Method for optimizing heat storage and release scheme of combined heat and power generation unit coupling molten salt heat storage system

Abstract

The invention discloses a heat storage and release scheme optimizing method for a combined heat and power generation unit coupling fused salt heat storage system, and relates to the technical field of combined heat and power generation heat supply units. According to the method, the optimal heat storage and release scheme is obtained through a particle swarm optimization algorithm and aiming at the electric heating load fluctuation condition in a period according to the fused salt heat storage and release process. According to the optimization method, the optimal heat storage and release scheme with the lowest energy consumption of the combined heat and power generation coupling molten salt heat storage system can be achieved, operation personnel of the combined heat and power generation coupling molten salt heat storage system can conveniently conduct adjustment under the condition of electric heating load fluctuation, and the overall energy consumption level is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of design of operation schemes for a cogeneration unit coupled with a molten salt heat storage system, and in particular to a method for optimizing heat storage and release schemes for a cogeneration unit coupled with a molten salt heat storage system. Background Art

[0002] At present, many coal-fired units supply industrial heating steam to industrial parks while generating electricity, but their operational flexibility will be affected. With the large-scale application of molten salt energy storage systems, the operational flexibility of industrial heating cogeneration units has been greatly improved. However, for cogeneration units with multiple heating sources, how to reasonably formulate an operation plan for the cogeneration unit coupled with the molten salt heat storage system to achieve the goal of minimizing energy consumption is an urgent problem to be solved. Summary of the invention

[0003] To solve the above problems, the purpose of the present invention is to provide a method for optimizing the heat storage and release scheme of a cogeneration unit coupled with a molten salt heat storage system. The method is based on the changes in the electric heat load within a cycle, optimizes the reheat steam heating extraction flow rate and the fourth steam extraction port heating extraction flow rate through a particle swarm algorithm, calculates the optimal reheat steam heating extraction flow rate and the fourth steam extraction port heating extraction flow rate in each time period, and finally obtains the minimum coal consumption of the cogeneration unit within a cycle, so that the energy consumption of the cogeneration unit coupled with the molten salt energy storage system is minimized.

[0004] In order to achieve the above object, the present invention adopts the following technical solution:

[0005] A method for optimizing heat storage and release schemes for a cogeneration unit coupled with a molten salt heat storage system is proposed. According to the fluctuation of electric and thermal loads within a cycle and taking the coal consumption within a cycle as the target, the values ​​of the reheat steam heating extraction flow rate D1 and the fourth steam extraction port heating extraction flow rate D2 in each time period are optimized, and a particle swarm optimization algorithm is used, including the following steps:

[0006] (I) Determine optimization variables, intermediate variables and optimization goals

[0007] A cycle is divided into n time periods, namely t1, t2...tn. The reheat steam heating extraction flow rate D1 and the fourth extraction port heating extraction flow rate D2 in each time period of the cogeneration unit are optimized variables, and the position X of a single particle is set accordingly, and its expression is:

[0008] X=[D 1,t1 ,D 2,t1 ,D 2,t2 ,D 1,t2 ,......,D 1,tn ,D 2,tn ]

[0009] Where X is a vector, representing the position of a single particle, and is composed of multiple elements; D 1,t1 D is the reheat steam heating extraction flow rate in the t1 period; 2,t1 D is the heating steam flow rate of the fourth steam extraction port in the time period t1; 1,t2 D is the reheat steam heating extraction flow rate in the t2 period; 2,t2 D is the heating steam flow rate of the fourth steam extraction port during the time period t2; 1,tn D is the reheat steam heating extraction flow rate in the tn period; 2,tn is the heating extraction steam flow rate of the fourth extraction port in the time period tn;

[0010] Among them, there are also intermediate variables in the calculation process, including the main steam flow D3, the molten salt heat storage flow D4, the molten salt heat release flow D5, and the molten salt redundancy M; the calculation can be expressed as:

[0011] D 3,t1 =f1(P t1 ,D 1,t1 ,D 2,t1 )

[0012] D 4,t1 =f2(D 1,t1 ,D 2,t1 )

[0013] D 5,t1 =f3(G t1 ,D 1,t1 ,D 2,t1 )

[0014]

[0015] D 3,t2 =f1(P t2 ,D 1,t2 ,D 2,t2 )

[0016] D 4,t2 =f2(D 1,t2 ,D 2,t2 )

[0017] D 5,t2 =f3(G t2 ,D 1,t2 ,D 2,t2 )

[0018] ......

