CN116979857A - PWM-DITC control method for switched reluctance motor based on novel multi-level power converter - Google Patents

Abstract

The invention discloses a PWM-DITC control method of a switched reluctance motor based on a new multi-level power converter. It belongs to the technical field of switched reluctance motors and is used to solve the problem of traditional direct instantaneous torque control (DITC) due to bus voltage limitations and The problem of large torque ripple caused by always maintaining the same voltage level between hysteresis limits. Utilizing the high-voltage rapid excitation and rapid demagnetization functions of the new multi-level power converter and redefining the commutation area, the conduction area is divided into a commutation area and a single-phase conduction area based on the turn-off angle, and the commutation area is The proposed PWM‑DITC control method is adopted in the phase area, and different control methods are formulated for the latest turn-on phase and the upcoming turn-off phase in the commutation area, thereby realizing the hysteresis-type DITC control method and small torque under large torque deviation. The PWM equivalent method under deviation, the optimized control method provides the appropriate phase voltage for the winding at a fixed frequency, effectively suppressing the torque pulsation of the switched reluctance motor.

Description

A PWM-DITC control of switched reluctance motor based on a new multi-level power converter Preparation method

Technical field

The present invention relates to the field of motor control technology, and in particular to a PWM-DITC control method of a switched reluctance motor based on a new multi-level power converter.

Background technique

Switched Reluctance Motor (SRM) has been widely used in electric vehicles, aviation, mining transportation, etc. due to its simple structure, low cost, large starting torque, flexible control method, and good adaptability to harsh working environments. field. However, due to the doubly salient pole structure of the reluctance motor, its output torque is a nonlinear function of the stator current and rotor position, which increases the torque ripple and limits the development of SRM. Therefore, how to suppress the torque ripple of SRM has become a core issue that scholars need to solve.

Domestic and foreign scholars have done a lot of research on the motor body design, drive topology, and control methods to address the problem of large torque ripple in switched reluctance motors. At present, the more common and effective control method to suppress torque ripple is to use the instantaneous torque as the control object and adjust the conduction status of the power device according to the deviation of the torque. According to different control methods, instantaneous torque control can be divided into indirect instantaneous torque control (IITC) and direct instantaneous torque control (DITC). IITC mainly obtains accurate reference current based on the reference signal, and controls the three-phase current to follow the reference current through the current controller, while DITC directly uses the instantaneous torque as the controlled object and generates it based on the error between the reference torque and the instantaneous output torque. The switching signal does not require precise control of the current waveform, which simplifies the structure of the control system and the difficulty of implementing the control algorithm. Currently, the hysteresis type DITC is commonly used, which always maintains the same voltage level within the hysteresis limit and cannot provide appropriate phase voltage to the winding.

As the speed of the switched reluctance motor increases, its back electromotive force increases, shortening its excitation and demagnetization time, and limited by the bus voltage of the asymmetric half-bridge power converter, it is difficult for the SRM to establish the desired phase current, resulting in current and The torque decreases and the total torque cannot follow the desired torque adjustment within the hysteresis loop. Chinese invention patent "A four-level power circuit of switched reluctance motor and method of use", the patent number is CN201711257094.0, the publication date is 2018.03.16, which discloses a new type of SRM multi-level power converter, which can Rapid excitation and rapid demagnetization of the winding are achieved, and each phase bridge arm can be independently switched among four level states, and the control method can be flexibly formulated. The present invention aims to propose a PWM-DITC control method based on the multi-level power converter to effectively suppress the torque ripple of the SRM.

Contents of the invention

The technical problem to be solved by the present invention is to provide a PWM-DITC control method for a switched reluctance motor based on a new multi-level power converter in view of the above-mentioned deficiencies in the prior art. The present invention aims to use the advantages of high-voltage rapid excitation and high-voltage rapid demagnetization of a new multi-level power converter to overcome the bus voltage limitation of an asymmetric half-bridge power converter and propose a PWM-DITC that can switch voltage levels within the hysteresis limit. The control method suppresses the torque ripple of SRM.

