Load sharing through interconnected generation

Abstract

To provide a module for load-sharing in a power generation system.SOLUTION: Systems and methods provide load sharing for maintaining a stable operation of a group of electrical power generators in different load sharing scenarios. Over an interconnection bus (170), a controller (104) of a gas-turbine generator (GTG) (102) receives an indication of power generated in a set of GTGs (including the GTG (102)) that are part of a power network, and an indication of a status change of the power network. Based on the status change and the power generated, the controller (104) of the GTG (102) determines whether a change in power generated by the power network is likely to occur and whether a new power level is to be generated by the GTG (102).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The subject matter disclosed herein generally relates to modules for load sharing in power generation systems. Specifically, the modules are used to maintain stable operation of a group of power generators in different load sharing scenarios. [Background technology]

[0002] Large industrial facilities, such as power plants, offshore drilling platforms, and oil rigs, may use multiple generators operating in a parallel configuration to maintain a reliable power supply. To ensure the stability of the power generation system, load sharing is used to distribute and share the load evenly across the generators in the fleet. A centralized controller may be used to manage load sharing and other parallel tasks. However, when the centralized controller is offline due to technical or environmental issues (e.g., an extreme weather event), parallel tasks may be hindered, causing uneven distribution of load among the generators and / or unstable power generation. Summary of the Invention

[0003] A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these particular embodiments, and that these aspects are not intended to limit the scope of the disclosure. Indeed, the disclosure may encompass a variety of aspects not set forth below.

[0004] In a first embodiment, a method is provided in which a controller of a gas turbine generator (GTG) receives an indication of the status of another GTG via an interconnection bus. Based on the status of the other GTG, the controller determines a power level to be generated by the GTG and drives the GTG to output the power level.

[0005] In a second embodiment, a non-transitory computer-readable medium storing instructions is provided. The instructions, when executed by one or more processors, cause the one or more processors to receive, at a controller of a gas turbine generator (GTG), an indication of power generated by a set of GTGs (including the GTG) that are part of a power network. The instructions also cause the one or more processors to receive, at the controller, an indication of a status change of a switch in the power network, the status change including toggling a connection of one of the set of GTGs to the power network or a connection of the power network to a grid, the indication being received via an interconnection bus interconnecting a set of controllers corresponding to the set of GTGs. The instructions also cause the one or more processors to determine whether a change in power generated by the power network will occur based on the status of the switch and the generated power. The instructions also cause the one or more processors to use the controller to drive the GTG based at least in part on the determination of whether to change the generated power.

[0006] In a third embodiment, a system is provided. The system includes a controller including a memory that stores instructions and a processor used to execute the instructions. The instructions, when executed by the processor, cause the processor to control power generation in gas turbine generators (GTGs) in an electric power network that includes a set of GTGs. Specifically, the instructions, when executed by the processor, cause the processor to receive an indication that another GTG of the set of GTGs is within a threshold of maximum power generation of the other GTG, the indication being received via an interconnection bus that interconnects the controllers of the set of GTGs. The instructions also cause the processor to receive a command that the GTG is to be shut down and, based on the indication, prevent the shutdown of the GTG and send a warning to an operator.

[0007] These and other features, aspects, and advantages of the present invention will be better understood from the following detailed description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts throughout the drawings. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram of a gas turbine engine configured to power a load according to one embodiment. [Figure 2] FIG. 1 is a block diagram illustrating a power grid system including multiple gas turbine generators having a controller with a load sharing module, according to one embodiment. [Figure 3] 3 is a plot of frequency versus power illustrating an isochronous speed control method that may be used by the multiple gas turbine generators of FIG. 2 according to one embodiment. [Figure 4] 3 is a plot of frequency versus power illustrating a droop speed control method that may be used by the multiple gas turbine generators of FIG. 2 according to one embodiment. [Figure 5] 3 is a flowchart illustrating a load sharing process for one of the gas turbine generators of FIG. 2 when another generator in the fleet is brought online or offline, according to one embodiment. [Figure 6] 3 is a flowchart illustrating a load sharing process for one of the gas turbine generators of FIG. 2 when an electrical switch changes state, according to one embodiment. [Figure 7] 3 is a flowchart illustrating a load sharing process for one of the gas turbine generators of FIG. 2 when a potential shutdown situation may occur, according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] One or more specific embodiments are described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described herein. It is understood that in the development of an actual implementation, such as an engineering or design project, many implementation-specific decisions must be made to achieve the developer's particular objectives, including, for example, meeting system-related and business-related constraints, and that these constraints may vary from implementation to implementation. Moreover, it is understood 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 in the art having the benefit of this disclosure.

[0010] 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 element. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements. Furthermore, any numerical examples in the following description are intended to be non-limiting, and therefore, additional numbers, ranges, and percentages are intended to be within the scope of the disclosed embodiments.

