Flexible frequency support control method and flexible frequency support control device

Abstract

The application relates to a kind of flexible direct frequency support control method and flexible direct frequency support control device, the control method comprises: when frequency deviation exceeds preset dead zone range, based on preset target virtual inertia coefficient, target frequency modulation coefficient, frequency deviation and frequency change rate, generate basic active power increment instruction;According to the preset sliding time window, the power deviation of each time in the window length time before current time is integrated, and the energy shortage in the window length time is obtained;Based on energy shortage, determine the power demand of flexible direct grid point, and obtain the available power margin of flexible direct current time, according to the power demand of each flexible direct grid point and power margin determine compensation power instruction;The basic active power increment instruction and compensation power instruction are superimposed, and the target active power instruction value is obtained;According to target active power instruction value, adjust the actual active power output of flexible direct grid point, by the application, improve the flexible direct frequency support capability.

Description

Technical Field

[0001] This application relates to the field of power system operation and control technology, and in particular to flexible DC frequency support control methods and devices. Background Technology

[0002] With the continuous advancement of the green and low-carbon energy transformation, the widespread integration of large-scale new energy power generation and high-capacity DC transmission systems has led to the power system gradually exhibiting the "dual high" characteristics of high-proportion power electronics and high-proportion new energy integration. This has resulted in increasingly prominent issues such as declining system inertia and insufficient frequency stability margin. Flexible DC transmission technology based on voltage source converters (VSC-HVDC, hereinafter referred to as flexible DC) has advantages such as independent active and reactive power regulation, flexible control, and high reliability, and has been widely applied in fields such as new energy transmission and grid interconnection. After flexible DC replaces traditional inter-regional AC tie lines, the frequencies of the AC systems at both ends are decoupled, and the sending-end units cannot sense frequency changes at the receiving end and naturally provide frequency support. Therefore, existing technologies typically add frequency control to the power control station of grid-connected flexible DC, introducing the receiving-end frequency information into the active power reference value of the sending-end converter station, enabling the flexible DC to provide active frequency support to the receiving-end grid by mimicking the inertia response and primary frequency regulation characteristics of a synchronous machine.

[0003] However, the aforementioned additional frequency control scheme faces two inherent drawbacks in practical engineering: First, to avoid frequent responses caused by small frequency fluctuations, frequency support control typically sets a certain frequency input dead zone. This results in the flexible DC power supply (DCPS) providing no support until the frequency deviation exceeds the dead zone threshold, delaying the response timing of frequency support and increasing the steady-state frequency deviation. Second, there is an unavoidable lag between the occurrence of a disturbance in the receiving-end grid frequency and the arrival of the DCPS power response. This includes the communication delay of the frequency signal being transmitted to the sending end via the communication link, as well as the response delay of the DCPS power control loop itself. These delays cause the power output of the DCPS to lag significantly behind the ideal support requirements during the critical initial period of the disturbance. The combined effect of these dead zones and delays results in the actual support energy fed into the receiving-end grid by the DCPS being significantly lower than the ideal level, weakening the DCPS's active support capability for the receiving-end AC grid frequency and deteriorating the system's frequency response characteristics.

[0004] There is currently no effective solution to the problem of weak frequency support capability of flexible DC due to control dead zone and response delay issues in related technologies. Summary of the Invention

[0005] This embodiment provides a flexible DC frequency support control method and a flexible DC frequency support control device to solve the problem of weak flexible DC frequency support capability caused by control dead zone and response delay in related technologies.

[0006] Firstly, this embodiment provides a flexible straight-line frequency support control method, including:

[0007] Real-time calculation of the frequency deviation and rate of change between the current grid frequency and the rated frequency at the receiving end of the AC power grid;

[0008] When the frequency deviation exceeds the preset dead zone range, a basic active power increment command is generated based on the preset target virtual inertia coefficient, target frequency modulation coefficient, the frequency deviation, and the frequency change rate.

[0009] By integrating the power deviation at each moment within the window length before the current moment according to the preset sliding time window, the energy deficit within the window length is obtained.

[0010] Based on the energy deficit, determine the power demand of the flexible DC grid connection point, obtain the available power margin of the flexible DC at the current moment, and upload the power demand and the power margin to the coordination controller.

[0011] Receive the compensation power command determined by the coordination controller based on the power demand and power margin of one or more flexible DC grid connection points participating in the support;

[0012] The base active power increment command and the compensation power command are superimposed to obtain the target active power command value;

[0013] Adjust the actual active power output of the flexible DC grid connection point according to the target active power command value, and input the adjusted actual active power output to the receiving end.

[0014] In some embodiments, integrating the power deviation over a window of length preceding the current moment according to a preset sliding time window to obtain the energy deficit over the window of length includes:

[0015] Within a preset sliding time window, the ideal support power at each moment is generated based on the preset target virtual inertia coefficient, target frequency regulation coefficient, frequency change rate at each moment, grid frequency at each moment, and the rated frequency.

[0016] Based on the actual active power output at each moment of the flexible DC grid connection point, the power output at the reference moment, and the corresponding ideal support power at each moment, the power deviation at each moment is calculated.

[0017] Integrating the power deviation at each time point yields the energy deficit within the window length.

[0018] In some embodiments, the reference time power output is the power output of the flexible DC grid connection point at the moment when the frequency deviation exceeds the preset dead zone range.

[0019] In some of these embodiments, the preset target virtual inertia coefficient and the target frequency modulation coefficient are determined by the maximum active power adjustment of the flexible DC grid connection point under the current operating state, the maximum rate of change of the system under the preset maximum frequency disturbance event, and the maximum frequency deviation.

[0020] In some embodiments, the window length of the preset sliding time window is greater than or equal to the sum of the communication delay of the target active power command value and the response delay of the flexible direct current.

[0021] In some embodiments, determining the power demand of the flexible DC grid connection point based on the energy deficit includes:

[0022] The power requirement is obtained by dividing the energy deficit by the window length.

[0023] In some embodiments, the compensation power command determination process includes:

[0024] The total system power demand is obtained by summing the power demands of each participating flexible DC grid-connected point through the coordination controller; the total power margin is obtained by summing the power margins of each participating flexible DC grid-connected point; a global allocation coefficient is calculated based on the preset global compensation gain and the ratio of the total system power demand to the total power margin; the global allocation coefficient is multiplied by the power margin of each corresponding flexible DC grid-connected point to obtain the compensation power command.

[0025] In some embodiments, the global allocation coefficient is subjected to amplitude limiting processing based on a preset value range, restricting the global allocation coefficient to the preset value range; when the global allocation coefficient reaches the boundary value of the value range, a preset emergency control strategy is triggered.

[0026] Secondly, this embodiment provides a flexible DC frequency support control device, including: a basic active power increment command generation module, a compensation power demand generation module, a coordination control module, and a control module;

[0027] The basic active power increment command generation module is used to calculate in real time the frequency deviation and frequency change rate between the current grid frequency and the rated frequency at the receiving end of the AC grid; when the frequency deviation exceeds the preset dead zone range, the basic active power increment command is generated based on the preset target virtual inertia coefficient, target frequency regulation coefficient, the frequency deviation and the frequency change rate.

