Patent Application
20210317782
The disclosure relates generally to the modeling and control of power plants. More specifically, embodiments of the disclosure provide an operational methodology to model and control a power plant by modeling and analysis of variant split loads for multiple gas turbines within the power plant.
Power plants typically include a variety of different turbomachines and/or systems that are used to generate a power output. Two conventional power systems used to generate power include gas turbine systems and combined cycle power plants, which typically include a gas turbine system(s). Conventional combined cycle power plants employ one or multiple gas turbine system(s) operatively coupled to one or multiple steam turbine system(s). The gas turbine system includes a compressor coupled to a gas turbine. The gas turbine is usually coupled to and drives an external component, such as a generator, for producing a load or power output. The steam turbine system includes a high pressure (HP) turbine portion operatively coupled to an intermediate pressure (IP) turbine portion that, in turn, is coupled to a low pressure (LP) turbine. Similar to the gas turbine of the gas turbine system, the HP, IP and LP turbines are employed to drive an external component (e.g., generator). In a typical combined cycle power plant, exhaust gas from the gas turbine is passed to a heat recovery steam generator (HRSG), which may be used to produce and reheat steam to the various turbines of the steam turbine system for enhanced efficiency of the system and/or power plant. Downstream of the HRSG the exhaust gas is released to the atmosphere through a stack.
The increased availability of alternative energy sources, such as various forms of renewable energy, has also increased the complexity of operating combined cycle power plants. Fluctuations in power generation demand on a combined cycle power plant often require the system to shift between different load conditions, varying the amount of generated power over time. The operation of a power plant at different amounts of load may affect several attributes of the power plant, including the internal temperature of various components and/or fuel consumption. In some cases, extended operation at varying loads may adversely affect efficiency or useful life of some components.
A first aspect of the disclosure provides a method for operating a combined cycle power plant (CCPP), the method including: generating a power plant model for operating the CCPP at an ambient condition and a load condition; determining whether at least two gas turbines in the power plant model of the CCPP generate a power output at the ambient condition and the load condition; modeling a fuel consumption of the CCPP for a baseline split ratio between the at least two gas turbines using the power plant model of the CCPP at the ambient condition and the load condition; creating a variant split ratio between the at least two gas turbines; determining, using the power plant model, whether the variant split ratio meets a quality threshold for the CCPP, the quality threshold including at least a minimum reduction in the fuel consumption; recalculating the variant split ratio in response to the variant split ratio not meeting the quality threshold; and adjusting the CCPP to use the variant split ratio in response to the variant split ratio meeting the quality threshold.
A second aspect of the disclosure provides a program product stored on a computer readable storage medium for operating a combined cycle power plant (CCPP), the computer readable storage medium including program code for causing a computer system to perform actions including: generating a power plant model for operating the CCPP at an ambient condition and a load condition; determining whether at least two gas turbines in the power plant model of the CCPP generate a power output at the ambient condition and the load condition; modeling a fuel consumption of the CCPP for a baseline split ratio between the at least two gas turbines using the power plant model of the CCPP at the ambient condition and the load condition; creating a variant split ratio between the at least two gas turbines; determining, using the power plant model, whether the variant split ratio meets a quality threshold for the CCPP, the quality threshold including at least a minimum reduction in the fuel consumption; recalculating the variant split ratio in response to the variant split ratio not meeting the quality threshold; and adjusting the CCPP to use the variant split ratio in response to the variant split ratio meeting the quality threshold.
A third aspect of the disclosure provides a system including: a combined cycle power plant (CCPP) having a gas turbine and a heat recovery steam generator (HRSG); and a system controller in communication with the gas turbine and the HRSG of the CCPP, the system controller being operable to: operate the CCPP at an ambient condition and a load condition; generate a power plant model of the CCPP for operating at the ambient condition and the load condition; model a fuel consumption using a baseline split ratio and the power plant model of the CCPP at the ambient condition and the load condition; create a variant split ratio for the CCPP; determine, using the power plant model, whether the variant split ratio meets a quality threshold for the CCPP, the quality threshold including at least a minimum reduction in the fuel consumption; modify the variant split ratio in response to the variant split ratio not meeting the quality threshold; and adjust the CCPP to use the variant split ratio in response to the variant split ratio meeting the quality threshold.
