CN112348343A - Uncertainty-considered multi-energy flow distribution network operation cost evaluation method - Google Patents
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Abstract
The invention discloses a method for evaluating the running cost of a multi-energy flow distribution power grid by considering uncertainty, belongs to the field of power distribution networks, and aims to solve the problem that the running cost of the power distribution network is not accurately evaluated by adopting the conventional model, and adopts the following technical scheme: a multi-energy flow distribution network operation cost assessment method considering uncertainty comprises the following steps: step 1, modeling a multi-energy flow distribution grid: establishing a natural gas network model; establishing a thermodynamic network model; establishing a power network model; and 2, evaluating the expected cost of the multi-energy flow distribution network by using a 2m +1 point estimation method. The method aims to evaluate the operation cost of the multi-energy flow distribution power grid, models the user behavior uncertainty, the renewable energy power generation uncertainty and the load uncertainty by adopting a 2m +1 point estimation method, decouples a multi-energy flow system, and solves the operation cost of each subsystem respectively, so that the operation cost of the multi-energy flow distribution power grid is obtained.
Description
Technical Field
The invention belongs to the field of power distribution networks, and particularly relates to a method for evaluating the operation cost of a multi-energy flow distribution network by considering uncertainty.
Background
With the increase of various energy consumption, the traditional independent network energy supply mode gradually changes into a multi-energy flow system with multiple energy sources supplying energy simultaneously. The system couples multiple energy sources together through the energy conversion equipment, and the energy utilization rate of the system is improved. Uncertainties in the system, such as load uncertainties, renewable power generation uncertainties, and energy price uncertainties, will all have an impact on system operation. In past studies, the uncertainty in the system was usually treated as a deterministic problem, but this approach did not take into account the effect of uncertainty on the system.
Some researches also consider uncertainty, but mainly model uncertainty of renewable energy power generation in the system, and lack of consideration of uncertainty of user behaviors existing in the system, so that cost estimation is not accurate.
Disclosure of Invention
Aiming at the problem that the operation cost of the power distribution network is not accurately evaluated by adopting the existing model, the invention provides the operation cost evaluation method of the multi-energy distribution network considering uncertainty, aiming at evaluating the operation cost of the multi-energy distribution network, modeling the user behavior uncertainty, the renewable energy power generation uncertainty and the load uncertainty by adopting a 2m +1 point estimation method, decoupling the multi-energy distribution network, and respectively solving the operation cost of each subsystem, thereby obtaining the operation cost of the multi-energy distribution network.
The technical scheme adopted by the invention is as follows: a multi-energy flow distribution network operation cost assessment method considering uncertainty comprises the following steps:
step 1, modeling a multi-energy flow distribution grid:
step 1.1, storing and conveying natural gas to users through pipelines and pressure stations, and accordingly building a natural gas network model;
step 1.2, the heat supply network is composed of insulated pipelines arranged between a heat generator (such as a gas boiler and the like) and a user, and heat is transmitted to the user through hot water or steam, so that a thermodynamic network model is established;
step 1.3, considering the coupling and uncertainty between preparations, establishing a power network model;
and 2, considering the user behaviors, various loads and uncertainty of renewable energy sources in the model established in the step 1, and evaluating the expected cost of the multi-energy distribution network by using a 2m +1 point estimation method.
The method aims to evaluate the operation cost of the multi-energy flow distribution power grid, models the user behavior uncertainty, the renewable energy power generation uncertainty and the load uncertainty by adopting a 2m +1 point estimation method, decouples a multi-energy flow system, and solves the operation cost of each subsystem respectively, so that the operation cost of the multi-energy flow distribution power grid is obtained.
Further, in the natural gas network model established in step 1.1,
gas flow f per pipegkAs follows:
in the formula: f. ofgkIs the flow rate of gas in the pipeline, m3/h;sign(fgk) Is a tracheal pressure sign function;for pipeline grade correction, kPa2;Hg、HkRespectively the height of the pipeline, m; pg、PkGas pressure, kPa, at node g and node k, respectively;is the average temperature of the gas in the pipeline, K; g is the acceleration of gravity, m/s2;Is the average pressure of the pipeline, kPa; cgkIs the pipe constant between node g and node k; t is0Is the reference temperature, K;is the diameter of the pipeline between the nodes g and K, mm; zaIs the gas compression factor at average temperature; l isgkThe length of the pipeline between the node g and the node k is mm; epIs qiAbsolute roughness of the pipe, mm; gamma rayGIs the specific gravity of gas and has no dimension;the friction coefficient of the air pipe is dimensionless and can be calculated according to a Kerbulke equation:
if the flow moves from node g to node k, fgkIs positive and vice versa. Therefore, if fgkIf > 0, sign (f)gk) Is +1, otherwise-1.