[0028] The compensation power demand generation module is used to integrate the power deviation at each moment within a window length period before the current moment according to a preset sliding time window to obtain the energy deficit within the window length period; and generate the power demand of the flexible DC grid connection point based on the energy deficit.

[0029] The coordination and control module is used to summarize the power demand of each participating flexible DC grid connection point to obtain the total system power demand; summarize the power margin of each participating flexible DC grid connection point to obtain the total power margin; calculate the global allocation coefficient based on the preset global compensation gain and the ratio of the total system power demand to the total power margin; and multiply the global allocation coefficient by the power margin of each corresponding flexible DC grid connection point to obtain the compensation power command.

[0030] The control module is used to superimpose the basic active power increment command and the compensation power command to obtain the target active power command value; and control the actual active power output of the flexible DC grid connection point according to the target active power command value, and input the adjusted actual active power output to the receiving end.

[0031] Thirdly, this embodiment provides a computer device including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the method described in the first aspect above.

[0032] Compared with related technologies, the flexible DC frequency support control method provided in this embodiment calculates the frequency deviation and frequency change rate between the current grid frequency and the rated frequency at the receiving end of the AC grid in real time. When the frequency deviation exceeds a preset dead zone range, a basic active power increment command is generated based on a preset target virtual inertia coefficient, a target frequency regulation coefficient, the frequency deviation, and the frequency change rate. The power deviation is integrated over a preset sliding time window for each moment before the current moment to obtain the energy deficit within the window. The flexible DC frequency support control method is then determined based on the energy deficit. The system calculates the power demand of the grid connection point and obtains the available power margin of the flexible DC transmission at the current moment. It then uploads the power demand and power margin to the coordination controller. The system receives compensation power commands determined by the coordination controller based on the power demand and power margin of one or more flexible DC transmission grid connection points participating in the support. It superimposes the basic active power increment command and the compensation power command to obtain a target active power command value. Based on the target active power command value, it adjusts the actual active power output of the flexible DC transmission grid connection point and inputs the adjusted actual active power output to the receiving end, thereby improving the frequency support capability of the flexible DC transmission.

[0033] Details of one or more embodiments of this application are set forth in the following drawings and description to make other features, objects and advantages of this application more readily apparent. Attached Figure Description

[0034] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0035] Figure 1 This is a hardware structure block diagram of the terminal of the flexible DC frequency support control method in this embodiment.

[0036] Figure 2 This is a structural diagram of the flexible DC transmission system in this embodiment.

[0037] Figure 3 This is a flowchart of the flexible-straight frequency support control method in this embodiment.

[0038] Figure 4 These are frequency response curves of the AC power grid in receiving region 2 under three different scenarios in this embodiment.

[0039] Figure 5 This is a graph showing the active power output curves of the flexible DC power in the receiving-end region 2 under three different scenarios in this embodiment.

[0040] Figure 6 This is a structural diagram of a multi-infeed flexible DC transmission system using the flexible DC frequency support control method of this embodiment.

[0041] Figure 7 This is a frequency response curve of the receiving-end AC grid under three conditions for the multi-infeed flexible DC transmission system of this embodiment.

[0042] Figure 8 This is a graph showing the active power output curves of the multi-infeed flexible DC transmission system in the receiving-end region under three different conditions.

[0043] Figure 9 This is a flowchart of another flexible straight frequency support control method in this embodiment.

[0044] Figure 10 This is a structural block diagram of the flexible straight frequency support control device in this embodiment.

[0045] Figure 11 This is a preferred structural block diagram of the flexible straight frequency support control device in this embodiment. Detailed Implementation

[0046] To better understand the purpose, technical solution, and advantages of this application, the application is described and illustrated below in conjunction with the accompanying drawings and embodiments.

[0047] Unless otherwise defined, the technical or scientific terms used in this application shall have the general meaning understood by one of ordinary skill in the art to which this application pertains. Words such as “a,” “an,” “an,” “the,” “the,” and “these” used in this application do not indicate quantitative limitation and may be singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that comprises a series of steps or modules (units) is not limited to the listed steps or modules (units) but may include steps or modules (units) not listed, or may include other steps or modules (units) inherent to these processes, methods, products, or devices. Words such as “connected,” “linked,” and “coupled” used in this application are not limited to physical or mechanical connections but may include electrical connections, whether direct or indirect. “Multiple” used in this application refers to two or more. “And / or” describes the relationship between related objects, indicating that three relationships may exist; for example, “A and / or B” can represent: A alone, A and B simultaneously, and B alone. Normally, the character " / " indicates that the objects before and after it are in an "or" relationship. The terms "first," "second," "third," etc., used in this application are merely to distinguish similar objects and do not represent a specific order of objects.

[0048] The method embodiments provided in this example can be executed on a terminal, computer, or similar computing device. For example, it can run on a terminal. Figure 1 This is a hardware structure block diagram of the terminal of the flexible DC frequency support control method in this embodiment. For example... Figure 1 As shown, a terminal may include one or more ( Figure 1 Only one is shown in the diagram. A processor 102 and a memory 104 for storing data are also included. The processor 102 may be, but is not limited to, a microprocessor (MCU) or a programmable logic device (FPGA). The terminal may also include a transmission device 106 for communication functions and an input / output device 108. Those skilled in the art will understand that… Figure 1 The structure shown is for illustrative purposes only and does not limit the structure of the terminal described above. For example, the terminal may also include components that are larger than... Figure 1 The more or fewer components shown, or having the same Figure 1 The different configurations shown are illustrated.

[0049] The memory 104 can be used to store computer programs, such as application software programs and modules, like the computer program corresponding to the flexible DC frequency support control method in this embodiment. The processor 102 executes various functional applications and data processing by running the computer program stored in the memory 104, thereby implementing the above-described method. The memory 104 may include high-speed random access memory, and may also include non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some instances, the memory 104 may further include memory remotely located relative to the processor 102, and these remote memories can be connected to the terminal via a network. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0050] The transmission device 106 is used to receive or send data via a network. This network includes a wireless network provided by the terminal's communication provider. In one example, the transmission device 106 includes a Network Interface Controller (NIC), which can connect to other network devices via a base station to communicate with the Internet. In another example, the transmission device 106 can be a Radio Frequency (RF) module used for wireless communication with the Internet.

[0051] For ease of understanding, the technical terms involved in the embodiments of this application will be introduced below.

[0052] 1. Flexible DC transmission technology: A power transmission technology based on voltage source converter (VSC) with high controllability and flexibility.

[0053] The basic principle is to achieve a high degree of controllability in power transmission by using VSC, self-turn-off devices, and PWM (Pulse Width Modulation) technology. By adjusting the output voltage amplitude and phase angle of the VSC, the transmission of active and reactive power can be controlled independently.

