A new energy power grid multi-direct current frequency controller strategy checking method and system

Abstract

The application discloses a new energy power grid multi-direct current frequency controller strategy checking method and system, wherein the method comprises the following steps: determining calculation conditions and key parameters; checking the key parameters to determine the numerical value of the checked key parameters; checking simultaneous misoperation of multiple direct current FCs to make the power grid system transient stable; and based on the calculation conditions and the numerical value of the checked key parameters, when the direct current back-off quantity of each direct current reaches a preset value, the maximum new energy off-grid quantity of the power grid system is calculated under the condition that the third defense line of the power grid system is not triggered. The application has obvious effectiveness in dealing with the system frequency problem caused by large-scale off-grid of new energy in a high-proportion new energy multi-direct current sending-out power grid, can improve the power grid frequency stability defense line, and creates obvious economic benefits.

Description

Technical Field

[0001] This invention relates to the field of safe and stable operation technology of large-scale AC / DC hybrid power grids, and more specifically, to a method and system for verifying the strategy of multi-DC frequency controllers in new energy power grids. Background Technology

[0002] When large-scale renewable energy transmission systems experience AC / DC faults, both DC and renewable energy active power drops significantly, resulting in substantial reactive power surpluses and prominent transient overvoltage issues at renewable energy generator terminals. To ensure the safe operation of both DC and renewable energy, a segmented control scheme is adopted, but the "seesaw" coupling characteristic between their outputs is prominent, affecting the transmission capacity of both renewable energy and DC. DC frequency control (FC) utilizes the rapid change of the DC converter's firing angle to quickly adjust DC power after a fault, which is crucial for grid frequency stability and can mitigate the significant frequency drop caused by large-scale disconnection of near-field renewable energy after a fault. However, currently, in the verification calculations of FC control strategies in actual power grids, there is no unified principle for selecting operating modes or standard for judging the adaptability of key controller parameters. Therefore, research on verification methods for multiple DC frequency controller strategies in power grids with a high proportion of renewable energy is urgently needed.

[0003] Therefore, a technology is needed to verify the multi-DC frequency controller strategy of new energy power grids. Summary of the Invention

[0004] The present invention provides a method and system for verifying the strategy of multiple DC frequency controllers in a new energy power grid, in order to solve the problem of how to verify the strategy of multiple DC frequency controllers in a new energy power grid.

[0005] To address the above problems, this invention provides a method for verifying the strategy of a multi-DC frequency controller in a new energy power grid, the method comprising:

[0006] Determine the calculation conditions and key parameters;

[0007] The key parameters are verified to determine their values.

[0008] Verification was performed on the simultaneous malfunction of multiple DC FC lines to ensure the transient stability of the power grid system;

[0009] Based on the calculation conditions and the verified values ​​of key parameters, when the DC pullback amount of each DC line reaches the preset value, the maximum amount of new energy disconnected from the grid system is calculated without triggering the third line of defense of the grid system.

[0010] Preferably, the determination of calculation conditions includes:

[0011] Determine a conservative power grid operation mode;

[0012] Under a protected grid operation mode, without DC FC functionality in the grid system, the frequency characteristics of the grid are simulated and calculated under different renewable energy disconnection rates after a fault. Based on the low-frequency load shedding threshold of the third line of defense of the grid, the maximum renewable energy disconnection rate P when the grid system frequency drops to the low-frequency load shedding threshold is simulated and calculated. t-max ;

[0013] A multi-DC configuration scheme is determined, and multiple DC lines with FC function are configured according to the scheme. The operating powers under the selected operating modes are: P1, P2, P3...P n .

[0014] Preferably, the key parameter includes: the inertial time constant T of the frequency measurement stage. f Frequency difference dead zone limitation F band , proportional gain K P DC power modulation limit P modmax DC power modulation lower limit P modmin .

[0015] Preferably, the step of verifying the key parameters and determining the values ​​of the verified key parameters includes:

[0016] The upper limit of the DC power modulation amount P modmax Set to 0;

[0017] The lower limit of DC power modulation P modmin The selection is based on the actual DC operation of the FC-enabled DC circuit, under conservative conditions, to determine the DC regulation values ​​for each line: P sj-1 P sj-2 ...P sj-n Determine the key parameter P modmin-1 P modmin-2 ...P modmin-n for:

[0018]

[0019] Based on the principle that a first-level safety and stability standard fault in the power grid system should not lead to multiple DC FC operations, an AC N-1 fault scan is performed on the entire power grid to determine the inertial time constant T of the frequency measurement link. f ;

[0020] Below the lowest point F of the power grid frequency after the fault min And considering a certain margin, determine the frequency deviation dead zone limit F. band ;

[0021] The proportional gain KP The value determines the DC modulation amount and modulation speed during frequency drop; the proportional gain coefficient Kp is selected through a rolling correction process, and a typical value K is initially selected based on experience. P1 Calculate the amount of new energy disconnected from the grid (P) t-max Under what conditions are the DC transient modulation quantities P tj-1 P tj-2 ...P tj-n Statistically calculate the percentage P of DC transient sag during the frequency drop period for each DC frequency. hj-n Comparison of various DC P hj-n Is it close to DC P? modmin-n If the conditions are met and a certain margin is allowed, then the proportional gain coefficient Kp value is determined. If not, the Kp value is increased, and the calculation is iterated continuously until the DC transient sag percentage P is reached. hj-n When the requirements are met, determine the value of the proportional gain coefficient Kp.

