Efficiency-optimal current search method for permanent magnet synchronous motors considering iron loss effect

Abstract

This invention discloses a method for searching the optimal current for a permanent magnet synchronous motor considering iron loss. The steps are as follows: 1. Construct a saturated flux linkage model and an iron loss model that can be scaled based on the speed in parallel. Calculate the torque matrix without considering iron loss based on the saturated flux linkage model. 2. Given a speed, calculate the iron loss matrix and the torque matrix lost due to iron loss under full current conditions at that speed based on the iron loss model, thus obtaining the torque matrix considering iron loss. 3. Search for the current and corresponding iron loss that satisfy the constraints under a given torque and calculate the copper loss, thereby obtaining the current operating point with the optimal efficiency. This invention, at a given speed, uses the calculated torque matrix considering iron loss to extract all current operating points and their coordinates that satisfy the given torque. It then eliminates current operating points that do not satisfy the current limit circle and voltage limit circle, calculates the copper loss of all remaining current operating points, and extracts the iron loss, obtaining the current operating point with the minimum loss, i.e., the optimal efficiency.

Description

Technical Field

[0001] This invention relates to the field of motor technology, and in particular to a method for searching the optimal current for permanent magnet synchronous motors considering iron loss effects. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) are synchronous motors that utilize permanent magnets to establish an excitation magnetic field. Their stator generates a rotating magnetic field, and the rotor is made of permanent magnet materials. Depending on the rotor structure, they can be classified as surface-mounted or internally mounted. Due to their advantages such as wide speed range, high starting torque, low noise, and low torque ripple, they are widely used in electric vehicles, rail transportation, aerospace, and wind power generation. Energy efficiency and power density, as crucial attributes of the motor, play a decisive role in its performance.

[0003] The core of various methods for finding the optimal current for permanent magnet synchronous motors (PMSMs) is to reduce motor losses by controlling the motor's flux linkage, thereby improving the motor's energy efficiency and power density. Traditional methods mostly establish a constant inductance model and, under the constraints of current and voltage limit circles, calculate and search for a smaller current that meets the required torque and speed to ensure low copper losses. However, these traditional methods have the following problems: 1. The performance of PMSMs is significantly affected by magnetic circuit saturation and space harmonics. Traditional constant inductance models cannot accurately and reasonably simulate the actual dynamic characteristics of the motor during operation. 2. Due to iron losses, the torque of a PMSM during actual operation is not equal to the torque calculated directly through the inductance or flux linkage model. Traditional methods fail to consider the impact of iron losses on torque. 3. Traditional methods only consider copper losses, not iron losses, thus not achieving true optimal efficiency. Furthermore, the search process involves iteratively cycling the current amplitude and phase angle, or the d-axis and q-axis currents, resulting in slow convergence and long search times. Summary of the Invention

[0004] In view of at least one deficiency of the prior art, the purpose of the present invention is to provide an efficiency-optimal current search method for permanent magnet synchronous motors that takes into account the iron loss effect, so as to solve the problems of traditional efficiency-optimal current search methods not considering the effects of saturation and cross-saturation on inductance and flux linkage, not considering the effect of iron loss on torque, slow search convergence speed, long search time, and only considering copper loss without considering iron loss, thus failing to achieve true efficiency optimization.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for searching the optimal efficiency current of a permanent magnet synchronous motor considering iron loss effect, the method comprising the following steps:

[0006] Step 1: Construct a saturated flux linkage model and an iron loss model that can be scaled based on rotational speed in parallel. Calculate the torque matrix without considering the iron loss effect based on the saturated flux linkage model.

[0007] Step 2: Given a rotational speed, calculate the iron loss matrix and the torque matrix due to iron loss under full current conditions at that rotational speed based on the iron loss model, thereby obtaining the torque matrix considering the iron loss effect.

[0008] Step 3: Search for the current and corresponding iron loss that satisfy the constraints under a given torque, and calculate the copper loss to obtain the current operating point with optimal efficiency.

