Method and device for determining voltage setting of fast loss-of-step splitting device

Abstract

The application discloses a kind of quick out-of-step splitting device voltage constant value determination method and device, the method includes: obtaining the position of quick splitting device installation and the conventional operation data of relevant power grid, determine the typical operation mode of relevant power grid;Typical fault mode that can cause out-of-step quick splitting action under the typical operation mode is obtained;Based on the typical operation mode and typical fault mode, limit operation mode is obtained;Based on the limit operation mode, set the voltage constant value of quick splitting device in simulation software, obtain the limit low voltage starting constant value of quick splitting under each fault mode;Based on the minimum value selected in the limit low voltage starting constant value of quick splitting under each fault mode, the final voltage constant value of quick splitting device under this operation mode is obtained, the system out-of-step section can be quickly split in the first asynchronous operation cycle, to prevent the spread of accident, avoid the occurrence of system blackout.

Description

Technical Field

[0001] This invention relates to a method and apparatus for determining the voltage setpoint of a fast out-of-step disconnection device, belonging to the field of power system stability control technology. Background Technology

[0002] With the construction of ultra-high-voltage power grids, the connections between regional power grids have been greatly strengthened, and the stability characteristics have become more complex. The establishment of electricity market mechanisms will allow power companies to fully utilize existing transmission and transformation equipment, causing the load on transmission lines to approach their stability limits. All of these pose challenges to the analysis, operation, and control technologies of modern power systems, and place increasingly higher demands on system safety. Long-term operational experience shows that no matter how stringent the requirements for system stability are or how comprehensive the preventative measures are, unexpected factors may always occur, leading to stability disruptions. When system stability is disrupted, the key issue is how to rationally and quickly quell the oscillations and rapidly restore the system to normal. Disconnecting the oscillating systems on both sides to quell the oscillations, and achieving rational disconnection in systems that have lost synchronization, can effectively prevent the spread of accidents and avoid system blackouts. Therefore, disconnection due to loss of synchronization, as the last line of defense against system collapse, is of great significance for eliminating asynchronous oscillations in power systems and preventing major blackouts.

[0003] Traditional, widely used out-of-step disconnection principles require at least one oscillation cycle to determine when a line is out of step. The system is only identified when the voltage at the oscillation center is continuous and has crossed zero. At this point, the power angles at both ends of the system have already exceeded 180 degrees, meaning the system has entered an asynchronous operating state. This method lacks out-of-step prediction capabilities. Furthermore, the uncertainty of the oscillation center makes it difficult for various out-of-step disconnection devices to coordinate with each other, failing to fully meet the needs of power grid stability control. Therefore, there is an urgent need for an adaptive fast out-of-step disconnection device with predictive capabilities that can automatically and accurately identify the location of the oscillation center to solve these problems. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method and apparatus for determining the voltage setpoint of a fast out-of-step disconnection device. In the process of determining the voltage setpoint, the actual operating conditions of the power grid and the impact of the severity of the fault are comprehensively considered, which is of great significance for guiding the reliable operation of the actual power grid.

[0005] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0006] In a first aspect, the present invention provides a method for determining the voltage setpoint of a fast out-of-step disconnection device, comprising:

[0007] Obtain the installation location of the fast disconnection device and the routine operation data of the relevant power grid to determine the typical operation mode of the relevant power grid;

[0008] Obtain the typical fault modes that may cause the fast-resolver to lose step under the typical operating mode;

[0009] Based on the typical operating modes and typical fault conditions, the extreme operating modes are obtained;

[0010] Based on the aforementioned extreme operating mode, the voltage setpoint of the fast disconnection device is set in the simulation software, and the voltage setpoint of the fast disconnection device is adjusted according to the simulation results to obtain the fast disconnection extreme low-voltage start-up setpoint under each fault condition.

[0011] Based on the minimum value selected from the fast-disconnection limit low-voltage start-up settings under each fault condition, the final voltage setting of the fast disconnection device under this operating mode is obtained.

[0012] Furthermore, the acquisition of typical fault modes that may cause the fast-resolve action to lose synchronization under the typical operating mode includes:

[0013] Based on relevant research on power grid safety and stability, identify typical fault modes that may cause out-of-step fast-break action under corresponding typical operating conditions; or, under each typical operating condition, perform fault scanning using simulation software, analyze the oscillation characteristics of the power grid based on the simulation results, and then determine the fault modes that may cause out-of-step fast-break action. This requires scanning line N-1 faults, line N-2 faults, DC faults, main transformer N-1 faults, single-phase instantaneous line faults, and outage faults.

[0014] Furthermore, obtaining the extreme operating mode based on the typical operating mode and typical fault mode includes:

[0015] Based on the typical operating mode, the line power at the installation location of the fast disconnection device is adjusted so that the power system is critically stable when the typical fault mode occurs. The operating mode at the critical stability is the extreme operating mode corresponding to the fault mode. The line power at the installation location of the fast disconnection device corresponding to the critical stability of the system under each fault mode is generally different. The fault mode and the extreme operating mode correspond one-to-one.

[0016] Furthermore, adjusting the voltage setpoint of the rapid disconnection device based on simulation results includes:

[0017] When the rapid disconnection device fails to operate due to a fault condition corresponding to the extreme operating mode, the voltage setting of the rapid disconnection device is increased; when the rapid disconnection device operates due to a fault condition corresponding to the extreme operating mode, the voltage setting of the rapid disconnection device is decreased.

[0018] Furthermore, obtaining the fast-solution limit low-voltage start-up setpoint under each fault condition includes:

[0019] When the voltage setpoint of the fast disconnect device is set to the set value X, the fast disconnect device will not operate when a fault condition corresponding to the extreme operating mode occurs. When the voltage setpoint of the fast disconnect device is set to the set value X + 0.02pu, the fast disconnect device will operate when a fault condition corresponding to the extreme operating mode occurs, the adjustment of the voltage setpoint of the fast disconnect device will end, and the fast disconnect extreme low voltage start setpoint under the corresponding fault will be set to the set value X.

