Jintae Cho

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.

Frequency Control Method of Grid Interconnected Microgrid Operating in Stand Alone Mode

Microgrid is a new electrical energy system that composed of various generators, renewable energy, batteries and loads located near the electrical customers. When Microgrid is interconnected with large power system, Microgrid don`t need to control the frequency. But in case of the outage or faults of power system, Microgrid should control the frequency to prevent the shutdown of Microgrid. This paper presents the frequency control methods using the droop function, being used by synchronous generators and EMS(Energy Management System). Using droop function, two battery systems could share the load based on locally measured signals without any communications between batteries. Also, we suggest that EMS should control the controllable distributed generators as P/Q control modes except batteries to overcome the weakness of droop function. Finally we suggest the two batteries systems to prolong the battery`s life time considering the economical view. The validation of proposed methods is tested using PSCAD/EMTDC simulations and field test sites at the same time.

Automatic Generation Control System for Operation Mode in Microgrid

The microgrid concept assumes a cluster of loads and microsources operating as a single controllable system that provides a new paradigm for defining the operation of distributed generation. This system can be operated as both grid-connected mode and islanded mode. In other words, the microgrid can be operated to meet their special need; such as economics in steady state and local reliability in islanded mode due to the grid fault. This paper presents the AGC (Automatic Generation Control) method for microgrid with EMS (Energy Management System).

Development of voltage control system for multi-terminal low-voltage DC distribution system

LVDC (Low Voltage Direct Current) distribution systems have advantages over conventional AC distribution systems in terms of power quality, power-conversion-loss reduction, renewable energy integration, and so on. There were pioneering researches into development of LVDC distribution systems but most of them considered radial distribution systems with one grid-connection converter. In this paper, we propose multi-terminal LVDC distribution system that has multiple grid-connection points and integration of distributed energy resources (DERs). The multi-terminal LVDC system can have more reliability and flexibility in electric power provision because it has multiple grid-interfacing AC/DC converters. However, multiple paths for power flows can increase the complexity in system operation and control. This paper proposes a new voltage control method for multi-terminal LVDC distribution systems using multi-agent system (MAS). This paper presents the hierarchical control algorithms to coordinate multiple AC/DC converters and DERs. Simulation studies demonstrates the performance of the proposed method.

Distributed and autonomous control system for voltage regulation in low-voltage DC distribution systems

The voltage regulation is a significant issue for low-voltage DC (LVDC) distribution systems because it directly determines the system size and hosting capacity of distributed energy resources (DERs) of the distribution systems. This paper proposes an autonomous monitoring and control system for voltage regulation of the LVDC distribution systems. To this end, we adopted the concept of multi-agent system (MAS) to effectively manage the distribution systems with DERs using locally collected information and distributed intelligent algorithms. In this paper, we propose a new communication architecture in field level communication between multiple agents system and design the middleware for the MAS-based control system. All the proposed ideas are implemented in real hardware and tested experimentally.

Voltage Measurement Accuracy Assessment System for Distribution Equipment of Smart Distribution Network

A new system for evaluating the voltage management errors of distribution equipment is presented in this paper. The main concept of the new system is to use real distribution live-line voltage to evaluate and correct the voltage measurement data from distribution equipment. This new approach is suitable for a new Distribution Management System (DMS) which has been developed for a distribution power system due to the connection of distributed generation growth. The data from distribution equipment that is installed at distribution lines must be accurate for the performance of the DMS. The proposed system is expected to provide a solution for voltage measurement accuracy assessment for the reliable and efficient operation of the DMS. An experimental study on actual distribution equipment verifies that this voltage measurement accuracy assessment system can assess and calibrate the voltage measurement data from distribution equipment installed at the distribution line.

An Improvement of Optical Fiber Composite Power Cable On-Line Monitoring System for Underground Distribution Network

Since power system is switching to smart grid, on-line monitoring technology has become necessary for underground distribution power cable. Therefore, the application of DTS(Distributed Temperature Sensing) technology using OFCPC(Optical Fiber Composite Power Cable) capable of monitoring underground distribution power cables has been developed. These can bring about reductions in faults and increases in operating capacity of underground distribution system. To date, the test-bed of optical fiber composite power cable on-line monitoring system has been constructed. Then, matters to be improved have been drawn through verification experiments. This paper presents the improvement and experiment results of the optical fiber composite power cable on-line monitoring system to apply to underground distribution lines in the field.