A method for controlling the maximum torque-to-current ratio of a doubly salient pole motor

Abstract

This invention discloses a method for controlling the maximum torque-to-current ratio of a doubly salient pole motor. This method changes the inverter's operating mode from a two-phase conduction mode to a three-phase conduction mode, simultaneously supplying power to the three-phase windings. In this mode, arbitrary continuous current vector trajectories can be generated, ensuring that the angle between the current vector and the torque current coefficient vector is zero, allowing them to operate in phase. This enables the output of the maximum instantaneous torque. The overall method employs... i d =0 control enables maximum torque-to-current ratio control. The maximum torque-to-current ratio control method for a doubly salient pole motor disclosed in this invention enables the motor to operate at its maximum torque-to-current ratio.

Description

Technical Field

[0001] This invention relates to the field of motor control, and more particularly to a method for controlling the maximum torque-to-current ratio (MTPA) of a doubly salient pole motor. Background Technology

[0002] Electrically excited doubly salient pole motors (DOSPMs) have broad application prospects in aviation starting / generating fields due to their simple structure, high reliability, and flexible and convenient control. DOSPMs belong to the variable reluctance motor category and operate according to the principle of minimum reluctance, meaning the magnetic flux linkage always closes along the path of least reluctance. They were developed from switched reluctance motors. DOSPMs have a simple structure and manufacturing process, with no windings on the rotor, resulting in stable and reliable operation. By adjusting the excitation current, the air gap magnetic field of an DOSPM can be changed. When combined with an inverter topology, the system can be used in brushless DC motor applications. Currently, a three-phase full-bridge inverter topology is commonly used, with the phase windings of the DOSPM connected in a star configuration and directly connected to the diode inverter topology.

[0003] The back EMF waveform of an electrically excited doubly salient pole motor is an irregular trapezoidal wave. It is typically controlled using a six-state square wave current chopper, similar to that of a permanent magnet brushless DC motor, differing only in the division of the conduction region. During motor operation, a sufficiently large and stable output torque is required to achieve a stable speed, which necessitates a suitable driving method. Currently, the most common driving method for electrically excited doubly salient pole motors is a square wave advance angle drive using current hysteresis chopper.

[0004] Under the traditional square wave control strategy, the torque current coefficient of an electrically excited doubly salient pole motor contains a large number of odd and even harmonics, resulting in severe waveform distortion. Furthermore, there is always an angle between the torque current coefficient vector and the current vector, preventing them from maintaining the same phase and thus preventing the motor from operating at its maximum torque-to-current ratio. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a method for controlling the maximum torque-to-current ratio (MTPA) of a doubly salient pole motor, which enables the motor to operate at its maximum torque-to-current ratio.

[0006] The technical solution of this invention is as follows:

[0007] A method for controlling the maximum torque-to-current ratio (MTPA) of a doubly salient pole motor includes the following steps:

[0008] Step 1, define the ratio of phase torque to phase current as the phase torque-current coefficient t. k (θ,i k i f Meanwhile, the average phase torque current coefficient t is defined. kave (θ,if The three-phase average phase torque current coefficient t under different excitation currents is obtained offline. a t b t c Establish a DSEM instantaneous torque calculation model;

[0009] Step 2: DSEM back EMF is measured offline, and then the (rotating) torque current coefficient vector position corresponding to the rotor position is obtained through coordinate transformation and arctangent calculation. A one-dimensional data table of the motor with respect to rotor position and torque current coefficient position is established. The real-time rotor position angle of the motor is obtained through the position sensor, and the real-time torque current coefficient vector position is obtained by the table lookup method.

[0010] Step 3: Based on MTPA control, achieve maximum torque-to-current ratio control. Specifically, establish the speed loop and current loop of motor control.

[0011] Based on the rotor position angle, the real-time torque current coefficient vector position is obtained using a lookup table method. The torque current coefficient vector position is then differentiated to obtain the torque current coefficient vector rotor speed. This torque current coefficient vector rotor speed is compared with a reference speed and input to the speed loop for dynamic adjustment, outputting i. q Given a current; set i q The given current, along with the position of the torque current coefficient vector, serves as the current loop input;

[0012] Step 4: Control the switching state of the inverter based on the current loop to make the motor operate in the desired state. Specifically, use the direct-axis current i d =0 control strategy, i q Control is performed as the target quantity, with the current loop input being the real-time (rotational) torque current coefficient vector position and the speed loop output being the i... q Given a current, the three-phase reference current is calculated through inverse transformation, and current tracking is achieved through hysteresis control to ensure that the motor operates at the maximum torque-to-current ratio.

