Method and apparatus for providing load dispatch and pollution control optimization

• US 9,771,834 B2
• Filed: 10/20/2004
• Issued: 09/26/2017
• Est. Priority Date: 10/20/2004
• Status: Active Grant

• Current Assignee: Emerson Process Management Power & Water Solutions Incorporated (Emerson Electric Company)
• Original Assignee: Emerson Process Management Power & Water Solutions Incorporated (Emerson Electric Company)
• Inventors: Cheng, Xu, Huff, Frederick C.
• Primary Examiner(s): Allen, Akiba
• Application Number:
  US10/969,752
• Publication Number:
  US 20060085363A1
• Time in Patent Office: 4,724 Days
• Field of Search: 705412, 705 1, 705 711, 700287, 60652
• CPC Class Codes: F01K 13/02 Controlling, e.g. stopping or starting
• CPC Class Codes: G06Q 10/04 Forecasting or optimisation specially adapted for administrative or management purposes, e.g. linear programming or "cutting stock problem" market predictions or forecasting for commercial activities G06Q30/0202
• CPC Class Codes: G06Q 10/0637 Strategic management or analysis, e.g. setting a goal or target of an organisation; Planning actions based on goals; Analysis or evaluation of effectiveness of goals
• CPC Class Codes: G06Q 30/0283 Price estimation or determination
• CPC Class Codes: Y02E 40/70 Smart grids as climate change mitigation technology in the energy generation sector
• CPC Class Codes: Y04S 10/50 Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
• CPC Class Codes: Y04S 50/14 Marketing, i.e. market research and analysis, surveying, promotions, advertising, buyer profiling, customer management or rewards

Abstract

An economic dispatch program allocates a load demand and an emission allowance of a power generation system among various power plants to determine the operational set-points and the pollution control set-points of each of the various power plants in a manner that minimizes the total operating cost for the power generation system, including the pollution control cost. The economic dispatch program uses the pollution control set-points and the load set-points of the various power plants as decision variables and takes into consideration the pollution control costs of the various power plants in allocating the load demand. During operation, the economic dispatch program takes into consideration the pollution credits available to the various power plants in allocating the load demand and pollution control level to determine the optimal operating solution for the power plants.

Claims

1. A method of operating a power generation system having a plurality of power generation devices, each of the power generation devices including one or more power generating units that produce an amount of energy based on a load set-point, and at least one of the power generation devices including one or more pollution control devices that are controllable independent of the power generation units and that operate at different levels based on pollution control set-points, wherein different values of a pollution control set-point cause a pollution control device to operate at different operating points to affect the amount of emission of pollutants emitted by a power generation device during operation of the power generation device, the method comprising:

obtaining, using a processor of a computing device, an objective function of the power generation system, wherein the objective function provides cost of operating the power generation system as a function of a plurality of variables, the plurality of variables including a load set-point for one of the power generating units of at least one of the plurality of power generation devices and a pollution control set-point of a pollution control device for the at least one of the plurality of power generation devices;

obtaining, using the processor of the computing device, a plurality of operating constraints of the power generation system;

obtaining, using the processor of the computing device, an optimal solution for the objective function within the plurality of operating constraints of the power generation system, wherein a candidate solution for the objective function is selected within the constraints and values of various variables are iteratively changed until the optimal solution is obtained, wherein the optimal solution for the objective function is representative of the cost of operating the power generation system, and wherein the cost of operating the power generation system includes a cost of operating the plurality of power generation devices and a cost of operating the one or more pollution control devices;

determining, using the processor of the computing device, load set-points and pollution control set-points, distinct from the load set-points, for the power generation devices based on the optimal solution for the objective function; and

using the determined load set-points to control the operation of the power generating units of the power generation devices and using the pollution control set-points to control the operation of the pollution control devices of the power generation devices.

2. A method of claim 1, wherein the objective function, subject to the plurality of operating constraints, is solved using a non-linear optimization routine.

3. A method of claim 1, wherein the objective function is solved using an iterative process and wherein a candidate solution for the objective function is selected within the plurality of operating constraints and values, of the plurality of variables, are iteratively changed until an optimal solution is obtained.

4. A method of claim 1, wherein a set of values, for various intermediate load set-points, is selected as a starting point, and optimal values of respective intermediate loads are determined iteratively.

5. A method of claim 1, wherein a set of values of pollution control set-points, of the pollution control devices, is selected as part of a candidate solution for the objective function and optimal values of the pollution levels are determined iteratively.

6. A method of claim 1, wherein an evolutionary algorithm is used to iteratively solve the objective function subject to one or more of the plurality of operating constraints.

7. A method of claim 1, wherein a set of candidate solution points within the plurality of operating constraints is selected, a set of localized solutions corresponding to the set of candidate solution points is obtained using an evolutionary algorithm, and one of the set of localized solutions is selected as the optimal solution of the objective function.

