This paper proposes a novel soft-switching control without zero-crossing detection for the cascaded buck-boost converters (CBBCs). The proposed soft-switching control consists of two parts: soft-switching modulation and closed-loop control. In the modulation, the employed PWM approach is constructed by introducing a small negative current into the conventional PWM, and the soft-switching modulation based on the negative-current-based PWM is presented by adding a new switching process controlled by a modulation variable in the CBBC. In the closed-loop control, the relationship between the models of the negative-current-based PWM and the soft-switching modulation is deduced, and by utilizing the deduced relationship, the closed-loop control is designed while the PWM is modified to achieve the softswitching. Meanwhile, to further reduce the ripple current and device losses, the parameter of the proposed control is optimized by refining the restrictive conditions. While the zero-crossing point of the inductor current is calculated with a given algorithm based on a current measurement, the circuit of zero-crossing detection is avoided. The validity and feasibility of the proposed soft-switching control approach are confirmed by the simulations and experiments on a 200-W prototype. INDEX TERMS Soft-switching control, negative-current-based PWM, zero-crossing detection, optimal design, CBBC.

No abstract

In this paper, a multi-objective optimal design for transformerless hybrid active power filter (HAPF) is proposed. The interactions between the active and passive circuits is analyzed, and by taking the interactions into consideration, a three-dimensional objective problem comprising of performance, efficiency and cost of HAPF system is formulated. To deal with the multiple constraints and the strong coupling characteristics of the optimization model, a novel constraint processing mechanism based on distance measurement and adaptive penalty function is presented. In order to improve the diversity of optimal solution and the local searching ability of the particle swarm optimization (PSO) algorithm, a chaotic mutation operator based on multistage neighborhood is proposed. The simulation results show that the optimums near the ordinate origin of the three-dimension space make better tradeoff among the performance, efficiency and cost of HAPF, and the experimental results of transformerless HAPF verify the effectiveness of the method for multi-objective optimization and design.

No abstract

In this paper, Co2Si(Co)/SiCN composite ceramics were synthesized by simple precursor‐derived ceramics method. The phase composition, morphology, and microwave absorption properties of Co2Si(Co)/SiCN composite ceramics at different pyrolysis temperatures (1000–1400°C) were studied. When pyrolysis temperature was 1300°C, carbon nanowires (CNWs), Co2Si, Si2N2O, SiC and Si3N4 were in situ generated and the best electromagnetic wave (EMW) absorption performance was obtained. The minimum reflection loss reached−50.04 dB at 4.81 mm, and the effective absorption bandwidth broadened to 3.48 GHz (14.52–18 GHz) at 1.31 mm. The excellent EMW absorption performance mainly comes from the coexistence of multiple loss mechanisms, including the magnetic loss of Co2Si, the conduction loss of CNWs, and the heterogeneous interfaces polarization between varieties of nanocrystals and amorphous ceramic matrix. By adjusting the sample thickness from 1 to 5 mm, the effective absorption of S1300 can cover the entire X and Ku bands, from 3.36 to 18 GHz. This study provides a simple way to synthesize high performance ceramic‐based microwave absorbing materials.