A switched reluctance motor PWM-DITC control system based on a new multi-level power converter, which is characterized in that the system includes: a speed PI controller (1), a torque calculation unit (2), and a boost capacitor voltage control controller (3), PWM-DITC torque controller (4), switch table (5), new multi-level power converter (6), switched reluctance motor (7), current sensor (8), position sensor ( 9), voltage sensor (10), speed calculation unit (11), among which:

The current sensor (8) is used to detect the current value i _K of the motor winding;

The position sensor (9) is used to detect the rotor position θ of the motor and provide it to other modules;

The voltage sensor (10) is used to detect the voltage U _C2 of the boost capacitor C2 in the new multi-level power converter (6);

The speed calculation unit (11) is used to calculate the actual speed of the motor;

The speed PI controller (1) generates a reference torque based on the deviation between the reference speed and the actual speed;

The torque calculation unit (2) receives the current value of each phase winding detected by the current sensor and the motor rotor position detected by the position sensor, and obtains the actual output torque of the motor through the look-up table method;

The boost capacitor voltage controller (3) receives the voltage U _C2 detected by the voltage sensor, and calculates the average voltage V _av through the average voltage calculation unit. The deviation between V _av and the reference voltage V _ref of the boost capacitor C2 is obtained through the PI regulator. Boost capacitor voltage control angle θ _h ;

The PWM-DITC torque controller (4) is the core of the control system. According to the opening angle θ _on , the closing angle θ _off , the torque deviation ΔT, the currently obtained rotor position θ and the boost capacitor voltage control angle θ _h , it is given by The PWM-DITC torque controller outputs the working status of the motor at the next moment. The calculation formula of the torque deviation is:

ΔT＝T _ref -T _est

Among them, T _ref is the reference torque and T _est is the instantaneous output torque. The switching table (5) converts the working state of the motor at the next moment into the switching state of the new multi-level power converter (6); the power conversion is controlled according to the switching state. By turning on or off the switching tubes of each phase bridge arm of the device, direct instantaneous torque control of the switched reluctance motor (7) is achieved by applying different voltages to the phase windings.

A PWM-DITC control method for switched reluctance motors based on a new multi-level power converter, including the following steps:

Step 1: Obtain the electromagnetic characteristic data of the SRM through experimental measurement or finite element simulation based on the design parameters of the switched reluctance motor body, and form a lookup table of torque-angle-current through modeling;

Step 2, taking the three-phase switched reluctance motor as an example, divide the area between the turn-on angles of two adjacent phases, that is, one-third of the electrical cycle, into commutation areas and single-phase with the turn-off angle as the boundary. The conduction area, taking A and B commutation as an example, the commutation area is from the B-phase opening angle to the A-related breaking angle, and the single-phase conduction area is from the A-related breaking angle to the C-phase opening angle;

Step 3. The new multi-level power converter has four working states. Each phase bridge arm can achieve high-voltage excitation, normal voltage excitation, freewheeling and high-voltage demagnetization states. Taking the A-phase bridge arm as an example, they correspond to "+2"","+1","0" and "-2" four level states; when the switch tubes S _A1 , S _A2 and S _A3 are all turned on, phase A works in the "+2" state, which is recorded as StateA＝+ 2; When switches S _A2 and S _A3 are turned on and S _A1 is turned off, phase A works in the "+1" state, recorded as StateA = +1; when S _A1 and S _A2 are turned off, S _A3 is turned on. Phase A works in the "0" state, recorded as StateA=0; when the switching tubes S _A1 , S _A2 , and S _A3 are all turned off and there is current in the winding, phase A works in the "-2" state at this time, recorded as StateA=0. For StateA=-2, the working states of other phase bridge arms are deduced in the same way;

Step 4. The latest turn-on phase and the upcoming turn-off phase in the commutation area have different working requirements, and different control methods are designed for them. Taking A and B commutation as an example, the conduction rules and methods are: 1) For torque The deviation ΔT is sampled, and the sampled torque deviation is maintained for one period Ts. The sampled torque deviation is recorded as ΔT ₁ ; 2) Compare ΔT ₁ with the hysteresis loop width. If ΔT ₁ is within the hysteresis loop, use PWM equivalent method, if ΔT ₁ is outside the hysteresis loop, use the hysteresis-type DITC method; 3) Compare ΔT ₁ with the triangular carrier intersection, if ΔT ₁ is greater than the triangular carrier, the high state is output, otherwise, the low state is output; The details applied to the commutation area are:

