A Full-Speed Range Control Method for Permanent Magnet Assisted Synchronous Reluctance Motor Based on Iterative Initial Point Optimization

Abstract

A full-speed range control method for a permanent magnet assisted synchronous reluctance motor based on iterative initial point optimization, which relates to the technical field of motor control. The present invention is to solve the problem that the iterative calculation amount of the full-speed range control algorithm of the permanent magnet assisted synchronous reluctance motor is large, and the algorithm cannot guarantee real-time performance, resulting in the decline of the motor operation performance. The present invention determines the operation region and the state boundary point according to the actual speed of the motor and the preset speed critical value; uses the Newton-Raphson iterative method to calculate the current and torque at the state boundary point; compares the torque at the state boundary point in each operation region with the reference torque to determine the operation working point in each operation region; uses the Newton-Raphson iterative method to calculate the current at the operation working point; takes the current at the operation working point as the current reference value of the motor to realize the optimized control of the permanent magnet assisted synchronous reluctance motor.

Description

Technical Field

[0001] The present invention belongs to the technical field of motor control. Background Art

[0002] The permanent magnet assisted synchronous reluctance motor has the characteristics of simple structure, low cost and good field weakening speed increasing performance, and has received extensive attention in the fields of industrial drive and electric vehicle applications in recent years. In the motor operation area with a wide speed range, different current control methods are required at different speeds. For example, the maximum torque per ampere (MTPA) control is adopted at low speeds and field weakening control is adopted at medium and high speeds. The optimal current control method determined based on different speeds is called the full speed range control algorithm.

[0003] The full speed range control method is the method for determining the optimal operating current point. After obtaining the real-time speed and torque reference during motor operation, the optimal operating point is determined as the intersection of two specific curves. According to the expressions of the two curve equations, this intersection is calculated by an iterative calculation method. The Newton-Raphson method has good convergence characteristics and a local second-order convergence speed, so it is widely used in the above intersection solving problem. However, the permanent magnet assisted synchronous reluctance motor has significant magnetic saturation characteristics, which makes its inductance model be modeled as a function of dq-axis currents. Compared with other motors, its curve equation is more complex and the look-up table calculation is increased, resulting in a significant increase in the calculation burden of the iterative calculation, and further causing a significant increase in the calculation time of the full speed range control algorithm.

[0004] The convergence result of the Newton-Raphson iterative method is directly related to the selection of the initial point. An unreasonable initial point of the iterative calculation can significantly increase the number of iterative calculations, thus increasing the calculation burden of the iterative calculation. In different motor operating states, the calculation burden of the full speed range control algorithm is not the same. When the calculation burden is relatively light, the full speed range control algorithm can be updated before the PWM output within one control cycle. When the calculation burden is relatively heavy, the update of the full speed range control algorithm will span multiple control cycles. The non-real-time update of the algorithm leads to a significant decline in control performance.

[0005] At present, the full speed range control algorithm of the permanent magnet assisted synchronous reluctance motor has the disadvantages of large iterative calculation amount and inability to guarantee real-time performance, which leads to a decline in the motor operation performance. Therefore, it has important application value to study an iterative initial point design method that reduces the iterative calculation burden and guarantees the real-time performance of the algorithm. Summary of the Invention

[0006] The present invention aims to solve the problem that the iterative calculation amount of the full-speed range control algorithm for a permanent magnet assisted synchronous reluctance motor is large, and the algorithm cannot guarantee real-time performance, resulting in a decline in the operating performance of the motor. Now, a full-speed range control method for a permanent magnet assisted synchronous reluctance motor based on iterative initial point optimization is provided.

