Switching three-phase distribution transformers with a vacuum circuit breaker: Analysis of overvoltages and the protection of the equipment

Electrical Engineering, Mathematics and Computer Scienc

General approach for accurate resonance analysis in transformer windings

In this paper, resonance effects in transformer windings are thoroughly investigated and analyzed. The resonance is determined by making use of an accurate approach based on the application of the impedance matrix of a transformer winding. The method is validated by a test coil and the numerical results are verified by an ATP-EMTP model. Further analysis is applied on a transformer winding for which the inductance and the capacitance matrix as well as the winding losses are previously determined. By having determined the amplification factor, it can be found the location where the most severe transients may occur. It is also shown that maximum resonance overvoltage depends on the duration of the excitation and its resonance frequency.Intelligent Electrical Power Grid

D-Decomposition Based Robust Discrete-Time Current Regulator for Grid-Connected VSI

The D-decomposition method allows to design control structures with prescribed locations of closed loop poles. Unlike the root locus method, D-decomposition natively handles two variable regulator parameters, which makes it suitable for more complex control structures. Moreover, an extension to more than two variable parameters is straightforward. In this paper, the advantages of the D-decomposition method are illustrated by synthesizing a robust low-order current regulator for a grid-connected voltage source inverter (VSI) with LCL filter. It is shown how to visualize the complete region in the low dimensional regulator parameter space satisfying certain robust performance criteria (with robust stability being a special case). The paper concludes by simulation results validating the robustness properties of the designed low-order regulator under substantial grid impedance variations.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Intelligent Electrical Power Grid

Analysis of Switching Transient Overvoltages in the Power System of Floating Production Storage and Offloading Vessel

Large transient overvoltages are normally caused by vacuum circuit breaker (VCB) switching operation during disconnection of induction motors. In this paper VCBs, cables, generators, busbars, induction motors and surge arresters are modeled by making use of ATP-EMTP. Switching transient overvoltages of four typical induction motors are analyzed under starting, full load and light load working conditions in a power system of a Floating Production Storage and Offloading (FPSO) vessel. A suitable protection against the switching transient overvoltage is proposed and the results are presented.Electrical Sustainable EnergyElectrical Engineering, Mathematics and Computer Scienc

Development of HVDC system-level mechanical circuit breaker model

The main goal of the paper is the modelling of the mechanical direct current circuit breaker (DC CB) with active current injection that includes different circuit breaker characteristics. System level models provide adequate representation of the circuit breakers for system analysis studies. The performance characteristics of the DC CB in those proposed models replicate the ones of the devices in practice. The developed mechanical circuit breaker model is realized for a 320 kV demonstration circuit in PSCAD environment and its limitations and robustness are analyzed. The performance of the model is investigated by different cases. The obtained results show that the DC CB model can be used with full success for both to simulate DC fault interruptions and to be used for different protection studies.Intelligent Electrical Power Grid

A Piece-wise Linearized Transformer Winding Model for the Analysis of Internal Voltage Propagation

In this paper, a piece-wise linearized transformer winding model is proposed for transient internal voltage distribution computations. In particular, the model is based on the linearization of the primitive non-linear, frequency dependent and invariant matrix of voltage distribution factors. This primitive matrix is utilized as a pattern from which, for any specific switching event and its frequency spectrum, the piecewise linearized matrix of voltage distribution factors can be computed. In this manner, a unified black-box to lumped-parameters combined transformer model successfully bypasses the need of geometrical data. The computations are also significantly reduced. The model is verified by measurements on a three-phase distribution transformer.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Intelligent Electrical Power Grid

Hybrid Islanding Detection Method of Photovoltaic-Based Microgrid Using Reference Current Disturbance