[0054] VSC is a core component of flexible direct current transmission systems, typically employing IGBTs (Insulated Gate Bipolar Transistors) or GTOs (Gate-Turn-Off Thyristors) as turn-off devices. These devices enable rapid switching and high-frequency modulation, thereby allowing for precise control of current and voltage.

[0055] 2. Dead Zone: In the field of power system stability and control technology, a dead zone generally refers to a fault or protection blind spot within a specific area. That is, a fault occurring in an area that cannot be covered by certain equipment or protection devices. These areas are usually formed due to limitations in the physical layout of the equipment or the protection logic.

[0056] In the typical protection dead zone problem of 220kV substations, due to defects in the working principle of the relay protection device itself, when a protected element fails within a specific small range, it may not be able to be disconnected in time, resulting in a dead zone fault. Although the probability of such faults is relatively small, their impact on the stable operation of the system is gradually increasing as the power grid becomes more complex.

[0057] This embodiment provides a flexible DC transmission system. Figure 2 This is a structural diagram of the flexible DC transmission system in this embodiment, as shown below. Figure 2 As shown, the flexible DC transmission system provided in this embodiment is a four-machine two-region system built and improved based on electromagnetic transient simulation software. The grid is divided into three functional sections: the sending-end AC region (region 1), the UHV flexible DC transmission channel, and the receiving-end AC region (region 2).

[0058] In this section, the sending-end area 1 is equipped with two synchronous generator sets, G1 and G2, which are connected to the regional AC bus via a step-up transformer. The bus is connected in parallel to the local AC load L1, and the sending-end voltage source converter VSC1 is also connected to the bus side, forming a flexible DC sending-end converter station. Support capacitors are configured on the AC side to achieve bus voltage filtering and reactive power buffering. The converter station is equipped with a grounding loop. The outer loop of the sending-end converter station VSC1 adopts a constant active power control mode, with the reference steady-state active power value set at 200MW. Under grid frequency support conditions, the target active power command value P is dynamically corrected. ref The active power transmission of the DC channel is increased, and more power is generated for the receiving area.

[0059] Receiving-end area 2 is equipped with two synchronous generator sets, G3 and G4, which are connected to the local AC bus via a step-up transformer. The bus is connected to the local AC load L2. The bus is connected to the receiving-end voltage source converter VSC2, with AC-side filter capacitors and grounding facilities to complete the power feed-in of DC power to the receiving-end AC grid. The outer loop of the receiving-end converter station VSC2 adopts a constant DC voltage control mode to maintain a constant DC line bus voltage as the control objective, balance the DC side active power surplus / deficit, ensure the voltage stability of the DC transmission system, and feed the DC power into the receiving-end AC system after inversion.

[0060] The DC transmission interconnection channel uses ±800kV UHV flexible DC transmission lines to connect VSC1 and VSC2, with DC active power flow P dcThe reference flow direction is from the sending end to the receiving end, and the rated active power transmission capacity of the line is 500MW.

[0061] When an active power disturbance (sudden load increase, power output drop) occurs in receiving-end area 2, the active power deficit in the area widens, and the AC system frequency experiences a frequency drop deviation; the proposed control scheme uses the active power command P from VSC1. ref To adjust the degrees of freedom without exceeding the 500MW rated transmission capacity of flexible DC transmission, the P value is increased. ref To increase the active power transmission level of the DC channel, supplement the active power to the receiving AC grid, fill the active power deficit caused by disturbances, suppress the frequency drop amplitude, accelerate the frequency recovery process, and complete the primary frequency active support for the receiving AC system.

[0062] Based on this, this embodiment provides a flexible straight frequency support control method. Figure 3 This is a flowchart of the flexible DC frequency support control method in this embodiment, as follows: Figure 3 As shown, the process includes the following steps:

[0063] Step S301: Calculate in real time the frequency deviation and frequency change rate between the current grid frequency and the rated frequency at the receiving end of the AC grid.

[0064] Specifically, the flexible DC frequency support control method in this embodiment is applicable to a two-terminal flexible DC transmission system employing grid-following control, where one converter station uses constant active power control and the other uses constant DC voltage control. During the active frequency support control process of the flexible DC interconnected grid, the system collects the grid frequency f of the AC grid to be supported at the receiving end in real time to obtain the dynamic frequency operating status of the grid. It should be noted that the receiving-end grid frequency refers to the frequency state of the receiving-end grid when electrical energy is transmitted from the generation side (sending end) to the consumption side (receiving end) via high-voltage DC transmission technology. Using the rated frequency f0 of the power system as a reference value (the rated frequency of the power frequency system is 50Hz), the grid frequency deviation is calculated in real time. With frequency change rate This allows for the capture of both the static deviation and dynamic fluctuation trends of the power grid frequency. The standard rated frequency f0 of the power system refers to the standard frequency value set under normal operating conditions. This reference value is the target for power system frequency control and an important indicator for measuring power system frequency stability. While the system frequency reference value may vary in different countries and regions, it is typically around 50Hz or 60Hz. Setting the system frequency reference value requires comprehensive consideration of various factors, including the power system's load characteristics, generation capacity, and transmission distance.

[0065] The formula for calculating frequency deviation is as follows:

[0066] ;

[0067] This frequency deviation reflects the magnitude of the current power grid frequency's offset from the rated power frequency, and is used to determine whether a frequency anomaly has occurred in the power grid and to initiate static primary frequency regulation; frequency change rate It is used to characterize the dynamic rate of frequency drop / rise in the power grid, and can predict the severity of the power grid active power supply and demand imbalance in advance. It provides a dynamic control basis for the rapid support of virtual inertia and makes up for the shortcomings of traditional primary frequency regulation, such as delayed response and inability to suppress rapid frequency fluctuations.

[0068] Step S302: When the frequency deviation exceeds the preset dead zone range, a basic active power increment command is generated based on the preset target virtual inertia coefficient, target frequency modulation coefficient, frequency deviation, and frequency change rate.

[0069] Specifically, to avoid frequent erroneous adjustments of the flexible DC converter station caused by minute frequency fluctuations, measurement noise, and steady-state frequency deviations under normal grid operation conditions, and to improve the steady-state stability of the control system, this paper sets a frequency regulation dead zone threshold and defines the positive dead zone threshold Δf. db+ With negative dead zone threshold Δf db- Construct an ineffective frequency control interval. When the grid frequency deviation is within the dead zone, i.e., satisfying... When the grid frequency is determined to be within the normal steady-state fluctuation range, the system's active power supply and demand are basically balanced, the base frequency support link is locked and not engaged, and the converter station maintains the preset steady-state active power transmission power unchanged to avoid unnecessary power disturbances.

[0070] When the power grid experiences load disturbances, unit output fluctuations, or other fault conditions, causing the frequency offset to exceed the preset dead zone threshold, that is, when the power grid meets the following conditions... (High grid frequency, active power surplus) or When the power grid frequency is too low and there is a shortage of active power, it is determined that there is an effective frequency deviation in the receiving end power grid and the problem of active power supply and demand imbalance is prominent. The basic frequency support control link is immediately unlocked and put into operation, and the active frequency regulation and control logic of the flexible DC system is started.

