Insu Paek

Kangwon National University · Department of Mechanical and Mechatronics Engineering

To compare and validate wind speed estimation algorithms applied to wind turbines, wind speed estimators were designed in this study, based on two methods presented in the literature, and their performance was validated using the NREL 5MW model. The first method for wind speed estimation involves a three-dimensional (3D) look-up table-based approac...

In this study, an H∞-fuzzy controller is proposed for application in wind turbines with uncertainties and nonlinearities. The performance of the proposed controller was validated via dynamic simulations using a commercial aero-elastic code and wind tunnel experiments employing a scaled wind turbine. The simulation and the experimental results were...

In this study, a power control algorithm of a variable-speed fixed-pitch horizontal-axis lift-type 20 kW small wind turbine (SWT) was proposed and verified through dynamic simulations. The power control algorithm proposed in this study consists of algorithms for Region II to track the maximum power coefficient, for Region II-1/2 to maintain the rat...

In this study, a power compensation control algorithm was designed and validated for commercial 100 kW medium wind turbine models for power compensation due to additional generator loss. Generally, torque control considering generator efficiency is applied to a controller of a medium wind turbine; however, a control corresponding to a decrease in g...

In this study, a pitch H-infinity control algorithm was developed for variable-speed–variable-pitch (VSVP) wind turbines to improve the rotor standard deviation of the wind turbines under normal and extreme wind conditions. The pitch H-infinity control algorithm only uses H-infinity control in the blade pitch control loop in the rated power region,...

In this study, a reference bias control (RBC) algorithm for variable speed and variable pitch wind turbines was designed and validated. To improve the performance of conventional PI control algorithms, the RBC algorithm applies biased references to power and pitch angle to the pitch and the torque control loops, respectively. To validate the contro...

Three different algorithms that can be used to estimate the available power of a wind turbine are investigated and validated in this study. The first method is the simplest and using the power curve with the measured nacelle wind speed. The other two are to estimate the equivalent wind speed first without using the measured Nacelle wind speed and t...

In this study, a demanded power point tracking (DPPT) control algorithm was designed for the application of multiple-input multiple-output (MIMO) modern control algorithms. The proposed DPPT control algorithm has been newly implemented as a multiple reference trajectory method for applying an MIMO control algorithm without mode switches. Dynamic si...

In this study, both mechanical power and the wind speed distribution in the wake of a wind turbine scaled model were analyzed using a commercial CFD program (Ansys CFX) along with experimental validation. For the simulation, two different turbulence models including the SST model and the k- model were used. The scaled model was originally designed...

In this study, the power performance of an H-Darrieus vertical-axis lift-type wind turbine is investigated. Computational fluid dynamics and double-multiple stream tube simulations are used to predict the power coefficient (aerodynamic efficiency) of the rotor. Additionally, the efficiency of the electrical systems, including the generator and the...

In this study, a linear quadratic regulator based on the fuzzy logic (LQRF) control algorithm for a variable-speed variable-pitch wind turbine was designed. In addition, to verify the optimum performance of the controller, simulations and wind tunnel tests were conducted. In the simulation, the performances of the proportional-integral (PI) and LQR...

In this study, the performance of an Archimedes spiral wind turbine is analyzed by simulation and validated by a field test. It is characterized as a horizontal-axis drag-type wind turbine. This type of wind turbine cannot be analyzed by the well-known Blade Element Momentum(BEM) theory or Double Stream Tube Method(DSTM) commonly used to analyze th...

In this study, a peak shaving algorithm known as a control method to reduce peak mechanical loads in multi-megawatt wind turbines was designed and implemented to a medium capacity 100 kW wind turbine to solve overspeeding shutdown problem due to low moment of inertia of the rotor. The algorithm consists of a look-up table having an input of measure...

This study was conducted to analyze the impact of surrounding environmental changes on the feedback gain and performance of a closed-loop wind farm controller that reduces the error between total power output of wind farm and power command of transmission system operator. To analyze the impact of environment changes on wind farm controller feedback...

In this study, an off-grid–type small wind turbine for street lighting was designed and analyzed. Its performance was predicted using a computational fluid dynamics model. The proposed wind turbine has two blades with a radius of 0.29 m and a height of 1.30 m. Ansys Fluent, a commercial computational fluid dynamics solver, was used to predict the p...

