MTPA control method, device and equipment of permanent magnet synchronous motor and medium
By constructing the relationship between electromagnetic torque and current and using the Ferrari root method to calculate the current, the problem of not being able to update the straight and intersimultaneous currents in real time when the motor parameters change is improved, and the torque control accuracy and reduction of permanent magnet synchronous motors are improved. Copper consumption.
Patent Information
- Application Number
- CN202411485603.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-23
- Publication Date
- 2025-01-03
AI Technical Summary
The existing MTPA control method of permanent magnet synchronous motor cannot update the direct and alternating shaft currents in real time when the motor parameters change, resulting in a decrease in torque control accuracy and an increase in motor copper consumption.
By obtaining the latest motor parameters and expected electromagnetic torque, we construct electromagnetic torque relationship and current relationship, use the Ferrari root method to calculate the values of the straight and intersection currents, and allocate the current based on these values to achieve real-time update .
It improves torque control accuracy, reduces motor copper consumption, and ensures the accuracy and adaptability of MTPA control methods.
Smart Images
Figure CN119254071A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of motor control technology, and in particular to a MTPA control method, device, equipment and medium for a permanent magnet synchronous motor. Background Art
[0002] In recent years, permanent magnet synchronous motors have been increasingly widely used in the field of new energy vehicles due to their high density, high power and high efficiency. The maximum torque per ampere (MTPA) control method of permanent magnet synchronous motors can reasonably distribute the magnitude of the direct and quadrature axis currents through an algorithm to achieve the maximum output electromagnetic torque generated by the unit amplitude current, thereby improving the torque control accuracy and reducing the motor copper loss. It is the most commonly used control method for permanent magnet synchronous motors.
[0003] However, the existing MTPA control methods are mainly divided into the following two categories: (1) Offline fitting method: Based on the fixed motor parameters, offline fitting is performed to obtain the equations about torque and DC-axis current that meet the MTPA control method, and the DC-axis current is calculated by this equation during operation; (2) Online table lookup method: A table about torque and DC-axis current that meets the MTPA control method is obtained in advance through calibration methods such as bench tests, and the DC-axis current is obtained by table lookup during operation.
[0004] However, both the offline fitting method and the online table lookup method rely on fixed motor parameters. When the motor parameters change, the direct and quadrature axis currents cannot be updated in real time, resulting in an error between the actual output torque and the expected torque, which reduces the torque control accuracy and increases the motor copper loss. Summary of the invention
[0005] Based on this, it is necessary to provide a MTPA control method, device, equipment and medium for a permanent magnet synchronous motor to address the above technical problems, which can update the direct and quadrature axis currents in real time when the motor parameters change, improve the torque control accuracy and reduce the motor copper loss.
[0006] In a first aspect, a MTPA control method for a permanent magnet synchronous motor is provided, the method comprising:
[0007] Get the latest motor parameters and expected electromagnetic torque;
[0008] According to the latest motor parameters and the expected electromagnetic torque, a relationship between the electromagnetic torque of the permanent magnet synchronous motor under the MTPA control mode is constructed; according to the latest motor parameters, a current relationship between the direct-axis current and the quadrature-axis current of the permanent magnet synchronous motor under the MTPA control mode is constructed;
[0009] Combining the torque relationship equation with the current relationship equation to calculate the values of the direct-axis current and the quadrature-axis current;
[0010] Corresponding currents are allocated to the direct axis and the quadrature axis respectively according to the values of the direct axis current and the quadrature axis current.
[0011] In combination with the first aspect, in a first possible implementation mode of the first aspect, the latest motor parameters include the number of motor pole pairs, the permanent magnet flux amplitude, the direct-axis inductance and the quadrature-axis inductance, and the electromagnetic torque relationship is a relationship between the desired electromagnetic torque, the latest motor parameters, the direct-axis current and the quadrature-axis current.
[0012] In combination with the first possible implementation of the first aspect, in a second possible implementation of the first aspect, the current relationship includes:
[0013]
[0014] represents the permanent magnet flux amplitude, L d represents the direct-axis inductance, L q represents the quadrature-axis inductance, i d represents the direct axis current, i q represents the quadrature-axis current.
[0015] In combination with the second possible implementation of the first aspect, in a third possible implementation of the first aspect, the electromagnetic torque relationship includes:
[0016]
[0017] T e represents the desired electromagnetic torque, n p Indicates the number of pole pairs of the motor.
