Control method and control device for permanent magnet motor

Abstract

Disclosed are a control method and a control device for a permanent magnet motor, wherein the control method comprises: determining active current reference initial values and reactive current reference initial values of the permanent magnet motor in a current control period; searching for optimal active current reference values and reactive current reference values in the current control period based on the active current reference initial values and the reactive current reference initial values, with the maximum torque current ratio in the current control period as the target; and controlling the permanent magnet motor to operate based on the optimal active current reference values and the reactive current reference values; wherein the torque current ratio is calculated based on a torque instruction value received by the permanent magnet motor from a fan main controller and an output current value of the permanent magnet motor. The technical solution of the disclosure can avoid the influence of parameter changes of the permanent magnet motor on the maximum torque current ratio control, thereby realizing accurate optimal torque current ratio control.

Description

Technical Field

[0001] This disclosure relates to the field of wind power generation technology, and more specifically, to a control method and control device for permanent magnet motors. Background Technology

[0002] Currently, when the permanent magnet motor is a salient pole motor or a non-salient pole motor with weak salient pole characteristics, the maximum output torque per unit current can be achieved by utilizing the salient pole characteristics. The optimal torque-current ratio algorithm is commonly used to obtain the optimal control current.

[0003] However, in the method described above, the accuracy of the calculated active current reference and reactive current reference is affected by the accuracy of the permanent magnet motor parameters. The motor parameters change in real time due to the influence of changes in ambient temperature and current value during operation. Therefore, the method of calculating active and reactive current references based on motor parameters has a large control deviation and cannot achieve optimal torque-to-current ratio control. Summary of the Invention

[0004] This disclosure provides a control method and control device for a permanent magnet motor from the perspective of solving the problem that the accuracy of generator parameters affects the control accuracy of conventional optimal torque-current ratio, so as to at least solve the technical problems mentioned in the background art.

[0005] According to one aspect of an exemplary embodiment of the present disclosure, a control method for a permanent magnet motor is provided, wherein the control method includes: determining an initial reference value for active current and an initial reference value for reactive current of the permanent magnet motor in a current control cycle; searching for an optimal reference value for active current and an optimal reference value for reactive current in the current control cycle, based on the initial reference values ​​for active current and reactive current, with the objective of maximizing the torque-to-current ratio in the current control cycle; and controlling the operation of the permanent magnet motor based on the optimal reference values ​​for active current and reactive current; wherein the torque-to-current ratio is calculated based on a torque command value received by the permanent magnet motor from a wind turbine main controller and an output current value of the permanent magnet motor.

[0006] According to another aspect of an exemplary embodiment of the present disclosure, a control device for a permanent magnet motor is provided, wherein the control device includes: an initial value determination unit configured to determine an initial reference value for active current and an initial reference value for reactive current of the permanent magnet motor in a current control cycle; a search unit configured to search for an optimal reference value for active current and an optimal reference value for reactive current in the current control cycle, based on the initial reference values ​​for active current and reactive current, with the objective of maximizing the torque-to-current ratio in the current control cycle; and a control unit configured to control the operation of the permanent magnet motor based on the optimal reference values ​​for active current and reactive current; wherein the torque-to-current ratio is calculated based on a torque command value received by the permanent magnet motor from a wind turbine main controller and an output current value of the permanent magnet motor.

[0007] According to another aspect of exemplary embodiments of the present disclosure, a computer-readable storage medium storing a computer program is provided, wherein when the computer program is executed by a processor, the control method for a permanent magnet motor described in the present disclosure is implemented.

[0008] According to another aspect of an exemplary embodiment of the present disclosure, an electronic device is provided, comprising: at least one processor; and at least one memory storing computer-executable instructions, wherein the computer-executable instructions, when executed by the at least one processor, cause the at least one processor to perform the permanent magnet motor control method of the present disclosure.

[0009] Using the technical solution provided in this disclosure, initial values ​​of active current and reactive current reference values ​​are calculated for the current control cycle. Then, with the maximum corresponding torque-to-current ratio as the search target, the optimal active current and reactive current reference values ​​are determined through online search (e.g., hill-climbing search). This corrects the calculation errors caused by parameter deviations, thus avoiding the impact of permanent magnet motor parameter changes on the maximum torque-to-current ratio control, thereby achieving precise optimal torque-to-current ratio control. Based on the determined maximum torque-to-current ratio, maximum torque output at minimum current can be achieved, reducing transmission system losses and improving system efficiency. It can also reduce heat generation during motor and converter operation, lowering the workload of motor and converter cooling equipment and extending their service life. Furthermore, the technical solution of this disclosure is mainly achieved through optimized software control, without adding any hardware equipment, avoiding increased costs and improving the applicability of the solution.

