CN111049130B - Method and system for determining maximum power transmission scale of power grid system - Google Patents

Method and system for determining maximum power transmission scale of power grid system Download PDF

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CN111049130B
CN111049130B CN201911267062.8A CN201911267062A CN111049130B CN 111049130 B CN111049130 B CN 111049130B CN 201911267062 A CN201911267062 A CN 201911267062A CN 111049130 B CN111049130 B CN 111049130B
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power
generator
operation mode
direct current
constraint
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CN111049130A (en
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张一驰
周勤勇
孙玉娇
杨京齐
黄丹
王喆
姜懿郎
刘天阳
郭瑾程
王炜
李宝昕
袁性忠
李晓东
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State Grid Corp of China SGCC
China Electric Power Research Institute Co Ltd CEPRI
Economic and Technological Research Institute of State Grid Shaanxi Electric Power Co Ltd
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State Grid Corp of China SGCC
China Electric Power Research Institute Co Ltd CEPRI
Economic and Technological Research Institute of State Grid Shaanxi Electric 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
    • 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
    • H02J3/02—Circuit arrangements for ac mains or ac distribution networks using a single network for simultaneous distribution of power at different frequencies; using a single network for simultaneous distribution of ac power and of dc 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
    • H02J3/36—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
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • 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]

Abstract

The invention provides a method and a system for determining the maximum power transmission scale of a power grid system. The method and the system take the collected installed capacity and load distribution state of the generator as input based on the current operation state of the transmitting end and the receiving end of the power grid system, and output the switching state and the power of each direct current loop of each generator of the alternating current and direct current transmitting end system under each operation mode when the power grid is continuously adjusted in n operation modes based on a pre-established objective function and constraint conditions for determining the power transmission scale in the topological structure of the transmitting end and the receiving end of the power grid system, and determine the maximum power transmission scale of the power grid system according to the output result. The method and the system simultaneously consider the influence of multi-loop direct current power regulation, the alternating current and direct current delivery economic benefit and the related running cost of the generator set, so that the maximization of the total delivery power of alternating current and direct current is realized when various running modes are continuously adjusted by coordinating the direct current power delivery and switching on and off the generator set on the premise of ensuring the safety and stability of a power grid system.

Description

Method and system for determining maximum power transmission scale of power grid system
Technical Field
The present invention relates to the field of power system simulation analysis, and more particularly, to a method and system for determining a maximum power transmission scale of a power grid system.
Background
In large-scale trans-regional power transmission, the combined power transmission capacity of the alternating current and direct current channels is fully exerted, the maximum scale of the power grid is deeply researched, and the energy utilization efficiency of a power supply base is improved while the safe and stable operation of the power grid is guaranteed.
At present, related research mainly focuses on the analysis of power transmission scale influence factors and the like, but the following considerations are not taken into account: (1) the economic benefit of the outgoing power and the power generation cost difference of different areas can cause the power transmission cost to change. (2) For a multi-sending-end interconnected power transmission structure, when the starting-up mode of each sending end is changed, the whole maximum power transmission scale may be changed accordingly. (3) If an alternating current/direct current outgoing channel exists in the sending-end power grid, when the direct current sending end is connected with an alternating current main grid (non-island power transmission, power needs to be collected from the grid), the coordination and coordination of direct current power, alternating current channel outgoing power and generating set output need to be considered. In addition, the conventional safety constraint unit combination model can calculate the on-off mode and the output level of the generator unit, and considers the constraints of system power balance, line power flow limit and the like, however, the constraints of a power flow equation are not taken into account, and meanwhile, the influence generated by direct current power output is not considered, so that the calculation requirement of the maximum power transmission scale cannot be met. Therefore, how to reasonably arrange the starting mode of each sending end while considering both the safety and stability constraint of the power grid and the direct-current power sending, the full play of the whole sending capacity of the sending end power grid is ensured, and the method has important significance for improving the reasonable optimization configuration capacity of the power grid resources.
Disclosure of Invention
In order to solve the technical problem that the prior art cannot ensure the maximization of the overall delivery capacity of a delivery-end power grid due to incomplete consideration of influence factors when the power transmission scale of the power grid is analyzed, the invention provides a method for determining the maximum power transmission scale of a power grid system, which comprises the following steps:
according to the node distribution information of the power grid system, a topological structure of a transmitting end and a receiving end of the power grid system is established;
collecting the installed capacity and the load distribution state of a generator at an AC/DC receiving end of a power grid system;
the method comprises the steps that collected installed capacity and load distribution state of a generator are used as input, and when an electric network is continuously adjusted in n operation modes in a topological structure of a power grid system transmitting and receiving end based on a pre-established objective function and constraint conditions for determining power transmission scale, the on-off state of each generator of an alternating current and direct current transmitting end system and the power of each direct current are output in each operation mode;
and arranging the switch of each generator set and the power of each return direct current according to the output result of the objective function for determining the power transmission scale, and determining the maximum power transmission scale of the power grid system by adding the power of the alternating current and direct current outgoing channels in each operation mode.
Further, the step of establishing the topological structure of the transmitting end and the receiving end of the power grid system according to the node distribution information of the power grid system refers to establishing the topological structure of the transmitting end and the receiving end of the power grid system according to the actual node distribution information of the power grid system.
