CN109524982B - AC/DC power grid transient stability risk assessment method - Google Patents

AC/DC power grid transient stability risk assessment method Download PDF

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CN109524982B
CN109524982B CN201811518505.1A CN201811518505A CN109524982B CN 109524982 B CN109524982 B CN 109524982B CN 201811518505 A CN201811518505 A CN 201811518505A CN 109524982 B CN109524982 B CN 109524982B
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power grid
fault
direct current
alternating current
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CN109524982A (en
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张国辉
李志中
刘萌
苏建军
王宾
张天宝
黄秉青
张婉婕
史方芳
杨超
李宽
赵斌超
王永波
李聪聪
梁正堂
石硕
李娜
佟新元
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Tsinghua University
State Grid Corp of China SGCC
Electric Power Research Institute of State Grid Shandong Electric Power Co Ltd
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State Grid Corp of China SGCC
Electric Power Research Institute of State Grid Shandong Electric Power Co Ltd
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Abstract

The invention discloses an AC/DC system transient stability risk assessment method, and belongs to the crossing field of the relay protection field and the artificial intelligence field of a power system transmission line. The invention adopts real-time measurement information under the large disturbance state of the direct current control system to carry out parallel analysis and evaluation of the rapid hypothetical fault set so as to obtain a continuous commutation failure risk estimation value of the disturbance based on the hypothetical fault set. The method provided by the invention can quickly evaluate the risk of continuous commutation failure of the direct current transmission system based on the measurement information after the alternating current disturbance occurs, overcomes the problem that the running risk of the direct current transmission system is difficult to evaluate, accelerates the calculation speed under the engineering field application based on the analysis of the equivalent model and the parallel calculation of the direct current converter station, and has wide engineering application prospect.

Description

AC/DC power grid transient stability risk assessment method
Technical Field
The invention belongs to the technical field of power system stability control, relates to crossing of relay protection and artificial intelligence of a power transmission line of a power system, and particularly relates to a direct current system running state risk assessment method of an alternating current-direct current hybrid system.
Background
With the rapid development of direct-current transmission technology in China, an alternating-current and direct-current hybrid transmission system with the largest scale and the highest voltage level in the world is formed in China. The converter valve of LCC-HVDC (based on the high-voltage direct-current transmission of the phase-changing rectifier of the power grid) is generally a thyristor, and the on-off state of the valve is continuously changed in the running process, so that strong nonlinearity is brought to an alternating current-direct-current hybrid system.
In order to improve the transient stability of the ac/dc hybrid power grid, a transient response mechanism of the dc power transmission system is proposed in the industry, that is, the power flow of the receiving-end power grid is controlled in advance before the ac/dc system generates large-scale power fluctuation caused by continuous commutation failure, so as to reduce the influence of power shortage caused by the continuous commutation failure of the dc system. However, the transient response mechanism depends on the advanced evaluation and early warning of the running state of the ac/dc system, and a reliable evaluation method is difficult to advance due to the complexity of the ac/dc system. How to evaluate the risk of transient instability of the dc system still is a technical problem.
Disclosure of Invention
The invention aims to solve the problem of transient stability risk assessment of an alternating current-direct current hybrid system under large disturbance, and is different from the traditional pure physical mechanism modeling method.
For the reader to better understand the technical solution of the present invention, before introducing the technical solution, the technical terms used in the present invention are first described as follows:
AC/DC control system: the system is characterized by comprising a series of controller sets including a direct current converter valve controller body and having the capacity of recording field operation data;
the direct current control system refers to a direct current system converter valve body controller and generally comprises a constant current controller, a constant voltage controller, a constant gamma angle controller, a current margin controller and αminA controller;
state variables of the direct current control system: the method mainly refers to the integrator output quantity of a related PI controller of a pole control stage of a direct current converter valve controller, and the integrator output quantity is output by an integrator and cannot be suddenly changed, so that the integrator output quantity is used as a state variable to carry out initial value iteration when numerical integration is solved; the output quantity of PI links of all controllers in the converter valve controller of the direct current system needs to be recorded in real time, and the output quantity of the PI links is the state variable of the control system;
in order to achieve the purpose, the invention specifically adopts the following technical scheme:
a transient stability risk assessment method for an alternating current-direct current power grid is characterized by comprising the following steps:
step 1: fault set for constructing AC/DC hybrid power grid
Figure GDA0002417906560000027
The fault concentration data includes off-line simulation data
Figure GDA0002417906560000028
And real recording data
Figure GDA0002417906560000029
Step 2: for the AC-DC series-parallel power grid fault set constructed in the step 1
Figure GDA00024179065600000210
Analyzing the data, calibrating the fault capacity delta P equivalent to the alternating current fault for each fault situation, namely disturbance situationacAt the same timeRecording state variables of a DC control system
Figure GDA0002417906560000021
And the delay flip angle of the inverting side
Figure GDA0002417906560000022
And step 3: in the running process of the AC-DC hybrid power grid, the AC-DC protection system carries out real-time online monitoring on the running state of the AC-DC hybrid power grid, and if AC disturbance occurs, the fault capacity of the AC system is estimated by estimation
Figure GDA0002417906560000023
And 4, step 4: using estimated fault capacity
Figure GDA0002417906560000024
To AC/DC series-parallel connection electric network fault set
Figure GDA00024179065600000211
Carrying out rapid parallel retrieval sampling to obtain N sampling values of response of the alternating current system under the fault capacity;
and 5: reading in the state variables of the DC control system recorded in step 2
Figure GDA0002417906560000025
And the delay flip angle of the inverting side
Figure GDA0002417906560000026
Inputting the N sampling values obtained in the step (4) into a dynamic phasor equivalent model of the direct current converter station for rapid parallel analytical calculation, and obtaining direct current responses corresponding to the sampling values of all alternating current systems under the equivalent model, namely expected responses of the direct current systems;
step 6: performing statistical analysis on the expected response of the direct current system obtained in the step 5, calibrating the number of events of the transient instability of the alternating current-direct current hybrid power grid under N sampling values, calculating the proportion of the events of the transient instability under the parallel sampling, and taking the proportion as the estimated value of the transient instability risk;
and 7: and returning to the step 2 to the step 6, repeating the steps for K times, calculating a corresponding updated risk index, namely an estimated value of the transient instability risk each time, and carrying out weighted average to obtain a final transient instability risk evaluation value of the alternating current/direct current power grid.
