A maximum efficiency torque ratio control method for an interior permanent magnet synchronous motor based on direct current injection

Abstract

The application discloses a maximum efficiency per torque (MEPT) control method of an embedded permanent magnet synchronous motor based on direct current injection. First, a torque observer based on direct current signal injection and direct current reactive power is proposed, which overcomes the precision error problem caused by magnetic saturation and iron loss change, and improves the accuracy of torque observation. Secondly, according to the designed torque observer, a MEPT control method with an online lookup function is proposed, which can realize the optimal efficiency operation of the motor under constant torque output. The method is suitable for the application field of optimal control of the embedded permanent magnet synchronous motor.

Description

Technical Field

[0001] This invention relates to an optimized control method for an embedded permanent magnet synchronous motor, belonging to the fields of electrical engineering, motor modeling, and motor control. Background Technology

[0002] Embedded permanent magnet synchronous motors (PMSMs) are widely used in rail transportation, aerospace, household motors, and wind power generation due to their advantages such as high torque density, wide speed range, fast dynamic response, and high constant power ratio. However, during application, the electrical parameters of PMSMs may change due to variations in the operating environment (such as temperature) or operating conditions (such as current and speed). This can make it difficult for the motor to achieve its maximum efficiency operating point at a specific torque. Therefore, accurate online optimal efficiency control is necessary to achieve high-performance operation and energy saving in PMSMs.

[0003] Existing optimal efficiency control methods can be divided into two types: model-based calculation and online search. Model-based methods calculate the maximum efficiency operating point using pre-calibrated model parameters, offering the advantage of fast response. However, these methods rely on numerical calculations, significantly increasing the computational burden. Furthermore, they are unable to adjust for unexpected motor characteristic deviations, such as irreversible demagnetization of permanent magnets. In contrast, online search methods adjust the current incrementally based on measured motor signals to find the maximum power point, thus identifying the maximum efficiency point even under unexpected characteristic deviations. Moreover, online search methods do not require solving complex model formulas, resulting in a lower computational burden and easier application.

[0004] However, to achieve maximum efficiency torque ratio control using online lookup, a crucial step is to accurately observe the changes in motor torque during operation. This requires not only overcoming the underrank characteristics of the motor's inherent equations but also considering the effects of magnetic saturation and iron losses. Summary of the Invention

[0005] To achieve optimal efficiency operation of embedded permanent magnet synchronous motors under specific torque conditions, this invention proposes a maximum efficiency per torque (MEPT) control method for embedded permanent magnet synchronous motors based on DC injection. This method improves the accuracy of the maximum efficiency operating point caused by variations in motor parameters and model calculation errors, thereby making the permanent magnet synchronous motor operate more efficiently and avoiding the loss of accuracy and speed reduction during online lookup.

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0007] A maximum efficiency torque ratio control method for an embedded permanent magnet synchronous motor based on DC injection includes: proposing a torque observer based on DC signal injection and DC reactive power; and proposing a maximum efficiency torque ratio control method with online lookup function based on the torque observer.

[0008] First, design the steady-state current timing sequence under DC signal injection. The specific steps are as follows:

[0009] (1) At the operating point of the 0th group of currents [I d0 ,I q0 Beforehand, four groups of currents were constructed by injecting DC signals, numbered as Group 1, Group 2, Group 3, and Group 4, respectively; d0 and I q0 These are the base values ​​of the d-axis motor current and the q-axis motor current, respectively.

[0010] (2) The output sequence of each current group is: Group 4, Group 3, Group 2, Group 1, Group 0;

[0011] (3) Define the operating point of the first group of currents as [I d1 ,I q1 The operating point of the second group of currents is defined as [I]. d2 ,I q2 The operating point of the third group of currents is defined as [I]. d3 ,I q3 The operating point of the fourth group of currents is defined as [I]. d4 ,I q4 ];

[0012] (4) The relationship between the operating points of each current satisfies:

[0013]

[0014] In the above equation, ΔI d1 ΔI d2 These are the set d-axis current increment 1 and the set d-axis current increment 2, respectively; ΔI q1 ΔI q2 These are the set q-axis current increment 1 and the set q-axis current increment 2, respectively.

