CN110224410B - Power grid dynamic reactive power optimization configuration method based on transient voltage safety constraint - Google Patents

Power grid dynamic reactive power optimization configuration method based on transient voltage safety constraint Download PDF

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CN110224410B
CN110224410B CN201910239559.2A CN201910239559A CN110224410B CN 110224410 B CN110224410 B CN 110224410B CN 201910239559 A CN201910239559 A CN 201910239559A CN 110224410 B CN110224410 B CN 110224410B
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svc
node
voltage
fault
reactive power
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CN110224410A (en
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廖卫平
周锐
谢锟
李少杰
朱业华
伍建炜
黄练栋
温健锋
廖汉才
刘海光
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Guangdong Power Grid Co Ltd
Jiangmen Power Supply Bureau of Guangdong Power Grid Co Ltd
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Guangdong Power Grid Co Ltd
Jiangmen Power Supply Bureau of Guangdong Power Grid Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/10—Flexible AC transmission systems [FACTS]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/30—Reactive power compensation

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Abstract

The invention relates to the technical field of power grid optimization, in particular to a power grid dynamic reactive power optimization configuration method based on transient voltage safety constraint, which comprises the following steps: firstly, calculating a voltage-reactive sensitivity (TSI) index through time domain simulation, and determining an SVC installation site according to the TSI; then determining an objective function for optimizing the SVC capacity according to the relation between the SVC capacity and the node voltage recovery; and finally, solving a multi-objective function by applying a CSO algorithm to determine the optimal capacity of the SVC. The method fully utilizes the characteristic of fast controllability of the SVC, provides dynamic reactive power support for voltage recovery of a load node of the power system after the fault, and enables the system to meet the requirement of safety and stability of transient voltage.

Description

Power grid dynamic reactive power optimization configuration method based on transient voltage safety constraint
Technical Field
The invention relates to the technical field of power grid optimization, in particular to a power grid dynamic reactive power optimization configuration method based on transient voltage safety constraint.
Background
At present, an electric power system is developing towards a large unit, ultra/extra-high voltage remote power transmission and large power grid interconnection direction, power grids in part of economically developed regions form a typical receiving-end power grid structure, and the problem of transient voltage stability of the receiving-end power grid is paid more and more attention. The receiving-end power grid is fed with multiple loops of direct current in a centralized manner, the direct current transmission capacity is large, and huge reactive power needs to be consumed. As the proportion of induction motors in the load is increased, especially during heavy load periods in summer, the air conditioner motor load will be in a large proportion, making the transient voltage stabilization problem more prominent. Transient voltage stabilization is primarily related to the dynamics of the induction motor load, i.e. after a large disturbance is required, the slip of the induction motor does not increase continuously to avoid an increase in the consumed reactive power. Maintaining dynamic reactive power supply and demand balance of a receiving-end power grid and ensuring the transient voltage stability of a system are important challenges for planning and operating the receiving-end power grid. In recent years, a large-area power failure caused by voltage instability due to continuous increase of load after system failure and mismatching of dynamic reactive power reserve occurs internationally. Compared with the traditional capacitor reactive compensation equipment, the dynamic reactive compensation device represented by a Static Var Compensator (SVC) has the characteristic of quick response, can effectively improve the dynamic reactive power reserve of a system, and improves the transient voltage stability of the system. However, there is no effective method to select the appropriate installation site and installation capacity of the SVC, which affects the SVC to perform the function of dynamic reactive power compensation.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, provides a power grid dynamic reactive power optimization configuration method based on transient voltage safety constraint, takes the relation between the reactive power characteristic of a dynamic reactive power compensation device SVC and node voltage recovery into consideration, plays the reactive power compensation role of the dynamic reactive power compensation device SVC, and has a better control effect.
