Permanent magnet auxiliary synchronous reluctance motor full-speed-domain current optimization control method for improving operation area judgment

Abstract

The invention discloses a permanent magnet auxiliary synchronous reluctance motor full-speed-domain current optimization control method for improving operation area judgment, and relates to the technical field of motor control. The objective of the invention is to solve the problem of motor performance reduction caused by regional judgment based on the rotating speed critical obtained offline. The method comprises the following steps: constructing a mathematical model of a motor, respectively describing curvilinear equations, and calculating feature points of an operation region; determining a current operation area of the motor and a state demarcation point in the current operation area according to the size relation between the voltage of each feature point and the current voltage limit value; and comparing the torque of the state demarcation point in the current operation area with a reference torque value, determining an optimal working point of full-speed-domain current optimization, and taking the coordinate of the optimal working point as a current reference value of the permanent magnet auxiliary synchronous reluctance motor to realize optimal control of the permanent magnet auxiliary synchronous reluctance motor.

Description

Technical Field

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

[0002] Permanent magnet-assisted Synchronous Reluctance Motor (PMaSynRM) has the characteristics of simple structure, low cost and wide speed range, and has received extensive attention in the fields of industrial drive and electric vehicle applications in recent years. Thanks to its excellent weak magnetic properties, the motor can operate stably in a wide speed range, so it is of practical significance to study its current optimization method in the full speed range.

[0003] The full-speed current optimization method is to design the optimal operating current point according to the operating status of the motor in different operating areas. This method covers two key steps: operating area judgment and operating working point determination. In different operating areas, the optimality indicators pursued by the motor system are different, so the method of determining the optimal working point is also different. Therefore, accurate operating area judgment is crucial to the determination of the operating point.

[0004] At present, the full-speed domain current optimization method of permanent magnet assisted synchronous reluctance motor is based on the critical speed results obtained offline to judge the operating area. The critical speed is calculated a priori according to the motor parameters, which includes the switching speed between maximum torque per ampere (MTPA) control, weak magnetic control and maximum torque per voltage (MTPV) control. However, the critical speed obtained offline cannot be updated in real time, which leads to inaccurate judgment results of the motor operating area when the motor parameters change.

[0005] At the same time, bus voltage changes will also significantly affect the critical speed results. The critical speed is directly related to the bus voltage. The DC bus voltage affected by load fluctuations is a dynamic curve, so the true critical speed is a dynamic result. The critical speed determined based on the constant bus voltage design value also leads to inaccurate judgment of the motor operating area. Inaccurate judgment of the operating area causes the designed motor operating point to be non-optimal, and even causes the operating point to exceed the effective operating area, resulting in system instability, which in turn affects the operating performance of the motor system.

[0006] Based on the introduction of the above background technology, it can be seen that the current full-speed domain current trajectory planning method of permanent magnet assisted synchronous reluctance motor often uses offline acquired speed criticality in the operation area judgment, and ignores the bus voltage change, which leads to the decline of motor operation performance. In order to ensure the accuracy of speed switching and improve the motor operation performance, it is of great significance to propose a real-time operation area judgment method. Summary of the invention

[0007] The present invention aims to solve the problem that in the existing full-speed current optimization method of a permanent magnet assisted synchronous reluctance motor, the operating area is determined by using the speed critical obtained offline and the bus voltage change is ignored, resulting in a decrease in the operating performance of the motor. A full-speed current optimization control method for a permanent magnet assisted synchronous reluctance motor with improved operating area judgment is provided.

[0008] A full-speed domain current optimization control method for a permanent magnet assisted synchronous reluctance motor with improved operation area judgment, comprising:

[0009] 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, a voltage limit curve equation and a constant torque curve equation of the permanent magnet assisted synchronous reluctance motor according to the mathematical model;

[0010] Under the current plane, the intersection point M between the maximum torque current ratio curve and the current limit curve, the intersection point N between the maximum torque voltage ratio curve and the current limit curve, and the intersection point O between the maximum torque current ratio curve and the origin are calculated respectively, and the intersection points M, N and O are used as characteristic points of the operating area;

[0011] Calculate the voltage of each characteristic point in the operating area respectively, and calculate the voltage of each characteristic point according to the current voltage limit value u lim The size relationship between them determines the current operation area of ​​the permanent magnet assisted synchronous reluctance motor and determines the state demarcation point within the area;

[0012] Compare the torque at the state boundary point in the current operating area with the reference torque value The size of is used to determine the optimal working point for full-speed current optimization, and the coordinates of the optimal working point are used 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.

