Stable control method for magnetic suspension flywheel energy storage system with time delay feedback

Abstract

The invention relates to the technical field of flywheel energy storage, in particular to a stability control method for a magnetic suspension flywheel energy storage system with time delay feedback. Determining axial bearing capacity and radial bearing capacity demand parameters of the flywheel energy storage device based on gravity and impact load of the flywheel rotor and centrifugal force and unbalanced force generated during high-speed rotation; according to the bearing capacity demand parameters, U-shaped stator structure design is carried out on the axial electromagnetic bearing, an inner ring and outer ring magnetic pole equal-area structure is adopted, the axial electromagnetic bearing is made of electrical pure iron, octupole electromagnetic bearing design is carried out on the radial electromagnetic bearing, and a stator and a rotor are made of silicon steel sheets formed through pressing; and carrying out temperature field distribution simulation analysis on the axial electromagnetic bearing and the radial electromagnetic bearing by adopting a bidirectional coupling mode of an electromagnetic field and a temperature field. The method further comprises the steps that an auxiliary bearing protection system is arranged, differential working mode control is adopted, and dynamic adjustment of the bearing capacity of the electromagnetic bearing under different working conditions is achieved by adjusting bias current and control current.

Description

Technical Field

[0001] The invention relates to the technical field of flywheel energy storage, in particular to a stable control method of a magnetic suspension flywheel energy storage system with time-delay feedback. Background Art

[0002] With the rapid development of new energy storage technologies, flywheel energy storage has been widely used in heavy-duty locomotives, power grid systems, rail vehicles, electric vehicles, satellite attitude adjustment and other fields due to its excellent characteristics such as high power density, long cycle life, and environmental protection. Traditional flywheel energy storage systems use mechanical bearings for support, which have problems such as large friction loss, short life, and high maintenance costs. With the increasing maturity of magnetic suspension bearing technology, the use of frictionless magnetic suspension support systems has become an important technical solution to solve the support problem of flywheel energy storage devices.

[0003] However, in the closed-loop control of the magnetic levitation flywheel energy storage system, the filtering processing of the sensor signal and the calculation of the control algorithm inevitably introduce time lag of the control signal. Time lag is a key factor affecting the stability of the system, especially when it may cause the Hopf bifurcation phenomenon. When the time lag reaches a critical value, the system will undergo Hopf bifurcation. As the input time lag increases, the amplitude of the stable periodic motion will gradually increase, and may even cause the system to lose control.

[0004] At present, the existing technology mainly focuses on the structural design and basic control methods of the magnetic levitation system, and there is little research on the time lag effect. Especially in static or highly disturbed environments (such as aerospace, vehicle-mounted and ship-mounted flywheel batteries), system stability is crucial for safe operation. Therefore, it is urgent to develop a control method that can effectively deal with the time lag effect and ensure the stable operation of the magnetic levitation flywheel energy storage system. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention is proposed.

[0006] Therefore, the problem to be solved by the present invention is how to solve the problem that in the closed-loop control of the magnetic levitation flywheel energy storage system, the filtering processing of the sensor signal and the calculation of the control algorithm inevitably introduce the time lag of the control signal. As a key factor affecting the stability of the system, the influence of the time lag is particularly significant, especially when the Hopf bifurcation phenomenon may be caused. When the time lag reaches a critical value, the system will undergo a Hopf bifurcation. As the input time lag increases, the amplitude of the stable periodic motion will gradually increase, and may even cause the system to lose control.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] In a first aspect, an embodiment of the present invention provides a stable control method for a magnetic suspension flywheel energy storage system with time-delay feedback, which includes determining the axial bearing capacity and radial bearing capacity requirement parameters of the flywheel energy storage device based on the gravity, impact load, and centrifugal force and unbalanced force generated during high-speed rotation of the flywheel rotor;

[0009] According to the load-bearing requirement parameters, a U-shaped stator structure is designed for the axial electromagnetic bearing, and an octapole electromagnetic bearing is designed for the radial electromagnetic bearing;

[0010] The temperature field distribution of the axial electromagnetic bearing and the radial electromagnetic bearing is simulated and analyzed by adopting a bidirectional coupling method of the electromagnetic field and the temperature field.

[0011] As a preferred solution of the stable control method of the magnetic levitation flywheel energy storage system with time-delay feedback described in the present invention, the axial bearing capacity requirement parameters include: the maximum static bearing capacity requirement, which is used to absorb the rotating shaft from a static state to stable suspension; the overload bearing capacity requirement, which is twice the static bearing capacity requirement, and is used to cope with disturbances during charging and discharging.

[0012] As an optimal solution of the stable control method of the magnetic levitation flywheel energy storage system with time-delay feedback described in the present invention, the U-shaped stator structure design includes: designing an equal-area structure of the inner ring and the outer ring magnetic poles, and the inner ring and the outer ring are made of electrical pure iron; designing a structure in which the thrust plate thickness is greater than the inner ring width; designing a preset single-sided air gap between the stator and the thrust plate, wherein the magnetic lines of force form a closed loop through the inner ring, the thrust plate, and the outer ring.

