Fuzzy adaptive inertia control method for supercapacitor energy storage type doubly-fed wind turbine based on soc

Abstract

This invention relates to a fuzzy adaptive inertia control method for a supercapacitor-based doubly-fed induction generator (DFIG) wind turbine, belonging to the field of power systems. The invention addresses the problems in existing wind-storage joint frequency regulation control methods, such as poor adaptability due to fixed parameters, susceptibility to overcharging and over-discharging due to lack of consideration for energy storage state-of-charge constraints, and the lack of a coordinated control mechanism for frequency support and voltage stability. The invention includes: establishing a doubly-fed induction generator (DFIG) and supercapacitor energy storage system; establishing a mathematical model of virtual rotational inertia and inertia coefficient; designing a fuzzy logic controller using frequency deviation, frequency change rate, DC bus voltage, and SOC as inputs, outputting inertia coefficient correction, voltage deviation coefficient correction, and energy storage output correction coefficient; updating the virtual rotational inertia and voltage compensation to synthesize a composite power command; and when the SOC enters the danger zone, the supercapacitor is deactivated, and the DFIG switches to VSG mode to compensate for active power deficit.

Description

Technical Field

[0001] This invention belongs to the field of power system stability analysis and new energy power generation technology, specifically involving a fuzzy adaptive inertia control method for a supercapacitor-based doubly-fed wind turbine. Background Technology

[0002] With the increasing penetration rate of wind power, the frequency stability problem of the power system is becoming increasingly prominent. Doubly fed wind turbines typically operate in maximum power point tracking mode, where the rotor speed is decoupled from the grid frequency. Unlike traditional synchronous generators, they cannot automatically respond to frequency changes, resulting in a decrease in system inertia and a weakening of frequency regulation capability, posing challenges to the safe and stable operation of the power grid.

[0003] To improve the grid-friendliness of wind power, energy storage systems are widely used in wind-storage joint frequency regulation scenarios due to their advantages such as fast response speed and flexible control. Supercapacitors, as a type of power storage element, have the characteristics of long cycle life and high power density, making them suitable for short-term, high-frequency power support.

[0004] However, existing control strategies for energy storage participating in grid frequency regulation are mostly based on traditional integrated inertial control, whose control parameters are usually fixed values, making it difficult to dynamically adjust according to system operating status and frequency changes, resulting in poor adaptability. At the same time, traditional methods often do not fully consider the state of charge and charge / discharge power boundaries of energy storage during the control process, which can easily lead to overcharging and over-discharging, affecting the service life of energy storage devices and the reliability of system operation.

[0005] Therefore, how to design a wind-storage joint control strategy that can adapt to frequency changes and take into account energy storage safety has become an urgent technical problem to be solved in the field of new energy grid connection. Summary of the Invention

[0006] To address the problems in existing wind-storage joint frequency regulation control methods, such as poor adaptability due to fixed parameters, susceptibility to overcharging and over-discharging due to lack of consideration for energy storage state of charge constraints, and lack of frequency support and voltage stability coordination control mechanisms, this invention provides a fuzzy adaptive inertia control method for supercapacitor-based doubly-fed wind turbines.

[0007] The fuzzy adaptive inertia control method for supercapacitor-based doubly-fed wind turbines based on SOC, as described in this invention, includes the following steps:

[0008] S1. Establish a grid-connected system model that includes doubly fed wind turbines and supercapacitor energy storage, and establish a voltage source type virtual synchronous machine control framework for the system based on the synchronous generator rotor motion equation.

[0009] S2. Based on the equivalent relationship between the rotational kinetic energy of a synchronous generator and the electrical energy stored in a supercapacitor, establish the virtual rotational inertia of the supercapacitor. With inertia coefficient Mathematical model;

[0010] S3. Monitor the frequency deviation of the synchronous generator. Rate of change of frequency DC bus voltage And the state of charge (SOC) of supercapacitors;

[0011] S4, the frequency deviation Rate of change of frequency DC bus voltage The state of charge (SOC) is input to a fuzzy adaptive controller, which dynamically outputs an adjustment to the inertia coefficient according to preset fuzzy rules. Inertia coefficient correction amount Voltage deviation coefficient Voltage deviation coefficient correction amount and the correction factor for energy storage output ;

[0012] S5. Based on the corrected inertia coefficient Update the virtual rotational inertia of the supercapacitor And based on the corrected voltage deviation coefficient Calculate DC bus voltage compensation Based on the dynamically adjusted virtual moment of inertia and voltage compensation, a composite power command is generated to control the charging and discharging of the supercapacitor.

[0013] S6. Based on the real-time state of charge (SOC) of the supercapacitor, adjust the energy storage output using the energy storage correction coefficient. Apply safety limits to its output power command;

[0014] S7. When the supercapacitor is unable to provide the required power support due to state of charge limitation, control the doubly fed wind turbine to switch to virtual synchronous machine control mode to compensate for the system's active power deficit.

[0015] Preferably, the virtual rotational inertia of the supercapacitor in step S2 With inertia coefficient The mathematical model is as follows:

[0016]

[0017] In the formula, This refers to the rated capacitance of the supercapacitor. This is the voltage of the supercapacitor. This represents the charge of the supercapacitor at time 0. This represents the synchronous angular velocity of the generator.

