Winding connection selection method and device for reducing short-circuit demagnetization risk of permanent magnet motor

Abstract

The invention relates to the technical field of permanent magnet motors, in particular to a winding connection selection method and device for reducing the short-circuit demagnetization risk of a permanent magnet motor, and the method comprises the steps: when the permanent magnet motor is in a three-phase short-circuit state, taking the relation between the torque loss ratio of star connection and delta connection at different permanent magnet temperatures and different starting rotor positions as the basis; finding a target permanent magnet temperature threshold value; if the permanent magnet temperature is higher than a target permanent magnet temperature threshold value, triangular connection is selected, and otherwise, star connection is selected; when the permanent magnet motor is in a two-phase short-circuit state, a first intersection rotor position and a second intersection rotor position at the current permanent magnet temperature are found on the basis of the relation between the torque loss ratio of star connection and triangular connection at the current permanent magnet temperature and different starting rotor positions, and then the two-phase short-circuit state of the permanent magnet motor is determined according to the intersection rotor positions. And a proper winding connection mode is selected. The operation reliability of the permanent magnet motor can be improved, and it is ensured that the short-circuit demagnetization risk of the permanent magnet motor is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of permanent magnet motors, and in particular to a winding connection selection method and device for reducing the risk of short-circuit demagnetization of a permanent magnet motor. Background Art

[0002] Permanent magnet motors play an important role in industrial applications due to their high torque density, efficiency and simple structure. However, the risk of irreversible demagnetization of permanent magnet materials cannot be ignored. Irreversible demagnetization will cause the average torque of the motor to decrease and aggravate the torque pulsation, which is unacceptable in high-cost applications such as large offshore wind turbines. Usually, demagnetization is caused by transient large peak currents generated by short-circuit faults, including two common types: three-phase short circuit and two-phase short circuit. Therefore, it is very important to study how to reduce the demagnetization risk caused by short-circuit faults to reduce the maintenance cost of permanent magnet motors and improve their reliability.

[0003] The choice of winding connection for permanent magnet motors is crucial and can change the magnitude of the short-circuit peak current. It usually includes two types of connections: star connection and delta connection. Existing technical solutions generally choose delta connection because star connection will produce a larger magnetomotive force and thus lead to more serious demagnetization, but this conclusion is drawn when the motor is in normal operation and does not take short-circuit faults into consideration. The peak current of the motor is small under normal operation. At this time, the demagnetization risk reduced by choosing a delta connection is tiny compared to a star connection. When a short-circuit fault occurs, the demagnetization risk of a delta connection and a star connection cannot be determined. If only a delta connection is chosen, the motor may be exposed to a demagnetization risk far higher than that of a star connection. Summary of the invention

[0004] To this end, the technical problem to be solved by the present invention is to overcome the problem that the prior art only considers the permanent magnet motor to select the winding triangle connection method under normal working conditions, does not consider the short-circuit fault, cannot effectively reduce the demagnetization risk, and cannot determine which winding connection should be selected to reduce the demagnetization risk when a short-circuit fault occurs in actual application.

[0005] In order to solve the above technical problems, the present invention provides a winding connection selection method for reducing the risk of short-circuit demagnetization of a permanent magnet motor, comprising:

[0006] Establish a finite element model of a permanent magnet motor;

[0007] Modify the finite element model circuit setting of the permanent magnet motor so that the permanent magnet motor is in a three-phase short-circuit state, and adjust the permanent magnet temperature so that when the permanent magnet is at different temperatures, respectively calculate the torque loss ratio of the permanent magnet motor winding star connection and the triangle connection at each starting rotor position corresponding to the first starting rotor position interval, and then find the target permanent magnet temperature threshold; when the permanent magnet temperature is less than or equal to the target permanent magnet temperature threshold, at each starting rotor position corresponding to the first starting rotor range, the torque loss ratio of the permanent magnet motor winding star connection is lower than the torque loss ratio of the triangle connection; when the permanent magnet temperature is greater than the target permanent magnet temperature threshold, at each starting rotor position corresponding to the first starting rotor range, the torque loss ratio of the permanent magnet motor winding star connection is higher than the torque loss ratio of the triangle connection;

[0008] When the permanent magnet motor is in a three-phase short-circuit state, if the permanent magnet temperature is greater than the target permanent magnet temperature threshold, the permanent magnet motor winding connection selects a delta connection mode; if the permanent magnet temperature is less than or equal to the target permanent magnet temperature threshold, the permanent magnet motor winding connection selects a star connection mode;

[0009] The circuit setting of the finite element model of the permanent magnet motor is modified to put the permanent magnet motor in a two-phase short-circuit state. At the current permanent magnet temperature, the torque loss ratios of the permanent magnet motor windings in star connection and triangle connection at each starting rotor position corresponding to the second starting rotor position interval are calculated respectively, and then the first intersection rotor position at the current permanent magnet temperature is found; when the starting rotor position is less than or equal to the first intersection rotor position, the torque loss ratio of the permanent magnet motor windings in star connection is lower than the torque loss ratio of the triangle connection; when the starting rotor position is greater than the first intersection rotor position, the torque loss ratio of the permanent magnet motor windings in star connection is higher than the torque loss ratio of the triangle connection;

