Coordinated control method and system for new energy through active support type flexible DC transmission

Abstract

The application relates to the technical field of flexible direct current coordinated control, in particular to a new energy active support type flexible direct current sending out coordinated control method and system, which comprises the following steps: obtaining active power, direct current voltage of a receiving end converter station and power grid frequency of a receiving end power grid; analyzing sudden fluctuation degree of the power grid frequency to extract a power grid frequency characteristic sequence, obtaining each characteristic subsequence through segmentation, evaluating instantaneous disturbance of each characteristic subsequence through peak fluctuation condition and peak fluctuation duration in the characteristic subsequence, obtaining a high-frequency peak characteristic value in combination with change significant degree of a high-frequency component in the power grid frequency characteristic sequence; obtaining high-frequency peak continuity through change condition of the high-frequency peak characteristic value, which is used for adjusting droop coefficients, and then performing active power-direct current voltage droop control on the receiving end converter station. The application can accurately inhibit power grid frequency change of the receiving end power grid and improve active support effect on the receiving end power grid frequency.

Description

Technical Field

[0001] This application relates to the field of flexible DC coordinated control technology, specifically to a coordinated control method and system for transmitting new energy through an actively supported flexible DC transmission line. Background Technology

[0002] Flexible direct current (DC) transmission, as an important means of transmitting new energy, offers significant advantages over traditional DC transmission technologies. These advantages include independent active and reactive power regulation, self-commutation, voltage polarity stability during power flow reversal, and the elimination of reactive power compensation equipment. It enables coordinated control between the DC transmission line and the power grid, and its control strategy determines the stability of the power system under low-inertia and weak grid conditions. Currently, the scale of new energy generation transmitted via flexible DC is continuously expanding, making it one of the optimal choices for ensuring transmission safety and reliability. Optimizing the active support capability of flexible DC transmission for the power grid is one of the urgent issues to be addressed in maintaining grid frequency stability.

[0003] Flexible DC transmission technology generally employs traditional inertia-supported control strategies. Specifically, the receiving-end converter station typically uses active power-DC voltage droop control to rapidly adjust the converter station's output power, thereby suppressing grid frequency variations and achieving active grid frequency support. However, because the receiving-end converter station needs to respond promptly to grid frequency changes, and given the abrupt and random nature of these changes in active power-DC voltage droop control, current technologies adjust the droop coefficient based on grid frequency deviation. This fails to adequately consider the abrupt and random nature of grid frequency changes, resulting in inaccurate suppression of grid frequency variations and impacting the effectiveness of active grid frequency support. Summary of the Invention

[0004] To address the aforementioned technical problems, the purpose of this application is to provide a coordinated control method and system for transmitting new energy via actively supported flexible DC transmission. The specific technical solution adopted is as follows:

[0005] This application provides a coordinated control method for transmitting new energy via actively supported flexible DC transmission, including the following steps:

[0006] Acquire the active power, DC voltage, and grid frequency of the receiving-end converter station within a local window at each acquisition time.

[0007] The degree of sudden fluctuation of power grid frequency within the local window at each acquisition time is analyzed to extract the power grid frequency feature sequence. After segmentation, each feature subsequence is obtained. The instantaneous disturbance of each feature subsequence is evaluated by the peak fluctuation situation and peak fluctuation duration within the feature subsequence. Combined with the significance of the change of high frequency components in the power grid frequency feature sequence, the high frequency peak feature value of the local window at each acquisition time is obtained.

[0008] The continuity of high-frequency spikes in the local window at the current acquisition time is obtained by measuring the changes in the characteristic values ​​of high-frequency spikes, and the droop coefficient is adjusted in the active power-DC voltage droop control process.

[0009] Active power-DC voltage droop control is performed on the receiving-end converter station based on the adjusted droop coefficient.

