Patent Publication Number: US-2017363006-A1

Title: System to enable spray intercooling in isochronous operation for power augmentation for spray intercooling engines

Description:
BACKGROUND 
     The subject matter disclosed herein relates to gas turbines, and more particularly, to controlling operation of a spray intercooling system of a gas turbine. 
     Frequently in power generation, turbine systems may be used to convert fuel and an oxidant into power. For example, a gas turbine may be used to provide power to one or more loads, such as conveyor belts, blowers, motors, electric generators, or other industrial equipment. The gas turbine may use one or more compressors to provide a compressed oxidant (e.g., air, oxygen, oxygen-enriched air, or oxygen-reduced air) that is combined with a fuel and combusted to rotate blades of the turbine to produce power. Gas turbines may have a spray intercooling system to cool the temperature of the compressed oxidant entering the gas turbine. Because the spray intercooling system often uses fluids that react slower than desirable to changes in power, it is desirable to improve how spray intercooling systems react to changes in power. 
     BRIEF DESCRIPTION 
     Certain embodiments commensurate in scope with the originally claimed disclosure are summarized below. These embodiments are not intended to limit the scope, but rather these embodiments are intended only to provide a brief summary of possible forms of the disclosure. Indeed, the disclosure may encompass a variety of forms that may be similar to or different from the embodiments set forth below. 
     In a first embodiment, a control system for a gas turbine system includes a virtual filter configured to receive a power signal of the gas turbine system having a spray intercooler, substantially remove sensor noise in the power signal and filter transient power changes of the gas turbine system to provide a filtered power signal, and provide the filtered power signal to a controller of the spray intercooler, wherein the controller is configured to control operation of the spray intercooler based on the filtered power signal. 
     In a second embodiment, a system includes a controller configured to control operations of a gas turbine having a spray intercooler, the controller comprising a processor configured to receive a power signal of the gas turbine system, apply a virtual filter to substantially remove sensor noise in the power signal and transient power changes of the gas turbine system to provide a filtered signal, and control operation of the spray intercooler based on the filtered signal. 
     In a third embodiment, a non-transitory computer-readable medium has computer executable code stored thereon, the code comprising instructions to receive a power signal of a gas turbine having a spray intercooler, apply a virtual filter to substantially remove sensor noise in the power signal and transient power changes of the gas turbine system to provide a filtered signal, and control operation of the spray intercooler based on the power signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
         FIG. 1  is a schematic diagram of an embodiment of a gas turbine system with a controller for a spray intercooling system; 
         FIG. 2  is a graph of an embodiment of power signals of the gas turbine system of  FIG. 1 ; 
         FIG. 3  is a schematic diagram of an embodiment of a filter for the controller of  FIG. 1 ; and 
         FIG. 4  is a flow chart of an embodiment of a process performed by the controller of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     One or more specific embodiments of the present disclosure will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. 
     The systems and methods described herein are directed to controlling a spray intercooling system of a gas turbine system. Typically, a gas turbine system may be used to provide mechanical power to one or more systems, such as motors, conveyor belts, blowers, electrical generators, or the like. To generate power, the gas turbine may combust an oxidant mixed with a fuel to rotate blades of the turbine. Frequently, the oxidant is compressed to allow the turbine to operate more efficiently. For example, the oxidant (e.g., air) may be compressed in a low pressure compressor and a high pressure compressor. 
     The gas turbine system may include a spray intercooling system that sprays a fluid, such as water, into the low pressure compressor and/or the high pressure compressor to reduce a temperature of the oxidant, thereby augmenting power generated by the gas turbine. For example, the spray intercooling system may control the temperature of the oxidant by spraying (e.g., via mist injection through a nozzle) the fluid atomized with air to allow heat from the oxidant to be absorbed by the fluid, as well as to increase mass flow. 
