A Novel Power Hardware In The Loop Interface Method For Grid Forming Inverter Systems Preprint
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A Novel Power Hardware In The Loop Interface Method For Grid Forming Inverter Systems Preprint
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Author :
language : en
Publisher:
Release Date : 2022
A Novel Power Hardware In The Loop Interface Method For Grid Forming Inverter Systems Preprint written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022 with categories.
Power Hardware-in-the-Loop (PHIL) simulation of grid-forming (GFM) inverter systems facilitates the testing of drastic scenarios like on-grid to off-grid transition, islanded microgrid operation without stiff grid etc. To the authors best knowledge, most of studies in literature are focused on PHIL simulation for grid-following inverter systems and only few studies are focused on GFM inverters and those are challenging and problematic especially for high-power applications. In this article, a novel PHIL simulation platform is proposed that enables interfacing of high-power GFM inverter systems. It proposes the concept of a virtual GFM inverter as a part of the proposed PHIL interface for GFM inverter. This addition of virtual GFM inverter in the PHIL interface expands the conventional Ideal Transformer Model (ITM) method and enables it to overcome the issues of instability of existing ITM methods. In the validation stage, a PHIL experiment is conducted on a 3-phase 480 V, 125 kVA GFM inverter system with proposed interfacing method. The results corroborates the fact that the proposed PHIL simulation method performs well and stable for GFM inverter system.
Restoration And Universal Operation Of Grid Forming Inverters
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Author : Fahmid Sadeque
language : en
Publisher:
Release Date : 2022
Restoration And Universal Operation Of Grid Forming Inverters written by Fahmid Sadeque and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022 with categories.
This dissertation presents novel control methods for frequency and voltage restoration, and universal operation of grid-forming (GFM) inverters. The developed controllers solve the technical challenges for a microgrid with multiple GFM inverters in synchronization and power-sharing, phase-angle detection under asymmetrical conditions, capability to operate in the grid-following (GFL) mode, and frequency and voltage restoration. First, two synchronization methods for GFM inverters are presented. In the output-sync method, an incoming GFM inverter synchronizes its output voltage parameters, i.e., amplitude, phase angle, and frequency, at its point of common coupling (PCC) before closing the circuit breaker. The task is uniquely performed by introducing two proportional-integral (PI) controllers that adjust the output voltage and the angular frequency of the inverter. In the controller-sync method, two sets of controller paths are run in parallel and kept synchronized to produce the same PWM reference. But, only one set of the controller is engaged at a time. The uniqueness of this method is that it allows an inverter to stay connected to the microgrid in a standby mode without injecting any power. Then, when enabled, the inverter gradually shifts to decentralized power-sharing mode without switching the controller. Finally, the controller seamlessly switches to GFM mode, where the inverters are completely independent but synchronized. Another noteworthy fact is that, unlike the output-sync method that used two sets of voltage measurements, the controller sync method only uses one set of voltage measurements. A state-space model of the GFM inverter with the controller-sync method is derived to show the stability at every mode. The efficacy of the developed methods is experimentally validated in a microgrid with both droop and virtual inertia for power-sharing. A new phase-angle detection method, called signal reformation-based direct phase-angle detection (DPD-SR), is developed that provides an enhanced phase-angle detection capability for the GFM inverter under asymmetrical conditions of the system. The developed DPD-SR can directly estimate the phase-angle by using a mathematical function. The unique signal-reformation technique used in this method can process the asymmetrical voltage measurements into a symmetrical form and extract the phase-angle of the system without using any complicated closed-loop control. The DPD-SR method is verified through hardware experiments and compared with state-of-the-art method. Eventually, a universal controller is developed that combines the feature of the controller-sync and the DPD-SR methods. Furthermore, the developed universal controller enables an inverter to operate in GFL and GFM mode is developed. With the universal controller, the inverter can inject desired active and reactive power to the grid or microgrid in GFL mode and seamlessly transit to GFM mode if islanding is detected. The universal controller has two sets of parallel paths, where one path provide GFM control and the other path provides the GFL control and synchronization. A frequency-based islanding detection is added to the developed controller. The uniqueness of the universal controller is, the two paths are always synchronized and can provide seamless GFL to GFM transition when a fault occurs. The controller's stability is analyzed through a state-space model, and the performance of the developed controller is verified in a microgrid for grid-connected and islanded operation in this dissertation. Finally, a frequency and voltage restoration controller is developed to overcome the frequency and voltage deviation problem with the droop controller for power-sharing. In droop-controlled power-sharing, the frequency and voltage are required to deviate from their nominal values. On the contrary, the frequency and voltage of the system are expected to be regulated by the GFM inverters. This dissertation develops a threshold-based frequency and voltage restoration method for the GFM inverters without compromising the effectiveness of the decentralized power-sharing methods. The novelty of this method is that the restoration control paths are only enabled when a load change or plug-in of an inverter is identified and disabled when the frequency and voltage parameters are restored. A state-space model is developed to perform stability analysis. The developed method is compared with a timer-based method to demonstrate its superiority. The efficacy of the restoration method is verified through experiments.
