High-reliability automatic voltage control method for parallel operation of low-voltage buses of wind power plant

Abstract

The invention discloses a high-reliability automatic voltage control method for parallel operation of low-voltage buses of a wind power plant, which relates to the technical field of voltage control, and comprises the following steps: when the voltage of a grid-connected point of the wind power plant does not meet a preset condition, calculating a full-field reactive increment under a rated voltage bus; when all the target voltage side bus voltages do not reach the early warning value, executing a full-field reactive similarity margin method; when the target voltage side bus voltage reaches the early warning value, executing a target voltage side bus voltage similarity margin algorithm in a non-early warning section, judging the relative size of the total reactive increment of the target voltage side bus in the non-early warning section and the whole-field reactive increment under the rated voltage bus, and executing a corresponding wind turbine generator adjustment strategy according to a judgment result; and in the early warning section, based on the voltage of the target voltage side bus and the locking value, a result is judged, corresponding partition locking operation is executed, and voltage regulation is ended. The active voltage supporting capability of the wind power plant to the power grid is improved.

Description

Technical Field

[0001] This invention relates to the field of voltage control technology, and more specifically, to a highly reliable automatic voltage control method for parallel operation of low-voltage busbars in wind farms. Background Technology

[0002] As wind farms expand to GW (gigawatt) scale, the parallel operation architecture of multiple low-voltage buses has become the mainstream solution for improving the utilization rate of system reactive power capacity. In such sites, wind turbine energy management platforms from multiple manufacturers are connected to the grid in parallel via 35kV low-voltage buses, sharing the voltage regulation task with dynamic reactive power compensation devices (SVG). Traditional wind farm automatic voltage control systems (AVC systems) automatically adjust reactive power output according to the reactive power similarity margin strategy of the entire site, based on real-time instructions issued by the power system dispatching master station or preset instructions, rapidly adjusting the reactive power of the entire site to control the voltage or reactive power at the wind farm's grid connection point within the set range.

[0003] The conventional method for adjusting the reactive power similarity margin of a wind farm (referred to as the "full-field reactive power similarity margin method") is as follows: Figure 9 As shown, in response to commands from the wind farm's dispatch master station, the system first determines whether the grid connection point voltage is in a dead zone or whether the reactive power of the entire wind farm has reached its adjustment limit. If the wind turbines have reactive power margin, the AVC system prioritizes adjusting the reactive power resources of the wind turbines, calculates and issues commands based on the reactive power similarity margin of the entire wind farm, and the wind turbines respond within seconds. At this time, the SVG maintains steady-state output, forming a coordinated control of "wind turbine priority adjustment - SVG dynamic standby". If the reactive power margin of the wind turbines is exhausted, the AVC system immediately switches to SVG adjustment mode to quickly correct the voltage deviation. At this time, the wind turbines maintain steady-state output, forming a safe transition of "wind turbine margin exhaustion - SVG seamless takeover".

[0004] Conventional reactive power similarity margin regulation methods for wind farms have significant drawbacks. They are only applicable to single-turbine manufacturer scenarios. In operating environments with multiple turbine manufacturers, the functions and regulation performance of the energy management platforms provided by each manufacturer vary, resulting in a wide variety of heterogeneous reactive power distribution strategies. When using the whole-farm reactive power similarity margin method, if the voltage of any low-voltage bus reaches the blocking condition, it will trigger the forced blocking of all connected turbines and SVG. Since wind turbines connected to the same manufacturer's energy management platform are generally distributed across multiple low-voltage bus sections, such blocking commands will cause a chain reaction, resulting in the blocking of normal wind turbines and SVG on non-faulty low-voltage bus sections. This leads to voltage regulation imbalance and reactive power circulation on the low-voltage bus, resulting in insufficient reactive power generation and idle reactive power resources, severely weakening the wind farm's support for grid voltage.

[0005] No effective solutions have yet been proposed to address the problems in the relevant technologies. SUMMARY

[0006] In view of the problems in the related art, the present application provides a high-reliability automatic voltage control method for parallel operation of a low-voltage bus in a wind farm to overcome the above technical problems existing in the prior art.

[0007] To this end, the present application adopts the following specific technical solutions:

[0008] The high-reliability automatic voltage control method for parallel operation of a low-voltage bus in a wind farm comprises:

[0009] The grid-connected point voltage of the wind farm is collected, and it is determined whether the grid-connected point voltage of the wind farm meets a preset condition. If yes, the voltage regulation is ended. If no, the rated voltage side system impedance, the target reactive power of the rated voltage side bus, and the total reactive power increment of the entire wind farm under the rated voltage bus are calculated in sequence.

[0010] When all the target voltage side bus voltages do not reach the warning value, the total reactive power similar margin method is executed. When there is a target voltage side bus voltage reaching the warning value, the target voltage side bus voltage similar margin algorithm is executed in the non-warning section, and the relative sizes of the total reactive power increment of the target voltage side bus in the non-warning section and the total reactive power increment of the entire wind farm under the rated voltage bus are determined, and corresponding wind turbine regulation strategies are executed according to the determination results.

[0011] In the warning section, corresponding partition locking operations are executed based on the size determination results of the voltage of the target voltage side bus and the locking value, and the voltage regulation is ended.

