CN101977016A - Singlechip-based induction motor variable frequency speed regulation control system - Google Patents

Abstract

A single-chip microcomputer-based induction motor frequency conversion speed regulation control system. The system includes main circuit, auxiliary power circuit, inverter circuit, control part, overcurrent protection circuit, speed detection circuit and other peripheral circuits. The system takes the 16-bit high-performance signal controller dsPIC30F4011 produced by Microchip as the control core, and controls the motor excitation based on vector to adjust the speed. The digital signal controller dsPIC30F4011 of the American Microchip Technology Company is a special chip for motor control, embedded with a DSP core, has a very fast data processing capability and rich input and output devices and interface circuits; IR's intelligent power module (IPM) IRAMSIOUP60A is an inverse The variable switching device constructs the frequency conversion speed regulation control system of the asynchronous motor, which has the characteristics of simple driving and easy realization.

Description

A Frequency Control System of Induction Motor Based on SCM

【Technical field】：

The invention belongs to the cross technical field of motor control, power electronics and microcomputer principles, and specifically relates to a 16-bit high-performance signal controller dsPIC30F4011 produced by Microchip Company as the control core to design a frequency conversion speed regulation control system for an induction motor.

【Background technique】:

In recent years, with the development of power electronics technology, digital control technology, and control theory, especially the invention of some advanced control technologies, the development of AC frequency conversion speed regulation is also getting faster and faster, making AC speed regulation more and more widely used. Its speed regulation performance is also continuously improved, overcoming many shortcomings that are difficult to overcome in DC speed regulation. The first-generation frequency converter adopts the constant voltage frequency ratio control method, which performs frequency conversion and speed regulation according to the linearity determined by the equivalent circuit of the asynchronous motor. Voltage refers to the effective value of the fundamental wave. Changing U/f can only adjust the steady-state flux and torque of the motor, not dynamic control. The main feature of the second-generation frequency converter is the use of vector control mode. It refers to the control mode of DC motors and decomposes the stator current space vector of asynchronous motors into rotor excitation components and torque components. The main disadvantage of this control method is the need for complex coordinate transformation operations, and the need to detect the speed signal. Therefore, a speed sensorless vector control method is further proposed, which calculates the observed value of the rotational speed according to the actual operating phase voltage and phase current of the asynchronous motor, as well as the parameters of the stator and rotor windings, so as to realize the field-oriented vector control. Since the accuracy of the speed observation value is affected by the deviation between the calculated parameters used and the actual operating parameters of the motor, the speed regulation accuracy and range of the sensorless vector control are lower than the vector control scheme with a speed encoder. Generally, the speed regulation accuracy of the former is 1%, and the minimum frequency when outputting the rated torque can only reach about 1Hz, while the speed regulation accuracy of the latter is 0.01%, and the minimum frequency is 0.1Hz. Developed in parallel with the vector control is the direct torque control method, which uses the torque of the asynchronous motor as the controlled quantity, emphasizes the direct control effect of the torque, and does not deliberately pursue the output current as a sinusoidal waveform. The direct torque control of the asynchronous motor is to directly calculate the magnitude of the flux linkage and the magnitude of the torque on the stator coordinates, and directly track and adjust it to obtain a rapid dynamic response, and its response speed can be as small as 1-2ms. From the perspective of torque control requirements, the flux linkage has a little error, which will not have a significant impact on the torque control performance. The advantage of this control method is that it is not sensitive to changes in motor parameters.

In recent years, intelligent control methods such as fuzzy self-optimization control and artificial neural network that do not rely on motor models have been introduced into AC speed control systems, which have become a new research and development direction for AC speed control theory and control technology.

