Method and system for determining unit combination of wind farm participating in power grid frequency support

Abstract

The present invention discloses a method and system for determining a unit combination of a wind farm participating in power grid frequency support, which firstly gives four decision indicators of wind farm output power; then, simulates and obtains active power response curves of each wind turbine in the wind farm under different wind speeds and different target degrees of system frequency drop processes and corresponding four indicator values; when it is detected that a large change occurs in the startup combination of synchronous generators in the system, it is necessary to update the system frequency response function for decision-making; when a major power shortage is detected in the system, the system frequency response function is used to determine the control target of the minimum value of the system frequency; then, according to the current wind speed of each wind turbine in the wind farm, the value or value range of each decision indicator of the wind farm output power is determined; then, each indicator is optimized step by step, and the specific value of each indicator is determined step by step; finally, the unit combination participating in frequency support in the wind farm is determined to realize the support of the wind farm to the system frequency.

Description

Technical Field

[0001] The present invention relates to the field of smart grid technology, in particular to grid system stabilization and control technology, and specifically to a method and system for determining a unit combination of a wind farm participating in grid frequency support. Background Art

[0002] The penetration rate of wind power generation in the power grid system is gradually increasing, and wind power generation has become a very important power source in the power grid. Due to the presence of power electronic converters, the rotor speed of wind turbine generators (WTGs) is decoupled from the frequency and cannot respond to frequency changes. Therefore, when large-scale wind power generation is connected to the grid, the frequency regulation capability of the entire system will be significantly weakened, which may threaten the frequency stability of the power grid system. Many countries have formulated grid specifications on how wind power generation can provide frequency support for the power grid system. Some grid specifications only stipulate that wind power generation can participate in primary frequency regulation, while other grid specifications also require the rapid frequency response capability of wind power generation.

[0003] WTG requires additional control strategies to respond to changes in system frequency. Among the control strategies, virtual inertia control and droop control increase the output power of wind turbines by releasing rotor kinetic energy, while overspeed control and pitch control are unloading control strategies that can reserve some reserve power for wind turbines. In some studies, two or more control strategies are used in combination to improve the frequency support effect of wind turbines. If the wind turbine does not adopt an unloading control strategy or partial energy storage device, the wind turbine will not be able to provide continuous power support when the frequency drops. However, unloading control affects the economic benefits of wind turbines. If only virtual inertia control or droop control is used, WTG can only participate in fast frequency response. In addition, after WTG participates in frequency support, the rotor speed will deviate from the maximum power tracking point, resulting in power loss during speed recovery. This power loss is the cost of WTG participating in fast frequency response.

[0004] When a large power shortage suddenly occurs in the power grid system, the frequency will drop rapidly. The frequency support methods available in the current power grid system include power modulation of DC transmission lines, pumped storage, precise removal of interruptible loads, and fast frequency response of wind turbines. Except for wind power generation, the support power provided by other methods has a fixed value; while the support power that wind power generation can provide is not a fixed value. There is currently no widely adopted method for determining the amount of wind power support for fast frequency response. Summary of the invention

[0005] The purpose of the present invention is to propose a method for determining the unit combination of a wind farm participating in grid frequency support, which is used to determine the grid system's demand for wind farm power support on the one hand, and to determine the unit combination in the wind farm that provides the power support required by the grid system on the other hand.

[0006] According to a first aspect of the present invention, a method for determining a unit combination of a wind farm participating in grid frequency support is provided, comprising the following steps:

[0007] Step 1: Given the wind farm output power decision indicators, including the maximum value of active power change △P MAX , the time when the active power change reaches the maximum value T M , the time T for active power change to return to zero Z and the minimum allowable value of active power change △P MIN ;

[0008] Step 2: Simulate and obtain the active power response curves of each wind turbine in the wind farm under different wind speeds and different target levels of system frequency drop and the values ​​of the four decision indicators corresponding to the step 1;

[0009] Step 3, determine whether the startup combination and power generation of the synchronous generators in the power grid system have changed as expected, if so, re-execute step 2, otherwise proceed to step 4;

