55 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
Differentiation and Passivity for Control of Brayton-Moser Systems
This paper deals with a class of Resistive-Inductive-Capacitive (RLC)
circuits and switched RLC (s-RLC) circuits modeled in Brayton Moser framework.
For this class of systems, new passivity properties using a Krasovskii's type
Lyapunov function as storage function are presented. Consequently, the
supply-rate is a function of the system states, inputs and their first
time-derivatives. Moreover, after showing the integrability property of the
port-variables, two simple control methodologies called output shaping and
input shaping are proposed for regulating the voltage in RLC and s-RLC
circuits. Global asymptotic convergence to the desired operating point is
theoretically proved for both proposed control methodologies. Moreover,
robustness with respect to load uncertainty is ensured by the input shaping
methodology. The applicability of the proposed methodologies is illustrated by
designing voltage controllers for DC-DC converters and DC networks
Distributed Optimal Load Frequency Control with Stochastic Wind Power Generation
Motivated by the inadequacy of conventional control methods for power
networks with a large share of renewable generation, in this paper we study the
(stochastic) passivity property of wind turbines based on the Doubly Fed
Induction Generator (DFIG). Differently from the majority of the results in the
literature, where renewable generation is ignored or assumed to be constant, we
model wind power generation as a stochastic process, where wind speed is
described by a class of stochastic differential equations. Then, we design a
distributed control scheme that achieves load frequency control and economic
dispatch, ensuring the stochastic stability of the controlled network.Comment: arXiv admin note: text overlap with arXiv:2010.1284
A Distributed control framework for the optimal operation of DC microgrids
In this paper we propose an original distributed control framework for DC
mcirogrids. We first formulate the (optimal) control objectives as an
aggregative game suitable for the energy trading market. Then, based on the
dual theory, we analyze the equivalent distributed optimal condition for the
proposed aggregative game and design a distributed control scheme to solve it.
By interconnecting the DC mcirogrid and the designed distributed control system
in a power preserving way, we steer the DC microgrid's state to the desired
optimal equilibrium, satisfying a predefined set of local and coupling
constraints. Finally, based on the singular perturbation system theory, we
analyze the convergence of the closed-loop system. The simulation results show
excellent performance of the proposed control framework
Adaptive Control for Flow and Volume Regulation in Multi-Producer District Heating Systems
Flow and storage volume regulation is essential for the adequate transport
and management of energy resources in district heating systems. In this paper,
we propose a novel and suitably tailored -- decentralized -- adaptive control
scheme addressing this problem whilst offering closed-loop stability
guarantees. We focus on a system configuration comprising multiple heat
producers, consumers and storage tanks exchanging energy through a common
distribution network, which are features of modern and prospective district
heating installations. The effectiveness of the proposed controller is
illustrated via numerical simulations
Robust Load Frequency Control of Nonlinear Power Networks
This paper proposes a decentralised second-order sliding mode (SOSM) control strategy for load frequency control (LFC) in power networks, regulating the frequency and maintaining the net inter-area power flows at their scheduled values. The considered power network is partitioned into control areas, where each area is modelled by an equivalent generator including second-order turbine-governor dynamics, and where the areas are nonlinearly coupled through the power flows. Asymptotic convergence to the desired state is established by constraining the state of the power network on a suitably designed sliding manifold. This manifold is designed relying on stability considerations made on the basis of an incremental energy (storage) function. Simulation results confirm the effectiveness of the proposed control approach
Port-Hamiltonian Modeling of Hydraulics in 4th Generation District Heating Networks
In this paper, we use elements of graph theory and port-Hamiltonian systems to develop a modular dynamic model describing the hydraulic behavior of 4th generation district heating networks. In contrast with earlier generation networks with a single or few heat sources and pumps, newer installations will prominently feature distributed heat generation units, bringing about a number of challenges for the control and stable operation of these systems, e.g., flow reversals and interactions
among pumps controllers, which may lead to severe oscillations. We focus thus on flexible system setups with an arbitrary number of distributed heat sources and end-users interconnected through a meshed, multi-layer distribution network of pipes. Moreover, differently from related works on the topic, we incorporate dynamic models for the pumps in the system and explicitly account for the presence of pressure holding units. By inferring suitable (power-preserving) interconnection ports,
we provide a number of claims about the passivity properties of the overall, interconnected system, which proves to be highly beneficial in the design of decentralized control schemes and stability analyses
- …