Hydrogen as an energy carrier holds promising potential for future power systems. An excess of electrical power from renewables can be stored as hydrogen, which can be used at a later moment by industries, households or the transportation system. The stability of the power system could also benefit from electrolysers as these have the potential to participate in frequency and voltage support. Although some electrical models of small electrolysers exist, practical models of large electrolysers have not been described in literature yet. In this publication, a generic electrolyser model is developed in RSCAD, to be used in real-time simulations on the real-time digital simulator. This model has been validated against field measurements of a 1 MW pilot electrolyser installed in the northern part of The Netherlands. To study the impact of electrolysers on power system stability, various simulations have been performed. These simulations show that electrolysers have a positive effect on frequency stability, as electrolysers are able to respond faster to frequency deviations than conventional generators.

The decommissioning of synchronous generators, and their replacement by decoupled renewable power plants, has a significant impact on the transient stability performance of a power system. This paper concerns with an investigation of the degree of transient stability enhancement that can be achieved in power systems with high shares (e.g., around 75%) of wind generation. It is considered that the wind generators can work either under the principle of current control or under the principle of fast local voltage control. In both cases, a power–angle modulation (PAM) controller is superimposed on the current control loops of the grid side converters of the wind generators. The investigation of the degree of enhancement takes into account different approaches of the tuning of PAM. It considers a simple approach in the form of parametric sensitivity, and also a sophisticated approach in the form of a formal optimization problem. Besides, the paper gives insight on what is a suitable objective function of the optimization problem, which entails the best performance of PAM. The whole investigation is conducted based on a synthetic model of the Great Britain (GB) system

This study presents an investigation of the impact of the quasi-stationary voltage support provided by a voltage source converter (VSC) connected to a single point of a power system. Based on the directional derivative concept, an analytical method is developed to quantify the sensitivities of the AC bus voltage with respect to the VSC reactive power control modes. Based on a real case study, it is shown that the method applies to VSC units that are part of VSC-HVDC systems, which can operate in a point-to-point or multi-terminal configuration. Time-domain simulations are performed to verify the findings from the application of the analytical method on a reduced size power system.

During the last few years, electric power systems have undergone a widespread shift from conventional fossil-based generation toward renewable energy-based generation. Variable speed wind generators utilizing full-scale power electronics converters are becoming the preferred technology among other types of renewable-based generation, due to the high flexibility to implement different control functions that can support the stabilization of electrical power systems. This paper presents a fundamental study on the enhancement of transient stability in electrical power systems with increasing high share (i.e., above 50%) of power electronic interfaced generation. The wind generator type IV is taken as a representative form of power electronic interfaced generation, and the goal is to investigate how to mitigate the magnitude of the first swing while enhancing the damping of rotor angle oscillations triggered by major electrical disturbances. To perform such mitigation, this paper proposes a power-angle modulation (PAM) controller to adjust the post-fault active power response of the wind generator type IV, after a large disturbance occurs in the system. Based on a small size system, the PAM concept is introduced. The study is performed upon time-domain simulations and analytical formulations of the power transfer equations. Additionally, the IEEE 9 BUS system and the test model of Great Britain's system are used to further investigate the performance of the PAM controller in a multi-machine context, as well as to perform a comparative assessment of the effect of different fault locations, and the necessary wind generators that should be equipped with PAM controllers.

The active power gradient (APG) control of MMC-HVDC links can contribute to frequency support in AC networks affected by severe active power imbalances. This functionality is particularly convenient if the coupled AC systems (through MMC-HVDC) have similar levels of available inertia. This paper tackles the problem of determining the optimal APG parameters that entail bounding frequency excursions within acceptable limits while helping to quickly damp out electromechanical oscillations. The tuning task is tackled as a single objective computationally expensive optimization problem. Since the optimization search procedure involves repetitive time-domain (RMS) simulations, the major challenge resides in solving the problem within reduced amount of fitness evaluations. In view of this, an emerging metaheuristic algorithm, namely, the mean-variance mapping optimization (MVMO) is selected. Numerical results prove the effectiveness of MVMO in finding the optimal solution within a few fitness evaluations.

