CN110148959B - Trans-regional direct-current tie line power optimization method considering reactive power equipment action times - Google Patents

Trans-regional direct-current tie line power optimization method considering reactive power equipment action times Download PDF

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CN110148959B
CN110148959B CN201910418483.XA CN201910418483A CN110148959B CN 110148959 B CN110148959 B CN 110148959B CN 201910418483 A CN201910418483 A CN 201910418483A CN 110148959 B CN110148959 B CN 110148959B
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CN110148959A (en
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张海波
申杰
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North China Electric Power University
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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
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • 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
    • H02J3/381—Dispersed generators
    • 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
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/76—Power conversion electric or electronic aspects
    • 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
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

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Abstract

The invention belongs to the technical field of operation and scheduling of power systems, and particularly relates to a cross-region direct-current tie line power optimization method considering the action times of reactive equipment, which comprises the following steps: establishing a cross-region direct-current connecting line power optimization main problem model based on direct current power flow, and controlling the action times of reactive equipment through the action time constraint of the reactive equipment; and establishing a power flow syndrome problem model to ensure that the optimal solution of the main problem meets safety constraint and the steady-state operation characteristic of the converter station, and respectively establishing reactive equipment connection constraint in the main problem and the sub problem to realize the unification of the reactive equipment solutions of the main problem and the sub problem. Iterative optimization of the main problem and the sub problems is carried out by adopting a Benders decomposition method, the sub problems feed back feasibility constraints to the main problem, and the optimization space of the main problem is corrected. The method fully excavates the coordination optimization benefit between the flexible regulation capability and the direct current reactive power regulation characteristic of the direct current connecting line, promotes the consumption of the wind power of the power grid at the sending end, reduces the peak regulation pressure of the thermal power generating unit, and realizes the operation economy of the direct current cross-regional interconnected power grid.

Description

Trans-regional direct-current tie line power optimization method considering reactive power equipment action times
Technical Field
The invention belongs to the technical field of operation and scheduling of power systems, and particularly relates to a cross-region direct-current tie line power optimization method considering the action times of reactive equipment.
Background
The large-scale wind power bases in China are mostly far away from load centers and are difficult to consume on the spot, so that the wind power bases need to be remotely conveyed to the load centers through high-voltage direct-current transmission to realize cross-regional consumption of the wind power and promote optimal allocation of resources. Traditional direct current day-ahead transmission plans are compiled according to load peak-valley difference of a receiving-end power grid, so that a transmitting-end power grid can generate abandoned wind, and peak regulation pressure of a thermal power generating unit of the transmitting-end power grid is increased. The flexible adjustment of the power of the direct current tie line is beneficial to alleviating the defects, but the power can cause frequent actions of reactive equipment such as alternating current filters, converter transformers and the like on two sides of a direct current line, increase the operation and maintenance cost of the reactive equipment, reduce the service life of the reactive equipment and influence the safety and the economical efficiency of a system. Therefore, how to establish a reasonable and effective power optimization model of the direct current tie line and reduce the action times of reactive power equipment while exerting the flexible adjustment capability of direct current transmission is an urgent problem to be solved in the current scheduling plan.
Document 1, "new mode for optimizing and improving new energy absorption capacity by using dc link operation mode", divides dc link power into N steps, and simulates the stepped operation characteristic of the dc link by using the idea of unit combination, but it makes the dc link power operate on a discrete power value, and it is difficult to fully exert the flexible regulation capacity of the dc system. Document 2 "optimization method of wind-fire island dc day-ahead power transmission plan in large energy base" proposes a dc link power optimization method for reducing the number of times of reactive equipment actions, but it regards the change of dc link power and the actions of reactive equipment as a linear relationship, and has a certain error with the actual operating characteristics of the converter station. The reactive power absorbed by the converter station is dependent on many other operating parameters, such as firing angle and cut-off angle, in addition to the real power, so it is not appropriate to consider the behavior of the reactive equipment as a linear relation to the change in the real power.
The above researches establish a direct current tie line power optimization model based on direct current power flow, and mostly do not consider the problem that the action of reactive equipment is caused by the change of the direct current tie line power. Although the reactive device operation problem is considered in document 2, the modeling of the direct-current both-side reactive device operation is very rough, and various factors affecting the reactive device operation are not sufficiently considered.
