CN116231672A - Reactive power optimization method and system for fan-containing power grid based on voltage weak point identification - Google Patents

Reactive power optimization method and system for fan-containing power grid based on voltage weak point identification Download PDF

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CN116231672A
CN116231672A CN202310189044.2A CN202310189044A CN116231672A CN 116231672 A CN116231672 A CN 116231672A CN 202310189044 A CN202310189044 A CN 202310189044A CN 116231672 A CN116231672 A CN 116231672A
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power
voltage
reactive power
node
reactive
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任正
王新宇
刘春晖
王俊芳
刘志强
龚庆武
张怀勋
赵洁
梁忆琳
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State Grid Corp of China SGCC
Wuhan University WHU
Electric Power Research Institute of State Grid Eastern Inner Mongolia Power Co Ltd
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State Grid Corp of China SGCC
Wuhan University WHU
Electric Power Research Institute of State Grid Eastern Inner Mongolia Power 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
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/008—Circuit arrangements for ac mains or ac distribution networks involving trading of energy or energy transmission rights
    • 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
    • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
    • 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
    • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
    • H02J3/1821—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators
    • 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
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • 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
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/50—Controlling the sharing of the out-of-phase component
    • 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
    • H02J2203/10—Power transmission or distribution systems management focussing at grid-level, e.g. load flow analysis, node profile computation, meshed network optimisation, active network management or spinning reserve management
    • 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]
    • 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
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/28—The renewable source being wind energy
    • 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

Abstract

The invention provides a reactive power optimization method and system for a fan-containing power grid based on voltage weak point identification. It comprises the following steps: acquiring structural parameters and electrical parameters of an electric power network; calculating the reactive power adjustable range of the power grid fan based on the doubly-fed fan power conversion model; after the large-scale wind turbine generator is connected with a power grid, node voltage change indexes are built, a continuous tide method is adopted to calculate a PV curve for each node voltage, the node voltage change indexes in a critical state are calculated, and voltage weak nodes in the power grid are judged; and finally, constructing a reactive power optimization model taking the voltage weak point as a reactive power compensation node, and solving by adopting a particle swarm optimization algorithm with improved weight. The method reduces the variable dimension in reactive power optimization, greatly improves the calculation efficiency, improves the stability of voltage in a new energy high-permeability scene, reduces the line loss, fully utilizes the reactive power allowance of the wind turbine, and has strong applicability and superiority.

Description

Reactive power optimization method and system for fan-containing power grid based on voltage weak point identification
Technical Field
The invention belongs to the technical field of power system planning, and particularly relates to a reactive power optimization method and system for a fan-containing power grid based on voltage weak point identification.
Background
With the background of 'double-carbon' target proposal and 'construction of a novel power system taking new energy as a main body', the large-scale new energy fan is increasingly popular to be connected into the power system, with the connection of the large-scale new energy fan, the network trend distribution condition of the original system is changed, and due to the characteristics of randomness and uncertainty of fan output, certain hidden danger can be brought to the stability of the voltage in the system, so that the safe operation of the whole power grid is influenced. Therefore, in order to improve the voltage stability level of the power grid, the reactive resource is necessary to be optimally configured, and the establishment of a voltage reactive power optimization model applicable to the power grid has great significance.
At present, most methods directly perform reactive power optimization by utilizing reactive power compensation equipment after a new energy source is connected into a power grid, directly adjust voltage by adopting the reactive power compensation equipment, neglect the adjustment of the reactive power compensation equipment to participate in the reactive power optimization by utilizing reactive power allowance of the new energy source, and involve a plurality of nodes connected into the reactive power compensation equipment, the number of the connected reactive power equipment is large, the number of variable dimensions in the optimization solution is directly increased, and the result is easy to fall into local convergence, so that the final optimization effect is poor, and the input cost of the reactive power compensation equipment is greatly increased.
Disclosure of Invention
Aiming at the problem of fluctuation of node voltage after the doubly-fed wind turbine is connected into a power grid, the invention provides a reactive power optimization method for the power grid with the wind turbine based on voltage weak point identification.