Universal Passive Synchronization Method For Grid Forming Inverters Without Mode Transition Preprint
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Author :
language : en
Publisher:
Release Date : 2023
Universal Passive Synchronization Method For Grid Forming Inverters Without Mode Transition Preprint written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023 with categories.
Power systems are transforming with increasing levels of inverter-based resources (IBRs). This transformation requires critical roles of grid-forming (GFM) inverters replacing synchronous generators for bulk power system stabilization and ancillary services, also allowing flexible power system operation, such as microgrid that is operated by multiple GFM IBRs to achieve system resilience against contingencies. To realize the resilient power systems allowing flexible in-and-out operation of GFM IBRs potentially programmed with different primary controls, a synchronization method universally applicable, i.e., independent of control types, would be beneficial to ease the integration process, but it has not been actively studied. To fill the gap, this paper proposes a universal synchronization method that achieves a passive synchronization to enable a smooth transition in a grid with off-nominal system parameters, i.e., voltage and frequency. The logic proposed requires no modification on the primary control, thus applicable to any type of GFMs with a voltage reference input. To validate the concept, a simulation of an IEEE 13-bus benchmark system modified with 3 GFM inverters is presented. It simulates an inverter-driven black start scenario in which GFM inverters autonomously turn on and connect to the grid under heavy loading, using the synchronization logic. The case study demonstrates that GFM inverters can tune their voltage reference to smoothly synchronize without severe transients, and contribute to a seamless black start of the grid under unbalanced load conditions. Two GFM methods-Droop and dispatchable virtual oscillator control-are used for the demo to validate feasibility and interoperability of the passive synchronization.
Enhanced Large Signal Stability Method For Grid Forming Inverters During Current Limiting Preprint
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Author :
language : en
Publisher:
Release Date : 2023
Enhanced Large Signal Stability Method For Grid Forming Inverters During Current Limiting Preprint written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023 with categories.
Grid-forming (GFM) inverters are a promising technology for the widespread integration of renewable energy sources in future power systems. As a key element of GFM inverter control, the primary controller governs the internal reference voltage and angle. During contingencies in the grid--such as faults, voltage drops, or frequency and phase jumps--an inverter can be forced into a current-limiting mode of operation modulating inverter dynamics, and, as a result, it is prone to losing synchronism with the grid. In this paper, we propose a novel GFM primary control method with an additional synchronization term that naturally activates during contingencies to improve the dynamic response. The method allows the inverter to remain synchronized with the grid, which improves the inverter's dynamic behavior both during and after current-limiting grid conditions and enhances grid support, including voltage support using full current capacity. The method is demonstrated for voltage, frequency, and phase jumps both in a single-machine-to-infinite-bus and a network-wide electromagnetic transient simulation of the IEEE 14-bus system with 5 GFM inverters. The simulations provide insights into the proposed synchronization method and confirm the high potential of the method, which robustly secures synchronism under severe contingencies.
Power Hardware In The Loop Evaluation Of Pv Inverter Grid Support On Hawaiian Electric Feeders Preprint
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Author :
language : en
Publisher:
Release Date : 2017
Power Hardware In The Loop Evaluation Of Pv Inverter Grid Support On Hawaiian Electric Feeders Preprint written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
As more grid-connected photovoltaic (PV) inverters become compliant with evolving interconnections requirements, there is increased interest from utilities in understanding how to best deploy advanced grid-support functions (GSF) in the field. One efficient and cost-effective method to examine such deployment options is to leverage power hardware-in-the-loop (PHIL) testing methods. Two Hawaiian Electric feeder models were converted to real-time models in the OPAL-RT real-time digital testing platform, and integrated with models of GSF capable PV inverters that were modeled from characterization test data. The integrated model was subsequently used in PHIL testing to evaluate the effects of different fixed power factor and volt-watt control settings on voltage regulation of the selected feeders. The results of this study were provided as inputs for field deployment and technical interconnection requirements for grid-connected PV inverters on the Hawaiian Islands.