[0012] Further, determining whether the grid-connected point voltage of the wind farm meets a preset condition comprises:

[0013] The grid-connected point voltage is monitored in real time by the automatic voltage control system of the wind farm; and it is determined whether the grid-connected point voltage is in a dead zone or whether the total adjustable reactive power of the wind farm has reached the upper / lower limit of regulation.

[0014] If yes, the preset condition is met. If no, the preset condition is not met.

[0015] Further, the rated voltage side system impedance, the target reactive power of the rated voltage side bus, and the total reactive power increment of the entire wind farm under the rated voltage bus are calculated in sequence, which comprises:

[0016] Based on the voltage and reactive power of the rated voltage side bus of the wind farm before and after multiple adjustments, the rated voltage side system impedance is calculated, and the range of the rated voltage side system impedance is limited.

[0017] The target reactive power of the rated voltage side bus is calculated by using the rated voltage side system impedance, in combination with the target voltage of the rated voltage side bus, the measured reactive power of the rated voltage side bus, and the measured voltage of the rated voltage side bus.

[0018] The absolute deviation between the target reactive power of the rated voltage side bus and the measured value of the reactive power of the rated voltage side bus is calculated to obtain the total reactive power increment of the full field under the rated voltage bus.

[0019] Further, when the target voltage side bus voltage reaches the early warning value, the similar margin algorithm of the target voltage side bus voltage is executed in the non-warning section, and the relative size of the total reactive power increment of the target voltage side bus in the non-warning section and the total reactive power increment of the full field under the rated voltage bus is judged, and the corresponding wind turbine adjustment strategy is executed according to the judgment result, including:

[0020] When the target voltage side bus voltage reaches the early warning value, the target voltage side system impedance in the non-warning section is calculated based on the voltage and reactive power before and after the target voltage side bus of the wind farm is adjusted multiple times;

[0021] The early warning value of the target voltage side bus voltage in the non-warning section is equal to the target value of the target voltage side bus voltage in the non-warning section;

[0022] The target voltage side system impedance in the non-warning section is used to calculate the target reactive power of the target voltage side bus in the non-warning section in combination with the target value of the target voltage side bus voltage in the non-warning section, the measured value of the target voltage side bus reactive power in the non-warning section and the measured value of the target voltage side bus voltage in the non-warning section.

[0023] The absolute deviation between the target reactive power of the target voltage side bus in the non-warning section and the measured value of the target voltage side bus reactive power in the non-warning section is calculated to obtain the total reactive power increment of each control object under the target voltage side bus in the non-warning section.

[0024] When the total reactive power increment of each control object under the target voltage side bus in the non-warning section is greater than the single adjustment step length parameter of the target voltage side bus reactive power, the total reactive power increment of each control object under the target voltage side bus in the non-warning section is equal to the single adjustment step length parameter of the target voltage side bus reactive power.

[0025] The total reactive power increment of each control object under the target voltage side bus in the non-warning section is summed to obtain the total reactive power increment of the full field of the target voltage side bus in the non-warning section.

[0026] According to the size relationship between the total reactive power increment of the target voltage side bus in the non-warning section and the total reactive power increment of the full field under the rated voltage bus, the corresponding wind turbine adjustment strategy is executed.

[0027] Further, the wind turbine adjustment strategy includes:

[0028] When the total reactive power increment of the non-warning section target voltage side bus is less than or equal to the total reactive power increment of the rated voltage bus, and each wind turbine under the non-warning section target voltage side bus has adjustable reactive power margin, the adjustable reactive power increment of the target voltage side bus participating in the adjustment is distributed according to the similar margin of the wind turbine.

[0029] Further, when the total reactive power increment of the non-warning section target voltage side bus is less than or equal to the total reactive power increment of the rated voltage bus, each wind turbine under the non-warning section target voltage side bus has no adjustable reactive power margin, and whether the dynamic reactive power compensation device under each non-warning section target voltage side bus has adjustable reactive power margin is determined.

[0030] If yes, voltage regulation is performed according to the similar margin of the dynamic reactive power compensation device, and if no, voltage regulation is ended.

[0031] Further, the wind turbine adjustment strategy further comprises:

[0032] When the total reactive power increment of the non-warning section target voltage side bus is greater than the total reactive power increment of the rated voltage bus, and each wind turbine under the non-warning section target voltage side bus has adjustable reactive power margin, the adjustable reactive power increment of the target voltage side bus participating in the adjustment is distributed according to the similar margin of the wind turbine.

[0033] Further, when the total reactive power increment of the non-warning section target voltage side bus is greater than the total reactive power increment of the rated voltage bus, if each wind turbine under the non-warning section target voltage side bus has no adjustable reactive power margin, whether the dynamic reactive power compensation device under each non-warning section target voltage side bus has adjustable reactive power margin is determined.

[0034] If yes, voltage regulation is performed according to the similar margin of the dynamic reactive power compensation device, and if no, voltage regulation is ended.

[0035] Further, in the warning section, based on the size of the voltage of the target voltage side bus and the blocking value, the corresponding partition blocking operation is performed, and the voltage regulation is ended, which comprises:

[0036] When the voltage of the warning section target voltage side bus is greater than or equal to the blocking value, the wind turbine and the dynamic reactive power compensation device under the corresponding target voltage side bus are blocked;

[0037] When the voltage of the warning section target voltage side bus is less than the blocking value, whether the warning section target voltage side bus reaches the warning value is determined, and voltage regulation is performed according to the determination result.