A reactive power optimization method for a fan-containing power grid based on voltage weak point identification comprises the following steps:
a plurality of wind power stations consisting of doubly-fed fans are connected into a power grid, and node voltage change indexes of each connected node are judged to obtain voltage weak points of the wind power stations after the wind power stations are connected into the power grid;
the method comprises the steps of taking a voltage weak point as a compensation node for reactive equipment access, and constructing a reactive power optimization model, wherein the reactive power optimization model takes the minimum node voltage deviation, the minimum line loss and the minimum total investment cost of the compensation node in reactive equipment in a power grid system as objective functions, and simultaneously meets load flow equation constraint and generator terminal voltage, on-load voltage regulating transformer taps, the input quantity of the reactive equipment and inequality constraint of a reactive power regulation range of a wind power station;
and (3) carrying out iterative updating on the control variable by adopting an intelligent optimization algorithm, calculating to obtain a solution meeting the reactive power optimization model, and outputting an optimal control variable.
In the method for optimizing reactive power of power grid with fan based on voltage weak point identification, when the doubly-fed fan is connected to power grid side to normally operate, the doubly-fed fan absorbs the mostHigh reactive power Q min Maximum reactive power Q absorbed for stator side smin Maximum reactive power Q absorbed by grid-side converter gmin The sum of the maximum reactive power Q emitted by the doubly-fed fans max Maximum reactive power Q emitted for stator side smax Maximum reactive power Q emitted by the grid-side converter gmax And (3) summing.
In the method for optimizing reactive power of the fan-containing power grid based on voltage weak point identification, the complete PV curve of each node in the power grid is obtained through a continuous tide method, the voltage amplitude of each node in the power transmission critical point state is determined, and the node voltage change index delta V is constructed i And judging the node voltage change index of each node to obtain a voltage weak point set consisting of voltage weak points of a plurality of wind power stations after the wind power stations are connected into a power grid.
According to the reactive power optimization method for the wind-containing power grid based on the voltage weak point identification, the control variables are the generator terminal voltage, the on-load transformer tap, the reactive power equipment access quantity of the compensation node and the reactive power allowance of the wind power station participating in optimization, the intelligent optimization algorithm is adopted to update the variables in an iterative manner, and the solution meeting the objective function, the equality and inequality constraint conditions in the reactive power optimization model is calculated.
In the method for optimizing reactive power of the wind-driven generator network based on voltage weak point identification, the constructed reactive power optimization model is solved according to the particle swarm optimization algorithm for improving inertia weight, and the initialization conditions in the algorithm are input, wherein the initialization conditions comprise iteration times m, population size s and speed update parameters c 1 And c 2 And the inertia weight parameter w is subjected to iterative calculation to obtain a solution meeting the objective function, the equality constraint condition and the inequality constraint condition.
In the method for optimizing reactive power of the power grid with the fan based on voltage weak point identification, when the doubly-fed fan connected to the power grid normally operates, the reactive power range Q of the doubly-fed fan is
Figure BDA0004104978790000021
In the formula (1), Q gmin Maximum reactive power absorbed by a power grid side converter of the doubly-fed wind turbine; q (Q) gmax Maximum reactive power sent by a power grid side converter of the doubly-fed wind turbine; q (Q) min Maximum reactive power absorbed by the doubly-fed wind machine; q (Q) max The maximum reactive power emitted by the doubly-fed wind turbine is used.
In the method for optimizing reactive power of the wind-containing power grid based on voltage weak point identification, a continuous tide method is adopted and node voltage change index delta V is combined i Judging a voltage weak node of the wind power station after being connected into a power grid, and is characterized in that: the PV curve corresponding to each node is obtained through a continuous power flow method, so that the voltage amplitude of each node in the state of the power transmission critical point is determined, and the node voltage change index delta V is constructed i Is that
Figure BDA0004104978790000031
V in formula (2) i0 The method comprises the steps that an initial voltage of a node i is obtained after a wind power station is connected into a power grid system; v (V) cri For the voltage corresponding to the node i in the critical state, after the wind power station is connected to the power grid, the node voltage change index delta V i The influence of the load or the branch transmission power change on the node voltage can be reflected, and the node voltage is more fragile as the node voltage change index is larger.
