A tie line planning method based on regional power grid equivalent

Abstract

The present invention belongs to the technical field of operation of power systems, and in particular to a method for planning interconnection lines based on the equivalent of regional power grids. First, the maximum and minimum values ​​of the power of the regional power grid ports are optimized and obtained, and then the interval composed of the minimum and maximum values ​​is evenly divided, and the regional power grid is dispatched for power generation at each segmentation point to obtain an equivalent model of the regional power grid, and the multi-regional interconnected power grid is optimized and analyzed to obtain the interconnection line plan of the multi-regional power grid. The advantage of the present invention is that the models of each region are equivalently compressed and sent to the superior dispatching center, avoiding the global optimization of large-scale interconnected power grids, and effectively improving the efficiency of solving the interconnection line plan under the premise of independent decision-making on power generation plans within each region. The present invention can be applied to the customization of interconnection line plans for multi-regional interconnected power grids.

Description

Technical Field

[0001] The invention belongs to the technical field of operation of electric power systems, and in particular relates to a tie line planning method based on regional power grid equivalence. Background Art

[0002] There are two difficulties in formulating the interconnection line plan for multi-regional large-scale interconnected power grids.

[0003] On the one hand, in large-scale interconnected power systems, the upper dispatch center generally needs the power generation and consumption information of the entire network when formulating the interconnection line plan between various regions. Under the premise of ensuring the safe operation within and between regional power grids, the interconnection line plan is optimized with the optimal cost as the goal. However, in the actual operation process, each regional power grid has its own independent dispatch center, that is, the lower dispatch center. The power components such as generators of the regional power grid are controlled by the lower dispatch center rather than the upper dispatch center. In addition, considering the privacy issues within the regional power grid, the upper dispatch center cannot know the power generation and consumption information of the entire network, let alone control the power components within the regional power grid, which makes it difficult to formulate the interconnection line plan in the multi-regional interconnected power grid.

[0004] On the other hand, due to the large scale of multi-regional interconnected power grids, if the entire large power grid is taken as the optimization object when formulating the interconnection line plan, the optimization problem will be too large and difficult to solve effectively in a short time. Furthermore, the inefficiency of the interconnection line plan decision will cause each regional power grid to be unable to obtain the information of externally exchanged power generation in a timely manner, affecting the decision-making efficiency of internal power generation scheduling. Therefore, for multi-regional large-scale interconnected power grids, it is still a major problem to efficiently formulate interconnection line plans while ensuring the independent operation of each region. Summary of the invention

[0005] The purpose of the present invention is to propose a method for interconnection line planning based on regional power grid equivalence. First, the maximum and minimum allowed power generation powers of the power grid gateways of each region are optimized, and then a function curve of the power generation cost of the regional power grid and the power of different gateways is established. Then, the power generation plan of each regional interconnection line is optimized with the minimum power generation cost of the whole network as the goal. This method avoids the global optimization of multi-regional interconnected power grids and effectively improves the efficiency of solving the interconnection line plan under the premise of independent decision-making on power generation plans within each region.

[0006] The interconnection line planning method based on regional power grid equivalent proposed in the present invention first optimizes and obtains the maximum and minimum values ​​of the regional power grid port power, then divides the interval composed of the minimum and maximum values ​​into equal parts, performs power generation dispatching on the regional power grid at each segment point, obtains the equivalent model of the regional power grid, optimizes and analyzes the multi-regional interconnected power grid, and obtains the interconnection line plan of the multi-regional power grid.

[0007] The tie line planning method based on regional power grid equivalence proposed by the present invention has the following characteristics and advantages:

[0008] The present invention firstly takes the gateway of the regional power grid, that is, the set of all tie lines connected to the regional power grid, as the analysis object, takes the maximum and minimum values ​​of the gateway power as the optimization target, considers the safety operation constraints within the regional power grid, and optimizes and solves to obtain the minimum and maximum values ​​of the gateway power of each region. Then, the obtained gateway power "minimum value-maximum value" interval is divided equally, and each equally divided point is used as the boundary condition of the regional power grid for optimization scheduling, and the minimum fuel cost is solved, and then the function of the fuel cost with respect to different gateway powers is obtained, that is, the equivalent model of the regional power grid. Finally, the equivalent model is sent to the dispatching center of the multi-regional interconnected power grid, and the superior dispatching center takes the total power generation balance of the whole network as the constraint and the minimum total fuel cost of the whole network as the goal for optimization scheduling, obtains the planned value of the gateway power of each region, and distributes the planned value to each tie line, thereby realizing the tie line plan of the multi-regional interconnected power grid. The advantage of the present invention is that the model of each region is equivalently compressed and sent to the superior dispatching center, avoiding the global optimization of the large-scale interconnected power grid, and effectively improving the efficiency of solving the tie line plan under the premise of independent decision-making on the power generation plan within each region. The present invention can be applied to the customization of tie line plans of multi-region interconnected power grids. DETAILED DESCRIPTION

