• Journal of Power Electronics
• /
• 제18권2호
• /
• pp.547-557
• /
• 2018

This work proposes a control method of frequency stabilization for grid integration of large-scale wind farms via the voltage source converter-based high-voltage direct current (VSC-HVDC) technology. First, the topology of grid integration of a large-scale wind farm via the VSC-HVDC link is provided, and simple control strategies for wind turbines, wind farm side VSC (WFVSC), and grid side VSC are presented. Second, a mathematical model between the phase angle of WFVSC and the frequency of the wind farm is established. The control principle of the large-scale wind power integrated system is analyzed in theory in accordance with the mathematical model. Third, frequency and AC voltage controllers of WFVSC are designed based on the mathematical model of the relationships between the phase angle of WFVSC and the frequency of the wind farm, and between the modulation index of WFVSC and the voltage of the wind farm. Corresponding controller structures are established by deriving a transfer function, and an optimization method for selecting the parameters of the frequency controller is presented. Finally, a case study is performed under different operating conditions by using the DIgSILENT/PowerFactory software. Results show that the proposed control method has good performance in the frequency stabilization of the large-scale wind power integrated system via the VSC-HVDC technology.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2013년도 전력전자학술대회 논문집
• /
• pp.540-541
• /
• 2013

본 논문에서는 PSCAD/EMTDC를 이용하여 MMC(Modular Multi-level Converter)를 기반으로 한 HVDC 시스템 시뮬레이션 모델을 개발하였다. 스위칭 레벨의 동작을 분석하기 위해 각 ARM당 10개의 SM(Sub-Module)과 2개의 RM(Redundancy-Module)을 구성하여 11-level의 MMC 출력 전압을 형성하였다. SM 동작시 발생하는 전압 불균등 문제를 해결하기 위하여 밸런싱 알고리즘을 적용하였으며, SM의 출력 전압에 발생하는 Ripple을 고려하여 Capacitor의 용량을 설계하고 이를 검증하였다. 또한 시뮬레이션을 이용하여 HVDC 성능 분석과 MMC의 성능개선을 위한 순환전류 알고리즘 및 Redundancy 투입 알고리즘을 구현하고 그 결과를 확인하였다.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2019년도 추계학술대회
• /
• pp.162-163
• /
• 2019

본 논문에서는 MMC-HVDC 시스템을 위한 서브모듈 시험회로를 제안한다. 서브모듈 시험회로는 MMC-HVDC 서브모듈의 신뢰성을 확보하기 위해 필요하며 서브모듈 시험회로는 2 고조파 성분과 DC 오프셋 성분을 가지는 암 전류를 모사하면서 서브모듈 커패시터 전압을 일정하게 유지해야한다. 제안하는 서브모듈 시험회로는 시험회로의 인덕턴스를 줄이기 위해 5 레벨 컨버터를 사용하여 암 전류를 모사하며 시뮬레이션을 통하여 시험회로의 타당성을 검증하였다.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2014년도 전력전자학술대회 논문집
• /
• pp.341-342
• /
• 2014

VSC-HVDC system based on Modular Multilevel Converter (MMC) is an emerging technology since compared to the conventional VSC-HVDC system an MMC presents several advantages such as modularity, low dv/dt, low harmonics, and low switching losses. In this paper, a comprehensive control strategy of an MMC-based VSC-HVDC system is proposed. In contrast to the conventional system control strategy, the DC side of the MMC operates as a controlled voltage source by the proposed method, and the dynamics of the transmission line voltage and current can be actively controlled. Validity of the proposed strategy was verified by 201-level full-scale computer simulation.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2004년도 추계학술대회 논문집 전력기술부문
• /
• pp.66-68
• /
• 2004

The current source HVDC using thyristor valves requires the reactive power compensator, the increasement of short circuit ratio(SCR) by AC source, and the harmonic filter in power transmission. The voltage source HVDC that controls active power and reactive power independently can minimize the requirements and also can be used as a reactive power source without additional reactive power compensators. In this paper, the solution of supplying active power using direct current transmission and compensating additional reactive power at the heavy load zone in metropolitan area is proposed and verified by simulations.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2019년도 전력전자학술대회
• /
• pp.336-337
• /
• 2019

본 논문에서는 MMC (Modular Multilevel Converter) 기반 HVDC (High Voltage Direct Current) 시스템을 위한 서브모듈 시험회로를 제안한다. 서브모듈 시험회로는 MMC 기반 HVDC 시스템의 한 암(arm)의 전류를 모사한 서브모듈 시험전류를 만들어 서브모듈 성능시험을 하기 위한 것이다. 본 논문에서는 시험회로의 인덕턴스를 줄이기 위해 5 레벨 인버터를 사용한 새로운 방식의 회로를 제안한다. 시뮬레이션을 통하여 제안하는 서브모듈 시험회로의 타당성을 검증하였다.

