• 전력전자학회논문지
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• 제24권5호
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• pp.334-341
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• 2019

This study proposes the control strategy for the seamless mode transfer of indirect current controlled parallel grid-connected inverters. Under the abnormal grid condition, the grid-connected inverter can convert the operation mode from grid-connected to stand-alone mode to supply power to the local load. For a seamless mode transfer, the time delay problems caused by the accumulated control variable error must be solved, and the indirect current control method has been applied as one of the solutions. In this study, the design of control parameters for the proportional-resonant-based triple-loop indirect current controller and the control strategy for the seamless mode transfer of parallel grid-connected inverters are described and analyzed. The validity of the proposed mode transfer method is verified by the PSiM simulation results.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2005년도 전력전자학술대회 논문집
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• pp.329-332
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• 2005

Distributed generation (DG) systems fall in islanding operation when they still in operation even when the main grid is out of electric power Islanding operation is further classified into intentional islanding and unintentional islanding operations. In intentional islanding operation, the DG backs up critical loads while it separates from the main grid on islanding detection. Intentional islanding operation increases utilization of the DG system during the islanding operation. This paper proposes reasonal inverter topology and its control algorithm for seamless transfer of DG systems in intentional islanding operation.

• 전력전자학회논문지
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• 제24권5호
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• pp.349-355
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• 2019

A grid-connected inverter with critical loads should be able to supply a stable voltage to critical loads at mode change and during clearing time while detecting unintentional islanding. This study proposes a mode transfer method for a grid-connected inverter with critical loads. The proposed method, which integrates the grid-connected and islanded mode control loops into one control block, provides an autonomous and seamless mode transfer from the current control to the voltage control. Therefore, the proposed scheme can supply a stable voltage to critical loads at mode change and during clearing time. Experimental results are provided to validate the proposed method.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2017년도 전력전자학술대회
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• pp.369-370
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• 2017

In this paper, a model predictive voltage control (MPVC) for the DC-DC buck-boost converters is proposed. It provides a fast seamless bidirectional control method to maintain the DC grid voltage, battery voltage and current within predefined limits. In addition, an inner current control loop is not employed, so that the bandwidth of controller can be higher compared with the PI controller.

• Journal of Power Electronics
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• 제19권1호
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• pp.254-264
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• 2019

This paper proposes an indirect current control technique based on a proportional resonant (PR) approach for the seamless mode transfer of utility interactive inverters. Direct-current and voltage hybrid control methods have been used for inverter control under grid-connected and islanded modes. A large bandwidth can be selected due to the structure of single-loop control. However, this results in poor dynamic transients due to sudden changes of the controller during mode changes. Therefore, inverter control based on indirect current is proposed to improve the dynamic transients by consistently controlling the output voltage under all of the operation modes. A PR-based indirect current control topology is used in this study to maintain the load voltage quality under all of the modes. The design processes of the PR-based triple loop are analyzed in detail while considering the system stability and dynamic transients. The mode transfer techniques are described in detail for both sudden unintentional islanding and islanded mode voltage quality improvements. In addition, they are described using the proposed indirect control structure. The proposed method is verified by the PSiM simulations and laboratory-scale VDER-HILS experiments.

• 정보처리학회논문지C
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• 제9C권2호
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• pp.257-266
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• 2002

3GPP2 방식의 무선 데이터 통신에서는 Macro Mobility 지원을 위하여 Mobile IP가 이용되며 PDSN은 Foreign Agent의 기능을 수행한다. 이때 하나의 PDSN에서 다른 PDSN으로 Mobile Station이 이동할 경우 지원되는 이동성을 Macro Mobility라 한다. 본 논문은 Macro Mobility에서 발생할 수 있는 패킷의 손실 및 순서변경에 대한 가능성을 살펴보고, 이러한 문제점을 보완하기 위한 방법으로 패킷의 Down Stream과 Up Stream의 각 경우에 대하여 Handoff Sequence Control을 적용한 PDSN간의 seamless 핸드오프 알고리즘을 제시한다.

• 정보처리학회논문지C
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• 제16C권1호
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• pp.117-124
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• 2009

최근 디지털 정보통신 기술의 발전으로 네트워크 기술 및 성능의 적용 범위가 모든 분야로 확대됨에 따라 모든 정보단말, 가전기기, 사물 등이 하나의 네트워크로 연결되는 차세대 통신환경으로 진화되고 있다. 이러한 차세대 통신 환경에서의 핵심기술인 IMS(IP Multimedia Subsystem) 기반 네트워크에서 원활한 통합서비스(convergence service)의 제공을 위해서는 사용하던 정보단말이 바뀌거나 네트워크가 변화하더라도 이용 받던 서비스들을 그대로 제공 받을 수 있는 끊김없는(seamless) 서비스가 가능하여야 한다. 본 논문은 IMS Enabler를 통한 통합서비스 제공환경에서 사용자의 네트워크 환경의 변화나 정보단말의 변화에도 끊김없는 서비스를 제공하기 위한 세션제어기법과 그 구조를 제안하고 그에 따른 서비스 세션 제어 프로토콜(Service Session Control Protocol : SSCP)을 제시한다.

• 융합보안논문지
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• 제7권1호
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• pp.99-106
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• 2007

제안한 분산 앵커(Anchor) CX 탐색 알고리즘은 무선 ATM 네트워크에서 빠르고 매끄러운 핸드오프를 지원해 주는데 중요한 역할을 한다. 본 방법은 그룹핑 한 네트워크 내에서 각 그룹은 Anchor 스위치가 그룹의 연결을 관리하고 Anchor과 Anchor 사이에는 정보교환을 위하여 작은 대역폭의 PVC를 할당한다. 제안한 알고리즘은 빠르게 CX를 찾을 수 있고, 전체 네트워크 관리가 용이하며, 시스템 오버헤드나 전달지연시간이 줄어 매끄러운 핸드오프를 지원 할 수 있다.

• 전력전자학회논문지
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• 제21권3호
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• pp.200-206
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• 2016

In the microgrid, inverters for energy storage system are generally constructed in a parallel structure because of capacity expandability, convenience of system maintenance, and reliability improvement. Parallel inverters are required to provide stable voltage to the critical load in PCC and to accurately share the current between each inverter. Furthermore, when islanding occurs, the inverters should change its operating mode from grid-connected mode to stand-alone mode. However, during clearing time and control mode change, the conventional control method has a negative impact on the critical load, that is, severe fluctuating voltage. In this study, a parallel operation control method is proposed. This method provides seamless mode transfer for the entire transition period, including clearing time and control mode change, and has accurate current sharing between each inverter. The proposed control method is validated through simulation and experiment.

• Journal of Power Electronics
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• 제15권4호
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• pp.1066-1073
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• 2015

This paper proposes a control strategy based on the frequency detection method, comprising a current control and a feed-forward voltage control loop, is proposed for grid-interactive power conditioning systems (PCS). For continuous provision of power to critical loads, PCS should be able to check grid outages instantaneously. Hence, proposed in the present paper are a frequency detection method for detecting abnormal grid conditions and a controller, which consists of a current controller and a feedforward voltage controller, for different operation modes. The frequency detection method can detect abnormal grid conditions accurately and quickly. The controller which has current and voltage control loops rapidly helps in load voltage regulation when grid fault occurs by changing reference and control modes. The proposed seamless transfer control strategy is confirmed by experimental results.