Adaptive frequency control method and system considering the cooperation of flexible direct current converter station and wind turbine generator
Patent Information
- Application Number
- CN202610283714.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-10
- Publication Date
- 2026-06-23
- Estimated Expiration
- 2046-03-10
Smart Images
Figure CN121813414B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of power system control technology, and particularly relates to an adaptive frequency control method and system that considers the coordination between flexible DC converter stations and wind turbine units. Background Technology
[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.
[0003] Building a new power system with new energy sources as the mainstay is a current development trend in the power system. Offshore wind power is an important direction for the development of new energy. my country has huge potential for offshore wind power development, is close to coastal load centers, and has a strong grid capacity to absorb wind power. Vigorously developing offshore wind power is of great strategic significance for promoting energy transformation in coastal areas, improving energy self-sufficiency, and ensuring energy security. Currently, China's offshore wind power development is showing a trend of clustering and deep-sea deployment. Against this backdrop, flexible DC transmission technology has become the mainstream solution for transmitting mid- to long-range offshore wind power due to its ability to effectively suppress the capacitive effect of AC submarine cables, its superior control characteristics, and its high level of technological maturity.
[0004] With the continuous increase in the penetration rate of new energy sources, offshore wind power systems will undertake increasingly important tasks in frequency regulation. Due to the frequency decoupling effect of flexible DC systems, offshore wind power cannot directly sense changes in the receiving-end grid frequency. Currently, nearshore areas mostly use wired communication to directly transmit the receiving-end grid frequency to the sending-end wind farm. This method has no frequency error, but it suffers from communication delays that vary with distance, and faces difficulties and high costs in constructing communication lines in mid-to-far-shore areas. To address this pain point, wireless communication has been proposed, which converts frequency information into DC voltage fluctuations to transmit frequency information to the sending-end grid. Furthermore, the capacitor energy storage of the flexible DC system can also participate in system frequency regulation as generalized inertia. Especially when disturbances occur in the receiving-end grid, the flexible DC converter station can sense the disturbance signal earlier than offshore wind turbines, and its early frequency support can effectively suppress the frequency fluctuation amplitude after system disturbances.
[0005] Mid-to-far sea: refers to the distance from the shore: usually more than 50 kilometers, or even more than 100 kilometers; water depth: usually more than 50 meters, entering deep water areas and deep sea areas with a depth of more than 60 meters.
[0006] Changes in offshore wind speeds, such as gusts and turbulence, can cause short-term, drastic fluctuations in the output power of wind turbines. Frequency regulation methods, such as inertial response and primary frequency regulation, are needed to smooth out these fluctuations. In addition, offshore wind power is connected to the grid through power electronic equipment, resulting in low system inertia and a rapid rate of frequency degradation during disturbances. This necessitates supplementing the system with virtual inertial control or fast frequency regulation resources.
[0007] To address the frequency regulation needs of offshore wind power, various frequency regulation strategies have been proposed in existing technologies based on the aforementioned two communication methods. However, these strategies generally suffer from significant technical shortcomings: Firstly, some strategies employ a site-level overall control mode for flexible DC converter stations. Due to DC voltage safety constraints, the energy margin of sub-module capacitors cannot be effectively utilized, resulting in the inertia support potential of the modular multilevel converter-HVDC transmission system not being fully released. Secondly, existing technologies do not use the adjustable capability as a basis for coordination. Even if corresponding strategies are proposed for the frequency regulation path of sub-module capacitor energy, the lack of an effective coordinated control mechanism between the wind power system and the flexible DC system makes it difficult to guarantee the stability, reliability, and efficiency of the frequency regulation process, thus failing to meet the actual frequency regulation requirements in offshore wind power scenarios. Summary of the Invention
[0008] To overcome the shortcomings of the prior art, the present invention provides an adaptive frequency control method and system that considers the coordination between the flexible DC converter station and the wind turbine, which can meet the actual frequency regulation requirements in the mid-to-far offshore wind power scenario.
[0009] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions:
[0010] Firstly, an adaptive frequency control method considering the coordination between the flexible DC converter station and the wind turbine is disclosed, including:
[0011] The wind turbine unit monitors its own operating status in real time and uploads the operating status data to the wind turbine controller. The wind turbine controller then transmits the data to the wind farm controller. The wind farm controller summarizes the status information of the wind turbine unit and uploads it to the dispatch center.
[0012] The flexible DC converter station detects the status of each of its bridge arms, including the number of available sub-modules, and uploads the above information to the dispatch center;
[0013] Based on the information uploaded by the wind turbines and the flexible DC converter station, the dispatch center assesses the frequency regulation capabilities of the wind turbine side and the converter station side. When the receiving-end grid detects a power disturbance, the wind turbine side and the converter station side allocate the disturbance power according to their adjustable capabilities and issue a frequency regulation command.
