SRM current continuous operation control system and method based on four-level power circuit

Abstract

The present invention belongs to the technical field of motor drive control, and proposes an SRM current continuous operation control system and method based on a four-level power circuit. When the SRM is running at high speed, a new driving scheme combining a current continuous mode with a four-level power circuit is adopted, and the high-voltage rapid excitation and high-voltage rapid demagnetization functions of the four-level power circuit are fully utilized. A current continuous mode MTPA control strategy based on the four-level power circuit is formulated, and a conduction angle closed-loop control, a boost capacitor voltage closed-loop regulation, and an active zero-voltage freewheeling control are adopted. Through the optimization of the control strategy and control parameters, the stable operation of the SRM current continuous mode is realized, the output torque and operating efficiency of the SRM drive system at high speed are improved, and the constant power operation range of the SRM is widened.

Description

Technical Field

[0001] The present invention belongs to the technical field of motor drive control, and in particular relates to a SRM current continuous operation control system and a method thereof based on a four-level power circuit. Background Art

[0002] Switched reluctance motor (SRM) is widely used in various industrial applications due to its simple structure, high reliability, low cost, good speed regulation performance and no need for rare earth permanent magnet materials. When the switched reluctance motor runs at high speed, due to the large back electromotive force, the excitation and demagnetization time per cycle shortens as the speed continues to increase, and the phase current is difficult to reach the expected value. The traditional single-pulse operation mode cannot meet the SRM wide speed range constant power operation. In order to improve the average output torque of the motor at high speed, a new current continuous operation control method is proposed.

[0003] The control method of continuous current operation is to make the conduction angle greater than 180°, that is, the opening time of the winding is greater than the closing time, so that the demagnetization current in each cycle will not drop to zero, and the initial current is greater than zero when it is turned on next time, so as to increase the phase current level, thereby increasing the output torque and output power in the high-speed weak magnetic area. Since the current does not return to zero at the end of each cycle, it is easy to make the system unstable, so the high-speed current continuous operation must be reasonably controlled to achieve stable operation.

[0004] When the switched reluctance motor drive system based on the traditional asymmetric half-bridge power circuit is running at high speed, its constant voltage excitation cannot overcome the current drop caused by the rotational electromotive force being greater than the bus voltage in the inductance rising area, and its constant voltage demagnetization cannot quickly reduce the phase current in the inductance falling area, limiting the output performance of the motor. The use of a power circuit with high-voltage rapid excitation and high-voltage rapid demagnetization capabilities can effectively improve the above problems. At the same time, when the motor is running continuously at high-speed current, the adjacent phases of the motor are often in an overlapping conduction operating state, so the power circuit needs to be able to achieve independent control of the operating mode between phases.

[0005] In summary, in order to improve the output performance of SRM at high speed, designing a switched reluctance motor continuous current control system with high-voltage rapid excitation and high-voltage rapid demagnetization capabilities and its corresponding control method are urgent issues to be solved. Summary of the invention

[0006] In view of the deficiencies of the prior art, the present invention proposes an SRM current continuous operation control system and method based on a four-level power circuit. Based on the high-voltage rapid excitation and high-voltage rapid demagnetization of the four-level power circuit and the function that the operation mode can be independently controlled when the adjacent phases of the motor are overlapped and turned on, when the SRM is running at high speed, a new driving scheme combining the current continuous mode with the four-level power circuit is adopted. Through the optimization of the control strategy and control parameters, the present invention not only realizes the stable operation of the current continuous operation state of the switched reluctance motor at high speed, but also solves the problem that the excitation current of the switched reluctance motor is difficult to reach the expected value and the demagnetization current is difficult to decay quickly at high speed, improves the output torque and operation efficiency of the switched reluctance motor drive system at high speed, and broadens the constant power operation range of the switched reluctance motor.

[0007] The technical solution of the present invention is: an SRM current continuous operation control system based on a four-level power circuit and a method thereof, characterized in that it includes a four-level power circuit, a switched reluctance motor, a controller, a voltage sensor, a current sensor and a position sensor.