Since the natural gas/electricity consuming compressor is used to maintain the pressure of the gas stream, various parameters of the compressor are defined:
in the formula: horsepower of compressorMatching;is compressor efficiency, dimensionless;the pressure of the input gas and the pressure of the output gas of the compressor are respectively kPa; lambda [ alpha ]GThe specific heat rate of natural gas is dimensionless;is the ratio of the pressures of the compressor output and input gases, dimensionless; p0Base pressure, kPa;
in the formula (I), the compound is shown in the specification,is the consumption coefficient of the compressor, and has no dimension;is the gas consumption of the gas compressor, m3/h;
Gas consumption f of gas generator in electric power sub-networkGGThe calculation is as follows:
in the formula: f. ofGGFor gas consumption of gas-fired generator, m3/h;agen、bgen、cgen、dgen、egenThe consumption coefficient of the gas generator is dimensionless;generating capacity of a gas generator, kWH;the minimum generated energy of the gas generator, kWH; GHV is natural gas heat value, kW.h/m3;
The gas consumption of the combined heat and power plant (CHP) is:
in the formula:for CHP gas consumption, m3/h;Is the efficiency of CHP, dimensionless; the coefficient 3.412 is used to convert W units to BTU/h units;active power of CHP, kW;is the heat production power of CHP, kW.
The gas flow analysis of the natural gas network must satisfy the natural gas balance of each node, and the formula is as follows:
in the formula:is the flow rate of gas injected at node g, m3/h;Is the gas demand at node g, m3H, associated with gas load uncertainty; f. ofGGFor gas consumption of gas-fired generator, m3/h;Is the gas consumption of the gas compressor, m3/h;Is the gas consumption of the gas boiler, m3/h;fgkIs the gas flow of the pipe between node g and node k, m3H; where gas boiler and CHP are considered grid loads, there is a demand side response uncertainty.
Further, in the thermodynamic network model of step 1.2, the flow rate Φ of each pipe ishbAnd the temperature at the end of each node is calculated by the following equation:
in the formula: flow rate phi of heat pipehb,m3/h;cpIs the specific heat capacity of water, J/(Kg ℃ C.);the mass flow of the pipeline between the node h and the node b is kg/h;is the length of the heat pipeline, mm; u is the heat conduction coefficient, W/m.K; t isgIs ambient temperature, K; t isstart,hThe hot water inflow temperature at node h, K; t isend,bThe hot water outflow temperature at node b, K.
The pressure loss in each thermal pipe due to friction was calculated by the Darcy-Weisbach equation
In the formula: pressure lossPa;The resistance coefficient of the heat pipeline is dimensionless; g is the acceleration of gravity, m/s2;ρWKg/m3 for water density;is the diameter of the heat pipeline, mm;is a symbolic function of the flow of the heat pipeline, and is dimensionless;the coefficient of friction of the heat pipeline is dimensionless.
In a heat supply network, four flow balance equations, namely a thermal power balance equation, a loop pressure drop equation, a water supply and return water temperature balance equation, must be satisfied;
the node thermal power balance in the hydraulic analysis is described as:
in the formula:the mass flow of hot water generated by the CHP at the node h and the gas boiler is kg/h after uncertainty is considered; phih,loadIs the thermal load power at node h, kW; t isstart,hThe hot water inflow temperature, K, is taken out of the node h; t isend,loadThe hot water outflow temperature at the thermal load, K; nh is the number of heat network nodes;
the loop pressure drop equation is:
in the formula, delta is the set of all pipelines in the loop; Δ hjThe pressure drop in the first and last sections of the pipeline j in the loop.
For the thermodynamic analysis of the heat network, a water supply and return temperature balance must be established for all nodes except the slack nodes:
in the formula: t isstart,CHP、Tstart,BoilerCHP and gas boiler outflow temperature, K, respectively;the heat load mass flow of the node h is kg/h; t isstart、TendThe temperature of the water flow at the head end and the tail end of the pipeline is K;
the temperature at the mixed heat node is defined as:
in the formula (I), the compound is shown in the specification,the flow rates of the water flows flowing in and out of the mixing heat node are kg/s respectively; t isin、ToutThe temperature of the incoming and outgoing water streams at the mixing hot node, K, respectively. It can be seen that the water flow temperature of each pipeline is different before mixing, and the water flow temperature flowing into other pipelines from the node is the same after mixing.