This paper proposes a new hybrid islanding detection method for grid-connected photovoltaic system (GCPVS)-based microgrid. In the presented technique, the suspicious islanding event is initially recognized whilst the absolute deviation of the point of common coupling (PCC) voltage surpasses a threshold. After an intentional delay, a transient disturbance is injected into the voltage source inverter’s d-axis reference current to decline the active power output. As a result, the PCC voltage reduces in islanding operating mode whilst its variation is negligible in the grid presence. Therefore, the simultaneous drop of PCC voltage and active power output is used as an islanding detection criterion. The effectiveness of the proposed algorithm is investigated for various islanding and non-islanding scenarios for a practical distribution network with three GCPVSs. The simulation results in MATLAB/Simulink show successful islanding detection with a small non-detection zone within 300 ms without false tripping during non-islanding incidents. In addition to the precise and fast islanding classification, the presented scheme is realized inexpensively; its thresholds are determined self-standing, and its output power quality degradation is eminently small. Moreover, the active power output is restored to the nominal set after islanding recognition, enhancing the chance of GCPVS generation at its highest possible level in the autonomous microgrid.Intelligent Electrical Power Grid

Revision of TRV Requirements for the Application of Generator Circuit-Breakers

The requirements imposed on generator circuitbreakers greatly differ from the requirements imposed on other transmission and distribution circuit-breakers. Due to the location of installation between the generator and the associated step-up transformer, a generator circuit-breaker must meet high technical requirements with respect to rated normal currents, short-circuit currents, fault currents due to out-of-phase conditions and transient recovery voltages. The question whether the transient recovery voltage requirements laid down in IEEE Std C37.013-1997 (R2008) and in its amendment IEEE Std C37.013a-2007 are still adequate for the application of generator circuit-breakers in modern power stations is considered in the present work. In order to quantify the transient recovery voltage requirements for the application of generator circuit-breakers a comprehensive survey of different fault conditions occurring in several power stations has been performed. The fault transients’ simulations have been performed by means of the Electromagnetic Transients Program (EMTP).Electrical Sustainable EnergyElectrical Engineering, Mathematics and Computer Scienc

Holonic architecture of the smart grid

With the growing concerns about sustainable energy, energy efficiency and energy security, the electrical power system is undergoing major changes. Distributed energy sources are becoming widely available at the lower parts of the grid. As a result, more and more end consumers are transforming from passive consumers to active “prosumers” that can autonomously generate, store, import and/or export power. As prosumers increasingly dominate the power system, the system demands capability that allows enormous number of stakeholders with heterogeneous types to exchange power on the grid. Unfortunately, the classical power system cannot efficiently handle this scenario since it was designed for centralized power distribution. Thus, restructuring the rather old power system is indispensable. In this paper, we apply the holonic approach to structure the smart grid as a system that is bottom-up organized from autonomous prosumers that are recursively clustered at various aggregation layers. Based on this, we present a control architecture of the smart grid using holonic concepts. Our control architecture is characterized by autonomy of the prosumers, distributed control, recursive self-similar control structures at different aggregation levels. Further, we present a service oriented architec-ture (SOA) framework that models the control functions that make up the holonic control architecture. Our proposed control architecture is tested using a simulation set-up.Intelligent SystemsElectrical Engineering, Mathematics and Computer Scienc

Robust Adaptive Back-Stepping Control Approach Using Quadratic Lyapunov Functions for MMC-Based HVDC Digital Twins

Due to its excellent performance, VSC-based high voltage direct current (HVDC) power systems draw significant attention. They are being heavily used in modern industrial applications, such as onshore and offshore wind farms, and for interconnection between asynchronous networks. However, the traditional proportional-integral (PI) control method is not robust enough to track the reference signal quickly and accurately during significant system disturbances. This paper proposes a robust adaptive back-stepping control (BSC) method that secures vulnerable power-electronic equipment. The adaptive BSC controller regulates the sum of capacitor energy, and the AC grid current through decoupled and closed control-loop design. The major advantage of the proposed control approach is the smooth transient response and accurate tracking ability, which is superior to classical control methods. In addition, the proposed methods have the merits of systematic and recursive design methodology and demand a low processing burden for Lyapunov functions and control laws. Moreover, the implementation particularities of the proposed approach are illustrated and verified for a power system digital twin using real-time digital simulator (RTDS).Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Intelligent Electrical Power Grid