• Journal of Electrical Engineering and Technology
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• v.4 no.3
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• pp.310-314
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• 2009

This paper presents the improvement of the voltage profiles of power system networks by the inclusion of Unified Power Flow Controller (UPFC). The mathematical model of the UPFC is incorporated in the load flow algorithm and the L-index is calculated for the different values of the control parameter r $and{\gamma}$. The positioning of the UPFC device is changed to minimize the sum of the squares of the L-indices at all load buses. The test cases considered for the improvement of voltage profile with the WSCC 9-bus and IEEE 30 bus system. With the best position of UPFC along with the control parameters the improvement in voltage profile of the power system networks are obtained. The results obtained are quite encouraging compared with other techniques used to identify the best location of UPFC.

• Journal of Electrical Engineering and Technology
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• v.4 no.4
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• pp.492-498
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• 2009

The placement of the UPFC is the major concern to ensure the full potential of utilization in the transmission network. Voltage stability enhancement with the optimal placement of UPFC using stability index such as modal analysis, Voltage Phasor method is made and the loss minimization including UPFC is formulated as an optimization problem. This paper proposes particle swarm optimization for the exact real power loss minimization including UPFC. The implementation of loss minimization for the optimal location of UPFC was tested with IEEE-14 and IEEE-57 bus system.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.147-150
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• 2005

Low actuation voltage and no contact stiction are the important factors to apply MEMS RF switches to mobile devices. Conventional electrostatic MEMS RF switches require several tens of voltages for actuation. In this paper we propose PAS MEMS RF switch which adopt PZT actuators and seesaw cantilevers to meet the above requirements. The fundamental structures of PAS MEMS switch were designed, optimized, and fabricated. Through the developed processes PAS SPDT MEMS RF switches were successfully fabricated on 4" wafers and they showed good electrical properties. The driving voltage was less than 5 volts. And the insertion loss was -0.5dB and the isolation was 35dB at 5GHz. The switching speed was about 5kHz. So these MEMS RF switches can be applicable to mobile communication devices or wireless multi-media devices at lower than 6GHz.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.349-352
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• 2001

FACTS technology is developed into the sophisticated system technology which combines conventional power system technology with power electronics, micro-process control, and information technology. Its objectives are achieving enhancement of the power system flexibility and maximum utilization of the power transfer capability through improvements of the system reliability, controllability, and efficiency [1]. As a series and shunt compensator, UPFC consists of two inverters with common dc link capacitor bank. It controls the magnitude of shunt bus voltage and real and reactive power flow of transmission line[2]. In this paper, we present the design, implementation and test results of developed 20kVA level prototype UPFC. It is applied to power system simulator and controls the real and reactive power flow and shunt bus voltage magnitude.

• Journal of Electrical Engineering and Technology
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• v.11 no.2
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• pp.329-337
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• 2016

With the increasing deployment of distributed generators in the distribution system, a very large search space is required when dynamic programming (DP) is applied for the optimized dispatch schedules of voltage and reactive power controllers such as on-load tap changers, distributed generators, and shunt capacitors. This study proposes a new optimal voltage and reactive power scheduling method based on dynamic programming with a heuristic searching space reduction approach to reduce the computational burden. This algorithm is designed to determine optimum dispatch schedules based on power system day-ahead scheduling, with new control objectives that consider the reduction of active power losses and maintain the receiving power factor. In this work, to reduce the computational burden, an advanced voltage sensitivity index (AVSI) is adopted to reduce the number of load-flow calculations by estimating bus voltages. Moreover, the accumulated switching operation number up to the current stage is applied prior to the load-flow calculation module. The computational burden can be greatly reduced by using dynamic programming. Case studies were conducted using the IEEE 30-bus test systems and the simulation results indicate that the proposed method is more effective in terms of saving electric charges and improving the voltage profile than loss minimization.