[0013] As a preferred solution of the stable control method of the magnetic levitation flywheel energy storage system with time-delay feedback described in the present invention, the design of the eight-pole electromagnetic bearing includes: using pressed silicon steel sheets to make the stator and rotor, and presetting an air gap between the stator and the rotor; arranging an installation space for the coil winding between adjacent poles, and the poles are evenly and symmetrically distributed in the circumferential direction; the heights of the stator and the rotor meet the magnetic conductivity requirements and avoid magnetic circuit saturation.

[0014] As a preferred solution of the stable control method of the magnetic levitation flywheel energy storage system with time-delay feedback described in the present invention, the bidirectional coupling simulation analysis includes: taking the coil copper loss and the core iron loss as heat sources to calculate the temperature field distribution; feeding back the calculation results of the temperature field to the electromagnetic field analysis to update the material resistivity; repeating the above calculation process until the temperature field distribution converges.

[0015] As a preferred solution of the stable control method of the magnetic levitation flywheel energy storage system with time-delay feedback described in the present invention, it also includes: arranging an auxiliary bearing protection system outside the bearing, and setting the protection gap between the auxiliary bearing and the electromagnetic bearing to be smaller than the working gap of the electromagnetic bearing; the auxiliary bearing is used to bear the weight of the rotor when the bearing is in the shutdown state.

[0016] As a preferred solution of the stable control method of the magnetic levitation flywheel energy storage system with time-delay feedback described in the present invention, it also includes: adopting differential working mode control for axial and radial electromagnetic bearings; by adjusting the bias current and the control current, dynamic adjustment of the bearing capacity of the electromagnetic bearing under different working conditions is achieved.

[0017] As a preferred solution of the stable control method of the magnetic levitation flywheel energy storage system with time-delay feedback described in the present invention, the temperature field distribution simulation analysis also includes: setting a natural air cooling heat dissipation method to determine the convective heat transfer coefficient between the magnetic pole and the air; determining the convective heat transfer coefficient between the coil winding and the air; using the convective heat transfer coefficient to calculate the temperature field distribution to ensure that the allowable operating temperature is not exceeded.

[0018] As a preferred solution of the stable control method of the magnetic levitation flywheel energy storage system with time-delay feedback described in the present invention, the U-shaped stator structure design also includes: making the inner ring and the outer ring with electrical pure iron material; dividing the stator into several sections along the circumferential direction to reduce eddy current losses.

[0019] As a preferred solution of the stable control method of the magnetic levitation flywheel energy storage system with time-delay feedback described in the present invention, the design of the radial electromagnetic bearing also includes: arranging the poles to be evenly and symmetrically distributed circumferentially; reserving space between adjacent poles for installing coils; and selecting the silicon steel sheet model according to the operating frequency and loss requirements.

[0020] In a second aspect, an embodiment of the present invention provides a computer device, including a memory and a processor, wherein the memory stores a computer program, wherein: when the computer program instructions are executed by the processor, the steps of the method for stabilizing the magnetic levitation flywheel energy storage system with time-delay feedback as described in the first aspect of the present invention are implemented.

[0021] In a third aspect, an embodiment of the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein: when the computer program instructions are executed by a processor, the steps of the method for stabilizing a magnetic levitation flywheel energy storage system with time-delay feedback as described in the first aspect of the present invention are implemented.

[0022] The beneficial effects of the present invention are as follows: the present invention determines the load-bearing capacity requirement parameters based on the gravity, impact load, centrifugal force and unbalanced force generated during high-speed rotation of the flywheel rotor, and combines the dual index design of maximum static load-bearing capacity and overload load-bearing capacity to achieve comprehensive protection of the system under various working conditions and improve the reliability of the system.

[0023] The U-shaped stator structure design, the equal area structure of the inner and outer ring magnetic poles and the optimization of the thrust plate thickness form an efficient magnetic closed loop, which significantly reduces the magnetic resistance and eddy current loss of the system. At the same time, the uniform and symmetrical design of the eight-pole electromagnetic bearing provides a stable radial bearing capacity and improves the dynamic characteristics of the system.

[0024] Through the bidirectional coupling analysis of electromagnetic field and temperature field, combined with the influence of coil copper loss and core iron loss, the accurate prediction and control of temperature field distribution is achieved. With the help of natural air cooling and reasonable heat transfer coefficient design, the temperature stability of the system in long-term operation is ensured.

