Microgrid management with a high share of renewable energy sources (original) (raw)
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A synchronization technique for microgrid reclosing after islanding operation
IECON 2012 - 38th Annual Conference on IEEE Industrial Electronics Society, 2012
The future electric grid concept will cover some small parts to be disconnected and work in an autonomous way isolated from the main utility. Control of microgridscomposed by the couple distributed sources-local loads -with the competence of operating in grid-connected and island mode is a trending research area. The presence of an efficient algorithm for synchronizing the microgrid with the main grid every time the recIosure is allowed is crucial for assuring a safe operation. The synchronization system presented in this work is compounded by two elements: Dual Second Order Generalized Integrator (DSOGI) and stationary reference frames phase locked loop (SRF-PLL). Besides, the voltage control of the microgrid plays a great role in the synchronization system performance.
Survey on microgrids: Unplanned islanding and related inverter control techniques
Renewable Energy, 2011
Nowadays, the importance of electrical generation based on renewable energies is increasing, due to its low emissions of greenhouse gases. At the same time, Distributed Generation and Microgrids (MG) are becoming an important research line because of their peculiar characteristics. MGs are composed of small power sources which can be renewable, placed near customer sites. Moreover, they have the inherent property of islanding: the disconnection of either the MG from the main grid or a portion of a MG from the rest of the MG. There are two kinds of islanding: intentional or planned (for maintenance purposes), and unintentional or unplanned. The latter is mainly due to disturbances and it is used to avoid damages in sources and loads. It is the most critical case because it must be detected as soon as possible to activate all the control systems which allow continuing the energy production and distribution despite the disconnection. In islanding, it is crucial to ensure the power and the electrical signal quality. In grid-connected mode, the inverters use the electrical signal of the main grid as reference. Once in islanding, the main grid reference is lost and new control techniques for the inverters are needed in order to obtain the correct values of voltage magnitude and frequency in the MG. The main objective of this paper is to make a survey on MGs focussed on two important features: unplanned islanding and control of inverters in that scenario. The idea is to present the basic architectures and regulation techniques of MGs and to study the islanding behaviour, mainly the different detection techniques and the inverters' control once islanded.
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.
An improved decentralised coordinated control scheme for microgrids with AC-coupled units
—Microgrids composed of solemnly AC-coupled distributed energy resources can be found in many real-life applications while their control has not been researched nearly enough to address some fundamental challenges, the most important of which is overall system reliability and fault tolerance. This paper proposes a droop-based coordinated control scheme for microgrids with AC-coupled units, a method that enables distributed energy resources units to hot swap between current source and voltage source grid-supporting control modes for satisfying load demand and ensuring energy storage systems will constantly be able to form the grid during islanded operation. The proposed control scheme has been realised in MATLAB/Simulink simulation model of a small-scale microgrid of AC-coupled units that corresponds to a real testbed in Northern Greece. Preliminary simulation results, in islanded mode, demonstrate the effectiveness of the proposed control scheme regarding power-sharing accuracy among the resources and state-of-charge balancing among storage units. Keywords—microgrids, hybrid power systems, maximum power point tracking, energy storage, droop control
Auto Synchronization of Microgrid with Main Grid After Islanding Operation - a Review
International Journal of Advance Engineering and Research Development, 2015
This paper provides a review of research concerning thesynchronization technique for microgrid reclosing after islanding operation. It offers a brief review on some of the published work on control for grid connected and intentional islanding operations of microgrid. The future electric grid concept will cover some small parts to be disconnected and work in an autonomous way isolated from the main utility. Control of microgridscomposed by the couple distributed sources-local loadswith the competence of operating in grid-connected and island mode is a trending research area. The presence of an efficient algori thm for synchronizing the microgrid with the main grid every time the reclosure is allowed is crucial for assuring a safe operation.DG units are significantly and conceptually very different from conventional power system in terms of load characteristics, power quality constraints, market participation strategies and the control and operational strategies.
Control Strategy of Microgrid During Grid-Connected Mode
2014
There has been a keen interest on Distributed Generation (DG) due to their restricted goals of meeting local loads and improving reliability of the overall system. Microgrids (MGs) are connected to the main grid through a Point of Common Coupling which separates the former from the latter. At the time of an intentional islanding or fault at the grid level, a microgrid is able to disconnect itself from the rest of the grid and operate by itself. A microgrid may contain both directly connected and inverter interfaced sources with different control configurations. When disconnected or islanded from the main grid there are various approaches to share the load, one of them being master-slave control where a storage device may become the reference DG to set the nominal voltage and frequency. When the main grid is brought back to normal operation, the microgrid is able to resynchronize itself to the main grid only when it meets certain conditions so as to avoid transients. All the microsou...