Grid Forming Inverters Enabling The Next Generation Grid
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Author :
language : en
Publisher:
Release Date : 2020
Grid Forming Inverters Enabling The Next Generation Grid written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020 with categories.
NREL's Power Electronic Grid Interface (PEGI) Workshop, held October 13, 2020, focused on the research challenges of operating power systems with ever-higher levels of inverter-based generation and power-electronic-based load. This presentation discusses grid-forming inverters and enabling the next generation grid.
Hardware In The Loop Hil Simulations For Smart Grid Impact Studies Preprint
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Author :
language : en
Publisher:
Release Date : 2018
Hardware In The Loop Hil Simulations For Smart Grid Impact Studies Preprint written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.
Hardware-in-the-loop (HIL) simulation is increasingly employed in power engineering as more inverter-based generation and smart appliances are connected to the electric grid. HIL techniques allow for co-simulation of analytical models with actual devices whose complex behavior is computationally inefficient or difficult to capture. It also allows for testing of the behavior of these devices under adverse conditions that only occur rarely in the field, but that are important to evaluate. An overview of how HIL simulation has been used to date is provided. This paper further proposes that HIL simulation should play an important role in evaluating new control strategies, especially at the distribution level, that are being proposed to allow for continued affordable and reliable operation of the electric grid with the introduction of these new technologies. It presents a new capability that was developed to enable evaluation of interactions between residential loads and the smart grid: smart home hardware-in-the-loop. The paper includes results from an HIL simulation that incorporates multiple technologies and controls.
Decentralized Schemes For Grid Forming Inverter System Efficiency Improvement And Online Inverter Detection
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Author : Ali Sheykhi
language : en
Publisher:
Release Date : 2021
Decentralized Schemes For Grid Forming Inverter System Efficiency Improvement And Online Inverter Detection written by Ali Sheykhi and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021 with Electric inverters categories.
Parallel grid-forming (GFM) inverters are used in many modern power system applications. Therefore, improving their system efficiency is of paramount importance for energy savings. The droop control method has been conventionally used to share the power among inverters proportional to their power ratings. However, the droop strategy does not guarantee an efficient power sharing especially at light loads, where the low power demand is divided among inverters, forcing them to supply a low power at a low efficiency according to their efficiency curve. Addressing the aforementioned issue while maintaining the advantages of parallel inverters used in residential areas is the focus of this thesis. A nested-loop control system for a single-phase inverter operating in standalone mode is introduced. The control system includes current, voltage, and harmonic control loops, and is designed based on the linear quadratic tracking (LQT) optimal control method. The designed controllers exhibit a satisfactory performance in tracking the reference signals and rejecting the unwanted harmonics in case of linear and nonlinear loads. Moreover, a total harmonic distortion (THD) of 1.65% is obtained when a nonlinear load is connected to the system. A decentralized modified droop strategy is also proposed to improve the system efficiency of parallel grid-forming inverters. The main idea is to control the power sharing among the inverters such that the output power of each inverter is maintained within a proper range with respect to the inverter efficiency curves. Hence, an optimal number of inverters supply the loads efficiently, and the unnecessary inverters do not share any power. In contrast to the existing methods, the proposed method does not have a single point of failure while it features modularity, flexibility, and reliability. Additionally, the reliability of the system is enhanced by extending the lifetime of inverters with higher power ratings which are considered as valuable assets of the system. Furthermore, a stability verification of the system within the designed operating range of the inverter no-load frequencies is conducted to ensure a stable operation. As in very-light load situations none of the inverters can operate within the proper power range with a high efficiency, an online-inverter detection (OID) method is proposed such that each inverter detects the online inverters and the unnecessary inverters stop injecting power to obtain a higher system efficiency. As the proposed OID is decentralized and modular, more inverters can be added to the system without adjusting the settings of installed inverters. Detailed derivations, simulations, and experimental results are presented to validate the effectiveness of the schemes.
