A generator starting control method and device based on model predictive control

Abstract

The present application belongs to the technical field of aviation motor starting control, and particularly relates to a generator starting control method and device based on model predictive control. The method includes: collecting the speed at the current moment, and determining the stator current command value required for the electromagnetic torque at the current moment according to the given corresponding relationship between the starting speed and the torque; collecting the three-phase current of the generator at the current moment, and performing vector transformation to obtain the stator current in the synchronous rotating coordinate system at the current moment; for all possible output gate signal combinations, the corresponding voltage vector is given; for any voltage vector, the stator current at the next moment is predicted according to a given prediction model; for the multiple stator currents obtained at the next moment, the follow-up cost values ​​are calculated respectively, and the stator current with the smallest follow-up cost value is found; the corresponding gate signal combination is determined, and the three-phase bridge arm switch state is controlled by the gate signal combination. The present application improves the system torque output dynamics and simplifies the system composition.

Description

Technical Field

[0001] The present application belongs to the technical field of aviation motor starting control, and in particular relates to a generator starting control method and device based on model predictive control. Background Art

[0002] The current starting control method in the three-stage synchronous starter / generator system mostly adopts a speed control method based on a speed loop plus a current loop, which is designed to control the aviation three-stage synchronous starter / generator to drive the engine load to the engine ignition speed, the engine performs the ignition operation, and then continues to increase the speed to the disengagement speed, and the starting control process is completed. At this time, the engine is fully running, and as a prime mover, it drives the three-stage synchronous starter / generator to enter the power generation state. The advantage of speed control is that the control index is clear, that is, it drives the engine load to increase the speed to the disengagement speed. However, the torque output affected by the inner loop current loop depends on the outer loop command, which is difficult to adjust directly and quickly. Moreover, between the ignition speed point and the disengagement speed point, the engine gradually begins to output. At this time, the relationship between the output torque of the three-stage synchronous starter / generator in the starting state and the output torque of the engine is difficult to describe. Improper handling will cause torque fluctuations on the shaft, which is not conducive to the life of the system, and may even cause the shaft to break. In recent years, some engine manufacturers have proposed clear output torque index requirements for the starting system through detailed research and experimental testing of engine characteristics, and clarified the torque-speed correspondence and detailed indicators, such as Figure 1 The traditional starting control method based on speed control cannot adapt to the new dynamic and static requirements of torque output. Summary of the invention

[0003] In order to solve the above technical problems, the present application provides a generator starting control method and device based on model predictive control, which realizes dynamic control of the starting system torque by quickly predicting and outputting the torque current to meet the torque index requirements for engine starting.

[0004] The first aspect of the present application provides a generator starting control method based on model predictive control, which mainly includes:

[0005] Step S1, collecting the current speed, and determining the stator current command value required for the electromagnetic torque at the current moment according to the given corresponding relationship between the starting speed and the torque;

[0006] Step S2, collecting the three-phase current of the generator at the current moment, and performing vector transformation to obtain the stator current in the synchronous rotating coordinate system at the current moment;

[0007] Step S3, for all possible output gate signal combinations, corresponding voltage vectors are given, wherein each gate signal combination represents a three-phase bridge arm switch state;

[0008] Step S4: for any voltage vector, predict the stator current at the next moment according to a given prediction model;

[0009] Step S5, for the multiple stator currents obtained at the next moment, respectively calculate the following cost values ​​used to characterize the difference between the stator current at the next moment and the current command value at the current moment, and find the stator current with the smallest following cost value;

[0010] Step S6, determining a corresponding voltage vector according to the stator current with the smallest following cost value, and determining a corresponding gating signal combination according to the voltage vector, and controlling the switch state of the three-phase bridge arm with the gating signal combination.

[0011] Preferably, in step S3, the gating signal combinations include eight types.