[0009] Steps one, two, and three constitute the optimal current search method for permanent magnet synchronous motors considering iron loss effects. This method employs a matrix calculation extraction approach. First, a saturated flux linkage model and an iron loss model scalable by speed scaling are constructed in parallel based on a small number of finite element calculations. Using these two models, the torque matrix without considering iron loss effects and the torque matrix considering iron loss effects at the required speed are calculated. Contour lines of the required torque value are generated using the torque matrix considering iron loss effects, allowing direct acquisition of the corresponding current values ​​(i) at each point on the torque contour lines. d value and i q The obtained current operating points can be used to further obtain the position coordinates of each point on the torque contour line in the torque matrix considering iron loss. Based on these position coordinates, the corresponding flux linkage and iron loss values ​​are extracted from the saturation flux linkage model matrix and the iron loss matrix. The next step is to calculate the current amplitude and voltage amplitude corresponding to each current operating point, and extract the current operating points that meet the current and voltage constraints. Then, the copper loss of all remaining current operating points is calculated. Based on the calculated copper loss and the extracted iron loss, the current operating point with the minimum loss and optimal efficiency is obtained. This method can be used to search for the current operating point with optimal efficiency under any operating condition and calculate the efficiency.

[0010] The process will now be described in detail. Preferably, the construction process of the saturated flux linkage model and the iron loss model that can be scaled based on the rotational speed in step one is as follows: Within the range encompassing the motor current limit circle, the d-axis current and q-axis current are divided at equal or unequal intervals, or the current amplitude and phase angle are divided as selected current operating points. The selected current operating points are calculated using the finite element method at a certain rotational speed ω, simultaneously obtaining the d-axis flux linkage matrix, the q-axis flux linkage matrix, and the iron loss matrix at that rotational speed. The matrices are interpolated to obtain the d-axis flux linkage matrix encompassing all current operating points within the motor current limit circle. q-axis flux linkage matrix and the iron loss matrix P at that rotational speed Fe_ω (i d i q The iron loss matrix includes the hysteresis loss matrix P. Fe_hys_ω (i d iq ,ω) and eddy current loss P Fe_eddy_ω (i d i q The matrix (ω) represents the saturation flux linkage model and the iron loss model that can be scaled based on rotational speed:

[0011]

[0012]

[0013] P Fe_hys_ω (i d i q ,ω)=P Fe_hys_ω (i m ,θ,ω)

[0014] P Fe_eddy_ω (i d i q ,ω)=P Fe_eddy_ω (i m ,θ,ω)

[0015] P Fe_ω (i d i q ,ω)=P Fe_ω (i m ,θ,ω)=P Fe_hys_ω (i d i q ,ω)+P Fe_eddy_ω (i d i q ,ω)

[0016] Where i d Let i be the d-axis current. q Let i be the q-axis current. m θ is the current amplitude, and θ is the current phase angle.

[0017] The current limit circle mentioned above refers to the maximum allowable current amplitude of the motor, where the current amplitude i is... m It can also be calculated from the d-axis current and q-axis current:

[0018]

[0019] Preferably, the torque matrix T1, which does not consider iron loss effect, mentioned in step one, is obtained by matrix calculation based on the d-axis flux linkage matrix, the q-axis flux linkage matrix, and the corresponding current matrix. The calculation formula is as follows:

[0020]

[0021] Where P is the number of pole pairs of the motor, i d_buTo construct the d-axis current matrix, i q_bu To construct the q-axis current matrix. The corresponding current matrix refers to the current matrix that corresponds to the saturation flux linkage matrix, the T1 matrix, and the iron loss matrix. Taking the saturation flux linkage matrix as an example, i... d_bu and i q_bu The d-axis flux linkage and q-axis flux linkage generated by the d-axis current value and q-axis current value at any coordinate position are the d-axis flux linkage value and q-axis flux linkage value corresponding to the same coordinate position in the saturation flux linkage matrix.

[0022] Furthermore, the iron loss matrix P under any given rotational speed ω' described in step two... Fe_ω' (i d i q The formula for calculating ω') is obtained from the iron loss model that can be scaled based on rotational speed obtained in step one.

[0023]

[0024]

[0025] P Fe_ω' (i d i q ,ω')=P Fe_hys_ω' (i d i q ,ω')+P Fe_eddy_ω' (i d i q ,ω')

[0026] Preferably, at a given rotational speed ω', the torque matrix T2 due to iron loss in step two is obtained using the iron loss matrix P. Fe_ω' The calculation is as follows:

[0027] T2 = P Fe_ω' / ω'

[0028] For an electric motor, at a given speed ω', the torque matrix T considering iron loss in step two is calculated by subtracting the torque matrix T2 due to iron loss from the torque matrix T1 that does not consider iron loss:

[0029] T = T1 - T2

[0030] For generators, the calculation method is to add the torque matrix T2 due to iron loss to the torque matrix T1 that does not consider the iron loss effect:

[0031] T = T1 + T2.