Further, before the method establishes a topological structure of a power transmission end and a power receiving end of the power grid system according to node distribution information of the power grid system, the method comprises the steps of establishing an objective function and a constraint condition for determining the power transmission scale of the power grid system, wherein the constraint condition comprises the following steps:
the calculation formula of the objective function is as follows:
maxR (1)
wherein R is defined as follows:
Figure BDA0002313146640000021
o represents the generator set of the AC/DC transmitting end system, GitGenerating power of generator i for t operation mode, witRepresenting the economic value of the unit transmission of the AC channel in the t-th operating mode, EjtRepresents the transmitted power of the direct current j in the t-th operation mode, djtRepresents the economic value of the unit transmission capacity of the direct current j under the t type of operation mode, IitShowing the on-off state of the generator i in the t-th operation mode, wherein 1 is the on state, 0 is the off state, f is the off stateitFixed cost, M, required for operation of generator i in the t-th mode of operationitIndicating the starting action of the generator, 1 indicating that the generator i is started at the initial moment in the t-th operation mode, 0 indicating that the starting action is not performed, and sitRepresents the cost required for the starting action of the generator i in the t-th operation mode, NitThe power generator shutdown operation is shown, 1 shows that the power generator i performs the shutdown operation at the initial time of the t-th operation mode, 0 shows that the power generator i does not perform the shutdown operation, and hitRepresenting the cost required by the shutdown action of the generator i in the t operation mode, wherein the preset constant is wit、djt、fit、sitAnd hitThe decision variable is Git，Iit，Ejt，MitAnd NitAnd I isit，Mit，NitAs discrete variables, NitAnd EjtIs a continuous variable, and the initial value of t is 1;
the constraint conditions comprise system direct current power flow constraint, power balance constraint, line transmission power constraint, generator power constraint, startup and shutdown constraint and direct current receiving end near-region generating power constraint, wherein:
the formula of the line transmission power constraint is as follows:
PBt＝(Dt×At)×θt (3)
-PB,max≤PBt≤PB,max (4)
in the formula, PBtIs the line tidal flow vector in the t-th operating mode, which is an arbitrary value satisfying the formula (4), AtAnd DtTo pre-input a value, AtFor the system correlation matrix in the t-th operating mode, DtIs a diagonal matrix, and the diagonal elements are susceptances, P, of each line in the t-th operation mode of the systemB,maxIs the upper limit of the line current, θ, input in advancetThe phase angle of each node of the system under the t-th operation mode is calculated and determined according to a formula (3);
the formula of the system direct current power flow constraint is as follows:
Pt＝Btθt (5)
wherein, BtIs a system admittance matrix theta in the t operation mode input in advancetThe phase angle, P, of each node of the system in the t-th operation modetInjecting active power into each node under the t-th operation mode;
the formula of the power balance constraint is:
Figure BDA0002313146640000031
wherein L istFor the load level under the t-th operation mode which is input in advance, according to the active power injected by each node determined by the formula (5), the power of a generator set in the power grid meets the formula (6);
the generator power constraint formula is:
Iit·Gmini≤Git≤Iit·Gmaxi (7)
wherein G ismaxiAnd GminiThe output upper limit and the output lower limit of the generator i are input in advance respectively;
the formula of the power generator on-off constraint is as follows:
Iit≤Ii(t-1)+Mit (8)
Iit≥Ii(t-1)-Nit (9)
the formula of the direct current receiving end near-zone generated power constraint is as follows:
Figure BDA0002313146640000041
wherein Q is a direct current receiving end near zone unit set, PGlimThe minimum power-on force required to be maintained in the near zone.
Further, when the output power grid is continuously adjusted in n operation modes based on a pre-established objective function and constraint conditions for determining the power transmission scale in the topological structure of the power grid system transmitting and receiving end by taking the collected installed capacity and load distribution state of the generator as input, the switching state and the power of each direct current of each generator of the alternating current/direct current transmitting end system under each operation mode comprises:
the collected installed capacity and load distribution state of the generator are used as the input of an objective function for determining the power transmission scale;
when t is 1, determining a decision variable G in the objective function according to the constraint condition in the t-th operation modeit，Iit，Ejt，MitAnd NitLet t be t + 1;
when t is more than or equal to 2 and less than or equal to n, determining a decision variable G in the objective function according to the generator switch state in the t-1 operation mode and the constraint condition in the t operation modeit，Iit，Ejt，MitAnd NitAnd let t be t + 1;
when t is n +1, according to decision variable G under n operation modesit，Iit，Ejt，MitAnd NitSeveral groups of calculation knots ofDetermining the maximum value of the objective function;
decision variable G in each operating mode when maximum value is obtained according to objective functionit，Iit，Ejt，MitAnd NitThe optimal calculation result determines the switching state of each generator of the alternating current-direct current transmission end system and the power of each return direct current in each operation mode.
Further, the algorithm adopted by the method for determining the decision variables in the objective function is a mixed integer linear programming algorithm.
According to another aspect of the present invention, there is provided a system for determining a maximum power transmission scale of a power grid system, the system including:
the topology establishing unit is used for establishing a topology structure of a transmitting end and a receiving end of the power grid system according to the node distribution information of the power grid system;
the data acquisition unit is used for acquiring the installed capacity and the load distribution state of a generator at an AC/DC receiving end of a power grid system;
the data calculation unit is used for taking the collected installed capacity and the load distribution state of the generator as input, and outputting the switching state and the power of each return direct current of each generator of the alternating current and direct current transmitting end system in each operation mode when the power grid is continuously adjusted in n operation modes based on a pre-established objective function and constraint conditions for determining the power transmission scale in the topological structure of the transmitting end and the receiving end of the power grid system;
and the output control unit is used for arranging the switch of each generator set and the power of each return direct current according to the output result of the objective function for determining the power transmission scale, and determining the maximum power transmission scale of the power grid system by adding the power of the alternating current/direct current outgoing channel under each operation mode.
Further, the topology establishing unit establishes the topology structure of the power grid system transmitting and receiving end according to the node distribution information of the power grid system, that is, the topology structure of the power grid system transmitting and receiving end is established according to the actual node distribution information of the power grid system.
Further, the system further comprises a model establishing unit for establishing an objective function and a constraint condition for determining the power transmission scale of the power grid system, wherein:
the calculation formula of the objective function is as follows:
maxR (1)
wherein R is defined as follows:
Figure BDA0002313146640000051
o represents the generator set of the AC/DC transmitting end system, GitGenerating power of generator i for t operation mode, witRepresenting the economic value of the unit transmission of the AC channel in the t-th operating mode, EjtRepresents the transmitted power of the direct current j in the t-th operation mode, djtRepresents the economic value of the unit transmission capacity of the direct current j under the t type operation mode, IitShowing the on-off state of the generator i in the t-th operation mode, wherein 1 is the on state, 0 is the off state, f is the off stateitRepresents the fixed cost, M, required by the generator i to operate in the t-th operation modeitIndicating the starting action of the generator, 1 indicating that the generator i is started at the initial moment in the t-th operation mode, 0 indicating that the starting action is not performed, and sitRepresents the cost required for the starting action of the generator i in the t-th operation mode, NitThe power generator shutdown operation is shown, 1 shows that the power generator i performs the shutdown operation at the initial time of the t-th operation mode, 0 shows that the power generator i does not perform the shutdown operation, and hitRepresenting the cost required by the shutdown action of the generator i in the t operation mode, wherein the preset constant is wit、djt、fit、sitAnd hitThe decision variable is Git，Iit，Ejt，MitAnd NitAnd I isit，Mit，NitAs discrete variables, NitAnd EjtIs a continuous variable, and the initial value of t is 1;
the constraint conditions comprise system direct current power flow constraint, power balance constraint, line transmission power constraint, generator power constraint, startup and shutdown constraint and direct current receiving end near-region generating power constraint, wherein:
the formula of the line transmission power constraint is as follows:
PBt＝(Dt×At)×θt (3)
-PB,max≤PBt≤PB,max (4)
in the formula, PBtIs the line tide vector in the t-th operating mode, which is an arbitrary value satisfying the formula (4), AtAnd DtTo pre-input a value, AtFor the system correlation matrix in the t-th operating mode, DtIs a diagonal matrix, and the diagonal elements are susceptances, P, of each line in the t-th operation mode of the systemB,maxIs the upper limit of the line current, θ, input in advancetThe phase angle of each node of the system under the t-th operation mode is calculated and determined according to a formula (3);
the formula of the system direct current power flow constraint is as follows:
Pt＝Btθt (5)
wherein, BtIs a system admittance matrix theta in the t operation mode input in advancetPhase angle, P, of each node of the system in the t-th operation modetInjecting active power into each node under the t-th operation mode;
the formula of the power balance constraint is:
Figure BDA0002313146640000061
wherein L istFor the load level under the t-th operation mode which is input in advance, according to the active power injected by each node determined by the formula (5), the power of a generator set in the power grid meets the formula (6);
the generator power constraint formula is:
Iit·Gmini≤Git≤Iit·Gmaxi (7)
wherein, GmaxiAnd GminiThe output upper limit and the output lower limit of the generator i are input in advance respectively;
the formula of the power generator on-off constraint is as follows:
Iit≤Ii(t-1)+Mit (8)
Iit≥Ii(t-1)-Nit (9)
the formula of the generated power constraint of the direct current receiving end near region is as follows:
Figure BDA0002313146640000071
wherein Q is a direct current receiving end near zone unit set, PGlimThe minimum start-up force that needs to be maintained in the near zone.