[0010] Step 4: Determine whether the power grid system has a predetermined power shortage. If so, proceed to step 5; otherwise, return to step 3;

[0011] Step 5: Use the system frequency response function to calculate the maximum drop of the system frequency when wind power does not participate in frequency regulation, and determine the control target f of the minimum value of the system frequency. min1 And the corresponding wind farm equivalent step support power △P step , determine the secondary frequency drop amplitude △f2 during the system frequency recovery process;

[0012] Step 6: Determine the value or value range of the wind farm output power decision indicator of the wind farm in step 1 according to the current wind speed of each wind turbine in the wind farm;

[0013] Step 7, optimizing each indicator step by step within the indicator value range determined in step 6, and determining the specific value of each indicator step by step;

[0014] Step 8: According to the specific values ​​of the various indicators of the wind farm output power obtained in step 7, determine the graph △P surrounded by the four indicators index (t), and accordingly determine the unit combination participating in frequency support in the wind farm.

[0015] According to a second aspect of the present invention, a system for determining a unit combination of a wind farm participating in grid frequency support is also provided, comprising:

[0016] one or more processors;

[0017] A memory storing operable instructions, wherein when the instructions are executed by the one or more processors, the one or more processors perform operations, wherein the operations include the process of the aforementioned method for determining a unit combination of a wind farm participating in grid frequency support.

[0018] According to a third aspect of the present invention, a computer-readable medium storing software is also proposed, wherein the software includes instructions that can be executed by one or more processors, and the instructions enable the one or more processors to perform operations through such execution, and the operations include the process of the aforementioned method for determining the unit combination of a wind farm participating in grid frequency support.

[0019] Compared with the prior art, the method and system for determining the unit combination of a wind farm participating in grid frequency support proposed in the present invention have the significant advantages that: the present invention can quickly make decisions on how the wind farm participates in grid frequency support. On the one hand, it is used to determine the power support demand of the power system for the wind farm, and on the other hand, it is used to determine the unit combination in the wind farm that provides the power support required by the power system. This can improve the efficiency of wind power participating in grid frequency support and can accurately achieve the expected support effect on the system frequency, which plays an important role in promoting the advancement of wind power participation in grid frequency support technology.

[0020] It should be understood that all combinations of the aforementioned concepts and the additional concepts described in more detail below can be considered as part of the inventive subject matter of the present disclosure as long as such concepts are not mutually inconsistent. In addition, all combinations of the claimed subject matter are considered as part of the inventive subject matter of the present disclosure.

[0021] The foregoing and other aspects, embodiments and features of the present invention can be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the present invention, such as the features and / or beneficial effects of the exemplary embodiments, will be apparent from the following description or learned from the practice of the specific embodiments according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in various figures may be represented by the same reference numeral. For clarity, not every component is labeled in every figure. Embodiments of various aspects of the present invention will now be described by way of example and with reference to the accompanying drawings, in which:

[0023] Figure 1A flow chart of a method for determining a unit combination for wind power participating in grid frequency support according to an exemplary embodiment of the present invention;

[0024] Figure 2 It is a schematic diagram of the combined control strategy of virtual inertia and droop control;

[0025] Figure 3 is the wind farm output power decision indicator diagram;

[0026] Figure 4 It is a schematic diagram of the IEEE-9 node system;

[0027] Figure 5 It is a fast simulation model diagram for the study of fast frequency response control of wind farms;

[0028] Figure 6 This is the relationship between each index and wind speed when the disturbance power is 49.80Hz;

[0029] Figure 7 It is an indicator determination model based on GSFR

[0030] Figure 8 is a schematic diagram for optimization;

[0031] Fig. 9 It is a simplified output power and index comparison chart after unit combination.

[0032] Fig.10 This is a comparison chart of wind farm output power before and after unit combination.

[0033] Fig.11 It is a comparison chart of frequency response before and after the unit combination participates in frequency modulation. DETAILED DESCRIPTION

[0034] In order to better understand the technical content of the present invention, specific embodiments are given and described as follows in conjunction with the accompanying drawings.

