Load determination method for combined cycle unit participating in primary frequency modulation

Abstract

A load determination method for a gas turbine combined cycle unit participating in primary frequency modulation, comprising: obtaining operation data of the combined cycle unit, including environmental parameters, operation modes and real-time operation parameters; based on the operation data, calculating a static power limit of the combined cycle unit as a basic boundary of the primary frequency modulation; based on the real-time operation parameters, calculating a real-time thermal stress of a rotor of a steam turbine; based on the operation modes and the real-time thermal stress, determining a dynamic margin of the combined cycle unit participating in the primary frequency modulation, wherein the dynamic margin is dynamically constrained based on the proximity of the real-time thermal stress to a maximum safe stress; based on the dynamic margin, correcting the basic boundary to obtain a load limit boundary of the primary frequency modulation. By coupling the static physical limit with the dynamic margin, a dynamically constrained boundary is formed, which can fully utilize the potential of the combined cycle unit under the premise of safety, and can calculate the load adjustment range for different modes respectively, so that the load limit of the primary frequency modulation is more accurate.

Description

Technical Field

[0001] This application relates to the field of gas turbine combined cycle unit technology, and more specifically, to a method for determining the load of a gas turbine combined cycle unit participating in primary frequency regulation. Background Technology

[0002] Combined cycle gas turbine units (hereinafter referred to as "combined cycle units") play an important role in peak shaving and frequency regulation in power systems due to their advantages such as rapid start-up and shutdown and high load regulation rate. Primary frequency regulation of combined cycle gas turbine units refers to the function of the unit's control system to sense changes when the grid frequency deviates from the rated value and increase or decrease the unit's active power output according to preset parameters in order to maintain grid frequency stability.

[0003] To ensure that combined cycle units can respond quickly to grid demands without exceeding the limits of their mechanical and thermal components, their control systems are equipped with a primary frequency regulation load command limiting module. This module defines the highest and lowest allowable loads for the combined cycle unit to participate in primary frequency regulation, and its accuracy directly determines the quality of the frequency regulation function and the unit's safety. Existing combined cycle units have several significant shortcomings in their primary frequency regulation control strategies and load determination methods.

[0004] First, in existing technologies, a fixed maximum adjustment range is used as the range for the unit to participate in primary frequency regulation. Typically, the design rated power of the combined cycle unit is used as the upper limit of the load, and the minimum stable combustion load of the combined cycle is used as the lower limit. However, the actual adjustable capacity of a combined cycle unit can be affected by various factors such as environmental factors, the aging of the gas turbine, the opening of the compressor inlet guide vanes (IGV), and the turbine sliding pressure curve. The static limiting method in existing technologies completely ignores the transient capacity of the combined cycle unit. Its fixed load range cannot reflect the real-time physical limits of the unit, leading to situations where, under specific operating conditions, the frequency regulation command exceeds the actual capacity of the combined cycle unit, resulting in regulation failure; or situations where the potential frequency regulation capacity of the combined cycle unit is not fully utilized. Furthermore, the fixed load range setting lacks dynamic adaptability and optimization capabilities.

[0005] Second, the operating conditions of combined cycle gas turbine units are extremely complex, encompassing different gas turbine combustion modes (such as premixed combustion and diffusion combustion), steam turbine thermodynamic cycle modes (such as pure condensing heating and extraction condensing heating), and shaft configuration modes (such as "one-to-one" and "two-to-one" modes). Under different operating modes, the thermal stress and load change rate limits experienced by the gas turbine and steam turbine are drastically different. Current technologies fail to decouple these operating modes from the underlying algorithms and do not define the load range for primary frequency regulation for different operating modes. In particular, they fail to accurately assess the power contribution capacity of the steam turbine side, which is significantly affected by thermal inertia. This leads to a disconnect between the calculated load range under different operating conditions and the actual load boundaries of the combined cycle unit.

[0006] Third, in existing technologies, to prevent the load of combined cycle units from exceeding safety boundaries, a conservative fixed safety margin is typically used (e.g., subtracting a fixed value from the maximum limit load and adding a fixed value to the minimum limit load). This can lead to situations where, in actual operation, combined cycle units may excessively limit the frequency regulation amplitude, wasting frequency regulation resources and affecting economic efficiency; or, under certain operating conditions, the actual load limit may be closer to the operating range of the combined cycle unit than the preset fixed safety margin, affecting safety.