[0038] Further, voltage regulation according to the determination result comprises:

[0039] When all the target voltage side busbars of the pre-warning section reach the pre-warning value, the target voltage side busbar voltage similarity margin algorithm is executed, and each target voltage side busbar voltage of the pre-warning section is adjusted to the closed state, and the voltage adjustment is ended;

[0040] When not all the target voltage side busbars of the pre-warning section reach the pre-warning value, the adjustable state of the corresponding pre-warning section busbar is maintained and the next adjustment cycle is waited;

[0041] Wherein, the pre-warning section target voltage side busbar reaching the closed condition is executed separately to isolate the fault influence range and realize partitioned closing.

[0042] The beneficial effects of the present application are:

[0043] The present application provides a high-reliability automatic voltage control method for parallel operation of low-voltage busbars in a wind farm, based on multi-section busbar parallel operation mode, re-grouping and aggregating various wind turbine manufacturers corresponding to the low-voltage busbar, wind turbines and dynamic reactive power compensation devices SVG under them as virtual reactive power regulation units, calculating reactive power increment according to voltage-reactive power droop characteristics, real-time monitoring of low-voltage busbar voltage operation condition, establishing a double-layer adaptive collaborative optimization control framework of wind farm reactive power similarity margin and segmented low-voltage busbar voltage similarity margin, and proposing a control algorithm strategy for differentiated regulation of wind farm reactive power resources. The present application solves the problem of associated closing caused by heterogeneous reactive power distribution strategy of multiple wind turbine manufacturers, can accurately isolate the influence range, provide full-field reactive power resources as much as possible, ensure stable operation of low-voltage busbar voltage, suppress reactive power circulation in the field, and significantly improve the voltage active support capability of the wind farm to the power grid. BRIEF DESCRIPTION OF DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0045] Figure 1 is one of the detailed flowcharts of the high-reliability automatic voltage control method for parallel operation of low-voltage busbars in a wind farm;

[0046] Figure 2 is the second detailed flowchart of the high-reliability automatic voltage control method for parallel operation of low-voltage busbars in a wind farm;

[0047] Figure 3 is the third detailed flowchart of the high-reliability automatic voltage control method for parallel operation of low-voltage busbars in a wind farm;

[0048] Figure 4 is a schematic diagram of a virtual reactive power regulation unit.

[0049] Figure 5 is a low-voltage side bus early warning monitoring diagram;

[0050] Figure 6 is a precise partition locking schematic diagram;

[0051] Figure 7 is a low-voltage bus voltage similar margin adjustment algorithm schematic diagram;

[0052] Figure 8 is a flowchart of a high-reliability automatic voltage control method for parallel operation of a low-voltage bus of a wind farm according to an embodiment of the present application;

[0053] Figure 9 is a flowchart of a conventional wind farm full-field reactive power similar margin adjustment method. DETAILED DESCRIPTION

[0054] To further illustrate the embodiments, the present application provides drawings which are part of the disclosure of the present application, mainly used to illustrate the embodiments, and can be used to explain the operating principle of the embodiments in conjunction with the related description of the specification. Those skilled in the art should be able to understand other possible implementations and advantages of the present application by referring to these contents. The components in the drawings are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0055] According to an embodiment of the present application, a high-reliability automatic voltage control method for parallel operation of a low-voltage bus of a wind farm is provided.

[0056] The present application will be further described in conjunction with the drawings and specific embodiments, as shown in Figure 8 The high-reliability automatic voltage control method for parallel operation of a low-voltage bus of a wind farm according to the embodiment of the present application includes:

[0057] S1, collecting the grid-connected point voltage of the wind farm, determining whether the grid-connected point voltage of the wind farm meets the preset condition, if yes, ending the voltage regulation, if not, calculating the rated voltage side system impedance, the rated voltage side bus target reactive power and the full-field reactive power increment under the rated voltage bus in turn.

[0058] S2, when all target voltage side bus voltages do not reach the early warning value, the full-field reactive power similar margin method is executed; when there is a target voltage side bus voltage reaching the early warning value, the target voltage side bus voltage similar margin algorithm is executed in the non-early warning section, and the relative size of the total reactive power increment of the target voltage side bus in the non-early warning section and the full-field reactive power increment under the rated voltage bus is determined, and the corresponding wind turbine regulation strategy is executed according to the determination result.

[0059] S3、in the pre-warning section, based on the voltage of the target voltage side bus and the size of the blocking value, the corresponding partition blocking operation is executed, and the voltage regulation is ended.

[0060] In one embodiment, determining whether the grid-connected point voltage of the wind farm meets the preset condition comprises:

[0061] The grid-connected point voltage is monitored in real time by the wind farm automatic voltage control system, and it is determined whether the grid-connected point voltage is in the dead zone or whether the full-field adjustable reactive power has reached the upper / lower limit of regulation. If yes, the preset condition is met, and if no, the preset condition is not met.

[0062] In one embodiment, the rated voltage side system impedance, the rated voltage side bus target reactive power and the full-field reactive power increment under the rated voltage bus are calculated in sequence, comprising:

[0063] Based on the voltage and reactive power before and after the multiple adjustments of the rated voltage side bus of the wind farm, the rated voltage side system impedance is calculated, and the range of the rated voltage side system impedance is limited. The rated voltage side bus target reactive power is calculated by using the rated voltage side system impedance, combined with the rated voltage side bus voltage target value, the rated voltage side bus reactive power measured value and the rated voltage side bus voltage measured value. The absolute deviation between the rated voltage side bus target reactive power and the rated voltage side bus reactive power measured value is calculated to obtain the full-field reactive power increment under the rated voltage bus.

