Dual active bridge (DAB) converters are applied widely due to the advantages of high efficiency, easy realization of soft switching and bidirectional isolation. For power converters, dead time effect is more and more difficult to be neglected because of the increasing switching frequency promoted by higher power density. However, most of the researches based on DAB converters focuses on optimal control strategies without considering dead time. Therefore, this paper gives a detailed analysis of DAB converters under EPS control with dead time consideration, and the intervals of inductor current zero point is used to distinguish conditions of each sub mode. Recessive-dead-time mode which is not affected by dead time is selected in this paper. Finally, the simulation results verify the correctness of the theoretical analysis.

Compared to the traditional magnetic integration technique, the emerging electromagnetic integration technique (EMIT) has a greater potential for compact design of power converters since it has the capacity to integrate both inductive and capacitive components. As the most representative method, the flexible multilayer foil (FMLF) technique still needs to be further studied for extending and promoting its applications. In this paper, the FMLF technique is utilized to improve harmonic filter design for single-phase voltage-source power converters, a unified integrated LC and LCL filtering module is proposed. In this design, two symmetrical regular FMLF windings and EIE-shape magnetic cores are employed. By sharing the gapped EIE cores and properly arranging the windings with three-terminal configuration, the integrated module can flexibly serve as an LC or LCL filter and realize magnetic decoupling between the two inductors. Taking a 1-kW single-phase SiC-MOSFET converter as the application scenario, simulations and experiments have been conducted to reflect feasibility of the proposed approach.

In order to further improve the boost ratio of the traditional impedance source inverter, and to improve the DC bus voltage spikes during switching transient caused by the leakage inductance of the coupled inductor. A new high-step up and low-spikes impendence inverter based two coupled inductors is proposed. By using two T-type coupled inductors to replace the inductance in the classic Z-source inverter, the proposed inverter can flexibly control the turns ratio of the two coupled inductors to obtain a much higher boost ratio. The DC bus voltage spike absorption circuit composed of several passive components effectively recovers the leakage inductance energy and suppresses the DC bus voltage spikes. In order to show the characteristics of the proposed topologies, the operating principles, analysis are shown in this paper. Experimental results verify the feasibility of the proposed inverters.

This paper presents a fully distributed finite-time dual-layer control system to guarantee an economic global load power sharing for DC multi-microgrids (MGs). Local and global coordination controllers are developed to handle respectively the optimal operation within a finite settling time for individual MGs and the entire cluster of interconnected MGs by using a dual-layer sparse communication network. In the local control layer, not only the incremental costs (ICs) of all DGs within each MG are equalized to realize optimal load sharing between DGs, but also the local generations and demands are balanced by MG's average voltage restoration using the finite time consensus protocol. Furthermore, the economic power flow among MGs is regulated by the distributed global controllers through fine-tuning of MGs local reference voltages to attain the minimal global total generation cost (TGC). The feasibility of the proposed controller is verified by simulation under various testing scenarios.

A novel current controlled scheme based on port-controlled Hamiltonian and energy-shaping control method has been proposed for the grid-connected inverter. Compared to traditional current controllers, such as proportional-resonant controller, only one control parameter requires to be tuned in the proposed energy-shaping controller. Moreover, the proposed energy-shaping control can not only realize a quick tracking response, but also improve the steady-state performance of the injected grid current whether or not the grid voltage is distorted. Simulation and experimental results have validated the correctness and feasibility of the proposed scheme through a 1 kW grid-connected inverter system.

In this paper, an isolated synchronous rectification DC-DC converter based on GaN HEMT is proposed, which can achieve soft-switching characteristics and reduce the conduction loss of the rectifier. In conventional rectifier converter, fast-recovery schottky diodes are used for resonant rectification, and the diode forward voltage drop results in larger diode conduction losses, which causes the power converter to be less efficient. To solve this problem, the proposed topology, whose rectifier diode is replaced by a synchronous switch, adopts synchronous rectification, which helps to improve the efficiency of power converters. Meanwhile, the transformers with magnetic core are also replaced by coreless planar transformers to reduce the volume. Thus, the system efficiency and power density can be improved. To achieve soft switching and reduce switching losses, the driving circuit of the rectifier circuit is optimized and the detailed design method of the proposed converter is analyzed. In tens of megahertz, the GaN HEMTs are adopted to reduce the driving loss, switching loss and conduction loss. A 20MHz prototype based on the proposed topology is designed in this paper. The experimental results verify the feasibility of the proposed converter and corresponding design method.

High impedance characteristics of weak grid can easily lead to some problems such as poor stability of photovoltaic (PV) power generation system, high grid-connected current harmonics and so on. For solving these problems, this paper establishes a system stability criteria based on impedance matching for current-source PV power generation system, deduces the output impedance model of single-phase grid-connected PV inverter, and studies the impact of weak grid on inverter stability and grid-connected current harmonics. Then proposes a control method based on virtual inductance for increasing the output impedance of inverter to improve the system stability, and adopts a grid synchronization method based on second-order generalized integrator phase locked loop (SOGI-PLL) to improve the quality of the grid-connected current. Finally, simulation and experimental results verify that the proposed method can effectively improve the stability of PV grid power system and reduce the grid-connected current harmonics under weak grid.

This paper presents an autonomous control scheme for DC micro-grid system both in grid-connected and islanding conditions. The proposed DC micro-grid architecture consists of a wind turbine generation unit, a photovoltaic generation unit, two battery stack units, a grid-connected inverter/rectifier and loads. Corresponding control strategy of each unit is presented. DC droop control method is adopted into voltage control loop to suppress the circulating current when two or more voltage sources are connected to DC bus. The energy that flows through each unit and different operating modes of the system both in grid-connected and islanding conditions are analyzed. Power management method to balance the energy of the system and stable the DC bus voltage is presented. Simulation results verify the effectiveness of the proposed control scheme in various operating conditions.