     To improve efficiency, the spray intercooling system may operate depending on a signal of the gas turbine, such as a power signal. For example, if a controller derives that electric power demand and/or power generated by the gas turbine suggests that the gas turbine would operate more efficiently by using the spray intercooling system, then the spray intercooling system may be turned on, e.g., via the controller. Similarly, if the controller derives that the electric power demand and/or power generated by the gas turbine suggests that the gas turbine would operate less efficiently by using the spray intercooling system, then the spray intercooling system may be turned off. 
     The systems that consume electric power (e.g., the grid) often expect to receive the electric power from the gas turbine system, e.g., via an electrical generator system, at a desired frequency and/or magnitude of electric power. To deliver electric power at the desired frequency and/or magnitude, the gas turbine may synchronize operation with one or more other gas turbines. To control power generated, the gas turbine system via the electrical generator may increase or decrease the frequency and/or phase angle in what is referred to as droop control. 
     In other cases, the gas turbine system may operate in isochronous mode, e.g., where the gas turbine is controlled to operate and maintain a set speed. For example, the gas turbine may operate at 3600 RPM to power the mechanically coupled systems described above, such as the electrical generator. In such cases, when operating in isochronous mode, the gas turbine system may operate standalone and not part of a citywide, statewide, or regional grid. While isochronous mode allows the gas turbine system to operate at a set speed, isochronous mode frequently involves adjusting power generated by the turbine system to account for changes in power demand from the loads. For example, a conveyor belt may operate using electric power received from the gas turbine via the electrical generator while operating in isochronous mode. When the conveyor belt is turned on, the turbine system may increase power generated to match an increase in the power demand. The power change may be a step increase or other rapid power change (e.g., instantaneous change). As the spray intercooling system operates based on the power signal of power demand and/or power generation, the power changes can cause the spray intercooling system to turn on and/or off to decrease the efficiency that the spray intercooling system provides. For instance, the power signal may overshoot or undershoot a steady state power level. Further, the power signal may include noise from the sensor, sampling, or the like. By including the filter, removing sensor noise may enable the spray intercooling system to operate in isochronous mode and to provide an increase in output (e.g., 0-5%). 
     As described herein, a virtual “filter” may be included to oversee the overshoots, undershoots, and/or sensor noise in the power signal to enable the spray intercooling system to operate during changes in electrical power demand and/or power generation when operating in isochronous mode. The filter may be configured to receive a power signal of a gas turbine. The filter may attenuate noise in the power signal from a sensor and power changes of the gas turbine. The filter may provide a transformed signal to the controller of the spray intercooling system where the transformed signal prevents the spray intercooling system from shutting off and/or turning on due to the overshoots, undershoots, and/or sensor noise. 
     Turning to the figures,  FIG. 1  is a schematic diagram of a power generation system  10  that includes a gas turbine system  12 . The gas turbine system  12  may receive an oxidant  14  (e.g., air, oxygen, oxygen-enriched air, or oxygen-reduced air) and a fuel  16  (e.g., gaseous or liquid fuel), such as natural gas, syngas, or petroleum distillates. The oxidant  14  may be pressurized and combined with the fuel  16  to be combusted in a combustor  18 . The combusted oxidant-fuel mixture may then be used to apply forces to blades of a turbine  20  to rotate a shaft  22  that is used by a generator  24  to provide electrical power to one or more loads  26 . 
     The gas turbine system  12  may include one or more compressors that increase the pressure of the oxidant  14  to improve efficiency during combustion. While two compressors are used herein, this is merely an example and any suitable combination of compressors may be used, such as a one, two, three (e.g., low pressure compressor, intermediate pressure compressor, and high pressure compressor), or more compressors. As depicted in  FIG. 1 , the gas turbine system  12  includes a low pressure compressor  28  and a high pressure compressor  34 . The low pressure compressor may be coupled to the high pressure compressor  34  via a conduit  29 . The oxidant  14  may enter the low pressure compressor  28  to be compressed before entering the conduit  29  to be further compressed by the high pressure compressor  34 . 