[0035] Various aspects of the present invention are described in this disclosure with reference to the accompanying drawings, in which many illustrative embodiments are shown. The embodiments of the present disclosure are not necessarily intended to include all aspects of the present invention. It should be understood that the various concepts and embodiments introduced above, as well as those described in more detail below, can be implemented in any of many ways, because the concepts and embodiments disclosed by the present invention are not limited to any implementation. In addition, some aspects disclosed by the present invention can be used alone or in any appropriate combination with other aspects disclosed by the present invention.

[0036] Combination Figure 1 The process example shown in the figure, according to the embodiment disclosed in the present invention, the method for determining the unit combination of a wind farm participating in the grid frequency support includes the following steps:

[0037] Step 1: Given the wind farm output power decision indicators, including the maximum value of active power change △P MAX , the time when the active power change reaches the maximum value T M , the time T for active power change to return to zero Z and the minimum allowable value of active power change △P MIN ;

[0038] Step 2: Simulate and obtain the active power response curves of each wind turbine in the wind farm under different wind speeds and different target levels of system frequency drop and the values ​​of the four decision indicators corresponding to the step 1;

[0039] Step 3, determine whether the startup combination and power generation of the synchronous generators in the power grid system have changed as expected, if so, re-execute step 2, otherwise proceed to step 4;

[0040] Step 4: Determine whether the power grid system has a predetermined power shortage. If so, proceed to step 5; otherwise, return to step 3;

[0041] Step 5: Use the system frequency response function to calculate the maximum drop of the system frequency when wind power does not participate in frequency regulation, and determine the control target f of the minimum value of the system frequency. min1 And the corresponding wind farm equivalent step support power △P step , determine the secondary frequency drop amplitude △f2 during the system frequency recovery process;

[0042] Step 6: Determine the value or value range of the wind farm output power decision indicator of the wind farm in step 1 according to the current wind speed of each wind turbine in the wind farm;

[0043] Step 7, optimizing each indicator step by step within the indicator value range determined in step 6, and determining the specific value of each indicator step by step;

[0044] Step 8: According to the specific values ​​of the various indicators of the wind farm output power obtained in step 7, determine the graph △P surrounded by the four indicators index (t), and accordingly determine the unit combination participating in frequency support in the wind farm.

[0045] As an optional implementation, in the aforementioned step 1, for a given wind farm output power decision indicator, wherein:

[0046] On the active power change graph, according to the points (0,0), (T M ,△P MAX ) and (T Z,0), construct a triangle representing the power support demand of the power grid system for the wind farm. When the power support provided by the wind farm is higher than the triangle, the frequency regulation target of the power grid system can be achieved; where △P MIN It indicates the minimum value of the output power change of the wind farm during the wind turbine rotor speed recovery stage. It is used to ensure that the secondary frequency drop during the frequency recovery process meets expectations.

[0047] As an optional implementation, in the aforementioned step 2, the system frequency drop process with different target degrees refers to using a system frequency response function to generate a system frequency drop process with different target degrees by setting different system power shortages according to the power-on combination of the power grid system.

[0048] As an optional implementation, in the aforementioned step 2, when calculating the active power response curves and corresponding four index values ​​of each wind turbine in the wind farm under different wind speeds and different target degrees of system frequency drop processes, the wind speed changes in steps of 0.1 m / s, and the range of change is determined according to the operating wind speed range of the wind turbine;

[0049] The frequency drop degree of the power grid system changes in steps of 0.05Hz from the lowest frequency point, and the drop range is 49.95Hz to 49.00Hz.

[0050] As an optional implementation, in the aforementioned step 6, determining the value or value range of the wind farm output power decision indicator in step 1 includes:

[0051] First, according to the control targets of the current wind speed of each wind turbine and the minimum value of the system frequency, the active power response curves of all turbines are queried from the results obtained in step 2, and the active power response curves of the wind farm are accumulated to obtain the active power response curve;

[0052] Then, the time when the wind farm output active power reaches the maximum value is taken as T M , take the maximum value of wind farm output active power as the index △P MAX The upper limit of the value is the equivalent step support power △P of the wind farm calculated in step 5. step The index △P MAX The lower limit of the value; the minimum value of the wind farm output active power is taken as the indicator △P MIN The lower limit of the value, index △P MIN The upper limit of the value is 0; take all wind turbines index T Z The maximum and minimum values ​​of Z The upper and lower limits of the value.