In the method for optimizing reactive power of the wind-containing power grid based on voltage weak point identification, the objective function is that
Figure BDA0004104978790000032
M in the formula (3) is the number of system nodes; v is the node number; u (U) v Is the actual voltage value of the current node; u (U) N Rated voltage value for the node; v (V) i 、V j And theta ij The voltage amplitude values of the nodes i and j and the phase angle difference between the two nodes are respectively; n (N) L Collecting all branches in the system; w is the reactive compensation node number, m is the capacitor of each groupAnd C is the number of capacitor banks connected to the reactive compensation node.
In the method for optimizing reactive power of the power grid with the fan based on voltage weak point identification, the equality constraint condition and the inequality constraint condition are as follows
Figure BDA0004104978790000033
Figure BDA0004104978790000034
Figure BDA0004104978790000035
P in the formulas (4) to (6) i 、Q i For the active power and reactive power of node i, G ij 、B ij For conductance and susceptance before node i and node j, U i 、U j The voltage values of the node i and the node j are obtained; u (U) Gi Is the generator terminal voltage of the ith node, T i For tap position of on-load voltage-regulating transformer, Q Ci The number of groups switched for the reactive compensation capacitor; q (Q) Gi 、Q Fi The reactive power of the generator and the doubly-fed wind machine.
A reactive power optimization system of a wind-containing machine power grid based on voltage weak point identification comprises
A first module: a plurality of wind power stations consisting of doubly-fed fans are connected into a power grid, and a first module judges node voltage change indexes of each connected node to obtain voltage weak points of the wind power stations after the wind power stations are connected into the power grid;
a second module: the reactive power optimization model is used for constructing a reactive power optimization model by taking the minimum node voltage deviation, the minimum line loss and the minimum total investment cost of the reactive power equipment input by the compensation node in a power grid system as objective functions, and simultaneously meeting load flow equation constraint and inequality constraint of generator terminal voltage, on-load voltage regulating transformer taps, the input quantity of the reactive power equipment and the reactive power adjustment range of a wind power station;
and a third module: the method is used for iteratively updating the control variable by adopting an intelligent optimization algorithm, calculating to obtain a solution meeting the reactive power optimization model, and outputting the optimal control variable.
The invention provides a continuous power flow method for identifying weak voltage nodes after a new energy fan is connected into a power system, wherein the continuous power flow method is used for judging the weak voltage nodes in the system by calculating the voltage amplitude of each node in a critical state in the power grid system and adopting node voltage change indexes, the weak voltage nodes are used as reactive compensation equipment access points, and then the reactive power margin of the fan is used for comprehensive reactive power optimization in optimization to perform the submerged-arc of the fan output capacity, so that the utilization rate of the new energy fan is improved while the power grid voltage is regulated, and a certain superiority is embodied.
According to the invention, based on the influence factors of the excavation adjustment capability of the doubly-fed wind turbine reactive adjustment model, the wind turbine reactive margin is released to participate in reactive power optimization of the system, the utilization rate of the overall output of the wind turbine is improved, the number of the reactive power equipment connected into the power grid system to participate in voltage reactive power optimization is reduced, the input cost of the reactive power equipment is saved, the voltage weak node is identified after the wind turbine is connected into the power grid by adopting a continuous tide method, the reactive power equipment connected compensation is carried out on the identified node, the variable dimension in optimization solution is greatly reduced, the redundant workload is reduced, and the voltage reactive power optimization efficiency is greatly improved.
Drawings
FIG. 1 is a graph of a doubly fed fan power conversion model.
FIG. 2 is a diagram of a doubly fed wind turbine access IEEE30 node system.
Fig. 3 shows a voltage change diagram before and after the fan is connected to the power grid.
FIG. 4 is a graph showing a continuous power flow method combined with node voltage change indicators.
Fig. 5 voltage weaknesses the node complete PV curve.
FIG. 6 is a flowchart of a voltage weak node solving and improved particle swarm algorithm.
FIG. 7 is a graph of system voltage changes before and after fan access and before and after optimization.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the present invention. In addition, the technical features described below in the various embodiments of the present invention may be combined with each other as long as they do not conflict with each other.