     The power generation system  10  may include a spray intercooling system  30  or an efficient spray intercooling system. The spray intercooling system  30  may reduce the temperature of the oxidant  14  in the one or more of the compressors  28  and  34  by providing a spray intercooling fluid  32 , such as water, into the air flow. That is, the spray intercooling system  30  may be configured to inject water into the one or more of the compressors  28  and  34  to increase a compression ratio, thereby increasing the power output. Spray intercooling may also be referred to as wet-compression. As an example, the spray intercooling system  30  may include one or more spray nozzles  36  and  37  to spray a mist of the spray intercooling fluid  32  mixed with air to transfer heat from the oxidant  14  to the mist. Further, the spray nozzles  36  and  37  may be mounted to a front frame, an inlet, or any suitable location on the compressors  28  and  34 . In some embodiments, the spray intercooling system  30  may use air (e.g., the oxidant  14 ) extracted from the high pressure compressor  34  to atomize the spray intercooling fluid  32  into a mist. 
     The supply of the spray intercooling fluid  32  may include a variety of components for flow control, flow distribution, and fluid treatment. The fluid supply may include a storage tank, a conduit, a freshwater source (e.g., a lake or river), a plant component (e.g., equipment in a power plant that provides a process fluid), a pump, a valve, a distribution manifold, a fluid treatment system (e.g., filter, solid-liquid separator, gas-liquid separator, and/or chemical absorber), or the like. 
     A flow of the spray intercooling fluid  32  from a supply to the nozzles  36  and  37  may be controlled based on a signal  39 . For example, the signal  39  may be a signal sent to a turn the spray intercooling system  30  on or off. Further, the signal  39  may be used by the spray intercooling system  30  to control a valve  38 , a solenoid, pump, or the like. To control the flow of the spray intercooling fluid  32  from the supply to the nozzle  36  and  37 , the valve  38  may be opened or closed based depending on the signal  39 . 
     The high pressure compressor  34  may further compress the oxidant that is misted by the spray intercooling system  30  before combustion in the combustor  18 . The combustor  18  may be coupled to one or more turbines  20 , such as a low pressure, medium pressure and/or high pressure turbine. While  FIG. 1  shows three turbines, any number of turbines may be included in the power generation system  10 . For example, the gas turbine system  12  may include 1, 2, 3, 4, or more turbines. The combusted air-fuel mixture creates forces on blades of the turbine to rotate the shaft  22 . The rotation of the shaft  22  enables the generator  24  to provide power to one or more loads  26 . The gas turbine system  12  may be used to generate power for one or more industrial loads, such as a conveyor belt, a blower, a motor, or the like. 
     The power generation system  10  may include a controller  44  to control operations of the gas turbine system  12 , the spray intercooling system  30 , the generator  24 , or the like. For example, the controller  44  may be a redundant controller having three processing cores (e.g., R, S, T cores) that may redundantly control an amount of oxidant  14  and an amount of fuel  16  (e.g., air-fuel ratio) that are used in the combustion process. Indeed, the controller  44  may include a processor  46  or multiple processors, memory  48 , and inputs/outputs (i.e., I/O). The processor  46  may be operatively coupled to the memory  48  to execute instructions for carrying out the presently disclosed techniques. These instructions may be encoded in programs or code stored in a tangible non-transitory computer-readable medium, such as the memory  48  and/or other storage. The processor  46  may be a general purpose processor (e.g., processor of a desktop/laptop computer), system-on-chip (SoC) device, or application-specific integrated circuit, or some other processor configuration. The memory  48 , in the embodiment, includes a computer readable medium, such as, without limitation, a hard disk drive, a solid state drive, diskette, flash drive, a compact disc, a digital video disc, random access memory (RAM), and/or any suitable storage device that enables the processor  46  to store, retrieve, and/or execute instructions and/or data. The memory  48  may include one or more local and/or remote storage devices. The controller  44  may include a wide variety of inputs/outputs (i.e. I/O) to receive and/or transmit one or more signals. For instance, the I/O may allow the controller  44  to receive and/or send one or more signals from spray intercooling system  30 , the gas turbine system  12 , the generator  24 , and/or one or more loads  26 . As an example, the I/O may receive a power signal from a sensor  50  indicating power demand, power generated, or the like. While the sensor  50  is shown coupled to the generator  24 , sensors may be located on the gas turbine system  12 , the spray intercooling system  30 , or any other suitable location. As a further example, the sensor  50  may be a high pressure compressor exhaust pressure sensor (e.g., PS3 sensor). 