[0007] CN116706877A discloses a method for calculating the primary frequency regulation capability of a gas-fired steam combined cycle unit. The method first calculates the theoretical maximum static power difference of the combined cycle unit as the maximum load margin. Then, a fixed variable load rate limit is preset, and a power amplitude boundary based on the speed limit is calculated within a preset time interval. Finally, the control system takes the smaller of the two values ​​as the final frequency regulation command limit boundary. This method calculates a rigid and non-real-time empirical boundary within a fixed time interval. Because this boundary is calculated based on a fixed variable load rate limit and the theoretical maximum static power difference, it is actually detached from the current actual physical state of the unit and cannot perceive the real-time physical limits of the steam turbine and gas turbine. This non-real-time sensing characteristic can lead to many negative consequences: On the one hand, when the thermal stress inside the unit (such as the turbine rotor) is already very high, an artificially high allowable boundary may still be calculated based on a fixed load rate, which can easily lead to equipment damage due to thermal fatigue; on the other hand, when the unit is running stably for a long time, the power amplitude boundary calculated based on a fixed load rate may still be less than the theoretical static power limit of the combined cycle unit, causing the combined cycle unit to be unable to fully respond to the grid demand, and its primary frequency regulation capability is blindly limited.

[0008] Therefore, there is an urgent need for a new method for determining the load of combined cycle units, which can achieve dynamic self-adaptation of safety margin, so as to fully utilize the potential of combined cycle units while ensuring safety; and can dynamically adjust the allowable load range of primary frequency regulation according to different operating modes of combined cycle units. Summary of the Invention

[0009] To address the aforementioned problems, this application provides a method for determining the load of a gas turbine combined cycle unit participating in primary frequency regulation, comprising the following steps:

[0010] Obtain operating data of a gas turbine combined cycle unit, which includes at least one gas turbine and at least one steam turbine. The operating data includes environmental parameters, operating modes, and real-time operating parameters.

[0011] Based on operational data, the static power limit of the gas turbine combined cycle unit is calculated, which serves as the basic boundary for the gas turbine combined cycle unit to participate in primary frequency regulation.

[0012] Based on real-time operating parameters, the real-time thermal stress of the turbine rotor is calculated, and based on the operating mode and real-time thermal stress, the dynamic margin for the gas turbine combined cycle unit to participate in primary frequency regulation is determined. The dynamic margin is dynamically adjusted based on the proximity of the real-time thermal stress to the corresponding maximum safe stress.

[0013] Based on the dynamic margin, the basic boundary is modified to obtain the load limit boundary for the gas turbine combined cycle unit to participate in primary frequency regulation, so as to limit the target command of primary frequency regulation within the load limit boundary.

[0014] Optionally, based on operating data, the static power limit of the gas turbine combined cycle unit is calculated, including:

[0015] Based on environmental parameters and operating mode, the static output limit of the gas turbine is calculated;

[0016] The static output limit of the steam turbine is calculated based on real-time operating parameters;

[0017] Calculate the static power limit based on the static output limit of gas turbines and steam turbines.

[0018] Optionally, based on the operating mode and real-time thermal stress, the dynamic margin for the gas turbine combined cycle unit to participate in primary frequency regulation is determined as follows:

[0019] Based on real-time thermal stress and the corresponding maximum safe stress, the maximum allowable instantaneous power impact amplitude of the steam turbine is calculated;

[0020] The dynamic margin is obtained by combining the maximum instantaneous power impact amplitude and the maximum regulation rate of the gas turbine.

[0021] Optionally, based on the dynamic margin, the basic boundary is modified to obtain the load limit boundary for the gas turbine combined cycle unit to participate in primary frequency regulation, including:

[0022] Calculate the static adjustable space based on the static power limit and the actual power output of the gas turbine combined cycle unit;

[0023] Compare the static adjustable space and the dynamic margin, and select the smaller value of the two as the target adjustable space;

[0024] Calculate the load limit boundary based on the target adjustable space and the actual generated power of the gas turbine combined cycle unit.

[0025] Optionally, the static power limit includes a static power upper limit, and the dynamic margin correspondingly includes an upward dynamic margin;

[0026] Based on static power limits and dynamic margins, the load limitation boundaries for gas turbine combined cycle units participating in primary frequency regulation are calculated as follows:

[0027] The difference between the upper limit of static power and the actual power generated by the gas turbine combined cycle unit is calculated as the upward static adjustable space.

[0028] Compare the upward static adjustable space with the upward dynamic margin, and select the smaller value of the two as the upward target adjustable space;

[0029] The upper limit of the frequency regulation load is obtained by adding the adjustable range of the upward target to the actual power generated by the gas turbine combined cycle unit.

[0030] Optionally, the static power limit includes a lower static power limit, and the dynamic margin correspondingly includes a downward dynamic margin.

[0031] Based on static power limits and dynamic margins, the load limitation boundaries for gas turbine combined cycle units participating in primary frequency regulation are calculated as follows:

[0032] The difference between the actual power output and the lower limit of the static power output of the gas turbine combined cycle unit is calculated as the downward static adjustable range.

