In this chapter, a generic model of fuel cells and electrolysers suitable for power system stability studies has been developed in PowerFactory. Both theoretical modelling background and software implementation of fuel cells and electrolysers are detailed. Furthermore, a case study based on a three area test system has been performed, which provides valuable insight into the benefits that the synergy between the electricity and hydrogen sectors can bring to power system stability.

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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.@en

In this chapter, a grid forming control approach called direct voltage control (DVC) for wind turbine control with restoration capability of power system with a high share of power electronic-based generation units is presented and discussed. All the detailed explanation, DSL-based control is presented for dynamic simulations in DIgSILENT software.

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In this book chapter, innovative protection schemes have been suggested to prevent bottlenecks of the power system considering the integration of offshore and onshore wind turbines and HVDC link. Four different countermeasures are proposed and investigated. Their effect on the system overloading and stability is also taken into account. The models for the simulation have been implemented in PowerFactory.

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In this book chapter, a benchmark test system has been studied for power system stability considering the high share of power electronic converter-based generation. Furthermore, both conventional PI controllers and grid forming control have been taken in to account in order to study the impact of the high penetration of power electronic converter on the dynamic response of the power system.

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This paper presents a coordinated control strategy based on direct Lyapunov theory to handle the consistency of AC grids in a multi-terminal (MT) modular multilevel converter (MMC)-HVDC systems during varying both loads and DC link voltage. As the first contribution, a set of dynamic equations is proposed based on separating the dynamics of MMCs upper and lower arms state variables. The dynamics consists of only their related upper/lower arms state variables leading to more effective components for the steady state terms of proposed control technique. To develop the dynamic parts of the controller, the global asymptotical stability of MT MMC-HVDC system is assessed by direct Lyapunov method. As another advantage of the separated dynamic equations, the Lyapunov theory is able to exploit very simple decoupled components for the dynamic parts of proposed control functions. Moreover, in order to specify the variation trend of Lyapunov coefficients, further stability analysis contributes to demonstrating the effects of Lyapunov coefficients on the MMCs state variable errors and its dynamic. As another main contribution of this paper, two independent capability curves based on the power injection capability of the MMCs upper and lower arms, are obtained which will be assessed through changing the input and output voltages as well as MMC parameters. Finally, simulation results in MATLAB software are utilized to verify the validity of proposed control strategy.

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This article presented a new structure for the grid-connected multilevel inverters (MLIs) circuit with the ability of the cascaded connection. The proposed inverter is capable of transformerless connection of distributed generation resources to the network. The control system manages the power injection to the grid by minimizing the output current harmonics as well as exchanging reactive power with the grid. The self-balancing state of the capacitors' voltage is occurred only with the switching technique without any measurement sensors. An enhanced phase-locked loop (EPLL) and a proportional resonant (PR) controller are employed for the proposed asymmetric MLI. An important feature of the proposed inverter is the ability of stable performance and fast dynamics of the control system to the changes of the reference values. Simulation and experimental results are presented in order to validate the performance accuracy of the proposed MLI.

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This chapter is dedicated to present some control mechanism to cope with the challenges due to the growth of the penetration level of the power electronic interfaced generation (PEIG) in sustainable interconnected energy systems. Specifically, this chapter presents different forms of fast active power injection (FAPI) control schemes for the analysis and development of different mitigation measures to address the frequency stability problem. Among the considered FAPI control schemes are the traditional droop-based scheme, and two propositions implemented in the form of a derivative-based control and a second-order virtual synchronous power (VSP)-based control. All the detailed explanation, DSL-based control is presented for the simulations in DIgSILENT software. Simulation results show that thanks to proposed FAPI controllers, it is possible to increase the maximum share of wind power generation without violating the threshold limits for frequency stability problem in low-inertia systems.

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The main objective in this chapter is to develop and present a generic model for wind turbine (WT) which can be used for both DFIG- and FSCG-based WT for large-scale multi-machine power system dynamic studies. The presented model is developed for RMS simulation on PowerFactory, and it can be used as a replacement for both DFIG- and FSCG-based WTs without making any changes in the generic model itself. The generic RMS model is appropriate for the stability studies of large grids where the detailed dynamics, i.e., control action in the range of milliseconds, of the power electronic converter-based controllers do not play an important role.

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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).@en

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.

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This paper aims to present a new structure of the parallel Z-source inverters (ZSIs) for dual-input single-phase grid-connected photovoltaic (PV) systems. The ZSI is a single-stage buck-boost converter that uses an inductor-capacitor network between the inverter bridge and the PV string and follows the maximum power point by applying the shoot-through vector. Therefore, a DC/DC converter is no longer needed to track the maximum power point, and the cost and complexity of the power conditioning system (PCS) are reduced. For controlling the proposed PCS, a cascade control structure is employed in this paper. The inner current loop injects the maximum active power with unity power factor sinusoidal current to the grid. The outer capacitor voltage loop is applied to control capacitors voltages in the Z-source networks. Additionally, an enhanced dual-string maximum power point tracking (eDS-MPPT) method is proposed to find MPPs with minimum burden competitional. The eDS-MPPT does not need the PVs voltages measurements compared to other MPPT methods. The simulation results confirm the accuracy of the performance of the system.

