인공 신경망 예측기를 이용한 새로운 데이터 모델 기반 PV 어레이 고장 진단용 기준 신호 발생 방법

김홍성,김유하,최해용,이승요 대한전기학회 2023 전기학회논문지 Vol.72 No.5

The power supply part of a PV system is called a PV array which is composed of many PV strings connected in parallel. A PV-string which is a set of PV-Modules is made by serial connection of many PV modules. PV modules presents irregularity of ouput power which is generated due to various factors such as average performance degradation of about 0.923% to 1.54% according to various researches and born power variations over production stages. Power degradation and born power variation are due to various factors such as material interactions(connection state of connectors between PV cells, corrosion, browning of encapsulation materials ...etc) and environment factors such as shading and soiling which refers to the accumulation of snow, dirt, leaves and bird droppings on PV modules. Such various minor factors can make side effects in safety side and economic one. Therefore several methodology for diagnosis of PV-array have been developed, which are classified into three types – image-based diagnosis approach, model-based approach and data-driven approach. In this paper, a new data-based approach(called data model) with good failure diagnosis reliability and economy is proposed, and verified by simulation using Python, published data and reasonable data generation. Based on the bathtub failure rate function, the fault diagnosis model requires a well-functioning predictor to generate a reference signal which evaluates the output characteristics of PV array under instantaneously varying environmental condition such as solar irradiance, temperature, etc. To implement a new data-based approach, an Artificial Neural Network (ANN) based predictor is applied as a reference generator for PV array’s fault diagnosis.  value and the RMSE(Root Mean Square Error) are used to evaluate how far away individual learned predictions are from the actual measured values. Based on the reliability obtained from the learning result for a specific PV string, it is confirmed through pair comparison analysis(called t-test) that the learning result(called clustering possibility) between PV strings under different installation conditions is also reliable.

지붕일체형 PV모듈의 온도에 따른 발전성능 분석

김현일(Kim Hyun-Il),서승직(Suh Seung-Jik),강기환(Kang Gi-Hwan),유권종(Yu Gwon-Jong),박경은(Park Kyung-Eun),노지희(Noh Ji-Hee) 한국건축친환경설비학회 2007 한국건축친환경설비학회 학술발표대회 논문집 Vol.- No.-

It is well-known that most of the solar radiation absorbed by photovoltaic (PV) module is not converted to electricity but contributes to increase the temperature of the module, thus reducing the electrical efficiency. It is also important to consider building integrated Photovoltaic (BIPV) as an integral part of the environmental systems of a building if the application of BIPV is to be successful, because just applying PV onto already designed building envelope, and treating the PV system as an element as if independent from the building, will not enable optimum performance. In this paper, roof integrated PV modules are studied. : Indoor experiment and outdoor exposure experiment. Difference of temperature between the front and back of PV module is about 13.4~22.3℃. If each layer of PV module measures temperature, we will know about heat transfer of PV cell and change of thermal environment of indoors in detail. Therefore this paper presents the comparison of electrical, architectural and thermal performance of roof integrated photovoltaic(PV) modules, which is composed of different hybrid structure layer such as insulation.

다세대주택 옥상 PV 연계 가정용 BESS의 에너지 절감 효과 분석

엄지영,김용기 한국태양에너지학회 2022 한국태양에너지학회 논문집 Vol.42 No.1

The discussion about carbon neutrality has recently spread worldwide in response to the climate crisis. In Korea, the concept of zero-energy buildings is one of the means to reduce carbon emissions in the construction sector. Photovoltaic (PV) power systems are the most commonly installed renewable energy systems in residential buildings. However, the installed PV capacity in apartment houses is limited because of difficulty in securing PV installation area and inability to process the surplus PV power. Battery energy storage systems (BESSs) are emerging as a means for the storage and reuse of surplus PV power. In this study, the energy-saving effect of a residential BESS connected to a rooftop PV system was analyzed for eight households in a multi-family house. The data of the main load power (grid supply) and PV+BESS power from households collected from August to October 2021 were analyzed. During the operation of the BESS, the surplus PV power was stored in the battery, and the PV+BESS power was continuously supplied to the load by discharging the battery regardless of the PV power time. Based on the average representative data for 6 days, the power saving rate was approximately 26.0% for the rooftop PV system and approximately 41.8% for the BESS.