[0071] The fundamental frequency support element is based on the preset target virtual inertia coefficient H. vsc With the target frequency modulation coefficient K vsc Combined with frequency deviation and rate of change of frequency Generate basic active power increment instructions Among them, the target virtual inertia coefficient H vsc Used to simulate the rotor inertial support characteristics of synchronous generator sets, based on the frequency change rate. Achieve dynamic and rapid support, suppressing instantaneous frequency changes and rapid drops / rises; target frequency modulation coefficient K. vscCorresponding to the static frequency regulation characteristics of traditional power grids, based on the steady-state frequency deviation This achieves steady-state power compensation and corrects static frequency offset errors. The basic active power increment command... It consists of two parts: virtual inertia support and primary frequency modulation. The specific formula is as follows:

[0072] .

[0073] Step S303: According to the preset sliding time window, integrate the power deviation of each moment within the window length before the current moment to obtain the energy deficit within the window length.

[0074] Specifically, the power deviation is integrated over a preset sliding time window for each moment within the window's length preceding the current moment to obtain the energy deficit within the window's length, including:

[0075] Within a preset sliding time window, the ideal supporting power for each moment is generated based on the preset target virtual inertia coefficient, target frequency regulation coefficient, frequency change rate at each moment, grid frequency at each moment, and rated frequency. The power deviation at each moment is calculated based on the actual active power output at the flexible DC grid connection point, the power output at the reference moment, and the corresponding ideal supporting power. The power deviation at each moment is integrated to obtain the energy deficit within the window length. The power output at the reference moment is the power output at the flexible DC grid connection point when the frequency deviation exceeds the preset dead zone range.

[0076] Specifically, to further quantify the dynamic difference between the theoretical support power and the actual output power during flexible DC frequency regulation and accurately characterize the degree of continuous active power imbalance in the receiving-end power grid, this embodiment introduces a sliding time window integration mechanism. By accumulating the power deviation within the window time domain, the system energy deficit is solved, achieving dynamic verification and correction of the frequency support effect. This step uses a preset fixed duration as the sliding window scale and performs point-by-point calculations and integration statistics on all time-series data within a complete window interval prior to the current moment using a real-time time-series traversal method. The complete energy deficit solution process consists of three layers of progressive calculation logic.

[0077] First, construct a structure of length T. w A sliding time window is used, which continuously slides over time to solve for the ideal support power at each moment within the window. Within the entire time domain covered by the sliding time window, the predetermined target virtual inertia coefficient H is used. vsc With the target frequency modulation coefficient K vsc Combined with the real-time power grid frequency f collected at each sampling time t Rated frequency f0 and frequency change rate The ideal support power corresponding to each time-series node is calculated iteratively at each time step. The theoretical frequency modulation power demand timing curve of the flexible DC system under no-delay conditions within the complete reconstruction window period is shown. The ideal supporting power in this embodiment is... To address the inherent lag characteristics of the system, such as communication delay and power response delay, under ideal operating conditions, the flexible DC converter station needs to provide the theoretically optimal active power increment command to the receiving end AC grid in real time to mitigate grid frequency disturbances and balance the system's active power supply and demand imbalance. The specific calculation formula is as follows:

[0078] ;

[0079] Secondly, after detecting that the frequency deviation at the receiving end exceeds the limit and the basic frequency support link is officially put into operation, the actual active power output P at each time point within the time window before the current time is obtained. pcc (t), the time t when the frequency deviation crosses the dead zone threshold. a Based on this, the actual active power output P at each moment of the flexible DC grid connection point is... pcc (t) and reference time t a Reference time power output P pcc (t a The difference is calculated to obtain the actual support power at each moment. The specific calculation formula is as follows:

[0080] .

[0081] Ideal support power at each moment Actual support power at the corresponding time The difference is calculated to obtain the power deviation at the current moment. The specific formula is as follows:

[0082] .

[0083] This power deviation reflects the real-time power deficit caused by the combination of control dead zone and response delay.

[0084] Finally, the time-domain energy deficit is solved by integration. The power deviation of consecutive time series within the sliding time window prior to the current moment is integrated in the time domain, accumulating the instantaneous power deviation over the window duration to obtain the cumulative energy deficit of the power grid within that sliding window interval. The specific calculation formula is as follows:

[0085] ;

[0086] This energy deficit index can effectively reflect the degree of insufficient or excessive regulation of the power of flexible DC frequency modulation over a period of time, making up for the deficiency that a single instantaneous power deviation cannot characterize continuous power imbalance.

[0087] Step S304: Determine the power demand of the flexible DC grid connection point based on the energy deficit, and obtain the available power margin of the flexible DC at the current moment. Upload the power demand and power margin to the coordination controller; receive the compensation power command determined by the coordination controller based on the power demand and power margin of one or more flexible DC grid connection points participating in the support.

[0088] For example, determining the power demand of a flexible DC grid connection point based on the energy deficit includes:

[0089] Divide the energy deficit by the window length to obtain the power demand.

[0090] Specifically, the time-domain cumulative energy deficit obtained by integrating the sliding time window is... Then, remove the energy deficit. s With window length T w To obtain the compensation power requirement The specific calculation formula is as follows:

[0091] .

[0092] Based on the steady-state maximum / minimum operating active power P of the power control station max P min and the initial active power reference value P ref0 Define the flexible DC power margin M to characterize the current adjustable active power margin of the flexible DC system. Its calculation formula is as follows:

[0093] .

[0094] Compensation power demand The power margin M is uploaded to the coordinating controller.

[0095] The coordination controller can receive compensation power demands generated by one or more flexible DC transmissions. If N flexible DC transmissions participate in the support, the coordination controller will number the received compensation power demands generated by the N participating flexible DC transmissions as follows: , … The power margins are numbered M1, M2, ..., M N Introduce a preset proportional gain coefficient K. comp Wherein, the proportional gain coefficient K compThese are tuned control parameters that can be rationally configured based on the inherent characteristics of system communication delay and power response delay to adapt to lag compensation requirements under different operating conditions. A global compensation coefficient μ is defined, and its specific calculation method is as follows:

[0096] .

[0097] The calculation method for the compensation power command for any flexible DC is as follows:

[0098] .

[0099] This compensation mechanism achieves coordinated correction of steady-state and dynamic deviations based on time-domain accumulated energy deviation, which can effectively offset the frequency support error caused by the lag in the flexible DC power response, improve the matching accuracy of frequency modulation power commands, and further optimize the dynamic recovery effect of the receiving-end power grid frequency.

[0100] Step S305: Superimpose the basic active power increment command and the compensation power command to obtain the target active power command value; adjust the actual active power output of the flexible DC grid connection point according to the target active power command value, and input the adjusted actual active power output to the receiving end.

[0101] Specifically, the basic active power increment command generated after the aforementioned frequency exceedance will be... Compensation power command obtained from the energy deficit correction stage After being superimposed, they are jointly added to the initial active power reference value P of the power control station. ref0 This forms the target active power command value P input to the outer loop controller. ref The specific calculation formula is as follows:

[0102] .