[0032] Step three, which involves searching for the current and corresponding iron loss that satisfy the constraints under a given torque, is a method for torque calculation and extraction. The specific method is as follows:

[0033] Step A1: For a given torque T', since matrix T is i d i q The function, in matrix T, with i d x-coordinate, i q By plotting contour lines of the required torque values ​​on the vertical axis, the corresponding values ​​of i at each point on the torque contour lines can be directly obtained. d value and i q Values ​​(can be obtained using MATLAB contour functions);

[0034] Step A2: Using x to correspond to the column position of matrix T and y to correspond to the row position of matrix T, extract the x and y values ​​corresponding to each current operating point obtained in Step A1 above. These values ​​are used as the position coordinates of each point on the torque contour line in the torque matrix T. Based on these position coordinates, calculate the iron loss matrix P under the given speed ω' and the saturation flux linkage model matrix. Fe_ω' (i d i q Extract the corresponding flux linkage and iron loss values ​​from ω'). The next step is to calculate the current amplitude corresponding to each of the above current operating points, and extract the current operating points that meet the current constraints and their corresponding flux linkage and iron loss.

[0035] Step A3: Using the current operating points and corresponding flux linkages that meet the current constraints extracted in Step A2, calculate the voltage values ​​at a given speed ω' and a given torque T'. Further extract the current operating points and iron losses that meet the voltage constraints to obtain all currents that satisfy the constraints. Then calculate the copper losses of all remaining current operating points to obtain the total loss of each current operating point. Further, the current operating point that minimizes both iron and copper losses can be obtained, which is the truly efficient current operating point at a given speed ω' and a given torque T'.

[0036] The voltage constraint mentioned above refers to the voltage amplitude being less than or equal to a given value, i.e., the existence of a voltage limit circle. The voltage amplitude U is calculated using the following formula:

[0037]

[0038] Among them, the d-axis voltage q-axis voltage

[0039] The copper loss P at the current operating point Cu The calculation formula is:

[0040]

[0041] Where Rs is the phase resistance of the motor.

[0042] The beneficial effects of this invention are:

[0043] (1) A saturated flux linkage model for a permanent magnet synchronous motor is provided, which fully considers the influence of nonlinear factors such as saturation and cross saturation on the motor and can be used to accurately calculate the actual dynamic characteristics of the motor during actual operation.

[0044] (2) A permanent magnet synchronous motor iron loss model based on speed scaling is provided, which can be constructed in parallel with the saturation flux linkage model. Finite element calculations are performed on a small number of current operating points at a certain speed. Given the speed, torque and current operating points, the iron loss of the corresponding operating conditions can be obtained accurately and quickly.

[0045] (3) A method for searching the most efficient current considering the effect of iron loss on torque is provided. Utilizing matrix calculation extraction, at a given speed, the calculated torque matrix considering iron loss extracts all current operating points and their coordinates that satisfy the given torque. Current operating points that do not satisfy the current limit circle and voltage limit circle are eliminated. The copper loss of all remaining current operating points is calculated, and the iron loss is extracted to obtain the current operating point with the minimum loss, i.e., the most efficient. This method uses matrix operations throughout, eliminating the need for iterative loops, resulting in a fast search speed. It not only considers the effect of iron loss on torque, making the current trajectory more accurate, but also comprehensively considers both copper and iron losses to achieve true efficiency optimization. Attached Figure Description

[0046] Figure 1 This is a flowchart of the method for searching the optimal current for permanent magnet synchronous motor considering iron loss effect according to the present invention.

[0047] Figure 2 It is a saturated flux linkage model of a permanent magnet synchronous motor, where (a) is the d-axis flux linkage model and (b) is the q-axis flux linkage model;

[0048] Figure 3 It is a speed-scalable iron loss model, where (a) is a speed-scalable hysteresis loss model, (b) is a speed-scalable eddy current loss model, and (c) is a speed-scalable total iron loss model.