[0014] The flexible DC converter station responds to its designated portion of the frequency regulation capability assessment by the dispatch center. Upon receiving power control commands, each wind turbine in the wind farm autonomously adjusts its output power according to preset parameters.
[0015] As a further technical solution, the dispatch center assesses the frequency regulation capabilities of both the wind turbine and converter station sides based on information uploaded from the wind farm's wind turbines and flexible DC converter stations. The assessment process involves calculating the energy margin Δ on the wind turbine side. EWG Energy margin Δ on the flexible straight side E MMC The process.
[0016] As a further technical solution, when the receiving-end power grid detects a power disturbance, the wind turbine side and the converter station side distribute the disturbance power according to their adjustable capabilities and issue a frequency regulation command:
[0017]
[0018] In the formula, Δ P WG Δ is the disturbance power borne by the wind turbine components. P MMC The disturbance power shared by the flexible DC converter station, and the sum of the two equals the disturbance power; Δ E MMC For the flexible straight side energy margin, Δ E WG For the energy margin on the wind turbine side, if the disturbance power is Δ P d Then we should have: Δ P WG +Δ P MMC =Δ P d .
[0019] As a further technical solution, the energy margin Δ on the wind turbine side... E WG The electromagnetic energy capacity that the wind turbine can absorb is Δ E WTp Rotor kinetic energy capacity Δ during the wind turbine response process E WTk The sum of;
[0020] Δ E MMC Energy margin Δ at the receiving-end converter station E r Energy margin Δ at the sending-end converter station E s The sum of.
[0021] As a further technical solution, the flexible DC converter station responds to its own portion of the frequency regulation capability assessment by the dispatch center, specifically including:
[0022] Adjust the number of sub-modules to be deployed;
[0023] The reference value of the DC bus voltage is adjusted, and the change of the reference value will change the DC bus voltage through the voltage outer loop control inside the receiving end converter station.
[0024] After detecting a change in the DC bus voltage, the sending-end converter station adjusts the number of its engaged sub-modules. Changing the number of engaged sub-modules alters the sub-module voltage, thus changing the energy of the flexible DC converter station and consequently affecting the frequency.
[0025] As a further technical solution, it also includes: tuning the virtual inertial time constant of the wind turbine based on the rotor kinetic energy capacity expression during the wind turbine response process and the tuning expression for the virtual inertia control of the wind turbine.
[0026] Secondly, an adaptive frequency control system that considers the coordination between the flexible DC converter station and the wind turbine is disclosed, including: wind turbine controller, wind farm controller and dispatch center;
[0027] The wind turbine unit monitors its own operating status in real time and uploads the operating status data to the wind turbine controller. The wind turbine controller then transmits the data to the wind farm controller. The wind farm controller summarizes the status information of the wind turbine unit and uploads it to the dispatch center.
[0028] The flexible DC converter station detects the status of each of its bridge arms, including the number of available sub-modules, and uploads the above information to the dispatch center;
[0029] The dispatch center assesses the frequency regulation capabilities of the wind turbine and converter station sides based on the information uploaded by the wind turbine and converter station. When the receiving-end grid detects a power disturbance, the wind turbine and converter station sides allocate the disturbance power according to their adjustable capabilities and issue a frequency regulation command.
[0030] Based on the dispatch center's assessment of frequency regulation capabilities, the flexible DC converter station responds to its own portion of the data. After receiving the power control command, each wind turbine in the wind farm autonomously adjusts its output power according to preset parameters.
[0031] The above one or more technical solutions have the following beneficial effects:
[0032] To address the issues of insufficient frequency support potential of the MMC-HVDC submodule capacitors in offshore wind-flexible DC systems during frequency regulation, and the lack of a collaborative mechanism between wind farms and flexible DC systems, this adaptive frequency control method, which considers the collaboration between flexible DC converter stations and wind turbines, establishes a flexible DC control architecture for frequency regulation and provides an overall implementation process for the adjustment method and strategy of wind turbines and flexible DC systems according to their adjustable control coefficients. The droop control coefficient of the wind turbine is adjusted according to equation (11). R WTp The virtual inertial time constant (also known as the inertial control coefficient) can be tuned by combining equations (12) and (13). H WTk The droop control coefficient of the receiving-end flexible DC converter station can be adjusted using the combined methods (14), (15), and (16).R Mr The droop control coefficient of the sending-end converter station can be set using a combined system (14)(17). R Ms The new strategy can effectively develop the frequency modulation potential of flexible DC and improve the frequency dynamic characteristics of the system after being subjected to active power disturbances.