[0018] In combination with the third implementable embodiment of the first aspect, in a fourth implementable embodiment of the first aspect, combining the torque relationship equation and the current relationship equation to calculate the values of the direct-axis current and the quadrature-axis current includes:
[0019] Inputting the current relationship into the torque relationship and sorting them out to obtain a target relationship between the desired electromagnetic torque and the direct axis current;
[0020] The target relationship is solved by using the Ferrari root-finding method to obtain the value of the direct-axis current;
[0021] The value of the direct-axis current is input into the electromagnetic torque relationship equation or the current relationship equation for calculation to obtain the value of the quadrature-axis current.
[0022] In combination with the fourth feasible implementation method of the first aspect, in a fifth feasible implementation method of the first aspect, the target relationship is solved by using the Ferrari root-finding method to obtain the value of the direct-axis current, including:
[0023] Taking the direct-axis current as an unknown variable and transforming the target relational expression according to the format of a quartic equation;
[0024] The transformed target relationship is solved by using the Ferrari root-finding method, and the negative real root obtained by the solution is used as the value of the direct-axis current.
[0025] In combination with the fourth implementable embodiment of the first aspect, in a sixth implementable embodiment of the first aspect, the target relational expression includes:
[0026]
[0027] In a second aspect, a MTPA control device for a permanent magnet synchronous motor is provided, the device comprising:
[0028] Parameter acquisition module, used to obtain the latest motor parameters and expected electromagnetic torque;
[0029] A relational expression building module, used to build an electromagnetic torque relational expression of the permanent magnet synchronous motor under the MTPA control mode according to the latest motor parameters and the expected electromagnetic torque; and to build a current relational expression of the permanent magnet synchronous motor about the direct axis current and the quadrature axis current under the MTPA control mode according to the latest motor parameters;
[0030] A current calculation module, used for combining the torque relationship equation and the current relationship equation to calculate the values of the direct-axis current and the quadrature-axis current;
[0031] The current distribution module is used to distribute corresponding currents to the direct axis and the quadrature axis respectively according to the values of the direct axis current and the quadrature axis current.
[0032] In a third aspect, a computer device is provided, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the steps of the MTPA control method for a permanent magnet synchronous motor described in any one of the first aspect or the first to sixth possible implementations of the first aspect are implemented.
[0033] On the other hand, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps of the MTPA control method of a permanent magnet synchronous motor described in any one of the first aspect or the first to sixth embodiments of the first aspect are implemented.
[0034] The MTPA control method, device, equipment and medium of the above-mentioned permanent magnet synchronous motor obtain the latest motor parameters and expected electromagnetic torque; construct the electromagnetic torque relationship of the permanent magnet synchronous motor under the MTPA control mode according to the latest motor parameters and the expected electromagnetic torque; construct the current relationship of the permanent magnet synchronous motor about the direct axis current and the quadrature axis current under the MTPA control mode according to the latest motor parameters; combine the electromagnetic torque relationship and the current relationship to calculate the values of the direct axis current and the quadrature axis current; and allocate corresponding currents to the direct axis and the quadrature axis respectively according to the values of the direct axis current and the quadrature axis current. It can be seen that compared with the prior art, the beneficial effect of the present application is that when the motor parameters and the torque command are updated, the latest direct axis current and the quadrature axis current can be calculated online in real time according to the expected electromagnetic torque corresponding to the latest motor parameters and the torque command, which solves the problem that the prior art cannot update the direct axis current and the quadrature axis current under the MTPA control mode after the motor parameters are updated, reduces the error between the actual output torque of the motor and the expected electromagnetic torque, ensures the accuracy of the MTPA control mode, and thus improves the torque control accuracy and reduces the copper loss of the motor. BRIEF DESCRIPTION OF THE DRAWINGS
[0035] Figure 1 1 is a flow chart of a MTPA control method for a permanent magnet synchronous motor in one embodiment;
[0036] Figure 2 A comparison diagram of the direct-axis current and the quadrature-axis current obtained by using the offline fitting method and the method described in the present application when the motor parameters do not change;
[0037] Figure 3 A comparison diagram of the direct-axis current and the quadrature-axis current obtained by using the offline fitting method and the method described in the present application when the motor parameters change;
[0038] Figure 4 A comparison chart of torque errors corresponding to the online table lookup method, the offline fitting method and the method described in this application when the motor parameters change;
[0039] Figure 5 A comparison chart of motor copper loss corresponding to the online table lookup method, the offline fitting method and the method described in this application when motor parameters change;
[0040] Figure 6 is a structural block diagram of an MTPA control device for a permanent magnet synchronous motor in one embodiment;
[0041] Figure 7 FIG. 4 is a diagram showing the internal structure of a computer device in one embodiment. DETAILED DESCRIPTION
[0042] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.
