• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.11
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• pp.69-75
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• 2013

This paper proposes a new algorithm for the optimal placement of a step voltage regulator(SVR) in distribution system with Distributed Generators(DG) using a Particle Swarm Optimization(PSO). The objective function of this algorithm is to find optimal placement for minimum loss while maintaining each node voltage fluctuations within upper and lower limits. In the objective function of proposed algorithm, the deviations to reference voltage and the distribution loss are considered. To verify effectiveness of the proposed method, simulation is implemented using MATLAB.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.542-545
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• 1998

This paper presents a new reference voltage generator(RVG) for advanced DRAM's. The proposed RVG with three temperature coefficient is independent of temperature variation, and supply voltage. This is used to shorten leakage current using the boosted sense ground(BSG). This circuit is designed in a 0.8.mu.m nwell CMOS, double-polysilicon, double-metal technology. The simulation resutls in jindependent temperature and supply voltage. In hspice simulation results, temperature dependency of RVG is 130.mu.V/.deg. C and supply voltage dependency is .+-.0.91%, $V_{cc}$ =3.3V.+-. 0.5V.3.3V.+-. 0.5V.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.143-146
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• 2011

A 50-MS/s 10-bit pipelined ADC with 1.2Vpp differential input range is proposed in this paper. The designed pipelined ADC consists of eight stage of 1.5bit/stage, one stage of 2bit/stage, digital error correction block, bias & reference driver, and clock generator. 1.5bit/stage is consists of sub-ADC, DAC and gain stage, Specially, a sample-and hold amplifier (SHA) is removed in the designed pipelined ADC to reduce the hardware and power consumption. Also, the proposed bootstrapped switch improves the Linearity of the input analog switch and the dynamic performance of the total ADC. The reference voltage was driven by using the on-chip reference driver without external reference. The proposed pipelined ADC was designed by using a 0.18um 1-poly 5-metal CMOS process with 1.8V supply. The total area including the power decoupling capacitor and power consumption are $0.95mm^2$ and 60mW, respectively. Also, the simulation result shows the ENOB of 9.3-bit at the Nyquist sampling rate.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.7
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• pp.550-555
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• 1999

This paper deals with the effect of lightning impulse current on electrical characteristics of ZnO blocks used in distribution lightning arrester. The electrical characteristics of ZnO blocks are degraded by overtime impulse current, and the degraded ZnO block is brought to a thermal runaway and finally destroyed. It is therefore important to estimate the change of electrical characteristics of ZnO blocks. In this study, an impulse current generator which can produce 8/20$[\mus]$, 3[㎄] and 4/10$[\mus]$, 5[㎄] waveform is designed and fabricated to simulate the lightning impulse current of power systems. Total energy applied to the ZnO blocks at each time is 739[J] in 8/20$[\mus]$, and 523[J] in 4/10$[\mus]$, impulse current, respectively. From the experimental results, the 3rd harmonic of the leakage current increases continuously with the number of applied impulse current, but no significant changes in residual voltage and in reference voltage are observed until the ZnO block is destroyed. Also, it is confirmed that the main factor on degradation of ZnO blocks is rather the total energy applied to ZnO blocks than the peak value of the impulse current.

• Journal of Power Electronics
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• v.10 no.2
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• pp.194-202
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• 2010

The main cause of degradation in an unbalanced stand-alone doubly-fed induction generator (DFIG) system is negative sequence components that exist in the generated stator voltages. To eliminate these components, a hybrid current controller composed of a proportional-integral controller and a resonant regulator is developed in this paper. The proposed controller is applied to the rotor-side converter of a DFIG system for the purpose of compensating the negative stator voltage sequences. The proposed current controller is implemented in a single positive rotating reference frame and therefore the controller can directly regulate both the positive and negative sequence components without the need for sequential decomposition of the measured rotor currents. In terms of compensation capability and accuracy, simulations and experimental results demonstrated the excellent performance of the proposed control method when compared to conventional vector control schemes.

• Journal of Power Electronics
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• v.16 no.4
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• pp.1551-1564
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• 2016

The high penetration level of inverter-based distributed generation (DG) power plants is challenging the low-voltage ride-through requirements, especially under unbalanced voltage sags. Recently, a flexible injection of both positive- (PS) and negative-sequence (NS) reactive currents has been suggested for the next generation of grid codes. This can enhance the ancillary services for voltage support at the point of common coupling (PCC). In light of this, considering distant grid faults that occur in a mainly inductive grid, this paper proposes a complete voltage support control scheme for the interface inverters of medium or high-rated DG power plants. The first contribution is the development of a reactive current reference generator combining PS and NS, with a feature to increase the PS voltage and simultaneously decrease the NS voltage, to mitigate voltage imbalance. The second contribution is the design of a voltage support control loop with two flexible PCC voltage set points, which can ensure continuous operation within the limits required in grid codes. In addition, a current saturation strategy is also considered for deep voltage sags to avoid overcurrent protection. Finally, simulation and experimental results are presented to validate the effectiveness of the proposed control scheme.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.10
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• pp.2237-2246
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• 2012

A bias circuit required for an oral sensor is manufactured inside the oral sensor chip to reduce its size and cost. The proposed DC-DC converter supplies the required reference and bias currents for their corresponding regulators by using IREF of the reference current generator. Their target voltages of the voltage regulators are regulated by the negative mechanism by generating their reference voltages required for their corresponding regulators. In addition, a constant current IB0/IB1 is supplied by being mirrored by a current mirror ratio and then VREF is generated. It is confirmed by measurements that the average volatge, ${\sigma}$, and $4{\sigma}$ of the designed DC-DC converter for intra oral sensors with a $0.18{\mu}m$ X-ray CMOS process are within their required ranges. And the line-pair pattern image shows a high-resolution characteristic without blurring. Also, a good oral image can be obtained.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.669-671
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• 2004

This paper presents a MIMO nonlinear controller for the power system consisting of a turbine and a synchronous generator connected to an infinite bus. The controller proposed is based on feedback input-output linearization; its main goal is to regulate the terminal voltage and frequency, and is to improve the transient stability under large disturbances and unexpected faults. It is guaranteed that the voltage converges to its reference value exponentially, and that the frequency and the mechanical/electrical power are bounded. The design procedure is tested on a single machine infinite bus power system through simulations, and is seen to be effective.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.55 no.1
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• pp.21-25
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• 2006

This paper describes the novel control techniques design of VSC(Voltage Sag Corrector) for the purpose of power line quality enhancement. A fast detecting technique of voltage sag is implemented through the detection of instantaneous value on synchronous rotating do-reference frame. The first order digital filter is added in the detection algorithm to protect the insensitive characteristics against the noise. The relationship between the total detection time and cut-off frequency of the filter is described. The size of the capacitor bank used as the energy storage element is designed from the point of view of input/output energy with circuit analysis. Finally, the validity of the proposed scheme is proven through the simulated results.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.907-909
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• 1998

This paper describes the effect of impulse current on degradation of ZnO blocks. In this study, an impulse current generator which can produce 8/20 [${\mu}s$], 3 [kA] and 4/10 [${\mu}s$], 5 [kA] waveform is designed and fabricated to simulate the lightning impulse current. The residual voltage, reference voltage, and leakage current flowing to the ZnO blocks are observed. The experimental results show that the leakage current increases continuously with the number of applied impulse current, but no significant changes in residual voltage and in operating voltage are observed until the ZnO block is destroyed. Also, it is confirmed that the main factor on degradation of ZnO blocks is rather the total energy applied to ZnO blocks than the peak value of the impulse current.