A fluctuation new energy power grid current protection method and device based on network WAMS

Abstract

This invention provides a method and device for current protection of fluctuating renewable energy power grids based on distribution network WAMS. Based on real-time upstream measurement information, the ratio of short-circuit current provided by traditional power sources and renewable energy sources during a short-circuit fault is obtained, thereby correcting the current protection settings. This solves the problem that the increasing proportion of renewable energy sources leads to weakened system fault characteristics and unpredictable grid operation, resulting in difficulties in setting segmented current protection settings and accurate protection operation. This invention proposes an overall method and hardware architecture for current protection of fluctuating renewable energy power grids; it obtains remote current information in real time through distribution network WAMS, and uses online statistical and correction methods to obtain the proportion of fault current components at the protection installation point; the ratio of short-circuit power provided by generators and short-circuit current provided by renewable energy sources at the protection installation point is determined qualitatively to establish the correction direction, and then the settings are corrected according to the proportional relationship.

Description

Technical Field

[0001] This invention relates to a method and device for protecting fluctuating new energy grid currents based on distribution network WAMS, belonging to the field of power system relay protection. Background Technology

[0002] Currently, electricity production still heavily relies on fossil fuels, consuming vast amounts of non-renewable resources and causing environmental pollution. Against this backdrop, renewable, pollution-free, and environmentally friendly new energy power generation is gaining popularity, and a high proportion of distributed renewable energy sources has become a key characteristic of new power systems.

[0003] The output of renewable energy sources exhibits strong nonlinear self-control characteristics, which are also related to the electrical distance between the source and the short-circuit point. Therefore, the volatility of distributed renewable energy generation connected to the grid leads to ambiguity in grid fault information and results in variable and unpredictable grid operating conditions. Consequently, there is an urgent need for real-time correction of current protection settings based on the real-time operating status of new power systems adapted to the volatility of distributed renewable energy grid connection. Summary of the Invention

[0004] The purpose of this invention is to provide a method and device for protecting fluctuating new energy power grid current based on distribution network WAMS, which can effectively solve the problem of difficulty in setting segmented current protection settings due to the increasing proportion of grid-connected new energy power sources and the unpredictability of grid operation status.

[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 protecting fluctuating renewable energy grid currents based on distribution network WAMS, comprising the following steps:

[0007] The initial values ​​of the fault current component proportion and protection setting are calculated for the new power system, and the initial values ​​of the fault current component proportion and protection setting are obtained; the new power system contains distributed new energy power sources and traditional generators;

[0008] Real-time acquisition of short-circuit current of traditional generators and short-circuit current of new energy power sources;

[0009] Obtain the measured value of the actual short-circuit current of the line;

[0010] Based on the short-circuit current of the traditional generator and the short-circuit current of the new energy power source, the measured values ​​of the actual short-circuit current of the line are merged online in real time to obtain the ratio of the short-circuit current provided by the generator and the short-circuit current provided by the new energy power source at the protection installation point of this line.

[0011] Based on the initial values ​​of the fault current component proportion and the initial values ​​of the protection settings, the protection settings are adjusted in real time according to the proportion of the short-circuit current component of the faulted line.

[0012] Furthermore, the initial values ​​for the proportion of fault current components and the initial values ​​for protection settings in the new power system are calculated, including:

[0013] In traditional generator models, line current protection is divided into three stages: Stage I, Stage II, and Stage III.

[0014] The circuit system has three busbars A, B, and C, with the lines between them being AB, BC, and CD, respectively; protection devices 1, 2, and 3 are installed between the three busbars.

[0015] Using a power system short-circuit model of a traditional generator, the initial value k0 of the fault current component proportion at the protection installation location and the current stage I protection setting are adjusted:

[0016]

[0017]

[0018] In the above formula, Z represents the short-circuit current supplied by each conventional generator when a short circuit occurs at the outlet of section BC; E represents the internal potential of each conventional generator; and Z represents the internal impedance of each conventional generator. AB The impedance of the entire length of line AB; This refers to the short-circuit current provided by each new energy power source when a short circuit occurs at the BC section outlet. During a short-circuit fault, the ratio of the short-circuit current supplied by the new energy source to the rated current; I N This is the rated current of the new energy power source.

[0019]

[0020]

[0021] In the above formula, This is the sum of the short-circuit currents provided by each conventional generator when a short circuit occurs at the BC section outlet. This is the sum of the short-circuit currents provided by each new energy source when a short circuit occurs at the BC section outlet.

[0022]

[0023]

[0024] In the above formula, k0 is the initial value of the proportion of fault current components, that is, the initial value of the proportion of short-circuit current provided by traditional generators and short-circuit current provided by new energy power sources at the new power system protection installation point. This is the setting value for the current stage I protection. To protect the reliability coefficient of section 1Ι.

[0025] Using a power system short-circuit model of a traditional generator, the protection settings for current stage II are adjusted:

[0026]

[0027]

[0028] In the above formula, Z represents the short-circuit current supplied by each conventional generator when a short circuit occurs at the output of section CD; AB Z BC These are the total impedances of lines AB and BC, respectively. This refers to the short-circuit current provided by each new energy power source when a short circuit occurs at the CD section outlet.