[0007] A full-speed range control method for a permanent magnet assisted synchronous reluctance motor based on iterative initial point optimization, comprising:

[0008] Construct a mathematical model of the permanent magnet assisted synchronous reluctance motor, and respectively describe the maximum torque current ratio curve equation, maximum torque voltage ratio curve equation, current limit curve equation, and voltage limit curve equation of the permanent magnet assisted synchronous reluctance motor according to the mathematical model;

[0009] Determine the motor operating region and the state demarcation points in each operating region according to the actual speed of the permanent magnet assisted synchronous reluctance motor and a preset speed critical value;

[0010] Take the current at the state demarcation point in the previous control cycle as the initial demarcation point current in this control cycle, use the Newton-Raphson iteration method to calculate the current at the state demarcation point in this control cycle, and calculate the corresponding torque according to the current at the state demarcation point in this control cycle;

[0011] Compare the torques at the state demarcation points in each operating region with the reference torque to determine the operating working points in each operating region;

[0012] Design the initial working point current according to the similarity or difference of the reference torques in two consecutive control cycles, and use the Newton-Raphson iteration method to calculate the current at the operating working point in this control cycle;

[0013] Take the current at the operating working point in this control cycle as the current reference value of the permanent magnet assisted synchronous reluctance motor to achieve optimized control of the permanent magnet assisted synchronous reluctance motor.

[0014] Further, the mathematical model of the permanent magnet assisted synchronous reluctance motor includes a voltage equation and a torque equation;

[0015] The expression of the voltage equation is:

[0016]

[0017] where, R s is the stator resistance, ω e is the electrical angular velocity, u d and u q are the voltages on the d-axis and q-axis respectively, i d and i q are the currents on the d-axis and q-axis respectively, and The flux linkage of the d-axis and q-axis respectively.

[0018] The expression of the torque equation is:

[0019]

[0020] Among them, T e is the motor torque, P n is the number of pole pairs of the motor.

[0021] Furthermore, the expression of the maximum torque current ratio curve equation is:

[0022]

[0023] The expression of the maximum torque voltage ratio curve equation is:

[0024]

[0025] The expression of the current limit curve equation is:

[0026]

[0027] Among them, I lim is the current limit value;

[0028] The expression of the voltage limit curve equation is:

[0029]

[0030] Furthermore, determining the motor operating region according to the actual speed of the permanent magnet assisted synchronous reluctance motor and the preset speed critical value includes:

[0031] When n ≤ n M , the operating region is I;

[0032] When n M <n ≤ n N , the operating region is II;

[0033] When n N <n ≤ n O , the operating region is III;

[0034] When n O <n, the operating region is IV;

[0035] Among them, n is the actual speed, n M is the base speed of the motor, n N and n O are two different critical speeds respectively.

[0036] Further, the method for determining the state demarcation points in each operating region is as follows:

[0037] The state demarcation point in operating region I is the intersection point of the maximum torque current ratio curve and the current limit curve;

[0038] The state demarcation points in operating region II are the intersection points of the voltage limit curve and the current limit curve and the intersection points of the voltage limit curve and the maximum torque current ratio curve;

[0039] The state demarcation points in operating region III are the intersection points of the voltage limit curve and the maximum torque voltage ratio curve and the intersection points of the voltage limit curve and the maximum torque current ratio curve;

[0040] The state demarcation point in operating region IV is the intersection point of the voltage limit curve and the maximum torque voltage ratio curve.

[0041] Further, the current of the state demarcation point in the previous control period is used as the initial demarcation point current of this control period through the following formula:

[0042]

[0043] where, and are the d-axis and q-axis currents of the initial demarcation point in the m control period respectively, and are the d-axis and q-axis currents of the state demarcation point in the m-1 control period respectively;

[0044] When m = 1, the initial demarcation point current is randomly selected within the region where the state demarcation point is located.

[0045] Further, calculating the current of the state demarcation point of this control period by using the Newton-Raphson iteration method includes:

[0046]

[0047] where, f 1 () and f 2 () respectively represent the iterative curve equations to be calculated determined according to the rotational speed, k represents the number of iterations, and are the d-axis and q-axis reference currents respectively, and J(k) is the Jacobian matrix at the kth iteration;

[0048] The convergence condition is:

[0049]

[0050] where, ε is the iteration precision.

