• Title, Summary, Keyword: Ultra-supercritical boiler (USC) power plant

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Supplementary Control of Conventional Coordinated Control for 1000 MW Ultra-supercritical Thermal Power Plant using Dynamic Matrix Control

  • Lee, Youngjun;Yoo, Euiyeon;Lee, Taehyun;Moon, Un-Chul
    • Journal of Electrical Engineering and Technology
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    • v.13 no.1
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    • pp.97-104
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    • 2018
  • This paper proposes supplementary control of conventional coordinated control of a power plant which directly affects network frequency. The supplementary control with dynamic matrix control is applied for 1000 MW power plant with ultra-supercritical (USC) once-through boiler. The supplementary control signal is added to the boiler feedforward signal in the existing coordinated control logic. Therefore, it is a very practical structure that can maintain the existing multi-loop control system. This supplementary controller uses the step response model for the power plant system, and on-line optimization is performed at every sampling step. The simulation results demonstrate the effectiveness of the proposed supplementary control in a wide operating range of a practical 1000 MW USC power plant simulator. These results can contribute the stable operation of power system frequency.

Study on the Improvement of Weld-joint Reliability in Waterwall Tubes of the Ultra Supercritical Coal Fired Boiler (석탄화력발전용 초초임계압(USC) 보일러 수냉벽 튜브 용접 신뢰성 향상에 대한 연구)

  • Ahn, Jong-Seok;Lee, Seung-Hyun;Cho, Sang-Kie;Lee, Gil-Jae;Lee, Chang-Hee;Moon, Seung-Jae
    • Journal of Welding and Joining
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    • v.28 no.1
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    • pp.41-46
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    • 2010
  • The low alloy-steel material(1.0Cr-0.5Mo, SA213T12), which has widely been used for the waterwall tube in the conventional power plant, do not have enough creep rupture strength for waterwall tubes of the Ultra-supercritical(USC) boilers. According to this reason, the high-strength low alloy-steel(2.25Cr-1.0Mo, SA213T22) has newly been adopted for the waterwall tube in the USC boilers. This paper presents failure analysis on weld-joint of the waterwall tubes in USC boilers. Visual inspections were performed to find out the characteristics of the fracture. Additionally both microscopic characteristics and hardness test were carried out on failed tube samples. Failures seem to happen mainly because the welding process has not been conducted strictly.(preheating, P.W.H.T and so forth). Thus, this paper has the purpose to describe the main cause of the poor welding process and to explain how to prevent similar failures in those weld-joints.

Reliability Improvement Method of Weld Zone in Water Wall Tube for an Ultra Supercritical Coal Fired Boiler (초초임계압 석탄화력 보일러 수냉벽 수관의 용접신뢰성 향상방안)

  • Ahn, Jong-Seok;Moon, Seung-Jae
    • Plant Journal
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    • v.6 no.3
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    • pp.53-61
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    • 2010
  • This paper presents failure analysis on weld-joint of the waterwall tubes in USC boilers. Visual inspections were performed to find out the characteristics of the fracture. Additionally both microscopic characteristics and hardness test were carried out on failed tube samples. Failures seem to happen mainly because the welding process such as preheating and PWHT(post-weld heat treatment) was not conducted strictly. Thus, this paper has the purpose to describe the main cause of the poor welding process and to explain how to prevent similar failures in those weld-joints.

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Study on the Microstructural Degradation of the Boiler Tubes for Coal-Fired Power Plants

  • Yoo, Keun-Bong;He, Yinsheng;Lee, Han-Sang;Bae, Si-Yeon;Kim, Doo-Soo
    • KEPCO Journal on Electric Power and Energy
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    • v.4 no.1
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    • pp.25-31
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    • 2018
  • A boiler system transforms water to pressured supercritical steam which drives the running of the turbine to rotate in the generator to produce electricity in power plants. Materials for building the tube system face challenges from high temperature creep damage, thermal fatigue/expansion, fireside and steam corrosion, etc. A database on the creep resistance strength and steam oxidation of the materials is important to the long-term reliable operation of the boiler system. Generally, the ferritic steels, i.e., grade 1, grade 2, grade 9, and X20, are extensively used as the superheater (SH) and reheater (RH) in supercritical (SC) and ultra supercritcal (USC) power plants. Currently, advanced austenitic steel, such as TP347H (FG), Super304H and HR3C, are beginning to replace the traditional ferritic steels as they allow an increase in steam temperature to meet the demands for increased plant efficiency. The purpose of this paper is to provide the state-of-the-art knowledge on boiler tube materials, including the strengthening, metallurgy, property/microstructural degradation, oxidation, and oxidation property improvement and then describe the modern microstructural characterization methods to assess and control the properties of these alloys. The paper covers the limited experience and experiment results with the alloys and presents important information on microstructural strengthening, degradation, and oxidation mechanisms.

Temperature Control of Ultrasupercritical Once-through Boiler-turbine System Using Multi-input Multi-output Dynamic Matrix Control

  • Moon, Un-Chul;Kim, Woo-Hun
    • Journal of Electrical Engineering and Technology
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    • v.6 no.3
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    • pp.423-430
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    • 2011
  • Multi-input multi-output (MIMO) dynamic matrix control (DMC) technique is applied to control steam temperatures in a large-scale ultrasupercritical once-through boiler-turbine system. Specifically, four output variables (i.e., outlet temperatures of platen superheater, finish superheater, primary reheater, and finish reheater) are controlled using four input variables (i.e., two spray valves, bypass valve, and damper). The step-response matrix for the MIMO DMC is constructed using the four input and the four output variables. Online optimization is performed for the MIMO DMC using the model predictive control technique. The MIMO DMC controller is implemented in a full-scope power plant simulator with satisfactory performance.