• 전기학회논문지
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• 제65권12호
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• pp.2189-2196
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• 2016

This paper proposes a new finite control set-model predictive control (FCS-MPC) method for induction motors. In the method, the reference state that satisfies the given torque and rotor flux requirements is derived. Cost indices for the FCS-MPC are defined using the state tracking error, and a linear matrix inequality is formulated to obtain a proper weighting matrix for the state tracking error. The on-line procedure of the proposed FCS-MPC comprises of two steps: select the output voltage vector of the two level inverter minimizing the cost index and compute the optimal modulation factor of the minimizing output voltage vector in order to reduce the state tracking error and torque ripple. The steady state tracking error is removed by using an integrator to adjust the reference state. The simulation and experimental results demonstrated that the proposed FCS-MPC shows good torque, rotor flux control performances at different rotating speeds.

• Journal of Power Electronics
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• 제9권4호
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• pp.654-666
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• 2009

Direct torque control (DTC) of induction machines (IM) is a well-known strategy of these drives control which has a fast dynamic and a good tracking response. In this paper a nonlinear DTC of speed sensorless IM drives is presented which is based on input-output feedback linearization control theory. The IM model includes iron losses using a speed dependent shunt resistance which is determined through some effective experiments. A stator flux vector is estimated through a simple integrator based on stator voltage equations in the stationary frame. A novel method is introduced for DC offset compensation which is a major problem of AC machines, especially at low speeds. Rotor speed is also determined using a rotor flux sliding-mode (SM) observer which is capable of rotor flux space vector and rotor speed simultaneous estimation. In addition, stator and rotor resistances are estimated using a simple but effective recursive least squares (RLS) method combined with the so-called SM observer. The proposed control idea is experimentally implemented in real time using a FPGA board synchronized with a personal computer (PC). Simulation and experimental results are presented to show the capability and validity of the proposed control method.

• Journal of Power Electronics
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• 제16권3호
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• pp.1056-1066
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• 2016

Wireless power transfer (WPT) technology is now recognized as an efficient means of transferring power without physical contact. However, frequency detuning will greatly reduce the transmission power and efficiency of a WPT system. To overcome the difficulties associated with the traditional frequency-tracking methods, this paper proposes a Direct Phase Control (DPC) approach, based on the Second-Order Generalized Integrator Phase-Locked Loop (SOGI-PLL), to provide accurate frequency-tracking for WPT systems. The DPC determines the phase difference between the output voltage and current of the inverter in WPT systems, and the SOGI-PLL provides the phase of the resonant current for dynamically adjusting the output voltage frequency of the inverter. Further, the stability of this control method is analyzed using the linear system theory. The performance of the proposed frequency-tracking method is investigated under various operating conditions. Simulation and experimental results convincingly demonstrate that the proposed technique will track the quasi-resonant frequency automatically, and that the ZVS operation can be achieved.

• 전력전자학회논문지
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• 제25권5호
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• pp.333-342
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• 2020

Power exchanges between the grid and the battery through a bidirectional DC-DC converter are essential for DC microgrid systems. In general, the battery is charged when the grid is connected, and the system is powered by the battery when the grid is disconnected. In this mode transition, the saturation of the voltage controller slows down output response and produces large transient errors in DC link voltage. To solve this problem, a novel anti-windup design is proposed to improve anti-windup performance further. The proposed method stabilizes DC bus voltage through a wider range of battery voltage with faster transition compared with that of conventional methods. The proposed method is verified through an experimental setup composed of a 125 W laboratory-scale DC microgrid system.

• 대한전기학회논문지
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• 제43권7호
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• pp.1206-1213
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• 1994

This paper presents the operation principle and design rule of the Rogowski coil which can measure the transient current and describes the calibration and application experimental results for performance evaluation. It is obtained that the response curves of the Robowski coil with the turns of 300 and the passive integrator to sinusoidal input give a good linearity up to the frequency of 500 [kHz] and the current measurement system gaving the Rogowski coil is the frequency bandwidth of 40 [Hz]~700 [kHz]. As an application experiment for the fabricated modeling power transmission line, the impulse current, which limitates the direct lightning return stroke to overhead ground wire, is measured by the Rogowski coil and its fast Fourier transformation is carried out. The equivalent circuit of the Rogowski coil considering the stray capacitances is proposed, and the theoretical analysis is in good agreement with the measurement results. Also, it is found that for high frequency domain the stray capacitance such as a distributed capacitance to the shield and the capacitance between windings of coil should be considered in designing the Rogowski coils since the resonance originates from the stray capacitance and the self-inductance of the Rogowski coil.

