Abstract
Under the background of a large number of converters connected to the power grid, the converter’s weak overcurrent capability and poor anti-interference ability bring challenges and hidden dangers to the transient safe and stable operation of the power grid. It is urgent to carry out the transient characteristics analysis of the converter. Numerical simulation calculation is an important means to study transient characteristics. However, numerical simulation is time-consuming and poor in generality, which greatly limits the study of transient characteristics of systems with multiple converters. In this paper, the vertical control is the object, and the inverter reduced-order simplified model suitable for different transient stability problems is studied. First, a full-order model of the droop control inverter is established, and the singular perturbation method is used to complete the extraction of system characteristic roots and the analysis of participating factors. Then, according to the droop control of the inverter’s power angle, voltage, and frequency transient response process, accuracy and rapidity are selected as the goals, and a reduced-order simplified model suitable for different transient stability analysis is obtained. The transient characteristic analysis of the numerical simulation of the converter system provides a reduced order reference.
Highlights
Converters have the problems of weak over-current capability and easy to be burned during transient processes such as short-circuit faults [1]
The converter lacks the physical inertia of the traditional RSG, resulting in poor anti-disturbance ability of the converter, and it is prone to serious stability problems when facing system disturbances, which brings challenges to system security [2]
The optimal selection of model state variables and the recommended value of model order under different transient characteristics analysis conditions are summarized through the comparative study of numerical simulation, in order to speed up the model calculation speed while preserving the system dynamic process to the greatest extent
Summary
Converters have the problems of weak over-current capability and easy to be burned during transient processes such as short-circuit faults [1]. In China, large-scale wind farms are offline due to stability issues, causing serious economic losses [4] These safe operation problems are prominent in the transient process. It is of great value and significance to analyze the transient characteristics of the converter represented by the droop controled inverter when subjected to large disturbances such as short-circuit faults. In response to this problem, this paper takes the droop controlled inverter as the research object. The optimal selection of model state variables and the recommended value of model order under different transient characteristics analysis conditions are summarized through the comparative study of numerical simulation, in order to speed up the model calculation speed while preserving the system dynamic process to the greatest extent
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