In a heating network, a heat pump is used to circulate hot water from a heat source to a user (heat load), and the power consumption of the heat pump can be calculated as follows:
in the formula:the power consumption of the heat pump is kW;the mass flow of water is kg/h; hPIs the heat pump lift, m; etaHPIs pump efficiency, dimensionless; g is the acceleration of gravity, m/s2;
The relationship between the gas consumption and the heat production of the gas boiler is as follows:
in the formula (I), the compound is shown in the specification,is the gas consumption of the gas boiler, m3/h;kW is the heat production of the gas boiler;is the largest of gas-fired boilersHeat production, kW; a isboil、bboilAre respectively the polynomial coefficients of the gas boiler and have no dimension.
Further, in the power network model of step 1.3, an active power and reactive power balance equation is established for each node:
in the formula:represents the power, kW, transmitted on the line between node i and node j; vi、VjThe amplitudes of the node i and the node j are respectively kV; y isijIs the line admittance, S; n is a radical ofEThe number of the power grid nodes is one;active power and reactive power, kW, of the CHP at the node i are respectively obtained; pi gen、Active power and reactive power, kW, of the generator at the node i are respectively obtained;active power and reactive power requirements at node i, kW, respectively; pi Pump、Pi compThe electric energy consumed by the heat pump and the compressor at the node i is kW;reactive power, kW, injected by a parallel capacitor at a node i;respectively for wind-powered electricity generation and photovoltaic power generation, kW, that have the uncertainty of generating electricity.
Further, the 2m +1 point estimation method adopted in the step 2 is carried out according to the following steps:
step 2.1, reading the multi-energy flow distribution power grid data in the multi-energy flow distribution power grid modeling, wherein the read data comprises user behaviors, renewable resources and various loads;
2.2, inputting uncertain input random variables into the multi-energy flow distribution network model, as shown in a formula (26);
step 2.3, calculating the skewness of the input random variable according to the formula (29);
step 2.4, calculating a standard position according to the result of the step 2.3 of the formula (28);
step 2.5, calculating a concentration position and a weight factor according to the formula (27) and the formula (30);
step 2.6, placing the load demand and the power generation power of the renewable energy source at corresponding centralized positions, and meanwhile, fixing other input random variables at the average value or the prediction point to calculate the operation cost, as shown in a formula (31) and a formula (32);
step 2.7, decomposing the power flow by adopting a pure embedding method in the power network model according to the formulas (24) to (25);
step 2.8, updating the gas consumption of the gas generator according to the formula (10);
step 2.9, decomposing thermodynamic flow in the established thermodynamic network model by adopting a graph theory method according to the formula (13) -formula (23);
step 2.10, respectively updating the gas consumption of the gas boiler, the gas consumption of the CHP and the power consumption of the heat pump according to the formula (23), the formula (11) and the formula (22);
step 2.11, decomposing the natural gas flow in the established natural gas network model according to the formula (1) to the formula (12);
step 2.12, updating the power consumption of the electric compressor according to the formula (8); if the calculation is converged, executing the step 2.13, and if the calculation is not converged, returning to the step 2.7;
and 2.13, judging whether random variables exist, if no random variable exists, ending, and if the random variables exist, executing the step 2.2, namely inputting the uncertain input random variables.
In step 2.2, the PES input random variable S is a variable Z containing m uncertain input variablesdI.e.:
S=F(z1,z2,...,zd,...,zm) (26)
in the invention, a PES (polyether sulfone) calculates statistical information of the operation cost of a multi-energy flow distribution network by converting an uncertainty problem with m input random variables into a 2m +1 equivalent certainty problem, wherein the m random variables comprise uncertainty of electricity, gas and heat loads, uncertainty of renewable energy power generation and uncertainty of user behavior;
each random variable consists of three centralized positions Zd,pP ═ 1, 2, 3 and the weighting factor ωd,pComposition, weight factor omegad,pDetermining the influence of the corresponding position on the total expected operation cost of the multi-energy flow distribution network;
standard position in step 2.4 isRandom variable skewness input from step 2.3Andand calculating to obtain:
concentration position Z in step 2.5d,pThe following requirements are met:
step 2.6, for each centralized position, calculating the operation cost of the multi-energy distribution network based on each sub-network as follows:
the expected operation cost of the multi-energy flow distribution grid considering the uncertainty of user behaviors, loads and renewable energy sources is as follows:
the invention has the following beneficial effects: the method aims to evaluate the operation cost of the multi-energy flow distribution power grid, models the user behavior uncertainty, the renewable energy power generation uncertainty and the load uncertainty by adopting a 2m +1 point estimation method, decouples a multi-energy flow system, and solves the operation cost of each subsystem respectively, so that the operation cost of the multi-energy flow distribution power grid is obtained.