[0008] The SRM current continuous operation control system and method based on the four-level power circuit adopts the current continuous operation control mode when the motor runs at high speed, and designs the switched reluctance motor drive system and control method based on the four-level power circuit;

[0009] The four-level power circuit includes a DC power supply, a voltage-stabilizing capacitor C1, a boost capacitor C2, and a bridge arm circuit composed of a switch tube and a diode; the voltage-stabilizing capacitor C1 is connected in parallel with the DC power supply; the negative electrode of the boost capacitor C2 is connected in series with the positive electrode of the voltage-stabilizing capacitor C1; the bridge arm circuit includes a switch tube Q X1 , Q X2 and Q X3 (X represents the different phases of the motor, for example, for a three-phase 12 / 8-pole motor, X represents A, B and C) and diode D X1 , D X2 and D X3 (X represents different phases of the motor, for example, for a three-phase 12 / 8-pole motor, X represents A, B and C), each bridge arm is connected to a phase motor winding; the upper end of the motor winding is connected to the switch tube Q X2 The emitter of the motor winding is connected to the switch tube Q X3 The collector of the bridge arm circuit; the switch tube Q X3 The emitter of the switch tube Q is connected to the negative pole of the DC power supply. X1 The collector of is connected to the positive electrode of the boost capacitor C2; the number of the bridge arm circuits is equal to the number of phases of the motor, and by increasing the number of bridge arm circuits, it can be applied to motors with any number of phases;

[0010] The voltage sensor is placed at both ends of the boost capacitor C2 of the four-level power circuit, collects the boost capacitor voltage value of the four-level power circuit and sends it to the controller; the current sensor is placed on each phase bridge arm of the four-level power circuit and connected to each phase winding of the motor, collects the current value of each phase of the switched reluctance motor and sends it to the controller; the position sensor is used to detect the rotor position of the switched reluctance motor, and sends the position data to the controller;

[0011] The controller is based on a given speed ω * As well as the voltage data, current data and rotor position, by checking the control parameter table, conduction angle closed-loop control, boost capacitor voltage closed-loop control and active zero-voltage freewheeling control in the current continuous mode, a control signal for driving the switch tube of each phase bridge arm of the four-level power circuit is obtained to realize SRM current continuous operation;

[0012] The controller of the SRM current continuous operation control system based on the four-level power circuit adopts a conduction angle closed-loop control. According to the deviation between the reference torque and the average electromagnetic torque of the motor, the conduction angle compensation value Δθ is obtained through the angle compensation controller. d , through real-time adjustment of the conduction angle, the excitation time is adjusted in real time to ensure that the flux and current at the end of each cycle are the same as at the end of the previous cycle, so as to achieve stable operation of the system when the current is running continuously, that is, to keep the flux increment ΔΨ within one electrical cycle to zero. The expression formula is:

[0013] The conduction angle closed-loop control strategy can be used to compensate for the influence of factors such as the change in motor winding resistance with temperature, power supply voltage fluctuation and load fluctuation in actual operation to ensure stable operation of the system;

[0014] The controller of the SRM current continuous operation control system based on the four-level power circuit adopts a closed-loop control strategy of the boost capacitor voltage. Set the reference value u of the boost capacitor ref The actual voltage The voltage deviation is processed by the boost capacitor voltage closed-loop regulation circuit to obtain the high-voltage excitation conduction angle

[0015] The controller of the SRM current continuous operation control system based on the four-level power circuit implements a maximum torque per ampere (MTPA) control strategy, and realizes the MTPA operation of the switched reluctance motor drive system through optimization control. The control method includes the following steps:

[0016] a. Based on the speed deviation between the real-time speed ω and the given speed ω*, the speed controller calculates and outputs the reference torque T ref ;