Step 4.1, in the phase about to turn off in the commutation area, when the torque error ΔT ₁ after sampling is greater than _TL , it can be seen that the output torque capacity of the phase about to turn off is insufficient, the system needs to increase the torque, and output the "+1" state , entering the excitation state to meet the system requirements; when ΔT ₁ is less than -T _H , it can be known that the output torque is too large, and it should be demagnetized as much as possible to output the "-2"state; when ΔT ₁ ∈ (0, T _L ), it can be known that the output torque Insufficient, use the "+1" state and "+0" state switching method to increase to provide the required torque; when ΔT ₁ is greater than the triangular carrier, the winding applies the "+1" state, when ΔT ₁ is less than the triangular carrier, the winding applies "0"state; when ΔT ₁ ∈ (-T _H , 0), it can be seen that the output torque has a slight excess, and the torque is reduced by switching between the "0" state and the "-2" state. When ΔT ₁ is greater than When the triangular carrier wave is applied, zero voltage is applied to the winding. When ΔT ₁ is less than the triangular carrier wave, the winding is applied to the "-2" state and is rapidly discharged, thereby rapidly reducing the torque output;

Step 4.2, in the latest opening phase of the commutation area, when the torque error ΔT ₁ after sampling is greater than 0, it can be seen that the output torque capacity should increase, and the "+n" state is output, so that the output torque increases; when ΔT ₁ is less than - T _L , it can be seen that the output torque is too large, the system should reduce the torque output, and the winding works in the "0"state; when ΔT ₁ ∈ (-T _L , 0), the torque is also increased, in the excitation state and Switch between "0" states to quickly establish current; among them, "+n" represents the "+2" state or the "+1" state, and its state logic depends on the location of the control angle θ _h . θ _h should be between [θ _{on_b} , θ _{on_c} ]. When phase B is in [θ _{on_b} , θ _h ], "+n" is the "+2"state; when phase B is in [θ _h , θ _{on_c} ], "+n" is the "+1" state, that is:

Step 4.3, in the single-phase conduction area, the B phase alone provides the required torque. The torque error is adjusted through the internal hysteresis loop composed of the B phase hysteresis threshold - T _L and T _L , and the demagnetization state is set at the hysteresis threshold. -T _H and -T _L constitute an external hysteresis loop.

Compared with the existing technology, the present invention has the following beneficial effects: using a new multi-level power converter with high-voltage rapid excitation and high-voltage rapid demagnetization functions, the excitation and demagnetization speed of the winding can be accelerated, and combined with the PWM-DITC control method, It can provide appropriate phase voltage to the winding, improve the torque tracking capability of the DITC method, and effectively suppress the torque ripple of SRM.

Description of the drawings

Figure 1 is a structural block diagram of a switched reluctance motor PWM-DITC control system based on a new multi-level power converter according to the present invention.

Figure 2 is the SRM torque nonlinear model of the present invention.

Figure 3 is a region dividing method of the new PWM-DITC control method of the present invention.

Figure 4 is a new multi-level power converter according to the present invention.

Figure 5 shows the four level states of the new multi-level power converter according to the present invention.

Figure 6 is the PWM-DITC control method based on the new multi-level power converter according to the present invention. Figure 6(a) is the control method of the phase that is about to be turned off in the commutation area; Figure 6(b) is the commutation area. The latest control method of the open phase; Figure 6(c) Control method of the single-phase conduction area.

Detailed ways

The present invention provides a PWM-DITC control method for a switched reluctance motor based on a new multi-level power converter. The present invention will be further described below with reference to the accompanying drawings.

