Arman Goudarzi | Searcharxiv

arXiv2021

Leaderless Consensus of a Hierarchical Cyber-Physical System

This paper models a class of hierarchical cyber-physical systems and studies its associated consensus problem. The model has a pyramid structure, which reflects many realistic natural or human systems. By analyzing the spectrum of the coupling matrix, it is shown that all nodes in the physical layer can reach a consensus based on the proposed distributed protocols without interlayer delays. Then, the result is extended to the case with interlayer delays. A necessary and sufficient condition for consensus-seeking is derived from the frequency domain perspective, which describes a permissible range of the delay. Finally, the application of the proposed model in the power-sharing problem is simulated to demonstrate the effectiveness and significance of the analytic results.

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arXiv2020

An Advanced Two-Stage Grid Connected PV System: A Fractional-Order Controller

A fractional-order (FO) based controller for a grid-connected PV system is presented in this paper. A single phase two-stage grid-connected photovoltaic generator (PVG) is used to test the performance of the FO controller. The main objectives of the proposed controller are: (1) To regulate the output voltage of PVG at a point where the maximum power is drawn. (2) Constant DC-link voltage control. (3) Power factor control (PFC) at the inverter output with low total harmonic distortion (THD). To solve the first problem, a non-linear control method known as fractional-order back-stepping control (FOBSC) is used to regulate the output voltage of PVG. A maximum power point tracking (MPPT) technique known as perturb and observe (P & O) is used to generate a reference voltage which is suitable for tracking the maximum power generation of PVG. The generated reference is used to regulate the output voltage of PVG using FOBSC. The DC-link voltage fluctuation issue is tackled using FO based PI controller. The last objective is achieved using FOBSC to obtain maximum power factor of the grid. Lyapunov candidate function is used to verify the stability of the system. To test the performance of the proposed controller, it is compared to conventionally known Integer-order (IO) controller. Results have shown a significant improvement in THD and efficiency of the system. The proposed controller offers 0.94%, 1.43% and 1.86% lower THD in comparison with IO controller at 100%, 80% and 70% of the power generation capacity of PVG, respectively. The overall efficiency of the system for 100%, 80%, and 70% of the dynamic powers of the system is noticed to be better in case of FO controller.

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