[0020] D 3,tn =f1(P tn ,D 1,tn ,D2,tn )

[0021] D 4,tn =f2(D 1,tn ,D 2,tn )

[0022] D 5,tn =f3(G tn ,D 1,tn ,D 2,tn )

[0023]

[0024] Where D 3,t1 is the main steam flow rate in the time period t1; D 4,t1 is the molten salt heat storage flow rate in the time period t1; D 5,t1 M is the heat release flow rate of the molten salt in the time period t1; t1 is the molten salt redundancy in the time period t1; P t1 is the electrical load in the time period t1; G t1 is the heat load in the time period t1; D 3,t2 is the main steam flow rate in the time period t2; D 4,t2 is the molten salt heat storage flow rate in the time period t2; D 5,t2 M is the heat release flow rate of the molten salt in the time period t2; t2 is the molten salt redundancy in the time period t2; t2 is the electrical load during the t2 period; G t2 is the heat load in the time period t2; D 3,tn is the main steam flow rate in the tn period; D 4,tn is the molten salt heat storage flow rate in the tn period; D 5,tn M is the heat release flow rate of the molten salt in the time period tn; tn is the molten salt redundancy in the time period tn; tn is the electrical load in the tn period; G tn is the heat load in the time period tn; dt is the time differential; f1 is the main steam flow calculation function; f2 is the molten salt heat storage flow calculation function; f3 is the molten salt heat release flow calculation function;

[0025] The optimization goal is to minimize the coal consumption c within a cycle, and the calculation formula is:

[0026] c t1 =g(D 1,t1 ,D 2,t1 ,D 3,t1 )

[0027] c t2 =g(D 1,t2 ,D 2,t2,D 3,t2 ) ......

[0029] c tn =g(D 1,tn ,D 2,tn ,D 3,tn )

[0030]

[0031] In the formula, c t1 is the coal consumption in the time period t1; c t2 is the coal consumption in the time period t2; c tn is the coal consumption in the time period tn; g is the coal consumption calculation function; c is the coal consumption in one cycle;

[0032] (II) Determine the boundary conditions of variables

[0033] The boundary value of the variable is determined according to the design data of the cogeneration unit; its expression is:

[0034] D 1,t1 ∈[D 1,min ,D 1,max ]

[0035] D 2,t1 ∈[D 2,min ,D 2,max ]

[0036] D 3,t1 ∈[D 3,min ,D 3,max ]

[0037] M t1 ∈[0,M max ]

[0038] D 1,t2 ∈[D 1,min ,D 1,max ]

[0039] D 2,t2 ∈[D 2,min ,D 2,max ]

[0040] D 3,t2 ∈[D 3,min ,D 3,max ]

[0041] M t2 ∈[0,M max ] ......

[0043] D 1,tn ∈[D 1,min,D 1,max ]

[0044] D 2,tn ∈[D 1,min ,D 1,max ]

[0045] D 3,tn ∈[D 3,min ,D 3,max ]

[0046] M tn ∈[0,M max ]

[0047] Where D 1,min The minimum design value of the reheat steam extraction flow rate, D 1,max The maximum design value of the extraction steam flow rate for reheat steam heating; D 2,min The design minimum value of the heating steam flow rate of the fourth extraction port, D 2,max The maximum design value of the heating steam flow rate of the fourth steam extraction port; D 3,min is the minimum design value of main steam flow, D 3,max The maximum design value of main steam flow rate; M max is the maximum capacity of the molten salt tank;

[0048] (iii) setting the initial value of the individual optimal value and the initial value of the global optimal value, calculating the intermediate variables of the cogeneration unit in one cycle and the coal consumption in one cycle corresponding to the position of the particle group; when the variable of a particle exceeds the boundary value described in step (ii), the coal consumption c of the cogeneration unit in one cycle is given a maximum value;

