With increased hazards such as the energy crisis, resource depletion and atmospheric pollution, our country has established new energy vehicles as strategic and emerging industries, with vehicle chargers as vehiclesElectric vehiclesAn important component is the combination of theoretical research and engineering applications. Figure 1 shows the structure of vehicle chargers using a combination of the front-end ac/dc and the back-up dc/dc。
When vehicle chargers are connected to the grid, there is a certain amount of harmonization, which contaminates the grid, and at the same time affects the working stability of the equipment used. In order to limit the amount of harmonization, the international electrotechnical commission has established the iec 61000-3-2 standard for the harmonization of electrical equipment, and we have issued the national standard gb/t17625. To meet the above criteria, vehicle chargers must be carried outPower factor correction(pfc) pfc ac/dc converters, which power the back-stage dc/dc system on the one hand and the auxiliary power on the other, are well designed and poorly designed to directly affect vehicle charger performance。
Figure 1 structure of electric vehicle loaders
In view of the stringent requirements for volume and harmonization of pure electric vehicle chargers, the design uses the power source factor correction (apfc) technology. The apfc has a variety of pivotal structures, and the main circuits of the boost pivot structure are selected because of their simple driving circuits, high pf values and the advantages of specially controlled chips. The average current control method, with the technical advantage of a mechanization, insensitivity to noise and a fixed switch frequency, was selected taking into account basic controls。
This paper focuses on pfc ac/dc converters, including system main circuits and controls, for pure electrical vehicle chargers with a power of 2 kw, taking into account the design needs in terms of band content, volume and disturbance resistanceCircuit designAnd on the basis of the above-mentioned study, a system simulation and experimental testing validation study is conducted, as shown in figure 2.
Figure 2 figure
1 boost pfc ac/dc converter
This paper uses the main circuit structure based on boost-up, as well as the average current control control policy under the continuous mode, for the 2 kw loader pfc ac/dc converter. Main circuits consist of whole-flow circuits and boost-up circuits; control circuits are controlled by double-closure loops using current inner loops and voltage rings, as shown in figure 3.
Figure 3 main circuits and control principles
2 pfc ac/dc converter main circuit design
The pfc ac/dc converter's main circuit consists of output filter caps, switches, voltage sensors, etc., with the following parameters。
2. 1 output filtering capacitation
The output wave capacity can be filtered out of the output voltage texture generated by the switch action, while maintaining the output voltage within a given range, and the selected device needs to perform the above two functions better。
2. 1. 1 consider output texture voltage
In form: co for the output of the filter capacity, pout for the main circuit output power, fin for the power input frequency for the grid, vout for the peak of the main circuit output line and vout for the main circuit output voltage。
2. 1. 2 consider voltage maintenance time
Where the main circuit output voltage drops from vout to vout (min)。
Based on calculations, 3 220 μf/400 v and 1 330 μf/400 v electrolytic capacitors were selected to be combined。
2. 2 switches
The following parameters are primarily considered in the selection of power tube switches: pressure resistance value, flux rate, and power tube switch frequency. In high switch frequency settings, mos tubes are often selected but individual mos tubes are smaller in flux and two mos tubes are selected to be combined in order to increase flow capacity. When the device is selected, the current of the mos tube is taken twice as large and the voltage of both ends of the mos tube is taken 1. 2 times as large. To increase flow capacity, two ipa60r165cp (650 v, 21 a) were selected and linked。
2. 3 litres of voltage
The design approach for voltage is to first calculate the amount of electrons, then select the appropriate magnetic core material, and finally select the appropriate amount and material in combination with the effect of magnetic saturation on the amount of electrons。
The electrons are calculated as:
Formula: vin enters a voltage for the main circuit, f for switch frequencies, lmin for the minimum amount of electrons and ilmax for the maximum amount of electrons. The minimum ejection value for voltage is then determined at 108 μh.
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