[0018] Preferably, the generation of composite power command in step S5 specifically includes:

[0019] Based on the virtual rotational inertia of the supercapacitor Calculate virtual inertial power components :

[0020]

[0021] According to voltage deviation coefficient and frequency deviation Calculate DC bus voltage compensation :

[0022]

[0023] Based on the voltage compensation amount Generate DC voltage stable power component :

[0024]

[0025] in, This is the equivalent capacitance value of the supercapacitor;

[0026] The DC voltage stabilized power component With the virtual inertial power component Composite power command :

[0027] .

[0028] Preferably, the inertia coefficient correction amount output by the fuzzy adaptive controller in step S4 Voltage deviation coefficient correction amount Used for real-time adjustment of control coefficients:

[0029]

[0030] In the formula, The constant is the coefficient of inertia in steady state; This is the correction amount for the steady-state voltage deviation coefficient.

[0031] Preferably, the fuzzy adaptive controller in step S4 performs fuzzification processing on the input variables, mapping each input quantity to a corresponding fuzzy subset;

[0032] The frequency deviation Rate of change of frequency DC bus voltage The four input quantities of the supercapacitor SOC and the inertia coefficient correction quantity. Voltage deviation coefficient correction amount Energy storage output correction factor The fuzzy subsets of the three output quantities are {VS represents very small, S represents small, RS represents relatively small, M represents medium, RB represents relatively large, B represents large, and VB represents very large}.

[0033] Preferably, the fuzzy rule includes rules based on frequency deviation. Rate of change of frequency and DC bus voltage Simultaneously adjust and Rules:

[0034] When the frequency deviation is negative:

[0035] If the frequency deviation, the rate of change of frequency, and the DC bus voltage are all VS, then Take RB, Take RS;

[0036] If the frequency deviation is VS, the rate of frequency change is negative and is M or RB and continues to decrease, and the DC bus voltage is M or RB, then Choose B. Choose M or RB;

[0037] If the frequency deviation is M or RB, the rate of frequency change is negative and is M or RB, and the DC bus voltage is S or RS, then Take RS, Take RB;

[0038] If the frequency deviation is B or VB, the rate of frequency change is negative and is VS, and the DC bus voltage is VS, then =0, Choose B or VB;

[0039] If the frequency deviation is M or RB, the rate of frequency change is positive and is S or RS, and the DC bus voltage is S or RS and begins to rise, then Take RS, Choose B or VB;

[0040] If the frequency deviation is S or RS, the rate of frequency change is positive and is S or RS, and the DC bus voltage is M, then Choose M or RB. Choose VS or S;

[0041] When the frequency recovers to its steady-state value, the DC bus voltage recovers as well. =0, =0;

[0042] When the frequency deviation is positive:

[0043] If the frequency deviation, the rate of change of frequency, and the DC bus voltage are all VS, then Take RB, Take RS;

[0044] If the frequency deviation is VS, the rate of frequency change is positive and is M or RB and continues to increase, and the DC bus voltage is M or RB, then Choose B. Choose M or RB;

[0045] If the frequency deviation is M or RB, the rate of frequency change is positive and is M or RB, and the DC bus voltage is S or RS, then Take RS, Take RB;

[0046] If the frequency deviation rate is 0, the DC bus voltage is at its highest. =0, Choose B or VB;

[0047] If the frequency deviation is M or RB, the rate of frequency change is positive and is S or RS, and the DC bus voltage is S or RS and begins to rise, then Take RS, Choose B or VB;

[0048] If the frequency deviation is S or RS, the rate of frequency change is positive and is S or RS, and the DC bus voltage is M, then Choose M or RB. Choose VS or S;

[0049] When the frequency recovers to its steady-state value, the DC bus voltage recovers as well. =0, =0.

[0050] Preferably, the fuzzy rule further includes rules based on frequency deviation. Rate of change of frequency Determine the energy storage output correction factor based on the supercapacitor's SOC. Rules:

[0051] When SOC is B or VB and frequency deviation is negative =1;

[0052] When SOC is RS or M Take RS or M, and change positively with SOC;

[0053] When SOC is VS or S =0.

[0054] Preferably, the safety limitation based on the real-time state of charge (SOC) of the supercapacitor in step S6 specifically includes:

[0055] The supercapacitor SOC is divided into three operating regions:

[0056] Workspace: SOC ;

[0057] Alert Zone: SOC ;

[0058] Danger Zone: SOC ;

[0059] And establish corresponding output rules: full output is allowed in the work area, output is restricted in the warning area, and output is prohibited in the danger area.

[0060] Preferably, the safety limit is determined by an energy storage output correction coefficient. accomplish:

[0061]

[0062] in, This is the actual output power after safety limits. The value selection rule is: work area =1, Warning Zone It increases with increasing SOC, decreases with decreasing SOC, and 0 < <1, Danger Zone =0.

[0063] Preferably, the step S7 of controlling the doubly fed wind turbine to switch to the virtual synchronous machine control mode specifically involves:

[0064] When the supercapacitor's state of charge (SOC) enters the danger zone, the supercapacitor shuts down, and the doubly-fed induction generator (DFIG) switches to virtual synchronous generator control mode. This mode provides inertial support to the system by adjusting the virtual moment of inertia and damping coefficient. The core equation for this virtual synchronous generator control is:

[0065]

[0066] In the formula, and These are the moment of inertia and the damping coefficient, respectively. and These are the VSG output angular frequency and the rated angular frequency, respectively. and These represent the electromagnetic power and mechanical power of the VSG, respectively.

[0067] The beneficial effects of this invention are:

[0068] 1. Simultaneous frequency and voltage regulation: While suppressing frequency fluctuations, it also ensures the stability of DC bus voltage, avoiding the fan disconnection caused by voltage fluctuations.