The inverter adopts thyristor semi-controlled devices to GTR full-controlled devices, and its output waveform has developed from AC square wave to pulse width modulation (PWM) waveform, which greatly reduces harmonic components and widens the frequency conversion speed regulation range of asynchronous motors. And reduce the pulsation amplitude of the torque. However, the working frequency of GTR is generally below 2kHz, the carrier frequency and the minimum pulse width are limited, and it is difficult to obtain an ideal sine wave pulse width modulation waveform, which makes the asynchronous motor generate noise during frequency conversion. The operating frequency of the IGBT can be between 10 and 20kHz. Compared with the GTR, not only the operating frequency is an order of magnitude higher, but also the voltage and current indicators have exceeded the GTR. Due to the increase of the carrier frequency of the inverter and the specific PWM waveform, the harmonic noise of the frequency conversion speed control controller of the asynchronous motor is greatly reduced. Intelligent power module (IPM) is a power integrated device (PIC) that uses IGBT as a switching device and contains a drive circuit and a protection circuit. The protection functions of IPM include overcurrent, short circuit, undervoltage, overvoltage and overheating, etc., and regenerative braking can also be realized. The inverter composed of IPM only needs to provide isolated PWM signals to each IGBT on the bridge arm. The integration of simple external circuit and control circuit greatly reduces the volume of the frequency converter. In addition, because the fault detection and protection circuit of the power switching device is close to the fault point, the expansion of the fault can be suppressed and the reliable operation of the device can be ensured.

Digitalization has greatly improved the controller's ability to process information, and many complex controls that are difficult to implement can be solved by using a microcomputer controller. A high-performance vector control system cannot be truly realized without the support of a microcomputer. In addition, microcomputer control technology adds many functions to the AC speed control system, especially the fault diagnosis technology has been fully realized.

The application of microcomputer control technology and large-scale integrated circuit improves the reliability of the AC speed control system, the diversity and flexibility of operation and setting, and reduces the cost and volume of the frequency converter speed control device. Practice shows that the performance of the microprocessor used in the speed control device will directly affect the performance of the device.

【Invention content】：

The purpose of the invention is to overcome the shortcomings of the existing speed regulation system and provide a frequency conversion speed regulation control system for an induction motor based on a single-chip microcomputer.

The invention adopts a high-performance microprocessor, which can simplify the structure of the device, improve the function of the device, realize complex and effective control strategies and improve the reliability of the control device. The digital signal controller dsPIC30F4011 of U.S. MicrochipTechnology company is the special-purpose chip of motor control, embedded DSP core, has quite fast data processing ability and abundant input and output equipment and interface circuit, so the present invention selects it to form control as core control device circuit. In the main circuit, the intelligent power module (IPM) IRAMSIOUP60A[40] of IR Company is used as the inverter switching device, and the frequency conversion speed regulation control system of the asynchronous motor is constructed.

Technical scheme of the present invention:

The frequency conversion speed regulation control system for induction motors based on single-chip microcomputers provided by the present invention is a typical AC-DC-AC voltage frequency conversion structure. The entire control system takes the dsPIC30F4011 chip as the core, including the main circuit, auxiliary power circuit, control part, and overcurrent protection. Circuit, speed detection circuit and other peripheral circuits, the specific composition is as follows:

Main circuit: powered by 220V AC, through a single-phase bridge uncontrolled rectifier circuit and capacitor filtering, a smooth DC voltage is obtained for the IPM module and auxiliary power circuit;

IPM module: The inverter circuit is one of the most important parts of the frequency conversion control. Its main function is to convert the DC voltage (current) output by the DC intermediate circuit into the AC voltage (current) of the required frequency to supply power to the asynchronous motor. The inverter circuit consists of six switching devices, and the fast recovery diodes connected in parallel with the switching devices are used to deal with reactive current, which are called freewheeling diodes. The IGBT of the inverter part is located on the inverter bridge, and its input terminal is connected in parallel with the electrolytic capacitor to buffer fluctuations and interference. Considering the economical safety factor, it does not need to be too large. The intelligent module (IPM) IRAMSIOUP60A [40 ] produced by IR Company has a withstand voltage of 600V and a rated current of 10A. It is a transitional product to the fourth-generation device power integrated circuit (PIC), and is the product of the combination of microelectronics technology and power electronics technology. IPM has the following characteristics: (1) fast switching speed, small driving current, and simpler control and drive; (2) adopts isolation technology, more uniform heat dissipation, and more compact volume; (3) high integration, it integrates on-chip The drive circuit, protection circuit, and even optocoupler are eliminated, which greatly shortens the development time; (4) The built-in current sensor can detect overcurrent and short-circuit current efficiently and quickly, and can provide sufficient protection for power chips, greatly reducing the failure rate; (5) Rich protection functions, such as current protection, voltage protection, temperature protection, etc., realize signal processing, fault diagnosis, self-protection and other intelligent functions, which not only reduces the size and weight, but also improves the Reliability; (6) Due to the optimization of the wiring design of the internal power supply circuit and drive circuit of the device, problems such as surge voltage, gate oscillation, and interference caused by noise can be effectively controlled; (7) Very high The cost performance of IPM has gradually approached that of IGBT, and the switching power supply capacity, the reduction of drive power capacity, the saving of devices and the improvement of comprehensive performance after adopting IPM have made the cost performance of the inverter composed of IPM higher than that of IGBT. The inverter has good economy.