[0049] (iv) judging whether the current coal consumption c is less than the current individual optimal value, if the current coal consumption c is less than the current individual optimal value, then updating the individual optimal value to the current coal consumption c, otherwise not updating the individual optimal value; judging whether the current coal consumption c is less than the current global optimal value, if the current coal consumption c is less than the current global optimal value, then updating the global optimal value to the current coal consumption c, otherwise not updating the global optimal value, after the particle position is updated, executing step (iii);

[0050] (V) After a preset number of iterations, if the global optimal value obtained in the last iteration is the same as the global optimal value obtained in the previous iteration, then the variables corresponding to the global optimal value obtained in the last iteration are taken as the optimal variables, and the coal consumption c corresponding to the global optimal value obtained in the last iteration is taken as the minimum coal consumption. 1,t1 ,D 2,t1 ,D 2,t2 ,D 1,t2 ,......,D 1,tn ,D 2,tnThe best solution is the combination.

[0051] Advantages of the present invention

[0052] (1) The present invention provides an optimal heat storage and release scheme for a cogeneration unit coupled with a molten salt energy storage system within a cycle, which can effectively reduce system energy consumption and facilitate operators to adjust the molten salt energy storage system;

[0053] (2) The present invention is simple to implement and takes into account the operation characteristics of cogeneration, thereby ensuring the safe operation of the unit. DETAILED DESCRIPTION

[0054] The present invention provides a method for optimizing a heat storage and release scheme of a cogeneration unit coupled with a molten salt heat storage system. The method optimizes the reheat steam heating extraction flow rate and the fourth steam extraction port heating extraction flow rate based on the change of electric heat load in one cycle by a particle swarm algorithm, calculates the optimal reheat steam heating extraction flow rate and the fourth steam extraction port heating extraction flow rate in each time period, and finally obtains the minimum coal consumption of the cogeneration unit in one cycle, so that the energy consumption of the cogeneration unit coupled with the molten salt energy storage system is minimized. The specific steps are as follows:

[0055] (I) Determine optimization variables, intermediate variables and optimization goals

[0056] A cycle is divided into n time periods, namely t1, t2...tn. The reheat steam heating extraction flow rate D1 and the fourth extraction port heating extraction flow rate D2 in each time period of the cogeneration unit are optimized variables, and the position X of a single particle is set accordingly, and its expression is:

[0057] X=[D 1,t1 ,D 2,t1 ,D 2,t2 ,D 1,t2 ,......,D 1,tn ,D 2,tn ]

[0058] Where X is a vector, representing the position of a single particle, and is composed of multiple elements; D 1,t1 D is the reheat steam heating extraction flow rate in the t1 period; 2,t1 D is the heating steam flow rate of the fourth steam extraction port in the time period t1; 1,t2 D is the reheat steam heating extraction flow rate in the t2 period; 2,t2 D is the heating steam flow rate of the fourth steam extraction port during the time period t2; 1,tn D is the reheat steam heating extraction flow rate in the tn period; 2,tn is the heating extraction steam flow rate of the fourth extraction port in the time period tn;

[0059] Among them, there are also intermediate variables in the calculation process, including the main steam flow D3, the molten salt heat storage flow D4, the molten salt heat release flow D5, and the molten salt redundancy M; the calculation can be expressed as:

[0060] D 3,t1 =f1(P t1 ,D 1,t1 ,D 2,t1 )

[0061] D 4,t1 =f2(D 1,t1 ,D 2,t1 )

[0062] D 5,t1 =f3(G t1 ,D 1,t1 ,D 2,t1 )

[0063]

[0064] D 3,t2 =f1(P t2 ,D 1,t2 ,D 2,t2 )

[0065] D 4,t2 =f2(D 1,t2 ,D 2,t2 )

[0066] D 5,t2 =f3(G t2 ,D 1,t2 ,D 2,t2 )

[0067] ......