Further, the data calculation unit includes:
the data input unit is used for taking the collected installed capacity and the load distribution state of the generator as the input of an objective function for determining the power transmission scale;
a first calculating unit, which is used for determining the decision variable G in the objective function according to the constraint condition in the t-th operation mode when t is 1it，Iit，Ejt，MitAnd NitLet t be t + 1;
a second calculation unit for determining a decision variable G in the objective function according to the generator switch state in the t-1 operation mode and the constraint condition in the t operation mode when t is more than or equal to 2 and less than or equal to nit，Iit，Ejt，MitAnd NitAnd let t be t + 1;
a third calculation unit for determining a decision variable G for the n operating modes when t is n +1it，Iit，Ejt，MitAnd NitDetermining a maximum value of the objective function from the plurality of sets of calculation results;
a result determination unit for determining a decision variable G for each operation mode when the maximum value is obtained from the objective functionit，Iit，Ejt，MitAnd NitDetermines the optimum calculation result under each operation modeThe switching state of each generator of the AC/DC transmitting end system and the power of each return DC.
The method and the system for determining the maximum power transmission scale of the power grid system provided by the technical scheme of the invention take the collected installed capacity and load distribution state of the power generator as input based on the current operation state of the power grid system transmitting and receiving ends, and in the topological structure of the power grid system transmitting and receiving ends, based on the pre-established objective function and constraint condition for determining the power transmission scale, when the output power grid is continuously adjusted in n operation modes, the switching state and the power of each direct current of each power generator of the alternating current and direct current transmitting end system under each operation mode, the switching of each power generator set and the power of each direct current are arranged according to the output result of the objective function for determining the power transmission scale, and the maximum power transmission scale of the power grid system is determined by adding the power of the alternating current and direct current outgoing channels under each operation mode. According to the method and the system, the reasonable control of the switch of the sending and receiving end unit is realized by referring to a safety constraint unit combination model, the maximum transmission power constraint of a line is realized by introducing a direct current power flow equation set on the basis, the influence of multi-loop direct current power regulation, the economic benefit of alternating current and direct current delivery and the related operation cost of the generator set are considered, and therefore on the premise of ensuring the safety and stability of a power grid system, the maximization of the total direct current and direct current delivery power is realized by coordinating the direct current power delivery and switching the generator set when various operation modes are continuously adjusted. Moreover, the mixed integer linear algorithm is adopted for solving, so that the high efficiency of calculation and the applicability of a large-scale system are ensured.
Drawings
A more complete understanding of exemplary embodiments of the present invention may be had by reference to the following drawings in which:
fig. 1 is a flow chart of a method of determining a maximum power delivery size of a power grid system in accordance with a preferred embodiment of the present invention;
FIG. 2 is a schematic diagram of a topology of a transmitting and receiving end of a power grid system according to a preferred embodiment of the present invention;
FIG. 3 is a schematic load level diagram of 4 continuous operation modes of the grid system according to the preferred embodiment;
FIG. 4 is a schematic diagram of the unit output levels for 4 continuous modes of operation in mode 1 in accordance with a preferred embodiment of the present invention;
FIG. 5 is a schematic diagram of the unit output levels for 4 continuous modes of operation in mode 2, in accordance with a preferred embodiment of the present invention;
FIG. 6 is a schematic diagram of DC delivery power in 4 continuous modes of operation in mode 1, in accordance with a preferred embodiment of the present invention;
FIG. 7 is a schematic diagram of DC delivery power in 4 continuous modes of operation in mode 2, in accordance with a preferred embodiment of the present invention;
fig. 8 is a schematic diagram of the maximum ac/dc power transmission scale in 4 continuous operation modes according to the preferred embodiment of the present invention;
FIG. 9 is a schematic diagram of the power flow calculation results in mode 1 operation mode, determined based on the PSD-BPA power flow calculation degree;
FIG. 10 is a schematic diagram of the power flow calculation results in mode 2 operating mode 1, determined based on the PSD-BPA power flow calculation degree;
fig. 11 is a schematic configuration diagram of a system for determining the maximum power transmission size of a power grid system according to a preferred embodiment of the present invention.
Detailed Description
The exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein, which are provided for complete and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, the same units/elements are denoted by the same reference numerals.
Unless otherwise defined, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Further, it will be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.
Fig. 1 is a flowchart of a method of determining a maximum power transmission size of a power grid system according to a preferred embodiment of the present invention. As shown in fig. 1, a method 100 for determining the maximum power transmission size of the power grid system according to the preferred embodiment starts at step 101.
In step 101, a topology structure of a transmitting end and a receiving end of the power grid system is established according to node distribution information of the power grid system.
Preferably, the establishing of the topology structure of the transmitting and receiving ends of the power grid system according to the node distribution information of the power grid system refers to establishing the topology structure of the transmitting and receiving ends of the power grid system according to the actual node distribution information of the power grid system.
Fig. 2 is a schematic diagram of a topology structure of a transmitting end and a receiving end of a power grid system according to a preferred embodiment of the invention. As shown in fig. 2, the preferred embodiment modifies the IEEE14 node standard system, and adds a generator set at nodes No. 2, 3, 4, and 12, and adds 1-turn dc output at nodes No. 4 and 2, respectively, and adds a dc feed at nodes No. 11 and 13; the load of the 2 nd node is reduced, and the loads of the 11 th, 12 th and 13 th nodes are increased. At the moment, the sending end of the whole system is concentrated at nodes No. 1-4 and No. 14, and the load center is shifted to the vicinity of nodes No. 11, 12 and 13. In order to simulate the situation that a plurality of generator sets are installed in a power plant in practice, the capacity of each set is set to be 50MW in the embodiment, 4 sets (set numbers 1-4) are accessed to a node No. 1, 2 sets (set numbers 5-6) are accessed to a node No. 2, 3 sets (set numbers 7-9) are accessed to a node No. 3, 2 sets (set numbers 10-11) are accessed to a node No. 4, 5 sets (set numbers 16-20) are accessed to a node No. 12, 4 sets (set numbers 12-15) are accessed to a node No. 14, and 20 sets are shared in the whole system. The system has 2 loops of direct current, the regulation range of each loop of direct current power is set to be 10-80MW, the upper limit of the single loop of line power flow is 200MW, and the minimum startup of the direct current receiving end near-zone power generation is set to be 50MW, namely, at least 1 set of receiving ends is ensured to be in a startup full power generation state. The system baseline capacity is 100 MW.
