High-rotation-speed switched reluctance motor winding commutation method based on detection of phase current peak pulse

Abstract

The invention provides a high-rotation-speed switched reluctance motor winding commutation method based on phase current peak pulse detection, and relates to the field of switched reluctance motors, and the method comprises the steps: firstly, employing a current sensor to measure the current of each phase winding of a switched reluctance motor, and carrying out the filtering and amplification processing; a current peak detection circuit is used to detect the current peak of each phase winding and generate a pulse signal, an MCU carries out level change capture on the current peak pulse signal and triggers interruption, and a rotor position estimation algorithm in the MCU calculates the next turn-off and turn-on opportunity of the motor winding so as to realize the commutation operation of the winding. According to the method, high-speed detection is performed on the peak value of the motor winding current by using a hardware scheme, the rotor position estimation speed of the switched reluctance motor at a high rotating speed is ensured, and commutation operation is performed according to the fixed mathematical relationship between the motor rotor position when the current peak value occurs and the motor rotor position when the winding is turned off and turned on. And the accumulative error of rotor position estimation is eliminated.

Description

Technical Field

[0001] The invention relates to the field of motor control, and in particular to a position sensorless commutation method for a switched reluctance motor. Background Art

[0002] The switched reluctance motor is a new type of speed-regulating motor. Its structure is simpler than any other motor. The rotor of the switched reluctance motor has no slip rings, windings, and permanent magnets. It has many advantages such as simple structure, low cost, high reliability, high efficiency, and low temperature rise. It is very suitable for new energy vehicles, wind power generation, aviation, aerospace military industries, and occasions with high speed and high temperature harsh environments.

[0003] The switched reluctance motor drive system requires the position signal provided by the rotor position sensor to excite or shut down the phase winding, and the motor speed is calculated from the position signal to achieve motor speed control. The introduction of traditional photoelectric, electromagnetic and magnetic sensitive position sensors not only increases the cost and complexity of the switched reluctance motor, but also reduces the reliability of the switched reluctance motor in high temperature and high speed environments.

[0004] The position-free control technology of the switched reluctance motor mainly realizes the commutation operation of the motor without a position sensor. The existing technology mainly revolves around flux observation and current gradient detection methods. The above methods all use complex software algorithms to observe the inductance and phase current of the motor to obtain the motor rotor position. These methods are suitable for low-speed applications and cannot be applied to high-speed applications due to software calculation speed issues. Summary of the invention

[0005] The object of the present invention is to provide a position sensorless winding commutation method for a switched reluctance motor at high speed, which uses a hardware circuit to detect the peak pulse of the motor phase current to achieve high-speed identification of the current peak, and uses a simple software algorithm to locate and calculate the rotor position according to the current peak pulse, thereby realizing the rotor position estimation and commutation operation of the high-speed switched reluctance motor.

[0006] A method for detecting winding commutation of a high-speed switched reluctance motor based on phase current peak pulses comprises the following steps:

[0007] S1, using a current sensor to measure the phase current of each winding of the switched reluctance motor in real time;

[0008] S2, filtering and amplifying the measured current signal using a filter circuit constructed by an operational amplifier;

[0009] S3, performing peak detection on the filtered current signal through a peak pulse detection circuit, and outputting a pulse signal of a fixed level;

[0010] S4, MCU circuit uses IO port to capture the high and low level changes of pulse signal and trigger MCU interrupt;

[0011] S5. In the MCU interrupt function, the rotor position estimation algorithm calculates the motor commutation period T according to the interrupt trigger time difference between the two previous detections. c , and according to T c The current motor rotor position is used to calculate the shutdown time t of the motor phase winding. off and the next winding conduction time t on .

