CN111277185A - Method for coordinately controlling damping force of permanent magnet generator and vibration force of conical magnetic bearing - Google Patents
Method for coordinately controlling damping force of permanent magnet generator and vibration force of conical magnetic bearing Download PDFInfo
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- CN111277185A CN111277185A CN202010176481.7A CN202010176481A CN111277185A CN 111277185 A CN111277185 A CN 111277185A CN 202010176481 A CN202010176481 A CN 202010176481A CN 111277185 A CN111277185 A CN 111277185A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P9/00—Arrangements for controlling electric generators for the purpose of obtaining a desired output
- H02P9/44—Control of frequency and voltage in predetermined relation, e.g. constant ratio
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
- H02P21/05—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation specially adapted for damping motor oscillations, e.g. for reducing hunting
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- Magnetic Bearings And Hydrostatic Bearings (AREA)
- Connection Of Motors, Electrical Generators, Mechanical Devices, And The Like (AREA)
- Control Of Eletrric Generators (AREA)
Abstract
The invention discloses a method for coordinately controlling damping force of a permanent magnet generator and vibration force of a conical magnetic bearing, and belongs to the technical field of coordinative control of permanent magnet synchronous motors. The control method comprises the following steps: (1) firstly, determining the relation between the vibration of a generator rotor and the direct-axis current when the load is suddenly changed; (2) establishing a prediction control model between the direct-axis current of the generator and the current of the magnetic bearing electro-magnetic excitation winding; (3) after the predicted value is obtained, a load feedforward method is adopted, and the predicted value is input to a vector controller of the permanent magnet generator through proportional integral and proportional resonance setting, so that the rotor vibration suppression control during sudden change of the load of the generator is realized. The invention reduces the vibration of the generator rotor, improves the stability and the dynamic regulation performance of the coordination control system under different conditions, and establishes the coordination control theory of the magnetic bearing and the generator based on the strong electromechanical coupling system.
Description
Technical Field
The invention discloses a method for coordinately controlling damping force of a permanent magnet generator and vibration force of a conical magnetic bearing, and belongs to the technical field of coordinative control of permanent magnet synchronous motors.
Background
The aircraft engine is used as a propulsion device of an aircraft, and meanwhile, needs to provide power supply, environment-controlled bleed air and hydraulic device driving force for an aircraft system. For a traditional engine, accessories such as a fuel pump, a lubricating oil pump and a generator extract engine power through an accessory casing, and the power extraction mode causes the structure of the engine to be complicated. The improved multi-electric engine based on traditional engine adopts built-in integral starting/generator to provide power supply for engine and airplane, uses all-electric gasifying transmission accessory to replace mechanical hydraulic transmission accessory, changes the control system of engine from centralized full-authority digital electronic control system to distributed control system, and changes the fuel pump, lubricating oil pump and actuator of engine to electric drive.
At present, many electric aircraft engines, which are electric machines integrating functions of a starter and a generator, are being researched in the united states and europe. Before the engine works stably, the engine works as an electric starter, the engine is driven to rotate to a certain rotating speed, after the engine is supplied with oil, ignited and burnt and enters a stable working state, the engine drives the motor in turn to enable the motor to become a generator, and power is supplied to the airplane and the electric equipment of the engine. The multi-electric aeroengine cancels the accessory mechanical transmission part, so that the weight of the engine is greatly reduced, the windward area is reduced, and simultaneously, higher electric power is easy to obtain. The application of the new technology greatly reduces the weight of the airborne equipment, can meet the requirement of modern airplanes on power supply, and is an important development trend of engine accessories. However, due to vibration caused by unbalanced force of the engine rotor, asymmetry of the mechanical structure, mutual friction and the like, the rotating shaft has multiple vibration modes. Meanwhile, the aerodynamic torque at the turbine shaft can cause the torque fluctuation of a transmission system, and when a torque difference exists between the aerodynamic torque and the torque of a generator, the rotating shaft is twisted to deform the rotating shaft, so that unbalanced torsional vibration is formed. The unbalanced torque forces at the two ends of the rotating shaft can affect the service life of the rotating shaft, and simultaneously cause sudden change of electrical loads of an engine and vibration of a rotor shafting.