[0064] In one embodiment, when there is a target voltage side bus voltage reaching the pre-warning value, the target voltage side bus voltage similar margin algorithm is executed in the non-pre-warning section, and the relative size of the non-pre-warning section target voltage side bus total reactive power increment and the full-field reactive power increment under the rated voltage bus is judged, and the corresponding wind turbine regulation strategy is executed according to the judgment result, comprising:

[0065] When the target voltage side bus voltage reaches the pre-warning value, the voltage and reactive power of the target voltage side bus before and after multiple adjustments are calculated to obtain the target voltage side system impedance in the non-warning section; the target voltage side bus voltage pre-warning value is equal to the target voltage side bus voltage target value in the non-warning section; the target voltage side system impedance is used in combination with the target voltage side bus voltage target value, the target voltage side bus reactive power measured value and the target voltage side bus voltage measured value to calculate the target reactive power of the target voltage side bus in the non-warning section; the absolute deviation between the target reactive power of the target voltage side bus in the non-warning section and the target voltage side bus reactive power measured value is calculated to obtain the total reactive power increment of each control object under the target voltage side bus in the non-warning section; when the total reactive power increment of each control object under the target voltage side bus in the non-warning section is greater than the target voltage side bus reactive power single adjustment step length parameter, the total reactive power increment of each control object under the target voltage side bus in the non-warning section is equal to the target voltage side bus reactive power single adjustment step length parameter; the total reactive power increment of each control object under each target voltage side bus in the non-warning section is summed to obtain the total reactive power increment of the whole field of the target voltage side bus in the non-warning section; according to the size relationship between the total reactive power increment of the target voltage side bus in the non-warning section and the total reactive power increment of the whole field under the rated voltage bus, the corresponding wind turbine adjustment strategy is executed.

[0066] In one embodiment, the wind turbine adjustment strategy comprises:

[0067] When the total reactive power increment of the target voltage side bus in the non-warning section is less than or equal to the total reactive power increment of the whole field under the rated voltage bus, and each wind turbine under the target voltage side bus in the non-warning section has adjustable reactive power margin, the adjustable reactive power increment of the target voltage side bus participating in adjustment is distributed according to the similar margin of the wind turbine.

[0068] In one embodiment, when the total reactive power increment of the target voltage side bus in the non-warning section is less than or equal to the total reactive power increment of the whole field under the rated voltage bus, each wind turbine under the target voltage side bus in the non-warning section has no adjustable reactive power margin, and it is determined whether the dynamic reactive power compensation device under each target voltage side bus in the non-warning section has adjustable reactive power margin; if yes, voltage adjustment is performed according to the similar margin of the dynamic reactive power compensation device, and if no, voltage adjustment is ended.

[0069] In one embodiment, the wind turbine adjustment strategy further comprises:

[0070] When the total reactive power increment of the target voltage side bus in the non-warning section is greater than the total reactive power increment of the whole field under the rated voltage bus, and each wind turbine under the target voltage side bus in the non-warning section has adjustable reactive power margin, the adjustable reactive power increment of the target voltage side bus participating in adjustment is distributed according to the similar margin of the wind turbine.

[0071] In one embodiment, when the total reactive power increment of the non-warning section target voltage side bus is greater than the total reactive power increment of the rated voltage bus, if each wind turbine under the non-warning section target voltage side bus has no adjustable reactive power margin, then it is determined whether the dynamic reactive power compensation device under each non-warning section target voltage side bus has an adjustable reactive power margin; if so, voltage adjustment is performed according to the similar margin of the dynamic reactive power compensation device, and if not, voltage adjustment is ended.

[0072] In one embodiment, in the warning section, based on the size of the voltage of the target voltage side bus and the locking value, the corresponding partition locking operation is performed, and the voltage adjustment is ended, including:

[0073] When the voltage of the warning section target voltage side bus is greater than or equal to the locking value, the wind turbine and the dynamic reactive power compensation device under the corresponding target voltage side bus are locked; when the voltage of the warning section target voltage side bus is less than the locking value, it is determined whether all the warning section target voltage side buses reach the warning value, and voltage adjustment is performed according to the determination result.

[0074] In one embodiment, the voltage adjustment according to the determination result includes:

[0075] When all the warning section target voltage side buses reach the warning value, the target voltage side bus voltage similar margin algorithm is executed, and after each warning section target voltage side bus is adjusted to the locking value, the voltage adjustment is ended; when not all the warning section target voltage side buses reach the warning value, the adjustable state of the corresponding warning section bus is maintained and the next adjustment period is waited; wherein, each time the warning section target voltage side bus that reaches the locking condition is executed separately to isolate the fault influence range and realize partition locking.

[0076] In order to facilitate understanding of the above technical solutions of the present application, the working principle of the present application in the actual process will be described in detail.

