• Proceedings of the KIPE Conference
• /
• 2004.07b
• /
• pp.511-514
• /
• 2004

Proposed about new inverter that can use in PV system in this paper. Multi_level inverter that used inverter makes use of 4 transformers is basis, primary winding of each transformer voltage as can do step_up or step_down to appropriate voltage space tap lake. Put circuit that tap that turn in transformer connects properly according to inhibit signal that sense change of input voltage (output voltage of solar cell place) and transformer secondary voltage controls point of contact of relay so that get into fixed output voltage. As a result, can minimise relative harmonic content despite change width of input voltage are wide because number of output voltage level of multi_level inverter does not decrease. Because proposed circuit manufactures is easy and control is easy and is no burden of cost price rise economically, commercialization expected to do easily and this study examined propriety of action as that compose and experiments proposed circuit.

• Proceedings of the KIEE Conference
• /
• 2009.07a
• /
• pp.1167_1168
• /
• 2009

This paper presents new configuration of a.c. traction power supply system. The proposed system includes autotransformer with variable tab. The voltage drop in traction power supply system can be reduced due to tap change of autotransformer. In this paper, fault current and Impedance is investigated, when fault occurs in traction power supply system.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.8 no.2
• /
• pp.69-76
• /
• 1994

An effective method for reducing the harmonics in double connected modified current source inverter[MCSI] by switching taps on auto transformer is presented in this paper. The proposed system operates as like a 24 step MCSI by adding only tap changing auxiliary circuit which consists of several taps and static switching elements to the 12 step multiple inverter, which is double connected three-phase six-step MCSI with an auto transformer. The basic theories of the proposed inverter systems for analyzing the output waveforms are described. And to optimize the effectiveness of the harmonic reduction, the optimum turn ratio and the tap changing control angle of auto transformer are decided by digital simulation and its validity is verified by experiment. Although the construction of the proposed inverter is very simple, it is clarified that the output waveform of the inverter is almost the same as that of the conventional 24 step multiple inverter under the optimum condition.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.27 no.9
• /
• pp.108-113
• /
• 2013

Change of supply voltage, customer load, output of distributed generation, etc cause voltage change in distribution system. OLTC and SVR are usually used to supply normal voltage at customer. But usage of these devices is inefficient and uneconomical in certain circumstances. To solve this problem, new pole transformer which has automatic tap changer is developed. The transformer changes tap when voltage changes. And it has latch switch and reactor for supplying power without outage. To verify normal operation of tap changer, test is conducted. SVR and 50kVA load is used for test.

• Journal of the Korea Society of Computer and Information
• /
• v.17 no.12
• /
• pp.31-39
• /
• 2012

In this paper, we propose a microprocessor-based automatic voltage regulator(AVR) to reduce consumers' electric energy consumption and to help controlling peak demanding power. Hybrid Switching Automatic Voltage Regulator (HS-AVR) consist of a toroidal core, several tap control switches, display and command control parts. The coil forms an autotransformer which has a serial main winding and four parallel auxiliary windings. It controls the output voltage by changing the combination of the coils and the switches. Relays are adopted as the link switches of the coils to minimize the loss. To make connecting and disconnecting time accurate, relays of the circuit have parallel TRIACs. A software phase locked loop(PLL) has been used to synchronize the timings of the switches to the voltage waveform. The software PLL informs the input voltage zero-crossing and positive/negative peak timing. The traditional voltage transformers and AVRs have a disadvantage of having a large mandatory capacity to accommodate maximum inrush current to avoid the switch contact damage. But we propose a suitable AVR for every purpose in smart grid with reduced size and increased efficiency.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.12
• /
• pp.26-31
• /
• 2017

The conventional method of improving the transient stability in a power system is the use of reactive power compensation devices, such as the STATCOM and SVC. However, this traditional method cannot prevent the rapid voltage collapse brought about by the stalling of the motor due to a system fault. On the other hand, the ESS (Energy Storage System) provides fast-acting, flexible reactive and active power control. The fast-acting power compensation provided by an energy storage system plays a significant role in enhancing the transient stability after a major fault in the power system. In this paper, a method of enhancing the transient stability using an energy storage system is proposed for power systems including a dynamic load, such as a large motor. The effectiveness of the energy storage system compared to conventional devices in enhancing the transient stability of the power system is presented. The results of the simulations show that the simultaneous injection of active and reactive power can enhance the transient stability more effectively.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.4
• /
• pp.2737-2743
• /
• 2015

The wind power plant must be able to produce reactive power at the POI bus of a wind farm connected to power system to keep or control the voltage of POI bus. But, the reactive power capability of wind turbines may not be sufficient to control the voltage of POI bus due to the reactive power losses in connection lines between wind farm and POI bus. The solution of this problem is to install an external STATCOM. The proposed cooperative control method of STATCOM and conventional reactive power compensators such as Switched-shunt and tap changing transformer can control the voltage of POI bus more efficiently. The simulation results are shown that the voltage drop of POI Bus of Test System with the arbitrary load change rate to initial loads is improved more than 60% and the voltage of load bus is maintained more than 95% of rated voltage.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.23 no.2
• /
• pp.53-61
• /
• 2009

This paper presents the improved voltage regulation method in power distribution system with multiple PV systems. At present, Line Drop Compensator (LDC) method has been used as voltage regulation method of power distribution system, which regulates the voltage using Under Load Tap Changer (ULTC), regarding the power flow of distribution system as one way. However, the method may be not able to regulate the voltage in a permissible range when the power flow is two ways. Thus, in this paper, we present the improved voltage regulation method of power distribution system using the voltage data of the point connected PV systems.

• Proceedings of the KIEE Conference
• /
• 2003.11a
• /
• pp.140-143
• /
• 2003

배전선로에서 부하가 증가함에 따라 주상변압기의 탭 조정만으로는 모든 수용가단 전압을 규정치($220{\pm}6%$) 이내로 유지시킬 수가 없게 된다. 따라서, 수용가단 전압의 품질을 규정치 이내로 유지할 수 있는 보강공사가 필요하게 된다. 현재는 수용가단 전압품질에 문제가 발생하지 않으나, 선로의 부하가 증가 될수록 통과전류의 양이 많아져, 전압강하가 높아지기 때문에 일부 수용가에 저전압이 발생하게 될 가능성이 있게 된다. 여기서는 부하증가(부하증가율 : 1%, 2%, 3%, 4%, 5%)에 대한 대책으로 다음과 같은 3가지 대안을 고려하기로 한다. 본 연구에서는 1) 선로전압조정장치(SVR)의 설치 2) 회선증강(ACSR $95mm^2$ $\rightarrow$ ACSR $160mm^2$) 3) 회선신설(전압강하 5%이상 지점에 회선 추가)에 대한 경제성을 현재가치 환산법에 의해 평가해 보고, 가장 적정한 대안을 제안하여 배전계통 계획 및 운용에 대한 합리적인 투자 대안을 제시한다.