In order to solve the technical problems, the invention adopts the technical scheme that:
the power grid dynamic reactive power optimization configuration method based on the transient voltage safety constraint comprises the following steps:
s10, inputting power grid basic data to the power system to perform time domain transient state simulation, and determining a key fault set { F) threatening the transient voltage stability of the power system1,F2,…,FNDetermining SVC installation nodes to be selected {1,2, …, m } according to voltage recovery levels of all nodes during a fault period;
and S20, respectively installing dynamic reactive power compensation devices SVC at each node, performing time domain transient simulation again, and calculating a voltage-reactive locus sensitivity index TSI of a node j (j is 1,2, …, m)j；
S30, TSI of each node according to the calculation result of the step S20jSorting to obtain the maximum TSIjThe node corresponding to the value is an SVC optimal installation node;
s40, setting CSO algorithm population parameters, initializing a CSO population and generating SVC initial capacity; performing time domain transient state calculation on an objective function value and fitness by adopting an implicit trapezoidal integral method, and checking whether the objective function value meets constraint conditions; if yes, go to step S50; otherwise, the fitness of the particle is added with a penalty item and then the step is carried out to step S50;
s50, storing the particles G with the best current CSO population fitnessbestAnd judging whether the end condition is met, if so, outputting an optimal value GbestAs the optimal configuration scheme, otherwise, turning to step S60;
s60, carrying out transverse crossing and longitudinal crossing operations on the CSO population, and generating a new CSO population through the competition operation of filial generations and parent generations;
s70, returning to the step S40, and performing transient calculation and objective function value calculation again on the new CSO population by adopting an implicit trapezoidal integration method; until step S50 satisfies the end condition, the optimal SVC configuration capacity is output.
According to the dynamic reactive power optimization configuration method of the power grid based on the transient voltage safety constraint, under the condition of the fault to be observed, the node voltage deviation after the fault and the SVC capacity of the dynamic reactive power compensation device are used as control objective functions, a reactive power compensation device SVC multi-objective optimization configuration model and method for controlling the transient voltage safety and stability are established, a proper installation place and installation capacity are selected, the effect of the dynamic reactive power compensation device is fully exerted, and the control effect is relatively remarkable.
Preferably, in step S20, after the node j installs the SVC, the node j' SVoltage-reactive trajectory sensitivity index TSIjThe incremental form is expressed as:
Figure BDA0002009230630000021
in the formula, S(SVC)Rated installation capacity of the reactive power compensation device is constant; delta Qj(SVC)The reactive power released after the SVC is installed for the node j changes along with the voltage change of the node j; vi(tk,Qj0+ΔQj(SVC)) For the fault to be investigated, the node j is provided with the installation capacity S(SVC)After SVC, the voltage V of node iiAt t ═ tkA value of a time of day; vi(tk,Qj0) Before the SVC is installed on the node j under the fault to be examined, the voltage V of the node iiAt t ═ tkThe value of the time of day. Because the reactive power of the injection system of the dynamic reactive power compensation device such as the SVC is changed along with the voltage change of the installation node, particularly after the voltage of the node is reduced to a certain value, the reactive power released by the SVC is proportional to the square of the voltage, and cannot be kept constant. Therefore, after installing SVC at node j, the V-Q track sensitivity index TSI of node j is calculatedjAnd (4) increasing.
Preferably, in step S40, the objective function J1Setting as follows:
Figure BDA0002009230630000031
wherein j is 1,2, …, n; qjThe installation capacity, Mvar, of the jth SVC installation node; krjAnd TrjSVC controller gain and time constant thereof of the jth SVC installation node respectively; u shapeBjIs the reference voltage, kV, of the jth SVC installation node; s is the integral sum S of transient voltage drop on all node V-t characteristic curves in delta t with respect to time; u shapekThe transient voltage of each node bus of the power system.
Objective function J1Defined as the integral of the sum of the squares of the deviations of the node voltages. Dynamic reactive power compensationThe compensation effect of the device SVC is visually reflected on the transient voltage recovery characteristic curve. Generally speaking, the larger the amount of dynamic reactive compensation, the faster the transient voltage recovers, and the better the transient voltage performance. In the fault clearing ts, the smaller the integral sum S of transient voltage drop on the V-t characteristic curves of all nodes of the system with respect to time, the better the transient voltage performance.
Preferably, in step S40, the constraint condition is:
the voltage of each load bus at 1s after the fault is removed is restored to 0.75pu or more, and is expressed as:
Figure BDA0002009230630000032
in the formula of Ui1The voltage of a load bus i under a certain fault; t is tcFor fault clearing time, tz1＝1s，Uz1min＝0.75pu，tz2＝3s，Uz2min0.01-0.02% can be selected as 0.9 pu; in order to ensure the stability of transient voltage of a power system, the current standard of China is that the voltage of each load bus is recovered to be more than 0.75pu when the fault is removed for 1 s;
when the system recovers to the steady state after the fault, the voltage of each node does not exceed the upper limit and the lower limit of the steady state voltage of the normal operation, and the voltage is represented as follows:
Figure BDA0002009230630000033
in the formula (I), the compound is shown in the specification,
Figure BDA0002009230630000034
after clearing for fault twThe voltage of the load bus i; t is tcFor fault clearing time, twThe time for recovering to the steady state after the system fault is removed; u shapewmaxAnd UwminIs the upper limit of the steady state voltage of the system. In the invention, Ui9The voltage of the load bus i is 9s after the fault is cleared; t is twTaking U as 9swmax＝1.1p.u.， Uwmin＝0.95pu。
Preferably, in step S50, the ending condition is expressed as:
Iter≥MaxIter
in the formula IterFor the number of iterations of the current particle, MaxIterIs the maximum number of iterations.