[0015] Secondly, establish the full-rank parameter observation equation based on DC reactive power. The specific steps are as follows:

[0016] (1) Using the current operating point [I d0 ,I q0 Based on ], the current operating point after injecting a DC signal is defined as [I]. d ,I q ], satisfying I d =I d0 +ΔId I q =I q0 +ΔI q ; where ΔI d and ΔI q These represent the amplitudes of the injected d-axis current signal and the q-axis current signal, respectively; at this time, at the current operating point [I d ,I q The expression for DC reactive power Q under [condition] is:

[0017] Q = 1.5ω[(ψ ad +L id ΔI d )I d +(ψ aq +L iq ΔI q )I q ]

[0018] =1.5ω[I d ψ ad +I q ψ aq +I d ΔI d L id +I q ΔI q L iq ]

[0019] In the above equation, I d and I q These are the d-axis motor current and the q-axis motor current, respectively, ψ ad and ψ aq These are the apparent flux linkages of the d-axis motor and the q-axis motor, respectively. id and L iq These are the incremental inductances of the d-axis motor and the q-axis motor, respectively, ΔI d and ΔI q These are the small-signal injection of d-axis current and the small-signal injection of q-axis current, respectively, where Q is the DC reactive power and ω is the electric angular velocity of the motor.

[0020] (2) Select the current operating points of groups 1, 2, 3, and 4, and define their DC reactive power as Q1, Q2, Q3, and Q4 respectively; similarly, use the current operating point [I d0 ,I q0 Using [a specific equation] as a reference, by simultaneously solving the four sets of DC reactive power expressions, the parameter observation equation can be obtained:

[0021] Q = 1.5ωAX

[0022] In the above equation, Q is the reactive power matrix, satisfying: Q = [Q1, Q2, Q3, Q4]T X is the torque observation parameter matrix, satisfying: X=[ψ ad ,ψ aq ,L id ,L iq ] T A is a coefficient matrix that satisfies:

[0023]

[0024] (3) To ensure that the parameter observation equation is of full rank, the determinant of the coefficient matrix A must be non-zero, i.e.:

[0025] detA=I q1 I q2 ΔI d1 ΔI d2 (ΔI q2 -ΔI q1 )(ΔI d2 -ΔI d1 )≠0

[0026] In the above equation, det is the determinant operator.

[0027] Next, the full-rank parameter observation equation based on DC reactive power is iteratively solved using the gradient descent method to obtain the torque observer parameters. The specific steps are as follows:

[0028] (1) For the DC reactive power corresponding to the current operating points of groups 1, 2, 3, and 4, the mean square error between their estimated and measured values ​​is used as the loss function J:

[0029]

[0030] In the above equation, Q i ′ is the estimated DC reactive power at the i-th current operating point, calculated from the estimated d-axis apparent flux linkage ψ. ad Estimate the apparent magnetic flux linkage ψ along the q-axis. aq Estimate the incremental inductance L along the d-axis. id Estimate the q-axis incremental inductance L iq Substituting into the expression for DC reactive power Q, we can calculate Q; i It is the measured reactive power value at the i-th current operating point, satisfying:

[0031] Q i =1.5(U qi I di -U di I qi )

[0032] In the above equation, U di U qiThese are the d-axis motor voltage and q-axis motor voltage at the i-th current operating point, respectively; I di I qi These are the d-axis motor current and q-axis motor current at the i-th current operating point, respectively.

[0033] (2) Based on the expression for DC reactive power Q, calculate the gradient of the loss function J with respect to each motor parameter:

[0034]

[0035]

[0036]

[0037]

[0038] In the above equation, ψ ad g ψ aq g L id g L iq g The loss function J is paired with the coefficient ψ. ad ψ aq L id L iq The gradient; ΔI gdi ΔI gqi Let ΔI be the d-axis current increment and q-axis current increment at the i-th current operating point, respectively, satisfying: ΔI gdi =I di -I d0 ΔI gqi =I qi -I q0 ;

[0039] (3) Based on the gradient of the loss function J with respect to each motor parameter, establish a torque observer parameter based on the gradient descent method.

[0040] The iterative solution process, specifically the steps, is as follows:

[0041] (3.1) Define the iteration error threshold ε; define the counting coefficient k = 0;

[0042] (3.2) Define the gradient matrix G, satisfying: G=[ψ ad g ,ψ aq g ,L id g ,L iq g ] TEstablish the estimated parameter matrix X′, satisfying: X′=[ψ ad ′,ψ aq ′,L id ′,L iq ′] T Define the estimated parameter matrix for the k-th iteration as X′(k), and assign initial values ​​to X′(k);

[0043] (3.3) Calculate the estimated DC reactive power values ​​Q1′, Q2′, Q3′, and Q4′ corresponding to the current operating point based on X′(k) and the DC reactive power Q expression;

[0044] (3.4) Based on the voltage and current sampled at the steady state of the current operating point, the measured values ​​of DC reactive power Q1, Q2, Q3, and Q4 are calculated;

[0045] (3.5) Based on the estimated DC reactive power obtained in step (3.3) and the measured DC reactive power obtained in step (3.4), calculate the loss function J(k) for the kth iteration; if the loss function J(k) > ε, proceed to step (3.6); if the loss function J(k) ≤ ε, proceed to step (3.9).

