• Journal of information and communication convergence engineering
• /
• 제13권1호
• /
• pp.1-6
• /
• 2015

In this study, we consider visible light communication in an indoor line-of-sight environment. It has been proved that among the multiple input multiple output (MIMO) techniques, spatial modulation (SM) performs better than repetition coding (RC) and spatial multiplexing (SMP). On the basis of a combination of SM and pulse amplitude modulation (PAM), here, we propose an enhanced SM algorithm to improve the bit error rate. Traditional SM activates only one light-emitting diode (LED) at one time, and the proposed enhanced SM activates two LEDs at one time and reduces the intensity levels of PAM by half. Under the condition of a highly correlated channel, power imbalance is used to improve the algorithm performance. The comparison between the two schemes is implemented at the same signal-to-noise ratio. The simulation results illustrate that the enhanced SM outperforms the traditional SM in both highly correlated and lowly correlated channels. Furthermore, the proposed enhanced SM scheme can increase the transmission rate in most cases.

• Journal of Power Electronics
• /
• 제15권2호
• /
• pp.504-517
• /
• 2015

This paper presents a novel switching voltage model and an offset-based pulse width modulation (PWM) scheme for multilevel inverters with unbalanced DC sources. The switching voltage model under a DC voltage imbalance will be formulated in general form for multilevel neutral-point-clamped topologies. Analysis of the reference switching voltages from active and non-active switching voltage components in abc coordinates can enable voltage implementation for an unbalanced DC-source condition. Offset voltage is introduced as an indispensable variable in the switching voltage model for multilevel voltage-source inverters. The PWM performance is controlled through the design of two offset components in a subsequence. One main offset may refer to the common mode voltage, and the other offset restricts its effect on the quality of PWM control in related DC levels. The PWM quality can be improved as the switching loss is reduced in a discontinuous PWM mode by setting the local offset, which is related to the load currents. The validity of the proposed algorithm is verified by experimental results.

• Journal of Power Electronics
• /
• 제19권1호
• /
• pp.89-98
• /
• 2019

This paper analyzes the input side performance of a conventional three-phase to single-phase matrix converter (3-1MC). It also presents the input-side waveform quality under this topology. The suppression of low-frequency input current harmonics is studied using the 3-1MC plus capacitance compensation unit. The constraint between the modulation function of the output and compensation sides is analyzed, and the relations among the voltage utilization ratio and the output compensation capacitance, filter capacitors and other system parameters are deduced. For a 3-1MC without large-capacity energy storage, the system performance is susceptible to input voltage imbalance. This paper decouples the inner current of the 3-1MC using a Lyapunov function in the input positive and negative sequence bi-coordinate axes. Meanwhile, the outer loop adopts a voltage-weighted synthesis of the output and compensation sides as a cascade of control objects. Experiments show that this strategy suppresses the low-frequency input current harmonics caused by input voltage imbalance, and ensures that the system maintains good static and dynamic performances under input-unbalanced conditions. At the same time, the parameter selection and debugging methods are simple.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2000년도 전력전자학술대회 논문집
• /
• pp.739-743
• /
• 2000

With significant development of power electronics technology the proliferation of nonlinear loads such as such as static power converters has deteriorated power quality in power transmission distribution systems. Notably voltage harmonics resulting from current harmonies produced by the nonlinear loads have become a serious problem in many systems Moreover momentary interruptions and voltage sags are responsible for many of the power quality problems found in typical industrial plants. Int his paper proposed 3 phase hybrid series active power filter is not only for harmonic compensation but also for harmonic isolation between supply and load and for voltage regulation and imbalance compensation Through computer simulations we have verified the effectiveness of the proposed system.

• Journal of Electrical Engineering and Technology
• /
• 제1권4호
• /
• pp.503-512
• /
• 2006

This paper proposes a new configuration for the Unified Power Quality Conditioner, which has a DC/DC converter with super-capacitors for energy storage. The proposed UPQC can compensate the reactive power, harmonic current, voltage sag and swell, voltage imbalance, and voltage interruption. The performance of the proposed system was analyzed through simulations with PSCAD/EMTDC software. The feasibility of system implementation is confirmed through experimental works with a prototype. The proposed UPQC has ultimate capability to improve the power quality at the point of installation on power distribution systems and industrial power systems.

