Minimum loss control method and system of built-in permanent magnet synchronous motor

Abstract

The invention belongs to the technical field of power control of pure electric vehicle models, and particularly relates to a minimum loss control method and system for a built-in permanent magnet synchronous motor, and the method comprises the steps: obtaining a virtual value of q-axis active current; obtaining the stator current of the d-axis and the q-axis at the current moment, and calculating the first active current at the current moment based on the stator current of the d-axis and the q-axis at the current moment; predicting a second active current under the action of the eight basic voltage vectors at the k + 1 moment according to the active current at the current moment; and calculating a value function corresponding to each voltage vector based on the virtual value of the q-axis active current and the second active current, and selecting an on-off state of the voltage vector which minimizes the value function to control the built-in permanent magnet synchronous motor. Under the constant-torque operation condition of the pure electric vehicle, the two-phase optimal reference current is directly obtained based on the virtual current signal, loss is effectively controlled to achieve the purpose of improving efficiency, and the problems that in the prior art, the calculation amount is large, universality is poor, and precision is low are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of power control for pure electric vehicle models, and particularly relates to a minimum loss control method and system for an interior permanent magnet synchronous motor. Background Art

[0002] Most existing electric vehicle manufacturers and electric drive suppliers control the constant torque region of the motor based on MTPA control. The most significant advantage of MTPA control is that it can effectively limit the stator current amplitude, thereby reducing the copper loss of the motor.

[0003] However, in the prior art, since the MTPA algorithm is very complex and requires solving a non-linear quartic equation, two problems are caused. One is the increased cost. The complex algorithm requires higher requirements for the chip. The other is the instability of the electric drive efficiency. The existing MTPA is mostly based on the look-up table method. Due to the inability to ensure the consistency of the motor manufacturing process, the look-up table method for a single motor cannot perfectly adapt to mass-produced vehicle models. Summary of the Invention

[0004] The purpose of the present invention is to provide a minimum copper loss and minimum iron loss control method for electric vehicles to solve the problem of reduced efficiency of the electric drive system caused by the high complexity and high operation cost of the MTPA algorithm in the prior art.

[0005] To achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present application discloses a minimum loss control method for an interior permanent magnet synchronous motor, including: Obtaining a virtual value of the q-axis active current; obtaining the stator currents of the d-axis and the q-axis at the current moment, and calculating the first active current at the current moment based on the stator currents of the d-axis and the q-axis at the current moment; Predicting the second active current under the action of 8 basic voltage vectors at the k + 1 moment according to the active current at the current moment; Calculating the value function corresponding to each voltage vector based on the virtual value of the q-axis active current and the second active current, and selecting the switching state of the voltage vector that minimizes the value function to control the interior permanent magnet synchronous motor.

[0006] Preferably, the calculating the first active current at the current moment based on the stator currents of the d-axis and the q-axis at the current moment is calculated by the following formula:

[0007]

[0008] In the formula, is the active current of the d-axis at the moment; is the d-axis Stator current at a moment is the q-axis active current at a moment is the q-axis stator current at a moment 、 、 are all coefficients is the iron loss resistance is the number of pole pairs is the mechanical angular velocity is the quadrature-axis inductance is the direct-axis inductance is the permanent magnet flux linkage

[0009] Preferably, the quadrature-axis inductance 、the direct-axis inductance and the permanent magnet flux linkage are determined by a parameter look-up table according to the stator currents of the d-axis and q-axis at the current moment

[0010] Preferably, the value function corresponding to each voltage vector is calculated based on the virtual value of the q-axis active current and the second active current, and the specific formula is as follows

[0011] In the formula is the value function is the virtual value of the q-axis active current is the predicted q-axis active current at the k + 1 moment is the predicted d-axis active current at the k + 1 moment, and A, B, C, D are all parameter coefficients

[0012] Preferably, the calculation methods of the parameter coefficients A, B, C, D are

[0013]