[0013] As a preferred option, the instantaneous torque model is:

[0014] T esti =t a ·i a +t b ·i b +t c ·i c +t f ·i f

[0015] Among them, T esti The instantaneous torque of the motor is t. a t b tc i represents the three-phase average phase torque current coefficient under different excitation currents. a i b i c For the three-phase armature current, i f For the excitation current, t f This is the excitation current coefficient.

[0016] Preferably, the armature winding of the DSEM is connected in a star configuration, and the drive circuit of the DSEM is a three-phase full-bridge inverter circuit.

[0017] Preferably, due to the asymmetry of the DSEM electromagnetic characteristics, the initial position of the torque current coefficient vector and the initial zero position of the rotor do not coincide, and there is a phase difference between them. Furthermore, the instantaneous and average values ​​of the torque current coefficient vector rotational speed and the rotor rotational speed are different. Therefore, it is necessary to establish a one-dimensional data table to obtain the real-time torque current coefficient vector position through offline measurement of the back EMF and transformation calculation. This is a prerequisite for ensuring that the two operate collinearly. In step 2, the torque current coefficient vector position corresponding one-to-one with the rotor position is obtained by offline measurement of the DSEM back EMF, followed by coordinate transformation and arctangent calculation.

[0018] As a preferred option, step 2 specifically involves:

[0019] Step 2.1, the three-phase average torque current coefficient (t) a ,t b ,t c ), three-phase armature current (i a i b i c Transformation from a three-phase coordinate system to a two-phase stationary coordinate system:

[0020]

[0021]

[0022] Where C 32 For the transformation matrix, in the α-β plane of the two-phase coordinate system, t α t β Let i be the torque current coefficient vector in a two-phase stationary coordinate system. α i β The armature current vector in a two-phase stationary coordinate system;

[0023] Step 2.2, convert the two-phase static torque current coefficient vector t α t β and armature current vector i α i β Synthesize the torque current coefficient vector t and the current vector i in the rotating coordinate system respectively:

[0024]

[0025]

[0026] In the formula, |t| and |i| are the magnitudes of vectors t and i; These are the arguments of the vectors;

[0027] Step 2.3: Establish a one-dimensional data table showing the correspondence between the natural commutation point position of the torque current coefficient and the vector position of the torque current coefficient. The corresponding torque current coefficient vector position can be obtained by determining the commutation point interval corresponding to the rotor position.

[0028] As a preferred option, the instantaneous torque model is:

[0029] T esti =t a ·i a +t b ·i b +t c ·i c +t f ·i f

[0030] Among them, T esti The instantaneous torque of the motor is t. a t b t c i represents the three-phase average phase torque current coefficient under different excitation currents. a i b i c For the three-phase armature current, i f For the excitation current, t f This is the excitation current coefficient.

[0031] Preferably, the armature winding of the DSEM is connected in a star configuration, and the drive circuit of the DSEM is a three-phase full-bridge inverter circuit.

[0032] Preferably, in step 2, the back EMF of the DSEM is measured offline, and then the torque current coefficient vector position corresponding to the rotor position is obtained by coordinate transformation and arctangent calculation.

[0033] Step 2 is as follows:

[0034] Step 2.1, the three-phase average torque current coefficient (t) a ,t b ,t c ), three-phase armature current (i a i b i c Transformation from a three-phase coordinate system to a two-phase stationary coordinate system:

[0035]

[0036]

[0037] Where C 32 For the transformation matrix, in the α-β plane of the two-phase coordinate system, t α t β Let i be the torque current coefficient vector in a two-phase stationary coordinate system. α i β The armature current vector in a two-phase stationary coordinate system;

[0038] Step 2.2, convert the two-phase static torque current coefficient vector t α t β and armature current vector i α i β Synthesize the torque current coefficient vector t and the current vector i in the rotating coordinate system respectively:

[0039]

[0040]

[0041] In the formula, |t| and |i| are the magnitudes of vectors t and i; These are the arguments of the vectors;

[0042] Step 2.3: Establish a one-dimensional data table showing the correspondence between the natural commutation point position of the torque current coefficient and the vector position of the torque current coefficient. The corresponding torque current coefficient vector position can be obtained by determining the commutation point interval corresponding to the rotor position.