[0103] This instruction generation method can simultaneously take into account the dynamic suppression of instantaneous grid frequency, steady-state deviation correction, system delay lag compensation, and the margin of each loop flexible DC, thus achieving an organic combination of coarse adjustment of basic frequency regulation and fine adjustment of deviation compensation.

[0104] The final generated target active power command value P ref Input to each flexible DC outer loop active power controller, relying on the converter station's power closed-loop regulation logic, dynamically correct the operating conditions of the voltage source converter, and adjust the actual active power output P at the flexible DC grid connection point. pccThe controller, through a dual-loop control structure of power outer loop and current inner loop, quickly eliminates the dynamic deviation between actual output power and commanded power, overcomes the impact of disturbances such as power electronic device response lag and system delay, and enables the actual active power output of the converter station to track the optimized active power reference command in real time, ensuring the speed and accuracy of power regulation. The regulated stable active power is continuously fed into the receiving-end AC grid through the flexible DC transmission channel, compensating for the active power deficit caused by load fluctuations and unit disturbances in the receiving-end system, suppressing grid frequency drops and dynamic oscillations, and achieving continuous, high-precision active frequency support for the receiving-end AC grid, completing the entire frequency regulation compensation closed-loop control process.

[0105] Based on this, the actual active power output P of the flexible DC grid connection point is collected in real time. pcc The measured output power is used as a system feedback quantity and is introduced into the power deviation calculation stage within the sliding time window in real time, continuously updating the power deviation and accumulated energy deficit in the time domain at each moment. Through closed-loop feedback iteration of the measured output power, the control stage can correct the dynamic deviation between the theoretical support power and the actual output power in real time, continuously offsetting the regulation lag caused by the delay in flexible DC communication and power response delay, forming a closed-loop adaptive compensation mechanism based on power-energy dual-dimensional feedback. This closed-loop architecture can effectively improve the robustness of frequency regulation control, enabling the active power output of the converter station to accurately match the real-time frequency support requirements of the receiving-end power grid, and improving the frequency dynamic stability and recovery characteristics of the power grid under disturbance conditions.

[0106] Through steps S301 to S305 above, the frequency deviation and frequency change rate between the current grid frequency and the rated frequency at the AC grid sending and receiving ends are calculated in real time. When the frequency deviation exceeds the preset dead zone range, a basic active power increment command is generated based on the preset target virtual inertia coefficient, target frequency regulation coefficient, frequency deviation, and frequency change rate. The power deviation at each moment within the window length before the current moment is integrated according to the preset sliding time window to obtain the energy deficit within the window length. The power demand of the flexible DC grid connection point is determined based on the energy deficit, and the available power margin of the flexible DC at the current moment is obtained. The power demand and power margin are uploaded to the coordination controller. The compensation power command determined by the coordination controller based on the power demand and power margin of one or more flexible DC grid connection points participating in the support is received. The basic active power increment command and the compensation power command are superimposed to obtain the target active power command value. The actual active power output of the flexible DC grid connection point is adjusted according to the target active power command value, and the adjusted actual active power output is input to the receiving end. Compared to existing technologies that directly control via additional frequency, this embodiment calculates the deviation between the ideal support energy and the actual support energy in real time, obtains the available power margin of each flexible DC power line at the current moment, and uses a coordination controller to uniformly allocate compensation power commands based on the power demand and power margin of each flexible DC power line grid connection point. This approach comprehensively considers the needs of each flexible DC grid connection point, continuously compensating for energy deficits. This ensures that the actual frequency support effect of the flexible DC approaches the ideal state of no dead zone and no delay, effectively compensating for power deficits caused by dead zones and delays, improving the system's lowest frequency and steady-state frequency, and enhancing the frequency support capability of the flexible DC. The compensation power command is calculated by averaging historical data within a sliding time window, significantly suppressing high-frequency measurement noise and harmonic interference, thus avoiding negative impacts on the converter and AC grid caused by high-frequency fluctuations in the power command. Furthermore, the compensation stage in this embodiment is superimposed on the traditional grid-connected flexible DC additional frequency control as an add-on module, without altering the original control structure, making it easy to promote and apply in existing projects.

[0107] In some of these embodiments, the preset target virtual inertia coefficient and target frequency regulation coefficient are determined by the maximum active power adjustment of the flexible DC grid connection point under the current operating state, the maximum rate of change of the system under the preset maximum frequency disturbance event, and the maximum frequency deviation.

[0108] Specifically, the target virtual inertia coefficient H vsc and target frequency modulation coefficient K vsc The upper limit value is not arbitrarily set, but is determined comprehensively by combining the operational constraints of the flexible DC system and the extreme disturbance conditions of the power grid. Specifically, it is defined by the maximum active power regulation margin that can be adjusted upwards and downwards under the current steady-state operation of the flexible DC system, as well as the maximum frequency deviation and maximum frequency change rate of the system corresponding to the most severe frequency disturbance scenario of the anticipated power grid fault concentration. This setting method can effectively avoid the problems of converter station power exceeding limits and regulation saturation caused by excessively large coefficient values, while avoiding insufficient frequency regulation support capability caused by excessively small coefficient values. It ensures that the virtual inertia support and primary frequency regulation control capability are adapted to the system power regulation limits and extreme disturbance requirements, and guarantees the safe and effective operation of the control strategy under all operating conditions. The upper limit expressions are as follows:

[0109] ;

[0110] in The maximum active power regulation that can be increased by flexible direct current. The maximum active power regulation that can be reduced by flexible direct current. To anticipate the maximum rate of frequency change under the most severe perturbation, This represents the maximum frequency deviation under the most severe anticipated disturbance.

[0111] In another embodiment, the window length of the preset sliding time window is greater than or equal to the sum of the communication delay of the target active power command value and the response delay of the flexible DC.

[0112] Specifically, the duration parameter T of the sliding time window wThe system needs to be constrained and tuned based on its inherent delay characteristics. To ensure compensation accuracy and control effectiveness, the window length must meet strict constraints.

[0113] ;

[0114] Where T D For the frequency control signal remote communication delay, T R The inherent power response delay of the flexible DC converter station, and the sum of these two delays constitute the total inherent lag time of the entire frequency support control link. Based on this principle, it can be ensured that the sliding window time domain range can fully cover the entire lag process from control signal generation and transmission to converter station power response adjustment. This ensures that the historical time series data accumulated within the window fully includes power deviation information within the delay interval, avoiding problems such as missing lag data and distortion of compensation calculations caused by insufficient window duration. This provides complete and effective time domain data support for subsequent energy deficit integration and delay compensation power correction.

[0115] Meanwhile, window integral averaging can endow the compensation power command with natural low-pass filtering characteristics, and its amplitude-frequency response follows a Sinc function distribution, with the corresponding first zero-point frequency satisfying... Based on this frequency domain characteristic, by reasonably increasing the sliding window length T... w This can shift the first zero point of the amplitude-frequency characteristic to a lower frequency band, effectively filtering out high-frequency fluctuation components introduced by frequency differentiation operation noise, high-frequency disturbances in the power grid, and power measurement errors, suppressing high-frequency oscillations in control commands, and improving the steady-state accuracy and operational robustness of the frequency modulation compensation stage.