[0014] In the formula is the quadrature-axis inductance is the direct-axis inductance is the permanent magnet flux linkage is the stator resistance is the iron loss resistance is the number of pole pairs is the mechanical angular velocity

[0015] Preferably, the second active current under the action of 8 basic voltage vectors at the k + 1 moment is predicted according to the active current at the current moment, and the specific calculation is carried out using the following formula

[0016] In the formula, is the active current of the q-axis at the predicted (k + 1)th moment; is the active current of the d-axis at the predicted (k + 1)th moment; is the quadrature-axis inductance; is the direct-axis inductance; is the discretized time; is the permanent magnet flux linkage; is the stator resistance; is the iron loss resistance; is the number of pole pairs; is the electrical angular velocity.

[0017] In a second aspect, the present application discloses a minimum loss control system for an interior permanent magnet synchronous motor, including: An acquisition and calculation unit, configured to acquire a virtual value of the active current of the q-axis; acquire the stator currents of the d-axis and the q-axis at the current moment, and calculate the first active current at the current moment based on the stator currents of the d-axis and the q-axis at the current moment; A calculation unit, configured to predict the second active current under the action of 8 basic voltage vectors at the (k + 1)th moment according to the active current at the current moment; A calculation and selection unit, configured to calculate the value function corresponding to each voltage vector based on the virtual value of the active current of the q-axis and the second active current, and select the switching state of the voltage vector that minimizes the value function to control the interior permanent magnet synchronous motor.

[0018] Preferably, in the calculation and selection unit, the value function corresponding to each voltage vector is calculated based on the virtual value of the active current of the q-axis and the second active current, and the specific formula is as follows:

[0019] In the formula, is the value function; is the virtual value of the active current of the q-axis; is the active current of the q-axis at the predicted (k + 1)th moment; is the active current of the d-axis at the predicted (k + 1)th moment, and A, B, C, and D are all parameter coefficients.

[0020] In a third aspect, the present application discloses an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, and when the processor executes the computer program, the steps of the minimum loss control method for the interior permanent magnet synchronous motor described in any one of the above are implemented.

[0021] Fourthly, the present application discloses a computer-readable storage medium storing a computer program, which when executed by a processor implements the steps of the minimum loss control method for the built-in permanent magnet synchronous motor described in any one of the above.

[0022] Compared with the prior art, the present invention has the following beneficial effects: The minimum loss control method for the built-in permanent magnet synchronous motor proposed by the present invention can optimize the motor loss without calculating the optimal current analytical solution of the motor. Under the constant torque operation condition of pure electric vehicles, the present invention uses the speed loop regulator to obtain the given virtual current signal, and directly obtains the two-phase optimal reference current based on the virtual current signal, which can effectively control the loss to achieve the purpose of improving efficiency, and at the same time solve the problems of large amount of calculation, poor versatility and low accuracy existing in the existing control strategies. Compared with other methods, the present method has the advantages of higher motor efficiency, strong robustness, fast dynamic response and strong practicability. Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0024] Figure 1 is the method flow chart of the present invention; Figure 2 is the control principle diagram of the present invention; Figure 3 is the 10kw bench test MTPA control comparison minimum copper loss / iron loss control result diagram in the embodiments of the present invention. Detailed Embodiments

[0025] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and shown here can be arranged and designed in various different configurations.

[0026] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0027] It should be noted that like reference numerals and letters denote like items in the following figures, and thus, once an item is defined in one figure, it is not necessary to further define and explain it in subsequent figures.

[0028] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the invention product is usually placed during use, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation on the present invention. In addition, terms such as "first", "second", etc. are only used for distinguishing descriptions and cannot be construed as indicating or implying relative importance.

[0029] In addition, if the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but it can be slightly inclined.