• Journal of Power Electronics
• /
• 제18권2호
• /
• pp.467-481
• /
• 2018

Modular multilevel converter (MMC)-based high-voltage direct current (HVDC) presents attractive technical advantages and contributes to enhanced system operation and reduced oscillation damping in dynamic MMC-HVDC systems. We propose an advanced small-signal multi-terminal MMC-HVDC based on dynamic phasors and state space for power system stability analysis to enhance computational accuracy and reduce simulation time. In accordance with active and passive network control strategies for multi-terminal MMC-HVDC, the matchable small-signal stability models containing high harmonics and dynamics of internal variables are conducted, and a related theoretical derivation is carried out. The proposed advanced small-signal model is then compared with electromagnetic-transient and traditional small-signal state-space models by adopting a typical multi-terminal MMC-HVDC network with offshore wind generation. Simulation indicates that the advanced small-signal model can successfully follow the electromechanical transient response with small errors and can predict the damped oscillations. The validity and applicability of the proposed model are effectively confirmed.

• 한국태양에너지학회 논문집
• /
• 제35권3호
• /
• pp.49-56
• /
• 2015

This paper presents a comparative operating characteristics of static var compensator(SVC) and static synchronous compensator(STATCOM) for compensating the reactive power in the Jeju power system. There are two kinds of reactive power compensating systems, which are active and passive system in the applications of the line commutated converter type high voltage direct current (LCC-HVDC). In the Jeju power system, two STATCOMs as active compensating system have been operating. Even though STATCOM has good performance compared with SVC, economical efficiency of former system is not good to the latter system. So, it is necessary to examine the performance and economical efficiency depend on the intention before appling the system. To compare the operating characteristics of two systems in the Jeju power system, simulations have been carried out for case studies that both of the HVDC system have transient state by using PSCAD/EMTDC program.

• 한국초전도ㆍ저온공학회논문지
• /
• 제17권1호
• /
• pp.32-35
• /
• 2015

Many kinds of high temperature superconducting (HTS) devices are being developed due to its several advantages. In particular, the advantages of HTS devices are maximized under the DC condition. A line commutated converter (LCC) type high voltage direct current (HVDC) transmission system requires large capacity of DC reactors to protect the converters from faults. However, conventional DC reactor made of copper causes a lot of electrical losses. Thus, it is being attempted to apply the HTS DC reactor to an HVDC transmission system. The authors have developed a 8 mH class HTS DC reactor and a model-sized LCC type HVDC system. The HTS DC reactor was operated to analyze its operational characteristics in connection with the HVDC system. The voltage at both ends of the HTS DC reactor was measured to investigate the stability of the reactor. The voltages and currents at the AC and DC side of the system were measured to confirm the influence of the HTS DC reactor on the system. Two 5 mH copper DC reactors were connected to the HVDC system and investigated to compare the operational characteristics. In this paper, the operational characteristics of the HVDC system with the HTS DC reactor according to firing angle are described. The voltage and current characteristics of the system according to the types of DC reactors and harmonic characteristics are analyzed. Through the results, the applicability of an HTS DC reactor in an HVDC system is confirmed.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2019년도 전력전자학술대회
• /
• pp.344-345
• /
• 2019

High Voltage Direct Current (HVDC) 시스템은 고압 직류 송전을 위한 시스템으로서 단위 유닛인 서브모듈로 구성된 모듈형 멀티레벨 컨버터 구조를 갖는다. 서브모듈의 신뢰성 확보 및 설계 검증은 HVDC 시스템의 성능과 효율, 크기를 결정짓는 중요한 요소이다. 본 논문에서는 (주)효성이 개발하는 200MW 모듈형 멀티레벨 컨버터 서브모듈의 성능을 검증하기 위한 특성시험을 나타낸다. 특성시험을 통해서 개발 중인 서브모듈의 성능과 보호동작을 검증한다.