[0010] At the current permanent magnet temperature, after respectively calculating the torque loss ratios of the permanent magnet motor winding star connection and the triangle connection at each starting rotor position corresponding to the third starting rotor position interval, the second intersection rotor position at the current permanent magnet temperature is found; when the starting rotor position is less than or equal to the second intersection rotor position, the torque loss ratio of the permanent magnet motor winding star connection is higher than the torque loss ratio of the triangle connection; when the starting rotor position is greater than the second intersection rotor position, the torque loss ratio of the permanent magnet motor winding star connection is lower than the torque loss ratio of the triangle connection;

[0011] By adjusting the permanent magnet temperature, the The first intersection rotor position under and the second intersection rotor position ;

[0012] When the permanent magnet motor is in a two-phase short-circuit state, the permanent magnet temperature In this case, when the starting rotor position is within one cycle, if the starting rotor position is less than or equal to or greater than , the permanent magnet motor winding connection selects the star connection mode; if the starting rotor position is greater than and less than or equal to , then the permanent magnet motor winding connection selects the triangle connection method, where, An interval represents a period; is an integer.

[0013] Preferably, the first starting rotor position interval is [0, 60°]; the second starting rotor position interval is [30°, 60°]; and the third starting rotor position interval is [120°, 150°].

[0014] Preferably, the step of adjusting the permanent magnet temperature so that when the permanent magnet is at different temperatures, respectively calculating the torque loss ratios of the permanent magnet motor windings at respective starting rotor positions corresponding to the star connection and the delta connection within the first starting rotor position interval, and then finding the target permanent magnet temperature threshold comprises:

[0015] Setting an initial temperature of the permanent magnet temperature, based on the first starting rotor position interval, and obtaining corresponding starting rotor positions within the first starting rotor position interval according to a first preset interval;

[0016] When the permanent magnet temperature is the initial temperature, the torque loss ratios of the permanent magnet motor windings at the corresponding starting rotor positions in the first starting rotor position interval under star connection and triangle connection are calculated respectively;

[0017] Determine the relationship between the torque loss ratio of the star connection of the permanent magnet motor winding and the torque loss ratio of the delta connection at each starting rotor position corresponding to the first starting rotor position interval when the permanent magnet temperature is the initial temperature;

[0018] If when the permanent magnet temperature is the initial temperature, at each starting rotor position corresponding to the first starting rotor position interval, the torque loss ratio of the permanent magnet motor winding star connection is lower than the torque loss ratio of the triangle connection, then the permanent magnet temperature is increased, and the torque loss ratio of the permanent magnet motor winding star connection and triangle connection at each starting rotor position corresponding to the first starting rotor position interval is recalculated, and the relationship between the torque loss ratio of the permanent magnet motor winding star connection and the torque loss ratio of the triangle connection is determined at this time, until when the permanent magnet temperature is When the torque loss ratio of the permanent magnet motor winding in star connection is higher than that of the triangle connection at each starting rotor position corresponding to the first starting rotor position interval, and when the permanent magnet temperature is When the torque loss ratio of the star connection of the permanent magnet motor winding is lower than the torque loss ratio of the triangle connection at each starting rotor position corresponding to the first starting rotor position interval, the permanent magnet temperature is stopped from being increased, and the As the target permanent magnet temperature threshold; where, for An integer multiple of ; Indicates the temperature change value.

[0019] Preferably, if when the permanent magnet temperature is the initial temperature, at each corresponding starting rotor position in the first starting rotor position interval, the torque loss ratio of the permanent magnet motor winding in star connection is higher than the torque loss ratio of the triangle connection, then the permanent magnet temperature is reduced, and the torque loss ratio of the permanent magnet motor winding in star connection and triangle connection at each corresponding starting rotor position in the first starting rotor position interval is recalculated, and the relationship between the torque loss ratio of the permanent magnet motor winding in star connection and the torque loss ratio of the triangle connection is determined at this time, until the permanent magnet temperature is When the torque loss ratio of the permanent magnet motor winding star connection is lower than that of the triangle connection at each starting rotor position corresponding to the first starting rotor position interval, and when the permanent magnet temperature is When the torque loss ratio of the star connection of the permanent magnet motor winding is higher than the torque loss ratio of the triangle connection at each starting rotor position corresponding to the first starting rotor position interval, the permanent magnet temperature reduction is terminated and the As the target permanent magnet temperature threshold; where, for An integer multiple of ; Indicates the temperature change value.

[0020] Preferably, the first preset interval does not exceed 10°.

[0021] Preferably, after respectively calculating the torque loss ratios of the permanent magnet motor windings at respective starting rotor positions corresponding to the star connection and the delta connection in the second starting rotor position interval at the current permanent magnet temperature, finding the first intersection rotor position at the current permanent magnet temperature comprises:

[0022] Set the initial temperature of the permanent magnet to , based on the second starting rotor position interval, obtaining each starting rotor position corresponding to the second starting rotor position interval according to the second preset interval;

[0023] When the current permanent magnet temperature is the initial temperature , respectively calculating the torque loss ratios of the permanent magnet motor windings in star connection and delta connection at each starting rotor position corresponding to the second starting rotor position interval;

[0024] If the starting rotor position is When the starting rotor position is When , the torque loss ratio of the permanent magnet motor winding in star connection is higher than that in delta connection;

[0025] Based on and The starting rotor position is obtained by calculating the first intersection rotor position at the current permanent magnet temperature, and its expression is:

[0026] ;

[0027] in, Indicates that the current permanent magnet temperature is the initial temperature The first intersection rotor position under ; for multiples of Belongs to the second starting rotor position interval; Indicates the second preset interval.

