Wide-range current high-precision sampling system of permanent magnet synchronous motor

Abstract

The invention relates to a wide-range current high-precision sampling system of a permanent magnet synchronous motor, and belongs to the field of electric high-stability control. Comprising a summation module, a PI control module, an SVPWM module, an inverter circuit module, a motor, a sampling resistor, a Sigma-delta modulator, a Hall current sensor, a fully differential amplifier and a current threshold judgment module. The method of combining the two sampling modes can obtain high-precision current sampling data in a rated working state and different working states of a large load. And then, through setting a threshold value, judging and calling different sampling data to carry out feedback calculation of current vector control. According to the method, low-current high-precision sampling of the motor in a wide-current sampling circuit based on a Hall current sensor is realized at the same time. In a motor control system with a large difference value between a peak working current and a rated working current, the stability of the motor control system can be effectively improved.

Description

Technical Field

[0001] The invention belongs to the field of electric high-stability control and relates to a permanent magnet synchronous motor wide-range current high-precision sampling system. Background Art

[0002] Vector control technology achieves high-performance control of AC motors through field-oriented control. Vector control systems provide higher control flexibility. By accurately controlling the motor current, fine control of the motor can be achieved. Therefore, accurate acquisition of current plays a key role in the control system.

[0003] Common current sampling methods include Hall current sensors, resistor sampling, and current transformers. Among them, Hall current sensors have the advantages of wide measurement frequency, good linearity, fast response, and simple use. Resistor sampling calculates the current by measuring the voltage drop across the resistor, which is suitable for occasions where the measured current is small. Current transformers have a large measurement range, but are large in size and expensive, and are not suitable for miniaturized, low-cost motor controllers. In many applications of motor control, there is a large difference between the rated current and the peak current of the motor. In order to meet the wide current range sampling, a large-range Hall current sensor is often used, but the sampling accuracy under the rated working state cannot be taken into account. Summary of the invention

[0004] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art and propose a permanent magnet synchronous motor wide range current high-precision sampling system, which solves the current sampling accuracy problem when the difference between the rated current and the peak current of the motor is large, and ensures that both small current accurate current sampling and wide range current sampling can be achieved.

[0005] The solution of the present invention is:

[0006] A permanent magnet synchronous motor wide range current high precision sampling system, comprising a summing module, a PI control module, an SVPWM module, an inverter circuit module, a motor, a sampling resistor, a Sigma-delta modulator, a Hall current sensor, a fully differential amplifier and a current threshold judgment module;

[0007] Summing module: receives the current command signal from the outside; receives the current feedback value from the current threshold judgment module; sums the current command signal and the current feedback value to generate a current difference signal, and sends the current difference signal to the PI control module;

[0008] PI control module: receives the current difference signal from the summing module, performs PI processing on the current difference signal, generates a voltage signal, and sends the voltage signal to the SVPWM module;

[0009] SVPWM module: receives the voltage signal from the PI control module, performs coordinate transformation and sector transformation, generates PWM signal, and sends the PWM signal to the inverter circuit module;

[0010] Inverter circuit module: receives the PWM signal from the SVPWM module, performs on-off processing of the inverter circuit according to the PWM signal, and generates a voltage signal to send to the motor;

[0011] Motor: Receives the voltage signal from the inverter circuit module and generates two feedback current signals; sends one feedback current signal to the sampling resistor; sends the other feedback current signal to the Hall current sensor;

[0012] Sampling resistor: receives a feedback current signal from the motor, performs voltage conversion on the feedback current signal, generates a voltage signal, and sends the voltage signal to the Sigma-delta modulator;

[0013] Sigma-delta modulator: receives the voltage signal from the sampling resistor, amplifies and filters the voltage signal, generates a 0 / 1 signal, and sends the 0 / 1 signal to the current threshold judgment module;

[0014] Hall current sensor module: receives another feedback current signal from the motor, converts the feedback current into a voltage, generates a voltage signal, and sends the voltage signal to the fully differential amplifier module;

[0015] Fully differential amplifier module: receives the voltage signal from the Hall current sensor module, converts the voltage signal from single-ended to differential, generates a voltage differential signal, and sends the voltage differential signal to the current threshold judgment module;

[0016] Current threshold judgment module: receives the 0 / 1 signal from the sigma-delta modulator; receives the voltage differential signal from the fully differential amplifier module; demodulates the 0 / 1 signal and converts it into a first current signal; samples the voltage differential signal and converts it into a second current signal; and selects the first current signal or the second current signal as the current feedback value and sends it to the summing module.

[0017] In the above-mentioned permanent magnet synchronous motor wide range current high precision sampling system, the sampling resistor is a four-pin resistor with 0.1% accuracy; the resistance value of the sampling resistor is 0.01Ω.