[0033] Compare the downward static adjustable space with the downward dynamic margin, and select the smaller of the two as the downward target adjustable space;

[0034] The load lower limit for primary frequency regulation is obtained by subtracting the actual power generated by the gas turbine combined cycle unit from the downward target adjustable space.

[0035] Optionally, the method for determining the load for a gas turbine combined cycle unit to participate in primary frequency regulation also includes:

[0036] Obtain the turbine exhaust temperature and compressor inlet guide vane opening of the gas turbine;

[0037] When the turbine exhaust temperature reaches the predetermined temperature control value and the compressor inlet guide vane opening reaches the maximum opening, the upper limit of the static power of the gas turbine is determined as the actual power generated by the gas turbine, so as to limit the upward static adjustment space.

[0038] Optionally, the method for determining the load for a gas turbine combined cycle unit to participate in primary frequency regulation also includes:

[0039] Obtain the compressor inlet guide vane opening of the gas turbine;

[0040] When the compressor inlet guide vane opening reaches the minimum opening limit, the actual power output of the gas turbine is calculated and determined as the lower limit of the static power output of the gas turbine, so as to limit the downward static adjustment space.

[0041] Optionally, the method for determining the load for a gas turbine combined cycle unit to participate in primary frequency regulation also includes:

[0042] Based on real-time operating parameters, the life loss coefficient of key parts of the rotor is calculated.

[0043] The dynamic margin is adjusted based on how close the lifetime loss coefficient is to the corresponding maximum lifetime loss of a single frequency modulation.

[0044] Optionally, the operating modes include unit shaft configuration, gas turbine combustion mode, and steam turbine cycle mode, wherein...

[0045] The unit's shaft system configuration includes at least one of single-shaft mode and multi-shaft mode;

[0046] Gas turbine combustion modes include at least one of premixed mode and diffusion mode;

[0047] The turbine cycle mode includes at least one of the following: pure condensing mode, extraction condensing mode, and back pressure mode.

[0048] Based on the technical solutions including the above embodiments, the load determination method for gas turbine combined cycle units participating in primary frequency regulation provided in this application couples static physical limits with dynamic margins to form dynamic constraint boundaries, dynamically calculates the maximum allowable power surge of the combined cycle unit in the rapid action of primary frequency regulation, and uses it to limit the load command of primary frequency regulation.

[0049] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0050] Figure 1 The following steps are shown in a method for determining the load of a gas turbine combined cycle unit participating in primary frequency regulation according to an embodiment of this application;

[0051] Figure 2 The final load limit boundary judgment logic of a load determination method for a gas turbine combined cycle unit participating in primary frequency regulation according to an embodiment of this application is shown. Detailed Implementation

[0052] The technical solutions in the embodiments of this application will now be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are preferred embodiments of this disclosure and should not be considered as excluding other embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0053] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0054] To address the aforementioned technical problems, this application provides a method for determining the load of a gas turbine combined cycle unit participating in primary frequency regulation. This method can be executed through a distributed control system (DCS) or a dedicated unit coordination controller. The gas turbine combined cycle unit, in terms of hardware, includes at least one gas turbine, one waste heat boiler, and one steam turbine, with each component coupled through a thermodynamic cycle system.

[0055] Figure 1 A schematic diagram of the main flow of a load determination method in an optional embodiment of this application is shown. Figure 1 As shown, the method for determining the load of a gas turbine combined cycle unit participating in primary frequency regulation includes the following steps:

[0056] Acquire operating data of the gas turbine combined cycle unit, including environmental parameters, operating modes, and real-time operating parameters.

[0057] Specifically, environmental parameters include, but are not limited to, ambient temperature and atmospheric pressure. These parameters directly determine the density of the gas turbine's intake air, thus affecting its upper limit of physical output. Operating modes are used to distinguish the complex thermodynamic state of the combined cycle unit, including but not limited to the shaft configuration, gas turbine combustion mode, and turbine cycle mode. In an optional embodiment, the shaft configuration includes single-shaft or multi-shaft modes, where single-shaft modes include a "one-to-one" configuration, and multi-shaft modes include "two-to-one" and "multiple-to-one" configurations; the gas turbine combustion mode includes premixing or diffusion modes; and the turbine cycle mode includes pure condensation, extraction-condensation, or back-pressure modes. Through decoupling and identifying operating modes, this application can invoke corresponding thermodynamic calculation models for different operating conditions. Real-time operating parameters are divided into operating parameters of combined cycle units, operating parameters of the gas turbine side, and operating parameters of the steam turbine side, including but not limited to the actual power generation of the combined cycle unit, the actual power generation of the gas turbine, the actual power generation of the steam turbine, the turbine exhaust temperature of the gas turbine, the opening degree of the compressor inlet guide vanes, the steam pressure, the main steam temperature, the reheat steam temperature, the pressure after the regulating stage of the steam turbine, the opening degree of the regulating valve of the steam turbine, and the metal temperature of the steam turbine rotor.