[0020] Furthermore, it also includes: when the voltage setting of the fast disconnect device is 0.7pu, if the fast disconnect fails to operate due to a fault condition corresponding to the extreme operating mode, the adjustment of the voltage setting of the fast disconnect device is terminated, and it is determined that the fast disconnect extreme low voltage start setting under the corresponding fault is greater than or equal to 0.7pu.

[0021] Furthermore, it also includes: if the final voltage setpoint is equal to the minimum value, then subtract 0.01 pu from the final voltage setpoint.

[0022] Secondly, the present invention provides a fast out-of-step disconnection method according to the method for determining the voltage setting of the fast out-of-step disconnection device as described in any of the preceding claims, wherein the criterion for fast out-of-step disconnection is:

[0023] 1) Determine if the oscillation center is within the protected area;

[0024] 2)

[0025] 3)

[0026] 4)U ECS <U SET

[0027] Rapid out-of-step disconnection will only activate when all four of the above conditions are met simultaneously; where δ is the voltage power angle difference between the two sides of the line, P is the active power of the line, and U... ECS U is the voltage at the center of oscillation. SET To quickly resolve the low-voltage start-up setting, during the transition from synchronous to asynchronous operation, the voltage power angle difference between the two sides of the line increases at an accelerating rate, but the active power of the line continuously decreases. When the oscillation center enters the protection range of the device and the voltage of the oscillation center is lower than the threshold value, the device issues a trip signal.

[0028] Thirdly, the present invention provides a fast out-of-step disconnection device according to the method for determining the voltage setting of the fast out-of-step disconnection device according to any one of the above claims, comprising:

[0029] The typical operation mode acquisition unit is used to acquire the installation location of the fast disconnection device and the normal operation data of the relevant power grid, and to determine the typical operation mode of the relevant power grid;

[0030] The typical fault mode acquisition unit is used to acquire typical fault modes that may cause the out-of-step fast solution action under the typical operating mode.

[0031] The extreme operation mode acquisition unit is used to acquire extreme operation modes based on the typical operation modes and typical fault modes;

[0032] The fast-disconnection extreme low-voltage start-up setting value calculation unit is used to set the voltage setting value of the fast disconnection device in the simulation software based on the extreme operating mode, adjust the voltage setting value of the fast disconnection device according to the simulation results, and obtain the fast-disconnection extreme low-voltage start-up setting value under each fault condition.

[0033] The final voltage setpoint acquisition unit is used to obtain the final voltage setpoint of the fast disconnection device under the operating mode based on the minimum value selected among the fast disconnection limit low voltage start-up setpoints under each fault condition.

[0034] Fourthly, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of any of the methods described above.

[0035] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0036] This invention provides a method and apparatus for determining the voltage setting of a fast out-of-step disconnection device, which effectively solves the problems of long judgment time and the requirement of at least one oscillation cycle for conventional out-of-step disconnection devices. When asynchronous oscillation occurs and the oscillation center falls within the protected area, the power system out-of-step fast disconnection device can quickly disconnect the out-of-step section of the system within the first asynchronous operating cycle, thereby preventing the spread of the accident and avoiding the occurrence of a major power outage. This invention proposes a method for determining the voltage setting of the fast disconnection device based on the fast disconnection mechanism, which is of great significance for guiding the reliable operation of actual power grids. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the equivalent system model of the regional interconnected power grid provided in an embodiment of the present invention;

[0038] Figure 2 This is the phasor diagram of the equivalent two-machine system provided in the embodiments of the present invention;

[0039] Figure 3 This is a schematic diagram of the system equivalent model provided in an embodiment of the present invention;

[0040] Figure 4 This is a schematic diagram of the bus voltage on both sides of the CN line in the asynchronous oscillation of two regional power grids provided in this embodiment of the invention;

[0041] Figure 5This is a flowchart of the method for determining the voltage setpoint of the fast out-of-step disconnection device provided in the embodiments of the present invention. Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0043] Example 1

[0044] like Figure 5 As shown in the figure, this embodiment introduces a method and apparatus for determining the voltage setting of a fast out-of-step disconnection device, including:

[0045] Obtain the installation location of the fast disconnection device and the routine operation data of the relevant power grid to determine the typical operation mode of the relevant power grid;

[0046] Obtain the typical fault modes that may cause the fast-resolver to lose step under the typical operating mode;

[0047] Based on the typical operating modes and typical fault conditions, the extreme operating modes are obtained;

[0048] Based on the aforementioned extreme operating mode, the voltage setpoint of the fast disconnection device is set in the simulation software, and the voltage setpoint of the fast disconnection device is adjusted according to the simulation results to obtain the fast disconnection extreme low-voltage start-up setpoint under each fault condition.

[0049] Based on the minimum value selected from the fast-disconnection limit low-voltage start-up settings under each fault condition, the final voltage setting of the fast disconnection device under this operating mode is obtained.

[0050] The method and apparatus for determining the voltage setpoint of the fast out-of-step disconnection device provided in this embodiment involve the following steps in their application:

[0051] Step 1: Obtain the installation location of the fast disconnection device and the routine operation data of the relevant power grid to determine the typical operation mode of the relevant power grid;

[0052] Step 2: Identify the typical fault modes that may cause the fast-resolver to lose sync under typical operating conditions;

[0053] Based on relevant research on power grid safety and stability, typical fault modes that may cause out-of-step fast-resolver operation under corresponding typical operating modes are identified; or, under each typical operating mode, fault scanning is performed using simulation software, and the oscillation characteristics of the power grid are analyzed based on the simulation results to determine the fault modes that may cause out-of-step fast-resolver operation. It is necessary to scan line N-1 faults, line N-2 faults, DC faults, main transformer N-1 faults, single-phase instantaneous line faults, and power outage faults, etc. The above faults do not consider the operation of safety control.

