Research On Bidirectional On-board Charger Of Electric Vehicle For V2G Application

The technology of vehicle to grid(V2G) means that electric vehicles could exchange power and information with the smart grid at real time. Electric vehi cles could provide peak shaving, frequency regulation, reactive power compensation, and spinning reserve and so on. In V2 G application, there are still some problems about harmoinc and efficiency while the charging is in the wide range power output mode.Since the gird current harmonic could rise due to the imcreasing ratio of the inductor current ripple in the decline of the output power of the bidirectional charger, a new method combined with PR control and current weight control is implementated to reduce current THD by inhibit the current ripple in the grid side. The hamornic suppress effects are compared between the proposed strategey and segmented PI control, etc. The validaty of the PR and current weight control is revealed. Furthermore, the efficiency of the dual active bridge converter under light load state is improved by taking PWM and phase shift(PWM-SPS) control to extend the range of ZVS operation zone. Besides, the control combination of the AC-DC converter and DC-DC converter is discussed in traditional charging mode and V2 G charging and discharging mode. The methods of the active and reactive power control were also given.The phenomena of dead-zone oscillation and MOSFET drive signal disruption, oscillation at the resonant frequency were considered in the design of the bidirectional charger prototype. The AC-DC converter which serves as a rectifier as well as as inverter when discharging, is prior to be a full-bridge PWM bi-directional AC-DC converter depicted in single-phase. While the DC-DC converter should better be the dual active bridge circuit, because it is safer and more efficient with less switching loss. And the power transfer inductor is designed according to the constant current charging strategy.Finally, according to the technical indexes for the 3.3k W bi-directional charger, main circuit parameters are given by related theories and formulas. The proposed controller is designed to allow the AC-DC converter to provide input power factor correction and a near-sinusoidal input current waveform with low current THD. Experiments were conducted to verify the strategy of ZVS range extension.