High magnetic circuit saturation permanent magnet synchronous motor MTPA control method based on partial derivative term compensation

Abstract

The invention discloses a high magnetic circuit saturation permanent magnet synchronous motor MTPA control method based on partial derivative term compensation, and the method comprises the steps: obtaining a relation between a phase current and a dq axis current, and obtaining a corresponding dq axis current relation based on an MTPA optimization equation considering a partial derivative term and an MTPA optimization equation ignoring the partial derivative term; obtaining a reference value, inductance, permanent magnet flux linkage, a partial derivative term and an MTPA angle of the iq, and obtaining dq-axis current according to an MTPA optimization equation considering the partial derivative term so as to perform motor control; wherein the MTPA angle is obtained based on an MTPA optimization equation in which partial derivative terms are ignored and by using a difference method. According to the invention, the MTPA angle of the high magnetic circuit saturation permanent magnet synchronous motor can be better tracked under different load conditions.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of permanent magnet synchronous motors, and in particular to a MTPA control method for a high magnetic circuit saturation permanent magnet synchronous motor based on partial derivative compensation. Background Art

[0002] Permanent magnet synchronous motor (PMSM) is widely used in key areas such as CNC machine tools, robots, advanced rail transportation equipment, and new energy vehicles due to its advantages such as high power density, high efficiency, and high reliability. However, with the increasing industrial demand for permanent magnet synchronous motors in terms of power density, light weight, and small size, the magnetic saturation effect of motors has become more and more significant. Especially in some high-end industrial equipment, such as special vehicles, aircraft, and space shuttles, their motors are not only limited by installation space and deadweight, but also need to face a series of high-load tasks in extreme environments, resulting in a high degree of saturation in the motor magnetic circuit. Compared with traditional motors, permanent magnet synchronous motors with higher magnetic circuit saturation (abbreviated as high magnetic circuit saturation permanent magnet synchronous motors, HSPMSM) have more complex changes in electromagnetic parameters with saturation, making it difficult to meet the performance requirements of motor systems in high-end industrial equipment with the traditional maximum torque circuit ratio control method of permanent magnet synchronous motors. Therefore, the research on MTPA control methods for high magnetic circuit saturation permanent magnet synchronous motors has important theoretical value and practical significance for promoting the innovative development of high-end industrial equipment in key areas.

[0003] Interior Permanent Magnet Synchronous Motor (PMSM) is widely used due to its high efficiency and high power density. Due to the asymmetry of the dq axis magnetic circuit, the electromagnetic torque of the interior permanent magnet synchronous motor contains reluctance torque. In order to make full use of the reluctance torque, the maximum torque current ratio (MTPA) control strategy is usually adopted to improve the efficiency and torque of the permanent magnet synchronous motor by optimizing the dq axis current combination.

[0004] Traditional MTPA control usually regards the parameters such as the inductance and flux of the motor as constants, and calculates the optimal current angle based on the dq mathematical model. However, in actual operation, the parameters such as the inductance and permanent magnet flux of the motor will change with the change of load, especially for motors with high magnetic circuit saturation, this change is particularly significant. Therefore, the MTPA control method that does not consider the parameter change cannot truly achieve the optimal distribution of the dq axis current of the built-in permanent magnet synchronous motor. In response to the problem of parameter changes in MTPA control, many scholars have proposed various methods.

[0005] Some prior arts use finite element simulation to obtain motor parameters and use them for MTPA control, but there is a large deviation between the actual motor parameters and the motor parameters of finite element simulation, which seriously affects the effectiveness of the method. The use of a lookup table (LUT) method or curve fitting can solve the shortcomings of the finite element method. Some prior arts measure the optimal dq axis current value of the motor under different working conditions offline through experiments, and save the data in the storage space of the controller, and select the optimal current given value according to the different working conditions of the permanent magnet synchronous motor. Some prior arts use numerical analysis methods to fit the results of offline measurements into a nonlinear flux linkage model, and use the model to calculate the optimal current angle. Some prior arts perform segmented fitting on the measured data to improve the accuracy of the optimal angle calculation. However, both the LUT method and the curve fitting method require time-consuming experimental processes and a large amount of experimental data, which affects their practicality. Some prior arts propose a search method, which searches for the MTPA angle corresponding to the minimum stator current online by injecting a signal. This method does not depend on the motor parameters, but it is easy to cause the current angle to oscillate at the extreme value, thereby affecting the stability of the system.

