• Journal of Power Electronics
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• v.18 no.2
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• pp.640-650
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• 2018

A TRIAC dimmable LED driver with a wide tuning range and a two-stage uniform dimming scheme is proposed in this paper. To solve the restricted dimming range problem caused by the limited conduction ratio of TRIAC dimmers, a conduction ratio compensation technique is introduced, which can increase the output current up to the rated output current when the TRIAC dimmer turns to the maximum conduction ratio. For further optimization, a two-stage uniform dimming diagram with a rapid dimming curve and a slow dimming curve is designed to make the LED driver regulated visually uniform in the whole adjustable range of the TRIAC dimmer. The proposed control chip is fabricated in a TSMC $0.35{\mu}m$ 5V/650V CMOS/LDMOS process, and verified on a 21V/500mA circuit prototype. The test results show that, in the 90V/60Hz~132V/60Hz ac input range, the voltage linear regulation is 2.6%, the power factor is 99.5% and the efficiency is 83%. Moreover, in the dimming mode, the dimming rate is less than 1% when the maximum dimming current is 516mA and the minimum dimming current is only about 5mA.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.709-718
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• 2015

Traditional transmission planning usually caters for rated wind power output. Due to the low occurrence probability of nominal capacity of wind power and huge investment in transmission, these planning methods will leads to low utilization rates of transmission lines and poor economic efficiency. This paper provides a novel transmission expansion planning method for integrating large-scale wind power. The wind power distribution characteristics of large-scale wind power output and its impact on transmission planning are analyzed. Based on the wind power distribution characteristics, this paper proposes a flexible and economic transmission planning model which saves substantial transmission investment through spilling a small amount of peak output of wind power. A methodology based on Benders decomposition is used to solve the model. The applicability and effectiveness of the model and algorithm are verified through a numerical case.

• Journal of Power Electronics
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• v.16 no.5
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• pp.1894-1903
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• 2016

In general, electrolytic capacitors are used to reduce power pulsations on PV-panels. However, this can reduce the reliability of the PV AC-module system, because electrolytic capacitors have a shorter lifetime than PV-panels. In addition, PV-panels generate irregular power and inject it into the grid because the output power of a PV-panel depends on the surrounding conditions such as irradiation and temperature. To solve these problems, a grid-connected photovoltaic (PV) AC-module with active power decoupling and energy storage is proposed. A parallel bi-directional converter is connected to the AC module to reduce the output power pulsations of PV-panels. Thus, the electrolytic capacitor can be replaced with a film capacitor. In addition, the irregular output power due to the surrounding conditions can be regulated by using a parallel energy storage circuit. To maintain the discontinuous conduction mode at low irradiation, the frequency control method is adopted. The design method of the proposed converter and the operation principles are introduced. An experimental prototype rated at 125W was built to verify the performance of the proposed converter.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.11
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• pp.511-518
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• 2005

This paper presents the design and drive characteristics of a switched reluctance motor for an electric power pallet vehicle. The designed switched reluctance motor is redesigned by using the finite element analysis(FEA) as a variation of the pole-arc angle for the purpose of an electric power pallet vehicle performance. The output power and torque characteristics of a switched reluctance motor are variable by switching angles of the commutator. Therefor this paper is studied about relationship between the output power and torque characteristics of a switched reluctance motor according to switching angles. The output power of the characteristic point of an electric power pallet vehicle has been shown by experiment. The designed motor drive system operates with the low voltage and high current with using the battery. The core and frame temperatures were described. In this paper, the designed motor is shown better drive characteristics than the DC motor from the rated to maximum, which is verified by the finite element analysis and experimental results.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.6
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• pp.527-534
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• 2017

This paper proposes a new DC link voltage controller for a single-phase power factor correction (PFC) boost converter. The load current of the PFC boost converter affects the capacitor current, whereas the load current changes the output voltage. However, previous works that compensate output current have failed to consider the relationship between load current and duty. Thus, they also fail to maintain a constant output voltage if the load fluctuates under the conditions of a non-rated input voltage. By considering the duty in the load current compensation, the proposed method improves the load transient response regardless of the input voltage. To demonstrate its effectiveness, the proposed method is compared with other control methods by conducting PSM simulations and experiments under a rapidly changing load.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.4_2
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• pp.443-451
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• 2021

