Abstract
This paper introduces a new operational scheme for several multilevel (five-level diode-clamped) inverters in the microgrid. The presented operational scheme has a central structure (different from the distributed controllers for droop schemes) to alleviate the drawback of the conventional droop control for microgrid operation. The contribution of this paper is focused on the suggested operational scheme, which has two contributory components. The first component is the novel smooth variable structure filters (SVSF), which are formulated to estimate the disturbances of voltage harmonics and voltage unbalance. The second component is an efficient adaptive sliding mode controller to operate these inverters. This proposed operational achieves equal power sharing among working inverters, compensating for voltage unbalance at the point of common coupling (PCC) at loads, and mitigation for voltage harmonics at the PCC. More importantly, the propounded operational scheme efficiently stabilizes voltage with the variation of balance, unbalanced and nonlinear loads in addition to the seamless transient and steady-state performance for injected power by inverters. The performance of the suggested operational scheme is justified by simulation results.
Highlights
The microgrid has become into the focus of research at the distribution system level because microgrid fetches some merits such as low-carbon emission, its modularity, integration of renewable dispersed energy sources, and its ability to work independently or connected to the central power grid (Jiayi et al, 2008; Mariam et al, 2013)
In addition to aforementioned merits, any microgrid has several challenges such as the stability of voltage and frequency with variable loads, existence of harmonics due to non-linear loads, control of dispersed energy sources, circulating current among inverters, existence of inverters associated with renewable energy sources, and procedure for connection/disconnection to/from the central grid (Parhizi et al, 2015; Hirsch et al, 2018)
The first subsection illustrates the performance of the smooth variable structure filters (SVSF) for estimation of the voltage harmonics and unbalance
Summary
The microgrid has become into the focus of research at the distribution system level because microgrid fetches some merits such as low-carbon emission, its modularity, integration of renewable dispersed energy sources, and its ability to work independently or connected to the central power grid (Jiayi et al, 2008; Mariam et al, 2013). The contribution of this paper includes two mains components, which are the development of the novel SVSF for the estimation of voltage harmonics/unbalance and the employment of adaptive sliding mode controller to operate the inverters. Both harmonics mitigation and unbalance compensation are realized after the extraction of their disturbances using the two estimation blocks depicted, and these disturbances are processed to generate corresponding control signals. This voltage correction adds more complexity to the employed control scheme
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