[0029]

[0030]

[0031] In the above formula, This is the sum of the short-circuit currents provided by each conventional generator when a short circuit occurs at the output of section CD. This is the sum of the short-circuit currents provided by each new energy source when a short circuit occurs at the CD segment outlet.

[0032]

[0033] In the above formula, The current protection setting for stage II is... To protect the reliability coefficient of section 1III, To protect the reliability coefficient of section 2Ι.

[0034] Set the current protection setting for the III stage:

[0035]

[0036]

[0037] In the above formula, It is the sum of the maximum load current of each new energy power source; I L.max This refers to the maximum load current of the line, including the load current provided by new energy sources. To protect the reliability coefficient of section 1III; K re.1 K is the return coefficient of the current relay. ss This is the self-starting coefficient.

[0038] In the initial state of the system, The initial value of the system current protection is

[0039] Furthermore, Take 1.2 to 1.5;

[0040] Take 1.1-1.2.

[0041] Take 1.1-1.2.

[0042] Take 1.1-1.2;

[0043] K re.1 It is 0.85-0.95;

[0044] K ss Greater than 1.

[0045] Furthermore, real-time acquisition of the short-circuit current of traditional generators and the short-circuit current of new energy power sources includes:

[0046] Real-time short-circuit currents of traditional generators and renewable energy sources can be obtained through the distribution network WAMS.

[0047]

[0048]

[0049] In the above formula, This is the sum of the real-time short-circuit current measurements of a traditional generator. The values ​​are the real-time short-circuit current measurements for each traditional generator. This is the sum of real-time short-circuit current measurements from new energy power sources. This provides the real-time short-circuit current measurement values ​​for each new energy power source.

[0050] Furthermore, the actual short-circuit current of the line is measured, including:

[0051] The actual short-circuit current I of the line is obtained through the protection device.

[0052] Furthermore, the measured values ​​of the actual short-circuit current of the line are aggregated online in real time to obtain the ratio of the short-circuit current supplied by the generator at the protection installation point of this line to the short-circuit current supplied by the new energy power source, including:

[0053] To ensure that the sum of the two short-circuit current measurements equals the actual short-circuit current measurement I, i.e., let I1 + I2 = I, for and Make corrections by multiplying by the correction factor N:

[0054]

[0055]

[0056]

[0057] In the above formula, I1 and I2 are the actual values ​​of the short-circuit current provided in real time by the traditional generator after correction and the actual values ​​of the short-circuit current provided in real time by the new energy power source after correction.

[0058] At this time, the proportion k of the fault current component at the protection installation point is:

[0059]

[0060] Furthermore, based on the proportion of short-circuit current components in the faulty line, the protection settings are adjusted in real time, including: real-time modification of the current protection settings based on the proportional relationship between the actual fault current values ​​I1 and I2; in the initial state of the system, The initial value of the system current protection is

[0061] If -Δε < k - k0 < Δε, the protection setting remains unchanged, and the initial current protection setting value under the initial state of the system is used. Δε is the error limit, which can be set according to the actual system conditions.

[0062] If k - k0 > Δε, it means that compared to the initial state, the generator capacity is larger, and the current-limiting characteristic is weakened. In this case, the short-circuit current flowing through the protection installation point is larger than under the initial conditions, thus requiring a positive correction to the initial protection setting.

[0063] I Set =I Set(0) +ΔI Set (20)

[0064]

[0065] In the above formula, I Set(0) The current protection setting value ΔI is the value set under initial conditions. Set K is the correction amount for the protection settings selected based on the actual system. rel For reliability coefficient, The sum of short-circuit currents provided to protect the corresponding new energy power sources.

[0066] The corresponding segmented current protection is as follows:

[0067]

[0068]

[0069]

[0070]

[0071]

[0072]

[0073] If k - k0 < -Δε, it means that compared to the initial state, the generator capacity is smaller and the current limiting characteristic is enhanced. At this time, the short-circuit current flowing through the protection installation point is smaller than that under the initial condition, and the initial value of the protection setting is corrected in the opposite direction.

[0074] I Set =I Set(0) +ΔI Set (28)

[0075]

[0076] The corresponding segmented current protection is as follows:

[0077]

[0078]

[0079]

[0080]

[0081]

[0082]

[0083] Furthermore, K rel Take 1.1-1.2.

[0084] Furthermore, after real-time correction of the setpoint, the protection action is determined according to the traditional three-stage current protection based on the corrected setpoint.

[0085] Furthermore, based on the revised settings, the protection action is determined according to the traditional three-stage current protection method:

[0086] If the actual short-circuit current measurement value I is greater than the operating setting value of the current protection stage I of this line, then the short-circuit fault is within the protection range of the current protection stage I of this line, and the corresponding protection will operate; otherwise (i.e., less than the operating setting value of the current protection stage I of this line), the current protection stage I of this line will not operate.

[0087] If the actual short-circuit current measurement value I is greater than the setting value of the current protection stage II of this line, the current protection stage II of this line will start timing. If the actual short-circuit current measurement value I drops sufficiently before the timing point arrives, it indicates that the fault occurred on the next line and has been cleared by the current protection stage I of the next line. If the actual short-circuit current measurement value I remains greater than the setting value of the current protection stage II of this line after the timing point arrives, it indicates that the fault occurred on this line or the protection of the next line failed to operate. Therefore, the fault is cleared by the current protection stage II of this line, realizing the full line protection of this line and the backup protection of the next line outlet.