[0012] Preferably, the prediction model comprises:

[0013] x e (k+1)=A e x e (k)+B e u e (k)+E e

[0014] in,

[0015] x e (k)=[i d (k) i q (k)] T

[0016] u e (k)=[u d (k) u q (k)] T

[0017]

[0018]

[0019]

[0020] Where, L is the stator inductance, R is the stator resistance, Ψ f is the magnetic flux value, ω e (k) is the electrical angular velocity of the rotor at time k.

[0021] Preferably, the stator inductance value, the stator resistance value and the flux linkage value are obtained through experiments, and the rotor electrical angular velocity is determined by the mechanical rotation speed.

[0022] Preferably, the following cost value is determined by a following cost function, and the following cost function is:

[0023]

[0024] Among them, i d * with i q * is the stator current command value required for the electromagnetic torque at the current moment, i d (k+1) and i q (k+1) is the stator current at the next moment.

[0025] The second aspect of the present application provides a generator starting control device based on model predictive control, which mainly includes:

[0026] The stator current command value determination module is used to collect the current speed and determine the stator current command value required for the electromagnetic torque at the current moment according to the corresponding relationship between the given starting speed and the torque;

[0027] The stator current determination module is used to collect the three-phase current of the generator at the current moment and perform vector transformation to obtain the stator current in the synchronous rotating coordinate system at the current moment;

[0028] A voltage vector calculation module is used to provide corresponding voltage vectors for all possible output gate signal combinations, wherein each gate signal combination represents a three-phase bridge arm switch state;

[0029] The stator current prediction module is used to predict the stator current at the next moment for any voltage vector according to a given prediction model;

[0030] A following cost calculation module is used to calculate the following cost value used to characterize the difference between the stator current at the next moment and the current command value at the current moment for the multiple stator currents obtained at the next moment, and find the stator current with the minimum following cost value;

[0031] The instruction selection module is used to determine the corresponding voltage vector according to the stator current with the smallest following cost value, and determine the corresponding gating signal combination according to the voltage vector, and control the switching state of the three-phase bridge arm with the gating signal combination.

[0032] Preferably, the prediction model comprises:

[0033] x e (k+1)=A e x e (k)+B e u e (k)+E e

[0034] in,

[0035] xe (k)=[i d (k) i q (k)] T

[0036] u e (k)=[u d (k) u q (k)] T

[0037]

[0038]

[0039]

[0040] Where, L is the stator inductance, R is the stator resistance, Ψ f is the magnetic flux value, ω e (k) is the electrical angular velocity of the rotor at time k.

[0041] Preferably, the stator inductance value, the stator resistance value and the flux linkage value are obtained through experiments, and the rotor electrical angular velocity is determined by the mechanical rotation speed.

[0042] Preferably, the following cost value is determined by a following cost function, and the following cost function is:

[0043]

[0044] Among them, i d * with i q * is the stator current command value required for the electromagnetic torque at the current moment, i d (k+1) and i q (k+1) is the stator current at the next moment.

[0045] The present application predicts the stator quadrature and direct axis currents after vector decoupling at the next sampling moment of the control system, and uses a preset cost function to compare a number of predicted values ​​with the expected instructions, and selects the control amount corresponding to the predicted value that best meets the expected current instruction to be output at the next sampling moment, which has the following advantages:

[0046] 1. This application aims at the new demand for aircraft engine starting, namely, clear torque-speed output correspondence and indicators, and comprehensively considers the torque control optimization method of the electrically excited synchronous motor in the three-stage starting / generating system, and provides a control method that does not require a speed controller, directly and accurately controls the torque current, thereby reducing the complexity of the system.

[0047] 2. The starting process of the aviation three-stage starting / generating system is itself a purely dynamic process. The model prediction starting control method proposed in this application has strong dynamics and is suitable for application in this working condition.

