Future electrical power systems will be dominated by power electronic converters, which are deployed for the integration of renewable power plants, responsive demand, and different types of storage systems. The stability of such systems will strongly depend on the control strategies attached to the converters. In this context, laboratory-scale setups are becoming the key tools for prototyping and evaluating the performance and robustness of different converter technologies and control strategies. The performance evaluation of control strategies for dynamic frequency support using fast active power regulation (FAPR) requires the urgent development of a suitable power hardware-in-the-loop (PHIL) setup. In this paper, the most prominent emerging types of FAPR are selected and studied: droop-based FAPR, droop derivative-based FAPR, and virtual synchronous power (VSP)-based FAPR. A novel setup for PHIL-based performance evaluation of these strategies is proposed. The setup combines the advanced modeling and simulation functions of a real-time digital simulation platform (RTDS), an external programmable unit to implement the studied FAPR control strategies as digital controllers, and actual hardware. The hardware setup consists of a grid emulator to recreate the dynamic response as seen from the interface bus of the grid side converter of a power electronic-interfaced device (e.g., type-IV wind turbines), and a mockup voltage source converter (VSC, i.e., a device under test (DUT)). The DUT is virtually interfaced to one high-voltage bus of the electromagnetic transient (EMT) representation of a variant of the IEEE 9 bus test system, which has been modified to consider an operating condition with 52% of the total supply provided by wind power generation. The selected and programmed FAPR strategies are applied to the DUT, with the ultimate goal of ascertaining its feasibility and effectiveness with respect to the pure software-based EMT representation performed in real time. Particularly, the time-varying response of the active power injection by each FAPR control strategy and the impact on the instantaneous frequency excursions occurring in the frequency containment periods are analyzed. The performed tests show the degree of improvements on both the rate-of-change-of-frequency (RoCoF) and the maximum frequency excursion (e.g., nadir). ... Read more

Urban areas rely on the wide implementation of X-Integrated Photovoltaic (X-IPV) systems to provide green electricity for the sustainable electrification. In this research, a modelling framework to accurately predicting their output energy yield and asses their impact on the low voltage distribution grid has been developed. This tool can compute a densely populated urban area at a pace of 2.5 seconds per building. In this contribution, we present the results of a pilot project executed in a Dutch neighborhood of 4873 separate roof owners located in the city of Amsterdam, the Netherlands. ... Read more

This paper concerns the feasibility of Fast Active Power Regulation (FAPR) in renewable energy hubs. Selected state-of-the-art FAPR strategies are applied to various controllable devices within a hub, such as a solar photovoltaic (PV) farm and an electrolyzer acting as a responsive load. Among the selected strategies are droop-based FAPR, droop derivative-based FAPR, and virtual synchronous power (VSP)-based FAPR. The FAPR-supported hub is interconnected with a test transmission network, modeled and simulated in a real-time simulation electromagnetic transient (EMT) environment to study a futuristic operating condition of the high-voltage infrastructure covering the north of the Netherlands. The real-time EMT simulations show that the FAPR strategies (especially the VSP-based FAPR) can successfully help to significantly and promptly limit undesirable large instantaneous frequency deviations. ... Read more

This study investigates the reactive power generation capability of the existing transformerless Photovoltaic Inverter Topologies (PVIT) with their conventional switching strategies. The topologies such as H5, families of H6 (H6, H6-I, H6-II, H6-III and H6-IV), HERIC, and clamped topologies (optimized H5, passive clamped H6 and HBZVR) have been selected for analysis. Matlab/Simulink simulation platform is employed for the analysis of PVIT. It has been observed that transformer-less PVIT with their conventional switching strategies are not suitable for reactive power injection. These topologies are generating highly distorted current at zero crossings during the reactive power flow. The improved switching strategies are needed to make these topologies suitable for the reactive power applications without any modification in the structure of the inverter. ... Read more

Traditionally, electrical power systems have been based on fossil-fuel fired generation plants to satisfy the load demand. However, due to environmental targets for significant CO2 reduction, a gradual decommission of the aforementioned plants is observed whereas renewable energy sources are gaining gradually increasing momentum, which entails radical changes in the dynamic behavior of electrical power systems. Among the existing renewable energy technologies, variable speed wind generators which utilize full–scale power electronics units, are a preferred technological solution to tackle the variability of renewable energy. Increasing renewable power generation caused a reduction of system inertia and short circuit capacity. This reduction challenges the rotor angle stability of remaining synchronous generators when large disturbance occur. This paper presents a study on modifications of the outer control loops of the grid side converter of wind generators type IV to limit the magnitude of the first rotor angle swing while increasing the overall damping performance of a power system. The study includes a comparison between three different wind generation controllers. Namely, a basic Low Voltage Right Through (LVRT) with a post-fault ramp in the active power injection strategy, a voltage dependent active power injection scheme and a Supplementary Damping control (SDC) method are examined and tested through a power hardware-in-the-loop (PHIL) based test bench. It has been found that SDC supports quick damping of oscillations and high reduction of magnitude of the first swing with respect to the other two control schemes. ... Read more