[0046] (3.6) Based on the estimated DC reactive power obtained in step (3.3) and the measured DC reactive power obtained in step (3.4), the gradient matrix G(k) of the kth iteration is calculated.

[0047] (3.7) Based on G(k) and X′(k), the estimated parameter matrix X′(k+1) for the (k+1)th iteration can be obtained:

[0048] X′(k+1)=X′(k)-ηG(k)

[0049] In the above equation, η is the update step size of gradient descent;

[0050] (3.8) k = k + 1, and proceed to step (3.3);

[0051] (3.9) At this point, the loss function J(k) is less than or equal to the iteration error threshold ε, and the corresponding estimated parameter matrix X′(k) is the torque observer parameter obtained by the final iterative solution;

[0052] (4) Based on the torque observer parameters obtained through iterative solution, a torque observer based on DC signal injection and DC reactive power is designed as follows:

[0053]

[0054] In the above equation, T is the motor torque, and n p This represents the number of pole pairs of the motor.

[0055] Then, calculate the increase in AC and DC axis current as the motor efficiency increases under constant torque. The specific steps are as follows:

[0056] (1) For the current operating points of groups 0, 1, 2, 3, and 4, calculate the current operating point of group 0 [I]. d0 ,I q0 The active power P0:

[0057] P0 = 1.5(U d0 I d0 +U q0 I q0 )

[0058] In the above equation, U d0 For the corresponding direct-axis current operating point I of group 0 d0 voltage, U q0 For the corresponding operating point I of the quadrature axis current group 0 q0 The voltage;

[0059] (2) Calculate the operating point of the second group of currents [I] d2 ,I q2 The active power P2:

[0060] P2 = 1.5(U d2 I d2 +U q2 I q2 )

[0061] In the above equation, U d2 For the second group of direct-axis current operating point I d2 voltage, U q2 For the second group of quadrature axis current operating point I q2 The voltage;

[0062] (3) Based on the calculated P0 and P2, calculate the direct-axis current increment ΔI according to their difference. dME :

[0063] ΔI dME =-λ(P2-P0) / (I d2 -I d0 )

[0064] In the above equation, λ is the update step size of the current disturbance observation;

[0065] (4) Finally, based on the torque observer parameters obtained from the iterative solution, the constant torque T is calculated. ref The quadrature axis current increment ΔI qME :

[0066] ΔI qME =[T ref / 1.5n p -(ψ ad I q0 -ψ aq I d0 )+(ψ aq -L id I q0 )ΔI dME ] / (ψ ad -L iq I d0 )

[0067] In the above equation, T ref This is the reference value for constant torque.

[0068] Finally, based on the calculated quadrature and direct axis current increments, current update timing control is implemented, specifically as follows:

[0069] (1) Based on the direct-axis current increment ΔI dME and cross-axis current increment ΔI qME Update the direct and quadrature axis reference currents I of the current controller. dref and I qref :

[0070]

[0071] In the above equation, I dref ′ and I qref ′ represents the updated direct-axis and quadrature-axis reference currents;

[0072] (2) Calculate the corresponding I dref ′ and I qref The active power P' output by the motor in state ′:

[0073]

[0074] In the above equation, U d ′ and U q ′ represents the updated direct-axis and quadrature-axis voltages;

[0075] (3) Compare the updated active power P′ with the original active power P; if the active power before and after the update are not equal, then recalculate the direct-axis current increment ΔI. dME and cross-axis current increment ΔI qME And update the reference values ​​of the direct and quadrature axis currents according to the formula in step (1), and finally the increments of the direct and quadrature axis currents gradually decrease and approach zero;

[0076] (4) Through continuous online searching and updating, the active power will be maintained at the maximum power output operating point, and the motor will operate at the optimal efficiency.

