The Hybrid DC/DC converter is proposed to be used in the condition of bidirectional asymmetric power flow between DC buses. Firstly, this paper analyzes the switching mode of the Hybrid DC/DC converter under Extended Phase Shift (EPS) Control. Then, this paper calculates the converter losses and models the losses of the power and magnetic devices based on soft-switching characterization. The losses of those are not only by their material characteristics, but also closely related to the phase shift ratio. Based on the loss model and transmission power model of the converter, the power optimization allocation control strategy is proposed with the goal of efficiency optimization. Finally, the optimization method is verified through simulation analysis.

The virtual oscillator control (VOC) strategy, as a grid-forming controller, demonstrates substantial potential for application in weak grid scenarios. However, research on voltage support strategies for VOC during grid sag faults remains limited. This paper establishes an Andronov-Hopf VOC (AH-VOC) system with voltage-current dual-loop control, then systematically analyzes the principles of inverter-based voltage support at the point of common coupling (PCC) during grid sag faults. The relationship between voltage support effectiveness, grid impedance ratio, and system short-circuit ratio (SCR) is thoroughly investigated. Specifically for AHVOC, an optimal power distribution strategy and a modified voltage reference scheme are proposed to achieve precise power regulation and optimal voltage support under grid sag fault conditions. The effectiveness of the proposed control strategies is validated through MATLAB/Simulink simulations.

As the core equipment of DC power system interconnection and energy transmission, the improvement of DC solid state transformers’ performances has an extremely important impact on the development and application of DC power system. In this paper, a Partial-Power-Processing (PPP) LLC-DAB DC/DC converter with a bridge arm reusing rectifier is proposed for DC microgrids. The proposed converter topology can not only decrease the switching devices’ quantity, but also increase the control freedom of the converter and improve the light load efficiency. The operation principles, soft switching characteristics and power loss analysis of the designed converter are carried out. Finally, the feasibility of the proposed topology and the correctness of the theoretical analysis were verified by simulation results.

Wireless power transfer (WPT) technology has advantages of safety, convenience and space flexibility, which can effectively improve the performance of traditional EV chargers. A novel variable structure WPT system is proposed, which has both CC mode and CV mode with characteristics of low-cost, compact volume, easy-controlled. Charging efficiency up to 70% in CC mode and 100% in CV mode. Finally, simulation results verify the theoretical analysis.

With the ascending popularity of renewable energy in power systems, DC microgrids offer an attractive solution to this trend. In order to prolong the lifetime and prevent excessive use of energy storage units in the DC microgrid, an adaptive droop control based on the state of charge of the energy storage unit is proposed considering the line impedance. By adaptively adjusting the droop coefficient, the mode transfer times between the shutdown mode and the droop control mode of the energy storage unit is reduced, and the loss caused by transfer among different modes is reduced. The reasonable power distribution of the energy storage unit is realized. The service cycle times of the energy storage unit are reduced and the bus voltage accuracy is improved. The proposed method in the DC microgrid is verified by simulation results.

As the conventional non-isolated photovoltaic inverters all have low voltage gain and the leakage current issues, a transformerless common-grounded inverter with a relatively higher boosting ability is introduced. The suggested inverter comprises of a conventional boost converter and a buck inverter and is suitable for photovoltaic applications. The proposed inverter provides a solid connection in the negative port between the DC input power and the output load, thus eliminating the leakage current in the photovoltaic systems. Also, the introduced inverter has a higher input-to-output voltage ratio than other converters named semi-quasi-z-source and half-z-source converters. Employing the CBB capacitors increases the reliability of the suggested inverter and prolongs its service life. The working principle of the suggested inverter is elaborated in detail. The control strategy applied is ordinary and the proposed inverter is a single-level topology during the switching period. Finally, the simulation model is built in Matlab/Simulink platform, so the performance of inverter can be verified.

The phenomena such as wideband oscillations caused by the high penetration of renewable energy into the system are challenges for the stable operation of microgrids. This paper describes the microgrids instability mechanism briefly, and reviews some DC microgrid small disturbance stability analysis methods. Finally, the development trends of microgrid stability research are discussed.

This paper investigates the design of passivity-based control for LCL-filtered grid-connected inverter based on the port-controlled Hamiltonian with dissipation (PCHD) model. The interconnection matrix is changed from the original antisymmetric matrix to the upper triangular matrix with zero corner elements, which simplifies the design process. What’s more, to enhance the stability of the system, the combination of classic control theory and modern control theory is proposed to design the damping parameters of the controller. The main idea is to ensure the inverter output impedance is passive. The relationship between the controller parameters and the external interaction stability is compared. The simulation results are carried out to validate the effectiveness and robustness of the proposed approach.