Predictive starting control method for aviation three-stage motor based on cascade coupling structure

Abstract

The application discloses a kind of aviation three-stage motor predictive starting control methods based on cascade coupling structure, by constructing the rotor current observer of exciter and stator current prediction model;Obtain the rotor terminal voltage, flux linkage and current information of exciter at current time, and predict the stator current of exciter at next time;According to the electromagnetic coupling relationship between main motor and exciter, obtain the rotor excitation current value of main motor at current time and the rotor excitation current prediction value at next time;According to the mathematical model of main motor, obtain the stator current prediction value of main motor at next time;By designing excitation control cost function and main motor control cost function, the excitation control of exciter and main motor is carried out respectively.Thus, by observer construction to consider the coupling between main motor and exciter, the problem that existing model predictive control method cannot be directly applied is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of alternating current motor control technology, and particularly relates to a cascade coupling structure-based aviation three-stage motor predictive starting control method. BACKGROUND

[0002] Starting / generating integrated technology as a key technology of more electric aircraft (MEA) has the core idea of using the reversible principle of the motor. Compared with the traditional starting mode, the starting / generating integrated technology cancels the traditional special starter, and instead makes the on-board generator run in the motor mode to start the engine; after the starting is completed, the on-board generator is switched to the generating mode to supply power to the on-board electrical equipment. The starting / generating integrated technology simplifies the accessory case and bleed air device of the engine, reduces the "dead weight" of the aircraft, and improves the reliability, maintainability and energy efficiency of the aircraft.

[0003] Three-stage starting / generating integrated technology is developed on the basis of three-stage generating technology. The existing three-stage generating system is usually composed of a main motor, an exciter, a sub-exciter and a rotating rectifier which are coaxially installed. Since the sub-exciter can only provide excitation current for the exciter when the system rotates, it does not participate in the starting process. In addition, the exciter of the three-stage motor in the generating mode is a direct current excitation mode. When the system is stationary or operates at low speed, even if a direct current is passed through the stator winding of the exciter through an external power supply, the main motor still cannot run in the motor mode. Therefore, the excitation problem of the main motor at zero or low speed is the key to realizing the three-stage starting / generating integrated function.

[0004] The active excitation control scheme with the exciter inverter has the advantages of high excitation regulation efficiency and good flexibility, and the structure can truly realize the collaborative optimization control of the main motor and the exciter. In recent years, the model predictive control method has received high attention in the field of alternating current motor control. This method has the advantages of good dynamic characteristics and simple operation. However, due to the special cascade coupling structure of the three-stage motor, combined with the fact that the rotor-side signals cannot be directly measured, the traditional model predictive control method cannot be directly used in the starting collaborative control of the three-stage motor. The model predictive control method which simplifies the main motor as a permanent magnet motor cannot consider the coupling between the motors, so it cannot truly realize the excitation current control. SUMMARY

[0005] The embodiment of the present application provides a cascade coupling structure-based aviation three-stage motor predictive starting control method. The coupling between the main motor and the exciter is considered through an observer, so that the problem that the existing model predictive control method cannot be directly applied can be solved.

[0006] To achieve the above object, the technical scheme of the embodiment of the present application is:

[0007] In the first aspect, the embodiment of the present application provides a cascade coupling structure-based aviation three-stage motor predictive starting control method, comprising: obtaining three-phase currents of stators of a three-stage main motor and an exciter in a three-phase stationary coordinate system respectively; constructing a rotor current observer of the exciter according to three-phase currents of the exciter stator and a mathematical model of the exciter to obtain an observed value of rotor current of the exciter at a current time; converting the three-phase currents of the exciter stator to a two-phase stationary coordinate system according to a preset first vector transformation strategy, thereby constructing a stator current prediction model of the exciter, and predicting the stator current of the exciter at a next time of the current time; converting the predicted value of the stator current of the exciter at the next time to the three-phase stationary coordinate system according to a preset second vector transformation strategy, and constructing a rotor excitation current prediction model of the main motor according to an electromagnetic coupling relationship between the main motor and the exciter, to obtain a predicted value of rotor excitation current of the main motor at the next time; converting the three-phase currents of the main motor stator to a two-phase rotating coordinate system according to a preset third vector transformation strategy, to obtain the stator current of the main motor in the two-phase rotating coordinate system at the current time; constructing a stator current prediction model of the main motor according to the stator current of the main motor in the two-phase rotating coordinate system at the current time and the mathematical model of the main motor, to obtain a predicted value of the stator current of the main motor at the next time; designing an excitation control cost function of the exciter inverter according to the predicted value of the rotor excitation current of the main motor at the next time; and designing a main motor control cost function of the main motor inverter according to the predicted value of the stator current of the main motor at the next time; predicting a first optimal voltage vector of the exciter inverter according to the excitation control cost function, and driving the exciter inverter to perform predictive control on the exciter through the first optimal voltage vector; predicting a second optimal voltage vector of the main motor inverter according to the main motor control cost function, and driving the main motor inverter to perform predictive control on the main motor through the second optimal voltage vector.