[0010] Further aspects and / or advantages of the general concept of this disclosure will be set forth in part in the description which follows, and in part will be clear from the description or may be learned by practice of the general concept of this disclosure. Attached Figure Description

[0011] The above and other objects and features of exemplary embodiments of this disclosure will become clearer from the following description taken in conjunction with the accompanying drawings, which exemplarily illustrate the embodiments, wherein:

[0012] Figure 1 This is a flowchart illustrating a control method for a permanent magnet motor according to an exemplary embodiment of the present disclosure;

[0013] Figure 2 This is a block diagram illustrating a control device for a permanent magnet motor according to an exemplary embodiment of the present disclosure;

[0014] Figure 3 This is a schematic diagram illustrating an application example of a control method for a permanent magnet motor according to an exemplary embodiment of the present disclosure. Detailed Implementation

[0015] The following detailed embodiments are provided to aid the reader in gaining a comprehensive understanding of the methods, apparatus, and / or systems described herein. However, various changes, modifications, and equivalents of the methods, apparatus, and / or systems described herein will become apparent upon understanding this disclosure. For example, the order of operations described herein is merely illustrative and is not limited to those orders set forth herein, but may be changed as will become clear upon understanding this disclosure, except for operations that must occur in a specific order. Furthermore, for clarity and conciseness, descriptions of features known in the art may be omitted.

[0016] The features described herein may be implemented in different forms and should not be construed as limited to the examples described herein. Rather, the examples described herein are provided only to illustrate some of the many feasible ways of implementing the methods, apparatus, and / or systems described herein, which will become clear upon understanding the disclosure of this application.

[0017] The terminology used herein is for the purpose of describing various examples only and is not intended to limit disclosure. Unless the context clearly indicates otherwise, the singular form is intended to include the plural form as well. The terms “comprising,” “including,” and “having” indicate the presence of the described features, quantities, operations, components, elements, and / or combinations thereof, but do not preclude the presence or addition of one or more other features, quantities, operations, components, elements, and / or combinations thereof.

[0018] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains upon understanding this disclosure. Unless expressly defined herein, terms (such as those defined in a general dictionary) shall be interpreted as having a meaning consistent with their meaning in the context of the relevant field and in this disclosure, and shall not be interpreted in an idealized or overly formalistic manner.

[0019] Furthermore, in the description of the examples, detailed descriptions of well-known related structures or functions will be omitted when it is believed that such detailed descriptions would lead to a vague interpretation of this disclosure.

[0020] Currently, the accuracy of the active and reactive current references calculated by the optimal torque-to-current ratio algorithm (MTPA) is affected by the accuracy of the permanent magnet motor parameters. During operation, the permanent magnet motor parameters change in real time due to the influence of changes in ambient temperature and current value. Therefore, the calculation of active and reactive current references based on motor parameters will have a large control deviation, thus failing to achieve optimal torque-to-current ratio control.

[0021] Therefore, the above problems can be solved by reducing or even eliminating the impact of the accuracy of permanent magnet motor parameters on the control accuracy of the conventional optimal torque-current ratio.

[0022] According to embodiments of this disclosure, an online search combined with the optimal torque-current ratio algorithm (MTPA) is provided. Specifically, active and reactive current references are calculated using the MTPA formula, and then a real-time search is performed based on the calculated values, with the maximum torque-current ratio as the search target. This corrects the errors in the calculated values ​​caused by parameter deviations, thereby achieving accurate optimal torque-current control.

[0023] Figure 1 This is a flowchart illustrating a control method for a permanent magnet motor according to an exemplary embodiment of the present disclosure. (Refer to...) Figure 1 The control method for the permanent magnet motor includes steps S110 to S130.

[0024] In step S110, the initial reference values ​​of active current and reactive current of the permanent magnet motor in the current control cycle are determined.

[0025] First, it should be noted that the reason for limiting the timeframe to "within the current control cycle" is that the main control commands (including control parameters, torque command values, etc.) issued by the wind turbine's main controller to the permanent magnet motor change in different control cycles. Therefore, the initial reference values ​​for active current and reactive current calculated for different control cycles may not be the same. Based on this, the "determination" step in S110 and the corresponding calculations in subsequent steps S120 and S130 must be completed "within the current control cycle".

[0026] For different control cycles, the optimal active current reference value and reactive current reference value can be updated as needed, which will be described in detail below.

[0027] It is understood that step S110 can be implemented in various ways. For example, in one optional implementation, step S110 may include: obtaining the motor parameters of the permanent magnet motor and the control parameters sent to the permanent magnet motor by the main controller of the wind turbine in the current control cycle; and calculating the initial reference values ​​of the active current and reactive current based on the aforementioned motor parameters and control parameters. Here, the motor parameters include, but are not limited to, the motor flux linkage ψ. m d-axis inductance L d q-axis inductance L q Control parameters include, but are not limited to, drive current I. s .