[0022] Preferably, the step of verifying the simultaneous malfunction of multiple DC FC lines to ensure the transient stability of the power grid system includes:

[0023] Multiple DC FCs, in coordination with the existing third line of defense in the power grid system, can simultaneously malfunction without causing high-frequency problems that trigger the high-frequency tripping defense. Simulation analysis shows that multiple DC FCs simultaneously reduce P... modmin-n The maximum increase in system frequency F max The action threshold F of the high-frequency switching defense line of the research power grid shall not exceed the threshold value. h-max This ensures the transient stability of the power grid system.

[0024] Preferably, based on the calculation conditions and the verified values ​​of key parameters, when the reduction in the DC transmission rate reaches a preset value, and without triggering the third line of defense of the power grid system, the maximum disconnection of new energy sources from the grid system is calculated, including:

[0025] The configured FC scheme and key parameter values ​​all achieve P in various DC droop values. modmin-n Without triggering the low-frequency load shedding threshold of the third line of defense in the power grid system, calculate the maximum disconnection amount P of new energy sources in the power grid system. x-max .

[0026] Based on another aspect of the present invention, the present invention provides a multi-DC frequency controller strategy verification system for new energy power grids, the system comprising:

[0027] Initial cells are used to determine computational conditions and key parameters;

[0028] A determining unit is used to verify the key parameters and determine the values ​​of the verified key parameters;

[0029] The verification unit is used to verify the simultaneous malfunction of multiple DC FC lines to ensure the transient stability of the power grid system. Based on the calculation conditions and the values ​​of the key parameters after verification, the maximum amount of new energy disconnection from the power grid system is calculated when the reduction of each DC line reaches the preset value, without triggering the third line of defense of the power grid system.

[0030] Preferably, the initial unit is used to determine the calculation conditions, including:

[0031] Determine a conservative power grid operation mode;

[0032] Under a protected grid operation mode, without DC FC functionality in the grid system, the frequency characteristics of the grid are simulated and calculated under different renewable energy disconnection rates after a fault. Based on the low-frequency load shedding threshold of the third line of defense of the grid, the maximum renewable energy disconnection rate P when the grid system frequency drops to the low-frequency load shedding threshold is simulated and calculated. t-max ;

[0033] A multi-DC configuration scheme is determined, and multiple DC lines with FC function are configured according to the scheme. The operating powers under the selected operating modes are: P1, P2, P3...P n .

[0034] Preferably, the key parameter includes: the inertial time constant T of the frequency measurement stage. f Frequency difference dead zone limitation F band , proportional gain K P DC power modulation limit P modmax DC power modulation lower limit P modmin .

[0035] Preferably, the determining unit is used to verify the key parameters and determine the values ​​of the verified key parameters, including:

[0036] The upper limit of the DC power modulation amount P modmax Set to 0;

[0037] The lower limit of DC power modulation P modmin The selection is based on the actual DC operation of the FC-enabled DC circuit, under conservative conditions, to determine the DC regulation values ​​for each line: P sj-1 P sj-2 ...P sj-n Determine the key parameter P modmin-1 P modmin-2 ...P modmin-n for:

[0038]

[0039] Based on the principle that a first-level safety and stability standard fault in the power grid system should not lead to multiple DC FC operations, an AC N-1 fault scan is performed on the entire power grid to determine the inertial time constant T of the frequency measurement link. f ;

[0040] Below the lowest point F of the power grid frequency after the fault min And considering a certain margin, determine the frequency deviation dead zone limit F. band ;

[0041] The proportional gain K P The value determines the DC modulation amount and modulation speed during frequency drop; the proportional gain coefficient Kp is selected through a rolling correction process, and a typical value K is initially selected based on experience. P1 Calculate the amount of new energy disconnected from the grid (P) t-max Under what conditions are the DC transient modulation quantities P tj-1 P tj-2 ...P tj-n Statistically calculate the percentage P of DC transient sag during the frequency drop period for each DC frequency. hj-n Comparison of various DC P hj-n Is it close to DC P? modmin-n If the conditions are met and a certain margin is allowed, then the proportional gain coefficient Kp value is determined. If not, the Kp value is increased, and the calculation is iterated continuously until the DC transient sag percentage P is reached. hj-n When the requirements are met, determine the value of the proportional gain coefficient Kp.

[0042] Preferably, the verification unit is used to verify the simultaneous malfunction of multiple DC FC lines to ensure the transient stability of the power grid system, including:

[0043] Multiple DC FCs, in coordination with the existing third line of defense in the power grid system, can simultaneously malfunction without causing high-frequency problems that trigger the high-frequency tripping defense. Simulation analysis shows that multiple DC FCs simultaneously reduce P... modmin-n The maximum increase in system frequency F max The action threshold F of the high-frequency switching defense line of the research power grid shall not exceed the threshold value. h-max This ensures the transient stability of the power grid system.

