CN112421994A - Current loop reconstruction method for controlling four-phase switch reluctance motor - Google Patents

Current loop reconstruction method for controlling four-phase switch reluctance motor Download PDF

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CN112421994A
CN112421994A CN202011071906.4A CN202011071906A CN112421994A CN 112421994 A CN112421994 A CN 112421994A CN 202011071906 A CN202011071906 A CN 202011071906A CN 112421994 A CN112421994 A CN 112421994A
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current
phase
theta
loop
reluctance motor
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CN112421994B (en
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孙建忠
杜呼和
贺锡之
白凤仙
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Dalian University of Technology
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
    • H02P6/06—Arrangements for speed regulation of a single motor wherein the motor speed is measured and compared with a given physical value so as to adjust the motor speed
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P23/00—Arrangements or methods for the control of AC motors characterised by a control method other than vector control
    • H02P23/0004—Control strategies in general, e.g. linear type, e.g. P, PI, PID, using robust control
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P25/00—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details
    • H02P25/02—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details characterised by the kind of motor
    • H02P25/08—Reluctance motors
    • H02P25/0805—Reluctance motors whereby the speed is regulated by measuring the motor speed and comparing it with a given physical value
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
    • H02P6/14—Electronic commutators
    • H02P6/16—Circuit arrangements for detecting position
    • H02P6/17—Circuit arrangements for detecting position and for generating speed information

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Control Of Electric Motors In General (AREA)

Abstract

A current loop reconstruction method for controlling a four-phase switch reluctance motor belongs to the technical field of switch reluctance motor control. The switched reluctance driving system is a rotating speed and current double closed-loop control system, and the outer loop is rotating speed loop control; the inner loop is a current loop control, and generally, four independent current sampling loops are needed for the four-phase switched reluctance motor, which increases the cost and volume of the control circuit. For this reason, in some applications with strict requirements on volume and cost, four phases are selected to share one sampling loop to detect current. When four phases share one current sampling loop, in order to enable the four-phase switched reluctance motor to accurately feed back each phase of current, a shape function of a current waveform is constructed, and a current distribution function of each phase is obtained through the shape function of each phase of current. The collected current is then multiplied by the distribution function of each phase. Thus, from a feedback current loop, a four-phase feedback current is reconstructed. And obtaining the actual accurate current of each phase of the motor. The purpose of accurate and stable operation of the motor is achieved.