[0018] In the above-mentioned permanent magnet synchronous motor wide range current high-precision sampling system, the Sigma-delta modulator is a second-order modulator; when the sampling resistor sends the voltage signal to the Sigma-delta modulator, the input voltage signal is digitized into a 1-bit output stream as the input of the Sigma-Delta modulator stage through the converter.

[0019] In the above-mentioned permanent magnet synchronous motor wide range current high-precision sampling system, the fully differential amplifier is a unit gain fully differential amplifier, and the input voltage signal is converted into a differential signal through the fully differential amplifier.

[0020] In the above-mentioned permanent magnet synchronous motor wide range current high-precision sampling system, the fully differential amplifier input voltage is 3V, the bias voltage is 1.5V, and the fully differential amplifier outputs a differential voltage signal of 0 to 3V.

[0021] In the above-mentioned permanent magnet synchronous motor wide range current high-precision sampling system, the resolution of the Sigma-delta modulator is 16 bits.

[0022] In the above-mentioned permanent magnet synchronous motor wide range current high-precision sampling system, the 0 / 1 signal output by the Sigma-delta modulator is a bit stream signal; the bit stream signal is demodulated by the SDFM to convert the bit stream signal into a first current signal.

[0023] In the above-mentioned permanent magnet synchronous motor wide range current high-precision sampling system, the first current signal obtained by SDFM demodulation is a coarse sampling signal, a threshold comparison is performed once in one PWM cycle, and the corresponding current signal is selected as the closed-loop current feedback value in real time.

[0024] In the above-mentioned permanent magnet synchronous motor wide range current high-precision sampling system, the method in which the current threshold judgment module selects the first current signal or the second current signal as the current feedback value is:

[0025] Set a threshold; compare the second current signal with the threshold in real time, and when the second current signal is greater than or equal to the set threshold, select the second current signal as the feedback current value; when the second current signal is less than the set threshold, select the first current signal as the feedback current value.

[0026] In the above-mentioned permanent magnet synchronous motor wide range current high-precision sampling system, the voltage differential signal output by the fully differential amplifier is differentially sampled by a 16-bit ADC and converted into a current value.

[0027] The beneficial effects of the present invention compared with the prior art are:

[0028] (1) The present invention adopts a method combining two sampling modes to obtain high-precision current sampling data under rated working conditions and high-load working conditions;

[0029] (2) The present invention sets a threshold value, selects the first current signal or the second current signal as the current feedback value, and feeds it back to the summing module for summing with the current command signal to generate a current difference signal, thereby continuously improving the sampling accuracy;

[0030] (3) The present invention realizes the simultaneous high-precision sampling of small currents in a wide current sampling circuit based on a Hall current sensor for a motor; in a motor control system where the difference between the peak operating current and the rated operating current is large, the stability of the motor control system can be effectively improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the wide range current high precision sampling system of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the embodiments.

[0033] The present invention provides a permanent magnet synchronous motor wide range current high-precision sampling system. The method combining two sampling modes can obtain high-precision current sampling data under rated working state and heavy load working state. Then, by setting the threshold, it is judged to call different sampling data for feedback calculation of current vector control. The method completes the motor to simultaneously realize small current high-precision sampling in a wide current sampling circuit based on a Hall current sensor. In a motor control system with a large difference between the peak working current and the rated working current, the stability of the motor control system can be effectively improved.

[0034] Permanent magnet synchronous motor wide range current high precision sampling system, such as Figure 1 As shown, it specifically includes a summing module, a PI control module, an SVPWM module, an inverter circuit module, a motor, a sampling resistor, a Sigma-delta modulator, a Hall current sensor, a fully differential amplifier and a current threshold judgment module.

[0035] Summing module: receives the current command signal from the outside; receives the current feedback value from the current threshold judgment module; sums the current command signal and the current feedback value to generate a current difference signal, and sends the current difference signal to the PI control module.

[0036] PI control module: receives the current difference signal from the summing module, performs PI processing on the current difference signal, generates a voltage signal, and sends the voltage signal to the SVPWM module.

[0037] SVPWM module: receives the voltage signal from the PI control module, performs coordinate transformation and sector transformation, generates PWM signal, and sends the PWM signal to the inverter circuit module.

[0038] Inverter circuit module: receives the PWM signal from the SVPWM module, performs on-off processing of the inverter circuit according to the PWM signal, and generates a voltage signal to be sent to the motor.

[0039] Motor: Receives the voltage signal from the inverter circuit module and generates two feedback current signals; sends one feedback current signal to the sampling resistor; and sends the other feedback current signal to the Hall current sensor.

[0040] Sampling resistor: Receives 1 feedback current signal from the motor, performs voltage conversion on the feedback current signal, generates a voltage signal, and sends the voltage signal to the Sigma-delta modulator. The sampling resistor is a four-pin resistor with a precision of 0.1%; the resistance of the sampling resistor is 0.01Ω.

