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Do you know the working principle of the inverter of the new energy hybrid electric vehicle?

Dec 16, 2020

Do you know the working principle of the inverter of the new energy hybrid electric vehicle?

There are inverters on hybrid and pure electric vehicles, such as Toyota Corolla Double Engine and BAIC EV160. The inverter of a car converts the mainstream voltage (power battery, storage battery) into alternating current, and is composed of an inverter bridge and logic circuits. An inverter is a transformer that converts DC to AC. It plays the opposite role of the converter and is a process of voltage inversion.

There is an inverter assembly with a converter on a hybrid vehicle

The hybrid control ECU (HV ECU) determines the state of the vehicle according to the accelerator pedal position sensor, gear sensor signals, battery voltage, current and temperature signals, engine ECU signals, and body stability control system ECU signals, and calculates the necessary Torque and power. Inverter assembly MG ECU controls the actions of generator MG1 and motor MG2 according to the command signals generated by HV ECU. Engine ECU controls engine speed and power according to HV ECU signals to achieve the best state.

Boost converter

As can be seen from the above figure, the boost converter boosts the DC (direct current) voltage of the power battery from 244.8V to a maximum of 650V alternating current (AC). The boost converter is composed of a booster IPM integrated control power module, which uses IGBT transistors to control the completion of voltage conversion by applying forward and reverse gate voltages.

The motor control unit ECU uses the built-in voltage sensor VL to detect the voltage before boosting, and the voltage sensor VH to detect the high voltage after boosting. Based on the comparison of these two voltages, the motor control unit ECU controls the operation of the boost converter , Adjust the voltage to an appropriate value.

DC-DC converter

The DC-DC converter can convert a fixed DC voltage into a variable DC voltage. As can be seen in the above figure, the DC-DC converter can convert DC244.8V into a voltage of 14V. 244.8V is the voltage of the power battery. The power voltage of the model is different. For example, the Toyota Corolla Dual Engine is 201.6V, and the Camry Dual Engine's power battery is 244.8V.

The 14V low-voltage power converted by the DC-DC converter is used to charge the battery and power the body electrical equipment. The DC-DC converter can control the charging voltage of the auxiliary battery into a constant voltage power supply, and feedback through the auxiliary battery sensor Signal to protect the DC-DC converter when the line fails.

Inverter (DC-AC inverter)

The DC-AC inverter is an electronic device that converts direct current to alternating current. The inverter converts DC 650V direct current to AC 650V alternating current according to the IGBT transistor control signal, and controls the operation of MG1 and MG2 motors under appropriate working conditions , Simply put, it is to convert the high-voltage mainstream electricity that the supercharger has into into alternating current.

For example, when the car starts, the high-voltage battery HV supplies power to the MG2 (so MG2 is called a motor, starter), and the MG2 drives the wheels through the drive axle. At this time, the engine is not working, which can reduce energy consumption.

In the process of deceleration, the engine generates electricity by driving the generator MG1, and the voltage of the inverter is converted to the high-voltage battery HV for charging.

After the MG1 and MG2 motors stop running, the hybrid power system control ECU sends a signal to the inverter to convert the alternating current generated by the two motors into direct current to charge the high-voltage battery.

Inverter on pure electric vehicle

HEV hybrid and EV pure electric vehicles use different motor models and specifications. Hybrid models have motors installed inside the transmission, and the power output is alternately changed by the engine and drive motor. EV vehicles always use motors. Drive to travel. The inverter of the EV vehicle controls the motor operation through the torque command value of CAN and the current feedback value.

The inverter on a pure electric vehicle is located in the motor controller (in the MCU). In addition to the inverter, the controller is also combined in the MCU. The MCU is the control center of the entire power system. The controller accepts the demand signal of the drive motor. When the vehicle is braking or accelerating, the controller controls the frequency of the frequency converter to increase and decrease to make the car drive.

The inverter receives the DC power output from the power battery, and inverts it into three-phase AC power for the motor to run, and plays the role of braking and recovering power during the braking process of the electric vehicle. As shown in the figure below, the inverter is composed of 6 IGBTs, and the x type arrangement is Sa-Sc. Each phase output line (Ia, Ib and Ic) of the motor and the positive and negative DC lines are connected to an IGBT.

When the temperature of the switching element IGBT in the inverter exceeds 150 degrees, the IGBT cannot function, so air-cooled or water-cooled heat dissipation measures must be used. When the car reports a fault in the drive motor system, such as the drive motor is overheated, the drive motor coolant temperature is overheated, etc., then we have to use the diagnostic instrument to read the specific fault code meaning, because the fault displayed on the dashboard is not very specific.

Summary: As a device that connects the high-voltage battery and the power of the motor, the inverter plays an important role in the normal driving of electric vehicles. In addition to the above-mentioned electric vehicles with inverters, other vehicles with inverters include Toyota Camry Shuangqing and Honda CRV hybrid models.