The following is a preferred embodiment of the present invention and further illustrates a specific application of the present invention with reference to the accompanying drawings.
The specific embodiment of the invention relates to a reactive power optimization method of a fan-containing power grid based on voltage weak point identification, which specifically comprises the following steps:
step one: acquiring structural parameters and electrical parameters of an electric power network, wherein the structural parameters comprise a grid adjacent matrix and a line length; the electrical parameters comprise network power flow data, power supply capacity, load data, line impedance parameters and a power grid system with fan access, and an IEEE30 node power grid system with fan access after improvement is built is shown in a figure 2.
The improved IEEE30 node power grid system comprises 41 branches, 6 traditional thermal power units are arranged in the system, a G1 unit is reserved, the other 5 traditional thermal power units are cut off, and double-fed fan units are respectively arranged at 3, 10, 12, 15 and 25 nodes, wherein the basic power of the system is 100MW, the total access capacity of 5 fans is 128MW, and the wind power permeability of the system after the fans are accessed is 40%.
Step two: and calculating the reactive power regulation range of the power grid fan according to the power conversion model of the doubly-fed fan shown in the attached drawing 1.
The power transmission and conversion model of the doubly-fed wind turbine is shown in figure 1, and for a conventional doubly-fed wind turbine, the reactive power range at the stator side is as follows
Q smin ≤Q s ≤Q smax (1)
Figure BDA0004104978790000051
Q in s Reactive power emitted by the stator side of the doubly-fed wind turbine; q (Q) smin Maximum reactive power absorbed by the stator side of the doubly-fed wind turbine; q (Q) smax Maximum reactive power emitted by the stator side of the doubly-fed wind turbine; q (Q) exi And exciting reactive power for the inside of the doubly-fed wind turbine. The voltage of the machine end of the doubly-fed fan is approximately unchanged in the normal operation process, but the reactive power which can be regulated in the doubly-fed fan is continuously reduced along with the increase of the active power output to the power grid side.
When the doubly-fed wind turbine is connected to the power grid side for normal operation, the reactive power output range of the doubly-fed wind turbine is directly related to the reactive power regulation capacity of the stator side and the power grid side converter. Active power P absorbed by power grid side converter during normal operation of doubly-fed fan g Active power P absorbed by rotor side r Active power P emitted from stator side s The satisfied relation is that
P g ＝P r ＝sP s (3)
Where s is slip on the rotor side of the doubly-fed wind turbine. Therefore, the reactive power regulation range of the power grid side converter of the doubly-fed wind turbine during normal operation is as follows
Figure BDA0004104978790000061
Figure BDA0004104978790000062
/>
S in g The rated capacity of the power grid side converter of the doubly-fed wind turbine is set; q (Q) g And the reactive power absorbed by the grid-side converter of the doubly-fed wind turbine is utilized.
In summary, when the doubly-fed wind turbine normally operates after being connected to the power grid, the reactive power adjustment range of the doubly-fed wind turbine is determined by the stator reactive power range and the power grid side converter reactive power range, so that the reactive power adjustment range of the doubly-fed wind turbine is obtained as follows
Figure BDA0004104978790000063
Figure BDA0004104978790000064
Q in gmin Maximum reactive power absorbed by a power grid side converter of the doubly-fed wind turbine; q (Q) gmax Maximum reactive power sent by a power grid side converter of the doubly-fed wind turbine; q (Q) min Maximum reactive power absorbed by the doubly-fed wind machine; q (Q) max The maximum reactive power emitted by the doubly-fed wind turbine is used.
And when the doubly-fed wind turbine normally operates after being connected to the power grid, the reactive power adjustment range of the doubly-fed wind turbine connected to the power grid is obtained as shown in the following table 1.
Table 1 IEEE30 node System Access to Fan reactive Regulation Range
Figure BDA0004104978790000065
Figure BDA0004104978790000071
Step three: after the large-scale wind turbine generator is connected into a power system, the output has randomness and fluctuation, so that the node voltage in the power grid can be greatly fluctuated under the condition of higher wind power permeability, the safe and stable operation of the power grid is further affected, the voltage change in the IEEE30 node system before and after wind power connection is shown as a figure 3, firstly, a continuous tide method is adopted to calculate the corresponding PV curve of each node in the power grid system, secondly, the voltage change index of each node is calculated under the critical state of the PV curve, and the voltage weak node is judged according to the node voltage change index.