[0010] Preferably, the rate of change of abrupt frequency changes of each power grid frequency within the local window at the current acquisition time is calculated: In the formula, This represents the rate of change of the i-th power grid frequency within the local window at the current acquisition time. and These are the i-th and (i-1)-th power grid frequencies within the local window at the current acquisition time, respectively, where a preset duration prior to the current acquisition time is used as the local window for the current acquisition time.

[0011] Preferably, all the abrupt frequency change rates within the local window are arranged in time sequence to form the power grid frequency feature sequence of the local window. The zero-crossing points of the power grid frequency feature sequence are extracted using the zero-crossing point algorithm. Each zero-crossing point is used as a segmentation point to segment the power grid frequency feature sequence, thereby obtaining each feature subsequence of the power grid frequency feature sequence.

[0012] Preferably, the ratio of the length of each characteristic subsequence to the total length of the power grid frequency characteristic sequence is recorded as the instantaneous ratio of each characteristic subsequence, and the ratio of the kurtosis of each characteristic subsequence to the instantaneous ratio is calculated as the evaluation result of the instantaneous disturbance of each characteristic subsequence.

[0013] Preferably, before obtaining the high-frequency spike feature value, the high-frequency component and low-frequency component of the first decomposition layer of the power grid frequency feature sequence are obtained using the wavelet decomposition algorithm. The high-frequency energy of the high-frequency component and the low-frequency energy of the low-frequency component are calculated respectively, and the ratio of high-frequency energy to low-frequency energy is used as the evaluation result of high-frequency disturbance in the local window at each acquisition time.

[0014] Preferably, the formula for obtaining the high-frequency spike characteristic values ​​of the local window at each acquisition time is: In the formula, Let be the high-frequency spike characteristic value of the local window at the t-th acquisition time. This represents the evaluation result of high-frequency disturbances within the local window at the t-th acquisition time. This represents the evaluation result of the instantaneous perturbation of the j-th feature subsequence within the local window at the t-th acquisition time. denoted as the number of feature subsequences corresponding to the local window at the t-th acquisition time.

[0015] Preferably, before acquiring the high-frequency peak continuity, the high-frequency peak feature values ​​of all local windows at all acquisition times within the local window at the current acquisition time are arranged in chronological order to form the high-frequency peak change sequence of the local window at the current acquisition time. The mean of the absolute values ​​of all first-order differences in the high-frequency peak change sequence is calculated and used as the high-frequency peak difference of the local window at the current acquisition time.

[0016] Preferably, the formula for obtaining the continuity of high-frequency spikes in the local window at the current acquisition time is: In the formula, This represents the continuity of high-frequency spikes within a local window at the current acquisition time. These are the high-frequency spike characteristic values ​​of a local window at the current acquisition time. This represents the high-frequency spike differences within a local window at the current acquisition time. This is the preset first parameter.

[0017] Preferably, the adjusted droop coefficient is obtained as follows: In the formula, This represents the adjusted droop coefficient at the current acquisition time. It is an exponential function with the natural constant as its base. This represents the continuity of high-frequency spikes within a local window at the current acquisition time. A fixed traditional droop coefficient is preset in the active power-DC voltage droop control.

[0018] This application also provides a coordinated control system for transmitting new energy via actively supported flexible DC transmission, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of any of the above-described coordinated control methods for transmitting new energy via actively supported flexible DC transmission.

[0019] As can be seen from the above, the coordinated control method and system for transmitting new energy via actively supported flexible DC transmission provided in this application have at least the following beneficial effects:

[0020] Based on the characteristics of power grid frequency mutations with peak fluctuations on the receiving-end power grid, this application analyzes the impact of instantaneous disturbances and high-frequency disturbances on the receiving-end power grid caused by load mutations. By combining the impact of instantaneous disturbances and high-frequency disturbances on the receiving-end power grid caused by load mutations, it can more accurately measure high-frequency peak fluctuations within a local window, thereby more clearly reflecting the impact of load mutations caused by the start-up or shutdown of large industrial equipment and peak industrial production periods.