[0028] Furthermore, the initial reference values ​​for active current and reactive current can be calculated in the following manner.

[0029] For example, referring to formula (1), based on the motor flux linkage ψ m d-axis inductance L d q-axis inductance L q and drive current I s Calculate the initial reference value i for reactive current dref0 Based on the driving current I s The active current reference initial value i is calculated from the reactive current reference initial value. qref0 .

[0030]

[0031] For example, one can refer to formula (2), based on the motor flux linkage ψ m d-axis inductance L d q-axis inductance L q and drive current I s The current vector angle θ of the permanent magnet motor is calculated using inverse cosine operation. MTPA Based on the driving current I s and current vector angle θ MTPA To calculate the initial reference value i of the active current qref0 With reactive current reference initial value i dref0 .

[0032]

[0033] In step S120, based on the initial active current and reactive current reference values ​​from step S110, the optimal active current and reactive current reference values ​​for the current control cycle are searched, with the goal of maximizing the torque-to-current ratio within the current control cycle. In step S130, the permanent magnet motor is controlled to operate based on the optimal active and reactive current reference values. Here, the torque-to-current ratio is calculated based on the torque command value received by the permanent magnet motor from the wind turbine main controller and the output current value of the permanent magnet motor.

[0034] Typically, step S120 can be implemented in several available ways. For example, within the current control cycle, the optimal active current reference value and reactive current reference value can be searched online using a hill-climbing method. Alternatively, within the current control cycle, the optimal active current reference value and reactive current reference value can be searched offline using a lookup table method, wherein the lookup table supporting offline search is obtained through a pre-executed online search, and the lookup table includes the optimal active current reference value and reactive current reference value corresponding to different torques, speeds, and / or power.

[0035] Optionally, when using the hill-climbing method to search for the optimal active current reference value and reactive current reference value online, the specific steps are as follows:

[0036] Step A: Within the current control cycle, keep the initial reference value of active current obtained in step S110 unchanged, and use it as the optimal reference value of active current.

[0037] Step B: Based on the initial reactive current reference value obtained in step S110, search for the reactive current reference value corresponding to the largest torque-current ratio in the current control cycle by accumulating or subtracting the reactive current reference value change by a preset step size, and use it as the optimal reactive current reference value.

[0038] It should be noted here that in step A, the formula for torque and active current can be:

[0039] Torque value = constant * active current value

[0040] Based on this formula, within the current control cycle, only one torque command value is given, and the initial reference value of the active current is a fixed value. No other calculations are performed, thereby maintaining the initial reference value of the active current unchanged, i.e., locking the initial reference value of the active current i. qref0 .

[0041] In step B, within the current control cycle, and at the initial reference value i of the active current... qref0 In the locked state, refer to the drive current I specified in formula (1). s With reactive current reference i d The relationship between them, thereby adjusting the reactive current reference i d Change the drive current I s This leads to the permanent magnet motor's response to different drive currents I. s The output current value is determined, and then multiple torque-current ratios are calculated based on the torque command value corresponding to the current control cycle. The maximum torque-current ratio is determined from these ratios, and then the optimal reactive current reference value is determined.

[0042] Depending on the circumstances, in step B above, the reactive current reference value can be searched in the following way.

[0043] For example, the reactive current reference initial value i can be used. dref0 Add the change in reactive current reference value ΔI with the preset step size, that is, in i dref0 Based on this, the reactive current reference is increased (accumulated ΔI). After the current output by the permanent magnet motor stabilizes, the ratio of the torque command value received by the permanent magnet motor from the wind turbine main controller to the output current (i.e., the torque-current ratio) is calculated to see if it increases. If the torque-current ratio does not increase, the initial value of the reactive current reference i is adjusted. dref0 Subtract the change in reactive current reference value ΔI from the preset step size, i.e., at i dref0 Based on this, reduce the reactive current reference (cumulative reduction ΔI). After the permanent magnet motor output current stabilizes, calculate whether the torque-current ratio increases. If the torque-current ratio does not increase, then adjust the initial value of the reactive current reference i. dref0 The optimal reactive current reference value within the aforementioned preset control cycle is determined.

[0044] In the search process for the optimal reactive current reference value as described above, based on the initial reactive current reference value i dref0 Forward search (i.e., reactive current reference initial value i) dref0 (Added to the change in reactive current reference value ΔI with a preset step size) and reverse search (i.e., the initial reactive current reference value i) dref0 After subtracting the change in reactive current reference value ΔI from the preset step size, the corresponding torque-current ratio did not increase. Therefore, it can be determined that the corresponding value is the initial reactive current reference value i. dref0 This refers to the case where the optimal reactive current reference value is reached.