[0030] In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and limited, if terms such as "set", "installed", "connected", "connected" are understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0031] The present invention will be further described in detail below with reference to the drawings: See Figure 1 , the present application discloses a minimum loss control method for an interior permanent magnet synchronous motor, including: S1: Obtain the virtual value of the q-axis active current; obtain the stator currents at the current moment of the d-axis and the q-axis, and calculate the first active current at the current moment based on the stator currents at the current moment of the d-axis and the q-axis. Since the technical solution of the predictive control strategy based on the real-time stator current is adopted, the technical effects of reducing the dependence on traditional models and parameter sensitivity are brought, the control accuracy and system stability are improved, and the problem of poor generality of the existing methods is solved.

[0032] S2: Predict the second active current under the action of 8 basic voltage vectors at the k + 1 moment according to the active current at the current moment; S3: Calculate the value function corresponding to each voltage vector based on the virtual value of the q-axis active current and the second active current, and select the switching state of the voltage vector that minimizes the value function to control the interior permanent magnet synchronous motor. The technical solution of directly generating two-phase optimal reference current based on virtual current signal is adopted, which brings the technical effect of avoiding complex calculation of optimal current analytical solution, significantly reduces the operation amount and improves the real-time control efficiency; The technical solution of multi-voltage vector prediction and value function minimization selection mechanism is adopted, which brings the technical effect of accurately predicting the current state at the k+1 moment and dynamically optimizing the voltage vector, realizes the minimum loss control, and improves the dynamic response speed and robustness at the same time; By integrating virtual current generation, multi-step prediction and dynamic optimization mechanism, this technical solution systematically optimizes the control process of the interior permanent magnet synchronous motor, and finally achieves the comprehensive technical effects of efficiency improvement, loss reduction and dynamic performance enhancement, which is applicable to the pure electric drive scenario with high real-time requirements.

[0033] In some embodiments, the first active current at the current moment is calculated based on the stator currents of the d-axis and q-axis at the current moment, and the calculation is carried out through the following formula:

[0034]

[0035] In the formula, is the active current of the d-axis at the moment; is the stator current of the d-axis at the moment; is the active current of the q-axis at the moment; is the stator current of the q-axis at the moment; and and are all coefficients; is the iron loss resistance; is the number of pole pairs; is the mechanical angular velocity; is the quadrature-axis inductance; is the direct-axis inductance; is the permanent magnet flux linkage.

[0036] In some embodiments, the quadrature-axis inductance , the direct-axis inductance and the permanent magnet flux linkage are determined through a parameter look-up table according to the stator currents of the d-axis and q-axis at the current moment.

[0037] In some embodiments, the value function corresponding to each voltage vector is calculated based on the virtual value of the q-axis active current and the second active current, and the specific formula is as follows:

[0038] In the formula, is the value function; is the virtual value of the q-axis active current; is the predicted q-axis active current at the (k + 1)th moment; is the predicted d-axis active current at the (k + 1)th moment. A, B, C, and D are all parameter coefficients.

[0039] In some embodiments, the calculation methods of the parameter coefficients A, B, C, and D are as follows:

[0040]

[0041] In the formula, is the quadrature-axis inductance; is the direct-axis inductance; is the permanent magnet flux linkage; is the stator resistance; is the iron loss resistance; is the number of pole pairs; is the mechanical angular velocity.

[0042] In some embodiments, the prediction of the second active current under the action of 8 basic voltage vectors at the (k + 1)th moment according to the active current at the current moment is specifically calculated using the following formula:

[0043] In the formula, is the predicted q-axis active current at the (k + 1)th moment; is the predicted d-axis active current at the (k + 1)th moment; is the quadrature-axis inductance; is the direct-axis inductance; is the discretized time; is the permanent magnet flux linkage; is the stator resistance; is the iron loss resistance; is the number of pole pairs; is the electrical angular velocity.

[0044] In some embodiments, a minimum loss control method for an interior permanent magnet synchronous motor, the specific control strategy is as follows Figure 2 as shown, and its steps are: 1) Obtain the reference value of the q-axis active current according to the PI regulator of the speed control loop for speed regulation control. Adopt the technical solution of dynamically obtaining the virtual value of the q-axis active current by the speed loop regulator, thus bringing the technical effect of adaptively adjusting the current signal under the constant torque working condition, and enhancing the versatility and adaptability of the system to different operating conditions; 2) Through the active current calculation module, calculate the active current iwdq(k) at the current moment according to the idq(k) collected at the current moment.