In step 102, the installed capacity and the load distribution state of the generator at the ac/dc receiving end of the power grid system are collected.
In step 103, the collected installed capacity and load distribution state of the generator are used as input, and in the topological structure of the power grid system transmitting and receiving end, based on the pre-established objective function and constraint conditions for determining the power transmission scale, the on-off state and the power of each return direct current of each generator of the alternating current and direct current transmitting end system in each operation mode are output when the power grid is continuously adjusted in n operation modes.
Fig. 3 is a schematic view of the load level of 4 continuous operation modes of the power grid system according to the preferred embodiment. As shown in fig. 3, the present preferred embodiment sets 4 typical operation modes in which the sending-end load level is kept constant and only the receiving-end load level and the load distribution are changed. Because the economic values of alternating current and direct current transmission are different, the alternating current transmission economic benefit is better than the direct current (mode 1) and the direct current transmission economic benefit is better than the alternating current (mode 2) in 2 modes, and the constraint conditions and the objective function are adopted to calculate 4 modes. The combination of the unit on-off states in the 4 operation modes corresponding to the mode 1 is shown in table 1. The combination of the unit on-off states in the 4 operation modes corresponding to the mode 2 is shown in table 2.
Table 1 mode 1 units combination
Figure BDA0002313146640000101
Figure BDA0002313146640000111
TABLE 2 MODE 2 COMBINATION OF SET IN FORMS
Figure BDA0002313146640000112
Figure BDA0002313146640000121
Fig. 4 is a schematic diagram of the unit output level in 4 continuous operation modes in mode 1 according to the preferred embodiment of the present invention. As shown in fig. 4, corresponding to the on/off states of the units in table 1, in the mode 1, the units 1 to 9, 13 and 15 of the sending-end system are turned on, the receiving-end system has the unit 19, and the output of the units other than the unit 15 are equal. The unit output levels in the other 3 operating modes also correspond to the startup state in table 1.
Fig. 5 is a schematic diagram of the unit output level in 4 continuous operation modes in mode 2 according to the preferred embodiment of the present invention. As shown in fig. 5, corresponding to the on/off states of the units in table 2, in the mode 1, the units 1 to 8, the units 13 to 15 of the sending-end system are turned on, the unit 20 of the receiving-end system is turned on, and the output forces of the units other than the unit 14 are equal. The unit output levels in the other 3 operating modes also correspond to the startup state in table 2.
Fig. 6 is a schematic diagram of dc outgoing power in 4 continuous operation modes in mode 1 according to the preferred embodiment of the present invention. As shown in fig. 6, in mode 1, the dc transmission power of the transmission end 1 and the transmission end 2 is varied.
Fig. 7 is a diagram illustrating dc outgoing power in 4 continuous operation modes in mode 2 according to a preferred embodiment of the present invention. As shown in fig. 7, in mode 2, the dc transmission power of the transmitting terminal 1 and the dc transmission power of the transmitting terminal 2 in the 4 operation modes are completely the same.
And step 104, arranging the switch of each generator set and the power of each return direct current according to the output result of the objective function for determining the power transmission scale, and determining the maximum power transmission scale of the power grid system by adding the power of the alternating current and direct current outgoing channel in each operation mode.
In the preferred embodiment, the method of the present invention performs maximum transmission of combined ac and dc power by coordinating the unit combination with the ac/dc power in 4 continuous operation modes, where the ac lines near the tidal current transmission limit in the 4 continuous operation modes in mode 1 and mode 2 are shown in tables 3 and 4.
Table 3 list of lines approaching the limit of tidal current transmission in 4 successive modes of mode 1
Figure BDA0002313146640000122
Figure BDA0002313146640000131
Table 4 list of lines approaching the limit of tidal current transmission in 4 successive modes of mode 2
Figure BDA0002313146640000132
As can be seen from fig. 3 to 7 and tables 3 and 4, when the load at the receiving end changes, the power-on and output levels of the sending and receiving end units and the dc transmission power change accordingly. In the case of mode 1 and mode 2, the change process between the modes is analyzed as follows:
(1) mode 1
Mode 1 → mode 2: as the load level increases, the unit output and dc delivered power rises, as shown in fig. 4 and 6. As can be seen from table 3, the power flow in the branch 4-5 reaches its upper limit in both the mode 1 and the mode 2, and the transmission-side ac power transmission scale is limited thereto. The 2-cycle dc output power is increased to the rated capacity in the mode 2. As can be seen from table 1 and fig. 4, 4 units of the receiving-end power grid are in the on state in the mode 2 to compensate for the power shortage caused by the increase of the receiving-end load.
Mode 2 → mode 3: the receiving grid load level continues to increase as shown in figure 3. As can be seen from fig. 4, when the sending end unit 10 is turned on, the branch 4-5 reaches the upper transmission limit in the mode 3, and the power level of the part of the line close to the power flow transmission limit is increased compared with the mode 2. The 2-loop direct current outgoing power is kept at the rated capacity.
Mode 3 → mode 4: the load level is reduced, the unit is shut down, and the direct current transmission power is reduced. In the mode, the economic benefit of alternating current transmission is considered to be better than that of direct current transmission, and the alternating current outgoing mode is preferentially adopted, so that the direct current power of 2 loops in the mode 4 is reduced to the lower limit value of the transmission power. The receiving-end unit No. 19 is still in the starting and full-sending state under the mode 4 by the minimum starting limit of the direct current near zone. The current level of the branch 4-5 is now the heaviest, but still with a large margin from the upper transmission limit.
(2) Mode 2
Mode 1 → mode 2: in the mode, the economic benefit of direct current transmission is considered to be superior to that of alternating current transmission, so that a direct current outgoing mode is preferentially adopted, and 2 loops of direct current outgoing power in 2 modes are rated capacity. In the mode 1, the load level is low, the power of the alternating current outgoing line does not reach the upper transmission limit, and as the load level increases, the branch lines 4-5 in the mode 2 reach the upper transmission limit, and meanwhile, the transmission power of each branch line is increased.
Mode 2 → mode 3: the load level of a receiving end power grid is increased, the transmission power of the lower branch 4-5 in the mode 3 keeps the transmission upper limit, and compared with the mode 2, the power level of a part of lines close to the power flow transmission limit is increased. The 2-loop direct current outgoing power is kept at the rated capacity.
