A dual-carrier modulation technique is proposed to improve the performance of the half-bridge resonant converter in this paper. By alternately using two different sawtooth waveforms as a carrier, the dual-carrier modulation combines the characteristics of both variable frequency modulation and fixed-frequency modulation. According to the structure of modulator, there are two kinds of dual-carrier modulation: type A and type B. Type A dual-carrier modulation is suitable for resonant converters operating in inductive region to achieve a wide zero voltage switching (ZVS) range, while type B dual-carrier modulation is preferred for resonant converters operating in capacitive region to obtain a wide zero current switching range. By utilizing both switching frequency modulation and duty ratio modulation, the proposed dual-carrier modulation not only extends soft-switching range of the resonant converter, but also reduces switching frequency variation range. In order to verify the benefits of the proposed modulation, a 500-W dual-carrier modulated LCC resonant converter operating in inductive region is designed and built. Simulation and experimental results show the prototype achieves ZVS soft-switching operation for 200–400 V input voltage and 100–500 W output power, with only about 10 kHz switching frequency variation.

The influence of filter inductor on steady state performance of parallel type resonant converter is elaborated and analyzed in this paper. By steady state operation analysis, it is shown the ripple current of filter inductor results in inaccurate prediction of fundamental har-monic approximation (FHA), and such problem would become serious when the filter inductance is small. In order to portray such fea-ture, an improved fundamental harmonic approximation (IFHA) is proposed. Unlike FHA equivalent circuit, an equivalent inductor is added on AC resistance parallelly in IFHA equivalent circuit. Due to that the equivalent inductor branch takes account of the ripple current of filter inductor, the IFHA is expected to own higher accuracy and can be used in parameter design procedure. In this paper, the equivalent inductor expressions of full-bridge (FB) rectifier and current-doubler (CD) rectifier are derived as examples. In order to verify the theoretical analysis, a 500W LCC resonant converter is built as a prototype. The close-loop experiment results show that small filter inductance would lead to the failure of output voltage regulation and hard-switching operation of power switches. And open-loop experiment results show the IFHA gives more accurate predictions than those of FHA.

An asymmetrical hybrid‐controlled half‐bridge LCC resonant converter which integrated a buck–boost converter and a half‐bridge LCC resonant converter is proposed. It benefits with wide soft switching range, low conduction loss and high power density. By utilising an asymmetrical hybrid control strategy, its switching frequency and duty ratio can be adjusted simultaneously. The proposed LCC resonant converter maintains output voltage regulation and zero‐voltage switching of switches in wide input voltage and load variation range. Experiment results of a 500 W prototype are provided to verify the theoretical analysis results.

A compact pseudo-interdigital bandpass filter with controllable transmission zero is presented by using open-circuited stepped-impedance resonators (SIRs) and step-impedance parallel-line couplers (SIC). When the filter is working at the odd resonance mode of the SIR, it has a virtual ground at the mid-point of the resonator such that the filter looks similar an interdigital topology. Therefore, the high band-selectivity of the interdigital topology is preserved. Particularly, the frequency of the close-in transmission zero can be controlled above or below the passband simply by changing the inter-coupling magnitude between the adjacent SIRs. Additionally, the wide stopband range is achieved by the appropriate impedance and line ratios of the SIR and the SIC. The simulation and measurement results are presented to demonstrate the control of the transmission zero and wide stopband range.

Secure and reliable electricity supply is a prerequisite for the development of smart cities, and the trustworthy and efficient transmission of electrical data is the foundation for the safe and stable operation of the power grid. This paper introduces a real‐time data transmission blockchain technique based on parallel proof of work algorithm. The new block generation process of proposed blockchain is divided into five subroutines: hash pointer computation, real‐time data pudding, signature value iteration, interruption, block header assembly. The real‐time data pudding and signature value iteration are parallel processed, which brings the effect of decreasing energy loss of blockchain system, and enhances the speed of new block generation and the bandwidth of data storage on blockchain. Computer simulation shows the proposed strategy can be effectively applied in real‐time electrical data transmission application, raising the data transmission reliability with no harm to real‐time data transfer function. This strategy provides a solution to guarantee data transmission safety in the digital conversion of power grid.