New energy and direct current cooperative control method and system for improving frequency stability

Abstract

The invention provides a new energy and direct current cooperative control method and system for improving frequency stability. The method comprises the steps that the direct current voltage and frequency of a sending end converter station are monitored in real time; when the frequency fluctuation of the sending end converter station is greater than a set value, judging that large disturbance occurs; obtaining power given bias based on the deviation between the square of the DC voltage of the monitoring sending end converter station and the square of the reference value of the DC voltage and a bias droop coefficient; and compensating the active power vacancy caused by disturbance by adjusting the power given bias, and obtaining the new energy output by adjusting the value of the bias droop coefficient.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy coordinated control, and in particular, relates to a method and system for coordinated control of new energy and direct current for improving frequency stability. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Under the background of energy transformation, the power system is gradually evolving from the traditional model to a new power system dominated by large-scale new energy such as wind power and photovoltaics. The construction of new energy bases has been developed by making full use of the rich wind and solar energy resources in deserts, Gobi and desert areas. In the next few years, the construction of about 455GW of wind and solar bases will be completed in China.

[0004] At present, wind turbines and photovoltaic power generation units in new energy bases generally use grid-following control converters with small inertia and weak anti-disturbance capabilities, which leads to a decrease in system inertia level and reduced voltage stability.

[0005] In the face of these challenges, grid-connected converters need to be introduced to enhance the system's regulation capability and stability.

[0006] The problems existing in the transmission of large-scale renewable energy DC power transmission systems using grid-connected converters are as follows: the power and status information of photovoltaic and wind turbines is not easy to obtain quickly and reliably, and the instantaneous power loss or permanent power loss in the DC transmission channel system is difficult to identify in a timely and effective manner.

[0007] At the same time, when large-scale renewable energy is transmitted through the DC transmission system, it becomes more difficult to obtain power and status information. The current method of obtaining power and status information is as follows: the system continuously collects the DC voltage and frequency of the sending-end converter station through a real-time monitoring device, and transmits the data to the control module for analysis.

[0008] The reason why the above methods are difficult to obtain: In large-scale new energy and DC transmission systems, it is quite challenging to obtain real-time power and frequency data. First, since new energy bases are often distributed in remote areas such as deserts and Gobi, it is difficult for sensors to maintain high precision in extreme environments, which affects the accuracy of the data. Secondly, delays and data loss often occur during the signal transmission process of long-distance DC transmission, making it difficult for the system to respond in time when monitoring large disturbances. Finally, the frequency response and voltage changes of each node need to be obtained synchronously, but the nodes in the system are widely distributed, and it is difficult to aggregate information. As a result, these technical difficulties in the acquisition process increase the complexity of the system to achieve efficient collaborative control. Subsequently, instantaneous or permanent power losses in the DC transmission channel are also difficult to effectively identify and handle. Summary of the invention

[0009] In order to overcome the deficiencies of the above-mentioned prior art, the present invention provides a method for coordinated control of renewable energy and direct current to enhance frequency stability, which is used to enhance renewable energy sites and realize effective integration of renewable energy power generation and stable operation of the power system through active power-frequency control.

[0010] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions:

[0011] In the first aspect, a method for coordinated control of new energy and direct current for improving frequency stability is disclosed, including:

[0012] Real-time monitoring of DC voltage and frequency at the sending-end converter station;

[0013] When the frequency fluctuation of the sending-end converter station is greater than the set value, it is judged that a large disturbance has occurred;

[0014] When a large disturbance occurs, the power given bias is obtained based on the deviation between the square of the DC voltage of the sending-end converter station and the square of its reference value and the bias droop coefficient;

[0015] By adjusting the active power given bias, the active power shortage caused by the disturbance is compensated, and by adjusting the value of the bias droop coefficient, the new energy output is obtained.

[0016] As a further technical solution, it also includes:

[0017] The defined index S is used to indicate the degree of change in the system frequency response;

[0018]

[0019] Where: Δf max,COI is the maximum frequency deviation of the system inertia center; ΔP d is the initial power disturbance; N is the number of nodes;

[0020] The index S reflects the significance of the frequency response distribution to a certain extent, that is, the larger the S value is, the more significant the temporal and spatial distribution of the system frequency response is;

[0021] The frequency threshold is then set based on the degree of frequency response change.

