• 대한전기학회논문지
• /
• 제41권4호
• /
• pp.369-378
• /
• 1992

This paper proposes a utility parallel processing inverter system, which consists of a voltage source PWM inverter, isolation transformer and a reactor linking the inverter to utility line. This system realizes following functions : (1) voltage phase frequency and amplitude synchronization between inverter and utility line at stand-alone mode. (2) current phase synchronization between inverter and load at parallel mode. Therefore, despite sudden increase in load current over setting point at stand-alone mode, inverter system can be transferred into parallel mode immediately without transient current. Furthermore, high frequency(18KHz) PWM control and sinusoidal filtering improve the inverter output waveform by eliminating high order harmonic components as well as low order. As a switching device, IGBT is used for high frequency switching and large current capacity.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1999년도 하계학술대회 논문집 F
• /
• pp.2656-2658
• /
• 1999

This paper presents a control scheme for a three-phase PWM converter system without any voltage sensors. Two input currents and one load current are measured. In a general PWM converter system, the required AC input and DC output voltage values in order to control the converter are estimated using the differential equations of the converter from the measured input currents and load current values in the switch modes of the converter circuit. The PI controller is used as DC voltage controller and sinusoidal tracking controller which tracks directly AC input current is used as input current controller. The Proposed method is verified by simulations. This paper describes the estimation method and configuration of the controller, and discusses steady state and transient performances of the converter

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 추계학술대회논문집A
• /
• pp.710-715
• /
• 2001

This research is presented for optimizing the coefficients of spring and damper by impact load which is applied to a trailer when the containers are loaded up trailer. The procedure utilize the condition that two containers, initial velocity of container, initial height of container and maximum of suspension stroke. The coefficients of spring and damper are calculated numerically through Newmark method uses finite difference expansions. The procedure of calculation is applied by one DOFs of mass-spring-damper system. The coefficients of spring and damper have large value as increase of height or decrease of stroke. The result of calculation is investigated and is used AGV design.

• Journal of Mechanical Science and Technology
• /
• 제16권5호
• /
• pp.639-646
• /
• 2002

In this paper, thrust equations for a rubber belt CVT are derived by considering the geometry and mechanism of the mechanical actuators. In order to solve the thrust equations, an algorithm to calculate the speed ratio is suggested for the given driver speed and load torque based on the actuator characteristic equations and existing formula for the belt thrust forces. Experiments are performed to investigate the driver speed-load torque-speed ratio characteristics at a steady state. The speed and torque efficiencies are measured and used to modify the actuator equations. It is found that the modified equations well predict the steady state characteristics. In addition, the shift dynamic model for a rubber belt CVT is derived experimentally. Simulation results of the CVT shift dynamics are in good accordance with the experiments and it is noted that different coefficients are required to describe the CVT shift dynamics for the upshift and the downshift.

• Nuclear Engineering and Technology
• /
• 제20권1호
• /
• pp.1-8
• /
• 1988

상업용 발전소의 가동시, 출력 변화에 의해 1차 계통 보론 농도의 변화가 요구되었을 때 CVCS보충 시스템에서의 보충 유량이 연속 방정식과 질량 평형 방정식을 이용하여 측정된다. 이를 위하여, 1차 계통, 가압기, 그리고 volume control tank가 각각 질량과 보론 농도를 가진 control volume으로 그리고 1차측과 가압기, CVCS를 연결하는 파이프들이 시간 지연 요소로 모델화 되었다. 14-2-6-2 (출력변화 100-50-100) 부하 추종운전의 경우(7호기 EOL에서)를 이 모델을 이용하여 계산하였다.

• 수산해양기술연구
• /
• 제14권2호
• /
• pp.89-95
• /
• 1978

A SCR static breaker was studied on the Resistive and inductive load, then on the overload break circuit using operational Amplifier. In this paper, the principal circuit required for forced commutation was voltage commutation by the introduction of a parallel Capacitor. The results obtained are follows; 1. In thecondition that the tima constant of R-C circuit is larger than the turn off time of SCR, the breaker has low transient phenomena and no recovery vol age. 2. By using OP Amplifier on the load circuit, overcurrent trip point will be able to adjust to the wide range of over current. 3. In the over current qrcuit, the power loss was reduced remarkably.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2008년도 제39회 하계학술대회
• /
• pp.446-447
• /
• 2008

In this paper, a calculation method of the short-time emergency by considering a initial load level and overload time is presented. short-time emergency analyze transient thermal rating and Long-time emergency analyze steady-state thermal rating. Using the suggested method in the paper, increasing the short-term allowable current.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
• /
• pp.336-340
• /
• 1998

In this paper, an effective control scheme of a single phase UPS inverter is proposed to have no steady state error of the output voltage and the fast response for the load request. The cosine wave tranfer function is proposed to control the output voltage. This controller clearly removes errors of magnitude and phase both in the steady state. On the other hand, a current controller is proposed to reduce the transient time of the voltage control and to improve the bad distorted factor of the output voltage waveform by the load fluctuation and the presences of nonlinear parameters in the plant. The current controller is designed parallel to the voltage controller and performs separately from it.

• Journal of Power Electronics
• /
• 제12권2호
• /
• pp.294-304
• /
• 2012

This paper proposes a fuzzy speed tracking controller and a fuzzy rotor angular acceleration observer for a surface-mounted permanent magnet synchronous motor (SPMSM) based on the Takagi-Sugeno (T-S) fuzzy model. The proposed observer-based controller is robust to load torque variations since it utilizes rotor angular acceleration information instead of the load torque value. Linear matrix inequality (LMI) sufficient conditions are given to compute the gain matrices of the speed tracking controller and the observer. In addition, it is mathematically verified that the proposed observer-based control system is asymptotically stable. Simulation and experimental results are presented to confirm that the proposed control algorithm assures a better transient behavior and less sensitivity under model parameter variations than the conventional PI control method.

• Journal of Power Electronics
• /
• 제18권3호
• /
• pp.736-745
• /
• 2018

This paper presents an extended state observer (ESO) based direct torque control (DTC) for use in induction motor systems to handle the issues of time delays, load torque disturbances and parameter uncertainties. Direct torque control offers an excellent torque response and it does not require a proportion integration (PI) controller in the current loop. However, a PI controller is still adopted in the outer speed loop to generate the torque reference value, which is a slow method. An ESO based compound control scheme is proposed to improve the response rate and accuracy of the torque reference signal, especially when load torque is injected. In addition, the time delay problem is analyzed and compensated for in this paper to reduce torque ripples. The proposed disturbance compensation technique based direct control scheme is shown to have good performance both in the transient and stable states via simulations and experimental results.