[0011] Power generation systems are used to convert energy sources into electricity. The energy sources may be hydroelectric, coal, natural gas, crude oil, nuclear, solar, or wind energy. Gas turbine (also called combustion turbine) power plants run on natural gas or liquid fuels. Gas turbine generators (GTGs) offer operational flexibility. For example, gas turbines are a type of internal combustion engine designed to rapidly respond to increases in power demand.

[0012] The main components of a gas turbine include an upstream rotary compressor, a combustor, a downstream turbine on the same shaft as the compressor, and a generator. A gas turbine is an engine used to generate motion that rotates a generator. A gas turbine is a combustion engine that converts natural gas or liquid fuel into rotational mechanical energy, which then drives a generator to produce electrical energy. More specifically, a gas turbine draws in air, compresses it, mixes it with fuel, and distributes the air-fuel mixture to a combustor, where combustion of the air-fuel mixture (triggered by ignition) generates hot, pressurized gases that spin the turbine blades. The spinning of the turbine blades drives a generator connected to the turbine blades (e.g., via a shaft), which converts the rotational energy into electricity.

[0013] Industrial facilities, such as factories, power plants, offshore oil platforms, or drilling rigs, may use multiple gas turbine engines (GTGs) operating in a parallel configuration to maintain reliable power supply levels. Systems using multiple GTGs synchronize the GTGs so that they operate in parallel. As part of the synchronization, load sharing distributes and shares the load (e.g., proportionally / equally) across the GTGs in the fleet. At least some of the GTGs in the fleet may have independent controllers that communicate with a centralized controller (master controller). The master controller can manage the fleet's parallel tasks (including load sharing). When the master controller is offline due to technical or environmental issues (e.g., troubleshooting, maintenance, or an extreme weather event), the parallel tasks may be switched over to manual operations performed by an on-site operator (e.g., using a switchboard configuration) or to a backup centralized controller, if available. However, using manual operations or a backup centralized controller increases operational complexity, potentially resulting in reduced efficiency and / or increased costs.

[0014] The subject matter described herein relates to a load sharing module that can be used to maintain stable operation of a group of GTGs in different load sharing scenarios. A reusable and flexible load sharing module located in one or more of the GTGs is configured to select a control mode (e.g., droop mode or isochronous mode) for each GTG. The control mode is based on status and / or other relevant information shared through communication between the GTGs in the group via an interconnecting data bus. Thus, a centralized controller or hierarchical control system for parallel tasks such as load sharing can be omitted, and / or operation can continue when communication with the centralized controller fails. Additionally or alternatively, load setpoints and other operational priorities may be set by a third-party controller.

[0015] Referring now to the drawings, Figure 1 is a block diagram of one embodiment of a gas turbine system 10. By way of example, the gas turbine system 10 may be part of a combined cycle system and / or may be combined with other gas turbine systems 10 to power one or more loads 12. Specifically, the gas turbine system 10 is generally configured to drive the loads 12 by burning a mixture of compressed air and fuel 15 (e.g., natural gas, light or heavy distillate oil, naphtha, crude oil, residual oil, or syngas). Combustion occurs in a combustor 16, which may include one or more combustion chambers. Air 14 enters an intake at a compressor 20, is filtered, and is compressed in the compressor 20 through one or more compression stages.

[0016] To initiate the combustion process in the combustor 16, the air 14 is injected into the compressor 20 through a compressed air stream 18. The compressed air stream 18 is mixed with fuel 15. Ignition may occur using the mixture of fuel 15 and air 14. The ignition generates hot combustion gases 26 that power the gas turbine system 10. More specifically, the hot combustion gases 26 flow through a turbine 28 having one or more compression stages that drive the load 12 via a shaft 30. For example, the combustion gases 26 may apply motive force (e.g., via convection, expansion, etc.) to turbine rotor blades within the turbine 28, causing the shaft 30 to rotate. In an exemplary process, the hot combustion gases 26 may drive turbine blades within the turbine 28 to rotate the shaft 30 along the axis of the gas turbine system 10. As shown, the drive shaft 30 may be connected to various components of the gas turbine system 10, including the compressor 20 or the load 12.

[0017] As mentioned above, the drive shaft 30 may connect the turbine 28 to the compressor 20 to form a rotor. The compressor 20 may include compressor blades coupled to the drive shaft 30. Thus, rotation of the turbine blades in the turbine 28 may cause the drive shaft 30, which connects the turbine 28 to the compressor 20, to rotate the compressor blades in the compressor 20. This rotation of the compressor blades in the compressor 20 causes the compressor 20 to compress the air 14 and generate the compressed airflow 18. As mentioned above, the compressed airflow 18 is then delivered to the combustor 16 and mixed with other combustion components. The shaft 30 may drive the compressor 20 in addition to or instead of the load 12. As an example, the load 12 may be an electrical generator for a gas turbine generator (GTG). Additionally or alternatively, the load 12 may include a propeller, a transmission, or a drive system, among others.