[0008] In some possible implementation manners, the rotor current observer of the exciter is constructed according to the three-phase currents of the exciter stator and the mathematical model of the exciter, and the observed value of the rotor current of the exciter at the current time is obtained, comprising:

[0009] The rotor current observer of the exciter is constructed according to the stator voltage, the stator flux linkage equation and the rotor current characteristic of the exciter;

[0010] The stator voltage of the exciter is expressed as:

[0011]

[0012] The stator flux linkage equation of the exciter is expressed as:

[0013]

[0014] The rotor current characteristics of the exciter machine include:

[0015] i ra +i rb +i rc = 0;

[0016] wherein u A , u B and u C are the terminal voltages of the three-phase stator winding of the exciter machine, i sA , i sB and i sC are the three-phase currents of the stator of the exciter machine, i ra , i rb and i rc are the three-phase currents of the rotor of the exciter machine, and are the three-phase fluxes of the stator of the exciter machine, R se is the phase resistance of the stator winding of the exciter machine, L se is the total self-inductance of the stator winding of the exciter machine, M sr is the mutual inductance amplitude of the stator and rotor windings of the exciter machine, and θ r is the rotor position of the exciter machine;

[0017] According to the rotor current observer of the exciter machine, an estimated expression of the rotor current of the exciter machine in a three-phase stationary coordinate system is determined, and the estimated expression of the rotor current of the exciter machine is expressed as:

[0018]

[0019] wherein A1 is a C-phase calculation factor, and A2 is a B-phase calculation factor;

[0020] According to the estimated expression of the rotor current of the exciter machine, an observed value of the rotor current of the exciter machine at the current time is determined.

[0021] In some possible implementation manners, a stator current prediction model of the exciter machine is constructed, and the stator current of the exciter machine at the next time is predicted at the current time, including:

[0022] Based on the mathematical equation of the exciter machine, the rotor flux and the rotor terminal voltage of the exciter machine at the current time are observed in a two-phase stationary coordinate system;

[0023] wherein the rotor flux of the exciter machine is expressed as:

[0024]

[0025] The rotor terminal voltage of the exciter machine is expressed as:

[0026]

[0027] wherein, is the rotor flux of the exciter, L r is the self-inductance of the exciter rotor winding, i s is the stator current of the exciter, L m is the mutual inductance of the exciter rotor winding, i r is the rotor current of the exciter; V r is the rotor terminal voltage of the exciter, R r is the phase resistance of the exciter rotor winding, is a differential operator, j is an imaginary unit, w is a rotor electrical angular velocity, and k represents a current time;

[0028] According to the stator current expression of the exciter and forward Euler discretization, an exciter stator current prediction model is constructed, and a current prediction value of the exciter stator at a next time is obtained through the exciter stator current prediction model; wherein the exciter stator current prediction model is expressed as:

[0029]

[0030] wherein, k+1 represents a next time of a current time, i s (k+1) is a current prediction value of the stator current of the exciter at a next time of a current time, T s is a sampling time of the system, k r is a magnetic coupling factor, R σ is an equivalent resistance, and σ is a leakage coefficient, τ r is a rotor time constant, τ σ is an instantaneous time constant, V s is an exciter stator terminal voltage.

[0031] In some possible implementation manners, according to an electromagnetic coupling relationship between the main motor and the exciter, a rotor excitation current prediction model of the main motor is constructed, and a rotor excitation current prediction value of the main motor at a next time is obtained, including:

[0032] The electromagnetic coupling relationship is expressed as:

[0033] |i ra |+|i rb |+|i rc |=2i f ;

[0034] wherein, i f is a main motor rotor excitation current value;

[0035] According to the electromagnetic coupling relationship and the observation result of the exciter rotor current observer, a rotor excitation current value of the main motor at the current time is obtained, which is represented as:

[0036]

[0037] wherein, i f (k) is the rotor excitation current value of the main motor at the current time, i ra (k) is the rotor excitation current value of the main motor at the current time, i rb (k) is the rotor excitation current value of the main motor at the current time, i rc (k) are three-phase current observation values of the exciter rotor at the current time, respectively.

[0038] According to the exciter rotor current observer and the stator current prediction value of the exciter at the next time, the rotor current of the exciter at the next time is predicted.

[0039] According to the electromagnetic coupling relationship and the rotor current prediction value of the exciter at the next time, a rotor excitation current prediction value of the main motor at the next time is determined; the rotor excitation current prediction value of the main motor at the next time is represented as:

[0040]

[0041] wherein, i f (k+1) is the rotor excitation current prediction value of the main motor at the next time at the current time, i ra (k+1) is the rotor excitation current prediction value of the main motor at the next time at the current time, i rb (k+1) is the rotor excitation current prediction value of the main motor at the next time at the current time, i rc (k+1) are three-phase current prediction values of the exciter rotor at the next time, respectively.

