Enhanced Large Signal Stability Method For Grid Forming Inverters During Current Limiting Preprint
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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.
Scientific And Technical Aerospace Reports
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Author :
language : en
Publisher:
Release Date : 1986
Scientific And Technical Aerospace Reports written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1986 with Aeronautics categories.
Novel Hybrid Current Limiter For Grid Forming Inverter Control During Unbalanced Faults Preprint
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Author :
language : en
Publisher:
Release Date : 2023
Novel Hybrid Current Limiter For Grid Forming Inverter Control During Unbalanced Faults 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) inverter controls have illustrated many desirable features to enable bulk integration of renewable sources into the future power grid. However, the performance of GFM inverters during unbalanced faults remains under-explored. In this paper, a novel current-limiting method is proposed for GFM inverters to handle unbalanced fault conditions while providing voltage support to the main grid. The proposed current limiter combines concepts of dynamic virtual-impedance and current-reference saturation limiting, all built-up in the stationary reference frame to achieve improved current-limiting performance under unbalanced load/fault conditions. System-wide full-order transient simulations with multiple GFM inverters demonstrate the potential of the method and benchmark the performance against state-of-the-art current limiters. Simulation results portray improved voltage balancing performance of the proposed method compared to both current-reference saturation and virtual-impedance limiting.
Stability Enhancement Methods Of Inverters Based On Lyapunov Function Predictive Control And Reinforcement Learning
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Author : Xin Zhang
language : en
Publisher: Springer Nature
Release Date : 2022-11-29
Stability Enhancement Methods Of Inverters Based On Lyapunov Function Predictive Control And Reinforcement Learning written by Xin Zhang and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022-11-29 with Technology & Engineering categories.
This book introduces a family of large-signal stability-based control methods for different power inverters (grid-connected inverter, standalone inverter, single-phase inverter, and three-phase inverter) in practical applications. Power inverters have stability issues, which include the inverter's own instability as well as the inverter's instability in relation to the other power electronic devices in the system (i.e., weak grid and the EMI filter). Most of the stability analyses and solutions are based on small-signal stability technology. Unfortunately, in actuality, the majority of practical instability concerns in power inverter systems are large-signal stability problems, which, when compared to small-signal stability problems, can cause substantial damage to electrical equipment. As a result, researchers must conduct a comprehensive investigation of the large-signal stability challenge and solutions for power inverters. This book can be used as a reference for researchers, power inverters manufacturers, and end-users. As a result, the book will not become obsolete in the near future, regardless of technology advancements.
Improved Control Strategy Of Grid Forming Inverters For Fault Ride Through In A Microgrid System Preprint
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Author :
language : en
Publisher:
Release Date : 2022
Improved Control Strategy Of Grid Forming Inverters For Fault Ride Through In A Microgrid System 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.
This paper develops improved control strategy of GFM inverter with fault ride-through (FRT) capabilities to guarantee stable operation of microgrid under fault conditions especially islanded microgrid and asymmetrical faults. The proposed control strategy includes dual control of positive-sequence and negative-sequence control, and the adaptive virtual impedance (VI) control. Unlike the existing works, the proposed strategy only applies the VI control for the d-component of the positive-sequence control and leaves the q-component of positive-sequence control and dq-component of negative-sequence control zero, thus achieving the improved stability and balanced three-phase voltage under asymmetrical faults. The adaptive feature of the VI control guarantees the stability of the GFM inverter under severe faults which could cause saturated inner current loop and instability if the VI is not adaptive. Simulation results of a phase-to-phase-ground fault show that the proposed control strategy improves the stability of GFM and achieves the stable and balanced output voltages in islanded microgrid.
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.
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
Small Signal Stability Support From Dynamically Configurable Grid Forming Following Inverters For Distribution Systems Preprint
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Author :
language : en
Publisher:
Release Date : 2022
Small Signal Stability Support From Dynamically Configurable Grid Forming Following Inverters For Distribution 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.
The growth of inverter-based resources (IBRs) in modern power systems can challenge system stability since they do not natively provide inertia, prompting a need to develop new methods to address the potential instabilities. In this paper, a dynamically configurable grid-forming (GFM) and grid-following (GFL) control is proposed, which enables inverters to flexibly transition to support system needs. The operation mode transition between GFM and GFL controls is adopted as an additional degree of control flexibility to adjust the small-signal stability margin. In addition, a holistic and detailed small-signal model for a distribution feeder that captures the dynamics from both synchronous generators (SGs) and IBRs is also derived and used to evaluate the effectiveness of the proposed GFM/GFL controls to augment the system small-signal stability margin. Case studies with varying levels of IBRs were implemented in MATLAB/Simulink to demonstrate the effectiveness of the proposed approach.
Design Power Control Strategies Of Grid Forming Inverters For Microgrid Application Preprint
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Author :
language : en
Publisher:
Release Date : 2021
Design Power Control Strategies Of Grid Forming Inverters For Microgrid Application 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 2021 with categories.
This paper compares two control schemes in the application control layer of a non-PLL grid-forming (GFM) inverter to gain the insights and understanding of how the two schemes affect the dynamic responses of the GFM inverters and the transition operation of microgrids. Both schemes can achieve smooth microgrid transition operation and power tracking, however, the first scheme expects to exhibit more transients due to the feedforward of the inverse dynamic model of the output filter. Simulation results show that both control schemes achieve successful transition operation with smooth transients, and the second control scheme exhibits slightly better transients in the system frequency during islanding operation and the first one has slightly superior transients in the system frequency during reconnection operation. The power tracking performance in the grid-connected mode is evaluated, which shows that the first scheme has better active power tracking and the second one has better reactive power tracking. The analysis and results are useful to develop reliable control schemes for non-PLL GFM inverters because more and more inverters will work as non-PLL grid-forming sources in the future grids due to better stability and reliability.
Improved Control Strategy Of Grid Forming Inverters For Fault Ride Through In A Microgrid System
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Author :
language : en
Publisher:
Release Date : 2022
Improved Control Strategy Of Grid Forming Inverters For Fault Ride Through In A Microgrid System 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.
This paper develops an improved control strategy of grid-forming (GFM) inverters with fault ride-through (FRT) capabilities to guarantee the stable operation of microgrids under fault conditions, especially islanded microgrids and asymmetrical faults. The proposed control strategy includes the dual control of positive-sequence and negative-sequence control as well as the adaptive virtual impedance (VI) control. Unlike existing works, the proposed strategy applies the VI control for only the d component of the positive-sequence control and leaves the q component of the positive-sequence control and the dq component of the negative-sequence control as zero, thus achieving improved stability and balanced three-phase voltages under asymmetrical faults. The adaptive feature of the VI control guarantees the stability of the GFM inverter under severe faults, which could cause the saturation of the inner current loop, and the instability if the VI is not adaptive. Simulation results of various unbalanced faults with high and low fault impedances show that the proposed control strategy improves the stability of the GFM inverter and achieves stable and balanced output voltages in islanded microgrids. And the algorithm also improves the stability of GFM inverters under balanced faults with high and low fault impedances.