CN111277185A - Method for coordinately controlling damping force of permanent magnet generator and vibration force of conical magnetic bearing - Google Patents

Abstract

The invention discloses a method for coordinated control of the damping force of a permanent magnet generator and the vibration force of a conical magnetic bearing, belonging to the technical field of coordinated control of a permanent magnet synchronous motor. The control method includes the following steps: (1) firstly determine the relationship between the generator rotor vibration and the direct-axis current when the load suddenly changes; (2) establish a predictive control model between the generator's direct-axis current and the magnetic bearing electrical excitation winding current ; (3) After the predicted value is obtained, the method of load feed-forward is adopted, through proportional integration and proportional resonance tuning, it is input to the permanent magnet generator vector controller to realize the rotor vibration suppression control when the generator load is abruptly changed. The invention reduces the vibration of the generator rotor, improves the stability and dynamic adjustment performance of the coordinated control system under different conditions, and establishes the coordinated control theory of the magnetic bearing and the generator based on the strong electromechanical coupling system.

Description

A coordinated control method for damping force of permanent magnet generator and vibration force of tapered magnetic bearing

technical field

The invention discloses a method for coordinated control of the damping force of a permanent magnet generator and the vibration force of a conical magnetic bearing, belonging to the technical field of coordinated control of a permanent magnet synchronous motor.

Background technique

As the propulsion device of the aircraft, the aero-engine also needs to provide the power supply, environmental control bleed air and hydraulic device driving force for the aircraft system. For traditional engines, accessories such as fuel pumps, lubricating oil pumps, and generators extract engine power through the accessory casing. This power extraction method makes the engine structure complicated. The multi-electric engine improved on the basis of the traditional engine adopts the built-in integral starter/generator to provide the required power for the engine and the aircraft, and replaces the mechanical and hydraulic transmission accessories with fully electrified transmission accessories. The control system of the engine is also controlled by a centralized The full-authority digital electronic control system was changed to a distributed control system, and the fuel pump, oil pump and actuator of the engine were also changed to electric drive.

At present, both the United States and Europe are researching multi-electric aero-engines, which are motors that integrate the functions of a starter and a generator. Work as an electric starter before the engine works stably, turn the engine belt to a certain speed, after the engine is supplied with fuel to ignite and burn and enter a stable working state, the engine in turn drives the motor, making it a generator to use electricity for the aircraft and the engine power to the device. Since the multi-electric aero-engine cancels the mechanical transmission part of the attachment, the weight of the engine is greatly reduced, the windward area is reduced, and it is also easy to obtain greater electrical power. The application of this new technology greatly reduces the weight of the airborne equipment and can meet the demand for power supply of modern aircraft, so it is an important development trend of engine accessories. However, due to the vibration caused by the unbalanced force of the engine rotor, the asymmetry of the mechanical structure and the mutual friction, the rotating shaft has various vibration modes. At the same time, the aerodynamic torque at the turbine shaft will cause torque fluctuations in the transmission system. When there is a torque difference between the aerodynamic torque and the generator torque, the shaft will twist and deform, resulting in unbalanced torsional vibration. . The unbalanced torque force at both ends of the rotating shaft will affect the life of the rotating shaft, and at the same time cause a sudden change in the electrical load of the engine, causing vibration of the rotor shafting.

SUMMARY OF THE INVENTION

The invention proposes a coordinated control method of the damping force of a permanent magnet generator and the vibration force of a conical magnetic bearing, and studies the coordinated control mechanism of the vibration force of the magnetic bearing and the damping force of the permanent magnet generator. To study the rotor vibration suppression method when the engine load is abrupt, with the goal of reducing the vibration displacement of the magnetic bearing rotor, firstly, the relationship between the generator rotor vibration and the direct-axis current when the load is abruptly changed; secondly, the generator direct-axis current and the magnetic bearing current are established. Predictive control model between field winding currents; finally, a rotor vibration suppression control strategy is proposed when the generator load is abruptly changed. In order to reduce the vibration of the generator rotor and keep the output power quality unchanged, the mathematical relationship between the vibration of the rotor of the generator and the direct-axis current of the generator is firstly studied; Influence law of inductance and back EMF; Finally, the coordinated control theory of magnetic bearing and generator based on strong electromechanical coupling system is established.

