Control for Seamless Formation and Robust Operation in DG Microgrids (original) (raw)
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MODELING, STABILITY ANALYSIS AND CONTROL OF MICROGRID
With the increase in the level of global warming, renewable energy based distributed generators (DGs) will increasingly play a dominant role in electricity production. Distributed generation based on solar energy (photovoltaic and solar thermal), wind, biomass, mini-hydro along with use of fuel cells and micro turbines will gain considerable momentum in the near future. A microgrid consists of clusters of load and distributed generators that operate as a single controllable system. The interconnection of the DG to the utility/grid through power electronic converters has raised concern about safe operation and protection of the equipments.
A Modified Control Scheme of Droop-Based Converters for Power Stability Analysis in Microgrids
Journal of Solar Energy, 2015
Microgrid is principally an active distribution network since it aggregates numerous DG systems through their interface converters and different loads at distribution level. This paper discusses the power sharing in autonomous AC-microgrid infrastructure by common P-f and Q-V˙ droop control schemes on parallel-connected converters. Moreover, this research work proposes a frequency and voltage restoration mechanism through the utilization of secondary control. Experimental results are presented for a two-50 kVA parallel-connected converter-based system, demonstrating the necessity for the proper operation of the secondary control in order to monitor the system’s capability to withstand any perturbations that may occur and to ensure the system’s security.
An improved control scheme based in droop characteristic for microgrid converters
Electric Power Systems Research, 2010
Power-quality a b s t r a c t In the present work, an improved version of the conventional-droop control for microgrid converter is presented. The modifications added to the control are based on a feed-forward current control that allows the converter to work in several modes, both when it is grid connected or in island. The use of this control represents the main contribution of this paper, permitting the inverter to work as a grid supporting source or ancillary services provider when it works grid connected. In this mode the converter varies the injected active and reactive power with the variation of voltage module and frequency using the same main control loop as when it is working in island mode.
Applicability of Droop Regulation Technique in Microgrid - A Survey
Engineering Journal, 2014
Currently, the worth of power generation on the basis of renewable sources is rapidly growing. Correspondingly the microgrids and the DG units are impressed the researchers for their peculiar features. Power sharing is the major concern when various DGs are connected to the microgrid via power electronic converters. It is mandatory to achieve an appropriate power sharing when the manifold DGs are activated in parallel. For that, the two ultimate quantities-power angle δ and voltage magnitude V are regulated to acquire the real and reactive power sharing correspondingly. Many innovative control techniques have been used for load sharing. The most common method of local load sharing is the droop characteristics. Subsequently, there is a swift momentum in the advancement of researchers to meet the challenges of the droop control techniques in the power sharing concerns, an extensive literature review on active and reactive power sharing, voltage and frequency control in microgrid has been emphasized. The various conventional and modified droop control techniques/strategies that relates to power sharing issues have been highlighted in this work.
Energy Conversion and Management, 2015
This paper describes a control technique for enhancing the stable operation of distributed generation (DG) units based on renewable energy sources, during islanding and grid-connected modes. The Passivity-based control technique is considered to analyse the dynamic and steady-state behaviours of DG units during integration and power sharing with loads and/or power grid, which is an appropriate tool to analyse and define a stable operating condition for DG units in microgrid technology. The compensation of instantaneous variations in the reference current components of DG units in ac-side, and dc-link voltage variations in dc-side of interfaced converters, are considered properly in the control loop of DG units, which is the main contribution and novelty of this control technique over other control strategies. By using the proposed control technique, DG units can provide the continuous injection of active power from DG sources to the local loads and/or utility grid. Moreover, by setting appropriate reference current components in the control loop of DG units, reactive power and harmonic current components of loads can be supplied during the islanding and grid-connected modes with a fast dynamic response. Simulation results confirm the performance of the control scheme within the microgrid during dynamic and steadystate operating conditions.
The energy sector is moving into the era of distributed generation (DG) and microgrids (MGs). The stability and operation aspects of converter-dominated DG MGs, however, are faced by many challenges. To overcome these difficulties, this paper presents a new large-signal-based control topology for DG power converters that is suitable for both grid connected and islanding modes of operation without any need to reconfigure the control system and without islanding detection. To improve MG stability and to guarantee stability and high performance of the MG system during sudden harsh transients such as islanding, grid reconnection, and large load power changes, a nonlinear MG stabilizer is proposed. We propose a novel control topology for microgrids which can work in both grid connected and islanding modes without reconfiguration so it does not require islanding detection technique, the controller is based on the concept of synchronverter In this paper, a radical step is taken to improve the synchronverter as a self-synchronized synchronverter by removing the dedicated synchronization unit.
Control of Microgrids: Aspects and Prospects
A microgrid is a controllable component of the smart grid defined as a part of distribution network capable of supplying its own local load even in the case of disconnection from the upstream network. Microgrids incorporate large amount of renewable and non-renewable distributed generation (DG) that are connected to the system either directly or by power electronics (PE) interface. The diversity of technologies used in DGs and loads, high penetration of DGs, economic operation of DGs, dynamics of low-inertia conventional DGs and PE interfaced inertialess DGs and smart operation by means of enhanced communication infrastructure have raised challenges in widespread utilization of microgrids as basis of smart grids. Power quality, protection, economic and secure operation, active management, communication, dynamics and control of microgrids are among the most important issues under research both in academy and industry. Technical concerns over dynamics of microgrids especially in autonomous (island) mode necessitate revision of current paradigms in control of energy systems. This paper addresses current challenges towards controlling microgrids and surveys dynamic modeling, stability and control of microgrids. Future trends in realizing smart grids through aggregation of microgrids and research needs in this path are discussed at the end of this paper.
IEEE Transactions on Power Systems, 2010
- Improvement of stability and load sharing in an autonomous microgrid using supplementary droop control loop. IEEE Transactions on Power Systems. (Unpublished) ABSTRACT: This paper investigates the problem of appropriate load sharing in an autonomous microgrid. High gain angle droop control ensures proper load sharing, especially under weak system conditions. However it has a negative impact on overall stability. Frequency domain modeling, eigenvalue analysis and time domain simulations are used to demonstrate this conflict. A supplementary loop is proposed around a conventional droop control of each DG converter to stabilize the system while using high angle droop gains. Control loops are based on local power measurement and modulation of the d-axis voltage reference of each converter. Coordinated design of supplementary control loops for each DG is formulated as a parameter optimization problem and solved using an evolutionary technique. The supplementary droop control loop is shown to stabilize the system for a range of operating conditions while ensuring satisfactory load sharing.
Control of Microgrid – A Review on Recent Trends
– The ever increasing demand for energy and changes in climatic conditions that give rise to increased carbon gas in atmosphere in the past few decades have initiated the advancements in renewable energy technologies. However, integration of these distributed generations to the grid has made adverse impacts on the existing grid and its interconnected operation. A solution to this problem is Microgrid concept that will make the existing grid suitable for increased integration of renewable energy sources to it. Power quality issues and condition will decide whether the Microgrid is to be in grid connected mode or islanded mode. In either of the cases, control of Microgrid plays a vital role. Several researchers have presented various control strategies for Microgrid under different conditions. This paper presents a review all possible control techniques discussed in the literature for the Microgrid in both autonomous and grid interconnected operations.