[0025] An auxiliary bearing protection system is set up, and a differential working mode control strategy is adopted to achieve dynamic adjustment of the electromagnetic bearing capacity, improving the anti-interference ability and safety reliability of the system. This multiple protection mechanism effectively solves the Hopf bifurcation problem caused by the time lag effect in the existing technology and achieves stable operation of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 A flow chart of a stable control method for a magnetic levitation flywheel energy storage system with time-delay feedback;

[0028] Figure 2 A computer device diagram for a stable control method of a magnetic levitation flywheel energy storage system with time-delay feedback;

[0029] Figure 3 A schematic diagram of a vertical magnetic bearing for a stable control method of a magnetically suspended flywheel energy storage system with time-delay feedback;

[0030] Figure 4 The time response curve comparison diagram of the system when τ = 0.011 for the stable control method of the magnetic suspension flywheel energy storage system with time-delay feedback;

[0031] Figure 5τ=τ for the stable control method of magnetic levitation flywheel energy storage system with time-delay feedback 0 Comparison of the system's time response curves when ;

[0032] Figure 6 This is a comparison diagram of the system's time response curves when τ=0.012 for the stable control method of the magnetic levitation flywheel energy storage system with time-delay feedback. DETAILED DESCRIPTION

[0033] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0034] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0035] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it a separate or selective embodiment that is mutually exclusive with other embodiments.

[0036] Example 1

[0037] Reference Figure 1-2 , which is the first embodiment of the present invention, provides a stable control method for a magnetic levitation flywheel energy storage system with time-delay feedback, comprising:

[0038] S100: Determine the axial bearing capacity and radial bearing capacity requirement parameters of the flywheel energy storage device based on the gravity, impact load, and centrifugal force and unbalanced force generated during high-speed rotation of the flywheel rotor;

[0039] In the embodiment of the present application, the basic gravity load is first calculated according to the rotor design parameters. The total gravity load of the rotor is the product of the rotor mass and the gravitational acceleration. For example, for a typical 120kg rotor, the gravity load is about 1176N. This gravity load is used as the reference value of the design parameters for subsequent load calculations. In practical applications, since the flywheel energy storage system will produce instantaneous impacts during startup and shutdown, the influence of the impact coefficient needs to be considered. According to engineering experience, the impact coefficient K is usually between 2.0 and 3.0, and the maximum impact load is the product of the static load and the impact coefficient.

[0040] Furthermore, the present invention also takes into account the centrifugal force generated when the flywheel rotates at high speed. The centrifugal force is calculated using the standard formula F = mω2 r, where ω represents the rotor angular velocity, which is usually in the range of 10,000 to 50,000 rpm in practical applications; r represents the eccentricity of the center of mass, which is generally controlled in the range of 0.01 to 0.05 mm according to the machining accuracy requirements. By accurately calculating the magnitude of the centrifugal force, the dynamic characteristics of the system at high speed can be effectively predicted.

[0041] In addition, the present invention also pays special attention to the influence of unbalanced forces. According to ISO 1940-1 standard, this system adopts G2.5 dynamic balancing requirements. The residual unbalance can be calculated by the formula U = 9549 × G × W / N, where G is the balance grade (mm / s), W is the rotor weight (kg), and N is the rated speed (rpm). This calculation method ensures the smooth operation of the system under various working conditions.

[0042] In a preferred embodiment of the present application, the system design also takes into account the impact of temperature changes on bearing performance. In the operating temperature range of -40°C to +85°C, the thermal expansion of the material will cause the air gap to change, thereby affecting the load-bearing capacity. Therefore, when determining the load-bearing capacity requirement parameters, it is necessary to comprehensively consider the impact of the temperature effect. Specifically, by establishing a thermal-mechanical coupling analysis model, the air gap change at different temperatures is calculated, and the load-bearing capacity parameters are adjusted accordingly.

[0043] In another preferred embodiment, the system also establishes a vibration response analysis model. By analyzing the vibration characteristics in the frequency range of 0.5Hz-2000Hz, the natural frequency and modal characteristics of the system are determined. This analysis is of great significance for preventing resonance phenomena and can effectively avoid severe vibration of the system at a specific speed.

[0044] More specifically, the present invention uses dual indicators of maximum static bearing capacity and overload bearing capacity in the process of determining the axial bearing capacity requirement parameters. The maximum static bearing capacity is mainly used to ensure that the system can stably lift the rotor from a static state to a suspended position, while the overload bearing capacity mainly considers various dynamic loads that the system may encounter during the charging and discharging process. According to engineering experience, the overload bearing capacity is usually twice the static bearing capacity to provide sufficient safety margin.

[0045] For the radial load requirement parameters, the present invention adopts a dynamic modeling method for analysis. By establishing a dynamic model of the rotor-bearing system, the radial force distribution under different working conditions is simulated and analyzed. This method not only considers the static load, but also includes the influence of the dynamic load, making the system design more reasonable and reliable.

[0046] It should be noted that the determination process of the above parameters fully considers the actual working environment of the system. Under the condition that the atmospheric pressure changes in the range of 0.8-1.1 standard atmospheric pressure, the suspension control performance of the system must remain stable. At the same time, when the relative humidity changes in the range of 0% to 95%, it should not have a significant impact on the system performance. This comprehensive environmental adaptability consideration ensures the reliable operation of the system under various actual working conditions.