[0077] The inventive principle of this invention is as follows:

[0078] To achieve accurate torque observation, a torque observer model was established using DC signal injection and DC reactive power construction. However, if the inherent voltage equations of a permanent magnet synchronous motor considering magnetic saturation losses are used to solve for the four unknown electrical parameters in the torque observer model, an underrank problem inevitably arises. To address this, a full-rank matrix for model parameter identification is constructed by injecting a DC bias signal along the dq axis and, based on the relationship between DC reactive power, apparent flux linkage, and incremental inductance, through steady-state current timing design. This matrix is ​​then iteratively solved using the gradient descent method, enabling online and accurate identification of the torque observer model parameters.

[0079] Based on the accurate identification of torque observer model parameters, an online search method is used to gradually adjust the motor current under constant torque to find the point of maximum efficiency. The direction of change in active power and the direction of change in current are used as the basis: if active power increases when current increases, the current continues to increase, and vice versa; if active power increases when current decreases, the current continues to decrease, and vice versa. Through continuous online search and iterative updates, the motor is ultimately made to operate at optimal efficiency.

[0080] The beneficial effects of this invention are as follows:

[0081] 1. By using DC signal injection, a full-rank matrix for online identification of apparent flux linkage and incremental inductance was constructed using reactive power under four different current vector states. This method considers the magnetic saturation phenomenon of the motor and avoids the influence of iron loss, thereby reducing the complexity of identification and improving the accuracy of observation.

[0082] 2. Employing an online-lookup MEPT control method, the current is gradually adjusted to find the actual maximum power point under a torque observer constructed through accurate parameter identification. For constant torque load operation, this reduces errors caused by parameter variations or model-based calculations, effectively improving the energy-saving performance of the permanent magnet synchronous motor. Attached Figure Description

[0083] Figure 1 MEPT control block diagram with online search function;

[0084] Figure 2 Steady-state current timing design diagram for DC signal injection. Detailed Implementation

[0085] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0086] This invention proposes a maximum efficiency torque ratio control method for an embedded permanent magnet synchronous motor based on DC injection, comprising: proposing a torque observer based on DC signal injection and DC reactive power; and proposing a maximum efficiency torque ratio control method with online lookup function based on the torque observer.

[0087] like Figure 1 The diagram shows the MEPT control block diagram for implementing an embedded permanent magnet synchronous motor with online lookup function based on DC injection. After calculating the direct and quadrature axis currents and reactive power of the embedded permanent magnet synchronous motor, the torque observer is input and the obtained torque observer parameters are used to calculate the quadrature and direct axis current increments with increasing motor efficiency under constant torque. By online lookup and iterative update of the current reference value, the maximum efficiency torque ratio control of the embedded permanent magnet synchronous motor is achieved.

[0088] First, design the steady-state current timing under DC signal injection, such as... Figure 2 As shown, the specific steps are as follows:

[0089] (1) At the operating point of the 0th group of currents [I d0 ,I q0 Beforehand, four groups of currents were constructed by injecting DC signals, numbered as Group 1, Group 2, Group 3, and Group 4, respectively; d0 and I q0 These are the base values ​​of the d-axis motor current and the q-axis motor current, respectively.

[0090] (2) The output sequence of each current group is: Group 4, Group 3, Group 2, Group 1, Group 0;

[0091] (3) Define the operating point of the first group of currents as [I d1 ,I q1 The operating point of the second group of currents is defined as [I]. d2 ,I q2 The operating point of the third group of currents is defined as [I]. d3 ,I q3 The operating point of the fourth group of currents is defined as [I]. d4 ,I q4 ];

[0092] (4) The relationship between the operating points of each current satisfies:

[0093]

[0094] In the above equation, ΔI d1 ΔI d2 These are the set d-axis current increment 1 and the set d-axis current increment 2, respectively; ΔI q1 ΔI q2These are the set q-axis current increment 1 and the set q-axis current increment 2, respectively.

[0095] Secondly, establish the full-rank parameter observation equation based on DC reactive power. The specific steps are as follows:

[0096] (1) Using the current operating point [I d0 ,I q0 Based on ], the current operating point after injecting a DC signal is defined as [I]. d ,I q ], satisfying I d =I d0 +ΔI d I q =I q0 +ΔI q ; where ΔI d and ΔI q These represent the amplitudes of the injected d-axis current signal and the q-axis current signal, respectively; at this time, at the current operating point [I d ,I q The expression for DC reactive power Q under [condition] is:

[0097] Q = 1.5ω[(ψ ad +L id ΔI d )I d +(ψ aq +L iq ΔI q )I q ]

[0098] =1.5ω[I d ψ ad +I q ψ aq +I d ΔI d L id +I q ΔI q L iq ]

[0099] In the above equation, I d and I q These are the d-axis motor current and the q-axis motor current, respectively, ψ ad and ψ aq These are the apparent flux linkages of the d-axis motor and the q-axis motor, respectively. id and L iq These are the incremental inductances of the d-axis motor and the q-axis motor, respectively, ΔI d and ΔI q These are the small-signal injection of d-axis current and the small-signal injection of q-axis current, respectively, where Q is the DC reactive power and ω is the electric angular velocity of the motor.