[0021] Furthermore, in order to more accurately adjust the droop coefficient of active power-DC voltage droop control, this invention analyzes the continuous state of high-frequency peak fluctuations in the grid frequency within a local window, and fully considers the differences in continuous changes of high-frequency peak fluctuations in the grid frequency within a local window, so as to more accurately reflect the continuous characteristics of high-frequency peak fluctuations in the grid frequency within a local window, thereby more effectively reflecting the sudden randomness of grid frequency changes.

[0022] This application fully considers the abrupt and random characteristics of power grid frequency changes, and adjusts and compensates the traditional droop coefficient in active power-DC voltage droop control based on high-frequency peak continuity, thereby enhancing the response capability of the receiving-end converter station to power grid frequency changes in a timely manner, thus more accurately suppressing the power grid frequency changes of the receiving-end power grid and improving the active support effect for the receiving-end power grid frequency. Attached Figure Description

[0023] To more clearly illustrate the technical solutions and advantages in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A flowchart illustrating the steps of the coordinated control method for transmitting new energy via actively supported flexible DC transmission provided in this application;

[0025] Figure 2 A block diagram of the coordinated control system for the active-supported flexible DC transmission of new energy provided in this application. Detailed Implementation

[0026] To further illustrate the technical means and effects adopted by this application to achieve the intended purpose of the invention, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of the coordinated control method and system for transmitting new energy via actively supported flexible DC transmission according to this application. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0027] Unless otherwise specified and limited, terms such as “comprising,” “including,” or any other variations thereof are intended to cover a non-exclusive inclusion, such that a circuit structure, article, or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase “comprising one…” does not exclude the presence of other identical elements in the article or device that includes said element. Furthermore, the term “and / or” as used herein includes any and all combinations of one or more of the associated listed items. All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0028] The following, in conjunction with the accompanying drawings, details the specific scheme of the coordinated control method and system for transmitting new energy via actively supported flexible DC transmission provided in this application.

[0029] Please see Figure 1 The document illustrates a flowchart of a coordinated control method for transmitting new energy via an actively supported flexible DC transmission system, according to an embodiment of this application. The method includes the following steps:

[0030] Step 1: Collect data on the active power, DC voltage, and grid frequency of the receiving-end converter station.

[0031] In the active power-DC voltage droop control of the receiving-end converter station, in order to effectively improve the active support effect on the grid frequency, it is necessary to accurately and effectively analyze the sudden randomness characteristics of the grid frequency change, and effectively adjust the droop coefficient in the active power-DC voltage droop control of the receiving-end converter station, so as to more accurately suppress the grid frequency change.

[0032] In this embodiment, flexible DC transmission technology (voltage sourced converter based high voltage direct current transmission, VSC-HVDC) is used for flexible DC transmission. The converter station for flexible DC transmission includes a sending-end converter station and a receiving-end converter station. The sending-end converter station is connected to a new energy power station, including photovoltaic power generation and wind power generation. The receiving-end converter station is connected to the receiving-end power grid. The receiving-end converter station adopts active power-DC voltage droop control to quickly adjust the output power of the receiving-end converter station, thereby suppressing grid frequency changes and achieving active support for grid frequency.

[0033] To enable active power-DC voltage droop control at the receiving-end converter station of flexible DC transmission, voltage and current transformers are used to synchronously collect three-phase current and three-phase voltage at the busbar connecting to the receiving-end power grid within the receiving-end converter station. Based on the three-phase current and three-phase voltage, the active power of the receiving-end converter station is obtained using a three-phase active power calculation method. DC voltage is collected at the DC busbar connected within the receiving-end converter station through a parallel RC voltage divider and isolation amplifier to obtain the DC voltage of the receiving-end converter station. The grid frequency of the receiving-end power grid is obtained at the busbar connecting to the receiving-end power grid within the receiving-end converter station.