Drawing a voltage PV curve of each node by adopting a continuous power flow method and calculating voltage change indexes of each node in a critical state, wherein a basic model of the continuous power flow method is an extended power flow equation, and judging whether the current state is stable or not by analyzing various state indexes of a system in the critical operation state, wherein the operation state when the transmission power of a certain branch reaches the maximum transmission power is the critical operation state.
Let the flow equation with n dimension parameters in the system be
f(x,λ)＝0 (8)
Where x is the node voltage amplitude and phase angle in the system and λ is the load growth factor.
When a general power flow calculation method calculates a critical point, the Jacobian matrix at the critical point is singular, so that the whole power flow calculation equation is not converged, a load increase parameter is introduced according to the situation in a continuous power flow method, the problem of the Jacobian matrix singular is overcome, and a node-complete PV curve is obtained, wherein the continuous power flow method consists of four parts of parameterization, prediction, step length and correction.
1) Parameterization of
Parameterization is to introduce a parameter lambda representing load change to change the structure of the Jacobian matrix on the premise of the original tide equation set, so as to avoid the Jacobian matrix singular problem when calculating to a critical point, and the local parameterization is selected in the invention
λ-λ (t) ＝0 (9)
The dimension of the tide equation set is increased by one dimension due to the introduction of the parameter lambda, and the equation (14) and the equation (15) can be solved simultaneously.
2) Prediction
The prediction is performed as a prediction of the next solution along the increasing direction of the load change parameter lambda, wherein the merits of the predicted values directly affect the efficiency of the subsequent calculation, and in general the more accurate the predicted values are chosen, the fewer the number of iterations of the overall calculation and vice versa even resulting in divergence.
The common prediction method is a tangent method and a line cutting method in the linear prediction method, in the prediction link, the tangent method is used for predicting one power flow solution, the line cutting method is used for predicting at least two power flow solutions, according to the characteristic, the tangent method is used for obtaining the other power flow accurate value in the first step of prediction, and the two power flow solutions are obtained and then are transferred into the line cutting method for prediction.
3) Step control and correction
The method selects dynamic adjustment step length, selects large step length at the position of the PV curve far from the critical point, and selects small step length near the critical point for solving.
The correction operation is to use the predicted value as an initial point, obtain an actual value through calculation, improve the correction operation based on a classical Newton-Laporton method, use a local correction method to carry out iterative calculation, and add an equation to obtain the correction operation
Figure BDA0004104978790000081
V in i (t) For the predicted value of the voltage amplitude, the Newton-Laportson method is adopted for iterative solution, and the iterative equation is that
Figure BDA0004104978790000082
The [ delta x, delta lambda ] is obtained according to the above] T Post substitution correction form
Figure BDA0004104978790000083
Correction values x, lambda can thus be obtained] T 。
The voltage change index of each node in the improved IEEE30 node power grid system under the critical state is shown in the figure 4, and the result shows that the nodes 5, 18, 29 and 30 are voltage weak nodes, namely when the load in the system is maximum, the voltage change index of the nodes is maximum in the system, and the complete PV curve corresponding to the voltage weak nodes is shown in the figure 5.
Step four: and (3) constructing a reactive power optimization model taking a voltage weak point as a compensation node, solving by adopting a particle swarm optimization algorithm with improved weight, and on the premise of 40% of high permeability of wind power, performing reactive power optimization by using generator terminal voltage, reactive power adjustment capacity of a wind turbine, transformation ratio adjustment of an on-load transformer and reactive power compensation equipment put in the weak node of load voltage, so as to improve the voltage stability of the system, and taking the generator terminal voltage, the on-load adjustable transformer, the reactive power compensation equipment and reactive power adjustment power of a fan in the system as control variables to be optimized. The thermal power generating units and the wind power generating units are arranged at the nodes 1, 3, 10, 12, 15 and 25 of the system, and the variable range of the voltage of the machine end is 0.9-1.1pu; load voltage regulating transformers with an adjusting range of +/-8 multiplied by 1.25% are arranged at the positions of the branches 6-10, 6-9, 4-12 and 27-28; at nodes 18, 29 and 30 there are 5 sets of capacitors each with a compensation capacity of 1.5Mvar and a cost of 1 per set of capacitors.