[0006] At the same time, some scholars have proposed to use changing parameters to calculate the optimal current angle through online parameter estimation. Some existing technologies use a signal processing technology based on virtual high-frequency signal injection to obtain inductance in real time. Some existing technologies use a rotating high-frequency voltage injection method to identify inductance and normalize the parameters. In addition, there are also literatures that use intelligent algorithms to obtain parameters under different loads, such as genetic algorithms, model reference adaptive algorithms, neural network algorithms, etc. However, such methods often ignore the changing trend of inductance and permanent magnet magnetic flux during the calculation process, that is, the partial derivative of the parameters. Therefore, there will still be a deviation between the calculated optimal current angle and the actual optimal current angle, which will affect the final optimization effect. Summary of the invention

[0007] In view of the technical problems existing in the prior art, the present invention provides a precise control method for a high magnetic circuit saturation permanent magnet synchronous motor MTPA based on partial derivative compensation.

[0008] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0009] A method for controlling a high magnetic circuit saturation permanent magnet synchronous motor MTPA based on partial derivative compensation comprises the following steps:

[0010] Obtain the relationship between the phase current and the dq axis current, and obtain the corresponding dq axis current relationship based on the MTPA optimization equation considering the partial derivative and the MTPA optimization equation ignoring the partial derivative;

[0011] Get i qThe reference value of inductance, permanent magnet flux, partial derivative and MTPA angle are obtained, and then the dq axis current is obtained according to the MTPA optimization equation considering the partial derivative for motor control; the MTPA angle is obtained based on the MTPA optimization equation ignoring the partial derivative and using the difference method.

[0012] Preferably, the relationship between the phase current and the dq axis current is specifically:

[0013]

[0014] In the formula, i d ,i q are d-axis and q-axis currents respectively; i s is the phase current vector; β is i s The angle between the current axis and the q axis is also called the current angle.

[0015] Preferably, the MTPA optimization equation considering the partial derivative is:

[0016]

[0017] F(β) is the sum of partial derivatives; the flux linkage ψ generated by the permanent magnet under load f Decomposed into the permanent magnet flux d-axis component ψ fd (id,iq) , and the q-axis component of the permanent magnet flux ψ fq (id,iq) ; In the dq axis coordinate system, the inductance is divided into the d-axis inductance L d (id,iq) And the q-axis inductance L q (id,iq) ; L Δ (id,iq) =L d (id,iq) -L q (id,iq) ;

[0018] Ignoring the partial derivative, the MTPA optimization equation is:

[0019]

[0020] Preferably, the dq axis current relationship considering the partial derivative is:

[0021]

[0022] in

[0023] Ignoring the partial derivative, the dq axis current relationship is:

[0024]

[0025] Preferably, the permanent magnet flux is obtained according to the following voltage equation, specifically:

[0026]

[0027] Where V d and V q is the dq axis voltage; R s is the resistance; ω e is the electrical angular velocity.

[0028] Preferably, the specific process of obtaining the MTPA angle based on the MTPA optimization equation considering the partial derivative and using the difference method is as follows:

[0029] First, the dq axis current relationship is rewritten as follows, ignoring the partial derivative:

[0030]

[0031] In the formula, i b for i d The compensation value is zero, and the initial value is zero. Under a certain load, adjust i b An increase or decrease in will cause β to decrease or increase;

[0032] After obtaining the MTPA angle using the rewritten dq axis current relationship with the partial derivative ignored, adjust i b And by comparing the time before and after adjustment s The size of Δβ is used to determine whether it is always greater than or less than zero;

[0033] Next, adjust i again b , the current angle will gradually approach the actual MTPA angle and i s Meet the preset requirements;

[0034] Finally, the difference method is used to calculate the partial derivatives of each parameter for compensation.