[0043] As a preferred option, i is based on MTPA control. q The position of the cross-axis coincides with the position of the torque current coefficient, meaning the two-phase rotating coordinate system and the torque current coefficient vector rotate synchronously. Since the rotor position and rotor angular velocity cannot approximate the position and angular velocity of the torque current coefficient vector, its position is determined by offline measurement of back EMF, coordinate transformation, arctangent calculation, and table lookup. Then, its rotational speed ω is obtained through a differential operator, and the target control current i is obtained by PI regulation with the given rotational speed. q * By using current loop control, the quadrature axis position can be made to coincide with the torque current coefficient vector at all times, and the starting position of the torque current coefficient vector can be made to coincide with the initial zero position of the rotor, thus achieving collinear operation.

[0044] As a preferred option, the three-phase reference current is used to determine the switching state of the inverter through hysteresis controller and transformation calculation. Under MTPA control, the motor operates in a three-phase conduction mode, which can generate a continuous current vector trajectory within a complete cycle on the rotating coordinate system, that is, it can output a circular rotating magnetic field to achieve the desired working state. Attached Figure Description

[0045] Figure 1 It is a DSEM drive circuit;

[0046] Figure 2 These are the DSEM torque-current coefficient and the ideal drive current waveform;

[0047] Figure 3 It is the rotation trajectory of the torque current coefficient vector and the current vector in the two-phase stationary coordinate system under the square wave control strategy;

[0048] Figure 4 It is the process of the torque current coefficient vector and the rotation of the current vector in sector 1;

[0049] Figure 5 This is the current vector trajectory when using the MTPA control strategy;

[0050] Figure 6 This invention relates to the DSEM drive control system based on the motor MTPA control strategy.

[0051] Figure 7 This is a comparison of the current trajectories under square wave control and MTPA control;

[0052] Figure 8 This is a comparison of simulation results for two control strategies under different operating conditions.

[0053] Beneficial effects:

[0054] (1) In the prior art, the motor under square wave current control operates in a two-to-two conduction manner, which results in a significant torque drop during commutation. Under MTPA control, the motor operates in a three-to-three conduction manner, which can generate any continuous current vector trajectory, eliminates the commutation process, and results in a smoother torque output.

[0055] (2) The motor can generate any continuous current vector trajectory, achieving collinearity where the angle between the current vector and the torque current coefficient vector is 0, and can output the maximum instantaneous torque; the overall design adopts i d =0 control to achieve maximum torque-to-current ratio control;

[0056] (3) The simulation results show that, regardless of light or heavy load, the MTPA control can achieve maximum torque-current ratio control and effectively reduce the harmonic content of the motor phase current, which is beneficial to reduce high-frequency iron loss. The peak-to-peak torque remains basically unchanged under different operating conditions, which indicates that the cogging torque is the main factor causing the large torque pulsation of DSEM. Detailed Implementation

[0057] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings:

[0058] This invention can be implemented in many different forms and should not be considered limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully express the scope of the invention to those skilled in the art. In the drawings, circuit elements are enlarged for clarity.

[0059] The present invention provides a MTPA control method for a doubly salient pole motor, wherein the doubly salient pole motor includes a full-bridge inverter, a position detector, and an electrically excited doubly salient pole motor.

[0060] Establish a DSEM instantaneous torque calculation model: Define the ratio of phase torque to phase current as the phase torque-current coefficient t. k (θ,i k i f This coefficient is a function of rotor position, phase current, and excitation current. Due to the influence of magnetic circuit saturation, the phase torque current coefficient under different phase currents exhibits slight differences depending on the degree of magnetic circuit saturation. The average phase torque current coefficient t can be used. kave (θ,i f Using the average phase torque current coefficient reduces the dimensionality of the independent variables; this coefficient is only a function of rotor position and excitation current.

[0061] Due to the asymmetry of the three-phase electromagnetic characteristics of the electrically excited doubly salient pole motor, it is necessary to obtain the three-phase average phase torque current coefficient t under different excitation currents offline. a t b t c The instantaneous torque of an electrically excited doubly salient pole motor can be estimated by the following formula.

[0062] T esti =t a ·i a +t b ·i b +t c ·i c +t f ·i f (1)

[0063] Among them, T esti The instantaneous torque of the motor is t.a t b t c i represents the three-phase average phase torque current coefficient under different excitation currents. a i b i c For the three-phase armature current, i f For the excitation current, t f This is the excitation current coefficient.