[0047] S101: The axial bearing capacity requirement parameters include: the maximum static bearing capacity requirement, which is used to lift the shaft from a static state to a stable suspension; the overload bearing capacity requirement, which is twice the static bearing capacity requirement, and is used to cope with disturbances during charging and discharging.

[0048] S200: Based on the load-bearing requirement parameters, a U-shaped stator structure is designed for the axial electromagnetic bearing, and an octapole electromagnetic bearing is designed for the radial electromagnetic bearing;

[0049] In the embodiment of the present application, the design of the U-shaped stator structure first considers the magnetic circuit design. In the magnetic circuit design, the control of the magnetic flux density is a key factor. The present invention controls the magnetic flux density within the range of 1.4-1.6T through precise calculation and simulation analysis. This range can not only ensure sufficient magnetic field strength, but also prevent the core material from entering the deep saturation area. At the air gap, the magnetic field strength is maintained between 0.5-0.8T. This design parameter fully considers the requirements of the linearity and control characteristics of the magnetic field. The design of the core cross-sectional area is based on the distribution characteristics of the magnetic flux, and the uniform distribution of the magnetic flux density is ensured through optimization calculation to avoid local saturation.

[0050] In terms of coil design, the present invention uses an accurate ampere-turn theorem calculation method to determine the number of coil turns. Specifically, the total ampere-turns of the coil are determined by the required magnetic field strength, air gap length, and magnetic circuit length. In actual design, considering the dynamic response requirements of the suspension system, enameled wire of appropriate specifications is selected, and a scientific winding method is adopted. For example, for a coil design of 160 turns, a layered winding method is adopted, and each layer controls the uniformity of the winding to ensure good heat dissipation performance.

[0051] The present invention adopts an equal-area structure in the design of the inner and outer ring magnetic poles of the U-shaped stator. This design can ensure the symmetry of the magnetic field distribution and help improve the control accuracy of the system. Both the inner and outer rings are made of high-quality electrical pure iron material, which has excellent magnetic permeability and low coercive force, and can effectively reduce hysteresis loss. The thickness design of the thrust plate specifically considers the influence of the inner ring width. By designing the thickness of the thrust plate to be greater than the inner ring width, the reasonable distribution of the magnetic flux path is ensured.

[0052] In terms of the design of the air gap between the stator and the thrust plate, the present invention adopts a precise single-sided air gap structure. This structure enables the magnetic lines of force to form a complete closed loop through the inner ring, the thrust plate, and the outer ring, thereby achieving the optimal magnetic field distribution. The size of the air gap is determined by precise calculations to ensure sufficient working space while maintaining a high magnetic field strength. Typically, the air gap value is set at about 1 mm, and this design parameter shows good stability and controllability in practical applications.

[0053] The design of the eight-pole electromagnetic bearing is also based on rigorous theoretical calculations and practical experience. The present invention uses pressed silicon steel sheets to make the stator and rotor, which has good magnetic properties and low eddy current losses. The air gap between the stator and the rotor is optimized to ensure that the power consumption is minimized while maintaining sufficient load-bearing capacity. In terms of pole design, sufficient coil winding installation space is reserved between adjacent poles, while ensuring that the poles are evenly and symmetrically distributed in the circumferential direction. This layout is conducive to generating uniform radial force.

[0054] Furthermore, the present invention adopts an innovative design scheme in optimizing the stator structure. By dividing the stator into multiple segments along the circumferential direction, eddy current loss is significantly reduced. This segmented structure not only reduces energy consumption, but also improves the dynamic response characteristics of the system. Each segment is isolated by non-magnetic materials, which effectively avoids magnetic flux leakage between segments. At the same time, the connection of each segment adopts a special mechanical fixing method, which not only ensures the structural strength, but also facilitates assembly and maintenance.

[0055] S201: The U-shaped stator structure design includes: designing a structure with equal area of ​​inner and outer ring magnetic poles, the inner and outer rings are made of electrical pure iron; designing a structure with thrust plate thickness greater than the width of the inner ring; designing a preset single-sided air gap between the stator and the thrust plate, in which the magnetic lines of force form a closed loop through the inner ring, thrust plate and outer ring.

[0056] S202: The design of the eight-pole electromagnetic bearing includes: using pressed silicon steel sheets to make the stator and rotor, with a preset air gap between the stator and the rotor; setting up installation space for the coil winding between adjacent poles, and the poles are evenly and symmetrically distributed in the circumferential direction; the height of the stator and the rotor meets the magnetic conductivity requirements and avoids magnetic circuit saturation.

[0057] S203: The U-shaped stator structure design also includes: the inner ring and the outer ring are made of electrical pure iron material; and the stator is divided into several sections along the circumferential direction to reduce eddy current loss.

[0058] S204: The design of the radial electromagnetic bearing also includes: setting the poles to be evenly and symmetrically distributed in the circumferential direction; reserving space between adjacent poles for installing the coil; and selecting the silicon steel sheet model according to the operating frequency and loss requirements.