The illustrative aspects of the present disclosure are designed to solve the problems herein described and/or other problems not discussed.
These and other features of this disclosure will be more readily understood from the following detailed description of the various aspects of the disclosure taken in conjunction with the accompanying drawings that depict various embodiments of the disclosure, in which:
It is noted that the drawings of the disclosure are not to scale. The drawings are intended to depict only typical aspects of the disclosure, and therefore should not be considered as limiting the scope of the disclosure. In the drawings, like numbering represents like elements between the drawings.
As an initial matter, in order to clearly describe the current technology it will become necessary to select certain terminology when referring to and describing relevant machine components within the various systems, components, and other embodiments of the disclosure. To the extent possible, common industry terminology will be used and employed in a manner consistent with its accepted meaning. Unless otherwise stated, such terminology should be given a broad interpretation consistent with the context of the present application and the scope of the appended claims. Those of ordinary skill in the art will appreciate that often a particular component may be referred to using several different or overlapping terms. What may be described herein as being a single part may include and be referenced in another context as consisting of multiple components. Alternatively, what may be described herein as including multiple components may be referred to elsewhere as a single part.
In addition, several descriptive terms may be used regularly herein, as described below. The terms “first,” “second,” and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a,” “an,” and “the,” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.
Where an element or layer is referred to as being “on,” “engaged to,” “connected to” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
Embodiments of the present disclosure provide methods, program products, and systems for controlling various attributes of a combined cycle power plant (CCPP) by actively redistributing the power output from multiple gas turbines of the CCPP. Embodiments of the disclosure may include, e.g., generating a power plant model based on the CCPP for operating at an ambient condition and a load condition. The generating of such a model may include verifying the model's accuracy based on the present and/or historical operating data for the CCPP. The method may include determining whether at least two gas turbines in the power plant model of the CCPP will generate a power output at the ambient condition and the load condition. The method may also include using the model to model a fuel consumption of the CCPP as it operates at the ambient condition and the load condition, and creating a variant split ratio for modifying the relative amounts of power generated by the two or more gas turbines. The method may include determining whether the variant split ratio meets one or more quality thresholds for the CCPP, and adjusting the CCPP to use the variant split ratio in cases that meet these requirements. The adjusting of the CCPP may affect other variables of the CCPP, e.g., amount of inlet bleed heat (IBH) flow, heat rate, expected remaining lifespan of one or more gas turbines, and/or other variables affecting the power output and operating characteristics of the CCPP.
CCPP 12 can further include at least one gas turbine (GT) system 30. Although CCPP 12 may include two, five, ten, one-hundred, or more GT systems 30, only one is shown in
Although CCPP 12 is shown in
CCPP 12 can further include a heat recovery steam generator (HRSG) 54 fluidly connected with ST system 18 (e.g., with HP portion 24 and/or IP portion 20 and/or LP portion 22) and GT system 30. As shown in the non-limiting example of
CCPP 12 can further include a condenser 62. Condenser 62 may be in fluid communication and/or may be fluidly coupled with various components of CCPP 12. In a non-limiting example, condenser 62 may be fluidly connected and/or coupled to LP portion 22 of ST system 18 via steam exhaust duct 64. Condenser 62 may be configured to condense exhaust flow and/or bypass flow (e.g., line connecting HP 24 to condenser 62) from ST system 18 and/or HRSG 54, and providing a condensed fluid (e.g., condensate water) to HRSG 54, as is known in the art.