[0035] Preferably, when Δβ is always less than zero, reduce i b , when i s When it is greater than the value at the last adjustment, the partial derivative is calculated;

[0036] When Δβ is always greater than zero, increase i b , when i s When is less than the value at the last adjustment, the partial derivative is calculated.

[0037] Preferably, the partial derivative of each parameter is calculated using the difference method according to the following formula, specifically:

[0038]

[0039] In the formula, the subscript k represents the adjustment i bThe number of times.

[0040] The present invention also discloses a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the method described above are executed.

[0041] The present invention further discloses a high magnetic circuit saturation permanent magnet synchronous motor MTPA control system based on partial derivative compensation, comprising an interconnected memory and a processor, wherein a computer program is stored on the memory, and the computer program executes the steps of the method described above when executed by the processor.

[0042] Compared with the prior art, the advantages of the present invention are:

[0043] The MTPA control method of the permanent magnet synchronous motor based on parameter partial derivative compensation of the present invention derives the MTPA optimization equation suitable for the high magnetic saturation permanent magnet synchronous motor by analyzing the changes in parameters; the relationship between the MTPA curves obtained by the two methods when the partial derivative is considered and ignored is compared and analyzed, and on this basis, the difference method is used to compensate for the error caused by ignoring the partial derivative in the MTPA optimization process. Simulation and experimental results show that the method proposed by the present invention can better track the MTPA angle of the high magnetic circuit saturation permanent magnet synchronous motor under different load conditions, verifying the effectiveness and accuracy of the method. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Graph showing the relationship between torque and current angle of the present invention.

[0045] Figure 2 It is a schematic diagram of the permanent magnet flux linkage offset in the d-axis direction of the present invention.

[0046] Figure 3 Schematic diagram of the effect of the dq axis current on the dq axis component of the permanent magnet flux linkage of the present invention; wherein (a) is i q The influence diagram on the dq axis component of the permanent magnet flux; (b) is i d Influence on the dq-axis component of the permanent magnet flux.

[0047] Figure 4 This is a diagram showing the relationship between torque and current angle when parameter changes are considered in the present invention.

[0048] Figure 5 In the present invention, s The curve relationship between β and β.

[0049] Figure 6 This is a flow chart of partial derivative compensation in the present invention.

[0050] Figure 7 It is a control block diagram of the present invention.

[0051] Figure 8 This is a diagram of the motor model in the present invention.

[0052] Fig. 9 This is the magnetic flux density diagram of the stator teeth in the present invention.

[0053] Fig.10 This is a parameter identification diagram in the present invention.

[0054] Fig.11 MTPA control charts under different methods.

[0055] Fig.12 It is a torque and MTPA curve diagram within the rated current range of the present invention.

[0056] Fig.13 It is the torque waveform diagram in the present invention.

[0057] Fig.14 Graphs showing the test results of the present invention; (a) showing the MTPA curve; and (b) showing the MTPA angle comparison graph. DETAILED DESCRIPTION

[0058] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0059] The traditional mathematical model and MTPA control method are described as follows:

[0060] In the traditional permanent magnet synchronous motor dq axis model, the dq axis flux equation is expressed as:

[0061]

[0062] In the formula, ψ d , ψ q are the total magnetic flux on the dq axis respectively; L d , L q are the dq axis inductance respectively; i d ,i q are dq axis current respectively; f It is the magnetic flux generated by the permanent magnet when it is no-load.

[0063] At the same time, the relationship between the phase current and the dq axis current can be expressed as:

[0064]

[0065] In the formula, i s is the phase current vector; β is i s The angle between the current axis and the q axis is also called the current angle.

[0066] In addition, the permanent magnet synchronous motor torque in the dq axis coordinate system can be expressed as:

[0067]

[0068] Where p is the pole pair; Te is the electromagnetic torque.