[0049] Figure 4 It is a torque matrix model under full current conditions that takes into account the effect of iron loss at a given speed;

[0050] Figure 5 This is a schematic diagram of the process of obtaining the optimal current operating point based on the idea of ​​torque calculation and extraction. Detailed Implementation

[0051] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0052] like Figures 1-5As shown, a method for searching the optimal current for permanent magnet synchronous motors considering iron loss effects is proposed. This method aims to solve the problems of traditional methods that do not consider the effects of saturation and cross-saturation on inductance and flux linkage, do not consider the effects of iron loss on torque, have slow convergence speed, long search time, and only consider copper loss without considering iron loss, thus failing to achieve true efficiency optimization.

[0053] like Figure 1 The present invention generally includes three steps:

[0054] 1. Construct a saturated flux linkage model and an iron loss model that can be scaled based on rotational speed in parallel, and calculate the torque matrix without considering the iron loss effect based on the saturated flux linkage model;

[0055] 2. Given a rotational speed, calculate the iron loss matrix and the torque matrix lost due to iron loss under full current conditions at that rotational speed based on the iron loss model, thereby obtaining the torque matrix considering the iron loss effect.

[0056] 3. Search for the current and corresponding iron loss that satisfy the constraints under a given torque and calculate the copper loss to obtain the current with the optimal efficiency.

[0057] Steps one, two, and three constitute the optimal current search method for permanent magnet synchronous motors considering iron loss effects. This method employs a matrix calculation extraction approach. First, a saturated flux linkage model and an iron loss model scalable by speed are constructed in parallel based on a small number of finite element calculations. Using these two models, the torque matrix without considering iron loss effects and the torque matrix considering iron loss effects at the required speed are calculated. Contour lines of the required torque values ​​are plotted using the torque matrix considering iron loss effects, and the corresponding current values ​​(i) at each point on the torque contour lines can be directly obtained. d i q The obtained current operating points can be used to further obtain the position coordinates of each point on the torque contour line in the torque matrix considering iron loss. Based on these position coordinates, the corresponding flux linkage and iron loss are extracted from the saturation flux linkage model matrix and the iron loss matrix. The next step is to calculate the current amplitude and voltage amplitude corresponding to each current operating point, and extract the current operating points that meet the current and voltage constraints. Then, the copper loss of all remaining current operating points is calculated. Based on the calculated copper loss and the extracted iron loss, the current operating point with the minimum loss and optimal efficiency is obtained. This method can be used to search for the current operating point with optimal efficiency under any operating condition and calculate the efficiency.

[0058] The above process will now be explained in detail using a 4-pole, 48-slot permanent magnet synchronous motor as an example.

[0059] First, a saturation flux linkage model and a speed-scalable iron loss model are constructed in parallel. Within the range encompassing the motor current limit circle, the d-axis and q-axis currents are divided at equal or unequal intervals, or the current amplitude and phase angle are divided separately as selected current operating points. For example, if the current limit value is 21A, then the d-axis current i d It can be equally divided into (0, -3, -6, -9, -12, -15, -18, -21) (A), q-axis current i q The current can be equally divided into (0, 3, 6, 9, 12, 15, 18, 21) (A), resulting in a total of 8*8 = 64 discrete current operating points. However, unequal division can also be made according to actual needs, for example, the d-axis current i... d It can be divided into (0, -2, -7, -9, -13, -16, -18, -21) (A) at unequal intervals, with the q-axis current i q The interval can be unequally divided into (0, 2, 6, 10, 12, 17, 18, 21)(A). Using the finite element method at a certain speed ω, the discrete current operating points are calculated, simultaneously obtaining the d-axis and q-axis flux linkage matrices and the iron loss matrix at that speed. After matrix interpolation, the d-axis and q-axis flux linkage matrices encompassing all current operating points within the motor's current limit circle are obtained. And the iron loss matrix at that rotational speed, the iron loss matrix P Fe_ω (i d i q ,ω) includes the hysteresis loss matrix P Fe_hys_ω (i d i q ,ω) and eddy current loss P Fe_eddy_ω (i d i q The ω) matrix, namely the saturation flux linkage model and the iron loss model that can be scaled based on rotational speed, are respectively as follows: Figure 2 and Figure 3 As shown:

