Seung Tae Cha

Driving Pattern Analysis for Electric Vehicle (EV) Grid Integration Study

In order to facilitate the integration of electric vehicles (EVs) into the Danish power system, the driving data in Denmark were analyzed to extract the information of driving distances and driving time periods which were used to represent the driving requirements and the EV unavailability. The Danish National Transport Survey data (TU data) were used to implement the driving data analysis. The average, minimum and maximum driving distances were obtained for weekdays, weekends and holidays to illustrate the EV users¿ driving requirements in different days. The EV availability data were obtained from the driving time periods to show how many cars are available for charging and discharging in each time period. The obtained EV availability data are in one hour time periods and one quarter time periods for different study purposes. The EV availability data of one hour time period are to be used for optimal EV charging study in energy power market. The EV availability data of quarter time periods are to be used to investigate the possibility of utilizing EVs for providing regulation power. The statistical analysis software, SAS, was used to carry out the driving data analysis.

Coordinated control scheme of battery energy storage system (BESS) and distributed generations (DGs) for electric distribution grid operation

This paper describes a coordinated control scheme of battery energy storage system (BESS) and distributed generations (DGs) for electric distribution grid operation. The BESS is designed to stabilize frequency and voltages as a primary control after the electric distribution system enters into the islanding operation mode, while the centralized joint load frequency control (CJLFC) utilizing DGs handles the secondary frequency regulation. The BESS with the associated controllers has been modelled in Real-time digital simulator (RTDS) in order to identify the improvement of the frequency and voltage response. The modified IEEE 9-bus system, which is comprised of several DG units, wind power plant and the BESS, has been employed to illustrate the performance of the proposed coordinated flexible control scheme using RTDS in order to verify its practical efficacy.

Electric Vehicle (EV) charging management with dynamic distribution system tariff

Electric Vehicles (EV) presents a unique opportunity for large-scale flexible demand, particularly when subject to intelligent charging. A smart charging algorithm is proposed here, with the dual objectives of minimizing charging costs and preventing grid congestion. EVs are charged according to individual user requirements while respecting the constraints of the local distribution grid. A day-ahead dynamic distribution system tariff (DT) scheme is proposed to avoid congestion on the local distribution system from the day-ahead planning perspective. Locational marginal pricing is used to determine the dynamic distribution system tariff based on predicted day-ahead spot prices and predicted charging behaviors. Case studies were carried out using distribution grids from the Danish island of Bornholm and the case studies demonstrate the efficacy of the proposed EV charging schedule algorithm

Real-Time Hardware-In-The-Loop (HIL) Testing for Power Electronics Controllers

This paper discusses general approaches and results of real-time hardware-in-the-loop (HIL) testing for power electronics controllers. Many different types of power electronic controllers can be tested by connecting them to a real-time digital simulator (RTDS) for closed-loop HIL testing. In this paper, two HIL digital controller tests are presented as application examples of the low-level signal interface in the closed-loop tests of power electronic controllers. In the HIL tests, the power system and the power electronics hardware are modeled in the RTDS. The required control functions of the power electronics hardware are not included in the RTDS. Instead, the control algorithms are coded using the native C code and downloaded to the dedicated digital signal processor (DSP)/microcontrollers. The two experimental applications illustrate the effectiveness of the HIL controller testing. Results of the HIL tests and hardware validations are presented to illustrate the real-time HIL testing method for power electronics controllers.

Impact study of electric vehicle (EV) integration on medium voltage (MV) grids

The impact study of electric vehicle (EV) integration on medium voltage (MV) grids has been done in order to investigate the effects of different EV charging scenarios on MV grids from the perspectives of power component loading and voltage profiles. The intent of the impact study of EV integration is to identify the bottlenecks of power systems for the EV grid integration, assess different EV charging scenarios and quantify the benefits from smart charging from the power component loading and voltage profile perspectives. Three charging scenarios, dumb charging, timed charging and fleet operator based charging, have been considered in the impact study. The vehicle driving pattern data in Denmark have been used to determine the EV charging demands of different charging scenarios. A MV grid from the Bornholm power system has been used to implement the case studies.