[0054] Step 3: Determine the extreme operating mode

[0055] Based on the typical operating mode, the line power at the installation location of the fast disconnection device is adjusted so that the power system is critically stable when the fault mode in step 2 occurs. The operating mode at the critical stability is the extreme operating mode corresponding to the fault mode. The line power at the installation location of the fast disconnection device corresponding to the critical stability of the system under each fault mode is generally different. The fault mode and the extreme operating mode correspond one-to-one.

[0056] Step 4: Calculation of fast-release limit low-voltage start-up setpoint under corresponding fault conditions

[0057] Under extreme operating conditions, the voltage setpoint of the fast disconnect device is set in the simulation software (such as BPA or integrated stability program). The voltage setpoint unit is pu. The voltage setpoint of the fast disconnect device is adjusted according to the simulation results. When the voltage setpoint of the fast disconnect device is the set value X, the fast disconnect device does not operate when a fault condition corresponding to the extreme operating conditions occurs. When the voltage setpoint of the fast disconnect device is the set value X + 0.02pu, the fast disconnect device operates when a fault condition corresponding to the extreme operating conditions occurs. The adjustment of the voltage setpoint of the fast disconnect device ends, and the fast disconnect extreme low-voltage start setpoint under the corresponding fault is set to the set value X. When the voltage setpoint of the fast disconnect device is 0.7pu, the fast disconnect device does not operate when a fault condition corresponding to the extreme operating conditions occurs. The adjustment of the voltage setpoint of the fast disconnect device ends, and it is determined that the fast disconnect extreme low-voltage start setpoint under the corresponding fault is greater than or equal to 0.7pu.

[0058] The method for adjusting the voltage setting of the fast disconnection device based on simulation results is as follows: when the fast disconnection device fails to operate due to a fault condition corresponding to the extreme operating mode, the voltage setting of the fast disconnection device is increased; when the fast disconnection device operates due to a fault condition corresponding to the extreme operating mode, the voltage setting of the fast disconnection device is decreased.

[0059] Step 5: Determine the final fast-release limit low-voltage start-up setpoint

[0060] The minimum value is selected from the fast-release limit low-voltage start-up settings under each fault condition. The final voltage setting of the fast-release device under this operating mode is determined based on this minimum value. For example, the final voltage setting is equal to the minimum value minus 0.01pu.

[0061] The following description, in conjunction with a preferred embodiment, illustrates the content designed in the above embodiments.

[0062] (1) The variation law of the oscillation center voltage when the system loses step

[0063] For interconnected power grids, each region consists of several generators and loads within that region, with very close electrical connections. However, the regional power grids are only connected by several tie lines. Therefore, when a system fault causes a loss of synchronism between regional power grids, it often manifests as synchronous operation within the same regional power grid, while the regional power grids operate asynchronously to each other. Thus, when a loss of synchronism occurs between regional power grids, the synchronously operating grids can be considered as an equivalent system; that is, the interconnected regional system can be viewed as a whole system composed of two equivalent systems interconnected. Therefore, this paper starts with an equivalent system model of an interconnected regional power grid to introduce and study the changing patterns of various state variables during the loss of synchronism in a power system.

[0064] like Figure 1 In the equivalent system model of the regional interconnected power grid shown, E m For the power supply at the sending end, E n Z is the receiving end power supply. m Z n The impedances of the two equivalent systems are Z and Z, respectively. l The combined impedance of the tie line between two equivalent systems.

[0065] To simplify the analysis, the following assumptions are made:

[0066] (1) The potential amplitudes of the two equal systems are equal, i.e., |E m |=|E n |, where |E m |、|E n | These represent the potential amplitudes of the two equivalent systems;

[0067] (2) Neglect network resistance and ensure that reactance does not change with frequency;

[0068] (3) The impact of intermediate loads is not considered;

[0069] (4) The electromotive forces of the two equivalent machines remain unchanged, and the generator adopts the E′ constant model;

[0070] (5) Impedance angle φ in the system eq They are all equal.

[0071] The vector graph of the system is as follows Figure 2 As shown, where, and Let δ be the electric potential of the two equivalent systems. and The phase angle difference, Let m be the voltage at busbar m. Let n be the voltage at bus n. This represents the voltage at the center of the system oscillation. This represents the total current on the tie line between the two equivalent systems.

[0072] Under normal operating conditions, the potential vectors of the two equivalent machines rotate at synchronous angular velocities, and the angle between the two potential vectors remains constant. When system stability is disrupted and asynchronous operation begins, the frequencies of the two systems are no longer identical, slip occurs, and the power angle continuously increases. The potential vectors and angles of the equivalent machines are as follows:

[0073]

[0074]

[0075] Where ω1 and ω2 are the power supply E at the sending end, respectively. m and receiving end power supply E n The angular frequency is given by t, where t is time, δ0 is the phase angle difference between the potentials of the two equivalent systems under normal operating conditions before the accident, and δ(t) is the potential of the two equivalent systems. and At time t, the phase angle difference, Δω, is the difference in angular frequencies between the two equal systems, i.e., the slip angular frequency. Equation 2 shows that the angle δ between the two potentials varies periodically from 0° to 360° according to the slip angular frequency Δω. Due to the effect of the regulating system, the slip angular frequency is not constant; it varies within a certain range.

