scholarly journals Electrical Damping Assessment and Stability Considerations for a Highly Electrified Liquefied Natural Gas Plant

Energies ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2612
Author(s):  
Lorenzo Bongini ◽  
Rosa Anna Mastromauro ◽  
Daniele Sgrò ◽  
Fabrizio Malvaldi
Keyword(s):  
Control System ◽  
Natural Gas ◽  
Gas Turbines ◽  
Ad Hoc ◽  
Power Converters ◽  
Liquefied Natural Gas ◽  
Variable Frequency ◽  
Torsional Vibrations ◽  
Variable Frequency Drives ◽  
Electrical Damping

In recent years, the Oil & Gas industry has been subjected to a progressive electrification process aiming to comply with global environmental requirements on CO2 emissions reduction. High-power electric motors fed by Variable Frequency Drives (VFDs) have replaced gas turbines as drivers for gas compression applications. In Liquefied Natural Gas (LNG) plants, unexpected downturns could be experienced in case of high torsional vibrations of power generations units. These torsional vibrations derive from the interaction among turbine-generator (TG) units and VFDs and are known as Sub-Synchronous Torsional Interactions (SSTIs). SSTIs can lead to instability when the overall electromechanical system lacks sufficient damping. In this scenario, electrical damping assessment is fundamental in order to ensure stability and reliable operation of an LNG plant. Negative electrical damping is strictly related to the negative incremental resistance behavior of the power converters and it is influenced by the converter’s control system. In this paper, a real case study based on Thyristor Variable Frequency Drives (TVFDs) is considered. Ad hoc dynamic models of the power converters and of the TG unit are developed and combined in order to provide an accurate estimation of the electrical damping. It is demonstrated that the electrical damping is affected by variations of the main control system parameters and how the use of a simplified model instead of an ad hoc model can impact the stability evaluation.

scholarly journals Electrical Damping Assessment and Sensitivity Analysis of a Liquefied Natural Gas Plant: Experimental Validation

Energies ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 4084
Author(s):  
Lorenzo Bongini ◽  
Rosa Anna Mastromauro ◽  
Daniele Sgrò ◽  
Fabrizio Malvaldi
Keyword(s):  
Sensitivity Analysis ◽  
Control System ◽  
Natural Gas ◽  
Experimental Validation ◽  
Power Conversion ◽  
Liquefied Natural Gas ◽  
Fine Tuning ◽  
Simulation Platform ◽  
Electrical Damping ◽  
Conversion Stage

Liquefied Natural Gas (LNG) plants are commonly island-operated weak grids where the interaction of high-power Variable Frequency Drives (VFDs) with the Turbine-Generator (TG) units might cause Sub-Synchronous Torsional Interaction (SSTI) phenomena. SSTI phenomena can lead the LNG plant to instability conditions. Each LNG plant configuration is characterized by a risk level, which is considered high when the electrical damping at the TG Torsional Natural Frequencies (TNFs) is negative. Starting from a real case study, a detailed electromechanical model of an LNG plant is presented. The model is comprehensive of the control system of the power conversion stage and of the TG unit. Sensitivity analysis, performed on control system parameters, allows one to detect the parameters that impact the electrical damping and the stability of the overall LNG plant. A complete simulation platform is developed. Experimental results are carried out on a real LNG plant considering four different configurations. The theoretical model and the simulation platform allow one to estimate the electrical damping and the results are confirmed by the experimental validation. It is demonstrated that fine tuning of the power conversion stage control parameters can reduce the risk related to torsional instability.

scholarly journals Phase-Controlled Thyristor Sub-Synchronous Damper Converter for a Liquefied Natural Gas Plant

Energies ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5238
Author(s):  
Lorenzo Bongini ◽  
Rosa Anna Mastromauro ◽  
Daniele Sgrò ◽  
Fabrizio Malvaldi
Keyword(s):  
Control System ◽  
Natural Gas ◽  
High Performance ◽  
Reference Signal ◽  
Liquefied Natural Gas ◽  
Torsional Vibrations ◽  
Successful Operation ◽  
Torsional Instability ◽  
The Stability ◽  
Plant Configuration

In electrified liquefied natural gas (LNG) plants variable frequency drives (VFDs) interact with turbine-generator (TG) units creating torsional vibrations known as sub-synchronous torsional interactions (SSTIs). Torsional vibrations can be dangerous for an LNG plant when they involve torsional instability. The stability of an LNG plant depends on the plant configuration and on the number of TG units and of VFDs. In such peculiar configurations stability cannot be achieved acting of the VFDs control system. Alternatively, dedicated equipment is needed to damp the torsional vibrations. In this paper, a sub-synchronous damper (SSD) converter is used to mitigate the SSTI phenomena. The SSD converter consists of a thyristor H-bridge regulating the phase of the additional torque provided at the TG unit air-gap. A phase control system is proposed and is based on the torsional torque oscillations measurement. An adaptive reference signal is employed, also guaranteeing high performance in island-mode operation. The proposed solution increases the damping of the LNG plant in all the considered configurations. The LNG plant successful operation is validated by comprehensive results.

scholarly journals A boil-off gas utilization for improved performance of heavy duty gas turbines in combined cycle