[0012] Preferably, in step S1, the current sensor is composed of a plurality of Hall current sensors, and the number of the Hall current sensors is consistent with the number of motor windings;

[0013] Preferably, in step S3, the peak pulse detection circuit further includes a voltage comparator and an average amplitude reference follower circuit, the average amplitude reference follower circuit is used to follow the filtered current signal and generate a reference voltage signal, the reference voltage signal and the filtered current signal are compared by the voltage comparator, when the reference voltage signal is less than the filtered current signal, the comparator outputs a high level, otherwise it outputs a low level;

[0014] Preferably, the rotor position estimation algorithm described in step S5 calculates the timing of winding disconnection and connection according to the following mathematical relationship:

[0015]

[0016] where t peak is the moment when the current peak pulse triggers the interruption; θ peak is the electrical angle position of the motor rotor when the current peak pulse is generated, θ peak is the angle at which the leading edge of the rotor is aligned with the trailing edge of the stator; θ off is the rotor angle when the current winding is turned off, t off The rotor rotates to θ off The time, θ on is the rotor angle when the next winding is turned on, t on The rotor rotates to θ on The time of θ peak is a fixed constant, θ on and θ off In PWM control mode, it is a constant. In other control modes, it is adjusted by on and θ off The angle size can realize motor speed regulation.

[0017] The calculation formula of motor speed ω is as follows:

[0018] ω=180° / T c / N, where N is the number of rotor poles of the switched reluctance motor.

[0019] Due to the adoption of the above technical solution, the present invention provides a high-speed switched reluctance motor winding commutation method based on detecting phase current peak pulses. The method has a simple principle and high commutation accuracy. The method first uses a hardware current peak pulse detection circuit to identify the peak value of each phase winding current of the switched reluctance motor, and realizes high-speed identification of the current peak through a hardware solution, thereby ensuring the rotor position estimation speed of the switched motor at high speed. In the rotor position estimation, the method uses the current peak value and the rotor specific position θ peak , Winding opening position θ on and the off position θ off The corresponding relationship is used to perform shutdown delay and opening delay operations, θ peak This method also plays an error correction role, which can help eliminate the estimated cumulative error and improve the real-time performance of software operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a main flow chart of the winding commutation method based on detecting the phase current peak pulse of the present invention;

[0021] Figure 2 The operational amplifier filter circuit of the present invention;

[0022] Figure 3 This is a schematic diagram of a current peak detection circuit of the present invention;

[0023] Figure 4 The current peak pulse waveform output by the current peak detection circuit of the present invention;

[0024] Figure 5 Schematic diagram of commutation logic of the switched reluctance motor of the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] Combination Figure 1 , as shown in the figure, a high-speed switched reluctance motor winding commutation method based on detecting phase current peak pulses provided by the present invention is divided into 5 steps, wherein steps S1 to S3 are completed by hardware circuits, and steps S4 to S5 are implemented by software algorithms; Figure 2 The hardware schematic diagram of the filter circuit corresponding to step S2; Figure 3 is the hardware schematic diagram of the current peak pulse detection circuit corresponding to step S3, Figure 4is the output waveform diagram corresponding to step S3; Figure 5 It is a schematic diagram of the switching timing corresponding to step S5.

[0027] Figure 1 The 5 steps of the process shown are as follows:

[0028] Step S1, using a Hall current sensor to measure the phase current of each phase winding of the switched reluctance motor. In this embodiment, a Hall current sensor is used for each phase winding. The Hall current sensor can not only measure the current data but also electrically isolate the motor power supply from the subsequent circuit, effectively reducing the electromagnetic interference caused by the motor.

[0029] Step S2, using a filter circuit to filter the current signal measured by the Hall current sensor, see Figure 2 As shown, U1 is an operational amplifier for amplifying the current signal; the resistor R4 and the capacitor C1 form an RC low-pass filter, IA is the current signal before filtering, and Ia is the current signal after filtering; in the embodiment of the present invention, a total of multiple Figure 2 In the filter circuit shown, each filter circuit corresponds to a Hall current sensor.

[0030] Step S3, using a current peak detection circuit to perform peak detection on the current signal filtered in step S2, see Figure 3 As shown, U2A is a voltage comparator. Resistors R5, R6, R7 and capacitor C3 form a current average amplitude reference follower circuit, which can track the average amplitude of current Ia and generate a reference voltage vref. The in-phase input terminal of U2A is directly connected to vref through resistor R6. R6 and R7 are used to generate hysteresis to ensure that there is no false switching during the conversion process. When the current Ia is in an upward trend, Figure 3 The circuit shown outputs a high level. When Ia is in a downward trend, Figure 3 The circuit shown outputs a low level. The moment when the pulse changes from high level to low level is the peak current moment. The waveform is shown in Figure 4 .