[0058] Operating data of combined cycle units can be collected through the real-time database of the unit's distributed control system (DCS) or the gas turbine control system. Optionally, the validity of the operating data can be checked at the same time as it is collected to eliminate bad data.

[0059] Based on operational data, the static power limit of the gas turbine combined cycle unit is calculated, serving as the fundamental boundary for the unit's participation in primary frequency regulation. The static power limit is calculated based on a steady-state thermodynamic model. Combining the performance curves provided by the manufacturer with the collected operational data, the static power limit of the combined cycle unit under current operating conditions is calculated. In this embodiment of the invention, the fundamental boundary is the power boundary of the gas turbine combined cycle unit's thermodynamic cycle system under steady-state operating conditions.

[0060] In an optional embodiment, the static power limit is obtained by combining the static outputs of the gas turbine and the steam turbine. The static power limit calculation process for a combined cycle unit includes: calculating the static output limit of the gas turbine based on environmental parameters and operating mode; calculating the static output limit of the steam turbine based on real-time operating parameters; and superimposing the static output limits of the gas turbine and the steam turbine, while considering losses such as electricity consumption, to calculate the static power limit of the combined cycle unit. The static power limit of the combined cycle unit represents the physical boundary that the combined cycle unit can achieve in a steady state without time constraints.

[0061] In an optional embodiment, the static power limit calculation of the combined cycle unit includes the following steps:

[0062] By using lookup table functions or polynomial fitting functions, and based on the currently acquired environmental parameters and operating mode, the maximum and minimum safe power output of the gas turbine under the current environment can be calculated in real time; that is, the upper and lower limits of the gas turbine's static output. The specific formula is as follows:

[0063] ;

[0064] ;

[0065] in, This represents the upper limit of the static output of the gas turbine. This represents the lower limit of the static output of the gas turbine. The current atmospheric temperature, Given the current atmospheric pressure, This refers to the current combustion mode of the gas turbine (e.g., premixed mode or diffusion mode). and This is a nonlinear mapping function calibrated and solidified through mechanistic thermodynamic experiments. The parameters introduced are... and This is because the ambient air density directly determines the mass flow rate of the air drawn into the compressor, thus physically limiting the upper limit of the fuel that can be injected. This is addressed by introducing parameters... This is to enable the switching of thermodynamic calculation models under different combustion modes of the gas turbine, ensuring the accuracy of the upper and lower limits of the static output of the gas turbine.

[0066] Since steam turbines typically operate in sliding pressure mode, their output is not entirely independent but primarily depends on the steam generation from the waste heat boiler, i.e., the exhaust energy of the gas turbine. Based on the gas turbine model, the exhaust temperature and flow rate are calculated or measured to determine the main steam pressure and temperature generated by the waste heat boiler. By consulting the steam turbine's sliding pressure operation curve and considering the maximum and minimum opening limits of the turbine's regulating valves, the theoretical maximum and minimum power of the steam turbine under current operating conditions can be calculated, i.e., the upper and lower limits of the steam turbine's static output. The specific formula is as follows:

[0067] ;

[0068] ;

[0069] in, This represents the upper limit of the static output of the steam turbine. This represents the lower limit of the static output of the steam turbine. The current main steam pressure, This is the current main steam temperature. This represents the maximum opening of the turbine regulating valve. This represents the minimum opening degree of the turbine regulating valve. and It is an interpolation function based on the turbine flow characteristic curve and the sliding pressure curve.

[0070] Based on the calculated upper and lower limits of the static output of individual units, the upper and lower limits of the static power of the entire combined cycle unit are obtained by superimposing them, as follows:

[0071] ;

[0072] ;

[0073] in, This refers to the upper limit of the static power of a combined cycle unit. This is the lower limit of the static power of the combined cycle unit.

[0074] Based on real-time operating parameters, the real-time thermal stress of the turbine rotor is calculated. During a single frequency regulation process, the addition of fuel to the gas turbine leads to an increase in its exhaust gas temperature, which in turn causes transient changes in the temperature and pressure of the main steam entering the turbine. This thermal shock creates a temperature gradient on the surface of the turbine rotor. In the embodiments of this application, a turbine rotor temperature calculation model can be established by collecting real-time operating parameters such as the rate of change of steam temperature after the regulating stage and the rotor surface temperature. The magnitude of the real-time thermal stress on the rotor surface can then be calculated in real time using the finite difference method or the transfer function method.

[0075] In an optional embodiment, the magnitude of real-time thermal stress is specifically expressed as:

[0076] ;

[0077] in, The rotor surface metal temperature, For the real-time thermal stress magnitude, The current main steam pressure, This is the current main steam temperature. This is a nonlinear mapping function characterizing finite difference logic or transfer function logic. Based on this formula, combined cycle units can accurately and in real-time monitor the stress inside the metal rotor when participating in primary frequency regulation, avoiding safety issues caused by pursuing higher frequency regulation speeds.