[0077] The method of the present application includes: based on the multi-section bus parallel operation mode, re-grouping and aggregating the multiple wind turbine manufacturers corresponding to the low-voltage bus, and the wind turbines and dynamic reactive power compensation devices SVG hung thereunder into a virtual reactive power regulation unit, calculating the reactive power increment according to the voltage-reactive power droop characteristic, monitoring the low-voltage bus voltage operation condition in real time, establishing a double-layer adaptive collaborative optimization control framework of the wind farm reactive power similar margin and the segmented low-voltage bus voltage similar margin, and proposing a control algorithm strategy for differentiated regulation of wind farm reactive power resources. The present application solves the problem of associated locking caused by the heterogeneous reactive power distribution strategy of multiple wind turbine manufacturers, can accurately isolate the influence range, provide full-field reactive power resources as much as possible, suppress the reactive power circulating current in the field while ensuring the stable operation of the low-voltage bus voltage, and significantly improve the voltage active support capability of the wind farm to the power grid.

[0078] The detailed flow chart of the high-reliability automatic voltage control method for the low-voltage bus of the wind farm operating in parallel is shown in Figures 1-3 , Figure 1 The line segment 1 in Figure 2 is connected to the line segment 1 in Figure 2 , and the line segment 2 in Figure 3 is connected to the line segment 2 in The control object and control process of the high-reliability automatic voltage control method for the low-voltage bus of the wind farm operating in parallel are described in detail below.

[0079] I. Control object

[0080] The traditional control mode is that the voltage target instruction is issued by the dispatching master station, the reactive power increment of the whole field is calculated by the AVC system, and the adjustment instruction is issued to the wind turbine control platform or SVG. In the innovative architecture proposed in the present application, as shown in Figure 4 , the control granularity is accurately controlled to the low-voltage bus segment level: each wind turbine control platform only responds to the exclusive reactive power target adjustment instruction of the 35kV low-voltage bus segment (such as segment I, segment II, and segment n) to which it is physically connected. At this time, the wind turbine control platform no longer receives the whole-field adjustment instruction, but the segmented reactive power target instruction allocated by the low-voltage bus segment where it is located. At the same time, the SVG device directly connected to the segment bus synchronously acquires the adjustment instruction, and then dynamically recombines with the wind turbines under its jurisdiction to form a virtual reactive power adjustment unit belonging to the segment bus. For example, Figure 4 In the 35kV segment I bus in , the wind turbine control platforms of multiple manufacturers, the wind turbines under their jurisdiction, and the directly connected SVGs jointly constitute an independent autonomous unit of the segment, and the other segment buses are the same. This architecture realizes the regionalization of control responsibility and the localization of adjustment resources, enabling accurate control of each virtual reactive power adjustment unit, and laying a foundation for subsequent control processes.

[0081] II. Control process. The core control process includes three parts: low-voltage bus (i.e. target voltage side) voltage early warning monitoring, accurate partitioning locking, and low-voltage bus voltage similar margin adjustment algorithm strategy:

[0082] 1. Low-voltage bus voltage early warning monitoring

[0083] In the traditional control process without early warning values, the response is triggered only when the bus voltage reaches the locking value, causing the whole field to be locked (including non-fault segment units), resulting in idle reactive power resources. By setting a low-voltage bus voltage early warning value and introducing an early warning judgment mechanism, the systemic defects caused by the lack of early warning mechanism in traditional reactive power regulation are fundamentally solved, and the non-fault segment continues to operate, greatly increasing the utilization rate of reactive power.

[0084] When the voltage target value is issued by dispatch, the grid-connected point voltage is monitored by the wind farm AVC system in real time to determine whether the grid-connected point voltage is in the dead zone or the full-field adjustable reactive power has reached the upper / lower limit of regulation. If the conditions are met, the regulation is ended and the next cycle is waited; otherwise, the main regulation channel is entered. The AVC system collects the high-voltage (rated voltage side) bus voltage U s and reactive power Q s , records multiple sets of voltage and reactive power data sets before and after regulation, and uses the following algorithm to obtain the high-voltage side system impedance X h .

[0085] Let the high-voltage bus voltage before the s-th adjustment be and the full-field reactive power be After adjustment, they are and Q s+ , respectively. The basic calculation formula of the system impedance is:

[0086]

[0087] The self-learning method is used to identify the system impedance, and the latest t adjustment parameters are taken for iterative calculation, so that

[0088]

[0089] Simplify as,

[0090]

[0091] Multiply both sides by

[0092]

[0093] , we get

[0094]

[0095] where ΔQ is the full-field reactive power increment before and after continuous adjustment, U is the arithmetic mean of the high-voltage bus voltage before and after continuous adjustment, and ΔU is the high-voltage bus voltage increment before and after continuous adjustment.

[0096] To prevent key sampling values from being abnormal and causing the identification result to exceed the reasonable range, the system impedance is limited and constrained:

[0097] (1) If the calculation result is greater than the set upper limit, i.e. X > 50Ω, then take X h = 50Ω; (corresponding to short-circuit current 4kA).(2) If the calculation result is less than the set lower limit, i.e. X < 10Ω, then take X h= 10 Ω; (corresponding to short circuit current 20 kA). (3) Special case: because the system impedance can only be calculated when the high voltage bus voltage changes, if the high voltage bus voltage fluctuates very little or remains near a stable voltage for a long time, the system impedance calculation value is easy to be distorted, at this time it is necessary to introduce the upper limit of the system impedance parameter for corresponding processing. When starting calculation, set the upper limit of the system impedance as the initial value, and obtain a more accurate system impedance after multiple adjustments. The inaccuracy of the initial value does not affect the adjustment results of the step-by-step approximation.