[0088] The current protection stage I and current protection stage II of all the above lines constitute a complete protection range in sequence.

[0089] In addition, a third stage of current protection needs to be set, with an operating setting value of approximately 1.5 to 2 times the rated current. If the actual short-circuit current measurement value I is greater than the third stage current protection setting value, timing begins; if the current still exceeds the limit after the timing time, it indicates that the fault or overload still exists, and therefore the circuit breaker trips; if the actual short-circuit current measurement value I is less than the third stage current protection setting value before the timing time is reached, it indicates that the fault or overload has disappeared, and the circuit breaker returns to its original state. Due to the strong nonlinearity of the power supply, the operating settings values ​​of the third stage current protection for each line are not significantly different. In this case, different delay times can be used, i.e., the delay time of the next line is less than the delay time Δt of the previous line, to achieve sequential operation of the third stage current protection for different lines.

[0090] Secondly, the present invention provides a fluctuating renewable energy grid current protection device based on distribution network WAMS, comprising:

[0091] Initial value calculation module: used to calculate the initial values ​​of the fault current component ratio and the protection setting for the new power system, and obtain the initial values ​​of the fault current component ratio and the protection setting.

[0092] Real-time current measurement module: used to acquire the short-circuit current of traditional generators and the short-circuit current of new energy power sources in real time;

[0093] Short-circuit current measurement module: used to obtain the measured value of the actual short-circuit current of the line;

[0094] Fault current component ratio calculation module: used to perform online real-time aggregation of the measured values ​​of the actual short-circuit current of the line based on the short-circuit current of the traditional generator and the short-circuit current of the new energy power source, so as to obtain the ratio of the short-circuit current provided by the generator and the short-circuit current provided by the new energy power source at the protection installation location of this line.

[0095] Correction module: Used to correct the protection settings in real time based on the initial values ​​of the fault current component proportion and the initial protection settings, according to the short-circuit current component proportion of the faulted line.

[0096] Thirdly, the present invention provides a fluctuating new energy grid current protection device based on distribution network WAMS, including a processor and a storage medium;

[0097] The storage medium is used to store instructions;

[0098] The processor is configured to operate according to the instructions to perform the steps of the method described in the first aspect.

[0099] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0100] 1. The present invention proposes a method and device for current protection of fluctuating new energy power grid based on distribution network WAMS, which can solve the problems of difficulty in setting segmented current protection settings and inaccurate protection operation caused by the gradual increase in the proportion of new energy power sources, which leads to the weakening of system fault characteristics and the difficulty in predicting the power grid operation status.

[0101] 2. This invention proposes an overall method and hardware architecture for current protection of fluctuating new energy power grids; and obtains remote current information in real time through the distribution network WAMS, and obtains the proportion of fault current components at the protection installation point of the line through online statistical and correction methods;

[0102] 3. The proportion of short-circuit power supplied by the generator and short-circuit current supplied by the new energy power source at the installation point of the protection of this invention is determined according to the qualitative nature of the problem, and then the correction setting is made according to the proportional relationship.

[0103] 4. The fluctuating new energy power grid current protection method and device based on distribution network WAMS proposed in this invention can make full use of existing power line relay protection devices, without the need for additional hardware installation. It only requires functional expansion at the software level, which greatly reduces the construction and operation costs of the power system. Attached Figure Description

[0104] Figure 1 For a new type of power system topology;

[0105] Figure 2 A short-circuit model for power systems using traditional generators and new energy sources;

[0106] Figure 3 For flowcharts;

[0107] Figure 4 This is a hardware block diagram. Detailed Implementation

[0108] The present invention will be further explained in detail below with reference to the accompanying drawings and specific embodiments, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0109] Example 1:

[0110] This embodiment provides a method and device for protecting fluctuating renewable energy grid currents based on distribution network WAMS, including the following steps:

[0111] 1. Real-time online aggregation of fault current components via distribution network WAMS:

[0112] Real-time acquisition of remote current information allows for the determination of the proportion of fault current components in the local line.

[0113] Applicants should note that data can also be obtained in real time by creating other measuring devices, but this requires creating new measuring devices, while WAMS is already relatively mature.

[0114] 2. Adjust the setting based on the proportion of fault current components.

[0115] Since the lower the generator capacity in the power supply configuration, the more obvious the current limiting characteristic, if the proportional relationship of the fault current is known, the correction direction can be determined according to the qualitative nature, and then the set value can be corrected according to the proportional relationship.

[0116] like Figure 1 As shown, the transmission network of the new power system connects to a small number of large-capacity centralized renewable energy power plants, while the distribution network connects to a large number of small-capacity distributed renewable energy power plants, powered simultaneously by both traditional generators and renewable energy sources. The integration of renewable energy sources into the grid makes the power system topology more complex, and their automatic control characteristics introduce nonlinear output problems, causing short-circuit calculations and current protection setting settings based on the grid topology to become nonlinear. Therefore, traditional current protection settings are no longer applicable to the new power system, and the impact of renewable energy sources must be taken into account.