[0078] The rate of change of power in a steam turbine reflects how fast it "reaches its end point" during a single frequency regulation, and it mainly depends on the thermal inertia and temperature gradient of the turbine rotor. If the regulation rate is too high, a large amount of high-temperature or low-temperature steam will enter the turbine instantaneously, forming a severe transient temperature gradient on the rotor surface and in areas such as the central bore, thereby triggering high real-time thermal stress.

[0079] Based on operating modes and real-time thermal stress, the dynamic margin for a gas turbine combined cycle unit to participate in primary frequency regulation is determined. The dynamic margin represents the power surge amplitude that the combined cycle unit can withstand within a short timeframe—the extremely short response time required by primary frequency regulation—while ensuring equipment safety. Therefore, in this step, a negative correlation mapping is established between real-time thermal stress and the dynamic margin: the dynamic margin is dynamically constrained by the proximity of the real-time thermal stress to the corresponding maximum safe stress; that is, the closer the real-time thermal stress is to the corresponding maximum safe stress, the smaller the determined dynamic margin.

[0080] The dynamic margin of a gas turbine combined cycle unit participating in primary frequency regulation includes the dynamic synthesis of the gas turbine side and the steam turbine side. Specifically, the gas turbine responds rapidly, and its thermal stress is usually negligible within the extremely short primary frequency regulation response time. The main constraints are its relatively fixed maximum regulation rate (i.e., ramp-up capability) and the current static output space. The steam turbine, on the other hand, has greater thermal inertia, and the main constraint is the real-time thermal stress of the rotor.

[0081] The process of determining the dynamic margin includes calculating the maximum allowable instantaneous power surge amplitude of the turbine based on real-time thermal stress and the corresponding maximum safe stress. In an optional embodiment, the maximum allowable instantaneous power surge amplitude of the turbine is specifically expressed as:

[0082] ;

[0083] in This refers to the permissible instantaneous power surge amplitude of the steam turbine. For the real-time thermal stress of the turbine rotor, The maximum safe stress allowed for the material of the steam turbine rotor. The thermal stress safety limiting function exhibits a monotonically decreasing nonlinear decay curve or a piecewise function. For example, when the real-time thermal stress... Approaching the corresponding maximum safe stress At this time A value close to 0 indicates that the turbine can no longer withstand the rapid power changes of a single frequency regulation. The instantaneous power surge amplitude defines the maximum power surge amplitude that the turbine can withstand without causing thermal fatigue damage to the turbine rotor. This amplitude represents how far the turbine load can "go" during a single frequency regulation.

[0084] In the embodiments of this application, a dual nonlinear model based on power impact amplitude and power change rate is constructed by real-time monitoring of thermal stress, which is superimposed with the power change rate of the steam turbine. This allows the adjustment step size limit of the steam turbine load during primary frequency regulation to take into account the adjustment slope limit during transient processes. By decoupling control mechanisms based on the same physical factors but acting on different physical boundaries, the combined cycle unit can simultaneously consider impact amplitude and transient thermal fatigue.

[0085] Combining the maximum instantaneous power surge amplitude and the dynamic response characteristics of the gas turbine, the dynamic margin is obtained. It should be noted that gas turbines possess inherent dynamic response characteristics, capable of rapidly and significantly altering their actual output power within a very short time, reaching their static processing physical boundaries. Therefore, compared to steam turbines, the thermal stress limitations of gas turbines can usually be ignored; only their rated maximum regulation rate needs to be considered. Superimposing the instantaneous surge amplitude on the steam turbine side, constrained by thermal stress, with the current available static output space on the gas turbine side yields the overall dynamic margin of the entire combined cycle unit.

[0086] In an optional embodiment, for the primary frequency regulation condition, the upward dynamic margin and downward dynamic margin are respectively expressed as:

[0087] ;

[0088] ;

[0089] in, For the upward dynamic margin of combined cycle units, For the downward dynamic margin of combined cycle units, This refers to the permissible instantaneous power surge amplitude of the steam turbine. The upper limit of the static output of the gas turbine calculated in the preceding steps is... The lower limit of the static output of the gas turbine is calculated using the steps described above. This represents the current actual power output of the gas turbine. The transient regulation capability of a combined cycle unit during primary frequency regulation is the sum of the turbine's thermal stress fatigue resistance margin and the gas turbine's remaining static output capacity.