[0043] It should be noted that the illustrations provided in this embodiment only illustrate the basic concept of the present application in a schematic manner, and therefore the drawings only show components related to the present application rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.
[0044] The structures, proportions, sizes, etc. illustrated in the drawings in this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with this technology. They are not used to limit the conditions under which this application can be implemented, and therefore have no substantive technical significance. Any structural modification, change in proportion or adjustment of size, without affecting the effects and purposes that can be achieved by this application, should still fall within the scope of the technical contents disclosed in this application.
[0045] The directions or positional relationships indicated by the terms "upper", "lower", "left", "right", "middle", "longitudinal", "lateral", "horizontal", "inner", "outer", "radial", "circumferential" and the like in this specification are based on the directions or positional relationships shown in the drawings and are only for the convenience of simplifying the description. They do not indicate or imply that the devices or elements referred to must have a specific direction, be constructed and operate in a specific direction, and therefore cannot be understood as limiting the present application. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.
[0046] At present, the MTPA control method of permanent magnet synchronous motor usually adopts offline fitting method or online table lookup method to calculate the direct-axis current and quadrature-axis current, but both methods need to rely on fixed motor parameters. When the motor parameters change, the direct-axis current and quadrature-axis current cannot be updated in real time, resulting in reduced torque control accuracy and increased motor copper loss.
[0047] To this end, the present application proposes a MTPA control method for a permanent magnet synchronous motor, which constructs an electromagnetic torque relationship of the permanent magnet synchronous motor under the MTPA control mode according to the latest motor parameters and the expected electromagnetic torque; constructs a current relationship of the permanent magnet synchronous motor under the MTPA control mode about the direct axis current and the quadrature axis current according to the latest motor parameters; combines the electromagnetic torque relationship and the current relationship to calculate, obtain the values of the direct axis current and the quadrature axis current, and allocates corresponding currents to the direct axis and the quadrature axis according to the values, so that the actual output torque meets the expected electromagnetic torque as much as possible. It can be seen that the present method calculates the direct axis current and the quadrature axis current in real time according to the expected electromagnetic torque corresponding to the latest motor parameters and the torque command, solves the problem in the prior art that the direct axis current and the quadrature axis current cannot be updated in real time when the motor parameters change, improves the torque control accuracy and reduces the motor copper loss.
[0048] In one embodiment, Figure 1 As shown, a MTPA control method for a permanent magnet synchronous motor is provided, comprising the following steps:
[0049] Step 202, obtaining the latest motor parameters and expected electromagnetic torque;
[0050] Step 204, constructing an electromagnetic torque relationship of the permanent magnet synchronous motor under the MTPA control mode according to the latest motor parameters and the expected electromagnetic torque; constructing a current relationship of the permanent magnet synchronous motor with respect to the direct axis current and the quadrature axis current under the MTPA control mode according to the latest motor parameters;
[0051] Step 206, combining the electromagnetic torque relationship equation and the current relationship equation to calculate the values of the direct-axis current and the quadrature-axis current;
[0052] Step 208 : allocating corresponding currents to the direct axis and the quadrature axis respectively according to the values of the direct axis current and the quadrature axis current.
[0053] It should be noted that in the analysis and control of permanent magnet synchronous motors, the direct axis (d axis) and the quadrature axis (q axis) are often used to describe the spatial distribution of the motor's current and flux. Among them, the d axis refers to the coordinate axis in the motor that is consistent with the direction of the rotor flux. The current on the d axis, that is, the direct axis current, mainly affects the motor's flux, but it does not directly generate torque; the effects of the d axis current include: when the d axis current is negative, it can play a demagnetizing role, that is, reduce the rotor's flux, and can be used to increase the motor's speed range in weak magnetic control; when the d axis current is positive, it can increase the rotor's flux, but in most cases it is unnecessary because the permanent magnet synchronous motor already has the flux provided by the permanent magnet. The q-axis refers to the coordinate axis that is perpendicular to the direction of the rotor magnetic flux. The current on the q-axis, that is, the quadrature-axis current, is directly related to the electromagnetic torque generated by the motor. Its functions include: the q-axis current is the main factor in generating the motor torque. By controlling the size of the q-axis current, the torque generated by the motor can be controlled; the q-axis current is also related to the energy transfer of the motor because it directly affects the armature reaction of the motor.