[0059] S300: The temperature field distribution of axial electromagnetic bearings and radial electromagnetic bearings is simulated and analyzed by using the bidirectional coupling method of electromagnetic field and temperature field.

[0060] In the embodiment of the present application, the bidirectional coupling analysis of the electromagnetic field and the temperature field adopts advanced multi-physics field simulation technology. First, a three-dimensional finite element model is established, which includes the complete geometric characteristics of the bearing system and sets accurate material property parameters. In the setting of boundary conditions, various constraints under actual working conditions are fully considered, including mechanical constraints and electromagnetic boundary conditions.

[0061] For electromagnetic field analysis, the present invention adopts a solution method based on Maxwell's equations. The calculation process takes into account the nonlinear characteristics of the material, especially the BH curve characteristics of the core material. Through iterative calculation, the accurate distribution of the electromagnetic field is obtained. This analysis method can not only accurately predict the electromagnetic characteristics of the system, but also provide heat source data for subsequent temperature field analysis.

[0062] In the temperature field analysis, the present invention focuses on three main heat sources: copper loss of the coil, iron loss of the core, and mechanical loss. Through precise modeling, the distribution characteristics of these heat sources under different working conditions are calculated. The heat conduction analysis adopts a heat transfer model that takes into account the anisotropy of the material, and the heat convection analysis is based on the experimentally verified convection heat transfer coefficient. In addition, the influence of thermal radiation is also considered, although its influence is relatively small at normal operating temperatures.

[0063] A major innovation of the present invention is the realization of real-time coupling calculation of electromagnetic field and temperature field. When the temperature field changes, the resistivity of the material will change accordingly. This change is fed back to the electromagnetic field analysis through the coupling equation, thereby updating the distribution of the electromagnetic field. Through this two-way coupling method, the system can more accurately predict the temperature distribution under actual working conditions, providing an important basis for the optimization of bearing design and control strategy.

[0064] In order to improve the computational efficiency, the present invention adopts an intelligent grid division strategy. Fine grids are used in key areas such as air gaps and coils, while relatively coarse grids are used in other areas. This adaptive grid technology not only ensures the computational accuracy, but also significantly improves the computational efficiency. At the same time, parallel computing technology is introduced to make full use of the computing power of multi-core processors, further shortening the analysis time.

[0065] It should be noted that the present invention pays special attention to the uniformity of temperature field distribution in simulation analysis. Through optimized design, the temperature gradient is controlled within a reasonable range to avoid performance degradation caused by local overheating. At the same time, through comprehensive thermal stress analysis, it is ensured that the system can maintain good mechanical strength and dimensional stability under various working conditions. These analysis results provide a reliable theoretical basis for the design and optimization of actual systems.

[0066] The multi-physics field coupling analysis method adopted by the present invention not only improves the accuracy of the design, but also significantly reduces the time and cost of actual experiments. Through virtual simulation, potential problems can be discovered and solved in the design stage, greatly improving development efficiency. The practicality and reliability of this method have been fully verified in actual engineering applications.

[0067] S301: The bidirectional coupling simulation analysis includes: taking the coil copper loss and the core iron loss as heat sources to calculate the temperature field distribution; feeding back the temperature field calculation results to the electromagnetic field analysis to update the material resistivity; repeating the above calculation process until the temperature field distribution converges.

[0068] S302: Also includes: setting an auxiliary bearing protection system outside the bearing, and setting the protection gap between the auxiliary bearing and the electromagnetic bearing to be smaller than the working gap of the electromagnetic bearing; the auxiliary bearing is used to bear the weight of the rotor when the bearing is stopped.

[0069] S303: Also includes: adopting differential working mode control for axial and radial electromagnetic bearings; and dynamically adjusting the bearing capacity of the electromagnetic bearings under different working conditions by adjusting the bias current and the control current.

[0070] S304: The temperature field distribution simulation analysis also includes: setting a natural air cooling method to determine the convective heat transfer coefficient between the magnetic pole and the air; determining the convective heat transfer coefficient between the coil winding and the air; and using the convective heat transfer coefficient to calculate the temperature field distribution to ensure that the allowable operating temperature is not exceeded.

[0071] In summary, by determining the load-bearing capacity requirement parameters based on the gravity, impact load, centrifugal force and unbalanced force of the flywheel rotor, combining the U-shaped stator structure and the eight-pole electromagnetic bearing design, as well as the two-way coupling analysis of the electromagnetic field and the temperature field, a complete magnetic levitation flywheel energy storage system control solution is formed. This system architecture can effectively solve the Hopf bifurcation problem caused by time lag in the existing technology and improve the stability and reliability of the system.

[0072] By dividing the load-bearing capacity requirement parameters into two levels: maximum static load-bearing capacity and overload load-bearing capacity, where the overload load-bearing capacity is set to twice the static load-bearing capacity, comprehensive protection of the system under static suction and dynamic disturbance conditions is achieved. This design not only ensures that the rotor can be stably suspended, but also provides sufficient dynamic load margin, effectively preventing system instability during charging and discharging.