Mode 3 → mode 4: when the load level is reduced, the sending end unit is shut down, the alternating current transmission power is reduced, and the 2-loop direct current power still maintains the rated capacity. The tidal current level of each alternating current branch is lower under the mode 4.
The above is the mutual coordination process of the alternating current and direct current outgoing power in the continuous adjustment process of different operation modes in 2 modes.
Fig. 8 is a schematic diagram of the maximum ac/dc power transmission scale in 4 continuous operation modes according to the preferred embodiment of the present invention. As shown in fig. 8, the power transmission scale changes during the continuous change of the mode due to different load distributions and limited by the transmission limit of the line, safety constraints and cost factors. The comparison shows that the power transmission scale of the mode 3 in the 2 modes is larger than that of the mode 2, because the receiving end load distribution in the mode 3 is more reasonable, the transmission capability of the line can be fully utilized; in the mode 4 in the mode 2, although the transmission power of the line does not reach the upper limit, because of the minimum starting-up constraint of the direct-current receiving end, a receiving end unit must maintain a specific starting-up amount to ensure the stability of the system, so the power transmission scale in the mode is small; comparing the power transmission scales in the modes 1 and 2, the direct current power transmission is preferentially adopted and the influence of the transmission upper limit of the alternating current channel is reduced in the alternating current and direct current networking mode, so that the integral alternating current and direct current external power transmission scale can be improved to a certain extent.
And (3) building a topological structure of the power grid system in a PSD-BPA flow calculation program, setting 4 operation modes according to a model calculation result, and performing flow calculation on the 4 operation modes by using the PSD-BPA flow calculation program.
Fig. 9 is a schematic diagram showing the power flow calculation result in the operation mode 1 of the mode 1 determined based on the PSD-BPA power flow calculation degree. As shown in FIG. 9, the load of the transmitting side system (total load of BUS1-4 and BUS 14) and the load of the receiving side system (total load of BUS 5-13) are 1.071p.u., and 4.732p.u., respectively (the system reference capacity is 100 MW). According to the calculation result of the invention, under the setting mode 1, the output of the generator set at the BUS1 is 2p.u. (1-4 units, each unit outputs 0.5p.u.), the output of the GEN2 generator set is 1p.u. (5-6 units, each unit outputs 0.5p.u.), the output of the GEN3 generator set is 1.5p.u. (7-9 units, each unit outputs 0.5p.u.), the output of the GEN4 generator set is 0(10-11 units, each unit outputs 0), the output of the generator set at the BUS14 is 0.81p.u. (12-15 units, BPA, 14 units output 0, 13 units output 0.5p.u., 15 units output 0.31p.u.), the output of the GEN12 generator set is 0.5p.u. (16-20 units, BPA, 19.5 p.u., 0, PSD is calculated by using the flow calculation mode to calculate the flow of the other units, the results show that the line power flow marked with arrows is approximately the same as the power flow calculation results in table 3.
Fig. 10 is a schematic diagram showing the power flow calculation result in the operation mode 1 of the mode 2 determined based on the PSD-BPA power flow calculation degree. As shown in FIG. 10, the load of the transmitting side system (total load of BUS1-4 and BUS 14) and the load of the receiving side system (total load of BUS 5-13) are 1.071p.u., and 4.732p.u., respectively (the system reference capacity is 100 MW). According to the calculation result of the invention, under the setting mode 1, the output of the generator set at BUS1 is 2p.u. (1-4 units, each unit outputs 0.5p.u.), the output of the generator set GEN2 is 1p.u. (5-6 units, each unit outputs 0.5p.u.), the output of the generator set GEN3 is 1p.u. (7-9 units, 7 and 8 units output 0.5p.u., and 9 units output 0), the output of the generator set GEN4 is 0(10-11 units, each unit outputs 0), the output of the generator set at a position 14 is 1.303p.u. (12-15 units, 12 units output 0, 13 and 15 units output 0.5p.u., 14 units output 0.303p.u.), and the output of the generator set 0.5p.u. (16-20 units, 20 units output 0.5p.u., and the other units output 0.0 p.0); the output power of HVDC1 and HVDC2 is set to be 0.8p.u., and similarly, the power flow calculation is carried out in the manner by using a PSD-BPA power flow calculation program, and the result shows that the line power flow marked with an arrow is approximately the same as the power flow calculation result in the table 4. The accuracy and the effectiveness of the method are further verified through the calculation, wherein the line with the arrow standard refers to a line with heavier tide.
Preferably, before the method establishes a topology structure of the power transmission and reception ends of the power grid system according to the node distribution information of the power grid system, the method includes establishing an objective function and a constraint condition for determining the power transmission scale of the power grid system, wherein:
the calculation formula of the objective function is as follows:
maxR (1)
wherein R is defined as follows:
Figure BDA0002313146640000161
o represents the generator set of the AC/DC transmitting end system, GitGenerating power of generator i for t operation mode, witRepresenting the economic value of the unit transmission of the AC channel in the t-th operating mode, EjtRepresents the transmitted power of the direct current j in the t-th operation mode, djtRepresents the economic value of the unit transmission capacity of the direct current j under the t type operation mode, IitShowing the on-off state of the generator i in the t-th operation mode, wherein 1 is the on state, 0 is the off state, f is the off stateitRepresents the fixed cost, M, required by the generator i to operate in the t-th operation modeitIndicating the starting action of the generator, 1 indicating that the generator i is carried out at the initial moment in the t-th operation modeOpen action is performed, 0 means that open action is not performed, sitRepresents the cost required for the starting action of the generator i in the t-th operation mode, NitThe power generator shutdown operation is shown, 1 shows that the power generator i performs the shutdown operation at the initial time of the t-th operation mode, 0 shows that the power generator i does not perform the shutdown operation, and hitRepresenting the cost required by the shutdown action of the generator i in the t operation mode, wherein the preset constant is wit、djt、fit、sitAnd hitThe decision variable is Git，Iit，Ejt，MitAnd NitAnd I isit，Mit，NitAs discrete variables, NitAnd EjtIs a continuous variable, and the initial value of t is 1;
the constraint conditions comprise system direct current power flow constraint, power balance constraint, line transmission power constraint, generator power constraint, startup and shutdown constraint and direct current receiving end near-region generating power constraint, wherein:
the formula of the line transmission power constraint is as follows:
PBt＝(Dt×At)×θt (3)
-PB,max≤PBt≤PB,max (4)
in the formula, PBtIs the line tidal flow vector in the t-th operating mode, which is an arbitrary value satisfying the formula (4), AtAnd DtTo pre-input a value, AtFor the system correlation matrix in the t-th operating mode, DtIs a diagonal matrix, and the diagonal elements are susceptances, P, of each line in the t-th operation mode of the systemB,maxIs the upper limit of the line current, θ, input in advancetCalculating and determining phase angles of all nodes of the system in the t operation mode according to a formula (3);
the formula of the system direct current power flow constraint is as follows:
Pt＝Btθt (5)
wherein, BtIs a system admittance matrix theta in the t operation mode input in advancetIn the t-th operation modePhase angle of each node of the system, PtInjecting active power into each node under the t operation mode;
the formula of the power balance constraint is:
Figure BDA0002313146640000171
wherein L istFor the load level under the t-th operation mode which is input in advance, according to the active power injected by each node determined by the formula (5), the power of a generator set in the power grid meets the formula (6);
the generator power constraint formula is:
Iit·Gmini≤Git≤Iit·Gmaxi (7)
wherein G ismaxiAnd GminiThe output upper limit and the output lower limit of the generator i are input in advance respectively;
the formula of the power generator on-off constraint is as follows:
Iit≤Ii(t-1)+Mit (8)
Iit≥Ii(t-1)-Nit (9)
the formula of the direct current receiving end near-zone generated power constraint is as follows:
Figure BDA0002313146640000172
wherein Q is a direct current receiving end near zone unit set, PGlimThe minimum start-up force that needs to be maintained in the near zone.
