Inertia demand based frequency regulation control method for wind turbine generator

Abstract

The method comprises the following steps: analyzing the main factors affecting the frequency response characteristics of the system; according to the analysis result, taking the frequency change rate as the constraint, evaluating the minimum inertia demand of the system; according to the analysis result, taking the maximum frequency deviation as the constraint, evaluating the minimum inertia demand of the system; taking the maximum value of the above two constraints as the minimum inertia demand of the system to ensure the inertia sufficiency of the system and improve the frequency stability of the system; according to the above result, constructing the objective function to obtain the output power of the wind turbine generator participating in the system frequency modulation. In view of the problems of the current comprehensive inertia simulation synchronous machine control and the incomplete consideration of the system minimum inertia evaluation factors, the optimal frequency output power control scheme of the rotor kinetic energy of the wind turbine generator based on the system minimum inertia demand is proposed, the flexibility and plasticity of the output power of the wind turbine generator converter control are fully utilized, and the frequency stability of the system is enhanced.

Description

TECHNICAL FIELD

[0001] The application relates to a wind storage frequency modulation control method, in particular to a wind turbine generator frequency modulation control method based on inertia demand, and belongs to the technical field of hybrid energy storage systems. BACKGROUND

[0002] In recent years, the construction of new power systems in China has accelerated, and the installed capacity of power sources has continued to expand. With the progress of wind power technology, more and more large-scale wind farms have been connected to the grid, and the proportion of doubly-fed induction generators (DFIG) connected to the system has increased, while the proportion of traditional synchronous machines has relatively decreased, which has become a trend in the development of future power systems. Because the variable-speed constant-frequency wind turbine generator widely used by doubly-fed wind power generators needs to be connected to the grid through power electronic devices, it usually works in the maximum power point tracking mode, and the active power and frequency are decoupled, so it cannot provide active standby power to support the frequency control of the power grid, and it does not have the ability to provide inertia support and primary frequency modulation. The current method is to add a frequency control loop in the rotor side controller of the doubly-fed wind power generator to simulate the inertia response and primary frequency modulation characteristics of the synchronous machine, release the rotor kinetic energy, and provide frequency support for the disturbed system. However, there are still problems such as the shortcomings of the synthetic inertia simulation synchronous machine control and the incomplete consideration of factors in the evaluation of the minimum inertia of the system. Therefore, it is urgent to solve the above problems and shortcomings. SUMMARY

[0003] In view of the problems and shortcomings in the prior art, the application provides a wind turbine generator frequency modulation control method based on inertia demand, which takes the virtual inertia control and primary frequency modulation control of the wind turbine generator as the target. The technical solution adopted by the application to achieve the above purpose is as follows:

[0004] The wind turbine generator frequency modulation control method based on inertia demand comprises the following steps: A. analyzing the main factors affecting the frequency response characteristics of the system;

[0005] B. According to the analysis result, the frequency change rate is taken as a constraint to evaluate the minimum inertia demand of the system;

[0006] C. According to the analysis result, the maximum frequency deviation is taken as a constraint to evaluate the minimum inertia demand of the system;

[0007] D. The maximum value of the above two constraints is taken as the minimum inertia demand of the system to ensure the inertia sufficiency of the system and improve the frequency stability of the system. The maximum value of the above two constraints is taken as the minimum inertia demand of the system, that is, the maximum value of the frequency change rate and the maximum frequency deviation in steps B and C is taken as the minimum inertia demand of the system, and the expression is as follows:

[0008] (1);

[0009] E. Based on the above results, construct an objective function to obtain the output power of the wind turbine, which will then participate in system frequency regulation; further, the output power of the wind turbine, obtained in step E, is expressed as follows:

[0010] (2);

[0011] In the formula, k p The output power coefficient is as follows:

[0012] (3);

[0013] Where, ω off This refers to the fan speed when frequency regulation is discontinued;

[0014] In the formula, P 0 This represents the initial output power of the wind turbine. P m This represents the maximum output power of the wind turbine. ω 0 represents the initial speed of the wind turbine, t off To exit FM time, P f For frequency modulation power, P off To exit FM power, It can be described as t off Approximate linear function, i.e.

