1,017 research outputs found
A Robust Consensus Algorithm for Current Sharing and Voltage Regulation in DC Microgrids
In this paper a novel distributed control algorithm for current sharing and
voltage regulation in Direct Current (DC) microgrids is proposed. The DC
microgrid is composed of several Distributed Generation units (DGUs), including
Buck converters and current loads. The considered model permits an arbitrary
network topology and is affected by unknown load demand and modelling
uncertainties. The proposed control strategy exploits a communication network
to achieve proportional current sharing using a consensus-like algorithm.
Voltage regulation is achieved by constraining the system to a suitable
manifold. Two robust control strategies of Sliding Mode (SM) type are developed
to reach the desired manifold in a finite time. The proposed control scheme is
formally analyzed, proving the achievement of proportional current sharing,
while guaranteeing that the weighted average voltage of the microgrid is
identical to the weighted average of the voltage references.Comment: 12 page
Plug-and-play and coordinated control for bus-connected AC islanded microgrids
This paper presents a distributed control architecture for voltage and
frequency stabilization in AC islanded microgrids. In the primary control
layer, each generation unit is equipped with a local controller acting on the
corresponding voltage-source converter. Following the plug-and-play design
approach previously proposed by some of the authors, whenever the
addition/removal of a distributed generation unit is required, feasibility of
the operation is automatically checked by designing local controllers through
convex optimization. The update of the voltage-control layer, when units plug
-in/-out, is therefore automatized and stability of the microgrid is always
preserved. Moreover, local control design is based only on the knowledge of
parameters of power lines and it does not require to store a global microgrid
model. In this work, we focus on bus-connected microgrid topologies and enhance
the primary plug-and-play layer with local virtual impedance loops and
secondary coordinated controllers ensuring bus voltage tracking and reactive
power sharing. In particular, the secondary control architecture is
distributed, hence mirroring the modularity of the primary control layer. We
validate primary and secondary controllers by performing experiments with
balanced, unbalanced and nonlinear loads, on a setup composed of three
bus-connected distributed generation units. Most importantly, the stability of
the microgrid after the addition/removal of distributed generation units is
assessed. Overall, the experimental results show the feasibility of the
proposed modular control design framework, where generation units can be
added/removed on the fly, thus enabling the deployment of virtual power plants
that can be resized over time
Distributed Apportioning in a Power Network for providing Demand Response Services
Greater penetration of Distributed Energy Resources (DERs) in power networks
requires coordination strategies that allow for self-adjustment of
contributions in a network of DERs, owing to variability in generation and
demand. In this article, a distributed scheme is proposed that enables a DER in
a network to arrive at viable power reference commands that satisfies the DERs
local constraints on its generation and loads it has to service, while, the
aggregated behavior of multiple DERs in the network and their respective loads
meet the ancillary services demanded by the grid. The Net-load Management
system for a single unit is referred to as the Local Inverter System (LIS) in
this article . A distinguishing feature of the proposed consensus based
solution is the distributed finite time termination of the algorithm that
allows each LIS unit in the network to determine power reference commands in
the presence of communication delays in a distributed manner. The proposed
scheme allows prioritization of Renewable Energy Sources (RES) in the network
and also enables auto-adjustment of contributions from LIS units with lower
priority resources (non-RES). The methods are validated using
hardware-in-the-loop simulations with Raspberry PI devices as distributed
control units, implementing the proposed distributed algorithm and responsible
for determining and dispatching realtime power reference commands to simulated
power electronics interface emulating LIS units for demand response.Comment: 7 pages, 11 Figures, IEEE International Conference on Smart Grid
Communication
Distributed Control Strategies for Microgrids: An Overview
There is an increasing interest and research effort focused on the analysis, design and implementation of distributed control systems for AC, DC and hybrid AC/DC microgrids. It is claimed that distributed controllers have several advantages over centralised control schemes, e.g., improved reliability, flexibility, controllability, black start operation, robustness to failure in the communication links, etc. In this work, an overview of the state-of-the-art of distributed cooperative control systems for isolated microgrids is presented. Protocols for cooperative control such as linear consensus, heterogeneous consensus and finite-time consensus are discussed and reviewed in this paper. Distributed cooperative algorithms for primary and secondary control systems, including (among others issues) virtual impedance, synthetic inertia, droop-free control, stability analysis, imbalance sharing, total harmonic distortion regulation, are also reviewed and discussed in this survey. Tertiary control systems, e.g., for economic dispatch of electric energy, based on cooperative control approaches, are also addressed in this work. This review also highlights existing issues, research challenges and future trends in distributed cooperative control of microgrids and their future applications
Review on Control of DC Microgrids and Multiple Microgrid Clusters
This paper performs an extensive review on control schemes and architectures applied to dc microgrids (MGs). It covers multilayer hierarchical control schemes, coordinated control strategies, plug-and-play operations, stability and active damping aspects, as well as nonlinear control algorithms. Islanding detection, protection, and MG clusters control are also briefly summarized. All the mentioned issues are discussed with the goal of providing control design guidelines for dc MGs. The future research challenges, from the authors' point of view, are also provided in the final concluding part
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