APRÈN. Portal de la producció docent del professorat de la UPC

El creciente interés en las microrredes y su integración en redes eléctricas ha impulsado la necesidad de algoritmos precisos para el cálculo de fasores, fundamentales para la monitorización y el control de sistemas eléctricos. Este trabajo analiza cuatro algoritmos específicos: AM, PM, IpDFT y DFT, evaluándolos mediante simulaciones en una microrred modelada en Matlab-Simulink y conectada a una red de alta tensión. En estas simulaciones, se estudiaron dos escenarios representativos: variaciones en la frecuencia y en el voltaje de la red. Los resultados mostraron que el algoritmo DFT fue el que mejor estimación del fasor obtuvo cuando se trabajó en torno a la frecuencia nominal, pero el peor cuando se operó fuera de ella. En estas condiciones, los algoritmos AM y PM lograron las mejores estimaciones.

The protection issues surrounding multiterminal High Voltage Direct Cur- rent (MT-HVDC) grids based on Voltage Source Converters (VSC) are ex- amined in this thesis, with an emphasis on the function of hybrid HVDC circuit breakers in reducing DC-side faults. The study emphasises how im- portant it is to isolate and detect faults quickly, accurately, and specifically as HVDC networks become more intricate as a result of the growing inte- gration of renewable energy sources. The study evaluates the performance of hybrid HVDC circuit breakers under various fault scenarios by compre- hensive modelling and simulation using Simulink, demonstrating their ef- ficiency in shortening fault clearing times and improving system stability. Undervoltage, overcurrent, and current/voltage derivative-based fault de- tection algorithms are compared, and the results show that voltage-based techniques perform better in high-resistance fault scenarios.Hybrid HVDC circuit breakers, which combine the reliability of mechanical disconnectors with the speed of solid-state devices, are identified as a promising solu- tion for modern MT-HVDC grids. This research contributes valuable insights into the design and application of hybrid HVDC circuit breakers and protection algorithms, showing that they significantly improve the operational safety and reliability of HVDC grids. Future studies ought to concentrate on lowering power losses that occur during regular operations and improving the scalability of hybrid HVDC circuit breaker designs for bigger grids. It is projected that improvements in self-triggering mechanisms and circuit breaker technology will further reduce conduction losses and speed up operation. Furthermore, the inte- gration of machine learning (ML) and artificial intelligence (AI) into fault detection algorithms presents a promising opportunity to enhance detec- tion efficiency and precision, all the while accommodating dynamic grid conditions. The effect of communication latency on problem detection may be lessened by investigating communication-independent protection systems, such as travelling wave-based methods. For a viable deployment, extensive testing and validation in real HVDC grid environments are nec- essary, and complicated failure scenarios should be simulated in order to better inform future implementations.By addressing these issues, HVDC grid protection will be improved, along with system efficiency, depend- ability, and capacity to handle the increasing needs of renewable energy integration.

High-voltage direct current (HVDC) grids has been identified as one of the promising solution for the ongoing energy transition but its deployment is being limited due to some challenges. This study provided a comprehensive overview of HVDC transmission systems and its extension into grids, and afterwards focused on protection of DC grids (one of the main challenges of the DC grids), particularly voltage source converter (VSC) based DC grids. It was studied that DC grids protection devices and protection philosophies differ in strength, and their area of applications influence their selection. A DC grid and a hybrid DC circuit breaker were modelled for the study. The converters in the DC grid are connected as symmeteric monopoles, and each of them is represented with an equivalent circuit of DC voltage source connected in parallel to a series RLC (resistance, inductor and capacitor). The study shows that the modelled hybrid DC breaker could open within 2.85 ms after the fault. Furthermore, the impact of the fault on other cables indicates the need for a more fast opening device and a robust control algorithm that could handle the control and operation of the DC circuit breakers within the network hence ensuring a resilient grid system with a fault-ride through capability.

HVDC systems have experimented and increase of popularity in recent years due to the fast development of power electronics technologies and the need to decarbonize energy generation systems by introducing new renewable energy sources (RESs). This new energy generation systems are based in HVDC networks, are capable of connecting long-distance power transmis- sion lines, since they require fewer conductors and incur less power loss than equivalent HVAC lines. Besides, HVDC systems are capable of connecting asynchronous networks improving controlla- bility and stability of the power flow, which will prevent propagation of fault and disturbances. These advantages have led to an emerging need for the development of multi-terminal HVDC (MT-HVDC) systems. [1] Protection of HVDC systems against DC faults is challenging not only because of the lack of zero crossing, which can have negative impacts for safe and reliable operations. But also because of the low impedance faults that result in large and fast current flows. Currently HVDC point-to point links are protected using circuit breakers on the AC side of the converters, but, in order to enable MT-HVDC grids, the fault must be cleared in the DC side to keep the rest of the grid operating normally. Which means, there is a need to develop fast and reliable DC switch-gear with low on-state losses and fast fault clearance. Several designs have been proposed for HVDC circuit breakers, but few are suitable for Voltage- sourced converters (VSC) applications. And, since today, few industrial prototypes have been developed. The aim of this project is to provide a detailed analysis on hybrid HVDC circuit breakers by modelling and simulating a Proactive Hybrid Circuit Breaker, which is currently considered the preferred approach on fast fault clearance [2].

Este proyecto tiene como objetivo aportar conocimientos valiosos a la creación de gemelos digi- tales de redes eléctricas mediante el estudio y desarrollo de la infraestructura de comunicaciones necesaria para el intercambio de datos entre una red simulada y su representación virtual. Utilizando un PC intermediario, se han estudiado y probado diferentes métodos de transmisión de datos, para transmitir tanto datos en tiempo real como datos de parámetros desde una red simulada, que se ejecuta en una plataforma Opal, a un servidor que actúa como gemelo digital. Una vez seleccionados los mejores métodos para cada tipo de dato y dispositivo, se establecen y evalúan las comunicaciones entre niveles y se implementa el tratamiento de datos necesario para cada tipo de dato. Para probar el flujo completo de datos a través de todos los niveles, se ha implementado un flujo de energía en el servidor usando GridCal, que utiliza los datos recibidos del Opal a través de las diferentes conexiones

High Voltage Direct Current (HVDC) transmission systems are key for power transmission in bulk quantities over long to very long distances to meet increasing power demands. They are ideal for interconnecting the onshore grid with distant renewable sources of energy like offshore wind power, tidal power, and others with very low chances of loss of power, efficiency, power frequency synchronization, and reliability. The main challenge, however, is that the DC faults in the offshore cables are almost always permanent until serviced. Communication channel with the connected DC grid protection plays a huge role where the accurate and timely recognition of the location of faults in cables is critical for performing servicing of the faults within the minimum time possible, in order to avoid loss of power, and downtime of the system hence saving a lot of money. The urgency of accurate DC fault location necessitates establishing a novel technique to learn from previous events of similar kinds with data flowing from sensors and measuring units in the electric grid. This study proposes a proof of concept for a scalable and effective fault location methodology for a transient waveform recorder from an HVDC station. The output could help HVDC Service better localize the fault incidence and the correct party responsible for clearing the fault can develop an efficient approach to clear it. The thesis expects to contribute towards a sustainable and reliable electric grid