[0064] The DSEM armature winding uses a star connection, therefore it is often driven by a three-phase full-bridge inverter circuit. The equivalent circuit is as follows: Figure 1 As shown.

[0065] The back EMF waveform of an electrically excited doubly salient pole motor is an irregular trapezoidal wave. Based on the characteristics of the DSEM back EMF waveform, the electrical angle of the motor's operation is divided into 6 sectors, labeled with Roman numerals I to VI, such as... Figure 2 As shown. The position of maximum flux linkage in phase A winding (back EMF is zero) is defined as the initial zero position. Due to the asymmetry of electromagnetic characteristics, the width of each sector is different.

[0066] Based on the theory of instantaneous reactive power in three-phase circuits, the three-phase average torque current coefficient (t) is... a ,t b ,t c ), three-phase armature current (i a i b i c Transformation from a three-phase coordinate system to a two-phase stationary coordinate system

[0067]

[0068]

[0069] Where C 32 The transformation matrix represents the torque current coefficient vector t in the α-β plane of the two-phase coordinate system (where both phases are stationary). α t β and armature current vector i α i β The (rotational) torque current coefficient vector t and the current vector i can be synthesized respectively.

[0070]

[0071]

[0072] In the formula, |t| and |i| are the magnitudes of vectors t and i; These are the arguments of the vectors.

[0073] Figure 3The trajectories of the torque current coefficient vector *t* and the current vector *i* in a two-phase stationary coordinate system under square wave control are given. As can be seen from the figure, due to the presence of numerous odd and even harmonics in the torque current coefficient, the waveform is severely distorted, and its trajectory is an irregular "hexagonal star". The initial position of the torque current coefficient vector does not coincide with the rotor's zero position; it is located on the positive half-axis of the β-axis, with a 90° phase difference between them. It can be easily proven using the 3 / 2 transformation that the correspondence between the six natural commutation points of the torque current coefficient and the position of the torque current coefficient vector is shown in Table 1.

[0074] Although the natural commutation points of the torque current coefficient are not uniformly distributed, the torque current coefficient vector positions corresponding to the commutation points are uniformly distributed, differing by 60° electrical degrees. This indicates that when the motor rotor rotates at a certain angular velocity, the torque current coefficient vector does not rotate at the synchronous speed; in some regions, the rotation speed is slower than the synchronous speed, while in other regions, the rotation speed is faster than the synchronous speed.

[0075] Table 1. Correspondence between the natural commutation point location and the vector location of the torque current coefficient.

[0076]

[0077] A three-phase ideal current in a stationary coordinate system is represented by six discrete current vectors, which can be expressed as follows:

[0078]

[0079] In the formula, I represents the amplitude of the square wave current. Connecting the discrete vertices of the current vectors yields the ideal current vector trajectory, as shown below. Figure 3 As shown by the dashed line, the current trajectory is a regular hexagon.

[0080] Driven by an ideal square wave current, the torque current coefficient vector of the DSEM moves along an irregular hexagonal star trajectory with time, while the voltage vector amplitude changes continuously with time; the current vector changes at 6 discrete positions in space, and its amplitude does not change with time.

[0081] The instantaneous torque is the vector product of the current vector and the torque-current coefficient vector. The instantaneous torque of a square wave drive changes continuously with the amplitude of the torque-current coefficient vector. Taking sector I as an example, the process of the torque-current coefficient vector and the current vector rotating within sector 1 is as follows: Figure 4 As shown.

[0082] Between 60° and 90°, the current vector remains constant, the magnitude of the torque current coefficient vector gradually increases, and the angle between the two gradually decreases. Obviously, their vector product gradually increases. When the torque current coefficient vector rotates to the position coinciding with the current vector, the vector product reaches its maximum value. Between 90° and 120°, the current vector remains constant, the magnitude of the torque current coefficient vector gradually decreases, and the angle between the two gradually increases. Their vector product gradually decreases. When the torque current coefficient vector rotates to the position of the next natural commutation point, the vector product reaches its minimum value.

[0083] Under square wave current control, the angle between the torque current coefficient vector and the current vector initially decreases and then increases in each operating sector. Due to this angle, the torque current coefficient vector and the current vector cannot always maintain the same phase, and the motor cannot operate at its maximum torque-to-current ratio.