[0076] The study focuses on the busbar m, assuming the equivalent impedance between the measurement point busbar and the oscillation center is Z. mo When the system is out of sync, the voltage at measurement point m is:

[0077]

[0078] After processing, the voltage amplitude at measurement point m is obtained:

[0079]

[0080] Equation 4 shows the intrinsic relationship between the voltage amplitude and the power angle at the measurement point during asynchronous operation. When the power angle varies from 0° to 180°, the voltage amplitude tends to decrease; when the power angle varies from 180° to 360°, the voltage amplitude tends to increase. Therefore, when δ = 180°, the voltage reaches its lowest value. The closer to the oscillation center, the lower the voltage amplitude, and the voltage at the oscillation center is 0.

[0081] When Z in equation 4 mo If the value is 0, then the calculated bus voltage is the oscillation center voltage, and the original formula can be simplified to:

[0082]

[0083] The expression for the power transmitted on the tie line is:

[0084]

[0085] From equation 6, we can obtain:

[0086]

[0087] Substituting equation 7 into equation 5 and rearranging, we get...

[0088]

[0089] Equation 8 represents the oscillation center voltage of the system when it operates at an unstable equilibrium point. Where: Z Σ1 Z is the tie line impedance under normal operating conditions before the accident, and δ0 is the phase angle difference between the two equivalent system potentials under normal operating conditions before the accident; Σ2 It is the tie line impedance after the fault is cleared, δ h It is the phase angle difference between the two equivalent system potentials after the fault is cleared, P0 is the transmitted power on the tie line, P Ⅱmax It is the statically stable maximum transmission power after the fault is cleared.

[0090] The PAC-1000 is a conventional fast out-of-synchronization tripping device. This device establishes out-of-synchronization tripping criteria based on factors such as the power variation trend of the transmission line, the voltage phase angle difference trend at both ends of the line, and the location of the system oscillation center. During the transition from synchronous to asynchronous operation, the voltage phase angle difference across the line increases at an accelerating rate, while the active power of the line continuously decreases. When the oscillation center enters the device's protection range and its voltage falls below a threshold value, the device issues a tripping signal.

[0091] Its criterion for rapid out-of-step release action is:

[0092] (1) ECS (Oscillation center is within the protection zone);

[0093] (2) (The angle of attack is increasing rapidly);

[0094] (3) (Reduced transmission power);

[0095] (4)U ECS <U SET (The voltage at the oscillation center is less than a certain level.)

[0096] Fast out-of-synchronization tripping will only activate when all four conditions mentioned above are met simultaneously. The fast out-of-synchronization tripping criterion has the following main characteristics: 1) Fast: It can issue a tripping signal within the first asynchronous operating cycle of the system. 2) Accurate: It can determine the location of the oscillation center and trip the system at the section where the oscillation center is located. 3) Simple: The signals required for the criterion calculation are only the line voltage and line current signals at the device installation point; no other auxiliary signals or remote signals are needed. 4) Reliable: It only issues a tripping signal during asynchronous oscillation; it reliably does not activate under conditions of synchronous oscillation, faults, system operation, PT and CT disconnection, etc. 5) Highly adaptable: The setting value of the criterion is only related to the line parameters and is not affected by changes in the power grid structure and operating mode.

[0097] This invention uses a specific implementation case to verify the correctness of the method by determining the voltage setting of the fast out-of-step disconnection device installed on the CN line of the two regional power grid interconnection. This report analyzes and studies the law of system out-of-step oscillation, applies the BPA calculation program to verify the stability of the two regional power grids under severe and extreme faults, the influence of the oscillation center position during asynchronous oscillation, and analyzes the calculation results. Specifically:

[0098] (1) Arrangement of methods

[0099] This embodiment studies the fast out-of-step disconnection voltage setting on the CN line of the interconnection between two regional power grids. The calculations are based on summer rolling data of the large regional power grid, selecting four operating modes: forward and reverse transmission of the CN line under the conditions of CN line series compensation being engaged and disengaged. The operating characteristics of the fast disconnection device under these four operating modes are analyzed. Here, the CN line refers to the interconnection channel between the two regional power grids; forward transmission of the CN line refers to power transmission from large regional power grid 1 to large regional power grid 2, and reverse transmission of the CN line refers to power transmission from large regional power grid 2 to large regional power grid 1.

[0100] With the CN line series compensation in operation, and the UHV CN line transmitting 5800MW forward and 5200MW backward, the power flow of each section of the large regional power grid 2 is arranged in a typical manner. Except for the unequal transmission power of the CN line, the power flow of the other sections of the large regional power grid 2 is the same.

[0101] With the CN line series compensation phased out, the transmission power of the CN line is reduced. Under the mode of UHV CN line forward transmission of 4500MW and UHV CN line reverse transmission of 4100MW, the power of each section of the large regional power grid 2 is arranged according to the typical mode. Except for the UHV CN line transmission power being unequal, the power flow of the other sections of the large regional power grid 2 is the same.

[0102] (2) Fault simulation settings

[0103] Based on historical research on the safety and stability of the two major regional power grids, typical fault modes that may cause out-of-synchronization fast-resolver operation under UHV forward and reverse transmission modes include: CN line single-instantaneous fault, CZ main transformer N-1 fault, NY-JM line N-1, TX-JS line N-1, large regional power grid 1 outage fault, large regional power grid 2 outage fault, BJ DC restart, and HW line N-2 fault. Safety control actions are not considered for these faults. In other embodiments, the fault modes can be determined through historical research results or through fault scanning.