Disclosure of Invention
The invention provides a method for coordinately controlling damping force of a permanent magnet generator and vibration force of a conical magnetic bearing, and researches the coordinately controlling mechanism of the vibration force of the magnetic bearing and the damping force of the permanent magnet generator. The method for suppressing the rotor vibration when the load of the engine suddenly changes is researched, the vibration displacement of a magnetic bearing rotor is reduced as a target, and the relation between the rotor vibration of a generator and the direct-axis current when the load suddenly changes is firstly researched; secondly, establishing a prediction control model between the direct-axis current of the generator and the current of the magnetic bearing electro-magnetic excitation winding; and finally, providing a rotor vibration suppression control strategy when the load of the generator suddenly changes. Firstly, researching a mathematical relation between the vibration of an engine rotor and the direct-axis current of a generator with the aims of reducing the vibration of the generator rotor and keeping the quality of output electric energy unchanged; secondly, researching the influence rule of eccentricity generated by the vibration of the generator rotor on unbalanced radial force, the inductance of the stator winding and back electromotive force; and finally, establishing a magnetic bearing and generator coordination control theory based on a strong electromechanical coupling system.
The invention adopts the following technical scheme for solving the technical problems:
a method for coordinately controlling damping force of a permanent magnet generator and vibration force of a conical magnetic bearing comprises the following steps:
(1) firstly, determining the relation between the vibration of a generator rotor and the direct-axis current when the load is suddenly changed;
(2) establishing a prediction control model between the direct-axis current of the generator and the current of the magnetic bearing electro-magnetic excitation winding;
(3) after the predicted value is obtained, a load feedforward method is adopted, and the predicted value is input to a vector controller of the permanent magnet generator through Proportional Integral (PI) and Proportional Resonance (PR) setting, so that the rotor vibration suppression control during the sudden change of the load of the generator is realized.
The specific process of the step (1) is as follows: and obtaining a rotor dynamics differential equation according to a Lagrange equation, deducing a nonlinear transfer relation between the rotor displacement variation at the magnetic bearing and the generator current on the basis, and establishing a coupling relation between the radial unbalanced force and the electromagnetic torque of the permanent magnet generator.
The specific process of the step (2) is as follows: according to the current sampling value delta id(n) and in the processSample values Δ i at different times before the sample timed(n-3)、Δid(n-2)、Δid(n-1) generating an original data column, establishing a whitening equation of gray prediction, solving the solution of a differential equation, and performing once accumulation and subtraction to generate a predicted value.
If the predicted value precision in the step (2) is lower, the final predicted value delta i is obtained through a predicted value correction moduled′。
And (3) the load feed-forward method is to feed forward the displacement break variable of the magnetic bearing or the power break variable of the generator to a corresponding current control loop by combining the whitening equation of the grey prediction, so as to inhibit the vibration displacement of the rotor shafting under the dynamic working condition.
The invention has the following beneficial effects:
the method for coordinately controlling the damping force of the permanent magnet generator and the vibration force of the conical magnetic bearing solves the problem of coupling of radial unbalanced force and electromagnetic torque of the permanent magnet generator, eliminates or weakens the influence of sudden change of electrical load of an engine on the vibration of a rotor shafting, and inhibits the output power oscillation of the rotor shafting caused by sudden change of working conditions of the engine.
Drawings
Fig. 1(a) is a diagram of a secondary energy power extraction mode of a conventional aircraft engine, and fig. 1(b) is a diagram of a secondary energy power extraction mode of a multi-electric aircraft engine.
FIG. 2 is a diagram of a system for coordinating and controlling vibration force of a permanent magnet biased conical magnetic bearing and damping force of a permanent magnet generator.
