1,721,031 research outputs found
WT Type 4 Benchmarks for IEC 61400-27-1
No full textSince several years there has been a constant effort at international level for the standardization and the validation of different types of wind turbine (WT) dynamic models. The paper focuses on the IEC 61400-27-1 type 4 model, proposing and fully describing two benchmark systems for the
assessment of dynamic performance. The first system is a simple setup and it is designed to specifically assess the transient response of the WT controls. The second system is based on the IEEE 9-bus test system, and it is a multi-machine configuration allowing for the inclusion of the typical power system dynamics of synchronous machines and corresponding primary regulators. System configurations, models and parameters are designated with the purpose of interoperability and replicability, aiming to models comparison and validation
Grid-Listening and Grid-Ringing: Alternative Concepts for Grid-Following and Grid-Forming within Power Systems Frequency Transients
Full text linkThe paper introduces the concepts of grid-listening and grid-ringing as alternative ways to interpret the classes of converter control commonly known as grid-following and grid-forming. The intrinsic nature of these two controls define their interaction within the frequency transients in power systems, and in particular with the disturbance propagation and the synchronization process. The grid-following interacts with the oscillations in the system just detecting them: for that, it can be regarded as grid-listening. The grid-forming interacts with the power-frequency oscillations contributing to them: for that, it can be regarded as grid-ringing. This conceptual revisiting is illustrated with a representative system, and further discussed with some examples on a benchmark power syste
Impact of Converter-Interfaced Generation to the Frequency Response of the European Power System
No full textThe increase of converter-interfaced generation (CIG) typically related to renewable energy sources is progressively causing a significant change of power systems operation. The curtailment of synchronous generation with the consequent reduction of the overall kinetic energy is one of the related issues, currently under investigation in academia and industry. The work considers the problem of overall inertia reduction from a large-scale point of view, analyzing the impact of different CIG integration levels to the frequency response of the power system of Continental Europe. The kinetic energy is evaluated for each country of the synchronous area, and the system is modified substituting conventional synchronous generation with converter-interfaced generation. The models of power converters and corresponding controls follow typical representation for stability studies: they are modeled as controlled current sources with active and reactive power control loops, implemented as user-written equations within the overall mathematical model of Continental Europe power system. Comprehensive time-domain simulations are performed for each scenario, assuming the system subjected to a power plant outage: the obtained frequencies for Western, Central and Eastern Europe are reported, and typical frequency metrics are used to evaluate the response of the system across the different scenarios. Results show how the penetration of CIG affects the frequency response of the system, in terms of instantaneous frequency deviation and maximum frequency rate. A significant change in the inter-area oscillations is also observed, with a progressive increase of the oscillation frequency of the East-West mode, as confirmed by the modal analysis of the system
Impact of the high share of converter-interfaced generation on electromechanical oscillations in Continental Europe power system
No full textThis study investigates the effects of converter-interfaced generation integration on the dynamic response of the power system of Continental Europe. The system is analysed with a large-scale dynamic model of the entire synchronous area, considering different instantaneous integration percentages of converter-interfaced generation across the system. The study focuses on the reduction of the overall available kinetic energy and the impact on frequency dynamics and system oscillations. The dynamic model of the system originally provided by ENTSO-E is further developed according to a specific methodology, replacing a determined amount of synchronous generation and introducing a corresponding amount of converter-controlled current sources. The reference incident of a generation loss in Western Europe specified by ENTSO-E is considered in the
analysis. The results of time-domain simulations and modal analysis show how the integration of non-synchronous generation affects the frequency dynamics of Western, Central and Eastern Europe, bringing to attention some relevant effects of the spatial distribution of different generation sources within an extensive system as the Continental Europe synchronous area
A Study of Power-Frequency Dynamics in Isolated Power Networks with 100% Converter-Interfaced Generation
No full textThe operation of a system with 100% converter-interfaced generation poses several questions and challenges regarding various aspects of the dynamic characteristics of the system. The effects related to the power-frequency control are among the most relevant issues which need to be investigated. The paper takes into examination the case of an existing isolated power network of a geographical island assuming a completely converter-interfaced generation. The factors playing a fundamental role in the assessment of which sources should be designated to be grid-forming are identified with a small signal model formulation of a generic multiple oscillators system. Simulations and analysis performed on the case study of the island’s power network performed with the software NEPLAN are used to show the impact of different aspects which can play a
role in the design and the operation of the system: these aspects are the operating mode of power converters control, location and distribution of the generation sources with grid-forming capabilities, as well as number and ratings of these sources. The impact of relevant control parameters such as virtual inertia constant and virtual impedance is also investigated