[0033] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description
[0034] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.
[0035] Figure 1 This is a schematic diagram of the frequency regulation energy source of the MMC-HVDC according to an embodiment of the present invention;
[0036] Figure 2 This is a control diagram of the MMC-HDVC sender and receiver terminals according to an embodiment of the present invention;
[0037] Figure 3 This is a flowchart of a method according to an embodiment of the present invention;
[0038] Figure 4 Simulation system network diagram;
[0039] Figure 5 Schematic diagram of simulated frequency variation;
[0040] Figure 6 Schematic diagram of wind turbine power variation;
[0041] Figure 7 A schematic diagram of DC voltage variation. Detailed Implementation
[0042] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.
[0043] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations of the present invention.
[0044] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.
[0045] Example 1
[0046] See appendix Figure 3 As shown, this embodiment discloses an adaptive frequency control method considering the collaboration between a flexible DC converter station and a wind turbine. Adaptive frequency control refers to controlling the frequency regulation characteristics of the wind turbine and the flexible DC converter station based on their adjustability, which is reflected in the process of tuning their frequency regulation parameters, and includes:
[0047] Step 1: The wind turbine monitors its own operating status in real time, including information such as rotational speed, and uploads the status data to the wind turbine controller. Finally, the wind farm summarizes the status information of the wind turbine and uploads it to the dispatch center.
[0048] Step 2: The converter station detects the status of each of its bridge arms, including the number of available sub-modules, and uploads the above information to the dispatch center.
[0049] Step 3: The dispatch center assesses the frequency regulation capabilities of the wind turbine side and the converter station side based on the information uploaded by the wind farm and the flexible DC converter station.
[0050] In this step, the evaluation process refers to determining the energy margin Δ on the wind turbine side. E WG Energy margin Δ on the flexible straight side E MMC The process for wind turbine generators can be calculated using equations (11) and (12), while the process for flexible vertical turbine generators can be calculated using equation (15) and the following equation:
[0051] In the formula, Δ E s For the energy margin of the sending-end converter station, C SM For a single submodule capacitor, U dc This is the DC bus voltage. N smin The minimum number of sub-modules to be deployed at the sending-end converter station; N s0 This indicates the number of sub-modules put into operation at the sending-end converter station in the initial state.
[0052] After the receiving-end power grid detects a power disturbance, the wind turbine side and the converter station side distribute the disturbance power according to their adjustable capabilities and issue a frequency regulation command:
[0053]
[0054] In the formula, Δ P WG Δ is the disturbance power borne by the wind turbine components. P MMC The disturbance power shared by the flexible DC converter station, and the sum of the two equals the disturbance power; Δ E WGThe energy margin on the wind turbine side is specifically Δ. E WTp With Δ E WTk The sum, Δ E WTp Δ represents the electromagnetic energy capacity that the wind turbine can absorb. E WTk Δ represents the rotor kinetic energy capacity during the wind turbine's response process. E WTp With Δ E WTk The results are obtained from equations (11) and (12) respectively; Δ E MMC Energy margin Δ at the receiving-end converter station E r Energy margin Δ at the sending-end converter station E s The sum of Δ P WG Δ is the disturbance power borne by the wind turbine components. P MMC The disturbance power shared by the flexible DC converter station is not required by either of these parameters; it is a result of the strategy output. Δ E r From equation (15), Δ E s This is obtained from the above formula. If the disturbance power is Δ... P d Then we should have: Δ P WG +Δ P MMC =Δ P d .
[0055] Disturbances occurring at the receiving end typically first reach the flexible DC converter station. The converter station then responds to its portion of the disturbance based on the dispatch center's assessment of its frequency regulation capabilities. Upon receiving power control commands, each wind turbine autonomously adjusts its output power according to preset parameters.
[0056] See appendix Figure 1 As shown, regarding the frequency regulation capability of the flexible DC converter station: the inertial support energy of the MMC-HVDC system includes the potential energy stored in the capacitors and the magnetic field energy stored in the inductors. Among them, the magnetic field energy stored in the system's inductors is very small. Therefore, the energy source for the frequency regulation capability of the flexible DC converter station is mainly the potential energy of the capacitors.
[0057] (1)
[0058] As shown in equation (1), Δ E C The potential energy stored in the capacitors of the MMC-HVDC system;N s The number of sub-modules deployed at the sending-end converter station; N r The number of sub-modules deployed at the receiving-end converter station; C SM For a single submodule capacitor; U SM , U SM0 These are the capacitor voltages and their rated values for the submodules. The amount of energy stored in the capacitors is determined by... C SM and U SM Decide, U SM The maximum short-term tolerable value can reach 1.5 times its rated value, which can increase the upper limit of energy storage of the MMC-HVDC system during frequency regulation to 2.25 times the rated capacitor energy, thereby effectively expanding the system's energy margin.