[0069] Substituting formula (1) into formula (3), we can obtain formula (4) after simplification, namely:

[0070]

[0071] Where, L Δ is the inductance difference of the dq axis, that is, L Δ =L d -L q .

[0072] Substituting equation (2) into equation (4), the torque equation can be rewritten as:

[0073]

[0074] From formula (5), we can see that when i s , L Δ and ψ f When it is constant, within a certain angle range, there is an optimal current angle that can maximize Te, such as Figure 1 shown.

[0075] When i s When the optimal current angle changes, the optimal current angle will also change. s The maximum torque point under β is connected to obtain the MTPA curve. In order to obtain the optimal current angle, the partial derivative of equation (5) with respect to β is:

[0076]

[0077] Let equation (6) be equal to zero, that is:

[0078]

[0079] Since the inductance and permanent magnet flux do not change with the current in the traditional MTPA control method, the partial derivative of the permanent magnet flux and inductance difference with respect to the current angle in formula (7) is zero; by solving, the expression of the current angle can be obtained as:

[0080]

[0081] However, in practice, the permanent magnet flux and inductance will change with the dq axis current, resulting in a large error between the MTPA angle calculated by equation (8) and the actual MTPA angle. In addition, in the traditional dq axis mathematical model, the q axis component of the permanent magnet flux due to the saturation effect is not taken into account, so equation (8) is not applicable to high magnetic circuit saturation permanent magnet synchronous motors.

[0082] The change of permanent magnet flux with dq axis current is analyzed as follows:

[0083] When the motor is running in motor mode, as the core saturation increases, the permanent magnet flux originally located in the d-axis direction will gradually shift to the negative direction of the q-axis, and the shift angle is γ, as shown in Figure 2 shown.

[0084] At this time ψ f It can be decomposed into a permanent magnet flux d-axis component ψ with the direction being the positive direction of the d-axis fd (id,iq) , and a permanent magnet flux q-axis component ψ in the negative direction of the q-axis fq (id,iq) , which can be expressed as:

[0085]

[0086] The dq axis current has an influence on ψ f The impact can be analyzed from the following two points:

[0087] (1) When i q As the saturation of the core increases, ψ f The deviation angle γ toward the negative direction of the q-axis also increases, resulting in ψ fd (id,iq) Reduce and fq (id,iq) It increases along the negative direction of the q axis, such as Figure 3 As shown in (a).

[0088] (2) When i d When the reverse direction increases, desaturation will occur in the d-axis direction, which will reduce the saturation degree of the core and the offset angle γ, thus causing ψ fd (id,iq) Increase and fq (id,iq) It decreases along the negative direction of the q axis, such as Figure 3 As shown in (b). Among them, Figure 3 The data in are obtained through finite element simulation.

[0089] At the same time, the inductance will also change with the change of current. qdecreases with the increase of i d Therefore, in the flux equation of the high magnetic circuit saturation permanent magnet synchronous motor, it is necessary to consider the changes of inductance and permanent magnet flux with dq axis current respectively, then equation (1) should be rewritten as:

[0090]

[0091] In the dq axis coordinate system, the inductance is divided into the d-axis inductance L d (id,iq) , and the q-axis inductance L q (id,iq) ; In the formula, the superscript (i d ,i q ) represents the real-time value of the corresponding parameter as the dq axis current changes.

[0092] Consider the MTPA control method with parameter partial derivatives:

[0093] Substituting equation (10) into equation (3), the torque expression can be rewritten as:

[0094]

[0095] Where, L Δ (id,iq) =L d (id,iq) -L q (id,iq) ; Te' is the electromagnetic torque considering parameter changes; Substituting equation (2) into equation (11), the torque expression can be expressed as i s and β are expressed as:

[0096]

[0097] when i s When a certain value is given, the relationship between Te' and β is as follows: Figure 4 shown.

