Application of Vector Control Frequency Converter in Hybrid Electric Vehicle
1 Introduction
Hybrid electric vehicles refer to the battery pack as the power source, and the wheels are driven by electric motors and engines. The motor does not emit harmful gas and the hybrid drive with the engine can greatly reduce the emission of harmful gas. At present, more than half of the total urban air pollution comes from the exhaust of fuel vehicles. Starting from the environmental protection of the atmosphere, since the 1960s, the progress of electric drive technology based on power electronics has provided advanced materials for the development of hybrid electric vehicles. Foundation; The rise and development of mechatronics technology has provided a very rich technical experience for the evolution of the typical mechanical product of fuel vehicles to the direction of mechatronics. The electromechanical integration configuration mode and control method of hybrid electric vehicles are still in the stage of full bloom, which is neither mature nor finalized. In order to ensure the harmonious and orderly development of hybrid electric vehicles, the country has created a good policy environment, market environment and consumer environment, because the development of hybrid electric vehicles is of great significance for energy conservation and mitigation of environmental pollution, and the automobile industry is fuel-efficient Large households, the fuel consumption of China's auto industry currently accounts for 1/4 of oil consumption. In 2004, China produced 170 million tons of domestic oil, imports exceeded 100 million, oil consumption accounted for nearly 20% of world oil consumption, but GDP only accounted for the world 4% of GDP. Under this circumstance, the development of hybrid electric vehicles that replace fuel-based transportation is crucial to the sustainable development of China's economy and society. In addition, the development of the automobile industry has brought relatively great pressure to environmental protection. The exhaust emissions of hybrid electric vehicles are few and the noise pollution is very small. The development of hybrid electric vehicles can greatly reduce the pressure on environmental pollution. The general transmission PI7000 vector control inverter has been successfully applied to a hybrid environment-friendly and energy-saving electric vehicle system. It has passed various tests and inspections for a long time and is now driving steadily on the highways in Macao, achieving the effects of environmental protection and energy saving.
2. Transmission system of hybrid electric vehicle
Automobiles are a kind of traveling machinery that operates on land in the open air, has a compact structure, and has on-board energy. It must be able to adapt to high-speed flying, frequent braking, rapid overtaking emergency braking on uphill and downhill slopes; it must be able to adapt to severe weather conditions such as snow, rain, severe summer and severe winter, and salt spray after snow, and it must be able to withstand roads. The bumpy vibration must also ensure the comfort and safety of the crew and passengers. The core of a hybrid electric vehicle is to replace its mechanical data propulsion system with a frequency converter to control the motor, and replace gasoline with a battery as an on-board energy source. On the premise of achieving zero or less emissions, it meets the performance and price of fuel-powered vehicles. Indicator requirements. Accordingly, the transmission system of a hybrid electric vehicle can be summarized as follows:
(1) Large torque below the base speed to meet the requirements of rapid start, acceleration, load climbing, frequent start and stop, etc., small torque above the base speed, constant power, wide speed range to adapt to the highest speed and highway overtaking, etc. Requirements, the above requirements can be achieved by simply setting the function parameters of PI7000 vector inverter.
(2) The efficiency of the entire torque / speed operating range is optimized to achieve the longest continuous relaxation distance after a single charge of the battery. A fuel car with 50kg of gasoline can travel about 700km. If it is converted into a hybrid electric car with a 400kg lead-acid battery, it can only travel 100km. It has recently been reported that the newly developed fuel cell can reach 450km. The development of new batteries with higher specific energy is the most fundamental solution, but reducing the loss of the electric drive system is also an important part. Using PI7000 vector frequency converter to control the motor can achieve high fuel efficiency and energy saving.
(3) The motor and electric control device have a solid structure, small size, light weight, maintenance-free or less maintenance, and anti-bump vibration. PI7000 vector inverter integrates PLC and signal device into one.
(4) The maneuverability conforms to the driver's driving habits, runs smoothly, rides comfortably, and has perfect measures for guaranteeing the replacement of the electrical system. For example, when the voltage command signal line, current feedback or speed sensor line is broken or short-circuited, it may cause the oscillation of the amplitude to reach positive and negative maximum output torque. Must have measures to detect such accidents in time, and immediately cut off the power supply of the motor when an accident is found. PI7000 vector inverter is used in conjunction with PLC, and has multiple protection functions such as rapid overcurrent, overload, overvoltage, PG line break, etc. Once the protection stops output voltage immediately, the driver can reset to normal working state by pressing the reset button. The battery power, running speed, working current, etc. are monitored very intuitively through the touch screen. The driver can also query the current, frequency, voltage, and status at the time of the fault through the touch screen. It is convenient and quick to operate and troubleshoot.