[0069] D 3,tn =f1(P tn ,D 1,tn ,D 2,tn )

[0070] D 4,tn =f2(D 1,tn ,D 2,tn )

[0071] D 5,tn =f3(G tn ,D 1,tn ,D 2,tn )

[0072]

[0073] Where D 3,t1is the main steam flow rate in the time period t1; D 4,t1 is the molten salt heat storage flow rate in the time period t1; D 5,t1 M is the heat release flow rate of the molten salt in the time period t1; t1 is the molten salt redundancy in the time period t1; P t1 is the electrical load in the time period t1; G t1 is the heat load in the time period t1; D 3,t2 is the main steam flow rate in the time period t2; D 4,t2 is the molten salt heat storage flow rate in the time period t2; D 5,t2 M is the heat release flow rate of the molten salt in the time period t2; t2 is the molten salt redundancy in the time period t2; t2 is the electrical load during the t2 period; G t2 is the heat load in the time period t2; D 3,tn is the main steam flow rate in the tn period; D 4,tn is the molten salt heat storage flow rate in the tn period; D 5,tn M is the heat release flow rate of the molten salt in the time period tn; tn is the molten salt redundancy in the time period tn; tn is the electrical load in the tn period; G tn is the heat load in the time period tn; dt is the time differential; f1 is the main steam flow calculation function; f2 is the molten salt heat storage flow calculation function; f3 is the molten salt heat release flow calculation function;

[0074] The optimization goal is to minimize the coal consumption c within a cycle, and the calculation formula is:

[0075] c t1 =g(D 1,t1 ,D 2,t1 ,D 3,t1 )

[0076] c t2 =g(D 1,t2 ,D 2,t2 ,D 3,t2 ) ......

[0078] c tn =g(D 1,tn ,D 2,tn ,D 3,tn )

[0079]

[0080] In the formula, c t1 is the coal consumption in the time period t1; c t2 is the coal consumption in the time period t2; c tnis the coal consumption in the time period tn; g is the coal consumption calculation function; c is the coal consumption in one cycle;

[0081] (II) Determine the boundary conditions of variables

[0082] The boundary value of the variable is determined according to the design data of the cogeneration unit; its expression is:

[0083] D 1,t1 ∈[D 1,min ,D 1,max ]

[0084] D 2,t1 ∈[D 2,min ,D 2,max ]

[0085] D 3,t1 ∈[D 3,min ,D 3,max ]

[0086] M t1 ∈[0,M max ]

[0087] D 1,t2 ∈[D 1,min ,D 1,max ]

[0088] D 2,t2 ∈[D 2,min ,D 2,max ]

[0089] D 3,t2 ∈[D 3,min ,D 3,max ]

[0090] M t2 ∈[0,M max ] ......

[0092] D 1,tn ∈[D 1,min ,D 1,max ]

[0093] D 2,tn ∈[D 1,min ,D 1,max ]

[0094] D 3,tn ∈[D 3,min ,D 3,max ]

[0095] M tn ∈[0,M max ]

[0096] Where D1,min The minimum design value of the reheat steam extraction flow rate, D 1,max The maximum design value of the extraction steam flow rate for reheat steam heating; D 2,min The design minimum value of the heating steam flow rate of the fourth extraction port, D 2,max The maximum design value of the heating steam flow rate of the fourth steam extraction port; D 3,min is the minimum design value of main steam flow, D 3,max The maximum design value of main steam flow rate; M max is the maximum capacity of the molten salt tank;

[0097] (iii) setting the initial value of the individual optimal value and the initial value of the global optimal value, calculating the intermediate variables of the cogeneration unit in one cycle and the coal consumption in one cycle corresponding to the position of the particle group; when the variable of a particle exceeds the boundary value described in step (ii), the coal consumption c of the cogeneration unit in one cycle is given a maximum value;

[0098] (iv) Determine whether the current coal consumption c is less than the current individual optimal value. If the current coal consumption c is less than the current individual optimal value, update the individual optimal value to the current coal consumption c, otherwise do not update the individual optimal value; determine whether the current coal consumption c is less than the current global optimal value. If the current coal consumption c is less than the current global optimal value, update the global optimal value to the current coal consumption c, otherwise do not update the global optimal value. After the particle position is updated, execute step (iii); use the following formula to update the speed and position of each particle:

[0099] v′ j =ωv j +e1r1(dbest(j)-x j )+k1r2(gbest-x j )

[0100] x′ j =x j +v′ j

[0101] Where j is the particle number, j = 1,...,R, R is the total number of particles in the particle group; v′ j is the particle velocity of the particle numbered j after update; ω is the inertia weight; v j is the particle velocity before the update of particle number j; e1 is the individual learning factor; k1 is the social learning factor; r1 and r2 are random numbers between [0,1]; dbest(j) is the individual optimal value of particle number j; gbest is the global optimal value of the particle group; x j Update the previous particle position for the particle numbered j; x′ j Update the particle position of the particle numbered j;

[0102] (V) After a preset number of iterations, if the global optimal value obtained in the last iteration is the same as the global optimal value obtained in the previous iteration, then the variables corresponding to the global optimal value obtained in the last iteration are taken as the optimal variables, and the coal consumption c corresponding to the global optimal value obtained in the last iteration is taken as the minimum coal consumption. 1,t1 ,D 2,t1 ,D 2,t2 ,D 1,t2 ,......,D 1,tn ,D 2,tn The best solution is the combination.

[0103] The optimization method of the present invention can realize the optimal heat storage and release scheme with the lowest energy consumption for the cogeneration coupled molten salt heat storage system, which is convenient for operators of the cogeneration coupled molten salt heat storage system to make adjustments under the condition of electric and thermal load fluctuations, thereby reducing the overall energy consumption level.