Preferably, when the output power grid is continuously adjusted in n operation modes based on a pre-established objective function and constraint conditions for determining the power transmission scale in the topological structure of the power grid system at the transmitting and receiving ends by taking the collected installed capacity and load distribution state of the generator as inputs, the switching state and the power of each direct current of each generator of the alternating current and direct current transmitting end system in each operation mode includes:
the collected installed capacity and load distribution state of the generator are used as the input of an objective function for determining the power transmission scale;
when t is 1, determining a decision variable G in the objective function according to the constraint condition in the t-th operation modeit，Iit，Ejt，MitAnd NitLet t be t + 1;
when t is more than or equal to 2 and less than or equal to n, determining a decision variable G in the objective function according to the generator switch state in the t-1 operation mode and the constraint condition in the t operation modeit，Iit，Ejt，MitAnd NitAnd let t be t + 1;
when t is n +1, according to decision variable G under n operation modesit，Iit，Ejt，MitAnd NitDetermining a maximum value of the objective function from the plurality of sets of calculation results;
decision variable G in each operating mode when maximum value is obtained according to objective functionit，Iit，Ejt，MitAnd NitThe optimal calculation result determines the switching state of each generator of the alternating current-direct current transmission end system and the power of each return direct current in each operation mode.
Preferably, the algorithm used by the method to determine the decision variables in the objective function is a mixed integer linear programming algorithm.
Fig. 11 is a schematic configuration diagram of a system for determining the maximum power transmission size of a power grid system according to a preferred embodiment of the present invention. As shown in fig. 11, a system 1100 for determining the maximum power transmission size of a power grid system according to the present preferred embodiment includes:
a model establishing unit 1101 for establishing an objective function and a constraint condition for determining the power transmission scale of the power grid system, wherein:
the calculation formula of the objective function is as follows:
maxR (1)
wherein R is defined as follows:
Figure BDA0002313146640000181
o represents the generator set of the AC/DC transmitting end system, GitGenerating power of generator i for t operation mode, witRepresenting the economic value of the unit transmission of the AC channel in the t-th operating mode, EjtRepresents the transmitted power of the direct current j in the t-th operation mode, djtRepresents the economic value of the unit transmission capacity of the direct current j under the t type operation mode, IitShowing the on-off state of the generator i in the t-th operation mode, wherein 1 is the on state, 0 is the off state, f is the off stateitRepresents the fixed cost, M, required by the generator i to operate in the t-th operation modeitIndicating the starting action of the generator, 1 indicating that the generator i is started at the initial moment in the t-th operation mode, 0 indicating that the starting action is not performed, and sitRepresents the cost required for the starting action of the generator i in the t-th operation mode, NitThe power generator shutdown operation is shown, 1 shows that the power generator i performs the shutdown operation at the initial time of the t-th operation mode, 0 shows that the power generator i does not perform the shutdown operation, and hitRepresenting the cost required by the shutdown action of the generator i in the t operation mode, wherein the preset constant is wit、djt、fit、sitAnd hitThe decision variable is Git，Iit，Ejt，MitAnd NitAnd I isit，Mit，NitAs discrete variables, NitAnd EjtIs a continuous variable, and the initial value of t is 1;
the constraint conditions comprise system direct current power flow constraint, power balance constraint, line transmission power constraint, generator power constraint, startup and shutdown constraint and direct current receiving end near-region generating power constraint, wherein:
the formula of the line transmission power constraint is as follows:
PBt＝(Dt×At)×θt (3)
-PB,max≤PBt≤PB,max (4)
in the formula, PBtIs the t-th transportLine tide vector in line mode, which is an arbitrary value satisfying equation (4), AtAnd DtTo pre-input a value, AtFor the system correlation matrix in the t-th operating mode, DtIs a diagonal matrix, and the diagonal elements are susceptances, P, of each line in the t-th operation mode of the systemB,maxUpper limit of line current, θ, input beforehandtCalculating and determining phase angles of all nodes of the system in the t operation mode according to a formula (3);
the formula of the system direct current power flow constraint is as follows:
Pt＝Btθt (5)
wherein, BtIs a system admittance matrix theta in the t operation mode input in advancetPhase angle, P, of each node of the system in the t-th operation modetInjecting active power into each node under the t-th operation mode;
the formula of the power balance constraint is:
Figure BDA0002313146640000191
wherein L istFor the load level under the t-th operation mode which is input in advance, according to the active power injected by each node determined by the formula (5), the power of a generator set in the power grid meets the formula (6);
the generator power constraint formula is:
Iit·Gmini≤Git≤Iit·Gmaxi (7)
wherein, GmaxiAnd GminiThe output upper limit and the output lower limit of the generator i are input in advance respectively;
the formula of the power generator on-off constraint is as follows:
Iit≤Ii(t-1)+Mit (8)
Iit≥Ii(t-1)-Nit (9)
the formula of the direct current receiving end near-zone generated power constraint is as follows:
Figure BDA0002313146640000201
wherein Q is a direct current receiving end near zone unit set, PGlimThe minimum start-up force that needs to be maintained in the near zone.
A topology establishing unit 1102, configured to establish a topology structure of a transmitting end and a receiving end of the power grid system according to node distribution information of the power grid system;
a data acquisition unit 1103, configured to acquire an installed capacity and a load distribution state of a generator at an ac/dc receiving end of a power grid system;
the data calculation unit 1104 is configured to take the collected installed capacity and load distribution state of the generator as input, and output a switching state and power of each current of each generator of the ac/dc transmitting-side system in each operation mode when the power grid is continuously adjusted in n operation modes in the topological structure of the transmitting-receiving side of the power grid system based on a pre-established objective function and constraint conditions for determining the power transmission scale;
and an output control unit 1105, configured to arrange the switch of each generator set and the power per dc return according to the output result of the objective function for determining the power transmission scale, and determine the maximum power transmission scale of the power grid system by adding the power of the ac/dc outgoing channel in each operation mode.
