Fractional-Order-Based Low-Order Harmonic Current Suppression Method Considering Asymmetrical Capacitor Parameters

The problem of the second harmonic current (SHC) on the dc bus side of the single-phase inverter system has attracted widespread attention. The active power decoupling method based on dual capacitors can suppress SHC effectively. However, the asymmetrical capacitor parameters will deteriorate the SHC suppression performance and lead to the first-order harmonic current. To eliminate these low-order harmonic currents, this article proposes a SHC suppression method based on the fractional-order capacitor (FOC), where no power supply is employed and little loss is incurred. The capacitance and the order of the proposed FOC can, both, be adjusted. The principle and operating mode of the FOC are analyzed, and the control strategy of adjustment is given. The method can realize the SHC suppression with the advantages of a simple control strategy, hot-swappable, and high flexibility. Most importantly, the method can effectively suppress the first-order harmonic current caused by the asymmetrical parameters of the capacitors. Finally, an 800 W prototype based on the proposed method is built, and the simulation and experimental results both verify the effectiveness of the proposed method.