[0048] 3. The model prediction starting control method proposed in this application can predict the torque current and directly output the inverter switching signal, which on the one hand improves the system torque output dynamics; on the other hand, it eliminates the space voltage vector pulse width modulation (SVPWM) in the traditional starting control system and simplifies the system composition.

[0049] 4. The model prediction starting control method proposed in this application is essentially a discrete control method, which is suitable for digital implementation and debugging. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a typical torque-speed correspondence requirement diagram for engine starting in this application.

[0051] Figure 2 This is a schematic diagram of a typical three-phase two-level inverter structure of this application.

[0052] Figure 3 This is a starting control block diagram of this application based on model predictive control.

[0053] Figure 4 This is the output torque curve of the starting process of this application.

[0054] Figure 5 This is the speed curve diagram of the starting process of this application.

[0055] Figure 6 It is the three-phase current waveform during the starting process of this application. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical scheme and advantages of the implementation of this application clearer, the technical scheme in the implementation of this application will be described in more detail in combination with the drawings in the implementation of this application. In the drawings, the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The described implementation is a part of the implementation of this application, not all of the implementations. The implementation described below with reference to the drawings is exemplary and is intended to be used to explain this application, and cannot be understood as a limitation on this application. Based on the implementation in this application, all other implementations obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. The implementation of this application is described in detail below in combination with the drawings.

[0057] The first aspect of the present application provides a generator starting control method based on model predictive control, which mainly includes:

[0058] Step S1, collecting the current speed, and determining the stator current command value required for the electromagnetic torque at the current moment according to the given corresponding relationship between the starting speed and the torque;

[0059] Step S2, collecting the three-phase current of the generator at the current moment, and performing vector transformation to obtain the stator current in the synchronous rotating coordinate system at the current moment;

[0060] Step S3, for all possible output gate signal combinations, corresponding voltage vectors are given, wherein each gate signal combination represents a three-phase bridge arm switch state;

[0061] Step S4: for any voltage vector, predict the stator current at the next moment according to a given prediction model;

[0062] Step S5, for the multiple stator currents obtained at the next moment, respectively calculate the following cost values ​​used to characterize the difference between the stator current at the next moment and the current command value at the current moment, and find the stator current with the smallest following cost value;

[0063] Step S6, determining a corresponding voltage vector according to the stator current with the smallest following cost value, and determining a corresponding gating signal combination according to the voltage vector, and controlling the switch state of the three-phase bridge arm with the gating signal combination.

[0064] In step S1, by collecting the current speed, the control system is determined by using a table lookup method at the current moment. Figure 1 The stator current command value i required for the specified output corresponding to the electromagnetic torque d * and i q * .

[0065] like Figure 1 As shown, this implementation example only lists the requirements for the constant torque zone during the starting phase, and the principle of the constant power zone is similar. The starting speed-torque correspondence is set as:

[0066] 0r / min-412r / min: 27.2N·m;

[0067] 412r / min-1373r / min: 39.5N·m;

[0068] 1373r / min-2100r / min: 47.2N·m;

[0069] 2250r / min: 44.2N·m;

[0070] 2250r / min-3400r / min: 44.2N·m.

[0071] In step S2, the three-phase current i of the three-stage synchronous starter / generator is collected. A ,i B ,i C , perform CLARK and PARK transformations on it according to the vector transformation strategy, and obtain the stator current i in the synchronous rotating coordinate system at the current time k d (k) and i q (k).

[0072] In step S3, all voltage vectors to be predicted are established. For the most commonly used three-phase two-level inverter in AC starting and generating systems, such as Figure 2 As shown, at the next moment (time k+1), all possible output gate signal combinations correspond to 8 switch states and voltage vectors, as shown in the following table.

[0073]

[0074]

[0075] Among them, S a , S b , S c They are the switch states of the A, B, and C phase bridge arms, respectively, and the expressions are as follows:

[0076]

[0077]

[0078]

[0079] In step S4, the prediction model is used in turn to predict the current value at time k+1 for the eight voltage vectors (V0 to V7) to be predicted in step S3.