The control variables are compared with the control variables before and after optimization as shown in table 2, the target result of reactive power optimization is shown in table 3, and the voltage changes of the grid nodes before and after optimization are shown in fig. 7.
TABLE 2 optimization of control variable results
Figure BDA0004104978790000091
TABLE 3 reactive optimization target results
Figure BDA0004104978790000092
The particle swarm optimization algorithm with improved weight is applied to reactive power optimization, so that the adaptation value of the particle swarm optimization algorithm is not trapped into local optimal circulation, the particle swarm optimization algorithm drops faster to other optimization algorithms, and the convergence is higher, and the particle swarm optimization algorithm has certain superiority for the calculation of the reactive power optimization in the invention. The voltage drop of the system node is serious after the fan replaces the original thermal power generating unit of the system, and the voltage level of the system is obviously improved along with the comprehensive optimization of the reactive compensation of the voltage weak node, the reactive margin of the fan, the generator terminal voltage and the transformer tap, so that the safe and stable operation of the system is ensured.

Claims (10)

1. The reactive power optimization method for the power grid with the wind turbine based on the voltage weak point identification is characterized by comprising the following steps of:
a plurality of wind power stations consisting of doubly-fed fans are connected into a power grid, and node voltage change indexes of each connected node are judged to obtain voltage weak points of the wind power stations after the wind power stations are connected into the power grid;
the method comprises the steps of taking a voltage weak point as a compensation node for reactive equipment access, and constructing a reactive power optimization model, wherein the reactive power optimization model takes the minimum node voltage deviation, the minimum line loss and the minimum total investment cost of the compensation node in reactive equipment in a power grid system as objective functions, and simultaneously meets load flow equation constraint and generator terminal voltage, on-load voltage regulating transformer taps, the input quantity of the reactive equipment and inequality constraint of a reactive power regulation range of a wind power station;
and (3) carrying out iterative updating on the control variable by adopting an intelligent optimization algorithm, calculating to obtain a solution meeting the reactive power optimization model, and outputting an optimal control variable.
2. The method for optimizing reactive power of power grid with fan based on voltage weak point identification according to claim 1, wherein the maximum reactive power Q absorbed by the doubly-fed fan is the maximum reactive power Q absorbed by the doubly-fed fan when the doubly-fed fan is connected to the power grid side for normal operation min Maximum reactive power Q absorbed for stator side smin Maximum reactive power Q absorbed by grid-side converter gmin The sum of the maximum reactive power Q emitted by the doubly-fed fans max Maximum reactive power Q emitted for stator side smax Maximum reactive power Q emitted by the grid-side converter gmax And (3) summing.
3. The reactive power optimization method for the wind-containing power grid based on voltage weak point identification according to claim 1, wherein the method is characterized in that a complete PV curve of each node in the power grid is obtained through a continuous tide method, the voltage amplitude of each node in a power transmission critical point state is determined, and a node voltage change index delta V is constructed i Judging the node voltage change index of each node to obtain a plurality of windAnd the electric field station is connected with the voltage weak point set formed by voltage weak points of the power grid.
4. The method for optimizing the reactive power of the power grid with the wind turbine based on the voltage weak point identification, which is disclosed in claim 1, is characterized in that the control variables are generator terminal voltage, on-load transformer taps, the number of reactive power equipment access of compensation nodes and the reactive power allowance of the wind power station participating in optimization, the intelligent optimization algorithm is adopted to update the variables in an iterative manner, and the solution meeting the objective function, equation and inequality constraint conditions in a reactive power optimization model is calculated.
5. The method for optimizing reactive power of a wind turbine power grid based on voltage weak point identification according to claim 1, wherein the method is characterized in that a particle swarm optimization algorithm for improving inertia weight solves a reactive power optimization model, and initialization conditions in the algorithm are input, wherein the initialization conditions comprise iteration times m, population size s and speed update parameters c 1 And c 2 And the inertia weight parameter w is subjected to iterative calculation to obtain a solution meeting the objective function, the equality constraint condition and the inequality constraint condition.