Figure 1 is a structural block diagram of a switched reluctance motor PWM-DITC control system based on a new multi-level power converter according to the present invention. Includes: speed PI controller (1), torque calculation unit (2), boost capacitor voltage controller (3), PWM-DITC torque controller (4), switch table (5), new multi-level power Converter (6), switched reluctance motor (7), current sensor (8), position sensor (9), voltage sensor (10), speed calculation unit (11); among them, the current sensor (8) is used to detect the motor The current value i _K of the winding; the position sensor (9) is used to detect the rotor position θ of the motor and is provided to other modules; the voltage sensor (10) is used to detect the voltage of the boost capacitor C2 in the new multi-level power converter (6) Voltage U _C2 ; the speed calculation unit (11) is used to calculate the actual speed of the motor; the speed PI controller (1) generates a reference torque based on the deviation between the reference speed and the actual speed; the torque calculation unit (2) receives the current sensor detection The current value of each phase winding and the motor rotor position detected by the position sensor are used to obtain the actual output torque of the motor through the look-up table method; the boost capacitor voltage controller (3) receives the voltage U _C2 detected by the voltage sensor and calculates it through the average voltage The unit calculates the average voltage V _av , and passes the deviation between V _av and the reference voltage V _ref of the boost capacitor C2 through the PI regulator to obtain the boost capacitor voltage control angle θ _h ; the PWM-DITC torque controller (4) is the control system Core, based on the opening angle θ _on , the closing angle θ _off , the torque deviation ΔT, the currently obtained rotor position θ and the boost capacitor voltage control angle θ _h , the PWM-DITC torque controller outputs the motor's work at the next moment. state, where the calculation formula of torque deviation is:

ΔT＝T _ref -T _est

Among them, T _ref is the reference torque and T _est is the instantaneous output torque; the switching table (5) converts the working state of the motor at the next moment into the switching state of the new multi-level power converter (6); the power conversion is controlled according to the switching state. By turning on or off the switching tubes of each phase bridge arm of the device, direct instantaneous torque control of the switched reluctance motor (7) is achieved by applying different voltages to the phase windings.

Figure 2 is the SRM torque nonlinear model of the present invention. Through experimental measurement or finite element simulation based on the design parameters of the switched reluctance motor body, the electromagnetic characteristic data of the SRM is obtained, and a lookup table of torque-angle-current is formed through modeling.

Figure 3 shows the area division method of the new PWM-DITC control method of the present invention. Taking a three-phase switched reluctance motor as an example, the area between the turn-on angles of two adjacent phases, that is, one third of the electrical cycle, is divided into a commutation area and a single-phase conduction area with the off angle as the boundary. , taking A and B commutation as an example, the commutation area is from the B-phase opening angle to the A-related breaking angle, and the single-phase conduction area is from the A-related breaking angle to the C-phase opening angle.

Figure 4 shows the new multi-level power converter according to the present invention. The new multi-level power converter has four working states. Each phase bridge arm can realize high-voltage excitation, normal voltage excitation, freewheeling and high-voltage demagnetization states respectively. As shown in Figure 5 , taking the A-phase bridge arm as an example, corresponding to There are four level states of "+2", "+1", "0" and "-2"; as shown in Figure 5(a), when the switch tubes S _A1 , S _A2 and S _A3 are all turned on, phase A works In the "+2" state, it is recorded as StateA=+2; as shown in Figure 5(b), when the switching tubes S _A2 and S _A3 are turned on and S _A1 is turned off, phase A works in the "+1" state, recorded as is StateA=+1; as shown in Figure 5(c), when S _A1 and S _A2 are turned off, S _A3 is turned on, and phase A works in the "0" state, which is recorded as StateA=0; Figure 5(d ), when the switches S _A1 , S _A2 , and S _A3 are all turned off and there is current in the winding, phase A is working in the "-2" state, which is recorded as StateA = -2. The operation of other phase bridge arms The status can be deduced in this way.