[0045] For example, if the reactive current reference value i dref0 After accumulating ΔI, the calculated torque-to-current ratio increases, then i dref0 Based on +ΔI, accumulate ΔI, and the latest reactive current reference value is i. dref0 +2△I. After the output current of the permanent magnet motor stabilizes, calculate the torque-to-current ratio and determine if it has increased. If the torque-to-current ratio has not increased, then i dref0 +2△I is determined as the optimal reactive current reference value; if the torque-current ratio increases, then continue with i. dref0 Based on +2ΔI, accumulating ΔI, the latest reactive current reference value is i. dref0 +3△I, and then after the current output by the permanent magnet motor stabilizes, continue to determine whether the torque-current ratio increases, and so on.

[0046] In the process of searching for the reactive current reference value as described above, if based on the initial reactive current reference value i dref0If the torque-to-current ratio increases after a forward search, the reactive current reference value is increased based on idref0, and the forward search continues cyclically until the torque-to-current ratio no longer increases. At this point, the reactive current reference value (i) is set to... dref0 +n△I, where n is a certain positive integer, is determined as the optimal reactive current reference value.

[0047] For example, if the reactive current reference value i dref0 After cumulatively reducing ΔI, the calculated torque-to-current ratio increases, then i dref0 Using -ΔI as a reference, subtract ΔI cumulatively, and the latest reactive current reference value is i. dref0 -2△I. After the output current of the permanent magnet motor stabilizes, calculate the torque-to-current ratio and determine if it has increased. If the torque-to-current ratio has not increased, then i dref0 -2ΔI is determined as the optimal reactive current reference value; if the torque-current ratio increases, then continue with i. dref0 Using -2ΔI as a baseline, subtract ΔI cumulatively; at this point, the latest reactive current reference value is i. dref0 -3△I, and then after the current output by the permanent magnet motor stabilizes, continue to determine whether the torque-current ratio increases, and so on.

[0048] In the process of searching for the reactive current reference value as described above, if based on the initial reactive current reference value i dref0 If the torque-to-current ratio increases after the reverse search, then the reactive current reference value is reduced based on idref0, and the reverse search continues in a loop until the torque-to-current ratio no longer increases. At this point, the reactive current reference value (i...) is... dref0 -m△I, where m is a certain positive integer, is determined as the optimal reactive current reference value.

[0049] It should be noted that in the actual search process, the above search methods can be combined and executed. The above search methods may involve "forward" and "reverse" processes. From the perspective of combining numbers and shapes, when ΔI is accumulated, the reactive current reference value can show a monotonically increasing curve, while when ΔI is decreased, the reactive current reference value can show a monotonically decreasing curve. Thus, the reactive current reference value curve corresponding to the entire search process will show peaks and troughs. Therefore, the above search method can be figuratively defined as "hill climbing search".

[0050] Furthermore, since the control time of the permanent magnet motor includes multiple control cycles, as mentioned above, the main control commands (e.g., control parameters, torque command values, etc.) issued by the main controller of the wind turbine to the permanent magnet motor may change in different control cycles. Therefore, the initial reference values ​​of active current and reactive current calculated for different control cycles may be different.

[0051] Therefore, when searching for the optimal active current reference value and reactive current reference value within the current control cycle using step S120, the following steps may also be included:

[0052] The determined initial reference values ​​for active and reactive current are compared with the optimal reference values ​​for active and reactive current found in the previous control cycle, respectively. If the comparison results for both active and reactive currents are consistent, the optimal reference values ​​for active and reactive current found in the previous control cycle are used as the optimal reference values ​​for active and reactive current in the current control cycle. If either comparison result is inconsistent, the optimal reference values ​​for active and reactive current in the current control cycle are searched based on the determined initial reference values ​​for active and reactive current.

[0053] As described above, by comparing the "initial reference values ​​of active current and reactive current" calculated in the current control cycle with the "optimal reference values ​​of active current and reactive current" from the previous control cycle, when the comparison results are consistent, the "optimal reference values ​​of active current and reactive current" from the previous control cycle are directly used to control the operation of the permanent magnet motor, saving the step of re-"searching" and improving the control efficiency of the control method.

[0054] The following reference Figure 3 The application examples are used to describe the control method of the permanent magnet motor disclosed herein.

[0055] Reference Figure 3 In step S310, within the current control cycle, the initial reference value of the active current i is calculated according to formula (1). qref0 With reactive current reference initial value i dref0 .

[0056] In step S302, the calculated initial reference value i of the active current in the current control cycle is determined. qref0 With reactive current reference initial value i dref0 Are the optimal active current reference value and reactive current reference value found in the previous control cycle the same?

[0057] In step S3201, in response to the fact that both are the same, the optimal active current reference value and reactive current reference value searched in the previous control cycle are used to control the permanent magnet motor to run, thereby saving the step of re-"searching" and improving the control efficiency of the control method.