[0013] Furthermore, the mathematical model of the permanent magnet assisted synchronous reluctance motor includes a voltage equation and a torque equation;

[0014] The voltage equation is expressed as:

[0015]

[0016] Among them, Rs is the stator resistance, ω e is the electrical angular velocity, u d and u q are the voltages of the d-axis and q-axis respectively, 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;

[0017] The torque equation is expressed as:

[0018]

[0019] Among them, T e is the motor torque, P n is the number of motor pole pairs.

[0020] Furthermore, the expression of the maximum torque current ratio curve equation is:

[0021]

[0022] The expression of the maximum torque voltage ratio curve equation is:

[0023]

[0024] The expression of the current limit curve equation is:

[0025]

[0026] Among them, I lim is the current limit value;

[0027] The voltage limit curve equation is expressed as:

[0028]

[0029] The expression of the constant torque curve equation is:

[0030]

[0031] Furthermore, the coordinates of the intersection point M are calculated by the following formula:

[0032]

[0033] The coordinates of the intersection point N are calculated by the following formula:

[0034]

[0035] The coordinates of the intersection point O are expressed as: O=(0,0).

[0036] Furthermore, the above-mentioned calculation of the voltage of the characteristic point of each operating area includes:

[0037] The voltage at the characteristic point of each operating area is calculated by the following formula:

[0038]

[0039] Among them, u y Represents the voltage at the characteristic point y in the operating area, y=M,N,O,i d,y and i q,y They represent the d-axis and q-axis currents of the characteristic point y in the operating area, respectively, and R s is the stator resistance, ω e is the electrical angular velocity, and are the magnetic flux along the d-axis and q-axis respectively.

[0040] Furthermore, the above current voltage limit value u lim The method to obtain is:

[0041] Collect the current bus voltage u dc , the current voltage limit value u is calculated by the following formula lim :

[0042]

[0043] Furthermore, when u M ≤u lim When , the operating area is I;

[0044] When u M >u lim ≥u N When , the operating area is II;

[0045] When u N >u lim ≥u O When , the operating area is III;

[0046] When u O >u lim , the operating area is IV.

[0047] Furthermore, the state demarcation point in the operation region I is the intersection of the maximum torque current ratio curve and the current limit curve;

[0048] 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;

[0049] 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;

[0050] The state dividing point within the operating area IV is the intersection of the voltage limit curve and the maximum torque voltage ratio curve.

[0051] Furthermore, in operation region I, when When the optimal working point is the intersection of the maximum torque current ratio curve and the current limit curve, When the optimal working point is the maximum torque current ratio curve and the torque value is The intersection of the constant torque curve;

[0052] In operating region II, when When , the optimal operating point is the intersection of the voltage limit curve and the current limit curve. When the optimal working point is the voltage limit curve and the torque value is The intersection of the constant torque curve is When the optimal working point is the maximum torque current ratio curve and the torque value is The intersection of the constant torque curve;

[0053] In operating region III, when When , the optimal working point is the intersection of the voltage limit curve and the maximum torque voltage ratio curve. When the optimal working point is the voltage limit curve and the torque value is The intersection of the constant torque curve is When the optimal working point is the maximum torque current ratio curve and the torque value is The intersection of the constant torque curve;

[0054] In operating region IV, when When , the optimal working point is the intersection of the voltage limit curve and the maximum torque voltage ratio curve; when When the optimal working point is the voltage limit curve and the torque value is The intersection of the constant torque curve;

[0055] Among them, T e,M is the torque at the intersection point M, 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;

[0056] Intersection point A is the intersection of the voltage limit curve and the current limit curve in operation area II.

