Don Hur

Economic Considerations Underlying the Adoption of HVDC and HVAC for the Connection of an Offshore Wind Farm in Korea

Wind energy is created in mega-sized wind farms situated kilometers off shore. In fact, two possibilities are considered for the transmission system between the offshore wind farm and the onshore grid: high-voltage direct current and high-voltage alternating current. From this point of view, the current paper aims to compare both systems for a 2 GW wind farm situated 80 km from the Point of Common Coupling on an economic basis using a discounted cash flow analysis. A tool is developed in Microsoft Excel to allow for quick insight in the variation of input parameters.

Towards Cyber Security Risks Assessment in Electric Utility SCADA Systems

This paper presents a unified model based assessment framework to quantify threats and vulnerabilities associated with control systems, especially in the SCADA (Supervisory Control and Data Acquisition) system. In the past, this system was primarily utilized as an isolated facility on a local basis, and then it started to be integrated with wide-area networks as the communication technology would make rapid progress. The introduction of smart grid, which is an innovative application of digital processing and communications to the power grid, might lead to more and more cyber threats originated from IT systems. However, an up-to-date power system often requires the realtime operations, which clearly implies that the cyber security would turn out to be a complicated but also crucial issue for the power system. In short, the purpose of this paper is to streamline a comprehensive approach to prioritizing cyber security risks which are expressed by the combination of threats, vulnerabilities, and values in the SCADA components.

Inertial Control of a DFIG-based Wind Power Plant using the Maximum Rate of Change of Frequency and the Frequency Deviation

In order to let a wind generator (WG) support the frequency control of a power system, a conventional inertial control algorithm using the rate of change of frequency (ROCOF) and frequency deviation loops was suggested. The ROCOF loop is prevailing at the initial stage of the disturbance, but the contribution becomes smaller as time goes on. Moreover, its contribution becomes negative after the frequency rebound. This paper proposes an inertial control algorithm of a wind power plant (WPP) using the maximum ROCOF and frequency deviation loops. The proposed algorithm replaces the ROCOF loop in the conventional inertial control algorithm with the maximum ROCOF loop to retain the maximum value of the ROCOF and eliminate the negative effect after the frequency rebound. The algorithm releases more kinetic energy both before and after the frequency rebound and increases the frequency nadir more than the conventional ROCOF and frequency loops. The performance of the algorithm was investigated under various wind conditions in a model system, which includes a doubly-fed induction generator-based WPP using an EMTP-RV simulator. The results indicate that the algorithm can improve the frequency drop for a disturbance by releasing more kinetic energy.

Optimized Installation and Operations of Battery Energy Storage System and Electric Double Layer Capacitor Modules for Renewable Energy Based Intermittent Generation

In this paper, a novel approach for optimized installation and operations of battery energy storage system (BESS) and electric double layer capacitor (EDLC) modules for the renewable energy based intermittent generation is presented for them to be connected with an electric power grid. In order to make use of not merely the high energy density of battery but also the high power density of EDLC modules, it is very useful to devise the hybrid system which combines BESS and EDLC modules. The proposed method adopts the linear programming to calculate the optimized capacity as well as the quadratic programming to transmit the optimal operational signals to BESS and EDLC modules. The efficiency of this methodology will be demonstrated in the experimental study with the real data of wind speed in Texas.

An Economic Analysis of Potential Cost Savings from the Use of Low Voltage DC (LVDC) Distribution Network

The proposed technical work attempts to compare the two key technologies of power distribution, i.e. direct current (DC) and alternating current (AC) in a fiscal manner. The DC versus AC debate has been around since the earliest days of electric power. Here, at least four types of a low voltage DC (LVDC) distribution are examined as an alternative to the existing medium voltage AC (MVAC) distribution with an economic assessment technique for a project investment. Besides, the sensitivity analysis will be incorporated in the overall economic analysis model to cover uncertainties of the input data. A detailed feasibility study indicates that many of the common benefits claimed for an LVDC distribution will continue to grow more profoundly as it is foreseen to arise with the increased integration of renewable energy sources and the proliferation of energy storage associated with the enhanced utilization of uninterruptible power supply (UPS) systems.

Economic Evaluation of Offshore Wind Farm in Korea

With an increase in the penetration of offshore wind farm, the need of an accurate economic evaluation of offshore wind farm has become crucial. This paper presents an economic evaluation method of offshore wind farm in Korea reflecting the cost of offshore wind farm infrastructure (offshore substation, submarine cable and foundation) in its cost model. Each cost of offshore substation, submarine cable, and foundation is represented as a function of installed capacity, distance to shore, and water level, respectively. We have applied the method to the case study of offshore in Jeju Island and analyzed the economics under various conditions. The results show that the distance to shore is of importance in economics of offshore wind farm.

A Techno-Economic Feasibility Analysis on LVDC Distribution System for Rural Electrification in South Korea

Low voltage direct current (LVDC) distribution system is a suitable techno-economic candidate which can create an innovative solution for distribution network development with respect to rural electrification. This research focuses on the use of LVDC distribution system to replace some of KEPCOs existing traditional medium voltage alternating current (MVAC) distribution network for rural electrification in South Korea. Considering the technical and economic risks and benefits involved in such project, a comparative techno-economic analysis on the LVDC and the MVAC distribution networks is conducted using economic assessment method such as the net present value (NPV) on a discounted cash flow (DCF) basis as well as the sensitivity analysis technique. Each would play a role in an economic performance indicator and a measure of uncertainty and risk involved in the project. In this work, a simulation model and a computational tool are concurrently developed and employed to aid the techno-economic analysis, evaluation, and estimation of the various systems efficiency and / or performance.

Power Curve of a Wind Generator Suitable for a Low Wind Speed Site to Achieve a High Capacity Factor

It is well known that energy generated by a wind generator (WG) depends on the wind resources at the installation site. In other words, a WG installed in a high wind speed area can produce more energy than that in a low wind speed area. However, a WG installed at a low wind site can produce a similar amount of energy to that produced by a WG installed at a high wind site if the WG is designed with a rated wind speed corresponding to the mean wind speed of the site. In this paper, we investigated the power curve of a WG suitable for Koreas southwestern coast with a low mean wind speed to achieve a high capacity factor (CF). We collected the power curves of the 11 WGs of the 6 WG manufacturers. The probability density function of the wind speed on Koreas southwestern coast was modeled using the Weibull distribution. The annual energy production by the WG was calculated and then the CFs of all of the WGs were estimated and compared. The results indicated that the WG installed on the Koreas southwestern coast could obtain a CF higher than 40 % if it was designed with the lower rated speed corresponding to the mean wind speed at the installation site.

Stochastic integrated generation and transmission planning method with gradient radar step (GRS)

This paper presents a stochastic optimization method to solve an integrated generation and transmission planning problem under uncertainty. The two-stage decomposition method is combined with gradient radar step (GRS) to enhance the computational efficiency. The numerical results are presented to validate the effectiveness of the proposed method.

Development of Customer Oriented Load Management Software for Savings on Utility Bills in the Electricity Market

For electricity markets to function in a truly competitive and efficient manner, it is not enough to focus solely on improving the efficiencies of power supply. To recognize price-responsive load as a reliability resource, the customer must be provided with price signals and an instrument to respond to these signals, preferably automatically. This paper attempts to develop the Windows-based load management system in competitive electricity markets, allowing the user to monitor the current energy consumption or billing information, to analyze the historical data, and to implement the consumption strategy for cost savings with nine possible scenarios adopted. Finally, this modeling framework will serve as a template containing the basic concepts that any load management system should address.