[0069] 2. Automatic parameter adjustment according to operating conditions: A fuzzy controller is used to adjust control parameters in real time based on frequency deviation, rate of change, DC bus voltage, and SOC. When the frequency drops rapidly, the inertia support is increased, and when the frequency recovers, the adjustment is smoothed out, making it more flexible than fixed parameters.

[0070] 3. Energy storage without overcharging or discharging: Based on SOC zone control, the safe zone outputs power normally, the warning zone restricts power output, and the danger zone stops power output, thus extending the service life of the supercapacitor.

[0071] 4. Wind turbine and energy storage work together: Under normal conditions, the wind turbine generates electricity in MPPT mode; when the frequency fluctuates, the energy storage responds first; when the energy storage capacity is insufficient, the wind turbine switches modes to continue supporting the frequency, ensuring that the system always has regulation capability.

[0072] 5. No hardware changes, only algorithm changes: Based on the existing system architecture, only the control program needs to be modified, making it convenient for engineering applications. Attached Figure Description

[0073] Figure 1 This is a schematic diagram of the doubly fed wind power and supercapacitor energy storage co-generation system described in this invention;

[0074] Figure 2 This is a block diagram of a dual closed-loop voltage regulation control for a DC / DC converter;

[0075] Figure 3 It is the curve of the change in the energy storage output regulation coefficient. Detailed Implementation

[0076] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0077] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0078] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0079] I. Overall System Structure

[0080] like Figure 1 As shown, the system of the present invention includes a doubly fed wind turbine generator, a supercapacitor energy storage system, a control system, and a grid connection interface.

[0081] The doubly-fed induction generator (DFIG) wind turbine consists of: a wind turbine, a DFIG, a rotor-side converter (RSC), and a grid-side converter (GSC). The wind turbine captures wind energy to drive the DFIG rotor. The DFIG stator is directly connected to the grid, and the rotor is connected to the DC bus via the RSC. The RSC is connected between the DFIG rotor windings and the DC bus to control the DFIG's electromagnetic torque and reactive power, achieving maximum power point tracking (MPPT). The GSC is connected between the DC bus and the grid to maintain stable DC bus voltage and ensure the sinusoidal nature of the grid-side current and controllable power factor.

[0082] The supercapacitor energy storage system consists of a supercapacitor (SC) and a bidirectional DC / DC converter. The SC is connected in parallel to the DC bus via the DC / DC converter to quickly respond to changes in grid frequency and provide or absorb instantaneous power. The DC / DC converter employs dual closed-loop control of voltage and current, combined with parameters such as frequency deviation and state of charge (SOC) to achieve adaptive control.

[0083] The control system includes: a fuzzy logic controller, a VSG control module (Virtual Synchronous Generator), an RSC controller, a GSC controller, and a DC / DC controller. Sensors collect real-time data on the power grid frequency deviation. Rate of change of frequency DC bus voltage The system inputs a supercapacitor (SOC) and transmits these signals to a fuzzy logic controller. The fuzzy logic controller then outputs an inertia coefficient correction value according to the input signals and preset fuzzy rules. Voltage deviation coefficient correction amount Energy storage output correction factor .

[0084] The grid connection interface includes a DC bus, a grid-side filter, and a transformer. The DC bus connects the RSC, GSC, and DC / DC converter, serving as a hub for energy exchange; the grid-side filter removes high-frequency harmonics from the GSC output current; and the transformer boosts the wind turbine output voltage before connecting it to the grid via the point of common coupling (PCC).

[0085] The VSG-controlled doubly-fed induction generator (DFIG) wind turbine model employs a traditional three-loop control strategy (voltage, current, and power loops) for the turbine-side converter (RSC) and a virtual synchronous generator (VSG) control strategy for the grid-side converter (GSC). During system operation, the RSC operates in MPPT (Maximum Power Point Tracking) mode, tracking the maximum power point based on real-time wind speed. The active power value corresponding to the maximum power point is used as the setpoint for the outer power loop, and rotor-side power regulation is achieved through dual voltage and current loop control, ensuring the turbine captures wind energy with maximum efficiency under any operating condition. The GSC consistently uses a VSG control strategy, simulating the rotor motion equations of a synchronous generator to provide virtual inertia and damping support for the system. When the system is undisturbed and the grid frequency is stable, the GSC maintains a stable DC bus voltage under VSG control and supplies power to the grid; at this time, the supercapacitor energy storage system is in standby mode and does not participate in active power regulation. When system disturbances cause grid frequency fluctuations, the supercapacitor energy storage system is prioritized to smooth out frequency changes. During this time, the wind turbines maintain their MPPT (Multi-Level Photovoltaic) mode and continue generating electricity at maximum efficiency. The supercapacitor energy storage system responds quickly, releasing or absorbing power based on frequency deviation and rate of change, autonomously participating in power system frequency regulation. When the supercapacitor cannot provide sufficient power support due to state-of-charge limitations, the doubly-fed induction generator (DFIG) wind turbines switch to VSG (Variable Inertia Generation) control mode, adjusting virtual moment of inertia and damping coefficients to provide continuous inertial support for the system, ensuring frequency regulation capability under all operating conditions.

[0086] The core equation of VSG control is:

[0087] (1)

[0088] In the formula, J and D are the moment of inertia and damping coefficient, respectively; and These are the VSG output angular frequency and the rated angular frequency, respectively. and These represent the electromagnetic power and mechanical power of the VSG, respectively.

