Keywords: New energy electric vehicle; motor drive system; performance
1. New energy electric vehicle motor drive system performance requirements
The performance of new energy electric vehicles depends largely on the motor control system, power supply system and motor drive system, the motor drive system is the system that provides power to the electric vehicle, is the core part to ensure the normal operation of the electric vehicle, a good motor drive system needs to have the following requirements: First, the cost of the electric vehicle drive system and the price of the internal combustion engine system is similar to no child, the price is relatively low: Second, it needs to have good performance, has a large instantaneous power and a wide range of constant power and starting torque, can quickly achieve acceleration. Second, it needs to have better performance, with larger instantaneous power and wider constant power and start torque, can quickly achieve acceleration, third, wide range of speed regulation, low-speed operation can climb and start, in the constant power area, low torque and have a high speed, so as to ensure that the car on a flat road normal driving, improve the range; fourth, with the best capacity Utilization rate, in a certain environment, can achieve the optimal mechanical efficiency and motor efficiency, effectively increase the use of energy efficiency of electric vehicles, can guarantee the smooth operation of the car in a variety of environments.
2. Analysis of key technologies of new energy vehicle drive motor
Power system and drive system together form the power system of new energy vehicles, so the power system is the key part to control the driving range and operating cost of new energy vehicles; the power performance of electric vehicles mainly depends on the drive system, which is composed of controller, drive motor and transmission.
Together, the most critical component in the drive system is the drive motor. It can be seen that the drive system is the core component of the car, so improving the performance of the drive system and the power system of new energy vehicles is the key to the effective development of new energy vehicles.
2.1 Drive motor technology
At present, DC motor drive system and AC motor drive system are the two electric drive systems applied in new energy vehicles. The drive system of DC motor drive system uses DC motor, also referred to as DC drive system uses DC motor has more advantages, for example, DC motor has better mechanical characteristics, easy speed adjustment and has good performance, easy to control, high timeliness has lower cost and mature technology, etc.. However, DC motor also has some problems to be improved, for example, the brush and commutator of DC motor are wearable parts, which need regular maintenance by human after being worn. The drive system of AC induction motor drive system is AC induction motor, which is also called AC drive system. Compared with DC motors, AC motors are more efficient, reliable, do not require maintenance and easy to cool, and generally have a longer service life.
Among various motors, permanent magnet motor has the highest power density. The drive motor of permanent magnet synchronous drive system is composed of brushless DC motor (BLDCM) and three-phase permanent magnet synchronous motor (PMSM), which is smaller in size and lighter in weight, and has higher efficiency and does not require special manpower for maintenance, and has been used in new energy vehicles.
The motor structure of switched reluctance motor drive system has higher efficiency, simpler and more reliable than induction motor, the rotor has no winding, which is more suitable for frequent forward and reverse rotation and shock load. The system has been well used in new energy vehicles because of its wide range of speed regulation, large torque at low speed and braking energy feedback. However, the disadvantage of this system is that the vibration noise generated is large.
2.2 Drive motor control technology
Drive motor control technology is currently developing towards a drive control system with wide speed range, wide torque variation and improved efficiency of the entire working conditions. DC motor as a drive motor drive system, the driver circuit uses chopper control, AC induction motor control inverter is more complex, on the one hand, compared to the DC drive system, the control of the number of high-power tubes used more, on the other hand, to obtain good speed performance, you need to take the vector control mode, in its inverter in addition to the need to use In addition to the need to use a better performance of the microprocessor, the software used is also more complex. With the rapid development of electronic technology, the inverter technology applied in the AC system is also becoming more and more mature.
The permanent magnet brushless synchronous motor can be divided into square wave type permanent magnet brushless DC motor and sine wave type permanent magnet brushless DC motor according to the distribution of the spatial air gap magnetic field. The basic way to regulate the speed of permanent magnet brushless synchronous motor is frequency control, PWM chopper control IGBT inverter is now widely used, in order to further strengthen the control of torque, it is necessary to increase the motor regulation control, so as to slow down the fluctuation of torque.
The stator and rotor of the switched reluctance motor (SRM) in the drive system of the new energy vehicle belong to the convex pole structure, which has a relatively simple control device and only needs to install the excitation winding of each phase at the convex end of the stator, and no winding is needed on top of the rotor. However, the torque pulsation is large and the noise generated is high. The inverter and motor lead wires are determined by virtue of the number of stator cams. At present, it is not widely used in practice, but with the improvement of technology, it has been gradually applied in new energy vehicles.