The invention further comprises the following preferred embodiments:
in step 1, the offline simulation data refers to TB-level operating data obtained by performing grid-type electromagnetic transient simulation on the ac/dc hybrid network, recording responses of the ac/dc system under various disturbance situations, and performing TB-level simulation.
The real wave recording data refers to real wave recording data obtained in the running process of the alternating current-direct current hybrid power grid.
In step 2, the state variable of the control system refers to the integrator output quantity of the related PI controller of the pole control stage of the DC converter valve controller.
In step 3, when the alternating current disturbance occurs to the alternating current/direct current hybrid power grid, the alternating current/direct current protection system measures and obtains a direct current power disturbance value delta PdcAnd estimating the fault capacity of the AC system based thereon
Figure GDA0002417906560000031
Estimation of the fault capacity of an ac system preferably by the following ac/dc power estimation formula
Figure GDA0002417906560000032
Figure GDA0002417906560000033
Where k is a scaling factor, derived from the fault set fitting, oa is the allowed residual error.
The proportion coefficient k is used for calibrating the fault capacity delta P equivalent to the alternating-current fault in each fault situation obtained in the step 2acAnd off-line simulation data in step 1
Figure GDA0002417906560000037
And fitting to obtain.
The permissible residual oa value range is 0.03p.u. -0.06p.u.
The allowed residual oa value is 0.05p.u.
In step 4, the fault set of the AC/DC hybrid power grid
Figure GDA0002417906560000038
In the method, relevant recording data under all fault situations are searched, as long as the power disturbance of the alternating current system of any fault situation meets the fault capacity of the alternating current system estimated in the step 3
Figure GDA0002417906560000034
And within the allowable residual error range, namely, taking the residual error as a fault situation required by risk assessment, wherein the wave recording data of the bus voltage of the inverter alternating-current system under the fault situation is a sampling value.
In step 4, the recorded wave recording data of the bus voltage of the inverter alternating current system under the fault situation takes 3-4 pieces of periodic wave data as a sampling value.
Preferably, the ac/dc power conversion formula is modified as follows:
Figure GDA0002417906560000035
then the residual error estimate of the fault capacity of the ac system
Figure GDA0002417906560000036
Satisfies the interval [ k delta Pdc-ò,kΔPdc+ò]In, i.e. in, the data set
Figure GDA0002417906560000039
Relevant recording data under all fault situations are searched, as long as the alternating current system power disturbance of any fault situation meets the condition of [ K delta Pdc-ò,kΔPdc+ò]Within the scope of fault scenarios required for their use as risk assessment.
The N sampling values refer to wave recording data of the first N fault situations meeting the conditions.
Wherein the value of N is determined based on a tradeoff between risk assessment speed and risk assessment accuracy.
When the rapidity requirement of the risk assessment is greater than the requirement on the accuracy of the risk assessment, N takes a relatively small numerical value, and the value range is as follows: [500,2000].
When the accuracy requirement of the risk assessment is greater than the rapidity requirement of the risk assessment, N takes a relatively large numerical value, and the value range is as follows: [20000,80000].
When the balance between the risk assessment speed and the risk assessment accuracy is considered, the value range of N is [5000,10000 ].
In step 5, the direct current converter station dynamic phasor equivalent model is an equivalent model of a direct current system electromagnetic transient level.
In step 6, an estimate of the risk of transient destabilization is calculated by:
Figure GDA0002417906560000041
in the above formula, hunstableThe (phi) is a discrimination function for judging whether the AC/DC system generates transient instability, and outputs 1 when the transient instability occurs, otherwise outputs 0;
Figure GDA0002417906560000042
is a direct current system response function based on a dynamic phasor method; x is the number ofiRefers to the ith generalized sample value vector that satisfies the sampling requirement.
Wherein the ith generalized sample value vector x satisfying the sampling requirementiIncluding state variables of the control system
Figure GDA0002417906560000043
Contravariant side flip angle
Figure GDA0002417906560000044
And recording the wave value of the alternating current bus voltage of the alternating current system.
In step 7, the value of K is 2-5. Preferably, K is 3.
Note the book
Figure GDA0002417906560000045
The instability risk assessment calculated for the i-th assessment,
Figure GDA0002417906560000046
a risk estimate calculated for the i +1 th assessment;
when the value of i is 1, the value of i,
Figure GDA0002417906560000047
when i >1, there are
Figure GDA0002417906560000048
s.t.α+β＝1,
α,β≥0
Final AC/DC power grid transient instability risk assessment value Rest＝RkWherein i +1 is less than or equal to K.
Wherein
Figure GDA0002417906560000049
The risk assessment value calculated for the (i + 1) th evaluation (the calculation method is the calculation process from step 2 to step 6), Ri+1For the i +1 th risk assessment value updated according to the αβ rule, the intention is that the next assessment is the calculated value of the next assessment
Figure GDA0002417906560000051
Risk estimate R updated from previous αβ ruleiThe weighted average of (2) to prevent a certain estimation value from being too different from the rest estimation values to cause great influence on the real estimation value.
Generally, α is given by human, the simplest method is to take the value of 0.5 respectively, however, there is also a trade-off between the volatility of the iterative process of risk assessment, if β is infinitely close to 1, then according to αβ ruleUpdated i +1 th risk assessment value depends mainly on last risk assessment value
Figure GDA0002417906560000052
In turn, if the risk estimation value which is updated according to the αβ rule each time has a very smooth updating process, the value of α should be as large as possible, so that the influence of each single estimation on the final estimation value is relatively limited, i.e. smooth updating of the risk estimation value updated according to the αβ rule can be realized.
