An online soft test method for transient torque of asynchronous motor

Abstract

The present invention relates to the field of motor control technology and discloses an online soft testing method for transient torque of an asynchronous motor, comprising the following steps: S1: establishing a mathematical model of the system; S2: constructing an integrated observer within the mathematical model; S3: the flux direction observer estimates slip based on current feedback and the mechanical speed obtained from the test, superimposing the slip and mechanical speed to obtain the synchronous speed, and integrating the synchronous speed to obtain the flux direction; S4: obtaining a simplified voltage loop equation based on the relationship between flux and current and the slip equation; S5: obtaining the rotor-side q-axis flux and the rotor-side d-axis current, obtaining the rotor-side d-axis flux, and obtaining the stator-side q-axis current; and S6: substituting the electromagnetic torque expression into the equation to obtain the electromagnetic torque including transient effects. The present invention can address the problem in the prior art that RFOC theoretical solutions always use a steady-state target as the basis for magnetic field orientation, resulting in a certain degree of uncertainty in the estimated electromagnetic torque.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and in particular to an online soft testing method for transient torque of an asynchronous motor. Background Art

[0002] Asynchronous motors offer excellent performance, including high reliability, high dynamic performance, high power, and low cost. Paired with synchronous motors, they leverage their respective strengths and have become a standard feature in high-end four-wheel drive electric vehicles. Asynchronous and synchronous motors operate on different principles. Because asynchronous motors lack a magnetic field in their rotors, they require an excitation method for proper control. After excitation, the magnetic field direction must be tracked in real time, making field orientation control (FOC) a key component of traditional control.

[0003] Currently, FOC solutions are mainly divided into two categories and three subcategories:

[0004] The first type is direct magnetic field orientation, which uses Hall elements to measure the air gap magnetic field in real time to complete magnetic field orientation. It is rarely used in actual applications.

[0005] The second type is indirect magnetic field orientation, which is widely used because it does not require testing the air gap magnetic field.

[0006] Indirect magnetic field orientation is divided into three categories:

[0007] The first category is based on rotor field orientation (RFOC), the second category is based on stator field orientation, and the third category is based on nonlinear control field orientation.

[0008] In rotor-orientation schemes, decoupling control is essential, especially for the calculation and analysis of active torsional vibration control. Furthermore, for efficiency considerations, a reference flux amplitude is required. This necessitates real-time online load torque estimation and torque equation calibration. Without considering the influence of rotor inertia, the motor's load torque can generally be assumed to be equal to the electromagnetic torque. Therefore, real-time online electromagnetic torque estimation is essential.

[0009] Existing RFOC solutions assume that the q-axis flux and d-axis current are zero, always using steady-state targets as the basis for magnetic field orientation. However, in reality, transient processes are inevitable. That is, when the stator-side d-axis current changes in a given synchronous coordinate system, the rotor-side q-axis flux and d-axis current will fluctuate and not be ideally zero. This problem is particularly serious when the current loop design is not sound. Therefore, the electromagnetic torque estimated by the RFOC theoretical solution has a certain degree of uncertainty. Summary of the Invention

[0010] In view of this, the purpose of the present invention is to provide an online soft testing method for transient torque of asynchronous motors, so as to solve the problem in the prior art that the RFOC theoretical scheme always uses the steady-state target as the basis for magnetic field orientation, and the estimated electromagnetic torque has certain uncertainty.

[0011] The present invention solves the above technical problems through the following technical means:

[0012] The present application provides an online soft testing method for transient torque of an asynchronous motor, comprising:

[0013] S1: Establish the mathematical model of the system based on the voltage loop equation in the synchronous coordinate system on the rotor side of the squirrel cage asynchronous motor;

[0014] S2: constructing an integrated observer in the mathematical model, wherein the integrated observer includes a flux direction observer and an electromagnetic torque observer;

[0015] S3: The flux direction observer estimates the slip based on the current feedback value and the mechanical speed obtained by the test, and superimposes the slip and the mechanical speed to obtain the synchronous speed, and integrates the synchronous speed to obtain the flux direction;

