Preliminary study on frequency conversion control technology of hydrogen energy generator air supply system Chen Haiqing (Engineering Engineering College of PLA University of Science and Technology, Nanjing 210007, China), based on the PEMFC hydrogen energy generation device air supply drive system using AC induction motor and vector control frequency conversion Speed ​​technology. By comparing several schemes of vector control, a vector control scheme of indirect rotor field oriented current injection induction motor is proposed and simulated. : Proton exchange membrane fuel cell; hydrogen energy generation; variable frequency speed regulation; due to the depletion of traditional energy resources, especially the impact of environmental pollution on human sustainable development in recent years, pollution-free, high-efficiency new energy generation technology And its research is highly valued worldwide. Fuel cells are recognized as the fourth generation of new power sources after thermal power, hydropower and nuclear power. They use hydrogen as fuel, oxygen or air as oxidant, and directly convert hydrogen energy into electrical energy through electrochemical reactions (so called hydrogen energy generation). Device), with clean and efficient features. Proton exchange membrane fuel cell (PEMFC) is a kind of fuel cell with polymer proton membrane as electrolyte. Because of its low operating temperature, low noise and smokeless gas emissions, it has become the best electric vehicle power supply in the 21st century. It is highly concerned and has set off a boom in R&D and application at home and abroad. As a key component of the PEMFC hydrogen power generation unit, the air feed system has become one of the key areas for the application of PEMFC hydrogen power generation technology. At present, the air supply drive system of the hydrogen energy generator mostly uses a DC motor to drive the blower to send air into the fuel cell stack. Although the system structure is simple and the design is easy, the motor capacity must be designed according to the maximum air volume of the power generation system, so that the air supply system The power is always close to the maximum value, resulting in high power consumption of the air supply system, high cost of the power generation system and large maintenance, and high requirements for the regulator valve, which greatly reduces the overall performance of the power generation system and affects the PEMFC stack body. The longevity has become one of the important obstacles hindering the practical use of hydrogen power generation systems. Due to the mechanical commutator of the DC motor, it has some fatal shortcomings, such as maintenance difficulty, short life and high cost. The single machine capacity and the maximum voltage are also limited, especially when the DC motor is commutated. Sparks can jeopardize the safety of hydrogen power plants. On the contrary, the current on the rotor side of the induction motor is generated by electromagnetic induction, without commutator, simple and firm structure, small size, light weight, reliable operation, convenient maintenance, low price, working in harsh environment, mature technology, etc. The induction motor replaces the conventional DC motor drive fan and adopts the frequency conversion speed control to form the hydrogen energy generator air feed drive system, which becomes an important direction for the practical application and product application research of the hydrogen energy power generation system. 1 induction motor frequency conversion speed control principle and control mode 1.1 induction motor frequency conversion speed regulation principle The general expression of induction motor speed is: f power frequency; s slip rate; p pole logarithm; from the above formula: asynchronous motor speed n is related to three parameters of power frequency /, slip rate s, pole pair p. Speed ​​adjustment can be achieved by changing any of the parameters. However, variable pole speed regulation is a stepwise speed regulation, and various speed control methods aiming at changing the slip rate s, such as stator voltage regulation speed regulation, electromagnetic speed regulation, rotor variable resistance speed regulation, are energy-consuming speed regulation. Method, only frequency conversion speed regulation is the most ideal speed control method. The frequency conversion speed regulation adjusts the motor speed by changing the power frequency /, and the motor speed can be changed evenly and smoothly as long as the power frequency of the input AC motor is uniformly changed. This is the basic principle of frequency control. The advantages of frequency conversion speed regulation are: high efficiency, wide application range, large speed regulation range, and the purpose of saving electricity and protecting the motor for occasions with low load running time or frequent starting and stopping operations. 1.2 Control method of frequency conversion speed regulation For the hydrogen energy generator air supply drive system, the amount of air supply directly affects the power generation capacity of the hydrogen power generation device, in order to make the hydrogen supply device air supply system meet the hydrogen energy generator air supply Supply the drive system motor for speed control. Although the induction motor has the above advantages, the induction motor speed regulation is difficult, so the early application mainly adopts the voltage regulation speed regulation, the electromagnetic slip clutch speed regulation, the winding type induction motor rotor series resistance speed regulation and the cascade speed regulation. Etc. These speed control methods are very inefficient and have limited application possibilities. The high-efficiency speed control method of induction motor is mainly frequency conversion speed regulation. It can not only realize stepless speed regulation, but also adjust the relationship between voltage and frequency according to different load characteristics, so that the motor always works in high efficiency area and guarantees good. Dynamic performance. In addition, the induction motor adopts variable frequency starting to significantly improve the starting