Compared with the prior art, the invention has the following beneficial technical effects:
the method provided by the invention can quickly evaluate the risk of continuous commutation failure of the direct current transmission system based on the measurement information after the alternating current disturbance occurs, overcomes the problem that the running risk of the direct current transmission system is difficult to evaluate, accelerates the calculation speed under the engineering field application based on the analysis of the equivalent model and the parallel calculation of the direct current converter station, and has wide engineering application prospect.
Drawings
FIG. 1 is a schematic flow chart of the risk assessment method for transient stability of an AC/DC power grid according to the present invention;
FIG. 2 is a block diagram of a DC converter station dynamic phasor equivalent model calculation (abstracted as
Figure GDA0002417906560000053
)。
Detailed Description
The technical scheme of the invention is further described in detail by combining the drawings and the specific embodiments in the specification.
The invention provides an AC/DC system transient stability risk assessment method based on a fault set and a DC converter station equivalent model, as shown in the attached figure 1, comprising the following steps:
step 1: construction ofFault set of AC-DC hybrid power grid
Figure GDA0002417906560000054
The fault concentration data includes off-line simulation data
Figure GDA0002417906560000055
And real recording data
Figure GDA0002417906560000061
The off-line simulation data refers to TB-level operation data obtained by performing grid-type electromagnetic transient simulation on the alternating current-direct current hybrid network, recording the response of the alternating current-direct current system under various disturbance situations, and performing TB-level simulation.
The real wave recording data refers to real wave recording data obtained in the running process of the alternating current-direct current hybrid power grid.
Step 2: for the AC-DC series-parallel power grid fault set constructed in the step 1
Figure GDA0002417906560000062
Analyzing the data, calibrating the fault capacity delta P equivalent to the alternating current fault for each fault situation, namely disturbance situationacWhile recording the state variables of the DC control system
Figure GDA0002417906560000063
And the delay flip angle of the inverting side
Figure GDA0002417906560000064
The state variable of the control system refers to the output quantity of an integrator of a related PI controller of a pole control stage of the direct current converter valve controller.
And step 3: in the running process of the AC-DC hybrid power grid, the AC-DC protection system carries out real-time online monitoring on the running state of the AC-DC hybrid power grid, and if AC disturbance occurs, the fault capacity of the AC system is estimated by estimation
Figure GDA0002417906560000065
When alternating current disturbance occurs to the alternating current and direct current hybrid power grid, a direct current power disturbance value delta P is measured and obtained by an alternating current and direct current protection systemdcAnd estimating the fault capacity of the AC system based thereon
Figure GDA0002417906560000066
Estimation of the fault capacity of an ac system preferably by the following ac/dc power estimation formula
Figure GDA0002417906560000067
Figure GDA0002417906560000068
Where k is a scaling factor, derived from the fault set fitting, oa is the allowed residual error.
Wherein, the proportion coefficient k is used for calibrating the fault capacity delta P equivalent to the alternating current fault in each fault situation obtained in the step 2acAnd off-line simulation data in step 1
Figure GDA0002417906560000069
And fitting to obtain.
The permissible residual oa value range is 0.03p.u. -0.06p.u.
And 4, step 4: using estimated fault capacity
Figure GDA00024179065600000610
To AC/DC series-parallel connection electric network fault set
Figure GDA00024179065600000611
Carrying out rapid parallel retrieval sampling to obtain N sampling values of response of the alternating current system under the fault capacity;
and 3-4 cycle data are taken as a sampling value from the recorded wave recording data of the bus voltage of the inverter alternating current system under the fault situation.
Preferably, the ac/dc power conversion formula is modified as follows:
Figure GDA00024179065600000612
then the residual error estimate of the fault capacity of the ac system
Figure GDA00024179065600000613
Satisfies the interval [ k delta Pdc-ò,kΔPdc+ò]In, i.e. in, the data set
Figure GDA0002417906560000071
Relevant recording data under all fault situations are searched, as long as the alternating current system power disturbance of any fault situation meets the condition that [ k delta P ]dc-ò,kΔPdc+ò]Within the scope of fault scenarios required for their use as risk assessment.
The N sampling values refer to wave recording data of the first N fault situations meeting the conditions.
Wherein the value of N is determined based on a tradeoff between risk assessment speed and risk assessment accuracy.
And 5: reading in the state variables of the DC control system recorded in step 2
Figure GDA0002417906560000072
And the delay flip angle of the inverting side
Figure GDA0002417906560000073
Inputting the N sampling values obtained in the step (4) into a dynamic phasor equivalent model of the direct current converter station for rapid parallel analytical calculation, and obtaining direct current responses corresponding to the sampling values of all alternating current systems under the equivalent model, namely expected responses of the direct current systems;
the direct current converter station dynamic phasor equivalent model is an equivalent model of direct current system electromagnetic transient level in the prior art. Referring to fig. 2, the dynamic phasor equivalent model is essentially an analytical expression of the switching function of the dc system based on the dynamic phasor method, thereby describing the dc system as a model of a voltage controlled current source. The model receives the voltages of the alternating current buses on the inversion side and the rectification side as input, and outputs an alternating current value which is injected into an alternating current system by a direct current system and has the same time length as the input alternating voltage.
Step 6: performing statistical analysis on the expected response of the direct current system obtained in the step 5, calibrating the number of events of the transient instability of the alternating current-direct current hybrid power grid under N sampling values, calculating the proportion of the events of the transient instability under the parallel sampling, and taking the proportion as the estimated value of the transient instability risk;
an estimate of the risk of transient destabilization is calculated by:
Figure GDA0002417906560000074
in the above formula, hunstableThe (phi) is a discrimination function for judging whether the AC/DC system generates transient instability, and outputs 1 when the transient instability occurs, otherwise outputs 0;
Figure GDA0002417906560000075
is a direct current system response function based on a dynamic phasor method; x is the number ofiRefers to the ith generalized sample value vector that satisfies the sampling requirement.
