• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.54 no.5
• /
• pp.251-258
• /
• 2005

Recently, the domestic and foreign power trends are the supply of high quality power and environment conservation technology based on the new energies development. So, the dispersed generation systems, such as photovoltaic, fuel cell, and battery are to be introduced in distribution systems. According to the situation change, power of high Quality and reliability are required in distribution systems with dispersed generation. Up to now, the voltage in distribution systems are regulated by ULTC of substation and pole transformer of primary feeders. These days, Step Voltage Regulator(SVR) is getting established at distribution feeders to regulate effectively voltage of primary ffeders that voltage drop exceeds $5\%$. But, because SVR is operated independently with ULTC of substation, SVR can not take play to its full effectivity. Under these circumstances, in order to deliver suitable voltages to as many customers as possible, new optimal voltage regulation algorithms are required in distribution system. So, this paper presents optimal voltage regulation algorithm to regulate voltage effectively for ULTC and SVR in distribution systems with dispersed generation systems.

• Journal of Power Electronics
• /
• v.9 no.6
• /
• pp.835-844
• /
• 2009

In this paper a new buck-boost type DC-DC converter is presented. Its voltage gain is positive, all active elements operate under soft-switching condition independent of loading, magnetic isolation and self output short-circuit protection exist, and very fast dynamic operation is achievable by a simple bang-bang controller. This converter also exhibits appropriate PFC characteristics since its input current is inherently proportional to the source voltage. When the voltage source is off-line, it is sufficient to add an inductor after the rectifier, then near unity power factor is achievable. All essential guidelines to design the converter as a DC-DC and a PFC regulator are presented. Simulation and experimental results verify the developed theoretical analysis.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.8 no.4
• /
• pp.748-757
• /
• 2007

This paper is intended to solve the technical problem that fails in large-capacity induction motor starting due to serious voltage drop during starting period. One induction motor that is established already can reach in steady-state using reactor starting method but the voltage magnitude of PCC (point of common coupling) has dropped down a little. When the same capacity induction motor is installed additionally in the PCC, where the existing induction motor is operating, voltage drop becomes more serious by starting of additional induction motor. As a result, the additional induction motor fails in starting. Therefore, voltage compensation method is proposed so that all of two induction motors can be started completely. First, modeling technique is described in order to implement starting characteristics of large induction motor. And then, this paper proposes strategic starting scheme by proper voltage compensation that use no-load transformer tap control (NLTC) and step voltage regulator (SVR) for starting of two large induction motors successfully and improving the feeding network voltage profile during the starting period. The induction motor discussed in this paper is the pumped induction motor of 2500kVA capacity that is operating by KOWACO (Korea Water Resources Corporation). Modeling and simulation is conducted using PSCAD/EMTDC software.

• Journal of Electrical Engineering and Technology
• /
• v.3 no.3
• /
• pp.354-362
• /
• 2008

In this paper, a new algorithm of optimal voltage control is proposed for the Distribution Automation System (DAS) based on constants of four terminal network modeling. In the proposed method, the voltage profiles along feeders are estimated from the measurement of the current and power factor by a Feeder Remote Terminal Unit (FRTU) installed at each node. Whenever the voltage profile violates the restriction, the voltage control strategy is applied to keep the voltage levels along the feeders within the pre-specified range through the modification and coordination of the transformer under-load tap changers (ULTC), step voltage regulator (SVR), as well as shunt condenser. In the case studies, the estimation and control of the voltages have been testified in a radial distribution system with 11 nodes.

• Journal of Power Electronics
• /
• v.4 no.1
• /
• pp.18-27
• /
• 2004

The output storage capacitor of the PFC converters is commonly designed for the selected hold-up time or the allowed output ripple voltage percentage. Nevertheless, this output capacitor is a main contribution factor to the PFC system stability. Moreover, seeking for a minimum output storage capacitor that assures the PFC desired operation under all condition, and providing the advantage of a small size and low cost is the main interesting target for engineering. Therefore, in this issue the design steps of the PFC converter have been discussed depending on three choices, output ripple, hold-up time, and stability. It is cleared that any design must take the minimum required storage capacitor for stability prospective as step-l in deign, then apply for any other specification like hold-up time or ripple percentage.

• Proceedings of the KAIS Fall Conference
• /
• 2010.05a
• /
• pp.67-70
• /
• 2010

국가차원의 신 재생에너지 활성화 방안에 따라 태양광, 풍력발전 등의 대규모 분산전원 단지의 도입이 이루어지고 있으며, 현재 배전계통의 전압조정 방법은 배전용 변전소의 부하시 탭 절환기(Under Load Tap Changer, 이하 ULTC)와 배전선로의 선로전압조정장치(Step Voltage Regulator, 이하 SVR)로 수용가에 규정전압(220${\pm}$6%)을 만족시키는 전압을 공급한다. 하지만 대규모의 태양광, 풍력 등의 분산 전원이 배전계통에 도입되는 경우, 전력품질[과전압/저전압]의 문제가 발생된다. 본 논문에서는 부하율에 따라 변화된 LDC 정정치를 적용 및 시뮬레이션을 통한 수용가 직하 및 말단의 규정전압(220${\pm}$6%) 즉 207V이하의 저전압, 233V이상의 과전압 여부를 검증함으로써 전력품질을 유지 할 수 있는 태양광전원이 연계된 배전계통의 최적전압운용 알고리즘을 개발하였다.