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This paper aims to present a novel switched-capacitor multi-level inverter. The presented structure generates a staircase near sinusoidal AC voltage by using a single DC source and a few capacitors to step-up the input voltage. The nearest level control (NLC) strategy is used to control the operation of the converter. These switching states are designed in a way that they always ensure the self-voltage balancing of the capacitors. Low switching frequency, simple control, and inherent bipolar output are some of the advantages of the presented inverter. Compared to other existing topologies, the structure requires fewer circuit elements. Bi-directional power flow ability of the proposed topology, facilitates the operation of the circuit under wide range of load behaviors which makes it applicable in most industries. Besides, a 13-level laboratory prototype is implemented to realize and affirm the efficacy of the MATLAB Simulink model under different load conditions. The simulation and experimental results accredit the appropriate performance of the converter. Finally, a theoretical efficiency of 92.73% is reached.

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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.@en

This paper presents a dynamic model of modular multilevel converters (MMCs), which are considered as an effective interface between energy sources and the power grid. By improving the converter performance, appropriate reactive power compensation is guaranteed. Modulation indices are calculated based on detailed harmonic evaluations of both dynamic and steady-state operation modes, which is considered as the main contribution of this paper in comparison with other methods. As another novelty of this paper, circulating current control is accomplished by embedding an additional second harmonic component in the modulation process. The proposed control method leads to an effective reduction in capacitor voltage fluctuation and losses. Finally, converter’s maximum stable operation range is modified, which provides efficiency enhancements and also stability assurance. The proficiency and functionality of the proposed controller are demonstrated through detailed theoretical analysis and simulations with MATLAB/Simulink.

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A new structure of switched capacitor multilevel inverter (SCMLI) capable of voltage boosting and with self-balancing ability is introduced in this article. This advantage is the result of a step by step rise of capacitor voltages in each module, supplied by just one DC voltage source. The proposed topology generates a sinusoidal output waveform with a magnitude several times greater than the input one. Higher output staircase AC voltage is obtained by applying a nearest level control (NLC) modulation technique. The most significant features of this configuration can be mentioned as: fewer semiconductor devices, remarkably low total harmonic distortion (THD), desirable operating under high/low frequency, high efficiency, inherent bipolar voltage production, easy circuit expansion, ease of control and size reduction of the circuit thanks to utilizing neither bulky transformer nor inductor. Moreover, the proposed SCMLI is comprehensively surveyed through theoretical investigation and a comparison of its effectiveness to recent topologies. Eventually, the operating principle of a 25-level prototype of the suggested SCMLI is validated by simulation in the MATLAB SIMULINK environment and experimental results.@en

In the future energy system, hydrogen as an energy carrier will play a role of increasing importance. Electrical energy can be converted into hydrogen locally by electrolysers and stored for a relatively long period. Then, the hydrogen can be used by final consumers like the transportation system or industries, as conceptually illustrated in Fig. 1. The flexibility of electrolysers offers promising possibilities for electrical grid support by the provision of ancillary services. Currently, a pilot power-to-gas facility with a 1-MW electrolyser is installed in the northern part of the Netherlands. A larger electrolysis plant of 300 MW may be installed in this area later. The feasibility of this large-scale plant, its impact on the stability of the electrical transmission network and the possibilities for ancillary services provision are currently being investigated in the project TSO2020 [1].@en

This paper presents a transformerless step-upmultilevel inverter based on a switched-capacitor structure. One of the main contributions of the proposed topology is replacing the separated DC voltage sourcewith capacitorswhich are charged at predetermined time intervals. Therefore, a high-level staircase voltage waveform can be achieved by discharging some of these capacitors on the load. The other contribution of the proposed structure is to eliminate themagnetic elements which traditionally boost the input DC voltage. In addition, asymmetrical or unequal amounts of capacitor voltages create more voltage levels, which enable voltage level increments without increasing the number of semiconductor devices. This paper introduces a self-balanced boost Switched-CapacitorsMultilevel Inverter (SCMLI) which is able to create a nearly sinusoidal voltage waveform with a maximum voltage of up to 45 times that of the input voltage DC source. Higher level output voltage levels are also achievable by extending the circuit topology. After determination of the switching angles and selecting the proper switching states for each level, an offline NLC method is used for modulation, which eases the control implementation. Analysis, simulation and experiments are carried out for a 91-level inverter (45 levels for positive and negative voltages and one for zero voltage) are presented.

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