Description

Current loop reconstruction method for controlling four-phase switch reluctance motor
Technical Field
The invention belongs to the technical field of switched reluctance motor control, and relates to a current loop reconstruction method of a switched reluctance motor control system.
Background
The Switched Reluctance Motor (SRM) has the advantages of simple and firm structure, wide speed regulation range, high efficiency, good fault tolerance, and the like. Particularly, the four-phase switch reluctance motor adopts a proper power converter main circuit, and can enable the energizing voltage of each phase winding to be equal to the power supply voltage under the condition of using less power devices. In addition, the four-phase switched reluctance motor has small low-speed torque pulsation and stable starting, so the four-phase switched reluctance motor is favored in the fields of household appliances and the like.
The motor speed regulation system generally adopts rotating speed and current double closed-loop control, the current loop control needs an accurate feedback value of each phase of current, each phase generally needs an independent current sampling, and the four-phase switched reluctance motor needs four independent current sampling loops, so that the cost and the volume of a control circuit are increased. For this reason, in some applications with strict requirements on volume and cost, a current detection scheme in which four phases share one sampling loop is selected.
The four phases share one current sampling loop, which brings great error to the detection of each phase current. Particularly, when the motor runs at a low speed, the current of the winding rises quickly, and is conducted alternately in a single phase and a double phase, and meanwhile, the influence of trailing current is also caused, so that a current sampling value mixes multi-phase current together, the current of each phase is difficult to distinguish, and great trouble is brought to current loop control of a four-phase switch reluctance motor. And when the switched reluctance motor runs at a low speed, torque pulsation exists, and when the current control error is large, large torque pulsation can be generated, so that the stable running of the switched reluctance motor is influenced. Therefore, a control method for accurately feeding back each phase current and enabling the motor to stably operate when only one current sampling loop exists in the four-phase switched reluctance motor needs to be invented.
Disclosure of Invention
The invention aims to solve the technical problem that when the four-phase switched reluctance motor only has one current sampling loop, the invention provides the control method capable of accurately feeding back each phase of current, thereby achieving the purpose of accurate and stable operation of the motor.
The technical scheme of the invention is as follows:
a current loop reconstruction method for controlling a four-phase switch reluctance motor is disclosed, wherein a switch reluctance driving system for completing the control method comprises a microcontroller 1, a four-phase switch reluctance motor 2, a power converter 3, a PWM driving unit 4, a current sampling resistor 5 and a position detection unit 6; the main circuit of the power converter 3 is a modified four-phase asymmetric half-bridge structure: the phase A and the phase C share one upper bridge arm, the phase B and the phase D share one upper bridge arm, and the lower bridge arms of the phase A, B, C, D are independent respectively; the switched reluctance driving system is a rotating speed and current double closed-loop control system, the outer ring is rotating speed loop control, the actual rotating speed is calculated through signals of the position detection unit 6, and the difference between the reference rotating speed and the actual rotating speed is obtained through a rotating speed regulator; the inner loop is controlled by a current loop, and the four-phase motor needs to control four-phase current respectively and needs four current loops. Therefore, the current sampling resistor 5 is measured to obtain the total current, and the actual current of each phase of the motor is obtained by a current reconstruction method; and then, making a difference between the reference current and each phase of actual current, obtaining four paths of PWM signals through a current loop PI regulating module, and generating a driving signal for controlling the power converter 3 under the combined action of the PWM signals and the on-off signals, controlling the on-off of the power switch and driving the motor to rotate. The specific method of the current reconstruction method is as follows:
(1) determining the mechanical angular width theta of each phase current from opening to rising to the current limiting value through the low-speed phase current waveform when the four-phase switched reluctance motor stably runs1And a mechanical angular width θ for the duration of the subsequent flow shutoff2. Constructed according to phase current waveformShape function f of A-phase currentA(theta) at thetaonTo theta1、θ1To thetaoffPiecewise function, and shape function f of other phase currentsB(θ)、fC(theta) and fD(theta) at thetaonTo thetaoffThe piecewise function of (2).
(2) Summing the shape function of the A-phase current and the shape functions of the other phase currents to obtain F (theta) ═ FA(θ)+fB(θ)+fC(θ)+fD(theta), where theta epsilon (theta)on,θoff). The shape function of the A-phase current is compared with the summation function to obtain the current distribution function of the A-phase
Figure BDA0002715198570000031
Where θ ∈ (θ)on,θoff) Obtaining accurate distribution functions of other phase currents in the same way; and multiplying the current value acquired by the sampling resistor by the distribution function of each phase of current to obtain an accurate actual current value of each phase.
(3) And comparing the obtained actual current values of the four phases serving as four current feedback values with current reference values respectively, and performing PI (proportional integral) regulation on the current difference values to form four current loops.
The four-phase 8/6 switched reluctance motor is taken as an example for further explanation:
(1) constructing shape function of low speed current waveform
The rotor pole pitch angle of the four-phase 8/6 switched reluctance motor is 60 degrees, and the misalignment position is used as the reference of the rotor position angle, namely theta is 0; the rotor position angle of the alignment position, θ, is 30. As can be seen from the current waveform, each phase of current rises from the on state to the current limiting value, and the angular width of the position is theta12.5 DEG, the continuous width of the subsequent flow is cut off is theta 25 deg. is equal to. As the phase A and the phase C share one upper bridge arm, and the phase B and the phase D share one upper bridge arm, in order to avoid the situation that the phase A and the phase C or the phase B and the phase D generate current at the same time, the turn-on angle position theta is setonOff angular position θ of 0off25, so that the output torque does not change.