Preferably, in step S60, the lateral intersection of the CSO algorithm is based on an intersection operation between all dimensions of two particles:
Figure BDA0002009230630000041
in the formula: r is1And r2Is [0,1 ]]A random number in between; c. C1And c2Is [ -1,1 [ ]]A random number in between. X (i, d) and X (j, d) are two different parent solutions; MS (Mass Spectrometry)hc(i, d) and MShcAnd (j, d) is a child solution generated after the parent solution is subjected to transverse intersection operation.
Preferably, in step S60, the vertical crossing is a crossing operation that occurs between two different dimensions of all particles, assuming that the d-th dimension of the particle x (i)1And d2The dimension is crossed, and then:
Figure BDA0002009230630000042
in the formula, MSvc(i,d1) Is X (i, d)1) And intermediate interpretation of X (i, d 2); r is uniformly distributed in [0,1 ]]The random number of (2); m is the population scale; d is the total number of particle dimensions.
Compared with the prior art, the invention has the beneficial effects that:
the power grid dynamic reactive power optimization configuration method based on the transient voltage safety constraint fully utilizes the characteristic of fast controllability of the SVC, and provides dynamic reactive power support for voltage recovery of a load node of a power system after a fault, so that the system meets the requirement of transient voltage safety and stability.
Drawings
Fig. 1 is a flow chart of a dynamic reactive power optimization configuration method of a power grid based on transient voltage safety constraints;
FIG. 2 is a schematic diagram of the physical significance of the V-Q trajectory sensitivity index;
FIG. 3 is a graph of node voltage dynamic trajectories after a fault;
FIG. 4 is a diagram illustrating a discretization method for determining the voltage recovery area SkA schematic diagram of (a);
FIG. 5 is a block diagram of an SVC model;
FIG. 6 is a net rack topology diagram of a new England 10 machine 39 node system;
FIG. 7 is a 3D view of voltages of nodes of a system when an SVC is not installed in a three-phase ground fault of a node 16;
FIG. 8 is a simulated waveform of voltages at nodes of a system when a three-phase ground fault at node 16 is not provided with an SVC;
FIG. 9 is a simulated waveform of node voltage when the three-phase ground short fault dynamic reactive compensation point of the node 16 is not installed with an SVC;
FIG. 10 is a motor slip curve for a node 16 three-phase ground fault dynamic reactive compensation point without an SVC installed;
FIG. 11 shows TSI index values of nodes of the power system;
fig. 12 is a 3D view of voltages at nodes of a system when an SVC is installed in a three-phase ground fault at node 16;
fig. 13 is a simulation waveform of voltages at nodes of a system when an SVC is installed in a three-phase ground short circuit fault at node 16;
fig. 14 shows motor slip when the node 16 three-phase earth short fault dynamic reactive compensation point is equipped with an SVC;
FIG. 15 is a graph of algorithm convergence characteristics;
fig. 16 is a grid topology diagram of the Guangdong power grid 47 machine 140 node system;
fig. 17 is a 3D view of voltages at nodes of the system when an SVC is not installed in a three-phase ground fault at node 91;
FIG. 18 is a simulated waveform of voltages at nodes of a system when a three-phase ground fault at node 91 is not provided with an SVC;
fig. 19 is a node voltage simulation waveform when the three-phase ground short fault dynamic reactive power compensation point of the node 91 is not installed with an SVC;
fig. 20 is a curved motor slip curve when the three-phase ground short fault dynamic reactive power compensation point of the node 91 is not equipped with the SVC;
FIG. 21 shows TSI metric values of nodes in the system;
fig. 22 is a 3D diagram of voltages at nodes of the system when the SVC is installed in a three-phase ground fault at node 91;
fig. 23 is a simulated waveform of voltages at nodes of a system when an SVC is installed in a three-phase ground fault at node 91;
fig. 24 shows the motor slip when the SVC is installed at the three-phase ground short fault dynamic reactive power compensation point of the node 91.