[0058] In step S3202, in response to the difference between the two, the optimal active current reference value and reactive current reference value within the current control cycle can be searched.

[0059] In summary, using the technical solution provided in this disclosure, initial values ​​of active current and reactive current reference values ​​are calculated for the current control cycle. Then, with the maximum corresponding torque-to-current ratio as the search target, the optimal active current and reactive current reference values ​​are determined through online search (e.g., hill-climbing search). This corrects the calculation errors caused by parameter deviations, thus avoiding the impact of permanent magnet motor parameter changes on the maximum torque-to-current ratio control, thereby achieving precise optimal torque-to-current ratio control. Furthermore, based on the determined maximum torque-to-current ratio, maximum torque output at minimum current can be achieved, reducing transmission system losses, improving system efficiency, and also reducing heat generation during motor and converter operation, lowering the workload of motor and converter cooling equipment, and extending service life. In addition, the technical solution of this disclosure is mainly achieved through optimized software control, without adding any hardware equipment, avoiding increased costs and improving the applicability of the solution.

[0060] Example Figure 2 This is a block diagram illustrating a control device for a permanent magnet motor according to an exemplary embodiment of the present disclosure. Since this control device is used to control the operation of the permanent magnet motor, it employs... Figure 1 The control method shown is used as a reference for the implementation of the control device. Therefore, the specific implementation of the control device can be referred to the implementation of the control method. Where the method is repeated, it will not be described again.

[0061] Reference Figure 2 The control device 200 includes an initial value determination unit 210, a search unit 220, and a control unit 230, and the units are communicatively coupled to each other.

[0062] The initial value determination unit 210 can determine the initial reference values ​​of active current and reactive current of the permanent magnet motor in the current control cycle; the search unit 220 can search for the optimal reference values ​​of active current and reactive current in the current control cycle based on the aforementioned initial reference values ​​of active current and reactive current, with the goal of maximizing the torque-to-current ratio in the current control cycle; the control unit 230 can control the operation of the permanent magnet motor based on the aforementioned optimal reference values ​​of active current and reactive current. The torque-to-current ratio is calculated based on the torque command value received by the permanent magnet motor from the wind turbine main controller and the output current value of the permanent magnet motor.

[0063] It should be understood that the specific features described above regarding the control method for permanent magnet motors in this disclosure can also be similarly applied to control devices for permanent magnet motors for similar extensions. For simplicity, they have not been described in detail.

[0064] Specifically, the initial value determination unit 210 can obtain the motor parameters of the permanent magnet motor and the control parameters sent to the permanent magnet motor by the main controller of the fan in the current control cycle. Then, based on the motor parameters and control parameters, it calculates the reference initial value of active current and the reference initial value of reactive current.

[0065] As mentioned above, the motor parameters include: motor flux linkage ψ m d-axis inductance L d q-axis inductance L q The control parameters include the drive current I. s Thus, the initial value determination unit 210 can be based on the motor flux linkage ψ. m d-axis inductance L d q-axis inductance L q and drive current I s Calculate the initial reference value of reactive current based on the drive current I. s Calculate the initial reference value of active current from the initial reference value of reactive current.

[0066] On the other hand, motor parameters include: motor flux linkage ψ m d-axis inductance L d q-axis inductance L q The control parameters include the drive current I. s Thus, the initial value determination unit 210 is further configured to: determine the value based on the motor flux linkage ψ. m d-axis inductance L d q-axis inductance L q and drive current I s The current vector angle of the permanent magnet motor is calculated using inverse cosine operation, based on the drive current I. s The reference initial values ​​of active current and reactive current are calculated using the current vector angle.

[0067] The search unit 220 can search for the optimal active current reference value and reactive current reference value online using the hill climbing method within the current control cycle, or it can search for the optimal active current reference value and reactive current reference value offline using the lookup table method within the current control cycle. The lookup table that supports offline search is obtained through a pre-executed online search, and the lookup table includes the optimal active current reference value and reactive current reference value corresponding to different torques, speeds and / or power.

[0068] Alternatively, the search unit 220 may also keep the initial active current reference value unchanged within the current control cycle as the optimal active current reference value, and search for the reactive current reference value corresponding to the largest torque-current ratio within the current control cycle by accumulating or subtracting the reactive current reference value change by a preset step size, based on the initial reactive current reference value, as the optimal reactive current reference value.

