The single-stage high-frequency (HF) isolated ac–dc converter has the advantages of high-power density, long life, and high efficiency. It has a broad application prospect in distributed power generation, ac microgrid, and energy storage system. In this article, its topologies are classified according to the energy storage components. The structure and operating principle of various topologies are introduced. Furthermore, the development of extended multiport single-stage HF isolated ac–dc converter is introduced. On this basis, the advantages and disadvantages, typical characteristics, cost, and power loss of various topologies are analyzed and summarized. Finally, the key issues that need to be solved are pointed out and the development trends are explored. This article aims to provide a reference for the subsequent research on single-stage HF isolated ac–dc converters and the advancement of their practicability.

In this paper, a cooperative triple-phase-shift (CTPS) control for the isolated dual active bridge DC-DC converter is proposed first to eliminate the dual-DC side flow back currents. Furthermore, the current characteristics of the proposed CTPS control with the main variable (the primary side inner phase shift) tuned in two different regions are derived in detail and compared with each other. The tuning region of the main variable with the optimal current characteristics is finally determined based on the comparison results. As a result, the current stress is reduced and the efficiency is enhanced. The detailed experimental results of CTPS control verify its validity and practicability. The advantages of CTPS control are also highlighted by comparing it with some conventional phase shift controls.

As one of the most promising solutions to mitigate the power quality (PQ) problem of the modern power systems, the unified PQ conditioner (UPQC) draws considerable attentions. Since the UPQC consists of two sets of power converters, it will greatly increase the manufacturing investment of the setup. In this paper, the optimal volt-ampere (VA) ratings of the converters in the UPQC are investigated due to system compensating requirements. The phase angle control (PAC) method is discussed and illustrated to have the feature of changing the online VA loading by adjusting the corresponding displacement angle. On the basis of the variable PAC method, a two-stage algorithm is utilized to optimize the ratings of the shunt and series converters in order to obtain the maximum utilization rates of the power converters in the UPQC. Moreover, the corresponding control algorithm is utilized to reduce the proposed UPQC online VA loadings for the different compensating operations. The proposed UPQC is compared with other approaches to highlight the advantage of the proposed optimization algorithm. The proposed algorithms are also validated with the simulation and the real-time control hardware-in-loop results of the designed system.

In order to solve the problems of existing three-port isolated dc-dc converter such as power decoupling and the nonzero instantaneous power of the standby port, a three-port isolated bidirectional current-fed series-resonant dc-dc converter is proposed in this article. The operational principle and general transfer power expressions of various ports are analyzed with the duty-cycle plus phase-shift control. Then, the power decoupling at the topology level is realized by setting the switching frequency equal to the resonant frequency of the resonant tank on the high-voltage side; thus, the transfer power of the two ports on the low-voltage sides can be controlled independently. Moreover, it is proved that the proposed converter realizes the zero instantaneous power of the standby port. On this basis, an optimized modulation strategy by taking the minimum root mean square value of the resonant current as the objective function is presented. The exact relationship between the desired transfer power and various phase shifts is accordingly obtained. The detailed experimental results verify the correctness of the proposed converter and corresponding modulation strategy.

Aiming at the problems of large switching loss and large output power fluctuation in the existing omnidirectional wireless power transfer (OWPT) system, a novel OWPT system with zero-switching-loss inverter and cylindrical transmitter coil is proposed. By introducing an auxiliary resonant network with simple structure and low-loss on each phase arm of the three-phase inverter, zero-voltage switching turn- on and zero-current switching turn- off within the full power range can be acquired. The switching loss in the main circuit of inverter is reliably eliminated. The transmitter coil is a cylindrical coil composed of the three curved rectangular coils, whose excitation current amplitude is equal and the phase difference is 120°. It can arise a spatial rotating magnetic field around the transmitter coil and provide an omnidirectional energy transmission channel. The operating principle of soft-switching is analyzed in detail, and the design rules of soft-switching in full power range and the parameter design method of coupler to reduce the fluctuation of output power are given. Ultimately, an experimental prototype is used to verify the feasibility of the proposed OWPT system. The experimental results indicate that the system output power is retained at 93.4–104.7 W and transfer efficiency is retained at 71.2%–78.1% under arbitrary angular misalignment of receiver.

When the conventional space vector phase-shifted modulation is applied to the dual active bridge (DAB)-based three-phase single-stage (DAB-3P1S) AC-DC converter, the AC side current error in a switching period is caused because of the coupling of high-frequency transformer currents in the adjacent switching periods and the imprecise dwell times of the active current vectors. By analogizing the DAB-3P1S AC-DC converter into the DAB based DC-DC converter, a dual-period-decoupled space vector phase-shifted modulation (DPD-SVPSM) based on triple phase shifts is proposed to decouple the transformer currents, thus eliminating the AC side current distortion. Moreover, taking the minimization of the RMS value of the transformer current per switching period as the constraint, the exact relationship between the desired AC side current and the three phase shifts is derived to realize the precise control of instantaneous AC side current and the efficiency improvement. Detailed experimental results validate the correctness of the theoretical analysis and the feasibility of the proposed modulation strategy.