[0073] The inner and outer rings are designed with equal area magnetic poles and made of electrical pure iron material. Combined with the structural feature that the thickness of the thrust plate is greater than the width of the inner ring, an efficient magnetic closed loop is formed. This structural design reduces magnetic resistance, improves magnetic field utilization, reduces eddy current loss, and improves the energy conversion efficiency of the system.

[0074] By using pressed silicon steel sheets to make the stator and rotor and reserving coil installation space between adjacent poles, a uniform and symmetrical radial force distribution is achieved. This design not only improves the load-bearing capacity, but also significantly improves the dynamic characteristics of the system and reduces vibration and noise.

[0075] Through the bidirectional coupling analysis of electromagnetic field and temperature field, the influence of coil copper loss and core iron loss is taken into account, and a more accurate prediction of temperature field distribution is achieved. This method can timely discover potential hot spots, optimize heat dissipation design, and improve the operating reliability and service life of the system.

[0076] By setting up an auxiliary bearing protection system and ensuring that its protection gap is smaller than the working gap of the electromagnetic bearing, the rotor load can be taken over in time when a system failure occurs. This design provides a reliable safety protection mechanism for the system, avoids equipment damage, and improves the safety of the system.

[0077] By adopting differential working mode control and adjusting the bias current and control current, the dynamic adjustment of the bearing capacity of the electromagnetic bearing under different working conditions is realized. This control strategy improves the dynamic response capability of the system and improves the anti-interference performance of the system.

[0078] Example 2

[0079] Reference Figure 2 - Figure 6 , which is the second embodiment of the present invention.

[0080] In the flywheel energy storage system, the system model of the single-degree-of-freedom vertical magnetic bearing differential control is as follows: Figure 3 In this system, the control current i and the bias current I b Share the same coil. The coil current i of the electromagnet 1 and i 2 The two electromagnets generate electromagnetic forces f in opposite directions. 1 and f 2 f 2 , thereby controlling the relative displacement z of the rotor in the horizontal direction. Considering only the external force on the rotor in this plane, ignoring the magnetic resistance, leakage flux, and edge effect of the magnetic flux of the magnetic conductor, and ignoring the loss of the core and coil, assuming that the rotor deflects downward, we have

[22]

[0081]

[0082] Where m is the rotor mass, z 0 is the desired suspension gap, z is the relative displacement of the rotor in the horizontal direction, μ 0 is the vacuum magnetic permeability, N is the number of coil turns, S is the bearing area,

[0083] The voltage equations of the electromagnets on both sides are [23-24]

[0084]

[0085] Among them, u 1 ,u 2 are the voltages of the electromagnet coils on both sides, and R is the coil resistance.

[0086] The voltage applied across the magnetic bearing is expressed as:

[0087]

[0088] Among them, u ec is the voltage value corresponding to the control current in the electromagnet, u b is the bias voltage of the electromagnet.

[0089] Let the state variable Output variable, the state space equation of the open-loop system is:

[0090]

[0091] In order to make the rotor in z 0 In order to achieve suspension balance, a closed-loop system needs to be formed through feedback control. Considering the time lag between the position feedback signal and the speed feedback signal, the voltage of the magnetic suspension system is controlled by the following PID controller:

[0092] u=k p x 1τ +k d x 2τ +k c x 3 (5)

[0093] Among them, x 1τ =x 1 (t-τ 1 ) represents the position signal with time lag, x 2τ =x 2 (t-τ 2 ) represents the speed signal with time lag, and τ 1 =τ 2 =τ. k p , k d and k care the control gains of position, speed and current feedback respectively. Equations (4) and (5) are the models of vertical magnetic bearing differential control system.

[0094] Hopf bifurcation analysis

[0095] In this section, we will linearize the system (4) and discuss the conditions for the occurrence of Hopf bifurcation. First, the equilibrium point of the system (4) is x 0 =[0,0,0]. In order to analyze the dynamic behavior of the system near the equilibrium point, we perform a first-order Taylor expansion on equation (4). 0 The first-order Taylor expansion at is:

[0096]

[0097] Among them, A 0 is the Jacobian matrix of the system at the equilibrium point, A 1 is the influence matrix of the delayed state on the system, and f represents a higher-order nonlinear term. Matrix A 0 and A 1 The specific expression is:

[0098]

[0099] in,

[0100] The characteristic equation of the linearized system is

[0101] λ 3 +a 2 λ 2 +a 1 λ+a 0 =0 (7)

[0102] Among them, the coefficient a 2 ,a 1 ,a 0 is a function of system parameters. Due to the delay effect in the system, these coefficients include the influence of time delay τ, which is specifically expressed as:

[0103] a i =a i0 +a i1 e -λτ (i=0,1,2) (8)

[0104] Among them, a i0 represents the system parameters without delay, a i1 Represents the impact of the delay term on the system. i0 and a i1 The specific expression is as follows:

[0105]

