Ungjin Oh

Development of Reliability Contribution Function of Power System including Wind Turbine Generators combined with Battery Energy Storage System

Abstract - This paper presents a study on reliability assessment and new contribution function development of power system including Wind Turbine Generator(WTG) combined with Battery Energy Storage System(BESS). This paper develops and proposes new reliability contribution function of BESS installed at wind farms. The methodology of reliability assessment, using Monte Carlo Simulation(MCS) method to simulate sample state duration, is proposed in detail. Forced Outage Rate(FOR) considered probabilistic approach for conventional generators is modelled in this paper. The penetration of large wind power can make risk to power system adequacy, quality and stability. Although the fluctuation of wind power, BESS installed at wind farms may smooth the wind power fluctuation. Using small size system as similar as Jeju island power system, a case study of reliability evaluation and new proposed contribution function of power system containing WTG combined with BESS is demonstrated in this paper, which would contributes to BESS reliability contribution and assessment tools of actual power system in future. Key Words : Wind turbine generator(WTG), Battery energy storage system(BESS), Monte carlo simulation(MCS), Reliability evaluation, ESS reliability contribution † Corresponding Author : Dept. of Electrical Eng., RIGET, ERI, Gyeongsang National University, Korea E-mail : jschoi@gnu.ac.kr* Dept. of Electrical Engineering, Gyeonsang National University , Korea ** KEPRI, KEPCO*** Dept. of Electrical Engineering, Daejin University, Korea Received : September 9, 2015; Accepted : February 19, 2016

Reliability Evaluation with Wind Turbine Generators and an Energy Storage System for the Jeju Island Power System

This paper proposes probabilistic reliability evaluation model of power system considering Wind Turbine Generator(WTG) integrated with Energy Storage System(ESS). Monte carlo sample state duration simulation method is used for the evaluation. Because the power output from WTG units usually fluctuates randomly, the power cannot be counted on to continuously satisfy the system load. Although the power output at any time is not controllable, the power output can be utilized by ESS. The ESS may make to smooth the fluctuation of the WTG power output. The detail process of power system reliability evaluation considering ESS cooperated WTG is presented using case study of Jeju island power system in the paper.

Development of One Day-Ahead Renewable Energy Generation Assessment System in South Korea

This paper proposes a probabi listic generatio n assessment mo del of renewable energy generators(REGs) considering uncertainty of resources, mainly focused on Wind Turbine Genera tor(WTG) and Solar Cell Generator(SCG) which are dispersed widely in South Korea The propos ed numerical analysis method as sesses the one day-ahead generation by combining equivalent generation characteristics function and probabilisti c distribution function of wind speed(WS) and solar radiation(S R) resources. The equivalent generat ion functions(EGFs) of the win d and solar farms are established by grouping a lot of the farms appropriately centered on W eather Measurement Station(WMS ). First, the EGFs are assessed by using regression analysis method based on typical least squ are method from the recorded a ctual generation data and hist orical resources(WS and SR). Second, the generation of the REGs is assessed by adding the on e day-ahead resources forecast, announced by WMS, to the EGFs which are formulated as third order degree polynomials usi ng the regression analysis. Third, a Renewable Energy Generation Assessment System(REGA S) including D/B of recorded a ctual generation data and hist orical resources is developed using the model and algorithm pre dicting one day-ahead power ou tput of renewable energy generators.