• Journal of Power Electronics
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• v.4 no.3
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• pp.138-151
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• 2004

In this paper, a constant frequency phase shifting PWM-controlled voltage source full bridge-type series load resonant high-frequency inverter using the $4^{th}$ generation IGBT power modules is presented for innovative consumer electromagnetic induction heating applications, such as a hot water producer, steamer and super heated steamer. The bridge arm side link passive capacitive snubbers in parallel with each power semiconductor device and AC load side linked active edge inductive snubber-assisted series load resonant tank soft switching inverter with a constant frequency phase shifted PWM control scheme is evaluated and discussed on the basis of the simulation and experimental results. It is proved from a practical point of view that the series load resonant and edge resonant hybrid high-frequency inverter topology, what is called, DE class type, including the variable-power variable-frequency regulation function can expand zero voltage soft switching commutation area even under low output power setting ranges, which is more suitable and acceptable for newly developed induction heated dual pack fluid heaters. Furthermore, even the lower output power regulation mode of this high-frequency load resonant tank inverter circuit is verified so that this inverter can achieve ZVS with the aid of the single auxiliary inductor snubber.

• Proceedings of the KIEE Conference
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• 2003.10a
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• pp.65-67
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• 2003

This paper describes a design of power supply for electrodeless lamp system to be easy to control electric power widely keeping the high power factor. Proposed system is composed of power factor correction(PFC) circuit, half bridge(HB) inverter, high voltage transformer, full wave rectifier to supply dc number kV's magnetron(MGT) anode voltage in the second of high voltage transformer and magnetron. It was confirmed that the proposed circuits can correct the 99.8[%] power factor and control input power of the magnetron up to 33.3[%] linearly by adjusting of pulse frequency of the inverter through the experiment.

• Bulletin of the Korean Chemical Society
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• v.28 no.3
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• pp.391-396
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• 2007

The three-dimensional structure of an inorganic crystal, CaMoO4 (space group I 41/a, a = 5.198(69) A and c = 11.458(41) A), was determined by electron crystallography utilizing a high voltage electron microscope. An initial structure of CaMoO4 was determined with 3-D electron diffraction patterns. This structure was refined by crystallographic image processing of high resolution TEM images. X-ray crystallography of the same material was performed to evaluate the accuracy of the TEM structure determination. The cell parameters of CaMoO4 determined by electron crystallography coincide with the X-ray crystallography result to within 0.033-0.040 A, while the atomic coordinates were determined to within 0.072 A.

• Journal of Power Electronics
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• v.14 no.4
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• pp.704-711
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• 2014

This paper proposes a combined fuzzy adaptive sliding-mode voltage controller (FASVC) for a three-phase UPS inverter. The proposed FASVC encapsulates two control terms: a fuzzy adaptive compensation control term, which solves the problem of parameter uncertainties, and a sliding-mode feedback control term, which stabilizes the error dynamics of the system. To extract precise load current information, the proposed method uses a conventional load current observer instead of current sensors. In addition, the stability of the proposed control scheme is fully guaranteed by using the Lyapunov stability theory. It is shown that the proposed FASVC can attain excellent voltage regulation features such as a fast dynamic response, low total harmonic distortion (THD), and a small steady-state error under sudden load disturbances, nonlinear loads, and unbalanced loads in the existence of the parameter uncertainties. Finally, experimental results are obtained from a prototype 1 kVA three-phase UPS inverter system via a TMS320F28335 DSP. A comparison of these results with those obtained from a conventional sliding-mode controller (SMC) confirms the superior transient and steady-state performances of the proposed control technique.

• Journal of Information Display
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• v.2 no.3
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• pp.13-17
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• 2001

The manganese-doped magnesium tin oxide with spinel structure was selected as a green phosphor for FED application and was synthesized by the solid state reaction. Its luminescence properties were investigated under low-voltage electron excitation. The $Mg_2SnO_4$:Mn phosphor showed green emission with the spectrum centered at 500 nm due to energy transfer from $^4T_1$ to $^6A_1$ of $Mn^{2+}$ ion. Optimum Mn concentration was 0.6 mole % and the decay time was shorter than 10 ms.