At this stage, most of the discussions on the key components of electric vehicles are mainly focused on the discussion of the power battery, while the discussion on the electrical control of the motor is very rare. The reason is that, on the one hand, with regard to the development of power battery technology, new technologies and new hot spots appear from time to time, which are easy to attract the attention of the media and readers. In terms of electric motor control, there are few new technologies and hot spots; second, in the field of electric motor control, especially in the field of electric control, domestic suppliers are still at a relatively early stage, and the products developed cannot reach the international level. Leading level, which also greatly limits consumers’ interest in motor and Electronic control technology. In view of space limitations, the author will only give you a brief introduction to the basic knowledge of motor and electronic control, and I hope it will be helpful to you.
Motor technology analysis
The so-called motor, as the name implies, is a kind of electrical component that converts electrical energy and mechanical energy. When electrical energy is converted into mechanical energy, the motor exhibits the operating characteristics of a motor; when electrical energy is converted into mechanical energy, the motor exhibits the operating characteristics of a generator. When most electric vehicles are braking, the mechanical energy will be converted into electrical energy, and the battery will be recharged through the generator.
The motor is mainly composed of rotor, stator winding, speed sensor, housing, cooling and other parts. 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 motor rotor to further improve the performance of the motor. The so-called synchronization means that the speed of the rotor and the current frequency of the stator winding are always consistent. Therefore, by controlling the input current frequency of the stator winding of the motor, the speed of the electric vehicle will finally be controlled. And how to adjust the current frequency is the problem that the electronic control part must solve.
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, compared to other types of motors, permanent magnet synchronous motors have the same mass and volume. It can provide the maximum power output and acceleration for new energy vehicles. This is also the main reason why permanent magnet synchronous motors are the first choice for the majority of automobile manufacturers in the new energy automobile industry with extremely high requirements for space and dead weight.
In addition to permanent magnet synchronous motors, asynchronous motors have also received widespread attention due to the use of Tesla. Compared with a synchronous motor, the rotor speed of the motor is always less than the speed of the rotating magnetic field (produced by the stator winding current). Therefore, the current frequency of the rotor and the stator winding is always “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, their disadvantages are that their power density and torque density are lower than permanent magnet synchronous motors. And why Tesla ModelS chooses asynchronous motors instead of permanent magnet synchronous motors. In addition to the main reason of cost control, it is also very important that the larger ModelS body has enough space for a relatively large asynchronous motor. factor.
In addition to synchronous motors and asynchronous motors, in-wheel motors are also a hot spot in the application of new energy vehicle motors. The biggest feature of the in-wheel motor is that it integrates the vehicle’s power unit, transmission and braking device into the hub. Compared with traditional power plants, the advantages of in-wheel motors are obvious. Because a large number of transmission parts are saved, the vehicle structure is relatively simple. Of course, in terms of synchronous control of motors and wading and sealing, there are still many problems for in-wheel motors. 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 in an electric car. In addition to motor control, the control of the on-board charger, DC-DC unit and other related components is also realized 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 what is needed to drive the motor is three alternating currents. Therefore, what the electronic control unit needs to achieve is a process called inversion in power electronics technology, which converts the direct current at the power battery end into the alternating current at the input side of the motor.
In order to achieve the Inverter process, the electronic control unit needs DC bus capacitors, IGBTs and other components to work together. After the current is output from the power battery terminal, it first needs to pass through the DC bus capacitor to eliminate the harmonic components. After that, through the control of the IGBT switch and the cooperation of other control units, the DC power is finally inverted into AC power, and finally used as the power motor. Input Current. As mentioned above, by controlling the frequency of the three input currents of the power motor and matching the feedback values of the speed sensor and temperature sensor on the power motor, the electronic control unit finally realizes the control of the motor.
In addition to controlling the motor, the electronic control unit is also the main control mechanism for the on-board charger, DC-DC unit and other components. Charging is the exact opposite of motor control. The AC power provided by the grid needs to be converted into DC power from the power battery, which is a process called rectification in power electronics. The DC-DC unit realizes the process of charging the 12V battery through the power battery. The electronic control unit needs to convert the high voltage at the power battery end into the low voltage end of the 12V battery to finally charge the new energy vehicle.