[0031] In step S4, the MCU circuit captures the pulse signal output in step S3, that is, identifies it according to the high and low level change process of the pulse. In this embodiment, the rising edge of the pulse signal triggers the MCU interrupt, and this step is implemented by the MCU interrupt system.

[0032] Step S5: The position estimation algorithm in the MCU interrupt function calculates the motor commutation period T according to the interval between two detected pulse changes. c , and calculate the motor speed ω according to the following formula:

[0033] ω=180° / T c / N, where N is the number of rotor poles of the switched reluctance motor;

[0034] Combination Figure 5 , the current winding shut-off and next phase winding opening time are calculated by the following formula,

[0036]

[0037] where t peak is the moment when the current peak pulse triggers the interruption; θ peak is the electrical angle position of the motor rotor when the current peak pulse is generated, θ peak is the angle at which the leading edge of the rotor is aligned with the trailing edge of the stator, θ off is the winding cut-off angle, θ on is the winding opening angle, t off is the current winding turn-off delay, t on Delay for the next winding to be turned on; θ on and θ off In PWM control mode, it is a constant. In other control modes, it is adjusted by on and θ off The angle size can realize motor speed regulation.

[0038] In step S5, the MCU off and t on By performing delay control and shutting down and turning on the corresponding winding, the commutation operation of the switched reluctance motor winding can be realized.

[0039] The above embodiments are only used to illustrate the design ideas and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. Therefore, any equivalent changes or modifications made based on the principles and design ideas disclosed by the present invention are within the protection scope of the present invention.

Claims

1. A high-speed switched reluctance motor winding commutation method based on detecting phase current peak pulses, characterized in that: The method comprises the following steps: S1, using a current sensor to measure the phase current of each winding of the switched reluctance motor in real time; S2, using an operational amplifier filter circuit to filter and amplify the measured current signal; S3, performing peak detection on the filtered current signal through a peak pulse detection circuit, and outputting a pulse signal of a fixed level; S4, the MCU circuit uses the IO port to capture the high and low level changes of the pulse signal output in step S3, and triggers the MCU interrupt; S5. In the MCU interrupt function, the rotor position estimation algorithm calculates the motor commutation period T according to the interrupt trigger time difference between the two previous detections. c , and according to T c The current motor rotor position is used to calculate the shutdown time t of the motor phase winding. off and the next winding conduction time t on .

2. A high speed switched reluctance motor winding commutation method based on detecting phase current peak pulses according to claim 1, characterized in that: The current sensor is composed of a plurality of Hall current sensors, and the number of the Hall current sensors is consistent with the number of motor windings.

3. The high speed switched reluctance motor winding commutation method based on detecting phase current peak pulse according to claim 1, characterized in that: The peak pulse detection circuit also includes a voltage comparator and an average amplitude reference follower circuit. The average amplitude reference follower circuit is used to follow the filtered current signal and generate a reference voltage signal. The reference voltage signal is compared with the filtered current signal through a voltage comparator. When the reference voltage signal is smaller than the filtered current signal, the comparator outputs a high level, otherwise it outputs a low level.

4. The high-speed switched reluctance motor winding commutation method based on detecting phase current peak pulses according to claim 1, characterized in that: The rotor position estimation algorithm calculates the motor commutation period T according to the interrupt trigger time difference between the two previous detections. c , and according to T c Calculate the motor speed ω. The motor speed calculation formula is as follows: ω=180° / T c / N, where N is the number of rotor poles of the switched reluctance motor; The rotor position estimation algorithm uses the following mathematical formula to calculate the current motor winding shut-off time t off and the next winding conduction time t on , where t peak is the moment when the current peak pulse triggers the interruption; θ peak is the electrical angle position of the motor rotor when the current peak pulse is generated, θ peak is the angle at which the leading edge of the rotor is aligned with the trailing edge of the stator; θ off is the rotor angle when the current winding is turned off, t off The rotor rotates to θ off The time, θ on is the rotor angle when the next winding is turned on, t on The rotor rotates to θ on The time of θ peak is a fixed constant, θ on and θ off In PWM control mode, it is a constant. In other control modes, it is adjusted by on and θ off The angle size can realize motor speed regulation.

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