[0034] Data on active power, DC voltage, and grid frequency of the receiving-end converter station are collected at a rate of 1 kHz. The data is then normalized; this embodiment uses the maximum value normalization method. The specific normalization process is existing technology and will not be elaborated here. In practical applications, implementers can also use other existing normalization methods to normalize the collected data; this embodiment does not impose any special restrictions on this. Furthermore, a 1-second time window preceding each acquisition moment is used as a local window for each acquisition moment, resulting in time-series data of active power, DC voltage, and grid frequency within the local window for each acquisition moment.

[0035] Step 2: Analyze the degree of sudden fluctuation of the power grid frequency within the local window at each acquisition time to extract the power grid frequency feature sequence. After segmentation, each feature subsequence is obtained. The instantaneous disturbance of each feature subsequence is evaluated by the peak fluctuation situation and peak fluctuation duration within the feature subsequence. Combined with the significance of the change of high frequency components in the power grid frequency feature sequence, the high frequency peak feature value of the local window at each acquisition time is obtained.

[0036] In active power-DC voltage droop control at receiving-end converter stations, grid frequency changes exhibit abrupt and random fluctuations. Existing technologies adjust the droop coefficient based on grid frequency deviations, failing to adequately consider these abrupt and random fluctuations. This results in an inability to accurately suppress grid frequency changes, impacting the active frequency support effect. Therefore, effective analysis of the abrupt and random fluctuations of grid frequency changes is needed to more accurately adjust the droop coefficient in active power-DC voltage droop control.

[0037] To analyze the abrupt and random fluctuations in power grid frequency, the abrupt frequency change rate is calculated based on the abrupt changes in the time series data of the power grid frequency within a local window at each acquisition time. In this embodiment, the formula for calculating the abrupt frequency change rate for the local window at the current acquisition time is as follows: In the formula, This represents the rate of change of the i-th power grid frequency within the local window at the current acquisition time. and These are the i-th and (i-1)-th grid frequencies within the local window at the current acquisition time, respectively. This allows us to obtain the rate of change of all abrupt frequency changes within the local window at each acquisition time, thereby more accurately reflecting the abrupt fluctuations of the grid frequency at each acquisition time relative to the previous acquisition time. At the same time, it eliminates the influence of the grid frequency dimension, enabling us to more effectively analyze the abrupt random fluctuations of grid frequency changes.

[0038] Due to the start-up or shutdown of large industrial equipment and the impact of peak industrial production periods, the receiving-end power grid connected to the receiving-end converter station is prone to load abrupt changes, causing sudden changes in the rate of change of abrupt frequency within a local window. Therefore, to analyze the load abrupt changes of abrupt frequency in the receiving-end power grid, a sequence of all abrupt frequency changes within a local window at each acquisition time is formed according to time sequence and recorded as the power grid frequency characteristic sequence for each acquisition time local window, which more accurately reflects the power grid frequency characteristics of load abrupt changes in the receiving-end power grid. Furthermore, the power grid frequency characteristic sequence is used as input to a zero-crossing algorithm. The algorithm obtains all zero-crossing points in the power grid frequency characteristic sequence, and each zero-crossing point in the power grid frequency characteristic sequence is used as a segmentation point to segment the power grid frequency characteristic sequence, obtaining each characteristic subsequence of the power grid frequency characteristic sequence, thereby accurately reflecting the load abrupt changes of abrupt frequency in the receiving-end power grid. In particular, if there are no zero-crossing points in the power grid frequency characteristic sequence, the power grid frequency characteristic sequence is treated as a single characteristic subsequence.