     The processor  46  may control the power, e.g., electrical power, generated  42  by the gas turbine system  12  to power the loads  26 . Each of the loads  26  may utilize various amounts of power. For example, when a conveyor belt is turned on, a power demand signal  40  may indicate an increase in power demand of the loads  26 . When operating in isochronous mode, it is desirable to increase power generated  42  according to increases in power demand. Moreover, the processor  46  may control parameters of the gas turbine system  12 , the spray intercooling system  30 , and/or the generator  24  to control the power generated  42  by the generator  24  based on changes in the power demand signal  40 . For example, when in isochronous mode, if the power demand signal  40  indicates increases in power demand, the processor  46  may control the gas turbine system  12  to utilize additional fuel  16  and/or oxidant  14  to maintain the speed of the turbines  20 . For instance, the processor  46  may send the signal  39  to turn off or turn on the spray intercooling system  30  to control flow of the spray intercooling fluid  32  and thereby regulating temperature of the oxidant  14 . 
     However, by turning on and/or turning off industrial loads when in isochronous operations, one of the power signals (e.g., power demand signal  40 , generated power signal  42 , etc.) may change (e.g., increase or decrease) faster than the spray intercooling system  30  can change the cooling rate of the oxidant  14 . In other words, the spray intercooling fluids  32  of the spray intercooling system  30  may not be designed to account for rapid changes in power demand and/or generation. Moreover, the power signal may include noise from the sensor  50  and/or a transient acceleration power that may cause overshoots and/or undershoots in controlling the spray intercooling system  30 . Removing sensor noise may enable the spray intercooling system to operate in isochronous mode and to provide an increase in output. 
     For the processor  46  to control the spray intercooling system  30 , the power signal may be transformed by a virtual filter  52 . The filter  52  may include a Tustin filter, a Euler filter, or the like. The filter  52  may be a first order lag filter that transforms a frequency response of the power signal by substantially removing sensor noise and/or substantially removing transient power changes of the gas turbine system  12  to provide a filtered power signal. For example, the first order lag filter may attenuate the power signal at one or more cutoff frequencies. The filter  52  may include circuitry separate from the controller  44  to provide a filtered power signal to the controller  44 . Alternatively and/or additionally, the filter  52  may include instructions stored in the memory  48  of the controller  44  and executed by the processor  46  (e.g., running code) to filter the power signal. The processor  46  may then control the spray intercooling system  30  based on the filtered power signal to improve efficiency of the gas turbine system  12 . 
     To control operation of the spray intercooling system  30 , the gas turbine system  12 , and/or the generator  24 , the processor  46  may send and/or receive one or more signals.  FIG. 2  is a set of graphs of various signals that may be utilized by the processor  46  of the controller  44 . While these graphs may be viewed on a display of the controller  44 , the processor  46  may perform the methods described herein without displaying the graphs. Moreover, it should be noted that these graphs are examples used to illustrate the processes herein, and other signals and inputs may be used. 
     Graph  58  shows an example of demand signal  59  of fuel  16  for the gas turbine system  12 . As shown in  FIG. 2 , at various times T 1 , T 2 , T 3 , and T 4 , fuel demand increases. These increases may correspond to increases in power demand indicated in the power demand signal  40 . For example, one or more electric motors may be turned on at each of times T 1 , T 2 , T 3 , and T 4  which cause an increase in power demand for the gas turbine system  12  to provide. To generate additional power to meet the increased power demand, the fuel demand of the gas turbine system  12  may rise as shown in graph  58 . 
     Graph  60  shows an example of a reference signal  61  of a power set point of the gas turbine system  12 , with an x-axis representative of time and a y-axis representative of signal  61  strength. When in isochronous mode, the power set point provides a desired power for the gas turbine system  12  to produce to maintain the desired speed. As shown in graph  60 , the changes in power that the gas turbine system  12  is desired to produce can be rapid changes (e.g., step changes). For example, prior to time T 1 , a motor may be initially off. When the motor is turned on after time T 1 , the gas turbine system  12  is asked to produce additional power to maintain speed. Similar events may occur at T 2 , T 3 , and T 4  when additional equipment is turned on. 