[0053] As an optional implementation, in the aforementioned step 7, the process of determining the value of each indicator step by step includes:

[0054] First, to achieve the minimum system frequency control target f min1 As a premise, f min1 With a step size of 0.05 Hz, the area T enclosed by the wind farm active power generation section Z △P MAX / 2 is the minimum optimization target, and the index △P is determined MAX and T Z The value of

[0055] Then, fix the determined △P MAX and T Z Numerical value, with index △P MIN The lower limit is the initial value, and △P is gradually increased. MIN , until the system frequency secondary drop amplitude △f2 requirement is met.

[0056] As an optional implementation, in the aforementioned step 8, determining the unit combination participating in frequency support in the wind farm includes the following process:

[0057] Step 8.1: Set △P at the nth iteration index (t) is denoted as turn up Maximum value The corresponding time The first iteration

[0058] Step 8.2: For the unselected wind turbines, Active power at all times With △P MIN_i The absolute value of the ratio, subscript i is the unit number, sorted in descending order, if If the size is the same, follow Sort from largest to smallest;

[0059] Step 8.3: If Greater than all unselected wind turbines The maximum active power at the moment, then select the wind turbine with the highest ranking in step 8.2, otherwise select the wind turbine from the top to the bottom in the ranking of the wind turbines in step 8.2. The active power at the moment is greater than and closest to Wind turbines, record the number of the selected wind turbines

[0060] Step 8.4: Minus wind turbines Active power response curve get Right now

[0061] Step 8.5: Repeat steps 8.1 to 8.4 until So far, a series of units have been selected That is, the combination of units that will participate in system frequency support.

[0062] Combination Figure 1 In the example shown, after determining the combination of units participating in the system frequency support, an instruction to participate in the frequency support is output to each selected unit, thereby realizing the support of the wind farm to the system frequency.

[0063] Next we will combine Figure 1-Figure 11 As shown, the exemplary implementation process of the above method of the present invention is described in more detail.

[0064] Step 1: Given the wind farm output power decision indicators, including the maximum value of active power change △P MAX , the time when the active power change reaches the maximum value T M , the time T for active power change to return to zero Z and the minimum allowable value of active power change △P MIN The specific values ​​and ranges of the above four decision indicators can be determined in subsequent steps.

[0065] In this embodiment, considering the economic efficiency of wind turbine operation, only the combined control strategy of virtual inertia control and droop control is considered.

[0066] As an embodiment of the present invention, a typical joint control strategy structure is as follows: Figure 2 As shown, K df is the inertia control coefficient, K pf is the droop control coefficient, ω r is the rotor speed, P meas is the active power of the wind turbine, f is the system frequency, and f0 is the rated frequency.

[0067] This control strategy achieves fast frequency response of the wind turbine by releasing the rotor kinetic energy according to the frequency deviation Δf and the frequency change rate df / dt. The equation corresponding to the control strategy is shown in (1):

[0068]

[0069] According to the morphological characteristics of the output power change of the wind turbine during the fast frequency response, the present invention proposes four power change indicators of ΔP to determine the active power that the wind farm needs to provide when participating in the fast frequency response, as shown in Table 1.

[0070] A graph surrounded by four indicators, such as Figure 3 shown.

