• 대한전기학회논문지:전기기기및에너지변환시스템부문B
• /
• 제54권12호
• /
• pp.592-600
• /
• 2005

In this paper, a low loss magnetic levitation(Maglev) system is suggested and tested. The suggested Maglev system includes four hybrid magnets which consist of permanent magnet and coil. In the steady state, the levitated module system can be supported by attraction force generated by permanent magnet. The coil current controls only dynamic loads due to external disturbances. The module systems are designed by using finite element method(FEM) software tools such as MAXWELL and ANSYS. Also, digital control systems are designed to keep the magnet airgap at a constant value. The control systems include a VME(versa module europa)-based CPU(central processing unit) board, AD(analog to digital) board, PWM(pulse width modulation) board, 4-quadrant chopper, and sensors. In order to estimate the vertical velocity of the magnet, we use second order state observer with acceleration and gap signals as input and output signals, respectively. The characteristics of the suggested low loss Maglev system are demonstrated by experimental results showing coil current of 0A in the steady state of 3m airgap and performance specifications are satisfied for reference gap and force disturbance.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2007년도 하계학술대회 논문집
• /
• pp.98-100
• /
• 2007

This paper proposes a robust digital controller for PWM voltage source inverter using CRA method. The usual inverter controller for the operation of constant voltage and constant frequency consists of a double looped PI controller for the outer voltage controller and the inner current controller, of which the order of characteristic polynomial is high and so the gain tuning is difficult. Considering the limited switching frequency of the devices and sampling frequency of the digital controller, the gain tuning is usually based on the engineering experiences with the try and error method. In this paper, the error-space approach is used to get the system model including the controller with low order, and the characteristic ratio assignment (CRA) method is proposed for the design of robust controller which has the advantage to design the optimal gain to meet the referenced response and overshoot within the limit range. The PSiM simulation and experience results are shown to verify the validity of the proposed controller.

• Journal of Power Electronics
• /
• 제10권6호
• /
• pp.673-679
• /
• 2010

Input-series-output-parallel (ISOP) connected DC-DC converters enable low voltage rating switches to be used in high voltage input applications. In this paper, a DSP is adopted to generate digital phase-shifted PWM signals and to fulfill the closed-loop control function for ISOP connected two full-bridge DC-DC converters. Moreover, a stable output current sharing control strategy is proposed for the system, with which equal sharing of the input voltage and the load current can be achieved without any input voltage control loops. Based on small signal analysis with the state space average method, a loop gain design with the proposed scheme is made. Compared with the conventional IVS scheme, the proposed strategy leads to simplification of the output voltage regulator design and better static and dynamic responses. The effectiveness of the proposed control strategy is verified by the simulation and experimental results of an ISOP system made up of two full-bridge DC-DC converters.

• ETRI Journal
• /
• 제35권5호
• /
• pp.927-930
• /
• 2013

We propose a visible light communication system in which the color and brightness are controllable. Pulse width modulation and variable pulse position modulation (VPPM) schemes are used to control the color and brightness, respectively. A digital algorithm to decode VPPM signals is suggested and implemented. A seamless transmission is observed in a testbed experiment under various environmental conditions. The proposed scheme can be applied to emotional-lighting-based wireless optical communication.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2013년도 추계학술대회 논문집
• /
• pp.79-80
• /
• 2013

MMC(Modular Multilevel Converter)는 여러 개의 Power Module을 직렬로 연결하여 정현파에 가까운 고전압의 파형을 얻을 수 있는 토폴로지로 대용량 전력변환 분야의 요구를 만족하면서 전력 품질을 향상시킬 수 있어 근래에 상당히 주목받고 있다. 당사에서는 5Mvar급 STATCOM(STATic synchronous COMpensator)을 MMC 형태로 제작하였다. 제작된 5Mvar급 STATCOM은 한 상당 12대의 Power Module로 구성하여 25-Level로 제작되었다. 제어시스템은 DSP(Digital Signal Processor)를 이용하였으며, 하나의 Main Controller와 다수의 Cell Controller, FPGA 보드 등으로 구성되어 있다. Controller 간의 상호 정보를 교환하기 위해 CAN 통신을 이용하였고, Power Module의 스위칭을 위한 보드는 각각에 연결되어 있으며, Cell Controller보드와는 절연을 위해 광신호로 연결하였다. 본 논문에서는 MMC 시스템의 제어기간 CAN 통신인터페이스와 Power Module의 PWM 동기화에 대해 설명을 하였다.