As shown in
In various embodiments, computing device(s) 66 can generate (i.e., create and/or verify) a power plant model 68 of CCPP 12. Power plant model 68 may model or otherwise simulate many aspects of CCPP 12 operation, including performance, economic variables, environmental data, and/or other attributes of CCPP 12. In some instances, power plant model 68 may be known as or referred to as a “digital twin” or “digital model,” and such terms are understood to be particular forms of power plant model 68 in various embodiments. Computing device 66 may be communicatively coupled to one or more sensors 70, as described herein, for provide input data for modeling and/or controlling CCPP 12. As discussed herein, computing device 66 can generate and/or modify power plant model 68. Computing device(s) 66 may rely upon the analysis and/or output from power plant model 68, as discussed below to control CCPP 12 and/or its various components to affect the operation of CCPP 12. For example, and as discussed herein, power plant model 68 may simulate various operational characteristics and/or settings of CCPP 12 (including power output and/or other parameters of ST system 18, GT system 30, HRSG 54, etc.) and the components included therein, to control the operation of system 10 and/or affect various attributes thereof.
In some cases, computing device 66 may include an operational control program (“Ops. Control Program”) 72 for interacting with and/or controlling various aspects of system 12. Operational control program 72 may take the form of any currently known or later developed control system for managing the operation of a power plant, e.g., a proportional-integral-derivative (PID) controller for managing transient operation of CCPP 12. Operational control program 72 additionally or alternatively may include a PID sub-system configured to operate selectively during various power generation modes of CCPP 12. A PID controller or sub-system, refers to a system configured to calculate an error value on a continuous basis as the difference between a desired target value and one or more predetermined variables. In the case of a PID controller, operational control program 72 may operate by detecting variance between one or more variable(s) and a corresponding target (e.g., in power plant model 68) and applying a corrective adjustment, i.e., instructions to vary one or more properties of CCPP 12, such as relative load output, component temperature, valve position, and/or other adjustable operating parameters. According to an example, the corrective adjustment by operational control program 72 may modify an instruction by computing device(s) 66, e.g., to adjust the power output from selected GT systems 30 (e.g., shifting between outputting 50% of the total power output to a higher or lower value). Further operations implemented by computing device(s) 66 may include, e.g., adjusting a valve for controlling the flow of fuel to a 90% capacity position, into a corrected instruction to adjust the valve to a 70% capacity position to reduce the firing temperature and/or combustion rate(s) of GT system(s) 30. Operational control program 72 thus may amplify or mitigate corrective actions output from other algorithms and/or controllers of CCPP 12, and/or may modify CCPP 12 to use the settings in power plant model 68. However implemented, corrective adjustments by operational control program 72 may be calculated from the variable(s) and target(s) based on proportional, integral, and derivative terms using variables within power plant model 68, those measured by sensor(s) 70, and/or other information within computing device(s) 66 and/or other devices in communication therewith.
As shown in
Although three sets of sensors 70 are shown, it is understood that system 10 may include more sensors 70 (e.g., as shown in
Referring to
As electrical grids diversify to include a wider variety of power sources, operation CCPP 12 or other systems at fixed load conditions has become less common. However, conventional implementations of CCPP 12 may not be structured to operate at such settings for extended time periods. In cases where CCPP 12 includes multiple GT systems 30 (e.g., systems 30A, 30B, 30C as shown), conventional methods for controlling CCPP 12 will evenly distribute the power generation burden across all GT systems 30 within CCPP 12, and/or allocate a higher power generation burden on selected GT system(s) 30 regardless of changes to load and/or ambient conditions. Embodiments of the disclosure provide a methodology for actively modeling and controlling the load split ratio (simply “split ratio” hereafter) between multiple GT system(s) 30 in CCPP 12 to maintain desired parameters and/or levels of efficiency when operating under conditions that differ from those predicted or otherwise contemplated in design specifications. Throughout the specification, “split ratio” may refer to the percent of load allocated to different GT system(s) 30 in CCPP 12, and additionally or alternatively may include the split ratio between GT system(s) 30 and other parameters such as changes to inlet guide vane (IGV) angle or inlet bleed heat (IBH) flow.