[0018] Once the turbine 28 extracts work from the hot combustion gases 26, the exhaust gas stream 32 may be provided to an exhaust section 34, where the exhaust gas 32 may be cooled or further processed. For example, the exhaust section 34 may include a catalyst section 36 that includes a carbon monoxide (CO) catalyst, a NOx catalyst, an unburned hydrocarbon catalyst, and / or any similar metal-based catalyst (e.g., a platinum-based catalyst). For example, in the illustrated embodiment, the catalyst section 36 may include a NOx catalyst configured to destroy NOx gases in the exhaust gas stream 32, or a CO catalyst. The exhaust gas stream 32 may then exit the exhaust section 34.

[0019] As shown, the gas turbine system 10 includes a controller 38. The controller 38 may include one or more processors 66 and memory 68 that may collectively be used to support operating systems, software applications, systems, and the like useful for implementing the techniques described herein. In particular, the controller 38 may include code or instructions stored in a non-transitory machine-readable medium (e.g., memory 68) and executed by one or more processors 66, which may be included in the controller 38, for example. The processor 66 may receive operational parameters from various components of the gas turbine system 10 (e.g., via one or more sensors), including shaft rotational speed, frequency of power generated by the gas turbine system in a generator driven by the shaft 30, voltage of the generated power, demand from one or more loads 12, or other suitable parameters. In some embodiments, some parameters are measured directly, and other parameters are determined indirectly from other measurements. For example, in certain embodiments, the controller 38 may utilize an algorithmic model or lookup table (e.g., stored in memory) to derive various parameters. The various parameters may include the operating speed of the shaft 30 or a connected GTG using electrical parameters. The electrical parameters may include the frequency or voltage of the power generated by the generator (e.g., the load 12). Additionally, the controller 38 may monitor the operation of various portions of the gas turbine system 10. The monitored parameters may be used to control (e.g., adjust) the operating parameters of one or more aspects of the gas turbine system 10.

[0020] As shown, the controller 38 includes a load sharing (LS) module 39 that can monitor and analyze shared operating data (e.g., online / offline status, output power, frequency, or voltage, etc.) from other online power generation systems (e.g., gas turbine generators) that reside on the same power grid as the gas turbine system 10. Based on the monitoring and analysis, the load sharing module 39 can determine an appropriate control mode (e.g., droop speed control mode) and / or an appropriate set point (e.g., frequency or voltage) that can contribute to stable operation of the gas turbine system 10 and / or the connected grid. The load sharing module 39 then causes the controller 38 to select the determined control mode and / or set point for the gas turbine system 10.

[0021] The controller 38 may receive shared operating data from controllers of other power generation systems in a plurality of power systems (e.g., a set of gas turbine systems). The load sharing module 39 may include physical circuitry or may be embodied at least in part using instructions stored in memory 68 and executed on the processor 66 of the controller 38.

[0022] Load sharing can be defined as the proportional division of the total load (e.g., kilowatts (kW) or kilovolt-ampere reactive (KVAR)) among multiple power generation systems on a power grid. Through intercommunication (e.g., via controller 38) between groups of GTGs serving the power grid, coordinated coordination can be achieved to distribute and share the power grid load proportionally across the online GTGs. For example, when the load on the power grid increases, at least some of the online GTGs can increase their power output in equal proportions to accommodate the load change. For example, a group of GTGs can operate in parallel to provide power to an offshore drilling platform. When one of the group of GTGs is offline, the other online GTGs can receive the offline signal through intercommunication, cause the controller to calculate a feasible new load distribution among the online GTGs, and increase their power output proportionally if the calculated new load distribution does not exceed the power ratings of the online GTGs in the group. Additionally or alternatively, the controller may call on backup GTGs to share the load if the calculated new load distribution exceeds the power ratings of one or more online GTGs in the group.

[0023] Load sharing can be used by a power grid with multiple power generation systems and various loads to avoid overload and / or stability issues. As previously described, for tasks (such as load sharing) within multiple power systems, the load sharing module 39 monitors data from each of the fleet members and determines appropriate methods to contribute to stable operation without a centralized controller. In other words, the control mechanism described herein provides a distributed control system. Controllers (e.g., controller 38) of two or more individual power generation systems receive operational status and other relevant information from the other power generation systems. The controllers of the individual power generation systems can make adjustments based on information provided by the other power generation systems. Such a control mechanism enables flexible operation of multiple power systems. For example, the operation of one or more power generation systems (e.g., gas turbine system 10) can be adjusted to meet the specific demands of gas turbine or field operation under normal and / or abnormal conditions, such as by adjusting startup or shutdown sequences and / or coupling breaker operation.

[0024] As a reusable and flexible module, the load sharing module 39 may be pre-installed in the controller 38 during manufacture of the gas turbine system 10, or may be later installed in the controller of an existing power generation system (e.g., a backup gas turbine system for multiple power systems) as a retrofit kit and / or software update. In one or more embodiments, implementations of the load sharing module 39 may not include additional instrumentation beyond that already present in the power generation system that enables any respective controller 38 of the power generation system to implement the techniques described herein (e.g., with a software update).