[0009] The method for planning a tie line based on regional power grid equivalents proposed by the present invention comprises the following steps: firstly, optimizing and obtaining the maximum and minimum values ​​of the power of the regional power grid ports, then evenly dividing the interval composed of the minimum and maximum values, performing power generation dispatching on the regional power grid at each segment point, obtaining an equivalent model of the regional power grid, optimizing and analyzing the multi-regional interconnected power grid, and obtaining a tie line plan for the multi-regional power grid.

[0010] The above-mentioned tie line planning method based on regional power grid equivalent specifically comprises the following steps:

[0011] (1) Establish an equivalent model of the regional power grid. The specific steps are as follows:

[0012] (1-1) An optimization model for solving the minimum power of regional power grid interface is established. The optimization model includes the objective function and the security constraints of the regional power grid. The specific method is as follows:

[0013] (1-1-1) The objective function is to minimize the regional power grid interface power, which is expressed as follows:

[0014]

[0015] Where T and A represent the number of dispatching periods and regional power grids, t and i represent the numbers of dispatching periods and regional power grids, respectively.i,t represents the gateway power of the ith regional power grid during period t, represents the minimum value of the power of the ith regional power grid at time t obtained by optimization, It is the symbol for "arbitrary" in mathematics;

[0016] (1-1-2) The constraints are the security constraints of the regional power grid, including:

[0017] (1-1-2-1) Regional power grid power balance constraint, the expression is as follows:

[0018]

[0019] in, and They represent the number of thermal power units, wind farms and loads in the i-th regional power grid, j, n and m represent the numbers of thermal power units, wind farms and loads, respectively. represents the planned output of the jth thermal power unit in the i-th regional power grid during the t-dispatching period, represents the predicted power generation of the nth wind farm in the i-th regional power grid, represents the power consumption of the mth load in the i-th regional power grid;

[0020] (1-1-2-2) Output of thermal power units in regional power grid The upper and lower bound constraints are as follows:

[0021]

[0022] in, and are the upper and lower limits of the power generation output of thermal power unit j in the i-th regional power grid;

[0023] (1-1-2-3) Regional power grid reserve constraint, the expression is as follows:

[0024]

[0025]

[0026]

[0027]

[0028] in, and They represent the positive reserve capacity and negative reserve capacity of the j-th thermal power unit in the i-th regional power grid during the t-th scheduling period, respectively. min{·} represents the minimum value of the elements in the set. and They represent the upward and downward climbing rates of the jth thermal power unit in the i-th regional power grid in unit time, ΔT represents the duration of a scheduling period, and are the minimum positive reserve demand and negative reserve demand of the ith regional power grid in the t dispatch period, respectively;

[0029] (1-1-2-4) Regional power grid line flow constraints, expressed as follows:

[0030]

[0031] in, is the transfer distribution factor of the gateway power of the lth line in the regional power grid i, G l,j,i is the transfer distribution factor of the active output of the jth thermal power generating unit from the lth line in the regional power grid i, G l,m,i is the active output transfer distribution factor of the lth line in regional power grid i to the mth renewable energy power station, G l,n,i is the transfer distribution factor of the lth line in the regional power grid i to the nth load. The above transfer distribution factors are obtained from the power grid dispatching center. i,l is the upper limit of active power on the lth line in regional power grid i;

[0032] (1-1-2-5) The interior point method is used to solve the optimization problem composed of the above formulas (1)-(8) to obtain the minimum value of the power of the i-th regional power grid at time t:

[0033] (1-2) An optimization model for solving the maximum power of regional power grid interface is established. The optimization model includes the objective function and the security constraints of the regional power grid:

[0034] (1-2-1) The objective function of the optimization model is to maximize the regional power grid interface power, which is expressed as follows:

[0035]

[0036] It represents the maximum value of the power of the ith regional power grid at time t obtained by optimization.