[0042] In some possible implementation manners, according to the stator current of the main motor in the two-phase rotating coordinate system at the current time and the mathematical model of the main motor, a stator current prediction model of the main motor is constructed to obtain the stator current prediction value of the main motor at the next time, including:

[0043] According to the model of the electrically excited synchronous motor, a voltage and flux linkage equation of the main motor is established;

[0044] wherein, the voltage equation of the main motor is represented as:

[0045]

[0046] wherein, u d is the d-axis voltage of the main motor stator, u q is the q-axis voltage of the main motor stator, u f is the rotor excitation winding voltage of the main motor, R sm is the stator resistance value of the main motor, R f is the rotor excitation winding resistance value of the main motor, i dis the d-axis current of the main motor stator, q is the q-axis current of the main motor stator, f is the rotor excitation current of the main motor, is the d-axis flux linkage of the main motor stator, is the q-axis flux linkage of the main motor stator, is the rotor excitation flux linkage of the main motor, e is the electrical angular velocity of the main motor,

[0047] The flux linkage equation of the main motor is represented as:

[0048]

[0049] wherein, L d is the d-axis equivalent inductance of the main motor stator winding, q is the q-axis equivalent inductance of the main motor stator winding, md is the mutual inductance between the d-axis equivalent inductance of the main motor stator winding and the rotor winding, f is the self-inductance of the excitation winding of the main motor,

[0050] The forward Euler discretization formula is applied to the voltage equation of the main motor to obtain the predicted value of the stator current of the main motor at the next time, which is represented as:

[0051]

[0052] wherein, i d is the d-axis current of the main motor stator at the k+1 time, q is the q-axis current of the main motor stator at the k+1 time.

[0053] In some possible implementations, the excitation control cost function under the constant excitation control mode is represented as:

[0054]

[0055] The main motor control cost function is represented as:

[0056]

[0057] wherein, g e is the excitation control cost function, g m is the main motor control cost function, is the rotor excitation current reference of the main motor, is the d-axis current reference of the main motor, is the q-axis current reference of the main motor.

[0058] In some possible implementations, according to the excitation control cost function, the first optimal voltage vector of the excitation machine inverter is predicted, including:

[0059] The exciter control cost function is used to evaluate a plurality of switch vector states of the exciter inverter, and a first optimal voltage vector is determined from voltage vectors corresponding to the plurality of switch vector states.

[0060] According to the main motor control cost function, a second optimal voltage vector of the main motor inverter is predicted, including:

[0061] The main motor control cost function is used to evaluate a plurality of switch vector states of the main motor inverter, and a second optimal voltage vector is determined from voltage vectors corresponding to the plurality of switch vector states.

[0062] The one or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0063] The prediction starting control method for the aviation three-stage motor based on the cascade coupling structure provided in the embodiments of the present application fully considers the cascade coupling structure of the three-stage motor by constructing an observer to consider the coupling between the main motor and the exciter, and realizes the model prediction collaborative starting control of the excitation current and the main motor, thereby making up for the technical problem that the traditional model prediction control method cannot be directly used for the collaborative starting control of the three-stage motor. DETAILED DESCRIPTION

[0064] In order to more clearly illustrate the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0065] Figure 1 It is a typical three-stage power generation system structure schematic diagram;

[0066] Figure 2 It is a three-stage motor starting control system structure diagram based on the existing three-phase active excitation structure;

[0067] Figure 3 It is an embodiment flowchart of the prediction starting control method for the aviation three-stage motor based on the cascade coupling structure provided in the embodiments of the present application;

[0068] Figure 4 It is a principle diagram of the prediction starting control method for the aviation three-stage motor based on the cascade coupling structure provided in the embodiments of the present application;

[0069] Figure 5 It is a structure schematic diagram of the three-phase two-level excitation inverter in the embodiments of the present application. DETAILED DESCRIPTION

[0070] With reference to the drawings, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort are within the protection scope of the present application.

[0071] In the related description of the embodiments, the terms "comprise, contain, have" and the like are open terms, which are generally preferred to be understood as including but not limited to; the term "at least one" is generally preferred to be understood as one or more, wherein "more" refers to two or more; the term "at least one of the following" or similar expressions refers to any combination of the terms, including any combination of single or multiple terms, for example, "at least one of a, b or c", or "at least one of a, b and c", which can represent a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, wherein a, b, and c can be single or multiple; the symbol "A / B" is used to describe the selection relationship of the associated objects, which generally represents the relationship of "or".