[0059] Formula (1) is used to explain that the energy of the flexible DC converter station can be changed by controlling the voltage change of the sub-modules; the energy of the flexible DC converter station can be changed by controlling the number of sub-modules put into operation to change the voltage of the sub-modules.
[0060] While MMC-HVDC possesses a certain energy margin, fully utilizing this margin requires a precise voltage control strategy. Compared to two-level converters, MMC's DC voltage control offers an additional adjustable number of input sub-modules, i.e., in equation (1). N s and N r Choose the right N r Control is applied to decouple the DC voltage from the energy of the submodule capacitor, thus fully releasing the frequency regulation capability of the submodule capacitor.
[0061] Under the decoupling strategy, and subject to the constraint of equation (2), the number of sub-modules deployed in each phase upper and lower bridge arm is... N r It is no longer a constant, but rather an adjustable quantity. Adjustment N r and U SM This allows for changes in the energy of the receiving-end converter station, thereby releasing the energy margin of the submodule capacitor frequency regulation, as shown in the following formula:
[0062] (2)
[0063] (3)
[0064] (4)
[0065] (5)
[0066] Equation (2) is the DC bus voltage U dc With submodule capacitor voltage U SM There is a constraint that is an inherent characteristic of flexible DC systems. By varying the number of input submodules according to equations (7) and (9), the energy can be changed, thereby affecting the frequency.
[0067] N r The number of sub-modules deployed in the receiving-end converter station. N r0 This indicates the number of sub-modules put into operation at the receiving-end converter station in the initial state; U SM This refers to the capacitor voltage of the submodule. U SM0 This refers to the rated voltage of the submodule capacitor.
[0068] In the formula: E 0 represents the energy contained in the capacitor of the flexible DC converter station submodule in the initial state. C SM For a single submodule capacitor. E Δ represents the energy contained in the capacitor of the flexible DC circulating station submodule after the number of submodules changes. E change The energy difference between the two states.
[0069] As shown in equations (3), (4), and (5), by adjusting the number of MMC sub-modules, the frequency regulation energy margin of the flexible DC converter station sub-module capacitors can be released as much as possible.
[0070] By varying the number of input sub-modules according to equations (7) and (9), the energy of the flexible DC converter station can be changed, thereby affecting the frequency change. The advantage of this adjustment is that it is more efficient than directly changing the DC bus voltage. U dc Changing the number of submodules allows for more efficient use of the energy margin of the submodule capacitors, absorbing more energy compared to changing the voltage.
[0071] Regarding the frequency regulation characteristics of wind turbines and flexible DC converter stations: Offshore wind power resources are abundant, and wind turbines themselves have excellent frequency regulation potential. This paper also focuses on the cooperation between flexible DC converter stations and wind turbines. The wind turbines adopt a control strategy that simulates the frequency regulation characteristics of synchronous generators, which can provide virtual inertia support for the system, thereby improving the system frequency stability.
[0072] (6)
[0073] Formula (6) is used to explain the frequency regulation characteristics of wind turbine units.
[0074] In the formula: Δ P WT Δ represents the change in electromagnetic power output by the wind turbine. f This represents the change in system frequency. H WT The virtual inertial time constant of the wind turbine. R WT This represents the droop control coefficient for wind turbines. The sending and receiving end converter stations employ droop characteristics, with the receiving end converter station detecting frequency changes and providing frequency support.
[0075] (7)
[0076] In the formula: N r The number of sub-modules deployed in the receiving-end converter station. N r0 This represents the number of submodules put into operation at the receiving-end converter station in the initial state, Δ. f This represents the change in system frequency. R Mr This represents the droop control coefficient for the receiving-end converter station.
[0077] To ensure that the DC side of the sending-end converter station reflects the frequency information of the receiving-end AC grid, the DC voltage of the receiving-end converter station is expressed by the following formula. f / U dc Sagging control:
[0078] (8)
[0079] In the formula, U dcref The DC voltage reference value is set for the receiving-end converter station. U dc0 The DC bus voltage in the initial state. R f for f / U dc Sag control factor, Δ f This represents the change in system frequency. f This refers to the system frequency.
[0080] After detecting DC voltage fluctuations, the sending-end converter station also adaptively adjusts the number of sub-modules put into operation through droop control. N s :
[0081] (9)
[0082] In the formula, N s The number of sub-modules deployed at the sending-end converter station. N s0 This represents the number of sub-modules put into operation at the sending-end converter station in the initial state, Δ. U dc This represents the change in DC bus voltage. R Ms This is the droop control coefficient for the sending-end converter station.