[0054] Since the motor parameters of the permanent magnet synchronous motor may change, in order to update the direct-axis current and the quadrature-axis current in real time and reduce the error between the actual output torque of the motor and the expected electromagnetic torque, it is necessary to obtain the latest motor parameters and the expected electromagnetic torque at the current moment. The latest motor parameters include the number of motor pole pairs, the permanent magnet flux amplitude, the direct-axis inductance and the quadrature-axis inductance. The expected electromagnetic torque is the electromagnetic torque output from the output end of the expected permanent magnet synchronous motor.
[0055] After obtaining the latest motor parameters and expected electromagnetic torque, the electromagnetic torque relationship of the permanent magnet synchronous motor under the MTPA control mode is constructed according to the latest motor parameters and the expected electromagnetic torque, and the current relationship of the salient pole permanent magnet synchronous motor under the MTPA control mode is constructed according to the latest motor parameters. Among them, the electromagnetic torque relationship includes:
[0056]
[0057] The current relationships include:
[0058]
[0059] T e represents the desired electromagnetic torque, n p represents the number of pole pairs of the motor, represents the permanent magnet flux amplitude, L d represents the direct-axis inductance, L q represents the quadrature-axis inductance, i d represents the direct axis current, iq represents the quadrature-axis current.
[0060] It can be seen that the electromagnetic torque relationship is a relationship between the expected electromagnetic torque and the latest motor parameters, direct-axis current and quadrature-axis current, and the latest motor parameters such as the motor pole pair number, permanent magnet flux amplitude, direct-axis inductance and quadrature-axis inductance, and the values of the expected electromagnetic torque are known. Then, the latest motor parameters and the values of the expected electromagnetic torque are substituted into expression (1) and sorted out. The electromagnetic torque relationship obtained is an equation about the two unknown parameters of direct-axis current and quadrature-axis current; similarly, the current relationship is a relationship between the latest motor parameters, direct-axis current and quadrature-axis current, and the latest motor parameters such as the permanent magnet flux amplitude, direct-axis inductance and quadrature-axis inductance are known. Then, the latest motor parameters are substituted into expression (2) and sorted out. The current relationship obtained is also an equation about the two unknown parameters of direct-axis current and quadrature-axis current.
[0061] Therefore, the combined electromagnetic torque relationship and current relationship can solve the values of the direct-axis current and the quadrature-axis current. Specifically, the following steps are included: inputting the current relationship into the torque relationship and sorting it out to obtain a target relationship for the desired electromagnetic torque and the direct-axis current; using the Ferrari root method to solve the target relationship to obtain the value of the direct-axis current; inputting the value of the direct-axis current into the electromagnetic torque relationship or the current relationship for calculation to obtain the value of the quadrature-axis current.
[0062] Since the current relationship is an expression for calculating the quadrature-axis current based on the direct-axis current, permanent magnet flux amplitude, direct-axis inductance, and quadrature-axis inductance, the current relationship can be substituted into the electromagnetic torque relationship, and the quadrature-axis current in the electromagnetic torque relationship can be replaced. After sorting, the target relationship of the permanent magnet synchronous motor under the MTPA control mode for the desired electromagnetic torque and direct-axis current can be obtained. Among them, the sorted target relationship includes:
[0063]
[0064] The specific meanings of the various parameters in the target relationship equation have been explained in the previous text. Please refer to the previous text for the relevant meanings and will not be repeated here.
[0065] After obtaining the target relationship, the target relationship is solved by using the Ferrari root-finding method to obtain the value of the direct-axis current. This step specifically includes: taking the direct-axis current as an unknown variable and transforming the target relationship according to the format of a univariate quartic equation; using the Ferrari root-finding method to solve the transformed target relationship, and using the negative real root obtained by the solution as the value of the direct-axis current.
[0066] Specifically, for the target relationship, the direct axis current is taken as the unknown variable, that is, let i d =x, transform the target relation into the standard form of a quartic equation, and obtain the coefficients of the standard form according to the latest motor parameters and the expected electromagnetic torque. The transformed target relation includes:
[0067] ax 4 +bx 3 +cx 2 +dx+e=0 (5)
[0068] The coefficients are:
[0069] a=1;b=3A;c=3A 2 ; d = A 3 ; e=-B (6)
[0070] Based on the transformed target relation, the first set of intermediate variables, including P, Q and D, are calculated. The expressions are as follows:
[0071]
[0072] Calculate the second set of intermediate variables, including u, v and m, and the expression is as follows:
[0073]
[0074] Calculate the third set of intermediate variables, including S and T, and its expression is as follows:
[0075]
[0076] Ferrari's root-finding formula contains x n (n=1, 2, 3, 4), a total of four roots, x n The expression is as follows:
[0077]
[0078] Among them, [] represents rounding operation.