[0022] As a further technical solution, the power given bias is obtained based on the deviation of the square of the DC voltage of the sending-end converter station from the square of its reference value and the bias droop coefficient, which is specifically:

[0023]

[0024] Where: ΔP is the active power given bias; K dc is the bias droop coefficient, V dcThe DC voltage from the inverter DC side of the sending-end converter station, V dc_ref is a given reference value.

[0025] As a further technical solution, when adjusting the value of the bias droop coefficient:

[0026] When the frequency change rate is less than the frequency change rate threshold set in the state of too small shortage of new energy and when the frequency change rate is less than the frequency change rate threshold set in the state of too large shortage of new energy, different bias droop coefficients are used.

[0027] Secondly, a coordinated control system of new energy and direct current for improving frequency stability is disclosed, including:

[0028] The data acquisition module is configured to: monitor the DC voltage and frequency of the sending-end converter station in real time;

[0029] The disturbance judgment module is configured to: when the frequency fluctuation of the sending-end converter station is greater than a set value, judge that a large disturbance occurs;

[0030] The active power given bias acquisition module is configured to: obtain the active power given bias based on the deviation between the square of the DC voltage of the sending-end converter station and the square of its reference value and the bias droop coefficient;

[0031] The control module is configured to: compensate for the active power shortage caused by disturbance by adjusting the active power given bias, and obtain the new energy output by adjusting the value of the bias droop coefficient.

[0032] One or more of the above technical solutions have the following beneficial effects:

[0033] The technical solution of the present invention monitors the DC voltage and frequency of the sending-end converter station in real time, and determines whether a large disturbance occurs according to a set frequency fluctuation threshold. For example, when the frequency fluctuation amplitude exceeds a preset value, the disturbance judgment module immediately identifies a fault signal.

[0034] After identifying a large disturbance, the system compensates for the power shortage by dynamically adjusting the active power given bias. At the same time, by optimizing the bias droop coefficient K dc The value of enables the output of renewable energy to flexibly respond to load fluctuations, thereby achieving precise regulation and stable control of system frequency. For example, when the power shortage is large, the system sets the droop coefficient to a smaller value to enhance the response speed; and when the power shortage is small, a larger droop coefficient is set to achieve flexible regulation.

[0035] Through the above identification and processing mechanism, this application effectively improves the frequency stability of the system, allowing renewable energy power generation and DC transmission to achieve coordinated operation and dynamic balance under large disturbance conditions.

[0036] The technical solution of this application is a systematic and practical multi-device dynamic collaborative control strategy for energy flow, which not only takes advantage of the control of each device, but also ensures the stable operation of the entire system under dynamic flow fluctuations to improve the frequency stability of the sending-end system.

[0037] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0039] Figure 1 This is a control structure diagram of a grid-type converter according to an embodiment of the present invention;

[0040] Figure 2 This is an active power control strategy diagram of an embodiment of the present invention;

[0041] Figure 3 (a) and (b) are schematic diagrams of the frequency change and frequency change rate of each node in the system respectively;

[0042] Figure 4 (a) and (b) are schematic diagrams of frequency change and frequency change rate change under working condition 1, respectively;

[0043] Figure 5 (a) and (b) are schematic diagrams of frequency change and frequency change rate change under working condition 2, respectively;

[0044] Figure 6 (a) is a schematic diagram for comparing the frequency change rate under working condition 1; (b) is a schematic diagram for comparing the frequency change rate under working condition 2. DETAILED DESCRIPTION

[0045] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0046] It should be noted that the terms used herein are for describing specific embodiments only and are not intended to be limiting of exemplary embodiments according to the present invention.

[0047] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0048] For new energy bases located in deserts, Gobi and wasteland areas, because they use grid-following control converters with small inertia and weak anti-disturbance ability, they face the problems of system inertia reduction and voltage stability.

[0049] Therefore, the technical solution of this embodiment proposes a coordinated control strategy of grid-connected renewable energy and direct current to improve frequency stability, and realizes the effective integration of renewable energy generation and the stable operation of the power system through active power-frequency control.

[0050] First, the system frequency distribution characteristics are analyzed:

[0051] Firstly, based on the new energy station model of the grid-building technology, the frequency distribution of each node in the system is analyzed. The active power control of the sending-end converter station adopts virtual synchronous machine control, the reactive power control adopts droop control, and the control block diagram of the sending-end converter station using grid-building control is shown in the figure. Figure 1 As shown. During the analysis, the new energy station model of the network-building technology was used to simulate the frequency response characteristics of each node under different working conditions. The analysis used real-time monitoring data and combined it with quantitative indicators of frequency fluctuations (such as frequency change rate) to observe the frequency distribution characteristics of each node.