[0051] Further, comparing the torque at the state demarcation point within each operating region with the reference torque value to determine the operating working point within each operating region, including:

[0052] Within operating region I, when the operating working point is the intersection of the maximum torque - current ratio curve and the current limit curve; when the operating working point is the intersection of the maximum torque - current ratio curve and the constant - torque curve with a torque value of ;

[0053] Within operating region II, when the operating working point is the intersection of the voltage limit curve and the current limit curve; when the operating working point is the intersection of the voltage limit curve and the constant - torque curve with a torque value of ; when the operating working point is the intersection of the maximum torque - current ratio curve and the constant - torque curve with a torque value of ;

[0054] Within operating region III, when the operating working point is the intersection of the voltage limit curve and the maximum torque - voltage ratio curve; when the operating working point is the intersection of the voltage limit curve and the constant - torque curve with a torque value of ; when the operating working point is the intersection of the maximum torque - current ratio curve and the constant - torque curve with a torque value of ;

[0055] Within operating region IV, when the operating working point is the intersection of the voltage limit curve and the maximum torque - voltage ratio curve; when the operating working point is the intersection of the voltage limit curve and the constant - torque curve with a torque value of ;

[0056] Among them, is the reference torque, T e,M is the torque at intersection point M, T e,A is the torque at intersection point A, T e,B is the torque at intersection point B, T e,C is the torque at intersection point C, T e,D is the torque at intersection point D, T e,E is the torque at intersection point E;

[0057] Intersection point M is the intersection of the maximum torque - current ratio curve and the current limit curve in operating region I,

[0058] Intersection point A is the intersection of the voltage limit curve and the current limit curve in operating region II,

[0059] The intersection point B is the intersection of the voltage limit curve and the maximum torque current ratio curve in operating region II.

[0060] The intersection point C is the intersection of the voltage limit curve and the maximum torque voltage ratio curve in operating region III.

[0061] The intersection point D is the intersection of the voltage limit curve and the maximum torque current ratio curve in operating region III.

[0062] The intersection point E is the intersection of the voltage limit curve and the maximum torque voltage ratio curve in operating region IV.

[0063] Furthermore, the initial operating point current is designed according to the similarity or difference of the reference torques in two consecutive control cycles, including:

[0064] When the reference torques in two consecutive control cycles are the same, the current at the operating point in the previous control cycle is used as the initial operating point current in this control cycle.

[0065] When the reference torques in two consecutive control cycles are different, the design is as follows:

[0066] When the operating point is the intersection of the maximum torque current ratio curve and the current limit curve, the intersection of the voltage limit curve and the current limit curve, or the intersection of the voltage limit curve and the maximum torque voltage ratio curve, the current at the operating point is directly obtained.

[0067] When the operating point is the intersection of the voltage limit curve and the constant torque curve with a torque value of T e * the initial operating point current is:

[0068]

[0069] where and are the d-axis and q-axis currents of the initial operating point in this control cycle respectively, y represents the state demarcation point on the right side of the voltage limit curve, z represents the state demarcation point on the left side of the voltage limit curve, T e,y and T e,z are the torques at point y and point z respectively, i d,y and i d,z are the d-axis currents at point y and point z respectively, i q,y and i q,z are the q-axis currents at point y and point z respectively;

[0070] When the operating point is the intersection of the maximum torque current ratio curve and the constant torque curve with a torque value of the initial operating point current is:

[0071]

[0072] wherein, i d,M and i q,M are respectively the d-axis and q-axis currents at the intersection point M.

[0073] Furthermore, the torque value is The constant torque curve equation for is:

[0074] wherein, P n is the number of pole pairs of the motor, and are respectively the magnetic fluxes of the d-axis and q-axis, and i d and i q are respectively the currents of the d-axis and q-axis.

[0075] The present invention adopts the MTPA equation and MTPV equation considering magnetic saturation. These two equations not only consider the variation of inductance with current, but also incorporate the partial derivative term of inductance with respect to current into the standard solution, fully considering the magnetic saturation characteristics of the permanent magnet assisted synchronous reluctance motor. The MTPA and MTPV equations more accurately describe the optimal curves of the motor in the full speed range, providing a basis for the high-performance operation of the motor in the full speed range.