[0083] Based on equations (7), (8), and (9), the control structure of the flexible DC transmission system is adjusted. The specific MMC-HDVC sender-receiver control scheme is as follows: Figure 2 As shown.
[0084] When a disturbance occurs, the system frequency will change. After the receiving-end converter station detects this frequency change, it will perform the following two operations:
[0085] 1. Adjust the number of sub-modules put into operation at the receiving-end converter station according to formula (7). N r ;
[0086] 2. Adjust the reference value of the constant DC voltage of the receiving-end converter station according to formula (8). U dcref Changes in the reference value will alter the DC bus voltage through the voltage outer loop control within the receiving-end converter station. U dc .
[0087] The DC bus voltage was detected at the sending-end converter station. U dc After the change, the number of sub-modules put into operation at the sending-end converter station is changed according to equation (9). N s Changing the number of submodules in operation will alter the submodule voltage (an inherent characteristic of flexible DC transmission), thus changing the energy level of the flexible DC converter station and affecting the frequency. For example, when an external disturbance such as a load reduction occurs, the frequency will rise. Upon detecting this frequency increase, the receiving-end converter station will reduce the number of submodules in operation and increase the DC bus voltage; conversely, if the sending-end converter station detects an increase in DC bus voltage, it will reduce the number of submodules in operation. With a reduced number of submodules, the submodule voltage will rise, allowing the flexible DC converter station to absorb excess energy in the system, thereby lowering the system frequency.
[0088] By setting the frequency regulation parameters of the wind turbine and the flexible DC converter station according to their adjustable capabilities, and distributing the disturbances according to their adjustable capabilities, a wind power-flexible DC coordinated frequency regulation architecture can be formed.
[0089] Regarding the adaptive frequency control parameter tuning for the coordinated operation of flexible DC converter stations and wind turbines: Wind turbines typically absorb excess energy from the system by converting it into rotor kinetic energy. However, during this conversion, their operating speed deviates from the MPPT (Maximum Power Point Test) operating point. Researchers now often utilize this characteristic to allow wind turbines to retain reserve power during steady-state operation through overspeed load shedding control.
[0090] (10)
[0091] in, P res This serves as the backup power for wind turbine units. d For wind turbine load reduction rate, P opt This represents the maximum active power achievable at the current wind speed. P deload This refers to the active power of the wind turbine after load reduction.
[0092] This is used to explain the process of overspeed load reduction. By utilizing the principle of load reduction, the energy change of the wind turbine before and after the disturbance can be analyzed as electromagnetic energy change and rotor kinetic energy change, and then the frequency regulation parameters can be adjusted. The droop control coefficient is adjusted by using the electromagnetic energy change formula (11), and the virtual inertial time constant of the wind turbine is adjusted by using the rotor kinetic energy change formulas (12) and (13).
[0093] By utilizing the principle of load reduction, the energy changes of the wind turbine before and after a disturbance can be analyzed as changes in electromagnetic energy and rotor kinetic energy, thereby allowing for the adjustment of frequency regulation parameters. The electromagnetic energy capacity Δ that the wind turbine can absorb before and after the speed change is... E WTp Expressed as:
[0094] (11)
[0095] In the formula, T res For one frequency response time, P res Δ is the standby power of the wind turbine. f m The permissible frequency deviation limit set for wind turbine frequency regulation. R WTp ' is the set value of the wind turbine droop control coefficient, Δ f m The permissible frequency deviation limit set for wind turbine frequency regulation. The electromagnetic energy capacity Δ that the wind turbine can absorb. E WTp Used to adjust the droop control coefficient R WTp .
[0096] Based on equation (11), the sag control coefficient of the wind turbine can be tuned. The virtual inertia support capacity of the wind turbine originates from the dynamic change of its rotor rotational kinetic energy, and the rotor kinetic energy capacity Δ during the wind turbine response process... E WTk Expressed as:
[0097] (12)
[0098] In the formula, J The moment of inertia of the wind turbine. ω de To reduce the operating speed under reduced load, ω MPPT To achieve the optimal speed under MPPT control, the tuning for the virtual inertia control of the wind turbine is as follows:
[0099] (13)
[0100] In the formula, T res For one frequency response time, H WTk ' is the virtual inertial time constant setting value of the wind turbine, Δ f m The allowable frequency deviation limit is set for the frequency regulation of the wind turbine. Equations (12) and (13) can be combined to tune the virtual inertial time constant of the wind turbine. H WTk .