[0028] Preferably, after respectively calculating the torque loss ratios of the permanent magnet motor windings at respective starting rotor positions corresponding to the star connection and the delta connection within the third starting rotor position interval at the current permanent magnet temperature, finding the second intersection rotor position at the current permanent magnet temperature comprises:

[0029] Set the initial temperature of the permanent magnet to , based on the third starting rotor position interval, obtaining each starting rotor position corresponding to the third starting rotor position interval according to the second preset interval;

[0030] When the current permanent magnet temperature is the initial temperature , respectively calculating the torque loss ratios of the permanent magnet motor windings at various starting rotor positions corresponding to the star connection and the delta connection in the third starting rotor position interval;

[0031] If the starting rotor position is When the starting rotor position is When , the torque loss ratio of the permanent magnet motor winding in star connection is lower than that in delta connection;

[0032] Based on and The starting rotor position is obtained by calculating the second intersection rotor position at the current permanent magnet temperature, and its expression is:

[0033] ;

[0034] in, Indicates that the current permanent magnet temperature is the initial temperature The second intersection rotor position below; for multiples of Belongs to the third starting rotor position interval; Indicates the second preset interval.

[0035] Preferably, the temperature of the permanent magnet is adjusted by introducing the BH curve of the permanent magnet at different temperatures.

[0036] Preferably, the expression of torque loss ratio is:

[0037] ;

[0038] in, Indicates the torque loss ratio; It indicates the average torque output by the permanent magnet motor during normal operation before demagnetization occurs; It indicates the average torque output by a permanent magnet motor when it runs for one electrical cycle under a short circuit fault and recovers to a normal working state after demagnetization occurs.

[0039] The present invention also provides a winding connection selection device for reducing the risk of short-circuit demagnetization of a permanent magnet motor, comprising:

[0040] Memory for storing computer programs;

[0041] A processor is used to implement the steps of the above-mentioned method for selecting a winding connection to reduce the risk of short-circuit demagnetization of a permanent magnet motor when executing the computer program.

[0042] The above technical solution of the present invention has the following beneficial effects compared with the prior art:

[0043] The present invention discloses a winding connection selection method for reducing the risk of short-circuit demagnetization of a permanent magnet motor. The method modifies the finite element model circuit setting of the permanent magnet motor so that the permanent magnet motor is under different short-circuit conditions. According to different short-circuit conditions, the torque loss ratio of the star connection and the triangle connection at different permanent magnet temperatures and starting rotor positions is calculated and analyzed. Under the three-phase short-circuit condition, the target permanent magnet temperature threshold is found. Under the two-phase short-circuit condition, the first intersection rotor position and the second intersection rotor position at different permanent magnet temperatures are found, thereby providing a basis for selecting a suitable winding connection method during three-phase short-circuit and two-phase short-circuit, and being able to quickly and correctly select the winding connection method of the permanent magnet motor under three-phase short-circuit and two-phase short-circuit. At the same time, it is able to comprehensively consider multiple factors, determine the winding connection more scientifically, improve the reliability of motor operation, and ensure that the risk of short-circuit demagnetization of the permanent magnet motor is effectively reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0045] Figure 1 It is the current waveform diagram of the star connection and triangle connection of the winding when the permanent magnet motor is working normally;

[0046] Figure 2 It is the demagnetization ratio distribution diagram of the star-connected winding when the permanent magnet motor is working normally;

[0047] Figure 3 It is the demagnetization ratio distribution diagram of the winding triangle connection when the permanent magnet motor is working normally;

[0048] Figure 4 It is the equivalent circuit diagram of the three-phase short-circuited permanent magnet motor winding connected in star shape;

[0049] Figure 5 It is the equivalent circuit diagram of the three-phase short-circuited permanent magnet motor winding connected in a triangle;

[0050] Figure 6 It is the equivalent circuit diagram of the two-phase short-circuited permanent magnet motor winding connected in star shape;

[0051] Figure 7 It is the equivalent circuit diagram of the two-phase short-circuited permanent magnet motor winding connected in a triangle;

[0052] Figure 8 It is a flow chart of a winding connection selection method for reducing the risk of short-circuit demagnetization of a permanent magnet motor provided by the present invention;

[0053] Fig. 9 It is the finite element model of permanent magnet motor;

[0054] Fig.10 It is the three-phase short-circuit torque loss ratio diagram of permanent magnet motor winding star connection and delta connection at permanent magnet temperature of 80℃;

[0055] Fig.11 It is the three-phase short-circuit torque loss ratio diagram of permanent magnet motor winding star connection and delta connection at permanent magnet temperature of 90℃;

[0056] Fig.12 It is the three-phase short-circuit torque loss ratio diagram of permanent magnet motor winding star connection and triangle connection at permanent magnet temperature of 100℃;

[0057] Fig.13 It is the three-phase short-circuit torque loss ratio diagram of permanent magnet motor winding star connection and delta connection at permanent magnet temperature of 110℃;

[0058] Fig.14It is the two-phase short-circuit torque loss ratio diagram between the star connection and the delta connection of the permanent magnet motor winding at the starting rotor position [30°, 60°];

[0059] Fig.15 It is the two-phase short-circuit torque loss ratio diagram between the star connection and the delta connection of the permanent magnet motor winding at the starting rotor position [120°, 150°]. DETAILED DESCRIPTION

[0060] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0061] The prior art believes that under the same conditions, the star connection of the winding will lead to more serious demagnetization than the delta connection. Figure 1 As shown in FIG. 1 , when a 10-pole / 12-slot permanent magnet motor is operating normally, the peak current of the star connection is 4A, which is greater than the peak current of the triangle connection of 3.1A. Figure 2 and Figure 3 The demagnetization ratio distribution diagram of the permanent magnet motor after running one electrical cycle is given, where the demagnetization ratio is defined as the ratio of the residual magnetism loss value to the initial residual magnetism value. It can be seen from the figure that the demagnetization ratio of the star connection is higher than that of the triangle connection only at the edge of the permanent magnet, and the difference is less than 0.5%.