[0039] Furthermore, the peak fluctuation characteristics of each characteristic subsequence are measured, and the kurtosis of each characteristic subsequence is calculated. The larger the kurtosis, the better it reflects the load mutation characteristics of peak fluctuations in the receiving-end power grid. Simultaneously, the ratio of the length of each characteristic subsequence to the total length of the power grid frequency characteristic sequence is calculated, denoted as the instantaneous ratio of each characteristic subsequence. The smaller the instantaneous ratio, the shorter the peak fluctuation time of load mutations in the receiving-end power grid, and the better it reflects the instantaneous peak fluctuations of load mutations in the receiving-end power grid. Therefore, by combining kurtosis and instantaneous ratio to measure the instantaneous peak characteristics in the receiving-end power grid frequency, and using the ratio of kurtosis to instantaneous ratio for each characteristic subsequence as the evaluation result of the instantaneous disturbance of each characteristic subsequence, the evaluation result reflects the instantaneous disturbance characteristics of the receiving-end power grid under load mutations. The more severe the load mutations caused by the start-up or shutdown of large industrial equipment and peak industrial production periods, the greater the impact of instantaneous disturbances on the receiving-end power grid, and the greater the evaluation result of the instantaneous disturbance.

[0040] Meanwhile, due to the presence of numerous electrical appliances or equipment at the distribution network end, high-frequency interference can occur on the receiving-end power grid, causing high-frequency variations in the receiving-end power grid frequency. Therefore, to analyze the high-frequency variations in the receiving-end power grid frequency, the power grid frequency feature sequence of each local window at each acquisition time is used as input to the wavelet decomposition algorithm. The preset decomposition level is 3, and the wavelet basis function is the db4 wavelet basis. The wavelet decomposition algorithm is used to obtain the high-frequency and low-frequency components of the first decomposition level. The high-frequency energy of the high-frequency component and the low-frequency energy of the low-frequency component in the first decomposition level are calculated respectively. The ratio of high-frequency energy to low-frequency energy is recorded as the evaluation result of high-frequency disturbance in each local window at each acquisition time. The more severe the load fluctuations caused by the start-up or shutdown of large industrial equipment and peak industrial production, the more significant the impact of high-frequency disturbances caused by load fluctuations on the receiving-end power grid, and the greater the evaluation result of high-frequency disturbance.

[0041] Based on the above analysis, and considering the impact of transient disturbances caused by load changes in the receiving-end power grid, as well as the impact of high-frequency disturbances, the high-frequency spike characteristic values ​​of the local window at each acquisition time are calculated:

[0042] In the formula, Let be the high-frequency spike characteristic value of the local window at the t-th acquisition time. This represents the evaluation result of high-frequency disturbances within the local window at the t-th acquisition time. This represents the evaluation result of the instantaneous perturbation of the j-th feature subsequence within the local window at the t-th acquisition time. denoted as the number of feature subsequences corresponding to the local window at the t-th acquisition time.

[0043] The evaluation results of transient disturbances represent the feature measurement results of each feature subsequence of the local window. The evaluation results of transient disturbances of feature subsequences are summed and averaged to reflect the transient disturbance impact of grid load changes within the local window. At the same time, combined with the high-frequency disturbance impact of grid load changes within the local window, a multiplication method is used to measure the high-frequency spike characteristics within the local window.

[0044] Understandably, the high-frequency spike characteristic value reflects high-frequency spike fluctuations within a local window. The more severe the load changes caused by the start-up or shutdown of large industrial equipment and the peak period of industrial production, the more significant the high-frequency spike fluctuations within the local window. Therefore, the high-frequency spike characteristic value needs to be adjusted more to regulate the droop coefficient of the active power-DC voltage droop control, so as to more accurately suppress grid frequency changes and more effectively improve the active support effect on grid frequency.

[0045] Step 3: Obtain the high-frequency peak continuity of the local window at the current acquisition time by observing the changes in the high-frequency peak characteristic values, and adjust the droop coefficient in the active power-DC voltage droop control process.

[0046] Furthermore, in order to more accurately adjust the droop coefficient of the active power-DC voltage droop control, it is necessary to analyze the change state of the high-frequency peak characteristics in the grid frequency within the local window at each acquisition time. The high-frequency peak characteristic values ​​of the local windows at all acquisition times within the local window at the current acquisition time are arranged into a sequence according to time sequence and recorded as the high-frequency peak change sequence of the local window at the current acquisition time, which reflects the change state of the high-frequency peak characteristics in the grid frequency within the local window at the current acquisition time.