Disclosure of Invention
In order to solve the above problems, the present invention provides a power optimization method for a cross-region dc link considering the number of actions of reactive equipment, including:
step 1, establishing a direct current tie line power optimization main problem model based on direct current power flow, and controlling the action times of reactive equipment through the action time constraint of the reactive equipment;
step 2, establishing a power flow syndrome problem model to ensure that the optimal solution of the main problem meets safety constraint and the steady-state operation characteristic of the converter station, and respectively establishing reactive equipment connection constraint in the main problem and the sub problem to realize the unification of the reactive equipment solutions of the main problem and the sub problem;
and 3, feeding back feasibility constraints to the main problem by the sub problems, and correcting the optimization space of the main problem.
And 3, performing iterative optimization of the main problem and the sub problems by adopting a Benders decomposition method.
The objective function of the main question comprises: the generating cost of send and receive end electric wire netting thermal power generating unit, abandon wind punishment cost and major-minor problem idle equipment deviation, the constraint condition includes: reactive equipment action constraint conditions, direct current regulation related constraint conditions and alternating current system related constraint conditions.
The reactive equipment action constraint conditions comprise: reactive equipment connection constraint and reactive equipment action frequency constraint; the direct current regulation related constraint condition comprises: the method comprises the following steps of direct current tie line output constraint, direct current adjacent time interval output adjustment constraint, direct current output adjustment frequency constraint, direct current output adjustment rate constraint, direct current adjustment interval constraint and direct current daily transaction amount constraint; the related constraint conditions of the communication system comprise: the method comprises the following steps of thermal power unit output restraint, thermal power unit climbing restraint, power balance restraint, positive and negative rotation standby restraint and wind power restraint.
The objective function of the sub-problem comprises: main sub problem deviation, main sub problem idle equipment deviation, the constraint condition includes: reactive power equipment connection constraint conditions, main and sub problem connection constraint conditions and power flow verification constraint conditions.
The power flow verification constraint condition comprises the following steps: node power balance constraint, converter station steady state operation constraint, branch tidal current upper and lower limit constraint, and upper and lower limit constraint of each variable.
The invention has the beneficial effects that:
(1) in the subproblems, the reactive characteristics of the converter station are accurately described based on a steady-state operation model of the converter station, various factors influencing the action of reactive equipment, including direct-current tie line power, a trigger angle, a turn-off angle and the like, are finely considered, and errors caused by the fact that the action of the reactive equipment and the direct-current tie line power are regarded as a linear relation are eliminated.
(2) Reactive equipment action constraints are established, including reactive equipment connection constraints and reactive equipment action frequency constraints, a large-scale mixed integer nonlinear programming problem is decomposed into a mixed integer linear programming main problem and a nonlinear programming sub-problem on the basis of a Benders decomposition method, unification of reactive equipment optimization values of the main problem and the sub-problem and discretization value of reactive equipment are achieved through the reactive equipment connection constraints, reactive equipment action frequency limits are achieved in the main problem through the reactive equipment action frequency constraints, the defects of coupling constraints and discrete variables between time periods when sub-problem single-time-period power flow verification cannot be processed are overcome, and the problem solving difficulty is reduced.
(3) The method comprises the steps of establishing a trans-regional direct-current tie line power optimization model considering the action times of the reactive power equipment, comprehensively considering the constraint conditions of direct-current tie line operation, alternating-current system safe operation, converter station steady-state operation and the like, reducing the action times of the reactive power equipment while optimizing the direct-current tie line power, prolonging the service life of the reactive power equipment, and improving the economy and the safety of the system. The method fully excavates the coordination optimization benefit between the flexible regulation capability and the DC reactive power regulation characteristic of the DC tie line, promotes the wind power consumption of the power grid at the sending end, reduces the regulation burden of the thermal power generating unit of the power grid at the sending end, better deals with the uncertainty of the wind power, and realizes the operation economy of the DC cross-regional interconnected power grid.
Drawings
FIG. 1 is a schematic diagram of main and sub iterations based on Benders decomposition method.
Fig. 2 is a schematic diagram of a cross-region direct-current interconnected power grid structure.
Fig. 3 is a load prediction curve of a transmission-end power grid.
FIG. 4 is a wind power prediction curve of a transmission-end power grid.
Fig. 5 is a two-mode dc link power optimization curve.
Fig. 6 is a diagram showing an operation period of the rectifying side filter.
Fig. 7 is a graph showing the operation period of the rectifier-side converter.
Fig. 8 is a power output curve of the thermal power generating unit of the power grid at the sending end.