Figure 6 is a PWM-DITC control method based on a new multi-level power converter according to the present invention. Figure 6(a) is a control method for the phase that is about to be turned off in the commutation area. When the torque error after sampling When ΔT ₁ is greater than _TL , it can be seen that the output torque capacity of the phase about to be turned off is insufficient, and the system needs to increase the torque, output the "+1" state, and enter the excitation state to meet the system requirements; when ΔT ₁ is less than -T _H , it can be known that the output torque If it is too large, it should be demagnetized as much as possible and output the "-2"state; when ΔT ₁ ∈ (0, T _L ), it can be seen that the output torque is insufficient, and the "+1" state and the "+0" state are used to increase it to provide the required rotation. moment; when ΔT ₁ is greater than the triangular carrier, the winding applies the "+1"state; when ΔT ₁ is less than the triangular carrier, the winding applies the "0"state; when ΔT ₁ ∈ (-T _H , 0), it can be seen that the output torque is For small overshoot, the torque is reduced by switching between "0" state and "-2" state. When ΔT ₁ is greater than the triangular carrier, zero voltage is applied to the winding. When ΔT ₁ is less than the triangular carrier, "-2" is applied to the winding. ” state, rapid discharge causes the torque output to decrease rapidly; Figure 6(b) is the control method of the latest open phase in the commutation area. When the torque error ΔT ₁ after sampling is greater than 0, it can be seen that the output torque capability should increases, the output "+n" state makes the output torque increase; when ΔT ₁ is less than -T _L , it can be seen that the output torque is too large, the system should reduce the torque output, and the winding works in the "0"state; when ΔT ₁ When ∈ (-T _L , 0), the torque is also increased, the work switches between the excitation state and the "0" state, and the current is quickly established, where "+n" represents the "+2" state or "+1" state, its state logic depends on the position of the control angle θ _h . θ _h should be between [θ _{on_b} , θ _{on_c} ]. When phase B is in [θ _{on_b} , θ _h ], "+n" is the "+2"state; when phase B is in [θ _h , θ _{on_c} ], "+n" is the "+1" state, that is:

Figure 6(c) In the single-phase conduction area, the B phase alone provides the required torque, and the torque error is adjusted through the internal hysteresis loop composed of the B-phase hysteresis threshold - T _L and T _L , and the demagnetization state is set at hysteresis The external hysteresis loop formed by the loop threshold -T _H and -T _L.

The above are only preferred implementation examples of the present invention and do not limit the present invention in any way. Any changes made to the above implementation examples based on the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims (3)