This paper examines the prospect of PEM (Proton Exchange Membrane) electrolyzers and fuel cells to partake in European electrical ancillary services markets. First, the current framework of ancillary services is reviewed and discussed, emphasizing the ongoing European harmonization plans for future frequency balancing markets. Next, the technical characteristics of PEM hydrogen technologies and their potential uses within the electrical power system are discussed to evaluate their adequacy to the requirements of ancillary services markets. Last, a case study based on a realistic representation of the transmission grid in the north of the Netherlands for the year 2030 is presented. The main goal of this case study is to ascertain the effectiveness of PEM electrolyzers and fuel cells for the provision of primary frequency reserves. Dynamic generic models suitable for grid simulations are developed for both technologies, including the required controllers to enable participation in ancillary services markets. The obtained results show that PEM hydrogen technologies can improve the frequency response when compared to the procurement with synchronous generators of the same reserve value. Moreover, the fast dynamics of PEM electrolyzers and fuel cells can help mitigate the negative effects attributed to the reduction of inertia in the system.

Due to the power electronic converter based interface and maximum power control strategy, wind generators cannot directly respond to power system transients. This brings new challenges on power system transient stability. Taking wind turbine type 4 (WT4) as one example, this paper analyses its influence on transient stability with respect to locations, low voltage ride through parameters, wind power plant installation capacity and penetration levels. Based on the sensitivity analysis carried out for the influence of WT4, a supplementary transient stability control is proposed. The results on a 3-area system show that this supplementary control can improve transient stability of power systems with high penetration of wind power.

When a PtP link is expanded into a multi-terminal HVDC (MTDC) system by interconnecting an additional offshore wind farm (OWF) converter, the existing operation strategy changes. The OWF power production should be considered as a determining factor to operate the system. In this paper, a new power capability curve for the existing converters is proposed. This new power capability curve is formulated as a function of OWF power production. Furthermore, different converter control strategies are also described and compared. It has been found that a multi-slope droop control strategy is the most suitable strategy for the 3-terminal HVDC system with an OWF converter.

The increase in renewable energy sources in addition to the decrease in conventional synchronous generators is leading to significant challenges for the power system operators to maintain generation load balance and to manage the system's decreasing inertia. Proton Exchange Membrane (PEM) fuel cells are characterised by high current density and fast power injection, which makes them ideal for frequency containment. This paper presents a generic model for PEM fuel cells developed in PowerFactory for frequency stability studies and provides an evaluation of its performance in a reduced-size dynamic model of the North Netherlands high voltage transmission network. The results show that the PEM fuel cell provides improved frequency response within the containment period when compared with synchronous generators for the same amount of support reserve.

The deployment of variable renewable energy based power plants is increasing all over the world, however, unlike conventional power plants these are mostly connected to the grid via power electronic interfaces. High penetration of power electronic interfaced generation (PEIG) has an important impact on the inertia of the system, which is of major concern for frequency and large disturbance rotor angle (transient) stability. Therefore, it is desirable to study the effectiveness of widely used approaches to assess the stability of a system with high penetration of PEIG. This paper concerns with the modelling and control aspects of a power system for the evaluation of the most widely used metrics (indicators) to assess the dynamics of the power system related to frequency and rotor angle stability. The functionalities of Python are used to automate the generation of operational scenarios, the execution of time domain simulations, and the extraction of signal records to compute the aforesaid indicators. The paper also provides a discussion about possible improvements in the application of these indicators in monitoring tasks.

This paper presents a strategy for regulation of power factor in an embedded high-voltage direct current (HVDC) system based on modular multilevel converter (MMC) technology. Field reported in existing literature are taken as a reference for qualitative assessment of the performance of the proposed strategy. The implication of adding such a type of control mode in an MMC-HVDC system is determined through software experiments performed in DIgSILENT PowerFactory. The results reveal that the power factor can be effectively controlled by an MMC-HVDC link within its power rating limits, even in the case of changes of the active power reference.