Preferably, the topology establishing unit 1102 establishes the topology structure of the transmitting and receiving ends of the power grid system according to the node distribution information of the power grid system, that is, establishes the topology structure of the transmitting and receiving ends of the power grid system according to the actual node distribution information of the power grid system.
Preferably, the data calculation unit 1104 includes:
a data input unit 1141 for inputting the collected installed capacity and load distribution state of the generator as an objective function for determining the power transmission scale;
a first calculating unit 1142, configured to determine the decision variable G in the objective function according to the constraint condition in the t-th operation mode when t is equal to 1it，Iit，Ejt，MitAnd NitLet t be t + 1;
a second calculating unit 1143 for determining the decision variable G in the objective function according to the generator switch state in the t-1 operation mode and the constraint condition in the t operation mode when t is more than or equal to 2 and less than or equal to nit，Iit，Ejt，MitAnd NitAnd let t be t + 1;
a third calculating unit 1144, configured to, when t is equal to n +1, determine a decision variable G according to the n operation modesit，Iit，Ejt，MitAnd NitDetermining a maximum value of the objective function;
a result determination unit 1145 for determining the variable G for each operation mode when the maximum value is obtained according to the objective functionit，Iit，Ejt，MitAnd NitThe optimal calculation result determines the switching state of each generator and the power of each return direct current of the alternating current-direct current transmitting end system under each operation mode.
The system for determining the maximum power transmission scale of the power grid system collects the operation data of the power grid system, and the steps for determining the maximum power transmission scale in the continuous operation mode are the same as the steps adopted by the method for determining the maximum power transmission scale of the power grid system, and the achieved technical effects are also the same, so that the details are not repeated.
The invention has been described with reference to a few embodiments. However, other embodiments of the invention than the one disclosed above are equally possible within the scope of the invention, as would be apparent to a person skilled in the art from the appended patent claims.
Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the [ device, component, etc ]" are to be interpreted openly as referring to at least one instance of said device, component, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.

Claims (6)

1. A method of determining a maximum power delivery size of a power grid system, the method comprising:
establishing an objective function and a constraint condition for determining the power transmission scale of the power grid system, wherein:
the calculation formula of the objective function is as follows:
maxR (1)
wherein R is defined as follows:
Figure FDA0003616307490000011
o represents the generator set of the AC/DC transmitting end system, GitGenerating power of generator i for t operation mode, witRepresenting the economic value of the unit transmission of the AC channel in the t-th operating mode, EjtRepresents the transmitted power of the direct current j in the t-th operation mode, djtRepresents the economic value of the unit transmission capacity of the direct current j under the t type operation mode, IitShowing the on-off state of the generator i in the t-th operation mode, wherein 1 is the on state, 0 is the off state, f is the off stateitFixed cost, M, required for operation of generator i in the t-th mode of operationitIndicating the starting action of the generator, 1 indicating that the generator i is started at the initial moment in the t-th operation mode, 0 indicating that the starting action is not performed, and sitRepresents the cost required for the starting action of the generator i in the t-th operation mode, NitIndicating the shutdown action of the generator, 1 TableIndicating that the generator i carries out shutdown operation at the initial moment of the t-th operation mode, 0 indicating that the shutdown operation is not carried out, and hitRepresenting the cost required by the shutdown action of the generator i in the t operation mode, wherein the preset constant is wit、djt、fit、sitAnd hitThe decision variable is Git，Iit，Ejt，MitAnd NitAnd I isit，Mit，NitAs discrete variables, NitAnd EjtIs a continuous variable, and the initial value of t is 1;
the constraint conditions comprise system direct current power flow constraint, power balance constraint, line transmission power constraint, generator power constraint, startup and shutdown constraint and direct current receiving end near-region generating power constraint, wherein:
the formula of the line transmission power constraint is as follows:
PBt＝(Dt×At)×θt (3)
-PB,max≤PBt≤PB,max (4)
in the formula, PBtIs the line tidal flow vector in the t-th operating mode, which is an arbitrary value satisfying the formula (4), AtAnd DtTo pre-input a value, AtIs the system incidence matrix in the t-th operation mode, DtIs diagonal matrix, and the diagonal elements are susceptances, P, of each line in the t-th operation mode of the systemB,maxIs the upper limit of the line current, θ, input in advancetThe phase angle of each node of the system under the t-th operation mode is calculated and determined according to a formula (3);
the formula of the system direct current power flow constraint is as follows:
Pt＝Btθt (5)
wherein, BtIs a system admittance matrix theta in the t operation mode input in advancetThe phase angle, P, of each node of the system in the t-th operation modetInjecting active power into each node under the t operation mode;
the formula of the power balance constraint is:
Figure FDA0003616307490000021
wherein L istFor the load level under the t-th operation mode which is input in advance, determining the active power injected into each node according to the formula (5), and enabling the power of a generator set in the power grid to meet the formula (6);
the generator power constraint formula is:
Iit·Gmini≤Git≤Iit·Gmaxi (7)
wherein G ismaxiAnd GminiThe output upper limit and the output lower limit of the generator i are input in advance respectively;
the formula of the power generator on-off constraint is as follows:
Iit≤Ii(t-1)+Mit (8)
Iit≥Ii(t-1)-Nit (9)
the formula of the direct current receiving end near-zone generated power constraint is as follows:
Figure FDA0003616307490000022
wherein Q is a direct current receiving end near zone unit set, PGlimMinimum startup output required to be maintained in the near zone;
according to the node distribution information of the power grid system, a topological structure of a transmitting end and a receiving end of the power grid system is established;
collecting the installed capacity and the load distribution state of a generator at an AC/DC receiving end of a power grid system;
the method comprises the steps of taking the collected installed capacity and load distribution state of the generator as input, outputting the switching state of each generator and the power of each return direct current of an alternating current-direct current sending end system in each operation mode when the power grid is continuously adjusted in n operation modes in the topological structure of the sending end and the receiving end of the power grid system based on a pre-established objective function and constraint conditions for determining the power transmission scale, wherein the switching state and the power of each return direct current of each generator of the alternating current-direct current sending end system in each operation mode comprise
The collected installed capacity and load distribution state of the generator are used as the input of an objective function for determining the power transmission scale;
when t is 1, determining a decision variable G in the objective function according to the constraint condition in the t-th operation modeit，Iit，Ejt，MitAnd NitLet t be t + 1;
when t is more than or equal to 2 and less than or equal to n, determining a decision variable G in the objective function according to the generator switch state in the t-1 operation mode and the constraint condition in the t operation modeit，Iit，Ejt，MitAnd NitAnd let t be t + 1;
when t is n +1, according to decision variable G under n operation modesit，Iit，Ejt，MitAnd NitDetermining a maximum value of the objective function from the plurality of sets of calculation results;
decision variable G in each operating mode when maximum value is obtained according to objective functionit，Iit，Ejt，MitAnd NitDetermining the switching state of each generator and the power of each return direct current of the alternating current-direct current transmitting end system in each operation mode according to the optimal calculation result;
and arranging the switch of each generator set and the power of each return direct current according to the output result of the objective function for determining the power transmission scale, and determining the maximum power transmission scale of the power grid system by adding the power of the alternating current and direct current outgoing channels in each operation mode.
