Mobile QR Code QR CODE : The Transactions of the Korean Institute of Electrical Engineers

리튬 배터리의 열화를 고려한 태양광 연계 에너지저장장치의 최적 용량 계산을 위한 알고리즘 제안 Algorithm for Optimal Sizing of Energy Storage System Paired with Photovoltaic Generation Considering Lithium-Ion Battery Degradation

신훈영(Hunyoung Shin)

There is growing interest in utilizing energy storage systems (ESS) to create combined "renewable energy plus storage" power plant. Lithium-ion battery based ESS draws much attention due to its high energy density and low self-discharge. Since Lithium-ion batteries are still costly, a power provider should determine ESS capacity in a sophisticate manner to secure profitability. Moreover, as Lithium-ion batteries are subject to degradation, this also needs to be considered in ESS capacity calculation. However, the degradation varies depending on the battery usage patterns and time and thus results in non-convexity in ESS capacity calculation. In this paper, we propose an iterative method to calculate the proper capacity of ESS paired with a PV system by considering battery degradation and profit maximization. ESS capacity calculation according to PV system size and economic evaluation according to REC weight change are conducted based on the case study of South Korea power market.

전류형 HVDC AC 필터 돌입전류 저감을 위한 차단기 투입시점 제어기법 및 투입저항기와 성능 비교 분석 Circuit Breaker Closing Control Technique for Mitigation of LCC HVDC AC Filter Inrush Current and Comparitive Analysis with Pre-Insertion Resistor

이기복(Ki-Bok Lee) ; 김희진(Hee-Jin Kim) ; 나종서(Jong-Seo Na) ; 허견(Kyeon Hur)

This paper presents the method for mitigating inrush current of AC filter circuits in Line Current Commutated (LCC) HVDC converter stations using circuit breaker closing control with comparative analysis data with Pre-Insertion resistor. Due to the capacitive characteristics of AC filter circuits, high inrush current is inevitable when a circuit breaker is closed. This causes mechanical stress to filter components. The inrush current is depending on several factors such as system's Short Circuit Level (SCL), application of Pre-Insertion Resistors (PR), tuning frequencies of an AC filter, circuit breaker close timing with respect to phase to ground voltage, and others. To mitigate it, circuit breaker closing controllers that make the closing of main contact at voltage zero can be used. Simulations on inrush current of AC filter circuits are conducted using PSCAD with considering operational conditions in Korea to verify its usefulness using comparative analysis with PR. The illustrations of switchgear configurations to use closing control effectively considering 154kV system in Korea are proposed.

발전운영 데이터 분석을 통한 육상대비 수상태양광발전시스템의 발전효율계수 도출 The Deduction of Generation Efficiency Coefficient of the Floating PV systems compared to Ground-mounted PV systems based on their operation-data analysis

권오극(Ogeuk Kwon) ; 이수민(Su-Min Lee) ; 권진성(Jinseong Kwon) ; 조현식(Hyunsik Jo) ; 차한주(Hanju Cha)

Photovoltaic(PV) power plants are growing all over the world as a promising renewable alternative to generate electricity. Floating PV(FPV) systems have been researched as a new concept in PV industry to mitigate negative environmental impacts instead of installing conventional PV facilities on land. It is well-known(commonly understood) that the efficiency of FPV is higher than that of ground mounted one due to the water cooling effect. However, there are not many sufficient and numerical supporting data to prove the cooling effect to of (over) FPV. Both two FPV sites in Hapcheon-dam and three ground-mounted PV sites near Hapcheon- dam are selected to compare their efficiency with three methods. The three solar radiation sources are analyzed by statistical methods, one of which is selected to use. The selected radiation is applied to evaluate the efficiency of both FPV and ground PV from 2013 to 2018.

지중송전케이블 종단접속함 실리콘 윤활제 거동 및 변색에 의한 절연파괴 메커니즘 분석 A Study on Breakdown Mechanism by Silicone Lubricant Behavior and Discoloration at Outdoor Termination in Underground Transmission Cables

정채균(Chaekyun Jung) ; 황재상(Jaesang Hwang) ; 강지원(Jiwon Kang) ; 김정태(Jeongtae Kim)

The relationship between the partial discharge and the discoloration of lubricant at the interface of the underground transmission cable outdoor termination analyzed in this paper. The possibility of discoloration of lubricant by partial discharge is firstly verified through simulation test of silicone lubricant discoloration. Then breakdown mechanism is proposed through various analysis such as the viscosity of lubricant, the possibility of partial discharge due to formation of thick circumferential silicone lubricant, and so on.