[0098] from Figure 4 It can be seen that in the range of 0°<β<90°, the electromagnetic torque waveform still maintains the characteristic of a single peak. Therefore, for MTPA control considering parameter changes, the MTPA angle can also be obtained by taking the partial derivative of the current angle. The partial derivative of equation (12) with respect to β is:

[0099]

[0100] Let (13) be equal to zero, that is:

[0101]

[0102] According to formula (14), each term in the equation is related to the change of the parameter. However, most of the improved MTPA formula methods currently consider the change of the parameter, but ignore the change rate of the parameter, that is, ignore the partial derivative.

[0103] Therefore, in order to further analyze the relationship between the MTPA curves obtained by the two methods when considering and ignoring the partial derivative, the partial derivative in formula (14) is extracted to construct the function and simplified to obtain:

[0104]

[0105] Where F(β) is the sum of partial derivatives; α is the auxiliary angle, that is:

[0106]

[0107] When the leakage inductance is not considered, ψ fd (id,iq) Can be equivalent to:

[0108]

[0109] In the formula, i f is the equivalent excitation current; then the total flux equation of the d-axis can be equivalent to:

[0110]

[0111] Due to ψ d (id,iq) and L d (id,iq) is greater than zero, so i f +i d >0; Substituting formula (18) into formula (16) yields:

[0112]

[0113] A qualitative analysis of formula (19) shows that when β increases, L d (id,iq) and L q (id,iq) At the same time, according to formula (18), we know that i f +i d >0, so equation (18) is greater than zero. In addition, when i d Reverse increase, i q When ψ decreases, fq (id,iq) will increase, that is will increase with the increase of β angle, then we can get:

[0114]

[0115] Substituting formula (20) into formula (16), we can obtain 0°<α<90°, and 0°<β+α<180°; combined with formula (15), we can see that F(β)>0.

[0116] In order to better illustrate the conclusion, the MTPA optimization equations when considering and ignoring partial derivatives are called method 1 and method 2, respectively, that is:

[0117] Method 1:

[0118] Method 2:

[0119] Based on the above analysis, we can conclude that since F(β) is always greater than zero, when the load is constant, the MTPA angles obtained by method 1 and method 2 are always different. In other words, there is no intersection between the MTPA curves obtained by the two methods, that is, the angle error Δβ of method 2 is always greater than zero or less than zero. Figure 5 shown.

[0120] Therefore, in order to accurately obtain the distribution relationship of the dq-axis current on the MTPA curve, in addition to obtaining the size of the inductance and permanent magnet flux in real time, it is also necessary to obtain the corresponding partial derivative.

[0121] Since it is difficult to simplify equations (21) and (22) into analytical expressions of β, these two equations cannot be used directly to complete MTPA control, but need to be converted. Substituting equation (2) into equations (21) and (22), the dq axis current relationship of method 1 and method 2 can be obtained as equations (23) and (24), respectively:

[0122]

[0123]

[0124] In vector control, the reference value of iq can be obtained by the speed loop through PI integration, the inductance can be obtained through parameter identification, and the permanent magnet flux can be obtained according to the voltage equation, that is:

[0125]

[0126] Where V d and V q is the dq axis voltage; R s is the resistance; ω e is the electrical angular velocity; wherein, the dq-axis inductance and resistance are obtained through parameter identification method.

[0127] In order to obtain the partial derivative in formula (23), the difference method can be used based on method 2. The specific method is as follows:

[0128] First, rewrite equation (24) as:

[0129]

[0130] In the formula, i b for i d The compensation value is zero, and the initial value is zero. Under a certain load, adjust i b An increase or decrease in will cause β to decrease or increase.

