• Journal of Institute of Control, Robotics and Systems
• /
• v.20 no.11
• /
• pp.1118-1124
• /
• 2014

This paper proposes a novel controller design scheme for multimachine power systems based on the explorized policy iteration. Power systems have several uncertainties on system dynamics due to the various effects of interconnections between generators. To solve this problem, the proposed method solves the LQR (Linear Quadratic Regulation) problem of isolated subsystems without the knowledge of a system matrix and the interconnection parameters of multimachine power systems. By selecting the proper performance indices, it guarantees the stability and convergence of the LQ optimal control. To implement the proposed scheme, the least squares based online method is also investigated in terms of PE (Persistency of Excitation), interconnection parameters and exploration signals. Finally, the performance and effectiveness of the proposed algorithm are demonstrated by numerical simulations of three-machine power systems with governor controllers.

• Proceedings of the KIEE Conference
• /
• 1998.07c
• /
• pp.1244-1246
• /
• 1998

This paper present a variety fault problem brought out with the multifunctional Battery Energy Storage System [MBESS] expected to be practical in the short future interconnected to power distribution system. Multifunctional BESS model and interconnection model to power system is simply configured, the problems of protection coordination and operation is studied. A line fault in the power distribution system are discussed such as line to ground and three phase fault in order to show the impact on power utilities, demand-side and BESS-side. In order to simulate a variable transient phenomenon due to 2 the BESS interconnection operation to power distribution system, in this paper, PSCAD/EMTDC simulation tools is used.

• Journal of Electrical Engineering and Technology
• /
• v.2 no.1
• /
• pp.1-9
• /
• 2007

This paper presents the effects of an increase or a decrease of a power reserve by load flow calculations under the seasonal load patterns of each country for the future power shortages faced by the metropolitan areas or by the southeastern area of South Korea in North-East Asia. In this paper, the various cases of the power system interconnections in Far-East Asia are presented, and the resulting interconnected power systems are simulated by means of a power flow analysis performed with the PSS/E 28 version tool. Data for simulation were obtained from the 2-th long term plan of electricity supply and demand in KEPCO. The power flow map is drawn from simulated data and the comparative study is done. In the future, a power flow analysis will be considered to reflect the effects of seasonal power exchanges. And the plan of assumed scenarios will be considered with maximum or minimum power exchanges during summer or winter in North-East Asian countries.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.65 no.1
• /
• pp.23-30
• /
• 2016

Wake effects cause wind turbine generators (WTGs) within a wind power plant (WPP) to produce different levels of active power and subsequent reactive power capabilities. Further, the impedance between a WTG and the point of interconnection (POI)-which depends on the distance between them-impacts the WPP's reactive power injection capability at the POI. This paper proposes a voltage control scheme for a WPP based on the available reactive current of the doubly-fed induction generators (DFIGs) and its impacts on the POI to improve the reactive power injection capability of the WPP. In this paper, a design strategy for modifying the gain of DFIG controller is suggested and the comprehensive properties of these control gains are investigated. In the proposed scheme, the WPP controller, which operates in a voltage control mode, sends the command signal to the DFIGs based on the voltage difference at the POI. The DFIG controllers, which operate in a voltage control mode, employ a proportional controller with a limiter. The gain of the proportional controller is adjusted depending on the available reactive current of the DFIG and the series impedance between the DFIG and the POI. The performance of the proposed scheme is validated for various disturbances such as a reactive load connection and grid fault using an EMTP-RV simulator. Simulation results demonstrate that the proposed scheme promptly recovers the POI voltage by injecting more reactive power after a disturbance than the conventional scheme.

• Proceedings of the KIPE Conference
• /
• 2000.07a
• /
• pp.392-395
• /
• 2000

This paper proposes a soft-switching current -source inverter with a sitched-capacitor module The system operation was analyzed by a theoretical approach with equivalent circuits and verified by a computer simulation with ISPICE software. The proposed system could be effectively applied for the power converter of photovoltaic power generation interconnected with the power system.