[0084] Therefore, without changing the circuit topology, the inverter's operating mode is changed to a three-phase-three-phase conduction mode, simultaneously supplying power to the three-phase windings of the motor. In this mode, any continuous current vector trajectory can be generated so that the angle between the current vector and the torque current coefficient vector is zero.

[0085] The key to ensuring the current vector consistently tracks the torque current coefficient vector lies in obtaining the position of the torque current coefficient vector. As analyzed earlier, the instantaneous values ​​and average values ​​of the torque current coefficient vector's rotational speed differ from the rotor's rotational speed; furthermore, there is a phase difference between them that varies with time. Due to severe distortion of the back EMF waveform, it is difficult to express precisely using an expression. This invention obtains the DSEM back EMF through offline measurement, then calculates the torque current coefficient vector position corresponding one-to-one with the rotor position through coordinate transformation and arctangent calculation. A one-dimensional data table is then established, and the torque current coefficient vector position is obtained in real time using a lookup table method. To ensure the current vector amplitude is minimized under the condition of generating the same torque, the angle between the torque current coefficient vector and the current vector should be eliminated, ensuring they are collinear throughout the entire operating cycle. The two-phase rotating coordinate system should rotate synchronously with the torque current coefficient vector, and the cross-axis position should coincide with the position of the torque current coefficient vector. The current vector trajectory is a circle, as shown below. Figure 5 As shown.

[0086] Design as Figure 6 The DSEM drive control system shown employs the MTPA control strategy.

[0087] The system acquires rotor position information through a position sensor, calculates the motor speed based on the rotor position information using differentiation, and measures the three-phase armature current through a Hall current sensor.

[0088] Based on the acquired rotor position information, the torque current coefficient vector position corresponding to the rotor position is obtained by looking up a table, which serves as the position angle input for the transformation of the given current from the dq two-phase rotating coordinate system to the abc three-phase stationary coordinate system.

[0089] Since the two-phase rotating coordinate system and the torque current coefficient vector rotate synchronously, the rotor position and rotor angular velocity cannot approximate the position and angular velocity of the torque current coefficient vector. Therefore, offline measurement of back EMF, coordinate transformation, arctangent calculation, and table lookup are used to determine the position of the torque current coefficient vector. Then, the rotational speed ω of the torque current coefficient vector is obtained through a differential operator, and the target control current i is obtained by PI regulation with the given rotational speed. q * .

[0090] The torque-current coefficient vector speed is compared with the reference speed and then input to the speed loop ASR. The speed loop output is used as the iq reference current. Maximum torque-current ratio control is achieved using id=0 control. The three-phase reference current after coordinate transformation is used for current tracking through hysteresis control. Direct-axis current i is used. d =0 can achieve the maximum torque current because let i = 0. d When =0, the control quantity is only i q The torque is affected by the quadrature-axis current i. q Controlling the quadrature axis current can directly affect the torque output.

[0091] Specifically, the obtained reference three-phase current is compared with the actual three-phase current, and then hysteresis control is applied to achieve current tracking. The output control quantity is transformed by coordinates to control the opening and closing of the switching transistors. Under MTPA control, the motor operates in a three-phase-three-phase conduction mode, without commutation. Compared to the two-phase conduction mode under square wave current control, the torque output is smoother, and full-cycle current tracking can be achieved, ensuring that the angle between the current vector and the torque current coefficient vector is zero, thus enabling the motor to operate in the desired state. In three-phase-three-phase conduction, the switching transistor conducts 180 electrical degrees within the operating cycle, commutating every 60 degrees. All three phase windings have current simultaneously, with no floating phases. This increases the winding utilization rate, reduces torque ripple, and improves the motor's output power. Figure 7 A comparison of the current trajectory waveforms under square wave current control and MTPA control is given. It can be seen that the current trajectory under square wave current control is a regular hexagon, while the current trajectory under MTPA control is a circle.

[0092] Figure 8 Simulation results comparing the two control strategies are presented. The simulation results show that, regardless of whether the load is light or heavy, MTPA control can achieve maximum torque-to-current ratio control and effectively reduce the harmonic content of the motor phase current, which is beneficial for reducing high-frequency iron losses.