[0131] After using equation (26) to obtain the MTPA angle, adjust i b And by comparing the time before and after adjustment s The size of method 2 is used to determine whether Δβ is always greater than or less than zero; taking always less than zero as an example, adjust i b Continue to decrease, at this time according to the analysis, the current angle will gradually approach the actual MTPA angle and i s Gradually decrease until i s is greater than the value at the last adjustment. Assume that the phase current and current angle are i s(k+1) and β (k+1) The phase current and current angle during the last adjustment are i s(k) and β (k) , then the actual MTPA angle is at β (k+1) and β (k) In a smaller range, the rate of change of the parameter with β can be regarded as a constant value, that is, the partial derivative is constant;

[0132] Finally, the partial derivatives of each parameter are calculated using the difference method according to formula (27) and brought into method 1 for compensation. The specific process is as follows: Figure 6 As shown, the overall control block diagram is as follows Figure 7 As shown:

[0133]

[0134] In the formula, the subscript (k) represents the adjustment i b The number of times.

[0135] Figure 7 In, θ e is the electrical angle of the rotor; ω m is the rotation speed; i dh and i qh are the high-frequency dq-axis currents injected for parameter identification respectively; the subscript ref is the corresponding reference value.

[0136] The present invention establishes a HSPMSM mathematical model on the basis of a traditional PMSM mathematical model, proposes an MTPA control optimization equation for the HSPMSM, and analyzes the variation of parameters in the optimization equation and the non-ignorability of the partial derivatives of the parameters on the current angle in the optimization equation; in order to simultaneously consider the influence of the variation of parameters and the partial derivatives, an MTPA control method based on partial derivative compensation is invented, and on the basis of considering the variation of parameters, the partial derivatives of the parameters are obtained by using the finite difference method, and the partial derivatives in the optimization equation are compensated; finally, it is verified through simulation and experiments that the traditional MTPA control method is not suitable for HSPMSM, and the method proposed by the present invention can accurately track the optimal current angle.

[0137] Specifically, in order to verify the effectiveness of the proposed method, the present invention establishes a finite element model of a high magnetic circuit saturation permanent magnet synchronous motor, such as Figure 8 Table 1 lists the main parameters of the model, including the dq-axis inductance and permanent magnet flux linkage when the dq-axis current is zero.

[0138] Table 1 Motor parameters

[0139]

[0140] For high magnetic circuit saturation permanent magnet synchronous motors under different load conditions, their stator cores are usually in a high saturation state, especially the maximum magnetic density of the stator teeth is usually greater than 1.8 T. In order to verify the saturation degree of the stator teeth, the motor speed is set to the rated speed. Then, the stator tooth magnetic density is simulated under different load conditions, such as Fig. 9 shown.

[0141] from Fig. 9 It can be seen that the stator tooth flux density exceeds 1.8T within 78% of the rated current. d =-275A and i q =605A, the motor can run at the rated torque with the minimum current, and the stator tooth flux density is 2.05T. Therefore, the saturation degree of this permanent magnet synchronous motor is relatively high. From the previous analysis, it can be seen that the inductance and permanent magnet flux linkage of the high magnetic circuit saturation permanent magnet synchronous motor will change nonlinearly with the load, so it is necessary to identify the parameters under different loads. Taking the MTPA trajectory (OA) as an example, Fig.10 shown.

[0142] from Fig.10 It can be seen that the identification value and the simulation value are close, which verifies the effectiveness of the parameter identification method. Figure 7 The control block diagram of MTPA is shown in Figure 1. The proposed method is used for MTPA control. In order to better illustrate the importance of parameter changes and partial derivatives in the MTPA optimization process, different methods are used for comparison, such as Fig.11 As shown, method 1 is the method proposed by the present invention; method 2 takes into account the variation of parameters but ignores the partial derivative; method 3 is the traditional MTPA control, which ignores the variation of parameters and the partial derivative.

[0143] from Fig.11 It can be seen that the traditional method has the largest error, and although method 2 reduces the error compared to the traditional method, it still deviates from the optimal angle due to the neglect of the partial derivative, and the error increases with the increase of load. Compared with other methods, the method proposed in the present invention is closer to the actual MTPA curve, which verifies the effectiveness of the analysis and proposed method of the present invention.