Control part: with dsPIC30F4011 chip as the core, plus phase current detection circuit, speed detection circuit, serial port communication circuit, buttons and fault protection circuit; dsPIC30F4011 chip outputs six PWM pulse signals to control the inverter part of the IPM module to obtain three-phase Controlled alternating current is supplied to the asynchronous motor;

The dsPIC30F4011 chip integrates a dedicated motor control module called MCPWM module. This setting greatly simplifies the control software and external hardware for generating PWM waveforms. Through programming, it can generate independent three-phase 6-way PWM with the same frequency and working mode. Waveform, and the RE port directly outputs 6 channels of PWM signals to the inverter, and the three-phase complementation does not overlap. We only need to define each register value to generate an ideal PWM signal. At the same time, in order to prevent the two power transistors on the same bridge arm from passing through and causing a short circuit, the generator can also set the dead zone interlock time through programming.

Fault protection circuit: The fault signal after fault synthesis is sent to the control part. If any fault occurs, the control part will turn off the PWM pulse signal.

Current detection circuit: A small power resistor is connected in series on the DC bus, and the current signal is converted into a voltage signal through the power resistor, and then the signal is amplified by the operational amplifier and sent to the control part; overcurrent causes the power driver to be One of the leading causes of burnout and damage. When the main circuit is performing current detection, once the current overcurrent of the main circuit is detected, the control signal output should be blocked immediately, and the control part should be notified to close the PWM and alarm.

Speed detection circuit: It is realized by the tachometer generator that comes with the motor.

Rectification circuits are generally divided into controllable rectification and uncontrolled rectification, among which controllable rectification is further divided into fully-controlled rectification and semi-controlled rectification. In the fully controlled rectification circuit, the rectifier devices are all composed of thyristors or other controllable devices, while the half-controlled rectification circuit is composed of diodes and thyristors; the uncontrolled rectification circuit is composed of rectifier diodes. The rectification part of the present invention uses rectifier diodes for single-phase uncontrollable bridge rectification, which can effectively suppress the harmonics caused by the change of the phase control angle in the controllable rectification, and can also improve the power factor of the speed regulating device.

The dsPIC30F4011 chip in the device needs +5V power supply, and the intelligent module IPM needs +15V power supply, so the auxiliary power supply is designed to meet this requirement. The VIPER12A chip produced by ST Company is selected, which can convert about 300V DC power into +15V DC power. Then use LM7805 to convert +15V to +5V power supply to supply to each chip.

Advantage and positive effect of the present invention:

The invention takes the 16-bit high-performance signal controller dsPIC30F4011 produced by Microchip Company as the control core, controls the excitation of the motor based on the vector, and performs speed regulation.

The digital signal controller dsPIC30F4011 of American Microchip Technology Company is a special chip for motor control, embedded with a DSP core, and has a fairly fast data processing capability and a wealth of input and output devices and interface circuits. The said DsPIC30F4011 integrates a dedicated motor control module called MCPWM module, which greatly simplifies the control software and external hardware for generating PWM waveforms, and can generate independent three-phase 6 PWM waveforms of 1 channel, and 6 channels of PWM signals are directly output from the RE port to the inverter, and the three-phase complementation does not overlap. Just define each register value to generate an ideal PWM signal. At the same time, in order to prevent the two power transistors on the same bridge arm from passing through and causing a short circuit, the generator can also set the dead zone interlock time through programming.