[0101] Regarding flexible direct current circulation stations: U SM The maximum short-term tolerable value is 1.5. U SM0 Considering DC bus voltage U DC The margin is only 0.05 pu, and transmitting frequency information via DC voltage also consumes part of the DC voltage margin. Therefore, when adjusting the parameters of the submodule, it is not considered. U DC The impact of fluctuations. Under this premise, the constraint on the number of flexible DC converter stations can be obtained based on equation (2):
[0102] (14)
[0103] In the formula, N rmin This represents the minimum number of submodules to be deployed in the receiving-end converter station. N smin This represents the minimum number of submodules required for the sending-end converter station. N r0This indicates the number of sub-modules put into operation at the receiving-end converter station in the initial state. N s0 This indicates the number of sub-modules put into operation at the sending-end converter station in the initial state.
[0104] The energy margin of the receiving-end converter station is as follows:
[0105] (15)
[0106] In the formula, Δ E r For the energy margin of the receiving-end converter station, C SM For a single submodule capacitor, U dc This is the DC bus voltage. N rmin This represents the minimum number of submodules to be deployed in the receiving-end converter station. N r0 This indicates the number of sub-modules put into operation at the receiving-end converter station in the initial state.
[0107] Set value of droop control coefficient for receiving-end converter station R Mr 'for
[0108] (16)
[0109] In the formula, R Mr 'Its specific set value, N r0 This indicates the number of sub-modules put into operation at the receiving-end converter station in the initial state. N rmin Δ is the minimum number of submodules to be put into operation at the receiving-end converter station. f SM The allowable frequency deviation limit set for the converter station is considered because the frequency regulation capability of the converter station is smaller than that of the wind turbine. Δ f SM Numerically than Δ f m The design should be smaller to quickly unleash its frequency modulation capabilities and achieve better frequency modulation results.
[0110] The setting principle for the droop control coefficient of the sending-end converter station is basically the same as that of the receiving-end converter station. The only difference is that the droop control coefficient of the sending-end converter station must be set based on the changing characteristics of the DC voltage.
[0111] (17)
[0112] In the formula, R Ms 'This is the set value for the droop control coefficient of the sending-end converter station, Δ'U DCm The change in DC bus voltage Δ U DC The maximum value, N s0 This indicates the number of sub-modules put into operation at the sending-end converter station in the initial state. N smin This represents the minimum number of sub-modules required for the sending-end converter station.
[0113] Simulation Comparison: A power system as shown in Figure 4 was constructed using Matlab / Simulink. The basic parameters of the system are as follows: the wind farm has a rated power of 240 MW, a wind speed of 8 m / s, a flexible DC bus rated voltage of 800 kV, and 400 submodules in the flexible DC converter station. A load shedding disturbance of 150 MW was applied to the receiving-end grid at 10 s. The simulation assumed a constant wind speed and did not consider the differences between the turbines within the wind farm. The different strategies used in the simulation comparison are shown in Table 1.
[0114] Table 1 Strategy Comparison
[0115] serial number Strategy Details 1 Using the strategy proposed in this paper 2 Wind turbines participate in frequency regulation, while flexible DC-DC converters use traditional coupling control for frequency regulation. 3 Wind turbines participate in frequency regulation, while flexible DC power units do not. 4 Wind turbines and flexible DC power units do not participate in frequency regulation.
[0116] Figure 5 This is a simulation of frequency variation. Figure 6 The graph shows the power variation of the wind turbine generators. From the perspective of peak frequency characteristics, Strategy 4 reaches a maximum frequency of 50.074Hz, while Strategy 2 and Strategy 3 reach 50.051Hz and 50.049Hz respectively. Strategy 1 has the lowest peak frequency at only 50.047Hz, and its rate of frequency rise and rate of frequency change are also at the lowest levels. Regarding the power regulation characteristics of the wind turbine generators, Strategy 1 results in a power change of -0.173 pu, which is 10% less than the -0.188 pu power reduction of Strategy 2 under the coupled control strategy. These results indicate that by controlling the number of sub-modules, the frequency regulation margin of the flexible DC converter station can be more fully released, reducing the frequency regulation pressure on the wind turbine generators and achieving better frequency regulation performance.
[0117] Figure 7 In response to changes in DC bus voltage, after a disturbance occurs, the flexible DC converter station using Strategy 1 adjusts the number of sub-modules put into operation based on a preset droop control coefficient to quickly release the frequency regulation capability of the sub-modules.
[0118] Example 2
[0119] The purpose of this embodiment is to provide a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps of the above-described method.
[0120] Example 3
[0121] The purpose of this embodiment is to provide a computer-readable storage medium.
[0122] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, performs the steps of the above method.