Drawings
FIG. 1 is a flow chart of step 2 of the present invention.
Detailed Description
The technical solutions of the embodiments of the present invention are explained and explained below with reference to the drawings of the present invention, but the following embodiments are only preferred embodiments of the present invention, and not all embodiments. Based on the embodiments in the implementation, other embodiments obtained by those skilled in the art without any creative effort belong to the protection scope of the present invention.
The uncertainty-considered operation cost evaluation method for the multi-energy distribution network comprises the following steps:
step 1, modeling a multi-energy flow distribution grid:
in the natural gas network model established in step 1.1,
gas flow f per pipegkAs follows:
in the formula: f. ofgkIs the pipeline gas flow, cfm; sign (f)gk) Is a pipeline pressure sign function;for pipeline grade correction, kPa2;Hg、HkRespectively the height of the pipeline, m; pg、PkGas pressure, kPa, at node g and node k, respectively;is the average temperature of the gas in the pipeline, K;is the average pressure of the pipeline, kPa; cgkIs the pipe constant between node g and node k; t is0Is the reference temperature, K;is the diameter of the pipeline between the nodes g and K, mm; zaIs the gas compression factor at average temperature; l isgkThe length of the pipeline between the node g and the node k is mm; epIs the absolute roughness of the gas pipeline, mm; gamma rayGIs the specific gravity of gas and has no dimension;the friction coefficient of the gas pipeline can be calculated according to a Kerbuke equation:
if the flow moves from node g to node k, fgkIs positive and vice versa. Therefore, if fgkIf > 0, sign (f)gk) Is +1, otherwise-1.
Since the natural gas/electricity consuming compressor is used to maintain the pressure of the gas stream, various parameters of the compressor are defined:
in the formula: horsepower of compressorMatching;is compressor efficiency, dimensionless;the pressure of the input gas and the pressure of the output gas of the compressor are respectively kPa; lambda [ alpha ]GThe specific heat rate of natural gas is dimensionless;is the ratio of the pressures of the compressor output and input gases, dimensionless; p0Base pressure, kPa.
in the formula (I), the compound is shown in the specification,is the consumption coefficient of the compressor, and has no dimension;
gas consumption f of gas generator in electric power sub-networkGGThe calculation is as follows:
in the formula: f. ofGGFor gas consumption of gas-fired generator, m3/h;agen、bgen、cgen、dgen、egenThe consumption coefficient of the gas generator is dimensionless;generating capacity of a gas generator, kWH;the minimum generated energy of the gas generator, kWH; GHV is natural gas heat value, kW.h/m3;
The gas consumption of the combined heat and power plant (CHP) is:
in the formula:consumption of gas for CHP,m3/h;Is the efficiency of CHP, dimensionless; the coefficient 3.412 is used to convert W units to BTU/h units;active power of CHP, kW;is the heat production power of CHP, kW.
The gas flow analysis of the natural gas network must satisfy the natural gas balance of each node, and the formula is as follows:
in the formula:is the flow rate of gas injected at node g, m3/h;Is the gas demand at node g, m3H, associated with gas load uncertainty; f. ofGGFor gas consumption of gas-fired generator, m3/h;Is the gas consumption of the gas compressor, m3/h;Is the gas consumption of the gas boiler, m3/h;fgkIs the gas flow of the pipe between node g and node k, m3H; where gas boiler and CHP are considered grid loads, there is a demand side response uncertainty.
Step 1.2, the heat supply network is composed of insulated pipelines arranged between a heat generator (such as a gas boiler and the like) and a user, and heat is conveyed to the user through hot water or steam, so that a thermodynamic network model is established:
flow rate phi per pipehbAnd the temperature at the end of each node is calculated by the following equation:
in the formula: flow rate phi of heat pipehb,m3/h;cpIs the specific heat capacity of water, J/(Kg ℃ C.);the mass flow of the pipeline between the node h and the node b is kg/h;is the length of the heat pipeline, mm; u is the heat conduction coefficient, W/m.K; t isgIs ambient temperature, K; t isstart,hThe hot water inflow temperature at node h, K; t isend,bThe hot water outflow temperature at node b, K.