Detailed Description
As shown in fig. 1, a method for optimizing power of a cross-regional dc link considering the number of actions of reactive devices includes the following steps:
(1) a main problem model of power optimization of a cross-region direct-current connecting line is established based on direct-current power flow, and action times of reactive equipment are controlled by introducing reactive equipment action constraint, wherein the action times of the reactive equipment mainly comprises reactive equipment connection constraint and reactive equipment action time constraint.
(2) And establishing a cross-region direct-current tie line power optimization load flow syndrome problem model, ensuring that the optimal solution of the main problem meets safety constraints, meanwhile, finely considering direct-current reactive power characteristics based on a converter station steady-state operation model, and connecting the direct-current reactive power characteristics with the main problem through reactive power equipment connection constraints.
(3) And feeding back Benders feasibility constraints to the main problem by the sub-problems, and correcting the optimization space of the main problem.
Preferably, reactive characteristics of the converter station are considered in a refined manner based on the converter station steady-state operation model, constraints of reactive equipment action time limitation are established, and main and sub iteration is performed on the basis of the Benders decomposition method, so that the solving difficulty is reduced.
According to the traditional operating characteristics of high-voltage direct-current transmission based on the power grid commutation converter, the reactive power of the converter is influenced by the active power and is also related to other operating parameters such as a trigger angle and a turn-off angle, and the steady-state operating model of the converter station can accurately describe the direct-current reactive power.
Due to the nonlinearity of the alternating current flow and the steady-state operation model of the converter station, the discrete value of the reactive power equipment and the multi-period coupling of the action times of the reactive power equipment, the problem solving difficulty is greatly increased. The invention decomposes the large-scale mixed integer nonlinear programming problem into a mixed integer linear programming main problem and a nonlinear programming sub problem on the basis of a Benders decomposition method, and specially processes reactive equipment, wherein the unification of the optimized values of the reactive equipment of the main problem and the sub problem is realized mainly through the connection constraint of the reactive equipment, the action times of the reactive equipment are limited in the main problem through the action time constraint of the reactive equipment, and meanwhile, the discrete value taking of the reactive equipment is realized in the main problem, so that the problem solving difficulty is greatly reduced.
The step (1) comprises the following steps:
firstly, establishing a main problem of a cross-region direct current tie line power optimization model considering the action times of reactive equipment
An objective function. The method mainly comprises the power generation cost, the wind abandoning penalty cost and the main and sub problem reactive equipment deviation of a power grid thermal power generating unit at a transmitting and receiving end.
Figure BDA0002065203340000051
In the formula:
Figure BDA0002065203340000052
the output of the thermal power generating unit i is a time period t;
Figure BDA0002065203340000053
the power generation cost coefficient is the power generation cost coefficient of the thermal power generating unit i;
Figure BDA0002065203340000054
the abandoned wind of the wind power plant w is in a time period t; eta is a wind curtailment penalty factor; t is the total number of the optimization time periods; n is a radical ofG、NWThe number of the thermal power generating units and the number of the wind power plants are respectively; Δ λ is the reactive device deviation.
Constraint conditions
a) And reactive equipment action constraint conditions are as follows:
reactive device action constraints include: reactive equipment connection constraint and reactive equipment action time constraint.
I) reactive plant connection constraints
Figure BDA0002065203340000055
Figure BDA0002065203340000056
Figure BDA0002065203340000057
In the formula: xi is a penalty factor, in order to ensure the optimality of the solution, the value of xi should be dynamically changed, when v is larger than 0.01 in the subproblem objective function, xi is equal to zero, and when v is smaller than 0.01, xi takes a proper positive number;
Figure BDA0002065203340000058
Figure BDA0002065203340000059
relaxation variables of the filter and the converter transformer are respectively; m is the number of converter stations; x is the number ofLCapacity of a single set of filters; x is the number ofHAdjusting step length for the converter transformer tap switch;
Figure BDA00020652033400000510
the integer variable represents the input group number of the alternating current filter in the time period t;
Figure BDA00020652033400000511
the step number is an integer variable and represents the gear of a tap changer of the converter transformer in a time period t; kHminThe lower limit of the converter transformer ratio is set;
Figure BDA00020652033400000512
and feeding back the sub-problems to the filter and the optimal value of the converter transformer of the main problem respectively.
