Frequency controller parameter optimization and control coefficient optimization method based on safety boundary constraint

Abstract

The invention relates to the technical field of new energy power generation, in particular to a safety boundary constraint-based frequency controller parameter optimization and control coefficient optimization method, which comprises the following steps of: constructing a RoCoF safety boundary by taking system inertia as an influence factor; analyzing influence factors of frequency change of a sending end, and setting a frequency segmentation interval of actions of the wind power plant and the interconnection region; optimizing a control coefficient of the frequency controller, and modulating the optimized coefficient to form an active power modulation instruction; detecting the frequency change of the wind power plant and the frequency controller by setting the value of the frequency segmentation interval; validity verification is carried out through simulation verification, and the influences of different control strategies on the dynamic characteristics of the system frequency are compared. The method has the beneficial effects that the response capability of the wind power plant to the frequency change of the power grid is enhanced by optimizing the control coefficient of the wind power plant; by dynamically adjusting the control coefficient, the wind power plant can provide more accurate active power support according to the real-time frequency state of the power grid.

Description

Technical Field

[0001] The present invention relates to the technical field of renewable energy power generation, and in particular to a method for optimizing frequency controller parameters and control coefficients based on safety boundary constraints. Background Art

[0002] In the field of renewable energy power generation, especially in the context of wind farm grid-connected operation, the existing technology has several deficiencies in grid frequency control. For example, traditional wind farms have limited response capabilities when facing grid frequency fluctuations, and due to the lack of effective frequency control strategies, wind farms are often unable to provide necessary active power support in a timely manner, resulting in a decrease in grid frequency stability; they fail to fully utilize the synergy between wind farms and interconnected areas for frequency modulation. When the grid is disturbed, the frequency modulation resources of wind farms and interconnected areas are not effectively integrated, which reduces the frequency modulation efficiency; the current control strategy of wind farms is relatively simple, and the control parameters are not dynamically adjusted according to the actual frequency state of the grid, which results in poor frequency modulation effects of wind farms when the grid frequency fluctuates greatly; after the grid is disturbed, there are also deficiencies in suppressing frequency fluctuations, and wind farms fail to give full play to their potential in grid frequency control, especially in the case of DC blocking in the interconnected area; there is a lack of rationality in the allocation of frequency modulation resources, resulting in a waste of frequency modulation resources; there is a lack of adaptive capability, and it is impossible to automatically adjust the frequency modulation strategy and control parameters according to the specific circumstances of grid frequency changes to achieve more effective frequency control.

[0003] These shortcomings limit the role of wind farms in grid frequency control and affect the stability and reliability of the grid. Therefore, it is urgent to design a new wind farm frequency regulation method in combination with the system frequency constraint safety boundary constraint to solve the problems in the existing technology, improve the frequency characteristics of the system, and ensure the safe operation of the wind farm. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is: based on the frequency change rate safety boundary of the system, to solve the problem that the current wind farm lacks an effective frequency control strategy and coordinated frequency regulation mechanism, resulting in insufficient frequency stability under grid disturbances, unreasonable allocation of frequency regulation resources, and lack of adaptive capability of the frequency regulation system.

[0005] The above technical problem is solved by the following technical solution: The present invention proposes a frequency controller parameter optimization method based on safety margin constraints, which includes constructing a safety margin of RoCoF by taking system inertia as an influencing factor;

[0006] Analyze the factors affecting the frequency change at the sending end and set the frequency segment intervals for the wind farm and the interconnected area;

[0007] Optimize the control coefficient of the frequency controller, and modulate the optimized coefficient to form an active power modulation instruction;

[0008] By setting the value of the frequency segment interval, the wind farm and the frequency controller detect frequency changes;

[0009] The effectiveness is verified through simulation and the effects of different control strategies on the frequency dynamic characteristics of the system are compared.

[0010] In a preferred implementation of the frequency controller parameter optimization method based on safety boundary constraints of the present invention: the influencing factors of the frequency change at the sending end include the system inertia time constant, the frequency change rate, the output increment of the synchronous machine and the new energy unit, the disturbance power size, the frequency deviation and the system damping.