[0062] This technical solution is determined when the permanent magnet motor is operating normally, and short-circuit faults are not considered. In this case, the difference in demagnetization caused by star connection and delta connection is very small, and even if a delta connection is selected, demagnetization cannot be effectively reduced. In practical applications, short-circuit faults are generally considered to be the main cause of demagnetization, because short circuits can generate peak currents that are 3-4 times the rated current. The demagnetization generated at this time is much more serious than during normal operation. Therefore, the choice of winding connection method is crucial and determines whether the risk of demagnetization can be effectively reduced. Common short-circuit faults include three-phase short circuits and two-phase short circuits. The equivalent circuit diagrams under different winding connections are shown below. Figure 4 , Figure 5 , Figure 6 and Figure 7 shown.

[0063] In summary, the prior art is based on the conclusion drawn under normal working conditions, and believes that the use of delta connection can reduce the risk of demagnetization compared with star connection, but the effect is very limited. The difference in demagnetization rate caused by delta connection and star connection basically does not exceed 0.5%; and the prior art does not take short-circuit faults into consideration. In practical applications, short-circuit faults are the main cause of demagnetization, and the demagnetization caused by short-circuit faults is far more serious than that in normal operation. The single selection method of the prior art, that is, selecting delta connection, is likely to put the permanent magnet under a higher risk of demagnetization.

[0064] Therefore, in order to solve the problem that when a short circuit fault occurs in a permanent magnet motor in actual application, it is impossible to determine which winding connection should be selected to reduce the risk of demagnetization, that is, when a short circuit fault occurs, it is impossible to determine whether the star connection or the triangle connection will cause more serious demagnetization. A winding connection selection method for reducing the risk of short circuit demagnetization of a permanent magnet motor is provided.

[0065] Reference Figure 8 As shown, Figure 8 A flow chart of a winding connection selection method for reducing the risk of short-circuit demagnetization of a permanent magnet motor provided by the present invention; specifically comprising:

[0066] S1: Establish the finite element model of permanent magnet motor;

[0067] S2: Modify the circuit settings of the finite element model of the permanent magnet motor to put the permanent magnet motor in a three-phase short-circuit state and select the permanent magnet motor winding connection method, including:

[0068] S21: by adjusting the permanent magnet temperature so that when the permanent magnet is at different temperatures, respectively calculating the torque loss ratios of the permanent magnet motor windings at various starting rotor positions corresponding to the star connection and the delta connection within the first starting rotor position interval, finding the target permanent magnet temperature threshold, including:

[0069] The initial temperature of the permanent magnet temperature is set, and based on the first starting rotor position interval, each corresponding starting rotor position in the first starting rotor position interval is obtained according to the first preset interval; wherein, the permanent magnet temperature is adjusted by importing the BH curve of the permanent magnet at different temperatures; the first starting rotor position interval is [0,60°]; the first preset interval does not exceed 10°; in a specific embodiment of the present invention, when searching for the target permanent magnet temperature threshold, the initial temperature of the permanent magnet temperature is set to 80°C, and the interval is selected to be 10°, that is, at different permanent magnet temperatures, the torque loss ratio of the permanent magnet winding star connection and the triangle connection is calculated once every 10°;

[0070] When the permanent magnet temperature is the initial temperature, the torque loss ratios of the permanent magnet motor windings at the corresponding starting rotor positions in the first starting rotor position interval under star connection and triangle connection are calculated respectively; wherein the expression of the torque loss ratio is:

[0071] ;

[0072] in, Indicates the torque loss ratio; It indicates the average torque output by the permanent magnet motor during normal operation before demagnetization occurs; It indicates the average torque output by the permanent magnet motor when it runs for one electrical cycle under a short circuit fault and recovers to the normal working state after demagnetization occurs;

[0073] Determine the relationship between the torque loss ratio of the star connection of the permanent magnet motor winding and the torque loss ratio of the delta connection at each starting rotor position corresponding to the first starting rotor position interval when the permanent magnet temperature is the initial temperature;

[0074] If when the permanent magnet temperature is the initial temperature, at each starting rotor position corresponding to the first starting rotor position interval, the torque loss ratio of the permanent magnet motor winding star connection is lower than the torque loss ratio of the triangle connection, then the permanent magnet temperature is increased, and the torque loss ratio of the permanent magnet motor winding star connection and triangle connection at each starting rotor position corresponding to the first starting rotor position interval is recalculated, and the relationship between the torque loss ratio of the permanent magnet motor winding star connection and the torque loss ratio of the triangle connection is determined at this time, until when the permanent magnet temperature is When the torque loss ratio of the permanent magnet motor winding in star connection is higher than that of the triangle connection at each starting rotor position corresponding to the first starting rotor position interval, and when the permanent magnet temperature is When the torque loss ratio of the star connection of the permanent magnet motor winding is lower than the torque loss ratio of the triangle connection at each starting rotor position corresponding to the first starting rotor position interval, the permanent magnet temperature is stopped from being increased, and the As the target permanent magnet temperature threshold; where, for An integer multiple of ; Indicates the temperature change value;