[0072] In the following description of the embodiments of the present application, the terms used in the embodiments of the present application are only for the purpose of describing the specific embodiments, and are not intended to limit the present application. The singular forms "a" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0073] Those skilled in the art should understand that in the following description of the embodiments of the present application, the order of the serial numbers does not mean the order of execution, and some or all steps can be executed in parallel or in sequence, and the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0074] Those skilled in the art should understand that the numerical ranges in the embodiments of the present application should be understood as also specifically disclosing each intermediate value between the upper limit and the lower limit of the range. Each smaller range between any stated value or stated range of values and any other stated value or stated range of values is also included within the present application. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0075] Technical / scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this application belongs unless otherwise indicated. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, preferred methods and materials are described. All publications mentioned in this specification are herein incorporated by reference to disclose and describe the methods and / or materials in connection with which the publications are cited. In case of conflict between the content of the specification and that of any incorporated literature, the content of the specification controls.

[0076] To illustrate the technical solutions of the present application, specific examples are described below.

[0077] The start / generate integrated technology is a key technology of the more electric aircraft (MEA), and its core idea is to use the reversible principle of the motor. Compared with the traditional starting method, the start / generate integrated technology cancels the traditional special starter, and instead uses the on-board generator to run in the motor mode to start the engine; after the starting is completed, the on-board generator is switched to the power generation mode to supply power to the on-board electrical equipment. The start / generate integrated technology simplifies the accessory case and the bleed air device of the engine, reduces the "dead weight" of the aircraft, and improves the reliability, maintainability and energy efficiency of the aircraft.

[0078] The three-stage start / generate integrated technology is developed on the basis of the three-stage power generation technology. For example Figure 1 is a typical three-stage power generation system structure diagram, which is composed of a main motor, an excitation motor, a sub-excitation motor and a rotating rectifier installed coaxially. Since the sub-excitation motor can only provide excitation current for the excitation motor when the system rotates, it does not participate in the starting process. In addition, the excitation motor of the three-stage motor in the power generation mode is a direct current excitation mode, and when the system is stationary or operates at low speed, even if a direct current is passed through the stator winding of the excitation motor through an external power source, the main motor still cannot be operated electrically. Therefore, the excitation problem of the main motor at zero or low speed stage is the key to realize the three-stage start / generate integrated function.

[0079] The active excitation control scheme with the excitation motor inverter has the advantages of high excitation regulation efficiency and good flexibility. The structure can truly realize the cooperative optimization control of the main motor and the excitation motor. For example Figure 2 is shown, Figure 2 is a three-stage motor starting control system structure diagram based on the existing three-phase active excitation structure.

[0080] In recent years, the model predictive control method has been highly concerned in the field of AC motor control, which has the advantages of good dynamic characteristics and simple operation. However, due to the special cascade coupling structure of the three-stage motor, combined with the fact that the rotor side signal cannot be directly measured, the traditional model predictive control method cannot be directly used in the starting cooperative control of the three-stage motor. The model predictive control method which simplifies the main motor as a permanent magnet motor cannot consider the coupling between the motors, so it cannot truly realize the excitation current control.

[0081] Based on this, the embodiment of the application provides a kind of aviation three-stage motor predictive starting control method based on cascade coupling structure, by observer construction to consider the coupling between main motor and exciter, it can solve the problem that existing model predictive control method cannot be directly applied.

[0082] Figure 3 For the embodiment of the application, an embodiment flowchart of the aviation three-stage motor predictive starting control method based on cascade coupling structure is provided, as shown in Figure 3 The method can include the following steps:

[0083] S301, the three-phase currents of the stators of the three-stage main motor and the exciter in the three-phase stationary coordinate system are acquired respectively;

[0084] The three-phase currents in the three-phase stationary coordinate system (i.e., abc coordinate system) can be measured by any existing sensor or monitoring device.

[0085] S302, a rotor current observer of the exciter is constructed according to the three-phase currents of the stator of the exciter and the mathematical model of the exciter, and the rotor current observation value of the exciter at the current time is obtained;

[0086] In some embodiments, the step S302 can include the following steps:

[0087] The rotor current observer of the exciter is constructed according to the stator voltage, the stator flux linkage equation and the rotor current characteristics of the exciter;

[0088] In the embodiment of the application, the stator voltage of the exciter can be represented as:

[0089]

[0090] The stator flux linkage equation of the exciter can be represented as:

[0091]

[0092] The rotor current characteristics of the exciter can be represented as:

[0093] i ra +i rb +irc = 0;

[0094] wherein, u A , u B and u C are the terminal voltages of the three-phase stator winding of the exciter, i sA , i sB and i sC are the three-phase currents of the stator of the exciter, i ra , i rb and i rc are the three-phase currents of the rotor of the exciter, and are the three-phase fluxes of the stator of the exciter, R se is the phase resistance of the stator winding of the exciter, L se is the total self-inductance of the stator winding of the exciter, M sr is the mutual inductance amplitude of the stator and rotor windings of the exciter, and θ r is the position of the rotor of the exciter.

[0095] Based on the rotor current observer constructed according to the above steps, the rotor current estimation expression of the exciter in the three-phase stationary coordinate system is further determined.

[0096] For example, the rotor current estimation expression of the exciter can be expressed as:

[0097]

[0098] wherein, A1 is the calculation factor of phase C, and A2 is the calculation factor of phase B.

