A Bandwidth Extension Method of SAPF DC Regulator Considering Harmonic Compensation Oscillation

During normal operation of SAPF, the bandwidth of DC voltage control is frequently restricted to ensure the stability. In previous studies, the restrictions of control bandwidth focused on the suppression of high-frequency oscillation. However, when the resonant points in SAPF system are close to the harmonic compensation frequency, harmonic oscillation occurs. The DC voltage control will alter the system's resonance characteristics, which may further induce harmonic oscillation. Therefore, the bandwidth of DC voltage control in SAPF is frequently restricted further, which slows the system's dynamic response. Based on load current detection SAPF, this paper establishes a small signal model of the DC voltage’s influence. Based on the model, the DC voltage control's bandwidth restrictions are analyzed. The bandwidth is constrained not only by the fundamental current loop, but also by the system's overall resonance characteristics. Therefore, dual filter control method is proposed for DC voltage control. It can effectively suppress the effect of DC voltage on system characteristics, so that the bandwidth of DC voltage control can be extended. Simulations are performed to confirm the correctness of the theoretical analysis and effectiveness of the proposed method.