[0089] Meanwhile, to simulate the primary frequency regulation characteristics of a synchronous generator, the VSG incorporates an active power-frequency droop control loop into its original control structure, expressed as follows:

[0090] (2)

[0091] Reactive power-voltage control is achieved through the VSG excitation regulator, and its reactive power-voltage droop control equation is as follows:

[0092] (3)

[0093] and These are reference values ​​for active and reactive power, respectively. This is the measured value of the power grid angular frequency; This is the measured value of reactive power; The active-frequency control droop coefficient, The reactive power-voltage control droop coefficient; This refers to the voltage amplitude of the power grid. This is the rated value of the terminal voltage amplitude.

[0094] In summary, in this invention, the supercapacitor transmits power to the grid through the grid-side converter. Therefore, the power of the supercapacitor needs to be superimposed on the outer loop of the grid-side converter's VSG power, as shown in equation (4).

[0095] (4)

[0096] This refers to the output power of the supercapacitor.

[0097] II. Mathematical Model of Virtual Moment of Inertia

[0098] This section corresponds to the virtual moment of inertia in step S2. With inertia coefficient The process of establishing a mathematical model.

[0099] According to the present invention, the conversion relationship between the rotational kinetic energy of the synchronous machine and the energy density of the supercapacitor under the change of power grid frequency is given. Inertia and damping often originate from the rotor mechanical part of the synchronous machine. Neglecting the effect of damping and assuming that the number of pole pairs is 1, the rotational kinetic energy of the rotor part is:

[0100] (5)

[0101] In the formula: The rotational kinetic energy of the generator; The moment of inertia of the generator; This represents the synchronous angular velocity of the synchronous generator.

[0102] Synchronous generators regulate active power through the kinetic energy stored in their rotors, while supercapacitors can regulate active power through rapid charging and discharging. The power equations of the two have similar structures, so supercapacitors can be regarded as energy storage components with virtual inertia.

[0103] According to the definition of the state of charge (SOC) of a supercapacitor, the charge at time t is:

[0104] (6)

[0105] In the formula: For supercapacitors in Charge at any given moment; This refers to the rated capacitance of the supercapacitor. For supercapacitors in The remaining battery power at any given time; For supercapacitors in Current at any given moment.

[0106] The energy stored in a supercapacitor can be obtained using equation (6):

[0107] (7)

[0108] In the formula: This represents the charge of the supercapacitor at time 0. This is the voltage of the supercapacitor. This represents the virtual rotational inertia of the supercapacitor.

[0109] Virtual rotational inertia of supercapacitor It is related to its own rated voltage, rated capacity, state of charge, and system frequency. According to equation (7), we can obtain

[0110] (8)

[0111] (9)

[0112] From equation (8), it can be seen that if the rate of change of charge of the supercapacitor is much greater than the rate of change of speed of the synchronous machine, that is... The value is much greater than 1, and since supercapacitors are stationary components with no rotational inertia and their power can be independently adjusted, therefore, supercapacitors are set... Its size is used to provide stable and effective support for the system.

[0113] The model establishes the inertia coefficient. With virtual moment of inertia The quantitative relationship between them, when the fuzzy controller outputs Correction back, This adaptive change subsequently affects the inertial response characteristics of the supercapacitor.

[0114] III. Generation of Composite Power Commands

[0115] This section corresponds to the process of generating the composite power command in step S5.

[0116] The power provided by the supercapacitor to suppress frequency changes due to inertia is:

[0117] (10)

[0118] In the formula: For system frequency; This represents the frequency deviation value.

[0119] Based on the above analysis, the supercapacitor is charged and discharged appropriately using inertial control, taking into account system frequency variations. To stabilize the DC bus voltage, a supercapacitor voltage deviation control system is designed.

[0120] Voltage deviation control is an important component of this invention, used to maintain DC bus voltage stability during frequency disturbances. For example... Figure 2 As shown, the DC / DC converter employs a dual closed-loop control structure for both voltage and current. Based on the traditional voltage outer loop, this invention introduces a voltage deviation coefficient. Establish frequency deviation DC bus voltage compensation Quantitative relationship between them:

[0121] (11)

[0122] To stabilize the DC bus voltage, a supercapacitor voltage deviation control system is designed. The DC-side supercapacitor employs a dual closed-loop control system (voltage and current) to compensate for frequency-dependent DC bus voltage variations. It is added to the DC bus voltage to ensure the DC side voltage is stable.

[0123] The physical meaning of voltage deviation control lies in mapping changes in grid frequency to the compensation requirement of DC bus voltage. When the system frequency decreases ( (negative) As the voltage decreases, the DC bus voltage reference value drops, and the DC / DC converter controls the supercapacitor to discharge, supplying power to the DC bus; when the system frequency increases ( (positive) As the voltage rises, the DC bus voltage reference value increases, and the DC / DC converter controls the supercapacitor to charge, absorbing power from the DC bus; as the power is gradually adjusted, the frequency tends to stabilize. As the voltage gradually returns to zero, the DC bus voltage recovers to its rated value, and the supercapacitor's absorbed / output power gradually decreases and approaches zero.

[0124] During the DC-side voltage change, the output power of the supercapacitor used to stabilize the DC bus voltage can be expressed as:

[0125] (12)

[0126] in, This is the equivalent capacitance value of the supercapacitor;

[0127] The total output power of the supercapacitor, i.e., the composite power command. for:

[0128] (13)

[0129] When a sudden increase in system load occurs, the DC bus voltage will fluctuate significantly. At this time, a supercapacitor is needed to absorb the high-frequency load components and stabilize the bus voltage. Due to the large... This allows supercapacitors to provide greater power in a short time, thus reducing DC bus voltage fluctuations more effectively.