Fig. 3(a) is a waveform diagram of the inductance of the motor winding under different eccentricities, fig. 3(b) is a waveform diagram of the back electromotive force of the motor under different eccentricities, and fig. 3(c) is a comparison diagram of the back electromotive force fourier decomposition of the motor under different eccentricities.
FIG. 4 is a diagram of a model of vibration displacement and vibration cross prediction.
FIG. 5 is a block diagram of the coordination control of the vibration force of the conical magnetic bearing and the damping force of the permanent magnet generator.
The reference numbers in the figures illustrate: omega1、Ω2The rotating speeds of the analog mass block 1 and the analog mass block 2 are respectively; i.e. ix11、ix12、ix21、ix22、iy11、iy12、iy21、iy22X, Y winding currents for magnetic bearings, respectively; i.e. ia、ib、icIs a three-phase winding current; x is the number of11、x12、y11、y12Representing the displacement of the magnetic bearing; Δ x1、Δx2、Δy1、Δy1Representing the variation of the radial displacement of the magnetic bearing, delta z representing the variation of the axial displacement of the magnetic bearing, delta r representing the variation of the unbalanced radial displacement of the generator and delta theta representing the variation of the unbalanced torsional displacement of the generator; u shape* dcTo output a direct current voltage; i isq、IdRespectively representing the feedback quantity of the quadrature-axis current and the direct-axis current of the generator,
Respectively represents the input quantity of the quadrature-axis current and the direct-axis current of the generator,
Respectively representing predicted current feedforward quantities; u shapeDC、UDC *Respectively representing input quantities of quadrature-axis current and direct-axis current of the generator; frx、FryRepresenting the radial forces in the horizontal and vertical directions, respectively; d1、D4、D12Represents a duty cycle; PI stands for proportional integral controller; a PR proportional resonant controller; t, P is a control coefficient.
Detailed Description
In order to make the purpose and technical solution of the embodiments of the present invention clearer, the following drawings of the embodiments of the present invention clearly and completely describe the technical solution of the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention without any inventive step, are within the scope of protection of the invention.
Fig. 1 is a graph comparing different power extraction modes of secondary energy. FIG. 1(a) represents a conventional aircraft engine, the engine outputting thrust as a primary energy source for the aircraft; meanwhile, the mechanical energy is converted into secondary energy in the forms of electric energy, hydraulic energy, air pressure energy and the like which can be provided for various devices on the airplane through the extraction shaft. However, in recent years, with the development of multi-electric/full-electric aircraft, the electric power demand of the aircraft is larger and larger, and a multi-electric aircraft engine such as fig. 1(b) appears. The multi-electric aero-engine is a novel aero-engine which is based on a traditional aero-gas turbine engine and is provided with new components and systems such as an active magnetic bearing, a built-in integrated starter/generator, a distributed electronic control system, an electric fuel pump, an electric actuator and the like. The multi-electric engine cancels mechanical units such as a transmission shaft, a gear, an extraction shaft and the like, and adopts an integrated coaxial design mode of a multi-electric engine rotating shaft, a magnetic suspension bearing and a starting generator, so that an electric system of an 'electric load-generator' and a mechanical system of an 'engine transmission rotor-generator rotating rotor' are closely coupled together. The multi-electric engine has the outstanding technical advantages of more compact structure, lighter weight, higher performance, better maintainability and adaptability, higher reliability, lower operation and maintenance cost and the like.
Fig. 2 is a diagram of a coordinated control system for vibration force of the permanent magnet biased conical magnetic bearing and 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 novel permanent magnet biased magnetic suspension bearing structure and is combined with a permanent magnet engine. The system adopts the vibration force active control technology of the conical magnetic bearing to eliminate the rigid displacement of the conical bearing, utilizes the damping force of the permanent magnet generator to actively control and weaken the flexible unbalanced displacement of the generator, and weakens the influence among vibration modes through the coordination control between the two, thereby solving the problem of strong electromechanical coupling in the engine; when the unbalanced radial damping force and the unbalanced torsional force of the generator are detected, the electromagnetic bearing is controlled by the magnetic bearing controller, and the vibration force of the conical magnetic bearing and the damping force of the permanent magnet generator are coordinated.