[0060]

[0061]

[0062] P Fe_hys_ω (i d i q ,ω)=P Fe_hys_ω (i m ,θ,ω)

[0063] P Fe_eddy_ω (i d i q ,ω)=P Fe_eddy_ω (i m ,θ,ω)

[0064] PFe_ω (i d i q ,ω)=P Fe_ω (i m ,θ,ω)=P Fe_hys_ω (i d i q ,ω)+P Fe_eddy_ω (i d i q ,ω)

[0065] Where i d Let i be the d-axis current. q Let i be the q-axis current. m θ is the current amplitude, and θ is the current phase angle.

[0066] The current limit circle mentioned above refers to the maximum allowable current amplitude of the motor, where the current amplitude i is... m It can also be calculated from the d-axis and q-axis currents:

[0067]

[0068] Preferably, the torque matrix T1, which does not consider iron loss effect, mentioned in step one, is obtained by matrix calculation based on the d-axis flux linkage matrix and the corresponding constructed d-axis current matrix. The calculation formula is as follows:

[0069]

[0070] Where P is the number of pole pairs of the motor, i d_bu To construct the d-axis current matrix, i q_bu To construct the q-axis current matrix. Constructing the current matrix means that the current matrix corresponds to the saturation flux linkage matrix, the T1 matrix, and the iron loss matrix. Taking the flux linkage matrix as an example, i... d_bu and i q_bu The d-axis and q-axis flux linkages generated by the d-axis and q-axis current values ​​at any coordinate position are the d-axis and q-axis flux linkage values ​​corresponding to the same coordinate position in the saturation flux linkage matrix.

[0071] Furthermore, the iron loss matrix P under any given rotational speed ω' described in step two... Fe_ω' (i d i q The formula for calculating ω') is obtained from the iron loss model that can be scaled based on rotational speed obtained in step one.

[0072]

[0073]

[0074] P Fe_ω' (i d iq ,ω')=P Fe_hys_ω' (i d i q ,ω')+P Fe_eddy_ω' (i d i q ,ω')

[0075] Preferably, at a given rotational speed ω', the torque matrix T2 due to iron loss in step two is obtained using the iron loss matrix P. Fe_ω' The calculation is as follows:

[0076] T2 = P Fe_ω' / ω'

[0077] Therefore, for an electric motor, at a given speed ω', the torque matrix T considering the iron loss effect described in step two is calculated by subtracting the torque matrix T2 due to iron loss from the torque matrix T1 that does not consider the iron loss effect:

[0078] T = T1 - T2

[0079] For generators, the calculation method is to add the torque matrix T2 due to iron loss to the torque matrix T1 that does not consider the iron loss effect:

[0080] T = T1 + T2

[0081] For example, for the aforementioned motor, at a given speed of 1000 rpm, the torque matrix considering iron loss effect is calculated using the above method, as shown below. Figure 4 As shown.

[0082] Step three, which involves searching for the current and corresponding iron loss that satisfy the constraints under a given torque, is a method for torque calculation and extraction. The specific method is as follows:

[0083] A1. For a given torque T', since matrix T is i d i q The function, in matrix T, with i d i q By plotting contour lines of the required torque values ​​on the horizontal and vertical axes, the corresponding values ​​of i at each point on the torque contour lines can be directly obtained. d i q Values ​​(can be obtained using MATLAB contour functions). For example, given a torque of 6 N·m in this case, plotting torque contour lines in the torque matrix considering iron loss effects yields... Figure 5 The torque contour lines shown are provided, and the d-axis and q-axis current values ​​corresponding to each point on the contour lines can be directly obtained.