Using the intelligent power module (IPM) IRAMSIOUP60A of IR company as the inverter switch device, the frequency conversion speed regulation controller of the asynchronous motor is constructed, which has the following characteristics: (1) The switching speed is fast, the drive current is small, and the control drive is simpler; ( 2) Using isolation technology, the heat dissipation is more uniform and the volume is more compact; (3) High integration, it integrates drive circuits, protection circuits, and even optocouplers on the chip, which greatly shortens the development time; (4) Contains a current sensor , can detect over-current and short-circuit current efficiently and quickly, can provide sufficient protection for power chips, and greatly reduce the failure rate; (5) Rich protection functions, such as current protection, voltage protection, temperature protection, etc., realize the Multiple intelligent functions such as signal processing, fault diagnosis, and self-protection not only reduce the size and weight, but also improve reliability; (6) Due to the optimization of the wiring design of the internal power supply circuit and drive circuit , so problems such as surge voltage, gate oscillation, and noise-induced interference can be effectively controlled; (7) High cost performance, the price of IPM has gradually approached IGBT, and the switching power supply capacity and drive power after using IPM Factors such as the reduction of capacity, the saving of components and the improvement of comprehensive performance make the cost performance of the frequency converter composed of IPM higher than that of the frequency converter composed of IGBT, which has good economy.

[Description of drawings]:

Figure 1 shows the overall structure of the control system;

Figure 2 is a structural block diagram of dsPIS30F4011;

Fig. 3 is the internal structure and external connection diagram of the inverter circuit IPM;

Figure 4 is a circuit diagram of the rotational speed detection hardware.

Fig. 5 is a rectification circuit structural diagram;

Figure 6 shows the entire auxiliary power supply circuit built with VIPER12A;

Fig. 7 is a current sampling circuit;

Figure 8 is the current detection circuit.

【Detailed ways】:

Example 1:

The following is a further description of this design in conjunction with the accompanying drawings: The overall structure of the control system is shown in Figure 1. The main circuit is powered by 220V AC. After single-phase bridge uncontrolled rectification and capacitor filtering, a smooth DC voltage is supplied to the IPM module and auxiliary power supply. circuit use.

In the inverter circuit part, dsPIC30F4011 outputs six PWM pulse signals to control the IPM module, and obtains three-phase controllable alternating current to supply the asynchronous motor.

The control part is based on dsPIC30F4011 chip as the core, plus phase current detection circuit, speed detection circuit, serial port communication circuit, key and fault protection circuit.

The fault protection circuit sends the fault signal after fault synthesis to the control part, and if any fault occurs, the PWM will be closed.

The overcurrent detection circuit converts the current signal into a voltage signal through a resistor, and then amplifies the signal through an operational amplifier and sends it to the control chip.

The speed detection circuit is realized by the tachometer generator that comes with the motor.

Figure 2 is a block diagram of dsPIC30F4011. The dsPIC30F series CPU module adopts a 16-bit improved Harvard structure with an enhanced instruction set, including strong support for DSP. The CPU instruction width is 24 bits, and the PC width is 23 bits, which can address up to 24X4M bit program space. There are 16 16-bit working registers, each of which can be used as a data, address or address offset register. This series of digital signal controllers has a rich instruction set, including a variety of seeking methods, and most of them are single-cycle instructions, which greatly speed up the running speed of the single-chip microcomputer. Instructions are mainly divided into two categories: MCU type and DSP type. These two types of instructions can be organically assembled into the framework and executed in the same execution unit. It also supports C language compiler programming, easy to develop. The dsPIC30F series CPU has a large internal storage capacity, and the RAM can reach up to 64KB. The data space is addressable as 32K words or 64K bytes and is divided into two blocks: X and Y data memory. Each memory block has its own address generation unit (AGU). MCU class instructions can only be operated through the X memory AGU, which can access the entire memory space as a linear space. Certain DSP type instructions with double operands read both operands through the X and Y AGUs. Additionally, the upper 32KB of the data memory space can be mapped to an 8-bit Program Space Visibility Page (PSVPAG). DsPIC30F4011 integrates a dedicated motor control module - Motor Control Pulse Width Modulation (CPwM) module. This setting greatly simplifies the control software and external hardware that generate PWM waveforms. It can be programmed to generate independent motors with the same frequency and working mode. The three-phase 6-way PWM waveform, and the RE port directly outputs 6-way PWM signals to the inverter, and the three-phase complementation does not overlap. We only need to define each register value to generate an ideal PWM signal. At the same time, in order to prevent the two power transistors on the same bridge arm from passing through and causing a short circuit, the generator can also set the dead zone interlock time through programming.