[0025] The distributed power generation system may use one of the following operating modes: standalone operation, parallel operation with connection to the power grid, and island operation. Each operating mode may be associated with specific control of the gas turbine (e.g., gas turbine fuel control) and / or generators in the power grid (e.g., generator excitation control).

[0026] With the foregoing in mind, Figure 2 illustrates a power grid system 100 including multiple gas turbine generators (GTGs) and respective GTG controllers. Each of the GTGs can operate in a particular mode (standalone, parallel, or islanded) depending on the power grid configuration, load, electrical switch (or breaker) states, etc. In the configuration of power grid system 100, all three operating modes are possible by opening and closing certain electrical switches.

[0027] As shown, power grid system 100 may include a main grid 160 (e.g., a power system), a local grid 150, and a generator grid 140. Generator grid 140 may include multiple GTGs 102, 112, 122, and 132 and respective GTG controllers 104, 114, 124, and 134. Any number (e.g., all) of the GTG controllers 104, 114, 124, and 134 may include the load sharing module 39 described in FIG. 1 . Power grid system 100 may include an interconnecting data bus 170 used to handle communications between the GTG controllers 104, 114, 124, and 134. Various electrical switches 106, 116, 126, 136, 152, and 162 may be used to toggle the connections in power grid system 100.

[0028] In standalone operation, the GTG is not connected to other GTGs and / or the main grid 160. For example, as shown in Figure 2, the GTG 102 operates in standalone operation when electrical switches 152 and 106 are closed and switches 162, 116, 142, 126, and 136 are open. As an isolated power generating unit, the GTG 102 supplies power to connected loads on the local grid 150.

[0029] In one or more embodiments, a standalone GTG may be an emergency GTG when the local grid 150 loses power from one or more GTGs assigned to the local grid 150. For example, in the example described above, GTG 102 may begin providing power to the local grid 150 that has lost power from its assigned group of GTGs (e.g., GTGs 122 and 132). Standalone operation may include features such as controlling the gas turbine fuel (e.g., fuel 15 in FIG. 1 ) supply to increase / decrease the output of GTG 102, controlling the excitation current to increase / decrease the voltage output of GTG 102, and other power management-related procedures (e.g., keeping bus frequency and voltage constant for a particular control mode). In standalone operation, the total load on the local grid 150 determines the output power of GTG 102.

[0030] In the parallel operation mode, the GTGs 102, 112, 122, and 132 operate in parallel to provide power to the main grid 160 and the local grid 150. In some embodiments, the main grid 160 can be considered an infinite bus. For example, as shown in FIG. 2 , when all electrical switches 162, 152, 106, 116, 142, 126, and 136 are closed, the GTGs 102, 112, 122, and 132 enter parallel operation. The GTGs 102, 112, 122, and 132 operating in parallel supply power to loads on the local grid 150 and / or the main grid 160.

[0031] In one or more embodiments, GTGs operating in parallel operation can be organized into one or more subgroups of GTGs within the power plant. For example, in the example above, GTGs 102 and 112 may form subgroup A, and GTGs 122 and 132 may form another subgroup B within the power plant. The two subgroups can cooperate to provide power to local grid 150 and main grid 160, or can operate when at least one of the subgroups is offline (e.g., due to maintenance). Parallel operation can include features such as controlling gas turbine fuel supplies to increase / decrease the active power of GTGs 102, 112, 122, and 132, controlling excitation currents to increase / decrease the reactive power of GTGs 102, 112, 122, and 132, controlling the difference between total power plant load and GTG output power, and other power management-related procedures (e.g., holding power constant). In parallel operation, main grid 160 determines operating parameters such as frequency output, voltage output, and speed.

[0032] In islanded operation, GTGs (e.g., GTGs 102, 112, 122, and 132) are connected with other GTGs, but the GTGs are isolated from the main grid 160. For example, as shown in Figure 2, GTGs 102, 112, and 122 operate in islanded operation when electrical switches 162 and 136 are open and other electrical switches 152, 106, 116, 142, and 126 are closed. GTGs 102, 112, and 122 operating in parallel supply power to all connected loads on the local grid 150.

[0033] In one or more embodiments, a group of GTGs operating in islanded operation can supply power to an isolated system, such as a ship, an offshore drilling platform, or a desert oil production area. For example, in the example described above, GTGs 102 and 112 can form a set of GTGs in a local power plant on an offshore drilling platform to provide power to local grid 150, which may include all electrical equipment / machinery / equipment on the offshore drilling platform. At least one GTG (e.g., GTG 122) can function as a backup GTG for emergency use only if one or more of the other GTGs (e.g., GTGs 102 and 112) are offline. Islanded operation can include features such as controlling gas turbine fuel to increase / decrease GTG active power and bus frequency, controlling excitation current to increase / decrease GTG reactive power and bus voltage, and other power management-related procedures (e.g., keeping bus frequency and voltage constant while proportionally or cost-effectively sharing the load among operating GTGs). In islanded operation, the total load on the local grid 150 can determine the total power generated using the operating GTGs.