[0076] The present invention gives the determination process of the optimal operating point of the motor during the full speed range control, determines the working partition of the motor operation based on the operating speed, and gives the selection scheme of the optimal current operating point within each partition. The adopted optimization process ensures the stability of the motor operation process and the smoothness of the switching process between different speed regions.

[0077] The iterative initial point design method proposed by the present invention is based on the local convergence characteristics of the Newton-Raphson iterative method. This method ensures the approximation of the iterative initial point to the final convergence point, ensuring that the present invention can reduce the computational burden. At the same time, the iterative initial point design method not only aims at the iterative solution of the operating working point, but also considers the iterative solution of the state boundary point. This consideration of all the solution possibilities of the intersection points ensures the low burden of the entire algorithm calculation process.

[0078] The present invention provides an iterative initial point design method for the full speed range control of a permanent magnet assisted synchronous reluctance motor. This method does not require additional signal injection and complex controller design, has a simple principle and is easy to implement. The proposed method significantly reduces the online calculation time of the full speed range control algorithm of the permanent magnet assisted synchronous reluctance motor, ensures the real-time performance of the full speed range control algorithm operation, and improves the full speed range operation performance of the permanent magnet assisted synchronous reluctance motor. Description of the Drawings

[0079] Figure 1Schematic diagram of two intersecting curves determined for different torque references of the motor in different operating regions, where (a) is operating region I, (b) is operating region II, (c) is operating region III, and (d) is operating region IV;

[0080] Figure 2 Iterative calculation flow chart based on Newton - Raphson iterative calculation;

[0081] Figure 3 Flow chart for determining the operating working point

[0082] Figure 4 Schematic diagram of the initial iterative point of the operating working point and its corresponding iterative convergence process when the torque reference changes; among them, (a) the intersection point is (b) the intersection point is

[0083] Figure 5 Experimental waveform diagram of the full - speed range control strategy, where (a) the rotational speed is constant and the torque reference increases step by step; (b) the torque reference is constant and the rotational speed increases linearly.

[0084] Figure 6 For Figure 5 Recorded waveforms, schematic diagram of the operating results mapped to the dq - axis current plane. Detailed implementation mode

[0085] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0086] Refer to Figures 1 to 6 Specifically describe this implementation mode. A full - speed range control method for a permanent - magnet assisted synchronous reluctance motor based on iterative initial point optimization described in this implementation mode includes:

[0087] Step 1, establish a mathematical model of the permanent - magnet assisted synchronous reluctance motor to describe the voltage equation and torque equation of the motor.

[0088] The specific expression of the voltage equation is:

[0089]

[0090] Among them, R s is the stator resistance, ω e is the electrical angular velocity, ud and u q are the voltages on the d-axis and q-axis respectively, and i d and i q are the currents on the d-axis and q-axis respectively. and are the magnetic fluxes on the d-axis and q-axis respectively.

[0091] The specific expression of the torque equation is:

[0092]

[0093] where T e is the motor torque, and P n is the number of pole pairs of the motor.

[0094] Step 2: According to the voltage equation and torque equation described in Step 1, solve the equations of the maximum torque per ampere (MTPA) curve and the maximum torque per voltage (MTPV) curve for the motor operation:

[0095] Solve the MTPA trajectory curve of the motor operation according to the mathematical model. The mathematical description form of the MTPA problem is:

[0096]

[0097] where f 1 is the MTPA optimization objective function, I lim is the current limit. Use the Lagrange multiplier method to solve the above optimization problem. The established solution equation is:

[0098]

[0099] where λ 1 is the Lagrange multiplier of the MTPA problem. The equation of the obtained MTPA curve is:

[0100]

[0101] Solve the MTPV trajectory curve of the motor operation according to the mathematical model. The mathematical description form of the MTPV problem is:

[0102]

[0103] where f 2 is the MTPV optimization objective function, u lim is the voltage limit. Similarly, use the Lagrange multiplier method to solve the above optimization problem. The established solution equation is:

[0104]

[0105] Among them, λ 2 is the Lagrange multiplier for the MTPV problem, and the equation of the obtained MTPV curve is:

[0106]

[0107] Step 3: According to the voltage limit value u lim and the current limit value I lim of the motor operation, determine the equations of the voltage limit curve and the current limit curve.