Generalized power-angle control for grid-forming converters: A structural analysis
No full textSeveral control schemes have been recently proposed and studied as grid-forming controls for power converters. In all these schemes, the power-angle control loop is the part which defines the fundamental capabilities of the grid-forming control: that control loop governs in fact the inherent synchronization mechanism of the power converter, the power sharing with the other generation sources in the system and the oscillatory characteristics of the converter-based resource. This article introduces a general formulation for the power-angle control characterizing the grid-forming concept for power converters. The generalized power-angle control is based on a polynomial fraction formulation, and it is arranged according to physical requirements and constraints. The structural analysis provides an insight into the capabilities and the design of the power-angle control loop of a grid-forming scheme. The generalized formulation is eventually applied to some common grid-forming controls like the power-synchronization control and the virtual synchronous machine, showing how the proposed generalized power-angle control can effectively realize different control structures
Grid-Following and Grid-Forming MODELS in ATP-EMTP for Power Systems Simulation
No full textThe paper presents the models of grid-following and grid-forming converters in the software ATP-EMTP for power systems simulation. The models are developed using the MODELS language, they are described in details discussing all issues and aspects related to the implementation, and they are also shared as open source models. The models are validated with a simulation-based approach, comparing the results with the models developed in MATLAB/Simulink and in NEPLAN, considering both the phasor RMS and EMT time domains, and thus performing a comprehensive cross-platform and cross-domain validation. In line with the spirit of the ATP software and community, the models of grid-following and grid-forming converters are developed with the purpose of sharing them, and contributing in this way to the creation of a common basis for the integration of these elements into the analysis and simulation of power systems
A Cost-Effective Solution for Clearing High-Impedance Ground Faults in Overhead Low-Voltage Lines
Full text linkDowned distribution conductors in overhead distribution systems may not be a concern for equipment but greatly challenge the safety of persons, as well as the integrity of properties. Standard overcurrent protective devices may not be able to detect the magnitudes of currents resulting from high-impedance ground faults. Sophisticated relays able to detect high-impedance ground faults have been available to electric utilities. However, their implementation is rather uncommon, especially in developing countries, most likely due to their costs. In this paper, the authors formalize the problem, and propose a possible cost-effective solution for low-voltage overhead lines with neutral wire. This solution consists of a metal hook underneath the line conductors, attached to the pole and connected to the neutral wire. In the case of a falling line, the hook would be contacted and a line-to-neutral short circuit would occur; this would positively activate existing standard overcurrent devices, which can therefore disconnect the supply. Costs related to the installation of the device to existing overhead lines are herein analyzed. The effectiveness of the proposed solutions for two different voltage levels (400 V in European countries and 240 V in the USA) is also discussed
On the de-energization of over-head low-voltage lines under high-impedance fault conditions
No full textDowned distribution conductors in overhead distribution systems, may not be a concern for equipment, but greatly challenge the safety of persons, as well as the integrity of properties. Upstream overcurrent protective devices may not be able to detect the magnitudes of fault currents resulting from these high-impedance faults. Even though protective devices capable to detect such faults have been available on the market, not all the utilities have equipped their stations with these products, likely due to the costs. In this paper, the authors formalize the problem, and propose a possible cost-effective solution for the low-voltage over-head lines with neutral wire. Such solution includes a metal hook underneath the line conductors, supported by the pole, and connected to the neutral wire. This arrangement would cause a line-to-neutral short circuit, positively activating existing over-current devices, which can therefore disconnect the supply. Costs and possible safety issues for workers related to the installation of the device to existing overhead lines are herein also delineated
Analysis and simulations of the primary frequency control during a system split in continental europe power system
Full text linkThe occurrence of system separations in the power system of Continental Europe has been observed in recent decades as a critical event which might cause power imbalances higher than the reference incident specified per system design, representing an actual challenge for the stability and safe operation of the system. This work presents an analysis and simulations of the primary frequency control in the Continental Europe synchronous area in conditions of system separation. The adopted approach is based on fundamental aspects of the frequency-containment reserve process. The analysis takes an actual event into consideration, which determined the separation of the system in January 2021. The main purpose of the work is the development of specific models and simulations able to reproduce the actual split event. Due to specific arrangements discussed in detail, it is possible to obtain a substantial match between the simulations and the frequencies registered after the system split. The work also provides insight into the importance of the temporal sequence of power imbalances and defensive actions in the primary frequency control process. The models developed in the work are finally used to investigate the separation event under different operating conditions, such as missing defensive actions and low inertia scenarios
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