Embodiments of the disclosure also account for differences in the operation of CCPP 12 under different “ambient conditions,” i.e., differences in the temperature, pressure, and/or other attributes of the setting where CCPP 12 is operating. For example, CCPP 12 may be operating in an area where the temperature is between approximately fifteen degrees Celsius (° C.) and twenty-five ° C. Embodiments of the disclosure may distinguish between different ambient conditions based on predetermined temperature ranges (e.g., of approximately five ° C.) above or below another ambient condition. Thus, the “ambient condition” refers to a characterization of external variables (temperatures, pressures, etc.) within a particular embodiment, and not within user control. Higher temperatures may affect variables such as inlet temperature, exhaust temperature, fluid flow, heat rate, etc., throughout various subcomponents of CCPP 12. Similar variations to the above-noted and/or other variables of CCPP 12 may result from higher or lower operating pressures. In any case, the variations caused by the ambient condition of CCPP 12 may be independent of the load condition of CCPP 12.
According to embodiments, system 10 may include CCPP 12 operating under varying load conditions and/or ambient conditions. As the power output of CCPP 12 varies across operating conditions, CCPP 12 may produce its maximum output, a reduced output, etc. In such cases, the operational schedule for CCPP 12 may disproportionately generate power from some system(s) 18, 30 over other system(s) in CCPP 12. This situation may be associated with undesired consequences, such as reduced efficiency of one or more GT systems 30 of CCPP 12 as operation continues.
To improve operation at varying ambient conditions and/or load conditions, computing device(s) 66 and/or operational control system(s) 72 coupled to system(s) 18, 30 may rely on power plant model 68 to adjust the split ratio of GT system 30, thereby changing the power generation burden on each GT system 30 as CCPP 12 operates. Where applicable, the variant split ratio may be implemented, e.g., by changing the amount of fuel provided to GT system 30, adjusting operation settings of one or more GT system 30 in CCPP 12, and/or other operations discussed herein for increasing and decreasing the amount of power generated by targeted GT systems 30. The generation and verification of power plant model 68, in turn, may be based on monitoring and modeling the firing rate, exhaust temperatures, and/or heat rates within turbine component 48 based on load and ambient conditions, and further modeling other parameters of GT system 30 based on the modeled variables. In various embodiments, operational control system 72 may modify further operational parameters such as IGV 36 position, a fluid flow through an inlet bleed heat (IBH) line 76, and/or other operational parameters to further increase CCPP 12 efficiency and/or bring CCPP 12 into operational alignment with power plant model 68.
Referring to
Computing device 66 can include a processor unit (PU) 158, an input/output (I/O) interface 160, memory 152, and a bus 164. Further, computing device 66 is shown in communication with an external I/O device 166 and a storage system 168. CCPP system 154 may provide power plant model 68, which in turn can operate using various modules 202 (e.g., a calculator, a determinator, a comparator, etc.) for implementing various functions and/or logical steps. CCPP system 154 additionally or alternatively may provide operational control program 72 with its own set of modules 212 (e.g., a calculator, determinator, comparator, etc.) for implementing respective functions and/or steps of operational control program 72. The various modules 202, 212 can use algorithm-based calculations, look up tables, and similar tools stored in memory 152 for processing, analyzing, and operating on data to perform their respective functions. In general, PU 158 can execute computer program code to run software, such as CCPP system 154, which can be stored in memory 152 and/or storage system 168. While executing computer program code, PU 158 can read and/or write data to or from memory 152, storage system 168, and/or I/O interface 160. Bus 164 can provide a communications link between each of the components in computing device 66. I/O device 166 can comprise any device that enables a user to interact with computing device 66 or any device that enables computing device 66 to communicate with the equipment described herein and/or other computing devices. I/O device 166 (including but not limited to keyboards, displays, pointing devices, etc.) can be coupled to controller 160 either directly or through intervening I/O controllers (not shown).