[0108] The expression of the voltage limit curve equation is:

[0109]

[0110] The expression of the current limit curve equation is:

[0111]

[0112] In this embodiment, the rated voltage of the 5.5kW permanent magnet assisted synchronous reluctance motor is selected as 380V, and the rated current is 14.7A. Therefore, the motor voltage limit is determined to be 311V, and the motor current limit is determined to be 20.78A. The determined voltage limit equation and current limit equation are:

[0113]

[0114]

[0115] Step 4: According to the actual speed n of the motor operation and the three speed critical values n M 、n N 、n O determine the operation area of the motor.

[0116] When n ≤ n M , the operation area is I;

[0117] When n M <n ≤ n N , the operation area is II;

[0118] When n N <n ≤ n O , the operation area is III;

[0119] When n O <n, the operation area is IV;

[0120] Among them, n M is the base speed of the motor, n N and nO They are two different critical speeds respectively.

[0121] In this embodiment, the base speed n of the motor M is 3270 rpm, the critical speed n N is 7650 rpm, and the critical speed n O is 15000 rpm.

[0122] Step 5: Determine the state boundary points of each region, design the current information at the iterative initial points when calculating each state boundary point, calculate the current information of the state boundary point through the Newton-Raphson iteration method, and then calculate the corresponding torque based on the torque equation in Step 1.

[0123] For operating region I, there is a state boundary point M (the intersection of the maximum torque current ratio curve and the current limit curve, denoted as C MTPA ∩C CL ).

[0124] For operating region II, there are two state boundary points A (the intersection of the voltage limit curve and the current limit curve, denoted as C VL ∩C CL ) and B (the intersection of the voltage limit curve and the maximum torque current ratio curve, denoted as C VL ∩C MTPA ).

[0125] For operating region III, there are two state boundary points C (the intersection of the voltage limit curve and the maximum torque voltage ratio curve, denoted as C VL ∩C MTPV ) and D (the intersection of the voltage limit curve and the maximum torque current ratio curve, denoted as C VL ∩C MTPA );

[0126] For operating region IV, there is a state boundary point E (the intersection of the voltage limit curve and the maximum torque voltage ratio curve, denoted as C VL ∩C MTPV ).

[0127] Among them, C MTPA is the MTPA curve, C MTPV is the MTPV curve, C VL is the voltage limit curve, and C CL is the current limit curve.

[0128] The schematic diagram of the state boundary points in different speed operating regions is as shown in Figure 1 .

[0129] The initial boundary point of the above-mentioned state boundary point is designed as follows: the current of the state boundary point in the previous control period is used as the initial boundary point current of this control period:

[0130]

[0131] Among them, among them, and are the d-axis and q-axis currents of the initial boundary point in the m control period respectively, and are the d-axis and q-axis currents of the state boundary point in the m-1 control period respectively, x = M, A, B, C, D, E.

[0132] When m = 1, the initial boundary point current is randomly selected within the area where the state boundary point is located.

[0133] Use the Newton-Raphson iteration method to calculate the current of the state boundary point in this control period:

[0134]

[0135] Among them, among them, f 1 () and f 2 () respectively represent the iterative curve equations to be calculated determined according to the rotational speed, k represents the number of iterations, and are the d-axis and q-axis reference currents respectively.

[0136] The Jacobian matrix J(k) at the k-th iteration is described as:

[0137]

[0138] The convergence condition for iterative calculation is:

[0139]

[0140] In this embodiment, the iteration accuracy ε is selected to be 0.04.

[0141] When the iteration meets the above convergence condition, obtain the dq current of the state boundary point, and then calculate the corresponding torque based on the torque equation in step 1.

[0142] The flowchart of the Newton-Raphson iterative calculation process is as Figure 2 shown.