[0052] When a large disturbance fault occurs at the sending end of the renewable energy power system, a control strategy needs to be designed to adjust the renewable energy output to restore normal operation. The strategy starts with the frequency of the system. The frequency of the system will change after a large disturbance fault occurs. First, the frequency distribution of the power system must be quantitatively analyzed, and then the frequency threshold is set according to the degree of frequency change. The relevant parameters in the control strategy are adjusted according to the threshold, thereby adjusting the renewable energy output and bringing the system to a new balance.

[0053] In order to quantify the frequency distribution characteristics of the power system, the following quantitative indicators and methods are used: First, the significance of the frequency response is measured by calculating the maximum frequency deviation and frequency change rate (RoCoF) of each node. Specifically, the frequency deviation reflects the maximum frequency change amplitude of the node, while the frequency change rate is used to describe the rate at which the frequency decreases or increases when a disturbance occurs. By accumulating the maximum frequency deviation of each node, the frequency response distribution characteristics of the entire system can be quantified.

[0054] By quantitatively analyzing the frequency variation characteristics of the system, a reasonable frequency variation threshold can be set to guide the response parameters in the control strategy. For example, based on historical data and simulation results, a specific frequency deviation value is set as a threshold (e.g., ±0.05Hz). When the frequency deviation of certain nodes in the system exceeds this threshold, it is determined to be a large disturbance state. At this time, the control system will initiate emergency adjustment measures to maintain frequency stability.

[0055] According to the judgment result of the frequency threshold, the system can dynamically adjust the relevant parameters in the control strategy to adapt to the current frequency change. For example, when the frequency deviation exceeds the threshold, the control system will reduce the active power bias of the renewable energy power generation unit to compensate for the power shortage caused by large disturbances. At the same time, by adjusting the bias droop coefficient, the renewable energy output can respond smoothly and gradually adjust the system frequency to a balanced state. This ensures that the system achieves stability and dynamic balance under frequency fluctuations.

[0056] The maximum frequency change rate indicator is used to describe the frequency response of the node. The frequency change rate is the ratio of the frequency drop value in the frequency rapid drop section after the disturbance occurs to the corresponding time width. In order to characterize the "dispersion degree" of the frequency response in the entire system, the defined indicator S is used to indicate the degree of change of the system frequency response.

[0057]

[0058] Where: Δf max,COI is the maximum frequency deviation of the system inertia center; ΔP d is the initial power disturbance; N is the number of nodes. The index S reflects the significance of the distribution of frequency response to a certain extent, that is, the larger the S value, the more significant the temporal and spatial distribution of the system frequency response.

[0059] The calculation of the maximum frequency change rate is based on the speed at which the system frequency decreases after a disturbance occurs. Specifically, in the interval where the frequency decreases rapidly, the ratio of the frequency decrease amplitude to the corresponding time width is calculated to obtain the frequency change rate of the interval. This frequency change rate can be calculated for each node, and the maximum value of each node is the maximum frequency change rate of the node.

[0060] The maximum frequency change rate and index S play an important role in frequency response analysis. The maximum frequency change rate is used to determine the node's ability to respond quickly under disturbance conditions, helping to identify the fastest or most vulnerable nodes. Index S characterizes the spatial distribution of the system's frequency response. The larger the S value, the greater the dispersion of the system's frequency response, and the greater the frequency deviation differences in different regions.

[0061] Through these indicators, the system can identify areas where the frequency response is weak or scattered, so that the control strategy can focus on adjusting these areas, optimize the balance of the frequency response, and improve the overall stability of the system. These analysis results provide data support for the optimization of the system frequency control strategy.

[0062] Through the analysis of the system frequency distribution, first, the frequency changes of each node in the system show a consistent trend overall, but when a large disturbance occurs, the frequency responses of different nodes show significant differences. In particular, the frequency fluctuations of nodes farther away from the DC bus are greater, which shows that the electrical distance has a direct impact on the stability of the node frequency.

[0063] In addition, the analysis also found that the distribution characteristics of node frequencies are closely related to the geographical distribution and electrical distance of the nodes. These results show that the frequency deviation is more significant in some areas of the system, which can be the focus of subsequent control strategies to more effectively improve the overall frequency stability of the system.