[0117] Under normal grid operation, the voltage at each node is relatively within its rated operating range. New energy power sources connected to the grid using constant power control have relatively constant output currents with minimal fluctuations. When a short-circuit fault occurs, the voltage at the grid connection point of new energy power sources far from the fault remains close to their rated voltage, thus their output current remains essentially unchanged. However, new energy power sources closer to the short-circuit point enter a low-voltage ride-through state, but undergo a brief transition process under a negative sequence suppression strategy, and their output quickly stabilizes and becomes symmetrical. Therefore, they can be considered as a single, variable-output current source. Figure 2 As shown, short-circuit models of power systems for traditional generators and new energy sources are constructed respectively.

[0118] By utilizing the WAMS (Wide-Area Measuring System) of the distribution network—that is, the measurement equipment at the feeder of each power generation unit—to provide real-time information from upstream measured points, the proportional relationship of fault current can be obtained in real time. The magnitude of the line short-circuit current is related to the ratio of traditional generator power supply and new energy power supply. In the power supply configuration, the lower the generator capacity, the more obvious the current limiting characteristic. Therefore, if the proportional relationship of fault current is known, the setpoint can be corrected in real time.

[0119] Figure 2 middle, These are the short-circuit currents supplied by each traditional generator and each new energy power source, respectively. Before using WAMS to obtain the proportion of fault current components in real time and then correcting the current protection settings, it is necessary to first... Figure 2 The novel power system shown calculates the initial values ​​of the proportion of fault current components (short-circuit current provided by traditional generators and short-circuit current provided by new energy sources) k0 and the initial values ​​of protection settings.

[0120] Using a power system short-circuit model of a traditional generator, the initial value k0 of the fault current component proportion at the protection installation location and the current stage I protection setting are adjusted:

[0121]

[0122]

[0123] In the above formula, Z represents the short-circuit current supplied by each conventional generator when a short circuit occurs at the outlet of section BC; E represents the internal potential of each conventional generator; and Z represents the internal impedance of each conventional generator. AB The impedance of the entire length of line AB; This refers to the short-circuit current provided by each new energy power source when a short circuit occurs at the BC section outlet. During a short-circuit fault, the ratio of the short-circuit current supplied by the new energy source to the rated current is typically taken as 1.2 to 1.5; N This is the rated current of the new energy power source.

[0124]

[0125]

[0126] In the above formula, This is the sum of the short-circuit currents provided by each conventional generator when a short circuit occurs at the BC section outlet. This is the sum of the short-circuit currents provided by each new energy source when a short circuit occurs at the BC section outlet.

[0127]

[0128]

[0129] In the above formula, k0 is the initial value of the proportion of fault current components (short-circuit current provided by traditional generators and short-circuit current provided by new energy power sources) at the installation point of the new power system protection. This is the setting value for the current stage I protection. To ensure the reliability coefficient of the protection for section 1I, it is generally taken as 1.1-1.2.

[0130] Using a power system short-circuit model of a traditional generator, the protection settings for current stage II are adjusted:

[0131]

[0132]

[0133] In the above formula, Z represents the short-circuit current supplied by each conventional generator when a short circuit occurs at the output of section CD; AB Z BC These are the total impedances of lines AB and BC, respectively. This refers to the short-circuit current provided by each new energy power source when a short circuit occurs at the CD section outlet.

[0134]

[0135]

[0136] In the above formula, This is the sum of the short-circuit currents provided by each conventional generator when a short circuit occurs at the output of section CD. This is the sum of the short-circuit currents provided by each new energy power source when a short circuit occurs at the CD section outlet.

[0137]

[0138] In the above formula, The current protection setting for stage II is... To protect the reliability coefficient of section 1III, To ensure the reliability coefficient of the protection for section 2I, it is generally taken as 1.1-1.2.

[0139] Set the current protection setting for the III stage:

[0140]

[0141]

[0142] In the above formula, It is the sum of the maximum load current of each new energy power source; I L.max This represents the maximum load current of the line. To ensure the reliability coefficient of the protection system in section 1III is protected, it is generally taken as 1.1-1.2; K re.1 K is the return coefficient for the current relay, typically 0.85-0.95; ss This is the self-starting coefficient, which is generally greater than 1.

[0143] After obtaining the initial value k0 of the fault current component ratio at the protection installation location and the current protection setting, as follows: Figure 1 As shown, firstly, the short-circuit current of traditional generators and the short-circuit current of new energy power sources are obtained in real time through the distribution network WAMS:

[0144]

[0145]

[0146] In the above formula, This is the sum of the real-time short-circuit current measurements of a traditional generator. The values ​​are the real-time short-circuit current measurements for each traditional generator. This is the sum of real-time short-circuit current measurements from new energy power sources. This provides the real-time short-circuit current measurement values ​​for each new energy power source.

[0147] Then, the measured values ​​are aggregated online in real time to obtain the ratio of the short-circuit current provided by the generator at the protection installation point to the short-circuit current provided by the new energy power source:

[0148] The actual short-circuit current I of the line is obtained through the distribution network WAMS. To ensure that the sum of the two short-circuit current measurements equals the actual short-circuit current I, i.e., let I1 + I2 = I, for... and Make corrections by multiplying each by a correction factor N.

