Modeless Start-Up Control for Operational Flexibility of Combined Cycle Power Plants

2020 ◽  
Vol 53 (10) ◽  
pp. 636-645
Author(s):  
Yasuhiro Yoshida ◽  
Yuya Tokuda ◽  
Takuya Yoshida ◽  
Yuki Enomoto ◽  
Nobuhiro Osaki ◽  
...  
Keyword(s):  
Power Plants ◽  
Combined Cycle ◽  
Operational Flexibility ◽  
Start Up

Coordinated Control of Gas and Steam Turbines for Efficient Fast Start-Up of Combined Cycle Power Plants

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Yasuhiro Yoshida ◽  
Kazunori Yamanaka ◽  
Atsushi Yamashita ◽  
Norihiro Iyanaga ◽  
Takuya Yoshida
Keyword(s):  
Thermal Stress ◽  
Steam Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Thermal Stresses ◽  
Control Method ◽  
Coordinated Control ◽  
Combined Cycle ◽  
Steam Turbines ◽  
Start Up

In the fast start-up for combined cycle power plants (CCPP), the thermal stresses of the steam turbine rotor are generally controlled by the steam temperatures or flow rates by using gas turbines (GTs), steam turbines, and desuperheaters to avoid exceeding the thermal stress limits. However, this thermal stress sensitivity to steam temperatures and flow rates depends on the start-up sequence due to the relatively large time constants of the heat transfer response in the plant components. In this paper, a coordinated control method of gas turbines and steam turbine is proposed for thermal stress control, which takes into account the large time constants of the heat transfer response. The start-up processes are simulated in order to assess the effect of the coordinated control method. The simulation results of the plant start-ups after several different cool-down times show that the thermal stresses are stably controlled without exceeding the limits. In addition, the steam turbine start-up times are reduced by 22–28% compared with those of the cases where only steam turbine control is applied.

Optimizing Lifetime Consumption and Increasing Flexibility Using Enhanced Lifetime Assessment Methods With Automated Stress Calculation From Long-Term Operation Data

2013 ◽  
Author(s):  
Jan Vogt ◽  
Thomas Schaaf ◽  
Klaus Helbig
Keyword(s):  
Power Plants ◽  
Low Cycle Fatigue ◽  
Combined Cycle ◽  
Transient Temperature ◽  
Steam Turbines ◽  
Transfer Coefficients ◽  
Term Operation ◽  
Flexible Mode ◽  
Start Up ◽  
Safety Margins

In the past most of the steam turbines were designed as base load machines. Due to new market requirements based on the effect of renewable energies, power plant operators are forced to operate with more frequent start-up events and load changes, resulting in a fundamental higher low cycle fatigue (LCF) lifetime consumption. Traditional methods of lifetime assessment often use representative start-ups, for the calculation of LCF damage, which can provide very conservative results with reasonable safety margins. For a high number of starts these safety margins may result in an overestimation of the LCF damage. At Alstom, an enhanced method for lifetime assessment has been developed, that evaluates the actual lifetime consumption from real operation data in an automated manner and provides much more realistic results. The operation data is used to calculate the transient temperature distribution and heat transfer coefficients along the rotor for each start-stop cycle. The corresponding stress distribution in the rotor is evaluated by means of a Finite-Element-method analysis. Finally the number of remaining cycles is extracted for the most critical locations using material data. In combination with the creep damage the lifetime consumption is evaluated. The entire process is highly automated, but also facilitates easy monitoring through the lifetime engineer by graphic presentation of calculation results. Using this enhanced method of lifetime assessment, the computed lifetime consumption is closer to the actual value, supporting the planning of overhauls and component replacements and minimizing the risk of failure or forced outages. The utilization of remaining lifetime can be optimized in favour of a more flexible mode of operation (e.g. low load operation and fast start-up) or extension of operational lifetime for conventional and combined cycle power plants.

CCPP Operational Flexibility Extension Below 30% Load Using Reheat Burner Switch-Off Concept

2015 ◽  
Author(s):  
Dirk Therkorn ◽  
Martin Gassner ◽  
Vincent Lonneux ◽  
Mengbin Zhang ◽  
Stefano Bernero
Keyword(s):  
Gas Turbine ◽  
Power Plants ◽  
Fast Response ◽  
Combined Cycle ◽  
Pollutant Emissions ◽  
Inlet Temperature ◽  
Operational Flexibility ◽  
Part Load ◽  
Combustion Technology ◽  
The Impact

Highly competitive and volatile energy markets are currently observed, as resulting from the increased use of intermittent renewable sources. Gas turbine combined cycle power plants (CCPP) owners therefore require reliable, flexible capacity with fast response time to the grid, while being compliant with environmental limitations. In response to these requirements, a new operation concept was developed to extend the operational flexibility by reducing the achievable Minimum Environmental Load (MEL), usually limited by increasing pollutant emissions. The developed concept exploits the unique feature of the GT24/26 sequential combustion architecture, where low part load operation is only limited by CO emissions produced by the reheat (SEV) burners. A significant reduction of CO below the legal limits in the Low Part Load (LPL) range is thereby achieved by individually switching the SEV burners with a new operation concept that allows to reduce load without needing to significantly reduce both local hot gas temperatures and CCPP efficiency. Comprehensive assessments of the impact on operation, emissions and lifetime were performed and accompanied by extensive testing with additional validation instrumentation. This has confirmed moderate temperature spreads in the downstream components, which is a benefit of sequential combustion technology due to the high inlet temperature into the SEV combustor. The following commercial implementation in the field has proven a reduction of MEL down to 26% plant load, corresponding to 18% gas turbine load. The extended operation range is emission compliant and provides frequency response capability at high plant efficiency. The experience accumulated over more than one year of successful commercial operation confirms the potential and reliability of the concept, which the customers are exploiting by regularly operating in the LPL range.