[0047] Generally, if the power grid at the receiving end is affected by the start-up or shutdown of large industrial equipment or the continuous peak of industrial production, the high-frequency spike fluctuations in the power grid frequency within a local window will exhibit a continuous state. In this case, it is even more necessary to increase the adjustment efforts to regulate the droop coefficient of the active power-DC voltage droop control. Therefore, the mean of the absolute values ​​of all first-order differences in the high-frequency spike change sequence of the local window at the current acquisition time is calculated and denoted as the high-frequency spike difference of the local window at the current acquisition time. The smaller the high-frequency spike difference, the more significant the continuous state of the high-frequency spike fluctuations in the power grid frequency within the local window.

[0048] Based on the above analysis, calculate the high-frequency peak continuity of the local window at the current acquisition time:

[0049] In the formula, This represents the continuity of high-frequency spikes within a local window at the current acquisition time. These are the high-frequency spike characteristic values ​​of a local window at the current acquisition time. This represents the high-frequency spike differences within a local window at the current acquisition time. The first parameter is preset to avoid the denominator being 0. Its value range is 0.01-0.1, and in this embodiment, it is set to 0.05.

[0050] Among them, the high-frequency peak difference reflects the continuous variation difference of high-frequency peak fluctuations in the power grid frequency within the local window, while the high-frequency peak characteristic value reflects the characteristic magnitude of high-frequency peak fluctuations within the local window. The high-frequency peak difference is inversely proportional to the high-frequency peak continuity, while the high-frequency peak characteristic value is directly proportional to the high-frequency peak continuity. Therefore, the ratio method is used to measure the continuity characteristics of high-frequency peak fluctuations in the power grid frequency within the local window.

[0051] In the above formula, the high-frequency peak continuity reflects the continuity of high-frequency peak fluctuations in the grid frequency within a local window. The more severe the impact of the receiving-end grid on the start-up or shutdown of large industrial equipment and the continuous impact of peak industrial production, the more significant the continuity of high-frequency peak fluctuations in the grid frequency within the local window, and the more prominent the abrupt randomness of grid frequency changes. In this case, the high-frequency peak continuity is greater, and more adjustment efforts are needed to regulate the droop coefficient of the active power-DC voltage droop control, thereby enhancing the receiving-end converter station's response capability to grid frequency changes. Conversely, if the receiving-end grid is less affected by the start-up or shutdown of large industrial equipment and the continuous impact of peak industrial production, the high-frequency peak continuity is smaller, and more adjustment efforts are needed to regulate the droop coefficient of the active power-DC voltage droop control, thereby enabling the receiving-end converter station to respond mildly to grid frequency changes and avoid affecting the stability of the receiving-end grid frequency.

[0052] Based on the above analysis, in order to adjust the droop coefficient of the active power-DC voltage droop control, the adjusted droop coefficient during the active power-DC voltage droop control process at the current acquisition time is calculated:

[0053] In the formula, This represents the adjusted droop coefficient at the current acquisition time. It is an exponential function with the natural constant as its base. This represents the continuity of high-frequency spikes within a local window at the current acquisition time. A fixed traditional droop coefficient is preset in the active power-DC voltage droop control. This traditional droop coefficient is a constant gain reference based on the rated active power and DC steady-state voltage margin of the receiving-end converter station. In the receiving-end converter station with a rated active power of 1000MW and a rated DC voltage of ±500KV, the preset fixed traditional droop coefficient is 0.2MW / kV.

[0054] This paper adjusts and compensates the traditional droop coefficient in active power-DC voltage droop control based on high-frequency peak continuity. High-frequency peak continuity reflects the continuity characteristics of high-frequency peak fluctuations in the grid frequency of the receiving-end grid. The more significant the continuity characteristics of high-frequency peak fluctuations in the grid frequency, the more prominent the sudden randomness of grid frequency changes, and the greater the adjustment and compensation force of the traditional droop coefficient in active power-DC voltage droop control. This enhances the response capability of the receiving-end converter station to grid frequency changes and avoids serious interference to the grid frequency of the receiving-end grid caused by a large number of electrical appliances or equipment in the distribution network.