3. System structure diagram and working principle of hybrid electric vehicles
Working principle: The hybrid power system mainly consists of three parts: energy supply system, electric drive system and mechanical transmission system.
(1) Energy supply system: It consists of power battery pack and engine DC generator set.
(2) Electric drive system: composed of frequency converter and motor.
(3) Mechanical transmission system: the mechanical output of the internal combustion engine and the electric motor is sent to the axle through the clutch and the reducer.
If the battery pack has insufficient power, start the engine to charge the battery pack through the DC generator to ensure sufficient energy supply. The frequency converter controls the motor to drive the front (or rear) axle through the reducer and differential gear, and the internal combustion engine is installed coaxially with the motor through an automatic clutch (as shown in Figure 1). When the vehicle starts or when driving in an urban area, only the battery pack supplies power to the motor through the frequency converter, that is, pure electric drive; when driving on the road, the clutch is turned on, and the internal combustion engine bears the driving axle. The generator runs and recharges the battery through the frequency converter; when driving at high speed and heavy load, the motor and the internal combustion engine simultaneously drive the axle, that is, the hybrid drive, to increase the driving power and achieve energy saving and environmental protection.
4. Motor control system
4.1 The composition of the motor control system
Figure 2 shows a schematic diagram of the system
(1) Battery: Provide DC336V direct current to the inverter.
(2) Frequency converter and PLC: signal control and adjust the speed of three-phase asynchronous motor and protect the motor from overcurrent, overload, overvoltage, etc.
(3) Three-phase asynchronous motor and speed sensor: realize vector control, drive front and rear or rear wheel axle through reducer and differential gear.
(4) Reducer, axles and wheels: to realize the functions of car forward, backward and stop.
4.2 PI7000 vector inverter main circuit structure diagram and selection of main components
(1) Working principle: The battery charges the electrolytic capacitor to keep the DC bus voltage constant at about 336V, and the charging resistor R is a current limiting resistor to limit the impact of the large charging current at the moment of power-on; after the power board works, it passes the delay The circuit causes the contactor to pull in and the current limiting resistor is shorted. IGBTs are used in parallel to form the upper and lower bridge arms, which are the inverter part, which converts DC power into variable three-phase AC power as the input working power of the three-phase asynchronous motor. When there is a large short-circuit current, the insurance FU is disconnected to protect the main components; when the DC bus has a high peak voltage, the absorption capacitor C absorbs the peak voltage to prevent the main components from overvoltage breakdown or frequent jump protection ,As shown in Figure 3.
(2) Selection of components. According to the three-phase asynchronous motor, the power is 90kW, the rated current is 340A, the rated voltage is 220V, the rated frequency is 37.5Hz, the maximum frequency is 140Hz, the fixed-selection inverter device IGBT is 1200A / 600V, and the energy storage electrolytic capacitor is 6 4700μF / 450V, connected in parallel at both ends of the high-voltage DC bus, the insurance is 600A; the PN terminal of each IGBT is connected in parallel with two 3μF / 600A absorption capacitors.
4.3 PI7000 vector inverter control board wiring diagram and description
Description of the control process: the state of the driver ’s foot pedal operation, gear shift, foot brake, reverse, etc., and the corresponding digital or analog signals are transmitted to the PLC. The PLC processes the program and transmits the required signals to the inverter ’s The connection terminals of the control board automatically control the inverter, and the inverter realizes the corresponding functions according to the set function parameters. The inverter adopts vector torque control to meet the low-frequency large torque output and high-speed dynamic characteristics of the automotive system, so that the three-phase asynchronous motor drives the wheel shaft to start, run, and stop quickly (without impact force), and the half-slope starting torque can be reached 200%, meeting the design requirements of hybrid electric vehicles, as shown in Figure 4.