[0104] Table 3 Failure Modes

[0105] 1 CN line single instant 2 CZ main transformer N-1 3 NY-JM Line N-1 4 TX-JS line N-1 5 Large regional power grid 1 outage fault 6 Large regional power grid 2 outage fault 7 BJ DC Restart 8 HW line N-2 fault

[0106] (3) Calculation process of rapid voltage setpoint for disconnection

[0107] 1) Determine the limit method

[0108] Based on the above four operating modes, the power of the CN line is adjusted. During the adjustment process, the adjustment principle is: the CN line remains positive after the adjustment, and the CN line remains negative after the adjustment. Software simulation is used to make the power system critically stable for each fault mode as shown in Table 3. The critically stable operating mode is the extreme operating mode corresponding to the fault mode. The CN line power corresponding to the critical stability of the system under each fault mode is generally different. The fault mode and the extreme operating mode correspond one-to-one.

[0109] 2) Calculation and verification of the fast-release limit low-voltage start-up setpoint under corresponding fault conditions

[0110] Under extreme operating conditions, the voltage setpoint of the fast disconnect device is set in simulation software (such as BPA or integrated stability program). Under the above constraints, the simulation checks whether the fast disconnect device operates under the fault conditions corresponding to the extreme operating conditions. The voltage setpoint of the fast disconnect device is adjusted based on the simulation results, and the critical voltage at which the fast disconnect device will not malfunction when the corresponding fault occurs is finally determined, with a calculation error of ±0.02 pu. For example, under CN line with series compensation and CN line reverse transmission mode, the CN line reverse transmission power is adjusted. When the CN line single instantaneous fault occurs and the critical stability is reached, the CN line reverse transmission power is 5500MW. Under this mode, the fast disconnect limit low-voltage start setting is set to 0.48 pu. When the CN line single instantaneous fault occurs, the fast disconnect device does not operate. If the voltage setpoint is set to 0.5 pu, the fast disconnect device will operate when the CN line single instantaneous fault occurs. Therefore, under CN line UHV line with series compensation and CN line reverse transmission mode, the CN line single instantaneous fault fast disconnect limit low-voltage start setting is 0.48 pu.

[0111] Quick disconnection voltage setting verification under corresponding fault conditions: Read the phase angle difference between the two busbars on both sides of the line where the oscillation center is located, add the power angle on both sides of the line, and estimate the relative power angle of the two systems. If the relative power angle value is less than 180 degrees, the quick disconnection voltage setting verification is correct; if the relative power angle value is less than 180 degrees, there is a problem with the quick disconnection voltage setting verification.

[0112] The steps for calculating the power angle at the moment of operation of the fast demodulator are as follows: Read the phase angle difference between the busbars on both sides of the line where the oscillation center is located, add the power angles on both sides of the line, and estimate the relative power angle of the two systems. The specific method for calculating the angle difference between the two systems is as follows: Figure 3 The system equivalent model diagram is shown below:

[0113] like Figure 3 As shown, the systems on both sides of bus 1 and bus 2 are equivalent, with voltages E1 and E2 respectively, and system impedances X respectively. S1 and X S2 The voltages and phase angles of busbars 2 and 3 are set as U1, U2 and θ1, θ2, respectively. T X L Let θ be the transformer impedance and line impedance between busbar 2 and busbar 3. Let δ1 be the angle difference between system 1 and busbar 2, δ2 be the angle difference between busbar 2 and busbar 3, and δ3 be the angle difference between busbar 3 and system 2. Calculate the phase angle difference between the buses on either side of the oscillation center at the moment the fast-resolver operates under extreme conditions, i.e., δ2 = θ2 - θ1. Assume that the power transmitted between busbar 1 and busbar 4 remains constant, and the equivalent electromotive force of both systems is 1.

[0114] Right now:

[0115]

[0116] but

[0117]

[0118]

[0119] The angular difference δ between system 1 and system 2 is

[0120] δ=δ1+δ2+δ3 (Equation 12)

[0121] 3) Determine the final voltage setting based on the fast-disconnection limit low-voltage start setting under each fault condition: Select the minimum value among the fast-disconnection limit low-voltage start setting under each fault condition, and use this minimum value as the benchmark to determine the final voltage setting of the fast disconnection device.

[0122] (4) Simulation Results and Analysis

[0123] Under four modes—CN line UHV transmission line series compensation connected to CN line forward transmission, series compensation connected to CN line reverse transmission, series compensation disconnected from CN line forward transmission, and series compensation disconnected from CN line reverse transmission—the fast-response low-voltage start-up setting value for typical faults was verified, and the results are shown in Tables 4 and 5.

[0124] With the CN line series compensation engaged, the fast-solution low-voltage start-up settings for typical faults were verified. The faults verified included CN line single-instantaneous faults, CZ main transformer N-1 faults, NY-JM line N-1 faults, TX-JS line N-1 faults, large area power grid 1 shutdown faults, large area power grid 2 shutdown faults, BJ DC restart faults, and HW line N-2 faults. The results are shown in Table 4.

[0125] The CN line series compensation was deactivated, the CN line power was reduced, and the fast-solve low-voltage start-up setting value of typical faults was checked. The faults checked included CN line single instantaneous fault, CZ main transformer N-1 fault, NY-JM line N-1 fault, TX-JS line N-1 fault, large area power grid 1 shutdown fault, large area power grid 2 shutdown fault, and BJ DC restart fault. The results are shown in Table 5.

[0126] As shown in Table 4 below, the simulation results are presented using the following examples: CN line single instantaneous fault, CN reverse transmission 5500MW and HW line N-2 fault, CN reverse transmission 3900MW, and 15-cycle fault clearing. The following table shows the simulation results for a single instantaneous fault on the CN line and the CN line reverse transmission at 5500MW: Under the CN line UHV line with series compensation and in the CN line reverse transmission mode, the CN line reverse transmission power is adjusted. When a single instantaneous fault occurs on the CN line, the CN line reverse transmission power is 5500MW at the critical stability point. Under this extreme operating mode, the fast-disconnect low-voltage start setting is set to 0.48pu. When a single instantaneous fault occurs on the CN line, the fast-disconnect does not operate. When the voltage setting is set to 0.5pu, when a single instantaneous fault occurs on the CN line, the CN line quickly disconnects 0.7s after the fault. Based on the above simulation results, it is determined that under the CN line UHV line with series compensation and in the CN line reverse transmission mode, the limit low-voltage start setting for the fast-disconnect of the CN line single instantaneous fault is 0.48pu. At the disconnection time, the angle difference between the disconnection bus, i.e., the two buses on both sides of the CN line, i.e., the CZ-NY bus, is 65°. The estimated power angle difference between the two systems on both sides of the CN line at the disconnection time is 108°. 108° is less than 180°, so the verification is correct.