[0130] Based on the second-order transfer function of the supercapacitor VSG control model, its natural oscillation angular frequency and damping ratio can be derived as follows:

[0131] (14)

[0132] In the formula: It is the natural angular frequency of oscillation; The damping ratio; U represents the actual value of the inverter-side voltage; U represents the actual value of the grid-side voltage. The system damping coefficient; This is the AC side filter reactance.

[0133] If set If it is a constant, then it is impossible to provide the corresponding inertia precisely based on the system's inertial requirements. If If it is too small, it will affect the process of system frequency descent. An excessively large value will hinder the system frequency recovery process. Therefore, setting... Dynamic changes in system frequency are particularly important. In power system frequency regulation, to ensure a fast response speed for the supercapacitor VSG during frequency regulation, a damping ratio of 0.1 < 0.1 is required. <0.8, the steady-state inertia coefficient can be obtained. The range of values ​​is

[0134] (15)

[0135] In conventional adaptive control, the coefficients are inflexible and exhibit phased changes, sometimes with spikes. To overcome these shortcomings, making the coefficients more flexible and eliminating spikes, we introduce the more adaptive fuzzy control theory and define the inertia coefficient:

[0136] (16)

[0137] In the formula: The constant is the coefficient of inertia in steady state; The correction amount for the steady-state voltage deviation coefficient. This is the correction amount for the inertia coefficient output by the fuzzy controller. The voltage deviation coefficient correction amount output by the fuzzy controller.

[0138] Based on the above analysis of the frequency deviation and frequency change rate, this invention proposes a fuzzy adaptive control strategy for energy storage that considers the frequency deviation, its rate of change, and the energy storage SOC. Its model is shown in equation (13). When a disturbance occurs in the system causing a frequency change, the supercapacitor participates in stabilizing the frequency through virtual inertia control, improving the system's anti-interference capability.

[0139] To balance the stability of DFIG operation with system frequency and voltage stability requirements, this paper proposes an inertial response and DC bus voltage stability control strategy for DFIG based on supercapacitor energy storage. Regulation is achieved through supercapacitor control, without modifying or adding to the original wind turbine structure and control scheme. However, because only virtual inertial control is used, it cannot effectively prevent the frequency drop rate and is prone to causing excessively low DC bus voltage, leading to turbine disconnection. The supercapacitor's ability to participate in frequency control varies under different operating conditions, and it is difficult to establish an accurate mathematical model between the control coefficient values ​​and the frequency difference change rate. Conventional fixed-coefficient control relies on experience for parameter values, resulting in inflexible changes. Fuzzy logic-based control, on the other hand, has advantages such as convenient language, strong robustness, and high fault tolerance. Therefore, it is only necessary to detect the rate of change of the grid-side frequency and dynamically adjust the power generated by the supercapacitor through a fuzzy logic controller.

[0140] Due to the limited energy storage capacity, if it operates at a high output continuously when participating in grid frequency regulation, its state of charge (SOC) is prone to exceeding limits, affecting its lifespan. Therefore, the SOC of supercapacitors during discharge is zoned. When the stored SOC is less than the minimum charge value... The time is defined as the danger zone; below the low battery value. And greater than the minimum power value The time is defined as the warning zone; less than the high battery level. And greater than the low battery value The time is defined as the safe zone. The energy storage output is adjusted in real time according to these different zones to ensure its safe and stable operation. If the supercapacitor's charge level is within the safe charging and discharging zone, the energy storage output correction coefficient can be controlled. The magnitude of the charge / discharge current indirectly controls the range of SOC variation, thereby controlling the charging and discharging current and creating a virtual moment of inertia to provide inertial support for the system. In the low inertia region, the supercapacitor can continue to provide virtual inertia for a short period until its charge / discharge capacity enters the charging / discharging prohibition region. If the charge / discharge capacity is in the discharging prohibition region (SOC < 0.2), its discharge current must be controlled to 0A, at which point the supercapacitor cannot operate. The doubly-fed induction generator (DFIG) needs to be switched to VSG control to compensate for the active power deficit.

[0141] The total output power of the supercapacitor, after being corrected for energy storage output, is expressed as:

[0142] (17)

[0143] IV. Fuzzy Subset Partitioning

[0144] This section corresponds to the fuzzy subset partitioning of the input and output variables of the fuzzy adaptive controller in step S4.

[0145] The inputs are supercapacitor SOC, DC bus voltage, frequency deviation, and frequency change rate. The fuzzy subsets of the input and output quantities are {VS (very small), S (small), RS (small), M (medium), RB (large), B (large), VB (very large)}, as detailed below:

[0146] (1) Frequency deviation Using the interval [-1, 1] can cover its range of variation.

[0147] (2) Rate of change of frequency Using the interval [-20, 20] can cover its range of variation.

[0148] (3) Supercapacitor SOC: The range [0.2, 0.8] can cover its variation range.

[0149] (4) DC bus voltage: The range [-30, 30] can cover its variation range.

[0150] The fuzzy adaptive controller performs fuzzification on the input variables, mapping each input quantity to a corresponding fuzzy subset, thus providing a foundation for subsequent fuzzy inference.

[0151] five, and Fuzzy rules

[0152] This section corresponds to the fuzzy rule tables in Tables 1 and 2, and provides a detailed explanation. and The adjustment rules.