[0044] Preferably, the verification unit is used to calculate the maximum disconnection of new energy sources from the power grid system based on the calculation conditions and the values ​​of the verified key parameters, when the reduction in the DC transmission rate of each line reaches a preset value, without triggering the third line of defense of the power grid system, including:

[0045] The configured FC scheme and key parameter values ​​all achieve P in various DC droop values. modmin-n Without triggering the low-frequency load shedding threshold of the third line of defense in the power grid system, calculate the maximum disconnection amount P of new energy sources in the power grid system.x-max .

[0046] This invention provides a method and system for verifying the strategy of multiple DC frequency controllers in a renewable energy power grid. The method includes: determining calculation conditions and key parameters; verifying the key parameters and determining their values; verifying simultaneous malfunctions of multiple DC FCs to ensure transient stability of the power grid system; and, based on the calculation conditions and the verified values ​​of the key parameters, calculating the maximum disconnection of renewable energy from the grid system without triggering the third line of defense, when the return loss of each DC line reaches a preset value. This invention proposes a multi-DC FC strategy verification method suitable for power grids with a high proportion of renewable energy, which is simple and easy to implement by following the calculation process. In power grids with a high proportion of renewable energy and multiple DC transmission lines, this invention is significantly effective in addressing system frequency problems caused by large-scale disconnection of renewable energy, improving the grid frequency stability defense line, and creating significant economic benefits. Attached Figure Description

[0047] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures:

[0048] Figure 1 This is a flowchart of a multi-DC frequency controller strategy verification method for a new energy power grid according to a preferred embodiment of the present invention;

[0049] Figure 2 A flowchart illustrating the verification process for a high-proportion renewable energy multi-DC FC strategy according to a preferred embodiment of the present invention;

[0050] Figure 3 This is a schematic diagram of a multi-DC FC configuration in the Northwest Power Grid according to a preferred embodiment of the present invention;

[0051] Figure 4 A schematic diagram of a frequency controller based on a single inertial element according to a preferred embodiment of the present invention; and

[0052] Figure 5 This is a structural diagram of a new energy power grid multi-DC frequency controller strategy verification system according to a preferred embodiment of the present invention. Detailed Implementation

[0053] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0054] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0055] Figure 1 This is a flowchart illustrating a multi-DC frequency controller strategy verification method for a renewable energy power grid according to a preferred embodiment of the present invention. The present invention proposes a multi-DC frequency controller strategy verification method suitable for renewable energy power grids with a high proportion of renewable energy, improving frequency stability characteristics after large-scale renewable energy disconnection. In renewable energy power grids with a high proportion of renewable energy, large-scale disconnection of renewable energy caused by AC / DC faults can lead to frequency stability problems, thereby triggering the third line of defense of the power grid. Therefore, the present invention proposes a multi-DC FC strategy verification method to address frequency problems caused by power loss from nearby renewable energy sources.

[0056] like Figure 1 As shown, this invention provides a method for verifying the strategy of a multi-DC frequency controller in a new energy power grid. The method includes:

[0057] Step 101: Determine the calculation conditions and key parameters;

[0058] Preferably, determining the calculation conditions includes:

[0059] Determine a conservative power grid operation mode;

[0060] Under a protected grid operation mode, without DC FC functionality in the grid system, the frequency characteristics of the grid are simulated and calculated under different renewable energy disconnection rates after a fault. Based on the low-frequency load shedding threshold of the third line of defense of the grid, the maximum renewable energy disconnection rate P when the grid system frequency drops to the low-frequency load shedding threshold is simulated and calculated. t-max ;

[0061] Determine the multi-DC configuration scheme, and configure multiple DC lines with FC function according to the multi-DC configuration scheme. The operating power under the selected operating mode is as follows: P1, P2, P3...P n .

[0062] Preferably, the key parameters include: the inertial time constant T of the frequency measurement stage. f Frequency difference dead zone limitation F band , proportional gain K P DC power modulation limit P modmax DC power modulation lower limit P modmin .

[0063] This invention first determines the calculation conditions. The choice of power grid mode should be relatively conservative, covering the main operating conditions that the power grid may experience. System frequency fluctuations after AC / DC faults are related to various factors, such as system spinning reserve capacity, system load, primary frequency regulation capability of conventional units, DC power operation level within the grid, and the proportion of renewable energy within the grid. A relatively conservative approach should be determined based on practical experience and sensitivity analysis to ensure coverage of all possibilities.

[0064] This invention analyzes the frequency characteristics of a system. Based on a relatively conservative approach, without DC FC functionality configured in the system, this invention simulates and calculates the grid frequency characteristics under different renewable energy disconnection rates after a fault. According to the low-frequency load shedding threshold of the grid's third line of defense, it simulates and calculates the maximum amount of renewable energy that can be disconnected from the grid, P, when the system frequency drops to the low-frequency load shedding threshold. t-max .

[0065] This invention determines a multi-DC FC configuration scheme. Based on factors such as the power grid structure, the geographical distribution characteristics of DC converter stations, DC capacity, the proportion of renewable energy in the DC vicinity, the DC receiving-end landing point, and the distribution of internal grid interconnection channels, this invention specifically selects the DC lines and the number of lines within the grid that enable FC function, and chooses a suitable multi-DC FC configuration scheme. Based on the configuration scheme, the operating power of the DC lines to be configured with FC function under the selected operating modes is statistically analyzed: P1, P2, P3...P n .