[0064] The analysis results provide a basis for designing frequency control strategies, enabling the control system to dynamically adjust and compensate for high frequency deviation areas preferentially according to the frequency distribution characteristics, thereby enhancing the coordinated stability of renewable energy and DC transmission systems.

[0065] The above analysis of the system frequency characteristics shows that the system frequency will increase when a large disturbance occurs. The farther the new energy generation part is from the system DC bus, the greater the value of S will be. Figure 2 The difference between the active reference value and the active measurement value increases, so it is necessary to design a control strategy to reduce the difference between them and improve the stability of the system.

[0066] By analyzing the frequency distribution characteristics of the model, the differences in the responses of different nodes to disturbances are clarified, providing a basis for identifying areas with large frequency fluctuations. In particular, nodes far away from the DC bus show more significant frequency fluctuations, a finding that can be used to optimize frequency control strategies.

[0067] In addition, through the analysis model, the results help the system allocate frequency regulation resources more accurately when large disturbances occur. For nodes with weaker frequency response, more regulation resources can be allocated preferentially to ensure that the system can quickly restore balance under large disturbance conditions. This result directly supports the coordinated control of the system, allowing each node to better cooperate in frequency control to improve the overall response speed and frequency stability.

[0068] In summary, the frequency distribution characteristics obtained through the analysis of the new energy station model of the grid-building technology not only provide a basis for dynamic adjustment and precise control, but also significantly improve the system's frequency stability and ability to adapt to large-scale new energy grid connection.

[0069] The sub-technical solution of this embodiment designs a new control strategy, which aims to reduce the difference between the active reference value and the active measurement value when a fault occurs, thereby improving system stability.

[0070] In order to cope with the significant fluctuation of system frequency under large disturbances, the core of this control strategy is to enhance the stability of the system by adjusting the difference between the reference value and the measured value of active power. Specifically, a droop control strategy based on DC capacitor voltage is designed to deal with the active power difference of the system during faults, and the DC voltage on the DC converter station side is introduced into the outer loop control of active power as the basis for regulation.

[0071] The droop control strategy based on DC capacitor voltage is as follows: When a fault occurs, the DC capacitor voltage usually increases, and this change reflects the deviation of active power supply and demand in the system. The droop control strategy monitors this voltage change and dynamically adjusts the active power bias to achieve power compensation regulation.

[0072] Since the DC capacitor voltage on the inverter side will increase during a fault, it is considered to add the square of the voltage at the DC capacitor voltage on the converter side and the droop characteristics of the active power to the active power outer loop of the DC converter station, as shown in formula (2).

[0073]

[0074] Where: ΔP is the active power given bias; K dc is the bias droop coefficient. V dc The DC voltage from the inverter DC side of the sending-end converter station, V dc_ref is a given reference value.

[0075] Embodiment 1

[0076] This embodiment discloses a method for collaboratively controlling new energy and direct current to improve frequency stability, including:

[0077] Step 1: Real-time monitoring of frequency and voltage: First, the system monitors the DC voltage and frequency changes of the sending-end converter station in real time and analyzes their deviation from the reference value. By monitoring the frequency fluctuation, when it exceeds the threshold, it is determined whether the system is in a state of large disturbance.

[0078] Step 2: Droop control adjustment: When a large disturbance occurs in the system, the control system automatically adjusts the droop control coefficient K dc , specifically:

[0079] If the system active power shortage is large (i.e. the frequency deviation is large), set it to a smaller value to enhance system stability;

[0080] If the system active power deficit is small (ie the frequency deviation is small), it is set to a larger value to achieve more flexible power regulation.

[0081] Step 3: Introduce active power regulation: By adjusting ΔP, the active power shortage caused by the disturbance is compensated, so that the system gradually returns to a stable state. In this process, the output of the new energy power generation unit is adjusted by adjusting K dc To smooth the changes and avoid the impact of large fluctuations on the system.

[0082] The system first calculates the current active power bias value ΔP and then uses the bias droop coefficient K dc The output of the renewable energy power generation unit is optimized by adjustment. (Formula 2)

[0083] The adjustment process is carried out dynamically according to the degree of disturbance: when the power shortage is large, the system increases K dc value to increase the active power bias and quickly compensate for the shortfall; when the power shortfall is small, appropriately reduce K dc This dynamic adjustment allows the system to flexibly respond to different power requirements and maintain stable output.