The present invention adopts following technical scheme for solving its technical problem:

A method for coordinated control of the damping force of a permanent magnet generator and the vibration force of a conical magnetic bearing, comprising the following steps:

(1) First determine the relationship between the generator rotor vibration and the direct-axis current when the load suddenly changes;

(2) Establish a predictive control model between the generator direct axis current and the magnetic bearing electrical excitation winding current;

(3) After the predicted value is obtained, the load feedforward method is used, and the proportional integral (PI) and proportional resonance (PR) are set, and then input to the permanent magnet generator vector controller to realize the rotor vibration suppression control when the generator load is abruptly changed. .

The specific process of step (1) is as follows: According to the Lagrange equation, the rotor dynamics differential equation is obtained, and on this basis, the nonlinear transfer relationship between the rotor displacement change at the magnetic bearing and the generator current is deduced, and a permanent magnet generator is established. The coupling relationship between radial unbalanced force and electromagnetic torque.

The specific process of step (2) is as follows: according to the current sampling value _Δid (n) and the sampling values _Δid (n-3), _Δid (n-2), _Δid (n- 1) Generate the original data column, establish the whitening equation of gray prediction, obtain the solution of the differential equation, and perform a cumulative reduction to obtain the predicted value.

If the accuracy of the predicted value in step (2) is low, the final predicted value _Δid ' is obtained through the predicted value correction module.

The load feed-forward method in step (3) is to feed forward the magnetic bearing displacement mutation or the generator power mutation, combined with the whitening equation of the gray prediction, to the corresponding current control loop to suppress the dynamic working condition. The vibration displacement of the rotor shafting.

The beneficial effects of the present invention are as follows:

The method for coordinated control of the damping force of the permanent magnet generator and the vibration force of the conical magnetic bearing proposed by the invention solves the coupling problem of the radial unbalanced force of the permanent magnet generator and the electromagnetic torque, and eliminates or weakens the sudden change of the electrical load of the engine. The influence on the vibration of the rotor shaft system suppresses the output power oscillation of the rotor shaft system caused by the sudden change of engine operating conditions.

Description of drawings

Figure 1(a) is a diagram of the extraction method of secondary energy power of traditional aero-engines, and Figure 1(b) is a diagram of secondary energy power extraction of multi-electric aero-engines.

Figure 2 is a diagram of a coordinated control system for the vibration force of the permanent magnet offset tapered magnetic bearing and the damping force of the permanent magnet generator.

Figure 3(a) is the waveform diagram of the motor winding inductance under different eccentricity, Figure 3(b) is the waveform diagram of the motor back EMF under different eccentricity, and Figure 3(c) is the Fourier decomposition comparison diagram of the motor back EMF under different eccentricity.

Fig. 4 is a model diagram of vibration displacement and vibration crossover prediction.

Figure 5 is a block diagram of the coordinated control of the vibration force of the conical magnetic bearing and the damping force of the permanent magnet generator.

分别表示发电机交轴电流和直轴电流输入量、

分别表示预测电流前馈量；U_DC、U_DC ^*分别表示发电机交轴电流和直轴电流输入量；F_rx、F_ry分别表示水平方向和竖直方向上的径向力；D₁、D₄、D₁₂代表占空比；PI代表比例积分控制器；PR比例谐振控制器；T、P为控制系数。Description of the _symbols in the _figure : _{Ω 1} and _{Ω 2} are the rotational _speeds of the _{simulated mass} 1 and the simulated _mass 2 respectively; Bearing X, Y winding currents; i _a , _ib , ic are three-phase winding currents; x ₁₁ , x ₁₂ , _{y 11} , y ₁₂ represent the displacement of the magnetic bearing; Δx ₁ , Δx ₂ , Δy ₁ , Δy ₁ represent Magnetic bearing radial displacement change, Δz represents the magnetic bearing axial displacement change, Δr is the generator unbalanced radial displacement change, Δθ is the generator unbalanced torsional displacement change; U ^* _dc is the output DC voltage; I _q , I _d represent the generator quadrature axis current and direct axis current feedback, respectively,

respectively represent the generator quadrature axis current and direct axis current input,

respectively represent the predicted current feedforward; U _DC , U _DC ^* represent the generator quadrature axis current and direct axis current input respectively; F _rx , F _ry represent the radial force in the horizontal and vertical directions, respectively; D ₁ , D ₄ and D ₁₂ represent duty cycle; PI represents proportional integral controller; PR proportional resonance controller; T and P are control coefficients.