The pressure loss in each thermal pipe due to friction was calculated by the Darcy-Weisbach equation
In the formula: pressure lossPa;The resistance coefficient of the heat pipeline is dimensionless; g is the acceleration of gravity, m/s2;ρWKg/m3 for water density;is the diameter of the heat pipeline, mm;is a symbolic function of the flow of the heat pipeline, and is dimensionless;the coefficient of friction of the heat pipeline is dimensionless.
In a heat supply network, four flow balance equations, namely a thermal power balance equation, a loop pressure drop equation, a water supply and return water temperature balance equation, must be satisfied;
the node thermal power balance in the hydraulic analysis is described as:
in the formula:the mass flow of hot water generated by the CHP at the node h and the gas boiler is kg/h after uncertainty is considered; phih,loadIs the thermal load power at node h, kW; t isstart,hThe hot water inflow temperature, K, is taken out of the node h; t isend,loadThe hot water outflow temperature at the thermal load, K; nh is the number of heat network nodes;
the loop pressure drop equation is:
in the formula, delta is the set of all pipelines in the loop; Δ hjThe pressure drop in the first and last sections of the pipeline j in the loop.
For the thermodynamic analysis of the heat network, a water supply and return temperature balance must be established for all nodes except the slack nodes:
in the formula: t isstart,CHP、Tstart,BoilerCHP and gas boiler outflow temperature, K, respectively;the heat load mass flow of the node h is kg/h; t isstart、TendRespectively the water flow temperature at the head end and the tail end of the pipeline, K;
the temperature at the mixed heat node is defined as:
in the formula (I), the compound is shown in the specification,the flow rates of the water flows flowing in and out of the mixing heat node are kg/s respectively; t isin、ToutThe temperature of the incoming and outgoing water streams at the mixing hot node, K, respectively. It can be seen that the water flow temperature of each pipeline is different before mixing, and the water flow temperature flowing into other pipelines from the node is the same after mixing.
In a heating network, a heat pump is used to circulate hot water from a heat source to a user (heat load), and the power consumption of the heat pump can be calculated as follows:
in the formula:the power consumption of the heat pump is kW;the mass flow of water is kg/h; hPIs the heat pump lift, m; etaHPIs pump efficiency, dimensionless; g is the acceleration of gravity, m/s2;
The relationship between the gas consumption and the heat production of the gas boiler is as follows:
in the formula (I), the compound is shown in the specification,is the gas consumption of the gas boiler, m3/h;kW is the heat production of the gas boiler;the maximum heat production capacity of the gas boiler is kW; a isboil、bboilAre respectively the polynomial coefficients of the gas boiler and have no dimension.
Step 1.3, considering the coupling and uncertainty between preparations, establishing a power network model:
establishing an active power and reactive power balance equation for each node:
in the formula:represents the power, kW, transmitted on the line between node i and node j; vi、VjThe amplitudes of the node i and the node j are respectively kV; y isijIs the line admittance, S; n is a radical ofEThe number of the power grid nodes is one;active power and reactive power, kW, of the CHP at the node i are respectively obtained; pi gen、Active power and reactive power, kW, of the generator at the node i are respectively obtained;active power and reactive power requirements at node i, kW, respectively; pi Pump、Pi compThe electric energy consumed by the heat pump and the compressor at the node i is kW;reactive power, kW, injected by a parallel capacitor at a node i;respectively for wind-powered electricity generation and photovoltaic power generation, kW, that have the uncertainty of generating electricity.