[0045] 3) Calculate the active current iwdq(k + 1) under the action of 8 basic voltage vectors at the k + 1 moment using the formula.

[0046] 4) Calculate the switching state corresponding to the voltage vector that minimizes the cost function for controlling the IPMSM.

[0047] The expression for calculating the active current at the current moment through the dq-axis stator current in step 2) is: (5) Among them, the calculation methods of the coefficients a, b, and c are: (6) In the formula, is the active current on the d-axis at the moment; is the stator current on the d-axis at the moment; is the active current on the q-axis at the moment; is the stator current on the q-axis at the moment; , , are all coefficients; is the iron loss resistance; is the number of pole pairs; is the mechanical angular velocity; is the quadrature-axis inductance; is the direct-axis inductance; is the permanent magnet flux linkage.

[0048] The specific steps for obtaining the motor parameters Lq, Ld, and ψf in step 2) are: According to the dq values of the stator current at the current moment, determine the magnitudes of the motor parameters Lq, Ld, and ψf at the current moment through the pre-obtained parameter look-up table.

[0049] The active current value at the current moment obtained by the active current calculation module in step 2) will be sent to the current prediction module described in step (3) to predict the active current value at the next moment.

[0050] The expression of the cost function of the cost function calculation module in step 4) is: (7) The calculation methods of coefficients A, B, C, and D are as follows: (8) In the formula, is the value function; is the virtual value of the q-axis active current; is the predicted q-axis active current at the (k + 1)th moment; is the predicted d-axis active current at the (k + 1)th moment. A, B, C, and D are all parameter coefficients; is the quadrature-axis inductance; is the direct-axis inductance; is the permanent magnet flux linkage; is the stator resistance; is the iron loss resistance; is the number of pole pairs; is the mechanical angular velocity.

[0051] Under the constant torque operation condition of a pure electric vehicle, the present invention uses a speed loop regulator to obtain a given virtual current signal, and directly obtains two-phase optimal reference currents based on the virtual current signal, which can effectively control the losses to achieve the purpose of improving efficiency. At the same time, it also solves the problems of large computational amount, poor generality, and low accuracy existing in the existing control strategies. See Figure 3 , which is the comparison result of the MTPA control and the minimum copper loss / iron loss control for a 10kW bench test. It can be seen from the figure that the motor efficiency of the traditional MTPA control is about 66% - 71%, the motor efficiency constraint of the minimum copper loss / iron loss control is about 72%, and the motor efficiency of the minimum copper loss / iron loss control of the present application is increased by about 0.16% - 1.11%; the average value of the efficiency increase is 0.51%.

[0052] The present invention also discloses an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the minimum loss control method for the interior permanent magnet synchronous motor described in any one of the above.

[0053] The present invention also discloses a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, it implements the steps of the minimum loss control method for the interior permanent magnet synchronous motor described in any one of the above.

[0054] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memory, CD-ROM, optical memory, etc.) that contain computer-usable program code.

[0055] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices produce a means for implementing the functions specified in Figure 1 one or more of the flows Figure 1 or blocks or the combination of blocks.

[0056] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory produce a manufactured article including an instruction means that implements the functions specified in Figure 1 one or more of the flows Figure 1 or blocks or the combination of blocks.

[0057] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to produce a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in Figure 1 one or more of the flows Figure 1 or blocks or the combination of blocks.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: still, the specific implementation manners of the present invention can be modified or equivalently replaced, and any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A method for minimizing the loss of an internal permanent magnet synchronous motor, characterized in that: include: Get the virtual value of the q-axis active current; Obtaining the stator currents of the d-axis and the q-axis at the current moment, and calculating the first active current at the current moment based on the stator currents of the d-axis and the q-axis at the current moment; Predicting the second active current under the action of 8 basic voltage vectors at time k+1 according to the active current at the current time; A cost function corresponding to each voltage vector is calculated based on the virtual value of the q-axis active current and the second active current, and a switching state of the voltage vector that minimizes the cost function is selected to control the interior permanent magnet synchronous motor.