In this paper, the previously proposed demanded power point tracking (DPPT) control is applied to a medium-capacity wind turbine. Based on the results of our previous studies, the control algorithm has modified to be advantageous for wind farm control and load reduction of individual wind turbines. The target turbine is a medium-capacity turbine wi...

This paper presents a modified version of the Ainslie eddy viscosity wake model and its accuracy by comparing it with selected exiting wake models and wind tunnel test results. The wind tunnel test was performed using a 1.9 m rotor diameter wind turbine model operating at a tip speed ratio similar to that of modern megawatt wind turbines. The contr...

Simple demanded power point tracking (DPPT) control algorithms with a mode switch are proposed and experimentally validated in this study. One is a torque-based control and uses the generator torque with fixed blade-pitch angle. The other is blade-pitch based and uses both the generator torque and blade pitch for DPPT control. Both control algorith...

Dynamic wind farm simulation tool developed from the previous study is used to study the annual power increase of the active induction wind farm control at an offshore site in Korea. The turbulent wind is generated from the veers model and the measured averaged wind data for 16 wind directions and used to estimate the power output of a virtual wind...

In renewable power systems for remote islands, a significant amount of electricity is curtailed for power balance. This study examines the effect of reducing electricity curtailment on optimal renewable power system design for remote islands. A Mixed-Integer Linear Programming problem for obtaining the optimal design of remote renewable power syste...

A new wind farm control algorithm that adjusts the power output of the most upstream wind turbine in a wind farm for power increase and load reduction was developed in this study. The algorithm finds power commands to individual wind turbines to maximize the total power output from the wind farm when the power command from the transmission system o...

A control algorithm for a 100 kW wind turbine is designed in this study. The wind turbine is operating as a variable speed variable pitch (VSVP) status. Also, this wind turbine is a permanent magnet synchronous generator (PMSG) Type. For the medium capacity wind turbine considered in this study, it was found that the optimum tip speed ratios to ach...

A control algorithm for a floating wind turbine installed on a large semi-submersible platform is investigated in this study. The floating wind turbine is different from other typical semi-submersible floating wind turbines in that the platform is so large that the platform motion is not affected by the blade pitch control. For simulation, the hydr...

In this study, the effect of active induction control of upstream wind turbines is investigated. Two scaled wind turbines having a rotor diameter of 1 m with a spacing of four times of the rotor diameter were used to experimentally validate the concept. Also, an in-house c code was used to simulate the same two wind turbines and see if the experime...

Commercial wind farm design tools and the national wind map are used to determine the implementation potential of offshore wind power in Korea in this study. For this, the territorial waters of Korea were divided into nine analysis regions and a commercial CFD code was used to obtain wind resource maps at 100m A.S.L. which is the hub height of a 5M...

Large-scale offshore floating wind turbines represent one of the most significant engineering challenges in wind energy at present. Since current fixed-bottom technology can support deployment up to water depths of about 30 m (shallow waters), the technology is now moving towards deeper waters, where the wind resource is extremely abundant. In this...

A strategy to increase the power output from a wind farm by regulating the most upstream wind turbine to a lower power than its available power is investigated in this study. A similar concept but using a fixed pitch angle of the most upstream wind turbine available in the literature was extended to use power demands from a wind farm controller, an...

A new control algorithm for a MW class spar-type floating offshore wind turbine has been developed to improve its performance and to reduce its mechanical load. The new blade pitch control having two PI control loops applied for different wind speed regions were designed. The bandwidth of the controller at near above-rated wind speed region was mad...

A time-domain simulation tool to predict the dynamic power output of wind turbines in an offshore wind farm was developed in this study. A wind turbine model consisting of first or second order transfer functions of various wind turbine elements was combined with the Ainslie’s eddy viscosity wake model to construct the simulation tool. The wind tur...

The MERRA reanalysis data provided online by NASA was applied to predict the monthly energy productions of Donghai Bridge Offshore wind farms in China. WindPRO and WindSim that are commercial software for wind farm design and energy prediction were used. For topography and roughness map, the contour line data from SRTM combined with roughness infor...

A feasibility study to estimate annual energy production of an offshore wind farm was performed using MERRA reanalysis data. Two well known commercial codes commonly used to wind farm design and power prediction were used. Three years of MERRA data were used to predict annual energy predictions of the offshore wind farm close to Copenhagen from 201...

romising onshore wind farm sites in Gangwon province of Korea were investigated in this study. Gangwon province was divided into twenty five simulation regions and a commercial program based on Reynolds averaged Navier-Stokes equation was used to find out wind resource maps of the regions. The national wind atlas with a period 2007-2009 developed b...