Step 2, considering the uncertainty of the user behavior, various loads and renewable energy in the model established in the step 1, estimating the expected cost of the multi-energy distribution grid by using a 2m +1 point estimation method, and performing the following steps:
step 2.1, reading the multi-energy flow distribution power grid data in the multi-energy flow distribution power grid modeling, wherein the read data comprises user behaviors, renewable resources and various loads;
step 2.2, inputting uncertain input random variables into the multi-energy flow distribution network model; PES input random variable S is a variable Z containing m uncertain input variablesdI.e.:
S=F(z1,z2,...,zd,...,zm) (26)
in the invention, a PES (polyether sulfone) calculates statistical information of the operation cost of a multi-energy flow distribution network by converting an uncertainty problem with m input random variables into a 2m +1 equivalent certainty problem, wherein the m random variables comprise uncertainty of electricity, gas and heat loads, uncertainty of renewable energy power generation and uncertainty of user behavior;
each random variable consists of three centralized positions Zd,pP ═ 1, 2, 3 and the weighting factor ωd,pComposition, weight factor omegad,pDetermining the influence of the corresponding position on the total expected operation cost of the multi-energy flow distribution network;
and 2.3, calculating the skewness of the input random variable according to the formula (29):
step 2.4, Standard position isRandom variable skewness input from step 2.3Andand calculating to obtain:
step 2.5, the concentration location and the weight factor ω are calculated according to the equations (27) and (30)d,p(ii) a The following requirements are met:
respective weight factor omega for each concentration locationd,pThe calculation is as follows:
step 2.6, the load demand and the power generation power of the renewable energy source are placed at corresponding centralized positions, meanwhile, other input random variables are fixed at the average value or the prediction point of the load demand and the power generation power of the renewable energy source to calculate the operation cost, and for each centralized position, the operation cost of the multi-energy flow distribution network based on each sub-network is calculated as follows:
the expected operation cost of the multi-energy flow distribution grid considering the uncertainty of user behaviors, loads and renewable energy sources is as follows:
(32)
step 2.7, decomposing the power flow by adopting a pure embedding method in the power network model according to the formulas (24) to (25);
step 2.8, updating the gas consumption of the gas generator according to the formula (10);
step 2.9, decomposing thermodynamic flow in the established thermodynamic network model by adopting a graph theory method according to the formula (13) -formula (23);
step 2.10, respectively updating the gas consumption of the gas boiler, the gas consumption of the CHP and the power consumption of the heat pump according to the formula (23), the formula (11) and the formula (22);
step 2.11, decomposing the natural gas flow in the established natural gas network model according to the formula (1) to the formula (12);
step 2.12, updating the power consumption of the electric compressor according to the formula (8); if the calculation is converged, executing the step 2.13, and if the calculation is not converged, returning to the step 2.7;
and 2.13, judging whether random variables exist, if no random variable exists, ending, and if the random variables exist, executing the step 2.2, namely inputting the uncertain input random variables.
The method aims to evaluate the operation cost of the multi-energy flow distribution power grid, models the user behavior uncertainty, the renewable energy power generation uncertainty and the load uncertainty by adopting a 2m +1 point estimation method, decouples a multi-energy flow system, and solves the operation cost of each subsystem respectively, so that the operation cost of the multi-energy flow distribution power grid is obtained.
While the invention has been described with reference to specific embodiments, the scope of the invention is not limited thereto, and those skilled in the art will appreciate that the invention includes, but is not limited to, the accompanying drawings and the description of the embodiments above. Any modification which does not depart from the functional and structural principles of the present invention is intended to be included within the scope of the claims.
Claims (10)
1. A multi-energy flow distribution network operation cost assessment method considering uncertainty is characterized by comprising the following steps:
step 1, modeling a multi-energy flow distribution grid:
step 1.1, storing and conveying natural gas to users through pipelines and pressure stations, and accordingly building a natural gas network model;
step 1.2, the heat supply network consists of insulated pipelines arranged between the heat generator and the user, and heat is transmitted to the user through hot water or steam, so that a thermodynamic network model is established;
step 1.3, considering the coupling and uncertainty between preparations, establishing a power network model;
and 2, considering the user behaviors, various loads and uncertainty of renewable energy sources in the model established in the step 1, and evaluating the expected cost of the multi-energy distribution network by using a 2m +1 point estimation method.