[0057] Intersection point B is the intersection of the voltage limit curve and the maximum torque current ratio curve in operating area II.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] The present invention provides a process for determining the optimal operating point of a permanent magnet assisted synchronous reluctance motor in the full-speed current optimization process, determines the motor's operating area based on the voltage relationship, and provides a selection scheme for the optimal current operating point in each operating area. The proposed method has a smooth switching process and a stable operating process. At the same time, the proposed method does not require additional signal injection and complex controller design, and has a simple principle and is easy to implement.

[0062] Compared with the traditional method of judging the operating area based on a priori acquired speed, the present invention fully considers the changes in motor parameters and bus voltage fluctuations, and can judge the operating area of ​​the motor online based on the real-time voltage relationship. The zoning result is more accurate, ensuring the accuracy of the online optimization result.

[0063] The online optimization control method of the present invention takes into account the magnetic saturation effect and the motor resistance term. The MTPA curve and MTPV curve adopted take into account the influence of magnetic saturation, and the motor resistance term is also considered in the voltage trajectory curve, which ensures the accuracy of the modeling standard in the optimization process, and further ensures the accurate calculation of the optimized operating point. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 Schematic diagrams of different operating areas, including (a) operating area I, (b) operating area II, (c) operating area III, and (d) operating area IV;

[0065] Figure 2 A flow chart for determining the operating point of the operation according to the present invention;

[0066] Figure 3 Schematic diagram of the effect of bus voltage change on voltage limit curve, where (a) is the speed of 3800rpm, (b) is the speed of 7000rpm;

[0067] Figure 4 The present invention is a flow chart of a full-speed current optimization control method for a permanent magnet assisted synchronous reluctance motor with improved operation area judgment. DETAILED DESCRIPTION

[0068] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0069] Reference Figures 1 to 4 Specifically describing this embodiment, the method for optimizing the current control of a permanent magnet assisted synchronous reluctance motor in full speed range with improved operation area judgment described in this embodiment includes:

[0070] 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.

[0071] In this embodiment, the specific expression of the voltage equation is:

[0072]

[0073] Among them, R s is the stator resistance, ω e is the electrical angular velocity, u d and u q are the voltages of the d-axis and q-axis respectively, i d and i q are the currents of the d-axis and q-axis respectively, and are the magnetic flux along the d-axis and q-axis respectively.

[0074] The specific expression of the torque equation is:

[0075]

[0076] Among them, T e is the motor torque, P n is the number of motor pole pairs.

[0077] Step 2, based on the motor mathematical model described in step 1, give equations for the motor's maximum torque per ampere (MTPA) curve, maximum torque per voltage (MTPV) curve, current limit (CL) curve, voltage limit (VL) curve and constant torque curve.

[0078] The expression of the established MTPA curve equation is:

[0079]

[0080] The expression of the established MTPV curve equation is:

[0081]

[0082] The expression of the established CL curve equation is:

[0083]

[0084] Among them, I lim In this embodiment, the rated current of the 5.5kW permanent magnet assisted synchronous reluctance motor is 14.7A, and the current limit equation determined is:

[0085] VL curve equation and real-time voltage limit value u lim Therefore, the equation of the VL curve is:

[0086]

[0087] In this embodiment, the constant torque curve equation is a series of different reference torque values The following equation can be generally expressed as:

[0088]

[0089] Step 3, before real-time calculation, the current coordinates of the characteristic points of the operating area are calculated according to the MTPA curve trajectory, MTPV curve trajectory, and CL curve trajectory in the current plane, including: the intersection M of the MTPA curve and the CL curve, the intersection N of the MTPV curve and the CL curve, and the intersection O of the MTPA curve and the origin. The intersections M, N, and O are used to calculate the characteristic points of each operating area.

[0090] The coordinate calculation equations of feature points M and N are described as:

[0091]

[0092] Among them, C x Represents the x curve, x=MTPA,MTPV,CL, then C x1 ∩C x2 Represents the intersection of curve x1 and curve x2.

[0093] The feature point O is the origin, and its coordinates are O=(i d,O ,i q,O)=(0,0). The feature points M and N are calculated using an iterative calculation method to obtain the calculation results. The coordinates of the feature points M and N are described as: (i d,M ,i q,M ) and (i d,N ,i q,N ).