As shown in Figure 3: The inverter circuit is one of the most important parts of the frequency conversion control. Its main function is to convert the DC voltage (current) output by the DC intermediate circuit into the AC voltage (current) of the required frequency to supply power to the asynchronous motor. The inverter part is composed of six switching devices, and the fast recovery diodes connected in parallel with the switching devices are used to deal with reactive current, which are called freewheeling diodes. The biggest difference between the voltage selection of the IGBT in the inverter part and the rectifier diode is that the input of the rectifier diode is directly connected to the power grid, and the power grid is vulnerable to external interference, so the selected safety factor is larger; while the IGBT is located on the inverter bridge, its input The terminal is connected in parallel with the electrolytic capacitor to buffer fluctuations and interference. Considering that the economic safety factor does not need to be too large, the rated voltage U of the IGBT can be selected according to formula (3):

U≥(U _DC ×1.15+150)×a

引起允许的尖峰电压；a是安全系数，一般取1.1。对单相交流220V输入电压，U_DC＝311V，这样得IGBT的额定电压U≥558V。额定电流值I_C，可按式(4)选择：In the formula, U _DC is the DC side voltage; 1.15 is the overvoltage coefficient; 150 is determined by

Cause the allowable peak voltage; a is the safety factor, generally 1.1. For single-phase AC 220V input voltage, U _DC = 311V, so the rated voltage of IGBT U≥558V. The rated current value I _C can be selected according to formula (4):

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; =</span>\frac{\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 1.5</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 1.4</span>}}{\mathrm{<span\; class="notranslate">\; 0.9</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; N</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Among them, 0.9 is the downward fluctuation coefficient of the grid voltage; 1.5 is the coefficient of 50% overload allowed to run for 1 minute, and 1.4 is the influence coefficient of temperature. Get I=2.5A from the nameplate of the motor, select the intelligent module (IPM) IRAMSIOUP60A [40 ] produced by IR Company, its withstand voltage value is 600V, and the rated current is IOA. It is a transitional product to the fourth-generation device power integrated circuit (PIC), and is the product of the combination of microelectronics technology and power electronics technology. It not only provides a certain power output capability, but also has logic, control, sensing, detection, protection and self-diagnosis functions.

Figure 3 is the internal structure and external connection diagram of the IPM module of the inverter circuit. It is driven by a single power supply +15V, and the PWM pulse sent by dsPIC30F4011 controls the opening and closing of the six IGBTN poles. P+ is the rectified DC input, and N- is the ground terminal. VDD is the operating voltage of the chip. The input square wave signal controls the on-off of the inverter bridge IGBT through the drive IC. When T/Itrip inputs high level, the internal drive will stop working, so as to protect the chip. The intelligent module (IPM) IRAMSIOUP60A [40 ] produced by IR Company selected for use has a withstand voltage of 600V and a rated current of IOA. It is a transitional product to the fourth-generation device power integrated circuit (PIC), and is the product of the combination of microelectronics technology and power electronics technology. It not only provides a certain power output capability, but also has logic, control, sensing, detection, protection and self-diagnosis functions. IPM has the following characteristics:

(1) The switching speed is fast, the drive current is small, and the control drive is simpler;

(2) The isolation technology is adopted, the heat dissipation is more uniform, and the volume is more compact;

(3) High integration, it integrates drive circuit, protection circuit, and even optocoupler on-chip, which greatly shortens the development time;

(4) It contains a current sensor, which can efficiently and quickly detect overcurrent and short circuit current, and can provide sufficient protection for power chips, greatly reducing the failure rate;

(5) Rich protection functions, such as current protection, voltage protection, temperature protection, etc., realize signal processing, fault diagnosis, self-protection and other intelligent functions, which not only reduces the size and weight, but also improves the reliability;

(6) Due to the optimization of the wiring design of the internal power supply circuit and drive circuit of the device, problems such as surge voltage, gate oscillation, and interference caused by noise can be effectively controlled;

(7) High cost performance. The price of IPM has gradually approached that of IGBT. After adopting IPM, the switching power supply capacity, the reduction of driving power capacity, the saving of devices, and the improvement of comprehensive performance make the inverter composed of IPM more cost-effective. It is already higher than the frequency converter composed of IGBT, and has good economy. The parameters of IRAMS10UP60A are shown in the table:

parameters describe maximum value unit Vbus Maximum DC bus voltage 450 V Vces Maximum IGBT turn-on voltage 600 V lo@Tc＝25℃ Mean square value of phase current 10 A Io@Tc＝100 Mean square value of phase current 4.5 A Ipk Maximum phase current peak value 15 A Fp Maximum PWM carrier frequency 20 KHz Pd Maximum power consumption per phase 10 W Rthj-c Thermal resistance per IGBT 4.5 ℃/W Viso insulation voltage 2000 Vrms Tc Working shell temperature -20-+100 ℃ Tj Working shell temperature -20-+150 ℃ T Mounting torque range 0.8-1.0 Nm