Detailed Description
The present invention will be further described with reference to the following embodiments. Wherein the showings are for the purpose of illustration only and are shown by way of illustration only and not in actual form, and are not to be construed as limiting the present patent; to better illustrate the embodiments of the present invention, some components of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
Example one
Fig. 1 is a flowchart of a dynamic reactive power optimization configuration method for a power grid based on transient voltage safety constraints, which includes the following steps:
s10, inputting power grid basic data to the power system to perform time domain transient state simulation, and determining a key fault set { F) threatening the transient voltage stability of the power system1,F2,…,FNDetermining SVC installation nodes to be selected {1,2, …, m } according to voltage recovery levels of all nodes during a fault period;
and S20, respectively installing dynamic reactive power compensation devices SVC at each node, performing time domain transient simulation again, and calculating a voltage-reactive locus sensitivity index TSI of a node j (j is 1,2, …, m)j；
S30, TSI of each node according to the calculation result of the step S20jSorting to obtain the maximum TSIjThe node corresponding to the value is an SVC optimal installation node;
s40, setting CSO algorithm population parameters, initializing a CSO population and generating SVC initial capacity; performing time domain transient state calculation on an objective function value and fitness by adopting an implicit trapezoidal integral method, and checking whether the objective function value meets constraint conditions; if yes, go to step S50; otherwise, the fitness of the particle is added with a penalty item and then the step is carried out to step S50;
s50, storing the particles G with the best current CSO population fitnessbestAnd judging whether the end condition is met, if so, outputting an optimal value GbestAs the optimal configuration scheme, otherwise, turning to step S60;
s60, carrying out transverse crossing and longitudinal crossing operations on the CSO population, and generating a new CSO population through the competition operation of filial generations and parent generations;
s70, returning to the step S40, and performing transient calculation and objective function value calculation again on the new CSO population by adopting an implicit trapezoidal integration method; until step S50 satisfies the end condition, the optimal SVC configuration capacity is output.
The invention relates to a power grid dynamic reactive power optimization configuration method based on transient voltage safety constraint, which comprises the steps of firstly calculating a voltage-reactive power sensitivity (TSI) index through time domain simulation, and determining an SVC installation site according to the TSI; then determining an objective function for optimizing the SVC capacity according to the relation between the SVC capacity and the node voltage recovery; and finally, solving a multi-objective function by applying a CSO algorithm to determine the optimal capacity of the SVC. The method fully utilizes the characteristic of fast controllability of the SVC, provides dynamic reactive power support for voltage recovery of a load node of the power system after the fault, and enables the system to meet the requirement of safety and stability of transient voltage.
In step S20, since the reactive power injected into the system by the dynamic reactive power compensator such as an actual SVC changes with the voltage of the installation node, particularly when the voltage of the installation node drops to a certain value, the reactive power released by the SVC is proportional to the square of the voltage, and cannot be kept constant. Thus, after node j installs the SVC, the incremental form of the V-Q trajectory sensitivity index TSIj for node j can be expressed as:
Figure BDA0002009230630000061
in the formula (1), S(SVC)Rated installation capacity of the reactive power compensation device is constant; delta Qj(SVC)The reactive power released after the SVC is installed on the node j changes along with the voltage change of the node j; vi(tk,Qj0+ΔQj(SVC)) In order to install the node j with the installation capacity S under the fault to be examined(SVC)After SVC, the voltage V of node iiAt t ═ tkA value of a time of day; vi(tk,Qj0) Before the SVC is installed on the node j under the fault to be examined, the voltage V of the node iiAt t ═ tkThe value of the time of day. Assuming Δ t is sufficiently small, equation (1) can be written as:
Figure BDA0002009230630000071
each cumulative term to the right of equation (2) represents the injection of Δ Q at node jj(SVC)Before and after the reactive power of (3), the voltage change curve V of each nodei(t) during a time interval [ t ]1,tN]The fixed integral difference value above, i.e. the shaded portion shown in fig. 2.
In FIG. 2, the area of the shaded portion is referred to as the V-t area increment of the voltage curve. Therefore, the TSI of node j can be found from equation (2)jThe physical meaning of (1) is that after a reactive power is injected into a node j, the voltage change curve of each node of the system along with time is in an interval [ t1，tN]The sum of the inner V-t area increments is divided by the rated installation capacity S of the SVC reactive power compensation device(SVC). TSI of formula (2)j(SVC)The characteristic that the reactive power actually output by the SVC changes along with the voltage change of the installation node is considered in detail by the V-Q index, so that the improvement effect of the SVC installed on each node on the transient voltage stability control of the system can be reflected more accurately in theory.