[0015] P off =P f +k f (t) off -t on (4);

[0016] in, t on This is the start time of frequency regulation for the wind turbine.

[0017] (5);

[0018] In the formula, K f This is the frequency modulation power withdrawal coefficient. K MPPT The maximum power point tracking coefficient, Hw Let be the inertial constant of the wind turbine.

[0019] Furthermore, by analyzing the main factors affecting the system's frequency response characteristics as described in step A, the system's frequency dynamic equation can be obtained, as shown in the following expression:

[0020] (6);

[0021] In the formula, Δf is the system frequency deviation, t is time, and Δ P G Δ represents the change in output power of the synchronous generator set. P W Δ represents the change in the output power of the wind turbine. P L S is the load power change, S is the system inertia, Hs is the system inertia constant, ΔP is the disturbance power, Hs is a named value, and the rest are per-unit values.

[0022] Furthermore, step B involves using the rate of change of frequency as a constraint to assess the minimum inertia requirement of the system, expressed as follows:

[0023] (7);

[0024] In the formula, t0 is the initial time of the disturbance, and H min Let F be the minimum inertia of the system, ΔP be the disturbance power, and F be the inertia of the system. max This represents the maximum rate of change of the system frequency.

[0025] Furthermore, the H min To determine the minimum inertia of the system, when considering the influence of induced loads, the disturbance power needs to be corrected to remove the static voltage equivalent inertia of the induced load. The expression is as follows:

[0026] (8);

[0027] In the formula, ΔP U It can be represented as:

[0028] (9);

[0029] In the formula, Δ Pu This is the correction amount for the disturbance power in response to the static voltage response of the induced load. P L0 Let U be the total active load of the system before the disturbance, U0 be the initial voltage before the disturbance, U be the voltage at the moment of the disturbance, and k be the voltage at the moment of the disturbance. z k is the proportional coefficient for constant impedance loads. i k is the proportional coefficient for constant current loads. p This is the proportional coefficient for constant power load.

[0030] Furthermore, the H min The minimum inertia of the system, considering the occurrence of AC line disconnection or synchronous motor tripping accidents, is expressed as follows:

[0031] (10);

[0032] where ΔH G is the inertia variation caused by the synchronous generator exiting or the AC line shorting.

[0033] Further, the step C is used to take the maximum frequency deviation as a constraint to evaluate the system minimum inertia demand, and the expression is as follows:

[0034] (11);

[0035] where ΔH t 1 is the time for the frequency to reach the maximum deviation, K L is the load frequency regulation effect coefficient, R W is the wind turbine rotor kinetic energy primary frequency modulation rate, R S is the thermal power unit primary frequency modulation rate, and Δf3 is the maximum frequency deviation.

[0036] A computer device includes a storage medium, a processor, and a computer program stored on the storage medium and executable on the processor, and the processor implements the steps of the wind turbine frequency modulation control method based on the inertia demand when executing the computer program.

[0037] A computer storage medium, and a computer program is stored on the computer storage medium, and the steps of the wind turbine frequency modulation control method based on the inertia demand are implemented when the processor executes the computer program.

[0038] Compared with the prior art, the advantages and effects are that:

[0039] 1. In view of the deficiencies of the current comprehensive inertia simulation synchronous machine control and the incomplete consideration of the system minimum inertia evaluation factors, a wind turbine rotor kinetic energy optimal frequency output power control scheme based on the system minimum inertia demand is proposed, which fully utilizes the flexibility and plasticity of the wind turbine converter control output power.