Memory 152 can also include various forms of data 220 pertaining to CCPP 12 or more specifically system(s) 18, 30 of CCPP 12. As discussed elsewhere herein, power plant model 68 can simulate the operation of CCPP 12 at particular ambient and/or load conditions, while operational control program 72 can adjust exhaust temperature, firing temperature, relative load, and/or other operating parameters of CCPP 12 to implement one or more variant split ratios output from power plant model 68. To implement methods according to the disclosure, CCPP system 154 can store and interact with data 220 subdivided into various fields. For example, ambient condition field 222 can store data pertaining to ambient conditions for CCPP at various temperatures, pressures, and/or other environmental variables independent of CCPP 12 specifications. Data 220 can also include a load condition field 224 for cataloguing specification data for operating at various levels of output, including fixed and non-fixed outputs. A set of split ratios for CCPP 12 can be stored in a split ratio field 226 which can include one or more distributions of operating load for GT systems 30. Each split ratio recorded in split ratio field 226 optionally may be expressed as a load-dependent schedule of split loads for CCPP 12 at different load and/or ambient conditions. The values for each parameter stored in split ratio field 226 can in some cases be based on calibrated data and/or simulated values from power plant model 68 for one or more parameters during non-base load operation. It is thereby understood that data 220 can include several measured and/or calculated variables that can be applied to and/or stored in split ratio field 226 to control the relative power output for a set of GT systems 30. Data 220 may also include, e.g., a quality threshold field 228 for cataloguing quality thresholds such as a minimum improvement to CCPP 12 performance (e.g., heat rate reduction, plant efficiency increase, fuel consumption reduction, plant capacity increase, etc.), compliance with emissions limits (e.g., Nox emissions, CO emissions, etc.), compliance with operational stability limits (e.g., compressor operability limits, combustion stability limits, gas turbine firing temperature(s), gas turbine exhaust temperature(s), turbine shaft torque limits for system(s) 18, 30, operational limits of HRSG 54, operational limits for ST system 18, condenser pressure limits, etc.), and/or other operational quality metrics for CCPP 12. As noted herein, quality threshold field 228 may define one or more parameters which CCPP 12 must meet in order to shift from one split ratio to another.
Computing device 66 can comprise any general purpose computing article of manufacture for executing computer program code installed by a user (e.g., a personal computer, server, handheld device, etc.). However, it is understood that computing device 66 is only representative of various possible equivalent computing devices and/or technicians that may perform the various process steps of the disclosure. In addition, computing device 66 can be part of a larger system architecture operable to model and/or control various aspects and elements of CCPP 12.
To this extent, in other embodiments, computing device 66 can comprise any specific purpose computing article of manufacture comprising hardware and/or computer program code for performing specific functions, any computing article of manufacture that comprises a combination of specific purpose and general purpose hardware/software, or the like. In each case, the program code and hardware can be created using standard programming and engineering techniques, respectively. In one embodiment, computing device 66 may include a program product stored on a computer readable storage device, which can be operative to automatically control elements of CCPP 12 (e.g., systems 18, 30, HRSG(s) 54, etc.) when executed.
Referring to
To initiate methods according to the disclosure, process P1 may include causing CCPP 12 to operate at a particular load condition and ambient condition. The load condition may refer to the power output from CCPP 12 during operation, and may include fixed or non-fixed loads to accommodate varying circumstances. As examples, a load condition for CCPP 12 may include peak load operation, base load operation, reduced load operation, variable load operation, and/or extended transient operation of CCPP 12. The ambient condition for operating CCPP 12 may refer to the external temperature, pressure, and/or other external variables affecting the operation of CCPP 12. The ambient condition of CCPP 12 may include, e.g., specification temperature operation, raised temperature operation, reduced temperature operation, transient temperature, operation, etc. Various load conditions, ambient conditions, and/or combinations thereof may cause CCPP 12 to exhibit operational parameters (e.g., temperatures, pressures, and flow rates) that differ significantly from their specification levels. Further processes according to the disclosure may simulate the operation of CCPP 12, and in some cases, modify the operation of CCPP 12 to prevent inefficient operation, greater than desired use of cooling fluid(s) and/or components, and/or to avoid negative consequences of operating outside specified ranges, by changing the relative power generation burden on multiple GT systems 30 within CCPP 12.