[0149]

[0150]

[0151]

[0152] In the above formula, I1 and I2 are the actual values ​​of the short-circuit current provided in real time by the traditional generator after correction and the actual values ​​of the short-circuit current provided in real time by the new energy power source after correction.

[0153] At this time, the proportion k of the fault current component at the protection installation point is:

[0154]

[0155] Finally, based on the proportional relationship between the actual fault current values ​​I1 and I2, the current protection settings are modified in real time: in the initial state of the system, The initial value of the system current protection is

[0156] If -Δε < k - k0 < Δε, the protection setting remains unchanged, and the initial current protection setting value under the initial state of the system is used. Δε is the error limit, which can be set according to the actual system conditions.

[0157] If k - k0 > Δε, it means that compared to the initial state, the generator capacity is larger, and the current-limiting characteristic is weakened. In this case, the short-circuit current flowing through the protection installation point is larger than under the initial conditions, thus requiring a positive correction to the initial protection setting.

[0158] I Set =I Set(0) +ΔI Set (20)

[0159]

[0160] In the above formula, I Set(0) The current protection setting value ΔI is the value set under initial conditions. Set K is the correction amount for the protection settings selected based on the actual system. rel The reliability factor is typically taken as 1.1-1.2. As can be seen from the above, this is the sum of the short-circuit currents provided to protect the corresponding new energy power sources.

[0161] The corresponding segmented current protection is as follows:

[0162]

[0163]

[0164]

[0165]

[0166]

[0167]

[0168] If k - k0 < -Δε, it means that compared to the initial state, the generator capacity is smaller and the current limiting characteristic is enhanced. At this time, the short-circuit current flowing through the protection installation point is smaller than that under the initial condition, and the initial value of the protection setting is corrected in the opposite direction.

[0169] I Set =I Set(0) +ΔI Set (28)

[0170]

[0171] The corresponding segmented current protection is as follows:

[0172]

[0173]

[0174]

[0175]

[0176]

[0177]

[0178] The process and hardware block diagram are as follows: Figure 4 As shown.

[0179] Note that, except for (5), all formulas (1) to (13) in this patent are formulas related to the initial protection value. There are three initial protection values. Traditional current protection initial value formula:

[0180]

[0181]

[0182]

[0183] In the formula, Z r Z is the equivalent internal impedance of a conventional generator; AB Z BC These are the total impedances of lines AB and BC, respectively; I L.max This represents the maximum load current of the line. The reliability coefficient for each protection section is typically taken as 1.1-1.2; K re.1 K is the return coefficient for the current relay, typically 0.85-0.95; ss The self-starting coefficient is generally greater than 1. However, the traditional three-stage current protection setting does not consider new energy power sources. This patent considers new energy power sources based on the traditional protection setting method. That is, the short-circuit current provided by the new energy power source is added during the protection setting process of stage I and stage II: equations (2)(4)(6)(8)(10)(11); the rated current of the new energy power source is added during the protection setting process of stage III: the maximum load current I in equation (13) L.max It can be measured when the power grid is operating normally, including the load current provided by new energy sources.

[0184] This invention provides a current protection method for fluctuating renewable energy power grids based on distribution network WAMS. Based on real-time upstream measurement information, it obtains the ratio of short-circuit current provided by traditional power sources and renewable energy sources during a short-circuit fault, thereby correcting the current protection settings. This solves the problem that the increasing proportion of renewable energy sources leads to weakened system fault characteristics and unpredictable grid operation, resulting in difficulties in setting segmented current protection settings and accurate protection operation. This invention proposes an overall method and hardware architecture for current protection of fluctuating renewable energy power grids; it obtains remote current information in real time through distribution network WAMS, and uses online statistical and correction methods to obtain the proportion of fault current components at the protection installation point; the ratio of short-circuit power provided by generators and short-circuit current provided by renewable energy sources at the protection installation point is determined qualitatively to determine the correction direction, and then the settings are corrected according to the proportional relationship.

[0185] The present invention will be further explained in detail below with reference to specific embodiments.

[0186] Real-time acquisition of remote current information allows for the determination of the proportion of fault current components on the local line. Since the lower the generator capacity in the power supply configuration, the more pronounced the current-limiting characteristics, knowing the proportional relationship of the fault current allows for the determination of the correction direction based on the qualitative nature of the fault current, followed by setting correction according to the proportional relationship.

[0187] like Figure 1 As shown, the transmission network of the new power system connects to a small number of large-capacity centralized renewable energy power plants, while the distribution network connects to a large number of small-capacity distributed renewable energy power plants, powered simultaneously by both traditional generators and renewable energy sources. The integration of renewable energy sources into the grid makes the power system topology more complex, and their automatic control characteristics introduce nonlinear output problems, causing short-circuit calculations and current protection setting settings based on the grid topology to become nonlinear. Therefore, traditional current protection settings are no longer applicable to the new power system, and the impact of renewable energy sources must be taken into account.

[0188] Under normal grid operation, the voltage at each node is relatively within its rated operating range. New energy power sources connected to the grid using constant power control have relatively constant output currents with minimal fluctuations. When a short-circuit fault occurs, the voltage at the grid connection point of new energy power sources far from the fault remains close to their rated voltage, thus their output current remains essentially unchanged. However, new energy power sources closer to the short-circuit point enter a low-voltage ride-through state, but undergo a brief transition process under a negative sequence suppression strategy, and their output quickly stabilizes and becomes symmetrical. Therefore, they can be considered as a single, variable-output current source. Figure 2 As shown, short-circuit models of power systems for traditional generators and new energy sources are constructed respectively.

