마이크로그리드에서 하이브리드 시스템의 Feeder Flow Mode 운영을 위한 제어 알고리즘

문대성(Dae-Seong Moon),서재진(Jae-Jin Seo),김윤성(Yun-Seong Kim),원동준(Dong-Jun Won) 대한전기학회 2011 전기학회논문지 Vol.60 No.1

Active power control scheme for distributed generation in microgrid consists of feeder flow control and unit power control. Feeder flow control is more useful than the unit power control for demand-side management, because microgrid can be treated as a dispatchable load at the point of common coupling(PCC). This paper presents detailed descriptions of the feeder flow control scheme for the hybrid system in microgrid. It is divided into three parts, namely, the setting of feeder flow reference range for stable hybrid system operation, feeder flow control algorithm depending on load change in microgrid and hysteresis control. Simulation results using the PSCAD/EMTDC are presented to validate the inverter control method for a feeder flow control mode. As a result, the feeder flow control algorithm for the hybrid system in microgrid is efficient for supplying continuously active power to customers without interruption.

능동 파괴 방호 구동제어기의 열 유동 해석

유봉조(Bong-Jo Ryu),오부진(Bu-Jin Oh),김영식(Youngshik Kim) 한국산학기술학회 2017 한국산학기술학회논문지 Vol.18 No.2

능동 파괴 방호 구동제어기는 기계, 항공 및 군사 분야 등에서 사용될 수 있는 제어기로서, 상대의 비행물체를 능동제어를 통해 추적 타격하는데 사용된다. 구동제어기를 이용하여 목표지점까지의 정밀도를 갖고 동작이 유지되어야 하기 때문에, 이에 대한 신뢰성 확보가 대단히 중요하다. 이러한 구동제어기가 사용되는 주위 환경의 온도는 약 -32℃∼50℃(241 °K∼358 °K)이다. 신뢰성을 갖기 위해 구동제어기에서 중요시 간주되는 문제 중의 하나는 구동제어기 내의 열 발생이 어느 한계수준(85℃ (358 °K )이하로 유지되어야 정밀도와 신뢰성을 확보할 수 있다는 점이다. 따라서 구동제어기 내의 열 유동특성에 대한 연구와 분석이 필요하게 된다. 본 논문의 수치시뮬레이션을 위해 저 레이놀드 수 κ-ϵ 난류모델과 비압축성 점성유동을 가정하였고, 상용 소프트웨어인 Solid-Works Flow Simulation을 사용하였다. 본 논문의 목적은 각종 칩이나 보드 등을 갖는 구동제어기 내부의 열 유동 특성을 해석하여 구동제어기의 안전한 설계를 하는데 있다. 해석으로부터, 보드들과 칩들의 온도분포가 어떤 한계 수준 이내에 있음을 보여준다. A driving controller for active destruction protections can be applied to machinery, aerospace and military fields. In particular, this controller can be used to track and attack enemy flying objects through the active control. It is important to ensure reliability of the driving controller since its operation should be kept with precision to the target point. The temperature of the environment where the driving controller is used is about -32 C ~ 50 C (241~323 ). Heat generated in the driving controller should be maintained below a certain threshold (85 C (358 )) to ensure reliability; therefore, the study and analysis of the heat flow characteristics in the driving controller are required. In this research, commercial software Solid-Works Flow Simulation was used for the numerical simulation assuming a low Reynolds number turbulence model and an incompressible viscous flow. The goal of this paper is to design the driving controller safely by analyzing the characteristics of the heat flow inside of the controller composed of chips or boards. Our analysis shows temperature distributions for boards and chips below a certain threshold.