[0040] 2. From the whole system, the frequency response characteristics of the load and the synchronous generator are comprehensively considered, and a system minimum inertia demand calculation model is established. According to the system minimum inertia demand evaluation results, combined with the optimization model of the wind turbine frequency modulation process, the improved genetic algorithm is used to solve the wind turbine optimal output power auxiliary system frequency modulation, including the frequency modulation output power and the speed recovery control.

[0041] 3. The system is quickly provided with certain inertia support, the frequency variation rate and the frequency deviation under the system power imbalance are reduced, the primary frequency modulation of the system has sufficient adjustment time, the third defense line of the safe and stable operation of the power system in China is avoided, and the frequency stability of the power system is enhanced.

[0042] 4. Considering the advantages of fast response speed and strong plasticity of wind turbine rotor kinetic energy control in participating in system frequency modulation, optimal rotor kinetic energy control considering the constraints of system frequency minimum value and system frequency change rate is proposed, which actively responds to system frequency fluctuation by quickly providing inertia support and improves the frequency response capability of the system. BRIEF DESCRIPTION OF DRAWINGS

[0043] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the following description, taken in conjunction with the following drawings, in which:

[0044] Figure 1 is a schematic diagram of a DFIG system structure;

[0045] Figure 2 is a schematic diagram of rotor kinetic energy control;

[0046] Figure 3 is a rotor kinetic energy control operation curve diagram;

[0047] Figure 4 is a system inertia output schematic diagram;

[0048] Figure 5 is a system frequency response process;

[0049] Figure 6 is a wind turbine exiting frequency modulation process diagram;

[0050] Figure 7 is a wind farm inertia control principle structure diagram. DETAILED DESCRIPTION

[0051] In order to more clearly understand the above-mentioned purposes, features and advantages of the present application, the present application will be further described in detail below in conjunction with the drawings and specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0052] In the following description, a large number of specific details are set forth in order to facilitate a thorough understanding of the present application, however, the present application can also be implemented in other ways different from those described herein, therefore, the protection scope of the present application is not limited by the specific embodiments disclosed below.

[0053] Embodiment 1

[0054] The grid-connected operation wiring of a doubly-fed wind turbine is shown in Figure 1 , which includes a wind turbine, a gear box, a doubly-fed motor, a machine-side converter, a grid-side converter and the like. The machine-side converter is directly connected to the DFIG, and mainly controls the maximum power output of the wind turbine; the grid-side converter is connected to the power grid on one side and to the stator side of the doubly-fed motor on the other side, and the grid-side converter mainly maintains the constant DC voltage.

[0055] Example 2

[0056] As shown in Figure 2 , the frequency modulation considers the inertia characteristics of synchronous generators in the power system, the primary frequency modulation characteristics of synchronous generators, the load frequency response characteristics, and the additional frequency response characteristics of wind turbines. Among them, ΔP W is the wind turbine output power change, ΔP L is the load absorbed power change, ΔP G is the synchronous generator mechanical power change, ΔP is the disturbance power, ΔP D is the system power imbalance, K L is the load frequency regulation benefit coefficient, Ts is the inertia time constant of the synchronous generator, K G is the frequency static characteristic coefficient of the synchronous generator, T G is the primary frequency modulation time constant of the synchronous generator, and ω i is the minimum limit of the exit frequency modulation speed. It needs to be determined according to the operating conditions of the wind turbine and the minimum inertia demand of the power system. It will be analyzed in detail later. In order to prevent the wind turbine from participating in frequency modulation and causing shutdown, when the speed is lower than the minimum limit ω i , the enable signal R is set to zero through the speed protection module, so that the wind turbine exits the frequency modulation mode.

[0057] Example 3

[0058] As shown in Figure 3 , the auxiliary frequency control is mainly used to determine the active power output by the wind turbine when the frequency modulation starts, and is superimposed with the maximum power point tracking (MPPT) power value in the normal operation to input the converter control module, to adjust the output power of the wind turbine, and realize primary frequency modulation.