[0098] The estimated target reactive power of the high-voltage side bus is:

[0099]

[0100] In the formula: Q hSet is the estimated bus reactive power set value (i.e. the target reactive power of the high-voltage side bus); U hTarget is the bus voltage target value; Q hMea is the measured bus reactive power; U hMea is the measured bus voltage; X h is the system impedance.

[0101] The total reactive power increment (full-field reactive power increment under the rated voltage bus) that needs to be allocated to each control object under the high-voltage bus by the AVC system is:

[0102] ΔQ h = |Q hSet -Q hMea |.

[0103] In order to prevent the estimated bus reactive power Q hSet resulting from incorrect key sampling values or other problems from exceeding a reasonable range, the calculated estimated bus reactive power set value is limited in range, and a single adjustment step size parameter Q hStep is added, which is filled in by the field AVC during testing according to the measured conditions. If ΔQ h > Q hStep , then the total reactive power increment ΔQ h of each control object under the high-voltage bus is Q hStep .

[0104] After calculating the full-field reactive power increment ΔQ h , the low-voltage (target voltage) bus voltage early warning monitoring is performed:

[0105] (1) If all low-voltage buses do not reach the early warning value, the full-field reactive power similar margin method (as shown in Figure 9 ) is executed, at which time the wind turbine or SVG executes the reactive power adjustment instruction. End of adjustment, wait for the next adjustment period. Figure 9The device layer includes a data transmission part and a device layer, and in addition, after judging the voltage state of the grid-connected point, if the voltage is in the dead zone or the adjustable reactive power of the full field reaches the upper / lower limit, the regulation is ended and the next regulation period is waited. Otherwise, voltage regulation is performed, it is judged whether the wind turbine has adjustable reactive power margin, if not, it is judged whether the SVG has adjustable reactive power margin, if not, the regulation is ended, if yes, the SVG is regulated, the full-field reactive power similar margin algorithm strategy is executed, and is connected with the SVG reactive power demand calculation of the device layer, the SVG responds to the regulation instruction and the wind turbine maintains a steady state, and is fed back to the AVC substation system. The AVC substation system is connected with the motion device receiving instruction part through remote signaling, remote measurement and motion issuing modes, and the motion device receiving instruction part is connected with the dispatching voltage target value issuing part through data uploading and remote control and remote adjustment modes. If there is a margin, the wind turbine is preferentially regulated, the full-field wind turbine state is collected, the full-field reactive power similar margin algorithm strategy is executed, and is transmitted to the device layer. The device layer includes a plurality of wind turbine capable platform total reactive power instructions and wind turbines. The wind turbine responds to the regulation instruction generated from the device layer and the SVG maintains a steady state, and is fed back to the AVC substation system, which is connected with the grid-connected point voltage state judgment process.

[0106] (2) If one or more low-voltage buses reach the warning value (i.e. ≥ upper warning limit or ≤ lower warning limit), the algorithm strategy is dynamically switched, and the low-voltage bus voltage similar margin algorithm strategy (referred to as "low-voltage bus voltage similar margin method") is started, as shown in Figure 7 .

[0107] As shown in Figure 5 , it is a low-voltage bus warning monitoring flow chart, which realizes real-time monitoring of the low-voltage bus voltage state and supports dynamic switching of the algorithm strategy.

[0108] 2. Precise partition locking, blocking cascading effect.

[0109] As shown in Figure 6 , it is continuously monitored whether the low-voltage bus voltage of the warning section reaches the locking value, if it reaches or exceeds the locking value, the wind turbines and SVG devices under the low-voltage bus are locked; if the voltage does not reach the locking value, it is judged whether all the remaining low-voltage buses reach the warning value: if not all the warning values are reached, the adjustable state of the warning section bus is maintained and the next regulation period is waited; if all the warning values are reached, the low-voltage bus voltage similar margin method (as shown in Figure 7 , low-voltage bus voltage similar margin algorithm strategy, make full use of the remaining reactive power margin of the full field) is used to regulate each low-voltage bus voltage to the end of the regulation after locking. In this process, each time the low-voltage section bus that meets the locking condition is executed individually, the fault influence range is accurately isolated, the partition locking is realized, and the normal regulation function of the non-fault section low-voltage bus is ensured.

[0110] 3. Low-voltage bus voltage similar margin adjustment algorithm strategy.

[0111] (1) Calculate the low-voltage bus system impedance X l of each non-warning section before the s-th adjustment, and the low-voltage bus voltage is The total reactive power of the virtual reactive power regulation unit aggregated under the low-voltage bus is After adjustment, they are and The same as the calculation method of the high-voltage side bus voltage system impedance, X l is obtained.

[0112] (2) Set the target voltage U lTarget of each non-warning section low-voltage bus for this adjustment, and let:

[0113] U lTarget = U lWar ;

[0114] In the formula, U lWar is the warning value of the non-warning section low-voltage bus voltage.

[0115] (3) Estimate the target reactive power Q lSet of each non-warning section low-voltage bus:

[0116]

[0117] In the formula: Q lSet is the estimated non-warning section low-voltage bus reactive power set value (i.e. the target reactive power of the non-warning section low-voltage bus); U lTarget is the target value of the non-warning section low-voltage bus voltage (i.e. the target voltage of the adjustment); Q lMea is the measured value of the non-warning section low-voltage bus reactive power; U lMea is the measured value of the non-warning section low-voltage bus voltage; X l is the system impedance.