[0037] (1-2-2) The constraints are the security constraints of the regional power grid, including: the above formula (1)–formula (8);

[0038] (1-2-3) The interior point method is used to solve the optimization problem composed of formula (2)-formula (9) to obtain the maximum value of the power of the i-th regional power grid at time t:

[0039] (1-3) Repeat steps (1-1) and (1-2) to obtain the minimum gateway power of all regional power grids in the power grid and maximum threshold power

[0040] (1-4) All regional power grids are processed, that is, the minimum value and maximum value The intervals composed of the grid are evenly divided, and the power generation of the regional grid is dispatched at each segment point to obtain the equivalent model of the regional grid, which specifically includes:

[0041] (1-4-1) The minimum value of all regional power grids and maximum value The interval composed of M is evenly divided into i,t Equal parts, M i,t Set by the dispatcher, M i,t Greater than or equal to the number of thermal power units in regional grid i The interval between each equal portion of the gateway power in the i-th regional power grid at time t is Δq i,t , the expression is as follows:

[0042]

[0043] According to formula (10), the vector of the equally divided power of the electrical gateway port in the i-th region at time t is obtained: By M i,t +1 element, vector The kth element in is:

[0044]

[0045] in, Representation vector The kth element of i,t +1;

[0046] (1-4-2) For all regional power grids, establish a gateway power of The optimization model for power generation dispatching of regional power grids includes objective function and constraint conditions. The specific method is as follows:

[0047] (1-4-2-1) The regional power grid has a power of When , the objective function of the optimization model of power generation dispatch is:

[0048]

[0049] Among them, a j,i , b j,i and c j,iare the quadratic coefficient, linear coefficient and constant term of the fuel cost of the j-th thermal power unit in the i-th regional power grid, respectively. i,t,k It means that the i-th regional power grid is at time t and the threshold power is The minimum fuel cost of the thermal power unit is represents the planned output of the jth thermal power unit in the i-th regional power grid during the t-dispatching period;

[0050] (1-4-2-2) The regional power grid has a power of The constraints of the optimization model of power generation scheduling are:

[0051] The constraints include the regional power grid operation safety constraint formulas (2)-(8) and the boundary condition constraint formula (13):

[0052]

[0053] Using the interior point method, the power generation dispatch optimization model composed of formulas (2)-(8) and formulas (12) and (13) is solved, and the power at the threshold is obtained. The i-th regional power grid at time t and the threshold power is The minimum fuel cost c of the thermal power unit i,t,k The value of

[0054] (1-4-3) Establish equivalent models of all regional power grids respectively, including the following steps:

[0055] For each of the above steps (1-4-1) Repeat steps (1-4-2-1) and (1-4-2-2) to obtain each The corresponding minimum fuel cost c of the thermal power unit i,t,k The value of c i,t,k ,by is the independent variable, c i,t,k As the dependent variable, all points Connecting them into a line constitutes a piecewise linear function of the fuel cost of regional power grid i with respect to the threshold power. This piecewise linear function is the equivalent model of the regional power grid, (k=1,2,...,M i,t +1);

[0056] (2) According to the equivalent model of the regional power grid obtained in step (1), a multi-regional interconnected power grid optimization model is established to obtain a tie line plan for the multi-regional power grid, including the following steps:

[0057] (2-1) The objective function expression of the multi-regional interconnected power grid optimization model is:

[0058]

[0059] Among them, λ i,t,k It is an auxiliary optimization variable, indicating whether the power generation cost of regional power grid i at time t in the multi-regional interconnected power grid is equal to the threshold power value. If relevant, then record λ i,t,k If the value of is greater than 0, if it is irrelevant, then record λ i,t,k The value of is equal to 0;

[0060] (2-2) Constraints for establishing the optimization model of multi-regional interconnected power grids include:

[0061] (2-2-1) The actual power constraint of the regional power gateway is as follows:

[0062]

[0063] in, represents the planned value of the power at the regional power grid i at time t;

[0064] (2-2-1) Optimize the auxiliary variable constraints, the expression is as follows:

[0065]

[0066]

[0067]

[0068] Among them, z i,t,k Indicates whether the gateway power of regional power grid i at time t in the multi-regional interconnected power grid is equal to If relevant, record z i,t,k The value of is equal to 1. If it is not relevant, then z i,t,k The value of is equal to 0, ∈ indicates that an element belongs to a certain set;

[0069] (2-3) The branch and bound method is used to solve the multi-regional interconnected power grid optimization model composed of formula (15)-formula (18), and we get Will As the gateway power of the i-th regional power grid in the t-th scheduling period, since the gateway of the regional power grid is usually composed of multiple interconnection lines, the gateway power Evenly distribute it to each tie line to obtain the planned value of the tie line power of the multi-regional interconnected power grid, and realize the customization of the tie line plan based on the equivalent value of the regional power grid.