[0075] If, when the permanent magnet temperature is the initial temperature, at each corresponding starting rotor position in the first starting rotor position interval, the torque loss ratio of the permanent magnet motor winding in star connection is higher than the torque loss ratio of the triangle connection, then the permanent magnet temperature is reduced, and the torque loss ratio of the permanent magnet motor winding in star connection and triangle connection at each corresponding starting rotor position in the first starting rotor position interval is recalculated, and the relationship between the torque loss ratio of the permanent magnet motor winding in star connection and the torque loss ratio of the triangle connection is determined at this time, until the permanent magnet temperature is When the torque loss ratio of the permanent magnet motor winding star connection is lower than that of the triangle connection at each starting rotor position corresponding to the first starting rotor position interval, and when the permanent magnet temperature is When the torque loss ratio of the star connection of the permanent magnet motor winding is higher than the torque loss ratio of the triangle connection at each starting rotor position corresponding to the first starting rotor position interval, the permanent magnet temperature reduction is terminated and the As the target permanent magnet temperature threshold; where, for An integer multiple of ; represents the temperature change value; in a specific embodiment of the present invention, , that is, increase the permanent magnet temperature by 10°C or reduce the permanent magnet temperature by 10°C;

[0076] At this time, the target permanent magnet temperature threshold is found , satisfying the following conditions: when the permanent magnet temperature is less than or equal to the target permanent magnet temperature threshold, at each corresponding starting rotor position within the first starting rotor range, the torque loss ratio of the permanent magnet motor winding in star connection is lower than the torque loss ratio of the triangle connection; when the permanent magnet temperature is greater than the target permanent magnet temperature threshold, at each corresponding starting rotor position within the first starting rotor range, the torque loss ratio of the permanent magnet motor winding in star connection is higher than the torque loss ratio of the triangle connection; wherein, the star connection and triangle connection of the permanent magnet motor winding are realized by modifying the circuit setting of the finite element model of the permanent magnet motor;

[0077] S22: When the permanent magnet motor is in a three-phase short-circuit state, if the permanent magnet temperature is greater than the target permanent magnet temperature threshold, the permanent magnet motor winding connection selects a delta connection mode; if the permanent magnet temperature is less than or equal to the target permanent magnet temperature threshold, the permanent magnet motor winding connection selects a star connection mode;

[0078] S3: Modify the circuit settings of the finite element model of the permanent magnet motor to put the permanent magnet motor in a two-phase short-circuit state, and select the permanent magnet motor winding connection method, including:

[0079] S31: at the current permanent magnet temperature, respectively calculating the torque loss ratios of the permanent magnet motor windings at the respective starting rotor positions corresponding to the star connection and the delta connection in the second starting rotor position interval, and finding the first intersection rotor position at the current permanent magnet temperature, including:

[0080] Set the initial temperature of the permanent magnet to , based on the second starting rotor position interval, obtaining each starting rotor position corresponding to the second starting rotor position interval according to the second preset interval; wherein the second starting rotor position interval is [30°, 60°];

[0081] When the current permanent magnet temperature is the initial temperature , respectively calculating the torque loss ratios of the permanent magnet motor windings in star connection and delta connection at each starting rotor position corresponding to the second starting rotor position interval;

[0082] If the starting rotor position is When the starting rotor position is When , the torque loss ratio of the permanent magnet motor winding in star connection is higher than that in delta connection;

[0083] Based on and The starting rotor position is obtained by calculating the first intersection rotor position at the current permanent magnet temperature, and its expression is:

[0084] ;

[0085] in, Indicates that the current permanent magnet temperature is the initial temperature The first intersection rotor position under ; for multiples of Belongs to the second starting rotor position interval; represents a second preset interval;

[0086] At this time, the first intersection rotor position under the current permanent magnet temperature found satisfies the following conditions: when the starting rotor position is less than or equal to the first intersection rotor position, the torque loss ratio of the permanent magnet motor winding in star connection is lower than the torque loss ratio of the triangle connection; when the starting rotor position is greater than the first intersection rotor position, the torque loss ratio of the permanent magnet motor winding in star connection is higher than the torque loss ratio of the triangle connection;

[0087] S32: at the current permanent magnet temperature, respectively calculating the torque loss ratios of the permanent magnet motor windings at the respective starting rotor positions corresponding to the star connection and the delta connection within the third starting rotor position interval, and finding the second intersection rotor position at the current permanent magnet temperature, including:

[0088] Set the initial temperature of the permanent magnet to , based on the third starting rotor position interval, and according to the second preset interval, obtaining each starting rotor position corresponding to the third starting rotor position interval; wherein the third starting rotor position interval is [120°, 150°];

[0089] When the current permanent magnet temperature is the initial temperature , respectively calculating the torque loss ratios of the permanent magnet motor windings at various starting rotor positions corresponding to the star connection and the delta connection in the third starting rotor position interval;

[0090] If the starting rotor position is When the starting rotor position is When , the torque loss ratio of the permanent magnet motor winding in star connection is lower than that in delta connection;

[0091] Based on and The starting rotor position is obtained by calculating the second intersection rotor position at the current permanent magnet temperature, and its expression is:

[0092] ;

[0093] in, Indicates that the current permanent magnet temperature is the initial temperature The second intersection rotor position below; for multiples of Belongs to the third starting rotor position interval; represents a second preset interval;

