Mitigating Line Frequency Instability of Boost PFC Converter under Proportional Outer-Voltage Loop with Additional Third Current-Harmonic Feedforward Compensation

For the average current mode (ACM)-controlled boost power factor correction (PFC) converter, there is line frequency instability under light load and small output capacitor conditions. The line frequency instability is characterized as self-oscillation in the form of period-doubling, which drastically increases the total harmonic distortion (THD) and additional losses. Regarding this line frequency instability, this paper proposes a stability control scheme incorporating an outer-voltage proportional controller and an additional third current-harmonic feedforward compensation (TCFC). Specifically, the outer-voltage proportional controller replaces the traditional low-pass filter (LPF) to mitigate the line frequency instability, and the TCFC aims to ensure an acceptable THD. Moreover, the dynamic response of the proposed current-feedforward-based stability control scheme outperforms the existing voltage-feedback-based schemes. Furthermore, the control parameters are determined by the harmonic averaged model, and the feasibility of the proposed scheme is verified by experiments based on IC UC3854BN. The experimental results demonstrate that the THD with the line frequency instability is 56.60%, while it is improved to 15.58% by using the proposed scheme.