During operation of CCPP 12, embodiments of the disclosure may include generating power plant model 68 of CCPP 12. As used herein, the term “generating” may include one or more processes for simulating the operation of CCPP 12 under a particular load condition and ambient condition, changing of an existing power plant model 68 to “as running” conditions, correcting of an existing power plant model 68 to “as running” conditions, tuning of an existing power plant model 68 to “as running” conditions, calibrating of an existing power plant model 68 to “as running” conditions, and additionally or alternatively verifying the accuracy of power plant model 68 based on concurrent operating data for CCPP 12 and/or other forms of data suitable for verifying the accuracy of power plant model 68. In the case of verifying based on comparing power plant model 68 to CCPP 12 operation, process P2 may include indicating whether power plant model 68 is valid based on whether one or more modeled parameter(s) of CCPP 12 are similar to (i.e., equal to or within a predetermined margin of error) to the actual CCPP 12 parameters. Such verification additionally or alternatively may include changing power plant model 68 to account for discrepancies between model parameters and actual CCPP 12 parameters, and subsequently verifying whether power plant model 68 is accurate after such adjustments occur. The terms “generating” and/or “changing,” with respect to power plant model 68, also encompass actions such as “correcting or calibrating or tuning or updating” the power plant model as CCPP plant performance changes over time, e.g., due to degradation, changes, upgrades, etc. In such cases, terms such as “as-running tuned power plant model” may refer to further revising an existing model to arrive at a desired split ratio. Process P2 thus may include determining whether power plant model 68 is acceptably accurate, e.g., based on meeting or exceeding a predetermined amount of accuracy (e.g., percentage of modeled parameters in compliance with CCPP 12, optionally over a predetermined time interval). Power plant model 68, once verified, may represent a baseline set of operating parameters for CCPP 12.
During their operation, implementations of CCPP 12 that feature multiple GT systems 30 may or may not generate power from more than one GT systems 30 at one time. For example, CCPP 12 with three GT systems 30A, 30B, 30C may output power from only one GT system 30 during a particular timespan, but may output power from multiple GT systems 30 during another timespan. Embodiments of the disclosure modify the load distribution on GT systems 30 only when multiple GT systems 30 are generating power at the same time. In decision D1, modules 202 of power plant model 68 may determine whether multiple GT systems 30 are generating power while CCPP 12 continues to operate at a set of ambient and load conditions. Where only one GT system 30 is generating power (i.e., “No” at decision D1), the method may return to process P1 of continuing to operate CCPP 12 at the existing load and ambient condition until one or both of the conditions change. Where multiple GT systems 30 are generating power (i.e., “Yes” at decision D1), the method may continue by evaluating whether changes in the split ratio between GT systems 30 of CCPP 12 will improve the performance of CCPP 12.
Embodiments of the disclosure may include modeling a fuel consumption of CCPP 12 using power plant model 68. The amount of fuel consumption may be with respect to a particular time interval for operating CCPP 12, and with respect to the above-noted ambient and/or load conditions for CCPP 12. The fuel consumption of CCPP 12 may be expressed as, e.g., a total amount of fuel expected to be consumed over a particular time interval, and/or by targeted GT system(s) 30, at the modeled load condition and ambient condition. Additionally or alternatively, the fuel consumption modeled in process P3 may be expressed as a percent efficiency, a percentage of fuel consumed relative to desired levels, relative amounts of fuel consumed by each GT system 30, or other load conditions and/or ambient conditions. The fuel consumption modeled in process P3 thus may include any conceivable metric for modeling the amount of fuel consumed by CCPP 12.
