Impedance Modeling and Stability Analysis of VSG Controlled Type-IV Wind Turbine System

Xu, Yunyang; Nian, Heng; Hu, Bin; Sun, Dan

doi:10.1109/tec.2021.3062232

Cited by 32 publications

(11 citation statements)

References 28 publications

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“…When L g is smaller than 1 mH, the characteristic root locus passes through the imaginary axis of the complex plane, and the system becomes unstable. The result of the small signal stability analysis above proves that the U‐VSG is suitable for weak grid and will destabilise in strong grid [16].…”

Section: The Characterization Methods Of the Boundary For The Multi‐m...mentioning

confidence: 99%

“…According to Equations ( 1)-( 3) and ( 7)-( 9), if the differential terms of the state equation are all 0, the steady-state operating point of the U-VSG can be solved, and the solution process has been shown in the Appendix. The small signal model of U-VSG is obtained by linearizing the mathematical model at its steady-state operation point, which is shown as Equation ( 12) [16,23,24]. The detailed derivation process has been shown in the Appendix.…”

Section: 2mentioning

confidence: 99%

“…The output power of U‐VSG, like conventional synchronous generator, is related to the voltage phase and amplitude, so the system can keep good stability even in a very weak power grid. However, when the grid impedance is small, the pole damping of the power outer loop is small, and the output power is prone to oscillate [16]. In light of the poor stability of the U‐VSG in strong grids, a virtual impedance is introduced in [17] to reshape the inverter output impedance to be approximate to inductive, which improves the stability of VSG in the strong power grid but reduces the amplitude of the inverter output voltage.…”

Section: Introductionmentioning

confidence: 99%

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An adaptive multi‐mode switching control strategy to improve the stability of virtual synchronous generator with wide power grid strengths variation

Liu

Qin

Zhou

et al. 2022

IET Generation Trans & Dist

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With the increasing proportion of renewable power generations in the power system, the power grid impedance may fluctuate greatly, and it is difficult for the virtual synchronous generator (VSG) with a single control structure to meet the stability requirements. Thus, the control principles of the two types of VSGs are compared to conclude that there are similarities in the control structure of the two VSGs. And the small signal models of the two types of VSGs are established to analyze the stability boundaries, coming to the conclusion that the stability region is complementary. Based on the conclusions, the paper puts forward the idea of switching operation modes: switch to the U‐VSG mode when the grid strength weakens and switch to the PQ‐VSG mode when greater, so that the inverter can keep stable in a wider range of grid strength. Therefore, the characterization method of the switching boundary with hysteresis properties is proposed. Then the improved recursive least squares (RLS) algorithm is introduced to identify the power grid impedance online without additional injected disturbance, based on which the adaptive multi‐mode smooth switching control strategy is proposed. Finally, the effectiveness of the analysis and the control strategy are verified by simulations.

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Section: The Characterization Methods Of the Boundary For The Multi‐m...mentioning

confidence: 99%

Section: 2mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

An adaptive multi‐mode switching control strategy to improve the stability of virtual synchronous generator with wide power grid strengths variation

Liu

Qin

Zhou

et al. 2022

IET Generation Trans & Dist

View full text Add to dashboard Cite

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“…( 6), the output transfer function of the VSG under active instruction is obtained using Eq. (9). 10) and ( 11), the natural oscillation frequency ω n and damping ratio ζ of the grid-connected VSG can be obtained as in Eqs.…”

Section: Frequency-domain Analysis Of Vsgmentioning

confidence: 99%

“…Due to the inconsistency of the coordination control between the VSGs and SGs, the low-frequency oscillation may be easily caused when the damping effect of the power system is limited. Thus, it is necessary to analyze the low-frequency oscillation mechanism to improve the power system stability [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Low-Frequency Oscillation Analysis of Grid-Connected VSG System Considering Multi-Parameter Coupling

Lu¹,

Wang²,

Liang³

et al. 2023

Computer Modeling in Engineering &Amp; Sciences

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With the increasing integration of new energy generation into the power system and the massive withdrawal of traditional fossil fuel generation, the power system is faced with a large number of stability problems. The phenomenon of low-frequency oscillation caused by lack of damping and moment of inertia is worth studying. In recent years, virtual synchronous generator (VSG) technique has been developed rapidly because it can provide considerable damping and moment of inertia. While improving the stability of the system, it also inevitably causes the problem of active power oscillation, especially the low mutual damping between the VSG and the power grid will make the oscillation more severe. The traditional time-domain state-space method cannot reflect the interaction among state variables and study the interaction between different nodes and branches of the power grid. In this paper, a frequency-domain method for analyzing low-frequency oscillations considering VSG parameter coupling is proposed. First, based on the rotor motion equation of the synchronous generator (SG), a secondorder VSG model and linearized power-frequency control loop model are established. Then, the differences and connections between the coupling of key VSG parameters and low-frequency oscillation characteristics are studied through frequency domain analysis. The path and influence mechanism of a VSG during low-frequency power grid oscillations are illustrated. Finally, the correctness of the theoretical analysis model is verified by simulation.

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Mechanical–electrical‐grid model for the doubly fed induction generator wind turbine system considering oscillation frequency coupling characteristics

Wang,

2023

Wind Energy

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With the evolution of renewable energies, many doubly fed induction generators (DFIGs) are being connected to the power grid, whose operation and grid‐connection stability have a major impact on the power grid. Currently, most studies focus on either modeling the mechanical–electrical section or the electrical‐grid section, and discussions have been limited to shaft oscillation or frequency coupling problems. In this study, a mechanical–electrical‐grid model of a DFIG was established to examine the impacts of wind speed and system control parameters on electrical damping and grid‐connection stability. The accuracy of the proposed model and validity of the analyses were verified using simulations. The following were observed: (1) In the case of changing wind speeds, the wind speed and the applied control model determine the shaft oscillation of DFIG, whereas the grid‐connected impedance on the rotor side is dependent on the wind speed. (2) At a constant wind speed, changes in control parameters under different control modes affect the dynamic characteristics of the drive train differently, whereas the grid‐connected impedance on the rotor side is primarily determined by the proportional gain of the inner/outer loop of the control system. The conclusions drawn from this study can further improve the safe and stable operation of DFIG wind power generation systems as well as their connection to the power grid.

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Impedance Modeling and Stability Analysis of VSG Controlled Type-IV Wind Turbine System

Cited by 32 publications

References 28 publications

An adaptive multi‐mode switching control strategy to improve the stability of virtual synchronous generator with wide power grid strengths variation

An adaptive multi‐mode switching control strategy to improve the stability of virtual synchronous generator with wide power grid strengths variation

Low-Frequency Oscillation Analysis of Grid-Connected VSG System Considering Multi-Parameter Coupling

Mechanical–electrical‐grid model for the doubly fed induction generator wind turbine system considering oscillation frequency coupling characteristics

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