[0011] In a preferred implementation of the frequency controller parameter optimization method based on safety margin constraints of the present invention: optimizing the control coefficient of the frequency controller includes amplifying the control gain coefficient and the filter coefficient;

[0012] The optimized coefficients are modulated, including modulation through a gain-inertia link and a power limiting link.

[0013] In a preferred implementation of the frequency controller parameter optimization method based on safety boundary constraints of the present invention: frequency changes are detected for wind farms and frequency controllers, including that within the first segmented interval, the wind farm participates in frequency modulation; within the second segmented interval, the interconnected area participates in frequency modulation to suppress frequency changes in the sending end area.

[0014] In a preferred implementation of the frequency controller parameter optimization method based on safety boundary constraints of the present invention: the wind farm participates in frequency regulation, including playing the role of the wind farm in the sending end area to suppress frequency fluctuations in the case of DC blocking in the interconnected area;

[0015] Interconnected areas participate in frequency regulation, including when wind farms are unable to suppress frequency fluctuations, to ensure system frequency stability.

[0016] In order to solve the above technical problems, the present invention also provides the following technical solutions: a method for optimizing a control coefficient of a frequency controller, which comprises simulating the inertia effect of a conventional wind farm synchronous generator by introducing a control coefficient;

[0017] Detect frequency deviation by real-time monitoring of grid frequency changes, and decide whether the wind farm needs to participate in frequency regulation based on the set control strategy;

[0018] Dynamically adjust the control coefficient of the wind farm according to the real-time frequency status of the power grid and the preset frequency segment interval;

[0019] Whether the wind farm participates in frequency regulation and the extent of its participation are determined based on the size and direction of the frequency change.

[0020] In a preferred implementation of the method for optimizing the control coefficient of a frequency controller of the present invention: the control coefficient provides or absorbs active power when the frequency of the wind farm power grid fluctuates, so as to mitigate the frequency change.

[0021] In a preferred implementation of the method for optimizing the control coefficient of a frequency controller of the present invention: the control coefficient includes adjusting the virtual inertia coefficient.

[0022] In a preferred implementation of the method for optimizing the control coefficient of a frequency controller of the present invention: the virtual inertia coefficient is adjusted to optimize the frequency regulation effect of the wind farm in different frequency ranges.

[0023] In a preferred implementation of the method for optimizing the control coefficient of a frequency controller of the present invention: the frequency change includes increasing the active power output if the frequency decreases, and reducing the active power output if the frequency increases.

[0024] The beneficial effects of the present invention are as follows: the present invention optimizes the control coefficient of the wind farm, thereby enhancing the responsiveness of the wind farm to the frequency change of the power grid, realizing the coordinated frequency modulation of the wind farm and the interconnected area, effectively integrating the frequency modulation resources, and improving the frequency modulation efficiency; by dynamically adjusting the control coefficient, the wind farm can provide more accurate active power support according to the real-time frequency status of the power grid; when the power grid is disturbed, the frequency fluctuation is effectively suppressed by adaptively coordinating the wind farm or the interconnected area to participate in the frequency modulation; the allocation of frequency modulation resources is optimized, the waste of frequency modulation resources is reduced, and the stability and reliability of the power grid are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings of the embodiments of the present invention. Obviously, the drawings in the following description only relate to some embodiments of the present invention, but are not intended to limit the present invention.

[0026] Figure 1 A frequency segmentation schematic diagram of a frequency controller parameter optimization method based on safety margin constraints is shown.

[0027] Figure 2 A schematic diagram of interconnected area DC blocking of a frequency controller parameter optimization method based on safety boundary constraints is shown.

[0028] Figure 3 A schematic diagram showing the interconnected area and wind farm participating in frequency regulation based on a frequency controller parameter optimization method based on safety boundary constraints is shown.

[0029] Figure 4 The system frequency simulation result diagram of the frequency controller parameter optimization method based on safety boundary constraints is shown.