[0017] b. Based on the reference torque T ref and real-time speed ω, and by checking the MTPA control parameter table, the optimized switched reluctance motor control parameters are obtained, including the opening angle θ at which the motor phase winding starts to be excited on , High voltage excitation opening angle Excitation conduction angle θ d , demagnetization cut-off angle θ end And the reference current I ref ;

[0018] c. Based on the actual voltage of the boost capacitor And given reference voltage U ref , through the automatic balance control of the boost capacitor voltage, the high-voltage excitation conduction angle of the switched reluctance motor is obtained

[0019] d. Based on the reference torque T ref and electromagnetic torque T, the conduction angle compensation value Δθ is obtained through conduction angle closed-loop control d , to correct the excitation conduction angle θ d .

[0020] The SRM current continuous operation control system and method based on the four-level power circuit adopts an active zero-voltage freewheeling control strategy, by setting the demagnetization cutoff angle θ of the previous cycle. end and the opening angle θ of this cycle on A period of zero-voltage follow-current is actively applied between the two phases to make the system run stably in the current continuous mode. It is not only used to maintain the phase current level to improve the output torque of the motor, but also to avoid the system's unstable operation caused by abnormal and frequent switching between the continuous and discontinuous current operating states.

[0021] The SRM current continuous operation control system based on the four-level power circuit and the method thereof are based on the high-voltage excitation and high-voltage demagnetization functions of the four-level power circuit, take the maximization of the torque-ampere ratio as the optimization goal, make full use of high-voltage rapid excitation to slow down the early conduction of the opening angle, reduce the negative torque generated in the inductance drop area due to the forward shift of the opening angle and the copper loss generated in the current establishment stage in the small inductance area; make full use of high-voltage rapid demagnetization, appropriately delay the turn-off angle, so as to increase the positive torque in the inductance rise area; through the optimization of control parameters, the excitation interval is moved more to the positive torque generation area, and the MTPA control strategy based on the current continuous mode of the four-level power circuit at high speed is formulated to improve the output torque and operation efficiency of the SRM current continuous operation drive system and broaden its constant power operation range;

[0022] The current continuous mode MTPA control strategy based on the four-level power circuit, the control parameter table includes the opening angle θ at which the motor phase winding starts to be excitedon , High voltage excitation opening angle Excitation conduction angle θ d , demagnetization cut-off angle θ end And the reference current I ref .

[0023] The control parameter table of the MTPA control strategy is characterized in that it is obtained by traversal optimization based on the high-voltage excitation and high-voltage demagnetization functions of the four-level power circuit, and the optimization steps include:

[0024] a. θ for different torque-speed operating points in the switched reluctance motor drive system based on the four-level power circuit on ,θ d , and θ end The traversal is based on the automatic balancing control of the boost capacitor voltage. Compare the performance indicators under each control parameter combination to find the control parameter combination that makes the motor most efficient;

[0025] b. When the current is running continuously, in order to protect the switched reluctance motor drive system based on the four-level power circuit, the reference current I is set according to the motor's tolerance ref , in order to limit the phase current peak.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention provides an SRM current continuous operation control system based on a four-level power circuit and a method thereof. A current continuous operation control mode is adopted when the motor is running at high speed. The power circuit adopts the four-level power circuit, and the four-level power circuit is combined with the optimization control of the current continuous operation mode. The high-voltage excitation and high-voltage demagnetization capabilities of the four-level power circuit are utilized to solve the problem that the excitation current is difficult to quickly establish and the demagnetization current is difficult to quickly decay when the traditional switched reluctance motor drive system is running at high-speed continuous current. Through the optimization of control strategies and control parameters, the output torque and operation efficiency of the current continuous operation drive system of the switched reluctance motor at high speed are improved. Through the closed-loop control strategy of the boost capacitor voltage and the closed-loop control strategy of the conduction angle, the bus voltage is stabilized and the stable operation of the current continuous mode at high speed is achieved, and the constant power operation range of the switched reluctance motor is broadened.