[0143] Step 6, according to the state boundary point and torque determined in step 5, determine the two intersecting curves where the motor operating point is located, design the iterative initial point of the operating point, and calculate the coordinates of the operating point by the Newton-Raphson iteration method.

[0144] Within operating region I, when the maximum torque current ratio curve intersects with the current limit curve, and the operating point is denoted as C MTPA ∩C CL ; when the maximum torque current ratio curve intersects with the constant torque curve with a torque value of , and the operating point is denoted as

[0145] Within operating region II, when the voltage limit curve intersects with the current limit curve, and the operating point is denoted as C VL ∩C CL ; when the voltage limit curve intersects with the constant torque curve with a torque value of , and the operating point is denoted as When the maximum torque current ratio curve intersects with the constant torque curve with a torque value of , and the operating point is denoted as

[0146] Within operating region III, when the voltage limit curve intersects with the maximum torque voltage ratio curve, and the operating point is denoted as C VL ∩C MTPV ; when the voltage limit curve intersects with the constant torque curve with a torque value of , and the operating point is denoted as When the maximum torque current ratio curve intersects with the constant torque curve with a torque value of , and the operating point is denoted as

[0147] Within operating region IV, when the voltage limit curve intersects with the maximum torque voltage ratio curve, and the operating point is denoted as C VL ∩C MTPV ; when the voltage limit curve intersects with the constant torque curve with a torque value of , and the operating point is denoted as

[0148] where, T e,M is the torque at the state boundary point M, T e,A is the torque at the state boundary point A, T e,B is the torque at the state boundary point B, T e,C is the torque at the state boundary point C, T e,D is the torque at the state boundary point D, Te,E is the torque at the state demarcation point E.

[0149] The expression of the constant torque curve equation is:

[0150]

[0151] The operating points in different regions are determined as shown in Figure 3 the flowchart shown.

[0152] In this embodiment, the design of the initial operating point current needs to first judge whether the reference torque changes in two consecutive control cycles:

[0153] A. When the reference torques in two consecutive control cycles are the same, the current of the operating point in the previous control cycle is used as the initial operating point current of this control cycle:

[0154]

[0155] Among them, and are the d-axis and q-axis currents of the initial operating point in the m control cycle respectively, and are the d-axis and q-axis currents of the operating point in the m-1 control cycle respectively.

[0156] When m = 1, the initial operating point current is randomly selected within the region where the operating point is located.

[0157] B. When the reference torques in two consecutive control cycles are different, the design is as follows:

[0158] When the operating point is C MTPA ∩C CL 、C VL ∩C CL and C VL ∩C MTPV , the operating point has been calculated a priori and the current of the operating point is known. There is no need to design the initial operating point, and the current of the operating point is directly obtained.

[0159] When the operating point is , the initial operating point current is designed as:

[0160]

[0161] Among them, and are the d-axis and q-axis currents of the initial operating point of this control cycle respectively. y represents the state demarcation point on the right side of the voltage limit curve, z represents the state demarcation point on the left side of the voltage limit curve, T e,y and T e,zThe torques at points y and z are respectively, i d,y and i d,z The d-axis currents at points y and z are respectively, i q,y and i q,z The q-axis currents at points y and z are respectively.

[0162] At the operating point the initial operating point current is designed as:

[0163]

[0164] wherein, i d,M and i q,M are the d- and q-axis currents at point M respectively.

[0165] In this example, the Newton-Raphson iteration algorithm is used to obtain the dq current coordinates at the operating point, which is the same as the calculation process of the state boundary point in step 5, and the convergence conditions are also the same. The convergence process of the proposed iteration method is as Figure 5 shown. Figure 6 The experimental waveforms of the entire algorithm implementation are given.

[0166] Finally, the current information of the operating point under the current online calculation is used as the current reference value of the permanent magnet assisted synchronous reluctance motor to realize the optimal control of the permanent magnet assisted synchronous reluctance motor.

[0167] Although the present invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed, as long as they do not depart from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the features described in the different dependent claims and in the present text can be combined in a manner different from that described in the original claims. It should also be understood that the features described in connection with a single embodiment can be used in other described embodiments.