[0016] S4: Based on the relationship between flux and current, and the glide difference equation, the simplified voltage loop equation is obtained, that is, the variation law of the rotor side q-axis flux and d-axis current in the synchronous coordinate system;

[0017] S5: The electromagnetic torque observer performs a differential operation on the fed-back stator-side d-axis current, uses the differential value as a non-homogeneous input of a simplified voltage loop equation, integrates the simplified voltage loop equation to obtain the rotor-side q-axis flux and the rotor-side d-axis current, substitutes the rotor-side d-axis current and the stator-side d-axis current into a flux-current relationship to obtain the rotor-side d-axis flux, and brings the stator-side d-axis current into an integral compensation scheme to obtain the stator-side q-axis current;

[0018] S6: Substitute the rotor side q-axis flux, rotor side d-axis flux, rotor side d-axis current and stator side q-axis current into the electromagnetic torque expression to obtain the electromagnetic torque including transient effects.

[0019] In some optional implementations, the voltage loop equation is:

[0020]

[0021] Among them, R r is the rotor resistance, w e is the synchronous speed, w r is the mechanical speed, is the q-axis current on the rotor side, is the rotor side d-axis current, is the d-axis magnetic flux on the rotor side, is the q-axis flux on the rotor side, p is the time derivative, and the superscript e indicates that the reference coordinate system is the synchronous reference coordinate system.

[0022] In some optional implementations, the relationship between the flux linkage and the current is:

[0023]

[0024]

[0025] Among them, L r is the rotor self-inductance, L m is the rotor mutual inductance, is the stator side d-axis current, is the q-axis current on the stator side.

[0026] The glide difference equation is:

[0027]

[0028] The simplified voltage loop equation is:

[0029]

[0030] In some optional implementations, the electromagnetic torque expression is:

[0031] Among them, P N is the number of motor poles.

[0032] In some optional embodiments, the mathematical model is provided with maximum torque per ampere (MTPA) and maximum torque per volt (MTPV) modules.

[0033] In some optional implementations, the mathematical model is provided with a signal acquisition module and a motor speed calculation module.

[0034] In some optional implementations, a data integration module is provided in the mathematical model.

[0035] In some optional implementations, the mathematical model is provided with a basic coordinate transformation module and a coordinate inverse transformation module.

[0036] In some optional implementations, a current regulator and a PWM module are provided in the mathematical model.

[0037] Beneficial effects of the present invention:

[0038] 1. The present invention adopts a transient torque compensation scheme to calculate and revise the unreasonable assumptions of magnetic field orientation in real time, avoid the defect of insufficient accuracy of steady-state solution, and improve control accuracy. This is the technical feature and advantage of this scheme in transient process analysis.

[0039] 2. The present invention adopts a "soft test" solution, which can solve the impact of the hardware low-pass filter circuit, avoid the reliability and cost issues brought by the hardware test solution, and avoid the adverse effects of testing the bus voltage and voltage fluctuations during battery discharge.

[0040] 3. The present invention adopts a "soft test" solution to provide internal feedback, increase system debugging capabilities, and solve the problem of too little feedback.

[0041] 4. It is suitable for bench calibration and can assist in completing the bench test torque closed-loop analysis. It can provide accurate feedback in the early stage of control algorithm design to facilitate the completion of control algorithm development and assist in the completion of functional fault safety diagnosis. This is the technical feature and advantage of this solution in steady-state process analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a flowchart of an online soft testing method for transient torque of an asynchronous motor according to the present invention;

[0043] Figure 2 This is a mathematical model diagram of an online soft test method for transient torque of an asynchronous motor according to the present invention;

[0044] Figure 3 It is a torque compensation integral diagram applied to an online soft test method of transient torque of an asynchronous motor according to the present invention;

[0045] Figure 4 The present invention compares the bench electromagnetic torque test results (Bench Tq) and the software test results (SoftwareTq); DETAILED DESCRIPTION

[0046] The following describes the embodiments of the present invention through specific embodiments. Those skilled in the art can understand the advantages and effects of the present invention from the contents disclosed in this specification. It should be noted that the illustrations provided in the following embodiments are for illustrative purposes only and are only schematic diagrams, not actual drawings. They should not be understood as limiting the present invention. In order to better illustrate the embodiments of the present invention, some parts in the figures may be omitted, enlarged or reduced, and do not represent the dimensions of the actual product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the figures.

