Fundamental grid impedance estimation using grid‐connected inverters: a comparison of two frequency‐based estimation techniques

Mohammed, Nabil; Ciobotaru, Mihai; Town, Graham

doi:10.1049/iet-pel.2019.1458

Cited by 22 publications

(15 citation statements)

References 44 publications

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“…These algorithms are categorised generally into three groups, i.e., active, passive, and hybrid techniques [25]. The GIE techniques based on single frequency injection are shown to provide very accurate results if its estimation time and disturbance amplitude are designed properly [26]. Therefore, the online active GIE based on 75 Hz injection is chosen in this paper [27].…”

Section: B Online Event-based Grid Impedance Estimation Algorithmmentioning

confidence: 99%

“…Therefore, the online active GIE based on 75 Hz injection is chosen in this paper [27]. To avoid estimation errors related to the presence of background inter/sub-harmonics in the grid voltage, the injection/estimation time is set for 200 ms [26]. This permits accurate measuring due to the use of 5 Hz resolutions as per "Interharmonics -Recommended Updates to IEEE 519" [28].…”

Section: B Online Event-based Grid Impedance Estimation Algorithmmentioning

confidence: 99%

“…Simultaneously with the injection of i d−inj and i q−inj , the current and voltage responses (v res (75 Hz), i res (75 Hz)) at the PCC of phase A, B or C are recorded. Then, the fundamental grid impedance (Z g (50 Hz)) is estimated by approximating its value to Z g (75 Hz) as shown in (39) [26], [27].…”

Section: B Online Event-based Grid Impedance Estimation Algorithmmentioning

confidence: 99%

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Online Grid Impedance Estimation-Based Adaptive Control of VSGs Considering Strong and Weak Grid Conditions

Mohammed¹,

Bahrani²,

Ravanji³

et al. 2022

Preprint

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<p>The conventional virtual synchronous generator (VSG) is normally designed to meet certain operational and control requirements in the islanded mode. However, once the VSG is switched to grid-connected mode (GCM), the robust operation cannot be guaranteed under different grid conditions. It can lead to, especially in strong grids, poor dynamic performance such as significant oscillation, long settling time, and high overshoot. In order to improve the VSG performance in the GCM, this article first analyzes in depth the inherent coupling between the active and reactive power and its dependence on the grid conditions, such as the short circuit ratio, grid impedance ratio Xg=Rg, and the wide grid impedance variations. Afterwards, an online grid impedance estimation-based adaptive VSG (AVSG) control strategy is proposed to ensure the robust operation of the VSG considering both strong and weak grid conditions. This technique allows the operator to specify the desired settling time of output power and damping ratio.To estimate the grid impedance in real time without extra hardware and reduce the associated impacts on power quality, an online event-based grid impedance estimation algorithm is embedded into the control loop of the AVSG. Both the simulation and experimental results indicate that, compared to the conventional fixed-parameters-based controller design method, the AVSG enables the desired performance such as no oscillation, specified time duration for the settling time, and minimal overshoot regardless of the grid conditions.</p>

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Section: B Online Event-based Grid Impedance Estimation Algorithmmentioning

confidence: 99%

Section: B Online Event-based Grid Impedance Estimation Algorithmmentioning

confidence: 99%

Section: B Online Event-based Grid Impedance Estimation Algorithmmentioning

confidence: 99%

See 1 more Smart Citation

Online Grid Impedance Estimation-Based Adaptive Control of VSGs Considering Strong and Weak Grid Conditions

Mohammed¹,

Bahrani²,

Ravanji³

et al. 2022

Preprint

Self Cite

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“…This transfer function is used to design the controller proposed in (8). Although there are many approaches for impedance estimation in the literature [40], [41], errors in the grid impedance estimation can occur in the system; thus, a robustness analysis of the system against impedance estimation errors is needed.…”

Section: Lpv Loop-shaping Control Designmentioning

confidence: 99%

Linear Parameter-Varying Control of A Power-Synchronized Grid-Following PLL-Less Inverter

Mansour¹,

Karimi²,

Bahrani³

2021

Preprint

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<div>This paper proposes a Linear Parameter-Varying loop-shaping controller for a power-synchronized Phase-locked Loop (PLL)-less grid-following inverter (GFLI). This control strategy regulates the inverter's output active and reactive powers at the terminal instead of the point of connection and does not require a PLL for extracting the voltage phase angle. Hence, the prevalent stability issues exhibited when GFLIs are connected to weak grids are not present, and the proposed GFLI control strategy can work under both very weak and strong grid conditions without being prone to instability. In this approach, the controller parameters are functions of the operating point and changed during the real-time operation such that the closed-loop performance is preserved in all operating points. Furthermore, since the grid impedance is a factor in the design process, a robustness analysis against grid impedance estimation error is conducted, and it is shown that discrepancies in estimated and real grid impedances are unlikely to make the system unstable. The performance of the proposed control design is validated in Matlab/PLECS and experiment for both strong and weak grids. </div><div><br></div>

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“…The new topology of ADNs necessitates modern simulation of network impedances under different grid conditions [25,26]. The newly added components lead to the need of modeling balanced and/or unbalanced ADNs using grid-connected inverters [27]. Reference [28] presents a review of power distribution planning models in ADNs where a lack of modeling networks containing an automatic voltage regulator (AVR) as a voltage control unit is noticed.…”

Section: Introductionmentioning

confidence: 99%

Active Distribution Network Modeling for Enhancing Sustainable Power System Performance; a Case Study in Egypt

et al. 2020

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The remarkable growth of distributed generation (DG) penetration inside electrical power systems turns the familiar passive ‎distribution networks (PDNs) into active distribution networks (ADNs). Based ‎on the backward/forward sweep method (BFS), a new power-flow algorithm was developed in this paper. The algorithm is flexible to handle the bidirectional flow of power that characterizes the ‎modern ADNs. Models of the commonly used distribution network components were integrated with the developed algorithm to ‎form a comprehensive tool. This tool is valid for modeling either balanced or unbalanced ADNs with an unlimited number of nodes or laterals. The ‎integrated models involve modeling of distribution lines, losses inside distribution transformers, automatic voltage regulators ‎‎(AVRs), DG units, shunt capacitor banks (SCBs) and different load models. To verify its validity, the presented algorithm was first applied to the unbalanced IEEE 37-node standard feeder in both passive and active states. Moreover, the algorithm was then ‎applied to a balanced 22 kV real distribution network as a case study. The selected network is located in a remote area in the western desert of Upper Egypt, far away from the Egyptian unified national grid. Accordingly, the paper examines the current and future situation of the Egyptian electricity market. Comparison studies between the ‎performance of the proposed ADNs and the classical PDNs are discussed. Simulation results are presented to demonstrate the ‎effectiveness of the proposed ADNs in preserving the network assets, improving the system performance and minimizing the ‎power losses‎.

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Fundamental grid impedance estimation using grid‐connected inverters: a comparison of two frequency‐based estimation techniques

Cited by 22 publications

References 44 publications

Online Grid Impedance Estimation-Based Adaptive Control of VSGs Considering Strong and Weak Grid Conditions

Online Grid Impedance Estimation-Based Adaptive Control of VSGs Considering Strong and Weak Grid Conditions

Linear Parameter-Varying Control of A Power-Synchronized Grid-Following PLL-Less Inverter

Active Distribution Network Modeling for Enhancing Sustainable Power System Performance; a Case Study in Egypt

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