A numerical simulation on the wake flow of a wind turbine which is a scaled version of a multi-megawatt wind turbine has been performed. Two different inlet conditions of averaged wind speed including one below and one above the rated wind speed were used in the simulation. Steady-state pitch angles of the blade associated with the two averaged win...

A new wind turbine simulation tool for a time-domain dynamic simulation was developed in this study. The tool consists of models of aerodynamics, drive train, generator, actuators, and controllers for pitch and yaw controls. For the wind turbine model, the NREL 5MW reference wind turbine was used. Using measured data, the developed tool was applied...

The MERRA reanalysis data provided online by NASA was applied to predict the annual energy productions of two largest wind farms in Korea. The two wind farms, Gangwon wind farm and Yeongyang wind farm, are located on complex terrain. For the prediction, a commercial CFD program, WindSim, was used. The annual energy productions of the two wind farms...

The effect of wake on the performance and load of a downstream wind turbine on a floating platform is investigated with a computer simulation in this study. The floating platform consists of a square platform having a dimension of 200m{\times}200m with four 2 MW wind turbines installed. For the simulation, only two wind turbines in series with the...

A study on the available power of a wind turbine to be used for wind farm control was performed in this study, To accurately estimate the available power it is important to obtain a suitable wind which represents the three dimensional wind that the wind turbine rotor faces and also used to calculate the power. For this, two different models, the eq...

This study considers the prediction of natural frequency to avoid resonance in a wind turbine tower-cable coupled system. An analytical model based on the Rayleigh-Ritz method is proposed to predict the resonance frequency of a wind turbine tower structure supported by four guy cables. To verify the validity of the analytical model, a small tower-c...

An aerodynamic design tool was developed for small wind turbine blades based on the blade element momentum theory. The lift and drag coefficients of blades that are needed for aerodynamic blade design were obtained in real time from the Xfoil program developed at University of Illinois. While running, the developed tool automatically accesses the X...

Effects of Weibull shape parameter, k, on capacity factors of wind turbines were investigated. Wind distributions with mean wind speeds of 5 m/s, 6 m/s, 7 m/s and 8 m/s were simulated and used to estimate the annual energy productions and capacity factors of a 2MW wind turbine for various Weibull shape parameters. It was found from the study that t...

A Fiber Bragg Grating (FBG) sensor imbedded small wind turbine blade was manufactured to experimentally investigate the feasibility to embed FBG sensors between layers of glass fiber to monitor dynamic strains of the wind turbine blade. The blade which is similar to a commercial 300 W wind turbine blade was manufactured with glass fiber as a reinfo...

A new method to estimate bending moments of a blade specimen having a constant cross section throughout was developed using fiber Bragg grating sensors. Based on theories of solid mechanics, strains of the simplified model of the specimen were evaluated for various pitching angles and the forces exerted. It was found by both theory and experiment t...

In this study, we found a relationship between wind shear exponent, , and a few factors such as the wind speed, , ruggedness index(), and the Weibull shape parameter, of sites in complex terrain in Korea. Wind shear exponents in main wind directions were calculated using wind speed data measured for one year from various heights of eleven meteorolo...

Predictions of wind speed for six different near-shore sites were made using the NCAR (National Center for Atmospheric Research) wind data. The distances between the NCAR sites and prediction sites were varied between 40km and 150km. A well-known wind energy prediction program, WindPRO, was used. The prediction results were compared with the measur...

Investigations on modeling methods of a CFD wind resource prediction program, WindSim for a ccurate predictions of wind speeds were performed with the field measurements. Meteorological Masts having heights of 40m and 50m were installed at two different sites in complex terrain. The wind speeds and direction were monitored from sensors installed on...

Selecting optimal wind turbine generators for wind farm sites in the capacity factor point of view is performed in this study. A program to determine the best wind turbine generator for the maximum capacity factor for a site was developed. The program uses both the wind characteristics of the site of interest and the power curves of the wind turbin...

In this study, we performed a sensitivity analysis to see how the true north error of a wind direction vane installed to a meteorological mast affects predictions of the annual-average wind speed and the annual energy production. For this study, two meteorological masts were installed with a distance of about 4km on the ridge in complex terrain and...

The dynamic behavior of a small wind-turbine blade was analyzed experimentally. Arrays of fiber Bragg-Grating (FBG) sensors attached along the blade were used to measure the strains of the blade surface. An impact test was performed to estimate the resonance frequencies of the fundamental and higher modes of the cantilever blade system developed fo...