[0047] The same or similar numbers in the figures of the embodiments of the present invention correspond to the same or similar parts. In the description of the present invention, it should be understood that if the terms "up", "down", "left", "right", "front", "back", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the figure. This is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the figures are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0048] like Figure 1-Figure 4 As shown,

[0049] The present application provides an online soft testing method for transient torque of an asynchronous motor, comprising:

[0050] Step 110: Establishing a mathematical model of the system according to a voltage loop equation in a synchronous coordinate system on the rotor side of the squirrel cage asynchronous motor;

[0051] Step 120: constructing an integrated observer in the mathematical model, where the integrated observer includes a flux direction observer and an electromagnetic torque observer;

[0052] Step 130: The flux direction observer estimates the slip based on the current feedback value and the mechanical speed obtained from the test, and superimposes the slip and the mechanical speed to obtain the synchronous speed. The synchronous speed is then integrated to obtain the flux direction.

[0053] Step 140: Based on the relationship between flux and current and the glide difference equation, a simplified voltage loop equation is obtained, i.e., the variation law of the rotor-side q-axis flux and d-axis current in the synchronous coordinate system;

[0054] Step 150: The electromagnetic torque observer performs a differential operation on the fed-back stator-side d-axis current, uses the differential value as an inhomogeneous input to a simplified voltage loop equation, integrates the simplified voltage loop equation to obtain the rotor-side q-axis flux and the rotor-side d-axis current, substitutes the rotor-side d-axis current and the stator-side d-axis current into the flux-current relationship to obtain the rotor-side d-axis flux, and substitutes the stator-side d-axis current into the integral compensation scheme to obtain the stator-side q-axis current.

[0055] Step 160: Substitute the rotor-side q-axis flux, the rotor-side d-axis flux, the rotor-side d-axis current, and the stator-side q-axis current into the electromagnetic torque expression to obtain the electromagnetic torque including transient effects.

[0056] In this embodiment, the voltage loop equation is:

[0057]

[0058] Among them, R r is the rotor resistance, w e is the synchronous speed, w r is the mechanical speed, is the q-axis current on the rotor side, is the rotor side d-axis current, is the d-axis magnetic flux on the rotor side, is the q-axis flux on the rotor side, p is the time derivative, and the superscript e indicates that the reference coordinate system is the synchronous reference coordinate system.

[0059] In this embodiment, the relationship between magnetic flux and current is:

[0060]

[0061]

[0062] Among them, L r is the rotor self-inductance, L m is the rotor mutual inductance, is the stator side d-axis current, is the q-axis current on the stator side.

[0063] The downslope equation is:

[0064]

[0065] The simplified voltage loop equation is:

[0066]

[0067] In this embodiment, the electromagnetic torque expression is:

[0068] Among them, P N is the number of motor poles.

[0069] In this embodiment, the mathematical model is provided with maximum torque per ampere (MTPA) and maximum torque per volt (MTPV) modules. The reference excitation current and torque current are given by MTPA and MTPV, which can effectively balance the torque dynamic response performance, motor efficiency, and torque control function.

[0070] In this embodiment, the mathematical model is provided with a signal acquisition module and a motor speed calculation module. The signal acquisition module collects three-phase current, resolver voltage signal, CAN bus transceiver signal, etc. to ensure the basic conditions for algorithm implementation.

[0071] In this embodiment, a data integration module is provided in the mathematical model, which mainly includes basic data operation functions such as data integration, floating-point product and summation. The integration scheme can adopt the simplest trapezoidal integration scheme, and the integration accuracy meets the analysis requirements at a high sampling rate (not less than 5000Hz).