[0189] By utilizing the WAMS (Wide-Area Measuring System) of the distribution network—that is, the measurement equipment at the feeder of each power generation unit—to provide real-time information from upstream measured points, the proportional relationship of fault current can be obtained in real time. The magnitude of the line short-circuit current is related to the ratio of traditional generator power supply and new energy power supply. In the power supply configuration, the lower the generator capacity, the more obvious the current limiting characteristic. Therefore, if the proportional relationship of fault current is known, the setpoint can be corrected in real time.

[0190] Example 2:

[0191] This embodiment provides a fluctuating renewable energy grid current protection device based on distribution network WAMS, including:

[0192] Initial value calculation module: used to calculate the initial values ​​of the fault current component ratio and the protection setting for the new power system, and obtain the initial values ​​of the fault current component ratio and the protection setting.

[0193] Real-time current measurement module: used to acquire the short-circuit current of traditional generators and the short-circuit current of new energy power sources in real time;

[0194] Short-circuit current measurement module: used to obtain the measured value of the actual short-circuit current of the line;

[0195] Fault current component ratio calculation module: used to perform online real-time aggregation of the measured values ​​of the actual short-circuit current of the line based on the short-circuit current of the traditional generator and the short-circuit current of the new energy power source, so as to obtain the ratio of the short-circuit current provided by the generator and the short-circuit current provided by the new energy power source at the protection installation location of this line.

[0196] Correction module: Used to correct the protection settings in real time based on the initial values ​​of the fault current component proportion and the initial protection settings, according to the short-circuit current component proportion of the faulted line.

[0197] Specifically, such as Figure 4 As shown, it includes the following modules:

[0198] Real-time current measurement module:

[0199] (1) Modules installed at each power source: used to obtain the short-circuit fault current value provided by each power source (traditional power source / new energy power source) in real time; that is, the real-time short-circuit current measurement value of each traditional generator. Real-time short-circuit current measurement values ​​of various new energy power sources

[0200] (2) Module installed at the protection device: used to obtain the total short-circuit current supplied to the fault location by each power source in real time, i.e., the actual short-circuit current measurement value I of the line.

[0201] Measurement Information Transmission Module: Used to transmit the short-circuit current values ​​measured at upstream information measurement points, i.e., the short-circuit current values ​​obtained by the real-time current measurement modules installed at each power source.

[0202] Fault current component ratio calculation module: used to calculate the proportion k of fault current components at the protection installation location, as shown in equations (16)(17)(18)(19) in the text.

[0203] The actual short-circuit current I of the line is obtained through the distribution network WAMS. To ensure that the sum of the two short-circuit current measurements equals the actual short-circuit current I, i.e., let I1 + I2 = I, for... and Make corrections by multiplying each by a correction factor N.

[0204]

[0205]

[0206]

[0207] In the above formula, I1 and I2 are the actual values ​​of the short-circuit current provided in real time by the traditional generator after correction and the actual values ​​of the short-circuit current provided in real time by the new energy power source after correction.

[0208] At this time, the proportion k of the fault current component at the protection installation point is:

[0209]

[0210] Upstream Measurement Information Receiving Module: Used to receive information transmitted by the measurement information transmitting module, i.e.

[0211] The K-value comparison and protection setting correction module is used to compare K with K0 and correct the protection setting based on the comparison result. Formulas (20)-(35) in the text.

[0212] If k - k0 > Δε, it means that compared to the initial state, the generator capacity is larger, and the current-limiting characteristic is weakened. In this case, the short-circuit current flowing through the protection installation point is larger than under the initial conditions, thus requiring a positive correction to the initial protection setting.

[0213] I Set =I Set(0) +ΔI Set (20)

[0214]

[0215] In the above formula, I Set(0) The current protection setting value ΔI is the value set under initial conditions. SetK is the correction amount for the protection settings selected based on the actual system. rel The reliability factor is typically taken as 1.1-1.2. As can be seen from the above, this is the sum of the short-circuit currents provided to protect the corresponding new energy power sources.

[0216] The corresponding segmented current protection is as follows:

[0217]

[0218]

[0219]

[0220]

[0221]

[0222]

[0223] If k - k0 < -Δε, it means that compared to the initial state, the generator capacity is smaller and the current limiting characteristic is enhanced. At this time, the short-circuit current flowing through the protection installation point is smaller than that under the initial condition, and the initial value of the protection setting is corrected in the opposite direction.

[0224] I Set =I Set(0) +ΔI Set (28)

[0225]

[0226] The corresponding segmented current protection is as follows:

[0227]

[0228]

[0229]

[0230]

[0231]

[0232]

[0233] Trip command output module: After the K-value comparison and protection setting correction module performs setting correction, it determines whether the tripping conditions are met. If they are met, a trip command is sent to the circuit breaker; otherwise, no command is sent.

[0234] The apparatus in this embodiment can be used to implement the method described in Embodiment 1.