[0071] Table 1 Output power decision indicators

[0072] symbol meaning <![CDATA[ΔP MAX ]]> Maximum value of power change <![CDATA[T M ]]> <![CDATA[The time when the power change reaches the maximum value ΔP MAX > <![CDATA[ΔP MIN ]]> Minimum power change <![CDATA[T Z ]]> Time for power change to return to zero

[0073] Combination Figure 2 , 3 As shown in the active power change diagram, according to the points (0,0), (T M ,△P MAX ) and (T Z ,0), a triangle representing the power support demand of the power system for the wind farm can be constructed. When the power support provided by the wind farm is higher than the triangle, the frequency regulation target of the power system can be achieved; △P MIN The minimum value of the output power change of the wind farm during the wind turbine rotor speed recovery stage is specified, which is used to ensure that the degree of secondary frequency drop during the frequency recovery process is in line with expectations.

[0074] Step 2: Simulate and obtain the active power response curves and the corresponding four index values ​​of each wind turbine in the wind farm under different wind speeds and different target degrees of system frequency drop.

[0075] In this example, the Figure 4 A typical IEEE-9 node simulation system is shown. Figure 4 In the figure, G1 and G2 are set as water turbines and steam turbines respectively; G3 is a wind farm equipped with 48 1.5MW DFIG wind turbines and is represented by a single-machine equivalent model. At the same time, in order to improve the speed of obtaining parameters, evaluation and decision-making under different wind speeds, an existing fast simulation model integrating wind turbines and power systems is used. Figure 5 shown.

[0076] In an optional example, a specific method for obtaining system frequency drop processes of different target degrees is: according to the power system startup combination, according to the existing technology, by adopting the system frequency response function, by setting different system power shortages to generate system frequency drop processes of different target degrees.

[0077] In an optional example, when performing simulation, the wind speed changes in steps of 0.1m / s, and the range of change is determined according to the operating wind speed range of the wind turbine; the system frequency drop degree changes in steps of 0.05Hz from the lowest frequency point, and the drop range is 49.95Hz to 49.00Hz.

[0078] Step 3: Determine whether the startup combination and power generation of the synchronous generators in the system have changed significantly. If so, re-execute step 2, otherwise proceed to step 4. In this example, no significant change has occurred, and proceed directly to step 4.

[0079] Step 4: Determine whether the system has a major power shortage. If so, proceed to step 5, otherwise return to step 3. The major power shortage in this example is a sudden increase of 15MW in the load power on bus 5. This power shortage is about 5.13% of the total power generation of the system, so proceed to step 5.

[0080] Step 5: Use the system frequency response function to calculate the maximum drop of the system frequency when wind power does not participate in frequency regulation, and determine the control target f of the minimum value of the system frequency after considering the capabilities of various conventional frequency regulation methods of the system. min1 (with a step size of 0.05Hz) and the corresponding wind farm equivalent step support power △P step , determine the secondary frequency drop amplitude △f2 during the system frequency recovery process.

[0081] In this example, the maximum drop of the system frequency when wind power does not participate in frequency regulation is 49.73Hz. Considering the capabilities of various conventional frequency regulation methods of the system, the control target f of the minimum value of the system frequency is determined. min1 =49.80Hz, the corresponding wind farm equivalent step support power △P step =0.055(pu), the secondary frequency drop amplitude △f2 during the system frequency recovery process =0.5Hz.

[0082] Step 6: Determine the value or value range of each decision indicator of the wind farm described in step 1 according to the current wind speed of each wind turbine in the wind farm.

[0083] In order to quickly determine the values ​​of the four decision indicators listed in Table 1, a fast simulation model based on a general system frequency response (GSFR) model is used in the embodiment of the present invention, such as Figure 5 shown. Figure 5 The middle index test module generates a power variation curve ΔP(t).

[0084] Furthermore, the specific method for determining the value or value range of each decision indicator includes the following steps:

[0085] First, according to the control targets of the current wind speed of each wind turbine and the minimum system frequency, the active power response curves of all turbines are queried from the results obtained in step 2, and the active power response curves of the wind farm are accumulated to obtain the active power response curves of the wind farm; the control target of the minimum system frequency in this embodiment is 49.80 Hz, and the curve queried in step 2 is as follows: Figure 6 As shown;

[0086] Then, the time when the wind farm output active power reaches the maximum value is taken as T M , take the maximum value of wind farm output active power as the index △P MAX The upper limit of the value is the equivalent step support power △P of the wind farm calculated in step 5.step The index △P MAX The lower limit of the value; the minimum value of the wind farm output active power is taken as the indicator △P MIN The lower limit of the value, index △P MIN The upper limit of the value is 0; take all wind turbines index T Z The maximum and minimum values ​​of Z The upper and lower limits of the value.