[0066] This invention identifies key parameters. Key parameters in the frequency controller model of a first-order inertial element include: the inertial time constant (T) of the frequency measurement element. f ), frequency difference dead zone limitation (F band ), proportional gain (K P DC power modulation limit (P) modmax DC power modulation lower limit (P) modmin ).

[0067] Step 102: Verify the key parameters and determine the values ​​of the verified key parameters;

[0068] Preferably, the key parameters are verified to determine their values, including:

[0069] The upper limit of DC power modulation P modmax Set to 0;

[0070] DC power modulation lower limit P modmin The selection is based on the actual DC operation of the FC-enabled DC circuit, under conservative conditions, to determine the DC regulation values ​​for each line: P sj-1 P sj -2......P sj-nDetermine the key parameter P modmin-1 P modmin- 2......P modmin-n for:

[0071]

[0072] Based on the principle that a first-level safety and stability standard fault in the power grid system should not lead to multiple DC FC operations, an AC N-1 fault scan is performed on the entire power grid to determine the inertial time constant T of the frequency measurement link. f ;

[0073] Below the lowest point F of the power grid frequency after the fault min And considering a certain margin, determine the frequency deviation dead zone limit F. band ;

[0074] Proportional Gain K P The value determines the DC modulation amount and modulation speed during frequency drop-off; the proportional gain coefficient Kp is selected through a rolling correction process, and a typical value K is initially chosen based on experience. P1 Calculate the amount of new energy disconnected from the grid (P) t-max Under what conditions are the DC transient modulation quantities P tj-1 P tj-2 ...P tj-n Statistically calculate the percentage P of DC transient sag during the frequency drop period for each DC frequency. hj-n Comparison of various DC P hj-n Is it close to DC P? modmin-n If the conditions are met and a certain margin is allowed, then the proportional gain coefficient K is determined. p If the value is not satisfied, the selected Kp value is increased, and the calculation is iterated continuously until the DC transient descent percentage P is reached. hj-n When the requirements are met, determine the value of the proportional gain coefficient Kp.

[0075] This invention verifies key parameters.

[0076] (1) Determine parameter P modmax P modmin

[0077] Considering that this invention addresses the low-frequency problem in the system caused by large-scale grid disconnection of new energy sources, the upper limit of DC power modulation P is set. modmax Set to 0; DC power modulation lower limit P modmin The selection should be made in a relatively conservative manner, based on the actual operating conditions of the DC lines where the FC function is to be configured, to determine the adjustable values ​​of each DC line: P sj-1 P sj-2 ...P sj-n Determine the key parameter P modmin-1 P modmin-2...P modmin-n The DC regulation is a key parameter for verification. The key parameter includes the DC regulation, which has an upper limit and a lower limit. In this application, the upper limit is set to 0, and only the lower limit of DC regulation needs to be determined based on the DC regulation.

[0078]

[0079] (2) Determine parameter T f

[0080] The choice of inertial time constant (Tf) affects the sensitivity of the FC (Fault-Coordinating Cell) to frequency fluctuations during system transients. A value that is too small may lead to frequent malfunctions; a certain margin should be considered when selecting it. Based on the principle that a first-level safety and stability standard fault in the power grid should not cause multiple DC FCs to operate, an AC N-1 fault scan of the entire power grid is performed to determine Tf. f parameter.

[0081] (3) Determine parameter F band

[0082] Considering the coordination of multiple DC FCs with the grid's second line of defense, the FCs should not activate when a fault included in the second-level safety and stability standard occurs. Simulation calculations are performed for faults such as AC N-2 and DC blocking across the entire grid, determining the frequency difference dead zone limiting parameter (F). band The selection should be lower than the lowest point F of the power grid frequency after the aforementioned fault. min And considering a certain margin, determine the parameter F. band .

[0083] (4) Determine parameter K p

[0084] Kp is the DC FC proportional gain coefficient, and its value determines the DC modulation amount and modulation speed during frequency sag. As Kp increases, the DC response rate during frequency sag accelerates, and the system frequency stability improves. The selection of the proportional gain coefficient Kp is a rolling correction process; a typical value K is initially selected based on experience. P1 Calculate the amount of new energy disconnected from the grid (P) t-max Under what conditions are the DC transient modulation quantities P tj-1 P tj-2 ...P tj-n Statistically calculate the percentage P of DC transient sag during the frequency drop period for each DC frequency. hj-n Comparison of various DC P hj-n Is it close to DC P? modmin-n If the conditions are met and a certain margin is allowed, then the value of Kp is determined. If not, the value of Kp is appropriately increased, and the calculation is iterated continuously until the percentage of DC transient retracement P is reached. hj-n The requirements are met, and the value of Kp is determined. Finally, the total power drop P during each DC transient period is calculated.tj-Z and the percentage of total power reduction P during each DC transient period hj-Z .

[0085]

[0086]

[0087]

[0088] Step 103: Verify the simultaneous malfunction of multiple DC FC lines to ensure the transient stability of the power grid system;

[0089] Preferably, the simultaneous malfunction of multiple DC-FC lines is checked to ensure the transient stability of the power grid system, including:

[0090] Multiple DC FCs, in coordination with the existing third line of defense in the power grid system, can simultaneously malfunction without causing high-frequency problems that trigger the high-frequency tripping defense. Simulation analysis shows that multiple DC FCs simultaneously reduce P... modmin-n The maximum increase in system frequency F max The action threshold F of the high-frequency switching defense line of the research power grid shall not exceed the threshold value. h-max This ensures the transient stability of the power grid system.