[0099] After the rotor current estimation expression of the exciter is determined, the rotor current value of the exciter can be calculated based on the expression, so as to determine the rotor current observation value of the exciter at the current time.

[0100] S303, according to the preset first vector transformation strategy, the three-phase stator currents of the exciter are converted to the two-phase stationary coordinate system, so as to construct a stator current prediction model to predict the stator currents of the exciter at the next time from the current time.

[0101] In some embodiments, the vector transformation strategy can be a specific mathematical formula or algorithm, such as Clarke transformation, etc. Taking Clarke transformation as an example, three-phase current can be directly converted from abc coordinate system to two-phase stationary coordinate system (or two-phase rotating coordinate system) through Clarke transformation. The specific manner of the first vector transformation strategy and the subsequent second vector transformation strategy and third vector transformation strategy can be selected according to actual needs, as long as the coordinate system conversion can be completed, and the embodiments of the present application do not make specific limitations thereon. Through coordinate conversion, the stator current can be represented and analyzed in a simpler manner, which is convenient for further control and processing.

[0102] Specifically, the step S303 can include:

[0103] Based on the mathematical equation of the exciter, the rotor flux and the rotor terminal voltage of the exciter at the current time are observed in the two-phase stationary coordinate system.

[0104] In some embodiments, the rotor flux of the exciter can be expressed as:

[0105]

[0106] The rotor terminal voltage of the exciter can be expressed as:

[0107]

[0108] wherein, is the rotor flux of the exciter, L r is the self-inductance of the exciter rotor winding, i s is the stator current of the exciter, L m is the mutual inductance of the exciter rotor winding, i r is the rotor current of the exciter; is the rotor terminal voltage of the exciter, R r is the rotor terminal voltage of the exciter, R r is the phase resistance of the exciter rotor winding, is the differential operator, j is the imaginary unit, w is the rotor electrical angular velocity, and k represents the current time.

[0109] Further, according to the stator current expression of the exciter and the forward Euler discretization method, an exciter stator current prediction model can be further constructed.

[0110] The exciter stator current value is predicted through the constructed exciter stator current prediction model, and the current prediction value of the exciter stator at the next time can be obtained.

[0111] In some embodiments, the exciter stator current prediction model can be expressed as:

[0112]

[0113] wherein k+1 represents the next time instant of the current time instant, i s (k+1) is the stator current prediction value of the exciter at the next time instant of the current time instant, T s is the sampling time of the system, k r is the magnetic coupling factor, R σ is the equivalent resistance, and σ is the leakage coefficient, τ r is the rotor time constant, τ σ is the transient time constant, V s is the exciter stator terminal voltage.

[0114] S304, according to the preset second vector transformation strategy, the predicted value of the stator current of the exciter at the next time instant is converted to the three-phase stationary coordinate system, and a rotor excitation current prediction model of the main motor is constructed according to the electromagnetic coupling relationship between the main motor and the exciter, to obtain the rotor excitation current prediction value of the main motor at the next time instant;

[0115] In some embodiments, the electromagnetic coupling relationship between the main motor and the exciter can be represented as:

[0116] |i ra |+|i rb |+|i rc |=2i f ;

[0117] wherein i f is the rotor excitation current value of the main motor.

[0118] Based on the same concept, the rotor excitation current value of the main motor at the current time instant can be obtained by the rotor current value of the exciter at the current time instant obtained by the above exciter rotor current observer, which can be represented by the following formula:

[0119]

[0120] wherein i f (k) is the rotor excitation current value of the main motor at the current time instant, i ra (k), i rb (k), i rc (k) are the three-phase current observation values of the rotor of the exciter at the current time instant, respectively.

[0121] According to the exciter rotor current observer and the predicted value of the stator current of the exciter at the next time instant, the rotor current of the exciter at the next time instant is predicted.

[0122] According to the electromagnetic coupling relationship and the rotor current prediction value of the exciter at the next moment, the rotor excitation current prediction value of the main motor at the next moment is determined;

[0123] For example, the rotor excitation current prediction value of the main motor rotor at the next moment can be represented as:

[0124]

[0125] Wherein, i f (k+1) is the rotor excitation current prediction value of the main motor at the next moment, i ra (k+1), i rb (k+1), i rc (k+1) are the three-phase current prediction values of the rotor of the exciter at the next moment.

[0126] S305, according to the preset third vector transformation strategy, the stator three-phase current of the main motor is converted to the two-phase rotating coordinate system, and the stator current of the main motor at the current moment in the two-phase rotating coordinate system is obtained;

[0127] S306, according to the stator current of the main motor at the current moment in the two-phase rotating coordinate system and the mathematical model of the main motor, a stator current prediction model of the main motor is constructed, and a stator current prediction value of the main motor at the next moment is obtained;

[0128] The mathematical model of the main motor usually includes voltage equation, flux linkage equation, torque equation and mechanical motion equation. For stator current prediction, the voltage equation and the flux linkage equation are mainly concerned because they are the basis of current change. Therefore, in the embodiment of the application, the stator current prediction model of the main motor can include the voltage and flux linkage equations of the main motor.