[0069] Alternatively, the search unit 220 can also use the reactive current reference initial value i dref0 The change in reactive current reference value ΔI is added to the preset step size to obtain the first reactive current reference value. After the output current of the permanent magnet motor stabilizes, it is determined whether the torque-current ratio corresponding to the first reactive current reference value has increased. If the torque-current ratio corresponding to the first reactive current reference value has not increased, the initial reactive current reference value i is adjusted. dref0 The change in reactive current reference value ΔI is subtracted from the preset step size to obtain the second reactive current reference value. After the output current of the permanent magnet motor stabilizes, it is determined whether the torque-current ratio corresponding to the second reactive current reference value has increased. If the torque-current ratio corresponding to the second reactive current reference value has not increased, the initial value of the reactive current reference i is adjusted. dref0 The optimal reactive current reference value is determined within the preset control cycle.

[0070] Optionally, the search unit 220 may also, in response to an increase in the torque-current ratio corresponding to the first reactive current reference value, add the first reactive current reference value to a preset step size of reactive current reference value change ΔI, and update the first reactive current reference value with the result of the addition. After the output current of the permanent magnet motor stabilizes, it determines whether the torque-current ratio corresponding to the updated first reactive current reference value has increased. If the torque-current ratio corresponding to the updated first reactive current reference value has not increased, the updated first reactive current reference value is determined as the optimal reactive current reference value. If the torque-current ratio corresponding to the updated first reactive current reference value has increased, the updated first reactive current reference value is added again to the preset step size of reactive current reference value change ΔI, and the result of the addition is used to continue updating the first reactive current reference value. Then, it returns to the step of determining whether the updated torque-current ratio corresponding to the first reactive current reference value has increased.

[0071] Optionally, the search unit 220 may also, in response to an increase in the torque-current ratio corresponding to the second reactive current reference value, subtract the second reactive current reference value from the reactive current reference value change ΔI of a preset step size, and update the second reactive current reference value with the result of the subtraction. After the output current of the permanent magnet motor stabilizes, it determines whether the torque-current ratio corresponding to the updated second reactive current reference value has increased. If the torque-current ratio corresponding to the updated second reactive current reference value has not increased, the updated second reactive current reference value is determined as the optimal reactive current reference value. If the torque-current ratio corresponding to the updated second reactive current reference value has increased, the updated second reactive current reference value is subtracted again from the reactive current reference value change ΔI of a preset step size, and the second reactive current reference value is updated again with the result of the subtraction. Then, the process returns to the step of determining whether the updated torque-current ratio corresponding to the second reactive current reference value has increased.

[0072] Optionally, the search unit 220 can also compare the determined initial reference values ​​for active and reactive current with the optimal reference values ​​for active and reactive current obtained in the previous control cycle, respectively. If the comparison results are consistent, the optimal reference values ​​for active and reactive current obtained in the previous control cycle are used as the optimal reference values ​​for active and reactive current in the current control cycle. If the comparison results are inconsistent, the optimal reference values ​​for active and reactive current in the current control cycle are searched based on the determined initial reference values ​​for active and reactive current.

[0073] It should be understood that the various units / modules in the control device for a permanent magnet motor according to exemplary embodiments of the present disclosure can be implemented as hardware components and / or software components. Those skilled in the art can implement the various units / modules, for example, using field-programmable gate arrays (FPGAs) or application-specific integrated circuits (ASICs), based on the processes performed by the defined various units / modules.

[0074] According to another aspect of exemplary embodiments of the present disclosure, a computer-readable storage medium storing a computer program is provided, wherein when the computer program is executed by a processor, the control method described in the present disclosure is implemented.

[0075] Specifically, the control methods according to exemplary embodiments of this disclosure may be transcribed as computer programs, code segments, instructions, or any combination thereof, and recorded, stored, or mounted on one or more non-transitory computer-readable storage media. The computer-readable storage medium is any data storage device capable of storing data read by a computer system. Examples of computer-readable storage media include: read-only memory, random access memory, read-only optical disc, magnetic tape, floppy disk, optical data storage device, and carrier waves (such as data transmission via the Internet through wired or wireless transmission paths).

[0076] According to another aspect of an exemplary embodiment of the present disclosure, an electronic device is provided, wherein the electronic device includes: at least one processor; at least one memory storing computer-executable instructions, wherein the computer-executable instructions, when executed by the at least one processor, cause the at least one processor to perform the control method described in the present disclosure.

[0077] Specifically, the electronic device can be broadly categorized as a tablet computer, smartphone, smartwatch, or any other electronic device with the necessary computing and / or processing capabilities. In one embodiment, the electronic device may include a processor, memory, network interface, communication interface, etc., connected via a system bus. The processor of the electronic device can be used to provide the necessary computing, processing, and / or control capabilities. The memory of the electronic device may include non-volatile storage media and internal memory. The non-volatile storage media may store an operating system, computer programs, etc. The internal memory can provide an environment for the operation of the operating system and computer programs in the non-volatile storage media. The network interface and communication interface of the electronic device can be used to connect and communicate with external devices via a network.

