Component parameters determine the modeling and control accuracy, and affect the performance and reliability of a power electronic system. Therefore, online identification of component parameters is very important. The existing identification methods mostly adopt the integer-order model, which is low in precision and inconsistent with practice. To solve these issues, the fractional-order model (FOM) of the buck converter is established by fractional calculus in this paper. Comparing the similarities in structure between the FOM and neural network, an identification method with the neural network is proposed. The method can realize the online identification of capacitance and order with high accuracy and fast convergence speed. Additionally, the identification results are influenced by the memory length of the FOM and the learning rate of the neural network. Finally, the experimental platform for parameter identification of buck converters is built, and the simulation and experimental results both verify the effectiveness of the proposed method.

Zero phase angle (ZPA) input is an effective way to improve the power transfer capability and minimize the volt-ampere (VA) rating, thus, it can effectively reduce the cost of devices. Affected by magnetic fields, control strategies and compensation networks, parameters detuning inevitably lead to the loss of ZPA input. Fractional-order circuits are concerned in wireless power transfer (WPT) system due to a higher degree of freedom. In this paper, a powerless fractional-order capacitor (P-FOC) construction method is proposed to achieve ZPA input in an arbitrary frequency-fixed WPT system, which can realize adaptive capacitance with order 1 or −1. No external high-voltage power supply is required compared with the conventional FOC. No feedback or communication circuit is employed, while it has a full range of impedance matching. The proposed P-FOC can be applied to adaptively offset the reactive power without considering the topology and parameters of the system. Then, the working mechanism and application scenarios are analyzed. To verify the feasibility, the P-FOC is introduced in the semi-active rectification (SAR) WPT system and ZPA input is realized. The experimental results verify the effectiveness of the proposed structure.

This paper proposed an innovative fractional-order circuit LC (FOC-LC) based resonant filtering method to suppress low-order harmonic currents in AC power system. By constructing the FOC-LC harmonic suppression branch and applying a corresponding modulation strategy, the impedance complex plane maintains symmetrical resonance inductance and capacitance. This leads to an extremely low equivalent impedance for different harmonic currents, effectively suppressing harmonics with diverse frequencies and magnitudes. The proposed method demonstrates robustness to device parameters and maintains reliable harmonic suppression performance within an acceptable error range. The utilization of fractional-order circuits allows for auxiliary charging, modifying output port capacitance, adjusting equivalent resistance, and even achieving negative resistance characteristics. This results in minimal resonance equivalent resistance in the harmonic suppression branch. To verify feasibility, a 1.2 kW prototype was implemented, yielding promising results. The experimental validation validates the practical applicability and effectiveness of this method.

Bridge modular switched-capacitor converter (BMSCC) has been reported with symmetric and modular structure, and featured less output voltage ripple, less components cost, and convenient voltage extension but weak output voltage regulation. This paper presents a phase shift plus pulse width modulation (PWM) control strategy for the novel resonant BMSCC. With this control method, output voltage regulation and the limitation of the loop peak current to a proper range are implemented. Also, output voltage ripple could be effectively controlled as well through the voltage ripple characteristics analysis in different cases. Detailed analyses of the relationships between the switching phases of MOSFETs and the output voltage, the switching-phases of MOSFETs and the loop peak current are performed. Meanwhile, through optimal switching sequence, the proposed control method ensures that almost all switching devices maintain zero current switching or zero voltage switching operation, which results in high system efficiency. Using simulation software of the saber and hardware platform, the soft switching, output voltage, and peak current characteristics are verified.

A novel quasi-Z-source ac-ac converter for voltage sag/swell compensation in smart grids is proposed in this paper. Derived from the basic ac-ac safe-commutation mechanism, a new voltage-based commutation strategy is developed, which is achieved without snub circuit and only by sampling the output voltage. Therefore, the control circuit is simplified greatly. Two switches in a one-phase loop are always turned on for current freewheel path in dead time, and current spike and voltage spike are solved well. Compared with conventional ac-ac converters, fewer switches conduct with soft switching during operation, resulting in high efficiency. Then, the proposed converter is analyzed, including the operating modes and voltage ration based on a state-space average. The experimental results validate the theoretical predication well. The safe-commutation strategy can also be easily applied to other converters of the proposed family.