Control Method for Grid-Connected/Islanding Switching of Hybrid AC/DC Microgrid

Qu, Zhengwei; Chong, Zhenxiao; Wang, Yun-Jing; Shi, Zhe; Yao, Yunxiao

doi:10.1007/s42835-022-01146-8

Cited by 5 publications

(4 citation statements)

References 25 publications

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“…Supported by bidirectional interlinking converters (BICs), distributed subgrids are interconnected to form a comprehensive small-scale electrical system [17]. Microgrids can operate in grid-connected and islanded modes, providing the end users flexibility, energy supply security, and improved power quality [18,19]. During normal operation, energy can flow flexibly via the BIC between the two subgrids [20].…”

Section: Introductionmentioning

confidence: 99%

Enhancing Grid-Forming Converters Control in Hybrid AC/DC Microgrids Using Bidirectional Virtual Inertia Support

Bakeer,

Chub,

Abid

et al. 2024

Processes

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This paper presents a new grid-forming strategy for hybrid AC/DC microgrids using bidirectional virtual inertia support designed to address weak grid conditions. The stability of hybrid AC/DC microgrids heavily relies on the AC mains frequency and the DC-link voltage, and deviations in these factors can lead to undesirable outcomes such as load curtailments and power system congestions and blackouts. This paper introduces a unique approach that leverages bidirectional virtual inertia support to enhance the stability and reliability of hybrid AC/DC microgrids under weak grid conditions. The proposed strategy employs virtual inertia as a buffer to mitigate rapid changes in DC-link voltage and AC frequency, thereby enhancing system stability margins. This strategy significantly contributes to a more stable and reliable grid operation by reducing voltage and frequency fluctuations. A standard hybrid AC/DC microgrid configuration is used to implement the bidirectional virtual inertia support, where a bidirectional interlinking converter control is adjusted to deliver inertia support to both the AC and DC subgrids. This converter utilizes the DC grid voltage and AC grid frequency as inputs, effectively managing active power balance and implementing auxiliary functions. Extensive simulations are conducted under weak grid conditions and standalone mode to validate the effectiveness of the proposed strategy. The simulation results demonstrate a remarkable improvement in frequency nadir, rate-of-change-of-frequency (RoCoF), and DC bus voltage deviation in the hybrid AC/DC microgrids. The bidirectional virtual inertia support substantially reduces voltage and frequency fluctuations, enhancing the microgrid stability and resilience. There is an improvement of over 45% and 25% in the frequency deviation and voltage deviation, respectively, achieved through implementing the proposed control strategy.

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Section: Introductionmentioning

confidence: 99%

Enhancing Grid-Forming Converters Control in Hybrid AC/DC Microgrids Using Bidirectional Virtual Inertia Support

Bakeer,

Chub,

Abid

et al. 2024

Processes

View full text Add to dashboard Cite

show abstract

“…Master-slave control [14][15][16] in a microgrid system comprises a master source and slave sources [17]. The master source is capable of receiving operational information from all the sources based on a communication system, optimizing the microgrid's operating state, and then transmitting control information to the respective slave source.…”

Section: Introductionmentioning

confidence: 99%

“…In the event of unplanned islanding in a mixed AC/DC microgrid operating under master-slave control, significant voltage and current fluctuations are identified in the high-voltage magnetic control system. To solve the above-mentioned fluctuations, [16] introduced state tracking control between constant power control and constant voltage control. When unplanned islanding is reported, the sudden change in the current reference signal can be converted into a smooth transition by replacing the controller of the main DC distributed generation.…”

Section: Introductionmentioning

confidence: 99%

A Seamless Switching Strategy for Hybrid AC/DC Microgrids under Varied Control Complexities

Zhang,

He,

Yuan

et al. 2024

IEEE Access

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In peer-to-peer controlled hybrid AC/DC microgrids, the grid-connected inverters switch between different control modes with the change of the operating conditions. However, the abovementioned mode transitions trigger transient disturbances in voltage, frequency, and current, causing power mismatch, such that the smooth operation of the microgrid will be hampered. To solve the above-mentioned problems, a composite control strategy is proposed in this study following droop control and PQ control, with the aim of achieving seamless switching between islanded and grid-connected modes. The proposed strategy couples the current inner loops of the above control methods (droop control and PQ control) to develop a dual-mode combined controller operating based on current tracking. This configuration enables the reference current of the input current inner loop controller to track the pre-switching state while maintaining the correct initial value. Moreover, a compensatory pre-synchronization control strategy is developed to cope with variations in frequency, phase, and amplitude. The voltage offset is improved from 19% to synchronize with the grid, and the microgrid islanded/grid-connected mode is smoothly switched. The reference value of the outer loop is changed by PQ control, so that the exchange power of the grid side and the microgrid side is 0. Thus, seamless switching between grid-connected and islanded modes can be achieved. The effectiveness and feasibility of the control strategy proposed in this study are verified in the simulation system.

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“…Meanwhile, a microgrid consisting of a large number of renewable-based DERs must be operated flexibly in consideration of intermittent energy fluctuations. For this purpose, an appropriate control strategy, such as interconnection with the existing utility grid or island mode, must be applied [4,5]. In particular, the voltage stability of the microgrid under such a control strategy is of utmost importance, and this is due to the following reasons.…”

Section: Introduction 1motivation and Incitementmentioning

confidence: 99%

Voltage Stability Assessment of a Campus DC Microgrid Implemented in Korea as a Blockchain-Based Power Transaction Testbed

Hwang,

Lee,

Choi

et al. 2023

Energies

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Recently, the generalization of P2P (peer-to-peer) technology with enhanced security due to blockchain technology and the expansion of renewable energy-based distributed energy resources have led to blockchain technology being applied in power transactions, thus giving the potential to become a new platform for DC microgrid operation. Meanwhile, the voltage of a DC microgrid represents the balance of energy supply and demand and also serves as a stability index. The balance is represented as a steady state; the stability is represented during and after events. This paper examines the stability of the DC microgrid built on a university campus in Korea and, in particular, the blockchain technology-based power transactions performed in the DC microgrid. The test is based on the pre-planned transaction schedule applied in the DC microgrid. The transaction schedule has used day-ahead and real-time bidding data. Although many technologies are included in the project, this paper focuses on the voltage stability of the DC microgrid. In addition, the DC protection is applied and evaluated. To consider general DC protection, the DC breaker was simplified with several IGBTs, diodes, capacitors, and arrestors and was designed to interrupt the fault current within five milliseconds. The stability was evaluated using a PSCAD/EMTDCTM.

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Control Method for Grid-Connected/Islanding Switching of Hybrid AC/DC Microgrid

Cited by 5 publications

References 25 publications

Enhancing Grid-Forming Converters Control in Hybrid AC/DC Microgrids Using Bidirectional Virtual Inertia Support

Enhancing Grid-Forming Converters Control in Hybrid AC/DC Microgrids Using Bidirectional Virtual Inertia Support

A Seamless Switching Strategy for Hybrid AC/DC Microgrids under Varied Control Complexities

Voltage Stability Assessment of a Campus DC Microgrid Implemented in Korea as a Blockchain-Based Power Transaction Testbed

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