[0055] Step 4: Perform active power-DC voltage droop control on the receiving-end converter station based on the adjusted droop coefficient.

[0056] Furthermore, active power-DC voltage droop control is implemented at the receiving-end converter station. The active power and DC voltage of the receiving-end converter station are collected in real time and input into the active power-DC voltage droop control. The rated active power of the receiving-end converter station is 1000MW and the rated DC voltage is ±500kV. By calculating the adjusted droop coefficient of the active power-DC voltage droop control at the current acquisition time in real time, the output power of the receiving-end converter station is controlled and adjusted using the active power-DC voltage droop control, thereby accurately suppressing the grid frequency changes of the receiving-end grid and improving the active support effect on the receiving-end grid frequency.

[0057] Based on the same inventive concept as the above method, this application also provides a coordinated control system for the transmission of new energy via actively supported flexible DC transmission, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of any of the above-described coordinated control methods for the transmission of new energy via actively supported flexible DC transmission.

[0058] Specifically, the block diagram of the coordinated control system for transmitting new energy via actively supported flexible DC transmission is as follows: Figure 2 As shown, the coordinated control system for new energy transmission via actively supported flexible DC transmission includes a data acquisition module, a high-frequency peak analysis module, a droop coefficient adjustment module, and a droop control module. The data acquisition module acquires the active power, DC voltage, and grid frequency of the receiving-end converter station within a local window at each acquisition time. The high-frequency peak analysis module analyzes the degree of abrupt fluctuations in grid frequency within a local window at each acquisition time to extract grid frequency characteristic sequences. These sequences are then segmented into characteristic subsequences. The instantaneous disturbances of each characteristic subsequence are evaluated based on the peak fluctuations and their duration. Combined with the significant changes in high-frequency components in the grid frequency characteristic sequence, the high-frequency peak characteristic values ​​of the local window at each acquisition time are obtained. The droop coefficient adjustment module obtains the high-frequency peak continuity of the local window at the current acquisition time based on the changes in the high-frequency peak characteristic values, and adjusts the droop coefficient during the active power-DC voltage droop control process. The droop control module performs active power-DC voltage droop control on the receiving-end converter station based on the adjusted droop coefficient.

[0059] It is understood that the order of the embodiments described above is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. Furthermore, the above description focuses on specific embodiments of this specification. Additionally, the processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired results. In some implementations, multitasking and parallel processing are possible or may be advantageous.

[0060] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0061] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Any equivalent structural or procedural transformations made based on the description and drawings of this application, or direct or indirect applications in other related technical fields, are similarly included within the protection scope of this application.

Claims

1. A coordinated control method for transmitting new energy via actively supported flexible DC transmission, characterized in that, Includes the following steps: Acquire the active power, DC voltage, and grid frequency of the receiving-end converter station within a local window at each acquisition time. The degree of sudden fluctuation of power grid frequency within the local window at each acquisition time is analyzed to extract the power grid frequency feature sequence. After segmentation, each feature subsequence is obtained. The instantaneous disturbance of each feature subsequence is evaluated by the peak fluctuation situation and peak fluctuation duration within the feature subsequence. Combined with the significance of the change of high frequency components in the power grid frequency feature sequence, the high frequency peak feature value of the local window at each acquisition time is obtained. The continuity of high-frequency spikes in the local window at the current acquisition time is obtained by measuring the changes in the characteristic values ​​of high-frequency spikes, and the droop coefficient is adjusted in the active power-DC voltage droop control process. Active power-DC voltage droop control is performed on the receiving-end converter station based on the adjusted droop coefficient.