[0127] Table 4 below shows the simulation results for HW line N-2 fault, CN reverse transmission 3900MW, and 15-cycle fault clearing: Under the CN line UHV line with series compensation, in CN line reverse transmission mode, adjusting the CN line reverse transmission power, HW line N-2 fault occurs and the fault is cleared in 15 cycles. Under critical stability conditions, the CN line reverse transmission power is 3900MW. Under this extreme operating mode, the fast-disconnect low-voltage start setting is set to 0.7pu. When HW line N-2 fault occurs, the fast disconnect does not operate. One of the criteria for fast disconnection is U... ECS<U SET U ECS U is the voltage at the center of oscillation. SET For the fast-delay low-voltage start-up setting to be met, the fast disconnection can only activate if this condition is met. Therefore, under the same conditions, the higher the fast-delay low-voltage start-up setting, the more likely the fast disconnection will be triggered. When the fast-delay low-voltage start-up setting is 0.7 pu, the fast demodulator does not activate, indicating that the oscillation center voltage U... ECS If the voltage setpoint is greater than or equal to 0.7 pu, then the fast disconnection will not activate when the voltage setpoint is less than 0.7 pu. Therefore, it is determined that under CN line series compensation and CN line reverse transmission mode, the fast disconnection limit low-voltage start setting for the N-2 fault on the HW line is greater than or equal to 0.7 pu. If the fast disconnection activation setting is too high, it may cause malfunctions. After determining that the fast disconnection limit low-voltage start setting is greater than or equal to 0.7 pu, this value is too high and will not be the final voltage setpoint, so no further adjustment will be made to reduce unnecessary workload.

[0128] The results of other faults in Tables 4 and 5 follow the same pattern.

[0129] Table 4. CN Line with Series Compensation and Fast Decompression Low-Voltage Start-Up Setting Fault Verification

[0130]

[0131]

[0132]

[0133] Table 5. Fault Verification of Low-Voltage Start-up Setting Value for Series Compensation Withdrawal from CN Line UHVDC Line

[0134]

[0135]

[0136]

[0137] Table 4 shows the results of verifying the low-voltage start-up setpoint of the fast demodulation device under the condition of series compensation on the CN line UHV line. The verification results are divided according to the location of the fast demodulation device as follows:

[0138] 1) In the calculation of the CN fast-delay limit low-voltage start-up setting value, the fast-delay limit low-voltage start-up setting value is between 0.6pu and 0.7pu when the faults are N-1 on the NY-JM line, the large area power grid 2 failure, and the CZ main transformer N-1, in the CN forward transmission mode; the faults are N-2 on the HW line, the large area power grid 1 failure, the CZ main transformer N-1, and the JL-HZ bipolar blocking fault. The setting value is between 0.5pu and 0.6pu when the faults are N-1 on the TX-JS line and N-1 on the NY-JM line in the CN reverse transmission mode. The setting value is between 0.4pu and 0.5pu when the CN single instantaneous fault is in the CN forward transmission and reverse transmission mode. The setting value is 0.38pu when the BJ DC blocking restart fault is in the CN forward transmission mode, and 0.27pu when the BJ DC blocking restart fault is in the CN reverse transmission mode. Under the CN line with series compensation and CN reverse transmission mode, the fast-release limit low-voltage start-up setting value under BJ DC blockage restart fault is the lowest, at 0.27 pu.

[0139] 2) When the N-2 fault of the CN-to-HW line is detected, the fast-decoder still does not operate when the low-voltage start-up setting reaches 0.7 pu.

[0140] Table 5 shows the results of verifying the low-voltage start-up setting of the fast decoder when the CN line series compensation is disabled. The CN fast decoder operates under all typical fault conditions, and the verification results are as follows:

[0141] 1) In CN reverse transmission mode, the setpoints for JL-HZ bipolar blocking fault, large area power grid 1 outage fault, NY-JM line N-1 fault, and large area power grid 2 outage fault in CN forward transmission mode are between 0.6 pu and 0.7 pu; in CN forward and reverse transmission modes, the setpoints for TX-JS line N-1 fault are between 0.5 pu and 0.6 pu; in CN forward and reverse transmission modes, the setpoints for CN line fast-release limit low-voltage start-up in CN single-instantaneous fault are between 0.4 pu and 0.5 pu. When CN line series compensation is disabled, the minimum setpoint for CN single-instantaneous fault in CN reverse transmission mode is 0.44 pu.

[0142] 2) When the N-1 fault of the NY-JM line under CN forward transmission mode, and the N-1 fault of the CZ main transformer under CN forward and reverse transmission modes, the device still does not operate when the fast-release low-voltage start-up setting reaches 0.7pu.

[0143] The following conclusions can be drawn from Tables 4 and 5:

[0144] 1) Compared with the method of CN line transmission power above 5000MW, after the CN line series compensation is removed and the CN line transmission power is reduced, the setting value of the fast decompression device changes slightly, with a change range of -0.04pu to 0.1pu. Among them, the setting value of CN reverse transmission CN single instantaneous and large area power grid 1 failure is reduced by about 0.04pu, while the setting value of CN forward transmission CN single instantaneous, TX-JS line N-1, JL-HZ double pole blocking, large area power grid 2 failure, NY-JM line N-1 failure, and CZ main transformer N-1 failure increases by about 0 to 0.1pu.