Wherein the ith generalized sample value vector x satisfying the sampling requirementiIncluding state variables of the control system
Figure GDA0002417906560000076
Contravariant side flip angle
Figure GDA0002417906560000077
And recording the wave value of the alternating current bus voltage of the alternating current system.
And 7: and returning to the step 2 to the step 6, repeating the steps for K times, calculating a corresponding updated risk index, namely an estimated value of the transient instability risk each time, and carrying out weighted average to obtain a final transient instability risk evaluation value of the alternating current/direct current power grid.
The value of K is 2-5. Preferably, k is 3.
Note the book
Figure GDA0002417906560000081
The instability risk assessment calculated for the i-th assessment,
Figure GDA0002417906560000082
a risk estimate calculated for the i +1 th assessment;
when the ratio of i =1, the ratio of the total of the number of the bits is set to be 1,
Figure GDA0002417906560000083
when i >1, there are
Figure GDA0002417906560000084
s.t.α+β＝1,
α,β≥0
Final AC/DC power grid transient instability risk assessment value Rest＝RkWherein i +1 is less than or equal to K.
Wherein
Figure GDA0002417906560000085
The risk assessment value calculated for the (i + 1) th evaluation (the calculation method is the calculation process from step 2 to step 6), Ri+1For the i +1 th risk assessment value updated according to the αβ rule, the intention is that the next assessment is the calculated value of the next assessment
Figure GDA0002417906560000086
Risk estimate R updated from previous αβ ruleiThe weighted average of (2) to prevent a certain estimation value from being too different from the rest estimation values to cause great influence on the real estimation value.
Generally, α is given by human, the simplest approach is to take the value of 0.5 respectively, however, this involves a trade-off of the volatility of the iterative process of risk assessment, if β is infinitely close to 1, then the i +1 th risk assessment updated according to αβ is mainly dependent on the last risk assessment
Figure GDA0002417906560000087
In turn, if the risk estimation value which is updated according to the αβ rule each time has a very smooth updating process, the value of α should be as large as possible, so that the influence of each single estimation on the final estimation value is relatively limited, i.e. smooth updating of the risk estimation value updated according to the αβ rule can be realized.
In order to better assist the reader in understanding the technical aspects of the present invention, the following examples are presented in detail.
Example 1:
a fault set and direct current converter station equivalent model-based alternating current and direct current system transient stability risk assessment method comprises the following steps:
step 1: fault set for constructing AC/DC hybrid power grid
Figure GDA0002417906560000088
The fault concentration data includes off-line simulation data
Figure GDA0002417906560000089
And real recording data
Figure GDA00024179065600000810
The off-line simulation data refers to TB-level operation data obtained by performing grid-type electromagnetic transient simulation on the alternating current-direct current hybrid network, recording the response of the alternating current-direct current system under various disturbance situations, and performing TB-level simulation.
The real wave recording data refers to real wave recording data obtained in the running process of the alternating current-direct current hybrid power grid.
Step 2: for the AC-DC series-parallel power grid fault set constructed in the step 1
Figure GDA0002417906560000091
Data go onAnalyzing, calibrating the fault capacity delta P equivalent to the alternating current fault for each fault situation, namely disturbance situationacWhile recording the state variables of the DC control system
Figure GDA0002417906560000092
And the delay flip angle of the inverting side
Figure GDA0002417906560000093
The state variable of the control system refers to the output quantity of an integrator of a related PI controller of a pole control stage of the direct current converter valve controller.
And step 3: in the running process of the AC-DC hybrid power grid, the AC-DC protection system carries out real-time online monitoring on the running state of the AC-DC hybrid power grid, and if AC disturbance occurs, the fault capacity of the AC system is estimated by estimation
Figure GDA0002417906560000094
When alternating current disturbance occurs to the alternating current and direct current hybrid power grid, a direct current power disturbance value delta P is measured and obtained by an alternating current and direct current protection systemdcAnd estimating the fault capacity of the AC system based thereon
Figure GDA0002417906560000095
Estimation of the fault capacity of an ac system preferably by the following ac/dc power estimation formula
Figure GDA0002417906560000096
Figure GDA0002417906560000097
Where k is a scaling factor, derived from the fault set fitting, oa is the allowed residual error.
In general, the value of k is related to the short-circuit ratio of the dc system, and is generally [1.2,8 ]]In example 1, the receiver ac system is a very weak system that receives power injection into the primary sourceFrom the direct current system, the rapidity requirement of risk assessment is greater than the requirement on the accuracy of risk assessment, and the fitting result of k is 1.2. Wherein, the proportion coefficient k is used for calibrating the fault capacity delta P equivalent to the alternating current fault in each fault situation obtained in the step 2acAnd off-line simulation data in step 1
Figure GDA0002417906560000098
And fitting to obtain.
In embodiment 1, the permissible residual oa takes the value 0.04p.u.
And 4, step 4: using estimated fault capacity
Figure GDA0002417906560000099
To AC/DC series-parallel connection electric network fault set
Figure GDA00024179065600000910
Carrying out rapid parallel retrieval sampling to obtain N sampling values of response of the alternating current system under the fault capacity;
and 3-4 cycle data are taken as a sampling value from the recorded wave recording data of the bus voltage of the inverter alternating current system under the fault situation.
Preferably, the ac/dc power conversion formula is modified as follows:
Figure GDA0002417906560000101
then the residual error estimate of the fault capacity of the ac system
Figure GDA0002417906560000102
Satisfies the interval [ k delta Pdc-ò,kΔPdc+ò]In, i.e. in, the data set
Figure GDA0002417906560000103
Relevant recording data under all fault situations are searched, as long as the alternating current system power disturbance of any fault situation meets the condition that [ k delta P ]dc-ò,kΔPdc+ò]Within the scope of fault scenarios required for their use as risk assessment.