[0078] In summary, using the technical solution provided in this disclosure, initial values ​​of active current and reactive current reference values ​​are calculated for the current control cycle. Then, with the maximum corresponding torque-to-current ratio as the search target, the optimal active current and reactive current reference values ​​are determined through online search (e.g., hill-climbing search). This corrects the calculation errors caused by parameter deviations, thus avoiding the impact of permanent magnet motor parameter changes on the maximum torque-to-current ratio control, thereby achieving precise optimal torque-to-current ratio control. Furthermore, based on the determined maximum torque-to-current ratio, maximum torque output at minimum current can be achieved, reducing transmission system losses and improving system efficiency. It can also reduce heat generation during motor and converter operation, lowering the workload of motor and converter cooling equipment and extending their service life. In addition, the technical solution of this disclosure is mainly achieved through optimized software control, without adding any hardware equipment, avoiding increased costs and improving the applicability of the solution.

[0079] While some exemplary embodiments of this disclosure have been shown and described, those skilled in the art will understand that modifications may be made to these embodiments without departing from the principles and spirit of this disclosure, which are defined by the claims and their equivalents.

Claims

1. A control method for a permanent magnet motor, characterized in that, The control method includes: The initial reference values ​​of active current and reactive current of the permanent magnet motor are determined in the current control cycle, wherein the initial reference values ​​of active current and reactive current are calculated by the optimal torque-current ratio algorithm. Based on the initial reference values ​​of active current and reactive current, with the goal of maximizing the torque-to-current ratio within the current control cycle, the optimal reference values ​​of active current and reactive current within the current control cycle are searched. The permanent magnet motor is controlled to operate based on the optimal active current reference value and reactive current reference value. The torque-to-current ratio is calculated based on the torque command value received by the permanent magnet motor from the main controller of the fan and the output current value of the permanent magnet motor. Based on the aforementioned initial reference values ​​for active and reactive current, the steps for searching for the optimal reference values ​​for active and reactive current in the current control cycle, with the objective of maximizing the torque-to-current ratio within the current control cycle, include: Within the current control cycle, the optimal active current reference value and reactive current reference value are searched online using the hill-climbing method, or... Within the current control cycle, the optimal active current reference value and reactive current reference value are searched offline using a lookup table method. The lookup table that supports offline search is obtained through a pre-executed online search.

2. The control method according to claim 1, characterized in that, The steps for determining the initial reference values ​​of the active current and reactive current of the permanent magnet motor in the current control cycle include: Obtain the motor parameters of the permanent magnet motor and the control parameters sent to the permanent magnet motor by the main controller of the fan in the current control cycle; Based on the motor parameters and the control parameters, the initial reference values ​​for active current and reactive current are calculated.

3. The control method according to claim 2, characterized in that, The motor parameters include: motor flux linkage, d-axis inductance, and q-axis inductance; the control parameters include drive current. The steps for calculating the initial reference values ​​of active current and reactive current based on the motor parameters and the control parameters include: The initial reference value of the reactive current is calculated based on the motor flux linkage, d-axis inductance, q-axis inductance, and drive current. The initial reference value of the active current is calculated based on the driving current and the initial reference value of the reactive current.

4. The control method according to claim 2, characterized in that, The motor parameters include: motor flux linkage, d-axis inductance, and q-axis inductance; the control parameters include drive current. The steps for calculating the initial reference values ​​of active current and reactive current based on the motor parameters and control parameters of the permanent magnet motor include: Based on the motor flux linkage, d-axis inductance, q-axis inductance, and drive current, the current vector angle of the permanent magnet motor is calculated using inverse cosine operation; The initial reference values ​​for active current and reactive current are calculated based on the driving current and the current vector angle.

5. The control method according to claim 1, characterized in that, The lookup table includes optimal active current reference values ​​and reactive current reference values ​​corresponding to different torques, speeds and / or power.

6. The control method according to claim 1, characterized in that, The steps of using the hill-climbing method to search online for the optimal active current reference value and reactive current reference value include: Within the current control cycle, the initial reference value of the active current is kept unchanged and used as the optimal reference value of the active current. Based on the initial reactive current reference value, the reactive current reference value corresponding to the largest torque-current ratio in the current control cycle is searched by accumulating or subtracting the reactive current reference value change by a preset step size, and this value is taken as the optimal reactive current reference value.

