Zuzhi Zhang

A unit power factor DC fast charger for electric vehicle charging station

Widely applications of electric vehicle rely on popularization of charging station. With the increase in the number of charging station, the problem of grid pollution becomes worse and worse, and the charging hours must be decreased to raise the utilization rate of electric vehicle. This article proposes a novel unit power factor DC fast charger for electric vehicle charging stations. This DC fast charger, mainly used in fast-charging station, includes two modules: the input module is three-phase PWM rectifier and the output module is the phase-shift full-bridge converter. The two modules are controlled by only one DSP - TMS320F2812. The three-phase PWM rectifier overcomes traditional rectifiers shortcomings of low power factor and large harmonic, and is higher power than three-phase one-switch or two-switch power factor correction circuit. The phase-shift full-bridge converter is the isolated high-frequency DC-DC converter, and apt to be used in high power situation. Furthermore, the volume and weight of the proposed charger are decreased than conventional converter with grid-frequency transformer. A prototype of 10 kW Charger is constructed. The experimental results show that the novel DC fast charger has excellent electrical characteristics, and it can be applied to the electric vehicle charging stations.

The photovoltaic charging station for electric vehicle to grid application in Smart Grids

The number and variety of EVs batteries connected to grid continue to grow rapidly, which result in a heavy burden on grid. To solve this problem, it was proposed that electric vehicles could act as a new power source for grid, which is the concept of Vehicle to Grid (V2G). This paper proposed the photovoltaic charging station architecture by using a combination of the Z-source boost converter based on the battery charging strategy with the bi-directional PWM Inverter-Rectifier based on the V2G strategy in Smart Grids. In the photovoltaic charging mode, the PV arrays charge the battery by the Z-source boost converter. In V2G mode, the PWM Inverter-Rectifier transfers the active power and passive power according to the grid requirement, thus the EV batteries could be applied for the peak regulation and frequency regulation in grid. Also the EV battery could be used as storage system for renewable power system. The prototype of bi-directional PWM Inverter-Rectifier and Z-source dc-dc converter is developed. Finally, V2G and battery storage experiments are tested. Meanwhile the Z-source dc-dc converter voltage boost experiments are tested. Simulation and experiment results demonstrate that the prototype implements the power bi-directional transformation between power grid and electric vehicles, and the Z-source dc-dc converter achieves the voltage boost. Consequently V2G could significantly increase the smart gird system flexibility, and storage intermittent renewable energy from wind and solar.

Application research of an electric vehicle DC fast charger in smart grids

Popularization of charging station promotes wide applications of electric vehicle (EV). With the increase in the number of charging station, the problem of grid pollution becomes worse and worse. To improve the utilization rate of EV, the charging hours must be decreased. At present, most EVs start charging instantaneously under almost rated power of the charger. Large-scale EVs charging without adjustment will impact the smart grids. The capability of smart grids will restrict the number of charging station; furthermore, it will affect applications of EV. To solve the above problem, it is necessary to design a smart charger, as an important part of charging station, with unit power factor and with the function of fast charging. This article proposes a novel unit power factor DC fast charger for EV charging stations. This DC fast charger includes two modules: the input module is three-phase PWM rectifier and the output module is the phase-shift full-bridge converter. The two modules are controlled by only one DSP - TMS320F2812, which has abundant outside interfaces, to improve cooperating ability of two converters and the dynamic response of the charger. A prototype of 10 kW Charger is constructed. The experimental results show that the novel DC fast charger has excellent electrical characteristics, and it can be applied to the EV charging stations in smart grids.

A novel limited double-polarity control scheme and implementation method of ZVS full-bridge inverter

To reduce the switching loss of traditional hard-switching PWM converter, in this paper, putting a new-type limited double poled ZVS control scheme and its implementation method in full bridge PWM converter. This new-type control scheme may reduce the number of the power supply of driving circuit. In the main circuit, by adopting the methods of blocking condenser and the resonant inductor, making four power tube of the full bridge PWM converter achieve zero voltage switching (ZVS). And auxiliary circuit is added of the first winding of transformer, using clamping diode to clamp the voltage at primary winding. At the same time of realizing ZVS and improving the efficiency of converter, suppressing the voltage oscillation effectively, eliminating the voltage spike and reducing the voltage stress of the outputting rectifier diode. Finally, Making a 500-watt experimental prototype, and by the experimental result, validating the availability and effectiveness of the new-type control scheme.

Design and control of the novel Z-SOURCE PWM rectifier-inverter

With the development and popularization of Electric Vehicle, the Electric vehicle charging systems are more and more important. This paper proposed the novel Z-Source rectifier-inverter for electric charging station. The Serial-Z-Network makes the shoot-through zero state possible, which regulates the output DC voltage. This paper includes the topology analysis, the control strategy and the PWM control methods of the novel Z-Source rectifier-inverter. The novel Z-Source rectifier-inverter, features lower dc voltage on Z-network capacitor. A 10kW prototype is designed and developed. Simulation and experimental results show that the output DC voltage can be reduced in the rectifier mode and the Z-Source capacitor voltage stress is very low. Meanwhile the Novel Z-Source rectifier-inverter can achieve the unity power factor and bi-directional energy transmission.

Third harmonic input current cancellation strategy for single-phase power factor correction with non-electrolytic capacitors

Electrolytic capacitors are widely applied because of low volume and cost, however their lifetime is quite limited typically less than 10000h. An improved control strategy for PFC converters with small storage capacitance suitable for medium and high power is proposed on the basis of conventional ACM PFC, which effectively eliminates third harmonic input current due to the low energy-storage capacitance. Compared to other methods to eliminate electrolytic capacitors, the proposed method has the advantage of nearly unity power factor, suitable for medium and large power application. A simulation analysis is made and a 325W digitally controlled prototype with a 50µF polyester film capacitor verifies the approach. The proposed method does not require additional components and it is easily implemented in practical situations.

An improved Totem-pole bridgeless power factor corrector with complementary driving signals

An improved Totem-pole bridgeless boost rectifier with low conduction losses and zero diode reverse-recovery is proposed for power-factor correction (PFC). Compared to the traditional totem-pole bridgeless boost rectifier, the proposed boost rectifier reduces the conduction losses by using complementary PWM driving and eliminate the diode reverse-recovery problems by an additional Silicon Carbide diode. Zero-current turn-off of the output diodes is guaranteed because of the zero reverse-recovery characteristic of Silicon Carbide diode. The proposed boost rectifier can work in continuous current mode (CCM) which is suitable for medium and high application. Experimental results for a 430W prototype are also discussed to show the performance of the proposed rectifier.

The topology analysis and PWM method of the novel Z-Source PWM rectifier-inverter

This paper proposed the novel Z-Source PWM rectifier-inverter which has the following advantages: the lower dc voltage on Z-Source capacitor, the reduced volume of capacitor and the simplified mechanical structures. Meanwhile the system is one stage and the efficiency is high. This paper studies the two kinds of Z-Source rectifier-inverter SVPWM method. In order to decrease the switching loss and increase the efficiency of the Z-Source rectifier-inverter, this paper has proposed two novel PWM methods: the novel Discontinuous Simple Control SVPWM and the novel Minimum Switching Number SVPWM. The proposed two novel PWM methods have the following advantages: the number of devices hard switching is reduced, thus the EMI and the switching loss is low. A lOkW prototype of the novel Z-Source PWM rectifier-inverter is designed and developed. The Simulation and experimental results verify the validity of the theoretical analysis.