Gilsung Byeon

Energy Management Strategy of the DC Distribution System in Buildings Using the EV Service Model

In this paper, a new energy management strategy (EMS) for a dc distribution system in buildings is being proposed. The dc distribution system is considered as a prospective system according to the increase of dc loads and dc output type distribution energy resources (DERs) such as photovoltaic (PV) systems and fuel cells. Since the dc distribution system has many advantages such as feasible connection of DERs and electric vehicles (EVs), reduction of conversion losses between dc output sources and loads, no reactive power issues, it is very suitable for industrial and commercial buildings interfaced with DERs and EVs. The establishment of an appropriate EMS based on the economic point of view can reduce energy costs of buildings and provide benefits to participants in energy management. Applicable elements for the dc distribution system are identified and the real-time decision-making-based algorithm for minimizing operating costs is proposed in this paper. The EV service model for the EMS to offer incentive to EV owners who participate in battery discharging is described. To verify the performances of the proposed algorithm, computer simulation and economic analysis are being performed where the results show that the proposed EMS reduces energy costs, motivates EV owners, and can be applied to the dc distribution buildings.

Modeling and Control of a Doubly-Fed Induction Generator (DFIG) Wind Power Generation System for Real-time Simulations

This paper presents a study of a DFIG wind power generation system for real-time simula- tions. For real-time simulations, the Real-Time Digital Simulator (RTDS) and its user friendly interface simulation software RSCAD are used. A 2.2MW grid-connected variable speed DFIG wind power generation system is modeled and analyzed in this study. The stator-flux oriented vector control scheme is applied to the stator/rotor side converter control, and the back-to-back PWM converters are implemented for the decoupled control. The real-wind speed signal extracted by an anemometer is used for a realistic, reliable and accurate simulation analysis. Block diagrams, a mathematical presenta- tion of the DFIG and a control scheme of the stator/rotor-side are introduced. Real-time simulation cases are carried out and analyzed for the validity of this work.

A research on the characteristics of fault current of DC distribution system and AC distribution system

In this paper, research on the comparison of the fault characteristics of the direct current (DC) distribution system and the alternating current (AC) distribution system has been conducted. Since the DC distribution system is a promising topology to be used in future smart distribution systems having high efficiency and reliability, it is expected that there would be an increase in the installation of DC distribution systems in houses and buildings. For the analysis, DC and AC networks to be analyzed are implemented using PSCAD/EMTDC. Simulation results show that the DC distribution system has several benefits compared to the regular AC distribution system such as improved voltage drop and power quality characteristics at the customer-end during a disturbance. This is because the DC/DC converters of DC distribution system can mitigate voltage fluctuations caused by disturbance and increase power quality.

A New DC Offset Removal Algorithm Using an Iterative Method for Real-Time Simulation

In this paper, a new dc offset removal algorithm for real-time simulations is proposed. Physically transferred signals in a real-time simulation interface tend to contain a dc offset component for various reasons. This component decreases the accuracy and stability of real-time simulations. The dc offset tends to change according to circumstances which include changes in the system configuration and effects of the external environment which makes the static dc offset removal scheme inefficient. The proposed algorithm can estimate and remove a dc offset component dynamically from the input signal of the hardware under test. In the proposed algorithm, the optimal constant for the condition equation is calculated by using an iterative method and is used to estimate the frequency, time, magnitude, and dc offset component of the input signal. Four sampling points are used to calculate the optimal constant in each step. The proposed algorithm has relatively fast speed and good accuracy in comparison to conventional dc offset removal algorithms. In order to verify the performances of the proposed algorithm, offline and real-time dc offset estimation simulation tests were performed. The results of the simulation tests showed that the proposed algorithm can estimate the dc offset component promptly and exactly and can be applied to real-time simulations.

Complementary Power Control of the Bipolar-type Low Voltage DC Distribution System

In this paper, a new power control strategy for the bipolar-type low voltage direct current (LVDC) distribution system is being proposed. The dc distribution system is considered as an innovative system according to the increase of dc loads and dc output type distribution energy resources (DERs) such as photovoltaic (PV) systems and energy storage systems (ESS). Since the dc distribution system has many advantages such as feasible connection of DERs, reduction of conversion losses between dc output sources and loads, no reactive power issues, it is very suitable solution for new type buildings and residences interfaced with DERs and ESSs. In the bipolar-type, if it has each grid-interfaced converter, both sides (upper, lower-side) can be operated individually or collectively. A complementary power control strategy using two ESSs in both sides for effective and reliable operation is proposed in this paper. Detailed power control methods of the host controller and local controllers are described. To verify the performances of the proposed control strategy, simulation analysis using PSCAD/EMTDC is being performed where the results show that the proposed strategy provides efficient operations and can be applied to the bipolar-type dc distribution system.

Power demand and power quality analysis of EV charging station using BESS in MicroGrid

Recently, the interest in EVs have increased owing to issues such as high oil prices and environmental pollution. The Korean government has to also expressed its commitment to develop EVs and is trying to accelerate the distribution of EVs by the mass production of various EVs ranging from small cars to buses by 2015. However, the absence of the EV charging infrastructure has hindered the propagation of EVs. Also, since the concept of V2G mentioned in the Smart Grid violates the original purpose of users convenience, the functionality of the V2G concept should be maintained but should be introduced in a different way. For this purpose, this problem can be solved by the installation of a BESS in an underground space is introduced along with the concept of the existing charging infrastructure similar to that of a gas station. In this paper, a novel method to utilize V2G by applying BESS has been proposed and the changes in load demand and the power quality problems are being analysed through simulations for the EV charging infrastructure linked with a BESS.

Low-cost power monitoring system using mobile handset

To step forward to the next phase of Smart grid, the customer should participate in the grid as an active player. Bi-directional data communication should be established to achieve the goal of Smart Grid, increasing energy efficiency in residential, industrial, commercial sectors and reliability for stable and high quality energy supply. Therefore Advanced Metering Infrastructure (AMI) which enables customers and utility to communicate, is crucial part of the Smart Grid. It can be helpful to deliver the information about the electrical power to the customer to show how the grid works and why the Smart Grid is needed. This paper presents very low-cost entry-level power monitoring system concept, potential and future works to be done.

Development of Daily Operation Program of Battery Energy Storage System for Peak Shaving of High-Speed Railway Substations

This paper proposed a program of an energy storage system(ESS) for peak shaving of high-speed railway substations The peak shaving saves cost of equipment and demand cost of the substation. To reduce the peak load, it is very important to know when the peak load appears. The past data based load profile forecasting method is easy and applicable to customers which have relatively fixed load profiles. And an optimal scheduling method of the ESS is helpful in reducing the electricity tariff and shaving the peak load efficiently. Based on these techniques, MS. NET based peak shaving program is developed. In case study, a specific daily load profile of the local substation was applied and simulated to verify performance of the proposed program.