performance, greatly reduce the starting current, and increase the starting torque. Therefore, the frequency conversion speed regulation is an ideal method for adjusting the speed of the induction motor. For the induction motor of the hydrogen energy generator air supply drive system, the control method of AC frequency conversion speed regulation is adopted, and the air supply quantity can better meet the above requirements. Since the breakthrough of the AC variable voltage frequency conversion technology in the 1960s and 1970s, it has been highly valued by people and has continuously invented new control methods with better control performance. AC frequency conversion technology can be divided into the following three types according to its control mode: open loop constant voltage frequency ratio control (V / f control) frequency conversion speed control The initial control method is V / f control, that is, speed open loop constant voltage frequency ratio control, The control scheme is simple in structure and low in cost, and is suitable for occasions where the dynamic performance of the speed control system is not high. Since then, due to the requirements of the closed-loop control of the speed, domestic and foreign scholars have proposed the slip frequency control, so that the torque can be indirectly controlled by controlling the slip frequency. However, this control method is based on the steady-state equivalent circuit and torque formula of the induction motor, so it is only established under steady state conditions, and in the dynamic process of rapid response of the rotational speed, due to the large transient current, There is a big difference between the dynamic torque and the steady state of the motor. Therefore, this control method is only suitable for occasions where the rotational speed changes slowly: 1415. In order to solve the problem of controlling the motor torque in the dynamic process, domestic and foreign scholars In-depth research was carried out and a more effective control scheme was proposed. The requirement of the change of the generator's power generation and the change of the load must be touched. It is also called the field-oriented control vector control technology to realize the dynamic control process of the motor, which is the direction of the magnetic field vector. As the reference direction of the coordinate axis, and according to the principle of magnetomotive force equivalent, the stator current is decomposed into the excitation component and the torque component by coordinate transformation, and the decoupling control of the magnetic flux and torque of the AC motor is realized, so that the AC motor obtains the equivalent. In the control performance of the DC motor, the decoupling control of the rotor flux and torque of the AC motor can be controlled, so that the AC motor can be controlled according to the control law of the DC motor, which overcomes the classical AC speed regulation and transformation, transformation, The disadvantages of stepped speed regulation such as rotor loop string resistance make up for the shortage of initial constant voltage frequency ratio (V / f) control and slip frequency control, which makes the dynamic performance of AC drive system significantly improved, and creates AC drive. The new era. Vector transformation involves a large number of numerical operations, mainly including coordinate transformation, vector operation and nonlinear complex operation. If it is realized by analog circuit, its design, manufacture and debugging are very troublesome, and some calculation functions cannot be realized at all. With the development and application of microcontrollers, this problem has been solved. Software implementation of vector control algorithms to standardize hardware circuits not only reduces costs but also improves reliability. The early microprocessors for motors are mainly 80C196MC series MCUs, which have rich hardware and software resources for real-time control, but they lack sufficient capacity when large data calculation processing or floating-point operations are required. In order to further improve the computing speed, digital signal processing (DSP) appeared in the early 1980s. This is a chip with strong computing power. Its on-chip peripheral resources are abundant, which can make the peripheral circuit of the speed control system less and compact. High reliability and easy to implement the entire control from the hardware. The difference between this control technique and the vector control technique is that it does not need to decompose the stator current of the motor into the excitation component and the torque component, but only controls the instantaneous input voltage of the motor by controlling the switching mode of the PWM inverter. Achieve direct control of torque and stator flux. Direct torque control does not require complex coordinate transformations, and the stator flux control only involves stator resistance, so the dependence on motor parameters is greatly reduced. This method has been rapidly developed due to its novel control ideas and simple and clear system structure. China Electric Power, 2003, (1): 6T70 5 Xu Tiezhu, Xu Guoqing. Frequency conversion speed control system of AC motor based on DSP. Journal of Power Systems and Automation, 2002, 14 (6) 6 Ren Haipeng. The application of DSP in the brushless DC motor servo system. Micromotor, 2002, (2) 21-24 Oxford University Press. 1990. 34-588 Yin Xianggen, Cheng Hanxiang. Frequency conversion speed forecast. Power automation set up 9 Yingjie, Wu Shouqi. Pulse width modulation control technology for electric drive M. Beijing: Mechanical Industry Press, 2002.23626810 Chen Boshi. Electric drag automatic control system M Bu Machinery Industry 11 Li Lei, Hu Yuwen. Research on Induction Motor Direct Torque Control System Based on Speed ​​Adaptive Flux State Observer. Journal of Electrical Engineering, 2001, 16 (4): 14 Weng Yingjun, Wu Shouqi, Yan Yingjie. Research on Speed ​​Sensorless Direct Torque Control for Induction Motors (Continued from page 8)
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Preliminary Study on Frequency Conversion Control Technology of Hydrogen Generator Air Supply System