[0235] Example 3:

[0236] This embodiment provides a fluctuating new energy grid current protection device based on distribution network WAMS, including a processor and a storage medium;

[0237] The storage medium is used to store instructions;

[0238] The processor is configured to operate according to the instructions to execute the steps of the method described in Embodiment 1.

[0239] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only used to facilitate the description of this embodiment and to simplify the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the protection content of this embodiment.

[0240] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0241] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0242] The above description is only a preferred embodiment of this embodiment. 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 this embodiment, and these improvements and modifications should also be considered within the protection scope of this embodiment.

Claims

1. A method for protecting fluctuating renewable energy grid current based on distribution network WAMS, characterized in that, Includes the following steps: The initial values ​​of the fault current component proportion and the initial values ​​of the protection settings are calculated for the new power system to obtain the initial values ​​of the fault current component proportion and the initial values ​​of the protection settings; the new power system includes traditional generators and distributed new energy power sources; Real-time acquisition of short-circuit current of traditional generators and short-circuit current of new energy power sources; Obtain the measured value of the actual short-circuit current of the line; Based on the short-circuit current of the traditional generator and the short-circuit current of the new energy power source, the measured values ​​of the actual short-circuit current of the line are merged online in real time to obtain the ratio of the short-circuit current provided by the generator and the short-circuit current provided by the new energy power source at the protection installation location of this line. Based on the initial values ​​of the fault current component proportion and the initial values ​​of the protection settings, the protection settings are adjusted in real time according to the proportion of the short-circuit current component of the faulted line. Obtain the measured value of the actual short-circuit current of the line, including: The actual short-circuit current I of the line is obtained through the protection device; The measured values ​​of the actual short-circuit current of the line are aggregated online in real time to obtain the ratio of the short-circuit current supplied by the generator at the protection installation point of this line to the short-circuit current supplied by the new energy power source, including: To ensure that the sum of the two short-circuit current measurements equals the actual short-circuit current measurement I of the line, that is, let ,right and Make corrections by multiplying by the correction factor N: (16) (17) (18) In the above formula, , The corrected real-time short-circuit current values ​​provided by traditional generators and the corrected real-time short-circuit current values ​​provided by new energy power sources. At this time, the proportion of fault current components at the protection installation location for: (19)； The protection settings are adjusted in real time based on the proportion of short-circuit current components in the faulty line, including: Based on the actual value of the fault current , The proportional relationship is used to modify the current protection setting in real time: In the initial state of the system, The initial value of the system current protection is , , ; in, This represents the initial value of the proportion of fault current components, specifically the initial proportion of short-circuit current supplied by traditional generators and short-circuit current supplied by new energy sources at the new power system protection installation location. To protect the proportion of fault current components at the installation location; like If the protection setting remains unchanged, the initial current protection setting value under the initial state of the system will be used, where The error limit should be set according to the actual system requirements. like This indicates that compared to the initial state, the generator capacity is larger, the current-limiting characteristic is weakened, and the short-circuit current flowing through the protection installation point is greater than under the initial conditions. Therefore, the initial protection setting is positively corrected. (20) (21) In the above formula, The current protection setting value is set under initial conditions. The correction amount is based on the protection setting selected according to the actual system. For reliability coefficient, The sum of short-circuit currents provided to protect the corresponding new energy power sources; The corresponding segmented current protection is as follows: (22) (23) (24) (25) (26) (27) like This means that compared to the initial state, the generator capacity is smaller, and the current limiting characteristic is enhanced. At this time, the short-circuit current flowing through the protection installation point is smaller than under the initial conditions, and the initial value of the protection setting is corrected in the opposite direction. (28) (29) The corresponding segmented current protection is as follows: (30) (31) (32) (33) (34) (35)。 2. The method for protecting fluctuating new energy grid current based on distribution network WAMS according to claim 1, characterized in that, The calculation of initial values ​​for the proportion of fault current components and initial values ​​for protection settings in the new power system includes: In the traditional generator short-circuit model, line current protection is divided into three stages: Stage I protection, Stage II protection, and Stage III protection. The circuit system has three busbars A, B, and C, with the lines between them being AB, BC, and CD, respectively; protection devices 1, 2, and 3 are installed between the three busbars. Using a traditional generator power system short-circuit model, the new energy power source is equivalent to a current source, and the initial value of the proportion of fault current component at the protection installation point is determined. and current Section protection settings are adjusted: (1) (2) In the above formula, This refers to the short-circuit current provided by each conventional generator when a short circuit occurs at the BC section outlet. For the internal potential of each traditional generator, Let n be the internal impedance of the nth conventional generator; The impedance of the entire length of line AB; This refers to the short-circuit current provided by each new energy power source when a short circuit occurs at the BC section outlet. During a short-circuit fault, the ratio of the short-circuit current provided by the new energy source to the rated current; This refers to the rated current of the new energy power supply. (3) (4) In the above formula, This is the sum of the short-circuit currents provided by each conventional generator when a short circuit occurs at the BC section outlet. This is the sum of the short-circuit currents provided by each new energy source when a short circuit occurs at the BC section outlet; (5) (6) In the above formula, This represents the initial value of the proportion of fault current components, specifically the initial proportion of short-circuit current supplied by traditional generators and short-circuit current supplied by new energy sources at the new power system protection installation location. For current Segment protection settings, To protect 1 Section protection reliability coefficient; Using a traditional generator's power system short-circuit model, the current... Section protection settings are adjusted: (7) (8) In the above formula, This refers to the short-circuit current provided by each conventional generator when a short circuit occurs at the CD section outlet. , These are the total impedances of lines AB and BC, respectively. This refers to the short-circuit current provided by each new energy power source when a short circuit occurs at the CD section outlet. (9) (10) In the above formula, This is the sum of the short-circuit currents provided by each conventional generator when a short circuit occurs at the output of section CD. This is the sum of the short-circuit currents provided by each new energy source when a short circuit occurs at the CD section outlet; (11) In the above formula, For current Segment protection settings, To protect 1 Section protection reliability coefficient, To protect 2 Section protection reliability coefficient; For current Section protection settings are adjusted: (12) (13) In the above formula, This is the sum of the maximum load current of each new energy power source; This refers to the maximum load current of the line, including the load current provided by new energy sources. To protect 1 Section protection reliability coefficient; This is the return coefficient of the current relay; This is the self-starting coefficient; In the initial state of the system, The initial value of the system current protection is , , .