[0090] Because the dynamic margin is based on the combination of two decoupled indices, it dynamically changes with the real-time thermal stress of the turbine rotor. When the combined cycle unit is operating smoothly or under low thermal stress, the overall dynamic margin reaches a high value, allowing the unit to respond to grid frequency changes at maximum power. When the combined cycle unit experiences a drastic load change, causing the turbine rotor thermal stress to approach the material's maximum safe stress, the overall dynamic margin will contract, limiting the execution range of subsequent frequency regulation commands. The dynamic margin will only expand and recover again as the rotor thermal stress gradually dissipates and returns to a safe level over time.

[0091] In an optional embodiment, a dynamic margin adjustment method based on the lifespan loss of the turbine rotor is also introduced. This includes calculating the lifespan loss coefficient of key rotor components in real time using the finite difference method or transfer function method based on the steam temperature change rate and rotor surface temperature; and adjusting the dynamic margin based on the proximity of the lifespan loss coefficient to the corresponding maximum lifespan loss for a single frequency regulation. When the lifespan loss coefficient approaches the maximum lifespan loss for a single frequency regulation, the dynamic margin can be actively narrowed to prevent the turbine rotor from wearing out too quickly. When the lifespan loss coefficient reaches or exceeds the maximum lifespan loss for a single frequency regulation, the dynamic margin is reduced to zero, so that the combined cycle unit no longer increases the magnitude of load fluctuations. This method can prevent the combined cycle unit from damaging the physical lifespan of the turbine in order to meet the frequency regulation range of the power grid.

[0092] Based on dynamic margin, the foundation boundary is corrected. Using the foundation boundary as the adjustment benchmark, it is dynamically adjusted in real time based on the dynamic margin. The control system uses the dynamic margin based on the stress limit of the turbine rotor as a constraint condition to adjust the static foundation boundary. By calculating the static foundation boundary and applying dynamic constraints on it, the non-real-time empirical boundary in traditional technology is transformed into a flexible dynamic safety boundary that can respond to the internal thermal stress state of the equipment and adjust in real time according to operating conditions. The corrected load limit boundary achieves a balance between equipment safety and performance, ensuring that the thermal stress of the equipment remains within a safe range while fully utilizing the frequency regulation capability of the combined cycle unit.

[0093] In an optional embodiment, for the operating condition of primary frequency regulation: the difference between the upper limit of static power and the actual power generated by the combined cycle unit is calculated as the upper static adjustable space; simultaneously, the upper dynamic margin calculated based on thermal stress is obtained, and the smaller value is selected as the upper target adjustable space. Adding the actual power generated by the combined cycle unit to the upper target adjustable space yields the upper limit of the load limit boundary for primary frequency regulation.

[0094] Similarly, in another optional embodiment, for the downward adjustment condition of primary frequency regulation: calculate the difference between the actual generated power of the combined cycle unit and the lower limit of the static power, as the downward static adjustable space; compare it with the downward dynamic margin, and take the smaller value as the downward target adjustable space. Subtracting the downward target adjustable space from the actual generated power of the combined cycle unit yields the lower limit of the load limiting boundary of primary frequency regulation.

[0095] Specifically, the load limit boundary value for primary frequency regulation can be expressed as:

[0096] ;

[0097] ;

[0098] in, This is the upper limit of the load for primary frequency regulation. This is the lower limit of the load for primary frequency regulation. This refers to the upper limit of the static power of a combined cycle unit. This is the lower limit of the static power of a combined cycle unit. This represents the actual power output of the combined cycle unit. For upward dynamic margin, This represents a downward dynamic margin.

[0099] In this embodiment, by taking the smaller value between the static adjustable space and the dynamic margin, it is ensured that the target command for primary frequency regulation does not exceed the load limit boundary. The static adjustable space represents the steady-state thermodynamic limit that the combined cycle unit can achieve, while the dynamic margin represents the transient impact limit that the unit can withstand while ensuring that the current equipment remains in a healthy state. This logic of taking the smaller value ensures that: if the combined cycle unit has a high load and is limited by its physical work capacity, its static adjustable space is small, and in this case, the static physical limit takes precedence; if the combined cycle unit has a large physical load capacity, but the current thermal stress of the rotor is high, then the dynamic margin constrained by dynamic thermal stress takes precedence. Through real-time optimization and arbitration of the two, the unit maximizes the frequency regulation space under the condition that the thermal stress is permissible, and strictly limits the frequency regulation command to protect the equipment when the rotor thermal stress is high. Thus, a balance is achieved between the output potential of the combined cycle unit and the safety of the equipment.