[0034] To share information among a group of operating GTGs (either in parallel or islanded operation), interconnect data bus 170 is used to handle communications between GTGs 102, 112, 122, and 132 via GTG controllers 104, 114, 124, and 134. Interconnect data bus 170 may include multiple cables / wires (coaxial signal cables, Ethernet cables, etc.) and / or wireless connections carrying signals including information related to load sharing using any suitable communication protocol for communicating between controllers 38 of GTGs 102, 112, 122, and 132. The load sharing information may include identification information of each GTG or GTG controller ID, online / offline operational status information of each GTG, power output information of each GTG, GTG configuration information (e.g., maximum power output), etc. The interconnect data bus 170 serves as a common highway for communication for the GTGs 102, 112, 122, and 132 to share status and related information with one another via the GTG controllers 104, 114, 124, and 134.

[0035] The controller 38 of each of the GTGs 102, 112, 122, and 132 may use one or more processors 66 to receive signals transmitted from the interconnection data bus 170 and store the received information in memory 68. The controller 38 of a GTG may use a load sharing module 39 to monitor and analyze operational data from other online GTGs on the same grid to determine a control mode (e.g., droop mode or isochronous mode) that may contribute to stable operation of the entire grid. The load sharing module 39 may then cause the controller 38 to select the determined control mode for the particular GTG. Furthermore, after a new control mode or a new setpoint is applied to a particular GTG, the controller 38 may use the load sharing module 39 to monitor operational data from the other GTGs to evaluate / verify the performance of the group of operating GTGs.

[0036] Each operating mode of the power generation systems on the power grid system 100 (e.g., standalone, parallel, or island) can be associated with a specific control mode for a group of GTGs within the power grid 100. As previously described, the use of standalone load sharing module 39 in the control mechanism enables flexible operation of the group of GTGs. Flexible operation can include GTG droop speed control mode, GTG isochronous speed control mode, and / or other power control methods to accommodate different island topologies and event transitions, such as GTG and / or other associated units coupling to or decoupling from the power grid 100. Controlling the power and speed of a group of GTGs relies on a coordinated effort based on the power demand of the group of GTGs, the number of available GTGs, parallel or island operation in a particular topology, and / or other relevant information, particularly during transient conditions and islanding events. Without coordination, multiple GTGs operating in parallel may experience unstable operation, such as overspeeding, loss of speed reference, erratic power fluctuations, etc. Such unstable operation can cause unexpected power outages and / or damage to GTGs or units on the power grid 100.

[0037] Figure 3 is a graph plotting active power 202 versus frequency 204 for an isochronous speed control mode that may be used by multiple GTGs of Figure 2. For alternating current (AC) generators (including GTGs), frequency (Hz) is directly related to speed (RPM). As shown, in isochronous speed control mode, the GTG's frequency line 220 returns to the original set point line 210 (e.g., 50 Hz) after a load is applied or rejected.

[0038] Isochronous speed control mode can be used when the GTG is in standalone operation or when the GTG is the largest (power) unit in a multiple GTG (e.g., islanded operation). In isochronous speed control mode, the energy generated by the prime mover (e.g., gas turbine 28 in gas turbine system 10) is tightly regulated in response to load changes. For example, a momentary load increase (e.g., when a new load is added to an existing power grid) may cause a transient frequency decrease, but in isochronous speed control mode, the prime mover energy is quickly regulated so that the frequency remains at or quickly returns to the setpoint. Similarly, a momentary load decrease (e.g., when an existing load is removed from an existing power grid) may cause a transient frequency increase, but in isochronous speed control mode, the prime mover energy is quickly regulated so that the frequency remains at or quickly returns to the setpoint.

[0039] In other words, in isochronous speed control mode, the GTG maintains a relatively constant speed regardless of load changes. When multiple GTGs in isochronous speed control mode are operating on the same grid and the load changes frequently, certain issues (e.g., instability) may occur. For example, in FIG. 2 , when electrical switches 162, 152, 106, and 116 are closed, GTGs 102 and 112 provide power in parallel to main grid 160. Main grid 160 can determine the frequency and voltage of the power generated by GTGs 102 or 112. When the speed setpoint is slightly low, controller 38 can cause the prime mover's (e.g., gas turbine 28) governor to adjust the gas turbine fuel supply (e.g., fuel 15) to reduce the speed. Similarly, when the speed setpoint is slightly high, controller 38 can cause the prime mover's (e.g., gas turbine 28) governor to at least partially open the gas turbine fuel supply to increase the speed. Thus, the power grid may experience relatively small but frequent frequency fluctuations due to frequent changes in load.