[0030] Figure 5 Schematic diagram of the RoCoF security boundary. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below in conjunction with specific implementation methods and drawings.

[0032] The terms used in the present invention are those general terms currently widely used in the art in consideration of the functions of the present invention, but these terms may vary according to the intention of a person of ordinary skill in the art, precedents, or new technologies in the art. In addition, specific terms may be selected by the applicant, and in this case, their detailed meanings will be described in the detailed description of the present invention. Therefore, the terms used in the specification should not be understood as simple names, but rather as a general description based on the meaning of the terms and the present invention.

[0033] Example 1

[0034] like Figure 1 to Figure 5 , this embodiment provides a frequency controller parameter optimization method based on safety margin constraints, including,

[0035] The safety margin of RoCoF is constructed by taking system inertia as an influencing factor;

[0036] It should be noted that RoCoF is the rate of change of system frequency. A safety margin based on RoCoF is constructed, where the safety margin takes the system inertia H as an influencing factor. The specific formula is as follows:

[0037]

[0038] Among them, the system inertia is affected by the inertia of the wind farm, H sg is the synchronous machine inertia, The inertia provided by the wind farm, ΔP Lmax is the maximum disturbance kilometers that the system can withstand, RoCoF max is the maximum frequency change rate of the system.

[0039] Analyze the factors affecting the frequency change at the sending end and set the frequency segment intervals for the wind farm and the interconnected area;

[0040] Optimize the control coefficient of the frequency controller, and modulate the optimized coefficient to form an active power modulation instruction;

[0041] By setting the value of the frequency segment interval, the wind farm and the frequency controller detect frequency changes;

[0042] The effectiveness is verified through simulation and the effects of different control strategies on the frequency dynamic characteristics of the system are compared.

[0043] Furthermore, the factors affecting the frequency change at the sending end include the system inertia time constant, the frequency change rate, the output increment of the synchronous machine and the new energy unit, the disturbance power size, the frequency deviation and the system damping.

[0044] It should be noted that in the power system, the response equation of the system frequency is as follows:

[0045]

[0046] Where M is the system inertia time constant, is the frequency change rate, ΔP G is the output increment of the synchronous machine under disturbance, ΔP N is the output increment of new energy units, ΔP L is the disturbance power, mostly active load disturbance, Δf is the frequency deviation, and D is the system damping.

[0047] Among them, the frequency fluctuation in the system is mainly caused by the unbalanced power ΔP um The formula is as follows:

[0048] ΔP um =ΣΔP G +ΣΔ P N-ΔP L

[0049] The larger the M is, the more obvious the frequency change rate is slowed down, and D mainly affects the system frequency deviation;

[0050] ΔP L It can cover various types of frequency disturbance events, such as synchronous machine cutting and new energy unit output fluctuation. The disturbance size can be expressed as ΔP L The disturbance power between different interconnected areas can be expressed as ΔP L Indicated as ΔP L =ΔP in +ΔP out , ΔP in is the disturbance power in the system area, ΔP out is the disturbance power outside the system area

[0051] After a frequency disturbance occurs, the system frequency gradually decreases or increases. If the frequency deviation exceeds the safety limit |Δf max |, which easily triggers low-frequency load shedding. Therefore, when the frequency in the sending-end area rises under the condition of DC blocking in the interconnected area, the wind farm in the sending-end area should be fully utilized to suppress frequency fluctuations. When the wind farm cannot suppress frequency fluctuations, the role of the interconnected area should be fully utilized.

[0052] Here, this patent sets 0-|Δf1| as the first segment interval, |Δf1|-|Δf max | is the second segment interval.

[0053] Further, the control coefficients of the frequency controller are optimized, including the amplification control gain coefficient and the filter coefficient;

[0054] It should be noted that the specific formula for the control coefficient of the optimized frequency controller is as follows:

[0055]

[0056] It should be further explained that the wind farm chooses whether to participate in the frequency modulation in the sending area according to the frequency change, where k i is the virtual inertia coefficient.