[0059] Example 4

[0060] The main indicators for evaluating the frequency response characteristics of the system include the maximum frequency drop rate, the maximum frequency deviation, and the steady-state frequency. The inertia control based on rotor kinetic energy can provide energy source for electromagnetic power, and does not provide unbalanced power for the system, but only provides a buffer for the unbalanced power. However, it plays an important role in maintaining the balance of active power supply and demand, can reduce the frequency fluctuation speed, and wins time for the primary frequency modulation of the system. It is an indispensable part of maintaining frequency stability, and plays a role in resisting frequency changes.

[0061] The system inertia described in the form of energy can be expressed as:

[0062] E=E SG +E NE +E IM +E L (12);

[0063] where E SG is the inertia of synchronous generator, E NE is the virtual inertia of new energy, E IM is the inertia of asynchronous motor, E L is the equivalent inertia of static load. The synchronous generator and load can provide non-delayed inertia support. The virtual inertia of new energy mainly includes two control modes, rotor kinetic energy control and virtual synchronous machine control, but the rotor kinetic energy control will have a certain delay, about 100 ms. The asynchronous motor provides little inertia at the beginning of frequency fluctuation due to the effect of slip, and then the rotational inertia fully responds to the frequency change. The schematic diagram of support power in the process of system inertia response is shown in Figure 4 .

[0064] The system inertia constant is:

[0065] (13).

[0066] where S is the system capacity.

[0067] The system frequency dynamic equation can be obtained as follows:

[0068] (6).

[0069] where Hs is the nominal value, and the rest are per unit values.

[0070] From the above expression, it can be seen that the main factors affecting the frequency change rate and the maximum frequency deviation are the system inertia, the generator primary frequency modulation, the load frequency characteristic and the wind turbine inertia.

[0071] Example 5

[0072] The maximum frequency change rate is obtained, and the frequency change rate value at this time is taken as a constraint to evaluate the minimum inertia demand of the system. Due to the initial disturbance, the system frequency is not deviated, and at this time the synchronous generator and the load cannot respond to the system frequency regulation effect, and the frequency change is only related to the system inertia and the disturbance power, and the expression is as follows:

[0073] (14).

[0074] The minimum inertia of the system under the frequency change rate constraint is:

[0075] (7).

[0076] The above expression shows that when the system has a disturbance power ΔP, in order to make the system frequency change rate not exceed the maximum value F max , the inertia output by the system after the disturbance must not be less than H minThe greater the disturbance power ΔP, the greater the minimum inertia required by the system, and vice versa.

[0077] The influence of induced load should also be considered at the moment of power disturbance. The disturbance power should be corrected by removing the static voltage equivalent inertia of the induced load, and the expression is as follows:

[0078] (8);

[0079] In the formula, ΔP U may be expressed as:

[0080] (9);

[0081] In the formula, U0 is the initial voltage before disturbance, U is the voltage at the moment of disturbance, k z is the constant impedance load proportionality coefficient; k i is the constant current load proportionality coefficient, and k p is the constant power load proportionality coefficient.

[0082] The above expressions do not consider how the disturbance power ΔP occurs. Generally speaking, the power disturbance that causes the frequency stability problem of the system is generally the tripping of large units or the power difference of tie lines. Different disturbance types have different effects on the inertia level of the system. For example, a DC blocking fault only produces disturbance power ΔP, but does not affect the inertia level of the entire system. If an AC line break or synchronous machine tripping accident occurs, not only does it cause system disturbance power ΔP, but also reduces the system inertia, further deteriorating the system frequency. Therefore, the minimum inertia of the system at this time is expressed as follows:

[0083] (10);

[0084] In the formula, ΔH G is the inertia change caused by the exit of a synchronous generator or the short line of an AC line.

[0085] Regarding the frequency change rate, China's power grid has not made a clear requirement, only the maximum frequency deviation is clearly specified. The distributed power equipment level anti-islanding protection setting of the British power grid is 0.125 Hz / s, but the system frequency change rate exceeds this setting during a blackout accident, resulting in nearly 350 MW of distributed power being disconnected from the grid. Therefore, with the gradual deepening of the power electronicization of the power system, the frequency change rate cannot be ignored.