     Graphs  62 ,  64 , and  66  show examples of signals  63 ,  65 ,  68  that may be used by the processor  46  to control the spray intercooling system  30 . The graphs include x-axes that are aligned with each other in time and y-axes that include increasing signal strength. For example, graph  66  includes a power signal  68  that indicates power demand or power generation of the gas turbine system  12 . If the processor  46  utilizes the power signal  68  to control the spray intercooling system  30 , then the processor  46  may send a signal to turn on the spray intercooling system  30  due to the power overshoots at time points  72 ,  74 , and  76  or turn off the spray intercooling system  30  due to undershoots at time points  78  and  80  caused by transient load changes (e.g., oscillation, underdamping, etc.). Further, due to the noise  82  and  84  from the sensors  50  of the power signal  68 , the spray intercooling system  30  may turn on and/or turn off. However, controlling operation of the spray intercooling system  30  based on the overshoots  72 ,  74 , and  76 , the undershoots  78 ,  80 , and/or the signal noise  82  and  84  would decrease the efficiency of the gas turbine system  12  due to expending more energy to operate the spray intercooling system  30  than energy saved from a cooler oxidant  14  by operation of the spray intercooling system  30 . 
     The processor  46  may increase spray intercooling system  30  efficiency by utilizing the virtual filter  52 . The filter  52  of the controller  44  may transform the transient overshoots, undershoots, and/or signal noise to provide a filtered (e.g., smoothed) power signal  86 , among other properties. For example, the processor  46  may receive the filtered power signal  86  and use the filtered power signal  86  to control operation of the spray intercooling system  30 . By controlling the spray intercooling system  30  with the filtered power signal  86  that does not include the overshoots  72 ,  74 , and  76 , the undershoots  78  and  80 , and the signal noise  82  and  84 , the processor  46  may operate the spray intercooling system  30  in a more efficient manner by turning on and/or off the spray intercooling system  30  based on a signal that more accurately represents a steady state load than the unfiltered. As such, the filter  52  provides the filtered power signal  86  to the processor  46  where the filtered power signal  86  prevents the spray intercooling system  30  from shutting off or turning on based on overshoots or undershoots caused by transient load changes or sensor noise. As shown in  FIG. 2 , the processor  46  may turn on the spray intercooling system  30  and control flow of the spray intercooling fluid  32 , via the valve  38 , to the nozzles  36  and  37  at points  88  and  90  based on the steady state load changes represented in the filtered power signal  86 . That is, the filtered power signal  86  allows the processor  46  to operate the spray intercooling system  30  based on steady state power during power changes from loads. By preventing the spray intercooling system  30  from shutting off and/or turning on based on inaccuracies in the power signal  68 , the gas turbine system  12  may save energy through operation of the spray intercooling system  30 , thereby enabling the spray intercooling system  30  to operate in isochronous mode and to provide an increase in output. 
     The filter  52  may be a Tustin filter that smoothes both transient load changes and sensor noise.  FIG. 3  is a diagram of an embodiment of a process  96  (e.g., virtual filter) including a Tustin filter performed by filter circuitry and/or the processor  46  to utilize the power signal  68  to provide the filtered power signal  86  for the processor  46  to control the spray intercooling system  30 . The process  96  may be stored in the memory  48  of the controller  44  and executed as instructions by the processor  46  (e.g., running code). The processor  46  may begin by receiving the power signal  68  indicating power demand or power generated by the power generation system  10 . The processor  46  may store an input state value  102  of the power signal  68  in the memory  48 . Further, the processor  46  may determine a compared value by comparing the input value of the power signal  68  with an output state value  106  (e.g., previous output) at comparator  104 . The processor  46  may then add the compared value with the input state value  102  at adder  108 , which is then compared at a second comparator  110  to the output state value  106  to determine a resultant value  112  (i.e. result). The additions and subtractions to determine the resultant value  112  are illustrated in the equation below: 
       result=(((input−output state)+input state)−output state)   (1)
 
