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In this paper, a fast and robust voltage sag detection algorithm, named VPS2D, is introduced. Using the DSOGI, the algorithm creates a virtual positive sequence voltage and monitories the fundamental voltage component of each phase. After calculating the aggregate value in the ±²-reference frame, the algorithm can rapidly identify the starting and the ending of symmetric and asymmetric voltage sags,...
In this paper, a hierarchical control system based on a novel autonomous current sharing controller for grid-connected microgrids (MGs) is presented. A three-level hierarchical control system is implemented to guarantee the power sharing performance among voltage controlled parallel inverters, while providing the required active and reactive power to the utility grid. A communication link is used...
In this paper, the power quality of multi-area microgrids is addressed. For this, Active Power Filters (APFs) and Distributed Generators (DGs) inverters are used. To achieve the reference value of power quality indices of different areas, a strategy based on cooperation between DGs and APFs is proposed. Hierarchical control is applied to control DGs inverters and APFs in a coordinated way. Primary...
In highly microgrid (MG) integrated distribution systems, problems such as a sudden cut out of the MGs due to grid faults may lead to adverse effects to the grid. As a consequence, ancillary services provided by MGs are preferred since it can make the MG a contributor to ride through the faults. In this paper, a voltage support strategy based on negative sequence droop control, which regulate the...
Plug-in electrical vehicles will play a critical role in future smart grid and sudden connection of electrical vehicles chargers may cause huge power-peaks with high slew-rates on grid. In order to cope with this issue, this paper applies a distributed cooperative control for fast charging station with dedicated paralleled flywheel-based energy storage system. The distributed DC-bus signaling method...
In a modular uninterruptible power supplies (UPS), each DC/AC module was designed to work in a circular way considering the reliability and power stress issues of the whole system. Thus unsynchronized PWMs will occur if any of the DC/AC modules is plugged in or out of the system at any time. On the other hand, modular difference is another issue that will bring such kind of circulating current. In...
The current trend in isolated microgrids is oriented to distributed renewable energy generators, such as photovoltaic (PV) generators and their corresponding distributed energy storage systems (ESS) as an unit denoted as active generator (PV+ESS). In an isolated microgrid, every distributed generator (ESS or PV) may operate in two operation modes (grid-forming or grid-following) in accordance to specific...
In islanded microgrids, the existence of nonlinear electric loads may cause voltage distortion and affect the performance of power quality sensitive equipment. Thanks to the prevalent utilization of interfacing power electronic devices and information/communication technologies, distributed generators can be employed as compensators to enhance the power quality on consumer side. However, conventional...
A microgrid is an energy subsystem composed of generation units, energy storage, and loads that requires power management in order to supply the load properly according to defined objectives. This paper proposes an online energy management system for a storage based grid-connected microgrid that feeds a critical load. The optimization problem aims to minimize the operating cost while maximizing the...
In this paper, two different control strategies are proposed to address the active power regulation issue in AC microgrids. The principle of power regulation in the droop controller is firstly introduced. Frequency scheduling and droop gain scheduling on top of droop control is proposed to successfully follow the active power command. The limitation of each method is discussed in term of small signal...
Microgrid, as a promising technology to integrate renewable energy resources in the distribution system, is gaining increasing research interests recently. Although many previous works have been done based on the droop control in a microgrid, they mainly focus on achieving proportional power sharing based on the power rating. With various types of distributed generator (DG) units in the system, factors...
The concept of a microgrid has drawn the interest of research community in recent years. The most interesting aspects are the integration of renewable energy sources and energy storage systems at the consumption level, aiming to increase power quality, reliability and efficiency. On top of this, the increasing of DC-based loads has re-open the discussion of DC vs AC distribution systems. As a consequence...
Smart buildings and homes are becoming a key player in the future green and sustainable energy grid, due to the integration of distributed energy sources and the demand control capabilities. Advanced smart metering systems are required for the operation of the future smart grid. Smart metering systems allow to monitor the energy consumption of end-users, while provides useful information regarding...
Three-phase inverters subject to droop control are widely used in islanded microgrids to interface distributed energy resources to a network and to properly share loads among different units. In this paper, a mathematical model for islanded microgrids with linear loads and inverters under frequency and voltage droop control is proposed. The model is constructed by introducing a suitable state-space...
This paper presents a two-level hierarchical control approach for voltage source inverters used to interface Distributed Generators (DGs) in microgrid applications. The control structure comprises primary and secondary levels. The primary level is a local controller, which consists of voltage and current inner control loops in order to fix the filter capacitor voltage and a virtual impedance loop...
Electrical vehicle (EV) chargers are going to occupy a considerable portion of total energy consumption in the future smart grid. Fast charging stations (FCS), as the most demanding representatives of charging infrastructure, will be requested to provide some ancillary services to the power system in order to support basic electrical operation. This paper proposes a local implementation of a hysteresis-based...
In this paper, a decentralized strategy based on fuzzy logic is proposed for balancing the state of charge of the energy storage units for distributed PV-based active generators. The proposed method, weights the action of conventional droop control loops for privileging the charge of the energy storage unit with the smallest state of charge or force a faster discharge of the energy storage system...
In this paper, a simplified control architecture, including individual layer control and recover layer control, is proposed for a modular online uninterruptible power supply (UPS) system is presented. The parallel control algorithm of for the DC/AC modules are mainly concentrates on the active power sharing performance due to the existence of the shunt active power filter (APF). APF will deal with...
Grid-connected microgrids with storage systems are reliable configurations for critical loads which can not tolerate interruptions of energy supply. In such cases, some of the energy resources should be scheduled in order to coordinate optimally the power generation according to a defined objective function. This paper defines a generationside power scheduling and economic dispatch of a grid-connected...
In this paper a control strategy for the parallel operation of three-phase inverters in a modular online uninterruptable power supply (UPS) system is proposed. The UPS system is composed of a number for DC/ACs with LC filter connected to the same AC critical bus and an AC/DC that forms the DC bus. The proposed control is designated in two layers, individual layer and recovery layer. In individual...
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