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As the inverter-based generation replaces the conventional synchronous generators, it may also need to fill in the missing ancillary service support. One of these ancillary services is dynamic reactive power provision and voltage control. This paper analyzes optimal strategy of reactive and active fault-current support of the inverter-based generation leading to fast voltage recovery of the system. For the purpose of the analysis, new ramping active current controller able to emulate different behavior of active current injection is proposed. By optimizing its parameters for different case studies of the system, the conclusions about optimal behavior of the inverter based generation with respect to system parameters and operating conditions are drawn. It is observed that the optimal combination of active and reactive fault-current is the most sensitive to the dynamic load component penetration levels in the system. With the increasing penetration levels, the significance of active fault-current injection increases. The results show that with higher penetration levels of dynamic load component in the heavy load areas, the ramping down of the inverter-based generation active fault-current results in slower voltage recovery of the system. Following this conclusion, a recommendation on update of current European grid codes is proposed., QC 20220404

In many power systems, the increased penetration of inverter-based renewable generation will cause a decrease in kinetic energy storage, leading to higher frequency excursions after a power disturbance. This is the case of the future Nordic Power System (NPS). The look-ahead study reported in this paper shows that the chosen units participating in Frequency Containment Reserves (FCR) cannot keep the frequency above the prescribed threshold following the outage of the largest plant. This analysis relies on a detailed model of the Northern European grid. The latter is compared to the classical single-mass equivalent, and the impact of voltage-dependent loads is assessed in some detail. Next, the paper focuses on emergency power control of the HVDC links that connect the NPS to the rest of the European grid, which can supplement or even replace part of the FCR. The proper tuning of that control is discussed. Finally, the analysis is extended to the HVDC links connecting the future North Sea Wind Power Hub under two configurations, namely low and zero inertia. The impact of outages in the latter sub-system is also assessed. The material to simulate the system with industrial software is made publicly available., QC 20221104

Dynamic state estimation (DSE) accurately tracks the dynamics of a power system and provides the evolution of the system state in real-time. This paper focuses on the control and protection applications of DSE, comprehensively presenting different facets of control and protection challenges arising in modern power systems. It is demonstrated how these challenges are effectively addressed with DSE-enabled solutions. As precursors to these solutions, reformulation of DSE considering both synchrophasor and sampled value measurements and comprehensive comparisons of DSE and observers have been presented. The usefulness and necessity of DSE based solutions in ensuring system stability, reliable protection and security, and resilience by revamping of control and protection methods are shown through examples, practical applications, and suggestions for further development.

The Frequency Containment Reserve (FCR) is one of the balancing actions to keep the frequency within acceptable limits. The objective of the FCR (also known as primary frequency control) is to stabilize the system frequency within a short time interval after a disturbance. Related to that, maximum steady-state frequency deviation and maximum Instantaneous Frequency Deviation (IFD) are defined. With higher integration of renewable energy sources, power systems will reduce its impact on pollution, but face much more often with low inertia scenarios. With low inertia values, the system decreases its inherent property to react to large power disturbances. In these cases, IFD is profoundly affected, and there is a need for fast and cost-effective solutions. High-Voltage Direct-Current (HVDC) links, with appropriate control strategies, could offer a solution to this problem. According to current system requirements, HVDC links must be capable of providing frequency support. Several studies have focused on control methods that adjust the power output of HVDC converters in response to frequency deviations; however, which method performs best in terms of reliability, robustness, and cost-effectiveness has still not been proved. The aim of this work is to apply and compare two control methods for HVDC frequency support in a test system representing the Nordic Power System (NPS), where this control mode is referred to as Emergency Power Control (EPC). The first method, the current paradigm in the NPS, is based on ramp power injections and frequency triggering activations. The second method, here proposed as the method for future EPC operation in the NPS, is a droop frequency-based EPC. The performance of these two methods is tested for two different disturbances, with the same EPC power capacities. The main objective of the EPC is to meet the frequency requirements and avoid any negative interactions. The results show how the new proposed method outperforms compared to the, The paper is presented in both CIGRE 2020 Symposium and CIGRE 2021 Symposium.QC 20240320

In this paper, strategies for a holistic integration of multiple HVDC links into existing power systems are presented. High Voltage Direct Current (HVDC) links can support the operation of AC grids on different timescales. Contrary to AC transmission lines, the power flow on HVDC links can be freely controlled. Due to their ability of rapidly controlling the power transmitted, they can help to stabilize the dynamic system response of interconnected power systems, e.g. providing fast frequency response. Moreover, they can be an important tool in controlling and in optimizing the operation of interconnected power system. In this paper, different strategies are presented, then their benefits and potential challenges are discussed.

The transmission system operators perform a series of time-domain simulations to assess the stability of the power system towards disturbances. Depending on the results, they can decide to take some preventive actions on the real power system. The dynamic models in use cover beyond the electrical grid they are supervising because of the existing couplings with neighboring grids. On the other hand, the same level of detail cannot be maintained across the entire power system model due to a limit of computing power. The simulation times must namely stay in line with the reaction times necessary to operate an electrical grid. This thesis tackles the problem of computational complexity by proposing a systematic procedure for constructing reduced models that meet the industrial needs. In the first step, the power system model is partitioned into a study area and a multitude of clusters. The study area preserves a full mathematical description as it forms the part of the power system where the stability is examined. The clusters can instead be simplified as long as this does not alter the dynamic behavior of the study area. The decision to modify some specific clusters is taken in the second step by evaluating the nonlinearity level displayed following a disturbance initiated in the study area. If a cluster behaves like a linear system, it has a place inside the reducible external area. Otherwise, it belongs to the buffer area that is left unchanged along with the study area. The last step of the procedure replaces the clusters of the external area with linear equivalent models. For each of them, a simple and effective model of the surrounding network is developed in order to preserve a proper dynamic behavior while limiting the computing load of the reduction process. All the techniques composing the systematic procedure are validated on an academic system and a representation of the power system in Continental Europe. In both cases, the algorithms run in the same way and, Doctorat en Sciences de l'ingénieur et technologie, info:eu-repo/semantics/nonPublished