Continuing to process P4, embodiments of the disclosure may include using power plant model 68 to create a variant split ratio for CCPP 12. The variant split ratio may be created in process P4 by any conceivable modeling operation, based on various operating parameters included within and/or modeled by power plant model 68. The variant split ratio may include alternate relative allocations of power generation across GT systems 30A, 30B, 30C. The variant split ratio may also include a schedule of alternative split ratios, each of which are dependent on the total load output from CCPP 12. However expressed, the variant split ratio may affect operational parameters and/or ranges of operational parameters which differ from their present values in power plant model 68. These parameters and other parameters may be modified indirectly, e.g., by modifying the load condition at which CCPP 12 operates. Such parameters may include one or more of inlet temperatures, outlet temperatures, inlet guide vane (IGV) pitch angle, inlet bleed heat (IBH) volume, firing rate, etc. variant split ratio may be biased in favor of specific GT systems 30 and/or allocation profiles based on an operating schedule for CCPP 12, e.g., to favor the use of newer GT systems 30 and/or those with operating specifications more closely aligned with the current ambient and/or load conditions, etc. The relative power generating burden on each GT system 30 in the variant split ratio may be determined, e.g., by random selection of a bias size and/or direction, and/or by applying predetermined logic for variant split ratios that are more likely to improve the operation of CCPP 12. Such logic may be based on power plant model 68, actual parameters of CCPP 12, and/or other variables or models relevant to CCPP 12.
The variant split ratio created in process P4 may include power output increases and/or reductions for each GT system 30 that is currently generating power in CCPP 12. In some cases, one or more quality thresholds of CCPP 12 may improve by modifying the split ratio between GT systems 30 in CCPP 12. In such cases, the variant split ratio may reduce the exhaust temperature/energy, thereby routing less fluid through attemperator(s) 74, and improve CCPP 12 efficiency by reducing fuel consumption for a fixed load. other cases, the variant split ratio may increase the temperature within the load path of CCPP 12. Specifically, the variant split ratio may propose higher or lower power outputs for each GT system 30 in CCPP 12. Such a modification may be desired in cases where one or more GT systems 30 are operating at higher-than-specification loads. Although several variant split ratios to improve efficiency, fuel consumption, system health, etc., may be possible at a particular time, process P4 may require any variant split ratios to have a minimum projected improvement before being power plant model is applied to control of CCPP 12.
After a variant split ratio is created from power plant model 68 in process P4, methods according to the disclosure may include several decisions for determining whether to modify the operation of CCPP 12 based on the variant split ratio created in process P4. At decision D2, modules 212 of operational control program 72 may evaluate whether applying the variant split ratio to CCPP 12 will continue to meet a quality threshold for CCPP 12 (e.g., maximum values of temperature, pressure, temperature, fuel consumption, etc.). According to an example, the quality threshold may be expressed as whether fuel consumption by CCPP 12 is reduced by at least a threshold amount. In this case, the reduction in fuel consumption may be defined as a percentage (e.g., at least approximately 1% reduction in fuel consumption over a specified timespan). In further examples, the quality threshold may include additional threshold improvements to CCPP 12 operation, e.g., a minimum heat rate reduction, a minimum plant efficiency increase, compliance with an emissions limit, and/or compliance with an operating stability limit for CCPP 12. The “emissions limit” may refer to a maximum allowable level of carbon dioxide and/or nitrogen oxide emissions levels for CCPP 12. The “operating stability limit” may refer a maximum amount by which the variant split ratio reduces the expected lifespan and/or exceeds specification limits for CCPP 12 and/or its subcomponents. As noted herein, the quality threshold(s) evaluated in decision D2 and stored in quality threshold field 228 may include metrics such as a minimum improvement to CCPP 12 performance (e.g., heat rate reduction, plant efficiency increase, fuel consumption reduction, plant capacity increase, etc.), compliance with emissions limits (e.g., Nox emissions, CO emissions, etc.), compliance with operational stability limits (e.g., compressor operability limits, combustion stability limits, gas turbine firing temperature(s), gas turbine exhaust temperature(s), turbine shaft torque limits for system(s) 18, 30, operational limits of HRSG 54, operational limits for ST system 18, condenser pressure limits, etc.), and/or other operational quality metrics for CCPP 12.
