Abstract
High-frequency oscillations caused by voltage source converters (VSCs) are constantly emerging in power systems with the increasing penetration of renewable energies. VSC models in current control timescale play a pivotal role in the analysis of these oscillation issues. Conventional VSC models show few physical mechanisms of VSC dynamics during system oscillations. Hence, this paper proposes a VSC model from the viewpoint of its internal voltage (namely, VSC output voltage), which is driven by current balancing between the current reference and the feedback in a stationary frame. The proposed model can be used to study VSC dynamic characteristics in an intuitionistic physical way. Based on the proposed model, it is found that VSC current reference in a stationary frame varies with internal voltage dynamic due to the essence of active and reactive current control in a current control timescale. Additionally, in a stationary frame, the dynamic relation between internal voltage and error current embodies a generalized integrating characteristic with adaptable center frequency determined by a phase-locked loop, which guarantees the zero steady state error of VSC current control. Comparisons of simulations between the proposed model and a switch-based model validates the effectiveness of the proposed model.
Highlights
With the wide application of voltage source converters (VSCs) in power systems, the emerging oscillations caused by VSC control dynamics show diverse forms in multiple timescales [1,2,3]
In order to intuitively reflect the influence of VSC on the system dynamics, this paper models the perspective the internal voltage, in which the internal voltage is paper models fromfrom the perspective of theofinternal voltage, in which the internal voltage is used used as the output interface of the proposed model, and the current reference and feedback are as the output interface of the proposed VSC model, and the current reference and feedback are used used the model interface
This paper proposed a VSC dynamic model that is established from the perspective of its internal voltage for power system dynamic analysis in current control timescale
Summary
With the wide application of voltage source converters (VSCs) in power systems, the emerging oscillations caused by VSC control dynamics show diverse forms in multiple timescales [1,2,3]. The emerging impedance-based frequency domain model, in which VSC is modeled separately from the external grid, is proposed [10,11,12,13]. In this kind of model, as all of the control branches in VSCs are lumped into the equivalent impedance, the motion process of the inner key state in VSC is concealed, which limits. In this paper, the proposed current-balancing driven internal voltage motion model of VSCs is carried out step by step in a stationary frame.
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