Overlapping Decentralized Controller Design for Descriptor-type Systems with Distributed Time-delay

Decentralized controller design using overlapping decompositions is considered for descriptor-type systems with distributed time-delay. The approach is based on the principle of extension. In this approach, a given large-scale system is decomposed overlappingly into a number of subsystems and expanded such that the overlapping parts appear as disjoint. A decentralized controller is then designed for the expanded system. This controller is then contracted for implementation on the original system. It is shown that if the decentralized controllers are designed to stabilize the expanded system and to achieve certain performance, then the contracted controller, which would have an overlapping decentralized structure, will stabilize the original system and will achieve corresponding performance

Robust control of a DC-DC three-port isolated converter

This work presents the design of state-feedback robust control law for a DC-DC three-port isolated converter, which interfaces a photovoltaic panel, a rechargeable battery, and an isolated output DC bus. First, the converter is represented through a state-space model that considers disturbances in both the photovoltaic and bidirectional (battery) input ports. The system is linearized around an average operational point, such that robust control techniques can be applied. Due to varying solar irradiation, battery charge, and load levels, the converter is subjected to step-like disturbances. The proposed controller is designed to maintain stabilization and voltage tracking performance in the presence of these disturbances. This approach is different from multiport control strategies usually employed in the literature, which are based on decentralized controllers that require the use of decoupling techniques that can lead to control problems. To ensure robustness, stabilization, and voltage tracking, an [Formula: see text] approach with pole placement restrictions and based on linear matrix inequality (LMI) constraints is formulated and solved. Finally, the performance of the proposed controller has been verified via hardware-in-the-loop (HIL) experiments and compared with a decentralized control strategy.

New Decentralized Control of Mesh AC Microgrids: Study, Stability, and Robustness Analysis

In this paper, we investigated the power sharing issues in mesh islanded microgrids that contain several distributed generators (DGs) and loads connected to different points of common coupling (PCC). Firstly, an improved decentralized droop control algorithm is proposed to achieve the active and reactive power sharing of different DGs in reconfigurable mesh islanded microgrids. Accurate power sharing was obtained even though line parameters or the mesh microgrid configuration were unknown. Secondly a state-space model of the whole mesh microgrid was developed, considering several generators with their decentralized controllers, line feeders, and dynamic loads. This model was used to design parameters of droop controllers, to study the asymptotic stability and the robustness properties of the system. All strategies and analyses were validated by simulation based on the generic microgrid detailed in the standard IEEE 9bus test feeder.

Robust Decentralized Tracking Voltage Control for Islanded Microgrids by Invariant Ellipsoids

This manuscript presents a robust tracking (servomechanism) controller for linear time-invariant (LTI) islanded (autonomous, isolated) microgrid voltage control. The studied microgrid (MG) consists of many distributed energy resources (DERs) units, each using a voltage-sourced converter (VSC) for the interface. The optimal tracker design uses the ellipsoidal approximation to the invariant sets. The MG system is decomposed into different subsystems (DERs). Each subsystem is affected by the rest of the system that is considered as a disturbance to be rejected by the controller. The proposed tracker (state feedback integral control) rejects bounded external disturbances by minimizing the invariant ellipsoids of the MG dynamics. A condition to design decentralized controllers is derived in the form of linear matrix inequalities. The proposed controller is characterized by rapid transient response, and zero error in the steady state. A robustness analysis of the control strategy (against load changes, load unbalances, etc.) is carried out. A MATLAB/SimPowerSystems (R2017b, MathWorks, Natick, MA, USA) simulation of the case study confirm the robustness of the proposed controller.

Optimal enforcement of liveness for decentralized systems of flexible manufacturing systems using Petri nets

The decentralized supervisory structure has drawn much attention in recent years. Many studies are reported in the paradigm of automata while few can be found in the Petri net model. This paper proposes a new method for decentralized supervisory control using the Petri net paradigm. Two efficient Algorithms are developed in the proposed method. Algorithm 1 is used to compute decentralized working zones from the given LS3PR Petri net model for flexible manufacturing systems. Algorithm 2 is used to compute the decentralized controllers that enforced liveness to the decentralized working zones. The sequential assembling is used to reconnect and controlled the working zones via decentralized controllers. The decentralized controller is added to the decentralized working zones that have common elements, that is, common transitions. The proposed method has the following advantages: (i) it can be applied to a complex Petri net model for flexible manufacturing systems, (ii) the proposed methods has less computational complexity when compared with the previous methods, (iii) the proposed method can obtain a minimal number of decentralized controllers that enforce liveness of the uncontrolled Petri net model. Experimental examples are presented to explore the applicability of the proposed methods.