• 전력전자학회:학술대회논문집
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• 전력전자학회 2019년도 추계학술대회
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• pp.148-149
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• 2019

Voltage unbalance can be occured in AC-DC microgrid systems when AC loads or AC systems are connected. To solve this problem, 3-phase 4-wire interlinking converter is used. This paper proposes in PLL method that can detect accurate phase and voltage magnitude.

• Journal of Electrical Engineering and Technology
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• 제12권3호
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• pp.1064-1072
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• 2017

The power of controlled generators in microgrids randomly fluctuate because of the stochastic volatility of the outputs of photovoltaic systems and wind turbines as well as the load demands. To address and dispatch these stochastic factors for daily operations, a dynamic economic dispatch model with the goal of minimizing the generation cost is established via chance-constrained programming. A Monte Carlo simulation combined with particle swarm optimization algorithm is employed to optimize the model. The simulation results show that both the objective function and constraint condition have been tightened and that the operation costs have increased. A higher stability of the system corresponds to the higher operation costs of controlled generators. These operation costs also increase along with the confidence levels for the objective function and constraints.

• 조명전기설비학회논문지
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• 제26권10호
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• pp.102-110
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• 2012

This paper propose the advanced topology of UPQC, its DC link is connected with Lithium battery, to compensate the momentary interruptions. The proposed system can be operated as UPS mode using the parallel inverter, which control the charge or discharge of battery, in case of the interruption. We dvelop 100kVA UPQC using the proposed topology to rise the power quality and the reliability of Microgrid. We verify its usefulness through voltage compensation test, UPS operation test and etc. using Microgrid test facility.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2017년도 전력전자학술대회
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• pp.120-121
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• 2017

This paper proposes an enhanced distributed generation (DG) unit with an adaptive virtual impedance control approach in order to address the inaccurate reactive power sharing problem. The proposed method can adaptively regulate the DG virtual impedance, and the effect of the mismatch in feeder impedances is compensated to share the reactive power accurately. The proposed control strategy is fully distributed and the need for the microgrid central controller is eliminated. Furthermore, the proposed method can be directly implemented without requirement of pre-knowledge of the feeder impedances. Simulations are performed to validate the effectiveness of the proposed control approach.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2008년도 추계학술대회 논문집
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• pp.106-108
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• 2008

This paper describes output characteristics analysis of outage and phase jump generator for microgrid. The outage and phase jump can be generated with 3-phase voltage disturbance generator. As soon as the outage occurs the STS(Solid Transfer Switch)s are switched off. At the beginning of the outage the PCS is required to limit the reverse current within the rated PCS output current. In case of phase jump the PCS output voltage phase should be adjusted. The generator output characteristics are analysed through simulation.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2015년도 전력전자학술대회 논문집
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• pp.371-372
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• 2015

Dc microgrid has the advantage of high efficiency as compared to the ac system. Droop method has been realized to suppress the current mismatching among the distributed sources. However, this method involves distribution loss due to the line impedance. In this paper, a novel droop method is proposed to minimize the distribution loss as well as the voltage deviation by adjusting the droop coefficient. The proposed droop method is verified by using the simulation based on PSCAD/EMTDC.

• 전기학회논문지P
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• 제65권3호
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• pp.219-223
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• 2016

DC microgrid system is attracted attention in the world, because DC distribution system is more energy efficient than AC distribution system. To analyse the contribution effects of distributed generation(DG) in LVDC distribution system through modeling the Rectifier, DC/DC converter, Energy Storage System(ESS) and Photovoltaic(PV). using PSCAD/EMTDC. This paper analyses fault response characteristics in LVDC distribution system according to the interconnection and islanding operation of DG. Based on research results on the paper, direction for development of fault current reduction method for LVDC distribution system is suggested.

• 전기학회논문지
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• 제57권4호
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• pp.582-588
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• 2008

Microgrids are new distribution level power networks that consist of various electronically-interlaced generators and sensitive loads. The important control object of Microgrids is to supply reliable and high-quality power even during the faults or loss of mains(islanding) cases. This paper presents power control methods to coordinate multiple distributed generators(DGs) against abnormal cases such as islanding and load power variations. Using speed-droop and voltage-droop characteristics, multiple distributed generators can share the load power based on locally measured signals without any communications between them. This paper adopts the droop controllers for multiple DG control and improved them by considering the generation speed of distribution level generators. Dynamic response of the proposed control scheme has been investigated under severe operation cases such as islanding and abrupt load changes through PSCAD/EMTDC simulations.

• Journal of Power Electronics
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• 제17권6호
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• pp.1650-1657
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• 2017

In this study, the distributed secondary voltage control of islanded microgrids with multi-agent consensus algorithm is investigated. As an alternative to a time-triggered approach, an event-triggered scheme is proposed to reduce the communication load among inverter-based distributed generators (DGs). The proposed aperiodic control scheme reduced unnecessary utilization of limited network bandwidth without degrading control performance. By properly establishing a distributed triggering condition in DG local controller, each inverter is only required to send voltage information when its own event occurs. The compensation of voltage amplitude deviation can be realized, and redundant data exchange related to fixed high sampling rate can be avoided. Therefore, an efficient use of communication infrastructure can be realized, particularly when the system is operating in steady state. The effectiveness of the proposed scheme is verified by simulations on a microgrid test system.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2019년도 전력전자학술대회
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• pp.416-417
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• 2019

In this paper, an effective power flow control strategy (PFCS) based on the centralized control approach and a DC-link (DCV) restoration algorithm for DC microgrid (DCMG) are presented. By investigating the statuses of system power units, eleven operating modes are given to ensure the system power balance under various conditions. To avoid the system power imbalance caused by the delay of grid fault detection, a reliable DCV restoration algorithm is proposed. In the proposed scheme, when an abnormal variation of the DCV is detected, the battery instantly starts a local emergency control mode to restore the DCV to the nominal value regardless of the control mode from the central controller. The simulations and experiments are carried out to prove the effectiveness of the PFCS and the proposed DCV restoration algorithm.