[0106] According to (8) and (9), the characteristic polynomial of system (6) can be expressed as:

[0107] P(λ,τ)=λ 3 +a 20 λ 2 +a 11 λe -λτ +a 01 e -λτ +a 00 (10)

[0108] When τ = 0, the delay term in the characteristic polynomial (10) disappears, and (10) is simplified to

[0109] P(λ,0)=λ 3 +a 20 λ 2 +a 11 λ+a 01 +a 00 =0 (11)

[0110] Lemma 2.1. The necessary and sufficient condition for the roots of equation (11) to have negative real parts is:

[0111] a 20 >0,a 20 a 11 >a 01 +a 00 ,a 01 +a 00 >0

[0112] From Lemma 2.1, we can find that the range of control parameters for which the roots of equation (11) all have negative real parts is

[0113]

[0114] Considering the time delay τ≠0, Lemma 3.1 cannot be used to guarantee the local stability of trivial solutions. Let the complex number λ=α+iβ(β>0, α, β are real numbers) be the root of the characteristic equation (10), substitute it into (10), separate the real part and the imaginary part, and we get

[0115]

[0116] When the roots of the characteristic equation (10) are purely imaginary roots (α = 0, λ = ±iβ), (13) can be simplified to

[0117]

[0118] We can further obtain the polynomial of β

[0119]

[0120] Equation (15) always has a positive root, that is, equation (10) always has a pair of pure imaginary characteristic roots ±iβ 0 From equation (14), we can get the corresponding time lag τ should satisfy

[0121]

[0122] When a pair of complex roots crosses the imaginary axis, the velocity is not zero, that is, the characteristic equation (10) is differentiated with respect to τ and its real part is taken to obtain

[0123]

[0124] in,

[0125] q=2a 20 β 0 -a 11 sinβ 0 τ 0 -a 11 τ 0 β 0 -a 01 τ 0 sinβ 0 τ 0 .

[0126] when Satisfy the crossing condition, when τ = τ j (j=0,1,2,…) Hopf bifurcation of the system occurs. In summary, we get the following theorem

[0127] The time-delay parameter τ of the system has a key influence on stability:

[0128] When τ<τ 0 , the system is asymptotically stable.

[0129] When τ=τ 0 When , the system has a periodic solution at the bifurcation point and produces a Hopf bifurcation.

[0130] When τ>τ 0 , the system becomes divergent.

[0131] Simulation Analysis

[0132] In order to explore the influence of time delay on Hopf bifurcation, we will use Matlab to perform numerical simulation on the magnetic suspension flywheel energy storage system, obtain the time response position curve and phase plane trajectory under different time delays, and analyze them. The parameters of the vertical magnetic suspension bearing used in the simulation are shown in Table 1. The control feedback parameter is selected as k c=0.18, k p =232, k d =8.

[0133]

[0134] The critical time lag calculated according to formula (16) is τ 0 =0.0115. The system is in τ 0 = 0.0115 near the simulation results are as follows Figure 4-6 shown.

[0135] from Figure 4 It can be seen that when the system delay τ=0.011<τ 0 When , the magnetic levitation flywheel energy storage system is in a stable state, and the state variable x gradually approaches zero, that is, the absolute displacement of the electromagnet in the vertical direction converges to the expected suspension gap x = 5×10 -4 m, the flywheel energy storage system remains stable. When τ=τ 0 , the system begins to oscillate periodically; when τ=0.012>τ 0 ,from Figure 6 It can be seen that the magnetic suspension system becomes unstable and the state variable x does not converge to 0. At this point, the closed-loop system enters an unstable state, the rotor collides with the bearing, and the flywheel energy storage system is completely out of control. The feedback lag is adjusted by the calculated critical value of the lag to keep the system stable.

[0136] In this paper, for the magnetic bearing with time lag in position and speed in the flywheel energy storage system, the critical time lag of the Hopf bifurcation of the system is obtained through equilibrium point linearization calculation. The simulation results show that when the system has time lag τ = τ 0 , the system undergoes Hopf bifurcation and the rotor undergoes periodic oscillation. If the system time delay exceeds the critical value, the stability of the nonlinear system will be destroyed, resulting in instability of the flywheel energy storage system.

[0137] Therefore, in order to avoid Hopf bifurcation and system instability, the system design parameters should ensure that the time delay is kept within [0, τ 0 ) range to ensure the stability of the magnetic levitation flywheel energy storage system.

[0138] Example 3

[0139] This embodiment also provides a computer device, which is applicable to a method for stabilizing a magnetic levitation flywheel energy storage system with time-delay feedback, and includes a memory and a processor; the memory is used to store computer executable instructions, and the processor is used to execute computer executable instructions to implement a forced oscillation detection and positioning method for a distribution network as proposed in the above embodiment.

[0140] This embodiment further provides a storage medium on which a computer program is stored. When the program is executed by a processor, a forced oscillation detection and positioning method for a distribution network is implemented as proposed in the above embodiment.