7. The control method according to claim 6, characterized in that, Using the initial reactive current reference value as a reference, the step of searching for the reactive current reference value corresponding to the largest torque-current ratio within the current control cycle by accumulating or subtracting the reactive current reference value changes by a preset step size includes: The initial reactive current reference value is added to the reactive current reference value change by a preset step size to obtain the first reactive current reference value. After the output current of the permanent magnet motor stabilizes, determine whether the torque-current ratio corresponding to the first reactive current reference value increases. In response to the fact that the torque-current ratio corresponding to the first reactive current reference value has not increased, the initial reactive current reference value is subtracted from the reactive current reference value change by a preset step size to obtain the second reactive current reference value. After the output current of the permanent magnet motor stabilizes, determine whether the torque-current ratio corresponding to the second reactive current reference value increases. In response to the fact that the torque-current ratio corresponding to the second reactive current reference value does not increase, the initial reactive current reference value is determined as the optimal reactive current reference value.

8. The control method according to claim 7, characterized in that, The step of searching for the reactive current reference value corresponding to the largest torque-current ratio within the current control cycle, based on the initial reactive current reference value and by accumulating or subtracting the reactive current reference value changes by a preset step size, further includes: In response to the increase in the torque-current ratio corresponding to the first reactive current reference value, the first reactive current reference value is added to the reactive current reference value change of a preset step size, and the first reactive current reference value is updated with the result of the addition. After the output current of the permanent magnet motor stabilizes, determine whether the torque-current ratio corresponding to the updated first reactive current reference value has increased. Since the torque-current ratio corresponding to the updated first reactive current reference value has not increased, the updated first reactive current reference value is determined as the optimal reactive current reference value. In response to the increase in the torque-current ratio corresponding to the updated first reactive current reference value, the updated first reactive current reference value is added to the change in the reactive current reference value by a preset step size, and the result of the addition is used to update the first reactive current reference value. Then, the process returns to the step of determining whether the updated torque-current ratio corresponding to the first reactive current reference value has increased.

9. The control method according to claim 7, characterized in that, The step of searching for the reactive current reference value corresponding to the largest torque-current ratio within the current control cycle, based on the initial reactive current reference value and by accumulating or subtracting the reactive current reference value changes by a preset step size, further includes: In response to the increase in the torque-current ratio corresponding to the second reactive current reference value, the second reactive current reference value is subtracted from the reactive current reference value change ΔI of the preset step size, and the result of the subtraction is used to update the second reactive current reference value. After the output current of the permanent magnet motor stabilizes, determine whether the torque-current ratio corresponding to the updated second reactive current reference value has increased. Since the torque-current ratio corresponding to the updated second reactive current reference value has not increased, the updated second reactive current reference value is determined as the optimal reactive current reference value. In response to the increase in the torque-current ratio corresponding to the updated second reactive current reference value, the updated second reactive current reference value is subtracted from the change in the reactive current reference value by a preset step size, and the result of the subtraction is used to update the second reactive current reference value. Then, the process returns to the step of determining whether the updated torque-current ratio corresponding to the second reactive current reference value has increased.

10. The control method according to claim 1, characterized in that, Based on the aforementioned initial reference values ​​for active and reactive current, the step of searching for the optimal reference values ​​for active and reactive current in the current control cycle, with the objective of maximizing the torque-to-current ratio within the current control cycle, further includes: The determined initial reference values ​​for active current and reactive current are compared with the optimal reference values ​​for active current and reactive current found in the previous control cycle, respectively. In response to the consistent comparison results, the optimal active current reference value and reactive current reference value searched in the previous control cycle are used as the optimal active current reference value and reactive current reference value in the current control cycle. In response to inconsistencies in the comparison results, within the current control cycle, based on the determined initial reference values ​​for active current and reactive current, the optimal reference values ​​for active current and reactive current within the current control cycle are searched.

11. A control device for a permanent magnet motor, characterized in that, The control device includes: The initial value determination unit is configured to: determine the initial reference values ​​of the active current and reactive current of the permanent magnet motor in the current control cycle, wherein the initial reference values ​​of the active current and reactive current are calculated by an optimal torque-current ratio algorithm; The search unit is configured to: based on the initial reference values ​​of active current and reactive current, and with the goal of maximizing the torque-current ratio within the current control cycle, search for the optimal reference values ​​of active current and reactive current within the current control cycle. The control unit is configured to control the operation of the permanent magnet motor based on the optimal active current reference value and reactive current reference value; The torque-to-current ratio is calculated based on the torque command value received by the permanent magnet motor from the main controller of the fan and the output current value of the permanent magnet motor. The search unit is also configured to: Within the current control cycle, the optimal active current reference value and reactive current reference value are searched online using the hill-climbing method, or... Within the current control cycle, the optimal active current reference value and reactive current reference value are searched offline using a lookup table method. The lookup table that supports offline search is obtained through a pre-executed online search.

12. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the control method for the permanent magnet motor as described in any one of claims 1 to 10.

13. An electronic device, characterized in that, include: At least one processor; At least one memory that stores computer-executable instructions. The computer-executable instructions, when executed by the at least one processor, cause the at least one processor to perform the control method for the permanent magnet motor as described in any one of claims 1 to 10.

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