[0057]

[0058] Among them, Figure 2 and Figure 3 As shown, K is the frequency controller amplification control gain coefficient, T r , T l is the filter coefficient of the frequency controller. After the disturbance, the system frequency will deviate. When the system frequency difference exceeds the dead zone limit of the frequency controller, the △f signal is converted into an active power output deviation signal through the gain-inertia link, and then passes through the power limiting link to finally form an active power modulation instruction.

[0059] The optimized coefficients are modulated, including modulation through a gain-inertia link and a power limiting link.

[0060] Furthermore, the wind farm and the frequency controller detect frequency changes, including that in the first segmented interval, the wind farm participates in frequency modulation; in the second segmented interval, the interconnected area participates in frequency modulation to suppress frequency changes in the sending end area.

[0061] It should be noted that the segmented optimization method specifically includes:

[0062] The power grid personnel set the value of the frequency segment interval |Δf1|;

[0063] The wind farm and the frequency controller detect frequency changes. If the frequency change is within the first segment interval, the wind farm participates in frequency modulation to suppress frequency changes in the sending end area. If the frequency change is within the second segment interval, the interconnected area participates in frequency modulation to suppress frequency changes in the sending end area.

[0064] Furthermore, wind farms participate in frequency regulation, including playing the role of wind farms in the sending-end area to suppress frequency fluctuations in the case of DC blocking in the interconnected area;

[0065] Interconnected areas participate in frequency regulation, including when wind farms are unable to suppress frequency fluctuations, to ensure system frequency stability.

[0066] In summary, the present invention optimizes the control coefficient of the wind farm, thereby enhancing the responsiveness of the wind farm to the frequency changes of the power grid, realizes the coordinated frequency modulation of the wind farm and the interconnected area, effectively integrates the frequency modulation resources, and improves the frequency modulation efficiency; by dynamically adjusting the control coefficient, the wind farm can provide more accurate active power support according to the real-time frequency status of the power grid; when the power grid is disturbed, the frequency fluctuation is effectively suppressed by adaptively coordinating the wind farm or the interconnected area to participate in the frequency modulation; the allocation of frequency modulation resources is optimized, the waste of frequency modulation resources is reduced, and the stability and reliability of the power grid are improved.

[0067] Example 2

[0068] like Figure 1 to Figure 4 This embodiment provides a frequency controller parameter optimization method based on safety boundary constraints, including: after the implementation of the segmented optimization method for the wind farm in the sending end area and the interconnected area to collaboratively participate in frequency regulation, the specific usage is as follows:

[0069] like Figure 2 As shown, there are three areas in total. Please note that the DC blocking fault in interconnected area 1 is coordinated according to the frequency change. The specific steps are as follows:

[0070] Within a certain range of frequency variation, wind farms participate in frequency regulation to suppress frequency variation;

[0071] When the frequency changes greatly, the interconnected area 2 participates in the frequency modulation to suppress the frequency change.

[0072] It should be noted that in this process, coordinated control needs to be achieved by optimizing the fan frequency controller, and the frequency controller DC controller of interconnected area 2 needs to be added with selection judgment control.

[0073] like Figure 4 As shown in the figure, it is the dynamic characteristics of the system frequency. It can be seen from the curve performance in the figure that different control strategies have different effects on the improvement of frequency. With the introduction of DC frequency controller frequency modulation, the frequency change rate, frequency low point and steady-state frequency of the system frequency are improved.

[0074] Specifically, the figure contains four different frequency modulation strategies:

[0075] The blue dotted line represents only thermal power frequency regulation. This strategy relies solely on thermal power units for frequency regulation. As can be seen from the figure, thermal power frequency regulation has a certain inhibitory effect on the increase of frequency in the early stage, but as time goes by, the frequency gradually decreases and fluctuates greatly;

[0076] The orange dotted line is the virtual inertia frequency regulation of thermal power and wind power. This strategy combines the virtual inertia frequency regulation of thermal power units and wind farms. Compared with the frequency regulation of thermal power only, this strategy provides better suppression effect in the frequency rise stage, with smaller frequency fluctuations, showing the positive role of wind farms in frequency regulation;

