A modified grid voltage feedforward method to improve the stability-robustness of the grid-connected voltage source converter under weak grid conditions

2016 ◽  
Author(s):  
Heng Wu
Keyword(s):  
Voltage Source ◽  
Voltage Source Converter ◽  
Grid Voltage ◽  
Weak Grid ◽  
Stability Robustness ◽  
The Stability

scholarly journals Modelling of a VSC-based multi-terminal HVDC network for dynamic stability analysis

2017 ◽  
Vol 36 (1) ◽  
pp. 240-257 ◽  
Author(s):  
Kosei Shinoda ◽  
Xavier Guillaud ◽  
Seddik Bacha ◽  
Abdelkrim Benchaib ◽  
Bruno Francois
Keyword(s):  
Dynamic Stability ◽  
Voltage Regulators ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Electrical System ◽  
Content Type ◽  
Grid Voltage ◽  
Technical Requirements ◽  
Power Dispatch ◽  
The Stability

Purpose Self-commuted voltage source converter (VSC) can significantly extend the flexibility and operability of an HVDC system and be used to implement the concept of multi-terminal HVDC (MTDC) grid. To take full advantage of MTDC systems, its overall behaviour must be characterized in quasi static and dynamic states. Based on the numerous literatures, a dedicated two-level VSC model and its local controllers and DC grid voltage regulators are developed for this purpose. Furthermore, the requirement of the system to guarantee all the physical constrains must be well assessed and concrete demonstrations must be provided by numerical simulations. Design/methodology/approach First, a two-level VSC model and its local controllers and DC grid voltage regulators are developed. Then, DC cable models are investigated and their characteristics are assessed in the frequency domain. Those developed models are combined to form a three-terminal HVDC grid system on Matlab/Simulink platform. To analyze the stability of this electrical system, the dynamics of the system against variations of power dispatch are observed. Findings To analyze the stability of this electrical system, the dynamics of the system against variations of power dispatch are observed. The differences in the DC grid voltage dynamics and the power flow of the converter stations coming from the embedded primary controls are analysed, and the technical requirements for both cases are assessed. Originality/value In this paper, the dynamic stability of an MTDC system has been analysed and assessed through an adequate simulation model, including its control scheme and the cable models. The interest of the improved PI model for cables is highlighted.

scholarly journals Offshore wind power integration to support weak grid voltage for industrial loads using VSC-HVDC transmission system

2021 ◽  
Vol 11 (3) ◽  
pp. 1876
Author(s):  
Ahmed A. Daoud ◽  
Ahmed F. Abouzeid ◽  
Sobhy S. Dessouky
Keyword(s):  
Wind Power ◽  
Load Condition ◽  
Offshore Wind ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Grid Voltage ◽  
Offshore Wind Power ◽  
Hvdc Transmission ◽  
Weak Grid ◽  
Voltage Variation

This paper investigates the integration of the offshore wind power plant into the grid using voltage source converter high-voltage direct current (VSC-HVDC). The paper proposes both offshore and onshore converter stations control to support voltage variation in grid. Heavy industrial loads result in a weak grid. In this paper, the effect on industrial loads by the grid strength is shown. Then the paper proposes a solution for the grid voltage support for industrial loads connected to weak grids. The results showed that the increase of grid voltage from 0.7 pu to 1 pu at full load condition that provides a continuous operation without any interruption. The system was modelled using MATLAB/Simulink package.

scholarly journals Analysis of Synchronization Stability for Multi VSCs Parallel-Connected to Weak Grids by Improved Net Damping Criterion

Energies ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 3316 ◽  
Author(s):  
Dong Wang ◽  
Xiaojie Zhang ◽  
Lei Yang ◽  
Yunhui Huang ◽  
Wei Huang ◽  
...  
Keyword(s):  
Voltage Regulation ◽  
Operating Conditions ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Signal Model ◽  
Detailed Model ◽  
Weak Grid ◽  
Grid Connection ◽  
Sensitivity Studies ◽  
Stability Enhancement

Recent studies show that the loss of stability for a voltage-source converter (VSC) in weak-grid connection is largely related to its synchronization unit, i.e., the phase-locked loop (PLL). This paper studies the synchronization stability of a system comprised by two VSCs in parallel connection to a weak grid. A reduced transfer function based small-signal model, which can allow for the interactions between PLL and converter outer power controls, is first proposed. Then, an improved net damping criterion is used to analyze the damping and stability characters of such system under various operating conditions and different controller configurations. Compared to the conventional net damping criterion, the used criterion has wider applicability in terms of stability judgment. Case studies show that the studied system tends to be unstable at weak-grid or heavy-loading conditions. The instability can be in the form of oscillations or monotonic divergence, in which, the latter is more likely to occur for the converters without grid voltage regulation capabilities. Besides, the net damping-based sensitivity studies can provide guidance on control tuning or design for stability enhancement. Detailed model-based time domain simulations are conducted to verify the analysis results.

scholarly journals Modeling and Analyzing the Effect of Frequency Variation on Weak Grid-Connected VSC System Stability in DC Voltage Control Timescale

Energies ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4458 ◽  
Author(s):  
Yang ◽  
Yuan
Keyword(s):  
Voltage Control ◽  
System Stability ◽  
Voltage Source ◽  
Frequency Variation ◽  
Voltage Source Converter ◽  
Small Signal ◽  
Small Signal Stability ◽  
Dc Voltage ◽  
Weak Grid ◽  
Dc Voltage Control

The effect of frequency variation on system stability becomes crucial when a voltage source converter (VSC) is connected to a weak grid. However, previous studies lack enough mechanism cognitions of this effect, especially on the stability issues in DC voltage control (DVC) timescale (around 100 ms). Hence, this paper presented a thorough analysis of the effect mechanism of frequency variation on the weak grid-connected VSC system stability in a DVC timescale. Firstly, based on instantaneous power theory, a novel method in which the active/reactive powers are calculated with the time-varying frequency of voltage vectors was proposed. This method could intuitively reflect the effect of frequency variation on the active/reactive powers and could also help reduce the system order to a certain extent. Then, a small-signal model was established based on the motion equation concept, to depict the effect of frequency variation on the weak grid-connected VSC system dynamics. Furthermore, an analytical method was utilized to quantify the effect of frequency variation on the system’s small-signal stability. The quantitative analysis considered the interactions between the DC voltage control, the terminal voltage control, phase-locked loop, and the power network. Finally, case studies were conducted, and simulation results supported the analytical analyses.

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