[0145] 2) In all the verification calculations, the CN fast solution limit low voltage start setting value is the lowest setting value of 0.27pu under the BJ DC blockage restart fault.

[0146] Based on the above calculations, with the CN line series compensation engaged, the minimum CN fast-detonation limit low-voltage start-up setting for a Binjin DC blockage restart fault is 0.27 pu. It is recommended that the CNI line out-of-step fast disconnection device setting be set to 0.26 pu with the CN line series compensation engaged. With the CN line series compensation disengaged, the minimum CN fast-detonation limit low-voltage start-up setting for a CN line single instantaneous fault is 0.44 pu. It is recommended that the CNI line out-of-step fast disconnection device setting be set to 0.43 pu with the CN line series compensation disengaged.

[0147] (5) Results Analysis

[0148] Because of the large system inertia on both sides of the CN line, the stability margin of the inter-provincial section between large regional power grid 1 and large regional power grid 2 is relatively large. Furthermore, the voltage at both ends of the CN line is relatively high when asynchronous oscillation occurs. Therefore, the disconnection of the CN line within one asynchronous oscillation cycle will not cause disconnection of other sections. The setting value of the CN line fast disconnection device can be considered relatively low. The bus voltages on both sides of the CN line under asynchronous oscillation between large regional power grid 1 and large regional power grid 2 are as follows: Figure 4 As shown in the figure, the oscillation center is located on the CZ 1050kV UHV bus. The voltage levels of the busbars on both sides of the oscillation center are increased, with the NY UHV busbar voltage at 0.6 pu and the CZ 500kV busbar voltage at 0.7 pu. The voltage level is better the farther away from the oscillation center, with the JA station busbar voltage at 0.7 pu and the JM station busbar voltage at 0.9 pu. The voltage gradient on both sides of the oscillation center is large. Therefore, the asynchronous oscillation of the large regional power grid 1 to the large regional power grid 2 has little impact on the system voltage on both sides of the CN line.

[0149] Under major disturbances such as the DC blocking restart fault of regional power grid 2, power outage of regional power grid 1, and power outage of regional power grid 2, the CN line experiences asynchronous oscillation instability. In such cases, if the fast-delay action setting is too high, it can easily cause maloperation, leading to frequency stability issues in the dry season mode of regional power grid 2. With the CN line series compensation engaged, the minimum setting for the CN fast-delay low-voltage start-up under the BJ DC blocking restart fault is 0.27 pu, and the setting for the CNI line out-of-synchronization fast disconnection device is set to 0.26 pu when the CN line series compensation is engaged. With the CN line series compensation disengaged, the minimum setting for the CN fast-delay low-voltage start-up under the CN line single instantaneous fault is 0.44 pu, and the setting for the CNI line out-of-synchronization fast disconnection device is set to 0.43 pu when the CN line series compensation is disengaged, which meets the requirements.

[0150] Example 2

[0151] This embodiment provides a fast out-of-step disconnection method according to the method for determining the voltage setting of the fast out-of-step disconnection device as described in any of the above claims. The criterion for fast out-of-step disconnection is:

[0152] 1) Determine if the oscillation center is within the protected area;

[0153] 2)

[0154] 3)

[0155] 4)U ECS <U SET

[0156] Rapid out-of-step disconnection will only activate when all four of the above conditions are met simultaneously; where δ is the voltage power angle difference between the two sides of the line, P is the active power of the line, and U... ECS U is the voltage at the center of oscillation. SET To quickly resolve the low-voltage start-up setting, during the transition from synchronous to asynchronous operation, the voltage power angle difference between the two sides of the line increases at an accelerating rate, but the active power of the line continuously decreases. When the oscillation center enters the protection range of the device and the voltage of the oscillation center is lower than the threshold value, the device issues a trip signal.

[0157] Example 3

[0158] This embodiment provides a fast out-of-step disconnection device according to the method for determining the voltage setting of the fast out-of-step disconnection device as described in any of the above claims, comprising:

[0159] The typical operation mode acquisition unit is used to acquire the installation location of the fast disconnection device and the normal operation data of the relevant power grid, and to determine the typical operation mode of the relevant power grid;

[0160] The typical fault mode acquisition unit is used to acquire typical fault modes that may cause the out-of-step fast solution action under the typical operating mode.

[0161] The extreme operation mode acquisition unit is used to acquire extreme operation modes based on the typical operation modes and typical fault modes;

[0162] The fast-disconnection extreme low-voltage start-up setting value calculation unit is used to set the voltage setting value of the fast disconnection device in the simulation software based on the extreme operating mode, adjust the voltage setting value of the fast disconnection device according to the simulation results, and obtain the fast-disconnection extreme low-voltage start-up setting value under each fault condition.

[0163] The final voltage setpoint acquisition unit is used to obtain the final voltage setpoint of the fast disconnection device under the operating mode based on the minimum value selected among the fast disconnection limit low voltage start-up setpoints under each fault condition.

[0164] Example 4

[0165] This embodiment provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of any of the following methods:

[0166] Obtain the installation location of the fast disconnection device and the routine operation data of the relevant power grid to determine the typical operation mode of the relevant power grid;

[0167] Obtain the typical fault modes that may cause the fast-resolver to lose step under the typical operating mode;

[0168] Based on the typical operating modes and typical fault conditions, the extreme operating modes are obtained;

[0169] Based on the aforementioned extreme operating mode, the voltage setpoint of the fast disconnection device is set in the simulation software, and the voltage setpoint of the fast disconnection device is adjusted according to the simulation results to obtain the fast disconnection extreme low-voltage start-up setpoint under each fault condition.