[0028] 2. The present invention provides a control strategy for active zero-voltage freewheeling based on a four-level power circuit during continuous current operation, by setting the demagnetization cutoff angle θ in the previous cycle. end and the opening angle θ of this cycle onA period of zero-voltage follow-current is actively applied between the two phases to make the system run stably in the current continuous mode. It is not only used to maintain the phase current level to improve the output torque of the motor, but also to avoid the system's unstable operation caused by abnormal and frequent switching between the continuous and discontinuous current operating states. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic diagram of the structure of a four-level power circuit adopted by the present invention;

[0030] Figure 2 It is a schematic diagram of a control block diagram of an SRM current continuous operation control system based on a four-level power circuit proposed in the present invention;

[0031] Figure 3 It is a schematic diagram of the control block diagram of the conduction angle closed-loop regulation loop of the SRM current continuous operation proposed by the present invention;

[0032] Figure 4 It is a schematic diagram of a closed-loop control circuit diagram of the boost capacitor voltage proposed by the present invention;

[0033] Figure 5 The figure is a comparison diagram of the current, voltage, torque and flux-current trajectory waveforms of phase A at 5400rpm when the active zero-voltage freewheeling control strategy proposed in the present invention is adopted. DETAILED DESCRIPTION

[0034] The present invention provides an SRM current continuous operation control system and method based on a four-level power circuit, and the present invention is further described below in conjunction with the accompanying drawings.

[0035] The SRM current continuous operation control system and method based on the four-level power circuit adopt a new driving scheme that combines the current continuous operation control mode with the four-level power circuit when the motor runs at high speed, and designs a switched reluctance motor drive system and control method based on the four-level power circuit.

[0036] The present invention adopts a four-level power circuit, such as Figure 1 As shown, it includes a DC power supply, a voltage-stabilizing capacitor C1, a boost capacitor C2, and a bridge arm circuit composed of a switch tube and a diode. Each bridge arm is connected to a phase motor winding. The number of bridge arm circuits is equal to the number of phases of the motor. By increasing the number of bridge arm circuits, it can be applied to motors with any number of phases. This implementation case takes a three-phase switched reluctance motor as an example. The voltage-stabilizing capacitor C1 is connected in parallel with the DC power supply, and the negative electrode of the boost capacitor C2 is connected in series with the positive electrode of the voltage-stabilizing capacitor C1. Since the bridge arm circuit parts of each phase are connected in the same way, phase A is taken as an example for explanation. The bridge arm circuit of phase A includes a switch tube Q A1 , Q A2 , QA3 , and diode D A1 , D A2 , D A3 .

[0037] The switch tube Q A1 The collector of is connected to the positive electrode of the boost capacitor C2, and the switch tube Q A1 The emitter of the switch tube Q A2 The collector of the switch tube Q A2 The emitter of is connected to the upper end of the motor A phase winding, and the switch tube Q A3 The collector of the motor is connected to the lower end of the A phase winding of the motor, and the switch tube Q A3 The emitter is connected to the negative pole of the DC power supply;

[0038] The diode D A3 The positive pole of the diode D is connected to the negative pole of the DC power supply. A3 The negative pole of the switch tube Q A2 The emitter of diode D A2 The positive pole of the switch tube Q A3 The collector of diode D A2 The negative electrode and the switch tube Q A1 The collector of the diode D A1 The positive electrode of the voltage stabilizing capacitor C1 is connected to the positive electrode of the diode D A1 The negative pole of the switch tube Q A2 The collector.

[0039] The control block diagram of the designed SRM current continuous operation control system based on the four-level power circuit is shown in the figure. Figure 2 As shown, the motor adopts dual closed-loop control of speed and torque. By checking the control parameter table, conducting angle closed-loop control and boost capacitor voltage closed-loop control, the current continuous control system can be operated efficiently and stably.