2. The uncertainty-considered multi-energy distribution grid operation cost evaluation method according to claim 1, characterized in that, in the natural gas network model established in step 1.1,
gas flow f per pipegkAs follows:
in the formula: f. ofgkIs the flow rate of gas in the pipeline, m3/h;sign(fgk) Is a tracheal pressure sign function;for pipeline grade correction, kPa2;Hg、HkRespectively the height of the pipeline, m; pg、PkGas pressure, kPa, at node g and node k, respectively;is the average temperature of the gas in the pipeline, K; g is the acceleration of gravity, m/s2;Is the average pressure of the pipeline, kPa; cgkIs the pipe constant between node g and node k; t is0Is the reference temperature, K;is the diameter of the pipeline between the nodes g and K, mm; zaIs the gas compression factor at average temperature; l isgkThe length of the pipeline between the node g and the node k is mm; epIs the absolute roughness of the gas pipeline, mm; gamma rayGIs the specific gravity of gas and has no dimension;the friction coefficient of the air pipe is dimensionless and can be calculated according to a Kerbulke equation: :
if the flow moves from node g to node k, fgkIs positive and vice versa; therefore, if fgkIf > 0, sign (f)gk) Is +1, otherwise-1;
since the natural gas/electricity consuming compressor is used to maintain the pressure of the gas stream, various parameters of the compressor are defined:
in the formula: horsepower of compressorMatching;is compressor efficiency, dimensionless;the pressure of the input gas and the pressure of the output gas of the compressor are respectively kPa; lambda [ alpha ]GIs the specific heat rate of natural gas;is the ratio of the pressures of the compressor output and input gases; p0Base pressure, kPa;
in the formula (I), the compound is shown in the specification,is the consumption coefficient of the compressor;is the gas consumption of the gas compressor, m3/h;
Gas consumption f of gas generator in electric power sub-networkGGThe calculation is as follows:
in the formula: f. ofGGFor gas consumption of gas-fired generator, m3/h;agen、bgen、cgen、dgen、egenThe consumption coefficient of the gas generator is dimensionless;the power generation capacity of the gas generator is MWH;the minimum generated energy of the gas generator, MWH; GHV is natural gas heat value, kcal/m3;
The gas consumption of the combined heat and power plant (CHP) is:
in the formula:for CHP gas consumption, m3/h;Is the efficiency of CHP, dimensionless; the coefficient 3.412 is used to convert W units to BTU/h units;active power for CHP, MW;heat generation power for CHP, MW;
the gas flow analysis of the natural gas network must satisfy the natural gas balance of each node, and the formula is as follows:
in the formula:is the flow rate of gas injected at node g, m3/h;Is the gas demand at node g, m3H, associated with gas load uncertainty; f. ofGGFor gas consumption of gas-fired generator, m3/h;Is the gas consumption of the gas compressor, m3/h;Is the gas consumption of the gas boiler, m3/h;fgkIs the gas flow of the pipe between node g and node k, m3H; where gas boiler and CHP are considered grid loads, there is a demand side response uncertainty.
3. The uncertainty-aware multi-energy distribution grid operating cost assessment method according to claim 2, wherein in the thermodynamic network model of step 1.2, the flow rate Φ per pipe ishbAnd the temperature at the end of each node is calculated by the following equation:
in the formula: flow rate phi of heat pipehb,m3/h;cpIs the specific heat capacity of water, J/(Kg ℃ C.);the mass flow of the pipeline between the node h and the node b is kg/h;is the length of the heat pipeline, mm; u is the heat conduction coefficient, W/m.K; t isgIs ambient temperature, K; t isstart,hThe hot water inflow temperature at node h, K; t isend,bIs the hot water outflow temperature at node b, K;
the pressure loss in each thermal pipe due to friction was calculated by the Darcy-Weisbach equation
In the formula: pressure lossPa;The resistance coefficient of the heat pipeline is dimensionless; g is the acceleration of gravity, m/s2;ρWIn terms of water density, kg/m3;Is the diameter of the heat pipeline, mm;is a symbolic function of the flow of the heat pipeline, and is dimensionless;the coefficient of friction of the heat pipeline is dimensionless;
in a heat supply network, four flow balance equations, namely a thermal power balance equation, a loop pressure drop equation, a water supply and return water temperature balance equation, must be satisfied;
the node thermal power balance in the hydraulic analysis is described as:
in the formula:the mass flow of hot water generated by the CHP at the node h and the gas boiler is kg/h after uncertainty is considered; phih,loadIs the thermal load power at node h, MW; t isstart,hThe hot water inflow temperature, K, is taken out of the node h; t isend,loadThe hot water outflow temperature at the thermal load, K; nh is the number of heat network nodes;
the loop pressure drop equation is:
in the formula, delta is the set of all pipelines in the loop; Δ hjThe pressure drop of the first section and the last section of the pipeline j in the loop;
for the thermodynamic analysis of the heat network, a water supply and return temperature balance must be established for all nodes except the slack nodes:
in the formula: t isstart,CHP、Tstart,BoilerCHP and gas boiler outflow temperature, K, respectively;the heat load mass flow of the node h is kg/h; t isstart、TendThe temperature of the water flow at the head end and the tail end of the pipeline is K;
the temperature at the mixed heat node is defined as:
in the formula (I), the compound is shown in the specification,the flow rates of the water flows flowing in and out of the mixing heat node are kg/s respectively; t isin、ToutThe temperature of the water flow flowing in and out of the mixing heat node, K; it can be seen that the water flow temperature of each pipeline is different before mixing, and the mixed water flows into other pipelines from the nodeThe water flow temperature is the same;
in a heating network, a heat pump is used to circulate hot water from a heat source to a user (heat load), and the power consumption of the heat pump can be calculated as follows:
in the formula:the power consumption of the heat pump is kW;the mass flow of water is kg/h; hPIs the heat pump lift, m; etaHPIs pump efficiency, dimensionless; g is the acceleration of gravity, m/s2;
The relationship between the gas consumption and the heat production of the gas boiler is as follows:
in the formula (I), the compound is shown in the specification,is the gas consumption of the gas boiler, m3H (in formula (12): isNeed to change to be consistent);kW is the heat production of the gas boiler;the maximum heat production capacity of the gas boiler is kW; a isboil、bboilAre respectively the polynomial coefficients of the gas boiler and have no dimension.
