How to realize energy-saving AC drive system of electric vehicle based on boost DC-DC bidirectional converter and inverter?
In electric vehicles, the battery and the electric drive system are the two keys, and their technical level largely determines the main performance of the electric vehicle. Different from general industrial and household electric drive systems, no matter which way is used to supply electric energy in electric vehicles, the energy is limited. Therefore, in order to meet the particularity of electric vehicles, the motor and power in the new electric drive system The conversion device should meet the following basic requirements:
① high efficiency;
② small size and light weight;
③ high starting torque multiple;
④ good speed control performance and controllability;
⑤ reliability must be high and the service life must be as long as possible , Less maintenance or even no maintenance;
⑥ Reduce noise and vibration, improve comfort.
At present, the electric drive system of electric vehicles is still mainly driven by DC motors, and the unidirectional energy transfer method from the battery to the power converter to the drive motor is generally used, which has many deficiencies. Specifically, although the DC motor has the advantages of simple structure, good controllability, wide speed range, large starting torque multiple, relatively simple control circuit, and low cost, its shortcomings can not be ignored. Brushed DC motors are prone to sparks, noise and vibration due to the presence of mechanical commutation components such as brushes or commutators. Electromagnetic interference problems are prominent. Moreover, maintenance of brushes or commutators is difficult and the service life is short. In addition, the volume of the motor is very large, resulting in a waste of limited space. Although the brushless DC motor overcomes some of the defects of the brushed motor, its rotor position detection is difficult, the price of the whole machine is quite high, and the cost performance is relatively low. From the point of view of system efficiency, since most systems use unidirectional power transfer, the vehicle wastes a lot of energy when decelerating the brake or sliding downhill. In addition, mechanical vibration and friction of brushes, commutators, etc. have also caused a reduction in system efficiency. Therefore, in view of the above problems and the basic requirements of the electric drive system, this paper proposes a new type of ZCZVS boost DC-DC bidirectional converter combined with an inverter to drive a squirrel cage asynchronous motor energy-saving electric vehicle AC drive system.
1. System design requirements and overall design The system is mainly used as a driving device for light electric vehicles such as electric motorcycles. Its basic technical parameters are as follows: the input voltage is 36V DC; the output voltage Vo of the DC converter is 150V DC; the drive motor capacity is not greater than 300W; Feedback function; realize acceleration and deceleration adjustable, soft start function; with over-current, over-voltage, under-voltage protection functions, etc. The basic structure of the energy-saving electric vehicle AC drive system includes battery V5, ZCZVS boost DC-DC converter, three-phase bridge inverter circuit, AC asynchronous motor and corresponding control and detection unit. The high-frequency inductance L and the electronic switch Su form a step-up DC-DC converter, which provides the input voltage for the inverter of the variable frequency governor composed of S1 ~ S6. The capacitor Csu is a buffer capacitor. The anti-parallel diode Dsu can provide energy feedback Freewheeling in mode; Sd is an energy feedback control switch, used to control the flow direction and size of energy, capacitor Csd is a snubber capacitor, and antiparallel diode Dsd can carry out freewheeling in electric operation mode. When the vehicle is decelerating or sliding downhill, the back-EMF of the AC motor terminal will be greater than the rated input voltage of the inverter and is in the state of power generation. Sd, the energy of the system is fed back to the power supply side. The three-phase bridge inverter circuit works in the VVVF mode. When the vehicle needs to adjust acceleration and deceleration according to demand, it is only necessary to change the frequency control circuit control under the given speed adjustment command to achieve speed adjustment. In addition, the squirrel cage asynchronous motor is used as the driving motor, which overcomes the shortcomings of the DC motor in structure, reduces maintenance work, improves the system capacity and speed of the whole machine, and greatly improves reliability and efficiency.
If you want to know more, our website has product specifications for converter, you can go to ALLICDATA ELECTRONICS LIMITED to get more information