Grid-Forming Inverters as Synchronous Machine Replacements: Stability Analysis and Overcurrent Protection Strategies-MASTER THESIS ENGINEERING ELERTRICAL-ROBERTO NETO-Università di Padova

 

Grid-Forming Inverters as Synchronous Machine Replacements: Stability Analysis and Overcurrent Protection Strategies-MASTER THESIS ENGINEERING ELERTRICAL-MASTER CANDIDATE-ROBERTO NETO-Università di Padova 

 Abstract The increasing integration of renewable energy sources into power systems is driving the progressive replacement of traditional synchronous generators with power electronic converters. While essential for decarbonization, this shift leads to a significant reduction in system inertia, thereby compromising frequency stability and dynamic performance. Grid-forming inverters (GFMs) have emerged as a promising solution to these challenges, as they autonomously regulate voltage and frequency, effectively emulating the behavior of conventional synchronous machines. This thesis presents a comprehensive study of three major grid-forming control strategies: droop control, Virtual Synchronous Machine (VSM), and dispatchable Virtual Oscillator Control (dVOC). Each approach is evaluated based on its dynamic response and stability characteristics. Time-domain simulations are carried out in MATLAB/Simulink on a modified IEEE 9-bus test system. Scenarios include systems dominated by synchronous machines, mixedgeneration configurations, and grids with 100% inverter-based renewable sources. The results highlight the critical role of GFMs in enhancing frequency stability and grid resilience. In addition, the thesis includes detailed modeling of the inverters DC-side power supply, consisting of a photovoltaic plant coupled with a Hybrid Energy Storage System (HESS) based on batteries and supercapacitors. This configuration reflects realistic operating conditions and ensures stable power injection into the AC grid. Finally, the thesis explores protection mechanisms to mitigate overcurrent conditions during disturbances. These control strategies are vital to ensure the secure operation of GFMs under fault scenarios and to support the long-term reliability of renewable-based power systems.

FULL THESIS: https://thesis.unipd.it/retrieve/7da633d3-120d-48a3-ad52-76b2fc66574e/Tonet_Roberto.pdf

Inverter Control Strategies for a Grid Stabilizing Power-to-Gas System = 전력가스화 (P2G) 시스템에서 계통 안정화를 위한 인버터 제어기법 -Gedeon Rusatira-Tech University of Korea

 

Inverter Control Strategies for a Grid Stabilizing Power-to-Gas System 전력가스화 (P2G) 시스템에서 계통 안정화를 위한 인버터 제어기법by  Gedeon Rusatira 

 A Ph.D. Dissertation Submitted to the Department of Energy and Electrical Engineering and the Graduate School of Tech University of Korea in partial fulfillment of the requirements for the Philosophy Degree in Engineering June 2024

Abstract 

Inverter Control Strategies for a Grid Stabilizing Power-to-Gas System 전력가스화 (P2G) 시스템에서 계통 안정화를 위한 인버터 제어기법 

The integration of Power-to-Gas (P2G) systems into modern power grids represents a pivotal advancement towards achieving a more sustainable and resilient energy infrastructure. However, this integration introduces both challenges and opportunities, particularly concerning grid stability and the effective incorporation of renewable energy sources. This thesis delves into the intricate dynamics of P2G system integration, with a specific focus on the role of inverter control strategies in ensuring grid stability and facilitating the seamless integration of renewable energy sources. Through an extensive review of existing literature and rigorous analysis, various control strategies tailored for P2G applications are explored, emphasizing their efficacy in addressing grid stability concerns. Key aspects examined include voltage and frequency regulation, active and reactive power control, ancillary services provision, and energy storage management. These factors are crucial for maintaining grid stability amidst the variability inherent in renewable energy generation and the intermittent nature of P2G systems. Additionally, the development and implementation of advanced control algorithms are discussed. These algorithms are designed to account for grid dynamics, renewable energy variability, and compliance with grid codes and regulations. A particular focus is placed on enhancing grid-forming capabilities within inverters, enabling autonomous operation even in weak grid conditions, thereby bolstering grid resilience. Practical case studies and simulations form an integral part of this research, allowing for the assessment of various control strategies’ performance under diverse grid scenarios. Insights gained from these analyses contribute to a deeper understanding of inverter control strategies and address regulatory and technical considerations associated with grid support functions. Ultimately, this thesis aims to serve as a valuable resource for policymakers, grid operators, and industry stakeholders, providing guidance on the implementation of effective control strategies for P2G applications. Novel distributed control systems specifically designed for P2G inverter applications are proposed, with the overarching goal of improving stability, efficiency, and dependability within the energy grid. By advancing our understanding of inverter control strategies and their role in P2G integration, this research contributes to the ongoing transition towards sustainable energy systems. This fosters a robust and environmentally friendly energy landscape, paving the way for a more resilient and equitable energy future.

