) The proposed method considers the impact of current on distortion caused by harmonic injection. A “zero-crossing removal interval” harmonic injection method improves the accuracy of capacitance parameter detection. (2) In the “zero-crossing removal interval” method, the capacitor current is obtained through algorithmic reconstruction, which avoids high-precision capacitor current sampling. The harmonic injection is achieved by the control algorithm without additional hardware equipment. (3) The proposed capacitance parameter calculation model is derived based on the AC-DC power balance, making it straightforward to extend to similar AC-DC converters.