[0040] When multiple GTGs are operating in parallel, a droop speed control mode can be used to avoid problems such as frequency fluctuations with load changes. FIG. 4 is a graph plotting active power 202 versus frequency 204 for a droop speed control mode that may be used by the multiple GTGs of FIG. 2. As shown, in droop speed control mode, as the GTGs are loaded from no load (0%) to full load (100%), the frequency line 220 of the GTGs decreases by a fixed percentage. The fixed percentage (e.g., 4%) can be predetermined based on the power grid configuration and the power ratings of the GTGs assigned to the power grid. An operator or power management system can adjust the speed setpoint depending on operating parameters. The droop speed control mode can provide a stable operating point for each load when operating in parallel relative to the primary grid 160.

[0041] Droop speed control mode can be used by AC power generators to reduce the power output of a GTG as line frequency increases. Droop speed control can be implemented using a governor on a prime mover (e.g., gas turbine 28) driving a synchronous GTG (e.g., GTG 102, 112, 122, or 132) connected to a power grid (e.g., power grid 100). It operates by controlling the speed of the power generated by the prime mover according to the grid frequency. Droop speed control mode allows synchronous GTGs to operate in parallel, thereby allowing load sharing among GTGs with the same or similar droop lines or curves. Furthermore, the droop curves used by a group of GTGs on a power grid may be nonlinear or different from one another. For example, the droop curves can be adjusted by an operator in proportion to their power ratings. Droop speed control mode responds to frequency changes, allowing multiple GTGs to operate in tandem by dividing the load in proportion to their power. The droop speed control mode may be appropriate when used on a power grid with multiple GTGs and / or when handling loads with large power fluctuations.

[0042] 5 is a flowchart illustrating a load sharing process for the power grid system 100 of FIG. 2 when GTGs in the power grid system 100 are brought online or offline. For example, in FIG. 2, when electrical switches 162 and 136 are open and electrical switches 152, 106, 116, 142, and 126 are closed, GTGs 102, 112, and 122 serve local grid 150 in parallel. Local grid 150 has a total load (e.g., 600 kW), and GTGs 102, 112, and 122 may have power ratings (e.g., 400 kW, 200 kW, and 200 kW, respectively). The total load on local grid 150 is a percentage (e.g., 75%) of the total combined power rating of GTGs 102, 112, and 122 (e.g., 400 kW + 200 kW + 200 kW = 800 kW). As previously described, to achieve load balancing operation, the power outputs of GTG102, GTG112, and GTG122 may be set to their respective outputs (e.g., 300 kW, 150 kW, and 150 kW). In other words, GTG102, GTG112, and GTG122 may be driven to the same percentage (75%) of load to achieve load balancing. GTG controller 104 (with load sharing module 39) may determine the power generated by GTG102 (300 kW) (block 402). GTG controller 104 may publish the generated power to other GTG controllers, such as GTG controller 114 and GTG controller 124 (block 404). Publishing occurs over interconnect data bus 170. The GTG controller 114 and the GTG controller 124 may determine the power generated by the GTG 112 and the GTG 122, respectively (e.g., 150 kW and 150 kW) and publish the generated power via the interconnect data bus 170. The GTG controller 104 may retrieve the power generated by other GTGs, such as the GTG 112 and the GTG 122 (block 406). The GTG controller 104 determines whether an online / offline GTG indication has been received (block 408).For example, the indication may be a signal from the other controller indicating that the GTG corresponding to the other controller is going or has gone offline. Additionally or alternatively, the indication may include not receiving communication from the other controller for a period longer than a threshold duration and / or reducing generated power by an amount indicating that the GTG has gone offline. If no indication is received, the GTG controller 104 resumes the load sharing process at block 402.

[0043] At a particular moment, if a GTG (e.g., GTG 122) is taken offline by opening its respective electrical switch (e.g., electrical switch 126), GTG controller 104 and / or GTG controller 114 receive an instruction from the offline GTG. If the remaining GTGs (e.g., GTGs 102 and 112) can meet the power demand of local grid 150 having a total load (e.g., 600 kW), GTG controller 104 and GTG controller 114 may determine a new power level to be generated (block 410). For example, GTG controller 104 and GTG controller 114 may determine the power generated by GTGs 102 and 112, respectively (e.g., 400 kW and 200 kW). GTGs 102 and 112 may receive instructions from GTG controller 104 and GTG controller 114, respectively, to increase their power output to compensate for the power supply loss due to offline GTG 122. The instructions may cause GTG 102 and GTG 112 to output new power levels (block 412). For example, GTG 102 and GTG 112 may operate at new power levels (e.g., 400 kW and 200 kW) to meet the power demands of local grid 150. If the remaining GTGs (e.g., GTGs 102 and 112) cannot meet the power demands of local grid 150, which has a total load (e.g., 700 kW), GTG controller 104 and GTG controller 114 may instruct GTG 102 and GTG 112 to go offline because the total load on local grid 150 exceeds the total capacity of the remaining GTGs.