[0040] The control parameters of the SRM current continuous operation control system based on the four-level power circuit include the excitation parameters of the normal voltage excitation and the high voltage excitation, including the opening angle θ at the start of excitation. on 、Conduction angle θ of constant voltage excitation d , demagnetization cut-off angle θ end , the opening angle of high voltage excitation High voltage excitation conduction angle And the reference current I ref .

[0041] The control method comprises the following steps:

[0042] a. Based on the speed deviation between the real-time speed ω and the given speed ω*, the speed controller calculates the reference torque 7 ref ;

[0043] b. Based on the reference torque T ref and real-time speed ω, and by checking the MTPA control parameter table, the control parameters of the optimized switched reluctance motor are obtained, including the opening angle θ at which the motor phase winding starts to be excited on , High voltage excitation opening angle Excitation conduction angle θ d , demagnetization cut-off angle θ end And the reference current I ref ;

[0044] c. At the same time, based on the actual voltage of the boost capacitor And given reference voltage U ref , through the closed-loop regulation circuit of the boost capacitor voltage, the high-voltage excitation conduction angle of the switched reluctance motor is obtained

[0045] d. Based on the reference torque T ref and electromagnetic torque T, the conduction angle compensation value Δθ is obtained through conduction angle closed-loop control d , to correct the excitation conduction angle θ d ;

[0046] e. Based on the actual current value i and the reference current I ref , through the current controller, the peak value of the winding current is limited and protected when the current is running continuously.

[0047] The control method for continuous current operation is to make the conduction angle greater than 180°, that is, the on time of the winding is greater than the off time, so that the demagnetization current in each cycle will not drop to zero, that is, the initial current of the phase current is greater than zero when it is turned on next time, so as to increase the phase current level, thereby increasing the output torque in the high-speed weak magnetic field area. However, the current and flux do not return to zero at the end of each cycle, which can easily make the system unstable. Therefore, high-speed current continuous operation must be reasonably controlled to make the flux and current the same at the end of each cycle as at the end of the previous cycle, that is, by adjusting the conduction width in real time, so that the average voltage applied to the phase winding in each cycle is equal to the total voltage drop across all resistors in the phase winding loop, so as to correct the offset of the flux and ensure that the flux increment ΔΨ of one electrical cycle is zero, as shown in formula (1):

[0048]

[0049] The schematic diagram of the control block diagram of the conduction angle closed-loop regulation loop of the SRM current continuous operation based on the four-level power circuit is shown in the figure. Figure 3 According to the deviation between the reference torque and the average electromagnetic torque of the motor, the compensation value Δθ of the conduction angle is obtained by the angle compensator. d, the excitation time is adjusted in real time by adjusting the conduction angle in real time to ensure that the flux and current are the same at the end of each cycle as at the end of the previous cycle, that is, to ensure that the initial value of the phase current in each cycle is the same, so as to achieve stable operation of the system when the current is continuously running. In the control of the conduction angle closed-loop regulation loop, if the torque deviation is positive, the conduction angle increases, the voltage integral on the phase winding increases, and the increase in phase current also brings higher losses, until the average value of the resistance voltage component is equal to the average voltage applied to the winding, and the operating point reaches a steady state. At this time, the average torque is equal to the reference torque, and the periodic increment of the flux is zero, thereby achieving continuous and stable operation of the current. In addition, in the current continuous operation mode, due to the influence of the temperature change of the motor winding on the resistance of the motor winding and the influence of factors such as power supply voltage fluctuations in actual operation, it will affect whether the increment ΔΨ of the flux per cycle in formula (1) is zero, thereby affecting the stable operation of the motor when the current is continuously running. The conduction angle closed-loop control strategy can be used to compensate for the influence of the temperature change of the motor winding on the resistance of the motor winding and the influence of factors such as power supply voltage fluctuations in actual operation to ensure stable operation of the system.

[0050] The schematic diagram of the closed-loop regulation circuit of the boost capacitor voltage with continuous operation of the SRM current based on the four-level power circuit is shown in Figure 4 As shown, the stable control of the high-voltage bus voltage is achieved through closed-loop regulation of the boost capacitor voltage.