2. The coordinated control method for transmitting new energy via actively supported flexible DC transmission as described in claim 1, characterized in that, Calculate the rate of change of abrupt frequency changes of each power grid frequency within the local window at the current acquisition time: In the formula, This represents the rate of change of the i-th power grid frequency within the local window at the current acquisition time. and These are the i-th and (i-1)-th power grid frequencies within the local window at the current acquisition time, respectively, where a preset duration prior to the current acquisition time is used as the local window for the current acquisition time.

3. The coordinated control method for transmitting new energy via actively supported flexible DC transmission as described in claim 2, characterized in that, The power grid frequency feature sequence of the local window is formed by arranging all the abrupt frequency change rates in time sequence. The zero-crossing points of the power grid frequency feature sequence are extracted by the zero-crossing point algorithm. Each zero-crossing point is used as a dividing point to divide the power grid frequency feature sequence, thus obtaining each feature subsequence of the power grid frequency feature sequence.

4. The coordinated control method for transmitting new energy via actively supported flexible DC transmission as described in claim 1, characterized in that, The ratio of the length of each characteristic subsequence to the total length of the power grid frequency characteristic sequence is denoted as the instantaneous ratio of each characteristic subsequence. The ratio of the kurtosis of each characteristic subsequence to the instantaneous ratio is calculated as the evaluation result of the instantaneous disturbance of each characteristic subsequence.

5. The coordinated control method for transmitting new energy via actively supported flexible DC transmission as described in claim 4, characterized in that, Before obtaining the high-frequency peak feature value, the high-frequency component and low-frequency component of the first decomposition layer of the power grid frequency feature sequence are obtained using the wavelet decomposition algorithm. The high-frequency energy of the high-frequency component and the low-frequency energy of the low-frequency component are calculated respectively. The ratio of high-frequency energy to low-frequency energy is used as the evaluation result of high-frequency disturbance in the local window at each acquisition time.

6. The coordinated control method for transmitting new energy via actively supported flexible DC transmission as described in claim 5, characterized in that, The formula for obtaining the high-frequency spike characteristic values ​​of the local window at each acquisition time is: In the formula, Let be the high-frequency spike characteristic value of the local window at the t-th acquisition time. This represents the evaluation result of high-frequency disturbances within the local window at the t-th acquisition time. This represents the evaluation result of the instantaneous perturbation of the j-th feature subsequence within the local window at the t-th acquisition time. denoted as the number of feature subsequences corresponding to the local window at the t-th acquisition time.

7. The coordinated control method for transmitting new energy via actively supported flexible DC transmission as described in claim 1, characterized in that, Before acquiring the high-frequency peak continuity, the high-frequency peak feature values ​​of all local windows at the current acquisition time are arranged in chronological order to form the high-frequency peak change sequence of the local window at the current acquisition time. The mean of the absolute values ​​of all first-order differences in the high-frequency peak change sequence is calculated and used as the high-frequency peak difference of the local window at the current acquisition time.

8. The coordinated control method for transmitting new energy via actively supported flexible DC transmission as described in claim 7, characterized in that, The formula for obtaining the continuity of high-frequency spikes in the local window at the current acquisition time is: In the formula, This represents the continuity of high-frequency spikes within a local window at the current acquisition time. These are the high-frequency spike characteristic values ​​of a local window at the current acquisition time. This represents the high-frequency spike differences within a local window at the current acquisition time. This is the preset first parameter.

9. The coordinated control method for transmitting new energy via actively supported flexible DC transmission as described in claim 1, characterized in that, The adjusted droop coefficient is obtained as follows: In the formula, This represents the adjusted droop coefficient at the current acquisition time. It is an exponential function with the natural constant as its base. This represents the continuity of high-frequency spikes within a local window at the current acquisition time. A fixed traditional droop coefficient is preset in the active power-DC voltage droop control.

10. A coordinated control system for transmitting new energy via actively supported flexible DC transmission, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the coordinated control method for transmitting new energy via active-supported flexible DC transmission as described in any one of claims 1-9.

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