Ii) reactive equipment action time constraint
Figure BDA0002065203340000061
Figure BDA0002065203340000062
In the formula:
Figure BDA0002065203340000063
is an integer variable representing a time periodt the number of filter operations;
Figure BDA0002065203340000064
the integer variable represents the action times of the converter flow in the time period t; zLScheduling the maximum allowable action times of the filter in a day; zLThe maximum allowable number of actions is changed for the scheduling day.
b) Direct current regulation related constraint conditions:
the direct current regulation related constraints include: the method comprises the following steps of direct current tie line output constraint, direct current adjacent time interval output regulation constraint, direct current output regulation frequency constraint, direct current output regulation rate constraint, direct current regulation interval constraint and direct current daily transaction amount constraint.
I) DC link line output constraints
Figure BDA0002065203340000065
In the formula:
Figure BDA0002065203340000066
the transmission power of the direct current tie line k is a time period t;
Figure BDA0002065203340000067
the power transmission lower limit and the power transmission upper limit of the direct current tie line are respectively.
Ii) direct current adjacent time interval output force regulation constraint
Figure BDA0002065203340000068
In the formula:
Figure BDA0002065203340000069
and the variable is a 0-1 variable which respectively represents whether the power of the direct current tie line in the time period t is up-regulated or down-regulated, and the value of the variable is determined by the aid of an equation (10).
Iii) direct current output adjustment times constraint
Figure BDA0002065203340000071
In the formula: x is the number ofk,tThe variable is 0-1 and represents whether the power of the direct current tie line is adjusted or not in a time period t; and W is the maximum adjusting frequency of the power of the direct current tie line in the dispatching day.
Iv) direct current output regulation rate constraint
Figure BDA0002065203340000072
In the formula:
Figure BDA0002065203340000073
respectively adjusting the lower limit and the upper limit of the power of the direct current tie line; m+、M-To assist large numbers to determine
Figure BDA0002065203340000074
The value of (c).
V) direct current regulation interval constraint
Figure BDA0002065203340000075
In the formula: n is a radical ofTFor a number of DC durations, i.e. one DC link power adjustment maintains NTThe time intervals are not changed.
Vi) daily trading volume constraints
Figure BDA0002065203340000076
In the formula: e is the daily transaction electric quantity of the direct current connecting line; rho is daily transaction electric quantity deviation, and the value is 0.02.
c) AC system dependent constraints (taking the sending end network A as an example)
Communicating system-related constraints includes: the output constraint of the thermal power generating unit, the climbing constraint of the thermal power generating unit,
Power balance constraint, positive and negative rotation standby constraint and wind power constraint.
I) output constraint of thermal power generating unit
Figure BDA0002065203340000077
In the formula (I), the compound is shown in the specification,
Figure BDA0002065203340000078
the lower limit and the upper limit of the output of the thermal power generating unit i are respectively.
Ii) thermal power generating unit climbing restraint
Figure BDA0002065203340000081
In the formula, RUi、RDiThe climbing and the landslide rates of the unit i are respectively.
Iii) Power balance constraints
Figure BDA0002065203340000082
In the formula (I), the compound is shown in the specification,
Figure BDA0002065203340000083
respectively a set of a generator, a wind power plant and a load node in the area A;
Figure BDA0002065203340000084
the output of the wind power field w is the time period t;
Figure BDA0002065203340000085
is the predicted value of the load of node l in the time period t.
Iv) Positive and negative rotation backup constraints
Positively rotating for standby:
Figure BDA0002065203340000086
in the formula:
Figure BDA0002065203340000087
the positive spare capacity required for zone a for time period t; w is auThe wind power positive standby coefficient; w is aLIs the load reserve factor.
Negative rotation for standby:
Figure BDA0002065203340000088
in the formula:
Figure BDA0002065203340000089
negative spare capacity required for zone a for time period t; w is adAnd the wind power negative standby coefficient.
V) wind power constraints
Figure BDA00020652033400000810
In the formula:
Figure BDA00020652033400000811
the output of the wind power field w is the time period t;
Figure BDA00020652033400000812
and (4) predicting the power of the wind power plant w for a time period t.
The step (2) comprises the following steps:
firstly, establishing a sub-problem objective function of a cross-region direct current tie line power optimization model considering the action times of reactive equipment. The method mainly comprises main and sub problem deviation and main and sub problem reactive power equipment deviation.
minv+Δγ (19)
Figure BDA0002065203340000091
Figure BDA0002065203340000092
In the formula:
Figure BDA0002065203340000093
a relaxation variable of the active power output of the generator;
Figure BDA0002065203340000094
the relaxation variable of the power of the direct current tie line;
Figure BDA0002065203340000095
relaxation variables of the filter and the converter transformer are respectively; xi is a penalty factor, and the value is equal to the value of the penalty factor in the formula (2).