[0094] In this embodiment, based on the selected 5.5kW permanent magnet assisted synchronous reluctance motor, the current coordinates of the three characteristic points can be calculated, which are:

[0095] M=(i d,M ,i q,M )=(-15.04,14.36)

[0096] N=(i d,N ,i q,N )=(20.22,4.40).

[0097] O=(i d,O ,i q,O )=(0,0)

[0098] Step 4: In the real-time calculation process, the voltage limit value is calculated based on the sampled bus voltage.

[0099] In this embodiment, the bus voltage u dc The voltage Hall sensor is used to sample and obtain the real-time voltage limit value based on the following formula:

[0100] Step 5: According to the coordinates of the three characteristic points M, N and O obtained before the real-time calculation, the voltage value at each point is calculated using the voltage equation.

[0101] In this embodiment, the voltage equation of the characteristic point is calculated according to the coordinates of the characteristic points M, N and O and the speed obtained in real time:

[0102]

[0103] Among them, y=M,N,O.

[0104] Step 6: Based on the voltage at the characteristic point and the voltage limit value u lim The relationship between determines the operating area of ​​the motor.

[0105] When u M ≤u lim When , the operating area is I;

[0106] When u M >u lim ≥u N When , the operating area is II;

[0107] When u N >u lim ≥u O When , the operating area is III;

[0108] When u O >u lim When , the operating area is IV;

[0109] The diagrams of different operating areas are as follows Figure 1 shown.

[0110] Step 7: Determine the state boundary points within each operating area according to the planned operating area.

[0111] For the operation area I, there is a state dividing point M (the intersection of the maximum torque current ratio curve and the current limit curve, expressed as C MTPA ∩C CL ).

[0112] For operation area II, there are two state dividing points A (the intersection of the voltage limit curve and the current limit curve, represented by C VL ∩C CL ) and B (the intersection of the voltage limit curve and the maximum torque current ratio curve, expressed as C VL ∩C MTPA ).

[0113] For operation area III, there are two state dividing 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, expressed as C VL ∩C MTPA );

[0114] For operation area IV, there is a state dividing point E (the intersection of the voltage limit curve and the maximum torque voltage ratio curve, expressed as C VL ∩C MTPV ).

[0115] The diagrams of the different state dividing points are as follows Figure 1 shown.

[0116] Step 8, giving the optimal operating point for full-speed current optimization according to the divided operating areas and state demarcation points.

[0117] For operating region I, when When the optimal working point is: the intersection of the maximum torque current ratio curve and the current limit curve (C MTPA ∩C CL );when When the optimal working point is: the maximum torque current ratio curve and the torque value are T e * The intersection of the constant torque curve

[0118] For operating zone II, when When the optimal working point is: the intersection of the voltage limit curve and the current limit curve (C VL ∩C CL );when When the optimal working point is: the voltage limit curve and the torque value are The intersection of the constant torque curve when When the optimal working point is: the maximum torque current ratio curve and the torque value are The intersection of the constant torque curve

[0119] For operating region III, when When the optimal working point is: the intersection of the voltage limit curve and the maximum torque voltage ratio curve (C VL ∩C MTPV );when When the optimal working point is: the voltage limit curve and the torque value are The intersection of the constant torque curve when When the optimal working point is: the maximum torque current ratio curve and the torque value are The intersection of the constant torque curve

[0120] For operating region IV, when When the optimal working point is: the intersection of the voltage limit curve and the maximum torque voltage ratio curve (C VL ∩C MTPV );when When the optimal working point is: the voltage limit curve and the torque value are The intersection of the constant torque curve

[0121] in, Indicates the torque value is Constant torque curve, T e,M is the torque at the intersection point M, 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.

[0122] At this point, the coordinates of the optimal operating point can be obtained and used as a current reference for the permanent magnet assisted synchronous reluctance motor to optimize the motor control performance.

[0123] Although the present invention is 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. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that the features described in conjunction with a single embodiment may be used in other described embodiments.

