Abstract
This paper presents small signal stability analysis of a hybrid microgrid from three different aspects. First, a generalized droop control of interlinking converter (ILC) is proposed which defines voltage and frequency droops at its terminals to achieve a bidirectional, autonomous power flow between grids. The impact of the droop gains on the stability is discussed and an operational range is defined for a stable system operation. Second, contrary to previous literature which have modeled the ac and dc grids by ideal sources and converters, the ac grid in this scheme is represented as a second-order synchronous generator and the dc grid is modeled as a PV system so as to analyze the dc grid dynamics in detail. It is observed that the dc link capacitor and inductor filter can lead to large system oscillations which can compromise stability. Third, the stability of the hybrid grid is analyzed from the aspect of short circuit ratio (SCR). Both rectifier and inverter mode of operation are used to understand how stability is affected with strength of ac grid. The time-domain simulations in PSCAD are used to confirm the validity of results obtained in frequency domain.
Highlights
Microgrids are a key component of smart grids as they enhance power system resilience, sustainability, economics and security [1]
To address the above mentioned problems, this paper presents small signal stability analysis of a standalone hybrid microgrid considering a generalized droop scheme of interlinking converter (ILC) and high PV penetration
SMALL SIGNAL MODEL OF ILC The structure of the hybrid microgrid under consideration is shown in Figure. 2 where different colored boxes are used for better visualization and interpretation
Summary
Microgrids are a key component of smart grids as they enhance power system resilience, sustainability, economics and security [1]. To support the hybrid microgrid and minimize the voltage deviations, a battery-based model-predictive supervisory control is used where the control scheme generates the set-points for charging and discharging of battery All these strategies involve switching between control modes under different loading conditions. A generalized approach towards small signal analysis of a hybrid microgrid is presented in [17] where the ILC is modeled by a synthetic droop characteristic In all these schemes, the ac and dc grids are modeled by ideal sources linked by inverters and the dynamics of the sources are ignored. To address the above mentioned problems, this paper presents small signal stability analysis of a standalone hybrid microgrid considering a generalized droop scheme of ILC and high PV penetration.
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