[0170] Based on the minimum value selected from the fast-disconnection limit low-voltage start-up settings under each fault condition, the final voltage setting of the fast disconnection device under this operating mode is obtained.

[0171] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for determining the voltage setpoint of a fast out-of-step disconnection device, characterized in that, include: Obtain the installation location of the fast disconnection device and the routine operation data of the relevant power grid to determine the typical operation mode of the relevant power grid; Obtain the typical fault modes that cause the out-of-step fast solution action under the typical operating mode; Based on the aforementioned typical operating modes and typical fault conditions, the extreme operating modes are obtained; including: Based on the typical operating mode, the line power at the installation location of the fast disconnection device is adjusted so that the power system is critically stable when the typical fault mode occurs. The operating mode at the critical stability is the extreme operating mode corresponding to the fault mode. The line power at the installation location of the fast disconnection device corresponding to the critical stability of the system under each fault mode is generally different. The fault mode and the extreme operating mode correspond one-to-one. Based on the aforementioned extreme operating mode, the voltage setpoint of the fast disconnection device is set in the simulation software, and the voltage setpoint of the fast disconnection device is adjusted according to the simulation results to obtain the fast disconnection extreme low-voltage start-up setpoint under each fault condition. Based on the minimum value selected among the fast-disconnection limit low-voltage start-up settings under each fault condition, the final voltage setting of the fast disconnection device under this operating mode is obtained. It also includes: the fast out-of-step solution method, wherein the criterion for fast out-of-step solution is: 1) Determine if the oscillation center is within the protected area; 2） 3） 4） The fast out-of-step release will only activate if all four of the above conditions are met simultaneously; among them... Let P be the voltage power angle difference across the line, and P be the active power of the line. The voltage at the center of oscillation. To quickly resolve the low-voltage start-up setting, during the transition from synchronous to asynchronous operation, the voltage power angle difference between the two sides of the line increases at an accelerating rate, but the active power of the line continuously decreases. When the oscillation center enters the protection range of the device and the voltage of the oscillation center is lower than the threshold value, the device issues a trip signal.

2. The method for determining the voltage setpoint of the fast out-of-step disconnection device according to claim 1, characterized in that: The acquisition of typical fault modes that cause out-of-step fast-resolve action under the typical operating mode includes: Based on relevant research on power grid safety and stability, determine the typical fault modes that cause out-of-step fast-resolver operation under corresponding typical operating modes; or, under each typical operating mode, perform fault scanning using simulation software, analyze the oscillation characteristics of the power grid based on the simulation results, and then determine the fault modes that cause out-of-step fast-resolver operation. It is necessary to scan line N-1 faults, line N-2 faults, DC faults, main transformer N-1 faults, single-phase instantaneous line faults, and outage faults.

3. The method for determining the voltage setpoint of the fast out-of-step disconnection device according to claim 1, characterized in that: The adjustment of the voltage setpoint of the rapid disconnection device based on simulation results includes: When the rapid disconnection device fails to operate due to a fault condition corresponding to the extreme operating mode, the voltage setting of the rapid disconnection device is increased; when the rapid disconnection device operates due to a fault condition corresponding to the extreme operating mode, the voltage setting of the rapid disconnection device is decreased.

4. The method for determining the voltage setpoint of the fast out-of-step disconnection device according to claim 1, characterized in that: The acquisition of the fast-solution limit low-voltage start-up setpoint under each fault condition includes: When the voltage setpoint of the fast disconnect device is set to the set value X, the fast disconnect device will not operate when a fault condition corresponding to the extreme operating mode occurs. When the voltage setpoint of the fast disconnect device is set to the set value X + 0.02pu, the fast disconnect device will operate when a fault condition corresponding to the extreme operating mode occurs, the adjustment of the voltage setpoint of the fast disconnect device will end, and the fast disconnect extreme low voltage start setpoint under the corresponding fault will be set to the set value X.

5. The method for determining the voltage setpoint of the fast out-of-step disconnection device according to claim 4, characterized in that, It also includes: when the voltage setting of the fast disconnect device is 0.7pu, if the fast disconnect fails to operate due to a fault condition corresponding to the extreme operating mode, the adjustment of the voltage setting of the fast disconnect device will be terminated, and it will be determined that the fast disconnect extreme low voltage start setting under the corresponding fault is greater than or equal to 0.7pu.

6. The method for determining the voltage setpoint of the fast out-of-step disconnection device according to claim 1, characterized in that: Also includes: If the final voltage setpoint is equal to the minimum value, then subtract 0.01 pu from the final voltage setpoint.

7. A fast out-of-step disconnection device according to any one of claims 1 to 6, characterized in that, include: The typical operation mode acquisition unit is used to acquire the installation location of the fast disconnection device and the normal operation data of the relevant power grid, and to determine the typical operation mode of the relevant power grid; The typical fault mode acquisition unit is used to acquire the typical fault modes that cause the out-of-step fast solution action under the typical operating mode. The extreme operation mode acquisition unit is used to acquire extreme operation modes based on the typical operation modes and typical fault modes; The fast-disconnection extreme low-voltage start-up setting value calculation unit is used to set the voltage setting value of the fast disconnection device in the simulation software based on the extreme operating mode, adjust the voltage setting value of the fast disconnection device according to the simulation results, and obtain the fast-disconnection extreme low-voltage start-up setting value under each fault condition. The final voltage setpoint acquisition unit is used to obtain the final voltage setpoint of the fast disconnection device under the operating mode based on the minimum value selected among the fast disconnection limit low voltage start-up setpoints under each fault condition.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When executed by a processor, the program implements the steps of the method according to any one of claims 1 to 6.

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