[0153] When the frequency deviation is negative, the frequency control process can be divided into the following stages, described in natural language:

[0154] (1) When the frequency deviation, the rate of change of frequency difference, and the DC bus voltage are all VS (very small), The value of RB is relatively large. The value should be RS (smaller).

[0155] (2) If the frequency deviation VS (very small), the frequency deviation rate is negative and M (medium) or RB (large) and continuously decreases, the DC bus voltage M (medium) or RB (large). The value of B (large) is taken. The value can be either M (medium) or RB (larger). It is a positive number.

[0156] (3) If the frequency deviation is M (medium) or RB (large), the frequency deviation rate is negative and M (medium) or RB (large), and the DC bus voltage is S (small) or RS (small). The value of RS is relatively small. The value of RB is relatively large. It is a positive number.

[0157] (4) If the frequency deviation is B (large) or VB (very large), the frequency deviation rate is negative VS (very small), and the DC bus voltage is VS (very small). =0, The value of B is either large or VB (very large). It is a positive number.

[0158] (5) If the frequency deviation M (medium) or RB (large), the frequency deviation rate is positive and S (small) or RS (small), the DC bus voltage S (small) or RS (small) and begins to rise, entering the frequency recovery stage. The value of RS is relatively small. The value can be either B (large) or VB (very large). It is a positive number.

[0159] (6) If the frequency deviation S (small) or RS (small), the frequency deviation rate is positive and S (small) or RS (small), and the DC bus voltage M (medium), the frequency recovery stage is basically completed. The value can be either M (medium) or RB (larger). The value can be either VS (very small) or S (small). It is a positive number.

[0160] (7) The frequency recovers to its steady-state value, and the DC bus voltage recovers. =0, =0, the supercapacitor stops outputting power.

[0161] When the frequency deviation is positive, the frequency control process can be divided into the following stages, described in natural language:

[0162] (1) When the frequency deviation, the rate of change of frequency difference, and the DC bus voltage are all VS (very small), The value of RB is relatively large. The value should be RS (smaller).

[0163] (2) If the frequency deviation VS (very small), the frequency deviation rate is positive and M (medium) or RB (large) and continuously decreases, the DC bus voltage M (medium) or RB (large). The value of B (large) is taken. The value can be either M (medium) or RB (larger). It is a negative number.

[0164] (3) If the frequency deviation is M (medium) or RB (large), the frequency deviation rate is positive and M (medium) or RB (large), and the DC bus voltage is S (small) or RS (small). The value of RS is relatively small. The value of RB is relatively large. It is a negative number.

[0165] (4) The frequency deviation rate is 0, and the DC bus voltage is the highest. =0, The value can be either B (large) or VB (very large). It is a negative number.

[0166] (5) If the frequency deviation M (medium) or RB (large), the frequency deviation rate is positive and S (small), RS (small), RB (large), B (large), and the DC bus voltage S (small) and RS (small) begin to rise, the frequency recovery stage begins. The value of RS is relatively small. The value can be either B (large) or VB (very large). It is a negative number.

[0167] (6) If the frequency deviation S (small) and RS (small), the frequency deviation rate is positive and S (small) and RS (small), and the DC bus voltage M (medium), the frequency recovery stage is basically completed. The value can be either M (medium) or RB (larger). The value can be either VS (very small) or S (small). It is a negative number.

[0168] (7) The frequency recovers to its steady-state value, and the DC bus voltage recovers. =0, =0, the supercapacitor stops outputting power.

[0169] Table 1 Adaptive Fuzzy Rule Table

[0170]

[0171] Table 2 Adaptive Fuzzy Rule Table

[0172]

[0173] VI. Fuzzy Rules

[0174] Based on different energy storage SOCs, the controller determines the energy storage SOC in real time, using frequency deviation, frequency change rate, and SOC as inputs. The frequency control process can be specifically divided into the following stages, described in natural language. , , .

[0175] (1) If SOC is less than 0.8 and greater than 0.3, the value of SOC is B (large) or VB (very large), and the maximum power output of the energy storage is determined by the energy storage output correction coefficient. =1.

[0176] (2) If the SOC is less than 0.3 and greater than 0.2, and the SOC value is RS (smaller) or M (medium), the energy storage output power should be appropriately reduced, and the energy storage output power correction coefficient should be adjusted accordingly. The value of RS (smaller) or M (medium) varies with SOC.

[0177] (3) If SOC is less than 0.2, the value of SOC is either VS (very small) or S (small). Energy storage does not generate power. =0, It is 0.

[0178] VII. SOC Partitioning and Security Restrictions

[0179] This section corresponds to the specific method for implementing safety limits based on the real-time state of charge of the supercapacitor in step S6.

[0180] like Figure 3 As shown, the supercapacitor SOC is divided into three working regions:

[0181] Safe Zone: SOC With ample energy storage, the supercapacitor can output its full capacity according to the composite power command, fully leveraging its frequency regulation capability.

[0182] Alert Zone: SOC The energy storage capacity is moderate but relatively low, requiring careful use. Within this area, the output power of the supercapacitor should be limited to prevent it from entering the danger zone too quickly.

[0183] Danger Zone: SOC< The energy storage capacity is severely insufficient; therefore, the supercapacitor output power is prohibited to prevent over-discharge and equipment damage. Simultaneously, the wind turbine backup compensation mechanism is activated.

[0184] The corresponding output rules are: full output is allowed in the work area, output is restricted in the warning area, and output is prohibited in the danger area.