4. The uncertainty-considered multi-energy distribution network operation cost evaluation method according to claim 3, characterized in that in the power network model of step 1.3, an active power and reactive power balance equation is established for each node:
in the formula:represents the power, kW, transmitted on the line between node i and node j; vi、VjThe amplitudes of the node i and the node j are respectively kV; y isijIs the line admittance, S; n is a radical ofEThe number of the power grid nodes is one;active power and reactive power, kW, of the CHP at the node i are respectively obtained; pi gen、Active power and reactive power, kW, of the generator at the node i are respectively obtained;active power and reactive power requirements at node i, kW, respectively; pi Pump、Pi compThe electric energy consumed by the heat pump and the compressor at the node i is kW;reactive power, kW, injected by a parallel capacitor at a node i;respectively for wind-powered electricity generation and photovoltaic power generation, kW, that have the uncertainty of generating electricity.
5. The uncertainty-considered multi-energy distribution network operation cost evaluation method according to claim 4, wherein the 2m +1 point estimation method adopted in the step 2 is performed according to the following steps:
step 2.1, reading the multi-energy flow distribution power grid data in the multi-energy flow distribution power grid modeling, wherein the read data comprises user behaviors, renewable resources and various loads;
step 2.2, inputting uncertain input random variables into the multi-energy flow distribution network model;
step 2.3, calculating the skewness of the input random variable;
step 2.4, calculating a standard position according to the result of the step 2.3;
step 2.5, calculating a centralized position and a weight factor;
step 2.6, placing the load demand and the power generation power of the renewable energy source at corresponding centralized positions, and simultaneously fixing other input random variables at the average value or a prediction point to calculate the operation cost;
step 2.7, decomposing the power flow by adopting a pure embedding method in the power network model;
step 2.8, updating the gas consumption of the gas generator;
step 2.9, decomposing the thermal flow in the established thermal network model by adopting a graph theory method;
step 2.10, respectively updating the gas consumption of the gas boiler, the gas consumption of the CHP and the power consumption of the heat pump;
2.11, decomposing the natural gas flow in the established natural gas network model;
step 2.12, updating the power consumption of the electric compressor; if the calculation is converged, executing the step 2.13, and if the calculation is not converged, returning to the step 2.7;
and 2.13, judging whether random variables exist, if no random variable exists, ending, and if the random variables exist, executing the step 2.2, namely inputting the uncertain input random variables.
6. The uncertainty-considered multi-energy distribution grid operation cost evaluation method according to claim 5, characterized in that in step 2.2, the PES input random variable S is a variable z containing m uncertain input variablesdI.e.:
S=F(z1,z2,...,zd,...,zm) (26)
wherein the m random variables comprise uncertainty of electricity, gas and heat load, uncertainty of renewable energy power generation and uncertainty of user behavior; each random variable consists of three centralized positions Zd,pP ═ 1, 2, 3 and the weighting factor ωd,pComposition, weight factor omegad,pThe influence of the corresponding position on the total expected operation cost of the multi-energy distribution network is determined.
7. The uncertainty-aware multi-energy distribution grid operating cost assessment method according to claim 6,
and 2.3, calculating the skewness of the input random variable according to the formula (29):
9. the uncertainty-aware multi-energy distribution grid operating cost assessment method according to claim 8, characterized by step 2.5, centralizing the location Zd,pThe following requirements are met:
respective weight factor omega for each concentration locationd,pThe calculation is as follows:
10. the uncertainty-aware multi-flow distribution grid operating cost estimation method according to claim 9, wherein step 2.6 calculates the multi-flow distribution grid operating cost based on each sub-network for each centralized location as follows:
the expected operation cost of the multi-energy flow distribution grid considering the uncertainty of user behaviors, loads and renewable energy sources is as follows:
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