[0084] Step 4: Improved control block diagram: Figure 2 As shown in the figure, the improved active power control strategy block diagram shows how to achieve coordinated control of renewable energy and DC transmission by introducing droop control characteristics. dc , to achieve dynamic regulation of active power, thereby reducing steady-state errors.

[0085] Step 5: State feedback and optimization: During the control process, the system continuously monitors the feedback state (such as the frequency change rate RoCoF) and further optimizes the control effect by adjusting the control parameters. After a fault occurs, the system gradually reduces the frequency deviation by introducing the control bias ΔP, and finally achieves system frequency stability.

[0086] The technical solution of this embodiment realizes adaptive adjustment:

[0087] Initial adjustment: After detecting the power shortage, the system first performs a quick initial adjustment to quickly increase or decrease K dc value to compensate for the shortfall.

[0088] Gradual transition: After the initial adjustment, the system gradually changes K in small steps. dc value, so that the active power output slowly approaches the target value and avoids secondary fluctuations caused by over-regulation.

[0089] Feedback adjustment: The system monitors the deviation between the output of the new energy power generation unit and the target value in real time, and dynamically adjusts K according to the feedback data. dc , further optimize output stability.

[0090] Observe the voltage source type VSG active control circuit, see attached Figure 1As shown in the figure, this control method obtains the rotor angle reference for system power generation. The active-frequency control simulates the inertia and primary frequency modulation characteristics of the synchronous generator. In order to improve the control accuracy, a voltage outer loop control link is added to the control loop. With the electromotive force reference output by the reactive-voltage control part, the equivalent output characteristic of the voltage source type VSG is closer to the voltage source, and the frequency signal can be established through the swing equation. Therefore, the voltage source type VSG has the ability to form a network and can be studied in the next step.

[0091] According to the generator rotor motion equation:

[0092]

[0093] Corresponding Figure 2 The corresponding active control part when ΔP is not added becomes:

[0094]

[0095] At the same time by Figure 2 We can also get ΔP ref The expression is:

[0096] ΔP ref =P ref -PD(ω ref -ω)+ΔP (5)

[0097] There are also:

[0098]

[0099] Arranged into differential form:

[0100]

[0101] Combining equations (2), (4)-(7), we can get:

[0102]

[0103] In the above formula, P ref is the given reference value of active power, P is the active output of new energy, ω ref is the rotor reference speed, ω is the generator speed, J is the inertia coefficient, D is the damping coefficient, s is the differential operator, and the other parameters have been explained above.

[0104] Formula (8) proves that the improved control strategy can reduce Figure 2 Medium power deviation for improved stability.

[0105] When a fault occurs at the receiving end, the steady-state error is reduced by introducing ΔP, and the output of new energy is adjusted by adjusting K dcAs shown in formula (9), the adjustment process is relatively smooth and no large fluctuations in the system will occur during the process.

[0106]

[0107] RoCoF1 and RoCoF2 are the frequency change rate thresholds set in the two states of too small and too large new energy shortage, RoCoF is the frequency change rate, K dc1 and K dc2 are the corresponding droop control coefficients under the two conditions respectively.

[0108] For example, when a commutation failure occurs in the system, the system will have an active power shortage, causing P ref -P value changes, making ΔP in equation (8) ref The value of V dc The change is small and can be regarded as a constant. The adjustable parameter is K dc , by adjusting K dc The value of P can be reduced ref -P increases, further enhancing the system stability, and then mobilizing new energy to reduce output to achieve coordinated control of new energy and DC. This strategy reduces the output of new energy to avoid excessive frequency deviation and improves the frequency stability of the system.

[0109] The sub-technical solution of this embodiment can enhance the stability of the system: by introducing a grid-type converter, the grid stability of the new energy station is improved. The control strategy of the grid-type converter increases the inertial response and voltage stability of the system to counteract disturbances in the system, especially when large-scale new energy is connected to the grid.

[0110] Dynamic balance optimization: The dynamic coordinated control strategy of multi-device energy flow can effectively manage and optimize the power flow fluctuations in the DC transmission system, especially in an environment where the power state changes rapidly and frequently, maintain the dynamic balance of the system, and reduce the risk of instability caused by power fluctuations.