변압기 프레스보드 Creepage Discharge와 유중가스 및 퓨란 생성물과의 상관성 분석 The analysis for the correlation between the creepage discharge of transformer pressboard and the amount of dissolved gases in the oil and the furanic products

손형욱(Hyeongwook Son) ; 김우빈(Woobin Kim) ; 이동준(Dongzoon Lee) ; 김정태(Jeongtae Kim)

In this study, the analysis for the correlation between the creepage discharge of transformer pressboard and the amount of dissolved gases in the oil and the furanic products has been performed. As a result, it was confirmed that a large and small discharge was concurrently generated until the tracking (carbonization) phenomenon on the pressboard occurred. It is found out that two kinds of process may exist in the correlation between the accumulated partial discharge quantity and the dissolved gas in oil, depending upon discharge pulse magnitude and the generating rate. The 'fast process' in which the average discharge pulse magnitude is large and the generating number per second (rate) is big, whereas 'slow process' is vice versa. According to the process, the dissolved gas in oil became different. In addition, the generation of CO gas was small during the tracking (carbonization) phenomenon of the pressboard, but there was a correlation with accumulated discharge quantity. On the contrary, CO2 gas showed no correlation with accumulated discharge quantity. The correlation between the accumulated discharge quantity and the furanic product was very weak, but it is confirmed that 5M2F which is a result of local overheating showed some correlation.

슬라이딩 모드 기반 관측기와 제어기를 이용한 역진자 시스템의 위치 및 안정화 제어 Position and Stabilization Control of Inverted Pendulum Systems using Sliding Mode based Control and Observer

허준서(Junseo Heo) ; 좌동경(Dongkyoung Chwa)

This paper proposes a position and stabilization control method for the inverted pendulum systems with disturbances such that an unstable equilibrium point is maintained and the position of the actuated body that can move freely is controlled. It is difficult to design the controller due to the dynamic coupling and nonlinear characteristics of the underactuated systems because the degree of freedom of the system is more than the number of the actuators. It is also a difficult problem to compensate for the disturbance. To solve this problem, we introduced an integral sliding mode based observer. Observer can be used to estimate and compensate for disturbance and system model errors, and state variables can also be estimated. Sliding mode controller for position and stabilization control is also proposed. Controller consists of the part that generates a reference value for the pendulum to move the actuated body to the desired position and the part that generates a control input to make the angle of the pendulum track the reference value. The stability of the overall pendulum systems using the proposed control schemes is provided and the feasibility of the proposed control methods is demonstrated through simulation results.

회전익항공기에 장착되는 종속 관성항법장치의 초기정렬기법 Initial Alignment Method of Slave Inertial Navigation System Applying for Rotorcraft

이형섭(Hyung-Sub Lee)

In this paper, we propose an initial alignment method of SINS(slave inertial navigation system) suitable for a rotorcraft using an adaptive notch filter. In the proposed method, adaptive notch filter is applied to eliminate the alignment error caused by the rotor vibration of the aircraft, We verify the performance improvement of the proposed alignment scheme comparing with the conventional transfer alignment method by rotorcraft test. The test result shows that the proposed alignment technique has improved alignment performance.

회전수 측정 센서를 이용한 진동 계측 기법 연구 A Study on Vibration Measurement based on the Rotational Speed Sensor

최은혜(Eun-hye Choi)

When conducting rotary test in wind tunnel, measuring rotational speed and vibration is important to protect the facility and the model. However, it is difficult to install the additional vibration sensor inside the test model since the space is narrow. In order to overcome this problem, this paper proposes noncontact method of vibration measurement without using additional vibration sensors in rotary wind tunnel testing. The proposed method exploits the noncontact rotational speed measurement system and uses the output signal of this system for measuring vibration displacement. The test results confirm that the proposed method can measure the vibration displacement of rotating machine properly.