Claims

1. A tie line planning method based on regional power grid equivalence, characterized in that: Firstly, the maximum and minimum values ​​of the power of the regional power grid interface are optimized, and then the interval composed of the minimum and maximum values ​​is evenly divided. At each segment point, the regional power grid is dispatched for power generation to obtain the equivalent model of the regional power grid. The multi-regional interconnected power grid is optimized and analyzed to obtain the interconnection line plan of the multi-regional power grid. (1) Establish an equivalent model of the regional power grid. The specific steps are as follows: (1-1) An optimization model for solving the minimum power of regional power grid interface is established. The optimization model includes the objective function and the security constraints of the regional power grid. The specific method is as follows: (1-1-1) The objective function is to minimize the regional power grid interface power, which is expressed as follows: Where T and A represent the number of dispatching periods and regional power grids, t and i represent the numbers of dispatching periods and regional power grids, respectively. i,t represents the gateway power of the ith regional power grid during period t, represents the minimum value of the power of the ith regional power grid at time t obtained by optimization, It is the symbol for "arbitrary" in mathematics; (1-2) An optimization model for solving the maximum power of regional power grid interface is established. The optimization model includes the objective function and the security constraints of the regional power grid: (1-2-1) The objective function of the optimization model is to maximize the regional power grid interface power, which is expressed as follows: represents the maximum value of the power of the ith regional power grid at time t obtained by optimization; (1-4) All regional power grids are processed, that is, the minimum value and maximum value The interval composed of the grid is evenly divided into two parts, and the power generation of the regional grid is dispatched at each segment point to obtain the equivalent model of the regional grid.