2018 ◽  
Vol 233 (1) ◽  
pp. 96-110 ◽  
Author(s):  
Stefano Mazzoni ◽  
Srithar Rajoo ◽  
Alessandro Romagnoli
Keyword(s):  
Heat Transfer ◽  
Natural Gas ◽  
Ambient Temperature ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Liquefied Natural Gas ◽  
Combined Cycle ◽  
Cooling Power ◽  
Heavy Duty ◽  
Cold Energy

The storage of the natural gas under liquid phase is widely adopted and one of the intrinsic phenomena occurring in liquefied natural gas is the so-called boil-off gas; this consists of the regasification of the natural gas due to the ambient temperature and loss of adiabacity in the storage tank. As the boil-off occurs, the so-called cold energy is released to the surrounding environment; such a cold energy could potentially be recovered for several end-uses such as cooling power generation, air separation, air conditioning, dry-ice manufacturing and conditioning of inlet air at the compressor of gas turbine engines. This paper deals with the benefit corresponding to the cooling down of the inlet air temperature to the compressor, by means of internal heat transfer recovery from the liquefied natural gas boil-off gas cold energy availability. The lower the compressor inlet temperature, the higher the gas turbine performance (power and efficiency); the exploitation of the liquefied natural gas boil-off gas cold energy also corresponds to a higher amount of air flow rate entering the cycle which plays in favour of the bottoming heat recovery steam generator and the related steam cycle. Benefit of this solution, in terms of yearly work and gain increase have been established by means of ad hoc developed component models representing heat transfer device (air/boil-off gas) and heavy duty 300 MW gas turbine. For a given ambient temperature variability over a year, the results of the analysis have proven that the increase of electricity production and efficiency due to the boil-off gas cold energy recovery has finally yield a revenue increase of 600,000€/year.

scholarly journals Fuel Control of Gas Turbines by Programmable Logic Controllers

1993 ◽  
Author(s):  
Dan A. King
Keyword(s):  
Control System ◽  
Natural Gas ◽  
Control Systems ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Programmable Logic Controller ◽  
Programmable Logic ◽  
Programmable Logic Controllers ◽  
Control Functions ◽  
Logic Controllers

NOVA Corporation of Alberta has developed a programmable logic controller based gas turbine fuel control system for natural gas compressor set applications. The system carries out all necessary fuel control functions and was integrated into the existing programmable logic controller used for sequencing and shutdown. The system has been successfully implemented on several different aero derivative gas turbines to date. This paper discusses the development of the system, its performance and advantages over standalone hardware-based fuel control systems typically used in the application.

Development of a Catalytic Combustor for Small Gas Turbines

1987 ◽  
Author(s):  
K. Mori ◽  
J. Kitajima ◽  
S. Kajita ◽  
S. Ichihara
Keyword(s):  
Natural Gas ◽  
Gas Turbines ◽  
Combustion Zone ◽  
Catalytic Combustion ◽  
Liquefied Natural Gas ◽  
Nox Emissions ◽  
Variable Geometry ◽  
Wide Range ◽  
Catalytic Combustor ◽  
Full Scale Tests

To reduce NOx emissions significantly, a catalytic combustor was developed. Full scale tests of catalytic combustors designed for application in Kawasaki S1A-O2 type gas trubines were conducted. The combustor consisted of a pre-combustion zone, a premixing zone, a catalytic combustion zone, and a variable geometry dilution zone. Liquefied Natural Gas (LNG) was burned in combustor rig tests and results indicated low NOx emissions and high combustion efficiencies over a wide range of air/fuel ratios and that the catalytic combustor can be applied to the engine tests.

scholarly journals USE OF GAS TURBINES FOR COMBINED ENERGY PRODUCTION

2020 ◽  
Vol 47 (1) ◽  
pp. 8-18
Author(s):  
V. A. Bulanin
Keyword(s):  
Natural Gas ◽  
Steam Turbine ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Ad Hoc ◽  
Combined Cycle ◽  
New Energy ◽  
State Of Research ◽  
Cis Countries

Abstract. Aim. Despite the obvious expediency of their widespread implementation, gas turbine (GT) and combined cycle gas turbine (CCGT) plants were only used in limited quantities in the former USSR and CIS countries. Due to the exhaustion of possibilities to increase the fuel use efficiency and return on investment (ROI) in steam-turbine combined heat and power (CHP) plants, the development of GT and CCGT plants becomes an urgent problem. In current global practice, the primary fuel for gas turbines and combined cycle gas turbines is natural gas. However, until recently, there has been a lack of experience in the design, construction and operation of GT and CCGT plants in the CIS countries. Method. Due to the ad hoc nature of research in this area, it was necessary to systematise the results of existing studies and assess the state of research at the world level taking regional characteristics into account. Results. The article presents the main considerations and potential effectiveness of the use of gas turbines. Basic gas turbine construction schemes are investigated along with their techno-economic characteristics and an assessment of their comparative utility. Conclusion. Considering the widespread availability of natural gas, it is recommended that gas turbine and combined-cycle plants be installed as part of the process of technical re-equipment in the fuel and energy complex, industry, agriculture and municipal energy sectors as part of the design and construction of new energy sources in the light of positive world experience and the current level of development of gas turbine technologies. Ubiquitous implementation of gas turbine units in the centres supplying heat and electric loads will reduce the regional economy’s need for energy fuel and ensure an increase in energy capacity without the need to construct new complex and uneconomic steam turbine power plants. 

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