Claims

1. A method for optimizing the current control of a permanent magnet assisted synchronous reluctance motor in full speed range with improved operation area judgment, 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, a voltage limit curve equation and a constant torque curve equation of the permanent magnet assisted synchronous reluctance motor according to the mathematical model; Under the current plane, the intersection point M between the maximum torque current ratio curve and the current limit curve, the intersection point N between the maximum torque voltage ratio curve and the current limit curve, and the intersection point O between the maximum torque current ratio curve and the origin are calculated respectively, and the intersection points M, N and O are used as characteristic points of the operating area; Calculate the voltage of each characteristic point in the operating area respectively, and calculate the voltage of each characteristic point according to the current voltage limit value u lim The size relationship between them determines the current operation area of ​​the permanent magnet assisted synchronous reluctance motor and determines the state demarcation point within the area; Compare the torque at the state boundary point in the current operating area with the reference torque value T e * The size of is used to determine the optimal working point for full-speed current optimization, and the coordinates of the optimal working point are used 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.

2. A method for optimizing the current control of a permanent magnet assisted synchronous reluctance motor in full speed range with improved operation area judgment 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, R s is the stator resistance, ω e is the electrical angular velocity, u d and u q are the voltages of the d-axis and q-axis respectively, 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; The torque equation is expressed as: Among them, T e is the motor torque, P n is the number of motor pole pairs.

3. A method for optimizing the current control of a permanent magnet assisted synchronous reluctance motor in full speed range with improved operation area judgment according to claim 2, characterized in that: 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: The expression of the constant torque curve equation is:

4. A method for optimizing the current control of a permanent magnet assisted synchronous reluctance motor in full speed range with improved operation area judgment according to claim 3, characterized in that: The coordinates of the intersection point M are calculated by the following formula: The coordinates of the intersection point N are calculated by the following formula: The coordinates of the intersection point O are expressed as: O=(0,0).

5. The method for optimizing the current control of a permanent magnet assisted synchronous reluctance motor in full speed range with improved operation area judgment according to claim 1 is characterized in that: The step of respectively calculating the voltages of the characteristic points of each operating area includes: The voltage at the characteristic point of each operating area is calculated by the following formula: Among them, u y Represents the voltage at the characteristic point y in the operating area, y=M,N,O,i d,y and i q,y They represent the d-axis and q-axis currents of the characteristic point y in the operating area, respectively, and R s is the stator resistance, ω e is the electrical angular velocity, and are the magnetic flux along the d-axis and q-axis respectively.

6. A method for optimizing the current control of a permanent magnet assisted synchronous reluctance motor in full speed range with improved operation area judgment according to claim 5, characterized in that: The current voltage limit value u lim The method to obtain is: Collect the current bus voltage u dc , the current voltage limit value u is calculated by the following formula lim :

7. A method for optimizing the current control of a permanent magnet assisted synchronous reluctance motor in full speed range with improved operation area judgment according to claim 6, characterized in that: When u M ≤u lim When , the operating area is I; When u M >u lim ≥u N When , the operating area is II; When u N >u lim ≥u O When , the operating area is III; When u O >u lim , the operating area is IV.

8. A method for optimizing the current control of a permanent magnet assisted synchronous reluctance motor in full speed range with improved operation area judgment according to claim 7, characterized in that: 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.

9. A method for optimizing the current control of a permanent magnet assisted synchronous reluctance motor in full speed range with improved operation area judgment according to claim 8, characterized in that: In operating region I, when When T e * <T e,M When the optimal working point is the maximum torque current ratio curve and the torque value is T e * The intersection of the constant torque curve; In the operating region II, when T e * ≥T e,A When T e,A >T e * ≥T e,B When the optimal working point is the voltage limit curve and the torque value is T e * The intersection of the constant torque curve, when T e * <T e,B When the optimal working point is the maximum torque current ratio curve and the torque value is T e * The intersection of the constant torque curve; In the operating region III, when T e * ≥T e,C When T e,C >T e * ≥T e,D When the optimal working point is the voltage limit curve and the torque value is T e * The intersection of the constant torque curve, when T e * <T e,D When the optimal working point is the maximum torque current ratio curve and the torque value is T e * The intersection of the constant torque curve; In the operating region IV, when T e * ≥T e,E When T e * <T e,E When the optimal working point is the voltage limit curve and the torque value is T e * The intersection of the constant torque curve; Among them, T e,M is the torque at the intersection point M, 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.

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