Synthetic Jet을 이용한 실속 박리의 폐루프 제어

이병현,김민희,최병훈,김현진,김종암 한국항공우주학회 2013 한국항공우주학회 학술발표회 논문집 Vol.2013 No.11

앞전 실속 상태의 NACA 64A210 에어포일에 대한 synthetic jet의 유동 제어 능력을 검증하기 위해 단계적인 실험 및 전산수치해석을 수행했다. 첫 번째 단계에서는 synthetic jet-off 조건에서 NACA 64A210 에어포일의 기본 공력 특성을 분석했고, 이를 바탕으로 유동 박리를 감지하는 파라미터를 도출했다. 그 다음 단계에서는 실속 받음각 조건에서 open-loop control 실험을 수행했고, 전산수치해석에 의한 유동 구조와 비교하여 synthetic jet 작동 조건 변화에 따른 유동 특성을 분석했다. 마지막 단계에서는 받음각 변화에 따른 유동 박리를 감지하여 closed-loop control로 구동되는 synthetic jet 시스템을 구성하여 실험을 수행했다. 다양한 실험 및 수치 해석 분석 결과, 에어포일의 앞전 실속을 제어하기 위한 synthetic jet 유동 제어 성능이 효과적임을 확인할 수 있었다. Step-by-step experimental and computational studies were conducted to verify the flow control capability of synthetic jet on a stalled NACA 64A210 airfoil. First, experimental and numerical data were examined by analyzing the baseline characteristics of NACA 64A210 when synthetic jet was off. Next, open-loop control experiments were carried out to demonstrate the flow separation control in the post-stall regime. Experimental results were analyzed with the help of the computed flow structures. Finally, closed-loop control experiments were conducted by detecting the onset of flow separation. Based on various comparisons, active flow control using synthetic jet was found to be effective for the leading-edge stalled airfoil.

Active Control of the Vortex Induced Pressure Fluctuations in a Hydro Turbine Model via Axial and Radial Jets at the Crown Tip

Ivan Litvinov,Daniil Suslov,Mikhail Tsoy,Evgeny Gorelikov,Sergey Shtork,Sergey Alekseenko,Kilian Oberleithner 한국유체기계학회 2023 International journal of fluid machinery and syste Vol.16 No.4

This paper presents an active method to control the pressure fluctuations induced by the rotating vortex rope (RVR) in a Francis hydro turbine model under part load conditions. The control method is based on the injection of axial or radial jets through a stagnant crown attached to the hydro turbine runner. A wide range of injection strategies are com-pared, and the effectiveness of suppressing pressure fluctuations is analyzed in terms of the spatial distribution of the jets and the flow rate required to suppress the oscillations. The experiments are performed on a fully automated aerody-namic test rig. The pressure fluctuations are quantified using data from the four acoustic sensors placed at a cross sec-tion in the cone of the hydro turbine draft tube. The best suppression of pressure fluctuations is achieved with a radial actuator. At a control flow rate of 2% of the main flow, the pressure fluctuations at the vortex rope frequency are re-duced by 80% in terms of PSD compared to the baseline case without control. The presented control method will be useful for extending the operating range of Francis hydro turbines.

A computational approach to the simulation of controlled flows by synthetic jets actuators

Ferlauto, Michele,Marsilio, Roberto Techno-Press 2015 Advances in aircraft and spacecraft science Vol.2 No.1

The paper focuses on the integration of a non-linear one-dimensional model of Synthetic Jet (SJ) actuator in a well-assessed numerical simulation method for turbulent compressible flows. The computational approach is intended to the implementation of a numerical tool suited for flow control simulations with affordable CPU resources. A strong compromise is sought between the use of boundary conditions or zero-dimensional models and the full simulation of the actuator cavity, in view of long-term simulation with multiple synthetic jet actuators. The model is integrated in a multi-domain numerical procedure where the controlled flow field is simulated by a standard CFD method for compressible RANS equations, while flow inside the actuator is reduced to a one-dimensional duct flow with a moving piston. The non-linear matching between the two systems, which ensures conservation of the mass, momentum and energy is explained. The numerical method is successfully tested against three typical test cases: the jet in quiescent air, the SJ in cross flow and the flow control on the NACA0015 airfoil.