Conversion Function and Relationship of Loss of Load Expectation Indices on Two Kinds of Load Duration Curve

This paper develops a conversion function and method transforming from daily peak load curve used LOLED [days/ year] to hourly load curve used LOLEH[hours/year]and describes relationship between LOLED [days/year] and LOLEH [hours/year]. The indices can not only be transformed just arithmetically but also have different characteristics physically because of using their different load curves. The conversion function is formulated as variables of capacity and forced outage rate of generator, hourly load daily load factor and daily peak load yearly load factor, etc. Therefore, the conversion function () can not be simple. In this study, therefore, the function is formulated as linear times of separated two functions. One is an exponential formed conversion function of daily load factor. Another is formulated with an exponential typed conversion function of daily peak load yearly load factor. Futhermore, this paper presents algorithm and flow chart for transforming from LOLED[days/year] to LOLEH[hours/year]. The proposed conversion function is applied to sample system and actual KPS(Korea Power System) in 2015. The exponent coefficients of the conversion functions are assessed using proposed method. Finally, assessment errors using conversion function for case studies of sample system and actual system are evaluated to certify the firstly proposed method.

Probabilistic evaluation of long-term stability considering secondary contingency scenarios

This paper studies the effects of secondary contingency (N-1-1) on stability of power system in long time duration transient state considering state probability. The Vietnam power system which includes all level voltages up to 500 kV is utilized. The only 500 kV level system is analyzed by N-1-1 contingency criterion to define vulnerabilities of power grid. The dynamic simulation is implemented in vulnerability-based power system scenarios to verify long-term stability. The dynamic models of generators, governor, excitation system, maximum excitation limiters, static VAR compensators and load tap changers are built up based on real data of Vietnam power system.

Capacity credit and reasonable ESS evaluation of power system including WTGs combined with BESS

This paper proposes a new method for evaluating Effective Load Carrying Capability(ELCC) and Capacity Credit(C.C.) of power system including Wind Turbine Generator(WTG) combined with Battery Energy Storage System(BESS). WTG can only generate electricity power when the fuel(wind) is available. Because of fluctuation of wind speed, WTG generates intermittent power. In view point of reliability of power system, intermittent power of WTG is similar with probabilistic characteristics based on power on-off due to mechanical availability of conventional generator. Therefore, high penetration of WTG will occur difficulties in power operation. The high penetration of numerous and large capacity WTG can make risk to power system adequacy, quality and stability. Therefore, the penetration of WTG is limited in the world. This study develops a new method to assess how much is penetration of WTG able to extended when WTG is combined with BESS. This paper demonstrates a various case studies of ELCC and C.C. of power system containing WTG combined with BESS using model system as similar as Korea power system.

Relation formulation between daily and hourly load curve based loss of load expectation indices

This paper develops a conversion function and method transforming from daily peak load curve used LOLED [days/year] to hourly load curve used LOLEH [hours/year] firstly. The indices can not only be conversed just arithmetically but also have different characteristics physically because of using their different load curves. The conversion function is formulated as variables of capacity and forced outage rate of generator, hourly load daily load factor and daily peak load yearly load factor, etc. Therefore, the conversion function (γ = φ(·)) can not be formulated in simple but in complex and difficult. In this study, therefore, the function is formulated as linear times of separated two functions. One is exponential formed conversion function of daily load factor. Another is formulated exponential typed conversion function of daily peak load yearly load factor. Furthermore, this paper presents algorithm and flow chart for conversing from LOLED [days/year] to LOLEH[hours/year]. The proposed conversion function is applied to sample system and actual KPS(Korea Power System) in 2015. The exponent coefficients of the conversion functions are assessed using proposed method. Finally, assessment errors using conversion function for case studies of sample system and actual system are evaluated to certify the firstly proposed method.

Probabilistic generation assessment system of renewable energy in Korea

AbstractThis paper proposes probabilistic generation assessment system introduction of renewable energy generators. This paper is focused on wind turbine generator and solar cell generator. The proposed method uses an assessment model based on probabilistic model considering uncertainty of resources (wind speed and solar radiation). Equivalent generation function of the wind and solar farms are evaluated. The equivalent generation curves of wind farms and solar farms are assessed using regression analysis method using typical least square method from last actual generation data for wind farms. The proposed model is applied to Korea Renewable Generation System of 8 grouped 41 wind farms and 9 grouped around 600 solar farms in South Korea.