[0087] In this example, the value ranges of the four decision indicators are shown in Table 2.

[0088] Table 2 Value ranges of the four decision indicators

[0089] index Value range index Value range <![CDATA[ΔP MAX (pu)]]> [0.055,0.266] <![CDATA[ΔP MIN (pu)]]> [-0.054,0] <![CDATA[T M (s)]]> 3.09 <![CDATA[T Z (s)]]> [8.61,9.32]

[0090] Step 7: Optimize each indicator step by step within the indicator value range determined in step 6, and determine the specific value of each indicator step by step.

[0091] As an optional implementation, the specific method of determining the value of each indicator step by step includes the following steps:

[0092] First, to achieve the minimum system frequency control target f min1 As a premise, the area T enclosed by the wind farm active power generation section Z △P MAX / 2 is the minimum optimization target, and the index △P is determined MAX and T Z Then, fix the determined △P MAX and T Z Numerical value, with index △P MIN The lower limit is the initial value, and △P is gradually increased. MIN Until the system frequency secondary drop amplitude △f2 requirement is met;

[0093] In this embodiment, ΔP MIN The lower limit is -0.054, and the increment step is 0.001;

[0094] Then, with area k (n) =T Z △P MAX / 2 is the optimization direction, that is, Figure 7 The direction indicated by the long grey arrow is optimal. If k (n) There is no △P that can achieve the minimum control target of system frequency. MAX and T Z , then increase the area so that k (n+1) =k (n) +△k, such as Figure 7 The black short arrow in the middle moves in the direction indicated by the(n+1) Continue to search for the optimal solution under the constraints until a △P that meets the frequency modulation requirements is found. MAX and T Z .

[0095] In this example, k (0) =0.474, Δk=0.001, using a computer with 8-core CPU, the result can be obtained within 0.2s through parallel computing. The index data obtained in this example are shown in Table 3.

[0096] Table 3 Values ​​of wind farm output power decision index

[0097] index Numeric index Numeric <![CDATA[ΔP MAX (pu)]]> 0.099 <![CDATA[ΔP MIN (pu)]]> -0.043 <![CDATA[T M (s)]]> 3.09 <![CDATA[T Z (s)]]> 8.62

[0098] Step 8: Based on the wind farm output power index obtained in step 7, the graph △P formed by the four indexes index (t), determine the unit combination participating in frequency support in the wind farm.

[0099] As an optional implementation, the process of determining the unit combination participating in frequency support in the wind farm specifically includes the following steps:

[0100] The first step is to convert △P at the nth iteration index (t) is denoted as turn up Maximum value The corresponding time (At the first iteration );

[0101] Step 2: For the unselected wind turbines, Active power at all times With △P MIN_i The absolute value of the ratio (subscript i is the unit number) is sorted in descending order. If the size is the same, follow Sort from largest to smallest;

[0102] Step 3: If Greater than all unselected wind turbines If the maximum active power is reached at the moment, the wind turbine with the highest ranking in the second step is selected; otherwise, the wind turbine with the highest ranking in the second step is selected from the front to the back. The active power at the moment is greater than and closest to Wind turbines, record the number of the selected wind turbines

[0103] Step 4: Minus wind turbines Active power response curve get Right now

[0104] Thus, repeat the above four steps until So far, a series of units have been selected That is, the combination of units that will participate in system frequency support.

[0105] Through calculation and simulation, the results of the unit combination in this example can be obtained within 0.07s. Figure 8 As shown in the figure, it can be seen that the simplified output power of the unit combination meets the requirements of the index.

[0106] Furthermore, instructions for participating in system frequency support can be output to each selected unit to achieve wind farm support for system frequency.