[0094] At this time, the second intersection rotor position at the current permanent magnet temperature found satisfies the following conditions: when the starting rotor position is less than or equal to the second intersection rotor position, the torque loss ratio of the permanent magnet motor winding in star connection is higher than the torque loss ratio of the triangle connection; when the starting rotor position is greater than the second intersection rotor position, the torque loss ratio of the permanent magnet motor winding in star connection is lower than the torque loss ratio of the triangle connection;

[0095] S33: By adjusting the permanent magnet temperature, the The first intersection rotor position under and the second intersection rotor position ; Wherein, in a specific embodiment of the present invention, when searching for the first intersection rotor position and the second intersection rotor position, the initial temperature of the permanent magnet temperature is set to 90°C, that is, ; Select the second preset interval as 5°, that is , then at different permanent magnet temperatures, the torque loss ratio of the permanent magnet winding star connection and triangle connection is calculated every 5°; at this time, and All are multiples of 5;

[0096] S34: When the permanent magnet motor is in a two-phase short-circuit state, the permanent magnet temperature Under this condition, when the starting rotor position is within one cycle, that is, Within the range, if the starting rotor position is less than or equal to or greater than , the permanent magnet motor winding connection selects the star connection mode; if the starting rotor position is greater than and less than or equal to , then the permanent magnet motor winding connection selects the triangle connection method, where, An interval represents a period; is an integer.

[0097] In summary, under the condition of three-phase short circuit, the present invention takes the magnitude relationship of the torque loss ratio of the star connection and the triangle connection at different permanent magnet temperatures and starting rotor positions as an important basis to find the temperature threshold; for three-phase short circuit, if the permanent magnet temperature is higher than the temperature threshold, the triangle connection is selected, otherwise the star connection is selected; under the condition of two-phase short circuit, the magnitude relationship of the torque loss ratio of the star connection and the triangle connection at different starting rotor positions is taken as an important basis to find the rotor position intersection; for two-phase short circuit, the winding connection selection method is closely related to the rotor position intersection; therefore, a winding connection selection method for reducing the risk of short-circuit demagnetization of a permanent magnet motor provided by the present invention can quickly and correctly select the winding connection mode of the permanent magnet motor under three-phase short circuit and two-phase short circuit, which is fast and is reflected in that the temperature calculation range and the starting rotor position calculation range are narrowed according to the torque loss ratio change characteristics of different winding connection modes of the permanent magnet motor at different permanent magnet temperatures and different starting rotor positions, unnecessary calculations are omitted, and calculation time is saved. The correctness is reflected in that the technical solution selects the winding connection mode based on the magnitude of the torque loss ratio, which can ensure that the demagnetization risk is effectively reduced.

[0098] Based on steps S1-S3, the present invention further provides a specific embodiment, including:

[0099] Step 1: Establish a finite element model of the permanent magnet motor. Fig. 9 As shown;

[0100] Step 2: When the permanent magnet motor is in a three-phase short-circuit state, select the permanent magnet motor winding connection method, including:

[0101] (1) Under three-phase short-circuit conditions, calculate the torque loss ratio of star connection and delta connection at different permanent magnet temperatures and starting rotor positions, and find the target permanent magnet temperature threshold, including:

[0102] First, the permanent magnet temperature is set to 80°C, and the torque loss ratio of the star connection and the triangle connection at different starting rotor positions is calculated, as shown in Fig.10 As shown in the figure, the torque loss ratio of the star connection is always lower than that of the triangle connection. Therefore, the permanent magnet temperature is increased by 10°C; the permanent magnet temperature is set to 90°C, and the torque loss ratio of the star connection and the triangle connection at different starting rotor positions is calculated, as shown in Fig.11 As shown in the figure, the torque loss ratio of the star connection is always lower than that of the triangle connection. Therefore, the permanent magnet temperature is continuously increased by 10°C until the following conditions are met: when the permanent magnet temperature is 100°C, the torque loss ratio of the star connection is always lower than that of the triangle connection, and when the permanent magnet temperature is 110°C, the torque loss ratio of the star connection is always higher than that of the triangle connection. The calculation is stopped and 100°C is determined as the temperature threshold. Fig.12 and Fig.13 As shown;

[0103] (2) If the permanent magnet motor is in a three-phase short-circuit state, when the permanent magnet temperature is higher than 100°C, select a delta connection, otherwise select a star connection;

[0104] Step 3: When the permanent magnet motor is in a two-phase short-circuit state, select the permanent magnet motor winding connection method, including:

[0105] (1) Under two-phase short-circuit conditions, calculate the torque loss ratio of star connection and delta connection at different permanent magnet temperatures and starting rotor positions, and find the first intersection rotor position and the second intersection rotor position, including:

[0106] Set the permanent magnet temperature to 90°C and calculate the torque loss ratio between star connection and delta connection at different starting rotor positions, such as Fig.14 and Fig.15 As shown; when the starting rotor position is between [30°, 60°], when the starting rotor position is 45°, the torque loss ratio of the star connection is less than that of the triangle connection, and when the starting rotor position is 50°, the torque loss ratio of the star connection is greater than that of the triangle connection, so the first intersection rotor position is 47.5°; when the starting rotor position is between [120°, 150°], when the starting rotor position is 145°, the torque loss ratio of the star connection is greater than that of the triangle connection, and when the starting rotor position is 150°, the torque loss ratio of the star connection is less than that of the triangle connection, so the second intersection rotor position is 147.5°;

[0107] (2) If the permanent magnet motor is in a two-phase short-circuit state, when the permanent magnet temperature is 90°C, when the starting rotor position is within one cycle, that is, Within the range, is an integer. When the starting rotor position is less than or equal to or greater than When the starting rotor position is greater than and less than or equal to Select triangle connection.