[0091] This invention undergoes an adaptive verification.

[0092] This invention simultaneously verifies malfunctions. It should consider the coordination between multiple DC FCs and the existing third line of defense in the power grid. Simultaneous malfunctions of multiple DC FCs should not cause high-frequency problems leading to the activation of the high-frequency tripping defense line. Simulation analysis shows that multiple DC lines simultaneously reduce P... modmin-n The maximum increase in system frequency F max It should not exceed the action threshold F of the high-frequency power grid switching defense line. h-max This ensures the transient stability of the power grid system.

[0093] Step 104: Based on the calculation conditions and the values ​​of the key parameters after verification, when the reduction of each DC return reaches the preset value, calculate the maximum amount of new energy disconnection from the grid system without triggering the third line of defense of the grid system.

[0094] Preferably, based on the calculation conditions and the verified values ​​of key parameters, when the reduction in the DC transmission rate reaches the preset value, and without triggering the third line of defense of the power grid system, the maximum disconnection of new energy sources from the grid system is calculated, including:

[0095] The configured FC scheme and key parameter values ​​all achieve P in various DC droop values. modmin-n Without triggering the low-frequency load shedding threshold of the third line of defense in the power grid system, calculate the maximum disconnection amount P of new energy sources in the power grid system. x-max .

[0096] This invention analyzes the maximum amount of new energy that can be disconnected from the grid.

[0097] Based on the above-described FC scheme and key parameter values, the DC droop rate reaches P in each case. modmin-n Without triggering the low-frequency load shedding threshold of the third line of defense in the power grid system, calculate and analyze the maximum amount of renewable energy that can be disconnected from the grid, P. x-max .

[0098] This invention proposes a multi-DC FC strategy verification method suitable for high-proportion renewable energy power grids. It is simple and easy to implement by following the calculation process. In high-proportion renewable energy multi-DC transmission power grids, it is significantly effective in addressing system frequency problems caused by large-scale renewable energy disconnection, thus improving grid frequency stability and creating significant economic benefits.

[0099] This invention includes the appendix to the invention description. Figure 4 The calculation process described in the text can be applied to the engineering practice of verifying the multi-DC frequency controller strategy in a high-proportion renewable energy power grid, thus forming the best implementation example for a specific application.

[0100] This invention is based on Figure 4 Taking the Northwest Power Grid multi-DC FC scenario shown in the figure as an example, the parameter verification method of the multi-DC frequency controller proposed in this invention will be explained.

[0101] Step 1: Determine the calculation conditions

[0102] (1) Verification was performed under the dry season of 2021.

[0103] (2) The rotating standby capacity is set according to the minimum capacity specified in the operating procedure.

[0104] (3) Conventional units are considered to be put into normal operation with primary frequency regulation, and thermal power units are set with a bidirectional regulation limit of 6%.

[0105] (4) Without FC configuration, 5360MW of new energy in the Northwest Power Grid were simultaneously disconnected from the grid, and the system frequency dropped to a minimum of 49.01Hz, which is close to the low-frequency load reduction threshold of 49Hz for the third line of defense of the Northwest Power Grid.

[0106] (5) The Northwest Power Grid has a "long chain" and "dumbbell" structure. The two major inertia centers of the eastern and western power grids, Xinjiang and the Northwest Interconnection Channel is the only channel connecting the eastern and western power grids. Taking into account the geographical location of the DC converter stations, DC capacity, the proportion of new energy sources in the DC near-area, the DC receiving end landing area, and the distribution of the Northwest Interconnection Channel, 6 DC FC lines are configured (Lingshao, Zhaoyi, Qingyu, Qishao, Tianzhong, and Jiquan).

[0107] (5) Determine the key parameters, T f Fband K p P modmin .

[0108] Step 2: Verify key parameters

[0109] (1) Determine the parameter Pmodmin

[0110] Under the low-power mode, the following DC lines are proposed to be configured with FC strategy: Qingyu DC, Lingshao DC, Tianzhong DC, Zhaoyi DC, Qishao DC, and Jiquan DC. Their operating power is shown in the table below:

[0111]

[0112] Considering the overload capacity of the UHVDC converter, P modmin Set to 10%.

[0113] (2) Determine parameter T f

[0114] In response to the first-level safety and stability standards of the Northwest Power Grid, all 750kV AC lines and interconnection channels in the DC near-field area were scanned for N-1 faults, and parameters were revised with the goal of not triggering DC FC action. According to simulation analysis, the lowest frequency fluctuation of the N-1 fault in the Shaanxi-Wuhan DC near-field area, from Shaanxi Shuofang to Shaanxi Yuheng, is 49.4Hz. To avoid DC FC malfunction, the inertial time constant Tf was set to 0.5s.