 keywords: Distributed control strategies, Grid stability, Inverter control, Power-to-Gas (P2G), Renewable energy integration 

FULL THESIS : https://www.riss.kr/search/detail/DetailView.do?p_mat_type=be54d9b8bc7cdb09&control_no=e4eef281c8f67286ffe0bdc3ef48d419&keyword=grid%20forming

인버터 주도 계통 안정도의 그리드 포밍 제어 영향 연구 = A study on the influence of grid forming control on inverter-driven grid stability

 

인버터 주도 계통 안정도의 그리드 포밍 제어 영향 연구 = A study on the influence of grid forming control on inverter-driven grid stability GwangwoonUniversity GraduateSchoolof ElectricalEngineering KimDongWhi

ABSTRACT Recently, as new and renewable power sources penetrate into the system, an increase in IBR (Inverter Based Resource) and a decrease in synchronous generators are occurring. In this paper, the system operation using GFM (Grid Forming) was studied as a solution. The comparison study has been performed with the existing GFL (Grid Following) and synchronous generator in terms of the reduction in system inertia and robustness in the grid. This paper proposes a method for calculating the optimal capacity of GFM to ensure system stability and apply the novel IBR protection system (FRT, Black Start). In the case of GFM optimal capacity calculation, a renewable power source system network is modeled and various (load fluctuations, ground faults, generator trip) simulations are conducted with the existing synchronous generator, GFL, and GFM for the power system stability analysis. The formulation was performed by measuring Nadir with Monte-Carlo simulation results using the system inertia, GFL & GFM ratio, and renewable energy penetration rate as parameters. With the result, it was possible to know frequency nadir and the optimal GFM capacity required depending on system situation. The fault current limiter proposed has been verified its performance on the grid-connected photovoltaic IBR system. In addition, a stand-alone black start of GFM was proposed and the contribution of stable recovery through synchronization control was confirmed.

ORIGINAL LINK : https://www.riss.kr/search/detail/DetailView.do?p_mat_type=be54d9b8bc7cdb09&control_no=b0edd4d81bb1ee59ffe0bdc3ef48d419&keyword=inverter%20grid%20forming

Development and Application of a Resilience-Based Index for Stability Assessment of Grid Integrated with Grid-Forming Inverters Lee Su-Ho Departmen of Electric and Electrical Engineering Graduate School Keimyung University

 

Development and Application of a Resilience-Based Index for Stability Assessment of Grid Integrated with Grid-Forming Inverters Lee Su-Ho Departmen of Electric and Electrical Engineering Graduate School Keimyung University (Supervised by Professor Park Young-Su) 

ABSTRACT 

This research focuses on analyzing the impact of Grid-Forming inverters in modern power systems with a growing share of renewable energy and develops a Frequency Stability Composite Index (FSCI) for evaluating their effectiveness particularly within the Jeju power grid. As Jeju Island progresses toward its "Carbon Free Island 2030" initiative incorporating Grid-Forming inverters has become essential to address the limitations of existing Grid-Following inverters in low-inertia systems. The study includes simulations based on the IEEE-9 bus test system and the Jeju grid exploring various disturbance scenarios to assess the contribution of Grid-Forming inverters. The evaluation spans scenarios with renewable energy penetration levels of 30% 50% 70% and 100%.

Furthermore the FSCI methodology is applied to quantitatively measure the dynamic frequency and voltage recovery characteristics providing insights into strategies for enhancing grid stability in high-renewable contexts.

Full Thesis translated from the original Korean language to English :

https://www.mediafire.com/file/ntj1bpziplb37cj/EvaluationoftheGridformingInverterinterconnectedsystemstability.pdf/file 

Understanding the insertion loss of filters in power electronics applications By Min Zhang, Founder and Principal EMC Consultant, Mach One Design