유압구동장치 서보밸브 옵셋 제거를 위한 유압궤환구조 PI제어기 설계 Design of Hydraulic Feedback Structure PI Controller for Removing Servovalve Offset in Hydraulic Actuation System

구정회(Jeong-Hoi Gu) ; 김인주(In-Ju Kim) ; 최장영(Jang-Young Choi) ; 이상정(Sang-Jeong Lee)

Servovalves have been used to control the position of the hydraulic actuation system for missile. However, the null shift of the servovalve can be vary depending on the supply pressure, vibration, shock and temperature. This problem causes position error in the hydraulic actuation system. Therefore, we designed an algorithm to remove the servovalve offset by adding an integrator to the existing proportional controller. However, the integrator usually has drawbacks such as stability and wind-up problems. To overcome this problem, we propose the design of a hydraulic feedback structure PI controller with a hydraulic pressure detector and an integral limiter that satisfies fault tolerance. Several experiments were performed to verify the proposed method. It is shown that the proposed hydraulic feedback structure PI controller is more stable than the conventional PI controller when the hydraulic pressure is supplied. Compared with conventional proportional controller, the proposed method is very efficient to overcome position error of the hydraulic actuation system caused by the null shift of the servovalve. Moreover, the dynamic response of the proposed method is similar to the existing proportional controller.

MUSIC 알고리즘 기반 LFMCW 기법을 이용한 원자력 케이블 진단 Diagnosis of Nuclear Cable using LFMCW Technique Based on MUSIC Algorithm

정문강(Moon Kang Jung) ; 최윤호(Yoon Ho Choi)

In this paper, we present a fault location method based on reflectometry for the diagnosis of a nuclear cable. The diagnosis system transmits the incident signal to a nuclear cable and measures the reflected signal. In the diagnosis system, a linear frequency modulated continuous wave(LFMCW) is used as the reference signal to eliminate the influences of external noise. To improve the spatial resolution of the reflectometry, we estimate the beat frequency using the multiple signal classification(MUSIC) method, which is known as super resolution method. The proposed method makes it possible to detect the impedance discontinuities in a nuclear cable with high spatial resolution. Finally, experiments are conducted on nuclear cables with the impedance discontinuities to verify the performance of the proposed method.

불확실 일반 선형 시스템의 레규레이션 제어를 위한 사전 제어 성능을 갖는 개선된 연속 변환된 적분 슬라이딩 모드 제어 An Improved Continuous Transformed Integral Sliding Mode Control(ICTISMC) with Prescribed Control Performance for Regulation Controls of Uncertain General Linear Systems

이정훈(Jung-Hoon Lee)

In this paper, an improved continuous transformed integral sliding mode control(ICTISMC) with the prescribed control performance is designed for simple regulation controls of uncertain general linear systems, as an alternative approach of [51] with the same performance. An transformed integral sliding surface with an integral state having a special initial condition is adopted for removing the reaching phase and predetermining the ideal sliding trajectory from a given initial state to the origin in the state space. The ideal sliding dynamics of the transformed integral sliding surface is dynamically obtained and the solution of the ideal sliding dynamics can predetermine the ideal sliding trajectory(transformed integral sliding surface) from the given initial state to the origin. Provided that the value of the transformed integral sliding surface is bounded by certain value by means of the continuous input, the norm of the state error to the ideal sliding trajectory is analyzed and obtained in Theorem 1. A corresponding discontinuous control input with the exponential stability is proposed to generate the perfect sliding mode on the every point of the pre-selected transformed integral sliding surface. The existence condition of the sliding mode together with the closed loop stability is proved in Theorem 2 for the complete formulation. For practical applications, the discontinuity of the VSS control input is approximated to be continuous based on the modified fixed boundary layer method. The bounded stability by the continuous input is investigated in Theorem 3. With combining the results of Theorem 1 and Theorem 3, as the prescribed control performance, the pre specification on the error to the ideal sliding trajectory is possible by means of the fixed boundary layer continuous input with the transformed integral sliding surface. The suggested algorithm with the continuous input can provide the effective method to increase the control accuracy within the boundary layer by means of the increase of the gain. Through an illustrative design example and simulation study, the usefulness of the main results is verified.

모바일 클라이언트 개발 지원을 위한 통신 프레임워크 개선 Improving Communication Framework for Supporting Development of Mobile Clients

임민규(Mingyu Lim)

In this paper, we propose a communication framework (CM) that supports both client and server applications development on desktop and mobile platforms. Previous versions of CM and other related frameworks did not specify the platform on which the application runs, or they limited the platform only to the desktop environment. By extending the existing CM client to the Android application, the proposed CM has been improved to enable developers to use various high-level communication services in a consistent way regardless of the application platform. First, the application can place the CM configuration file in an arbitrary path and edit it through a new application programming interface (API) to solve the management problem of separate files in the Android platform. We also changed CM APIs such that CM internally makes the network-related functions called by a separate thread rather than the main thread that is forbidden from calling the network function in the Android platform.