Claims

1. A full-speed range control method for a permanent magnet assisted synchronous reluctance motor based on iterative initial point optimization, characterized in that: include: Constructing a mathematical model of a permanent magnet assisted synchronous reluctance motor, and describing a maximum torque current ratio curve equation, a maximum torque voltage ratio curve equation, a current limit curve equation, and a voltage limit curve equation of the permanent magnet assisted synchronous reluctance motor according to the mathematical model; The expression of the maximum torque current ratio curve equation is: The expression of the maximum torque voltage ratio curve equation is: The expression of the current limit curve equation is: Among them, I lim is the current limit value; The voltage limit curve equation is expressed as: R s is the stator resistance, ω e is the electrical angular velocity, i d and i q are the currents of the d-axis and q-axis respectively, and are the magnetic flux of d-axis and q-axis respectively; Determine the motor operation area and the state demarcation point in each operation area according to the actual speed of the permanent magnet assisted synchronous reluctance motor and the preset speed critical value; The current at the state demarcation point of the previous control cycle is used as the initial demarcation point current of the current control cycle, the current at the state demarcation point of the current control cycle is calculated using the Newton-Raphson iteration method, and the corresponding torque is calculated according to the current at the state demarcation point of the current control cycle; Compare the torque at the state boundary point in each operating area with the reference torque to determine the operating point in each operating area; The initial operating point current is designed according to the similarities and differences of the reference torques in two consecutive control cycles, and the current of the operating point of this control cycle is calculated using the Newton-Raphson iteration method; The initial operating point current is designed according to the similarities and differences of the reference torques in two consecutive control cycles, including: When the reference torques in two consecutive control cycles are the same, the current of the operating point in the previous control cycle is used as the initial operating point current in the current control cycle; When the reference torque in two consecutive control cycles is different, the design is as follows: When the operating point is the intersection of the maximum torque current ratio curve and the current limit curve, the intersection of the voltage limit curve and the current limit curve, or the intersection of the voltage limit curve and the maximum torque voltage ratio curve, the current of the operating point is directly obtained; When the operating point is the voltage limit curve and the torque value is T e * When the constant torque curve of the initial working point is at the intersection, the initial working point current is: in, is the reference torque, and are the d-axis and q-axis currents of the initial working point of this control cycle, y represents the state demarcation point on the right side of the voltage limit curve, z represents the state demarcation point on the left side of the voltage limit curve, T e,y and T e,z are the torques at point y and point z respectively, i d,y and i d,z are the d-axis currents at points y and z, respectively, i q,y and i q,z are the q-axis currents at points y and z respectively; When the operating point is the maximum torque current ratio curve and the torque value is When the constant torque curve of the initial working point is at the intersection, the initial working point current is: Among them, T e,M is the torque at the intersection point M, i d,M and i q,M are the d-axis and q-axis currents at the intersection point M, respectively. The intersection point M is the intersection point of the maximum torque current ratio curve and the current limit curve in the operating region I; The current at the operating point of the control cycle is used as a current reference value of the permanent magnet assisted synchronous reluctance motor to achieve optimized control of the permanent magnet assisted synchronous reluctance motor.

2. A permanent magnet assisted synchronous reluctance motor full speed range control method based on iterative initial point optimization according to claim 1, characterized in that: The mathematical model of the permanent magnet assisted synchronous reluctance motor includes a voltage equation and a torque equation; The voltage equation is expressed as: Among them, u d and u q are the voltages of the d-axis and q-axis respectively; The torque equation is expressed as: Among them, T e is the motor torque, P n is the number of motor pole pairs.

3. The method for full-speed control of a permanent magnet assisted synchronous reluctance motor based on iterative initial point optimization according to claim 1, characterized in that: Determining the motor operation area according to the actual speed of the permanent magnet assisted synchronous reluctance motor and a preset speed critical value includes: When n≤n M When , the operating area is I; When n M <n≤n N , the operating area is II; When n N <n≤n O When , the operating area is III; When n O When <n, the operation area is IV; Where n is the actual speed, n M is the motor base speed, n N and n O There are two different critical speeds.