Fig. 3 shows a graph of the influence of different eccentricity modes on the main electrical parameters of the generator. When the engine works in dynamic working conditions such as takeoff and descending, the vibration displacement of the rotor of the engine is increased, the uneven distribution of the air gap of the coaxial generator is aggravated, and the unbalanced radial force of the generator is further increased. In order to meet the requirement of a safe air gap of an engine rotor, a surface-mounted permanent magnet generator is adopted, and the air gap is large (1.2mm), so that the armature reaction is reduced. The preliminary simulation shows that different eccentric modes have little influence on the inductance, the counter potential amplitude and the harmonic distribution of the generator and are consistent with the waveform shown in the figure. Meanwhile, the power generation system adopts a common direct current bus mode, so that the influence range of the eccentricity of a generator rotor on the variable speed constant voltage control of the engine in a safe range is small.
As shown in FIG. 4, the vibration force of the conical magnetic bearing and the damping force of the permanent magnet generator are controlled in coordination. When the working condition of the engine suddenly changes and the load of the generator suddenly changes, the radial vibration, the axial vibration and the torsional vibration are mutually influenced, and particularly under the dynamic working condition, the vibration displacement change forms of the rotor of the engine are various, such as (a) - (d) in fig. 4. Fig. 4(a) bearing radial displacement, fig. 4(b) bearing axial displacement, fig. 4(c) generator unbalanced radial displacement, fig. 4(d) generator unbalanced torsional displacement. Therefore, it is necessary to investigate the correspondence function relationship between different rotor vibration displacements and the magnetic bearings and the generator current by using a vibration displacement prediction model.
As shown in FIG. 5, it is a block diagram for coordinated control of vibration force of conical magnetic bearing and damping force of permanent magnet generator, when the load of generator suddenly changes, the alternating-direct axis current of generator will change, and the electromagnetic torque and radial magnetic pull of rotor will oscillate for a short time, causing the radial and axial vibration displacement of rotor shafting, therefore, it is necessary to establish prediction model of direct axis current and vibration displacement of generator, and then obtain I through dq/αβ transformationsx、IsyThe feed-forward is carried out to a magnetic bearing current loop, and the influence of the sudden change of the electrical load of the engine on the vibration of a rotor shafting is restrained. In addition, when the engine works in dynamic working conditions such as takeoff and descending, vibration displacement of an engine rotor is increased, uneven distribution of an air gap of the coaxial generator is aggravated, and unbalanced radial force of the generator is further increased. If the restraining eccentricity is not added, the rotor shafting can be caused to resonate, so that the output power is oscillated, and finally the operation safety of the generator and the airplane power supply and distribution system is damaged. Therefore, it is necessary to establishPrediction model of generator direct axis current and vibration displacement, namely obtaining radial displacement x by displacement sensor1～y2And then, in combination with the mode of feedforward of vibration displacement of the magnetic bearing to a current control loop of the generator, obtaining the direct-axis current given I of the permanent magnet generator through a prediction modeld1 *And current tracking control is realized, so that output power oscillation of a rotor shafting caused by sudden change of working conditions of the engine is restrained.
Although the present invention has been described with reference to the above embodiments, it should be understood that various changes and modifications can be made without departing from the spirit and scope of the invention.
Claims (5)
1. A method for coordinately controlling damping force of a permanent magnet generator and vibration force of a conical magnetic bearing is characterized by comprising the following steps:
(1) firstly, determining the relation between the vibration of a generator rotor and the direct-axis current when the load is suddenly changed;
(2) establishing a prediction control model between the direct-axis current of the generator and the current of the magnetic bearing electro-magnetic excitation winding;
(3) after the predicted value is obtained, a load feedforward method is adopted, and the predicted value is input to a vector controller of the permanent magnet generator through proportional integral and proportional resonance setting, so that the rotor vibration suppression control during sudden change of the load of the generator is realized.