Modeling Techniques And Control Strategies For Inverter Dominated Microgrids
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Author : Gkountaras, Aris
language : en
Publisher: Universitätsverlag der TU Berlin
Release Date : 2017-02-15
Modeling Techniques And Control Strategies For Inverter Dominated Microgrids written by Gkountaras, Aris and has been published by Universitätsverlag der TU Berlin this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017-02-15 with Technology & Engineering categories.
The character of modern power systems is changing rapidly and inverters are taking over a considerable part of the energy generation. A future purely inverter-based grid could be a viable solution, if its technical feasibility can be first validated. The focus of this work lies on inverter dominated microgrids, which are also mentioned as 'hybrid' in several instances throughout the thesis. Hybrid, as far as the energy input of each generator is concerned. Conventional fossil fuel based generators are connected in parallel to renewable energy sources as well as battery systems. The main contributions of this work comprise of: The analysis of detailed models and control structures of grid inverters, synchronous generators and battery packs and the utilization of these models to formulate control strategies for distributed generators. The developed strategies accomplish objectives in a wide time scale, from maintaining stability during faults and synchronization transients as well as optimizing load flow through communication-free distributed control. Die Struktur der modernen Energieversorgung hat sich in den letzten Jahrzehnten massiv geändert. Dezentrale Generatoren, die auf Wechselrichtern basieren, übernehmen einen großen Teil der Energieerzeugung. Ein ausschließlich wechselrichterbasiertes Netz wäre ein realistischer Ansatz, wenn seine technische Machbarkeit verifiziert werden könnte. Die wichtigste Beiträge dieser Arbeit sind: Die Analyse von Modellen und Regelstrukturen von Netzwechselrichtern, Synchrongeneratoren und Batterieanlagen. Die entwickelten Modelle werden verwendet, um Regelstrategien für dezentrale Generatoren in Mittelspannungsinselnetzen zu formulieren. Die erste Strategie ist eine Synchronisationsmethode für netzbildende Wechselrichter. Zweitens wird die Leistungsaufteilung in Mittelspannungsinselnetzen mittels Droop Regelung analysiert. Weiterhin erfolgt die Untersuchung der transienten Lastaufteilung zwischen netzbildenden Einheiten mit unterschiedlichen Zeitkonstanten. Beim Betrieb mehrerer paralleler Wechselrichter wird der Einfluss der Netzimpedanz auf die transiente Lastaufteilung analysiert. Die dritte entworfene Regelstrategie umfasst die Integration der Sekundärregelung in die Primärregelung. Der Ladezustand von Batterien wird mit der Lastaufteilung gekoppelt, um die Autonomie des Netzes zu stärken. Abschließend wird eine Kurzschlussstrategie für netzbildende und netzspeisende Wechselrichter entwickelt. Ziel der Strategie ist die Maximierung des Kurzschlussstromes. Als zusätzliche Randbedingung soll keine Kommunikation zwischen Generatoren stattfinden.
Grid Forming Power Inverters
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Author : Nabil Mohammed
language : en
Publisher: CRC Press
Release Date : 2023-02-28
Grid Forming Power Inverters written by Nabil Mohammed and has been published by CRC Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023-02-28 with Technology & Engineering categories.
Grid-Forming Power Inverters: Control and Applications is the first book dedicated to addressing the operation principles, grid codes, modelling and control of grid-forming power inverters. The book initially discusses the need for this technology due to the substantial annual integration of inverter-based renewable energy resources. The key differences between the traditional grid-following and the emerging grid-forming inverters technologies are explained. Then, the book explores in detail various topics related to grid-forming power inverters, including requirements and grid standards, modelling, control, damping power system oscillations, dynamic stability under large fault events, virtual oscillator-controlled grid-forming inverters, grid-forming inverters interfacing battery energy storage, and islanded operation of grid-forming inverters. Features: Explains the key differences between grid-following and grid-forming inverters Explores the requirements and grid standards for grid-forming inverters Provides detailed modelling of virtual synchronous generators Explains various control strategies for grid-forming inverters Investigates damping of power system oscillations using grid-forming converters Elaborates on the dynamic stability of grid-forming inverters under large fault events Focuses on practical applications