[0072] In this embodiment, the mathematical model is provided with a basic coordinate transformation module and a coordinate inverse transformation module. It includes a 3-phase stationary coordinate system to a 2-phase stationary coordinate system, corresponding to Figure 2 The 3s / 2s transformation module in the 2-phase stationary coordinate system transforms to the 2-phase rotating coordinate system, corresponding to Figure 2 The H(θ) transformation in the equation is the inverse transformation, which corresponds to Figure 2 H(θ)-1 in .

[0073] In this embodiment, the mathematical model is provided with a current regulator and a PWM module, as shown in the attached Figure 2 As shown in the figure, Rid represents the d-axis current regulator, which includes a conventional PI controller; Riq represents the q-axis current regulator, which also includes a conventional PI controller. The PWM module calculates the voltage vector based on the volt-second equivalence principle, controls the power module, and ultimately forms a closed loop with the actual asynchronous motor (M).

[0074] The above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art will appreciate that the technical solutions of the present invention may be modified or replaced with equivalents without departing from the spirit and scope of the technical solutions of the present invention, and such modifications or equivalents shall be encompassed by the claims of the present invention. Any techniques, shapes, and structures not described in detail herein are well known.

Claims

1. An online soft test method for transient torque of an asynchronous motor, characterized in that: include: S1: Establish the mathematical model of the system based on the voltage loop equation in the synchronous coordinate system on the rotor side of the squirrel cage asynchronous motor; S2: constructing an integrated observer in the mathematical model, wherein the integrated observer includes a flux direction observer and an electromagnetic torque observer; The relationship between the flux linkage and the current is: ； ； in, is the rotor self-inductance, is the rotor mutual inductance, is the stator side d-axis current, is the q-axis current on the stator side; The downslope equation is: ； The simplified voltage loop equation is: ； in, is the rotor resistance, is the synchronous speed, is the mechanical speed, is the q-axis current on the rotor side, is the rotor side d-axis current, is the d-axis magnetic flux on the rotor side, is the q-axis magnetic flux on the rotor side, To obtain the derivative with respect to time, the superscript e indicates that the reference frame is a synchronous reference frame; S3: The flux direction observer estimates the slip based on the current feedback value and the mechanical speed obtained by the test, and superimposes the slip and the mechanical speed to obtain the synchronous speed, and integrates the synchronous speed to obtain the flux direction; S4: Based on the relationship between flux and current, and the glide difference equation, the simplified voltage loop equation is obtained, that is, the variation law of the rotor side q-axis flux and d-axis current in the synchronous coordinate system; S5: The electromagnetic torque observer performs a differential operation on the fed-back stator-side d-axis current, uses the differential value as a non-homogeneous input of a simplified voltage loop equation, integrates the simplified voltage loop equation to obtain the rotor-side q-axis flux and the rotor-side d-axis current, substitutes the rotor-side d-axis current and the stator-side d-axis current into a flux-current relationship to obtain the rotor-side d-axis flux, and brings the stator-side d-axis current into an integral compensation scheme to obtain the stator-side q-axis current; S6: Substitute the rotor side q-axis flux, rotor side d-axis flux, rotor side d-axis current and stator side q-axis current into the electromagnetic torque expression to obtain the electromagnetic torque including transient effects.

2. The method for online soft testing of transient torque of an asynchronous motor according to claim 1, characterized in that: The voltage loop equation is: 。 3. The method for online soft testing of transient torque of an asynchronous motor according to claim 1, characterized in that: The electromagnetic torque expression is: ,in, is the number of motor poles.

4. The method for online soft testing of transient torque of an asynchronous motor according to claim 1, characterized in that: The mathematical model is provided with MTPA and MTPV modules.

5. The online soft testing method for transient torque of an asynchronous motor according to claim 1, characterized in that: The mathematical model is provided with a signal acquisition module and a motor speed calculation module.

6. The method for online soft testing of transient torque of an asynchronous motor according to claim 1, characterized in that: A data integration module is provided in the mathematical model.

7. The method for online soft testing of transient torque of an asynchronous motor according to claim 1, characterized in that: The mathematical model is provided with a basic coordinate transformation module and a coordinate inverse transformation module.

8. The online soft testing method for transient torque of an asynchronous motor according to claim 1, characterized in that: The mathematical model is provided with a current regulator and a PWM module.

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