[0079] It should be noted that, since the direct-axis inductance of the salient-pole permanent magnet synchronous motor is smaller than the quadrature-axis inductance, this inductance difference is called the salient-pole effect. By utilizing this inductance difference, the operation of the motor can be optimized by properly adjusting the direct-axis current and the quadrature-axis current, such as reducing copper loss by demagnetizing operation, or increasing the direct-axis current to enhance the torque output of the motor. Therefore, according to the magnitude relationship between the direct-axis inductance and the quadrature-axis inductance, it can be determined that A in expression (4) is less than zero and B is greater than zero. Furthermore, according to the positive and negative values of A and B, the positive and negative values of b, m, S and T can be derived through expressions (6)-(14).
[0080] By substituting a large number of motor parameters and expected electromagnetic parameters into the above expression (15), it can be found that: among the four roots, generally speaking, two roots are imaginary roots, one root is a negative real root, and one root is a positive real root; since the direct-axis current can play a demagnetizing role when it is negative, reducing the magnetic flux of the rotor and increasing the speed range of the motor, the negative real root is used as the value of the direct-axis current. By deriving the positive and negative of b, m, S and T, it can be further deduced that when n = 2, x2 is a negative real root, and the expression for calculating the value of the direct-axis current is as follows:
[0081]
[0082] Substituting expressions (4), (6)-(14) into expression (16), expression (16) can be transformed into expression (17) as follows:
[0083]
[0084] in,
[0085] To avoid ambiguity, it should be noted that in the last term of expression (17), the term under the square root consists of the following four terms: as well as
[0086] From the expression for calculating the direct-axis current, it can be intuitively seen that the direct-axis current is only related to the latest motor parameters and the expected electromagnetic torque; the value of the direct-axis current can be calculated by substituting the values of the latest motor parameters and the expected electromagnetic torque into expression (17); the value of the direct-axis current can be obtained by substituting the value of the direct-axis current into the electromagnetic torque relationship or the current relationship. In one embodiment, the electromagnetic torque relationship is transformed to obtain the following expression for calculating the quadrature-axis current:
[0087]
[0088] It should be noted that the MTPA control method of the permanent magnet synchronous motor of the present application can have two implementation methods when calculating the direct-axis current and the quadrature-axis current. In one implementation method, the latest motor parameters and the values of the expected electromagnetic torque can be obtained first; then the electromagnetic torque relationship and the current relationship can be constructed according to the latest motor parameters and the values of the expected electromagnetic torque; then the current relationship is substituted into the electromagnetic torque relationship and organized into the standard form of a quartic equation; then the values of intermediate variables such as P, Q, D, u, v, m, S and T are calculated; finally, the direct-axis current value is calculated according to the values of these intermediate variables and the Ferrari root formula, and the direct-axis current value is substituted into the electromagnetic torque relationship or the current relationship to obtain the quadrature-axis current value.
[0089] In another embodiment, the electromagnetic torque relationship and the current relationship can also be constructed first, and the expected electromagnetic torque and the latest motor parameters are both represented by symbols; then the current relationship is substituted into the electromagnetic torque relationship and organized into the standard form of a univariate quartic equation; then the expressions of intermediate variables such as P, Q, D, u, v, m, S and T are determined; then based on the expressions of these intermediate variables and using the Ferrari root formula, the expression for calculating the direct-axis current is obtained, and the electromagnetic torque relationship is deformed to obtain the expression for calculating the quadrature-axis current; finally, the latest motor parameters and the expected electromagnetic torque are obtained, and the latest motor parameters and the expected electromagnetic torque are substituted into the expression for calculating the direct-axis current to obtain the numerical value of the direct-axis current, and then the numerical value of the direct-axis current is substituted into the expression for calculating the quadrature-axis current to obtain the numerical value of the quadrature-axis current.
[0090] The following experimental data illustrate the beneficial effects of the direct calculation method of the present application compared with the offline fitting method and the online table lookup method.