[0086] Example 6

[0087] To prevent the system from being tripped due to low-frequency load shedding during a power shortage disturbance, causing a power outage accident, the minimum frequency point of the system after a fault should not be lower than the first round of action value of the third defense line low-frequency load shedding. The maximum frequency offset is taken as a constraint condition for the evaluation of the minimum inertia requirement of the system.

[0088] After the disturbance occurs, the system frequency begins to deviate from its normal value. Initially, due to the small frequency deviation and the dead zones of the frequency regulation devices, none of them operate, and only the load participates in the system frequency response. Because wind turbines have a faster frequency response speed and the frequency response capability of rotor kinetic energy is not sustained, the primary frequency regulation control of the wind turbines begins to operate, and the overall system imbalance gradually decreases. Subsequently, the primary frequency regulation control of the thermal power units begins to take effect. When the output power of the primary frequency regulation control equals the initial imbalance power, the system frequency will reach its limit value. Therefore, the system frequency response occurs in three processes. For this reason, a piecewise linearization method is used to simulate the system's frequency response process, specifically as follows: Figure 5 As shown.

[0089] Figure 5 In the diagram, t1 corresponds to Δf1, t2 to Δf2, and t3 to Δf3. t1 represents the time corresponding to the dead zone of the system's frequency response; t2 represents the time corresponding to the end of frequency regulation for the wind turbine rotor kinetic energy control; and t3 represents the time corresponding to the end of system frequency regulation. During this period, the primary frequency regulation of the thermal power unit mainly bears the system power deficit. For ease of analysis, the system power required for the wind turbine to resume control is also considered during this period. The system frequency response participates throughout the entire process until the power deficit ΔP = 0. Δf3 is the maximum frequency offset, and this frequency deviation is used to assess the system's minimum inertia requirement.

[0090] From the time of the fault occurrence 0 to the time when the system frequency deviation reaches its extreme value t3, the piecewise linearization method is used to integrate and solve equation (1), as follows:

[0091] (15);

[0092] Where, ΔP L =K L Δf, then equation (16) can be expressed as:

[0093] (16);

[0094] In formula (16), The integration should be performed piecewise, as follows:

[0095] During the 0-t1 phase, all frequency control devices are activated, and the system's active power imbalance ΔP remains constant.

[0096] (17);

[0097] During the t1-t2 phase, the wind turbine rotor kinetic energy-assisted frequency control is started. At this time,

[0098] (18);

[0099] wherein R W is the wind turbine rotor kinetic energy primary frequency modulation rate, specifically:

[0100] (19);

[0101] In the t2-t3 stage, the thermal power unit primary frequency modulation is started, at this time,

[0102] (20);

[0103] wherein R S is the thermal power unit primary frequency modulation rate, specifically:

[0104] (21);

[0105] Since the t2-t3 stage considers the power absorbed by the wind turbine recovery control, the actual generator provided frequency modulation power is

[0106] (22).

[0107] Example 7

[0108] According to the expressions in Examples 5 and 6, the minimum inertia required by the system is:

[0109] (11);

[0110] According to the power system low-frequency load shedding setting method and setting scheme, the frequency setting value of the first round of load shedding of low-frequency load shedding is 49 Hz, and therefore Δf3 is 1 Hz. Since the system is simultaneously constrained by the frequency change rate and the maximum frequency deviation, the minimum inertia requirement of the system should take the maximum value under the two constraints to ensure the inertia of the system and improve the frequency stability of the system, specifically as follows:

[0111] (1).

[0112] Example 8

[0113] The wind turbine provides inertia support to the system through the releasable rotor kinetic energy, and the wind turbine rotor kinetic energy equation is:

[0114] (23);

[0115] wherein H W is the wind turbine inertia, ω is the wind turbine rotor speed, P We is the wind turbine electromagnetic power, and P Wm is the wind turbine mechanical power.