In step S40, the objective function J1The compensation effect of the dynamic reactive compensation device SVC is visually reflected on the transient voltage recovery characteristic curve. In general, the greater the amount of dynamic reactive compensation, the transientThe faster the voltage recovery, the better the transient voltage performance. The smaller the integral sum S of transient voltage drops over time on the V-t characteristic curves of all nodes of the system within 3S of fault clearance. After the fault is cleared, the integral S of the transient voltage drop on a certain node V (t) characteristic curve with respect to time in the voltage recovery processiIs the area of the shaded portion shown in fig. 3. From the above, the objective function J can be obtained1Setting as follows:
Figure BDA0002009230630000072
in formula (4), i is 1,2, …, n; n is the total number of system nodes; t is tcTime for fault removal, unit: s; u shapeiThe unit is the bus transient voltage of each node of the system: pu; u shapei0The unit is the steady state value of the bus voltage of each node of the system: pu.
Since the transient voltage-time characteristic curve of the node bus is difficult to express by using a determined continuity mathematical expression, the discretization processing of S is required. Dividing 3s time into 300 parts, each part of delta t is 0.01s, starting from fault removal, and obtaining voltage value U every delta tk(k-1, …, 300), using UkAnd Uk+1Is calculated as Δ SkI.e. by
Figure BDA0002009230630000073
Such that the node
Figure BDA0002009230630000081
As shown in particular in fig. 4. By the discretization process, the objective function becomes as shown in equation (5):
Figure BDA0002009230630000082
fig. 5 shows a block diagram of a model of a dynamic reactive power compensation device SVC, which has a state equation as shown in formula (6):
Figure BDA0002009230630000083
in formula (6), UrefIs SVC side reference voltage amplitude; u is the SVC side actual voltage amplitude, KrAnd TrThe SVC controller gain and its time constant, respectively. The SVC node injection reactive power calculation formula is as follows:
Q＝-BCVU2 (7)
since the SVC installation node voltage has high sensitivity to the compensation capacity, the mathematical relationship of the compensation capacity to the node voltage can be expressed by the following equations (6) and (7):
Figure BDA0002009230630000084
after the formula (8) is subjected to per unit, the formula (7), U is combinedcFor mounting nodes for SVC
Figure BDA0002009230630000085
Is composed of
Figure BDA0002009230630000086
Dividing system nodes into SVC installation nodes and non-installation nodes, S of SVC installation nodesiThe compensation capacity can be expressed by an intuitive mathematical expression as shown in the following formula:
Figure BDA0002009230630000087
assuming that there are m SVC installation nodes in the system, the objective function equation (7) can be converted by equation (9) as follows:
Figure BDA0002009230630000088
in formula (10), j is 1,2, …, n; qjThe unit of the installation capacity of the jth SVC installation node is as follows: MVar; krjAnd TrjSVC controller gain and timing for jth SVC installation node respectivelyAn inter constant; u shapeBjIs a reference voltage of the jth SVC mounting node, unit: kV.
Usually, the instability of the load of the induction motor is obviously represented by the voltage of the bus, and the voltage of the bus generally drops to 0.6pu or so greatly. Therefore, the transient voltage stabilization constraint of the present invention is applied from the voltage point of view, and requires that the voltage of the load bus is restored to 0.9pu or more within 3s after the fault is removed. For the constraint of the acceptable degree of transient voltage drop, according to the national standard, the voltage is required to be recovered to be more than 0.75pu after the fault is removed for 1 s. Therefore, the constraint conditions in step S40 of the present embodiment are as follows:
1) in order to ensure the transient voltage stability of the power system, the current standard of China is that the voltage of each load bus is recovered to be more than 0.75pu 1s after the fault is removed, and the voltage is expressed by a mathematical formula as follows:
Figure BDA0002009230630000091
wherein: u shapei1The voltage of a load bus i under a certain fault; t is tcFor fault clearing time, tz1＝1s，Uz1min＝0.75pu，tz2＝3s，Uz2min0.01 to 0.02 is preferred.