[0115] (3) Determine parameter F band

[0116] For the second-level safety and stability standard of the Northwest Power Grid, the coordination between the FC function and the existing second-line defense operation should be considered. Under the 3000MW Southwest-to-Northwest transmission mode of the Debao DC line, the frequency surge caused by bipolar blocking is the most serious fault under the second-line defense standard. In this fault situation, after taking emergency measures to reduce the Lingbao DC line to 600MW according to the established strategy, the system frequency can recover to above 49.55Hz. Considering a certain margin, the frequency dead zone setting of the FC is set to 0.5Hz.

[0117] (3) Determine parameter K p

[0118] When the proportional gain coefficient is set to Kp = 2000, the Northwest New Energy grid disconnection capacity is 5360MW. During the fault, the power response of the Qingyu DC FC is 10%, the Lingshao DC is 3%, the Tianzhong DC is 5%, the Zhaoyi DC is 10%, the Qishao DC is 7%, and the Jiquan DC is 5%. The total power response of the six DC lines is 1975MW, with a response ratio of approximately 5.7%, which is significantly different from Pmodmin (set value 10%).

[0119] When the proportional gain coefficient is set to Kp = 5000, the Northwest New Energy grid disconnection capacity is 5360MW. During the fault, the power response of the Qinghai-Henan DC FC is 10%, the Lingnan-Shaoyang DC is 4%, the Tianzhong DC is 6%, the Zhaoyi DC is 10%, the Qishao DC is 8%, and the Jiquan DC is 6%. The total power response of the six DC lines is 2250MW, with a response ratio of approximately 6.5%.

[0120] When Kp = 5000, the active power response ratio of DC FC is relatively high during the transient period, so Kp is set to 5000.

[0121] Step 3: Adaptability Check

[0122] (1) Simultaneous malfunction

[0123] When six DC FC lines—Lingshao, Zhaoyi, Qingyu, Qishao, Tianzhong, and Jiquan—malfunction simultaneously, the maximum emergency power reduction of 10% of the rated transmission power of each of the three DC lines will result in a total power reduction of 3450MW in the Northwest. The maximum increase in system frequency will be 50.405Hz, which will not trigger the high-frequency switching defense line (50.6Hz). The network channel will remain stable, and the system voltage will remain stable.

[0124] (2) Maximum disconnection amount

[0125] With each DC power drop reaching 10% of the operating power, Northwest New Energy's maximum grid disconnection capacity is 8500MW without triggering the system's third line of defense.

[0126] Figure 5 This is a structural diagram of a multi-DC frequency controller strategy verification system for a new energy power grid according to a preferred embodiment of the present invention. Figure 5 As shown, this invention provides a multi-DC frequency controller strategy verification system for new energy power grids, the system comprising:

[0127] Initial unit 501 is used to determine the calculation conditions and key parameters;

[0128] Preferably, the initial unit 501 is used to determine the calculation conditions, including:

[0129] Determine a conservative power grid operation mode;

[0130] Under a protected grid operation mode, without DC FC functionality in the grid system, the frequency characteristics of the grid are simulated and calculated under different renewable energy disconnection rates after a fault. Based on the low-frequency load shedding threshold of the third line of defense of the grid, the maximum renewable energy disconnection rate P when the grid system frequency drops to the low-frequency load shedding threshold is simulated and calculated. t-max ;

[0131] Determine the multi-DC configuration scheme, and configure multiple DC lines with FC function according to the multi-DC configuration scheme. The operating power under the selected operating mode is as follows: P1, P2, P3...P n .

[0132] Preferably, the key parameters include: the inertial time constant T of the frequency measurement stage. f Frequency difference dead zone limitation F band , proportional gain K P DC power modulation limit P modmax DC power modulation lower limit P modmin .

[0133] Unit 502 is used to verify the key parameters and determine the values ​​of the verified key parameters.

[0134] Preferably, the determining unit 502 is used to verify the key parameters and determine the values ​​of the verified key parameters, including:

[0135] The upper limit of DC power modulation P modmax Set to 0;

[0136] DC power modulation lower limit P modmin The selection is based on the actual DC operation of the FC-enabled DC circuit, under conservative conditions, to determine the DC regulation values ​​for each line: P sj-1 P sj-2 ...P sj-n Determine the key parameter P modmin-1 P modmin- 2......P modmin-n for:

[0137]

[0138] Based on the principle that a first-level safety and stability standard fault in the power grid system should not lead to multiple DC FC operations, an AC N-1 fault scan is performed on the entire power grid to determine the inertial time constant T of the frequency measurement link. f ;

[0139] Below the lowest point F of the power grid frequency after the fault min And considering a certain margin, determine the frequency deviation dead zone limit F. band ;

[0140] Proportional Gain K P The value determines the DC modulation amount and modulation speed during frequency drop-off; the proportional gain coefficient Kp is selected through a rolling correction process, and a typical value K is initially chosen based on experience. P1 Calculate the amount of new energy disconnected from the grid (P) t-max Under what conditions are the DC transient modulation quantities P tj-1 Ptj-2 ...P tj-n Statistically calculate the percentage P of DC transient sag during the frequency drop period for each DC frequency. hj-n Comparison of various DC P hj-n Is it close to DC P? modmin-n If the conditions are met and a certain margin is allowed, then the proportional gain coefficient Kp value is determined. If not, the Kp value is increased, and the calculation is iterated continuously until the DC transient sag percentage P is reached. hj-n When the requirements are met, determine the value of the proportional gain coefficient Kp.

