Optimizing control method and optimizing control system for power plant

• US 6,681,155 B1
• Filed: 04/20/2001
• Issued: 01/20/2004
• Est. Priority Date: 08/31/1998
• Status: Expired due to Term

• Current Assignee: Mitsubishi Chemical Corporation (Mitsubishi Chemical Group Corp.)
• Original Assignee: Mitsubishi Chemical Corporation (Mitsubishi Chemical Group Corp.)
• Inventors: Nakagawa, Seiji, Fujita, Kaoru, Takeshita, Toshihiko, Emoto, Genichi
• Primary Examiner(s): Picard, Leo
• Assistant Examiner(s): KOSOWSKI, ALEXANDER J
• Application Number:
  US09/763,861
• Time in Patent Office: 1,005 Days
• Field of Search: 700/28, 700/29, 700/287, 700/291, 290/52, 606/60, 606/67, 606/76, 705/412
• US Class Current: 700/287
• CPC Class Codes: G05B 13/042 in which a parameter or coefficient is automatically adjusted to optimise the performance
• CPC Class Codes: H02J 2203/20 Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
• CPC Class Codes: H02J 3/38 Arrangements for parallely feeding a single network by two or more generators, converters or transformers
• CPC Class Codes: Y02E 40/70 Smart grids as climate change mitigation technology in the energy generation sector
• CPC Class Codes: Y02E 60/00 Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
• 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 40/20 Information technology specific aspects, e.g. CAD, simulation, modelling, system security

Abstract

In a power plant including a plurality of parallel-operated generating elements supplying electricity and steam, boilers and turbines are controlled in an optimum condition depending on the successive changes of the demand for steam and electricity by: estimating parameters of characteristics and state of the generating elements, which cannot be directly measured, among parameters of the generating elements needed for calculation of the optimum load distribution for each of the generating elements, based on a physical model of each of the generating elements and an input process state quantity; and controlling each of the generating elements by determining an optimum load distribution for the each of the generating elements while using the estimated parameters of the each of the generating elements, to minimize a total cost of the power plant depending on the successive changes of the demand for steam and electricity.

Claims

1. An optimizing control method, for use in a power plant including a plurality of parallel-operated generating elements supplying electricity and steam, to control the generating elements by using an optimum load distribution while satisfying a balance between demand and supply of the electricity and the steam, said method comprising the steps of:

estimating parameters of characteristics and state of the generating elements, which cannot be directly measured, among parameters of the generating elements needed for calculation of the optimum load distribution for each of the generating elements, based on a physical model of each of the generating elements and an input process state quantity; and

controlling each of the generating elements by determining an optimum load distribution for the each of the generating elements while using the estimated parameters of the each of the generating elements, to minimize a total cost of the power plant,

wherein the physical model includes steam enthalpies of steam inlet and steam outlet.

2. The optimizing control method for a power plant as defined in claim 1, wherein schedule control data indicating the parameters of the each of the generating elements and factors of fluctuations of running cost of the power plant in specified period are input, a schedule calculation is executed for obtaining a schedule to operate the power plant while minimizing cost in the specified period based on the input schedule control data and a model for the power plant, and the optimum load distribution of the each of the generating elements is calculated depending on the parameters of the each of the generating elements and the input process state quantity based on the obtained schedule.

3. The optimizing control method for a power plant as defined in claim 1, wherein said controlling step of each of the generating elements based on the optimum load distribution and the input process state quantity includes obtaining a control quantity based on a multi-variable model calculation.

4. The optimizing control method for a power plant as defined in claim 1, wherein the parallel-operated generating elements include a plurality of boilers and a plurality of turbines.

5. The optimizing control method for a power plant as defined in claim 4, wherein the physical model of the turbines is a physical model in consideration of pressure loss characteristics which depend on a steam flow rate through a turbine steam control valve.

10. The optimizing control method for a power plant as defined in claim 1, wherein the steam enthalpies comprise steam enthalpies at steam inlet and outlet of a steam control valve in the each of the generating elements.

6. An optimizing control system, for use in a power plant including a plurality of parallel-operated generating elements supplying electricity and steam, for controlling the generating elements by using an optimum load distribution while satisfying a balance between demand and supply of the electricity and the steam, said optimizing control system comprising:

an optimizing system for estimating parameters of characteristics and state of the generating elements, which cannot be directly measured, among parameters of the generating elements needed for calculation of the optimum load distribution for each of the generating elements, based on a physical model of each of the generating elements and an input process state quantity, to determine an optimum load distribution of each of the generating elements which minimizes total cost of the power plant; and

a multi-variable control system for obtaining and setting a control quantity of each of the generating elements based on a multi-variable model predictive control using the optimum load distribution determined by said optimizing system and input process quantity,

wherein the physical model includes steam enthalpies of steam inlet and steam outlet.

7. The optimizing control system for a power plant as defined in claim 6, wherein said optimizing system includes a scheduling system for inputting schedule control data indicating information of fluctuating factors of running cost of the power plant in a specified period, and executing a schedule calculation for obtaining a schedule to operate the power plant while minimizing the running cost in the specified period based on the input schedule control data and the model for the power plant, and an optimizing operation system for calculating the optimum load distribution of the each of the generating elements depending on the parameters of the each of the generating elements and the input process state quantity based on the schedule obtained by the schedule calculation.

8. The optimizing control system for a power plant as defined in claim 6, wherein said parallel-operated generating elements include a plurality of boilers and a plurality of turbines.

9. The optimizing control system as defined in claim 8, wherein the physical model of the turbines is a physical model in consideration of pressure loss characteristics which depend on a steam flow rate through a turbine steam control valve.

11. The optimizing control system for a power plant as defined in claim 6, wherein the steam enthalpies comprise steam enthalpies at steam inlet and outlet of a steam control valve in the each of the generating elements.