[0100] Based on the dynamic margin calculation in this application's technical solution, the system can capture the thermal stress of the turbine rotor in real time. When the real-time thermal stress is high, the calculated dynamic margin will shrink significantly. After arbitration by taking the minimum value, the system, responding to the correction of the basic boundary by the dynamic margin, will strictly limit the frequency regulation action within the dynamic margin range. At this time, the load limit boundary range is limited to the basic boundary range due to the correction of the dynamic margin, thereby ensuring absolute protection of the equipment. When the combined cycle unit operates stably for a long time, the turbine rotor temperature is uniform, the thermal stress is small, and the static output space of the gas turbine is sufficient, the combined cycle unit has a very strong instantaneous power impact withstand capability. At this time, the dynamic margin calculated in real time can exceed the static power limit of the combined cycle unit. After arbitration by taking the minimum value, the system will use the basic boundary as the limit of the frequency regulation action to ensure that the combined cycle unit can make full use of its theoretical response space.

[0101] Furthermore, in an optional embodiment, when the gas turbine is adjusting upward load, if the gas turbine has entered the temperature control zone—that is, the turbine exhaust temperature reaches a set value and the compressor inlet guide vane (IGV) opening reaches a preset maximum limit—then the gas turbine has no upward adjustment capability. Under this condition, the upper limit of the gas turbine's static power is determined as the actual generated power, thus reducing the upward static adjustable space to zero and ultimately limiting the load limit of the primary frequency regulation to the current power. This prevents the gas turbine from overheating and being damaged during upward power adjustment.

[0102] In another optional embodiment, when the combined cycle unit operates at low load and downward load adjustment is performed, lean combustion shutdown of the gas turbine combustor may occur. Under this condition, based on environmental parameters and fuel characteristics, the minimum stable combustion load boundary of the gas turbine is calculated, and a load preset value is set. When the difference between the actual power output of the combined cycle unit and the minimum stable combustion load boundary is less than the load preset value, it is determined that the actual operating load has entered the minimum load zone, and the downward dynamic margin is forcibly narrowed. This ensures that the lower limit of the primary frequency regulation load is not less than the sum of the minimum stable combustion load boundary and the load preset value, preventing gas turbine shutdown.

[0103] In an optional embodiment, when the compressor inlet guide vane (IGV) opening reaches a preset minimum limit, it is determined that the actual operating load has entered the minimum load zone. Under this condition, the lower limit of the static power of the gas turbine is determined as the actual power generated by the gas turbine, so that the combined cycle unit no longer participates in the primary frequency regulation, and the lower limit of the primary frequency regulation load is limited to the current power.

[0104] In another alternative embodiment, such as Figure 2As shown, the load limit boundary judgment logic includes judgments on the temperature control zone and the minimum load zone. In the temperature control zone logic branch, the judgment conditions are whether the current turbine exhaust temperature has reached the predetermined temperature control value and whether the compressor inlet guide vanes have reached their maximum physical limit. If both conditions are met simultaneously, it indicates that the combined cycle unit has entered the temperature control zone, and the gas turbine's thermodynamic cycle under the current intake volume has reached its peak, losing any physical ability to adjust the load upwards. At this time, forced intervention is triggered, locking the gas turbine's static power upper limit to its current actual power output. In the minimum load zone logic branch, the difference between the current actual gas turbine power output and the minimum stable combustion load boundary is calculated. When this difference is less than the set load predetermined value, it indicates that the combined cycle unit has entered the minimum load zone, and the gas turbine is at risk of lean combustion shutdown. At this time, the downward dynamic margin is actively reduced so that the lower limit of the primary frequency regulation load is not less than the sum of the minimum stable combustion load boundary and the load predetermined value. If the combined cycle unit is neither in the temperature control zone nor the minimum load zone, it indicates that the unit is in the normal regulation range. At this point, without additional intervention, the upper and lower load limits of the primary frequency regulation obtained in the preceding steps are directly output to the combined cycle unit. Based on this embodiment, overheating of the combined cycle unit can be avoided under high load, and shutdown of the combined cycle unit can be avoided under low load, effectively ensuring unit safety.

[0105] In summary, the method provided by this invention, by decoupling the operating modes of the combined cycle unit and coupling the static physical limits and dynamic margins to form a dynamic constraint boundary, enables the gas turbine combined cycle unit to release its maximum regulation potential in primary frequency regulation while ensuring safety. Simultaneously, it can call different calculation models for different modes to calculate the adjustable ranges of the gas turbine and steam turbine separately, ultimately synthesizing a more accurate primary frequency regulation load range for the entire combined cycle unit.

[0106] The above description is merely a specific embodiment of this application, but the scope of protection of this invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this invention should be included within the scope of protection of this invention. Therefore, the scope of protection of this invention should be determined by the scope of the claims.