Constraint conditions
a) Reactive equipment connection constraint conditions:
Figure BDA0002065203340000096
Figure BDA0002065203340000097
in the formula:
Figure BDA0002065203340000098
respectively transmitting the main problem to the sub problem filter and the optimal solution of the converter transformer; qLmReactive power output of the alternating current filter is a direct current node m; kHmThe current transformation ratio is the direct current node m.
b) Main and sub problem connection constraint conditions:
Figure BDA0002065203340000099
Figure BDA00020652033400000910
Figure BDA00020652033400000911
in the formula:
Figure BDA00020652033400000912
respectively transmitting the main problem to the optimal solution of the active output of the sub-problem generator and the power of the direct current tie line; because the network loss is not considered in the main problem, a certain deviation margin alpha% needs to be reserved for the sub-problem, and the value of the deviation margin alpha% is set according to the network loss values of different systems.
c) And flow verification constraint conditions:
i) node power balance constraints
Figure BDA00020652033400000913
Figure BDA00020652033400000914
In the formula: f. of1Indicating whether the node i is connected with the wind turbine generator or not, if so, f 11, otherwise, f1＝0；f2Indicating whether the node i is a converter station node or not, if the node i is a rectifier node, f2If 1, if it is an inversion node, f2Not, f2＝0；Ui、θiThe voltage amplitude and the phase angle of the node i are shown; vdm、IdmVoltage and current of a direct current node m;
Figure BDA0002065203340000101
is the power factor of the converter station m;
Figure BDA0002065203340000102
is windThe reactive output of the generator set is assumed to be operated by the constant power factor of the wind turbine generator set, so that the value of the reactive output is represented by
Figure BDA0002065203340000103
And (6) determining.
Ii) converter station steady state operation constraints
Vdm-KHmVt cosθdm+XdmIdm＝0 (29)
Figure BDA0002065203340000104
Udr＝Udi+RdcId (31)
In the formula: thetadmTo change the phase angle; xdmIs a commutation reactance; k is a radical ofγIn order to consider a constant coefficient introduced by commutation failure, 0.995 is generally taken; rdcIs a direct current line resistor; r represents the rectification side; i represents the inversion side.
In addition, the power flow check constraint also comprises branch power flow upper and lower limit constraint, converter station constant reactive power control constraint, upper and lower limit constraint of each variable and the like.
The step (3) comprises the following steps:
Figure BDA0002065203340000105
the above formula is Benders feasibility constraint, and when the sub-problem trend check fails, the constraint is fed back to the main problem to correct the feasible space. Lambda [ alpha ]di、
Figure BDA0002065203340000106
Lagrange multipliers for each constraint reflect the sensitivity of the main problem optimal solution increment to the sub problem optimal solution.
The invention uses a double-zone 48-node system to carry out test analysis, and the system respectively simulates a sending end A and a receiving end B by two modified IEEE-24 node systems. No. 9 nodes between the two systems are connected through HVDC links, and FIG. 2 is a schematic structural diagram of a cross-region direct-current interconnected power grid. The load prediction curve of the transmitting-end power grid is shown in fig. 3, the load of the receiving-end power grid is set to be 2 times of the load of the transmitting-end power grid, the node 3 and the node 9 of the transmitting-end power grid comprise two wind power plants, and the wind power prediction curve is shown in fig. 4. The upper limit of the transmission power of the direct current junctor is 2000MW, the daily transaction electric quantity is 33GWH, and the daily maximum adjusting times of the power of the direct current junctor is 6 times. The test analysis selects a per unit value, the reference power is 1000MW, the per unit value of the capacity of a group of filters is 0.04, and the action step length of a tap changer of the converter transformer is 0.0125.
The related calculation is completed on a 3.00GHz and 8GB memory computer of an Intel core i5-7400 processor, the main problem calls Gurobi 8.1.0 to solve, and the subproblems adopt a self-editing primal dual interior point method to solve.
In order to comparatively analyze the effectiveness and the correctness of the optimized model established by the invention, the following two operation modes are established:
mode 1: the power of the direct current tie line is limited and optimized, and the action times of reactive equipment are not considered;
mode 2: and (4) power limitation optimization of the direct current tie line, and the action times of the reactive equipment are considered.
In mode 2, the upper limits of the number of operations of the filter and the converter flow are set to 4.
Fig. 5 is a dc link power optimization curve for two modes, the solid line representing mode 1 and the dashed line representing mode 2. From the figure, it can be seen that: compared with the mode 1, the mode 2 has the advantages that the direct-current tie line power is increased in the load valley period, the direct-current tie line power is reduced in the load peak period, the peak-valley difference of the direct-current tie line power change is reduced, and the action times of the reactive equipment are reduced.