[0141] The computer device may be a terminal, and the computer device includes a processor, a memory, a communication interface, a display screen and an input device connected via a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The communication interface of the computer device is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner can be achieved through WIFI, an operator network, NFC (near field communication) or other technologies. The display screen of the computer device may be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device may be a touch layer covering the display screen, or a key, trackball or touchpad provided on the housing of the computer device, or an external keyboard, touchpad or mouse, etc.

[0142] If the function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods of each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc. Various media that can store program codes.

[0143] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0144] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering, or processing in another suitable manner as necessary, and then stored in a computer memory.

[0145] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, any one of the following technologies known in the art or a combination thereof can be used to implement: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0146] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A stable control method for a magnetic suspension flywheel energy storage system with time-delay feedback, characterized in that: Including, based on the gravity, impact load, centrifugal force and unbalanced force generated by the flywheel rotor during high-speed rotation, determining the axial bearing capacity and radial bearing capacity requirement parameters of the flywheel energy storage device; According to the load-bearing requirement parameters, a U-shaped stator structure is designed for the axial electromagnetic bearing, and an octapole electromagnetic bearing is designed for the radial electromagnetic bearing; The temperature field distribution of the axial electromagnetic bearing and the radial electromagnetic bearing is simulated and analyzed by adopting a bidirectional coupling method of the electromagnetic field and the temperature field.

2. The stable control method of a magnetic suspension flywheel energy storage system with time-delay feedback according to claim 1, characterized in that: The axial bearing capacity requirement parameters include: a maximum static bearing capacity requirement, which is used to lift the rotating shaft from a static state to a stable suspension; an overload bearing capacity requirement, which is twice the static bearing capacity requirement and is used to cope with disturbances during charging and discharging.

3. The method for stable control of a magnetic levitation flywheel energy storage system with time-delay feedback according to claim 2, characterized in that: The U-shaped stator structure design includes: designing an equal-area structure of the inner ring and the outer ring magnetic poles, wherein the inner ring and the outer ring are made of electrical pure iron; designing a structure in which the thickness of the thrust plate is greater than the width of the inner ring; and designing a preset single-sided air gap between the stator and the thrust plate, wherein the magnetic lines of force form a closed loop through the inner ring, the thrust plate, and the outer ring.

4. The method for stable control of a magnetic levitation flywheel energy storage system with time-delay feedback according to claim 3, characterized in that: The design of the eight-pole electromagnetic bearing includes: using pressed silicon steel sheets to make the stator and the rotor, with an air gap preset between the stator and the rotor; providing an installation space for the coil winding between adjacent poles, with the poles being evenly and symmetrically distributed in the circumferential direction; and the heights of the stator and the rotor meeting the magnetic conductivity requirements and avoiding magnetic circuit saturation.

5. The method for stable control of a magnetic levitation flywheel energy storage system with time-delay feedback according to claim 4, characterized in that: The bidirectional coupling simulation analysis includes: taking the coil copper loss and the core iron loss as heat sources to calculate the temperature field distribution; feeding back the temperature field calculation results to the electromagnetic field analysis to update the material resistivity; and repeating the above calculation process until the temperature field distribution converges.

6. The method for stable control of a magnetic levitation flywheel energy storage system with time-delay feedback according to claim 5, characterized in that: Also includes: An auxiliary bearing protection system is arranged outside the bearing, and the protection clearance between the auxiliary bearing and the electromagnetic bearing is set to be smaller than the working clearance of the electromagnetic bearing; the auxiliary bearing is used to bear the weight of the rotor when the bearing is stopped.

7. The method for stable control of a magnetic levitation flywheel energy storage system with time-delay feedback according to claim 6, characterized in that: Also includes: A differential working mode is adopted for axial and radial electromagnetic bearings; by adjusting the bias current and the control current, the bearing capacity of the electromagnetic bearings under different working conditions can be dynamically adjusted.

8. The method for stable control of a magnetic suspension flywheel energy storage system with time-delay feedback according to claim 7, characterized in that: The temperature field distribution simulation analysis also includes: setting a natural air cooling heat dissipation method to determine the convective heat transfer coefficient between the magnetic pole and the air; determining the convective heat transfer coefficient between the coil winding and the air; and using the convective heat transfer coefficient to calculate the temperature field distribution to ensure that the allowable operating temperature is not exceeded.

9. The method for stable control of a magnetic levitation flywheel energy storage system with time-delay feedback according to claim 8, characterized in that: The U-shaped stator structure design also includes: the inner ring and the outer ring are made of electrical pure iron material; and the stator is divided into several sections along the circumferential direction to reduce eddy current loss.

10. The method for stable control of a magnetic levitation flywheel energy storage system with time-delay feedback according to claim 9, characterized in that: The design of the radial electromagnetic bearing also includes: arranging the poles to be evenly and symmetrically distributed in the circumferential direction; reserving space between adjacent poles for installing the coil; and selecting the model of the silicon steel sheet according to the operating frequency and loss requirements.

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