[0093] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0094] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for controlling the maximum torque-to-current ratio of a doubly salient pole motor, characterized in that, Includes the following steps: Step 1, define the ratio of phase torque to phase current as the phase torque-current coefficient t. k (θ,i k i f Meanwhile, the average phase torque current coefficient t is defined. kave (θ,i f The three-phase average phase torque current coefficient t under different excitation currents is obtained offline. a t b t c Establish a DSEM instantaneous torque calculation model; Step 2: Establish a one-dimensional data table of motor rotor position and torque current coefficient position; Step 3: Based on MTPA control, achieve maximum torque-to-current ratio control. Specifically, establish the speed loop and current loop of motor control. Based on the rotor position angle, the real-time torque current coefficient vector position is obtained using a lookup table method. The torque current coefficient vector position is then differentiated to obtain the torque current coefficient vector rotational speed. This rotational speed is compared with a reference speed and input to the speed loop for dynamic adjustment, outputting a given current i. q * ;Given a current i q * The torque current coefficient vector position together serves as the current loop input; Step 4: Control the switching state of the inverter based on the current loop to make the motor operate in the desired state. Specifically, use the direct-axis current i d =0 control strategy, i q Control is performed as the target quantity, using the current loop input, namely the real-time torque current coefficient vector position and the given current i. q * The three-phase reference current is obtained by inverse transformation calculation, and current tracking is achieved by hysteresis control to ensure that the motor operates at the maximum torque-to-current ratio.

2. The maximum torque-to-current ratio control method for a doubly salient pole motor according to claim 1, characterized in that, The instantaneous torque model is as follows: T esti =t a ·i a +t b ·i b +t c ·i c +t f ·i f Among them, T esti The instantaneous torque of the motor is t. a t b t c i represents the three-phase average phase torque current coefficient under different excitation currents. a i b i c For the three-phase armature current, i f For the excitation current, t f This is the excitation current coefficient.

3. The maximum torque-to-current ratio control method for a doubly salient pole motor according to claim 2, characterized in that, The DSEM armature winding adopts a star connection, and the DSEM drive circuit is a three-phase full-bridge inverter circuit.

4. The maximum torque-to-current ratio control method for a doubly salient pole motor according to claim 3, characterized in that, In step 2, the back EMF of the DSEM is measured offline, and then the torque current coefficient vector position corresponding to the rotor position is obtained by coordinate transformation and arctangent calculation.

5. The maximum torque-to-current ratio control method for a doubly salient pole motor according to claim 4, characterized in that, Step 2 is as follows: Step 2.1, the three-phase average torque current coefficient (t) a ,t b ,t c ), three-phase armature current (i a i b i c Transformation from a three-phase coordinate system to a two-phase stationary coordinate system: Where C 32 For the transformation matrix, in the α-β plane of the two-phase coordinate system, t α t β Let i be the torque current coefficient vector in a two-phase stationary coordinate system. α i β The armature current vector in a two-phase stationary coordinate system; Step 2.2, convert the two-phase static torque current coefficient vector t α t β and armature current vector i α i β Synthesize the torque current coefficient vector t and the current vector i in the rotating coordinate system respectively: In the formula, |t| and |i| are the magnitudes of vectors t and i; These are the arguments of the vectors; Step 2.3: Establish a one-dimensional data table showing the correspondence between the natural commutation point position of the torque current coefficient and the vector position of the torque current coefficient. The corresponding torque current coefficient vector position can be obtained by determining the commutation point interval corresponding to the rotor position.

6. The method for controlling the maximum torque-to-current ratio of a doubly salient pole motor according to any one of claims 1 to 5, characterized in that, Based on MTPA control, i q The position of the cross-axis coincides with the position of the torque current coefficient, meaning the two-phase rotating coordinate system and the torque current coefficient vector rotate synchronously. Since the rotor position and rotor angular velocity cannot approximate the position and angular velocity of the torque current coefficient vector, its position is determined by offline measurement of back EMF, coordinate transformation, arctangent calculation, and table lookup. Then, the rotational speed ω of the torque current coefficient vector is obtained through a differential operator, and the target control current i is obtained by PI regulation with a given rotational speed. q * By using current loop control, the quadrature axis position can be made to coincide with the torque current coefficient vector at all times, and the starting position of the torque current coefficient vector can be made to coincide with the initial zero position of the rotor, thus achieving collinear operation.

7. The maximum torque-to-current ratio control method for a doubly salient pole motor according to claim 6, characterized in that, The three-phase reference current is calculated by the hysteresis controller and the converter to determine the switching state of the inverter. Under the control of MTPA, the motor operates in a three-phase conduction mode, which can generate a continuous current vector trajectory within a complete cycle on the rotating coordinate system, that is, it can output a circular rotating magnetic field to achieve the desired working state.

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