[0107] As an example, in the actual power grid system, the wind farm output power results before and after the unit combination are as follows: Fig. 9 As shown in the figure, it can be seen that the selected unit combination can just cover the indicators without causing too much waste, thereby improving the efficiency of wind power participating in grid frequency support; the frequency response results before and after the unit combination participates in frequency regulation in the actual system are as follows Fig.10 As shown in the figure, it can be seen that the minimum value of the first frequency drop is effectively increased to above 49.80Hz, and the second frequency drop is also less than 0.05Hz, which can accurately achieve the expected support effect on the system frequency. In this embodiment, the total time from step 5 to step 9 after the fault occurs is 0.34s. It can be seen that the method of the present invention can quickly make decisions on how wind farms participate in grid frequency support.

[0108] In combination with the implementation of the above method for determining the unit combination of a wind farm participating in grid frequency support, according to the embodiments disclosed in the present invention, a system for determining the unit combination of a wind farm participating in grid frequency support is also proposed, including: one or more processors and a memory. The memory is configured to store operable instructions, which, through such execution, enable the one or more processors to perform operations, including the process of the method for determining the unit combination of a wind farm participating in grid frequency support as in any of the above embodiments.

[0109] In combination with the implementation of the above method of identifying the proportion of power load components using large disturbance data, a computer-readable medium for storing software is also proposed according to the embodiments disclosed in the present invention, wherein the software includes instructions that can be executed by one or more processors, and these instructions enable the one or more processors to perform operations through such execution, and these operations include the process of a method for determining the combination of units of a wind farm participating in grid frequency support as in any of the aforementioned embodiments.

[0110] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. A person with ordinary knowledge in the technical field to which the present invention belongs may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the definition of the claims.

Claims

1. A method for determining the unit combination of a wind farm participating in power grid frequency support, characterized in that: The following steps are involved: Step 1: Given the wind farm output power decision indicators, including the maximum value of active power change △P MAX , the time when the active power change reaches the maximum value T M , the time T for active power change to return to zero Z and the minimum allowable value of active power change △P MIN ; Step 2: Simulate and obtain the active power response curves of each wind turbine in the wind farm under different wind speeds and different target levels of system frequency drop and the values ​​of the four decision indicators corresponding to the step 1; Step 3, determine whether the startup combination and power generation of the synchronous generators in the power grid system have changed as expected, if so, re-execute step 2, otherwise proceed to step 4; Step 4: Determine whether the power grid system has a predetermined power shortage. If so, proceed to step 5; otherwise, return to step 3; Step 5: Use the system frequency response function to calculate the maximum drop of the system frequency when wind power does not participate in frequency regulation, and determine the control target f of the minimum value of the system frequency. min1 And the corresponding wind farm equivalent step support power △P step , determine the secondary frequency drop amplitude △f2 during the system frequency recovery process; Step 6: Determine the value or value range of the wind farm output power decision indicator of the wind farm in step 1 according to the current wind speed of each wind turbine in the wind farm; Step 7, optimizing each indicator step by step within the indicator value range determined in step 6, and determining the specific value of each indicator step by step; Step 8: According to the specific values ​​of the various indicators of the wind farm output power obtained in step 7, determine the graph △P surrounded by the four indicators index (t), and accordingly determine the unit combination participating in frequency support in the wind farm.

2. The method for determining the unit combination of a wind farm participating in the grid frequency support according to claim 1, characterized in that: In step 1, for a given wind farm output power decision indicator, where: On the active power change graph, according to the points (0,0), (T M ,△P MAX ) and (T Z ,0), construct a triangle representing the power support demand of the power grid system for the wind farm. When the power support provided by the wind farm is higher than the triangle, the frequency regulation target of the power grid system can be achieved; where △P MIN It indicates the minimum value of the output power change of the wind farm during the wind turbine rotor speed recovery stage. It is used to ensure that the secondary frequency drop during the frequency recovery process meets expectations.

3. The method for determining the unit combination of a wind farm participating in the grid frequency support according to claim 1, characterized in that: In step 2, the system frequency drop process with different target degrees refers to generating system frequency drop processes with different target degrees by setting different system power shortages using a system frequency response function according to the power-on combination of the power grid system.