The N sampling values refer to wave recording data of the first N fault situations meeting the conditions. The rapidity requirement of the risk assessment of the embodiment 1 is greater than the requirement on the accuracy of the risk assessment, and the value range of N is [500,2000], which is taken as 500.
And 5: reading in the state variables of the DC control system recorded in step 2
Figure GDA0002417906560000104
And the delay flip angle of the inverting side
Figure GDA0002417906560000105
Inputting the N sampling values obtained in the step (4) into a dynamic phasor equivalent model of the direct current converter station for rapid parallel analytical calculation, and obtaining direct current responses corresponding to the sampling values of all alternating current systems under the equivalent model, namely expected responses of the direct current systems;
the direct current converter station dynamic phasor equivalent model is an equivalent model of direct current system electromagnetic transient level in the prior art.
Step 6: performing statistical analysis on the expected response of the direct current system obtained in the step 5, calibrating the number of events of the transient instability of the alternating current-direct current hybrid power grid under N sampling values, calculating the proportion of the events of the transient instability under the parallel sampling, and taking the proportion as the estimated value of the transient instability risk;
an estimate of the risk of transient destabilization is calculated by:
Figure GDA0002417906560000106
in the above formula, hunstableThe (phi) is a discrimination function for judging whether the AC/DC system generates transient instability, and outputs 1 when the transient instability occurs, otherwise outputs 0; i (-) is an indicator function;
Figure GDA0002417906560000107
is a direct current system response function based on a dynamic phasor method; x is the number ofiRefers to the ith generalized sample that satisfies the sampling requirementA vector of values.
Wherein the ith generalized sample value vector x satisfying the sampling requirementiIncluding state variables of the control system
Figure GDA0002417906560000108
Contravariant side flip angle
Figure GDA0002417906560000109
And recording the wave value of the alternating current bus voltage of the alternating current system.
And 7: and returning to the step 2 to the step 6, repeating the steps for K times, calculating a corresponding updated risk index, namely an estimated value of the transient instability risk each time, and carrying out weighted average to obtain a final transient instability risk evaluation value of the alternating current/direct current power grid.
And K is 3.
Note the book
Figure GDA00024179065600001010
The instability risk assessment calculated for the i-th assessment,
Figure GDA00024179065600001011
a risk estimate calculated for the i +1 th assessment;
when the value of i is 1, the value of i,
Figure GDA0002417906560000111
when i >1, there are
Figure GDA0002417906560000112
s.t.α+β＝1,
α,β≥0
Final AC/DC power grid transient instability risk assessment value Rest=RkWherein i +1 is less than or equal to 3.
The allowed residual oa value is 0.05p.u.
Example 2: a fault set and direct current converter station equivalent model-based alternating current and direct current system transient stability risk assessment method comprises the following steps:
step 1: fault set for constructing AC/DC hybrid power grid
Figure GDA0002417906560000113
The fault concentration data includes off-line simulation data
Figure GDA0002417906560000114
And real recording data
Figure GDA0002417906560000115
The off-line simulation data refers to TB-level operation data obtained by performing grid-type electromagnetic transient simulation on the alternating current-direct current hybrid network, recording the response of the alternating current-direct current system under various disturbance situations, and performing TB-level simulation.
The real wave recording data refers to real wave recording data obtained in the running process of the alternating current-direct current hybrid power grid.
Step 2: for the AC-DC series-parallel power grid fault set constructed in the step 1
Figure GDA0002417906560000116
Analyzing the data, calibrating the fault capacity delta P equivalent to the alternating current fault for each fault situation, namely disturbance situationacWhile recording the state variables of the DC control system
Figure GDA0002417906560000117
And the delay flip angle of the inverting side
Figure GDA0002417906560000118
The state variable of the control system refers to the output quantity of an integrator of a related PI controller of a pole control stage of the direct current converter valve controller.
And step 3: in the running process of the AC-DC hybrid power grid, the AC-DC protection system carries out real-time online monitoring on the running state of the AC-DC hybrid power grid, and if AC disturbance occurs, the fault capacity of the AC system is estimated by estimation
Figure GDA0002417906560000119
When alternating current disturbance occurs to the alternating current and direct current hybrid power grid, a direct current power disturbance value delta P is measured and obtained by an alternating current and direct current protection systemdcAnd estimating the fault capacity of the AC system based thereon
Figure GDA00024179065600001110
Estimation of the fault capacity of an ac system preferably by the following ac/dc power estimation formula
Figure GDA00024179065600001111
Figure GDA00024179065600001112
Where k is a scaling factor, derived from the fault set fitting, oa is the allowed residual error. The receiving end communication system is a medium-intensity system, the rapidity requirement of risk assessment is the same as the accuracy requirement of risk assessment, and the fitting result of k is 4.
Wherein, the proportion coefficient k is used for calibrating the fault capacity delta P equivalent to the alternating current fault in each fault situation obtained in the step 2acAnd off-line simulation data in step 1
Figure GDA0002417906560000121
And fitting to obtain.
In embodiment 2, the permissible residual oa takes the value 0.05 pu..
And 4, step 4: using estimated fault capacity
Figure GDA0002417906560000122
To AC/DC series-parallel connection electric network fault set
Figure GDA0002417906560000123
Carrying out rapid parallel retrieval sampling to obtain N sampling values of response of the alternating current system under the fault capacity;
and 3-4 cycle data are taken as a sampling value from the recorded wave recording data of the bus voltage of the inverter alternating current system under the fault situation.
Preferably, the ac/dc power conversion formula is modified as follows:
Figure GDA0002417906560000124
then the residual error estimate of the fault capacity of the ac system
Figure GDA0002417906560000125
Satisfies the interval [ k delta Pdc-ò,kΔPdc+ò,]In, i.e. in, the data set
Figure GDA0002417906560000126
Relevant recording data under all fault situations are searched, as long as the alternating current system power disturbance of any fault situation meets the condition that [ k delta P ]dc-ò,kΔPdc+ò,]Within the scope of fault scenarios required for their use as risk assessment.