• 한국태양에너지학회 논문집
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• 제33권6호
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• pp.92-97
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• 2013

This paper proposes DC offset current compensation method of transformerless fuel cell/PV PCS. DC offset current is generated by the unbalanced internal resistance of the switching devices in full bridge topology. The other cause is the sensitivity of the current sensor, which is lower than DSP in resolution. If power converter system has these causes, the AC output current in the inverter will generate the DC offset. In case of transformerless grid-connected inverter system, DC offset current is fatal to grid-side, which results in saturating grid side transformer. Several simulation results show the difficulties of detecting DC offset current. Detecting DC offset current method consists of the differential amplifiers and PWM is compensated by the output of the Op amp circuit with integrator controller. PSIM simulation verifies that the proposed method is simpler and more effective than using low resolution current sensor alone.

• 대한전자공학회논문지
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• 제27권11호
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• pp.83-91
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• 1990

전압제어 발진기(VCO:coltage controlled oscillator)는 FM 신호 변조, 주파수 안정기와 디지탈 클럭 재생과 같은 부분의 적용에 필수적인 기본회로이다. 본 논문에서는 BiCMOS 회로를 이용한 차동 증폭기를 사용하여 OTA(operational transconductance amplifier)회로와 OP amp를 설계하고 이를 토대로 하여 VCO 회로를 설계하였다. 그리고 이 VCO는 OTA와 전압 제어 적분기, 그리고 슈미트 트리거 회로로 구성이 되어 있다. 종래에는 CMOS를 사용하여 VCO를 설계하였지만 여기서는 구동능력이 좋은 BiCMOS를 사용하여 VCO를 설계하였다. 이 회로를 SPICE로 시뮬레이션 한 결과 출력 주파수는 105KHz에서 141KHz이며 변화 감도는 15KHz였다.

• 대한전자공학회논문지
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• 제26권3호
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• pp.8-13
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• 1989

부가성 가우시안 잡음 상황하에서, 미지의 확률 분포를 갖는 양극성 2진 불규칙 수형파 신호의 중요한 파라미터인, 진폭과 위상을 Gauss-Markov 추정기를 사용하여 동시에 추정하므로써 전송된 디지탈 데이타를 복원하였다. 그러나, Gauss-Markov 추정기가 이용되기 위해서는 승산기와 적분기로 구성된 상관기를 사용하여, 수신 신호를 표본화 급수로 변환하고 관측된 데이타 벡타를 얻기 위한 사전 처리단계가 필요하게 됨을 알게 되었다.

• 전기전자학회논문지
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• 제21권4호
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• pp.424-427
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• 2017

원점이나 원점 근방에 있는 극을 포함하고 있는 시간지연시스템에 대하여 스미스 예측제어기를 적용할 경우 외란에 의한 정상상태 오차가 발생한다. 또한 모델링 오차가 존재할 경우에도 외란에 의한 오차 발생으로 인하여 제어기 구성이 어렵게 된다. 이에, 본 논문에서는 이러한 시스템들에 대한 외란의 영향을 제거하기 위한 새로운 제어기를 구성하였다. 외란을 측정할 수 있는 외란관측자를 제안하였으며, 관측된 외란을 이용하여 외란의 효과를 소거할 수 있는 제어기를 구성하였다. 그 결과, 외란 및 모델링 오차의 영향을 제거할 수 있는 새로운 제어기를 설계할 수 있었다. 구성된 제어기를 발전소 과열기 및 증기압 제어에 적용하여 제안한 시스템의 효용성을 입증하였다.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 1993년도 Fifth International Fuzzy Systems Association World Congress 93
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• pp.891-894
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• 1993

To improve limitations of fuzzy PI controller especially when applied to high order systems, we propose two types of fuzzy logic controllers that take out appropriate amounts of accumulated control input according to fuzzily described situations in addition to the incremental control input calculated by conventional fuzzy PI controllers. The structures of the proposed controller were motivated by the problems of fuzzy PI controllers that they generally give inevitable overshoot when one tries to reduce rise time of response especially when one tries to reduce rise time of response especially when a system of order higher than one is under consideration. Since the undesirable characteristics of the fuzzy PI controller are caused by integrating operation of the controller, even though the integrator itself is introduced to overcome steady state error in response, we propose two fuzzy controllers that fuzzily clear out integrated quantities according to situation. The first contr ller determines the fuzzy resetting rate by situations described fuzzily by error and error rate, and the second one by error and control input. The two structures both give reduced rise time as well as small overshoot. To show the usefulness of the proposed controller, that are applied to systems that are difficult to get satisfactory response by conventional fuzzy PI controllers.