[0118] (4) Calculate the reactive power increment of each non-warning section low-voltage bus. The total reactive power increment calculation formula that needs to be allocated to each control object under the non-warning section low-voltage bus of the automatic voltage control AVC system is:

[0119]

[0120] To prevent key sampling values from being wrong or other problems from causing the estimated low-voltage bus reactive power Q lSet to exceed a reasonable range, the estimated low-voltage bus reactive power set value calculated is limited in range, and a low-voltage bus reactive power single adjustment step size parameter Q lStep is added, which is filled in by the field AVC during testing according to the measured situation. If The total reactive power increment of each control object under each non-warning section low-voltage bus is:

[0121]

[0122] (5) The reactive power increment of each non-warning section low-voltage bus is summed up to calculate the total reactive power increment of the wind farm

[0123] The total reactive power increment calculation formula of the wind farm is:

[0124]

[0125] 1) When :

[0126] At this time, the adjustable reactive power increment of each low-voltage bus participating in the adjustment is First, it is judged whether the wind turbine under each non-warning section low-voltage bus has adjustable reactive power margin. If there is adjustable margin, the reactive power margin is distributed according to the similar margin of the wind turbine group At this time, the wind turbine group under each low-voltage bus corresponds to a reactive power increment The wind turbine group executes the adjustment instruction, ends the adjustment, and waits for the next adjustment period. If there is no adjustable margin, it is judged whether the SVG under each non-warning section low-voltage bus has adjustable reactive power margin. If it has, the SVG is adjusted according to the similar margin. If there is no margin, the adjustment is ended.

[0127] 2) When :

[0128] The adjustable reactive power margin of the low-voltage bus voltage is distributed according to the proportion of the low-voltage bus voltage h , to obtain the adjustable reactive power increment of the low-voltage bus participating in the adjustment It is continuously judged whether the wind turbine under each non-warning section low-voltage bus has adjustable reactive power margin. If there is margin, the wind turbine group is distributed according to the similar margin At this time, the wind turbine group under each low-voltage bus corresponds to a reactive power increment The wind turbine group executes the adjustment instruction, ends the adjustment, and waits for the next adjustment period. If there is no adjustable margin, it is judged whether the SVG under each non-warning section low-voltage bus has adjustable reactive power margin. If it has, the SVG is adjusted according to the similar margin. If there is no margin, the adjustment is ended.

[0129] ​In summary, the application provides a new type of cooperative control method compatible with multi-source heterogeneous fan function pipe platform, comprising: constructing a virtual reactive power regulation unit bound to the physical topology of the multi-section low-voltage bus, eliminating the reactive power regulation strategy barrier across the fan manufacturers; establishing a multi-section low-voltage bus voltage similarity margin partition autonomous mechanism, designing an early warning judgment mechanism to realize accurate isolation of the fault section; proposing a voltage margin weight redistribution mechanism to realize balanced regulation of the multi-section low-voltage bus and fully release the reactive power regulation capacity of the multi-section low-voltage bus parallel architecture. Completely solve the problem of idle reactive power resources and associated lockout in the operation environment of the station coexisting with multiple wind turbine manufacturers, and support the stable operation of the power grid voltage to the limit.

[0130] The above only describes the preferred embodiments of the application and is not intended to limit the application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A method for operating a wind farm low voltage bus in parallel with a high reliability automatic voltage control, characterized in that, The method comprises the following steps: Collecting the grid-connected point voltage of the wind farm, judging whether the grid-connected point voltage of the wind farm meets preset conditions, if yes, ending the voltage regulation, if not, calculating the rated voltage side system impedance, the rated voltage side bus target reactive power and the total reactive power increment of the entire wind farm under the rated voltage bus in sequence; When all the target voltage side bus voltages do not reach the warning value, the similar margin method of the total reactive power is executed; when there is a target voltage side bus voltage reaching the warning value, the similar margin algorithm of the target voltage side bus voltage is executed in the non-warning section, and the relative size of the total reactive power increment of the target voltage side bus in the non-warning section and the total reactive power increment of the entire wind farm under the rated voltage bus is judged, and corresponding wind turbine regulation strategies are executed according to the judgment result; In the warning section, corresponding partition locking operations are executed according to the size judgment result of the voltage of the target voltage side bus and the locking value, and the voltage regulation is ended.

2. The method according to claim 1, wherein, The judgment whether the grid-connected point voltage of the wind farm meets preset conditions comprises the following steps: The grid-connected point voltage is monitored in real time by the automatic voltage control system of the wind farm; it is determined whether the grid-connected point voltage is in the dead zone or whether the total adjustable reactive power of the entire wind farm has reached the upper / lower limit of regulation; If yes, the preset conditions are met, if not, the preset conditions are not met.