6. The method for optimizing reactive power of power grid with fan based on voltage weak point identification according to claim 1, wherein the reactive power range Q of the doubly-fed fan after being connected into the power grid is as follows in normal operation
Figure FDA0004104978780000021
In the formula (1), Q gmin Maximum reactive power absorbed by a power grid side converter of the doubly-fed wind turbine; q (Q) gmax Maximum reactive power sent by a power grid side converter of the doubly-fed wind turbine; q (Q) min Maximum reactive power absorbed by the doubly-fed wind machine; q (Q) max The maximum reactive power emitted by the doubly-fed wind turbine is used.
7. A base according to claim 1A reactive power optimization method for a fan-containing power grid for identifying voltage weak points is characterized by adopting a continuous tide method and combining node voltage change indexes delta V i Judging voltage weak nodes of the wind power station after being connected into a power grid, obtaining PV curves corresponding to all the nodes through a continuous tide method, determining voltage amplitude values of all the nodes in a power transmission critical point state, and constructing node voltage change indexes delta V i Is that
Figure FDA0004104978780000022
/>
V in formula (2) i0 The method comprises the steps that an initial voltage of a node i is obtained after a wind power station is connected into a power grid system; v (V) cri For the voltage corresponding to the node i in the critical state, after the wind power station is connected to the power grid, the node voltage change index delta V i The influence of the load or the branch transmission power change on the node voltage can be reflected, and the node voltage is more fragile as the node voltage change index is larger.
8. The method for optimizing reactive power of a wind turbine generator grid based on voltage weak point identification according to claim 1, wherein the objective function is
Figure FDA0004104978780000023
M in the formula (3) is the number of system nodes; v is the node number; u (U) v Is the actual voltage value of the current node; u (U) N Rated voltage value for the node; v (V) i 、V j And theta ij The voltage amplitude values of the nodes i and j and the phase angle difference between the two nodes are respectively; n (N) L Collecting all branches in the system; w is the number of reactive compensation nodes, m is the cost of each group of capacitors, and C is the number of capacitor groups connected to the reactive compensation nodes.
9. The method for optimizing reactive power of a power grid with a fan based on identification of weak points of voltage according to claim 1, wherein the equality constraint condition and the inequality constraint condition are as follows
Figure FDA0004104978780000031
Figure FDA0004104978780000032
Figure FDA0004104978780000033
P in the formulas (4) to (6) i 、Q i For the active power and reactive power of node i, G ij 、B ij For conductance and susceptance before node i and node j, U i 、U j The voltage values of the node i and the node j are obtained; u (U) Gi Is the generator terminal voltage of the ith node, T i For tap position of on-load voltage-regulating transformer, Q Ci The number of groups switched for the reactive compensation capacitor; q (Q) Gi 、Q Fi The reactive power of the generator and the doubly-fed wind machine.
10. A reactive power optimization system of a wind-containing machine power grid based on voltage weak point identification is characterized by comprising
A first module: a plurality of wind power stations consisting of doubly-fed fans are connected into a power grid, and a first module judges node voltage change indexes of each connected node to obtain voltage weak points of the wind power stations after the wind power stations are connected into the power grid;
a second module: the reactive power optimization model is used for constructing a reactive power optimization model by taking the minimum node voltage deviation, the minimum line loss and the minimum total investment cost of the reactive power equipment input by the compensation node in a power grid system as objective functions, and simultaneously meeting load flow equation constraint and inequality constraint of generator terminal voltage, on-load voltage regulating transformer taps, the input quantity of the reactive power equipment and the reactive power adjustment range of a wind power station;
and a third module: the method is used for iteratively updating the control variable by adopting an intelligent optimization algorithm, calculating to obtain a solution meeting the reactive power optimization model, and outputting the optimal control variable.
CN202310189044.2A 2023-03-01 2023-03-01 Reactive power optimization method and system for fan-containing power grid based on voltage weak point identification Pending CN116231672A (en)

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