[0116] In some embodiments, the compensation power command determination process includes:

[0117] The total system power demand is obtained by summarizing the power demand of each flexible DC grid connection point participating in the support by the coordination controller; the total power margin is obtained by summarizing the power margin of each flexible DC grid connection point participating in the support; the global allocation coefficient is calculated based on the preset global compensation gain and the ratio of the total system power demand to the total power margin; the global allocation coefficient is multiplied by the power margin of each corresponding flexible DC grid connection point to obtain the compensation power command.

[0118] Specifically, following the method in step S304 above, the power demand of each participating flexible DC grid connection point is calculated, and the calculated power demands of each flexible DC grid connection point are added together to obtain the total system power demand. The power margin of each participating flexible DC is obtained, and the power margins of each flexible DC are added together to obtain the total power margin. The global allocation coefficient μ is calculated by the coordination controller based on the preset global compensation gain and the ratio of the total system power demand to the total power margin. The specific calculation formula is as follows:

[0119] ;

[0120] Multiplying the global allocation coefficient μ by the power margin of each corresponding flexible DC grid connection point yields the compensation power command:

[0121] .

[0122] Furthermore, as the core control parameter in the compensation process, the proportional gain coefficient K... comp With sliding window length T w Significant dynamic coupling constraint characteristics exist: increasing the proportional gain coefficient K comp While it can significantly improve the power lag compensation amplitude and accelerate the frequency deviation correction speed, excessively high gain can compress the gain margin and phase margin of the control system, weaken the system's damping characteristics, and easily lead to problems such as power command oscillation and regulation instability. Therefore, the window length T w With proportional gain coefficient K comp Since it cannot be tuned independently, it requires a hard constraint on the stability margin of the control system. A synergistic optimization is needed, comprehensively balancing the compensation response speed and high-frequency noise suppression capability, to achieve the optimal match between the speed of delay compensation and the smoothness of steady-state operation while ensuring the stability and reliability of the control closed loop. This is based on the adjusted proportional gain coefficient K. comp According to the above compensation power command calculation formula, "Recalculate the global allocation coefficient μ to further enhance the frequency support capability of flexible DC transmission."

[0123] In some embodiments, the global allocation coefficient is limited based on a preset value range, restricting the global allocation coefficient to within the preset value range; when the global allocation coefficient reaches the boundary value of the value range, a preset emergency control strategy is triggered.

[0124] Specifically, when the global allocation coefficient μ exceeds the boundary of [-1,1], it needs to be limited to [-1,1], and an emergency control strategy, such as low-frequency load reduction, needs to be activated.

[0125] Based on the flexible DC frequency support control method described in the above embodiments, for Figure 2 The flexible DC transmission system shown has the following system parameters: Units G1 and G2 in Region 1 each have an output of 700MW, with load L1 of 1159MW; Units G3 and G4 in Region 2 each have an output of 700MW, with load L2 of 1575MW; the rated transmission capacity of the flexible DC system is 500MW, using grid-connected control, with constant active power at the sending end and constant DC voltage at the receiving end. During normal operation, the reference value for active power at the sending end is set to 200MW. The simulation system characteristic parameters are set as follows: communication delay T... D =30ms, the flexible DC equivalent power response delay T obtained from the power step test adjustment. R=60ms. The above delay parameter reflects the inherent response characteristics of the simulated flexible DC system.

[0126] In addition, the control parameters set based on the method of this embodiment are as follows: the dead zone threshold is symmetrically set to... Target virtual inertia coefficient Target frequency modulation coefficient After optimization, the parameters of the compensation stage were selected. , .

[0127] For the operating condition of a 160MW power step disturbance (approximately 10% of the total AC system load in Region 2) occurring at load L2 in Region 2, simulations were conducted to compare the following three scenarios: ① Flexible DC without active support strategy (no active support); ② Flexible DC with traditional additional frequency control (traditional support method); ③ Flexible DC with the control method described in this embodiment (proposed support method). Table 1 shows the key frequency support indicators for this embodiment:

[0128] Table 1

[0129]

[0130] Figure 4 These are frequency response curves of the AC power grid in receiving-end region 2 under three different scenarios in this embodiment. Figure 4 The horizontal axis represents time, and the vertical axis represents the AC power grid frequency (Hz). Figure 5 These are the active power output curves of the receiving-end region 2 under three different scenarios in this embodiment. Figure 5 The horizontal axis represents time, and the vertical axis represents the flexible DC active power output (MW). From Figure 4 , Figure 5 As shown in Table 1, compared with not applying an active support strategy, the flexible DC frequency support control method described in this embodiment can rapidly increase active power, effectively suppress frequency drops in the receiving-end AC grid, and significantly improve both the system's lowest frequency and steady-state frequency. Compared with traditional additional frequency control, the compensation stage further compensates for the power deficit caused by dead zones and delays, resulting in improvements in both maximum support power and steady-state support power. The lowest frequency and steady-state frequency are further improved, and the compensation power command remains smooth without triggering power oscillations. These results verify the effectiveness and engineering applicability of the flexible DC frequency support control method described in this embodiment.

[0131] Figure 6 This is a structural diagram of a multi-infeed flexible DC transmission system based on the flexible DC frequency support control method described in this embodiment. Figure 6 The system parameters for the multi-infeed flexible DC transmission system shown are as follows:

[0132] Three flexible DC transmission lines, HVDC1, HVDC2, and HVDC3, are fed into the receiving-end power grid, each with a rated active power transmission capacity of 660MW. All lines employ grid-following control, with a fixed active power at the sending end and a fixed DC voltage at the receiving end. During normal operation, the reference values ​​for the active power at the sending end are set to 650MW, 632MW, and 540MW, respectively. The characteristic parameters of the three flexible DC simulation system are all set as follows: communication delay TD = 30ms, and the equivalent power response delay TR obtained from the power step test adjustment = 60ms. These delay parameters reflect the inherent response characteristics of the simulated flexible DC system.

[0133] In addition, the control parameters set based on the method of this embodiment are as follows: the dead zone threshold is symmetrically set to... Target virtual inertia coefficient Target frequency modulation coefficient After optimization, the parameters of the compensation stage were selected. , .