[0129] In some embodiments, the voltage equation of the main motor can be represented as:

[0130]

[0131] Wherein, u d is the main motor stator d-axis voltage, u q is the main motor stator q-axis voltage, u f is the main motor rotor excitation winding voltage, R sm is the main motor stator resistance value, R f is the main motor rotor excitation winding resistance value, i d is the main motor stator d-axis current, i q is the main motor stator q-axis current, i f is the main motor rotor excitation current, is the main motor stator d-axis flux linkage, is the main motor stator q-axis flux linkage, is the rotor flux linkage of the main motor, w e is the electrical angular velocity of the main motor;

[0132] The flux equation of the main motor can be expressed as:

[0133]

[0134] wherein, L d is the equivalent inductance of the d-axis stator winding of the main motor, L q is the equivalent inductance of the q-axis stator winding of the main motor, L md is the mutual inductance between the equivalent inductance of the d-axis stator winding of the main motor and the rotor winding, L f is the self-inductance of the excitation winding of the main motor;

[0135] Then, the forward Euler discretization formula can be applied to the voltage equation of the main motor to obtain the stator current prediction value of the main motor at the next time, which can be expressed as:

[0136]

[0137] wherein, i d is the stator d-axis current of the main motor at the k+1 time, i q is the stator q-axis current of the main motor at the k+1 time.

[0138] S307, according to the rotor current prediction value of the main motor at the next time, designing the excitation control cost function of the excitation machine inverter; and according to the stator current prediction value of the main motor at the next time, designing the main motor control cost function of the main motor inverter;

[0139] In some embodiments, the excitation control cost function in the constant excitation control mode can be expressed as:

[0140]

[0141] The constant excitation control mode refers to keeping the size and direction of the excitation current unchanged for a period of time to maintain the stable operation of the device. In the constant excitation control mode, the excitation control system will automatically adjust the size of the excitation current according to the operating state of the device and the preset control target, so as to keep the device stable in the rated operating condition. Specifically, when the load of the device changes, the excitation control system will detect and respond to these changes by adjusting the excitation current to keep the output voltage, current or power factor and other parameters of the device stable.

[0142] The main motor control cost function can be expressed as:

[0143]

[0144] wherein, ge is a field control cost function, g m is a main motor control cost function, is a main motor rotor field current reference, is a main motor d-axis current reference, is a main motor q-axis current reference.

[0145] S308, according to the excitation control cost function, the first optimal voltage vector of the excitation machine inverter is predicted, and the excitation machine is controlled by driving the excitation machine inverter through the first optimal voltage vector; according to the main motor control cost function, the second optimal voltage vector of the main motor inverter is predicted, and the main motor is controlled by driving the main motor inverter through the second optimal voltage vector.

[0146] Wherein, according to the excitation control cost function, the first optimal voltage vector of the excitation machine inverter is predicted, including:

[0147] The multiple switch vector states of the excitation machine inverter are evaluated through the excitation control cost function, and the first optimal voltage vector is determined from the voltage vectors corresponding to the multiple switch vector states;

[0148] According to the main motor control cost function, the second optimal voltage vector of the main motor inverter is predicted, including:

[0149] The multiple switch vector states of the main motor inverter are evaluated through the main motor control cost function, and the second optimal voltage vector is determined from the voltage vectors corresponding to the multiple switch vector states.

[0150] The method provided by the embodiment of the application fully considers the cascade coupling structure of the three-stage motor, realizes the model predictive collaborative starting control of the excitation current and the main motor, and makes up for the technical problem that the traditional model predictive control method cannot be directly used for three-stage motor collaborative starting control.

[0151] The method provided by the embodiment of the application will be described below with a specific embodiment.

[0152] Figure 4 The method provided by the embodiment of the application is a cascade coupling structure based aviation three-stage motor predictive starting control method principle diagram. Referring to Figure 4As shown, by collecting the exciter stator current information and the main motor stator current respectively, the corresponding three-phase currents in the three-phase stationary coordinate system are obtained; the exciter stator three-phase current is converted to the two-phase stationary coordinate system through coordinate transformation, the stator current of the exciter in the two-phase stationary coordinate system is obtained, and the rotor flux and the rotor open circuit terminal voltage are calculated respectively through the rotor current observer of the exciter constructed, and then based on the rotor flux and the rotor open circuit terminal voltage, the stator current at the next moment is predicted through the stator current prediction model. Then, the stator current at the next moment is converted to the three-phase stationary coordinate system through coordinate transformation again, and then based on the electromagnetic coupling relationship between the main motor and the exciter, the rotor current value of the main motor at the next moment is predicted according to the rotor current value at the current moment and the rotor current prediction value at the next moment of the exciter. Then, the stator three-phase current of the main motor is further converted to the two-phase rotating coordinate system, and the stator current prediction value of the main motor at the next moment is determined according to the mathematical model of the main motor and the rotor current prediction value at the current moment of the main motor, so as to construct the excitation control cost function and the main motor control cost function respectively. Finally, the switching vector state of the inverter is selected according to the cost function, and the optimal switching vector is output to drive the corresponding inverter, so as to realize the control of the main motor and the exciter.