A task for new power generation technologies, interfaced to the electrical grid by power electronic converters, is to stiffen the rate of change of frequency (RoCoF) at the initial few milliseconds (ms) after any variation of active power balance. This task is defined in this article as fast active power regulation (FAPR), a generic definition of the FAPR is also proposed in this study. Converters equipped with FAPR controls should be tested in laboratory conditions before employment in the actual power system. This paper presents a power hardware-in-the-loop (PHIL) based method for FAPR compliance testing of the wind turbine converter controls. The presented PHIL setup is a generic test setup for the testing of all kinds of control strategies of the grid-connected power electronic converters. Firstly, a generic PHIL testing methodology is presented. Later on, a combined droop- anFd derivative-based FAPR control has been implemented and tested on the proposed PHIL setup for FAPR compliance criteria of the wind turbine converters. The compliance criteria for the FAPR of the wind turbine converter controls have been framed based on the literature survey. Improvement in the RoCoF and and maximum underfrequency deviation (NADIR) has been observed if the wind turbine converter controls abide by the FAPR compliance criteria. ... Read more

In this study, a novel methodology is proposed for sensitivity-based tuning and analysis of derivative-based fast active power injection (FAPI) controllers in type-4 wind turbine units integrated into a low-inertia power system. The FAPI controller is attached to a power electronic interfaced generation (PEIG) represented by a generic model of wind turbines type 4. It consists of a combination of droop and derivative controllers, which is dependent on the measurement of the frequency. The tuning methodology performs parametric sensitivity to search for the most suitable set of parameters of the attached FAPI that minimises the maximum frequency deviation in the containment period. The FAPI is adjusted to safeguard system stability when increasing the share of PEIG. Since the input signal of the FAPI is the measured frequency, the impact of different values and parameter settings of the phase-locked loop used for the FAPI controller is also investigated. Detailed validation with a full-scaled wind power converter is also provided with a real-time digital simulator testbed. Obtained simulation results using a three-area test system, identify the maximum achievable degree of increase in the share of wind power when a proper combination of wind park locations considering their suggested settings for inertia emulation. ... Read more

Power System Stability is a major domain of renewed interest for electrical power system researchers worldwide. Among the different stability classification domains, large disturbance rotor angle (transient) stability studies are of high concern due to the decommissioning of conventional power plants which leads to a dramatic decrease of inertia and shortcircuit capacity. In this paper, the superiority of a proposed Supplementary Damping Control (SDC) scheme, concerning with transient stability enhancement, is demonstrated against other existing controls, namely, a common form of low-voltage ride through (LVRT) controller with a post-fault ramp, and Voltage Dependent Active Power Injection (VDAPI) control strategy. Based on the analysis done with the modified IEEE 9 bus system with 52% and 75 % share of wind generation, it has been found that proposed SDC has quick damping of oscillations, and also causes a higher reduction of the magnitude of the first rotor angle swing, and has lesser impact on the overall system frequency performance. The controllers’ performance against rotor angle stability threats is tested via EMT modelling and simulation with RSCAD software, which is a real-time digital simulation (RTDS) platform. ... Read more

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. ... Read more

This paper presents a comparative assessment of fast active power regulation (FAPR) control strategies implemented on megawatt-scale controllable electrolysers, with the goal of achieving enhanced frequency support during large active power imbalances that lead to major under-frequency deviations. The FAPR control strategies consist of three different types of controllers, namely, droop, derivative and Virtual Synchronous Power (VSP). Each of these controllers has been implemented on a 300 MW electrolyser plant with proton exchange membrane (PEM) electrolysers. The compared FAPR controllers are individually set to perform a fast adjustment of the active power consumption of the plant-based on the dynamic grid conditions. The modelling and comparative assessment is done in a platform for computationally efficient simulations of Electromagnetic Transients (EMT) in real-time. A synthetic model of the Northern Netherlands Network (N3 Network) is prototyped as a test bench to simulate and evaluate the performance of the implemented FAPR controllers. The EMT simulations show the superiority of the VSP based FAPR developed for controlling and exploiting the boundaries for active power adjustment of the Voltage Source Converter (VSC) that interfaces the PEM electrolyser plant with the N3 Network. ... Read more

This paper deals with the implementation of a Fast Active Power Injection (FAPI) controller in a Type-4 Wind Turbine. Two different FAPI controllers, droop-based and a modified derivative-based controller are proposed and investigated under real-time simulation platform. The implementation is done in a Real-Time Digital Simulator (RTDS) by using the functionalities of RSCAD software. The IEEE 9 bus system is taken as a case study to quantitatively check the suitability of the implemented controller. The response of the wind turbine observed in EMT simulations is compared against the response obtained via numerical simulations with a generic wind turbine model built-in DIg SILENT PowerFactory software. The details of the model implemented in RSCAD provides better insight on capturing the impacts of controller parameters. Obtained results clearly demonstrate how the proposed controller can effectively improve the dynamic frequency performance of the power system. ... Read more