2. The minimum loss control method of an interior permanent magnet synchronous motor according to claim 1, characterized in that: The first active current at the current moment is calculated based on the stator current of the d-axis and the q-axis at the current moment, and is calculated by the following formula: In the formula, is the d-axis Active current at all times; is the d-axis The stator current at the moment; is the q-axis Active current at all times; is the q-axis The stator current at the moment; , , All are coefficients; is the iron loss resistance; is the pole pair number; is the mechanical angular velocity; is the quadrature-axis inductance; is the direct-axis inductance; is the permanent magnet flux.

3. The minimum loss control method of an interior permanent magnet synchronous motor according to claim 2, characterized in that: The quadrature-axis inductance , direct axis inductor and permanent magnet flux It is determined by a parameter lookup table based on the stator current of the d-axis and q-axis at the current moment.

4. The minimum loss control method for an interior permanent magnet synchronous motor according to claim 1, characterized in that: The value function corresponding to each voltage vector is calculated based on the virtual value of the q-axis active current and the second active current. The specific formula is as follows: In the formula, is the value function; is the virtual value of the q-axis active current; is the predicted active current of the q axis at time k+1; is the predicted active current of the d-axis at time k+1, and A, B, C, and D are all parameter coefficients.

5. The minimum loss control method for an interior permanent magnet synchronous motor according to claim 4, characterized in that: The calculation method of parameter coefficients A, B, C, and D is: In the formula, is the quadrature-axis inductance; is the direct-axis inductance; is the permanent magnet flux; is the stator resistance; is the iron loss resistance; is the pole pair number; is the mechanical angular velocity.

6. The minimum loss control method for an interior permanent magnet synchronous motor according to claim 1, characterized in that: The second active current under the action of eight basic voltage vectors at time k+1 is predicted based on the active current at the current time, and is specifically calculated using the following formula: In the formula, is the predicted active current of the q axis at time k+1; is the predicted active current of the d-axis at time k+1; is the quadrature-axis inductance; is the direct-axis inductance; is the discretized time; is the permanent magnet flux; is the stator resistance; is the iron loss resistance; is the pole pair number; is the electrical angular velocity.

7. A minimum loss control system for an internal permanent magnet synchronous motor, characterized in that: include: An acquisition calculation unit is used to obtain a virtual value of the q-axis active current; Obtaining the stator currents of the d-axis and the q-axis at the current moment, and calculating the first active current at the current moment based on the stator currents of the d-axis and the q-axis at the current moment; A calculation unit, used for predicting a second active current at time k+1 under the action of eight basic voltage vectors according to the active current at the current time; The calculation selection unit is used to calculate the value function corresponding to each voltage vector based on the virtual value of the q-axis active current and the second active current, and select the switching state of the voltage vector that minimizes the value function to control the interior permanent magnet synchronous motor.

8. The minimum loss control system of an interior permanent magnet synchronous motor according to claim 7, characterized in that: In the calculation and selection unit, the value function corresponding to each voltage vector is calculated based on the virtual value of the q-axis active current and the second active current. The specific formula is as follows: In the formula, is the value function; is the virtual value of the q-axis active current; is the predicted active current of the q axis at time k+1; is the predicted active current of the d-axis at time k+1, and A, B, C, and D are all parameter coefficients.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the minimum loss control method for a built-in permanent magnet synchronous motor as described in any one of claims 1 to 6 when executing the computer program.

10. A computer-readable storage medium storing a computer program, wherein the computer program, when executed by a processor, implements the steps of the minimum loss control method for an interior permanent magnet synchronous motor according to any one of claims 1 to 6.

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