[0080] The prediction model includes:

[0081] x e (k+1)=A e x e (k)+B e u e (k)+E e

[0082] in,

[0083] x e (k)=[i d (k) i q (k)] T

[0084] u e (k)=[u d (k) uq (k)] T

[0085]

[0086]

[0087]

[0088] Where, L is the stator inductance, R is the stator resistance, Ψ f is the magnetic flux value, ω e (k) is the electrical angular velocity of the rotor at time k.

[0089] In some optional implementations, the stator inductance value, the stator resistance value and the flux linkage value are obtained through experiments, and the rotor electrical angular velocity is determined by the mechanical rotation speed.

[0090] This step can obtain 8 sets of predicted values ​​i of d and q axis currents at time k+1. d (k+1), i q (k+1), corresponding to the 8 voltage vectors in step S3 respectively.

[0091] In step S5, the optimal voltage vector is determined by the cost function. The design current following cost function is shown as follows:

[0092]

[0093] Substitute the 8 sets of current prediction values ​​in step 4 into the 8 cost function values, and replace the set of current prediction values ​​i with the smallest cost function value. d (k+1), i q The voltage vector corresponding to (k+1) is the optimal voltage vector.

[0094] Finally, the optimal voltage vector is outputted. At the next sampling time (time k+1) of the control system, the switch states of the A, B, and C phase bridge arms corresponding to the optimal voltage vector evaluated in step S5 are directly outputted.

[0095] Figure 4 is the electromagnetic torque waveform output by this method, Figure 5 is the motor speed waveform, Figure 6 It is the phase current waveform of the whole process. It can be seen from the figure that this method realizes the rapid torque output and speed increase of the three-stage synchronous motor according to the planned torque curve, and the current control effect is good, meeting the predetermined requirements.

[0096] The second aspect of the present application provides a generator starting control device based on model predictive control corresponding to the above method, mainly comprising:

[0097] The stator current command value determination module is used to collect the current speed and determine the stator current command value required for the electromagnetic torque at the current moment according to the corresponding relationship between the given starting speed and the torque;

[0098] The stator current determination module is used to collect the three-phase current of the generator at the current moment and perform vector transformation to obtain the stator current in the synchronous rotating coordinate system at the current moment;

[0099] A voltage vector calculation module is used to provide corresponding voltage vectors for all possible output gate signal combinations, wherein each gate signal combination represents a three-phase bridge arm switch state;

[0100] The stator current prediction module is used to predict the stator current at the next moment for any voltage vector according to a given prediction model;

[0101] A following cost calculation module is used to calculate the following cost value used to characterize the difference between the stator current at the next moment and the current command value at the current moment for the multiple stator currents obtained at the next moment, and find the stator current with the minimum following cost value;

[0102] The instruction selection module is used to determine the corresponding voltage vector according to the stator current with the smallest following cost value, and determine the corresponding gating signal combination according to the voltage vector, and control the switching state of the three-phase bridge arm with the gating signal combination.

[0103] In some optional embodiments, the prediction model includes:

[0104] x e (k+1)=A e x e (k)+B e u e (k)+E e

[0105] in,

[0106] x e (k)=[i d (k) i q (k)] T

[0107] u e (k)=[u d (k) u q (k)] T

[0108]

[0109]

[0110]

[0111] Where, L is the stator inductance, R is the stator resistance, Ψ f is the magnetic flux value, ω e (k) is the electrical angular velocity of the rotor at time k.

[0112] In some optional implementations, the stator inductance value, the stator resistance value and the flux linkage value are obtained through experiments, and the rotor electrical angular velocity is determined by the mechanical rotation speed.

[0113] In some optional implementations, the following cost value is determined by a following cost function, and the following cost function is:

[0114]

[0115] Among them, i d * with i q * is the stator current command value required for the electromagnetic torque at the current moment, i d (k+1) and i q (k+1) is the stator current at the next moment.