Shown in Fig. 4: Rotating speed detection hardware circuit. The motor itself has a tachometer generator. Every time the motor rotates, it will send 8 trigger pulses. The tachometer generator outputs 8 pulses. The speed can be obtained by calculating the time of the pulse. Each revolution of the motor, this circuit can shape the output pulse and output a standard square wave. Then send it into the chip to measure its speed. The voltage value is increased through the pull-up resistor, and then the high-frequency interference is filtered out through the two-stage low-pass filter, and the RC low-pass filter is selected here. Here, a hysteresis comparator composed of LM393 is used to convert the sine wave into a square wave. Since it is an OC gate output, it needs to be pulled up, and this signal can be sent to the chip port.

As shown in Figure 5: the rectification part in this design uses rectifier diodes for single-phase uncontrollable bridge rectification, which can effectively suppress the harmonics caused by the change of the phase control angle in the controllable rectification, and can also improve the regulation efficiency. The power factor of the speed system. It is a single-phase uncontrollable bridge circuit, where the selection of the rectifier diode is a key issue, and the withstand voltage is selected according to formula (1):

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; RPM</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; AC</span>}}<span\; class="notranslate">\; \&times;</span>\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 1.1</span>}\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Among them, U _AC is the power grid voltage. Considering its peak fluctuations, lightning strikes and other factors, the fluctuation coefficient is 1.1, and the safety factor a=2. When the AC power grid voltage is 220V, U _RPM = 684V, so the withstand voltage of the diode is taken The rating is 800V. The rated current of the rectifier diode is determined according to formula (2):

$\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; \&Greater\; Equal;</span>\mathrm{<span\; class="notranslate">\; 2</span>}\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; N</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

In the formula, _IN is the rated current value of the motor. According to the nameplate of the motor, I _N = 2A, I = 2.5A. The voltage and current limit of the rectifier module KBJ1508 is 800V, 15A, and the rectifier module KBJ1508 is selected according to the above calculation.

电容应满足RC＝(3-5)T/2的条件，C＝285-476Uf。故我们选择470uF/450V的滤波电容。The filter circuit is composed of a filter capacitor. This capacitor has a large enough capacity. Seen from the inverter to the DC power supply after full-wave rectification by the rectifier circuit, the internal resistance of the power supply is very small, which is similar to a constant voltage source and ensures the stability of the DC voltage. When the system is connected to 220 AC, the peak value of the rectified voltage is 311V. Considering the fluctuation range of the grid voltage ±10%, the withstand voltage of the capacitor should be greater than

The capacitance should meet the condition of RC=(3-5)T/2, C=285-476Uf. Therefore, we choose a filter capacitor of 470uF/450V.

As shown in Figure 6: dsPIC30F4011 in the system needs a +5V power supply, while the intelligent module IPM needs a +15V power supply, so we design an auxiliary power supply to meet this requirement. The VIPER12A chip produced by ST Company is selected here, which can convert about 300V DC power into +15V DC power, and then use LM7805 to convert +15V into +5V power supply to supply to each chip. The entire auxiliary power supply circuit is composed of VIPER12A. In this circuit, the voltage stabilizing element adopts LM7805, D9 adopts IN4148, D6 and D7 adopt STTH1L06U to meet the needs of high frequency and low consumption. L1 is a high frequency filter inductance. 500mA inductor. D9 and C43 are buffer circuits, and C47 is used to filter 15V DC. After normal operation, the chip is powered by the self-excited winding. The working process of the circuit is that the input DC voltage makes the chip start, the power MOSFET works, the DC enters S through the power MOSFET, and charges the inductor L1, and the voltage at both ends of the regulator tube is fed back to FB through D6 and D8. When the voltage at both ends of the regulator tube When it is greater than 0.23V, the overcurrent comparator will be triggered and the power MOSFET will be turned off. Then VIPER12A will be restarted and then shut down, so that the rectified DC power is converted into rectangular waves with different pulse widths, and a stable 15V DC voltage is output after being filtered by inductors and capacitors. 15V then passes through LM7805 to get 5V voltage, C48 filters the 5V voltage, and lights up the indicator light to show whether the auxiliary power supply is working normally.