[0100] (2) Select the current operating points of groups 1, 2, 3, and 4, and define their DC reactive power as Q1, Q2, Q3, and Q4 respectively; similarly, use the current operating point [I d0 ,I q0 Using [a specific equation] as a reference, by simultaneously solving the four sets of DC reactive power expressions, the parameter observation equation can be obtained:

[0101] Q = 1.5ωAX

[0102] In the above equation, Q is the reactive power matrix, satisfying: Q = [Q1, Q2, Q3, Q4] T X is the torque observation parameter matrix, satisfying: X=[ψ ad ,ψ aq ,L id ,L iq ] T A is a coefficient matrix that satisfies:

[0103]

[0104] (3) To ensure that the parameter observation equation is of full rank, the determinant of the coefficient matrix A must be non-zero, i.e.:

[0105] detA=I q1 I q2 ΔI d1 ΔI d2 (ΔI q2 -ΔI q1 )(ΔI d2 -ΔI d1 )≠0

[0106] In the above equation, det is the determinant operator.

[0107] Next, the full-rank parameter observation equation based on DC reactive power is iteratively solved using the gradient descent method to obtain the torque observer parameters. The specific steps are as follows:

[0108] (1) For the DC reactive power corresponding to the current operating points of groups 1, 2, 3, and 4, the mean square error between their estimated and measured values ​​is used as the loss function J:

[0109]

[0110] In the above equation, Q i ′ is the estimated DC reactive power at the i-th current operating point, calculated from the estimated d-axis apparent flux linkage ψ. ad Estimate the apparent magnetic flux linkage ψ along the q-axis. aq Estimate the incremental inductance L along the d-axis. id Estimate the q-axis incremental inductance Liq Substituting into the expression for DC reactive power Q, we can calculate Q; i It is the measured reactive power value at the i-th current operating point, satisfying:

[0111] Q i =1.5(U qi I di -U di I qi )

[0112] In the above equation, U di U qi These are the d-axis motor voltage and q-axis motor voltage at the i-th current operating point, respectively; I di I qi These are the d-axis motor current and q-axis motor current at the i-th current operating point, respectively.

[0113] (2) Based on the expression for DC reactive power Q, calculate the gradient of the loss function J with respect to each motor parameter:

[0114]

[0115]

[0116]

[0117]

[0118] In the above equation, ψ ad g ψ aq g L id g L iq g The loss function J is paired with the coefficient ψ. ad ψ aq L id L iq The gradient; ΔI gdi ΔI gqi Let ΔI be the d-axis current increment and q-axis current increment at the i-th current operating point, respectively, satisfying: ΔI gdi =I di -I d0 ΔI gqi =I qi -I q0 ;

[0119] (3) Based on the gradient of the loss function J with respect to each motor parameter, an iterative solution process for the torque observer parameters based on the gradient descent method is established. The specific steps are as follows:

[0120] (3.1) Define the iteration error threshold ε; define the counting coefficient k = 0;

[0121] (3.2) Define the gradient matrix G, satisfying: G=[ψ ad g ,ψ aq g ,L id g ,L iq g ] T Establish the estimated parameter matrix X′, satisfying: X′=[ψ ad ′,ψ aq ′,L id ′,L iq ′] T Define the estimated parameter matrix for the k-th iteration as X′(k), and assign initial values ​​to X′(k);

[0122] (3.3) Calculate the estimated DC reactive power values ​​Q1′, Q2′, Q3′, and Q4′ corresponding to the current operating point based on X′(k) and the DC reactive power Q expression;

[0123] (3.4) Based on the voltage and current sampled at the steady state of the current operating point, the measured values ​​of DC reactive power Q1, Q2, Q3, and Q4 are calculated;

[0124] (3.5) Based on the estimated DC reactive power obtained in step (3.3) and the measured DC reactive power obtained in step (3.4), calculate the loss function J(k) for the kth iteration; if the loss function J(k) > ε, proceed to step (3.6); if the loss function J(k) ≤ ε, proceed to step (3.9).