4. The method for determining the unit combination of a wind farm participating in the grid frequency support according to claim 2, characterized in that: In step 2, when calculating the active power response curves and corresponding four index values ​​of each wind turbine in the wind farm under different wind speeds and different target degrees of system frequency drop, the wind speed changes in steps of 0.1 m / s, and the change range is determined according to the operating wind speed range of the wind turbine; The frequency drop degree of the power grid system changes in steps of 0.05Hz from the lowest frequency point, and the drop range is 49.95Hz to 49.00Hz.

5. The method for determining the unit combination of a wind farm participating in the grid frequency support according to claim 1, characterized in that: In step 6, determining the value or value range of the wind farm output power decision indicator in step 1 includes: First, according to the control targets of the current wind speed of each wind turbine and the minimum value of the system frequency, the active power response curves of all turbines are queried from the results obtained in step 2, and the active power response curves of the wind farm are accumulated to obtain the active power response curve; Then, the time when the wind farm output active power reaches the maximum value is taken as T M , take the maximum value of wind farm output active power as the index △P MAX The upper limit of the value is the equivalent step support power △P of the wind farm calculated in step 5. step The index △P MAX The lower limit of the value; the minimum value of the wind farm output active power is taken as the indicator △P MIN The lower limit of the value, index △P MIN The upper limit of the value is 0; take all wind turbines index T Z The maximum and minimum values ​​of Z The upper and lower limits of the value.

6. The method for determining the unit combination of a wind farm participating in the grid frequency support according to claim 5, characterized in that: In step 7, the process of determining the value of each indicator step by step includes: First, to achieve the minimum system frequency control target f min1 As a premise, f min1 With a step size of 0.05 Hz, the area T enclosed by the wind farm active power generation section Z △P MAX / 2 is the minimum optimization target, and the index △P is determined MAX and T Z The value of Then, fix the determined △P MAX and T Z Numerical value, with index △P MIN The lower limit is the initial value, and △P is gradually increased. MIN , until the system frequency secondary drop amplitude △f2 requirement is met.

7. The method for determining the unit combination of a wind farm participating in the grid frequency support according to claim 1, characterized in that: In step 8, determining the unit combination participating in frequency support in the wind farm includes the following processes: Step 8.1: Set △P at the nth iteration index (t) is denoted as turn up Maximum value The corresponding time The first iteration Step 8.2: For the unselected wind turbines, Active power at all times With △P MIN_i The absolute value of the ratio, subscript i is the unit number, sorted in descending order, if If the size is the same, follow Sort from largest to smallest; Step 8.3: If Greater than all unselected wind turbines The maximum active power at the moment, then select the wind turbine with the highest ranking in step 8.2, otherwise select the wind turbine from the top to the bottom in the ranking of the wind turbines in step 8.

2. The active power at the moment is greater than and closest to Wind turbines, record the number of the selected wind turbines Step 8.4: Minus wind turbines Active power response curve P i n (t)Get Right now Step 8.5: Repeat steps 8.1 to 8.4 until So far, a series of units have been selected That is, the combination of units that will participate in system frequency support.

8. The method for determining the unit combination of a wind farm participating in the grid frequency support according to any one of claims 1 to 7, characterized in that: The method further comprises the following steps: Output frequency support participation instructions to each selected unit to achieve wind farm support for system frequency.

9. A system for determining the unit combination of a wind farm participating in power grid frequency support, characterized in that: include: one or more processors; A memory storing operable instructions, wherein when the instructions are executed by the one or more processors, the one or more processors are caused to perform operations, wherein the operations include the process of a method for determining a unit combination of a wind farm participating in grid frequency support as described in any one of claims 1 to 8.

10. A computer-readable medium storing software, characterized in that: The software includes instructions that can be executed by one or more processors, and the instructions enable the one or more processors to perform operations through such execution, and the operations include the process of the method for determining the unit combination of a wind farm participating in grid frequency support as described in any one of claims 1-8.

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