8. A method of operating a power generation system having a plurality of power generation devices, each of the power generation devices including one or more power generating units that produce an amount of energy based on a load set-point, and at least one of the power generation devices including one or more pollution control devices that are controllable independent of the power generation units and that operate at different levels based on pollution control set-points, wherein different values of a pollution control set-point cause a pollution control device to operate at different operating points to affect the amount of emission of pollutants emitted by a power generation device during operation of the power generation device, the method comprising:

receiving, from a workstation, an operating instruction specifying a load demand function and a pollutant emission allowance of the power generation system;

determining, using a processor of a computing device, an objective function of the power generation system, wherein the objective function specifies an operating condition of the power generation system as a function of a plurality of variables including a load set-point and a pollution control set-point of at least one of the plurality of power generation devices;

determining, using the processor of the computing device, an optimal solution of the objective function to generate operating set-points for the plurality of power generation devices that allows the power generation system to meet the load demand function while the total pollutant emissions generated by the power generation system are below the pollutant emission allowance, wherein the optimal solution for the objective function is representative of a cost of operating the power generation system, and wherein the cost of operating the power generation system includes a cost of operating the plurality of power generation devices and a cost of operating the one or more pollution control devices;

determining, using the processor of the computing device, load set-points and pollution control set-points, distinct from the load set-points, for the power generation devices based on the optimal solution of the objective function; and

using the determined load set-points to control the operation of the power generating units of the power generation devices and using the pollution control set-points to control the pollution control devices of the power generation devices, wherein the load demand function includes a load ramp, between a beginning time T₀ and a ramp time T_e, wherein the load demand is L₀ at time T₀ and L_e at the ramp time T_e L_e T_e {T₀,T} {t₀,t₁} {t₁,t₂} {t_N-1,t_N} t₀=T₀ t_NT T_e L₁, L₂, . . . , L_N T₀ T_e L_k k=1, . . . , N L₀ L_e

L_k=L₀+k·

(L_e−

L₀)/(T_e−

T₀)t_k≦

T_e

L_k=L_et_k>

T_e.

17. A method of claim 8, wherein the load ramp, between times T₀ and T_e, is a linear ramp, and wherein intermediate target loads L_k (k=1, . . . , N) are computed, respectively, as a linear interpolation between the initial load L₀ and the final load L_e is:

L_k=L₀+k·

(L_e−

L₀)/(T_e−

T₀) (for t_k≦

T_e)) and

L_k=L_e (for t_k>

T_e).

18. A method of claim 17, wherein fuel consumption cost associated with an i^th power generation unit, wherein i=1 to n, at a time t_k is:

F_i^k=L_i^k·

H_i^k·

f_i

wherein;

L_i^k=load for the i^th unit at time t_k;

H_i^k=heat rate for the i^th unit at time t_k; and

f_i=fuel price for the i^th unit.

19. A method of claim 18, wherein cost of pollution control at time t_k is:

20. A method of claim 19, wherein total emission credits available for the j^th pollutant at time t_k are:

21. A method of claim 20, wherein a total cost J_k of providing load L_k is:

22. A method of claim 21, wherein the total cost J_k further includes at least one of:

a cost of transmitting power, a cost of fuel storage, or a time value of money.

23. A method of claim 22, wherein an aggregate cost J of providing load during the time interval {T₀,T}, is:

24. A method of claim 8, wherein load constraints are:

$\underset{i=1}{\overset{n}{\sum <br><br>}}<br><br>L_{i,k}=L_k$$L_{i,\min }\le <br><br>L_{i,k}\le <br><br>L_{i,\max }$
L_i,min≦

L_i,k≦

L_i,max

wherein;

L_i,k is a load demand for the i^th power generation device at time t_k, and L_i,min and L_i,max are minimum load and the maximum load, respectively, for an i^th power generation device.

25. A method of claim 8, wherein a maximum unit ramp constraint is:

−

M_i≦

L_i,k+1−

L_i,k≦

M_i

wherein;

M_i is a maximum ramp rate for the power generation devices during any time interval {t<sub>k−

1</sub>,t_k}.

26. A method of claim 23, wherein a total emission constraint is:

28. A method of claim 8, wherein the load demand function includes a load ramp, between a beginning time T₀ and a ramp time T_e, wherein the load demand is L₀ at time T₀ and L_e at the ramp time T_e, wherein the load demand is constant at L_e from the ramp time T_e to an ending time T, wherein an overall time period {T₀, T} is divided into N time segments ({t₀, t₁}, {t₁, t₂} . . . {T_N-1,t_N}) with t₀=T₀, t_N=T, and T is greater than or equal to T_e, and wherein a load demand at the end of each of the time segments is denoted by L₁, L₂, . . . , L_N.

