• Title/Summary/Keyword: Variable speed

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The Analysis of Life Cycle Cost and Cooling Water Circulating Pump Energy Saving According to Variable Speed Pressure Differential Setpoint Control Strategy

  • Kim, Seo-Hoon;Kim, Jong-Hun;Jang, Cheol-Yong;Song, Kyoo-dong
    • KIEAE Journal
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    • v.15 no.4
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    • pp.37-43
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    • 2015
  • Purpose : The study applied control strategy to reduce through optimal control and operation of pump by applying control on variable speed to the circulation pump of HVAC system in the office building. The study has the purpose to review validity of control on variable speed as ESMs(Energy Saving Measures) and establish the control technology on variable speed pump. The study performed reduction analysis of building energy and economic evaluation of pump through energy effectiveness control strategy of HVAC system. Method: The study sought possible reduction through energy control strategy which can provide proper flow fitting to building load by applying control on variable speed pump. The study applied control strategy to reduce through pressure differential set-point control and operation of pump by applying control on variable speed to the circulation pump of HVAC system in the office building. Result : The results showed that about 16-35% of pump energy could be saved by using these optimal control strategies. In the result of analysis on 10 years life cycle cost of analysis on payback period of initial investment pump, variable speed pump control showed 5.1 years.

High Performance MPPT Based on Variable Speed Generator Driven by Wind Power Generation in Battery Applications

  • Padmanabhan, Sutha;Kaliyappan, Kannan
    • Journal of Electrical Engineering and Technology
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    • v.9 no.1
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    • pp.205-213
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    • 2014
  • A wind generator (WG) maximum power point tracking (MPPT) system is presented here. It comprises of a variable-speed wind generator, a high-efficiency boost-type dc/dc converter and a control unit. The advantages of the aimed system are that it does not call for the knowledge of the wind speed or the optimal power characteristics and that it operates at a variable speed, thus providing high efficiency. The WG operates at variable speed and thus suffers lower stress on the shafts and gears compared to constant-speed systems. It results in a better exploitation of the available wind energy, especially in the low wind-speed range of 2.5-4.5 m/s. It does not depend on the WG wind and rotor-speed ratings or the dc/dc converter power rating. Higher reliability, lower complexity and cost, and less mechanical stress of the WG. It can be applied to battery-charging applications.

A Study on the Performance Evaluation of Variable-speed Drive Pump (가변속펌프의 성능평가방법에 관한 연구)

  • Suh, Sang-Ho;Kim, Hyoung-Ho;Rakibuzzaman, Rakibuzzaman;Kim, Kyung-Wuk;Yoon, In-Sik
    • The KSFM Journal of Fluid Machinery
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    • v.17 no.5
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    • pp.83-88
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    • 2014
  • Pumps are widely used in industrial plants, energy systems, ships etc. Generally they consume nearly 20% each nation's total electrical energy. The objective of this study is to find performance evaluating method for variable-speed drive pump. In order to evaluate the variable-speed pump performance energy saving rate for the variable-speed pump is applied and compared with that of constant-speed pump.

Modeling of a Variable Speed Wind Turbine in Dynamic Analysis

  • Kim, Seul-Ki;Kim, Eung-Sang;Jeon, Jin-Hong
    • KIEE International Transactions on Power Engineering
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    • v.4A no.2
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    • pp.51-57
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    • 2004
  • This paper describes the dynamic performance of a variable speed wind turbine system responding to a wide variety of wind variations. Modeling of the wind generation using power electronics interface is proposed for dynamic simulation analysis. Component models and equations are addressed and their incorporations into a transient analysis program, PSCAD/EMTDC are provided. A wind model of four components is described, which enables observing dynamic behaviors of the wind turbine resulting from wind variations. Controllable power inverter strategies are intended for capturing the maximum power under variable speed operation and maintaining reactive power generation at a pre-determined level for constant power factor control or voltage regulation control. The components and control schemes are modeled by user-defined functions. Simulation case studies provide variable speed wind generator dynamic performance for changes in wind speed

Study on Vibration Characteristics after Applying Variable Speed Control to Constant Speed Fans used in a Power Plant (발전소 통풍계통의 가변속 적용 후 진동특성에 관한 연구)

  • Cho, C.W.;Song, O.S.;Yang, K.H.;Kim, G.Y.;Cho, S.T.;Moon, H.D.
    • Journal of Power System Engineering
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    • v.13 no.6
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    • pp.88-94
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    • 2009
  • In this paper, vibration characteristics after applying variable speed control to fans with a rated speed used in a power plant are studied by performing experiments and analyzing finite element models. Then the campbell diagram is presented to verify the reason of the abnormal vibration measured from fan structure during variable operation of Forced Draft Fan & Induced Draft Fan. According to results, it is found that amplitude of acceleration increases abruptly when a 2X harmonic component meets the natural frequency of fan rotor. Therefore it is very important thing that investigate exactly dynamic characteristics for the rotor at variable speed zone before applying variable speed control to a rotor with a rated speed.