[0044] FIG. 6 is a flowchart illustrating a load sharing process for the power grid system 100 of FIG. 2 when an electrical switch changes state. For example, a state change event (from off to on state, or vice versa) may occur when a GTG is brought online or offline from an operator's action via a distribution panel, or when the electrical switch is tripped due to excessive electricity flowing through the electrical switch. The electrical switch state change event can be reported to a power management system within the power grid system 100 in which the electrical switch is installed. The power management system can receive the published event directly from the power management system or publish the electrical switch state change event to associated power units (e.g., GTGs 102, 112, 122, and 132 of FIG. 2 ) that have communication devices (e.g., GTG controllers 104, 114, 124, and 134) for receiving shared information related to published events from other power units via intercommunication (e.g., using interconnect data bus 170).

[0045] The first three blocks 402, 404, and 406 in Figure 6 are the same as those in Figure 5. Using the previous example, when electrical switches 162 and 136 in Figure 2 are open and electrical switches 152, 106, 116, 142, and 126 are closed, GTG 102, GTG 112, and GTG 122 serve the local grid 150 in parallel. GTG 102 determines the generated power (block 402), publishes the generated power to other GTG controllers (block 404), and can extract the power generated by the other GTGs (block 406). When an electrical switch (e.g., electrical switch 162) is closed, the operating mode may change. GTG controller 104 may determine whether a state change event has occurred (block 508). GTG controller 104 may determine whether the state change corresponds to a change in mode of operation to make the change (block 510). For example, a change in power grid configuration can correspond to a change between modes (e.g., isochronous mode vs. droop mode). For example, before switch 162 is closed, GTG 102 is connected to local grid 150 with other GTGs, such as GTG 112 and GTG 122, forming an isolated system. As previously described, in an isolated system, GTG 102, GTG 112, and GTG 122 operate in island operation to supply power to all connected loads on local grid 150. Thus, GTG 102 can be selected to operate in isochronous speed control mode to maintain a constant speed (frequency) despite load changes on local grid 150 (e.g., an oil field isolated from a nearby power system).

[0046] After connecting to the primary grid 160, the GTG controller 104 can monitor and analyze relevant information to determine whether to switch the speed control mode of the GTG 102. The relevant information may include the frequency and voltage of the primary grid 160, the varying loads on the primary grid 160 and / or the local grid 150, the power generated by other online GTGs, including the GTG 112 and the GTG 122, and the like. As described above, when a GTG operates in parallel with the primary grid 160 and the load changes frequently, continuing to operate in the isochronous speed control mode may cause instability issues because a GTG in the isochronous speed control mode tends to maintain a constant speed regardless of load changes. Based on the monitoring and analysis, the load sharing module 39 can determine a new appropriate control mode that contributes to stable operation of the primary grid 160. The load sharing module 39 can then cause the GTG controller 104 to switch the mode of the GTG 102 (block 512). For example, the control mode of the GTG 102 can be switched from the previous isochronous speed control mode to a droop speed control mode, resulting in a constant rate decrease in speed as previously described.

[0047] If the load sharing module 39 determines that no change will be made (block 510), the load sharing module 39 may determine a new power level based on the load (on the main grid 160 and / or the local grid 150) and the power output from the other GTGs (e.g., GTGs 112 and 122) (block 514). The load sharing module 39 may cause the GTG controller 104 to change the setpoint of the GTG 102 to output at the new power level to accommodate load changes on the power grid and / or power output changes to the GTG (block 515).

[0048] 7 is a flowchart illustrating a load sharing process for the power grid system 100 of FIG. 2 when a potential shutdown situation may occur. As previously mentioned, in the power grid system 100 of FIG. 2, GTG 102 and GTG 112 may form subgroup A, and GTG 122 and GTG 132 may form subgroup B. Each of the subgroups, and / or the power grid system 100, may implement cooperative operations. GTGs 102, 112, 122, and 132 may provide power to meet demands on the local grid 150 and / or the main grid 160.

[0049] At a particular moment, an electrical switch (e.g., electrical switch 126) is tripped, causing the GTG to go offline. The remaining GTGs in the subgroup or power grid system 100 can receive instructions to increase their power output to compensate for the power supply loss due to the offline GTG. The instructions can leave the remaining GTGs to meet demand above their power rating (e.g., 200 kW) but within the limits of maximum power (e.g., 220 kW). However, the remaining GTGs may not be recommended to operate within the maximum power threshold (e.g., 95% of maximum power) for a certain period of time. Each GTG controller (e.g., GTG controller 104) can receive an indication that another GTG (e.g., GTG 132) is within an unacceptable / undesirable threshold of maximum power (block 602). The instruction can also indicate that the other GTG will go offline after a certain period of time. Additionally, the GTG controller may receive a command that yet another GTG (GTG 102) is to be shut down because the total load (e.g., 630 kW) on the local grid 150 exceeds the combined capacity of the remaining GTGs (e.g., GTGs 102 and 112) (block 604). By using the load sharing module 39 to analyze the indication that the other GTG is within a maximum power threshold and other relevant information, the GTG controller 104 may determine to increase the power output of online GTGs other than the other GTG (GTG 132) (e.g., power rating from 70% to 78.75%). Accordingly, the other GTG controller (GTG controller 134) may determine to decrease the power output (e.g., power rating from 105% to 78.75%) so that the predicted offline condition does not occur. Furthermore, the GTG controller 104 may prevent the shutdown of GTG 102 based at least in part on the change (block 606). For example, maintenance may be delayed and / or shutdown conditions may change due to power production adjustments via interconnect data bus 170 .The GTG controller 104 may generate and send an alert to an operator indicating that a shutdown of the GTG 102 may be prevented.