2. The method for coordinately controlling damping force of a permanent magnet generator and vibration force of a conical magnetic bearing according to claim 1, wherein the specific process of step (1) is as follows: and obtaining a rotor dynamics differential equation according to a Lagrange equation, deducing a nonlinear transfer relation between the rotor displacement variation at the magnetic bearing and the generator current on the basis, and establishing a coupling relation between the radial unbalanced force and the electromagnetic torque of the permanent magnet generator.
3. The method for coordinately controlling damping force of permanent magnet generator and vibration force of conical magnetic bearing according to claim 1, wherein the step (2) is specifically performedThe process is as follows: according to the current sampling value delta id(n) and a sampling value Δ i at a different time before the sampling timed(n-3)、Δid(n-2)、Δid(n-1) generating an original data column, establishing a whitening equation of gray prediction, solving the solution of a differential equation, and performing once accumulation and subtraction to generate a predicted value.
4. The method as claimed in claim 3, wherein when the predicted value in step (2) has low accuracy, the predicted value correction module obtains the final predicted value Δ id′。
5. The method for coordinately controlling damping force of a permanent magnet generator and vibration force of a conical magnetic bearing according to claim 4, wherein the method for feeding forward the load in step (3) is to feed forward the sudden change of magnetic bearing displacement or the sudden change of generator power to the corresponding current control loop in combination with the whitening equation for gray prediction, so as to suppress the vibration displacement of the rotor shafting under the dynamic condition.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112096738A (en) * | 2020-09-30 | 2020-12-18 | 华中科技大学 | Current vibration suppression method and system applied to magnetic suspension bearing |
| CN115680887A (en) * | 2022-10-13 | 2023-02-03 | 中国航发四川燃气涡轮研究院 | System and method for controlling magnetic bearing of aero-engine |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105048913A (en) * | 2015-07-31 | 2015-11-11 | 河南科技大学 | Current compensation-based unbalance vibration control system for bearingless asynchronous motor |
| CN108566129A (en) * | 2018-05-31 | 2018-09-21 | 南京航空航天大学 | A kind of permanent magnet generator system and its control method reducing DC voltage fluctuation |
| CN110460280A (en) * | 2019-08-29 | 2019-11-15 | 西安理工大学 | A kind of permasyn morot control method based on sliding formwork load torque observer |
-
2020
- 2020-03-13 CN CN202010176481.7A patent/CN111277185B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105048913A (en) * | 2015-07-31 | 2015-11-11 | 河南科技大学 | Current compensation-based unbalance vibration control system for bearingless asynchronous motor |
| CN108566129A (en) * | 2018-05-31 | 2018-09-21 | 南京航空航天大学 | A kind of permanent magnet generator system and its control method reducing DC voltage fluctuation |
| CN110460280A (en) * | 2019-08-29 | 2019-11-15 | 西安理工大学 | A kind of permasyn morot control method based on sliding formwork load torque observer |
Non-Patent Citations (2)
| Title |
|---|
| 许颖等: "无轴承永磁同步电机系统及其关键技术发展综述" * |
| 赵韩等: "飞轮储能磁轴承系统动力学模型与控制系统设计" * |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112096738A (en) * | 2020-09-30 | 2020-12-18 | 华中科技大学 | Current vibration suppression method and system applied to magnetic suspension bearing |
| CN112096738B (en) * | 2020-09-30 | 2021-06-11 | 华中科技大学 | Current vibration suppression method and system applied to magnetic suspension bearing |
| CN115680887A (en) * | 2022-10-13 | 2023-02-03 | 中国航发四川燃气涡轮研究院 | System and method for controlling magnetic bearing of aero-engine |
| CN115680887B (en) * | 2022-10-13 | 2024-05-17 | 中国航发四川燃气涡轮研究院 | Aeroengine magnetic bearing control system and method |
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