The N sampling values refer to wave recording data of the first N fault situations meeting the conditions. Wherein the value of N is determined based on a tradeoff between risk assessment speed and risk assessment accuracy.
The rapidity requirement and the accuracy requirement of risk assessment in embodiment 2 are the same, and the value range of N is [5000,10000], which is assumed to be 5000 here.
And 5: reading in the state variables of the DC control system recorded in step 2
Figure GDA0002417906560000127
And the delay flip angle of the inverting side
Figure GDA0002417906560000128
Inputting the N sampling values obtained in the step (4) into a dynamic phasor equivalent model of the direct current converter station for rapid parallel analytical calculation, and obtaining direct current responses corresponding to the sampling values of all alternating current systems under the equivalent model, namely expected responses of the direct current systems;
the direct current converter station dynamic phasor equivalent model is an equivalent model of direct current system electromagnetic transient level in the prior art.
Step 6: performing statistical analysis on the expected response of the direct current system obtained in the step 5, calibrating the number of events of the transient instability of the alternating current-direct current hybrid power grid under N sampling values, calculating the proportion of the events of the transient instability under the parallel sampling, and taking the proportion as the estimated value of the transient instability risk;
an estimate of the risk of transient destabilization is calculated by:
Figure GDA0002417906560000131
in the above formula, hunstableThe (phi) is a discrimination function for judging whether the AC/DC system generates transient instability, and outputs 1 when the transient instability occurs, otherwise outputs 0; i (-) is an indicator function;
Figure GDA0002417906560000132
is a direct current system response function based on a dynamic phasor method; x is the number ofiRefers to the ith generalized sample value vector that satisfies the sampling requirement.
Wherein the ith generalized sample value vector x satisfying the sampling requirementiIncluding state variables of the control system
Figure GDA0002417906560000133
Contravariant side flip angle
Figure GDA0002417906560000134
And recording the wave value of the alternating current bus voltage of the alternating current system.
And 7: and returning to the step 2 to the step 6, repeating the steps for K times, calculating a corresponding updated risk index, namely an estimated value of the transient instability risk each time, and carrying out weighted average to obtain a final transient instability risk evaluation value of the alternating current/direct current power grid.
And K is 4.
Note the book
Figure GDA0002417906560000135
The instability risk assessment calculated for the i-th assessment,
Figure GDA0002417906560000136
a risk estimate calculated for the i +1 th assessment;
when the value of i is 1, the value of i,
Figure GDA0002417906560000137
when i >1, there are
Figure GDA0002417906560000138
s.t.α+β＝1,
α,β≥0
Final AC/DC power grid transient instability risk assessment value Rest=RkWherein i +1 is less than or equal to 4.
The allowed residual oa value is 0.05p.u.
Example 3:
a fault set and direct current converter station equivalent model-based alternating current and direct current system transient stability risk assessment method comprises the following steps:
step 1: fault set for constructing AC/DC hybrid power grid
Figure GDA0002417906560000139
The fault concentration data includes off-line simulation data
Figure GDA00024179065600001310
And real recording data
Figure GDA00024179065600001311
The off-line simulation data refers to TB-level operation data obtained by performing grid-type electromagnetic transient simulation on the alternating current-direct current hybrid network, recording the response of the alternating current-direct current system under various disturbance situations, and performing TB-level simulation.
The real wave recording data refers to real wave recording data obtained in the running process of the alternating current-direct current hybrid power grid.
Step 2: for the AC-DC series-parallel power grid fault set constructed in the step 1
Figure GDA0002417906560000141
Analyzing the data, calibrating the fault capacity delta P equivalent to the alternating current fault for each fault situation, namely disturbance situationacWhile recording the state variables of the DC control system
Figure GDA0002417906560000142
And the delay flip angle of the inverting side
Figure GDA0002417906560000143
The state variable of the control system refers to the output quantity of an integrator of a related PI controller of a pole control stage of the direct current converter valve controller.
And step 3: in the running process of the AC-DC hybrid power grid, the AC-DC protection system carries out real-time online monitoring on the running state of the AC-DC hybrid power grid, and if AC disturbance occurs, the fault capacity of the AC system is estimated by estimation
Figure GDA0002417906560000144
When alternating current disturbance occurs to the alternating current and direct current hybrid power grid, a direct current power disturbance value delta P is measured and obtained by an alternating current and direct current protection systemdcAnd estimating the fault capacity of the AC system based thereon
Figure GDA0002417906560000145
Estimation of the fault capacity of an ac system preferably by the following ac/dc power estimation formula
Figure GDA0002417906560000146
Figure GDA0002417906560000147
Wherein k is a proportionality coefficient consisting ofThe fault set is derived from the fitting, oa being the permissible residual. The receiving end communication system is a strong system, the requirement on the accuracy of risk assessment is far higher than the requirement on the rapidity of risk assessment, and the fitting result of k is 8. Wherein, the proportion coefficient k is used for calibrating the fault capacity delta P equivalent to the alternating current fault in each fault situation obtained in the step 2acAnd off-line simulation data in step 1
Figure GDA0002417906560000148
And fitting to obtain.
In embodiment 3, the permissible residual oa takes the value 0.05 pu..
And 4, step 4: using estimated fault capacity
Figure GDA0002417906560000149
To AC/DC series-parallel connection electric network fault set
Figure GDA00024179065600001410
Carrying out rapid parallel retrieval sampling to obtain N sampling values of response of the alternating current system under the fault capacity;
and 3-4 cycle data are taken as a sampling value from the recorded wave recording data of the bus voltage of the inverter alternating current system under the fault situation.
Preferably, the ac/dc power conversion formula is modified as follows:
Figure GDA00024179065600001411
then the residual error estimate of the fault capacity of the ac system
Figure GDA00024179065600001412
Satisfies the interval [ k delta Pdc-ò,kΔPdc+ò,]In, i.e. in, the data set
Figure GDA00024179065600001413
Relevant recording data under all fault situations are searched, as long as the alternating current system power disturbance of any fault situation meets the condition that [ k delta P ]dc-ò,kΔPdc+ò,]Within the range ofI.e. the fault scenario required for its risk assessment.
