• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2003년도 하계학술대회 논문집 B
• /
• pp.1356-1358
• /
• 2003

This paper describes the control of grid connected transformerless type PV power conditioning system, which is simple and more efficient than the usual transformer type system. With the modeling and analysis of power system, the validity of control strategy is well verified through the simulation and experimental results.

• Journal of Power Electronics
• /
• 제15권5호
• /
• pp.1338-1347
• /
• 2015

DC injection is a critical issue in transformerless grid-connected inverters. DC injection control based on virtual capacitor has the advantages of low cost, low loss, high accuracy and easy implementation. In this paper, the principle of DC injection control based on virtual capacitor was analyzed. In addition, the applicable conditions, working process, steady state error and advantages were also discussed in detail. The design of the control parameters based on virtual capacitor was proposed in a grid-connected inverter with LCL filter. The robustness of the control parameters was also discussed. Simulation and experimental results verify the validity of the analysis and demonstrate that this research has a certain value in engineering applications.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2016년도 전력전자학술대회 논문집
• /
• pp.201-202
• /
• 2016

본 논문에서는 고효율을 갖는 3-level 3-phase 무변압기형 양방향 인버터를 제안한다. 제안된 인버터는 두 개의 직류링크 커패시터를 통해 연결된 3-level dc-dc 컨버터와 T-type 인버터로 구성된다. 따라서 낮은 전압 스트레스를 가지며 스위칭 및 도통 손실이 줄어들고 변압기가 없어 높은 전력 밀도와 고효율을 달성한다. 스위칭에 의해 발생하는 직류링크 중성점 변화에 따른 출력 전압왜곡은 제안된 중성점 제어 알고리즘을 통해 직류링크 전압의 균형을 맞추어 최소화된다. 또한 T-type 인버터는 제안하는 제어 알고리즘을 통해 높은 품질의 계통전류를 출력한다. 본 논문에서는 제안된 인버터의 이론적 해석 및 시작품의 실험을 수행하여 타당성을 검증하였다.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
• /
• pp.576-580
• /
• 2001

This paper presents a casca multilevel PWM rectifier without the isolation transformers for energy build-up at each inverter modules; The features and advantages of the proposed PWM rectifier can be summarized as follows; 1) It realizes the high power high voltage AC/DC power conversion, 2) It uses no transformer which is bulky and heavy, 3) It has hybrid structure so that switching devices can be effectively utilized, 4) It produces high quality AC current even in high power high voltage applications, 5) The input power factor remains unity by simple modulation index control. The multilevel rectifier is analyzed by using the circuit DQ transformation whereby the characteristics and control equations are obtained. Finally, it will be shown that the system simulation reveals the validity of analyses

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2000년도 전력전자학술대회 논문집
• /
• pp.670-673
• /
• 2000

This paper describes a new inverter active inverter between a photovoltaic(PV) array and single-phase utility that avoid the bulky input(60Hz) transformer on the AC side. The interface employs a pwm boost converter on the DC side followed by a pwm boost converter on the DC side followed by a pwm current-forced single-phase rectifier for injecting the power from the PV array into the mains. The current waveform at the AC side remains sinusoidal and exactly in phase at all time. The circuit also has the advantage of requiring fewer switching device than high-frequency link system. This paper describes modeling of PV array and new system topology. Simulation results on the performance of the connection are also presented.

• Journal of Power Electronics
• /
• 제10권5호
• /
• pp.572-578
• /
• 2010

This paper discusses a transformerless shunt static compensator (STATCOM) based on a modular multilevel converter (MMC). It introduces a new time-discrete appropriate current control algorithm and a phase-shifted carrier modulation strategy for fast compensation of the reactive power and harmonics, and also for the balancing of the three-phase source side currents. Analytical formulas are derived to demonstrate the accurate mechanism of the stored energy balancing inside the MMC. Various simulated waveforms verify that the MMC based STATCOM is capable of reactive power compensation, harmonic cancellation, and simultaneous load balancing, while controlling and balancing all of the DC mean voltages even during the transient states.

• Journal of Electrical Engineering and Technology
• /
• 제11권2호
• /
• pp.393-404
• /
• 2016

In this paper, a carrier-based pulse with modulation (PWM) strategy for three-phase three-level inverter is dealt with, which can keep the common mode voltage constant with minimized switching frequency. The voltage gain and the switching frequency in overall operating ranges including overmodulation are investigated and the analytic equations are presented. Finally, the leakage current reduction effect is confirmed by carrying out simulation and experiment. It will be pointed out that the leakage current cannot be perfectly eliminated because of the dead time.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2004년도 전력전자학술대회 논문집(2)
• /
• pp.606-609
• /
• 2004

Maximum power point tracking(MPPT) is usually used for a solar power system. Many maximum power tracking techniques have been considered in the past. The microprocessors with appropriate MPPT algorithms are favored because of their flexibility and compatibility with different solar arrays. In this paper, four MPPT algorithms are analyzed and studied. Perturbation and Observation(P&O), Incremental Conductance(IncCond), which are used from the past. Improved P&O and Two-mode , which are developed P&O and IncCond algorithms. Also, the author introduces grid-connected fransformerless PV PCS to apply MPPT control. MPPT efficiency is measured by changing irradiance from $0.1kW/m^2\;to\;1kW/m^2$ and simulation was performed for each MPPT algorithm.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 하계학술대회 논문집 B
• /
• pp.1293-1295
• /
• 2001

Recently, according to developing industry and life style, power consumption have been increased year after year. Currently these much power demand from power consumer weakening the allowable power reverse margin in summer. As on of the remedies about this problem, the small scale grid-connected photovoltaic system is considered for auxiliary power source. Generally, grid-connected inverter have a isolation transformer for electrical isolation from utility. This paper proposed transformerless system topology an inquiry validity simulation.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2004년도 춘계학술대회 논문집
• /
• pp.1334-1339
• /
• 2004

This paper proposes transformerless power conversion system consisting of a single-phase diode rectifier and a shunt hybrid filter for the electric-railway system. The hybrid filter consists of a single tuned LC filter per a phase and a low-rated NPC type multi-level inverter. Compared with conventional active filters. Transformers are not used. Also, LC filter works as not only a harmonic filter tuned at the 5th harmonic frequency but also a switching-ripple filter. The rating of the active filter can be decreased by using a NPC type multi-level inverter. The simulation results confirm the validity of the system.