[0125] (3.6) Based on the estimated DC reactive power obtained in step (3.3) and the measured DC reactive power obtained in step (3.4), the gradient matrix G(k) of the kth iteration is calculated.

[0126] (3.7) Based on G(k) and X′(k), the estimated parameter matrix X′(k+1) for the (k+1)th iteration can be obtained:

[0127] X′(k+1)=X′(k)-ηG(k)

[0128] In the above equation, η is the update step size of gradient descent;

[0129] (3.8) k = k + 1, and proceed to step (3.3);

[0130] (3.9) At this point, the loss function J(k) is less than or equal to the iteration error threshold ε, and the corresponding estimated parameter matrix X′(k) is the torque observer parameter obtained by the final iterative solution;

[0131] (4) Based on the torque observer parameters obtained through iterative solution, a torque observer based on DC signal injection and DC reactive power is designed as follows:

[0132] T = 1.5n p (ψ ad I q -ψ aq I d )

[0133] In the above equation, T is the motor torque, and n p This represents the number of pole pairs of the motor.

[0134] Then, calculate the increase in AC and DC axis current as the motor efficiency increases under constant torque. The specific steps are as follows:

[0135] (1) For the current operating points of groups 0, 1, 2, 3, and 4, calculate the current operating point of group 0 [I]. d0 ,I q0 The active power P0:

[0136] P0 = 1.5(U d0 I d0 +U q0 I q0 )

[0137] In the above equation, U d0 For the corresponding direct-axis current operating point I of group 0 d0 voltage, U q0 For the corresponding operating point I of the quadrature axis current group 0 q0 The voltage;

[0138] (2) Calculate the operating point of the second group of currents [I] d2 ,I q2 The active power P2:

[0139] P2 = 1.5(U d2 I d2 +U q2 I q2 )

[0140] In the above equation, U d2 For the second group of direct-axis current operating point I d2 voltage, U q2 For the second group of quadrature axis current operating point I q2 The voltage;

[0141] (3) Based on the calculated P0 and P2, calculate the direct-axis current increment ΔI according to their difference. dME :

[0142] ΔI dME =-λ(P2-P0) / (I d2 -I d0 )

[0143] In the above equation, λ is the update step size of the current disturbance observation;

[0144] (4) Finally, based on the torque observer parameters obtained from the iterative solution, the constant torque T is calculated. ref The quadrature axis current increment ΔI qME :

[0145] ΔI qME =[T ref / 1.5n p -(ψ ad I q0 -ψ aq I d0 )+(ψ aq -L id I q0 )ΔI dME ] / (ψ ad -L iq I d0 )

[0146] In the above equation, T ref This is the reference value for constant torque.

[0147] Finally, based on the calculated quadrature and direct axis current increments, current update timing control is implemented, specifically as follows:

[0148] (1) Based on the direct-axis current increment ΔI dME and cross-axis current increment ΔI qME Update the direct and quadrature axis reference currents I of the current controller. dref and I qref :

[0149]

[0150] In the above equation, I dref ′ and I qref ′ represents the updated direct-axis and quadrature-axis reference currents;

[0151] (2) Calculate the corresponding I dref ′ and I qref The active power P' output by the motor in state ′:

[0152]

[0153] In the above equation, U d ′ and U q ′ represents the updated direct-axis and quadrature-axis voltages;

[0154] (3) Compare the updated active power P′ with the original active power P; if the active power before and after the update are not equal, then recalculate the direct-axis current increment ΔI. dME and cross-axis current increment ΔI qME And update the reference values ​​of the direct and quadrature axis currents according to the formula in step (1), and finally the increments of the direct and quadrature axis currents gradually decrease and approach zero;

[0155] (4) Through continuous online searching and updating, the active power will be maintained at the maximum power output operating point, and the motor will operate at the optimal efficiency.

