Three Control Strategies to Improve the Microgrid Transient Dynamic Response During Isolated Mode: A Comparative Study

Kamel, Rashad M.; Chaouachi, Anis; Nagasaka, Ken

doi:10.1109/tie.2012.2209609

Cited by 90 publications

(53 citation statements)

References 40 publications

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“…2. The UPS system consists of a battery, a bidirectional DC/DC converter [17], and a bidirectional three-phase DC/AC converter with an output LCL filter. The DC/AC converter parameters are given in Table I Fig.…”

Section: System Overviewmentioning

confidence: 99%

Line-Interactive UPS for Microgrids

Abusara

Guerrero

Sharkh

2014

IEEE Trans. Ind. Electron.

160

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Abstract-Line interactive Uninterruptable Power Supply (UPS) systems are good candidates for providing energy storage within a microgrid to help improve its reliability, economy and efficiency. In grid-connected mode, power can be imported from the grid by the UPS to charge its battery. Power can also be exported when required, e.g., when the tariffs are advantageous. In stand-alone mode, the UPS supplies local distributed loads in parallel with other sources. In this paper, a line interactive UPS and its control system are presented and discussed. Power flow is controlled using the frequency and voltage drooping technique to ensure seamless transfer between grid-connected and stand-alone parallel modes of operation. The drooping coefficients are chosen to limit the energy imported by the USP when re-connecting to the grid and to give good transient response. Experimental results of a microgrid consisting of two 60kW line interactive UPS systems are provided to validate the design. Index Terms-Line interactive UPS, microgird, distributed generation. I. INTRODUCTIONO INCREASE reliability, energy storage systems within a microgrid are essential. Energy is stored while in grid-connected mode, when the microgrid's Distributed Generation (DG) systems produce excess power, to be used later to supply critical loads during power outages. In stand-alone mode, they can be used to boost the power supplied by the microgrid if the DG systems cannot meet the expected level of power. To meet these demands, the energy storage system needs to be able to work in grid-connected and stand-alone modes. In the latter mode of operation, the system needs to operate in parallel with other DG systems to meet the variable power demand of the load. More importantly, it needs to switch seamlessly between the two modes.Line interactive UPS systems are good candidates for providing energy storage within microgrids as they can be connected in parallel with both the main grid and local load. The classical topology of line interactive UPS systems [1], [2] is simpler, cheaper, more efficient and more reliable than the on-line double conversion UPS. This topology, however, does not provide voltage regulation to the load. Voltage regulation is M. A. Abusara was with Bowman Power Group, UK and now he is with the Renewable Energy Research Group, University of Exeter, Cornwall Campus, Penryn, TR10 9EZ, U.K. (e-mail: m.abusara@exeter.ac.uk).J. M. Guerrero is with the Department of Energy Technology, Aalborg University, 9220 Aalborg, Denmark (e-mail: joz@et.aau.dk).S. M. Sharkh is with the Electro-Mechanical Engineering Research Group, University of Southampton, Highfield Campus, Southampton, SO17 1BJ, U.K. (e-mail: suleiman@soton.ac.uk).possible as in series-parallel or delta conversion line-interactive UPS [3]-[6] at the expense of lower efficiency and extra size and cost due to the use of extra inverter and bulky transformer. However, this topology is still more efficient than classical on-line double conversion UPS because the complementary inverte...

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Section: System Overviewmentioning

confidence: 99%

Line-Interactive UPS for Microgrids

Abusara

Guerrero

Sharkh

2014

IEEE Trans. Ind. Electron.

160

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“…Firstly, the partially reserved wind energy by blade pitching of WT [11][12][13] can be utilized to stabilize the grid frequency. This scheme requires WTs not to operate at their maximal power tracking point, which enables WTs to release partial reserved energy by increasing pitch angle or curtail excessive wind energy by decreasing pitch angle when system needs.…”

Section: Introductionmentioning

confidence: 99%

Coordinated Control Schemes of Super-Capacitor and Kinetic Energy of DFIG for System Frequency Support

Xiong

Zhu

et al. 2018

Energies

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This paper mainly focuses on how to provide frequency supports by the doubly fed induction generator (DFIG) during system disturbances. Two coordinated controls that enable system frequency supports by DFIG-based wind turbines (WTs) are proposed in this paper. The first control scheme seeks to render system support via simultaneously utilizing the energy from the installed super-capacitor between the back-to-back converter of DFIG, and WT rotational kinetic energy (KE). The second one stabilizes system frequency by firstly exerting the installed super-capacitor energy and then WT rotational KE via a unique cascading control. Both proposed coordinated control schemes jointly utilize two virtual inertia sources, namely super-capacitor in the DFIG and rotor rotational mass in the WT to fast provide system frequency support. However, the second proposed one stands itself out by reducing its impaired impacts on the overall wind energy production. Two proposed controls on rapidly providing frequency support are effectively verified and compared in detail by different system disturbances in the DIgSILENT/Powerfactory software.

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“…In this context, the MG is considered as one of the most promising and growing concepts [2]. The MG is an active distribution network which enables a high penetration level of renewable DGs such as PV and wind turbines.…”

Section: Introductionmentioning

confidence: 99%

“…The MG is an active distribution network which enables a high penetration level of renewable DGs such as PV and wind turbines. Existence of DGs in the MG enhances the reliability and the power quality of the power supply especially at the end users [2].…”

Section: Introductionmentioning

confidence: 99%

Standalone micro grid power quality improvement using inertia and power reserves of the wind generation systems

Kamel

2016

Renewable Energy

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Keywords:Standalone MG MG frequency regulation Inertia and frequency droop DFIG inertia Pitch angle power reserve DFIG reactive power capability a b s t r a c t This paper proposes two controllers for employing part of variable speed wind generation systems kinetic energy in supporting the standalone MG frequency. The first controller acts similar to the frequency droop control, while the second controller emulates both the inertia response and the frequency droop control simultaneously. The MG frequency dropped only to 49.9 Hz with employing the proposed controllers compared with 49.68 Hz without employing the proposed controllers. Also, the injected active power from the storage device dropped from 20 kW to only 3 kW after employing the proposed controllers. In addition, the reactive power capability of the Double Fed Induction Generator (DFIG) wind generation system has been employed to maintain the standalone MG bus voltage at acceptable level. If there are fixed speed wind generation systems in the standalone MG, this paper proposed using the pitch angle controller to employ a suitable wind turbine power reserve in MG frequency supporting during the standalone mode. Results proved the effectiveness of the proposed controllers in improvement the MG overall performance during and subsequent the islanding occurrence.

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Three Control Strategies to Improve the Microgrid Transient Dynamic Response During Isolated Mode: A Comparative Study

Cited by 90 publications

References 40 publications

Line-Interactive UPS for Microgrids

Line-Interactive UPS for Microgrids

Coordinated Control Schemes of Super-Capacitor and Kinetic Energy of DFIG for System Frequency Support

Standalone micro grid power quality improvement using inertia and power reserves of the wind generation systems

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