Rotor-Blade Interaction During Blade Resonance Drive-Through

2021 ◽  
Author(s):  
Roland Grein ◽  
Ulrich Ehehalt ◽  
Christian Siewert ◽  
Norbert Kill
Keyword(s):  
Power Plants ◽  
Renewable Energy Sources ◽  
Cyclic Fatigue ◽  
Combined Cycle ◽  
Plant Design ◽  
Steam Turbines ◽  
Rotating Speed ◽  
Start Up ◽  
Blade Vibrations ◽  
Fast Start

Abstract In the future energy landscape, combined cycle power plants will increasingly take the role of providing balancing power for fluctuating renewable energy sources due to their high availability and fast start-up times. This implies more frequent cycling, a larger number of speed cycles and thus new challenges for plant design and operation. One of these challenges is a potential increase of cyclic fatigue incurred by last-stage blades during start-up and coast-down. Blade vibrations might be induced by synchronous shaft vibrations when the blade resonance is excited by lateral shaft vibrations. In this paper, we report measurement results of shaft and blade vibrations observed at some Siemens Energy steam turbines. Apart from the expected increase of blade vibrations when the double rotating speed crosses the blade resonance, a distinctive dip of shaft vibrations at the low-pressure turbine bearings is observed. We argue that this phenomenon is likely related to the aforementioned interaction between blade and shaft vibrations and present a theoretical framework to describe this interaction and the observed effect.

Optimizing the start-up operations of combined cycle power plants using soft computing methods

2011 ◽  
Vol 20 (4) ◽  
pp. 648-656 ◽  
Author(s):  
I. Bertini ◽  
M. De Felice ◽  
A. Pannicelli ◽  
S. Pizzuti
Keyword(s):  
Soft Computing ◽  
Power Plants ◽  
Computing Methods ◽  
Combined Cycle ◽  
Start Up ◽  
Soft Computing Methods

The Effect and Remedy of Nozzle Loads on Boiler Feed Pumps

2004 ◽  
Author(s):  
Alan P. Flory ◽  
William C. Livoti
Keyword(s):  
Power Plants ◽  
Base Plate ◽  
Combined Cycle ◽  
Real Cost ◽  
Start Up ◽  
Commercial Operation ◽  
Current Design ◽  
Ring Section ◽  
Section Type ◽  
Motor Vibration

Many frequently encountered start-up and operational problems in current design combined cycle power plants can be traced to pipe strain and nozzle loads placed upon pumps. This is most dramatic when the boiler feed pump is affected. Many of the symptoms are significant and can include misalignment, dynamic (changing) alignment, pump or motor vibration, bearing problems, mechanical seal failures and seizure of equipment on start-up and shutdown. While these are all nuisance items that can plague plant shake-down and commissioning, some can generate huge costs and plant unscheduled outages. More profoundly, these symptoms are often all present, making accurate diagnosis of the true cause very difficult. The real cost of these problems can be seen in plants missing commercial operation dates. Some of the piping issues that can cause these symptoms will be discussed, items including hydraulic aspects of the piping design, straight runs, horizontal runs, venting, location of minimum flow valve, and pipe hanger location. Also, the use of pre-fabricated pipe and spool pieces will be discussed. A short discussion will also be presented on how these piping issues impact various designs of pumps, such as barrel pumps, horizontal split case and ring section type pumps. This will also include some comments on pump mounting issues such as base-plate installation, the use of pin & key blocks and pedestal design. All of the discussions will be summarized and then presented with several recommendations for piping repair, operational changes, and material reinforcement. Optional pump features will be presented, indicating what items can be used to improve operation and reliability when abnormal nozzle loads are expected, including comments on internal clearances, wear part metallurgy and bearing upgrades. These recommendations will be compared against several field experiences for confirmation, with some focus on nozzle load data vs. design, and operation prior to and after strain removal. This combination of field results and engineering analysis of this topic should prove quite useful to the engineer attempting to diagnose any symptoms found in the field. Often times several symptoms may be present, making diagnosis difficult and it is only the methodical steps of symptom elimination that will get the new power plant on the way to commercial operation.

Thermal Modeling of HRSG Transient Behavior in Combined Cycle Power Plants

2006 ◽  
Author(s):  
Sepehr Sanaye ◽  
Moein Rezazadeh ◽  
Jalaleddin Oladi ◽  
Gholam Hossein Sadeghpoor ◽  
Farid Bashiri ◽  
...  
Keyword(s):  
Steady State ◽  
Power Plants ◽  
Cold Start ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Master Program ◽  
Load Change ◽  
Start Up ◽  
Program Software ◽  
Transient And Steady State

Combined Cycle Power Plants (CCPP) are attractive electricity generation systems due to high cycle efficiency and quick response of the system to load change. Heat recovery steam generator (HRSG) is an important part of a CCPP and it is important to predict the HRSG operating conditions in transient and steady state modes. It should be emphasized that the biggest pressure and thermal stresses are imposed on HRSG superheater and evaporator tubes banks during transient periods (cold start up and load change). Due to these effects a software program was developed for analyzing the HRSG transient and steady state operating conditions. The HRSG software included arbitrary number of pressure levels (usually up to three) and any number of elements (superheater, evaporator, economizer, desuperheater and duct burner). In this paper theories and equations (mass/energy balance and heat transfer coefficients) applied for HRSG thermal analysis are described. Also HRSG program software outputs were compared with real data collected from HRSG cold start-up at Tehran CCPP with specified geometry and arrangement of elements. The closeness of two groups of data in this transient and steady state modes was acceptable. The numerical outputs in steady state condition also were found very close to GT MASTER program software outputs.

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