[0116] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A generator starting control method based on model predictive control, characterized in that: include: Step S1, collecting the current speed, and determining the stator current command value required for the electromagnetic torque at the current moment according to the given corresponding relationship between the starting speed and the torque; Step S2, collecting the three-phase current of the generator at the current moment, and performing vector transformation to obtain the stator current in the synchronous rotating coordinate system at the current moment; Step S3, for all possible output gate signal combinations, corresponding voltage vectors are given, wherein each gate signal combination represents a three-phase bridge arm switch state; Step S4: for any voltage vector, predict the stator current at the next moment according to a given prediction model; Step S5, for the multiple stator currents obtained at the next moment, respectively calculate the following cost values ​​used to characterize the difference between the stator current at the next moment and the current command value at the current moment, and find the stator current with the smallest following cost value; Step S6, determining a corresponding voltage vector according to the stator current with the smallest following cost value, and determining a corresponding gating signal combination according to the voltage vector, and controlling the switch state of the three-phase bridge arm with the gating signal combination; Wherein, the prediction model includes: x e (k+1)=A e x e (k)+B e u e (k)+E e in, x e (k)=[i d (k)i q (k)] T in e (k)=[u d (to) q (k)] T Where, L is the stator inductance, R is the stator resistance, Ψ f is the magnetic flux value, ω e (k) is the electrical angular velocity of the rotor at time k; The following cost value is determined by a following cost function, and the following cost function is: Among them, i d * with i q * is the stator current command value required for the electromagnetic torque at the current moment, i d (k+1) and i q (k+1) is the stator current at the next moment.

2. The generator starting control method based on model predictive control according to claim 1, characterized in that: In step S3, the gating signal combinations include eight types.

3. The generator starting control method based on model predictive control according to claim 1, characterized in that: The stator inductance value, stator resistance value and flux linkage value are obtained through experiments, and the rotor electrical angular velocity is determined by the mechanical rotation speed.

4. A generator starting control device based on model predictive control, characterized in that: include: The stator current command value determination module is used to collect the current speed and determine the stator current command value required for the electromagnetic torque at the current moment according to the corresponding relationship between the given starting speed and the torque; The stator current determination module is used to collect the three-phase current of the generator at the current moment and perform vector transformation to obtain the stator current in the synchronous rotating coordinate system at the current moment; A voltage vector calculation module is used to provide corresponding voltage vectors for all possible output gate signal combinations, wherein each gate signal combination represents a three-phase bridge arm switch state; The stator current prediction module is used to predict the stator current at the next moment for any voltage vector according to a given prediction model; A following cost calculation module is used to calculate the following cost value used to characterize the difference between the stator current at the next moment and the current command value at the current moment for the multiple stator currents obtained at the next moment, and find the stator current with the minimum following cost value; An instruction selection module is used to determine a corresponding voltage vector according to a stator current with a minimum follow-up cost value, and to determine a corresponding gate signal combination according to the voltage vector, and to control the switch state of the three-phase bridge arm with the gate signal combination; Wherein, the prediction model includes: x e (k+1)=A e x e (k)+B e u e (k)+E e in, x e (k)=[i d (k) i q (k)] T in e (k)=[u d (k) in q (k)] T Where, L is the stator inductance, R is the stator resistance, Ψ f is the magnetic flux value, ω e (k) is the electrical angular velocity of the rotor at time k; The following cost value is determined by a following cost function, and the following cost function is: Among them, i d * with i q * is the stator current command value required for the electromagnetic torque at the current moment, i d (k+1) and i q (k+1) is the stator current at the next moment.

5. The generator starting control device based on model predictive control according to claim 4, characterized in that: The stator inductance value, stator resistance value and flux linkage value are obtained through experiments, and the rotor electrical angular velocity is determined by the mechanical rotation speed.

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