4. A permanent magnet assisted synchronous reluctance motor full speed range control method based on iterative initial point optimization according to claim 3, characterized in that: The method for determining the state demarcation points in each operating area is: The state demarcation point in the operating area I is the intersection of the maximum torque current ratio curve and the current limit curve; The state demarcation points in the operation area II are the intersection points of the voltage limit curve and the current limit curve and the intersection points of the voltage limit curve and the maximum torque current ratio curve; The state demarcation points in the operation area III are the intersection points of the voltage limit curve and the maximum torque voltage ratio curve and the intersection points of the voltage limit curve and the maximum torque current ratio curve; The state dividing point within the operating area IV is the intersection of the voltage limit curve and the maximum torque voltage ratio curve.

5. The method for full-speed control of a permanent magnet assisted synchronous reluctance motor based on iterative initial point optimization according to claim 1, characterized in that: The current at the state demarcation point of the previous control cycle is used as the initial demarcation point current of this control cycle through the following formula: in, and are the d-axis and q-axis currents at the initial demarcation point in the m control cycle, and are the d-axis and q-axis currents at the state boundary points in the m-1 control cycle respectively; When m=1, the initial demarcation point current is randomly selected in the region where the state demarcation point is located.

6. The method for full-speed control of a permanent magnet assisted synchronous reluctance motor based on iterative initial point optimization according to claim 1, characterized in that: The method of calculating the current of the state demarcation point of the control cycle by using the Newton-Raphson iteration method includes: Wherein, f1() and f2() represent the iterative curve equations to be calculated according to the rotation speed, k represents the number of iterations, and are the d-axis and q-axis reference currents, respectively, and J(k) is the Jacobian matrix at the kth iteration; The convergence conditions are: Among them, ε is the iteration accuracy.

7. A permanent magnet assisted synchronous reluctance motor full speed range control method based on iterative initial point optimization according to claim 4, characterized in that: The step of comparing the torque of the state demarcation point in each operating area with the reference torque value to determine the operating point in each operating area includes: In operating area I, when When the operating point is the intersection of the maximum torque current ratio curve and the current limit curve, When the operating point is the maximum torque current ratio curve and the torque value is The intersection of the constant torque curve; In operating region II, when When , the operating point is the intersection of the voltage limit curve and the current limit curve; when When the operating point is the voltage limit curve and the torque value is The intersection of the constant torque curve; when When the operating point is the maximum torque current ratio curve and the torque value is The intersection of the constant torque curve; In operating region III, when When the operating point is the intersection of the voltage limit curve and the maximum torque voltage ratio curve, When the operating point is the voltage limit curve and the torque value is The intersection of the constant torque curve is When the operating point is the maximum torque current ratio curve and the torque value is The intersection of the constant torque curve; In operating region IV, when When the operating point is the intersection of the voltage limit curve and the maximum torque voltage ratio curve, When the operating point is the voltage limit curve and the torque value is The intersection of the constant torque curve; Among them, T e,A is the torque at the intersection point A, T e,B is the torque at the intersection point B, T e,C is the torque at the intersection point C, T e,D is the torque at the intersection point D, T e,E is the torque at the intersection point E; Intersection point A is the intersection of the voltage limit curve and the current limit curve in operation area II. Intersection point B is the intersection of the voltage limit curve and the maximum torque current ratio curve in operating area II. The intersection point C is the intersection point of the voltage limit curve and the maximum torque voltage ratio curve in the operating area III. The intersection point D is the intersection point of the voltage limit curve and the maximum torque current ratio curve in the operating area III. The intersection point E is the intersection point of the voltage limit curve and the maximum torque voltage ratio curve in the operating region IV.

8. According to the method for full-speed control of a permanent magnet assisted synchronous reluctance motor based on iterative initial point optimization according to claim 1, the torque value is The constant torque curve equation is: in, P n is the number of motor pole pairs, and are the magnetic flux of d-axis and q-axis respectively, i d and i q are the currents of the d-axis and q-axis respectively.

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