The N sampling values refer to wave recording data of the first N fault situations meeting the conditions. Wherein the value of N is determined based on a tradeoff between risk assessment speed and risk assessment accuracy.
The requirement for rapidity of risk assessment in embodiment 3 is much lower than the requirement for accuracy of risk assessment, and the value range of N is [20000,80000], which is assumed here to be 80000.
And 5: reading in the state variables of the DC control system recorded in step 2
Figure GDA0002417906560000151
And the delay flip angle of the inverting side
Figure GDA0002417906560000152
Inputting the N sampling values obtained in the step (4) into a dynamic phasor equivalent model of the direct current converter station for rapid parallel analytical calculation, and obtaining direct current responses corresponding to the sampling values of all alternating current systems under the equivalent model, namely expected responses of the direct current systems;
the direct current converter station dynamic phasor equivalent model is an equivalent model of direct current system electromagnetic transient level in the prior art.
Step 6: performing statistical analysis on the expected response of the direct current system obtained in the step 5, calibrating the number of events of the transient instability of the alternating current-direct current hybrid power grid under N sampling values, calculating the proportion of the events of the transient instability under the parallel sampling, and taking the proportion as the estimated value of the transient instability risk;
an estimate of the risk of transient destabilization is calculated by:
Figure GDA0002417906560000153
in the above formula, hunstableThe (phi) is a discrimination function for judging whether the AC/DC system generates transient instability, and outputs 1 when the transient instability occurs, otherwise outputs 0; i (-) is an indicator function;
Figure GDA0002417906560000154
is a direct current system response function based on a dynamic phasor method; x is the number ofiRefers to the ith generalized sample value vector that satisfies the sampling requirement.
Wherein the ith generalized sample value vector x satisfying the sampling requirementiIncluding state variables of the control system
Figure GDA0002417906560000155
Contravariant side flip angle
Figure GDA0002417906560000156
And recording the wave value of the alternating current bus voltage of the alternating current system.
And 7: and returning to the step 2 to the step 6, repeating the steps for K times, calculating a corresponding updated risk index, namely an estimated value of the transient instability risk each time, and carrying out weighted average to obtain a final transient instability risk evaluation value of the alternating current/direct current power grid.
And K is 4.
Note the book
Figure GDA0002417906560000157
The instability risk assessment calculated for the i-th assessment,
Figure GDA0002417906560000158
a risk estimate calculated for the i +1 th assessment;
when the value of i is 1, the value of i,
Figure GDA0002417906560000159
when i >1, there are
Figure GDA0002417906560000161
s.t.α+β＝1,
α,β≥0
Final AC/DC power grid transient instability risk assessment value Rest＝RkWherein i +1 is less than or equal to 4.
The allowed residual oa value is 0.05p.u.
While the best mode for carrying out the invention has been described in detail and illustrated in the accompanying drawings, it is to be understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the scope of the invention should be determined by the appended claims and any changes or modifications which fall within the true spirit and scope of the invention should be construed as broadly described herein.

Claims (23)

1. A transient stability risk assessment method for an alternating current-direct current power grid is characterized by comprising the following steps:
step 1: fault set for constructing AC/DC hybrid power grid
Figure FDA0002459301860000011
The fault concentration data includes off-line simulation data
Figure FDA0002459301860000012
And real recording data
Figure FDA0002459301860000013
Step 2: for the AC-DC series-parallel power grid fault set constructed in the step 1
Figure FDA0002459301860000014
Analyzing the data, calibrating the fault capacity delta P equivalent to the alternating current fault for each fault situation, namely disturbance situationacWhile recording the state variables of the DC control system
Figure FDA0002459301860000015
And the delay flip angle of the inverting side
Figure FDA0002459301860000016
And step 3: at the intersectionIn the operation process of the direct current hybrid power grid, the alternating current and direct current protection system carries out real-time online monitoring on the operation state of the alternating current and direct current hybrid power grid, and if alternating current disturbance occurs, the fault capacity of the alternating current system is estimated
Figure FDA0002459301860000017
And 4, step 4: using estimated fault capacity
Figure FDA0002459301860000018
To AC/DC series-parallel connection electric network fault set
Figure FDA0002459301860000019
Carrying out rapid parallel retrieval sampling to obtain N sampling values of response of the alternating current system under the fault capacity;
and 5: reading in the state variables of the DC control system recorded in step 2
Figure FDA00024593018600000110
And the delay flip angle of the inverting side
Figure FDA00024593018600000111
Inputting the N sampling values obtained in the step (4) into a dynamic phasor equivalent model of the direct current converter station for rapid parallel analytical calculation, and obtaining direct current responses corresponding to the sampling values of all alternating current systems under the equivalent model, namely expected responses of the direct current systems;
step 6: performing statistical analysis on the expected response of the direct current system obtained in the step 5, calibrating the number of events of the transient instability of the alternating current-direct current hybrid power grid under N sampling values, calculating the proportion of the events of the transient instability under the parallel sampling, and taking the proportion as the estimated value of the transient instability risk;
and 7: and returning to the step 2 to the step 6, repeating the steps for K times, calculating a corresponding updated risk index, namely an estimated value of the transient instability risk each time, and carrying out weighted average to obtain a final transient instability risk evaluation value of the alternating current/direct current power grid.
2. The ac/dc power grid transient stability risk assessment method according to claim 1, wherein:
in step 1, the offline simulation data refers to operation data obtained by performing grid-type electromagnetic transient simulation on the ac/dc hybrid network, recording responses of the ac/dc system under various disturbance situations, and acquiring the responses.
3. The ac/dc power grid transient stability risk assessment method according to claim 2, wherein:
in step 1, the real recording data refers to real recording data obtained in the operation process of the alternating current-direct current hybrid power grid.