1. A switched reluctance motor PWM-DITC control system based on a new multi-level power converter, characterized in that the system includes: speed PI controller (1), torque calculation unit (2), boost capacitor Voltage controller (3), PWM-DITC torque controller (4), switch table (5), new multi-level power converter (6), switched reluctance motor (7), current sensor (8), position Sensor (9), voltage sensor (10), speed calculation unit (11); The current sensor (8) is used to detect the current value i _K of the motor winding; The position sensor (9) is used to detect the rotor position θ of the motor and provide it to other modules; The voltage sensor (10) is used to detect the voltage U _C2 of the boost capacitor C2 in the new multi-level power converter (6); The speed calculation unit (11) is used to calculate the actual speed of the motor; The speed PI controller (1) generates a reference torque based on the deviation between the reference speed and the actual speed; The torque calculation unit (2) receives the current value of each phase winding detected by the current sensor and the motor rotor position detected by the position sensor, and obtains the actual output torque of the motor through the look-up table method; The boost capacitor voltage controller (3) receives the voltage U _C2 detected by the voltage sensor, and calculates the average voltage V _av through the average voltage calculation unit. The deviation between V _av and the reference voltage V _ref of the boost capacitor C2 is obtained through the PI regulator. Boost capacitor voltage control angle θ _h ; The PWM-DITC torque controller (4) is the core of the control system. According to the opening angle θ _on , the closing angle θ _off , the torque deviation ΔT, the currently obtained rotor position θ and the boost capacitor voltage control angle θ _h , it is given by The PWM-DITC torque controller outputs the working status of the motor at the next moment. The calculation formula of the torque deviation is: ΔT＝T _ref -T _est Among them, T _ref is the reference torque and T _est is the instantaneous output torque; the switching table (5) converts the working state of the motor at the next moment into the switching state of the new multi-level power converter (6); the power conversion is controlled according to the switching state. By turning on or off the switching tubes of each phase bridge arm of the device, direct instantaneous torque control of the switched reluctance motor (7) is achieved by applying different voltages to the phase windings. 2. A PWM-DITC control method for a switched reluctance motor based on a new multi-level power converter, which is characterized by including the following steps: Step 1: Obtain the electromagnetic characteristic data of the SRM through experimental measurement or finite element simulation based on the design parameters of the switched reluctance motor body, and form a lookup table of torque-angle-current through modeling; Step 2, taking the three-phase switched reluctance motor as an example, divide the area between the turn-on angles of two adjacent phases, that is, one-third of the electrical cycle, into commutation areas and single-phase with the turn-off angle as the boundary. The conduction area, taking A and B commutation as an example, the commutation area is from the B-phase opening angle to the A-related breaking angle, and the single-phase conduction area is from the A-related breaking angle to the C-phase opening angle; Step 3. The new multi-level power converter has four working states. Each phase bridge arm can achieve high-voltage excitation, normal voltage excitation, freewheeling and high-voltage demagnetization states. Taking the A-phase bridge arm as an example, they correspond to "+2"","+1","0" and "-2" four level states; when the switch tubes S _A1 , S _A2 and S _A3 are all turned on, phase A works in the "+2" state, which is recorded as StateA＝+ 2; When switches S _A2 and S _A3 are turned on and S _A1 is turned off, phase A works in the "+1" state, recorded as StateA = +1; when S _A1 and S _A2 are turned off, S _A3 is turned on. Phase A works in the "0" state, recorded as StateA=0; when the switching tubes S _A1 , S _A2 , and S _A3 are all turned off and there is current in the winding, phase A works in the "-2" state at this time, recorded as StateA=0. For StateA=-2, the working states of other phase bridge arms are deduced in the same way; Step 4. The latest turn-on phase and the upcoming turn-off phase in the commutation area have different working requirements, and different control methods are designed for them. Taking A and B commutation as an example, the conduction rules and methods are: 1) For torque The deviation ΔT is sampled, and the sampled torque deviation is maintained for one period Ts. The sampled torque deviation is recorded as ΔT ₁ ; 2) Compare ΔT ₁ with the hysteresis loop width. If ΔT ₁ is within the hysteresis loop, use PWM equivalent method, if ΔT ₁ is outside the hysteresis loop, use the hysteresis type DITC control method; 3) Compare ΔT ₁ with the triangle carrier intersection, if ΔT ₁ is greater than the triangle carrier, the output is high state, otherwise, the output is low state . 3. A PWM-DITC control method for a switched reluctance motor based on a new multi-level power converter according to claim 2. Step 4 is to design a suitable PWM-DITC control method based on the different working requirements of the latest turn-on phase and the upcoming turn-off phase. Control methods, specifically: Step 4.1, in the phase about to turn off in the commutation area, when the torque error ΔT ₁ after sampling is greater than _TL , it can be seen that the output torque capacity of the phase about to turn off is insufficient, the system needs to increase the torque, and output the "+1" state , entering the excitation state to meet the system requirements; when ΔT ₁ is less than -T _H , it can be known that the output torque is too large, and it should be demagnetized as much as possible to output the "-2"state; when ΔT ₁ ∈ (0, T _L ), it can be known that the output torque Insufficient, use the "+1" state and "+0" state to switch to provide the required torque; when ΔT ₁ is greater than the triangular carrier, the winding applies the "+1"state; when ΔT ₁ is less than the triangular carrier, the winding applies "0"state; when ΔT ₁ ∈ (-T _H , 0), it can be seen that the output torque has a slight excess, and the torque is reduced by switching between the "0" state and the "-2" state. When ΔT ₁ is greater than the triangle When the carrier wave is running, zero voltage is applied to the winding. When ΔT ₁ is less than the triangular carrier wave, the winding applies a "-2" state and discharges quickly, thereby rapidly reducing the output torque; Step 4.2, in the latest opening phase of the commutation area, when the torque error ΔT ₁ after sampling is greater than 0, it can be seen that the output torque capacity should increase, and the "+n" state is output, so that the output torque increases; when ΔT ₁ is less than - T _L , it can be seen that the output torque is too large, the system should reduce the torque output, and the winding works in the "0"state; when ΔT ₁ ∈ (-T _L , 0), the torque also increases and works in the excitation state and "0" state to quickly establish current, where "+n" represents the "+2" state or the "+1" state, and its state logic depends on the position of the control angle θ _h . θ _h should be between [θ _{on_b} , θ _{on_c} ]. When phase B is in [θ _{on_b} , θ _h ], "+n" is the "+2"state; when phase B is in [θ _h , θ _{on_c} ], "+n" is the "+1" state, that is: Step 4.3, in the single-phase conduction area, the B phase alone provides the required torque. The torque error is adjusted through the internal hysteresis loop composed of the B phase hysteresis threshold - T _L and T _L , and the demagnetization state is set at the hysteresis threshold. -T _H and -T _L constitute an external hysteresis loop.