• Journal of Power Electronics
• /
• 제14권2호
• /
• pp.271-281
• /
• 2014

Fluctuating wind conditions necessitate the use of a variable speed wind turbine (VSWT) with a AC/DC/AC converter scheme in order to harvest the maximum power from the wind and to decouple the synchronous generator voltage and frequency from the grid voltage and frequency. In this paper, a combination of a three phase diode bridge rectifier (DBR) and a modified topology of the diode clamped multilevel inverter (DCMLI) has been considered as an AC/DC/AC converter. A control strategy has been proposed for the DCMLI to achieve the objective of grid interface of a wind power system together with local load compensation. A novel fixed frequency current control method is proposed for the DCMLI based on the level shifted multi carrier PWM for achieving the required control objectives with equal and uniform switching frequency operation for better control and thermal management with the modified DCMLI. The condition of the controller gain is derived to ensure the operation of the DCMLI at the fixed frequency of the carrier. The converter current injected into the distribution grid is controlled in accordance with the wind power availability. In addition, load compensation is performed as an added facility in order to free the source currents being fed from the grid of harmonic distortion, unbalance and a low power factor even though the load may be unbalanced, non-linear and of a poor power factor. The results are validated using PSCAD/EMTDC simulation studies.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2000년도 하계학술대회 논문집 B
• /
• pp.1336-1338
• /
• 2000

This paper proposed the single phase multi-level PWM AC/DC converter using binary combine which controls input current by combining buck converters to improve input current characteristic, and confirmed its validity throughout simulation and experiment. This method, which is multiplying and duplicating output of converter of equal capacity, has the advantage of being able to control unit power factor of input current and reducing of the problem caused by high frequency switching, and appling to high power converter because filter is not necessary etc.

• Journal of Power Electronics
• /
• 제7권2호
• /
• pp.146-158
• /
• 2007

A multi-pulse GTO based voltage source converter (VSC) topology together with a fundamental frequency switching mode of gate control is a mature technology being widely used in static synchronous compensators (STATCOMs). The present practice in utility/industry is to employ a high number of pulses in the STATCOM, preferably a 48-pulse along with matching components of magnetics for dynamic reactive power compensation, voltage regulation, etc. in electrical networks. With an increase in the pulse order, need of power electronic devices and inter-facing magnetic apparatus increases multi-fold to achieve a desired operating performance. In this paper, a competitive topology with a fewer number of devices and reduced magnetics is evolved to develop an 18-pulse, 2-level $\pm$ 100MVAR STATCOM in which a GTO-VSC device is operated at fundamental frequency switching gate control. The inter-facing magnetics topology is conceptualized in two stages and with this harmonics distortion in the network is minimized to permissible IEEE-519 standard limits. This compensator is modeled, designed and simulated by a SimPowerSystems tool box in MATLAB platform and is tested for voltage regulation and power factor correction in power systems. The operating characteristics corresponding to steady state and dynamic operating conditions show an acceptable performance.

• 전기학회논문지
• /
• 제64권8호
• /
• pp.1193-1201
• /
• 2015

This paper presents a study of circulating current of modular multi-level converter (MMC) based a high voltage direct current (HVDC) system under unbalanced grid conditions. Due to the connection of a dependent DC source in each phase, the MMC system inherently generates the power ripple of double-line-frequency components in the AC-side and as a result, the additional sinusoidal current named circulating current flows through the each arm. Reliability improvement of HVDC system under an unbalanced grid condition is one of the important criteria. Generally, the modeling of the circulating current is based on the power relation between DC-side and AC-side. However, the method is not perfectly matched in the MMC system due to the difference of the structural characteristic. In this paper, improved modeling method of circulating current is proposed, which is based on the inner arm power. The proposed method is verified by several simulations to have good agreement of the circulating current components.

• Journal of Electrical Engineering and Technology
• /
• 제13권3호
• /
• pp.1052-1059
• /
• 2018

This paper deals with commutation failure of the line-commutated converter high voltage direct current (LCC HVDC) system caused by a three phase fault in the ac power system. An analytic calculation method is proposed to estimate the maximum permissible voltage drop at the LCC HVDC station on various operating point and to assess the area of vulnerability for commutation failure (AOV-CF) in the power system based on the residual phase voltage equation. The concept is extended to multi-infeed HVDC power system as the area of severity for simultaneous commutation failure (AOS-CF). In addition, this paper presents the implementation of a shunt compensator applying to the proposed method. An analysis and simulation have been performed with the IEEE 57 bus sample power system and the Jeju island power system in Korea.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2016년도 전력전자학술대회 논문집
• /
• pp.127-128
• /
• 2016