[0153] In the embodiment of the application, the above-mentioned main motor inverter and exciter inverter can be three-phase two-level excitation inverters, for example, Figure 5 The structure of the three-phase two-level excitation inverter in the embodiment of the application is shown in the schematic diagram, which includes three switching states A, B and C, and can form eight switching vector states in total, each switching state having a corresponding output voltage vector. Specifically, it can be as shown in Table 1 below:

[0154] Table 1:

[0155]

[0156] Among them, S a , S b , S c respectively represent the conduction state of each phase upper arm, "1" represents opening, "0" represents closing, and V0 to V7 respectively represent the output voltage vector corresponding to each switching state.

[0157] Each embodiment in the specification is described in a progressive manner, and the same or similar parts between each embodiment can be referred to each other, and each embodiment mainly explains the difference from other embodiments.

[0158] The above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can still be modified, or some or all of the technical features thereof can be replaced by equivalents; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.

Claims

1. A predictive starting control method for a three-stage aerospace motor based on a cascaded coupling structure, characterized in that, include: The three-phase currents of the stator of the three-stage main motor and the exciter in the three-phase stationary coordinate system are obtained respectively. Based on the three-phase current of the exciter stator and the mathematical model of the exciter, a rotor current observer of the exciter is constructed to obtain the observed value of the rotor current of the exciter at the current moment. According to the preset first vector transformation strategy, the stator three-phase current of the exciter is transformed into a two-phase stationary coordinate system, thereby constructing a stator current prediction model of the exciter and predicting the stator current of the exciter at the next moment of the current moment. According to the preset second vector transformation strategy, the predicted value of the stator current of the exciter at the next moment is transformed into the three-phase stationary coordinate system, and according to the electromagnetic coupling relationship between the main motor and the exciter, the rotor excitation current prediction model of the main motor is constructed to obtain the predicted value of the rotor excitation current of the main motor at the next moment. According to the preset third vector transformation strategy, the stator three-phase current of the main motor is transformed into a two-phase rotating coordinate system to obtain the stator current of the main motor in the two-phase rotating coordinate system at the current moment. Based on the stator current of the main motor in the two-phase rotating coordinate system at the current moment and the mathematical model of the main motor, a stator current prediction model of the main motor is constructed to obtain the predicted value of the stator current of the main motor at the next moment. Based on the predicted value of the rotor excitation current of the main motor at the next moment, design the excitation control cost function of the exciter inverter; and based on the predicted value of the stator current of the main motor at the next moment, design the main motor control cost function of the main motor inverter. Based on the excitation control cost function, a first optimal voltage vector of the exciter inverter is predicted, and the exciter inverter is driven by the first optimal voltage vector to perform predictive control of the exciter; based on the main motor control cost function, a second optimal voltage vector of the main motor inverter is predicted, and the main motor inverter is driven by the second optimal voltage vector to perform predictive control of the main motor.

2. The method according to claim 1, characterized in that, The step of constructing a rotor current observer for the exciter based on the three-phase stator current and the mathematical model of the exciter to obtain the observed rotor current value of the exciter at the current moment includes: A rotor current observer for the exciter is constructed based on the stator voltage, stator flux linkage equation, and rotor current characteristics of the exciter. The stator voltage of the exciter is expressed as: The stator flux linkage equation of the exciter is expressed as: The rotor current characteristics of the exciter are expressed as follows: i ra +i rb +i rc =0; Among them, u A u B and u C i is the terminal voltage of the three-phase stator windings of the exciter. sA i sB and i sC For the three-phase current of the exciter stator, i ra i rb and i rc The three-phase current of the exciter rotor. and For the three-phase flux linkage of the exciter stator, R se L is the phase resistance of the exciter stator winding. se M is the total self-inductance of the exciter stator winding. sr θ represents the mutual inductance amplitude between the stator and rotor windings of the exciter. r This refers to the position of the exciter rotor; Based on the exciter's rotor current observer, the estimation expression for the exciter's rotor current in the three-phase stationary coordinate system is determined; the estimation expression for the exciter's rotor current is expressed as: Where A1 is the calculation factor for phase C and A2 is the calculation factor for phase B; Based on the exciter rotor current estimation expression, determine the observed value of the exciter rotor current at the current moment.