The comparison of the number of actions of the dc two-sided reactive device in the two modes is shown in table 1:
TABLE 1 number of actions of two-mode reactive power equipment
Figure BDA0002065203340000111
As can be seen from table 1, the number of times of operation of the reactive power plant in the mode 2 is significantly reduced compared to that in the mode 1, which shows that the present invention plays a good role in limiting the number of times of operation of the reactive power plant.
Fig. 6 and 7 illustrate the action conditions of the ac filter and the converter transformer in different time periods in two modes by taking the rectifying side as an example, where a positive value represents that a group of filters or converter transformer tapping switches are put into a higher gear, and a negative value represents that a group of filters or converter transformer tapping switches are cut off or a lower gear is adopted, so that the action rule of the reactive equipment when the power of the dc link line changes can be obtained.
Fig. 8 is a power output optimization curve of the thermal power generating unit of the transmission-end power grid, and compared with the mode 1, the power output peak-valley difference of the mode 2 thermal power generating unit is slightly reduced, which shows that the mode 2 reduces the adjustment burden of the thermal power generating unit of the transmission-end power grid while reducing the number of times of actions of the reactive equipment. In addition, the air abandoning rate in the two modes is zero, so that the defect of the traditional two-section constant-power operation mode of the direct-current connecting line is overcome.
The comparison of the interconnected system power generation cost versus iteration number for the two modes is shown in table 2:
TABLE 2 Generation costs and iteration counts
Mode(s) Cost of power generation/$ Number of iterations
Mode
1 2.884×106 7
Mode 2 2.885×106 11
As can be seen from table 2, the power generation cost of the mode 2 is slightly increased compared to the mode 1, but the number of times of operation of the reactive power plant is reduced, so that the self-economy is better and the safety is higher. Compared with the mode 1, the number of main and sub iterations of the mode 2 is increased, but both modes can be converged within 12 iterations, and the convergence is better.
The present invention is not limited to the above embodiments, and any changes or substitutions that can be easily made by those skilled in the art within the technical scope of the present invention are also within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (1)

1. A cross-region direct-current tie line power optimization method considering reactive equipment action times is characterized by comprising the following steps:
step 1, establishing a direct current tie line power optimization main problem model based on direct current power flow, and controlling the action times of an alternating current filter and a converter transformer through reactive equipment action time constraint;
step 2, establishing a power flow check subproblem model, wherein the subproblem describes the reactive characteristics of the converter station based on a steady-state operation model of the converter station, considers various factors influencing the action of the reactive equipment, including the power of the direct-current connecting line, a trigger angle and a turn-off angle, eliminates errors caused by the fact that the action of the reactive equipment and the power of the direct-current connecting line are regarded as a linear relation, and respectively establishes reactive equipment connection constraints in the main subproblem to realize the unification of reactive equipment solutions of the main subproblem;
step 3, the subproblems feed back feasibility constraints to the main problem and modify the optimization space of the main problem;
step 3, iteration optimization of the main problem and the sub problems is carried out by adopting a Benders decomposition method;
the objective function of the main question comprises: the generating cost of send and receive end electric wire netting thermal power generating unit, abandon wind punishment cost and major-minor problem idle equipment deviation, the constraint condition includes: reactive equipment action constraint conditions, direct current regulation related constraint conditions and alternating current system related constraint conditions;
the reactive equipment action constraint conditions comprise: reactive equipment connection constraint and reactive equipment action frequency constraint; the direct current regulation related constraint condition comprises: the method comprises the following steps of direct current tie line output constraint, direct current adjacent time interval output adjustment constraint, direct current output adjustment frequency constraint, direct current output adjustment rate constraint, direct current adjustment interval constraint and direct current daily transaction amount constraint; the related constraint conditions of the communication system comprise: the method comprises the following steps of thermal power unit output constraint, thermal power unit climbing constraint, power balance constraint, positive and negative rotation standby constraint and wind power constraint;
the objective function of the sub-problem comprises: main sub problem deviation, main sub problem idle equipment deviation, the constraint condition includes: reactive equipment connection constraint conditions, main and sub problem connection constraint conditions and power flow verification constraint conditions;
the power flow verification constraint condition comprises the following steps: node power balance constraint, converter station steady state operation constraint, constant reactive power control constraint and branch load flow upper and lower limit constraint.
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