2) When the system is gradually recovered to a steady state after a fault, the voltage of each node cannot exceed the upper limit and the lower limit of the steady state voltage of normal operation, and is expressed by a mathematical expression:
Figure BDA0002009230630000092
wherein: u shapei9The voltage of the load bus i is 9s after the fault is cleared; t is twFor the time for recovering to the steady state after the system fault is removed, t is takenw＝9s；UwmaxAnd UwminFor the upper limit of the steady-state voltage of the system, U can be takenwmax＝1.1p.u.， Uwmin＝0.95pu。
When a system faces a problem of safety and stability of transient voltage after large disturbance, emergency control of optimal coordination is implemented from the perspective of centralized control, multiple targets need to be optimized and multiple control means need to be coordinated, and this embodiment describes this problem as a multi-target hybrid optimal control model in the following form:
Figure BDA0002009230630000093
equation (13) may describe the dynamics of the elements of the power system, including the dynamics of the generator and its excitation system, load and dynamic reactive power compensation device. In formula (13): j of the 1 st equation1And J2Is an objective function; the 2 nd expression and the 3 rd expression represent a differential algebraic equation system for describing the transient voltage dynamic process of the system, and x and y represent all state variables and all algebraic variables of the system respectively; u represents a continuous control variable for implementing the transient voltage safety and stability control, and is an adjustment quantity of a node voltage area curve in the invention; v represents a discrete control variable for implementing the safe and stable control of the transient voltage, and is the switching quantity of the reactive compensation device in the invention; equations 4-7 represent constraints imposed on system variables. Wherein x ismaxAnd xminRepresenting the upper and lower limits of the system state variable, including some amplitude limiting links in the excitation control system; y ismaxAnd yminRepresenting the upper and lower limits of an algebraic variable, including acceptable constraints of node transient voltage drop; according to the national standard, the constraint is set to be that the voltage is recovered to be more than 0.75pu after the fault is removed for 1 s; u. ofmaxAnd uminRepresenting the upper and lower limits of the continuous control variable, namely the upper and lower limits of the regulation of the excitation voltage reference value; omega represents a value set of discrete control variables, namely the reactive power compensation device installation position combination.
Wherein the second objective function J2Defined as the sum (per unit value) of the rated compensation capacities of the reactive compensation device SVC. Objective function J2Can be set as follows:
Figure BDA0002009230630000101
in step S50, the termination condition is expressed as:
Iter≥MaxIter
in the formula IterFor the number of iterations of the current particle, MaxIterIs the maximum number of iterations.
In step S60, the lateral intersection of the CSO algorithm is based on the intersection operation between all dimensions of the two particles:
Figure BDA0002009230630000102
in the formula: r is1And r2Is [0,1 ]]A random number in between; c. C1And c2Is [ -1,1 [ ]]A random number in between. X (i, d) and X (j, d) are two different parent solutions; MS (Mass Spectrometry)hc(i, d) and MShcAnd (j, d) is a child solution generated after the parent solution is subjected to transverse intersection operation.
In step S60, the vertical crossing is a crossing operation that occurs between two different dimensions of all particles, assuming that the d-th dimension of the particle X (i)1And d2The dimension is crossed, and then:
Figure BDA0002009230630000103
in the formula, MSvc(i,d1) Is X (i, d)1) And intermediate interpretation of X (i, d 2); r is uniformly distributed in [0,1 ]]The random number of (2); m is the population scale; d is the total number of particle dimensions.
In each iteration of evolution, the CSO algorithm particle performs a transverse crossing operation and a longitudinal crossing operation according to the formula (15) and the formula (16) respectively. The solution obtained by the cross operation is called a Mediocre Solution (MS)hc,MSvc) (ii) a The middle-aged solution competes with the parent particles according to the competition strategy, the fitness superior people live, and the solution obtained by competition is called the Dominant Solution (DS)hc, DSvc). Intermediate interpretation of transverse cross-generation MShcThen cross with the longitudinal direction to generate dominant solution DSvcCompete with each other; longitudinally crossingIntermediate interpretation of fork generation MShcDominant solution DS also generated across the transverse directionhcCompete with each other, and the operations are continuously alternated. In the new generation of individuals, only particles with better fitness than the parent survive, while other particles are eliminated in competition. The competition mechanism ensures that the vertical and horizontal cross search is always maintained in the historical optimal population, thereby increasing the accuracy of the solution and accelerating the convergence speed.
In the embodiment, the CSO algorithm is used for solving the multi-objective SVC optimization configuration problem. In solving the problem, each CSO particle represents a potential solution, and the expression of the particle is shown in equation (17):
Xi＝[S(SVC)1，S(SVC)2，…，S(SVC)m] (17)
in formula (17): s(SVC)1，S(SVC)2，…，S(SVC)mThe installation capacity (per unit value) of the dynamic reactive compensation device SVC at each of the candidate points 1,2, …, m; and m is the number of SVC installation points.