[0084] A2. Using x to correspond to the column position of matrix T and y to correspond to the row position of matrix T, extract the x and y values ​​corresponding to each current operating point obtained in A1, and use them as the position coordinates of each point on the contour line in the torque matrix T. Taking a certain i... d i q Taking current combination as an example, since the columns and rows of torque T correspond to different i... d i q The value of the current can be used as two vectors to find the position of the current combination in the vectors and assign them to x and y as position coordinates. Then, based on these position coordinates, the iron loss matrix P under the given rotational speed ω' is calculated using the saturation flux linkage model matrix and the iron loss matrix P. Fe_ω' (i d i q Extract the corresponding flux linkage and iron loss from ω'). The next step is to calculate the current amplitude corresponding to each current operating point mentioned above, and extract the current operating points that meet the current constraints and their corresponding flux linkage and iron loss;

[0085] A3. Using the current operating points and corresponding flux linkages extracted in A2 that meet the current constraints, calculate the voltage values ​​at a given speed ω' and a given torque T'. Further extract the current operating points and iron losses that meet the voltage constraints to obtain all currents that satisfy the constraints. Then calculate the copper losses of all remaining current operating points to obtain the total loss at each current point. Further, the current operating point that minimizes both iron and copper losses can be obtained, which is the truly efficient current operating point under a given speed ω' and a given torque T'.

[0086] The voltage constraint refers to the voltage amplitude being less than or equal to a given value, i.e., the existence of a voltage limit circle. The voltage amplitude U is calculated using the following formula:

[0087]

[0088] in,

[0089] For example, in this case, at a speed of 1000 rpm, the motor current limit is 21A and the voltage limit is 100V. To make the process of this invention more intuitive, the following calculations are performed: Figure 5 The current limit circle and voltage limit circle are shown. The current operating points corresponding to the torque contour lines in the shaded area are all feasible current operating points under the condition of 1000 rpm speed and 6 N·m torque.

[0090] Furthermore, the copper loss P is calculated for all current operating points that satisfy the constraints. Cu The calculation formula is:

[0091]

[0092] Where Rs is the phase resistance of the motor. Further, the current operating point that minimizes both iron and copper losses can be obtained, i.e., the current operating point with optimal efficiency at a given speed ω' and a given torque T'. In this example, the current operating point with optimal efficiency at a given speed of 1000 rpm and a given torque of 6 N·m is as follows: Figure 5 As shown, the current value is i d =-6.9, i q =8.6.

[0093] The above method can quickly and accurately find the current operating point of a permanent magnet synchronous motor that achieves true optimal efficiency under various operating conditions. This method uses matrix calculations throughout the process, does not require iterative loops, and has a fast search speed and high accuracy.

[0094] Finally, it should be noted that the above are only specific embodiments of the present invention. Of course, those skilled in the art can make modifications and variations to the present invention. If these modifications and variations fall within the scope of the claims of the present invention and their equivalents, they should be considered as being within the protection scope of the present invention.