[0123] Example 4
[0124] The purpose of this embodiment is to provide an adaptive frequency control system that takes into account the coordination between the flexible DC converter station and the wind turbine, including: a wind turbine controller, a wind farm controller, and a dispatch center;
[0125] The wind turbine unit monitors its own operating status in real time and uploads the operating status data to the wind turbine controller. The wind turbine controller then transmits the data to the wind farm controller. The wind farm controller summarizes the status information of the wind turbine unit and uploads it to the dispatch center.
[0126] The flexible DC converter station detects the status of each of its bridge arms, including the number of available sub-modules, and uploads the above information to the dispatch center;
[0127] The dispatch center assesses the frequency regulation capabilities of the wind turbine side and the converter station side based on the information uploaded by the wind turbines and the flexible DC converter station. When the receiving end grid detects a power disturbance, it allocates the disturbance power according to the ratio of the wind turbine side and the load side regulation capabilities and issues a frequency regulation command.
[0128] Based on the dispatch center's assessment of frequency regulation capabilities, the flexible DC converter station responds to its own portion of the data. After receiving the power control command, each wind turbine in the wind farm autonomously adjusts its output power according to preset parameters.
[0129] Example 5
[0130] The purpose of this embodiment is to provide a computer program product containing instructions that, when run on a computer, cause the computer to perform the methods and functions involved in any of the above embodiments.
[0131] The steps and methods involved in the apparatus of the above embodiments correspond to those in Embodiment 1. For specific implementation details, please refer to the relevant description section of Embodiment 1. The term "computer-readable storage medium" should be understood as a single medium or multiple media including one or more instruction sets; it should also be understood as including any medium capable of storing, encoding, or carrying an instruction set for execution by a processor and enabling the processor to perform any of the methods in this invention.
[0132] Those skilled in the art will understand that the modules or steps of the present invention described above can be implemented using general-purpose computer devices. Optionally, they can be implemented using computer-executable program code, thereby allowing them to be stored in a storage device for execution by a computer device, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. The present invention is not limited to any particular combination of hardware and software.
[0133] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.
Claims
1. Considering an adaptive frequency control method for coordinated operation of a flexible DC converter station and a wind turbine, characterized by: include: The wind turbine unit monitors its own operating status in real time and uploads the operating status data to the wind turbine unit controller. The wind turbine controller then transmits the data to the wind farm controller. The wind farm controller summarizes the wind turbine unit status information and uploads it to the dispatch center. The flexible DC converter station detects the status of each of its bridge arms, including the number of available sub-modules, and uploads the above information to the dispatch center; Based on the information uploaded by the wind turbines and the flexible DC converter station, the dispatch center assesses the frequency regulation capabilities of both the wind turbine and converter station sides. This assessment process involves calculating the energy margin Δ on the wind turbine side. E WG Energy margin Δ on the flexible straight side E MMC In this process, when the receiving-end power grid detects a power disturbance, the wind turbine side and the converter station side distribute the disturbance power according to their adjustable capabilities and issue a frequency regulation command: In the formula, Δ P WG Δ is the disturbance power borne by the wind turbine components. P MMC The disturbance power shared by the flexible DC converter station and the sum of the two equals the disturbance power; Δ E MMC For the flexible straight side energy margin, Δ E WG For the energy margin on the wind turbine side, if the disturbance power is Δ P d Then we should have: Δ P WG +Δ P MMC =Δ P d ; Wind turbine side energy margin Δ E WG The electromagnetic energy capacity that the wind turbine can absorb is Δ E WTp Rotor kinetic energy capacity Δ during the wind turbine response process E WTk The sum; Δ E MMC Energy margin Δ at the receiving-end converter station E r Energy margin Δ at the sending-end converter station E s The sum of, among which, Electromagnetic energy capacity Δ that wind turbines can absorb E WTp Expressed as: In the formula, T res For one frequency response time, P res Δ is the standby power of the wind turbine. f m The permissible frequency deviation limit set for wind turbine frequency regulation. R WTp ' is the set value of the wind turbine droop control coefficient, Δ f m The permissible frequency deviation limit set for wind turbine frequency regulation; Rotor kinetic energy capacity Δ during wind turbine response process E WTk Expressed as: In the formula, J The moment of inertia of the wind turbine. ω de To reduce the operating speed under reduced load, ω MPPT The optimal speed under MPPT control; Energy margin Δ at the receiving end converter station E r Expressed as: In the formula, C SM For a single submodule capacitor, U dc This is the DC bus voltage. N rmin This represents the minimum number of submodules to be deployed in the receiving-end converter station. N r0 This indicates the number of sub-modules put into operation at the receiving-end converter station in the initial state; Energy margin Δ of sending-end converter station E s Expressed as: In the formula, C SM For a single submodule capacitor, U dc This is the DC bus voltage. N smin The minimum number of sub-modules to be deployed at the sending-end converter station; N s0 This indicates the number of sub-modules put into operation at the sending-end converter station in the initial state; Based on the dispatch center's assessment of frequency regulation capabilities, the flexible DC converter station responds to its own portion of the data. After receiving the power control command, each wind turbine in the wind farm autonomously adjusts its output power according to preset parameters.