3. The method according to claim 2, characterized in that, The construction of the stator current prediction model for the exciter, which predicts the stator current of the exciter at the next time step from the current time step, includes: Based on the mathematical equations of the exciter, the rotor flux linkage and rotor terminal voltage of the exciter at the current moment are observed in the two-phase stationary coordinate system. The rotor flux linkage of the exciter is represented as follows: The rotor terminal voltage of the exciter is expressed as: in, For the rotor flux linkage of the exciter, L r For the self-inductance of the exciter rotor winding, i s L is the stator current of the exciter. m For the mutual inductance of the exciter rotor windings, i r V is the exciter rotor current; r R is the rotor terminal voltage of the exciter. r The phase resistance of the exciter rotor winding. Here, j is the imaginary unit, w is the rotor electric angular velocity, and k represents the current time. Based on the stator current expression of the exciter and forward Euler discretization, a stator current prediction model for the exciter is constructed. The predicted current value of the exciter stator at the next moment is obtained through this model. The exciter stator current prediction model is expressed as follows: Where k+1 represents the next time step after the current time step, i s (k+1) represents the predicted stator current of the exciter at the next time step, T. s k is the system sampling time. r It is the magnetic coupling factor. Rσ is the equivalent resistance, and σ is the leakage flux coefficient. τ r The rotor time constant, τ σ It is the instantaneous time constant. V s This is the stator terminal voltage of the exciter.

4. The method according to claim 3, characterized in that, The step of constructing a rotor excitation current prediction model for the main motor based on the electromagnetic coupling relationship between the main motor and the exciter, and obtaining the predicted value of the rotor excitation current of the main motor at the next moment, includes: The electromagnetic coupling relationship is expressed as follows: |and ra |+|and rb |+|and rc |=2i f ; Among them, i f The rotor excitation current value of the main motor; Based on the electromagnetic coupling relationship and the observation results of the exciter rotor current observer, the rotor excitation current value of the main motor at the current moment is obtained, expressed as: Among them, i f (k) is the rotor excitation current value of the main motor at the current moment, i ra (k), i rb (k), i rc (k) represents the observed three-phase current of the exciter rotor at the current moment; Based on the exciter rotor current observer and the predicted value of the exciter stator current at the next moment, the rotor current of the exciter at the next moment is predicted. Based on the electromagnetic coupling relationship and the predicted rotor current of the exciter at the next moment, the predicted rotor excitation current of the main motor at the next moment is determined; the predicted rotor excitation current of the main motor at the next moment is expressed as: Among them, i f (k+1) represents the predicted value of the main motor rotor excitation current at the next time step, i ra (k+1),i rb (k+1),i rc (k+1) represent the predicted three-phase current values ​​of the exciter rotor at the next moment.

5. The method according to claim 4, characterized in that, The step of constructing a stator current prediction model for the main motor based on the current stator current of the main motor in the two-phase rotating coordinate system and the mathematical model of the main motor at the current moment, and obtaining the predicted stator current value of the main motor at the next moment, includes: Based on the model of the electrically excited synchronous motor, the voltage and flux linkage equations of the main motor are established; The voltage equation for the main motor is expressed as: Among them, u d Main motor stator d-axis voltage, u q Main motor stator q-axis voltage, u f The voltage of the main motor rotor excitation winding, R sm The stator resistance value of the main motor, R f The resistance value of the rotor excitation winding of the main motor, i d Main motor stator d-axis current, i q Main motor stator q-axis current, i f The main motor rotor excitation current The stator d-axis flux linkage of the main motor The main motor stator q-axis flux linkage. Main motor rotor excitation flux linkage, w e The main motor's electric angular velocity; The flux linkage equation of the main motor is expressed as: Among them, L d The equivalent inductance of the d-axis of the main motor stator winding, L q The equivalent inductance of the q-axis of the main motor stator winding, L md The mutual inductance between the d-axis equivalent inductance of the main motor stator winding and the rotor winding, L f The self-inductance of the main motor excitation winding; Applying the forward Euler discretization formula to the voltage equation of the main motor, the predicted value of the stator current of the main motor at the next moment is obtained, expressed as: Among them, i d (k+1) represents the stator d-axis current of the main motor at time k+1, i q (k+1) is the stator q-axis current of the main motor at time k+1.

6. The method according to claim 5, characterized in that, The excitation control cost function under constant excitation control mode is expressed as: The main motor control cost function is expressed as follows: Among them, g e Let g be the excitation control cost function. m The main motor control cost function Reference for the rotor excitation current of the main motor Reference for the d-axis current of the main motor. Used as a reference for the q-axis current of the main motor.

7. The method according to claim 6, characterized in that, The step of predicting the first optimal voltage vector of the exciter inverter based on the excitation control cost function includes: The excitation control cost function is used to evaluate multiple switching vector states of the exciter inverter, and the first optimal voltage vector is determined from the voltage vectors corresponding to the multiple switching vector states. The step of predicting the second optimal voltage vector of the main motor inverter based on the main motor control cost function includes: The main motor control cost function is used to evaluate multiple switching vector states of the main motor inverter, and the second optimal voltage vector is determined from the voltage vectors corresponding to the multiple switching vector states.

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