[0091] On the one hand, taking the offline fitting method as an example, when the motor parameters do not change, the direct-axis current and quadrature-axis current corresponding to different expected electromagnetic torques under the MTPA control mode are calculated by using the offline fitting method and the direct calculation method of the present application, respectively, and the following can be obtained: Figure 2 The comparison results shown in the figure show that the calculation results of the two methods are almost completely consistent. When the motor parameters change, the direct-axis current and quadrature-axis current corresponding to different expected electromagnetic torques under the MTPA control mode are calculated by using the offline fitting method and the direct calculation method of the present application, respectively, and the following can be obtained: Figure 3 As shown in the comparison results, at this time, the direct calculation method of the present application can update the current calculation results in real time, while the offline fitting method cannot update the current calculation results in real time, resulting in deviations between the calculation results of the direct-axis current and the quadrature-axis current and the accurate values.
[0092] It can be seen that through the MTPA control method of the permanent magnet synchronous motor of the present application, when the motor parameters change, the corresponding direct-axis current and quadrature-axis current can be calculated in real time according to the latest motor parameters and the expected electromagnetic torque, avoiding the problem that the prior art cannot adaptively change the direct-axis current and quadrature-axis current according to the changes in the motor parameters.
[0093] On the other hand, simulation experiments were conducted on the online table lookup method, the offline fitting method and the direct calculation method of the present application. The simulation steps include the following steps: (1) Modeling: Use simulation software (such as MATLAB / Simulink, PSCAD, PSpice, etc.) to build a model of the permanent magnet synchronous motor, set electrical parameters (such as resistance, inductance and permanent magnet strength, etc.), mechanical parameters (such as moment of inertia and friction coefficient, etc.) and control strategy for the model, and set the motor flux to 1.05 times the original value; (2) Define simulation parameters: Set the simulation time step and simulation duration, etc., set the initial conditions of the motor, such as the initial speed and initial current, etc.; (3) adopting MTPA control mode and combining it with current distribution algorithm, the current distribution algorithm includes online table lookup method, offline fitting method and direct calculation method described in this application; (4) loading and disturbance test: setting different load conditions, such as different torque, speed, etc.; introducing disturbances, such as sudden changes in load, grid voltage fluctuations, etc., to test the robustness of the system; (5) recording data: recording the output torque, direct axis current and quadrature axis current of the motor; (6) calculating torque error: calculating the torque error between the actual output torque and the expected electromagnetic torque; (7) calculating copper loss: calculating the copper loss P by the following expression Cu : R s represents the stator resistance; (8) repeatedly changing the expected electromagnetic torque and motor parameters such as the number of motor poles, permanent magnet flux amplitude, direct-axis inductance, quadrature-axis inductance, etc., repeating the simulation test, recording the data, calculating the torque error and calculating the copper loss; (9) plotting the expected electromagnetic torque and torque error as well as the expected electromagnetic torque and motor copper loss in each test into corresponding line graphs and other charts.
[0094] By giving different expected electromagnetic torques and motor parameters, the effects of the three methods on torque accuracy and copper loss are tested according to the above steps, and the following results can be obtained: Figure 4-5 The simulation results shown; Figure 4 The line graphs of the expected electromagnetic torque and torque error corresponding to the three methods are shown. The torque error is the torque difference between the actual output torque and the expected electromagnetic torque. Figure 4 It can be seen that when the motor parameters change, under the same expected electromagnetic torque, the torque error corresponding to the online table lookup method and the offline fitting method is large, while the torque error corresponding to the direct calculation method is very small; Figure 5 The following are the line graphs of the expected electromagnetic torque and motor copper loss corresponding to the three methods. Figure 5 It can be seen that when the motor parameters change, under the same expected electromagnetic torque, the motor copper loss corresponding to the online table lookup method and the offline fitting method is greater than the motor copper loss corresponding to the direct calculation method of the present application.
[0095] It should be noted that when the permanent magnet synchronous motor uses the MTPA control method, the copper loss can be reduced by optimizing the direct-axis current and the quadrature-axis current to obtain the maximum torque output at a given current level, or using the minimum current at the required torque output. The reasons why the MTPA control method can reduce copper loss are: (1) Reducing reactive current: In a permanent magnet synchronous motor, the direct-axis current is usually used to produce a demagnetization effect, while the quadrature-axis current is used to produce torque; through proper control, the direct-axis current can be adjusted to provide only the necessary demagnetization effect, thereby reducing the reactive current component. In this way, more current can be used to generate torque, while the total current demand is reduced; (2) Optimizing current distribution: The MTPA control method attempts to find an optimal combination of direct-axis current and quadrature-axis current so that the total stator current (i.e., ) is minimized; due to the copper loss and Proportional to the stator current, reducing the stator current means reducing the copper loss; (3) Utilizing the characteristics of permanent magnets: Since permanent magnet motors have permanent magnets inside, they can provide magnetic fields without additional excitation current, which means that by properly controlling the direct-axis current, the demagnetization characteristics of the permanent magnets can be used to reduce the required excitation current, thereby reducing the total current and reducing copper loss. Therefore, by optimizing the direct-axis current and the quadrature-axis current, the motor copper loss can be reduced.