• 한국조명전기설비학회:학술대회논문집
• /
• 한국조명전기설비학회 2007년도 추계학술대회 논문집
• /
• pp.279-285
• /
• 2007

Since the residential load is an AC load and the output of solar cell is a DC power, the photovoltaic system needs the DC/AC converter to utilize solar cell. In case of driving to interact with utility line, in order to operate at unity power factor, converter must provide the sinusoidal wave current and voltage with same phase of utility line. Since output of solar cell is greatly fluctuated by insolation, it is necessary that the operation of solar cell output in the range of the vicinity of maximum power point. In this paper, DC/AC converter is three phase PWM converter with smoothing reactor. And then, feedforward control used to obtain a superior characteristic for current control and digital PLL circuit used to detect the phase of utility line.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1997년도 하계학술대회 논문집 F
• /
• pp.1954-1956
• /
• 1997

In this paper, a variable structure current control scheme for field-oriented induction motor drive is presented. The current controller based on space voltage vector PWM scheme consists of feedforward, decouple and variable structure control. The proposed current controller tracks reference value quickly, has robust property against parameter variation and disturbance, reduces switching frequency and improves performance of induction motor drive. Finally, the proposed current controller is verified by digital simulation

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1996년도 하계학술대회 논문집 A
• /
• pp.312-317
• /
• 1996

This paper compares the output voltage control strategies of three-phase PWM inverter for uninterruptible power supply. The feedforward control, feedforward/feedback control, and decoupled feedback control in both the synchronous reference frame and the stationary reference frame are examined. In particular, it is shown that the response of the decoupled feedback controller in the synchronous reference frame can be improved by pole-zero cancellation method. It is also shown that the pole-zero cancellation method reduces to the deadbeat control, when it is implemented with digital controller.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
• /
• pp.803-807
• /
• 2001

This paper presents a new control scheme for a DVR (Dynamic Voltage Restorer) system consisting of series voltage source PWM converters. To control the negative sequence components of the source, it is necessary to detect the negative sequence components. Generally, a filtering process is used which has some undesirable effects. This paper suggests a new method for separating positive and negative sequences components. This control system is designed using differential controllers and digital filters. The positive and negative sequences are extracted and controlled individually. The performance of the presented controller and scheme are confirmed through simulation and actual experiment with a 2.5kVA prototype DVR system.

• 전력전자학회논문지
• /
• 제5권1호
• /
• pp.1-10
• /
• 2000

본 논문에서는 무정전전원장치(UPS)에 사용되는 3상 PWM 인버터의 정전압 제어특성 향상을 위해 개선된 형태의 데드비트 제어방식을 제안하고 이의 설계를 수행한다. 일반적으로 UPS는 전압제어 루프 안에 전류제어기를 두는 형태의 이중 제어 루프 구조를 가지며, 빠른 과도응답 제어 특성을 얻기 위해 데드비트 제어기가 많이 적용되어 왔다. 그러나 전압, 전류의 이중 제어구조를 갖는 데드비트 제어기의 경우 동일한 극배치 특성으로 인해 기존의 제어 시스템은 불안정한 측면을 갖게된다. 이러한 제어특성의 개선을 위하여 분리된 극배치를 가지는 제어기구조를 제안하며, 이는 전압제어기 출력으로 1차 지수함수 응답을 사용하는 변형된 형태의 데드비트 제어기로 구성된다. 아울러 부하 변동에 따른 부하전류의 외란성분을 전향보상하기 위하여 전차원 외란 관측기를 설계하고 시뮬레이션 및 실험을 통하여 제안된 시스템의 우수성을 확인한다.