[0077] The yellow dotted line represents the thermal power and frequency controller droop control participating in frequency regulation. This strategy uses the thermal power unit and frequency controller droop control to regulate the frequency. This strategy can stabilize the frequency quickly after the frequency rises, but the frequency fluctuation still exists in the whole process;

[0078] The purple solid line represents the frequency modulation of thermal power, wind power and frequency controller DC droop control. This is the strategy proposed by the present invention, which combines the frequency modulation method of thermal power units, wind farms and frequency controller DC droop control. As can be seen from the figure, this strategy performs best among all strategies. After the frequency rises, it can stabilize the fastest and has the smallest fluctuation, showing the best frequency modulation effect.

[0079] In summary, the present invention optimizes the control coefficient of the wind farm, thereby enhancing the responsiveness of the wind farm to the frequency changes of the power grid, realizes the coordinated frequency modulation of the wind farm and the interconnected area, effectively integrates the frequency modulation resources, and improves the frequency modulation efficiency; by dynamically adjusting the control coefficient, the wind farm can provide more accurate active power support according to the real-time frequency status of the power grid; when the power grid is disturbed, the frequency fluctuation is effectively suppressed by adaptively coordinating the wind farm or the interconnected area to participate in the frequency modulation; the allocation of frequency modulation resources is optimized, the waste of frequency modulation resources is reduced, and the stability and reliability of the power grid are improved.

[0080] Example 3

[0081] This embodiment provides a method for optimizing a control coefficient of a frequency controller, including simulating the inertia effect of a conventional wind farm synchronous generator by introducing a control coefficient;

[0082] Detect frequency deviation by real-time monitoring of grid frequency changes, and decide whether the wind farm needs to participate in frequency regulation based on the set control strategy;

[0083] Dynamically adjust the control coefficient of the wind farm according to the real-time frequency status of the power grid and the preset frequency segment interval;

[0084] Whether the wind farm participates in frequency regulation and the extent of its participation are determined based on the size and direction of the frequency change.

[0085] Furthermore, the control coefficient provides or absorbs active power when the wind farm grid frequency fluctuates to mitigate the frequency variation.

[0086] Furthermore, the control coefficient includes adjusting a virtual inertia coefficient.

[0087] Furthermore, the virtual inertia coefficient is adjusted to optimize the frequency regulation effect of the wind farm in different frequency ranges.

[0088] Furthermore, the frequency change includes increasing the active power output if the frequency decreases, and reducing the active power output if the frequency increases.

[0089] It should be noted that the control coefficient, that is, the virtual inertia coefficient, is defined as follows:

[0090] I virtual = k·I real

[0091] Among them, I virtual is the virtual inertia coefficient, k is a proportional factor, I real is the actual inertia.

[0092] The process of virtual inertia coefficient providing or absorbing active power when the wind farm grid frequency fluctuates includes:

[0093] Frequency response equation formula:

[0094]

[0095] Where Δf is the frequency change, H is the system inertia, and ΔP is the power change.

[0096] Active power output adjustment:

[0097] P output =P base +D·Δf

[0098] Among them, P output is the adjusted active power output, P base is the basic active power output, D is the damping coefficient, and Δf is the frequency deviation.

[0099] The relationship between the frequency change rate and inertia:

[0100]

[0101] Where H is the system inertia and ΔP is the power change.

[0102] The wind field modulation control formula is as follows:

[0103]

[0104] Among them, P wind is the active power output of the wind farm, P wind，base It is the basic active power output of the wind farm.

[0105] According to the above calculation results, the frequency controller output is finally obtained as:

[0106]

[0107] Among them, P FLC is the active power output of the frequency controller, K p , K i and K d They are proportional, integral and derivative gains respectively.