[0111] Precision frequency control: Through the frequency dynamic modeling analysis of the time-space distribution characteristics and the improved active power control strategy, the present invention can accurately adjust the frequency response and reduce the fluctuation range of the system frequency, thereby improving the operational flexibility and response speed of the entire power system.

[0112] Improve grid reliability: Since grid-connected converters can quickly respond to grid disturbances, enhance the reactive power support and power compensation of the system, the grid can quickly adjust its operating status and maintain stability under large disturbances, thereby improving the overall reliability of the grid and reducing the risk of power outages.

[0113] Strong adaptability: The control strategy of the present invention is not only applicable to newly built wind power and photovoltaic bases, but also to the upgrade of existing power systems, providing a flexible and efficient solution, especially suitable for deserts, Gobi and wasteland areas with complex geographical environments and rich resources.

[0114] Model validity verification

[0115] First, the effectiveness of the model is verified. The simulation environment DigSILENT / Powerfactory is used to establish a simplified model of the DC transmission system with grid-type control. The system is set to have a renewable energy share of more than 50%. Then, a fault is set at t=2s, and the frequency and frequency change rate at the load node are observed as shown in (a) and (b) in the figure.

[0116] As can be seen from the figure, the frequencies of each node in the system are generally the same, but when a fault occurs, due to the different temporal and spatial distribution characteristics, there is a slight difference in the frequency change, which is reflected in the frequency change rate shown in Figure (b). This result verifies the effectiveness of the model.

[0117] According to the above theoretical analysis and model verification, the frequencies at each node of the system are not exactly the same. The following two working conditions are set: condition 1: small shortage of new energy and condition 2: large shortage of new energy to observe the different parts of the changes in the system node frequency under different faults, respectively. Figure 4 (a) and (b) in Figure 5 As shown in (a) and (b) in .

[0118] according to Figure 4 and Figure 5 The simulation results show that when a large disturbance occurs, the frequency change trend of each node in the system is the same. As the load disturbance degree increases, the threshold of the frequency change rate will become larger, that is, the degree of frequency change will be greater.

[0119] Taking working condition 1 as an example, in this case, the simulated wind farm is very close to the sending grid and the distance from the sending grid to the receiving grid is far. Due to the influence of the electrical distance, the frequency change of the wind turbine grid-connected point is significantly larger than that of other nodes. The second largest fluctuation is the frequency of the photovoltaic grid-connected point. Therefore, as the electrical distance increases, the frequency fluctuation of the grid-connected point becomes larger.

[0120] Improve strategy effectiveness verification

[0121] According to the above analysis, the active power droop characteristic is added to the active power outer loop of the DC converter station side. According to different large disturbance conditions, K dc The value of K is used to coordinate the energy flow of each node, thereby improving the stability of the system. When the system fails and the active power derating is small, dcThe value is adjusted to 0.01. When the active power is derated, K dc The value is adjusted to 0.002, and the frequency change rate before and after the change is compared. Figure 6 As shown in (a) and (b), it can be seen that after the introduction of this control strategy, the threshold of the frequency change rate is reduced, which can prove that this control strategy can improve the stability of the system.

[0122] Embodiment 2

[0123] 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 implements the steps of the above method when executing the program.

[0124] Embodiment 3

[0125] The purpose of this embodiment is to provide a computer-readable storage medium.

[0126] A computer-readable storage medium stores a computer program, which executes the steps of the above method when executed by a processor.

[0127] Embodiment 4

[0128] The purpose of this embodiment is to provide a coordinated control system of new energy and direct current for improving frequency stability, including:

[0129] The data acquisition module is configured to: monitor the DC voltage and frequency of the sending-end converter station in real time;

[0130] The disturbance judgment module is configured to: when the frequency fluctuation of the sending-end converter station is greater than a set value, judge that a large disturbance occurs;

[0131] The active power given bias acquisition module is configured to: obtain the active power given bias based on the deviation between the square of the DC voltage of the sending-end converter station and the square of its reference value and the bias droop coefficient;

[0132] The control module is configured to: compensate for the active power shortage caused by disturbance by adjusting the active power given bias, and obtain the new energy output by adjusting the value of the bias droop coefficient.

[0133] Embodiment 5

[0134] The purpose of this embodiment is to provide a computer program product containing instructions, which, when running on a computer, enables the computer to execute the methods and functions involved in any of the above embodiments.