Effects of Frequency and Amplitude of Local Dynamic Hump and Inlet Turbulence Intensity on Flow Separation Control in Low-Pressure Turbine

Rongfei Yang,Hao Wang,Dongdong Zhong,Ning Ge 한국항공우주학회 2023 International Journal of Aeronautical and Space Sc Vol.24 No.3

Dynamic hump is an active control method, which has been proved to be able to suppress laminar flow separation on the suction surface of high-loaded low-pressure turbine (LPT) blades at low Reynolds number (Re). This paper further discusses the effectiveness of dynamic hump with different parameters for flow separation control. The Pak-B cascade working at Re = 25,000 was selected as the research object, and a small-sized two-dimensional dynamic hump designed in a half-sinusoidal configuration was placed just upstream of the peak velocity point on the suction surface. At inlet free-stream turbulence intensity (FSTI or Tu) of 1.5%, the controlled cascade loss and flow mechanism under different hump-oscillating frequency and amplitude was numerically analyzed in detail. The results show that the development characteristics of vortices/separation bubbles attached to the suction surface of the blade were significantly changed under the influence of the dynamic hump, which contributed to the variations of cascade loss accordingly. When the separation bubble at the trailing edge of the hump was forced to form shedding vortices, the large-sized separation bubble on suction surface of uncontrolled cascade was replaced by small-sized vortices with a certain spacing, thus inhibited the flow separation. The increase in amplitude and frequency of hump promote the formation of shedding vortices at the trailing edge of the hump. The optimal amplitude should be slightly less than the local boundary layer thickness at the position of hump on the uncontrolled cascade. Under the optimal hump amplitude, the effective hump-oscillating frequency is 50–250 Hz, which is approximately 0.5–2.7 times of the characteristic frequency defined by blade exit velocity and the distance between the hump trailing edge and the blade trailing edge. When inlet FSTI of the controlled cascade is reduced from 1.5 to 0.08%, the profile loss is approximately unchanged due to the same characteristics of the boundary layer in the hump region and upstream.

교통조건에 따른 간선도로변 도로교통소음 특성에 관한 실험적 연구

조창근(Chang-Geun Cho) 한국생활환경학회 2010 한국생활환경학회지 Vol.17 No.5

Noise barrier has the limitation of reducing the road traffic noise in low frequency bands because of its diffraction phenomenon. In order to maximize the noise reduction performance of noise barrier, it is necessary that diffracted noise in low frequency bands should be effectively reduced. The purpose of this study is to investigate the characteristic of traffic noise in main roads and frequency characteristic of it for designing noise barrier by active noise control. Field measurement of road traffic noise at 1~5 m high from the ground on the 6 roads was carried out, and the variation characteristic by traffic flow condition was analyzed in this study. As a result, the road traffic noise showed high in mid and high frequency bands and the highest in 1 ㎑. Especially, the noise showed very high levels in 1 ㎑ in case of high speed of vehicles. Dominant frequency of the noise was appeared in low frequency bands under 100 ㎐, especially in 50~87.5 ㎐. It is thought that low frequency badns under 100 ㎐ should be considered to make noise source for active noise control. It is necessary that passive noise control should be applied for reducing the noise in mid and high frequency bands of 1 ㎑ in designing noise barrier. In addition, active noise control technique should be applied for decreasing the noise in low frequency bands under 100 ㎐ in order to maximize the noise reduction performance of noise barrier.

Synthetic Jet을 이용한 능동유동제어 실험

이준희(Junhee Lee),김종암(Chongam Kim) 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.12

본 논문은 능동유동제어 장치의 하나인 synthetic jet을 이용한 유동박리 제어를 다루고 있다. 먼저 synthetic jet의 원형출구 지름과 간격을 조절하여 유동제어에 효과적인 jet 출구형상을 찾았다. 두 번째로 설계된 구동기를 2차원 airfoil에 적용하여 양항비 향상에 효과적인 작동주파수와 작동조건에 대해 조사하였다. 마지막으로 복잡한 유동조건을 가진 blended wing body 형상의 3차원 날개에 적용하여 힘과 모멘트 변화를 분석하였다. 그 결과 synthetic jet은 다양한 유동조건에서 유동박리제어에 효과적임을 확인할 수 있었다. This paper deals with experimental study of active flow control via synthetic jet for separated flow. First, we designed jet exit configuration to improve flow control performance by adjusting some key parameters, such as a hole diameter and hole gap. Second, the designed actuator was applied to an airfoil to find optimal operating frequencies and conditions for increasing the lift/drag ratio. finally, the synthetic jet was applied to the blended wing body configuration having a complex flow structure to investigate forces and moments acting on the wing. As a result, we found that the synthetic jet can be effective to the separation control under various flow conditions.