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Voltage Impacts of a Variable Speed Wind Turbine on Distribution Networks

  • Kim, Seul-Ki;Kim, Eung-Sang
    • KIEE International Transactions on Power Engineering
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    • v.3A no.4
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    • pp.206-213
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    • 2003
  • The main purpose of this paper is to present a simulation model for assessing the impacts of a variable speed wind turbine (VSWT) on the distribution network and perform a simulation analysis of voltage profiles along the wind turbine installed feeder using the presented model. The modeled wind energy conversion system consists of a fixed pitch wind turbine, a synchronous generator, a rectifier and a voltage source inverter (VSI). Detailed study on the voltage impacts of a variable speed wind turbine is conducted in terms of steady state and dynamic behaviors. Various capacities and different modes of variable speed wind turbines are simulated and investigated. Case studies demonstrate how feeder voltages are influenced by capacity and control modes of wind turbines and changes in wind speed under different network conditions. Modeling and simulation analysis is based on PSCAD/EMTDC a software package.

On-line Fault Detection and Diagnosis for Heat Exchanger of Variable Speed Refrigeration System Based on Current Information (전류정보를 이용한 가변속냉동시스템의 열교환기 실시간 고장 진단)

  • Lee, Dong-Gyu;Jeong, Seok-Kwon
    • Proceedings of the SAREK Conference
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    • pp.88-94
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    • 2007
  • This study deals with on-line fault detection and diagnosis for heat exchanger of variable speed refrigeration system. Conventional studies about fault of heat exchanger in refrigeration system have used temperature and pressure information. The temperature and pressure are able to be used valuably for faults detection of constant speed refrigeration system. However in case of variable speed refrigeration system, the temperature and pressure are no longer useful information for fault detection due to compensation effect of feedback controller. While current information is possible to detect faults of variable speed refrigeration system. The current information was detected in an inverter, it was used after transforming rms value. The faults of variable speed refrigeration system are divided into electrical faults and mechanical faults. We performed fault detection and diagnosis about heat exchanger among mechanical faults such as condenser fouling and evaporator fan fouling through some experiments.

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A Study of Control Method of SRM for Variable Speed Control

  • Park, Heesung;Hwang, Yeongseong;Seong, Sejin;Choi, Jaedong
    • Proceedings of the KIPE Conference
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    • pp.754-757
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    • 1998
  • In this paper, the fuzzy control logic of Switched Reluctance Motor(SRM) is introduced to apply the variable speed drive system. Since the speed-torque property of SRM has high speed variation to the changes of torque like a DC motor, to apply SRM to the variable speed driving system, the optimal speed-torque control method is required. As the control method like this, the fuzzy logic and PI control are proposed, and characteristics of them are compared and verified through the experimental results

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A Study on the Switching Strategy of SRM for Variable Speed Control (SRM의 가변 속도 제어를 위한 스윗칭 기법에 관한 연구)

  • Lee, Tae-Gyoo;Huh, Uk-Youl
    • Proceedings of the KIEE Conference
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    • pp.1044-1046
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    • 1993
  • This paper describes a switching strategy for variable speed control and low torque ripple of Switched Reluctance Motor(SRM). The main advantage of this strategy is simple control. Therefore it can be constructed easily. And a design principle of SRM is represented for the proposed switching strategy. The proposed switching method is tested by simulation and experiment on various SRM type. As a result, The SRM drive with the proposed scheme is effective in reducing the torque ripple and variable speed control.

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Implementation and Control of AC-DC-AC Power Converter in a Grid-Connected Variable Speed Wind Turbine System with Synchronous Generator (동기기를 사용한 계통연계형 가변속 풍력발전 시스템의 AC-DC-AC 컨버터 구현 및 제어)

  • Song Seung-Ho;Kim Sung-Ju;Hahm Nyon-Kun
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.54 no.12
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    • pp.609-615
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    • 2005
  • A 30kW electrical power conversion system is developed for a variable speed wind turbine. In the wind energy conversion system(WECS) a synchronous generator with field current excitation converts the mechanical energy into electrical energy. As the voltage and the frequency of the generator output vary according to the wind speed, a 6-bridge diode rectifier and a PWM boost chopper is utilized as an ac-dc converter maintaining the constant dc-link voltage with only single switch control. An input current control algorithm for maximum power generation during the variable speed operation is proposed without any usage of speed sensor. Grid connection type PWM inverter converts dc input power to ac output currents into the grid. The active power to the grid is controlled by q-axis current and the reactive power is controlled by d-axis current with appropriate decoupling. The phase angle of utility voltage is detected using software PLL(Phased Locked Loop) in d-q synchronous reference frame. Experimental results from the test of 30kW prototype wind turbine system show that the generator power can be controlled effectively during the variable speed operation without any speed sensor.