The wind data obtained from an AWS(Automated Weather Station) was used to predict the AEP(annual energy production) of Gangwon wind farm having a total capacity of 98 MWin Korea. A wind energy prediction program based on the Reynolds averaged Navier-Stokes equation was used. Predictions were made for three consecutive years starting from 2007 and t...

The dynamic response of a multi-MW wind turbine to a sudden change in wind speed is usually slow, because of the slow pitch control system. This could cause a large excursion of the rotor speed and an output power over the rated. A feedforward pitch control can be applied to minimize the fluctuations of these parameters. This paper introduces the c...

The wind data measured from automated weather stations (AWS) at complex terrain in Korea was used to predict the wind speed at nearby sites that are several kilometers away. The 10-minute averaged wind data was measured at a height of 10 meters. A commercial CFD code, WindSIM, based on the Reynolds averaged Navier-Stokes equation was employed. The...

The performance of a working prototype, operated with and without water flow through the heat exchangers, was measured and found to be in reasonably close agreement to predictions from a simulation code, DELTAE, based on linear thermoacoustic theory. Further analysis and DELTAE simulations showed that the coefficient of performance may be significa...

This paper proposes an emergency locking unit (ELU) for a seat belt retractor which is mounted on the back frame of a vehicle seat. The proposed unit uses a recliner sensor based on a MEMS acceleration sensor and solenoid mechanism. The seat has an upper frame supported to tilt on a lower frame. The retractor in belt in seat (BIS) system is support...

Dynamic behavior of a small wind turbine blade has been analyzed experimentally. Arrays of Fiber Bragg Grating (FBG) sensors and strain gauges were used to extract mode shapes of a small wind turbine blade made of fiber reinforced plastic (FRP). The root of the blade was fixed by a cantilever system developed for this study and dynamic strains from...

Investigations on the relations between the phase angle of the acoustic impedance at the driver piston and the system performance of a standing wave thermoacoustic cooler were performed. The system performance measured at a fixed acoustic power showed that the coefficient of performance of the standing wave thermoacoustic cooler increases as the ph...

The most promising applications for standing-wave thermoacoustic cooling were investigated from the perspective of the ratio of coefficient of performance (COP) to the reversible COP or COPR. A design optimization program based on the thermoacoustic simulation program known as DELTAE was developed. The program was applied to two standing-wave therm...

Hot wire anemometry was used to measurevelocity and temperature fluctuations inside a thermoacousticrefrigerator. In an oscillating flow with zero‐mean velocity, such as in an acoustic standing wave,heat transfer is different from heat transfer in a steady flow. A dynamic calibration of the system is required. This calibration was done inside the r...

The thermal performance of heat exchangers within a thermoacoustic cooler was investigated. Experimental procedures and calculation methods to evaluate the oscillating flow heat transfer coefficients were developed. Dimensionless heat transfer coefficients, or Colburn-j factors, were estimated based on the oscillating-flow variables and compared wi...

Thermoacoustic cooler prototypes developed so far can be divided into three categories based on their cold-side operating temperatures: cryogenic, refrigeration, and the third is the air-conditioning. For most prototypes developed so far, the coefficient of performance (COP), defined as the cooling power divided by the acoustic power, was well abov...

The electroacoustic efficiency of high-power actuators used in thermoacoustic coolers may be estimated using a linear model involving a combination of six parameters. A method to identify these equivalent driver parameters from measured total electrical impedance and velocity-voltage transfer function data was developed. A commercially available, m...

A standing wave thermoacoustic cooler is composed of three critical components: (1) the electroacoustic driver; (2) the heat exchangers; and (3) the stack. Accurate models of the behavior of these components are necessary to characterize the performance of thermoacoustic coolers, and to improve design. The electroacoustic driver performance was cha...

The efficiency of transducers used in electromechanically driven standing wave thermoacoustic coolers is governed by six parameters. The maximum efficiency is obtained around the frequency at which the total electrical input reactance is zero. The parameters in a linear circuit representation of the dynamic behavior of the driver are often frequenc...

Standing wave thermoacoustic coolers require heat exchangers to move heat in and out of the working gas. Within most finned-tube type heat exchangers, heat is transferred from the oscillating gas to a liquid flowing through the tubes. Experiments were performed to evaluate the thermal performance of heat exchangers immersed in a standing wave therm...