2. The adaptive frequency control method considering the coordination between the flexible DC converter station and the wind turbine as described in claim 1, characterized in that, The flexible DC converter station responds to its own portion of the frequency regulation capability assessment by the dispatch center, specifically including: Adjust the number of sub-modules to be used; The reference value of the DC bus voltage is adjusted, and the change of the reference value will change the DC bus voltage through the voltage outer loop control inside the receiving end converter station. After the sending-end converter station detects a change in the DC bus voltage, it changes the number of sub-modules it connects. This change in the number of sub-modules will alter the voltage of the sub-modules, thus changing the energy of the flexible DC converter station and affecting the frequency.
3. The adaptive frequency control method considering the coordination between the flexible DC converter station and the wind turbine as described in claim 1, characterized in that, it also... include: The virtual inertial time constant of the wind turbine is tuned based on the rotor kinetic energy expression during the wind turbine response process and the tuning expression for the virtual inertia control of the wind turbine.
4. An adaptive frequency control system considering the coordination between the flexible DC converter station and the wind turbine generator, characterized by: include: Wind turbine controllers, wind farm controllers and dispatch centers; The wind turbine unit monitors its own operating status in real time and uploads the operating status data to the wind turbine controller. The wind turbine controller then transmits the data to the wind farm controller. The wind farm controller summarizes the status information of the wind turbine unit and uploads it to the dispatch center. The flexible DC converter station detects the status of each of its bridge arms, including the number of available sub-modules, and uploads the above information to the dispatch center; The dispatch center assesses the frequency regulation capabilities of both the wind turbine and converter station sides based on information uploaded from the wind farm's wind turbines and flexible DC converter stations. This assessment process involves calculating the energy margin Δ on the wind turbine side. E WG Energy margin Δ on the flexible straight side E MMC In this process, when the receiving-end power grid detects a power disturbance, the wind turbine side and the converter station side distribute the disturbance power according to their adjustable capabilities and issue a frequency regulation command: In the formula, Δ P WG Δ is the disturbance power borne by the wind turbine components. P MMC The disturbance power shared by the flexible DC converter station and the sum of the two equals the disturbance power; Δ E MMC For the flexible straight side energy margin, Δ E WG For the energy margin on the wind turbine side, if the disturbance power is Δ P d Then we should have: Δ P WG +Δ P MMC =Δ P d ; Wind turbine side energy margin Δ E WG The electromagnetic energy capacity that the wind turbine can absorb is Δ E WTp Rotor kinetic energy capacity Δ during the wind turbine response process E WTk The sum; Δ E MMC Energy margin Δ at the receiving-end converter station E r Energy margin Δ at the sending-end converter station E s The sum of, among which, Electromagnetic energy capacity Δ that wind turbines can absorb E WTp Expressed as: In the formula, T res For one frequency response time, P res Δ is the standby power of the wind turbine. f m The permissible frequency deviation limit set for wind turbine frequency regulation. R WTp ' is the set value of the wind turbine droop control coefficient, Δ f m The permissible frequency deviation limit set for wind turbine frequency regulation; Rotor kinetic energy capacity Δ during wind turbine response process E WTk Expressed as: In the formula, J The moment of inertia of the wind turbine. ω de To reduce the operating speed under reduced load, ω MPPT The optimal speed under MPPT control; Energy margin Δ at the receiving end converter station E r Expressed as: In the formula, C SM For a single submodule capacitor, U dc This is the DC bus voltage. N rmin This represents the minimum number of submodules to be deployed in the receiving-end converter station. N r0 This indicates the number of sub-modules put into operation at the receiving-end converter station in the initial state; Energy margin Δ of sending-end converter station E s Expressed as: In the formula, C SM For a single submodule capacitor, U dc This is the DC bus voltage. N smin The minimum number of sub-modules to be deployed at the sending-end converter station; N s0 This indicates the number of sub-modules put into operation at the sending-end converter station in the initial state; Based on the dispatch center's assessment of frequency regulation capabilities, the flexible DC converter station responds to its own portion of the data. After receiving the power control command, each wind turbine in the wind farm autonomously adjusts its output power according to preset parameters.
5. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the method of any one of claims 1 to 3.
6. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps of the method described in any one of claims 1-3.
7. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it performs the steps of the method described in any one of claims 1-3 above.