[0051] The high-voltage excitation and high-voltage demagnetization of the four-level power circuit involve the discharge and charging process of the passive boost capacitor C2, and the discharge and charging of C2 will cause bus voltage fluctuations. The designed closed-loop regulation circuit of the boost capacitor voltage monitors the voltage value of the boost capacitor and adjusts the voltage according to the actual voltage. and reference voltage U ref The conduction width of the high voltage excitation is adjusted through the capacitor voltage regulation circuit. The boost capacitor voltage is balanced by changing the discharge amount of the boost capacitor during the high-voltage excitation stage to achieve bus voltage stability and eliminate the impact of bus voltage fluctuations on the stable operation of the SRM.

[0052] The SRM current continuous operation control system and method based on the four-level power circuit proposes an active zero-voltage freewheeling control strategy. end and the next cycle opening angle θ on A zero-voltage continuous current is actively applied between the two operating states to avoid the system from switching abnormally frequently between the continuous and discontinuous current states, which may cause the system to be unstable. Figure 5As shown in the figure, the switch reluctance motor control system based on the four-level power circuit is 5400rpm, the opening angle is -9.64°, the conduction angle is 23.24°, and whether the active zero-voltage freewheeling control is adopted or not, the current, voltage, torque and flux-current trajectory waveform of phase A are compared. Among them, the blue dotted line is not using active zero-voltage freewheeling control, and high voltage demagnetization is continuously applied during the demagnetization stage until the phase current drops to zero, and then the diode D A2 and diode D A3 Reverse cutoff, the demagnetization voltage passively returns to zero, and the motor operates in a single pulse state. At this time, the area of ​​the magnetic energy is small and the output power is 913W; the red dotted line is the use of active zero-voltage follow-current control. Compared with not using active zero-voltage follow-current, through active zero-voltage follow-current control, the phase current is maintained in a continuous state, maintaining the phase current level, and the output power is increased to 1100W.

[0053] In order to improve the operating efficiency of the switched reluctance motor based on the four-level power circuit, the torque-ampere ratio is maximized as the optimization goal, and full use is made of high-voltage rapid excitation to slow down the early conduction of the opening angle, reduce the negative torque generated in the inductance drop zone of the previous cycle due to the forward shift of the opening angle, and reduce the copper loss generated in the current establishment stage in the small inductance area; make full use of high-voltage rapid demagnetization and appropriately delay the turn-off angle to increase the positive torque in the inductance rise zone. By optimizing the control parameters, the excitation interval is moved more toward the positive torque generation area, and a current continuous mode MTPA control strategy based on the four-level power circuit at high speed is formulated to improve the torque density and operating efficiency of the SRM current continuous operation drive system and broaden its constant power operation range. The control parameter table of its MTPA control strategy includes the opening angle θ at which the motor phase winding starts to be excited. on , High voltage excitation opening angle Excitation conduction angle θ d , demagnetization cut-off angle θ end And the reference current I ref The control parameter table is characterized by high voltage excitation and high voltage demagnetization based on the four-level power circuit, which is obtained by traversal optimization. The optimization steps include:

[0054] a. θ for different torque-speed operating points in the switched reluctance motor drive system based on the four-level power circuit on ,θ d , and θ end The traversal is based on the automatic balancing control of the boost capacitor voltage. Compare the performance indicators under each control parameter combination to find the control parameter combination that makes the motor most efficient;

[0055] b. When the current is running continuously, the reference current I refIt plays a role in limiting the peak value of phase current. Set I according to the motor's bearing capacity. ref , to protect the drive system and power circuit.