[0041] Sigma-delta modulator: receives the voltage signal from the sampling resistor, amplifies and filters the voltage signal, generates a 0 / 1 signal, and sends the 0 / 1 signal to the current threshold judgment module. The Sigma-delta modulator is a second-order modulator; when the sampling resistor sends the voltage signal to the Sigma-delta modulator, the input voltage signal is digitized into a 1-bit output stream as the input of the Sigma-Delta modulator stage through the converter. The resolution of the Sigma-delta modulator is 16 bits.

[0042] Hall current sensor module: receives another feedback current signal from the motor, converts the feedback current into a voltage, generates a voltage signal, and sends the voltage signal to the fully differential amplifier module.

[0043] Fully differential amplifier module: receives the voltage signal from the Hall current sensor module, converts the voltage signal from single-ended to differential, generates a voltage differential signal, and sends the voltage differential signal to the current threshold judgment module.

[0044] In the present invention, the fully differential amplifier is a unit gain fully differential amplifier, and the input voltage signal is converted into a differential signal by the fully differential amplifier. The input voltage of the fully differential amplifier is 3V, the bias voltage is 1.5V, and the differential voltage signal of 0 to 3V is output by the fully differential amplifier. The voltage differential signal output by the fully differential amplifier is differentially sampled by a 16-bit ADC and converted into a current value.

[0045] Current threshold judgment module: receives the 0 / 1 signal from the sigma-delta modulator; receives the voltage differential signal from the fully differential amplifier module; demodulates the 0 / 1 signal and converts it into a first current signal; samples the voltage differential signal and converts it into a second current signal; and selects the first current signal or the second current signal as the current feedback value and sends it to the summing module.

[0046] The 0 / 1 signal output by the Sigma-Delta modulator is a bit stream signal; the bit stream signal is demodulated by the SDFM to convert the bit stream signal into a first current signal.

[0047] The first current signal obtained by SDFM demodulation is a coarse sampling signal, and a threshold comparison is performed once in one PWM cycle to select the corresponding current signal as the closed-loop current feedback value in real time.

[0048] The method for the current threshold judgment module to select the first current signal or the second current signal as the current feedback value is: setting a threshold; comparing the second current signal with the threshold in real time, and when the second current signal is greater than or equal to the set threshold, selecting the second current signal as the feedback current value; when the second current signal is less than the set threshold, selecting the first current signal as the feedback current value.

[0049] The present invention solves the current sampling accuracy problem when the difference between the rated current and the peak current of the motor is large. It ensures that both small current accurate current sampling and wide range current sampling can be achieved. The combination of the two adoption methods can achieve high stability control of the control system.

[0050] In vector control, PWM controls the inverter circuit bridge arm to turn on and off and output the corresponding voltage to the motor end. The Hall current sensor is connected in series between the inverter circuit output end and the motor to measure the phase current. The Hall current sensor converts the current into a voltage value and outputs it.

[0051] The voltage signal is buffered and isolated by a unity gain op amp and then connected to a differential amplifier. The differential amplifier performs differential input of the output voltage signal to the DSP with higher sampling accuracy.

[0052] In addition to the Hall sensor, there is also a precision current sampling circuit at the inverter circuit and motor end. The resistor selected is a high-precision square resistor. The sampling resistor has a resistance of 0.01Ω and a very small output voltage. The voltage value corresponding to the current is directly output through the resistor.

[0053] To improve sampling accuracy, the resistor voltage is input into the Sigma-Delta modulator, whose input stage is a fully differential amplifier that feeds the switched capacitor input of the second-order Sigma-Delta modulator stage that digitizes the input signal into a 1-bit output stream. The isolated data output of the converter provides a digital 1 and 0 bit stream synchronized with the internally generated clock. The average time of this serial bit stream output is proportional to the analog input voltage. The voltage signal is converted into a Delta-Sigma modulated signal and input into the DSP.

[0054] The present invention is based on the current signals collected by the two channels, takes the coarse and fine wide-range sampling circuits as the judgment basis, detects the current during the interruption, uses the fine channel current data as the feedback of the current loop when it is less than the threshold, and uses the coarse channel current data as the feedback of the current loop when it exceeds the threshold.

[0055] The present invention adopts a method combining two sampling modes to obtain high-precision current sampling data under different working conditions of rated working state and heavy load.

[0056] The present invention sets a threshold value, selects the first current signal or the second current signal as the current feedback value, and feeds it back to a summing module for summing with a current command signal to generate a current difference signal, thereby continuously improving sampling accuracy.

[0057] The present invention realizes high-precision sampling of small currents in a wide current sampling circuit based on a Hall current sensor for a motor at the same time; in a motor control system with a large difference between the peak operating current and the rated operating current, the stability of the motor control system can be effectively improved.