2. The method according to claim 1, wherein the step of establishing the topological structure of the transmitting and receiving ends of the power grid system according to the node distribution information of the power grid system is performed by establishing the topological structure of the transmitting and receiving ends of the power grid system according to the actual node distribution information of the power grid system.
3. The method of claim 1, wherein the algorithm used by the method to determine the decision variables in the objective function is a mixed integer linear programming algorithm.
4. A system for determining a maximum power delivery size of a power grid system, the system comprising:
the model establishing unit is used for establishing an objective function and a constraint condition for determining the power transmission scale of the power grid system, wherein:
the calculation formula of the objective function is as follows:
maxR (1)
wherein R is defined as follows:
Figure FDA0003616307490000041
o represents the generator set of the AC/DC transmitting end system, GitGenerating power of generator i for t operation mode, witRepresenting the economic value of the unit transmission of the AC channel in the t-th operating mode, EjtRepresents the transmitted power of the direct current j in the t-th operation mode, djtRepresents the economic value of the unit transmission capacity of the direct current j under the t type operation mode, IitShowing the on-off state of the generator i in the t-th operation mode, wherein 1 is the on state, 0 is the off state, f is the off stateitRepresents the fixed cost, M, required by the generator i to operate in the t-th operation modeitIndicating the starting action of the generator, 1 indicating that the generator i is started at the initial moment in the t-th operation mode, 0 indicating that the starting action is not performed, and sitRepresents the cost required for the starting action of the generator i in the t-th operation mode, NitThe power generator shutdown operation is shown, 1 shows that the power generator i performs the shutdown operation at the initial time of the t-th operation mode, 0 shows that the power generator i does not perform the shutdown operation, and hitRepresenting the cost required by the shutdown action of the generator i in the t operation mode, wherein the preset constant is wit、djt、fit、sitAnd hitThe decision variable is Git，Iit，Ejt，MitAnd NitAnd I isit，Mit，NitBeing a discrete variable, NitAnd EjtIs a continuous variable, and the initial value of t is 1;
the constraint conditions comprise system direct current power flow constraint, power balance constraint, line transmission power constraint, generator power constraint, startup and shutdown constraint and direct current receiving end near-region generating power constraint, wherein:
the formula of the line transmission power constraint is as follows:
PBt＝(Dt×At)×θt (3)
-PB,max≤PBt≤PB,max (4)
in the formula, PBtIs the line tide vector in the t-th operating mode, which is an arbitrary value satisfying the formula (4), AtAnd DtTo pre-input a value, AtFor the system correlation matrix in the t-th operating mode, DtIs a diagonal matrix, and the diagonal elements are susceptances, P, of each line in the t-th operation mode of the systemB,maxIs the upper limit of the line current, θ, input in advancetThe phase angle of each node of the system under the t-th operation mode is calculated and determined according to a formula (3);
the formula of the system direct current power flow constraint is as follows:
Pt＝Btθt (5)
wherein, BtIs a system admittance matrix theta in the t operation mode input in advancetThe phase angle, P, of each node of the system in the t-th operation modetInjecting active power into each node under the t operation mode;
the formula of the power balance constraint is:
Figure FDA0003616307490000051
wherein L istFor the pre-input load level under the t-th operation mode, the active power injected into each node is determined according to the formula (5), so that the generator set in the power grid has the active powerThe power satisfies formula (6);
the generator power constraint formula is:
Iit·Gmini≤Git≤Iit·Gmaxi (7)
wherein G ismaxiAnd GminiThe output upper limit and the output lower limit of the generator i are input in advance respectively;
the formula of the power generator on-off constraint is as follows:
Iit≤Ii(t-1)+Mit (8)
Iit≥Ii(t-1)-Nit (9)
the formula of the generated power constraint of the direct current receiving end near region is as follows:
Figure FDA0003616307490000052
wherein Q is a direct current receiving end near zone unit set, PGlimMinimum startup output required to be maintained in the near zone;
the topology establishing unit is used for establishing a topology structure of a transmitting end and a receiving end of the power grid system according to the node distribution information of the power grid system;
the data acquisition unit is used for acquiring the installed capacity and the load distribution state of a generator at an AC/DC receiving end of a power grid system;
a data calculation unit, configured to use the collected installed capacity and load distribution state of the generator as inputs, and in a topology structure of a transmitting end and a receiving end of the power grid system, based on a pre-established objective function and constraint conditions for determining a power transmission scale, when an output power grid is continuously adjusted in n operation modes, in each operation mode, a switching state and a power per dc of each generator of an ac/dc transmitting end system, where the data calculation unit includes:
the data input unit is used for taking the collected installed capacity and the load distribution state of the generator as the input of an objective function for determining the power transmission scale;
first of allA calculating unit, which is used for determining the decision variable G in the objective function according to the constraint condition in the t-th operation mode when t is 1it，Iit，Ejt，MitAnd NitAnd let t be t + 1;
a second calculation unit for determining a decision variable G in the objective function according to the generator switch state in the t-1 operation mode and the constraint condition in the t operation mode when t is more than or equal to 2 and less than or equal to nit，Iit，Ejt，MitAnd NitAnd let t be t + 1;
a third calculation unit for determining a decision variable G for the n operating modes when t is n +1it，Iit，Ejt，MitAnd NitDetermining a maximum value of the objective function from the plurality of sets of calculation results;
a result determination unit for determining a decision variable G for each operation mode when the maximum value is obtained from the objective functionit，Iit，Ejt，MitAnd NitDetermining the switching state of each generator and the power of each return direct current of the alternating current-direct current transmitting end system in each operation mode according to the optimal calculation result;
and the output control unit is used for arranging the switch of each generator set and the power of each return direct current according to the output result of the objective function for determining the power transmission scale, and determining the maximum power transmission scale of the power grid system by adding the power of the alternating current/direct current outgoing channel under each operation mode.
5. The system according to claim 4, wherein the topology establishing unit establishes the topology structure of the transmitting and receiving ends of the power grid system according to the node distribution information of the power grid system, which means that the topology structure of the transmitting and receiving ends of the power grid system is established according to the actual node distribution information of the power grid system.
6. The system of claim 4, wherein the algorithm employed by the data computation unit to determine the decision variables in the objective function is a mixed integer linear programming algorithm.
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