• 한국정보통신학회논문지
• /
• 제24권5호
• /
• pp.666-669
• /
• 2020

Energy harvesting sensor networks have the ability to collect energy from the environment to overcome the power limitations of traditional sensor networks. The sensor network, which has a limited transmission range, delivers data to the destination node through a multi-hop method. The routing protocol should consider the power situation of nodes, which is determined by the residual power and energy harvesting rate. At this time, if only considering the magnitude of the power, power imbalance can occur among nodes and it can induce instantaneous power shortages and reduction of network lifetime. In this paper, we designed a routing protocol that considers the balance of power as well as the residual power and energy harvesting rate.

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제15권6호
• /
• pp.629-633
• /
• 2015

An active balun using current steering for phase correction is presented. The proposed active balun is constructed with two different unit balun structures based on current steering to reduce phase and amplitude errors. This type of topology can be compared with the conventional phase and amplitude correction techniques which do not incorporate the current steering. Designed and fabricated active balun in $0.18{\mu}m$ CMOS process operates over 0.95 - 1.45 GHz band, showing input reflection coefficient under -15 dB, phase error of $11^{\circ}$ and gain error of 0.5 dB. Gain is measured to be 0.3 dB maximum and power consumption of 7.2 mW is measured.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2019년도 전력전자학술대회
• /
• pp.186-188
• /
• 2019

현재 신재생에너지 발전원은 계속 증가되고 있으며, 발전기의 용량 또한 점점 증가하고 있다. 늘어나는 신재생에너지 발전원에 의해 계통 연계의 중요성이 증대되고 있고 아울러 계통에서 발생할 수 있는 여러 가지 사고로 인한 발전기의 PCS의 고장에 대한 문제 또한 중요해지고 있다. 본 논문에서는 신재생발전원의 용량이 증가함에 따라서 각 스위치의 전기적 스트레스를 줄일 수 있는 3-level NPC 타입의 컨버터회로를 기반으로 이중 전류 제어기를 이용하였고, 계통 사고시에도 강인한 위상 추종 특성을 가지는 DDSRF(Decoupled Double Synchronous Reference Frame 이하 DDSRF)방식의 PPL을 채택하여 시뮬레이션을 진행하였다. 현재 계통의 사고에 의한 사고전압은 ABC 분류에 의해서 크게 A~G 타입으로 나타내고 있다. 본 논문에서는 각 타입별 사고전압의 불평형 지수(Imbalance Factor, 이하 IF)에 따른 중성점 전류의 고조파 성분을 분석하여 도식화 하고자 한다. 이는 계통사고 발생 시 계통연계형 컨버터의 제어 및 계통탈락 여부에 활용 할 수 있을 것으로 예상된다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2003년도 추계학술대회 논문집 전력기술부문
• /
• pp.34-37
• /
• 2003

The frequency of power system will change when the load-generation equilibrium is disturbed. Insufficiency of generation from the imbalance between load and generation decreases the power system frequency. In case of the severe emergency, the under frequency load shedding scheme is applied for the power system defense plan. In this paper, we analyzed the dynamic characteristics of under frequency load shedding using new Transient Security Assessment Tool ; TSAT. We applied the actual UFLS scheme to these studies and considered the possible contingency.

• KEPCO Journal on Electric Power and Energy
• /
• 제8권2호
• /
• pp.143-149
• /
• 2022

As ESS safety issues increase recently, there is a need to more precisely monitor the temperature of the ESS. In this paper, DTS technology for temperature monitoring of ESS batteries is introduced and the temperature measurement principle is explained. The temperature of the battery module is measured using the DTS system, and the thermal deviation between battery cells inside the battery module is analyzed. In order to analyze how thermal imbalance affects the charging and discharging performance of the battery, an accelerated degradation test was conducted. Cycle life characteristics analysis, battery surface temperature change, and AC impedance characteristics were conducted to analyze how the performance of battery cells differs according to temperature conditions.