실물 실험을 통한 태양광 모듈의 표면온도와 태양광 발전량과의 관계에 대한 연구

조성우(Sung-Woo Cho) 한국지열·수열에너지학회 2018 한국지열에너지학회논문집 Vol.14 No.3

PV module power is calculated on PV module surface temperature adjustment by irradiation on the summer and autumn in NOCT(Nominal Operating Cell Temperature) conditions. The summer and autumn periods were selected because of large variation in outdoor air temperature and irradiation. This study was performed to understand relationship between PV module surface temperature and photovoltaic power using field measurement. As a results, it was determined that the amount of irradiation was proportional to the amount of photovoltaic power in the field measurement. However, it was also identified that the PV power generation decreased by increased PV module surface temperatures due to irradiation.

배전계통에서의 PV 인버터 제어 특성을 고려한 고장해석 방법

심기도(Gi-Do Sim),안선주(Seon-Ju Ahn),최준호(Joon-Ho Choi),홍지송(Ji-Song Hong),윤상윤(Sang-Yun Yun) 대한전기학회 2019 전기학회논문지 Vol.68 No.12

Photovoltaic(PV) generations in power distribution networks are dramatically increasing. As PV increases, there is a needs to consider the contribution of fault current. PV is connected to the grid through an inverter, and the control method has different current contributions from conventional generators. In this paper, we propose a fault analysis method considering the control characteristics of PV inverter for power distribution networks. The current and power of PV during a fault are determined by the terminal voltage and control methods of the inverter. To reflect the inverter control characteristics, 3 phase unbalanced power flow is used for the fault analysis. For this, we present the 3 phase models of distribution networks, such as line, transformer and PV. Admittance and impedance matrix representations were performed for the models. We use Implicit Zbus Method for the 3 phase unbalanced power flow. In the case studies for an example network, we compare the results between the proposed methods and MATLAB simulation. Through the case studies, we verify the accuracy of the proposed fault analysis method.

Polycarbonate-Photovoltaic Module for Flexibility, Toughness, and High Temperature

Bae Jin-Yong 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.2

This study aims to discuss the development of Polycarbonate-Photovoltaic (PC-PV) modules with flexibility, toughness, and high temperature properties. It proposes a method for laminating a single crystal silicon PV cell on a PC substrate to afford PC-PV modules with flexibility, toughness, and high-temperature properties. Furthermore, a novel method is proposed to laminate ETFE and EVA films over single crystal silicon PV cell to protect the PV-PC Module. To confirm the feasibility of the proposed PC-PV module, a 3-mm-thick, 600 × 400 mm2, and 35-W-class PC-PV module was manufactured. The effectiveness of the PC-PV module was verified with flexibility, toughness, and high temperature.

홀수스트링 PV모듈의 바이패스 다이오드 배치에 의한 전기적 특성

신우균(Shin Woo-Gyun),고석환(Go Seok-Hwan),주영철(Ju Young-Chul),송형준(Song Hyung-Jun),강기환(Kang Gi-Hwan) 한국태양에너지학회 2017 한국태양에너지학회 논문집 Vol.37 No.4

Most PV modules are fabricated by 6 cell-strings with solar cells connected in series. Moreover, bypass diodes are generally installed every 2 cell-strings to prevent PV modules from a damage induced by current mismatch or partial shading. But, in the case of special purpose PV module, like as BIPV (Building Integrated Photovoltaic), the number of cell-strings per module varies according to its size. Differ from a module employing even cell-strings, the configuration of bypass diode should be optimized in the PV module with odd strings because of oppositely facing electrodes. Hence, in this study, electrical characteristics of special purposed PV module with odd string was empirically and theoretically studied depending on arrangement of bypass diode. Here, we assumed that PV module has 3 strings and the number of bypass diodes in the system varies from 2 to 6. In case of 2 bypass diodes, shading on a center string increases short circuit current of the module, because of a parallel circuit induced by 2 bypass diodes connected to center string. Also, the loss is larger, as the shading area in the center string is enlarged. Thus, maximum power of the PV module with 2 bypass diode decreases by up to 59 (%) when shading area varies from 50 to 90 (%). On the other hand, In case of 3 and 6 bypass diodes, the maximum power reduction was within about 3 (W), even the shading area changes from 50 to 90 (%). As a result, It is an alternative to arrange the bypass diode by each string or one bypass diode in the PV module in order to completely bypass current in case of shading, when PV module with odd string are fabricated.