It is essential to examine and analyze the power output and load responses together using real-world turbulent wind speeds. In this paper, the power controller and the drive train damper are simultaneously considered using the NREL 5MW wind turbine model, and the damage equivalent load(DEL) of the low speed shaft torque and power output responses according to the natural frequency of the second order low pass filter are simultaneously investigated. Numerical testing is carried out above rated wind speed using commercially available Bladed software. From the viewpoints of DEL reduction of the drive train shaft torque and power output responses, it is shown that the natural frequency of the low pass filter is appropriately about 6 to 10rad/s. And the reduction ratio of the DEL of the low-speed shaft torque decreases as the wind speed becomes higher, and it is confirmed that the reduction ratio is limited to about 20% at high wind speeds.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.2
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• pp.165-173
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• 2022

The electrification trend of mobility increases every year due to the development of power semiconductor and battery technology. Accordingly, the development and distribution of fast chargers for electric vehicles (EVs) are in demand. In this study, we propose a design and implementation method of an LLC converter for fast chargers. Two 15 kW LLC converters are configured in parallel to have 30 kW rated output power, and the control algorithm and driving sequence are designed accordingly and verified. In addition, the improved power conversion efficiency is confirmed through zero-voltage switching (ZVS) of the LLC converter and reduction of turn-off loss through snubber capacitors. The implemented 30 kW LLC converters show a wide output voltage range of 200-950 V. Experiments applying various load conditions verify the converter performance.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.4
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• pp.254-259
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• 2014

In this paper, we describe construction of a wind stabilization demo-site and effects of output power control of wind turbines for suppression of ramp rate using ESS (Energy Storage System). It is difficult to control the output power of distributed generator such as wind turbine which of variation is very large. If the large capacity wind farm be interconnected into power system may cause blackout due to Power Quality. For these reasons, the international standards such as Grid-Code is limited to less than 10 [%/min] of renewable energy ramp rate. The case of Korea, government actively conducts propagating large-scale renewable energy for green growth policy, to interconnecting more renewable energy into power system is necessary for stabilization technology. For these reasons, the POSCO consortium has constructed a wind stabilization demo-site that is configured as 500 [kWh] battery energy storage systems can output up to 3 [C-Rate] and two wind turbines rated 750 [kW]. In POSCO consortium, which implements various methods stabilizing output power of wind turbine such as smoothing, section firming and ramp control, we derive the results of long-term demonstration that can be controlled to satisfy to the international standard about ramp rate [%/kW] of wind turbine output power.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.4
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• pp.309-316
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• 2016

In this study, we described the design of a three-axis force/torque sensor for measuring the force and torque in a lower-limb rehabilitation robot. The three-axis force/torque sensor is composed of Fx force sensor, Fz force sensor and Tz torque sensor. The sensing element for Fx force sensor and Tz torque sensor is used in a two-step parallel plate beam, and that of Fz force sensor is used in a parallel plate beam. The rated loads of Fx force sensor, Tz torque sensor and Fz force sensor are 300 N, 15 N m and 100 N, respectively. The three-axis force/torque sensor was designed using the finite element method, and manufactured using strain-gauges. The three-axis force sensor was further characterized. As a result, the interference error of the three-axis force/torque sensor was < 1.24%, the repeatability error of each sensor was < 0.03%, and the non-linearity was < 0.02%.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1320-1321
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• 2011

According to the advance that solar power plants go into the desert, power plants are getting greater capacity. The desert is unspoiled resources and it is well suited to build a solar power plant, because of abundant solar radiation and long sunshine duration. but existing PV modules have several weaknesses and don't generate lower the rated power, because it wasn't designed to produce in extreme environments like a desert climate. The one of the weaknesses of PV modules is that the characteristics of the temperature of the Encapsulants(EVA sheet) are not good in a desert climate, because the EVA sheet is melt at high temperature. In this study, a decrease phenomenon of the transmittance depending on the melting point of the Encapsulant(PV module using EVA sheet : $75^{\circ}C$ PV module using PVB film : $110^{\circ}C$) is suggested, it would be the one of the important factors to achieve rated output of the PV modules in high temperature climate regions.