[0116] In the process of rotor kinetic energy control, the rotor speed of the wind turbine is limited by the lower limit of the minimum rotor speed, so the maximum inertia provided by the wind turbine is:

[0117] (24);

[0118] In the formula, E N is the rotor kinetic energy corresponding to the rated speed ω N of the wind turbine, E0 is the rotor kinetic energy corresponding to the lower limit of the rotor speed protection ω0, and P N is the rated power of the wind turbine. Therefore, the inertia corresponding to any rotor speed ω between the rated speed ω N and the lower limit of the rotor speed protection ω0 is:

[0119] (25);

[0120] In the formula, E ω is the rotor kinetic energy corresponding to the rotor speed ω.

[0121] In order to quantitatively describe the inertia that the wind turbine can provide for the system, the available inertia factor k H of the wind turbine is defined as:

[0122] (26);

[0123] In the present application, ω0=0.7ω N , so formula (3) can be expressed as:

[0124] (27);

[0125] In the formula, ω* is a unit value, when ω* is 1, k H =1, when ω* is 0.7, k H =0, so, .

[0126] The essence of the inertia provided by the rotor kinetic energy control of the wind turbine is to provide power support for the system, and the output power is mainly limited by the upper and lower limits of the power of the converter. In the process of rotor kinetic energy control, the electromagnetic power output by the wind turbine is limited by the capacity of the converter, and the specific constraint equation is:

[0127] (28);

[0128] The rotor kinetic energy control causes the rotor speed of the wind turbine to change, which causes the mechanical power output by the wind turbine to change, that is, the power difference in formula (6) changes. According to the literature, the relationship between the mechanical power P Wm output by the wind turbine and the rotor speed can be described as:

[0129] (29);

[0130] Since the working conditions of each wind turbine in the wind farm are different, the output inertia of the wind turbine is different, and the output inertia of the entire wind farm is:

[0131] (30);

[0132] In the formula, P Ni is the rated power of the i th wind turbine, k Hi is the available inertia factor of the i th wind turbine, H maxi is the maximum inertia of the i th wind turbine. Wherein,

[0133] (31);

[0134] Increasing the primary frequency modulation rate and reducing the adjustment time of the frequency modulation device can reduce the inertia demand of the system, which is beneficial to the primary frequency modulation of the system. For a thermal power unit, the frequency modulation rate is constrained by the physical characteristics and stability of the unit itself, and is usually fixed and cannot be improved. As for the adjustment time, advanced communication technology can be used to adopt active control based on fault driving, so as to shorten the adjustment time and improve the frequency response capability of the system.

[0135] Embodiment 9

[0136] The primary frequency modulation of the wind turbine based on the converter control output power has no physical constraint on the control parameters, and the output power can be designed according to the actual demand of the system, which can quickly respond to the system frequency output active power, and can be equivalent to increasing the frequency modulation rate and reducing the adjustment time. Through rotor kinetic energy control, the minimum inertia demand of the system can be effectively reduced, and the frequency modulation capability of the system can be improved. Through rotor kinetic energy control, the target is to reduce the minimum inertia demand of the system, and the specific objective function is:

[0137] min (H min ) (32);

[0138] According to the mathematical model established in the foregoing, then, according to the objective function constructed, the output power of the wind farm is solved, and the primary frequency modulation of the system is actively participated.

[0139] Embodiment 10

[0140] The output power process of the wind turbine is shown in Figure 6 When the speed of the wind turbine reaches the lower limit value, the wind turbine exits the frequency modulation mode and enters the speed recovery stage. In order to prevent the occurrence of secondary frequency drop accidents, the wind turbine exit frequency modulation time and the frequency modulation power need to be considered comprehensively, and the primary frequency modulation of the thermal power unit is cooperated to realize the smooth exit of the wind turbine from the frequency modulation and the recovery of the speed to the state before the frequency modulation.