3. The method according to claim 1, characterized in that, The calculation of the rated voltage side system impedance, the rated voltage side bus target reactive power and the total reactive power increment of the entire wind farm under the rated voltage bus in sequence comprises the following steps: Based on the voltage and reactive power of the rated voltage side bus of the wind farm before and after multiple adjustments, the rated voltage side system impedance is calculated, and the range of the rated voltage side system impedance is limited; The rated voltage side system impedance is used to calculate the target reactive power of the rated voltage side bus in combination with the target voltage of the rated voltage side bus, the measured reactive power of the rated voltage side bus and the measured voltage of the rated voltage side bus; The total reactive power increment of the entire wind farm under the rated voltage bus is obtained by calculating the absolute deviation between the target reactive power of the rated voltage side bus and the measured reactive power of the rated voltage side bus.

4. The method according to claim 1, characterized in that, When there is a target voltage side bus voltage reaching the warning value, the similar margin algorithm of the target voltage side bus voltage is executed in the non-warning section, and the relative size of the total reactive power increment of the target voltage side bus in the non-warning section and the total reactive power increment of the entire wind farm under the rated voltage bus is judged, and corresponding wind turbine regulation strategies are executed according to the judgment result, which comprises the following steps: When there is a target voltage side bus voltage reaching the warning value, the target voltage side system impedance in the non-warning section is calculated based on the voltage and reactive power of the target voltage side bus of the wind farm before and after multiple adjustments; The warning value of the target voltage side bus voltage in the non-warning section is equal to the target value of the target voltage side bus voltage in the non-warning section; The target reactive power of the target voltage side bus in the non-warning section is calculated by using the target voltage side system impedance in the non-warning section in combination with the target voltage of the target voltage side bus in the non-warning section, the measured reactive power of the target voltage side bus in the non-warning section and the measured voltage of the target voltage side bus in the non-warning section; The total reactive power increment of each control object under the target voltage side bus in the non-warning section is obtained by calculating the absolute deviation between the target reactive power of the target voltage side bus in the non-warning section and the measured reactive power of the target voltage side bus in the non-warning section. When the total reactive power increment of each control object under the non-warning section target voltage side bus is greater than the single adjustment step length parameter of the target voltage side bus, the total reactive power increment of each control object under the non-warning section target voltage side bus is equal to the single adjustment step length parameter of the target voltage side bus; The total reactive power increment of each control object under each non-warning section target voltage side bus is summed to obtain the total reactive power increment of the whole field of the non-warning section target voltage side bus; According to the size relationship between the total reactive power increment of the non-warning section target voltage side bus and the total reactive power increment of the whole field under the rated voltage bus, a corresponding wind turbine adjustment strategy is executed.

5. The method according to claim 4, wherein, The wind turbine adjustment strategy includes: When the total reactive power increment of the non-warning section target voltage side bus is less than or equal to the total reactive power increment of the whole field under the rated voltage bus, and each wind turbine under the non-warning section target voltage side bus has adjustable reactive power margin, the adjustable reactive power increment of the target voltage side bus participating in adjustment is distributed according to the similar margin of the wind turbine.

6. The method according to claim 5, wherein, When the total reactive power increment of the non-warning section target voltage side bus is less than or equal to the total reactive power increment of the whole field under the rated voltage bus, each wind turbine under the non-warning section target voltage side bus has no adjustable reactive power margin, whether the dynamic reactive power compensation device under each non-warning section target voltage side bus has adjustable reactive power margin is determined. If yes, voltage adjustment is performed according to the similar margin of the dynamic reactive power compensation device, and if no, voltage adjustment is ended.

7. The method according to claim 4, characterized in that, The wind turbine adjustment strategy also includes: When the total reactive power increment of the non-warning section target voltage side bus is greater than the total reactive power increment of the whole field under the rated voltage bus, and each wind turbine under the non-warning section target voltage side bus has adjustable reactive power margin, the adjustable reactive power increment of the target voltage side bus participating in adjustment is distributed according to the similar margin of the wind turbine.

8. The method according to claim 7, characterized in that, When the total reactive power increment of the non-warning section target voltage side bus is greater than the total reactive power increment of the whole field under the rated voltage bus, if each wind turbine under the non-warning section target voltage side bus has no adjustable reactive power margin, whether the dynamic reactive power compensation device under each non-warning section target voltage side bus has adjustable reactive power margin is determined. If yes, voltage adjustment is performed according to the similar margin of the dynamic reactive power compensation device, and if no, voltage adjustment is ended.

9. The method for high-reliability automatic voltage control of wind farm low-voltage bus parallel operation according to claim 1, characterized in that, In the warning section, based on the size of the voltage of the target voltage side bus and the blocking value, a corresponding partition blocking operation is performed, and voltage adjustment is ended, which includes: When the voltage of the warning section target voltage side bus is greater than or equal to the blocking value, the wind turbine and the dynamic reactive power compensation device under the corresponding target voltage side bus are blocked; When the voltage of the warning section target voltage side bus is less than the blocking value, whether the warning section target voltage side bus has reached the warning value is determined, and voltage adjustment is performed according to the determination result.

10. The method according to claim 9, wherein, The voltage adjustment according to the determination result includes: When the warning section target voltage side bus has reached the warning value, the target voltage side bus voltage similar margin algorithm is executed, and after each warning section target voltage side bus voltage is adjusted, voltage adjustment is ended; When the warning section target voltage side bus has not reached the warning value, the adjustable state of the corresponding warning section bus is maintained and the next adjustment period is waited. In the method, each bus on the side of the target voltage of the pre-warning section reaching the lockout condition is executed with a separate lockout operation to isolate the fault influence range and realize partition lockout.

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