[0108] In a specific embodiment of the present invention, a winding connection selection device for reducing the risk of short-circuit demagnetization of a permanent magnet motor is also provided, comprising:

[0109] Memory for storing computer programs;

[0110] A processor is used to implement the steps of the above-mentioned method for selecting a winding connection to reduce the risk of short-circuit demagnetization of a permanent magnet motor when executing the computer program.

[0111] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0112] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0113] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0114] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0115] Obviously, the above embodiments are merely examples for the purpose of clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A winding connection selection method for reducing the risk of short-circuit demagnetization of a permanent magnet motor, characterized in that: include: Establish a finite element model of a permanent magnet motor; Modify the circuit setting of the finite element model of the permanent magnet motor so that the permanent magnet motor is in a three-phase short-circuit state. By adjusting the temperature of the permanent magnet so that the permanent magnet is at different temperatures, respectively calculate the torque loss ratio of the permanent magnet motor winding star connection and triangle connection at each starting rotor position corresponding to the first starting rotor position interval, and then find the target permanent magnet temperature threshold; When the permanent magnet temperature is less than or equal to the target permanent magnet temperature threshold, at each corresponding starting rotor position within the first starting rotor range, the torque loss ratio of the permanent magnet motor winding in star connection is lower than the torque loss ratio of the triangle connection; when the permanent magnet temperature is greater than the target permanent magnet temperature threshold, at each corresponding starting rotor position within the first starting rotor range, the torque loss ratio of the permanent magnet motor winding in star connection is higher than the torque loss ratio of the triangle connection; When the permanent magnet motor is in a three-phase short-circuit state, if the permanent magnet temperature is greater than the target permanent magnet temperature threshold, the permanent magnet motor winding connection selects a delta connection mode; if the permanent magnet temperature is less than or equal to the target permanent magnet temperature threshold, the permanent magnet motor winding connection selects a star connection mode; The circuit setting of the finite element model of the permanent magnet motor is modified to put the permanent magnet motor in a two-phase short-circuit state. At the current permanent magnet temperature, the torque loss ratios of the permanent magnet motor windings in star connection and triangle connection at each starting rotor position corresponding to the second starting rotor position interval are calculated respectively, and then the first intersection rotor position at the current permanent magnet temperature is found; when the starting rotor position is less than or equal to the first intersection rotor position, the torque loss ratio of the permanent magnet motor windings in star connection is lower than the torque loss ratio of the triangle connection; when the starting rotor position is greater than the first intersection rotor position, the torque loss ratio of the permanent magnet motor windings in star connection is higher than the torque loss ratio of the triangle connection; At the current permanent magnet temperature, after respectively calculating the torque loss ratios of the permanent magnet motor winding star connection and the triangle connection at each starting rotor position corresponding to the third starting rotor position interval, the second intersection rotor position at the current permanent magnet temperature is found; when the starting rotor position is less than or equal to the second intersection rotor position, the torque loss ratio of the permanent magnet motor winding star connection is higher than the torque loss ratio of the triangle connection; when the starting rotor position is greater than the second intersection rotor position, the torque loss ratio of the permanent magnet motor winding star connection is lower than the torque loss ratio of the triangle connection; By adjusting the permanent magnet temperature, the The first intersection rotor position under and the second intersection rotor position ; When the permanent magnet motor is in a two-phase short-circuit state, the permanent magnet temperature In this case, when the starting rotor position is within one cycle, if the starting rotor position is less than or equal to or greater than , the permanent magnet motor winding connection selects the star connection mode; if the starting rotor position is greater than and less than or equal to , then the permanent magnet motor winding connection selects the triangle connection method, where, An interval represents a period; is an integer.

2. A winding connection selection method for reducing the risk of short-circuit demagnetization of a permanent magnet motor according to claim 1, characterized in that: The first starting rotor position interval is [0, 60°]; the second starting rotor position interval is [30°, 60°]; and the third starting rotor position interval is [120°, 150°].

3. A winding connection selection method for reducing the risk of short-circuit demagnetization of a permanent magnet motor according to claim 1, characterized in that: The method of adjusting the permanent magnet temperature so that the permanent magnet is at different temperatures and respectively calculating the torque loss ratios of the permanent magnet motor windings at respective starting rotor positions corresponding to the star connection and the delta connection within the first starting rotor position interval, then finding the target permanent magnet temperature threshold comprises: Setting an initial temperature of the permanent magnet temperature, based on the first starting rotor position interval, and obtaining corresponding starting rotor positions within the first starting rotor position interval according to a first preset interval; When the permanent magnet temperature is the initial temperature, the torque loss ratios of the permanent magnet motor windings at the corresponding starting rotor positions in the first starting rotor position interval under star connection and triangle connection are calculated respectively; Determine the relationship between the torque loss ratio of the star connection of the permanent magnet motor winding and the torque loss ratio of the delta connection at each starting rotor position corresponding to the first starting rotor position interval when the permanent magnet temperature is the initial temperature; If when the permanent magnet temperature is the initial temperature, at each starting rotor position corresponding to the first starting rotor position interval, the torque loss ratio of the permanent magnet motor winding star connection is lower than the torque loss ratio of the triangle connection, then the permanent magnet temperature is increased, and the torque loss ratio of the permanent magnet motor winding star connection and triangle connection at each starting rotor position corresponding to the first starting rotor position interval is recalculated, and the relationship between the torque loss ratio of the permanent magnet motor winding star connection and the torque loss ratio of the triangle connection is determined at this time, until when the permanent magnet temperature is When the torque loss ratio of the permanent magnet motor winding in star connection is higher than that of the triangle connection at each starting rotor position corresponding to the first starting rotor position interval, and when the permanent magnet temperature is When the torque loss ratio of the star connection of the permanent magnet motor winding is lower than the torque loss ratio of the triangle connection at each starting rotor position corresponding to the first starting rotor position interval, the permanent magnet temperature is stopped from being increased, and the As the target permanent magnet temperature threshold; where, for An integer multiple of ; Indicates the temperature change value.