The actual current shape function of each phase is constructed by phase current waveform, and A phase conduction is adopted belowThe description will be given by taking the general period as an example. ThetaonIndicating the position of the opening angle, thetaoffIndicating the off angular position. By a piecewise function fA(theta) represents the actual current of the A phase, fB(theta) represents the actual current of the B phase, fC(theta) represents the actual current of the C phase, fD(θ) represents the D-phase actual current.
Figure BDA0002715198570000032
Figure BDA0002715198570000041
fC(θ)＝0 θ∈(θon,θoff) (3)
Figure BDA0002715198570000042
Where h is the limit of the current.
(2) Constructing a current distribution function ISF
As can be seen from the above equations (1), (2), (3) and (4), since there is only one sampling resistor, the feedback current is equal to
F(θ)＝fA(θ)+fB(θ)+fC(θ)+fD(θ) θ∈(θon,θoff) (5)
The joint type (1) and (5) can obtain the distribution function of the A-phase current
Figure BDA0002715198570000043
θ∈(θon,θoff) (6)
The current distribution functions of the B phase, the C phase and the D phase are obtained by the same method as the A phase. And processing the acquired current value by a four-phase current distribution function to obtain four current feedback values. Thus, from a feedback current loop, a four-phase feedback current is reconstructed.
(3) Four current loops are constructed
And comparing the four obtained current feedback values with current reference values respectively, and performing PI regulation on the current difference value to form four current loops.
The invention has the following remarkable effects:
1) only one current detection is needed, and other devices such as external current detection and the like are not needed.
2) On the premise of controlling the circuit cost, the problem that the data of each opposite feed current is inaccurate when only one current sampling loop is provided is solved.
3) The control method is easy to realize, has obvious effect, and can realize the low-cost and high-performance operation of the four-phase switched reluctance motor.
Drawings
Fig. 1 is a hardware configuration diagram of a switched reluctance motor control system.
Fig. 2 is a low-speed current waveform of a four-phase switched reluctance motor.
Fig. 3 is a diagram of an 8/6 four-phase switched reluctance motor embodiment.
In the figure: 1 is a microcontroller; 2 is a four-phase switch reluctance motor; 3 is a power converter; 4 is a PWM driving unit; 5 is a current sampling resistor; and 6, a position detection unit.
Detailed Description
In the embodiment of the invention shown in fig. 1, the microcontroller 1 is STM32F030C6, and the power converter 3 adopts a modified four-phase asymmetric half-bridge structure. The switched reluctance motor 2 is a four-phase 8/6-pole switched reluctance motor with the rated rotating speed of 13000r/min, is supplied by a power converter 3, detects the sum of currents flowing through four-phase windings by a current sampling resistor 5, inputs the sum to an ADC0 port of the microcontroller 1, and a position detection unit 6 consists of a rotor position measuring fluted disc, two groove type Hall switching devices and corresponding circuits. The microcontroller 1 determines the current position of the rotor by entering a capture interrupt to obtain the state of the two hall switches.
The switched reluctance motor adopts the double closed-loop control of rotating speed and current. The actual rotating speed of the motor and the current position of the rotor are calculated by inputting a captured position signal through the position sensor, the difference is made between the reference rotating speed and the actual rotating speed, and the reference current is obtained through the rotating speed loop PI adjusting module. The sum of the four-phase currents obtained by the sampling resistor is transmitted to an ADC port of the microcontroller 1, and the microcontroller 1 converts the analog signal into a digital signal. And then, the current distribution function values of the four phases are obtained according to the current position of the rotor, and the digital signals and the current distribution function values of each phase are multiplied to obtain the digital signals of the actual current of the four phases. And then, making a difference between the reference current and each phase of actual current, obtaining four paths of PWM signals through a current loop PI regulating module, and generating a driving signal for controlling the power converter 3 under the combined action of the PWM signals and the turn-on and turn-off signals to control the on and off of a main switching element of the power converter so as to drive the motor to rotate.
The conditions of the rotating speed overshoot and the rotating speed fluctuation under different given rotating speeds are respectively shown in the table 1 and the table 2. Therefore, the dynamic performance and the operation stability of the motor can be effectively improved by adopting the control strategy. When the control strategy is not adopted, the switched reluctance motor has large rotating speed overshoot and can not stably run at low speed.
TABLE 1 comparison of rotational speed overshoot under two control strategies
Given rotational speed 40r/min 100r/min 200r/min 500r/min
No current loop reconstruction 300％ 200％ 120％ 100％
The invention 25％ 18％ 15％ 10％
(Note: overshoot is the ratio of instantaneous maximum speed deviation to target speed during start-up)
TABLE 2 comparison of speed fluctuations during steady operation under two control strategies
Given rotational speed 40r/min 100r/min 200r/min 500r/min
No current loop reconstruction 250％ 150％ 120％ 80％
The invention 15％ 12％ 8％ 5％
(Note: the ratio of the absolute value of the deviation of the rotational speed at steady operation to the target rotational speed: the fluctuation of the rotational speed)
The reconstruction strategy of the current loop of the switched reluctance motor solves the problems that the four-phase current detection is difficult to accurately detect and control when the four-phase switched reluctance motor has only one current sampling loop, can effectively improve the low-speed running stability of the four-phase switched reluctance motor, saves the cost of a control circuit and reduces the volume of the control circuit.