[0144] In order to further verify the method proposed in this invention, relevant experiments were carried out. A 300kW internal permanent magnet synchronous motor prototype was produced, and the design model and parameters of the prototype were as follows: Figure 8 As shown in Table 1. In the experiment, an 800kW induction motor with a rated speed of 3000rpm was used to drive the prototype, and water cooling was adopted. 30℃ cooling water was passed into the water jacket of the prototype at a water flow rate of 60L / min to prevent excessive temperature rise. In order to ensure the accuracy of torque measurement, a torque sensor (ATESTEO:DF3) with a rated torque of 2kNm and an accuracy of ±0.04% was installed. At the same time, a high-speed recorder from HiTechnologies was used to observe the data in real time, and the data was exported through PC software.

[0145] First, torque measurements are performed on the prototype to find the actual MTPA curve. d Run the prototype under no-load conditions; then gradually increase the load, measure the torque and record the dq axis current under different load conditions; finally, gradually reduce i d Repeat the previous steps; the torque within the rated current range is obtained as Fig.12 As shown, the actual MTPA trajectory (OB) is plotted.

[0146] Due to certain technical and assembly errors in the prototype manufacturing process, the actual torque value and the simulated value under different load conditions are different. For example, the minimum current under rated torque is different from the simulated value. When the prototype is running under rated torque, the dq axis currents are i and d =-350A and i q =580A, torque waveform is as follows Fig.13 shown.

[0147] Next, follow Figure 7 The control block diagram of the experiment was carried out using different methods, and the MTPA curve obtained was as follows Fig.14As shown in (a), the MTPA angles of different loads under the corresponding methods are extracted for comparison, as shown in Fig.14 As shown in (b).

[0148] Fig.14 It shows that within the rated load range, the maximum error of the MTPA angle is -2.8° when using method 2. The main reason for the error is that the partial derivative in the MTPA optimization control is not considered. The maximum error of the MTPA angle is 9.1° when using method 3. The main reason for the error is that the change of parameters is not considered. In addition, due to certain differences between the simulation model and the actual prototype, the maximum error of the MTPA angle between the simulation results and the test results is 6.1°. The MTPA angle error of the method proposed in the present invention is relatively stable, with a maximum error of 1.3°. Compared with other methods, this method can obtain better accuracy, which verifies the effectiveness and accuracy of the method.

[0149] The MTPA control method of the permanent magnet synchronous motor based on parameter partial derivative compensation of the present invention derives the MTPA optimization equation suitable for the high magnetic saturation permanent magnet synchronous motor by analyzing the changes in parameters; the relationship between the MTPA curves obtained by the two methods when the partial derivative is considered and ignored is compared and analyzed, and on this basis, the difference method is used to compensate for the error caused by ignoring the partial derivative in the MTPA optimization process. Simulation and experimental results show that the method proposed by the present invention can better track the MTPA angle of the high magnetic circuit saturation permanent magnet synchronous motor under different load conditions, verifying the effectiveness and accuracy of the method.

[0150] The present invention also discloses a computer-readable storage medium, on which a computer program is stored, and the computer program executes the steps of the above method when it is run by a processor. The present invention further discloses a high magnetic circuit saturation permanent magnet synchronous motor MTPA control system based on partial derivative compensation, including an interconnected memory and a processor, on which a computer program is stored, and the computer program executes the steps of the above method when it is run by the processor. The medium and system of the present invention correspond to the above method and also have the advantages described in the above method.

[0151] The present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by hardware related to computer program instructions. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned method embodiment when executed by the processor. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. Computer-readable storage media include: any entity or device that can carry computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electric carrier signal, telecommunication signal and software distribution medium. The memory is used to store computer programs and / or modules, and the processor implements various functions by running or executing computer programs and / or modules stored in the memory, and calling data stored in the memory. The memory may include high-speed random access memory and may also include non-volatile memory, such as a hard disk, an internal memory, a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card (Flash Card), at least one disk storage device, a flash memory device, or other volatile solid-state storage devices.

