This paper presents a switching bi-directional buck-boost converter (SBBBC) for vehicles-togrid (V2G) system. The topology can provide an energy bi-directional flow path for energy exchange between the Li-battery/supercapacitor (SC) hybrid energy storage system (HESS) of the electric vehicle and the grid. This topology not only has buck-boost capability, but also has the function of energy management. In this paper, the state-space averaging method is used to analyze the stability of the topology in boost and buck modes. The control strategy is given according to the state of charge (SOC) of the energy storage system to ensure that the output voltage and current are stable. And the Li-battery is charged in constant current (CC) and constant voltage (CV) mode. The voltage and current controllers are designed in the frequency domain based on bode plots. Finally, the electrical feasibility of the topology, the suitability of the design controller and control strategy are verified by simulation and experiment.

Due to the popularity of plug-in electric vehicles (PEV)and the development of converter technology, the electric-drive-reconstructed onboard converter(EDROC)is widely used in the charging system which can work in vehicle to grid(V2G) mode or grid to vehicle(G2V) mode. In this article, an EDROC for V2G/G2V energy management system is proposed. The EDROC uses permanent magnet synchronous motor as a charging inductor in V2G/G2V mode without additional equipment. Meanwhile, this article proposes a hierarchical V2G/G2V energy management system and the corresponding hierarchical control strategy with the proposed EDROC. This system can realize the energy distribution between PEVs, and avoid PEV overcharging. The proposed EDROC and control strategy are verified by simulation and experiment.

In this paper, an Electric-drive-reconstructed onboard converter (EDROC) based on a switching network in the DC side is proposed. The system can utilize the existing hardware of electric vehicles and does not need extra equipment. When the EDROC connects to the power grid through the power outlet at the office or home, there is not any additional equipment (filter or relay) on the AC side. Compare with traditional EDROC, the proposed novel EDROC has advantages in cost and volume. The EDROC can realize the unity power factor in the charging mode and discharges to drive the motor in the driving mode. A proof-of-concept prototype has been built to verify the charging function and driving function of the proposed EDROC.

Grid impedance variation and voltage harmonics may cause instability of the grid-connected inverter system and reduce the grid current quality under weak grid. Switching losses and electromagnetic interference of inverter can be reduced by using lower switching frequency. However, it is a challenging task to achieve stable operation of LCL-type grid-connected inverter using the active damping method at the low switching frequency. In this paper, an improved control strategy is proposed for the dual-frequency inverter, which contains a power inverter and an auxiliary converter. For the proposed control strategy, the ability to suppress the influence of the grid voltage harmonics and the robustness against grid impedance variation are analyzed. In order to reduce the switching losses, the electrical energy is delivered to the power grid through the power inverter at a low switching frequency. By using the switching ripple compensation method and the grid voltage feedforward scheme, the switching current ripple caused by the power inverter and the current harmonics caused by the grid voltage harmonics can be suppressed. Since the filters used in the proposed inverter are all L type filters, the system stability is guaranteed under weak grid. The simulation and experimental results are provided to verify the effectiveness of the proposed grid-connected inverter system under weak grid.

This paper presents a non-isolated three-port switching boost converter and applies it to photovoltaic systems. The topology combines the characteristics of the switching boost network. By controlling three degrees of freedom, the ports have boost, buck, and buck-boost characteristics. It expands the three-port converter (TPC) working range with the advantages of simple structure, small size, and low cost. The operating mode and power flow direction of the TPC are determined according to the state of charge (SOC) of the energy storage system. Analyses of the working state of the topology in different working modes further verify the power flow of the system and explain its control strategy to complete the smooth switching of different working modes. Finally, the correctness of the above theory and its feasibility in photovoltaic system are verified by simulation and experiment.