[0185] eight, Implement security restrictions

[0186] This section explains the energy storage output correction coefficient. How to implement security restrictions.

[0187] Actual output power after safety limits From composite power command Multiply by the energy storage output correction factor get:

[0188] (18)

[0189] The rules for determining the value are as follows:

[0190] Work area: =1, Composite power command executed in full.

[0191] Warning zone: 0 <1, and It is positively correlated with SOC, that is, the higher the SOC... The larger the value, the lower the SOC. The smaller the value, the smoother the output limit.

[0192] Danger Zone: =0, composite power command is completely blocked, supercapacitor stops outputting power.

[0193] This mechanism ensures that the supercapacitor will not be over-discharged under any SOC state, effectively extending the service life of energy storage equipment.

[0194] IX. Real-time adjustment of control coefficients

[0195] This section addresses how the correction value output by the fuzzy adaptive controller in step S4 is used to adjust the control coefficients in real time.

[0196] The fuzzy adaptive controller outputs three correction quantities: inertia coefficient correction quantity. Voltage deviation coefficient correction amount Energy storage output correction factor .in and Used for real-time adjustment of control coefficients:

[0197]

[0198] Set according to the DC bus voltage control requirements. and The fuzzy controller dynamically outputs based on the real-time state of the system, enabling the control coefficients to adaptively track frequency changes and voltage fluctuations.

[0199] Revised Substitute equation (8) to update J~SC~, and the corrected J~SC~ is obtained. Substitute into equation (11) to calculate Calculate the sum (12) This allows for adaptive adjustment of control parameters.

[0200] 10. Wind Turbine Backup Compensation Mechanism

[0201] This section describes the wind turbine backup compensation mechanism in step S7 when the supercapacitor cannot provide power support due to SOC limitations.

[0202] When the SOC of a supercapacitor enters the danger zone (SOC < 0.2), =0, the supercapacitor is shut down. At this time, to ensure that the system still has inertia support capability, the doubly-fed wind turbine switches to virtual synchronous generator control mode.

[0203] The core equation of VSG control is:

[0204] (19)

[0205] In the formula, and These are the moment of inertia and the damping coefficient, respectively. and These are the VSG output angular frequency and the rated angular frequency, respectively. and These represent the electromagnetic power and mechanical power of the VSG, respectively.

[0206] In VSG mode, the doubly-fed induction generator (DFIG) simulates the inertia and damping characteristics of a synchronous generator by adjusting the virtual moment of inertia J and damping coefficient D, providing continuous inertia support for the system. The values ​​of J and D can be dynamically adjusted according to the system frequency to ensure good response characteristics under different operating conditions.

[0207] This backup compensation mechanism achieves wind-storage synergistic optimization: during normal operation, the wind turbine operates in MPPT mode to ensure power generation efficiency; during frequency disturbances, the supercapacitor responds quickly and preferentially; when the energy storage capacity is insufficient, the wind turbine switches to VSG mode to continue supporting the frequency, ensuring that the system has sufficient frequency regulation capability under all operating conditions.

[0208] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A fuzzy adaptive inertia control method for supercapacitor-based doubly-fed wind turbines with SOC (System-on-Chips) energy storage, characterized in that... Includes the following steps: S1. Establish a grid-connected system model that includes doubly fed wind turbines and supercapacitor energy storage, and establish a voltage source type virtual synchronous machine control framework for the system based on the synchronous generator rotor motion equation. S2. Based on the equivalent relationship between the rotational kinetic energy of a synchronous generator and the electrical energy stored in a supercapacitor, establish the virtual rotational inertia of the supercapacitor. With inertia coefficient Mathematical model; S3. Monitor the frequency deviation of the synchronous generator. Rate of change of frequency DC bus voltage And the state of charge (SOC) of supercapacitors; S4, the frequency deviation Rate of change of frequency DC bus voltage The state of charge (SOC) is input to a fuzzy adaptive controller, which dynamically outputs an adjustment to the inertia coefficient according to preset fuzzy rules. Inertia coefficient correction amount Voltage deviation coefficient Voltage deviation coefficient correction amount and the correction factor for energy storage output ; S5. Based on the corrected inertia coefficient Update the virtual rotational inertia of the supercapacitor And based on the corrected voltage deviation coefficient Calculate DC bus voltage compensation Based on the dynamically adjusted virtual moment of inertia and voltage compensation, a composite power command is generated to control the charging and discharging of the supercapacitor. S6. Based on the real-time state of charge (SOC) of the supercapacitor, adjust the energy storage output using the energy storage correction coefficient. Apply safety limits to its output power command; S7. When the supercapacitor is unable to provide the required power support due to state of charge limitation, control the doubly fed wind turbine to switch to virtual synchronous machine control mode to compensate for the system's active power deficit.

2. The fuzzy adaptive inertia control method for supercapacitor-based doubly-fed wind turbines according to claim 1, characterized in that, The virtual rotational inertia of the supercapacitor mentioned in step S2 With inertia coefficient The mathematical model is as follows: In the formula, This refers to the rated capacitance of the supercapacitor. This is the voltage of the supercapacitor. This represents the charge of the supercapacitor at time 0. This represents the synchronous angular velocity of the generator.