4. The AC/DC power grid transient stability risk assessment method according to claim 1 or 3, wherein:
in step 2, the state variable of the control system refers to the integrator output quantity of the related PI controller of the pole control stage of the DC converter valve controller.
5. The AC/DC power grid transient stability risk assessment method according to claim 4, wherein:
in step 3, when the alternating current disturbance occurs to the alternating current/direct current hybrid power grid, the alternating current/direct current protection system measures and obtains a direct current power disturbance value
Figure FDA0002459301860000021
And estimating fault capacity of the AC system based thereon
Figure FDA0002459301860000022
6. The AC/DC power grid transient stability risk assessment method according to claim 5, wherein:
estimating fault capacity of AC system by AC/DC power estimation formula
Figure FDA0002459301860000023
Figure FDA0002459301860000024
Where k is a scaling factor, derived from the fault set fitting, oa is the allowed residual error.
7. The AC/DC power grid transient stability risk assessment method according to claim 6, wherein:
the proportion coefficient k is used for calibrating the fault capacity delta P equivalent to the alternating-current fault in each fault situation obtained in the step 2acAnd off-line simulation data in step 1
Figure FDA0002459301860000025
And fitting to obtain.
8. The ac/dc power grid transient stability risk assessment method according to claim 7, wherein:
the permissible residual oa value range is 0.03p.u. -0.06p.u.
9. The ac/dc power grid transient stability risk assessment method according to claim 8, wherein:
the allowed residual oa value is 0.05p.u.
10. The ac/dc power grid transient stability risk assessment method according to claim 1, wherein:
in step 4, the fault set of the AC/DC hybrid power grid
Figure FDA0002459301860000026
In the method, relevant recording data under all fault situations are searched, and the fault capacity of the alternating current system is estimated in the step 3 as long as the alternating current system power disturbance of any fault situation occurs
Figure FDA0002459301860000027
And within the allowable residual error range, namely, taking the residual error as a fault situation required by risk assessment, wherein the wave recording data of the bus voltage of the inverter alternating-current system under the fault situation is a sampling value.
11. The ac/dc power grid transient stability risk assessment method according to claim 10, wherein:
in step 4, the recorded wave recording data of the bus voltage of the inverter alternating current system under the fault situation takes 3-4 pieces of periodic wave data as a sampling value.
12. The AC/DC power grid transient stability risk assessment method according to claim 6, wherein:
in step 4, firstly, the ac/dc power estimation formula is modified as follows:
Figure FDA0002459301860000028
then the residual error estimate of the fault capacity of the ac system
Figure FDA0002459301860000031
Satisfies the interval [ k delta Pdc-ò,kΔPdc+ò]I.e. in the data set
Figure FDA0002459301860000032
Relevant recording data under all fault situations are searched, as long as the alternating current system power disturbance of any fault situation meets the condition that [ k delta P ]dc-ò,kΔPdc+ò,]Within the scope of fault scenarios required for their use as risk assessment.
13. The ac/dc power grid transient stability risk assessment method according to claim 12, wherein:
the N sampling values refer to the AC system power disturbance power satisfaction estimationCalculating fault capacity of AC system
Figure FDA0002459301860000033
And recording data of the bus voltage of the inverter alternating current system under the first N fault situations in the allowable residual error range.
14. The ac/dc power grid transient stability risk assessment method according to claim 13, wherein:
wherein the value of N is determined based on a tradeoff between risk assessment speed and risk assessment accuracy.
15. The ac/dc power grid transient stability risk assessment method according to claim 14, wherein:
when the rapidity requirement of the risk assessment is greater than the requirement on the accuracy of the risk assessment, N takes a relatively small numerical value, and the value range is as follows: [500,2000].
16. The ac/dc power grid transient stability risk assessment method according to claim 14, wherein:
when the accuracy requirement of the risk assessment is greater than the rapidity requirement of the risk assessment, N takes a relatively large numerical value, and the value range is as follows: [20000,80000].
17. The ac/dc power grid transient stability risk assessment method according to claim 14, wherein: when the balance between the risk assessment speed and the risk assessment accuracy is considered, the value range of N is [5000,10000 ].
18. The ac/dc power grid transient stability risk assessment method according to claim 1, wherein:
in step 5, the direct current converter station dynamic phasor equivalent model is an equivalent model of a direct current system electromagnetic transient level.
19. The ac/dc power grid transient stability risk assessment method according to claim 1, wherein:
in step 6, an estimate R of the risk of transient instability is calculated by the following equationest：
Figure FDA0002459301860000034
In the above formula, hunstableThe (phi) is a discrimination function for judging whether the AC/DC system generates transient instability, and outputs 1 when the transient instability occurs, otherwise outputs 0;
Figure FDA0002459301860000035
is a direct current system response function based on a dynamic phasor method; x is the number ofiRefers to the ith generalized sample value vector that satisfies the sampling requirement.
20. The ac/dc power grid transient stability risk assessment method according to claim 19, wherein:
wherein the ith generalized sample value vector x satisfying the sampling requirementiIncluding state variables of the control system
Figure FDA0002459301860000041
Contravariant side flip angle
Figure FDA0002459301860000042
And recording the wave value of the alternating current bus voltage of the alternating current system.
21. The ac/dc power grid transient stability risk assessment method according to claim 1, wherein:
in step 7, the value of K is 2-5.
22. The ac-dc power grid transient stability risk assessment method according to claim 21, wherein:
note the book
Figure FDA0002459301860000043
The instability risk assessment calculated for the i-th assessment,
Figure FDA0002459301860000044
a risk estimate calculated for the i +1 th assessment;
when the value of i is 1, the value of i,
Figure FDA0002459301860000045
when i >1, there are
Figure FDA0002459301860000046
s.t.α+β＝1,
α,β≥0
Final AC/DC power grid transient instability risk assessment value Rest＝RkWherein i +1 is less than or equal to K.
23. The ac-dc power grid transient stability risk assessment method according to claim 22, wherein:
and K is 3.
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