Detailed ways

In order to make the purpose and technical solutions of the embodiments of the present invention clearer, the attached drawings of the embodiments of the present invention are as follows, to clearly and completely describe the technical solutions of the embodiments of the present invention. Obviously, the described embodiments are some, but not all, embodiments of the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

As shown in Figure 1, it is a comparison diagram of different power extraction methods of secondary energy. Figure 1(a) represents the traditional aero-engine. On the one hand, the engine outputs thrust as the primary energy of the aircraft; at the same time, the mechanical energy is converted into various forms of equipment on the aircraft, including electrical energy, hydraulic energy and air pressure energy, by extracting the shaft. secondary energy. However, in recent years, with the development of multi-electric/all-electric aircraft, the demand for aircraft electric power is increasing, and multi-electric aero-engines have appeared as shown in Figure 1(b). Multi-electric aero-engines are based on traditional aviation gas turbine engines and are equipped with new components and systems such as active magnetic bearings, built-in integrated starter/generators, distributed electronic control systems, electric fuel pumps and electric actuators. A new type of aircraft engine. The multi-electric engine cancels the transmission shaft, gear, extraction shaft and other mechanical units, and adopts the integrated coaxial design method of the multi-electric engine rotating shaft, magnetic suspension bearing and starter generator, which makes the electrical system of "electrical load-generator" and "electrical load-generator". The engine-driven rotor-generator rotating-rotor" mechanical system is tightly coupled together. This makes the multi-electric engine have outstanding technical advantages such as more compact structure, lighter weight, higher performance, better maintainability and adaptability, higher reliability, and lower operation and maintenance costs.

As shown in Figure 2, it is a diagram of a coordinated control system for the vibration force of the permanent magnet biased conical magnetic bearing and the damping force of the permanent magnet generator. The coordinated control system of the vibration force of the magnetic bearing and the damping force of the generator adopts a new type of permanent magnet biased magnetic suspension bearing structure combined with a permanent magnet motor. The system adopts the vibration force active control technology of the conical magnetic bearing to eliminate the rigid displacement of the conical bearing, uses the damping force of the permanent magnet generator to actively control the flexible unbalanced displacement of the generator, and then weakens the vibration through the coordinated control between the two. The influence between the modes, and then solve the problem of strong electromechanical coupling in the engine; when the unbalanced radial damping force and unbalanced torsional force of the generator are detected, the electromagnetic bearing is controlled by the magnetic bearing controller, and the conical magnetic bearing is coordinated. Bearing vibration force and permanent magnet generator damping force.

As shown in Figure 3, it is the influence diagram on the main electrical parameters of the generator under different eccentricity modes. When the engine works in dynamic conditions such as take-off and descent, the vibration displacement of the engine rotor increases, which intensifies the uneven distribution of the air gap of the coaxial generator, resulting in a further increase in the unbalanced radial force of the generator. In order to meet the safety air gap requirement of the engine rotor, a surface-mounted permanent magnet generator is used, and its air gap is large (1.2mm), which reduces the armature reaction. Preliminary simulations show that different eccentricity modes have little effect on the inductance, back-EMF amplitude and harmonic distribution of the generator, which are consistent with the waveform shown in the figure. At the same time, the power generation system adopts a common DC bus, so the influence of the eccentricity of the generator rotor on the variable speed constant voltage control of the engine is small within a safe range.