3. The fuzzy adaptive inertia control method for supercapacitor-based doubly-fed wind turbines based on SOC as described in claim 2, characterized in that, The generation of composite power commands in step S5 specifically includes: Based on the virtual rotational inertia of the supercapacitor Calculate virtual inertial power components : According to voltage deviation coefficient and frequency deviation Calculate DC bus voltage compensation : Based on the voltage compensation amount Generate DC voltage stable power component : in, This is the equivalent capacitance value of the supercapacitor; The DC voltage stabilized power component With the virtual inertial power component Composite power command : 。 4. The fuzzy adaptive inertia control method for supercapacitor-based doubly-fed wind turbines according to claim 1, characterized in that, The inertia coefficient correction amount output by the fuzzy adaptive controller in step S4 Voltage deviation coefficient correction amount Used for real-time adjustment of control coefficients: In the formula, The constant is the coefficient of inertia in steady state; This is the correction amount for the steady-state voltage deviation coefficient.

5. The fuzzy adaptive inertia control method for supercapacitor-based doubly-fed wind turbines according to claim 1, characterized in that, The fuzzy adaptive controller described in step S4 performs fuzzification processing on the input variables, mapping each input quantity to a corresponding fuzzy subset; The frequency deviation Rate of change of frequency DC bus voltage The four input quantities of the supercapacitor SOC and the inertia coefficient correction quantity. Voltage deviation coefficient correction amount Energy storage output correction factor The fuzzy subsets of the three output quantities are {VS represents very small, S represents small, RS represents relatively small, M represents medium, RB represents relatively large, B represents large, and VB represents very large}.

6. The fuzzy adaptive inertia control method for supercapacitor-based doubly-fed wind turbines according to claim 5, characterized in that, The fuzzy rules include those based on frequency deviation. Rate of change of frequency and DC bus voltage Simultaneously adjust and Rules: When the frequency deviation is negative: If the frequency deviation, the rate of change of frequency, and the DC bus voltage are all VS, then Take RB, Take RS; If the frequency deviation is VS, the rate of frequency change is negative and is M or RB and continues to decrease, and the DC bus voltage is M or RB, then Choose B. Choose M or RB; If the frequency deviation is M or RB, the rate of frequency change is negative and is M or RB, and the DC bus voltage is S or RS, then Take RS, Take RB; If the frequency deviation is B or VB, the rate of frequency change is negative and is VS, and the DC bus voltage is VS, then =0, Choose B or VB; If the frequency deviation is M or RB, the rate of frequency change is positive and is S or RS, and the DC bus voltage is S or RS and begins to rise, then Take RS, Choose B or VB; If the frequency deviation is S or RS, the rate of frequency change is positive and is S or RS, and the DC bus voltage is M, then Choose M or RB. Choose VS or S; When the frequency recovers to its steady-state value, the DC bus voltage recovers as well. =0, =0; When the frequency deviation is positive: If the frequency deviation, the rate of change of frequency, and the DC bus voltage are all VS, then Take RB, Take RS; If the frequency deviation is VS, the rate of frequency change is positive and is M or RB and continues to increase, and the DC bus voltage is M or RB, then Choose B. Choose M or RB; If the frequency deviation is M or RB, the rate of frequency change is positive and is M or RB, and the DC bus voltage is S or RS, then Take RS, Take RB; If the frequency deviation rate is 0, the DC bus voltage is at its highest. =0, Choose B or VB; If the frequency deviation is M or RB, the rate of frequency change is positive and is S or RS, and the DC bus voltage is S or RS and begins to rise, then Take RS, Choose B or VB; If the frequency deviation is S or RS, the rate of frequency change is positive and is S or RS, and the DC bus voltage is M, then Choose M or RB. Choose VS or S; When the frequency recovers to its steady-state value, the DC bus voltage recovers as well. =0, =0.

7. The fuzzy adaptive inertia control method for supercapacitor-based doubly-fed wind turbines according to claim 5, characterized in that, The fuzzy rules also include those based on frequency deviation. Rate of change of frequency Determine the energy storage output correction factor based on the supercapacitor's SOC. Rules: When SOC is B or VB and frequency deviation is negative =1; When SOC is RS or M Take RS or M, and change positively with SOC; When SOC is VS or S =0.

8. The fuzzy adaptive inertia control method for supercapacitor-based doubly-fed wind turbines according to claim 1, characterized in that, The safety limitation based on the real-time state of charge (SOC) of the supercapacitor in step S6 specifically includes: The supercapacitor SOC is divided into three operating regions: Workspace: SOC ; Alert Zone: SOC ; Danger Zone: SOC ; And establish corresponding output rules: full output is allowed in the work area, output is restricted in the warning area, and output is prohibited in the danger area.

9. The fuzzy adaptive inertia control method for supercapacitor-based doubly-fed wind turbines according to claim 8, characterized in that, The safety limit is adjusted by the energy storage output coefficient. accomplish: in, This is the actual output power after safety limits. The value selection rule is: work area =1, Warning Zone It increases with increasing SOC, decreases with decreasing SOC, and 0 < <1, Danger Zone =0.

10. The fuzzy adaptive inertia control method for supercapacitor-based doubly-fed wind turbines according to claim 8, characterized in that, Step S7, which involves controlling the doubly fed wind turbine to switch to the virtual synchronous machine control mode, specifically includes: When the supercapacitor's state of charge (SOC) enters the danger zone, the supercapacitor shuts down, and the doubly-fed induction generator (DFIG) switches to virtual synchronous generator control mode. This mode provides inertial support to the system by adjusting the virtual moment of inertia and damping coefficient. The core equation for this virtual synchronous generator control is: In the formula, and These are the moment of inertia and the damping coefficient, respectively. and These are the VSG output angular frequency and the rated angular frequency, respectively. and These represent the electromagnetic power and mechanical power of the VSG, respectively.

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