9. An economic analysis system for optimizing operation of a power generation system having a plurality of power generation devices, each of the power generation devices including one or more power generating units that produce an amount of energy based on a load set-point, and at least one of the power generation devices including one or more pollution control devices that are controllable independent of the power generation units and that operate at different levels based on pollution control set-points, wherein different values of a pollution control set-point cause a pollution control device to operate at different operating points to affect the amount of emission of pollutants emitted by a power generation device during operation of the power generation device, the economic analysis system comprising:

a first module adapted to store an objective function of the power generation system, wherein the objective function provides cost of operating the power generation system as a function of a plurality of variables, the plurality of variables including a load set-point and a pollution control set-point of at least one of the plurality of power generation devices;

a second module adapted to store a plurality of operating constraints of the power generation system;

a third module adapted to obtain an optimal solution for the objective function within the plurality of operating constraints of the power generation system, wherein a load demand function includes a load ramp, and wherein the objective function, subject to the plurality of operating constraints, is solved using a non-linear optimization routine, wherein the optimal solution for the objective function is representative of the cost of operating the power generation system, and wherein the cost of operating the power generation system includes a cost of operating the plurality of power generation devices and a cost of operating the one or more pollution control devices; and

a fourth module adapted to determine load set-points and pollution control set-points, distinct from the load set-points, for the power generation devices based on the optimal solution for the objective function, wherein the determined load set-points are adapted to control the operation of the power generating units of the power generation devices and the determined pollution control set-points are adapted to control the operation of the pollution control devices of the power generation devices.

10. A system of claim 9, wherein the pollution control set-point is a desired level of a pollutant generated by the one of the plurality of power generation devices.

11. A system of claim 9, wherein the objective function provides the cost of operating the power generation system further as a function of a pollution credit available to one of the plurality of power generation devices.

12. A system of claim 9, wherein the power generation system is a power grid and the plurality of power generation devices includes a plurality of power plants.

13. A system of claim 9, wherein the third module is further adapted to obtain an optimal solution for the objective function using an evolutionary solution method.

14. A power generation system, comprising:

a plurality of power generation devices, each of the power generation devices including one or more power generating units that produce an amount of energy based on a load set-point, and at least one of the power generation devices including one or more pollution control devices that are controllable independent of the power generation units and that operate at different levels based on pollution control set-points, wherein different values of a pollution control set-point cause a pollution control device to operate at different operating points to affect the amount of emission of pollutants emitted by a power generation device during operation of the power generation device;

a first module adapted to obtain, using a processor of a computing device, a load demand for the plurality of power generation devices;

a second module adapted to obtain, using the processor of the computing device, a pollutant emission allowance for the plurality of power generation devices;

a third module adapted to obtain, using the processor of the computing device, an objective function of the power generation system, wherein the objective function provides cost of operating the power generation system as a function of a plurality of variables, the plurality of variables including a load set-point and a pollution control set-point of at least one of the plurality of power generation devices;

a fourth module adapted to obtain, using the processor of the computing device, a plurality of operating constraints of the power generation system;

a fifth module adapted to obtain, using the processor of the computing device, an optimal solution for the objective function so that when the power generation devices are operated as per the optimal solution the plurality of power generation devices satisfies the load demand and the total pollutant emission output of the plurality of generation devices is less than the pollutant emission allowance, wherein the optimal solution for the objective function is representative of the cost of operating the power generation system, and wherein the cost of operating the power generation system includes a cost of operating the plurality of power generation devices and a cost of operating the one or more pollution control devices; and

a sixth module adapted to determine, using the processor of the computing device, load set-points and pollution control set-points, distinct from the load set-points, for the power generation devices based on the optimal solution for the objective function, wherein the determined load set-points are adapted to control the operation of the power generating units of the power generation devices and the determined pollution control set-points are adapted to control the operation of the pollution control devices of the power generation devices L_e T_e {T₀,T} {t₀,t₁} {t₁,t₂} {t_N-1,t_N} t₀=T₀ t_N=T T_e L₁, L₂, . . . , L_N T₀ T_e L_k k=1, . . . , N L₀ L_e

L_k=L₀+k·

(L_e−

L₀)/(T_e−

T₀)t_k≦

T_e

L_k=L_et_k>

T_e.

15. A system of claim 14, wherein the load demand function includes a load ramp, and wherein the objective function, subject to the plurality of operating constraints, is solved using a non-linear optimization routine.

16. A system of claim 15, wherein the load demand function includes a load ramp, wherein the objective function is solved using an iterative process, and wherein a candidate solution for the objective function is selected within the plurality of operating constraints and values, of the plurality of variables, are iteratively changed until an optimal solution is obtained.

27. A system of claim 14, wherein the load demand function includes a load ramp.