Overview:
In order to improve the power factor of the DC600 V power supply of the passenger car and reduce the fluctuation of the output voltage, a design based on "diode uncontrolled rectification + IGBT step-down chopping" is proposed for the main circuit, and the PSIM simulation of the main circuit shows that the circuit It can greatly improve the power factor of DC600 V power supply, and stabilize the output voltage at 600 V. It has achieved the design purpose, can meet the quality requirements of passenger car power supply, and ensure the normal operation of power equipment.
At present, in the electrification section, the train power supply system, the 25 kV single-phase AC power sent by the contact net and the pantograph by the bus power supply device installed in the locomotive (trailer) is filtered by the step-down rectification to 600 V DC. Voltage, train supply busbar with DC600 V electric level. Each air-conditioned passenger car sends one of the 600 V DCs into the air conditioner inverter power supply unit (referred to as the inverter) and the DC 110 V power supply unit (referred to as the charger) through the power distribution cabinet power supply selection switch, respectively, to the air conditioner, electric water heater, refrigerator It is powered by a three-phase AC electrical load, a single-phase 220 V outlet such as a TV set, and supplies power to a DC load such as lighting and power supply control while charging the battery. Because the main circuit of the existing passenger car DC600 V power supply device is a single-phase semi-controlled rectifier circuit of thyristor, the power factor is low, the output voltage often oscillates between 500~700 V, and the voltage fluctuation is unstable, which easily leads to the inverse on the passenger car. The transformer and charger are protected from shutdown or damage.
In view of the above problems, this paper puts forward the technical scheme of "diode rectification + ICBT step-down chopper" for the main circuit of passenger car DC600V power supply. The main circuit is designed and simulated by PSIM software.
1 Design idea of ​​main circuit of passenger car DC600 V power supply
1.1 Technical parameters According to the actual requirements of passenger car power, the bus DC600 V power supply should meet the following technical requirements.
Rated output voltage of the power supply unit: DC600 V
Output voltage fluctuation range: ±10 V
Rated output power: 2×40HD kW
Rated output current: 2 × 670 A
Output overload current: 2 × ≯ 750 A
1.2 Design Ideas The existing bus DC600 V power supply adopts a single-phase bridge thyristor half-controlled rectifier circuit, so that the total power factor fluctuation range of the network side is 0.5~0.85. When the network is connected to the high network voltage, the network side always The power factor is as low as 0.5; the fundamental power factor fluctuation range of the network side is 0.65~1, and the high network voltage is as low as 0.65; and the output voltage often oscillates between 500~700V, and the voltage fluctuation is unstable.
In all single-phase rectifier circuits, the power factor of the diode uncontrolled rectifier circuit is constant at 0.9, the fundamental power factor of the grid side is close to 1, relatively high, and the ripple factor is small, and the rectified voltage is 0.9 Ud; therefore, the main circuit The diode rectifier bridge can effectively improve the power factor of the DC600 V power supply n of the passenger car. The rated input voltage of the device is 860 V AC, and the DC voltage output through the diode rectification is 774 V, which is higher than the 600 V required by the passenger car. Therefore, the step-down link is required.
In addition, the input voltage of the power supply fluctuates with the network voltage of the contact network at any time, and the step-down ratio of the step-down link should also change accordingly. Therefore, the IGBT chopper circuit is used, and the switching duty ratio of the chopper circuit is adopted. Adjust the output voltage to stabilize at around 600V to reduce the fluctuation of the output voltage. Therefore, the technical scheme of "diode rectification + IGBT step-down chopper" is designed for the main circuit.
Block diagram of the main circuit of passenger car DC600V power supply:
(Please read the PDF for details)
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