4. A winding connection selection method for reducing the risk of short-circuit demagnetization of a permanent magnet motor according to claim 3, characterized in that: If, when the permanent magnet temperature is the initial temperature, at each corresponding starting rotor position in the first starting rotor position interval, the torque loss ratio of the permanent magnet motor winding in star connection is higher than the torque loss ratio of the triangle connection, then the permanent magnet temperature is reduced, and the torque loss ratio of the permanent magnet motor winding in star connection and triangle connection at each corresponding starting rotor position in the first starting rotor position interval is recalculated, and the relationship between the torque loss ratio of the permanent magnet motor winding in star connection and the torque loss ratio of the triangle connection is determined at this time, until the permanent magnet temperature is When the torque loss ratio of the permanent magnet motor winding star connection is lower than that of the triangle connection at each starting rotor position corresponding to the first starting rotor position interval, and when the permanent magnet temperature is When the torque loss ratio of the star connection of the permanent magnet motor winding is higher than the torque loss ratio of the triangle connection at each starting rotor position corresponding to the first starting rotor position interval, the permanent magnet temperature reduction is terminated and the permanent magnet temperature is As the target permanent magnet temperature threshold; where, for An integer multiple of ; Indicates the temperature change value.

5. A winding connection selection method for reducing the risk of short-circuit demagnetization of a permanent magnet motor according to any one of claims 3-4, characterized in that: The first preset interval does not exceed 10°.

6. A winding connection selection method for reducing the risk of short-circuit demagnetization of a permanent magnet motor according to claim 1, characterized in that: After respectively calculating the torque loss ratios of the permanent magnet motor windings at the respective starting rotor positions corresponding to the star connection and the delta connection in the second starting rotor position interval at the current permanent magnet temperature, finding the first intersection rotor position at the current permanent magnet temperature comprises: Set the initial temperature of the permanent magnet to , based on the second starting rotor position interval, obtaining each starting rotor position corresponding to the second starting rotor position interval according to the second preset interval; When the current permanent magnet temperature is the initial temperature , respectively calculating the torque loss ratios of the permanent magnet motor windings in star connection and delta connection at each starting rotor position corresponding to the second starting rotor position interval; If the starting rotor position is When the starting rotor position is When , the torque loss ratio of the permanent magnet motor winding in star connection is higher than that in delta connection; Based on and The starting rotor position is obtained by calculating the first intersection rotor position at the current permanent magnet temperature, and its expression is: ； in, Indicates that the current permanent magnet temperature is the initial temperature The first intersection rotor position under ; for multiples of Belongs to the second starting rotor position interval; Indicates the second preset interval.

7. A winding connection selection method for reducing the risk of short-circuit demagnetization of a permanent magnet motor according to claim 1, characterized in that: After respectively calculating the torque loss ratios of the permanent magnet motor windings at the respective starting rotor positions corresponding to the star connection and the delta connection within the third starting rotor position interval at the current permanent magnet temperature, finding the second intersection rotor position at the current permanent magnet temperature comprises: Set the initial temperature of the permanent magnet to , based on the third starting rotor position interval, obtaining each starting rotor position corresponding to the third starting rotor position interval according to the second preset interval; When the current permanent magnet temperature is the initial temperature , respectively calculating the torque loss ratios of the permanent magnet motor windings at various starting rotor positions corresponding to the star connection and the delta connection in the third starting rotor position interval; If the starting rotor position is When the starting rotor position is When , the torque loss ratio of the permanent magnet motor winding in star connection is lower than that in delta connection; Based on and The starting rotor position is obtained by calculating the second intersection rotor position at the current permanent magnet temperature, and its expression is: ； in, Indicates that the current permanent magnet temperature is the initial temperature The second intersection rotor position below; for multiples of Belongs to the third starting rotor position interval; Indicates the second preset interval.

8. A winding connection selection method for reducing the risk of short-circuit demagnetization of a permanent magnet motor according to claim 1, characterized in that: The permanent magnet temperature can be adjusted by importing the BH curve of the permanent magnet at different temperatures.

9. A winding connection selection method for reducing the risk of short-circuit demagnetization of a permanent magnet motor according to claim 1, characterized in that: The expression of torque loss ratio is: ； in, Indicates the torque loss ratio; It indicates the average torque output by the permanent magnet motor during normal operation before demagnetization occurs; It indicates the average torque output by a permanent magnet motor when it runs for one electrical cycle under a short circuit fault and recovers to a normal working state after demagnetization occurs.

10. A winding connection selection device for reducing the risk of short-circuit demagnetization of a permanent magnet motor, characterized in that: include: Memory for storing computer programs; A processor, configured to implement the steps of a winding connection selection method for reducing the risk of short-circuit demagnetization of a permanent magnet motor as described in any one of claims 1 to 9 when executing the computer program.

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