Through the steps, the optimal installation position and capacity of the SVC can be obtained, and dynamic reactive support is provided for voltage recovery of a load node of the power system after the fault.
Example two
The embodiment is an application example of the method in the first embodiment in time domain transient simulation calculation of a 39-node grid of a new england 10 machine, all loads of a power system are configured by adopting a proportion of 60% of induction motors and 40% of constant impedance loads, and the load model parameters of the induction motors adopt values in table 1.
TABLE 1 Induction Motor load model parameters
Figure BDA0002009230630000111
The calculation example of the embodiment only considers one specific fault, the system has a three-phase short-circuit fault when the system time domain transient simulation calculation time is 10s, and when t is 1s, the fault disappears when t is 1.1s, and the fault point is uniformly arranged at a node where transient voltage instability of the system occurs before the SVC is installed.
The grid topological diagram of the 330kV power grid of the 39-node of the new England 10 machine is shown in FIG. 6, and when a three-phase short-circuit fault occurs at the node 16, transient voltage instability occurs in the system, as shown in FIGS. 7-10. For this fault, the V-Q sensitivity index TSI of the actual SVC model is calculated, as shown in FIG. 10. According to fig. 11, a node sensitive to reactive power variation is selected from all nodes in the system to install the SVC, and the installation sites of the SVC are selected as follows: and 8, 15, 18, 24 and 28. The SVC capacity of the node installation is optimally configured by adopting the proposed model and algorithm, and the SVC capacity of the bus 8, 15, 18, 24 and 28 after optimization is 81.9MVar, 59.1MVar, 6.3MVar, 109.3MVar and 110.8MVar in sequence. The voltage change when the SVC is installed after the system failure is examined, as shown in FIGS. 12-14. As can be seen from fig. 11-12, after installation of the SVC, the system can remain stable under investigation failure.
EXAMPLE III
The embodiment is an application example of the method in the first embodiment to time domain transient simulation calculation in a large power grid with 47 machine 140 nodes in the Guangdong power grid, all loads of a power system are configured by adopting 60% of induction motors and 40% of constant impedance load proportion, and the load model parameters of the induction motors adopt the values in table 1. In addition, only one specific fault is considered in the embodiment, the time domain transient simulation calculation time of the system is 10s, when t is 1s, the system has a three-phase short-circuit fault, when t is 1.1s, the fault disappears, and the fault point is uniformly arranged at a node where transient voltage instability of the system occurs before the SVC is installed.
The grid structure of the Guangdong power grid 47 machine 140 node 220kV power grid is shown in FIG. 16. For convenience of explanation, only one specific fault is considered, and the fault form is that a three-phase short-circuit fault occurs in the node 91 when t is 1s, and the fault is removed when t is 1.1 s. Without the SVC installed, the system will exhibit transient voltage instability under this fault, as in fig. 17-20.
For this fault, the V-Q sensitivity index TSI of the actual SVC model is calculated, as shown in FIG. 21. According to fig. 21, a node sensitive to reactive power variation is selected from all nodes in the system to install the SVC, and the installation sites of the SVC are selected as follows: 83, 96, 107, 118, 136. The SVC capacity installed on the nodes is optimally configured by adopting the proposed model and algorithm, and the SVC capacity installed on the nodes 83, 96, 107, 118 and 136 after optimization is 92.3MVar, 113.7MVar, 96.1MVar, 87.9MVar and 103.2MVar in sequence. The voltage change when the SVC is installed after a system failure is examined as shown in fig. 22-24. It can be seen from fig. 22-24 that after the SVC is installed, the system can remain stable under fault investigation.