[0056] The present invention provides a SRM current continuous operation control system based on a four-level power circuit and a method thereof. By optimizing the control strategy and utilizing the high-voltage excitation and high-voltage demagnetization capabilities of the four-level power circuit, the problem that the excitation current is difficult to reach the expected value and the demagnetization current is difficult to decay rapidly when the motor is running at high speed in the traditional switched reluctance motor drive system is solved; through the boost capacitor voltage closed-loop control strategy and the conduction angle closed-loop control strategy, the bus voltage is stabilized and the current continuous mode is stable at high speed. In addition, the present invention provides an active zero-voltage freewheeling control strategy based on a four-level power circuit during high-speed current continuous operation, by setting the demagnetization cutoff angle θ in the previous cycle. end and the opening angle θ of this cycle on A period of zero-voltage continuous current is actively applied between the two states to avoid the instability of the system operation caused by frequent switching between the continuous and discontinuous current states, and the stable operation of the system in the continuous current operation stage is achieved. Finally, by optimizing the control parameters and making full use of its high-voltage excitation and high-voltage demagnetization functions, a current continuous mode MTPA control strategy based on a four-level power circuit is formulated, which improves the output torque and operating efficiency of the switched reluctance motor drive system at high speed and broadens the constant power operation range of the switched reluctance motor.

[0057] The above description is only a preferred implementation case of the present invention and is not intended to limit the present invention. Without departing from the purpose of the present invention, any technical scheme and implementation example similar to the technical scheme that are designed without creative design shall fall within the protection scope of the present invention.

Claims

1. A SRM current continuous operation control system and method based on a four-level power circuit, characterized in that: It includes a four-level power circuit, a switched reluctance motor, a controller, a voltage sensor, a current sensor and a position sensor; The SRM current continuous operation control system and method based on the four-level power circuit adopts the current continuous operation control mode when the motor runs at high speed, and designs the switched reluctance motor drive system and control method based on the four-level power circuit; The four-level power circuit includes a DC power supply, a voltage-stabilizing capacitor C1, a boost capacitor C2, and a bridge arm circuit composed of a switch tube and a diode; the voltage-stabilizing capacitor C1 is connected in parallel with the DC power supply; the negative electrode of the boost capacitor C2 is connected in series with the positive electrode of the voltage-stabilizing capacitor C1; the bridge arm circuit includes a switch tube Q X1 , Q X2 and Q X3 And diode D X1 , D X2 and D X3 , where X represents different phases of the motor. For a three-phase 12 / 8-pole motor, X represents A, B and C. Each bridge arm is connected to a phase of the motor winding; the upper end of the motor winding is connected to the switch tube Q X2 The emitter of the motor winding is connected to the switch tube Q X3 The collector of the bridge arm circuit; the switch tube Q X3 The emitter of the switch tube Q is connected to the negative pole of the DC power supply. X1 The collector of is connected to the positive electrode of the boost capacitor C2; the number of the bridge arm circuits is equal to the number of phases of the motor, and by increasing the number of bridge arm circuits, it can be applied to motors with any number of phases; The voltage sensor is placed at both ends of the boost capacitor C2 of the four-level power circuit, collects the boost capacitor voltage value of the four-level power circuit and sends it to the controller; the current sensor is placed on each phase bridge arm of the four-level power circuit and connected to each phase winding of the motor, collects the current value of each phase of the switched reluctance motor and sends it to the controller; the position sensor is used to detect the rotor position of the switched reluctance motor, and sends the position data to the controller; The controller is based on a given speed ω * As well as the voltage data, current data and rotor position, by checking the control parameter table, conduction angle closed-loop control, boost capacitor voltage closed-loop control and active zero-voltage freewheeling control in the current continuous mode, a control signal for driving the switch tube of each phase bridge arm of the four-level power circuit is obtained to realize SRM current continuous operation; The controller of the SRM current continuous operation control system based on the four-level power circuit adopts a conduction angle closed-loop control. According to the deviation between the reference torque and the average electromagnetic torque of the motor, the conduction angle compensation value Δθ is obtained through the angle compensation controller. d , through real-time adjustment of the conduction angle, the excitation time is adjusted in real time to ensure that the flux and current at the end of each cycle are the same as at the end of the previous cycle, so as to achieve stable operation of the system when the current is running continuously, that is, to keep the flux increment ΔΨ within one electrical cycle to zero. The expression formula is: The conduction angle closed-loop control strategy can be used to compensate for the influence of factors such as the change in motor winding resistance with temperature, power supply voltage fluctuation and load fluctuation in actual operation to ensure stable operation of the system; The controller of the SRM current continuous operation control system based on the four-level power circuit adopts a closed-loop control strategy of the boost capacitor voltage. Set the reference value of the boost capacitor U ref The actual voltage The voltage deviation is processed by the boost capacitor voltage closed-loop regulation circuit to obtain the high-voltage excitation conduction angle The controller of the SRM current continuous operation control system based on the four-level power circuit executes the MTPA control strategy, and realizes the MTPA operation of the switched reluctance motor drive system through optimization control. The control method includes the following steps: a. Based on the speed deviation between the real-time speed ω and the given speed ω*, the speed controller calculates and outputs the reference torque T ref ; b. Based on the reference torque T ref and real-time speed ω, and by checking the MTPA control parameter table, the optimized switched reluctance motor control parameters are obtained, including the opening angle θ at which the motor phase winding starts to be excited on , High voltage excitation opening angle Excitation conduction angle θ d , demagnetization cut-off angle θ end And the reference current I ref ; c. Based on the actual voltage of the boost capacitor And given reference voltage U ref , through the automatic balance control of the boost capacitor voltage, the high-voltage excitation conduction angle of the switched reluctance motor is obtained d. Based on the reference torque T ref and electromagnetic torque T, the conduction angle compensation value Δθ is obtained through conduction angle closed-loop control d , to correct the excitation conduction angle θ d .