     The processor  46  may then multiply the resultant value  112  by a filter coefficienta  116  at multiplier  114 . By using a Tustin filter, the processor  46  may utilize the filter coefficienta  116  with a time constant and a sampling time. For example, the filter coefficient may be determined using the following equation: 
     
       
         
           
             
               
                 
                   
                     coefficient 
                     a 
                   
                   = 
                   
                     1 
                     
                       
                         2 
                          
                         
                             
                         
                          
                         τ 
                       
                       + 
                       T 
                     
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
     In equation (2), τ may be a time constant of the filter and T may be the sampling time (e.g., a scan rate of the code routine). By accounting for the sampling time in the filter coefficient, the Tustin filter may reduce signal noise in the power signal at or approximately near the sampling time to provide the filtered power signal  86  that is used to improve operation of the spray intercooling system  30 . For example, if a sample were taken at 40 milliseconds intervals (e.g., 25 Hz or approximately 20-30 Hz), the filtered power signal  86  may filter noise at or near (e.g., within 5 Hz, 10 Hz, 20 Hz) 25 Hz (e.g., filter noise above 10 Hz, 15 Hz, 20 Hz, etc.). This can allow the controller  44  to operate at a sampling frequency where noise may otherwise cause the spray intercooling system  30  to shut off or turn on. By removing noise that can cause the controller  44  to shut off and/or turn on, efficiency of the gas turbine system  12  may be improved. 
     The resultant value  112  may then be limited by a limiter  120  to limit the resultant value  112  value to maximum and/or minimum values. The processor  46  may then multiply the resultant value  112  by the sampling time T  126  at multiplier  124 . For example, the sampling time may be 4 seconds or other desired value (e.g., 000.1 to 40 seconds). The resultant value  112  may then be added to the output state value  106  at adder  130  to generate the filtered power signal  86  as the output. The filtered power signal  86  may then be stored as the next output state. The filtered power signal  86  may then be used by the processor  46  to control the spray intercooling system  30 . 
       FIG. 4  is a diagram of an embodiment of a process  140  performed by the virtual filter  52 . One or more steps of the process  140  may be stored in the memory  48  of the controller  44  and executed as instructions by the processor  46  (e.g., running code). The filter  52  may receive a power signal of the gas turbine system  12  with an spray intercooling system  30  (block  142 ). The filter  52  may substantially remove, via the filter circuitry and/or the processor  46 , noise in the power signal from sensors and filter noise from changes in loads of the gas turbine  12  (block  144 ). Then the filter  52  may provide, via the filter circuitry and/or the processor  46 , a filtered signal to the controller  44  of the spray intercooling system  30 , where the filtered signal prevents the spray intercooling system  30  from shutting off or turning on due to sensor noise or noise from changes in loads (block  146 ).The gas turbine system  12  may control operation of the gas turbine based on the filtered signal to prevent the gas turbine from shutting down or turning on due to power changes (e.g., noise or oscillations due to changes in loads). 
     Technical effects of the present embodiments relate to gas turbine systems using a spray intercooling system. A controller of the gas turbine system controls whether the spray intercooling system cools an oxidant entering the gas turbine system. In some embodiments, the controller may include a filter that provides a filtered power signal to control the spray intercooling system. By using the filtered power signal from the filter, the spray intercooling system may operate when the spray intercooling system would provide more power than it uses. As such, the spray intercooling system may operate in isochronous mode to provide increased power output. By sending a filtered power signal to the gas turbine system in real time, the controller may provide a post-solution activity in controlling operation of the turbine based on the filtered power signal. 
     This written description uses examples to disclose various embodiments, including the best mode, and also to enable any person skilled in the art to practice the embodiments, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.