Reliability evaluation considering structures of a large scale wind farm

Wind energy is one of the most widely used renewable energy resources. Wind power has been connected to the grid as large scale wind farm which is made up of dozens of wind turbines, and the scale of wind farm is more increased recently. Due to intermittent and variable wind source, reliability evaluation on wind farm is necessarily required. Also, because large scale offshore wind farm has a long repair time and a high repair cost as well as a high investment cost, it is essential to take into account the economic aspect. One of methods to efficiently build and to operate wind farm is to construct wind farm which is able to enhance a capability of delivering a power instead of controlling an uncontrollable output of wind power. Therefore, this paper introduces a method to evaluate the reliability depending upon structures of wind farm and to reflect the result to the planning stage of wind farm.

A real-time simulation platform for power system operation

This paper describes the real-time digital simulation platform that can be used for power system operation, analysis, and power system modeling. This particular platform gives grid operators, planners and researchers the opportunity to observe how a power system behaves and can be used to demonstrate modeling, system disturbances of various types, and proper recovery actions, as well as to illustrate complex power system concepts. The Kundur power system consists of two fully symmetrical areas linked together by two 230kV lines is modeled by using RSCAD in order to carry out simulations in real time. Various phenomena commonly encountered when dealing with the two-area system is studied. Despite its small size, it mimics very closely the behavior of typical systems in actual operation. The electromagnetic transient type of simulation made in RSCAD enables the study of fast and detailed phenomena like single-phase faults in the two-area network and to observe their effects on a larger time scale. Also, the case study of 16 bus system with 5 generators has been also used and the results are presented.

Storage application in smart grid with high PV and EV penetration

Rapid deployment of renewable energy sources (RES) and concerns regarding their impacts on power systems provide new opportunities for utilizing more electrical energy storage system (EESS) in power systems. Peak-shaving in high Photovoltaic (PV) penetration conditions and providing ancillary service in high load conditions are among the applications of EESS in distribution systems. In this paper, a new method is developed based on the voltage sensitivity analysis of the network in order to calculate the EESS capacity required for prevention of voltage rise and voltage drop in distribution grids with residential PVs and Electric Vehicles (EVs). The effect of EV home charging on EESS capacity in high PV penetration is also addressed. The results indicate that increasing the EV penetration in the network can decrease the EESS capacity need. This decrease is highest in situations with low PV penetration.

Offshore wind power planning in Korea

Wind power generation is globally recognized as the most universal and reliable form of renewable energy. Korea is currently depending mostly on coal and petroleum to generate electrical power and is now trying to replace them with renewable energy such as offshore wind power generation. To make this possible, Korea has announced the National offshore power roadmap and is now in pursuit. However, large scale offshore wind farms can incur many problems, such as power quality problems, when connecting to a power system. [1][2] Thus, KEPCO is on the process of a research study to evaluate the effects that connecting offshore wind power generation to a power system has on the power system. This paper looks over offshore wind power planning in Korea and describes the development of impact assessment technology of offshore wind farms.

A generic danish distribution grid model for smart grid technology testing

This paper describes the development of a generic Danish distribution grid model for smart grid technology testing based on the Bornholm power system. The proposed approach uses a coherency based dynamic equivalent technique along with relation & participation factors, and is suitable for use with real time digital simulator (RTDS). In particular, the frequency dependent network equivalent (FDNE) method has been combined with parameter randomization in order to accurately preserve the desired properties and characteristics of the original Bornholm power system. The validity and efficiency of the proposed approach is demonstrated by comparing the transient response of the original Bornholm power system model and the developed generic model under significant fault conditions. The results clearly show that the equivalent generic distribution grid model retains the dynamic characteristics of the original system, and can be used as a generic Smart Grid benchmark model for testing purposes.