[0096] In summary, in the MTPA control method of the permanent magnet synchronous motor mentioned above, the electromagnetic torque relationship and the current relationship are constructed by the latest motor parameters and the expected electromagnetic torque. The electromagnetic torque relationship and the current relationship are equations about the direct-axis current and the quadrature-axis current. The electromagnetic torque relationship and the current relationship can be solved to obtain the values of the direct-axis current and the quadrature-axis current. The corresponding currents are allocated to the direct axis and the quadrature-axis according to the values of the direct-axis current and the quadrature-axis current calculated in real time, respectively. This solves the problem that the existing online table lookup method and offline fitting method cannot update the direct-axis current and the quadrature-axis current after the motor parameters are updated, reduces the error between the actual output torque of the motor and the expected electromagnetic torque, thereby improving the torque control accuracy of the permanent magnet synchronous motor and reducing the copper loss of the motor.
[0097] It should be understood that although Figure 1 The steps in the flowchart are shown in sequence as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, Figure 1At least part of the steps may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least part of the sub-steps or stages of other steps.
[0098] In one embodiment, Figure 6 As shown, a MTPA control device for a permanent magnet synchronous motor is provided, comprising: a parameter acquisition module, a relational formula building module, a current calculation module and a current distribution module, wherein:
[0099] Parameter acquisition module, used to obtain the latest motor parameters and expected electromagnetic torque;
[0100] A relational expression building module, used to build an electromagnetic torque relational expression of the permanent magnet synchronous motor under the MTPA control mode according to the latest motor parameters and the expected electromagnetic torque; and to build a current relational expression of the permanent magnet synchronous motor about the direct axis current and the quadrature axis current under the MTPA control mode according to the latest motor parameters;
[0101] A current calculation module, used for combining the torque relationship equation and the current relationship equation to calculate the values of the direct-axis current and the quadrature-axis current;
[0102] The current distribution module is used to distribute corresponding currents to the direct axis and the quadrature axis respectively according to the values of the direct axis current and the quadrature axis current.
[0103] In a specific implementation, the latest motor parameters include the number of motor pole pairs, permanent magnet flux amplitude, direct-axis inductance and quadrature-axis inductance, and the electromagnetic torque relationship is a relationship between the desired electromagnetic torque, the latest motor parameters, the direct-axis current and the quadrature-axis current.
[0104] In a specific implementation, the current relationship includes:
[0105]
[0106] represents the permanent magnet flux amplitude, L d represents the direct-axis inductance, L q represents the quadrature-axis inductance, i d represents the direct axis current, i q represents the quadrature-axis current.
[0107] In a specific implementation, the electromagnetic torque relationship includes:
[0108]
[0109] T e represents the desired electromagnetic torque, n p Indicates the number of pole pairs of the motor.
[0110] In a specific implementation, the current calculation module is used to combine the electromagnetic torque relationship and the current relationship to calculate the values of the direct-axis current and the quadrature-axis current, specifically including: inputting the current relationship into the torque relationship and sorting it out to obtain a target relationship between the desired electromagnetic torque and the direct-axis current; using the Ferrari root method to solve the target relationship to obtain the value of the direct-axis current; inputting the value of the direct-axis current into the electromagnetic torque relationship or the current relationship for calculation to obtain the value of the quadrature-axis current.
[0111] In a specific implementation, the current calculation module is used to use the Ferrari root method to solve the target relationship to obtain the value of the direct-axis current, specifically including: taking the direct-axis current as the unknown variable and transforming the target relationship according to the format of a quartic equation; using the Ferrari root method to solve the transformed target relationship, and using the negative real root obtained as the value of the direct-axis current.
[0112] In a specific implementation, the target relationship includes:
[0113]
[0114] The specific definition of the MTPA control device of the permanent magnet synchronous motor can be found in the definition of the MTPA control method of the permanent magnet synchronous motor mentioned above, which will not be repeated here. Each module in the above-mentioned MTPA control device of the permanent magnet synchronous motor can be implemented in whole or in part by software, hardware and a combination thereof. The above-mentioned modules can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above modules.