[0108] In summary, the present invention constructs a safety boundary constrained by the frequency change rate, guides the optimization of the frequency regulation control coefficient of the wind farm, enhances the response capability of the wind farm to the frequency change of the power grid, improves the frequency characteristics of the system, realizes the coordinated frequency regulation of the wind farm and the interconnected area, effectively integrates the frequency regulation resources, and improves the frequency regulation efficiency; by dynamically adjusting the control coefficient, the wind farm can provide more accurate active power support according to the real-time frequency status of the power grid; when the power grid is disturbed, the frequency fluctuation is effectively suppressed by adaptively coordinating the wind farm or the interconnected area to participate in the frequency regulation; optimizes the allocation of frequency regulation resources, reduces the waste of frequency regulation resources, and improves the stability and reliability of the power grid.

[0109] Finally, it should be pointed out that the methods and devices described in detail above are only embodiments, and those skilled in the art can modify these embodiments in different ways without departing from the scope of the present invention.

Claims

1. A frequency controller parameter optimization method based on safety margin constraints, characterized in that: include, The safety margin of RoCoF is constructed by taking system inertia as an influencing factor; Analyze the factors affecting the frequency change at the sending end and set the frequency segment intervals for the wind farm and the interconnected area; Optimize the control coefficient of the frequency controller, and modulate the optimized coefficient to form an active power modulation instruction; By setting the value of the frequency segment interval, the wind farm and the frequency controller detect frequency changes; The effectiveness is verified through simulation and the effects of different control strategies on the system frequency dynamic characteristics are compared.

2. The frequency controller parameter optimization method based on safety margin constraints according to claim 1, characterized in that: The factors affecting the frequency change at the sending end include system inertia time constant, frequency change rate, output increment of synchronous machine and new energy unit, disturbance power size, frequency deviation and system damping.

3. The frequency controller parameter optimization method based on safety margin constraint according to claim 2, characterized in that: The control coefficient of the optimized frequency controller includes an amplification control gain coefficient and a filter coefficient; The optimized coefficients are modulated, including modulation through a gain-inertia link and a power limiting link.

4. The frequency controller parameter optimization method based on safety margin constraint according to claim 3, characterized in that: The frequency change detection of the wind farm and the frequency controller includes that in the first segmented interval, the wind farm participates in the frequency modulation; in the second segmented interval, the interconnected area participates in the frequency modulation to suppress the frequency change of the sending end area.

5. The frequency controller parameter optimization method based on safety margin constraint according to any one of claims 3 or 4, characterized in that: The wind farm participates in frequency regulation, including playing the role of the wind farm in the sending end area to suppress frequency fluctuations in the case of DC blocking in the interconnected area; The interconnected areas participate in frequency regulation, including when the wind farm cannot suppress frequency fluctuations, the interconnected areas should participate in frequency regulation to ensure the stability of the system frequency.

6. A method for optimizing the control coefficient of a frequency controller, applicable to the above-mentioned method for optimizing the parameters of a frequency controller based on safety margin constraints, characterized in that: include, The inertia effect of synchronous generators in traditional wind farms is simulated by introducing control coefficients; Detect frequency deviation by real-time monitoring of grid frequency changes, and decide whether the wind farm needs to participate in frequency regulation based on the set control strategy; Dynamically adjust the control coefficient of the wind farm according to the real-time frequency status of the power grid and the preset frequency segment interval; Whether the wind farm participates in frequency regulation and the extent of its participation are determined based on the size and direction of the frequency change.

7. The frequency controller parameter optimization method based on safety margin constraint according to claim 6, characterized in that: The control coefficient provides or absorbs active power when the wind farm grid frequency fluctuates, so as to mitigate the frequency change.

8. The method for optimizing the control coefficient of a frequency controller according to claim 7, characterized in that: The control coefficient includes adjusting the virtual inertia coefficient.

9. The method for optimizing the control coefficient of a frequency controller according to claim 8, characterized in that: The adjustment of the virtual inertia coefficient is used to optimize the frequency modulation effect of the wind farm in different frequency ranges.

10. The method for optimizing the control coefficient of a frequency controller according to claim 9, characterized in that: The frequency change includes increasing the active power output if the frequency decreases, and reducing the active power output if the frequency increases.

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