[0050] The techniques described in this disclosure may be applicable to various power generation systems (such as gas turbine generators, steam turbine generators, and hydroelectric turbine generators). The load sharing module provides solutions for different load sharing scenarios, such as load sharing in isochronous mode, load sharing on islands that may include separable islands, and load sharing in parallel mode when frequent load changes occur. Independent operation can be achieved because a master controller (a centralized controller) is not implemented and the GTG controller (equipped with the load sharing module) can determine an appropriate method (e.g., speed control mode) that contributes to stable operation based on information provided by other generators. The load sharing module enables flexible operation of a set of generators, which can be adjusted to meet the specific needs of field operation under normal or abnormal conditions. For example, if a GTG controller loses communication with other GTG controllers, the GTG controller can instruct the corresponding GTG to maintain the mode in which the corresponding GTG is currently operating. Additionally or alternatively, load setpoints and other operational priorities (e.g., operating modes) may be set by the customer via an appropriate device, such as a third-party controller.

[0051] This written description uses examples to disclose the invention, including the best mode, and to enable any person skilled in the art to practice the invention, including making and using any device or system and performing any incorporated methods. The patentable scope of the invention 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 that have no substantial differences from the literal language of the claims. [Explanation of symbols]

[0052] 10 Gas Turbine System 12 Load 14 Air 15 Fuel 16 Combustor 18 Compressed Air Flow 20 Compressor 26 Hot combustion gases 28 Gas Turbine 30 Drive shaft 32 Exhaust gas flow, exhaust gas 34 Exhaust section 36 Catalyst Section 38 Controller 39 Standalone Load Sharing (LS) Modules 66 processors 68 memory 100 Power grid system, power grid 102 Gas Turbine Generator (GTG) 104 GTG Controller 106 Electric Switch 112 GTG 114 GTG Controller 116 Electric Switch 122 GTG 124 GTG Controller 126 Electric Switch 132 GTG 134 GTG Controller 136 Electric Switch 140 Generator Grid 142 Electric Switch 150 local grid 152 Electric Switch 160 Main Grid 162 Electric Switch 170 Interconnect Data Bus 202 Active Power 204 Frequency 210 Setting dotted line 220 frequency line

Claims

1. receiving, at a controller (104) of a gas turbine generator (GTG) (102), an indication of the status of other GTGs (122) via an interconnection bus (170); determining (410) a power level to be generated by the GTG (102) using the controller (104) based on the status of the other GTG (122); driving (412) the GTG (102) using the controller (104) to output the power level; 1. A method comprising: determining (408) that the GTG (102) was scheduled to go offline prior to receiving the instruction; and determining that the remaining online GTGs in the plurality of connected GTGs, including the GTG (102) and the other GTG (122), cannot meet the threshold power of the connected GTGs with the GTG (102) offline; It further includes The method, wherein determining (410) the power level includes stopping (606) the scheduled shutdown of the GTG (102) from occurring in response to determining that the remaining online GTGs cannot meet the threshold power.

2. The method of claim 1 , wherein the instruction comprises a message from another controller (124) of the other GTG (122) via the interconnect bus (170).

3. The method of claim 1 , wherein the interconnect bus (170) comprises a wireless connection for the controller (104).

4. The method of claim 1 , comprising determining (402) a generated power of the GTG (102).

5. The method of claim 4, further comprising publishing (404) the generated power to the interconnect bus (170).

6. The method of claim 5, comprising extracting (406) power generated by a connected GTG in a power network comprising the GTG (102) and the other GTG (122).

7. 1. A controller (104) comprising: a memory (68) storing instructions; and a processor (66) configured to execute the instructions to cause the processor (66) to control power generation in a gas turbine generator (GTG) (102) in an electric power network comprising a plurality of GTGs, the instructions, when executed by the processor (66), cause the processor (66) to: receiving (602) an indication that another GTG (132) of the plurality of GTGs is within a threshold of maximum power generation of the other GTG (132), the indication being received via an interconnect bus (170) interconnecting the controllers (104) of the plurality of GTGs; Receive a command that the GTG (102) be shut down (604); Preventing (606) the shutdown of the GTG (102) based on the instruction and sending a warning to an operator. A controller (104) configured to A system (10) comprising:

8. The system (10) of claim 7, wherein the shutdown corresponds to a scheduled maintenance or offline period for the GTG (102).

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