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Electrical energy generation is evolving from centralized towards distributed energy resources (DER) like wind and solar power plants. In such power systems, new challenges arise for the design of voltage source converter (VSC) control strategies. In the last few years synchronverters have gained interest from the research community due to their capability of emulating synchronous machines (SMs) and...
Unpredictable power quality (PQ) events such as, balanced and unbalanced voltage sag/swell, frequency shift, phase jump and harmonic distortions in the utility grid voltage drastically affects the performance of a grid interfaced distributed generation (DG) systems due to unreliable synchronization. This paper presents adaptive synchronization based dq-current control technique for three-level NPC...
The massive penetration of renewable energy sources in grid-tied systems has boosted the improvement of conventional control solutions to fulfill the requirements demanded during grid faults. In this paper, balanced positive-sequence reference extraction method (BPSC) is proposed with the predictive technique to control the 3L-NPC inverter under grid sags. Only positive sequence extraction is needed...
Low-inertia AC microgrids are a collection of heterogeneous renewable-energy resources and energy-storage devices (such as photovoltaic arrays, batteries, fuel cells) that are interfaced to a distribution system through power-electronic inverters. In this work, we focus on islanded microgrids that are controlled and operated independently from the bulk power system. Such systems are envisioned to...
Micro grid is a latest concept for upcoming energy distribution system that enables, renewable energy integration. It generally combination of multiple distributed generations (DG's), that are usually connected to the grid through power inverters. During the islanding operation (autonomous mode) of grid, important task are to share the load demand among multiple parallel connected inverters proportionately,...
In this paper, a single-phase self-synchronized inverter with current limiting capability without a dedicated synchronization unit is presented. It offers an approach for power systems to control distributed renewable energy sources. The proposed system has the capability to synchronize itself with the utility grid before connection and track the grid frequency after connection without a phase-locked...
This paper addresses the modeling and control of the grid connected photovoltaic system. The system contains a PV panel that converts irradiation to electrical power, a boost converter which increases the voltage of the PV, and a grid connected inverter to convert the DC power to three Phases AC power. MPPT control is developed in order to track the maximum power provided by the photovoltaic generator...
This paper proposes a bi-directional grid-tied converter with GPS capability for smart-grid applications. The novelty of this converter is that time-stamped grid voltage angle received via network communication channels has been used to synchronize the converter to the grid. Therefore, all grid-tied converters in a microgrid with this development will not require line voltage sensing and phase-locked...
This paper presents a novel active synchronization control strategy of multi-bus microgrid based on distributed cooperation technology. The method can reconnect microgrid back to utility grid (UG) seamlessly with sparse communication channels. Through the cross product of voltage vectors in the synchronizer, the frequency and phase of microgrid can track the main grid simultaneously. The voltage differences...
In this paper, control of a grid-tied converter as a voltage controlled converter is investigated for distribution level grids. Small signal model of the converter is presented and a control structure is designed to deliver desired active and reactive power. This controller is using power flow equations to control the converter as a synchronous machine and without the need for a dedicated synchronization...
This study presents different control strategies for standalone and grid connected Photovoltaic Systems (PVS) and comparison of these different strategies has been done. This paper is intended to choose an efficient control strategy for standalone and grid connected PVS.
To assure power quality and stability of the electricity network it is important to perform control and synchronization of the inverters which are used in the connection of distributed DC power generation units to the grid. It is proven that the model of the inverters, is a differentially flat one. By exploiting differential flatness properties it is shown that the multiple inverters model can be...
In this paper, a single-phase self-synchronized inverter that mimics synchronous generators (Synchronverter) without a dedicated synchronization unit is investigated. It offers a mechanism for power systems to control distributed renewable energy sources. It can synchronize itself with the grid before connection and track the grid frequency very well after connection without a phase-locked loop (PLL)...
Micro-grid should be able to operate in both islanding mode and grid-connected mode, but how to transfer smoothly between these two modes is a question. This paper presents a seamless transition strategy for droop-controlled inverters to operate in both islanding and grid-connected modes and transfer smoothly between these two modes. The control principle and pre-synchronization control strategy are...
In this paper, an improvement in power sharing for Autonomous Microgrid is well established. All previous studies were based on voltage and frequency droop control to share power between distributed generators. This paper develops a new robust voltage and angle droop control to share power, where its advantage over the common frequency droop is in less frequency variation. The synchronization of Power...
This paper presents a controller for three-phase DC/AC converters that is able to operate the converter in grid-connected and stand-alone modes and ensure seamless transition between these modes without reconfiguration of the control structure. The proposed controller provides control over real and reactive powers in grid-connected mode and it performs voltage support in the islanded mode. It integrates...
Microgrid is intended and featured to be able to operate in both grid-connected and islanded mode to ensure high quality and reliable power supply. In order to achieve stable operation of the microgrid-connected voltage source inverter (MVSI) units under paralleled or grid-connected mode, a novel synchronization method based on droop control is proposed in this paper. The difference of phase and amplitude...
The increased trend in using the renewable energy instead of fossil fuel based generation due to its low environmental impact and to facilitate the increased consumption has led to extensive use of distributed generation. The use of power electronics with renewable energy offers wide advantages including greater controllability of generated power and fulfilling the requirements for grid connected...
This paper presents a three phase grid connected DC/AC inverter with active and reactive power (VAR) control for medium size renewable and distributed DC energy sources. The inverter, based on a voltage sourced inverter (VSI) configuration, allows the local residential energy generation to actively supply reactive power to the utility grid, at the same time, this topology allows to work this installation...
The main contribution of this paper is to describe a robust Phase-Locked-Loop approach for three phase generation system with power flow control. This method, which is used to synchronize the inverter and the network voltages, is based on a comparison between the grid and the inverter angular positions, and correction of modulator period. The Solution presented in this paper is applied to the three...
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