2. A method for planning a tie line based on regional power grid equivalence according to claim 1, characterized in that: The following steps are involved: (1-1-2) An optimization model for solving the minimum power of regional power grid gateways is established, in which the constraints are the security constraints of the regional power grid, including: (1-1-2-1) Regional power grid power balance constraint, the expression is as follows: in, and They represent the number of thermal power units, wind farms and loads in the i-th regional power grid, j, n and m represent the numbers of thermal power units, wind farms and loads, respectively. represents the planned output of the jth thermal power unit in the i-th regional power grid during the t-dispatching period, represents the predicted power generation of the nth wind farm in the i-th regional power grid, represents the power consumption of the mth load in the i-th regional power grid; (1-1-2-2) Output of thermal power units in regional power grid The upper and lower bound constraints are as follows: Among them, P j,i and are the upper and lower limits of the power generation output of thermal power unit j in the i-th regional power grid; (1-1-2-3) Regional power grid reserve constraint, the expression is as follows: in, and They represent the positive reserve capacity and negative reserve capacity of the j-th thermal power unit in the i-th regional power grid during the t-th scheduling period, respectively. min{·} represents the minimum value of the elements in the set. and They represent the upward and downward climbing rates of the jth thermal power unit in the i-th regional power grid in unit time, ΔT represents the duration of a scheduling period, and are the minimum positive reserve demand and negative reserve demand of the ith regional power grid in the t dispatch period, respectively; (1-1-2-4) Regional power grid line flow constraints, expressed as follows: in, is the transfer distribution factor of the gateway power of the lth line in the regional power grid i, G l,j,i is the transfer distribution factor of the active output of the jth thermal power generating unit from the lth line in the regional power grid i, G l,m,i is the active output transfer distribution factor of the lth line in regional power grid i to the mth renewable energy power station, G l,n,i is the transfer distribution factor of the lth line in the regional power grid i to the nth load. The above transfer distribution factors are obtained from the power grid dispatching center. i,l is the upper limit of active power on the lth line in regional power grid i; (1-1-2-5) The interior point method is used to solve the optimization problem composed of the above formulas (1)-(8) to obtain the minimum value of the power of the i-th regional power grid at time t: (1-2-2) An optimization model for solving the maximum power of a regional power grid gateway is established, in which the constraints are the security constraints of the regional power grid, including: the above formula (1)-formula (8); (1-2-3) The interior point method is used to solve the optimization problem composed of formula (2)-formula (9) to obtain the maximum value of the power of the i-th regional power grid at time t: (1-3) Repeat steps (1-1) and (1-2) to obtain the minimum gateway power of all regional power grids in the power grid and maximum threshold power (1-4) Specifically include: (1-4-1) The minimum value of all regional power grids and maximum value The interval composed of M is evenly divided into i,t Equal parts, M i,t Set by the dispatcher, M i,t Greater than or equal to the number of thermal power units in regional grid i The interval between each equal portion of the gateway power in the i-th regional power grid at time t is Δq i,t , the expression is as follows: According to formula (10), the vector of the equally divided power of the electrical gateway port in the i-th region at time t is obtained: By M i,t +1 element, vector The kth element in is: in, Representation vector The kth element of i,t +1; (1-4-2) For all regional power grids, establish a gateway power of The optimization model for power generation dispatching of regional power grids includes objective function and constraint conditions. The specific method is as follows: (1-4-2-1) The regional power grid has a power of When , the objective function of the optimization model of power generation dispatch is: Among them, a j,i , b j,i and c j,i are the quadratic coefficient, linear coefficient and constant term of the fuel cost of the j-th thermal power unit in the i-th regional power grid, respectively. i,t,k It means that the i-th regional power grid is at time t and the threshold power is The minimum fuel cost of the thermal power unit is represents the planned output of the jth thermal power unit in the i-th regional power grid during the t-dispatching period; (1-4-2-2) The regional power grid has a power of The constraints of the optimization model of power generation scheduling are: The constraints include the regional power grid operation safety constraint formulas (2)-(8) and the boundary condition constraint formula (13): Using the interior point method, the power generation dispatch optimization model composed of formulas (2)-(8) and formulas (12) and (13) is solved, and the power at the threshold is obtained. The i-th regional power grid at time t and the threshold power is The minimum fuel cost c of the thermal power unit i,t,k The value of (1-4-3) Establish equivalent models of all regional power grids respectively, including the following steps: For each of the above steps (1-4-1) Repeat steps (1-4-2-1) and (1-4-2-2) to obtain each The corresponding minimum fuel cost c of the thermal power unit i,t,k The value of c i,t,k ,by is the independent variable, c i,t,k As the dependent variable, all points Connecting them into a line constitutes a piecewise linear function of the fuel cost of regional power grid i with respect to the threshold power. This piecewise linear function is the equivalent model of the regional power grid, (k=1,2,...,M i,t +1); (2) According to the equivalent model of the regional power grid obtained in step (1), a multi-regional interconnected power grid optimization model is established to obtain a tie line plan for the multi-regional power grid, including the following steps: (2-1) The objective function expression of the multi-regional interconnected power grid optimization model is: Among them, λ i,t,k It is an auxiliary optimization variable, indicating whether the power generation cost of regional power grid i at time t in the multi-regional interconnected power grid is equal to the threshold power value. If relevant, then record λ i,t,k If the value of is greater than 0, if it is irrelevant, then record λ i,t,k The value of is equal to 0; (2-2) Constraints for establishing the optimization model of multi-regional interconnected power grids include: (2-2-1) The actual power constraint of the regional power gateway is as follows: in, represents the planned value of the power at the regional power grid i at time t; (2-2-1) Optimize the auxiliary variable constraints, the expression is as follows: Among them, z i,t,k Indicates whether the gateway power of regional power grid i at time t in the multi-regional interconnected power grid is equal to If relevant, record z i,t,k The value of is equal to 1. If it is not relevant, then z i,t,k The value of is equal to 0, ∈ indicates that an element belongs to a certain set; (2-3) The branch and bound method is used to solve the multi-regional interconnected power grid optimization model composed of formula (15)-formula (18), and we get Will As the gateway power of the i-th regional power grid in the t-th scheduling period, the gateway power Evenly distribute it to each tie line to obtain the planned value of the tie line power of the multi-regional interconnected power grid, and realize the customization of the tie line plan based on the equivalent value of the regional power grid.

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