As shown in Figure 4, it is the coordinated control of the vibration force of the conical magnetic bearing and the damping force of the permanent magnet generator. When the engine operating condition is abruptly changed and the generator load is abruptly changed, the radial vibration, axial vibration and torsional vibration will affect each other. Especially under dynamic conditions, the vibration displacement of the engine rotor changes in various forms, as shown in Figure 4 (a)～( d). Figure 4(a) The radial displacement of the bearing, Figure 4(b) The axial displacement of the bearing, Figure 4(c) The unbalanced radial displacement of the generator, and Figure 4(d) The unbalanced torsional displacement of the generator. Therefore, it is necessary to explore the corresponding functional relationship between different rotor vibration displacements and magnetic bearing and generator currents through the vibration displacement prediction model.

As shown in Figure 5, it is a block diagram of the coordinated control of the vibration force of the conical magnetic bearing and the damping force of the permanent magnet generator. When the generator load changes abruptly, the AC and DC axis currents of the generator will change, causing the rotor electromagnetic torque and radial magnetic pulling force to oscillate for a short time, causing radial and axial vibration and displacement of the rotor shaft system. Therefore, it is necessary to establish a prediction model of the generator's direct shaft current and vibration displacement, and then obtain _Isx and _Isy through dq/αβ transformation to feed forward to the magnetic bearing current loop to suppress the impact of sudden changes in the electrical load of the engine on the vibration of the rotor shafting. In addition, when the engine works in dynamic conditions such as take-off and descent, the vibration and displacement of the engine rotor increases, which intensifies the uneven distribution of the coaxial generator air gap, resulting in a further increase in the unbalanced radial force of the generator. If the eccentricity is not suppressed, the rotor shafting will be resonated, which will cause the output power to oscillate, and ultimately endanger the operation safety of the generator and the power supply and distribution system of the aircraft. Therefore, it is necessary to establish a prediction model of the generator's direct-axis current and vibration displacement, that is, first obtain the radial displacement x ₁ ～ y ₂ from the displacement sensor, and then combine the vibration displacement of the magnetic bearing to feed forward to the generator current control loop. The prediction model obtains the direct-axis current given I _d1 ^* of the permanent magnet generator, and realizes the current tracking control, thereby suppressing the output power oscillation of the rotor shaft system caused by the sudden change of the engine operating condition.

Although the present invention has been disclosed above by embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the present invention.

Claims (5)

1. a method for coordinated control of the damping force of a permanent magnet generator and the vibration force of a conical magnetic bearing, is characterized in that, comprises the steps: (1) First determine the relationship between the generator rotor vibration and the direct-axis current when the load suddenly changes; (2) Establish a predictive control model between the generator direct axis current and the magnetic bearing electrical excitation winding current; (3) After the predicted value is obtained, the load feedforward method is adopted, and the proportional integral and proportional resonance tuning are input to the permanent magnet generator vector controller to realize the rotor vibration suppression control when the generator load is abruptly changed. 2. a kind of permanent magnet generator damping force and conical magnetic bearing vibration force coordination control method according to claim 1, is characterized in that, the concrete process of step (1) is as follows: obtain rotor dynamics differential equation according to Lagrange equation On this basis, the nonlinear transfer relationship between the rotor displacement variation at the magnetic bearing and the generator current is derived, and the coupling relationship between the radial unbalance force and the electromagnetic torque of the permanent magnet generator is established. 3. a kind of permanent magnet generator damping force and conical magnetic bearing vibration force coordination control method according to claim 1, is characterized in that, the concrete process of step (2) is as follows: according to current sampling value _Δid (n) and the sampling values Δi _d (n-3), Δi _d (n-2), and Δi _d (n-1) at different times before the sampling time to generate the original data column, establish the whitening equation of gray prediction, and obtain the differential equation The solution of , do a cumulative subtraction again to get the predicted value. 4. The method for coordinated control of the damping force of a permanent magnet generator and the vibration force of the tapered magnetic bearing according to claim 3, wherein when the predicted value accuracy is low in step (2), the predicted value correction module , to get the final predicted value _Δid '. 5 . The method for coordinated control of the damping force of a permanent magnet generator and the vibration force of the conical magnetic bearing according to claim 4 , wherein the load feed-forward method described in step (3) is to change the displacement of the magnetic bearing abruptly. 6 . Combined with the whitening equation of the gray prediction, it is fed forward to the corresponding current control loop to suppress the vibration and displacement of the rotor shaft system under dynamic conditions.

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