[0141] Verification unit 503 is used to verify the simultaneous malfunction of multiple DC FC lines, so as to ensure the transient stability of the power grid system. Based on the calculation conditions and the values ​​of key parameters after verification, when the reduction of each DC line reaches the preset value, the maximum disconnection of new energy in the power grid system is calculated without triggering the third line of defense of the power grid system.

[0142] Preferably, the verification unit 503 is used to verify the simultaneous malfunction of multiple DC FC lines, thereby ensuring the transient stability of the power grid system, including:

[0143] Multiple DC FCs, in coordination with the existing third line of defense in the power grid system, can simultaneously malfunction without causing high-frequency problems that trigger the high-frequency tripping defense. Simulation analysis shows that multiple DC FCs simultaneously reduce P... modmin-n The maximum increase in system frequency F max The action threshold F of the high-frequency switching defense line of the research power grid shall not exceed the threshold value. h-max This ensures the transient stability of the power grid system.

[0144] Preferably, the verification unit 503 is used to calculate the maximum disconnection of new energy sources from the power grid system based on the calculation conditions and the values ​​of the key parameters after verification, when the reduction in the DC return rate of each DC line reaches the preset value, without triggering the third line of defense of the power grid system, including:

[0145] The configured FC scheme and key parameter values ​​all achieve P in various DC droop values. modmin-n Without triggering the low-frequency load shedding threshold of the third line of defense in the power grid system, calculate the maximum disconnection amount P of new energy sources in the power grid system. x-max .

[0146] The preferred embodiment of the present invention provides a new energy power grid multi-DC frequency controller strategy verification system 500, which corresponds to the preferred embodiment of the present invention provides a new energy power grid multi-DC frequency controller strategy verification method 100, and will not be described in detail here.

[0147] The invention has been described with reference to a few embodiments. However, as will be known to those skilled in the art, and as defined in the appended claims, other embodiments besides those disclosed above fall equivalently within the scope of the invention.

[0148] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the art, unless otherwise expressly defined herein. All references to “a / / the [device, component, etc.]” ​​are openly interpreted as at least one instance of the device, component, etc., unless otherwise expressly stated. The steps of any method disclosed herein need not be performed in the exact order disclosed unless explicitly stated otherwise.

Claims

1. A method for verifying the strategy of a multi-DC frequency controller in a new energy power grid, the method comprising: The calculation conditions and key parameters are determined, including: Determine a conservative power grid operation mode; Under a protected grid operation mode, without DC FC functionality in the grid system, the frequency characteristics of the grid are simulated and calculated under different renewable energy disconnection rates after a fault. Based on the low-frequency load shedding threshold of the third line of defense of the grid, the maximum amount of renewable energy disconnection when the grid system frequency drops to the low-frequency load shedding threshold is simulated and calculated. P t-max ; A multi-DC configuration scheme is determined, and multiple DC lines with FC function are configured according to the multi-DC configuration scheme. The operating power under the selected operating mode is as follows: P 1. P 2. P 3...... P n ; The key parameters include: the inertial time constant of the frequency measurement stage. T f Frequency dead zone limitation F band Proportional gain K P DC power modulation limit P modmax DC power modulation lower limit P modmin ; The key parameters are verified to determine their values. Verification was performed on the simultaneous malfunction of multiple DC FC lines to ensure the transient stability of the power grid system; Based on the calculation conditions and the verified values ​​of key parameters, when the DC pullback amount of each DC line reaches the preset value, the maximum amount of new energy disconnected from the grid system is calculated without triggering the third line of defense of the grid system.

2. The method according to claim 1, wherein verifying the key parameters and determining the values ​​of the verified key parameters includes: The upper limit of the DC power modulation amount P modmax Set to 0; The lower limit of DC power modulation P modmin The selection method involves determining the DC regulation values ​​for each line based on the actual DC operation under the conservative approach and the configuration of the FC function: P sj-1 , P sj-2 ... .P sj-n Determine key parameters P modmin-1 , P modmin- 2...... P modmin-n for: ； Based on the principle that a first-level safety and stability standard fault in the power grid system should not lead to multiple DC FC operations, an AC N-1 fault scan is performed on the entire power grid to determine the inertial time constant of the frequency measurement link. T f ; Below the lowest point of the power grid frequency after the fault F min And considering a certain margin, determine the frequency deviation dead zone limit. F band ; The proportional gain K P The value determines the amount of DC modulation and the modulation speed during the frequency drop period; proportional gain coefficient K p is chosen as the rolling correction process, and a typical value is initially selected based on experience. K P1 Calculate the amount of new energy sources disconnected from the grid. P t-max DC transient modulation quantities under various conditions P tj-1 , P tj-2 ...... P tj-n Statistical calculation of the percentage of DC transient sag during the frequency drop period for each DC frequency. P hj-n Comparison of various DC P hj-n Is it close to DC? P modmin-n If the conditions are met and a certain margin is allowed, then the proportional gain coefficient is determined. K If the p-value is not satisfied, then increase it. K The p-value is selected and iterative calculations are performed continuously until the percentage of DC transient reflux is reached. P hj-n When the requirements are met, determine the proportional gain coefficient. K The value of p.

