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The investiture in Distributed Generations (DGs) technologies have begun to monopolies transmission system's architecture instantaneously after announcing its liberation and deregulation of the energy market to the public. Such movement has propelled vicious competitions among power generation companies to initiate superior innovations in meeting consumers' needs, administering high power quality...
By intensifying renewable energy sources integration to the power grid and forming the microgrids (MGs) concept, many studies have been done to investigate MGs operation, control, protection, and etc. The performance of loads can play a major role in the MG behavior. Different load models can be implemented in MGs. The voltage and frequency (VF) dependent load is a substantial load model which few...
A multi-time scale coordinated voltage control strategy in an islanded microgrid (MG) is proposed in this paper. The strategy is comprised of local voltage control of distributed generators (DGs), secondary voltage control (SVC) based on PI regulators and a proposed tertiary voltage control (TVC) strategy. A multi-objective function of the TVC is designed to achieve a compromise among three objectives:...
The voltage source inverters operating in islanded microgrid are used as sources of power similar to synchronous generators (SG) in conventional power system. Unlike synchronous generators, these inverters neither have a natural droop (P-f and Q-V) characteristics nor rotational inertia. The electrical time constant is much lesser than mechanical time constant and hence the load changes will show...
Solid state transformers (SSTs) can be interconnected with each other through a distribution feeder to form a smart grid. When the main grid is disconnected, SSTs form an islanded microgrid. With available communications, master-slave microgrid control structure can be adopted. The system-level stability analysis can be simplified by considering only the grid interface stage of the SST. The loop feeder...
The droop control technology, which can achieve an autonomous power sharing among distributed resources interface converters, provides the advantages of enhanced system reliability and reduced complexity. However, the reactive power sharing accuracy of the conventional Q — V droop method can be degraded due to its dependence on the line impedances. The Q — V droop control method was proposed to reduce...
This work proposes and investigates a renewable energy distributed generation system involving a matrix converter with an output filter working as a stable voltage supply. This is especially relevant for the stand-alone operation of a renewable energy microgrid where a stable sinusoidal voltage with prescribed amplitude and frequency under various load conditions is the main control objective. A controllable...
This paper highlights the power limited nature of the Distributed Generation inverter and demonstrates the practical way to integrate them into the microgrid. Since the energy source of Distributed Generation inverters is power limited in nature, they constrain the operation of inverters to which they are coupled. If the power demanded from these inverters is beyond their capability, their DC-link...
This paper proposes a new control method for two stage converters to realize the virtual synchronous generator (VSG) operation, which also can help eliminate circulating power between energy storage (ES) converters. It is proven in this paper that the proposed method shares stronger resemblances with synchronous generators (SGs) than traditional VSG in aspects of power conversion process and mathematical...
Power quality of ac bus voltage is a key issue for microgrids. A model-predictive-control (MPC)-based distributed bus voltage compensation methods using inverter-interfaced distributed generators (DGs) connected to the concerned bus is proposed. The presented method can compensate bus voltage unbalance and harmonics and share the compensated current between inverters autonomously, with neither communication...
This work investigates a linear model predictive control (MPC) in conjunction with a voltage source inverter with a grid-interfacing passive filter. In an ideal grid, standard linear MPC demonstrates fast transient and excellent steady-state performance while respecting the imposed constraints. Nevertheless, its direct application onto the grid-connected converters operating with a distorted grid...
Application areas such as electric vehicles, data centers and microgrids increasingly rely on power electronic converters and electric motor drives to control loads. These tightly regulated converters act as Constant Power Loads (CPLs) in the context of the entire system. The negative incremental impedance of a CPL causes inherent instability which may lead to a grid collapse. This paper reviews the...
To address the DC link voltage regeneration issue in parallel Uninterruptible Power Supply (UPS) system, a DC link voltage protection (DCVP) method through online virtual resistance regulation is proposed. The proposed control strategy is able to protect the DC link from overvoltage that may trigger the protection mechanism of the UPS system. Moreover, a current sharing control strategy by regulating...
In order to address the economical dispatch problem in cascaded microgrids, this digest proposes an optimal economical-sharing scheme via decentralized approach only with the local information. This overcomes the limitations of centralized control, where the central controller and external information exchange are needed. The frequency and current are used as carriers driven the distributed generators...
Recently, DC distribution has been more and more considered in shipbuilding industry as an emerging solution due to its potential to enhance the system performance in terms of fuel economy, reliability, volume and weight. Moreover, there is a growing trend to integrate alternative power sources (APSs) and energy storage systems (ESSs) into next-generation ships, and thus reducing cost and emission...
This paper proposes the application of advanced modelling and control strategies for a single phase Dual Active Bridge (DAB) based Medium Voltage DC (MVDC) Shipboard Power System (SPS). In these systems the tightly controlled point of load (POL) converters exhibit a constant power load (CPL) behaviour, which has a destabilising effect on the bus voltage. In this work, a Multiple Input Single Output...
Chaotic nature of renewable energy sources connected with nonlinear loads may cause serious problems to the utility grid, e.g. voltage and frequency disturbances, harmonic pollution. Due to that, many European governments have set strict regulations to the grid energy injection. As a result, the power quality has become one of the major obstacles for nearly zero energy buildings to be connected with...
Fault current limiters (FCLs) are one class of solutions to cope with the upcoming challenges in microgrid protection. Considering high penetration of distributed generations (DGs) in microgrids, the necessity of designing cheap and effective FCL is getting higher. This paper attempts to fill this gap by proposing an embedded FCL operating based on modifying the secondary control of DGs. As this method...
This paper proposes a novel universal control for multi-bus AC microgrid with the capability to operate in both grid-connected (GC) and islanded (IS) modes. The control scheme is based on distributed manner, and the leader-follower consensus protocol is designed. Only few leader distributed generators (DGs) receive the correction signals from the unified mode controller, which is installed at the...
A robust grid structure, which makes use of distributed renewable energy generation, should consist of grid sections, which are able to seamlessly switch between grid-connected and islanding mode of operation. This way, failures in the upper level part of the grid can be mitigated. This contribution discusses local and supervisory control strategies, and requirements for microgrids. A robust hierarchical...
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