[0115] In one embodiment, a computer device is provided. The computer device may be a server, and its internal structure diagram may be as follows: Figure 7As shown. The computer device includes a processor, a memory and a network interface connected through a system bus. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The network interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, a MTPA control method for a permanent magnet synchronous motor is implemented.
[0116] Those skilled in the art will understand that Figure 7 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.
[0117] In one embodiment, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the MTPA control method for the permanent magnet synchronous motor described in the above embodiment are implemented.
[0118] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps of the MTPA control method of the permanent magnet synchronous motor described in the above embodiment are implemented.
[0119] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).
[0120] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0121] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.
Claims
1. A MTPA control method for a permanent magnet synchronous motor, characterized in that: The method comprises: Get the latest motor parameters and expected electromagnetic torque; According to the latest motor parameters and the expected electromagnetic torque, a relationship between the electromagnetic torque of the permanent magnet synchronous motor under the MTPA control mode is constructed; according to the latest motor parameters, a current relationship between the direct-axis current and the quadrature-axis current of the permanent magnet synchronous motor under the MTPA control mode is constructed; Combining the electromagnetic torque relationship equation with the current relationship equation to calculate the values of the direct-axis current and the quadrature-axis current; Corresponding currents are allocated to the direct axis and the quadrature axis respectively according to the values of the direct axis current and the quadrature axis current.
2. The MTPA control method of a permanent magnet synchronous motor according to claim 1, characterized in that: The latest motor parameters include the number of motor pole pairs, permanent magnet flux amplitude, direct-axis inductance and quadrature-axis inductance, and the electromagnetic torque relationship is a relationship between the desired electromagnetic torque, the latest motor parameters, the direct-axis current and the quadrature-axis current.
3. The MTPA control method of a permanent magnet synchronous motor according to claim 2, characterized in that: The current relationship includes: represents the permanent magnet flux amplitude, L d represents the direct-axis inductance, L q represents the quadrature-axis inductance, i d represents the direct axis current, i q represents the quadrature-axis current.
4. The MTPA control method of a permanent magnet synchronous motor according to claim 3, characterized in that: The electromagnetic torque relationship includes: T e represents the desired electromagnetic torque, n p Indicates the number of pole pairs of the motor.
5. The MTPA control method of a permanent magnet synchronous motor according to claim 4, characterized in that: Combining the electromagnetic torque relationship and the current relationship to calculate the values of the direct-axis current and the quadrature-axis current includes: Inputting the current relationship into the torque relationship and sorting them out to obtain a target relationship between the desired electromagnetic torque and the direct axis current; The target relationship is solved by using the Ferrari root-finding method to obtain the value of the direct-axis current; The value of the direct-axis current is input into the electromagnetic torque relationship equation or the current relationship equation for calculation to obtain the value of the quadrature-axis current.
6. The MTPA control method of a permanent magnet synchronous motor according to claim 5, characterized in that: The target relationship is solved by using the Ferrari root-finding method to obtain the value of the direct-axis current, including: Taking the direct-axis current as an unknown variable and transforming the target relational expression according to the format of a quartic equation; The transformed target relationship is solved by using the Ferrari root-finding method, and the negative real root obtained by the solution is used as the value of the direct-axis current.
7. The MTPA control method of a permanent magnet synchronous motor according to claim 5, characterized in that: The target relationship includes:
8. A MTPA control device for a permanent magnet synchronous motor, characterized in that: The device comprises: Parameter acquisition module, used to obtain the latest motor parameters and expected electromagnetic torque; A relational expression building module, used to build an electromagnetic torque relational expression of the permanent magnet synchronous motor under the MTPA control mode according to the latest motor parameters and the expected electromagnetic torque; and to build a current relational expression of the permanent magnet synchronous motor about the direct axis current and the quadrature axis current under the MTPA control mode according to the latest motor parameters; A current calculation module, used for combining the torque relationship equation and the current relationship equation to calculate the values of the direct-axis current and the quadrature-axis current; The current distribution module is used to distribute corresponding currents to the direct axis and the quadrature axis respectively according to the values of the direct axis current and the quadrature axis current.
9. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the MTPA control method for the permanent magnet synchronous motor according to any one of claims 1 to 7 are implemented.
10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the MTPA control method for a permanent magnet synchronous motor according to any one of claims 1 to 7 are implemented.