Switched reluctance motor is a new type of motor (as shown) developed with modern microcomputer control technology, power electronics technology and computer aided design technology in recent years. The motor has simple structure, many controllable parameters, good fault tolerance and efficiency. High in cost and low in cost, it has been widely used in traction transportation, general industry, household appliances and other fields. It allows energy to flow in both directions, so it can be used both as a motor and as a generator under an electronic controller. When used in an automotive system, the vehicle starter and generator can be combined to simplify the structure of the car and reduce the cost. And improve power density and reliability.

Cross-section of three-phase 6/4-pole SR motors With the rapid development of microelectronics technology, complex programmable logic devices (CPLDs) are fast, high-performance, large-capacity, small, reprogrammable and micro-power-consuming. The unique advantages have been increasingly applied. CPLD control technology has become another emerging control mode after the control of single-chip microcomputer and PLC. As one of the standardized hardware description languages, VHDL has strong portability, which is very suitable for the application design of complex programmable logic devices, greatly improving the efficiency of electronic system design and promoting the wide application of programmable logic devices.

In view of the poor working environment of the switch reluctance starter/generator (high temperature, high humidity, vibration, dust) and the low anti-interference ability of software control, this paper proposes a pure hardware circuit based on CPLD to realize the switch reluctance start. / Control of the power generation system. Because the pure hardware control circuit is simple and reliable, it can adapt to the complex working environment, so it can effectively simplify the structure of the switched reluctance starter/generator control system and improve its fault tolerance.

2 Switched Reluctance Motor Start/Generation Control Strategy The control strategy of the switched reluctance motor is flexible. It has three control modes: angular position control (APC), current chopping control (CCC) and pulse width modulation control (PWM). For the working requirements of the automotive switched reluctance motor and the characteristics of the vehicle power supply, a segmented control strategy is adopted for the automotive switched reluctance starter/generator.

When the motor speed rises to the idle speed of the car engine (about 800r/min), the motor will move from the starting state to the assisting state (the throttle is at the maximum position) or the power generation state, the boosting state is running in the electric mode, and the generating state is running. In the power generation mode, the motor still uses current chopper control. When the engine speed reaches a certain high speed (about 2000r/min), on the one hand, the phase current period is shortened, and on the other hand, the motion potential is large, so that the current peak is small, so the output of the large system and the power generation efficiency are improved. It is not appropriate to use current chopping control and should be changed to angular position control.

3 control system composition and optimization based on CPLD switching reluctance start / power generation control system structure as shown, the system is mainly composed of automotive engine, three-phase SR motor, 24V low-voltage battery pack, power conversion circuit and CPLD controller and The peripheral circuit is constructed, wherein the CPLD controller and its peripheral circuits are the core parts of the system. The window comparator is used to extract the voltage range signal, and the hysteresis comparator is used to extract the upper limit value of the phase current signal and the throttle position signal to control the operating state of the reluctance motor and realize overvoltage and overcurrent protection.

The battery acts as an energy buffer in the system. When the switched reluctance motor is used for electric operation, it is excited. When the switched reluctance motor is used for power generation, it absorbs the electric energy generated by the motor. Since the battery is an important part of the vehicle power supply, it is necessary. To realize the effective management of the power supply, it is necessary to control the charging and discharging process of the battery. The battery can be charged and discharged independently to complete the real-time detection of the motor speed. It can control the switching reluctance motor to effectively complete the starting, generating and assisting functions and realize the freedom of the three. Switch. The CPLD controller is mainly composed of modules such as drive, control, chopping, speed detection, and pulse width modulation. The programming is implemented by standard hardware description language VHDL and top-down design method, in which the control module's control status table is The characteristic is that when the motor is in the power generating state, the charging of the battery is divided into two stages, namely constant current charging and constant voltage charging, and the current and voltage are adjusted by a peripheral closed loop adjusting circuit, which is composed of an analog switch, a PI regulator and The angle adjustment circuit is composed of an analog switch to select a parameter to be adjusted, and an angle adjustment circuit is used to generate a pulse width adjustment signal to enter the CPLD controller.

The CPLD controller is implemented using Altera's chip EPM7160SLC10, which not only generates an effective drive and state transition signal, but also shows the operating state of the motor under different conditions as shown in the table below.

According to the characteristics of the phase current operation of the switched reluctance motor, the control process is optimized with the maximum output and power generation efficiency as optimization targets. Both analysis and practice show that the phase current waveform is closely related to the opening angle ft, the turn-off angle 02 and the current chopping upper limit of the main switch, and the phase current changes slowly with respect to 01 in the case of the fixed chopping upper limit. Linear, relative ft is more sensitive and changes drastically. Therefore, when the control process is actually manipulated, the turn-off angle ft is generally fixed according to the optimized value, and then the opening angle ft and the chopping upper limit of the phase current are adjusted by the closed loop to adjust the maximum output and power generation efficiency of the switched reluctance motor.

4 Experimental Results The test sample machine uses a three-phase 6/4 structure switched reluctance motor. The required DC power supply is a 24V low-voltage battery pack, which also serves as an energy buffer for the reluctance generator.

For the controller, the initial rotation speed of 1000r/min is set, the cut-off angle ft/02 is set to a 3-42 (mechanical angle), and the drive of the switch tube is controlled by the current At (about 300) current chopping control and the angular position control. The measured waveform of the signal and the phase winding current, wherein channel 1 is the phase winding current waveform, and channel 2 is the driving signal of the switching tube. It can be seen from the measured waveform that when the switch tube is turned on, due to the small value of the winding inductance, the phase current change rate is very large, and the current chopping frequency is very high; when the motor rotates through a certain angle, the inductance is larger. When the value is near, the phase current change rate is small and the current chopping frequency is low.

Table CPLD internal control state conversion table condition control state z condition reset signal invalid reset signal effective throttle bottom throttle not reset state automatic switching manual switching automatic switching manual switching current chopping angle position current chopping angle position 800r/min electric dynamic 800r/ Min 5 Conclusion From the experimental results, the pure hardware circuit based on single-chip CPLD can effectively realize the switched reluctance start/generation control system. With the wide application of switched reluctance motors and the continuous development of CPLD control technology, the pure hardware control scheme applied to motor control will surely be further improved.

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