Claims

1. A method for controlling the maximum efficiency torque ratio of an embedded permanent magnet synchronous motor based on DC injection, characterized in that, First, a torque observer based on DC signal injection and DC reactive power is proposed; then, based on the torque observer, a maximum efficiency torque ratio control method with online lookup function is proposed. The proposed method is a torque observer based on DC signal injection and DC reactive power. Specifically, the steady-state current timing sequence under DC signal injection is designed, and a full-rank parameter observation equation based on DC reactive power is established. The full-rank parameter observation equation based on DC reactive power is iteratively solved using the gradient descent method to obtain the torque observer parameters. The maximum efficiency torque ratio control method with online lookup function specifically includes: Calculate the quadrature-axis and direct-axis current increments as the motor efficiency increases under constant torque; Based on the aforementioned quadrature and direct axis current increments, current update timing control is achieved; The specific steps for designing the steady-state current timing sequence under DC signal injection are as follows: (1) At the operating point of the 0th group of currents [I d0 , I q0 Beforehand, four groups of currents were constructed by injecting DC signals, numbered as Group 1, Group 2, Group 3, and Group 4, respectively; d0 and I q0 These are the base values ​​of the d-axis motor current and the q-axis motor current, respectively. (2) The output sequence of each current group is: Group 4, Group 3, Group 2, Group 1, Group 0; (3) Define the operating point of the first group of currents as [I d1 , I q1 The operating point of the second group of currents is defined as [I]. d2 , I q2 The operating point of the third group of currents is defined as [I]. d3 , I q3 The operating point of the fourth group of currents is defined as [I]. d4 , I q4 ]; (4) The relationship between the operating points of each current satisfies: ， Where, ΔI d1 ΔI d2 These are the set d-axis current increment 1 and the set d-axis current increment 2, respectively; ΔI q1 ΔI q2 These are the set q-axis current increment 1 and the set q-axis current increment 2, respectively. The specific steps for establishing the full-rank parameter observation equation based on DC reactive power are as follows: (1) Using the current operating point [I d0 , I q0 Based on ], the current operating point after injecting a DC signal is defined as [I]. d , I q ], satisfying I d = I d0 +ΔI d I q = I q0 +ΔI q ; where ΔI d and ΔI q These represent the amplitudes of the injected d-axis current signal and the q-axis current signal, respectively; at this time, at the current operating point [I d , I q The expression for DC reactive power Q under [condition] is: Among them, I d and I q These are the d-axis motor current and the q-axis motor current, respectively, ψ ad and ψ aq These are the apparent flux linkages of the d-axis motor and the q-axis motor, respectively. id and L iq These are the incremental inductances of the d-axis motor and the q-axis motor, respectively, where Q is the DC reactive power and ω is the electric angular velocity of the motor. (2) Select the current operating points of group 1, group 2, group 3, and group 4, and define their DC reactive power as Q1, Q2, Q3, and Q4 respectively; similarly, use the current operating point [I d0 , I q0 Using [a specific equation] as a reference, by simultaneously solving the four sets of DC reactive power expressions, the parameter observation equation can be obtained: Where Q is the reactive power matrix, satisfying: Q = [Q1, Q2, Q3, Q4] T X is the torque observation parameter matrix, satisfying: X = [ψ] ad , ψ aq , L id , L iq ] T A is a coefficient matrix that satisfies: (3) To ensure that the parameter observation equation is of full rank, the determinant of the coefficient matrix A must be non-zero, i.e.: Here, det is the determinant operator.