3. New energy electric vehicle motor drive control system
A good drive system can ensure the smooth operation of new energy electric vehicles, so in the process of manufacturing new energy electric vehicles need to be matched with a good drive control unit, so as to ensure that the electric vehicles have a good operating effect. Vector control (VC) and direct torque control (DTC) are the more common combinations of units used for drive control, which can ensure the smooth operation of the car in the process of control and effectively avoid errors. Therefore to record the zero number of vector control and direct torque control, comparing vector control and direct torque control, from the data specifications, direct torque control is smoother than mass control: from the power device switching frequency point of view, vector control is more advantageous: from the analysis of system complexity, vector control and direct torque control are poorly, vector control performs well at low system speeds, and Direct torque control is not smooth enough, vector control is smooth and favorable in system starting performance, through direct torque control vehicle will cause a larger wear and tear on the vehicle, vector control has a smaller system torque pulse compared to direct torque control, and vector control has a wider range of speed control than direct torque control. In summary, compared with direct torque control, vector control has better performance in low-speed performance, speed range and starting performance.
With the implementation of some national environmental protection policies, the special research on electric vehicle controller and the research on the safety hazards involved in the key parts of electric vehicles have been gradually developed in the direction of systematization. However, the focus of the research is not accurate enough, for the core of the electric vehicle drive control center research is not deep enough, specifications and operating temperature are not within the specified range, beyond the standard limit, the system is not intelligent enough, the drive system can not be self-test for faults reduce the safety performance of electric vehicles.
4. Advantages of new energy electric vehicle control system
The energy of the new energy electric vehicle mainly comes from the electric motor. The excellent performance of the new energy electric vehicle motor control system can provide a better operating condition for the electric vehicle. In complex road conditions and bad weather, the vehicle needs to have high performance. In the process of driving the vehicle, the driver manually operates the vehicle in order to change the operating status of the vehicle. The vehicle controller receives the driver's control signals such as accelerating throttle, braking, etc., and then starts the vehicle control system. After the motor controller receives the command, it sends the operation information to the drive motor and realizes the control of the steering and speed of the drive motor by changing the voltage, current and frequency of the power supply. During the driving process of the vehicle, the positive rotation of the motor can keep the direction of the vehicle forward, and the reverse rotation of the motor is to prepare for reversing. When the vehicle decelerates, the current generated by the sub-torque of the drive motor needs to be integrated and shunted for processing to charge the power battery pack, and then the received motor speed information is fed back to the vehicle instrumentation to ensure the real-time detection of the motor running status, and in order to improve the precision of the control, the motor needs to be Various data integration analysis, and constantly adjust therefore, as the core components of the electric vehicle motor control system, need to meet the following three advantages: First, the motor control system can meet the frequent start and stop, in the more severe weather and complex environment, electric vehicles in the human start and stop operation can still maintain a stable running state. Second, upgrade the indicators and control of electric vehicles, in order to maximize the value of the tram energy, need to strengthen the durability of the battery, and make the components have good compatibility. Thirdly, after a long period of complicated and frequent operation, the motor still has strong sensitivity, and when the temperature difference of the external environment is in the range of 30-130C, the motor can still operate effectively.
The core components of a new energy electric vehicle are the motor and the control system, both of which are electronic components with extremely advanced and complex technologies. The performance of the motor and control system is directly related to the safety performance of the electric vehicle. At present, there are still some technical problems to be solved in the research of driving range and energy of new energy vehicles, but with the development of human technology to a certain level, these technical problems will be solved in the near future. Under the situation that the earth's environment is polluted and the earth's energy is decreasing, domestic and foreign countries are on the same level of new energy vehicle R&D and manufacturing, but in China, there are energy advantages and policy support and encouragement, and the resources used to manufacture batteries and motors for new energy electric vehicles are more abundant in China, in addition, the country is vigorously supporting new energy electric vehicles, and some industries are actively carrying out In addition, the country is vigorously supporting new energy electric vehicles, and some industries are actively upgrading industrial research and development, constantly improving the standardization of drive chips, motor control chips and motor control systems, and under the dedicated research of the industry, we believe that China's new energy electric vehicles will achieve rapid development.