[0134] For the N-1 outage of synchronous generator No. 30 in the receiving-end power grid, simulations were conducted to compare the following three scenarios: ① Flexible DC without active support strategy (no active support); ② Flexible DC with traditional additional frequency control (traditional support method); ③ Flexible DC with the control method described in this embodiment (proposed support method). Table 2 shows the key frequency support indicators for this embodiment:

[0135] Table 2

[0136]

[0137] Figure 7 This is a graph showing the frequency response of the receiving-end AC grid under three different conditions for the multi-infeed flexible DC transmission system of this embodiment. Figure 7 The horizontal axis represents time, and the vertical axis represents the AC power grid frequency (Hz). Figure 8 This is a graph showing the active power output curves of the multi-infeed flexible DC transmission system in the receiving-end region under three different conditions, according to this embodiment. Figure 8 The horizontal axis represents time, and the vertical axis represents the flexible DC active power output (MW). From Figure 7 , Figure 8As shown in Table 2, compared with not applying an active support strategy, the flexible DC frequency support control method described in this embodiment enables the flexible DC to rapidly increase active power, effectively suppressing frequency drops in the receiving-end AC grid, and significantly improving both the system's minimum frequency and steady-state frequency. Compared with traditional additional frequency control, the compensation stage further compensates for the power deficit caused by dead zones and delays, reducing the support burden of flexible DC with insufficient margin, while flexible DC with sufficient margin undertakes more compensation power. The overall system minimum frequency is improved, and both the minimum frequency and steady-state frequency are further improved. Moreover, the compensation power command remains smooth and does not induce power oscillations. The above results verify the effectiveness and engineering applicability of the flexible DC frequency support control method in this embodiment.

[0138] This embodiment also provides a flexible straight frequency support control method. Figure 9 This is a flowchart of another flexible DC frequency support control method in this embodiment, such as... Figure 9 As shown, the process includes the following steps:

[0139] Step S901: Calculate in real time the frequency deviation and frequency change rate between the current grid frequency and the rated frequency at the receiving end of the AC grid.

[0140] Step S902: When the frequency deviation exceeds the preset dead zone range, a basic active power increment command is generated based on the preset target virtual inertia coefficient, target frequency modulation coefficient, frequency deviation and frequency change rate.

[0141] Step S903: Within a preset sliding time window, based on the preset target virtual inertia coefficient, target frequency regulation coefficient, frequency change rate at each moment, grid frequency at each moment, and rated frequency, the ideal support power at each moment is generated; based on the actual active power output at each moment of the flexible DC grid connection point, the power output at the reference moment, and the corresponding ideal support power at each moment, the power deviation at each moment is calculated; the power deviation at each moment is integrated to obtain the energy deficit within the window length.

[0142] Step S904: Divide the energy deficit by the window length to obtain the power demand, and obtain the available power margin of the flexible DC at the current moment. Upload the power demand and power margin to the coordinating controller.

[0143] Step S905: The power demand of each flexible DC grid connection point participating in the support is summarized by the coordination controller to obtain the total power demand of the system; the power margin of each flexible DC grid connection point participating in the support is summarized to obtain the total power margin; the global allocation coefficient is calculated based on the preset global compensation gain and the ratio of the total power demand of the system to the total power margin; the global allocation coefficient is multiplied by the power margin of each corresponding flexible DC grid connection point to obtain the compensation power command.

[0144] Step S906: Receive the compensation power command, and superimpose the basic active power increment command and the compensation power command to obtain the target active power command value.

[0145] Step S907: Adjust the actual active power output of the flexible DC grid connection point according to the target active power command value, and input the adjusted actual active power output to the receiving end.

[0146] Through steps S901 to S907, compared with the prior art of directly adding frequency control, this embodiment calculates the deviation between the ideal support energy and the actual support energy in real time, obtains the available power margin of each flexible DC at the current moment, and obtains a compensation power command by coordinating the controller to uniformly allocate power according to the power demand and power margin of each flexible DC grid connection point. This compensation power command comprehensively considers the needs of each flexible DC grid connection point, continuously compensating for energy deficits, making the actual frequency support effect of the flexible DC approach the ideal state of no dead zone and no delay, thus improving the frequency support capability of the flexible DC. Furthermore, this embodiment uses the actual power of the flexible DC grid connection point as the feedback quantity, and compensates for the power deficit caused by dead zone and delay through continuous integral compensation of energy deviation; the integral averaging characteristic of the sliding time window can effectively smooth the compensation power command and suppress high-frequency noise introduced by the frequency differentiation link and power measurement; finally, the compensation link is superimposed on the traditional grid-connected flexible DC additional frequency control in the form of an additional module, without changing the original control structure, and has good engineering applicability.

[0147] This embodiment also provides a flexible direct current frequency support control device, which is used to implement the above embodiments and preferred embodiments, and will not be repeated as described previously. The terms "module," "unit," "subunit," etc., used below can refer to a combination of software and / or hardware that performs a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0148] Figure 10 This is a structural block diagram of the flexible straight frequency support control device in this embodiment, as shown below. Figure 10 As shown, the device includes: a basic active power increment command generation module 11, a compensation power demand generation module 12, a coordination control module 13, and a control module 14.

[0149] The basic active power increment command generation module 11 is used to calculate the frequency deviation and frequency change rate between the current grid frequency and the rated frequency at the receiving end of the AC grid in real time; when the frequency deviation exceeds the preset dead zone range, it generates a basic active power increment command based on the preset target virtual inertia coefficient, target frequency regulation coefficient, frequency deviation and frequency change rate.

[0150] The power demand generation module 12 is used to integrate the power deviation of each moment within a window length period before the current moment according to a preset sliding time window to obtain the energy deficit within the window length period; and generate the power demand of the flexible DC grid connection point based on the energy deficit.

[0151] The coordination control module 13 is used to summarize the power demand of each flexible DC grid connection point participating in the support to obtain the total power demand of the system; summarize the power margin of each flexible DC grid connection point participating in the support to obtain the total power margin; calculate the global allocation coefficient based on the preset global compensation gain and the ratio of the total power demand of the system to the total power margin; and multiply the global allocation coefficient by the power margin of each corresponding flexible DC grid connection point to obtain the compensation power command.

[0152] The control module 14 is used to superimpose the basic active power increment command and the compensation power command to obtain the target active power command value; and to control the actual active power output of the flexible DC grid connection point according to the target active power command value, and input the adjusted actual active power output to the receiving end.

[0153] Figure 11 This is a preferred structural block diagram of the flexible straight frequency support control device in this embodiment, as shown below. Figure 11 As shown, the device includes a basic support power generation module, a compensation demand calculation module, a dead zone judgment module, a power margin calculation module, a coordination controller, and a power control station outer loop controller.

[0154] The system collects the receiving-end power grid frequency f in real time and calculates the frequency deviation. With frequency change rate By setting a preset frequency dead zone, erroneous adjustments caused by steady-state small fluctuations and measurement noise are avoided. The control loop only engages when the frequency deviation exceeds the limit, based on a preset virtual inertia coefficient H. vsc s and frequency modulation coefficient K vsc Generate basic active power increment commands containing inertial support and primary frequency regulation. .

[0155] To compensate for the control lag caused by the delay in flexible DC communication and the power response delay, a method is introduced that satisfies... The constrained sliding time window is based on a preset virtual inertia coefficient H. vsc s, frequency modulation coefficient K vsc Actual active power output at each time point Rate of change of frequency at each time point The power deviation at each moment is generated by considering the grid frequency f and the rated frequency f0. The time-domain energy deficit is statistically calculated using window integration. The delay compensation power requirement is generated through average calculation. Window integration possesses the low-pass filtering characteristics of the Sinc function, effectively suppressing high-frequency measurement noise, while T... w With K comp The system needs to be tuned in a way that balances stability margin, response speed, and noise reduction capability.