다결정 실리콘 PV모듈의 하절기 표면온도 예측을 위한 알고리즘 검토 및 외부인자별 영향 평가

정동은(Jung, Dong-Eun),염규환(Yeom, Gyuhwan),이찬욱(Lee, Chanuk),도성록(Do, Sung-Lok) 대한건축학회 2019 大韓建築學會論文集 : 構造系 Vol.35 No.8

Recently, electric power usages and peak loads from buildings are increasing due to higher outdoor air temperatures and/or abnormal climate during the summer period. As one of the eco-friendly measures, a renewable energy system has been received much attention. Particularly, interest on a photovoltaic (PV) system using solar energy has been rapidly increasing in a building sector due to its broad applicability. In using the PV system, one of important factors is the PV efficiency. The normal PV efficiency is determined based on the STC(Standard Test Condition) and the NOCT(Nominal Operating Cell Temperature) performance test. However, the actual PV efficiency is affected by the temperature change at the module surface. Especially, higher module temperatures generally reduce the PV efficiency, and it leads to less power generation from the PV system. Therefore, the analysis of the relation between the module temperature and PV efficiency is required to evaluate the PV performance during the summer period. This study investigates existing algorithms for calculating module surface temperatures and analyzes resultant errors with the algorithms by comparing the measured module temperatures.

비동일한 방위각에 의한 PV모듈의 발전성능

김현일(Kim Hyun-Il),박경은(Park Kyung-Eun),이기옥(Lee Ki-Ok),강기환(Kang Gi-Hwan),유권종(Yu Gwon-Jong),서승직(Suh Sung-Jik) 한국태양에너지학회 2009 한국태양에너지학회 학술대회논문집 Vol.2009 No.11월

In 2008, the global photovoltaic(PV) market reached 5.6GW and the cumulative PV power installed totalled almost 15GW compared to 9GW in 2007. Due to a favourable feed-in-tariff, Korea emerged in 2008 as the 4th largest PV market worldwide. PV power installation rose 495.5 percent to 268㎿ in 2008 compare to 45㎿ in 2007. However many PV systems are not installed in suitable part which is concerned about geometrical factor. It is generally recognized that the actual output of PV system in field is a function of orientation, tilt angle, irradiance, temperature, soiling and various system-related losses. Thus this paper shows that a experimental result of PV modules(A group) with uniform azimuth angle and PV modules(B group) with non-uniform azimuth angle. As a result, the electrical output of B group is decreased 48.8% as compared with electrical output of A group.

Field Exposed PV모듈의 열화 사례 분석

이창구(Lee Chang-Goo),김경수(Kim Kyung-Soo),강기환(Kang Gi-Hwan) 한국태양에너지학회 2010 한국태양에너지학회 학술대회논문집 Vol.2010 No.11

In this paper, we studied and analyzed the degradation phenomenon and the power drop for 53 sites among photovoltaic (PV) module sites installed between 1988 and 2008 year in Korea. In this study, PVmodules from 4sites exposed for³20 years in the field showed humidity intrusion, EVA sheet de-lamination, electrode oxidation, yellow discoloring, white discoloring and glass breakage. The degradation of PV module from these sites was seen to be about 100 % by the naked eyes test and seemed to be too aged to work properly. However the power output of these PV modules got reduced only by about 20-30 % of the initial production value. The PV modules from 10 sites used for ~10 years in the field showed the similar degradation phenomenon to ones for ≥20 years old and the aging degree was about 80 %. In here, the drop rate of power output was 13.5 - 57.9 %, compared to the initial power output. The degradation phenomenon was also found in PV modules used for ~5 years and about 30 % of these PV modules showed electrode oxidation, humidity intrusion, de-lamination, white discoloring and bus bar ribbon oxidation. Some of modules had yellow discoloring, cell corrosion, power cable corrosion, insulation breakage, back sheet white discoloring and et al. The degradation rate of these modules was ~30 % and power output drop was 13-13.5 % of the initial one. The some PV modules installed recently, less than 5 years, also showed electrode oxidation, de-lamination, yellow discoloring, hot spot. The aging rate and power output drop were ~10 % and 1.7 - 14.6 % with very wide variations, respectively.