[0141] Figure 6 In the middle, t on is the starting time of the wind turbine frequency modulation, t off is the time when the wind turbine exits the frequency modulation, t end is the end time of the wind turbine speed recovery control, P0 is the initial power value of the wind turbine, P f is the frequency modulation power, P off is the frequency modulation exit power.

[0142] During the speed recovery process, the rotor speed change is still determined by the wind turbine rotor motion equation, and by simultaneously integrating both sides of equation (23), the output power P e (t) of the wind turbine rotor speed recovery control can be obtained.

[0143] The present application proposes to use piecewise linearization to approximate the solution. Assuming that a linearization is taken to describe, the expression of the output power is:

[0144] (2) ;

[0145] In the formula, k p is the output power coefficient, specifically:

[0146] (3) ;

[0147] Where, ω off is the wind turbine speed at the time of exiting the frequency modulation.

[0148] In the formula, can be described as t off approximate linear function, that is

[0149] P off =P f +k f (t off -t on ) (4) ;

[0150] Where,

[0151] (5) ;

[0152] The same method can obtain the output power curve of multiple linearization, and realize the recovery control of the wind turbine speed. The speed recovery control mainly depends on the exit frequency modulation time t off , the frequency modulation power P f and the exit frequency modulation power P off , and P f and P off are determined by the real-time inertia of the wind turbine.

[0153] At the same time, in order to ensure the normal operation of the wind turbine speed recovery, the speed change rate is set, specifically:

[0154] (33) ;

[0155] Combined with the frequency modulation characteristics of the thermal power unit and the load, the wind turbine auxiliary frequency modulation equation is established, and the optimization objective function is solved.

[0156] Embodiment 11

[0157] Based on the same inventive concept, the embodiment of the present application also provides a computer device, which comprises a storage medium, a processor and a computer program stored in the storage medium and executable on the processor. The processor executes the computer program to realize the steps of the wind turbine frequency modulation control method based on inertia demand in the embodiment 1.

[0158] Embodiment 12

[0159] Based on the same inventive concept, the embodiment of the present application also provides a computer storage medium, which has a computer program stored thereon. The computer program is executed by a processor to realize the steps of the wind turbine frequency modulation control method based on inertia demand in the embodiment 1.

[0160] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system or a computer program product. Therefore, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0161] The present application is described with reference to flowcharts and / or block diagrams of the method, device (system) and computer program product according to the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of the flows and / or blocks in the flowcharts and / or block diagrams can be realized by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device that implements the functions specified in the flowcharts and / or block diagrams. Figure 1 The device that implements the functions specified in one flow or multiple flows and / or blocks Figure 1 The device that implements the functions specified in one flow or multiple flows and / or blocks

[0162] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instructions which implement the flow Figure 1 one or more flows and / or blocks Figure 1 one or more blocks or multiple blocks.

[0163] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the flow Figure 1 one or more flows and / or blocks Figure 1 one or more blocks or multiple blocks.

[0164] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0165] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application rather than limiting them, although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that: the specific embodiments of the present application can be modified or replaced by the same, without departing from the spirit and scope of the present application, any modification or equivalent replacement, which should be covered in the protection scope of the claims of the present application.