[0152] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A MTPA control method for a high magnetic circuit saturation permanent magnet synchronous motor based on partial derivative compensation, characterized in that: Includes steps: Obtain the relationship between the phase current and the dq axis current, and obtain the corresponding dq axis current relationship based on the MTPA optimization equation considering the partial derivative and the MTPA optimization equation ignoring the partial derivative; Get i q The reference value, inductance, permanent magnet flux, partial derivative and MTPA angle are obtained, and then the dq axis current is obtained according to the MTPA optimization equation considering the partial derivative to control the motor; The MTPA angle is obtained based on the MTPA optimization equation with partial derivatives ignored and using the difference method.

2. The MTPA control method for a high magnetic circuit saturation permanent magnet synchronous motor based on partial derivative compensation according to claim 1 is characterized in that: The relationship between the phase current and the dq axis current is specifically: In the formula, i d ,i q are d-axis and q-axis currents respectively; i s is the phase current vector; β is i s The angle between the current axis and the q axis is also called the current angle.

3. The MTPA control method for a high magnetic circuit saturation permanent magnet synchronous motor based on partial derivative compensation according to claim 2 is characterized in that: The MTPA optimization equation considering partial derivatives is: F(β) is the sum of partial derivatives; the flux linkage ψ generated by the permanent magnet under load f Decomposed into the permanent magnet flux d-axis component ψ fd (id,iq) , and the q-axis component of the permanent magnet flux ψ fq (id,iq) ; In the dq axis coordinate system, the inductance is divided into the d-axis inductance L d (id,iq) And the q-axis inductance L q (id,iq) ; L Δ (id,iq) =L d (id,iq) -L q (id,iq) ; Ignoring the partial derivative, the MTPA optimization equation is:

4. The MTPA control method for a high magnetic circuit saturation permanent magnet synchronous motor based on partial derivative compensation according to claim 3 is characterized in that: The dq axis current relationship considering the partial derivative is: in Ignoring the partial derivative, the dq axis current relationship is:

5. The MTPA control method for a high magnetic circuit saturation permanent magnet synchronous motor based on partial derivative compensation according to claim 4 is characterized in that: The permanent magnet flux is obtained according to the following voltage equation: Where V d and V q is the dq axis voltage; R s is the resistance; ω e is the electrical angular velocity.

6. The MTPA control method for a high magnetic circuit saturation permanent magnet synchronous motor based on partial derivative compensation according to claim 5 is characterized in that: The specific process of obtaining the MTPA angle based on the MTPA optimization equation considering partial derivatives and using the difference method is as follows: First, the dq axis current relationship is rewritten as follows, ignoring the partial derivative: In the formula, i b for i d The compensation value is zero, and the initial value is zero. Under a certain load, adjust i b An increase or decrease will cause β to decrease or increase; After obtaining the MTPA angle using the rewritten dq axis current relationship with the partial derivative ignored, adjust i b And by comparing the time before and after adjustment s The size of Δβ is used to determine whether it is always greater than or less than zero; Next, adjust i again b , the current angle will gradually approach the actual MTPA angle and i s Meet the preset requirements; Finally, the difference method is used to calculate the partial derivatives of each parameter for compensation.

7. The MTPA control method for a high magnetic circuit saturation permanent magnet synchronous motor based on partial derivative compensation according to claim 6 is characterized in that: When Δβ is always less than zero, reduce i b , when i s When it is greater than the value at the last adjustment, the partial derivative is calculated; When Δβ is always greater than zero, increase i b , when i s When is less than the value at the last adjustment, the partial derivative is calculated.

8. The MTPA control method for a high magnetic circuit saturation permanent magnet synchronous motor based on partial derivative compensation according to claim 6 is characterized in that: The partial derivatives of each parameter are calculated using the difference method according to the following formula: In the formula, the subscript k represents the adjustment i b The number of times.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the computer program performs the steps of the method according to any one of claims 1 to 8.

10. A high magnetic circuit saturation permanent magnet synchronous motor MTPA control system based on partial derivative compensation, comprising a memory and a processor connected to each other, wherein a computer program is stored in the memory, characterized in that: When the computer program is executed by a processor, the computer program performs the steps of the method according to any one of claims 1 to 8.

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