2. The method for controlling the maximum efficiency torque ratio of an embedded permanent magnet synchronous motor based on DC injection according to claim 1, characterized in that, The gradient descent method is used to iteratively solve the full-rank parameter observation equation based on DC reactive power to obtain the torque observer parameters. The specific steps are as follows: (1) For the DC reactive power corresponding to the current operating points of groups 1, 2, 3, and 4, the mean square error between their estimated and measured values ​​is used as the loss function J: Among them, Q i ' is the estimated DC reactive power value at the i-th current operating point, derived from the estimated d-axis apparent flux linkage ψ ad 'Estimation of the q-axis apparent magnetic flux ψ' aq 'Estimating the incremental inductance L along the d-axis' id 'Estimating the q-axis incremental inductance L' iq Substituting into the expression for DC reactive power Q, we can calculate Q; i It is the measured reactive power value at the i-th current operating point, satisfying: Among them, U di U qi These are the d-axis motor voltage and q-axis motor voltage at the i-th current operating point, respectively; I di I qi These are the d-axis motor current and q-axis motor current at the i-th current operating point, respectively. (2) Based on the expression for DC reactive power Q, calculate the gradient of the loss function J with respect to each motor parameter: Where, ψ ad g ψ aq g L id g L iq g The loss function J is paired with the coefficient ψ. ad ψ aq L id L iq The gradient; ΔI gdi ΔI gqi Let ΔI be the d-axis current increment and q-axis current increment at the i-th current operating point, respectively, satisfying: ΔI gdi = I di - I d0 ΔI gqi = I qi - I q0 ; (3) Based on the gradient of the loss function J with respect to each motor parameter, establish the iterative solution process for the torque observer parameters based on the gradient descent method. The specific steps are as follows: (3.1) Define the iteration error threshold ε; define the counting coefficient k = 0; (3.2) Define the gradient matrix G, satisfying: G = [ψ ad g , ψ aq g , L id g , L iq g ] T Establish an estimated parameter matrix X', satisfying: X' = [ψ ad ', ψ aq ', L id ', L iq '] T Define the estimated parameter matrix for the k-th iteration as X'(k), and assign initial values ​​to X'(k); (3.3) Calculate the estimated DC reactive power values ​​Q1', Q2', Q3', and Q4' corresponding to the current operating point based on X'(k) and the expression for DC reactive power Q; (3.4) Based on the voltage and current sampled at the steady state of the current operating point, the measured values ​​of DC reactive power Q1, Q2, Q3, and Q4 are calculated; (3.5) Based on the estimated DC reactive power obtained in step (3.3) and the measured DC reactive power obtained in step (3.4), the loss function J(k) of the kth iteration is calculated; if the loss function J(k) > ε, then proceed to step (3.6); if the loss function J(k) ≤ ε, then proceed to step (3.9). (3.6) Based on the estimated DC reactive power obtained in step (3.3) and the measured DC reactive power obtained in step (3.4), the gradient matrix G(k) of the kth iteration is calculated. (3.7) Based on G(k) and X'(k), the estimated parameter matrix X'(k+1) for the (k+1)th iteration can be obtained: Where η is the update step size of gradient descent; (3.8) k = k +1, and proceed to step (3.3); (3.9) At this point, the loss function J(k) is less than or equal to the iteration error threshold ε, and the corresponding estimated parameter matrix X'(k) is the torque observer parameter obtained by the final iterative solution; (4) Based on the torque observer parameters obtained through iterative solution, the torque observer based on DC signal injection and DC reactive power is obtained as follows: Where T is the motor torque, n p This represents the number of pole pairs of the motor.

3. The method for controlling the maximum efficiency torque ratio of an embedded permanent magnet synchronous motor based on DC injection according to claim 2, characterized in that, The specific steps for calculating the increase in AC and DC axis current as the motor efficiency increases under constant torque are as follows: (1) For the current operating points of groups 0, 1, 2, 3, and 4, calculate the current operating point of group 0 [I]. d0 ,I q0 The active power P0: Among them, U d0 For the corresponding direct-axis current operating point I of group 0 d0 voltage, U q0 For the corresponding operating point I of the quadrature axis current group 0 q0 The voltage; (2) Calculate the operating point of the second group of currents [I] d2 , I q2 The active power P2: Among them, U d2 For the second group of direct-axis current operating point I d2 voltage, U q2 For the second group of quadrature axis current operating point I q2 (3) Based on the calculated P0 and P2, calculate the direct-axis current increment ΔI according to their difference. dME : Where λ is the update step size of the current disturbance observation; (4) Finally, based on the torque observer parameters obtained by iterative solution, the constant torque T is calculated. ref The quadrature axis current increment ΔI qME : Among them, T ref This is the reference value for constant torque.

4. The method for controlling the maximum efficiency torque ratio of an embedded permanent magnet synchronous motor based on DC injection according to claim 3, characterized in that, The current update timing control based on the calculated quadrature and direct axis current increments is specifically as follows: (1) Based on the direct-axis current increment ΔI dME and cross-axis current increment ΔI qME Update the direct-axis and quadrature-axis reference currents I of the current controller. dref and I qref : Among them, I dref ' and I qref ' The updated direct-axis and quadrature-axis reference currents; (2) Calculate the corresponding I dref ' and I qref ' The active power P output by the motor in this state ' : Among them, U d ' and U q ' For the updated direct-axis and quadrature-axis voltages; (3) Compare the updated active power P ' The active power P before and after the update is calculated; if the active power before and after the update is not equal, the direct-axis current increment ΔI is calculated again. dME and cross-axis current increment ΔI qME And update the reference values ​​of the direct and quadrature axis currents according to the formula in step (1), and finally the increments of the direct and quadrature axis currents gradually decrease and approach zero; (4) Through continuous online search and update iteration, the active power will be maintained at the maximum power output operating point, and the motor will operate at the optimal efficiency.

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