정지 상태 추정 알고리즘과 간접 칼만 필터를 이용한 AHRS 개발 AHRS Development Using Still-State Estimation and Indirect Kalman Filter

홍효성(Hyosung Hong) ; 원문철(Mooncheol Won)

The AHRS(Attitude and Heading Reference System) estimates the attitude (roll, pitch, and yaw angles) by using sensor fusion technique from an IMU(Inertial Measurement Unit) which comprises 3-axis acceleration and angular velocity information. Compared to maritime vessels or aircraft, the ground vehicle's attitude changes rapidly, which requires an exquisite attitude estimation algorithm. This paper suggests a sensor fusion AHRS algorithm which utilizes still-state estimation algorithm along with indirect Kalman filter for attitude estimation. Also, we applied this algorithm on AHRS hardware to evaluate its performance. We implemented three kinds of experiments to verify the suggested algorithm: lateral acceleration rejection test, 3-axis robot simulator test, and vehicle field test.

AZO 버퍼층을 이용한 ZnO/NiO 이종접합 금속 산화물 투명 광전소자 특성 향상 Functional AZO Layer for Transparent ZnO/NiO Heterojunction Photoelectric Devices

반동균(Dong-Kyun Ban) ; 김은정(Eunjeong Kim) ; 오정현(Junghyun Oh) ; 김준동(Joondong Kim)

All transparent metal oxide photoelectric device was fabricated with structure of Ag nanowire/NiO/ZnO/AZO/FTO by magnetron sputtering system. In order to achieve p/n junction, p-type NiO was deposited onto the n-type ZnO layer. The AZO (Aluminium- doped zinc oxide) was applied as buffer layer for effective transport and collection of the photo-induced electrons. Under light illumination, electrons and holes are generated in the hetero-junction of p-type NiO and n-type ZnO. The AZO layer between ZnO and NiO layers induces the efficient carrier collection from the ZnO side to the negative electrode, due to the similar structure of AZO to ZnO. In addition, the AZO insertion layer is efficient to suppress the loss of hole carriers, resulting in the low leakage current value. The overall transparency of the Ag nanowire/NiO/ZnO/AZO/FTO device is about 70% for visible light range, and thus which can be applied in the invisible transparent electronics, including photodetectors and solar cells.

전력용 콘덴서 설치위치에 따른 분기선로의 전력손실 최소화 방안 Minimization of Power Loss of Branch Line due to a Power Capacitor Installation Location

이재환(Jae-Hwan Lee) ; 김영달(Young-Dal Kim) ; 이대동(Dae-Dong Lee)

To reduce energy consumption, consumers are reducing electricity costs by reducing power loss by power factor improvement by installing a power capacitor. However, since the installation location of the power capacitor is not specified in detail, it is difficult to loss reduction effect of the branch line because the customer is installed in the motor control center due to the maintenance and management convenience. Therefore, the power capacitor should be installed at the end (load terminal) of the line, which can greatly improve the power factor. In this paper, we propose a method to minimize the power loss of the branch line according to the optimum location of the power capacitor after calculating the loss reduction of the branch line through the installation and operation of the power capacitor.

태양광 전력설비의 효율 향상을 위한 피드포워드 차동전력조절기(DPP)의 적용 검증 Application and Verification of Differential Power Processing to Improve the Efficiency for PV Power Facility

김동은(Dong-Eun Kim) ; 박승화(Seung-Hwa Park) ; 손진근(Jin-Geun Shon)

Differential power processing (DPP) is a power facility architecture that configures dc-dc converters in parallel with the PV string to improve its power yield. The parallel nature of the DPP architecture brings a number of benefits, such as low converter power rating and low power losses. In this paper, feedfoward DPP structure is applied to improve the efficiency of photovoltaic(PV) power facility. DPP structure is considered to a solution to problems were caused by solar irradiance mismatch. The effectiveness of DPP struture is confirmed by comparing module integrated converter (MIC) structure. Experiments and simulation with feedfoward structure using a DSP(TMS320F28335) hardware design were conducted and the improvement in performance with DPP converters was experimentally confirmed.