3. The method for protecting fluctuating new energy grid current based on distribution network WAMS according to claim 2, characterized in that, Take 1.2~1.5; Take 1.1-1.2; Take 1.1-1.2; Take 1.1-1.2; Take 1.1-1.2; It is 0.85-0.95; Greater than 1.

4. The method for protecting fluctuating new energy grid current based on distribution network WAMS according to claim 1, characterized in that, Real-time acquisition of short-circuit current of traditional generators and short-circuit current of new energy power sources, including: Real-time short-circuit currents of traditional generators and renewable energy sources can be obtained through the distribution network WAMS. (14) (15) In the above formula, This is the sum of the real-time short-circuit current measurements of a traditional generator. Real-time short-circuit current measurements for each traditional generator; This is the sum of real-time short-circuit current measurements from new energy power sources. This provides the real-time short-circuit current measurement values ​​for each new energy power source.

5. The method for protecting fluctuating new energy grid current based on distribution network WAMS according to claim 1, characterized in that, Take 1.1-1.

2.

6. The method for protecting fluctuating new energy grid current based on distribution network WAMS according to claim 1, characterized in that, After real-time correction of the setpoint, the protection action is determined according to the traditional three-stage current protection based on the corrected setpoint.

7. The method for protecting fluctuating new energy grid current based on distribution network WAMS according to claim 6, characterized in that, Based on the revised settings, the protection action is determined according to the traditional three-stage current protection method, including: If the actual short-circuit current measurement value I is greater than the operating setting value of the current protection stage I of this line, then the short-circuit fault is within the protection range of the current protection stage I of this line, and the corresponding protection will operate; otherwise, the current protection stage I of this line will not operate. If the actual short-circuit current measurement value I is greater than the setting value of the current protection stage II of this line, the current protection stage II of this line will start timing; if the actual short-circuit current measurement value I drops to a sufficiently low level before the timing point arrives, it indicates that the fault occurred on the next line and has been cleared by the current protection stage I of the next line; if the actual short-circuit current measurement value I remains greater than the setting value of the current protection stage II of this line after the timing point arrives, it indicates that the fault occurred on this line or the protection of the next line failed to operate, so the fault is cleared by the current protection stage II of this line, realizing the full line protection of this line and the backup protection of the next line outlet; The current protection stage I and current protection stage II of all the above lines constitute a complete protection range in sequence; In addition, a third stage of current protection needs to be set, with an operating setting of 1.5 to 2 times the rated current. If the actual short-circuit current measurement value I is greater than the current protection stage III setting value, then timing begins. If the current still exceeds the limit after the timing time, it indicates that the fault or overload still exists, and therefore the circuit breaker trips. If the actual short-circuit current measurement value I is less than the current protection stage III setting value before the timing time is reached, it indicates that the fault or overload has disappeared, and the circuit breaker returns to its original state. Due to the strong nonlinearity of the power supply, the operating setting values ​​of the current protection stage III on each line are not significantly different. In this case, different delay times are adopted, that is, the delay time of the next line is less than the delay time of the previous line by one time interval. This enables the sequential operation of different line current protection stages III.

8. A fluctuating renewable energy grid current protection device based on distribution network WAMS for performing the method as described in claim 1, characterized in that, include: Initial value calculation module: used to calculate the initial values ​​of the fault current component ratio and the protection setting for the new power system, and obtain the initial values ​​of the fault current component ratio and the protection setting. Real-time current measurement module: used to acquire the short-circuit current of traditional generators and the short-circuit current of new energy power sources in real time; Short-circuit current measurement module: used to obtain the measured value of the actual short-circuit current of the line; Fault current component ratio calculation module: used to perform online real-time aggregation of the measured values ​​of the actual short-circuit current of the line based on the short-circuit current of the traditional generator and the short-circuit current of the new energy power source, so as to obtain the ratio of the short-circuit current provided by the generator and the short-circuit current provided by the new energy power source at the protection installation location of this line. Correction module: Used to correct the protection settings in real time based on the initial values ​​of the fault current component proportion and the initial protection settings, according to the short-circuit current component proportion of the faulted line.

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