Claims

1. A method for optimizing heat storage and release schemes for a cogeneration unit coupled with a molten salt heat storage system, characterized in that: According to the fluctuation of electric heat load in one cycle, taking the coal consumption in one cycle as the target, the values ​​of the reheat steam heating extraction flow rate D1 and the fourth extraction port heating extraction flow rate D2 in each time period are optimized, and the particle swarm optimization algorithm is used, including the following steps: (I) Determine optimization variables, intermediate variables and optimization goals A cycle is divided into n time periods, namely t1, t2...tn. The reheat steam heating extraction flow rate D1 and the fourth extraction port heating extraction flow rate D2 in each time period of the cogeneration unit are optimized variables, and the position X of a single particle is set accordingly, and its expression is: X=[D 1,t1 ,D 2,t1 ,D 2,t2 ,D 1,t2 ,......,D 1,tn ,D 2,tn ] Where X is a vector, representing the position of a single particle, and is composed of multiple elements; D 1,t1 D is the reheat steam heating extraction flow rate in the t1 period; 2,t1 D is the heating steam flow rate of the fourth steam extraction port in the time period t1; 1,t2 D is the reheat steam heating extraction flow rate in the t2 period; 2,t2 D is the heating steam flow rate of the fourth steam extraction port during the time period t2; 1,tn D is the reheat steam heating extraction flow rate in the tn period; 2,tn is the heating extraction steam flow rate of the fourth extraction port in the time period tn; Among them, there are also intermediate variables in the calculation process, including the main steam flow D3, the molten salt heat storage flow D4, the molten salt heat release flow D5, and the molten salt redundancy M; the calculation expression is: D 3,t1 =f1(P t1 ,D 1,t1 ,D 2,t1 ) D 4,t1 =f2(D 1,t1 ,D 2,t1 ) D 5,t1 =f3(G t1 ,D 1,t1 ,D 2,t1 ) D 3,t2 =f1(P t2 ,D 1,t2 ,D 2,t2 ) D 4,t2 =f2(D 1,t2 ,D 2,t2 ) D 5,t2 =f3(G t2 ,D 1,t2 ,D 2,t2 ) ...... D 3,tn =f1(P tn ,D 1,tn ,D 2,tn ) D 4,tn =f2(D 1,tn ,D 2,tn ) D 5,tn =f3(G tn ,D 1,tn ,D 2,tn ) Where D 3,t1 is the main steam flow rate in the time period t1; D 4,t1 is the molten salt heat storage flow rate in the time period t1; D 5,t1 M is the heat release flow rate of the molten salt in the time period t1; t1 is the molten salt redundancy in the time period t1; P t1 is the electrical load in the time period t1; G t1 is the heat load in the time period t1; D 3,t2 is the main steam flow rate in the time period t2; D 4,t2 is the molten salt heat storage flow rate in the time period t2; D 5,t2 M is the heat release flow rate of the molten salt in the time period t2; t2 is the molten salt redundancy in the time period t2; t2 is the electrical load during the t2 period; G t2 is the heat load in the time period t2; D 3,tn is the main steam flow rate in the tn period; D 4,tn D is the molten salt heat storage flow rate in the tn period; 5,tn M is the heat release flow rate of the molten salt in the time period tn; tn is the molten salt redundancy in the time period tn; tn is the electrical load in the tn period; G tn is the heat load in the time period tn; dt is the time differential; f1 is the main steam flow calculation function; f2 is the molten salt heat storage flow calculation function; f3 is the molten salt heat release flow calculation function; The optimization goal is to minimize the coal consumption c within a cycle, and the calculation formula is: c t1 =g(D 1,t1 ,D 2,t1 ,D 3,t1 ) c t2 =g(D 1,t2 ,D 2,t2 ,D 3,t2 ) ...... c tn =g(D 1,tn ,D 2,tn ,D 3,tn ) In the formula, c t1 is the coal consumption in the time period t1; c t2 is the coal consumption in the time period t2; c tn is the coal consumption in the time period tn; g is the coal consumption calculation function; c is the coal consumption in one cycle; (II) Determine the boundary conditions of variables The boundary value of the variable is determined according to the design data of the cogeneration unit; its expression is: D 1,t1 ∈[D 1,min ,D 1,max ] D 2,t1 ∈[D 2,min ,D 2,max ] D 3,t1 ∈[D 3,min ,D 3,max ] M t1 ∈[0,M max ] D 1,t2 ∈[D 1,min ,D 1,max ] D 2,t2 ∈[D 2,min ,D 2,max ] D 3,t2 ∈[D 3,min ,D 3,max ] M t2 ∈[0,M max ] ...... D 1,tn ∈[D 1,min ,D 1,max ] D 2,tn ∈[D 1,min ,D 1,max ] D 3,tn ∈[D 3,min ,D 3,max ] M tn ∈[0,M max ] Where D 1,min The minimum design value of the reheat steam extraction flow rate, D 1,max The maximum design value of the extraction flow rate for reheat steam heating; D 2,min The design minimum value of the heat extraction steam flow rate at the fourth extraction port, D 2,max The maximum design value of the heating steam flow rate of the fourth steam extraction port; D 3,min is the minimum design value of main steam flow, D 3,max The maximum design value of main steam flow rate; M max is the maximum capacity of the molten salt tank; (iii) setting the initial value of the individual optimal value and the initial value of the global optimal value, calculating the intermediate variables of the cogeneration unit in one cycle and the coal consumption in one cycle corresponding to the position of the particle group; when the variable of a particle exceeds the boundary value described in step (ii), the coal consumption c of the cogeneration unit in one cycle is given a maximum value; (iv) judging whether the current coal consumption c is less than the current individual optimal value, if the current coal consumption c is less than the current individual optimal value, then updating the individual optimal value to the current coal consumption c, otherwise not updating the individual optimal value; judging whether the current coal consumption c is less than the current global optimal value, if the current coal consumption c is less than the current global optimal value, then updating the global optimal value to the current coal consumption c, otherwise not updating the global optimal value, after the particle position is updated, executing step (iii); (V) After a preset number of iterations, if the global optimal value obtained in the last iteration is the same as the global optimal value obtained in the previous iteration, then the variables corresponding to the global optimal value obtained in the last iteration are taken as the optimal variables, and the coal consumption c corresponding to the global optimal value obtained in the last iteration is taken as the minimum coal consumption. 1,t1 ,D 2,t1 ,D 2,t2 ,D 1,t2 ,......,D 1,tn ,D 2,tn The best solution is the combination.

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