As shown in Figure 7 is the current sampling circuit. Connect high-precision small resistance resistors to the ground terminals of U, V, and W to convert the current signal into a voltage signal, and then the voltage signal is amplified by the operational amplifier LM258 and sent to the CPU for processing. Through experiments and calculations, the parameters can be obtained as follows: R _o is 10KΩ, R ₂ is 100KΩ, R ₃ is 20KΩ, and the amplification factor is (R ₂ +R ₃ )/R ₃ =6.

As shown in Figure 8 is the current detection circuit. The current overcurrent detection is to string a small power resistor on the DC bus, convert the current signal into a voltage signal and send it to the voltage comparator. The voltage comparator usually outputs high level FLTA, and the output of the comparator is low level. Transistor 3904 will not act. When over-current occurs, the comparator outputs a high level, and T/ITRIP will get a high voltage, which will stop the inverter drive chip from working, and at the same time turn on the triode, and output a low level to the chip fault pin signal, CPU Generate overcurrent protection. The phase current I _S is converted into a voltage signal through the resistor R _1. The precision of this resistor must be relatively high. Here, a detection resistor with a precision of 0.5% and a resistance value of 0.06Ω is used, and the capacitor C ₁ uses 0.1uF (104) to filter it . R ₂ and R ₃ provide an overcurrent threshold by dividing the voltage of 5V. After experimental analysis, R ₂ is selected as 10KΩ, and R ₃ is 2KQ. When the detected voltage is greater than 0.18V, that is, when the current exceeds 3A, it is considered overcurrent. The comparator LM393 will output a low level, and the chip detects this signal to trigger the fault interrupt subroutine, turn off the PWM output, and at the same time, the PWM drive circuit will also be turned off. The current does not exceed 3A to operate normally.

Claims (1)

1. A kind of induction motor variable frequency speed regulation control system based on single-chip microcomputer, it is characterized in that, this system comprises main circuit, auxiliary power supply circuit, control part, current detection circuit, rotating speed detection circuit and other peripheral circuits, concrete composition is as follows: Main circuit: powered by 220V AC, through a single-phase bridge uncontrolled rectifier circuit and capacitor filtering, a smooth DC voltage is obtained for the IPM module and auxiliary power circuit; IPM module: one of the most important parts of the frequency conversion control of the inverter part, its main function is to convert the DC voltage output by the DC intermediate circuit into the AC voltage of the required frequency, and supply power to the asynchronous motor; Inverter part: It consists of six switching devices, and the fast recovery diode connected in parallel with the switching device is used to process reactive current, which is called a freewheeling diode; the IGBT in the inverter part is located on the inverter bridge, and its input terminal is connected in parallel with the electrolytic capacitor. Play the role of buffering fluctuations and disturbances, considering the economic safety factor does not need to be too large; Control part: with dsPIC30F4011 chip as the core, plus phase current detection circuit, speed detection circuit, serial port communication circuit, keys and fault protection circuit; the inverter circuit is outputted by dsPIC30F4011 six-way PWM pulse signal to control the IPM module, and the three-phase can be obtained The dsPIC30F4011 chip integrates a special motor control module called MCPWM module. This setting greatly simplifies the control software and external hardware that generate PWM waveforms. It can generate independent PWM waveforms with the same frequency and working mode through programming. The three-phase 6-way PWM waveform, and the RE port directly outputs 6-way PWM signals to the inverter circuit, and the three-phase complementation does not overlap; Fault protection circuit: send the fault signal after fault synthesis to the control part, and if any fault occurs, the control part will close the PWM; Current detection circuit: A power resistor is connected in series on the DC bus, and the current signal is converted into a voltage signal through the power resistor, and then the signal is amplified by the operational amplifier and sent to the control part; when the current detection is performed in the main circuit, once detected If the current to the main circuit is overcurrent, the control signal output should be blocked immediately, and the control part should be notified to close the PWM and alarm; Speed detection circuit: It is realized by the tachometer generator that comes with the motor.

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