3. The method according to claim 1, wherein the step of verifying the simultaneous malfunction of multiple DC FC lines to achieve transient stability of the power grid system includes: Multiple DC FCs coordinate with the existing third line of defense in the power grid system. Simultaneous malfunction of multiple DC FCs does not cause high-frequency problems that trigger the high-frequency tripping defense. Simulation analysis shows that multiple DC FCs simultaneously reduce voltage. P modmin-n Maximum increase in system frequency F max Not exceeding the action threshold of the high-frequency power grid switching defense line. F h-max This ensures the transient stability of the power grid system.

4. The method according to claim 2, wherein, based on the calculation conditions and the verified values ​​of key parameters, when the reduction in the DC transmission rate of each line reaches a preset value, the maximum disconnection of new energy sources from the power grid is calculated without triggering the third line of defense of the power grid system, including: The configured FC scheme and key parameter values ​​all achieved the desired DC hysteresis reduction. P modmin-n Without triggering the low-frequency load shedding threshold of the third line of defense in the power grid system, calculate the maximum amount of renewable energy disconnected from the grid. P x-max .

5. A multi-DC frequency controller strategy verification system for a new energy power grid, the system comprising: Initial cells are used to determine computational conditions and key parameters; The initial unit is used to determine the calculation conditions, including: Determine a conservative power grid operation mode; Under a protected grid operation mode, without DC FC functionality in the grid system, the frequency characteristics of the grid are simulated and calculated under different renewable energy disconnection rates after a fault. Based on the low-frequency load shedding threshold of the third line of defense of the grid, the maximum amount of renewable energy disconnection when the grid system frequency drops to the low-frequency load shedding threshold is simulated and calculated. P t-max ; A multi-DC configuration scheme is determined, and multiple DC lines with FC function are configured according to the multi-DC configuration scheme. The operating power under the selected operating mode is as follows: P 1. P 2. P 3...... P n ; The key parameters include: the inertial time constant of the frequency measurement stage. T f Frequency dead zone limitation F band Proportional gain K P DC power modulation limit P modmax DC power modulation lower limit P modmin ; A determining unit is used to verify the key parameters and determine the values ​​of the verified key parameters; The verification unit is used to verify the simultaneous malfunction of multiple DC FC lines to ensure the transient stability of the power grid system. Based on the calculation conditions and the values ​​of the key parameters after verification, the maximum amount of new energy disconnection from the power grid system is calculated when the reduction of each DC line reaches the preset value, without triggering the third line of defense of the power grid system.

6. The system according to claim 5, wherein the determining unit is used to verify the key parameters and determine the values ​​of the verified key parameters, including: The upper limit of the DC power modulation amount P modmax Set to 0; The lower limit of DC power modulation P modmin The selection method involves determining the DC regulation values ​​for each line based on the actual DC operation under the conservative approach and the configuration of the FC function: P sj-1 , P sj-2 ... .P sj-n Determine key parameters P modmin-1 , P modmin- 2...... P modmin-n for: ； Based on the principle that a first-level safety and stability standard fault in the power grid system should not lead to multiple DC FC operations, an AC N-1 fault scan is performed on the entire power grid to determine the inertial time constant of the frequency measurement link. T f ; Below the lowest point of the power grid frequency after the fault F min And considering a certain margin, determine the frequency deviation dead zone limit. F band ; The proportional gain K P The value determines the amount of DC modulation and the modulation speed during the frequency drop period; proportional gain coefficient K p is chosen as the rolling correction process, and a typical value is initially selected based on experience. K P1 Calculate the amount of new energy sources disconnected from the grid. P t-max DC transient modulation quantities under various conditions P tj-1 , P tj-2 ...... P tj-n Statistical calculation of the percentage of DC transient sag during the frequency drop period for each DC frequency. P hj-n Comparison of various DC P hj-n Is it close to DC? P modmin-n If the conditions are met and a certain margin is allowed, then the proportional gain coefficient is determined. K If the p-value is not satisfied, then increase it. K The p-value is selected and iterative calculations are performed continuously until the percentage of DC transient reflux is reached. P hj-n When the requirements are met, determine the proportional gain coefficient. K The value of p.

7. The system according to claim 5, wherein the verification unit is used to verify the simultaneous malfunction of multiple DC FC lines to ensure transient stability of the power grid system, comprising: Multiple DC FCs coordinate with the existing third line of defense in the power grid system. Simultaneous malfunction of multiple DC FCs does not cause high-frequency problems that trigger the high-frequency tripping defense. Simulation analysis shows that multiple DC FCs simultaneously reduce voltage. P modmin-n Maximum increase in system frequency F max Not exceeding the action threshold of the high-frequency power grid switching defense line. F h-max This ensures the transient stability of the power grid system.

8. The system according to claim 6, wherein the verification unit is configured to, based on the calculation conditions and the values ​​of the verified key parameters, calculate the maximum disconnection amount of new energy sources in the power grid system without triggering the third line of defense of the power grid system, when the DC return rate drops to a preset value, including: The configured FC scheme and key parameter values ​​all achieved the desired DC hysteresis reduction. P modmin-n Without triggering the low-frequency load shedding threshold of the third line of defense in the power grid system, calculate the maximum amount of renewable energy disconnected from the grid. P x-max .

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