3차원 고속철도 모델의 DBD 플라즈마 유동제어를 위한 예비 풍동시험

윤수환,김태규 한국항공우주학회 2012 한국항공우주학회 학술발표회 논문집 Vol.2012 No.11

플라즈마 유동제어를 통한 공기저항저감을 위해 DBD (Dielectric barrier discharge) 플라즈마 액츄에이터를 이용하여 3차원 고속철도 모델의 풍동시험을 수행하였고 항력 저감을 검증하였다. 유동박리제어를 위해 시험모델의 전두부에 3개의 DBD 액츄에어티를 순차적으로 부착하였다. 각각의 단일 DBD 액츄에이터를 구동하여 풍동시험을 수행하였고, 유동 박리 제어 효과를 증가시키기 위해 2개의 DBD 액츄에이터를 조합하여 풍동시험을 수행하였다. 효과적으로 유동 박리를 제어하기 위해서는 DBD 액츄에이터의 위치가 중요함을 알 수 있었고, 단일 DBD 액츄에이터를 사용하는 것보다 DBD 액츄에이터를 조합하여 순차적으로 사용하는 것이 유동 박리 제어 효과가 증가함을 알 수 있었다. DBD (Dielectric barrier discharge) plasma actuator was used to reduce aerodynamic drag through plasma flow control, and the drag reduction was verified by wind-tunnel tests of three-dimensional train model. Three DBD actuators were installed on the front head of the test model for flow separation control. The individual DBD actuator was operated during wind-tunnel tests, and two DBD actuators were operated simultaneously in order to improve the effect of flow separation control. The location of DBD actuator was important to control successfully the flow separation. In addition, the flow separation control was more improved using the several DBD actuators simultaneously compared to using the single DBD actuator individually.

NACA0015 익형의 압력항력 감소를 위한 인공신경망 기반의 피드백 유동 제어

백지혜(Ji-Hye Baek),박수형(Soo-Hyung Park) 한국항공우주학회 2021 韓國航空宇宙學會誌 Vol.49 No.9

본 연구에서는 실속 받음각 근처에 발생하는 익형 위의 유동박리를 억제하기 위하여 인공신경망 기반의 피드백 유동제어를 NACA0015 익형에 수치적으로 적용하였다. 익형 위 박리영역 크기의 축소화라는 제어 목표를 달성하기 위해 익형의 박리 지점 근처에 인위적 외란(Blowing & Suction)제어 신호를 적용하였다. 유동의 운동을 나타내는 시스템 모델링 단계에서 압력데이터에 적합직교분해(Proper Orthogonal Decomposition)를 적용하여 유동제어에 필요한 운동 모드를 추출하고 유동의 특성을 분석하였다. 분해된 모드를 기반으로 NARX(Nonlinear AutoRegressive Exogenous) 구조의 인공 신경망을 학습하여 유동의 운동을 나타내도록 하였으며, 최종적으로 피드백 제어루프에 작동시켰다. 예측된 제어신호를 CFD 해석에 적용하였으며 제어 유/무에 따른 공력특성을 분석하고 익형 주변의 고유 공간모드의 변화를 비교하여 제어 효과를 분석하였다. 본 연구에서 진행된 피드백 제어는 약 29%의 압력항력 감소효과를 보여주었으며, 이는 익형 뒷전의 큰 압력회복으로 인해 나타나는 것을 확인하였다. Feedback flow control using an artificial neural network was numerically investigated for NACA0015 Airfoil to suppress flow separation on an airfoil. In order to achieve goal of flow control which is aimed to reduce the size of separation on the airfoil, Blowing&Suction actuator was implemented near the separation point. In the system modeling step, the proper orthogonal decomposition was applied to the pressure field. Then, some POD modes that are necessary for flow control are extracted to analyze the unsteady characteristics. NARX neural network based on decomposed modes are trained to represent the flow dynamics and finally operated in the feedback control loop. Predicted control signal was numerically applied on CFD simulation so that control effect was analyzed through comparing the characteristic of aerodynamic force and spatial modes depending on the presence of the control. The feedback control showed effectiveness in pressure drag reduction up to 29%. Numerical results confirm that the effect is due to dramatic pressure recovery around the trailing edge of the airfoil.