[0058] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A permanent magnet synchronous motor wide range current high precision sampling system, characterized by: It includes a summing module, a PI control module, a SVPWM module, an inverter circuit module, a motor, a sampling resistor, a Sigma-delta modulator, a Hall current sensor, a fully differential amplifier and a current threshold judgment module; Summing module: receives the current command signal from the outside; Receive the current feedback value transmitted by the current threshold judgment module; The current command signal and the current feedback value are summed to generate a current difference signal, and the current difference signal is sent to the PI control module; PI control module: receives the current difference signal from the summing module, performs PI processing on the current difference signal, generates a voltage signal, and sends the voltage signal to the SVPWM module; SVPWM module: receives the voltage signal from the PI control module, performs coordinate transformation and sector transformation, generates PWM signal, and sends the PWM signal to the inverter circuit module; Inverter circuit module: receives the PWM signal from the SVPWM module, performs on-off processing of the inverter circuit according to the PWM signal, and generates a voltage signal to be sent to the motor; Motor: Receives the voltage signal from the inverter circuit module and generates two feedback current signals; sends one feedback current signal to the sampling resistor; sends the other feedback current signal to the Hall current sensor; Sampling resistor: receives a feedback current signal from the motor, performs voltage conversion on the feedback current signal, generates a voltage signal, and sends the voltage signal to the Sigma-delta modulator; Sigma-delta modulator: receives the voltage signal from the sampling resistor, amplifies and filters the voltage signal, generates a 0 / 1 signal, and sends the 0 / 1 signal to the current threshold judgment module; Hall current sensor module: receives another feedback current signal from the motor, converts the feedback current into a voltage, generates a voltage signal, and sends the voltage signal to the fully differential amplifier module; Fully differential amplifier module: receives the voltage signal from the Hall current sensor module, converts the voltage signal from single-ended to differential, generates a voltage differential signal, and sends the voltage differential signal to the current threshold judgment module; Current threshold judgment module: receives the 0 / 1 signal from the sigma-delta modulator; receives the voltage differential signal from the fully differential amplifier module; demodulates the 0 / 1 signal and converts it into a first current signal; Sampling the voltage differential signal and converting it into a second current signal; The first current signal or the second current signal is selected as the current feedback value and sent to the summing module.

2. A permanent magnet synchronous motor wide range current high precision sampling system according to claim 1, characterized in that: The sampling resistor is a four-pin resistor with a precision of 0.1%; the resistance value of the sampling resistor is 0.01Ω.

3. A permanent magnet synchronous motor wide range current high precision sampling system according to claim 1, characterized in that: The Sigma-Delta modulator is a second-order modulator; when the sampling resistor sends a voltage signal to the Sigma-Delta modulator, the input voltage signal is digitized into a 1-bit output stream as the input of the Sigma-Delta modulator stage through a converter.

4. A permanent magnet synchronous motor wide range current high precision sampling system according to claim 1, characterized in that: The fully differential amplifier is a unit gain fully differential amplifier, and the input voltage signal is converted into a differential signal through the fully differential amplifier.

5. A permanent magnet synchronous motor wide range current high precision sampling system according to claim 4, characterized in that: The fully differential amplifier has an input voltage of 3V and a bias voltage of 1.5V, and outputs a differential voltage signal of 0 to 3V through the fully differential amplifier.

6. A permanent magnet synchronous motor wide range current high precision sampling system according to claim 1, characterized in that: The resolution of the sigma-delta modulator is 16 bits.

7. A permanent magnet synchronous motor wide range current high precision sampling system according to claim 1, characterized in that: The 0 / 1 signal output by the Sigma-delta modulator is a bit stream signal; the bit stream signal is demodulated by the SDFM to convert the bit stream signal into a first current signal.

8. A permanent magnet synchronous motor wide range current high precision sampling system according to claim 7, characterized in that: The first current signal obtained by the SDFM demodulation is a coarse sampling signal, and a threshold comparison is performed once in one PWM cycle to determine and select the corresponding current signal as the closed-loop current feedback value in real time.

9. A permanent magnet synchronous motor wide range current high precision sampling system according to claim 8, characterized in that: The method for the current threshold judgment module to select the first current signal or the second current signal as the current feedback value is: Set thresholds; The second current signal is compared with the threshold in real time. When the second current signal is greater than or equal to the set threshold, the second current signal is selected as the feedback current value; when the second current signal is less than the set threshold, the first current signal is selected as the feedback current value.

10. A permanent magnet synchronous motor wide range current high precision sampling system according to claim 1, characterized in that: The voltage differential signal output by the fully differential amplifier is differentially sampled by a 16-bit ADC and converted into a current value.

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