[0156] Calculate the power margin M of the flexible DC at the current moment to compensate for the power demand. The power margin M is uploaded to the coordination controller. The system receives compensation power commands from the coordination controller, which are uniformly allocated based on the power demand and power margin of one or more flexible DC-DC grid connection points participating in the support. .

[0157] Will and The initial active power reference value P is corrected after superposition. ref0 The final target active power command value P is obtained. ref The active power output of the flexible DC grid connection point is regulated by the outer loop controller of the power control station. The system collects the actual active power output P. pcc The closed-loop feedback to the deviation calculation stage forms a complete adaptive closed-loop control, which accurately compensates for the active power deficit of the receiving-end power grid and effectively improves the frequency dynamic stability of the interconnected power grid.

[0158] It should be noted that the above modules can be functional modules or program modules, and can be implemented through software or hardware. For modules implemented through hardware, the above modules can reside in the same processor; or the above modules can be located in different processors in any combination.

[0159] This embodiment also provides a computer device, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the method described in any of the above method embodiments.

[0160] Furthermore, in conjunction with the flexible DC frequency support control method provided in the above embodiments, this embodiment can also provide a storage medium for implementation. The storage medium stores a computer program; when executed by a processor, the computer program implements any of the flexible DC frequency support control methods described in the above embodiments.

[0161] It should be understood that the specific embodiments described herein are merely illustrative of the application and not intended to limit it. All other embodiments derived by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0162] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties.

[0163] Obviously, the accompanying drawings are merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar situations based on these drawings without any creative effort. Furthermore, it is understood that although the work done in this development process may be complex and lengthy, for those skilled in the art, certain design, manufacturing, or production modifications made based on the technical content disclosed in this application are merely conventional technical means and should not be considered as insufficient disclosure of this application.

[0164] The term "embodiment" in this application refers to a specific feature, structure, or characteristic described in connection with an embodiment that may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily imply the same embodiment, nor does it imply that it is mutually exclusive with or independent of other embodiments. It will be clearly or implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0165] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments described above. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0166] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of patent protection. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. A flexible direct current frequency support control method, characterized in that, include: Real-time calculation of the frequency deviation and rate of change between the current grid frequency and the rated frequency at the receiving end of the AC power grid; When the frequency deviation exceeds the preset dead zone range, a basic active power increment command is generated based on the preset target virtual inertia coefficient, target frequency modulation coefficient, the frequency deviation, and the frequency change rate. By integrating the power deviation at each moment within the window length before the current moment according to the preset sliding time window, the energy deficit within the window length is obtained. Based on the energy deficit, determine the power demand of the flexible DC grid connection point, obtain the available power margin of the flexible DC at the current moment, and upload the power demand and the power margin to the coordination controller. Receive the compensation power command determined by the coordination controller based on the power demand and power margin of one or more flexible DC grid connection points participating in the support; The base active power increment command and the compensation power command are superimposed to obtain the target active power command value; Adjust the actual active power output of the flexible DC grid connection point according to the target active power command value, and input the adjusted actual active power output to the receiving end.

2. The flexible linear frequency support control method according to claim 1, characterized in that, The step of integrating the power deviation at each moment within a preset sliding time window to obtain the energy deficit within the window length includes: Within a preset sliding time window, the ideal support power at each moment is generated based on the preset target virtual inertia coefficient, target frequency regulation coefficient, frequency change rate at each moment, grid frequency at each moment, and the rated frequency. Based on the actual active power output at each moment of the flexible DC grid connection point, the power output at the reference moment, and the corresponding ideal support power at each moment, the power deviation at each moment is calculated. Integrating the power deviation at each time point yields the energy deficit within the window length.

3. The flexible straight frequency support control method according to claim 2, characterized in that, The reference time power output is the power output of the flexible DC grid connection point at the moment when the frequency deviation exceeds the preset dead zone range.

4. The flexible direct current frequency support control method according to claim 1, characterized in that, The preset target virtual inertia coefficient and the target frequency regulation coefficient are determined by the maximum active power adjustment of the flexible DC grid connection point under the current operating state, the maximum rate of change of the system under the preset maximum frequency disturbance event, and the maximum frequency deviation.

5. The flexible linear frequency support control method according to claim 1, characterized in that, The window length of the preset sliding time window is greater than or equal to the sum of the communication delay of the target active power command value and the response delay of the flexible direct current.

6. The flexible direct current frequency support control method according to claim 1, characterized in that, The determination of the power demand of the flexible DC grid connection point based on the energy deficit includes: The power requirement is obtained by dividing the energy deficit by the window length.

7. The flexible direct current frequency support control method according to claim 1, characterized in that, The compensation power command determination process includes: The total power demand of the system is obtained by summing the power demand of each flexible DC-DC grid connection point participating in the support through the coordination controller. The total power margin is obtained by summing up the power margins of each flexible DC power unit involved in the support. The global allocation coefficient is calculated based on the preset global compensation gain and the ratio of the total power demand of the system to the total power margin. The compensation power command is obtained by multiplying the global allocation coefficient by the power margin of each corresponding flexible DC grid connection point.

8. The flexible straight frequency support control method according to claim 7, characterized in that, The method further includes: Based on a preset value range, the global allocation coefficient is subjected to amplitude limiting processing, restricting the global allocation coefficient to the preset value range. When the global allocation coefficient reaches the boundary value of the value range, a preset emergency control strategy is triggered.

9. A flexible straight frequency support control device, characterized in that, include: The module includes a basic active power increment command generation module, a compensation power demand generation module, a coordination control module, and a control module. The basic active power increment command generation module is used to calculate in real time the frequency deviation and frequency change rate between the current grid frequency and the rated frequency at the receiving end of the AC grid; when the frequency deviation exceeds the preset dead zone range, the basic active power increment command is generated based on the preset target virtual inertia coefficient, target frequency regulation coefficient, the frequency deviation and the frequency change rate. The compensation power demand generation module is used to integrate the power deviation at each moment within a window length period before the current moment according to a preset sliding time window to obtain the energy deficit within the window length period; and generate the power demand of the flexible DC grid connection point based on the energy deficit. The coordination and control module is used to summarize the power demand of each flexible DC grid connection point participating in the support to obtain the total power demand of the system. The total power margin is obtained by summing up the power margins of each flexible DC power supply participating in the support; the global allocation coefficient is calculated based on the preset global compensation gain, the ratio of the total power demand of the system to the total power margin; the global allocation coefficient is multiplied by the power margin of each corresponding flexible DC power supply point to obtain the compensation power command. The control module is used to superimpose the basic active power increment command and the compensation power command to obtain the target active power command value. The system controls the actual active power output of the flexible DC grid connection point according to the target active power command value, and inputs the adjusted actual active power output to the receiving end.

10. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 8.

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