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Analysis of electric control technology of electric vehicle motor

Data :2016-02-24   浏览:636次

At this stage, most of the discussions on key components of electric vehicles are mainly focused on the discussion of power batteries, but there are few discussions on the electrical control of motors. The reason is that, on the one hand, it is about the development of power battery technology. From time to time, new technologies and new hot spots appear, which are easy to attract the attention of the media and readers. In terms of motor electronic control, there are few new hotspots in new technologies; second, in the field of motor electronic control, especially in the field of electronic control, domestic suppliers are still in a relatively primary stage, and the products developed have not yet reached the international level. The leading level, which also greatly limits the consumers' concern about the electric control technology of the motor. In view of the space limitation, the author only gives a brief introduction to the basic knowledge of motor electrical control, and I hope it can be helpful to everyone.
         The motor is mainly composed of rotor, stator winding, speed sensor, housing, cooling and other components. In the field of new energy vehicles, permanent magnet synchronous motors are widely used. The so-called permanent magnet refers to the addition of permanent magnets when manufacturing the rotor of the motor, so that the performance of the motor is further improved. The so-called synchronization means that the rotation speed of the rotor and the current frequency of the stator winding are always consistent. Therefore, by controlling the frequency of the stator winding input current of the motor, the speed of the electric vehicle will be finally controlled. How to adjust the current frequency is the problem to be solved by the electronic control part. Compared with other types of motors, the biggest advantage of permanent magnet synchronous motors is that they have higher power density and torque density. To put it bluntly, it is compared to other types of motors. Under the same quality and volume, permanent magnet synchronous motors It can provide maximum power output and acceleration for new energy vehicles. This is also the main reason why the permanent magnet synchronous motor is the first choice for the majority of automobile manufacturers in the new energy automobile industry with extremely high requirements on space and dead weight. In addition to permanent magnet synchronous motors, asynchronous motors are also widely concerned because of the use of Tesla. Compared with synchronous motors, the speed of the motor rotor is always less than the speed of the rotating magnetic field (generated by the stator winding current). Therefore, the current frequency of the rotor and the stator winding always looks "inconsistent", which is why it is called an asynchronous motor. Compared with permanent magnet synchronous motors, asynchronous motors have the advantages of low cost and simple process; of course, the disadvantage is that their power density and torque density are lower than those of permanent magnet synchronous motors. Why Tesla ModelS chooses asynchronous motors instead of permanent magnet synchronous motors, in addition to the main reason for control costs, the larger ModelS car body can have enough space for a relatively large asynchronous motor, which is also very important factor. In addition to synchronous motors and asynchronous motors, hub motors are also a hot spot for new energy automotive motor applications. The biggest feature of the wheel hub motor is that it integrates the vehicle's power device, transmission device and brake device into the wheel hub. Compared with traditional power plants, the advantages of in-wheel motors are obvious. Due to the saving of a large number of transmission parts, the vehicle structure is relatively simple; of course, there are still many problems in the in-wheel motors in terms of synchronous control of the motor and wading sealing. solve.
Electronic control technology analysis

       The electronic control unit is equivalent to the ECU of a traditional car, and is the main execution unit for controlling high-voltage components on electric vehicles. In addition to the motor control, the control of the car charger, DC-DC unit and other related components is also achieved by the electronic control unit.

       The core of the electronic control unit is the control of the drive motor. The provider of the power unit-the power battery provides direct current, and the motor needs three alternating currents. Therefore, what the electronic control unit wants to achieve is a process called inversion in power electronics technology, that is, converting the DC power at the power battery end into AC power at the input side of the motor. In order to realize the inverter process, the electronic control unit needs DC bus capacitors, IGBT and other components to work together. When the current is output from the power battery terminal, it first needs to pass the DC bus capacitor to eliminate the harmonic component. Then, by controlling the IGBT switch and the cooperation of other control units, the DC power is finally inverted into AC power, and finally as the power Input Current. As mentioned above, by controlling the frequency of the three input currents of the power motor and the feedback values of the speed sensor and the temperature sensor on the power motor, the electronic control unit finally realizes the control of the motor. In addition to the control of the motor, the electronic control unit is also the main control mechanism for components such as on-board chargers and DC-DC units. Charging is just the opposite of motor control. It needs to convert the alternating current provided by the power grid into the direct current of the power battery, which is a process called rectification in power electronics. The DC-DC unit is the process of charging the 12V battery through the power battery. The electronic control unit needs to convert the high voltage of the power battery terminal to the low voltage end of the 12V battery to finally charge the new energy vehicle.