• Proceedings of the KIEE Conference
• /
• 2005.04a
• /
• pp.271-273
• /
• 2005

Islanding of PV systems occurs when the utility grid is removed but local sources continue to operate and provide power to local loads. Islanding is one of the serious problems in an electric power system connected with dispersed power sources. Also, this can present safety hazards and the possibility of damage to other electric equipments. If the real and reactive power of RLC load and PV system are closely matched, islanding phenomena can't be detected by the passive methods. Several active methods were proposed to detect islanding phenomena. The most effective method is SFS method which was suggested by Sandia National Laboratory. In this paper, a new anti-islanding algorithm is proposed and its validity is verified through simulation and experimental results for utility interconnection of PV system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.17 no.11 s.114
• /
• pp.1105-1111
• /
• 2006

In this paper, using low-temperature co-fired ceramic(LTCC) based system-in-package(SiP) technology, a very compact power amplifier LTCC module was designed, fabricated, and then characterized for 60 GHz wireless transmitter applications. In order to reduce the interconnection loss between a LTCC board and power amplifier monolithic microwave integrated circuits(MMIC), bond-wire transitions were optimized and high-isolated module structure was proposed to integrate the power amplifier MMIC into LTCC board. In the case of wire-bonding transition, a matching circuit was designed on the LTCC substrate and interconnection space between wires was optimized in terms of their angle. In addition, the wire-bonding structure of coplanar waveguide type was used to reduce radiation of EM-fields due to interconnection discontinuity. For high-isolated module structure, DC bias lines were fully embedded into the LTCC substrate and shielded with vias. Using 5-layer LTCC dielectrics, the power amplifier LTCC module was fabricated and its size is $4.6{\times}4.9{\times}0.5mm^3$. The fabricated module shows the gain of 10 dB and the output power of 11 dBm at P1dB compression point from 60 to 65 GHz.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.13 no.4
• /
• pp.127-133
• /
• 1999

Ths paper deals with the active and reactive power control of Battery Energy Storage System (BESS) during its interconnection operation to power distribution system When an interconnection operation of BESS to power distribution system, it is well suited for peak load shaving and distribution voltage compensation by controlling the real and reactive power. Equivalent mxiel of the distribution system and the BESS is derived and power flow equations are presented to control the real and reactive power of BESS. In this paper, to control the active and reactive power of BESS, $P-\delta$ and Q-V control method and ntJIrerical description is presented. To verify the proposed control method, using PSCAD/EMTDC program simulates the active and reactive power control of BESS.f BESS.

• Progress in Superconductivity and Cryogenics
• /
• v.22 no.1
• /
• pp.7-11
• /
• 2020

As demand for electricity in urban areas increases, it is necessary to improve electric power stability by interconnecting neighboring substations and high temperature superconductor (HTS) power cables are considered as a promising option due to its large power capacity. However, the interconnection of substations reduces grid impedance and expected fault current is over 45 kA, which exceeds the capacity of a circuit breaker in Korean grid. To reduce the fault current below 45 kA, a HTS power cable having a fault current limiting (FCL) function is considered by as a feasible solution for the interconnection of substations. In this study, a FCL HTS power cable of 600 MVA/154 kV, transmission level class, is considered to reduce the fault current from 63 kA to less than 45 kA by generating an impedance over 1 Ωwhen the fault current is induced. For the thermal design of FCL HTS power cable, a parametric study is conducted to meet a required temperature limit and impedance by modifying the cable core from usual HTS power cables which are designed to bypass the fault current through cable former. The analysis results give a minimum cable length and an area of stainless steel former to suppress the temperature of cable below a design limit.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.65 no.11
• /
• pp.1800-1805
• /
• 2016

The micro-grid designed as bipolar ${\pm}750V$ low-voltage DC power distribution system demonstrated by KEPRI, demands interconnection of a number of small decentralized power source including variable renewable generator. Therefore, variable researches for the influence of interconnection with the bipolar typed DC grid and these variable power sources are required for superior quality of power distribution. Renewable power generation simulators for the bipolar ${\pm}750V$ low-voltage DC power distribution system are necessary for such researches. In this paper, we carry out a research on the photovoltaic simulator that be actually able to interconnect with a bipolar ${\pm}750V$ low-voltage micro-grid. Simulator for this research is not only able to simulate photovoltaic generation according to weather informations and PV modules characteristics, but also contribute to stabilization of bipolar ${\pm}750V$ low-voltage of the system. Therefore, the simulator was designed to develop a system that can situationally respond to variable control algorithms such as the MPPT control, droop control, EMS power control, etc.