Claims (2)

1. A current loop reconstruction method for controlling a four-phase switch reluctance motor is characterized in that a switch reluctance driving system for completing the control method comprises a microcontroller (1), the four-phase switch reluctance motor (2), a power converter (3), a PWM driving unit (4), a current sampling resistor (5) and a position detection unit (6); the main circuit of the power converter (3) is a modified four-phase asymmetric half-bridge structure which comprises the following components: the phase A and the phase C share one upper bridge arm, the phase B and the phase D share one upper bridge arm, and the lower bridge arms of the phase A, B, C, D are independent respectively; the switched reluctance driving system is a rotating speed and current double closed-loop control system, the outer ring is rotating speed loop control, the actual rotating speed is calculated through signals of the position detection unit (6), and the difference between the reference rotating speed and the actual rotating speed is obtained through a rotating speed regulator; the inner loop is controlled by a current loop, four-phase motors need to control four-phase currents respectively, and four current loops are needed; therefore, the current sampling resistor (5) is measured to obtain the total current, and the actual current of each phase of the motor is obtained by a current reconstruction method; and then, making a difference between the reference current and each phase of actual current, obtaining four paths of PWM signals through a current loop PI regulating module, and generating a driving signal for controlling the power converter (3) under the combined action of the PWM signals and the on-off signals to control the on-off of the power switch and drive the motor to rotate.
2. The current loop reconstruction method for controlling the four-phase switched reluctance motor according to claim 1, wherein the current reconstruction method is specifically as follows:
(1) determining the mechanical angular width theta of each phase current from opening to rising to the current limiting value through the low-speed phase current waveform when the four-phase switched reluctance motor stably runs1And a mechanical angular width θ for the duration of the subsequent flow shutoff2(ii) a Constructing shape function f of A-phase current according to phase current waveformA(theta) at thetaonTo theta1、θ1To thetaoffPiecewise function, and shape function f of other phase currentsB(θ)、fC(theta) and fD(theta) at thetaonTo thetaoffThe piecewise function of (2);
(2) summing the shape function of the A-phase current and the shape functions of the other phase currents to obtain F (theta) ═ FA(θ)+fB(θ)+fC(θ)+fD(theta), where theta epsilon (theta)on,θoff) (ii) a The shape function of the A-phase current is compared with the summation function to obtain the current distribution function of the A-phase
Figure FDA0002715198560000011
Where θ ∈ (θ)on,θoff) Obtaining accurate distribution functions of other phase currents in the same way; the current value acquired by the sampling resistor is multiplied by the distribution function of each phase of current to obtain the accurate actual current value of each phase;
(3) and comparing the obtained actual current values of the four phases serving as four current feedback values with current reference values respectively, and performing PI (proportional integral) regulation on the current difference values to form four current loops.
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