Claims

1. A frequency regulation control method for wind turbine units based on inertia requirements, characterized in that, The steps include: A. Analyzing the main factors affecting the system's frequency response characteristics; B. Based on the analysis results, the rate of change of frequency is used as a constraint to evaluate the minimum inertia requirement of the system; C. Based on the analysis results, the maximum frequency offset is used as a constraint to evaluate the minimum inertia requirement of the system, as shown in the following expression: （11）； In the formula, t1 is the time when the frequency reaches its maximum offset, and K L R is the load frequency regulation effect coefficient. W R is the primary frequency regulation rate of the wind turbine rotor kinetic energy. S Δf3 is the primary frequency regulation rate of the thermal power unit, ΔP is the maximum frequency offset, and ΔP is the frequency regulation rate of the thermal power unit. W ΔP represents the change in the output power of the wind turbine, and ΔP represents the disturbance power. D. Use the maximum value of the above two constraints as the minimum inertia requirement of the system to ensure sufficient inertia and improve the frequency stability of the system; using the maximum value of the above two constraints as the minimum inertia requirement of the system means using the maximum value of the frequency change rate and the maximum frequency offset constraints in steps B and C as the minimum inertia requirement of the system, as expressed below: （1）； E. Based on the above results, construct an objective function to obtain the output power of the wind turbine, which will then participate in system frequency regulation. The expression for obtaining the output power of the wind turbine is as follows: （2）； In the formula, k p The output power coefficient is as follows: （3）； Where, ω off This refers to the fan speed when frequency regulation is discontinued; In the formula, P0 is the initial output power of the wind turbine, P m ω0 represents the maximum output power of the wind turbine, ω0 represents the initial speed of the wind turbine, and t0 represents the initial speed of the wind turbine. off To exit FM time, P f For frequency modulation power, P off To exit FM power, It can be described as t off Linear function, i.e. P off =P f +k f (t off -t on ) (4); Among them, t on This is the start time of frequency regulation for the wind turbine. （5）； In the formula, K f K is the frequency modulation power withdrawal factor. MPPT is the maximum power point tracking coefficient, and Hw is the inertial constant of the wind turbine.

2. The wind turbine frequency regulation control method based on inertia demand according to claim 1, characterized in that, Step A describes the analysis of the main factors affecting the system's frequency response characteristics, which yields the system's frequency dynamic equation, expressed as follows: （6）； In the formula, Δf is the system frequency deviation, t is time, and ΔP is... G ΔP represents the change in output power of the synchronous generator set. W ΔP represents the change in the output power of the wind turbine. L S is the load power change, S is the system inertia, Hs is the system inertia constant, ΔP is the disturbance power, Hs is a named value, and the rest are per-unit values.

3. The wind turbine frequency regulation control method based on inertia demand according to claim 1, characterized in that, Step B involves using the rate of change of frequency as a constraint to assess the minimum inertia requirement of the system, and its expression is as follows: （7）； In the formula, t0 is the initial time of the disturbance, and H min Let F be the minimum inertia of the system, ΔP be the disturbance power, and F be the inertia of the system. max Δf is the maximum rate of change of the system frequency, t is the system frequency deviation, and t is time.

4. The wind turbine frequency regulation control method based on inertia demand according to claim 3, characterized in that, The H min To determine the minimum inertia of the system, when considering the influence of induced loads, the disturbance power needs to be corrected to remove the static voltage equivalent inertia of the induced load. The expression is as follows: （8）； In the formula, ΔP U It can be represented as: （9）； In the formula, ΔPu is the correction factor for the disturbance power by the static voltage response of the induced load, and P L0 Let U be the total active load of the system before the disturbance, U0 be the initial voltage before the disturbance, U be the voltage at the moment of the disturbance, and k be the voltage at the moment of the disturbance. z k is the proportional coefficient for constant impedance loads. i k is the proportional coefficient for constant current loads. p This is the proportional coefficient for constant power load.

5. The wind turbine frequency regulation control method based on inertia requirement according to claim 3, characterized in that, The H min The minimum inertia of the system, considering the occurrence of AC line disconnection or synchronous motor tripping accidents, is expressed as follows: （10）； In the formula, ΔH G This refers to the change in inertia caused by the disconnection of a synchronous generator or a short circuit in the AC line.

6. A computer device, comprising a storage medium, a processor, and a computer program stored on the storage medium and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the frequency regulation control method for wind turbine generators based on inertia requirements as described in any one of claims 1-5.

7. A computer storage medium, characterized in that, The computer storage medium contains a computer program, which, when executed by a processor, implements the steps of the wind turbine frequency regulation control method based on inertia requirements as described in any one of claims 1-5.

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