Autonomous control of microgrids
2006 IEEE Power Engineering Society General Meeting, 2006
Application of individual distributed generators can cause as many problems as it may solve. A better way to realize the emerging potential of distributed generation is to take a system approach which views generation and associated loads as a subsystem or a "microgrid". The sources can operate in parallel to the grid or can operate in island, providing UPS services. The system will disconnect from the utility during large events (i.e. faults, voltage collapses), but may also intentionally disconnect when the quality of power from the grid falls below certain standards. Utilization of waste heat from the sources will increase total efficiency, making the project more financially attractive. Laboratory verification of the Consortium for Electric Reliability Technology Solutions (CERTS) microgrid control concepts are included. Index Terms-CHP, distributed generation, intentional islanding, inverters, microgrid, power vs. frequency droop, voltage droop, 1 This work was supported in part by the California Energy Commission (150-99-003).
TECHNICAL CHALLENGES ON MICROGRIDS
Microgrids are becoming increasingly attractive to consumers and as such in the future, a great number of them will be installed at consumer's sites. In this situation, conventional distribution networks that accept distributed generation connections may face serious difficulty when its control and protection functions become more complicated. This incurs a burden to the network operation and some technical limitations will appear when a great number of distributed generations are installed. One way of overcoming such problems, a micro grid system is formed to provide reliable electricity and heat delivering services by connecting distributed generations and loads together within a small area. A microgrid is usually connected to an electrical distribution network in an autonomous way and employs various distributed generation technologies such as micro-turbine, fuel cell, photovoltaic system together with energy storage devices such as battery, condenser and flywheel. Micro grids can cause several technical problems in its operation and control when operated as autonomous systems. This paper is a review of three technical challenges on micro grid with respect to voltage and frequency control, islanding and protection of microgrids.
IEEE Access
In recent years, integrating renewable energy sources (RESs) has achieved significant attention due to the growing demand for sustainable energy solutions. Inverter-interfaced Islanded Microgrids (IGs) have appeared as an advantageous approach to integrating RESs into the power grid. Grid-forming inverters (GFIs) are a critical component of IGs, and their synchronization is essential for stable and reliable operation. The literature has widely proposed soft transition, pre-synchronization, and re-synchronization to synchronize IGs to the main grid. However, methods for synchronizing GFIs in the islanded microgrid are restricted. Parallel operation of GFIs is required to guarantee the high-power demand of IG and improve voltage-frequency stability. For parallel operation, GFIs must be synchronized with each other. In the conventional synchronization control systems that are highly nonlinear, the linear proportional-integral (PI) controllers are commonly used in synchronization loops without considering the nonlinearity resulting from the initial condition dependency and cross-coupling. Thus, conventional synchronization methods can be exposed to concerns of stable operation, narrow operation area, and performance degradation. This study proposes a new linearized synchronization control system for GFIs in IGs. In this way, it is possible to analytically design robust linear controllers and ensure a stable operation, high performance, and wide (full) operation area. In addition, a new soft-commissioning method is proposed to deactivate synchronization loops and soft-start the synced GFI. The proposed system has been tested in real-time and CHIL hardware setups for two 550 kW GFIs operating in parallel, and the results in the perfect agreement are presented in this study. INDEX TERMS Commissioning, control hardware-in-the-loop (CHIL), grid-forming inverter, islanded microgrid, load sharing, microgrid, synchronization. ÖZHAN ATMACA received the B.Sc. and M.Sc. degrees from Sakarya University, Sakarya, Turkey, in 2015 and 2018, respecively. In 2017, he joined as a Research and Development Engineer with the Elkon Marine and Electric Technologies Research and Development Center, Elkon Elektrik San. ve Tic. A.Ş, where he has been a Lead Research and Development Engineer, since 2020. He is also the Co-Founder with REGBES, Amsterdam, The Netherlands, a company that develops autonomous charging systems and shore power systems for e-ferries, cruises, and other marine vessels. His current research interests include power converters, electric drives, wind energy systems, and microgrids.
Dynamic modeling of microgrid for grid connected and intentional islanding operation
2012 International Conference on Advances in Power Conversion and Energy Technologies (APCET), 2012
Microgrid is defined as the cluster of multiple distributed generators (DGs) such as renewable energy sources that supply electrical energy. The connection of microgrid is in parallel with the main grid. When microgrid is isolated from remainder of the utility system, it is said to be in intentional islanding mode. In this mode, DG inverter system operates in voltage control mode to provide constant voltage to the local load. During grid connected mode, the Microgrid operates in constant current control mode to supply preset power to the main grid. The main contribution of this paper is summarized as 1) Design of a network based control scheme for inverter based sources, which provides proper current control during grid connected mode and voltage control during islanding mode. 2) Development of an algorithm for intentional islanding detection and synchronization controller required during grid reconnection. 3) Dynamic modeling and simulation are conducted to show system behavior under proposed method using SIMULINK. From the simulation results using Simulink dynamic models, it can be shown that these controllers provide the microgrid with a deterministic and reliable connection to the grid.