It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. It will be apparent to those skilled in the art that other variations and modifications can be made on the basis of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims (4)

1. The power grid dynamic reactive power optimization configuration method based on the transient voltage safety constraint is characterized by comprising the following steps of:
s10, inputting power grid basic data to the power system to perform time domain transient state simulation, and determining a key fault set { F) threatening the transient voltage stability of the power system1,F2,…,FNDetermining SVC installation nodes to be selected {1,2, …, m } according to voltage recovery levels of all nodes during a fault period;
and S20, respectively installing dynamic reactive power compensation devices SVC at each node, performing time domain transient simulation again, and calculating a voltage-reactive locus sensitivity index TSI of a node j (j is 1,2, …, m)j；
S30, TSI of each node according to the calculation result of the step S20jSorting to obtain the maximum TSIjThe node corresponding to the value is an SVC optimal installation node;
s40, setting CSO algorithm population parameters, initializing a CSO population and generating SVC initial capacity; performing time domain transient state calculation on an objective function value and fitness by adopting an implicit trapezoidal integral method, and checking whether the objective function value meets constraint conditions; if full ofIf yes, go to step S50; otherwise, the fitness of the particle is added with a penalty item and then the step is carried out to step S50; wherein the objective function J1Setting as follows:
Figure FDA0002647994190000011
in the formula, n is the number of node buses in the system; t is tcThe unit is the fault removal time in seconds; u shapeiThe unit is pu for the transient voltage of each node bus of the system; u shapeciThe unit is pu for the normal voltage of each node bus of the system; j is 1,2, …, n; qjThe unit of the installation capacity of the jth SVC installation node is Mvar; krjAnd TrjSVC controller gain and time constant thereof of the jth SVC installation node respectively; u shapeBjIs the reference voltage, kV, of the jth SVC installation node; s is the integral sum S of transient voltage drop on all node V-t characteristic curves in delta t with respect to time; siThe voltage recovery area is the ith bus node voltage; s represents a transfer function; u shapekThe transient voltage of each node bus of the power system is obtained; the constraint conditions are as follows:
the voltage of each load bus at 1s after the fault is removed is restored to 0.75pu or more, and is expressed as:
Figure FDA0002647994190000012
in the formula of Ui1The voltage of a load bus i under a certain fault; t is tcFor fault clearing time, tz1＝1s，Uz1min＝0.75pu，tz2＝3s，Uz2min0.01-0.02% can be selected as 0.9 pu;
when the system recovers to the steady state after the fault, the voltage of each node does not exceed the upper limit and the lower limit of the steady state voltage of the normal operation, and the voltage is represented as follows:
Figure FDA0002647994190000021
in the formula (I), the compound is shown in the specification,
Figure FDA0002647994190000022
after clearing for fault twThe voltage of the load bus i; t is tcFor fault clearing time, twThe time for recovering to the steady state after the system fault is removed; u shapewmaxAnd UwminIs the steady state upper voltage limit of the system;
s50, storing the particles G with the best current CSO population fitnessbestAnd judging whether the end condition is met, if so, outputting an optimal value GbestAs the optimal configuration scheme, otherwise, turning to step S60; the end condition is expressed as:
Iter≥MaxIter
in the formula IterFor the number of iterations of the current particle, MaxIterIs the maximum iteration number; s60, carrying out transverse crossing and longitudinal crossing operations on the CSO population, and generating a new CSO population through the competition operation of filial generations and parent generations;
s70, returning to the step S40, and performing transient calculation and objective function value calculation again on the new CSO population by adopting an implicit trapezoidal integration method; until step S50 satisfies the end condition, the optimal SVC configuration capacity is output.
2. The dynamic reactive power optimization configuration method for power grid based on transient voltage safety constraint of claim 1, wherein in step S20, after the node j is installed with the SVC, the voltage-reactive trajectory sensitivity index TSI of the node j is obtainedjThe incremental form is expressed as:
Figure FDA0002647994190000023
in the formula, S(SVC)Rated installation capacity of the reactive power compensation device is constant; delta Qj(SVC)The reactive power released after the SVC is installed for the node j changes along with the voltage change of the node j; vi(tk,Qj0+ΔQj(SVC)) In order to be under examinationUnder fault, the node j installation capacity is S(SVC)After SVC, the voltage V of node iiAt t ═ tkA value of a time of day; vi(tk,Qj0) Before the SVC is installed on the node j under the fault to be examined, the voltage V of the node iiAt t ═ tkThe value of the time of day.
3. The grid dynamic reactive power optimization configuration method based on transient voltage safety constraint according to claim 1 or 2, characterized in that in step S60, the algorithm of the horizontal intersection is expressed as:
Figure FDA0002647994190000024
in the formula: r is1And r2Is [0,1 ]]A random number in between; c. C1And c2Is [ -1,1 [ ]]X (i, d) and X (j, d) are two different parent solutions; MS (Mass Spectrometry)hc(i, d) and MShcAnd (j, d) is a child solution generated after the parent solution is subjected to transverse intersection operation.
4. The dynamic reactive power optimization configuration method for power grid based on transient voltage safety constraint of claim 3, wherein in step S60, the algorithm of vertical crossing is expressed as:
Figure FDA0002647994190000031
in the formula, MSvc(i,d1) Is X (i, d)1) And intermediate interpretation of X (i, d 2); r is uniformly distributed in [0,1 ]]The random number of (2); m is the population scale; d is the total number of particle dimensions.
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