SUB SYNCHRONOUS OSCILLATIONS IN MODERN TRANSMISSION GRIDS DESIGN AND VALIDATION OF NOVEL CONCEPTS FOR MITIGATING ADVERSE DFIG-SSR INTERACTIONS

SUB SYNCHRONOUS OSCILLATIONS IN MODERN TRANSMISSION GRIDS DESIGN AND VALIDATION OF NOVEL CONCEPTS FOR MITIGATING ADVERSE DFIG-SSR INTERACTIONS

Dissertation for the degree of Doctor at Delft University of Technology, by the authority of the Rector Magnificus Prof.dr.ir. T.H.J.J. van der Hagen, Chair of the Board for Doctorates, to be defended in public on Thursday, 24 June 2021 at 15:00 by Vinay Naraindatt SEWDIEN Civil Engineer, KU Leuven, Belgium born in Paramaribo, Suriname 

 SUMMARY 

The ongoing energy transition results on the one hand in a proliferation of power electronics interfaced devices and on the other hand in a decreasing availability of conventional synchronous generation. These developments pose important challenges for transmission system operators to operate a low inertia power system. As part of my research I have created a list of 28 related challenges, validated by industry, that are grouped into three categories: (i) Reduced Voltage and Frequency Support, (ii) New Operation of the Power System and (iii) New Behaviour of the Power System. The focus of this research is on category (iii) and addresses the sub synchronous resonance (SSR) phenomenon between a doubly fed induction generator (DFIG) and a series compensated transmission line. This phenomenon is denoted as DFIG-SSR in this thesis. Failing to adequately address resonances results in among others degradation of the power quality, protection tripping, physical damage to power system equipment and ultimately instability in the power system. The main objective of this research is to investigate and validate the degree of effectiveness of the existing phase imbalance compensation concept, as well as to design and validate a new prediction gain scheduling control concept for mitigating DFIG-SSR. For these investigation, design and validation activities, electromagnetic transient (EMT) simulation models of the DFIG wind turbine are developed using Power System Computer Aided Design (PSCAD). In line with common practice, the topology of the IEEE First Benchmark Model is used as a smallsize study model, whereas the larger IEEE 39-Bus Model is used for validation of the obtained results. The impedance based stability method is used to quantify the impact of potential mitigation solutions on DFIG-SSR. This dissertation has three main contributions. First, recommendations are developed to obtain the frequency-dependent impedance of power electronics interfaced devices through numerical EMT simulations of black box, non-linear simulation models. These recommendations are crucial to perform interaction studies. The influence of the impedance calculation time, model granularity and composition of the perturbation signal on the obtained impedance is presented and guidelines are given on how to select the correct model and parameters for the numerical simulations. Second, a methodology is developed that enables the systematic assessment and design of the phase imbalance compensation concept for mitigating DFIG-SSR. The phase imbalance compensation concept is an alternative way of fixed series compensation, where the imbalance is implemented as a series or as a parallel resonance scheme in either one or two phases of the transmission line. The influence of the series and parallel schemes as well as the influence of their different degrees of asymmetry on the stability of the system are rigorously investigated. The series scheme introduces one series resonance in the power system, where the resonance frequency increases as a function of the degree of asymmetry. The increase is more pronounced viii SUMMARY when the series scheme is implemented in two phases. The parallel scheme on the other hand decreases the series resonance frequency and this decrease is more pronounced when the scheme is implemented in two phases. However, the parallel scheme introduces an additional parallel resonance with a frequency between 20 and 30 Hz, the stability of which depends on the degree of asymmetry.

FULL THESIS :https://research.tudelft.nl/files/93510648/Thesis_for_ONLINE_v2.pdf

Satellite Electrical Power System -Nuno Laranjeira Ramo Thesis to obtain the Master of Science Degree in Electronics Engineering -INSTITUTO SUPERIOR DE LISBOA

Satellite Electrical Power System by Nuno Laranjeira Ramo Thesis to obtain the Master of Science Degree in Electronics Engineering -INSTITUTO SUPERIOR DE LISBOA 

 Abstract The Electrical Power System (EPS) is an electronic circuit board that is designed to supply and manage process the energy in an efficient way. This document describes the design architecture and circuits involved for an EPS deployed in the ISTsat ONE nano satellite project. The EPS generates energy through its solar panels which is stored in the battery and then, using DC-DC switching voltage regulators, converts it to the final voltage of +3.3 V and +5 V, supplying these voltage rails for the rest of the subsystems of the satellite. This architecture meets the performance and size requirements of CubeSat architecture (cubic shape with 10 cm of edge, satellite with less than 10 kg). The EPS is composed by various systems, namely: Maximum Power Point Tracking mechanism to achieve maximum efficiency in the conversion of solar energy, a 20.8 Wh battery, solar panels and redundant circuitry to continuously ensure the power supply to the satellite. The EPS is a subsystem of the ISTsat ONE and as such, it communicates with other subsystems present in the satellite sending data logs, error warnings as well as receiving commands.

FULL THESIS: https://istsat-one.tecnico.ulisboa.pt/~istsat-one.daemon/docs/thesis_NunoRamos_EPS_2018.pdf

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