In cases where the variant split ratio does not meet the quality threshold (i.e., “No” at decision D2), the method may proceed to process P5 of modifying the variant split ratio. Such modifications may be random changes, and/or may be based on a schedule of possible changes governed by logic within power plant model 68, and/or may be based on results of plant power plant model (“e.g., a “digital twin”) based experimentation and/or computations. In cases where the quality threshold is met (i.e., “Yes” at decision D2), the method may continue to further operations for applying the variant split ratio to CCPP 12. In some cases, methods according to the disclosure may test only a predetermined number of variant split ratios (e.g., five, ten, fifty, or one hundred or more variant split ratios). In such an example, the method may conclude (“Done”) after decision D2 indicates that none of the tested variant split ratios meet the relevant quality threshold(s).
In cases where the variant split ratio meets the quality threshold, methods according to the disclosure may include process P6 in which operational control system 72 adjusts CCPP 12 to use the variant split ratio. Process P6 may involve operational control system 72 applying one or more modifications to GT system(s) 30 (e.g., temperatures such as firing temperature, inlet temperature, exhaust temperature, etc.) to modify their output as defined in the variant split ratio. In some cases, operational control system 72 may adjust and/or otherwise modify the varied parameters based on one or more properties of the specific CCPP 12 unit that is being controlled. In any case, the parameters (e.g., temperatures) being modified may be biased substantially in real time as CCPP 12 continues to operate. After CCPP 12 is adjusted in process P6, the method may conclude (“Done”) and CCPP 12 may continue to operate using the variant split ratio. In further examples, the method may return to process P1 of operating CCPP 12 at a particular load and ambient condition, and where applicable repeating all subsequent processes in the event that the load or ambient condition of CCPP 12 changes from its previous state to a new state.
Adjusting CCPP 12 to use the variant split ratio in process P6 may affect one or more additional operations as a result of implementing the variant split ratio. According to one example, the adjusting affect the fluid flow through attemperator(s) 74 to attain the desired temperature increase or reduction within CCCPP 12. In another example, the adjusting may affect a pitch angle of IGV(s) 36, thereby changing the inlet temperature within GT system 30 and/or the temperatures of other fluidly connected components. In yet another example, the adjusting may affect an amount of compressor exhaust fluid routed through IBH line 76, thereby also modifying both the inlet and outlet temperature(s) of compressor 32. In still another example, the modifying may affect a steam output from HRSG 54 to further modify one or more temperatures within ST system 18 and/or GT system 30.
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Advantages of the disclosure allow for agile deployment and use of CCPP 12 in a power grid with a variety of energy sources, and/or in non-base load operating settings. In embodiments of the disclosure, CCPP 12 can allow more efficient use of GT system(s) 30, and their underlying use of fuel, when shifting between different amounts of power output and/or different operating conditions. Embodiments of the disclosure thus allow CCPP 12 to compensate internally for fluctuations in energy demand, unavailability of other power sources, etc. with minimal effect on the health of each GT system 30. The improvements to CCPP 12 may reduce fuel consumption and improve efficiency during operation, thereby extending the lifespan of individual GT systems 30 and their components. Operating CCPP 12 in a mode where the split ratio between each GT system 30 is modified actively can provide significant lifespan extension, and lower maintenance requirements. Additionally, embodiments of the disclosure may be implemented without significant changes to CCPP 12 hardware by modifying existing control logic, circuits, etc., to accommodate the operational methodologies described herein.
Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about,” “approximately” and “substantially,” are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged; such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. “Approximately” as applied to a particular value of a range applies to both end values, and unless otherwise dependent on the precision of the instrument measuring the value, may indicate +/−10% of the stated value(s).
The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present disclosure has been presented for purposes of illustration and description but is not intended to be exhaustive or limited to the disclosure in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. The embodiment was chosen and described in order to best explain the principles of the disclosure and the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated.