본 논문에서는 모듈형 멀티레벨 컨버터(Modular Multi-level Converter)의 전고조파 왜곡률(Total Harmonic Distortion)을 개선하기 위한 새로운 모듈레이션 기법에 대해서 기술하고 있다. 제안하는 모듈레이션 기법의 타당성을 검증하기 위해 PSCAD/EMTDC 소프트웨어를 이용하여 시뮬레이션을 수행하였으며, 한 암당 12개의 서브모듈로 구성된 모듈형 멀티레벨컨버터 모델을 개발하였다. 이를 통하여 제안하고자하는 옵셋 전압 방식의 모듈레이션 기법을 적용하고 타당성을 분석하였다. 또한 시뮬레이션을 통해 분석한 내용을 실험적으로 검증하기 위해 10kVA 용량의 하드웨어 축소모형을 제작하고 실험을 실시하였다.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2017년도 전력전자학술대회
• /
• pp.240-241
• /
• 2017

멀티레벨 방식의 Dual Active Bridge 컨버터는 기존의 컨버터와 비교하여 높은 자유도의 스위칭 방식을 가진다. 본 논문에서는 멀티 레벨 방식의 DAB 컨버터의 동작원리를 분석하고, 인덕터 전류의 RMS 값과 THD를 최소화하기 위하여 기본파를 제외한 3 고조파와 5 고조파를 감쇄하는 스위칭 방식을 제안한다. 다양한 스위칭 패턴에 따른 인덕터 전류 RMS 값과 THD를 비교하여 제안하는 스위칭 방식의 타당성을 검증하고자 한다.

• 한국철도학회논문집
• /
• 제19권3호
• /
• pp.297-303
• /
• 2016

본 논문은 철도차량에 사용되는 보조전원장치(APS)의 고효율화 및 경량화를 위한 방안으로 새로운 철도차량용 보조전원장치의 회로 구조를 제안한다. 제안하는 회로 구조는 기존의 보조전원장치 전력변환 흐름에서 중복 수행되고 있는 전력변환 단계를 단순화 하여, 스위치 소자의 부담을 경감하고 수동소자의 크기를 줄여 전력밀도를 높이는 것을 목적으로 하고 있다. 본 연구에서 제안하는 회로 구조는 기존 철도차량용 보조전원장치에 널리 이용되는 멀티레벨 컨버터를 기본 회로로 하고 있으며, 기존 회로의 1차 측 구조에 커패시터 소자를 추가하여 전력변환 스위치의 소프트스위칭 조건을 용이하게 하는 효과를 얻음과 동시에 추가되는 커패시터를 별도의 저전압 전원소스로 활용하고자 한다. 판토그래프 단에 위치하는 새로운 전원소스를 활용하여 철도차량에 탑재되는 배터리 충전용 컨버터의 에너지를 직접 공급받음으로써, 기존 주 전력변환 컨버터 용량 및 사이즈가 절감되는 효과를 얻을 수 있을 뿐만 아니라 전력변환 단계의 축소로 에너지 변환 효율도 향상되는 효과를 얻을 수 있다. 본 연구에서는 도시철도차량에서 사용되는 보조전원장치의 스펙을 적용하여 제안하는 회로를 디자인하고 타당성을 검증하였다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2004년도 하계학술대회 논문집 B
• /
• pp.1319-1321
• /
• 2004

This paper presents a model and simulation for the korean type multi-propulsion system consisting of a gas turbine driven synchronous alternator coupled to a rectifier and dc-to-dc converter. The simulation modules include turbine system, alternator and rectifier, dc-to-dc converter, power management module. A modular, system level simulation of the propulsion system prototype is presented in order to confirm stability for loads with uncertain input impedances and uncertain control loop speeds.

• Journal of Power Electronics
• /
• 제18권6호
• /
• pp.1791-1804
• /
• 2018

To achieve a fast dynamic response and to solve the multi-objective control problems of the output currents, capacitor voltages and system constraints, this paper proposes a deadbeat and hierarchical predictive control with space-vector modulation (DB-HPC-SVM) for five-level nested neutral point piloted (NNPP) converters. First, deadbeat control (DBC) is adopted to track the reference currents by calculating the deadbeat reference voltage vector (DB-RVV). After that, all of the candidate switching sequences that synthesize the DB-RVV are obtained by using the fast SVM principle. Furthermore, according to the redundancies of the switch combination and switching sequence, a hierarchical model predictive control (MPC) is presented to select the optimal switch combination (OSC) and optimal switching sequence (OSS). The proposed DB-HPC-SVM maintains the advantages of DBC and SVM, such as fast dynamic response, zero steady-state error and fixed switching frequency, and combines the characteristics of MPC, such as multi-objective control and simple inclusion of constraints. Finally, comparative simulation and experimental results of a five-level NNPP converter verify the correctness of the proposed DB-HPC-SVM.