• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.720-725
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• 1991

In this thesis, the lead-lag compensator is designed to improve output characteristics of flyback zero voltage switching quasi-resonant converters. The switch and the diode are assumed ideally. And the SMPS is modelled by state equations with four operation modes. And the model for controller design is also achived by using a state space averaging method, which is continuous time average of state variables every period. The lag, the lead and the lead-lag compensator is designed the SMPS respectively. The time domain analysis and the frequency domain analysis are done for each compensated circuit. It is possible increasing the phase margin and improving the transient response by the compensators. The phase lag compensator has small overshoot comparatively. But the bandwidth is narrower than the others, so it has longest settling time. For the phase lead compensator, the response come to steady-state within short period. But the overshoot is the largest due to its large peak gain. Finally, the phase lead-lag compensator has medium characteristics in the overshoot and the settling time.

• Journal of Power Electronics
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• 제11권3호
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• pp.375-380
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• 2011

A STATic synchronous COMpensator (STATCOM) is a shunt connected voltage source converter (VSC) based FACTS controller using Gate Turn Off (GTO) power semiconductor devices employed for reactive power control. The operation principal is similar to that of a synchronous condenser. A typical application of a STATCOM is voltage regulation at the midpoint of a long transmission line for the enhancement of power transfer capability and/or reactive power control at the load centre. This paper presents the modeling of STATCOM with twenty four pulse three level VSC and Type-1 controller to regulate the reactive current or the bus voltage. The performance is evaluated by transient simulation. It is observed that, the STATCOM shows excellent transient response to step change in the reactive current reference. While the eigenvalue analysis is based on D-Q model, the transient simulation is based on both D-Q and 3 phase models of STATCOM (which considers switching action of VSC).

• 수산해양기술연구
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• 제32권1호
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• pp.59-66
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• 1996

This paper considers robust stability and transient behavior of the Two - Degree - of - Freedom(2DOF) servosystem. A class of uncertainties allowed in the plant model is obtained, to which the servosystem is robustly stable for any gain of the integral compensator. This result implies that if the plant uncertainty is the allowable set defined by the condition, a high - gain compensation can be carried out preserving stability to achieve a high - speed tracking response. The transient behavior attainable by the limit of the high - gain compensation is calculated using the singular perturbation approach.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제4B권3호
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• pp.134-145
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• 2004

This paper presents and analyses protection schemes for a series active compensator, which consists of a Unified Power Quality Conditioner (UPQC) or a hybrid active power filter. The proposed series active compensator operates as a high impedance "k(D)" for the fundamental components of the power frequency during over current conditions in the distribution system. Two control strategies are proposed in this paper. The first strategy detects the fundamental source current using the p-q theory. The second strategy detects the fundamental component of the load current in the Synchronous Reference Frame (SRF). When over currents occur in the power distribution system momentarily, the proposed schemes protect the series active compensator without the need for additional protection circuits, and achieves excellent transient response. The validity of the proposed protection schemes is investigated through simulation and compared with experimental results using a hybrid active power filter systems.

• 전력전자학회논문지
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• 제17권1호
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• pp.41-47
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• 2012

This paper proposes a calculation of compensation current using phase shift to eliminate ripple components of instantaneous active power under unbalanced or non-linear loads condition. The proposed phase shift method instead of existing method(LPF; Low Pass Filter) to remove ripple components and this proposed method improves performances of transient and steady state response. To compare proposed method with existing method, experiments have been done for calculating an average active power at load side. Their results show that transient response and steady state response of proposed method is improved.

• 전력전자학회논문지
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• 제19권4호
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• pp.332-341
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• 2014

A cascaded H-bridge multi-level STATCOM(STATic synchronous COMpensator), which is composed of many cell inverters with independent dc-sources, generates inevitably dc-side voltage unbalance among phases when it compensates unbalanced load. It comes from the difference of flowing active power in each phase when this compensator makes negative-sequence current to eliminate the unbalance of source-side current. However, this unbalance can be controlled by injecting zero-sequence current which is decoupled with grid currents, so the compensator can work well during this balancing process. Both a feedback control algorithm, which produces zero-sequence current proportional to dc-side voltage unbalance within each phase, and a feedforward control algorithm, which makes zero-sequence current directly from the compensator's negative-sequence current, were proposed. The dc-side voltage of each phase can be controlled stably by these proposed algorithms in both steady-state and transient, so the compensator can have fast response to satisfy control performance under rapid changing load. These balancing controllers were implemented and verified via simulation and experiment.