Claims

1. A method for searching the efficiency-optimal current of a permanent magnet synchronous motor considering iron loss effects, characterized in that, The method includes the following steps: Step 1: Construct a saturated flux linkage model and an iron loss model that can be scaled based on rotational speed in parallel. Calculate the torque matrix without considering the iron loss effect based on the saturated flux linkage model. Step 2: Given a rotational speed, calculate the iron loss matrix and the torque matrix due to iron loss under full current conditions at that rotational speed based on the iron loss model, thereby obtaining the torque matrix considering the iron loss effect. Step 3: Search for the current and corresponding iron loss that satisfy the constraints under a given torque, and calculate the copper loss to obtain the current operating point with optimal efficiency. The construction process of the saturated flux linkage model and the iron loss model that can be scaled based on rotational speed in step one is as follows: Within the range encompassing the motor current limit circle, the d-axis current and q-axis current are divided at equal or unequal intervals, or the current amplitude and phase angle are divided as selected current operating points; the selected current operating points are calculated using the finite element method at a certain rotational speed ω, and the d-axis flux linkage matrix, q-axis flux linkage matrix, and iron loss matrix at that rotational speed are obtained simultaneously. The matrices are interpolated to obtain the d-axis flux linkage matrix encompassing all current operating points within the motor current limit circle. q-axis flux linkage matrix and the iron loss matrix P at that rotational speed Fe_ω (i d i q The iron loss matrix includes the hysteresis loss matrix P. Fe_hys_ω (i d i q ,ω) and eddy current loss P Fe_eddy_ω (i d i q The matrix (ω) represents the saturation flux linkage model and the iron loss model that can be scaled based on rotational speed: P Fe_hys_ω (i d ,i q ,ω)=P Fe_hys_ω (i m ,θ,ω) P Fe_eddy_ω (i d ,i q ,ω)=P Fe_eddy_ω (i m ,θ,ω) P Fe_ω (i d ,i q ,ω)=P Fe_ω (i m ,θ,ω)=P Fe_hys_ω (i d ,i q ,ω)+P Fe_eddy_ω (i d ,i q ,ω) Where i d Let i be the d-axis current. q Let i be the q-axis current. m θ is the current amplitude, and θ is the current phase angle; In step two, the iron loss matrix P is given at any rotational speed ω'. Fe_ω' (i d i q The formula for calculating ω') is obtained from the iron loss model that can be scaled based on rotational speed obtained in step one. P Fe_ω' (i d ,i q ,ω')=P Fe_hys_ω' (i d ,i q ,ω')+P Fe_eddy_ω' (i d ,i q ,ω'); Step three, which involves searching for the current and corresponding iron loss that satisfy the constraints under a given torque, is a method for torque calculation and extraction. The specific method is as follows: Step A1: For a given torque T', since matrix T is i d i q The function, in matrix T, with i d x-coordinate, i q By plotting contour lines of the required torque values ​​on the vertical axis, the corresponding values ​​of i at each point on the torque contour lines can be directly obtained. d value and i q value; Step A2: Using x to correspond to the column position of matrix T and y to correspond to the row position of matrix T, extract the x and y values ​​corresponding to each current operating point obtained in Step A1 above. These values ​​are used as the position coordinates of each point on the torque contour line in the torque matrix T. Based on these position coordinates, calculate the iron loss matrix P under the given speed ω' and the saturation flux linkage model matrix. Fe_ω' (i d i q Extract the corresponding flux linkage and iron loss values ​​from ω'); the next step is to calculate the current amplitude corresponding to each current operating point mentioned above, and extract the current operating points that meet the current constraints and the corresponding flux linkage and iron loss. Step A3: Using the current operating points and corresponding flux linkages that meet the current constraints extracted in Step A2, calculate the voltage values ​​at a given speed ω' and a given torque T'. Further extract the current operating points and iron losses that meet the voltage constraints to obtain all currents that satisfy the constraints. Then calculate the copper losses of all remaining current operating points to obtain the total loss of each current operating point. Further, the current operating point that minimizes both iron and copper losses can be obtained, which is the truly efficient current operating point at a given speed ω' and a given torque T'.

2. The method for searching the optimal efficiency current of a permanent magnet synchronous motor considering iron loss effect according to claim 1, characterized in that: The current limit circle refers to the maximum allowable current amplitude of the motor, where the current amplitude i is... m It can also be calculated from the d-axis current and q-axis current:

3. The method for searching the optimal efficiency current of a permanent magnet synchronous motor considering iron loss effect according to claim 1, characterized in that: The torque matrix T1, which does not consider iron loss effects, mentioned in step one, is obtained through matrix calculation based on the d-axis flux linkage matrix, the q-axis flux linkage matrix, and the corresponding current matrix. The calculation formula is as follows: Where P is the number of pole pairs of the motor, i d_bu To construct the d-axis current matrix, i q_bu To construct the q-axis current matrix, the corresponding current matrix refers to the current matrix that corresponds to the saturation flux linkage matrix, T1 matrix, and iron loss matrix.

4. The method for searching the optimal efficiency current of a permanent magnet synchronous motor considering iron loss effect according to claim 1, characterized in that: At a given rotational speed ω', the torque matrix T2 due to iron loss mentioned in step two is obtained using the iron loss matrix P. Fe_ω' The calculation is as follows: T2=P Fe_ω' / oh'; For an electric motor, at a given speed ω', the torque matrix T considering iron loss in step two is calculated by subtracting the torque matrix T2 due to iron loss from the torque matrix T1 that does not consider iron loss: T = T1 - T2 For generators, the calculation method is to add the torque matrix T2 due to iron loss to the torque matrix T1 that does not consider the iron loss effect: T = T1 + T2.

5. The method for searching the optimal efficiency current of a permanent magnet synchronous motor considering iron loss effect according to claim 1, characterized in that: The voltage constraint means that the voltage amplitude must be less than or equal to a given value, i.e., there exists a voltage limit circle; the voltage amplitude U is calculated according to the following formula: Among them, the d-axis voltage q-axis voltage The copper loss P at the current operating point Cu The calculation formula is: Where Rs is the phase resistance of the motor.

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