Eung-Sang Kim

PSCAD/EMTDC-Based Modeling and Analysis of a Gearless Variable Speed Wind Turbine

This paper presents dynamic modeling and simulation of a grid connected variable speed wind turbine (VSWT) using PSCAD/EMTDC, a widely used power system transient analysis tool. The variable speed wind system with a direct-drive generator and power electronics interface is modeled for dynamic analysis. Component models and equations are addressed and their implementations into PSCAD/EMTDC are described. Controllable power inverter strategy is intended for capturing the maximum energy from varying wind speed and maintaining reactive power generation at a pre-determined level for constant power factor or voltage regulation. The component models and entire control scheme are constructed by user-defined function provided in the program. Simulation studies provide control performance and dynamic behavior of a gearless VSWT under varying wind speeds. In addition, the system responses to network fault conditions have been simulated. This modeling study can be employed to evaluate the control scheme, output performance and impacts of a VSWT on power grid at planning or designing stage.

Modeling and Control of a Grid-connected Wind/PV Hybrid Generation System

This paper deals with power control of a wind and solar hybrid generation system for interconnection operation with electric distribution system. The proposed system consists of a variable-speed direct-drive wind generator, wind-side converter, solar array, dc-dc converter and grid interface inverter. Power control strategy is to extract the maximum energy available from varying condition of wind speed and solar irradiance while maintaining power quality at a satisfactory level. In order to capture the maximum power, variable speed control is employed for wind turbine and maximum power point tracking is applied for photovoltaic system. The grid interface inverter transfers the energy drawn from the wind turbine and PV array into the grid by keeping common dc voltage constant. Modeling and simulation study on the entire control scheme is carried out using a power system transient analysis tool, PSCAD/EMTDC. The simulation results show the control performance and dynamic behavior of the wind/PV system

Coordinated Control Algorithm for Distributed Battery Energy Storage Systems for Mitigating Voltage and Frequency Deviations

Energy storage systems (ESSs) are essential in future power systems because they can improve power usage efficiency. In this paper, a novel coordinated control algorithm is proposed for distributed battery ESSs (BESSs). The neighboring BESSs of a simulation system are grouped and controlled by a main control center. The main control center sends charging or discharging operation signals to each BESS. The primary objective of the proposed coordinated control scheme is to mitigate voltage and frequency deviations. In order to verify the proposed algorithm, the BESSs are connected to a distribution system of the Korea Electric Power Corporation. The results are compared with those obtained using uncoordinated control scheme with on-load tap changer considering aspects of power quality (voltage and frequency variation). The simulation results show that the voltage and frequency deviations are reduced with the proposed coordinated control algorithm.

Modeling of Battery for EV using EMTP/ATPDraw

As environmentally friendly energy takes center stage, interests for Electric Vehicles/Plug in Hybrid Electric Vehicles (EVs/PHEVs) are getting increase. With this trend, there is no doubt EVs will take large portion to penetrations of total cars. Therefore, accurate EV modeling is required. Battery is one of the main components with the power system view of aspect. Hence, in this paper, reviews and discussions of some types of batteries for EV are contained by considering energy density and weight of the batteries. In addition, simulations of Li-Ion battery are accomplished with various variables such as temperature, capacity fading and charge/discharge current. It is confirmed that temperature is the main factor of capacity fading. Validation of the modeled battery is also conducted by comparing it with commercialized battery.

Evaluation of Voltage Sag and Unbalance due to the System Connection of Electric Vehicles on Distribution System

Due to increased concerns for rising oil prices and environmental problems, various solutions have been proposed for solving energy problems through tightening environmental regulations such as those regarding CO₂ reduction. Among them, Electrical Vehicles (EVs) are evaluated to be the most realistic and effective approach. Accordingly, research and development on EVs and charging infrastructures are mainly proceeding in developed countries. Since EVs operate using electric energy form a battery, they must be connected to the power system to charge the battery. If many EVs are connected during a short time, power quality problems can occur such as voltage sag, voltage unbalance and harmonics which are generated from power electronics devices. Therefore, when EVs are charged, it is necessary to analyze the effect of power quality on the distribution system, because EVs will gradually replace gasoline vehicles, and the number of EVs will be increased. In this paper, a battery for EVs and a PWM converter are modeled using an ElectroMagnetic Transient Program (EMTP). The voltage sag and unbalance are evaluated when EVs are connected to the distribution system of the Korea Electric Power Corporation (KEPCO). The simulation results are compared with IEEE standards.

Development of Simulator System for Microgrids with Renewable Energy Sources

This paper deals with the design and testing of a simulator system for microgrids with distributed generations. This system is composed of a Real Time Digital Simulator (RTDS) and a power amplifier. The RTDS parts are operated for real time simulation for the microgrid model and the distributed generation source model. The power amplifiers are operated for amplification of the RTDSs simulated output signal, which is a node voltage of the microgrid and distributed generation source. In this paper, we represent an RTDS system design, specification and test results of a power amplifier and simulation results of a PV (Photovoltaic) system and wind turbine system. The proposed system is applicable for development and performance testing of a PCS (Power Conversion System) for renewable energy sources.

A Study on Voltage Sag Considering Real-Time Traffic Volume of Electric Vehicles in South Korea

This paper analyzes the effect of voltage sag on distribution systems due to the connection of Electric Vehicles (EVs). In order to study the impact of the voltage sag on the power system, two scenarios have been selected in this paper. The distribution system and EVs are modeled using the Electro Magnetic Transients Program (EMTP). The numbers of EVs are predicted based on the number of vehicles in distribution system of Seoul. In addition, the number of EVs is set up using realtime traffic in Seoul to simulate Scenario I and II. The simulation results show that voltage sag can occur if the distribution system has more than 30% of the total number of vehicles.

Modeling of battery for electric vehicle using EMTP/MODELS

Accurate battery modeling is one of the most important factors in electric vehicle (EV) and plug-in hybrid electric vehicle (PHEV) design process. Therefore, investigation of characteristics of battery is essential. In this paper, the modeling of the battery for EV and PHEV is presented. Electro-Magnetic Transient Program (EMTP)/MODELS is used to model the battery for EV and PHEV. To analyze characteristics of battery, this work use State Of Charge (SOC) and Depth Of Discharge (DOD) to calculate batterys internal resistances, capacitors and output voltage when the battery is charged and discharged. The simulation results are compared with other previous works to ensure its validity.

A Study on the Voltage Sag During the EVs Charging Considering Domestic Data

In order to charge EVs, they have to be connected to distribution system. Therefore, if unprecedented numbers of EVs are connected to power systems, it could result in deterioration of power quality, overload, and other system problems. In this paper, the effects of voltage sag on the distribution system due to the connection of EVs is evaluated by considering related field data of Republic of Korea such as the number of gasoline-fueled vehicles, seasonal load of power system and the monthly and daily real-time traffic volume. The distribution system and EVs are modeled using the Electro Magnetic Transients Program (EMTP).