[0135] The steps involved in the apparatus of the above embodiment correspond to the method embodiment 1, and the specific implementation method can refer to the relevant description part 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 to include any medium that can store, encode or carry an instruction set for execution by a processor and enable the processor to execute any method in the present invention.

[0136] Those skilled in the art should understand that the modules or steps of the present invention described above can be implemented by a general-purpose computer device, or alternatively, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. The present invention is not limited to any specific combination of hardware and software.

[0137] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it 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 on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A method for cooperatively controlling new energy and direct current to improve frequency stability, characterized in that: include: Real-time monitoring of DC voltage and frequency at the sending-end converter station; When the frequency fluctuation of the sending-end converter station is greater than the set value, it is judged that a large disturbance has occurred; The power setting bias is obtained based on the deviation of the square of the DC voltage of the sending-end converter station from the square of its reference value and the bias droop coefficient; By adjusting the active power given bias, the active power shortage caused by the disturbance is compensated, and by adjusting the value of the bias droop coefficient, the new energy output is obtained.

2. The method for coordinated control of new energy and direct current for improving frequency stability according to claim 1, characterized in that: include: The defined index S is used to represent the degree of change of the system frequency response, and the maximum frequency change rate index is used to describe the frequency response of the node; Where: Δf max,COI is the maximum frequency deviation of the system inertia center; ΔP d is the initial power disturbance; N is the number of nodes; The index S reflects the significance of the frequency response distribution to a certain extent, that is, the larger the S value is, the more significant the temporal and spatial distribution of the system frequency response is; The frequency threshold is then set based on the degree of frequency response change.

3. The coordinated control method of new energy and direct current for improving frequency stability as claimed in claim 1 is characterized in that: The power reference bias is obtained based on the deviation of the square of the DC voltage of the sending-end converter station from the square of its reference value and the bias droop coefficient, which is specifically: Where: ΔP is the active power given bias; K dc is the bias droop coefficient, V dc The DC voltage from the inverter DC side of the sending-end converter station, V dc_ref is a given reference value.

4. The method for coordinated control of new energy and direct current for improving frequency stability as claimed in claim 1, characterized in that: When adjusting the value of the bias droop coefficient: When the frequency change rate is less than the frequency change rate threshold set in the state of too small shortage of new energy and when the frequency change rate is less than the frequency change rate threshold set in the state of too large shortage of new energy, different bias droop coefficients are used.

5. The coordinated control method of new energy and direct current for improving frequency stability as claimed in claim 1 is characterized in that: By adjusting the active power given bias, the active power shortage caused by the disturbance is compensated, specifically: Initial adjustment: After detecting the power shortage, first make a quick initial adjustment to quickly increase or decrease K dc value to compensate for the shortfall; Gradual transition: After the initial adjustment, the system gradually changes K in small steps. dc value, so that the active power output slowly approaches the target value and avoids secondary fluctuations caused by over-regulation; Feedback adjustment: The system monitors the deviation between the output of the new energy power generation unit and the target value in real time, and dynamically adjusts K according to the feedback data. dc , further optimize output stability.

6. The method for coordinated control of new energy and direct current for improving frequency stability as claimed in claim 2, characterized in that: The calculation of the maximum frequency change rate is based on the speed at which the system frequency drops after a disturbance occurs. Specifically, in the interval where the frequency drops rapidly, the ratio of the frequency drop amplitude to the corresponding time width is calculated to obtain the frequency change rate of the interval. This frequency change rate can be calculated for each node, and the maximum value of each node is the maximum frequency change rate of the node.

7. A coordinated control system of new energy and direct current for improving frequency stability, characterized by including: The data acquisition module is configured to: monitor the DC voltage and frequency of the sending-end converter station in real time; The disturbance judgment module is configured to: when the frequency fluctuation of the sending-end converter station is greater than a set value, judge that a large disturbance occurs; The active power given bias acquisition module is configured to: obtain the active power given bias based on the deviation between the square of the DC voltage of the sending-end converter station and the square of its reference value and the bias droop coefficient; The control module is configured to: compensate for the active power shortage caused by disturbance by adjusting the active power given bias, and obtain the new energy output by adjusting the value of the bias droop coefficient.

8. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the method according to any one of claims 1 to 6 is implemented.

9. 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, the steps of the method described in any one of claims 1 to 6 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method described in any one of claims 1 to 6 are performed.

Images