Claims

1. A method for determining the load of a gas turbine combined cycle unit participating in primary frequency regulation, characterized in that, Includes the following steps: The operating data of a gas turbine combined cycle unit is obtained, wherein the gas turbine combined cycle unit includes at least one gas turbine and at least one steam turbine, and the operating data includes environmental parameters, operating modes and real-time operating parameters; Based on the operating data, the static power limit of the gas turbine combined cycle unit is calculated, which serves as the basic boundary for the gas turbine combined cycle unit to participate in primary frequency regulation. Based on the real-time operating parameters, the real-time thermal stress of the turbine rotor is calculated, and based on the operating mode and the real-time thermal stress, the dynamic margin for the gas turbine combined cycle unit to participate in primary frequency regulation is determined, wherein the dynamic margin is dynamically constrained based on the proximity of the real-time thermal stress to the corresponding maximum safe stress. Based on the dynamic margin, the basic boundary is corrected to obtain the load limit boundary for the gas turbine combined cycle unit to participate in primary frequency regulation, so as to limit the target of primary frequency regulation within the load limit boundary.

2. The method according to claim 1, characterized in that, The calculation of the static power limit of the gas turbine combined cycle unit based on the operating data includes: Based on the environmental parameters and the operating mode, the static output limit of the gas turbine is calculated; Based on the real-time operating parameters, the static output limit of the steam turbine is calculated; The static power limit is calculated based on the static output limits of the gas turbine and the steam turbine.

3. The method according to claim 1, characterized in that, The determination of the dynamic margin for the gas turbine combined cycle unit to participate in the primary frequency regulation based on the operating mode and the real-time thermal stress includes: Based on the real-time thermal stress and the corresponding maximum safe stress, the maximum allowable instantaneous power impact amplitude of the steam turbine is calculated; The dynamic margin is obtained by combining the maximum instantaneous power impact amplitude and the maximum adjustment rate of the gas turbine.

4. The method according to claim 1, characterized in that, The process of correcting the basic boundary based on the dynamic margin to obtain the load limitation boundary for the gas turbine combined cycle unit to participate in the primary frequency regulation includes: Based on the static power limit and the actual power output of the gas turbine combined cycle unit, calculate the static adjustable space; Compare the static adjustable space with the dynamic margin, and select the smaller of the two as the target adjustable space; The load limit boundary is calculated based on the target adjustable space and the actual power output of the gas turbine combined cycle unit.

5. The method according to claim 4, characterized in that, The static power limit includes a static power upper limit, and the dynamic margin correspondingly includes an upward dynamic margin. The calculation of the load limitation boundary for the gas turbine combined cycle unit to participate in primary frequency regulation based on the static power limit and the dynamic margin includes: The difference between the upper limit of static power and the actual power generated by the gas turbine combined cycle unit is calculated as the upward static adjustable space; Compare the upward static adjustable space with the upward dynamic margin, and select the smaller of the two as the upward target adjustable space; The upper limit of the primary frequency regulation load is obtained by adding the adjustable upward target space to the actual power generated by the gas turbine combined cycle unit.

6. The method according to claim 4, characterized in that, The static power limit includes a lower static power limit, and the dynamic margin correspondingly includes a downward dynamic margin. The calculation of the load limitation boundary for the gas turbine combined cycle unit to participate in primary frequency regulation based on the static power limit and the dynamic margin includes: The difference between the actual power output of the gas turbine combined cycle unit and the lower limit of the static power output is calculated as the downward static adjustable range. Compare the downward static adjustable space with the downward dynamic margin, and select the smaller of the two as the downward target adjustable space; The load lower limit of the primary frequency regulation is obtained by subtracting the actual power generated by the gas turbine combined cycle unit from the downward target adjustable space.

7. The method according to claim 5, characterized in that, Also includes: The turbine exhaust temperature and compressor inlet guide vane opening of the gas turbine are obtained; When the turbine exhaust temperature reaches the preset temperature control value and the compressor inlet guide vane opening reaches the maximum opening limit, the actual power output of the gas turbine is calculated and determined as the upper limit of the static power output of the gas turbine, so as to limit the upward static adjustment space.

8. The method according to claim 6, characterized in that, Also includes: Obtain the compressor inlet guide vane opening of the gas turbine; When the compressor inlet guide vane opening reaches the minimum opening limit, the actual power output of the gas turbine is calculated and determined as the lower limit of the static power output of the gas turbine, so as to limit the downward static adjustment space.

9. The method according to claim 1, characterized in that, Also includes: Based on the real-time operating parameters, the life loss coefficient of the key parts of the rotor is calculated; The dynamic margin is adjusted based on how close the lifetime loss coefficient is to the corresponding maximum lifetime loss of a single frequency modulation.

10. The method according to any one of claims 1 to 9, characterized in that, The operating modes include unit shaft configuration, gas turbine combustion mode, and steam turbine cycle mode, wherein... The unit's shaft system configuration includes at least one of a single-shaft mode and a multi-shaft mode; The gas turbine combustion mode includes at least one of a premixed mode and a diffusion mode; The turbine cycle mode includes at least one of pure condensing mode, extraction condensing mode, and back pressure mode.

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