• Proceedings of the KIEE Conference
• /
• 2004.11b
• /
• pp.5-8
• /
• 2004

최근 생활수준의 향상과 정보통신 산업의 급속한 발전으로 인하여 전세계적으로 전력품질에 대한 관심이 높아져, 각종 전력품질 개선장치로부터 최적 공급시스템에 이르기까지 다양한 각도에서 전력품질을 향상하기 위한 연구개발이 수행되고 있으며, 특히 정보통신기기 및 정밀제어기기 등의 보급증가로 전압품질에 대한 관심이 높아져가고 있다. 지금까지 배전계통의 전압관리는 배 전용변전소 ULTC(Under Load Tap Changer)와 고압배전선로의 주상변압기에 의해 조정되어 왔으며 최근에 고압배전선로의 전압강하가 5%를 초과하는 선로에 대한 효율적 전압관리를 위해 선로전압조정장치(SVR- Step Voltage Regulator)가 도입되고 있다. 그러나 배 전용변전소와 고압배전선로의 선로전압 조정장치가 서로 독립적으로 운용되고 있기 때문에 선로전압조정장치의 효율성이 떨어지고 있는 실정이다. 그러므로 본 논문에서는 배 전용변전소와 선로전압조정장치의 ULTC 송출전압의 최적 전압조정을 위한 협조운용 방안을 제시하고자 한다.

• Proceedings of the KIEE Conference
• /
• summer
• /
• pp.94-97
• /
• 2004

최근 생활수준의 향상과 정보통신 산업의 급속한 발전으로 인하여 전세계적으로 전력품질에 대한 관심이 높아져, 각종 전력품질 개선장치로부터 최적 공급시스템에 이르기까지 다양한 각도에서 전력품질을 향상하기 위한 연구개발이 수행되고 있으며, 특히 정보통신기기 및 정밀제어기기 등의 보급증가로 전압품질에 대한 관심이 높아져가고 있다. 지금까지 배전계통의 전압관리는 배전용 변전소 ULTC(Under Load Tap Changer)와 고압배전선로의 주상변압기에 의해 조정되어 왔으며 최근에 고압배전선로의 전압강하가 $5\%$를 초과하는 선로에 대한 효율적 전압관리를 위해 선로전압조정장치(SVR- Step Voltage Regulator)가 도입되고있다. 그러나 배전용 변전소 ULTC와 고압배전선로의 SVR이 서로 독립적으로 운용되고 있기 때문에 SVR의 효율성이 멀어지고 있는 실정이다. 그러므로 본 논문에서는 변전소 ULTC와 SVR 송출전압의 최적 전압조정을 위한 협조운용 방안을 제시하고자 한다.

• Journal of Satellite, Information and Communications
• /
• v.7 no.3
• /
• pp.135-139
• /
• 2012

A digital controller can simply realize a complex operation algorithm and power control process which can not be applied by an analog circuit for a solar array regulator(SAR). The digital resistive control(DRC) makes an equivalent input impedance of the SAR be resistive characteristic. The resistance of the solar array varies largely in a voltage source region and slightly in a current source region. Therefore when the solar array regulator is controlled by the DRC, the Advanced Incremental Conductance MPPT Algorithm with a Variable Step Size(AIC-MPPT-VSS) is suitable. The AIC-MPPT-VSS, however, using small signal resistance and large signal resistance of the solar array can not limit the absolute value of the solar array power. In this paper, the solar array power limiter is suggested and the BUCK-BOOST type SAR which is fully controlled by the digital controller is verified by simulation.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.67 no.7
• /
• pp.824-832
• /
• 2018

According to the government's policy to demonstrate and expand the renewable energy sources, distributed generators such as PV and WP are installed and operated in distribution systems. However, there are many issues related to power quality problems including over voltage and under voltage of customers. In order to overcome these problems, the electric power company have installed a step voltage regulator (SVR) in primary feeders interconnected with distributed generators, and also have established the technical guidelines for the distributed generators to stabilize the customer voltages in distribution systems. However, it is difficult to maintain the customer voltages within allowable limit. Therefore, this paper reviews the problems of voltage control by SVR in a distribution systems interconnected with a large amount of PV systems, and proposes characteristics of operating range and voltage control limit of the small hydropower generators. Also, with the estimation of the influence to the power system voltages from the voltage control mode of generators, this paper proposes the optimal voltage control algorithm of the small hydropower generators. By programming the proposed algorithm into control simulator of exciter, it is confirmed that the proposed algorithm can contribute the voltage stabilization in distribution systems interconnected with large scaled PV systems.