• 한국산학기술학회논문지
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• 제16권6호
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• pp.4115-4120
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• 2015

풍력단지가 연계된 전력계통의 과도안정도를 보장하기 위해서는 전력계통과 풍력단지의 접속점에 풍력발전기가 충분한 무효전력을 공급할 수 있어야 한다. 하지만 개별의 풍력터빈은 안정도를 유지하기 위한 충분한 무효전력 공급능력을 가지지 못한다. 또한 풍력단지와 접속점 사이의 케이블은 리액턴스가 크고 이에 따른 무효전력 손실도 크다. STATCOM(Static Synchronous Compensator)은 고속으로 동작할 수 있고 충분한 무효전력을 공급할 능력을 가지고 있기 때문에 과도안정도를 향상시킬 수 있다. 본 논문에서는 풍력단지가 연계된 전력계통의 과도안정도 향상에 있어서 STATCOM의 유효성을 보인다. 접속점에 STATCOM을 설치하고 동적 모의를 한 결과 과도 안정도가 향상되는 결과를 얻을 수 있었다.

• Transactions on Electrical and Electronic Materials
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• 제17권3호
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• pp.172-177
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• 2016

Miller feedback compensation is introduced in a low dropout regulator (LDO) in order to obtain a capacitor-free regulator and improve the fast transient response. The conventional LDO has a limited bandwidth because of the large-size output capacitor and parasitic gate capacitance in the power MOSFET. In order to obtain a stable frequency response without the output capacitor, LDO is designed with resistor-capacitor (R-C) compensation and this is achieved with a connection between the gain-stage and the power MOS. An R-C compensator is suggested to provide a pole and zero to improve the stability. The proposed LDO is designed with the 0.35 μm CMOS process. Simulation testing shows that the phase margin in the Bode plot indicates a stable response, which is over 100^o. In the load regulation, the transient time is within 55 μs when the load current changes from 0.1 to 1 mA.

• 대한기계학회논문집
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• 제16권7호
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• pp.1332-1340
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• 1992

본 연구에서는 제어기에 관심을 갖던 기존의 방법에서 탈피해서 포화요소에 촛점을 맞추어 와인드업 현상을 해결하는 방법을 제시하고자 한다. 이 방법은 단입 출력 시스템에서는 역계산방법(back calculation method)과 동일하나 제어기와 보상기 를 분리하여 설계한 후 보상기를 각각의 엑추에이터 앞에 설치함으로써 다입 출력 시 스템에 쉽게 적용될 수 있다는 점에서 새로운 제안이라 할 수 있다. 또한 제어기를 바꾸지 않고도 보상기만을 추가로 설치하여 와인드업을 방지할 수 있으므로 이미 설치 된 시스템에의 적용이 용이함도 특기할 만하다.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제4B권2호
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• pp.65-72
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• 2004

Switching power supply systems are widely used in many industrial fields. Power factor correction (PFC) circuits have a tendency to be applied in new power supply designs. The input active power factor correction (APFC) circuits can be implemented in either the two-stage approach or the single-stage approach. The two-stage approach can be classified into boost type PFC circuit and dc/dc converter. The power factor correction circuit with a boost converter used as an input power source is studied in this paper. In a boost power factor correction circuit there are two feedback control loops, which are a current feedback loop and a voltage feedback loop. In this paper, the regulation performance of output voltage and compensator to improve the transient response presented at the continuous conduction mode (CCM) of the boost PFC circuit is analyzed. The validity of designed boost PFC circuit is confirmed by MATLAB simulation and experimental results.