5. PI7000 vector inverter function parameter setting and description
Table 1 shows the inverter parameter settings and their description
6. Debugging steps of PI7000 vector inverter in hybrid electric gas vehicle system
6.1 Laboratory commissioning
(1) No-load test
Connect the DC 311V to the input terminal of the inverter, set the corresponding function parameters, run to 50Hz, use a rectifier pointer multimeter to measure the three-phase output voltage is normal; the DC bus voltage value monitored by the keyboard is consistent with the value measured by the multimeter, otherwise pass Modify the function parameter L01 for correction.
(2) Load test
In the standby state, connect the input line of the motor to the output end of the inverter, and then power on after no error. The frequency is raised to full frequency a little bit. Use a multimeter to test whether the three-phase output voltage is balanced. Use an embedded current meter to test whether the three-phase output current of the motor is balanced. Observe the keyboard monitoring: output frequency, output current, output current percentage, motor speed, Is there any abnormality in the IGBT temperature, etc .; adjust the function parameter L01 to adjust the output current percentage, that is, the current output by the inverter is consistent with the current monitored by the keyboard; adjust the parameter bits R35 and R37 on the power board to make the inverter reach 2.6 times The current protection is skipped when the rated current is reached. Power off, and connect the wiring of the speed sensor to the PG card terminal of the inverter one by one.
(3) Motor parameter measurement
When power is turned on, the function parameter b13 is set to be effective, and the inverter starts to automatically measure the motor's stator resistance, rotor resistance, motor leakage inductance, motor excitation inductance and other parameters and automatically stores them in b05-b09.
(4) Direction determination of PG
Set function parameters: F01 is set to 2, which is the vector control mode with PG; F02 is set to 5Hz, that is, the given frequency is 5Hz, F09 is set to 5S, that is, the acceleration time is 5S, F10 is set to 5S, that is, the deceleration time is 5S . Then run it manually, if the motor can run normally to 5Hz, it means that the b12PG rotation direction is set correctly; if the motor can only run below 1Hz, it means that the PG rotation direction needs to be corrected by b12.
(5) Motor direction determination
Given the forward running command, if the motor is forward, the motor direction is set correctly; if the motor is reversed, the motor direction is opposite to the command direction, the terminal command needs to be changed, and the wiring terminals of FWD and REV are reversed.
(6) If there is any abnormality in the above test, immediately find the cause and eliminate the fault.
6.2 Dynamic debugging
(1) Only after checking the correct connection of the inverter in the automobile system, can the inverter be powered on for debugging.
(2) Empty vehicle debugging
The driver hangs the gear in the D gear (high speed gear), steps on the accelerator, and advances, reverses, runs smoothly, turns, and stops the car. Using the keyboard, the acceleration and deceleration time of the function parameters F09 and F10 is gradually reduced, so that It can start quickly without impact and without jump protection.
(3) Car loading and debugging
Fill the car with buckets full of water to simulate passengers. The driver hangs the gear in the D position, steps on the accelerator, and performs forward, reverse, smooth, cornering, and climbing operations on the car, and monitors the inverter keyboard to see if it skips flow and overvoltage protection; , Gradually increase the torque given by function parameter C04, gradually decrease the excitation given by C05, and gradually increase the initial section of S curve acceleration F18; if the voltage protection is skipped, gradually increase the function parameter L13 inverter overvoltage protection point, do not exceed 400V (withstand voltage of electrolytic capacitor is 450V), F19 in the initial section of S curve deceleration gradually increases. The driver puts the gear in the L gear (that is, the low-speed gear, this gear is engaged at half-slope start), and repeats the above operation and debugging. Note: When modifying the parameters of the inverter, you need to tell the driver to go into neutral.
(4) Automobile road test
After the above debugging is not abnormal, the driver drives the car to the simulation test at each station 3-4 times a day. Observe whether any monitoring is abnormal through the keyboard, and make a record.
(5) If there is any abnormality in the above commissioning test, immediately find the cause and eliminate the fault. PI7000 vector inverter fault and abnormal handling, see Table 2.
7. Conclusion
The application of the general transmission PI7000 vector frequency converter in the torque control of the hybrid electric gas vehicle system is not only energy-saving but also environmentally friendly. After continuous testing and continuous improvement of the software, it has the advantages of reliable quality, stable performance, convenient debugging, strong anti-interference ability, simple maintenance, etc. The user is very satisfied. The hybrid electric vehicle system adopts inverter speed regulation technology and is worth promoting.
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