2. According to the SRM current continuous operation control system and method based on the four-level power circuit of claim 1, an active zero-voltage freewheeling control strategy is adopted, by setting the demagnetization cutoff angle θ of the previous cycle to end and the opening angle θ of this cycle on A period of zero-voltage follow-current is actively applied between the two phases to make the system run stably in the current continuous mode. It is not only used to maintain the phase current level to improve the output torque of the motor, but also to avoid the system's unstable operation caused by abnormal and frequent switching between the continuous and discontinuous current operating states.

3. According to claim 1, the SRM current continuous operation control system and method based on the four-level power circuit, based on the high-voltage excitation and high-voltage demagnetization functions of the four-level power circuit, taking the torque-ampere ratio maximization as the optimization goal, making full use of high-voltage rapid excitation to slow down the early conduction of the opening angle, reducing the negative torque generated in the inductance drop area due to the forward shift of the opening angle and the copper loss generated in the current establishment stage in the small inductance area; making full use of high-voltage rapid demagnetization, appropriately delaying the turn-off angle, so as to increase the positive torque in the inductance rise area; by optimizing the control parameters, the excitation interval is moved more to the positive torque generation area, and the MTPA control strategy based on the current continuous mode of the four-level power circuit is formulated at high speed, so as to improve the output torque and operation efficiency of the SRM current continuous operation drive system, and broaden its constant power operation range; The current continuous mode MTPA control strategy based on the four-level power circuit, the control parameter table includes the opening angle θ at which the motor phase winding starts to be excited on , High voltage excitation opening angle Excitation conduction angle θ d , demagnetization cut-off angle θ end And the reference current I ref ; The control parameter table of the MTPA control strategy is characterized in that it is obtained by traversal optimization based on the high-voltage excitation and high-voltage demagnetization functions of the four-level power circuit, and the optimization steps include: a. θ for different torque-speed operating points in the switched reluctance motor drive system based on the four-level power circuit on ,θ d , and θ end The traversal is based on the automatic balancing control of the boost capacitor voltage. Compare the performance indicators under each control parameter combination to find the control parameter combination that makes the motor most efficient; b. When the current is running continuously, in order to protect the switched reluctance motor drive system based on the four-level power circuit, the reference current I is set according to the motor's tolerance ref , in order to limit the phase current peak.

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