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• Efficient dynamic modelling framework for the analysis of fair-sized DC microgrids. • Nodal formulation combined with Newton–Raphson and implicit trapezoidal methods. • BESS, CHP units, PV plants and series connected DC/DC converters can be studied. • Results are validated versus EMT simulation conducted in Simscape Electrical. • Small errors are obtained with a small fraction of time taken by the EMT simulation. This paper introduces a novel modelling framework for conducting dynamic analysis of DC microgrids (MG), considering components such as battery energy storage systems (BESS), combined heat and power (CHP) cogeneration, photovoltaic (PV) plants and DC/DC converters. The MG dynamics are accurately captured using well-founded modelling practices of the power system transient analysis field. Firstly, the power device models are derived based on fundamental operating principles using a lumped-type parameter modelling approach. Secondly, the DC microgrid is formulated using nodal power injections, which is combined with Newton–Raphson and implicit trapezoidal methods to efficiently solve fair-sized networks of arbitrary topology. The dynamic outcomes of a 13-bus MG were compared with those of an electromagnetic transient (EMT) simulation conducted in Simscape Electrical for load and solar irradiance changes and for a DC/DC converter outage. For these events, errors smaller than 2.5% were yielded by the new approach, only requiring 3.1% of the computing time employed by the EMT simulation. The method's applicability was also showcased by assessing the dynamic performance of a larger DC microgrid containing 118 buses, twelve distributed generators and five BESS, which was subjected to typical contingencies such as load increases and distribution line disconnections. [ABSTRACT FROM AUTHOR]

• Solar photovoltaics use inverters to interface with the AC power system. • Inverters do not possess the rotational characteristics of synchronous generators. • High instantaneous inverter penetrations complicate traditional stability approaches. • Control techniques seen as the primary barrier to high inverter penetrations. • Research indicates no fundamental challenges to high inverter penetrations. As power system renewable energy penetrations increase, the ways in which key renewable technologies such as wind and solar photovoltaics (PV) differ from thermal generators become more apparent. Many studies have examined the variability and uncertainty of such generators and described how generation and load can be balanced for a wide variety of annual energy penetrations, at timescales from seconds to years. Another important characteristic of these resources is asynchronicity, the result of using inverters to interface the prime energy source with the power system as opposed to synchronous generators. Unlike synchronous generators, whose frequency of alternating current (AC) injection is physically coupled to the rotation of the machine itself, inverter based asynchronous generators do not share the same physical coupling with the generated frequency. These subtle differences impact the operations of power systems developed around the characteristics of synchronous generators. In this paper we review current knowledge and open research questions concerning the interplay between asynchronous inverter-based resources (IBRs) and cycle- to second-scale power system dynamics, with a focus on how stability and control may be impacted or need to be achieved differently when there are high instantaneous penetrations of IBRs across an interconnection. This work does not seek to provide a comprehensive review of the latest developments, but is instead intended to be accessible to any reader with an engineering background and an interest in power systems and renewable energy. As such, the paper includes basic material on power electronics, control schemes for IBRs, and power system stability; and uses this background material to describe potential impacts of IBRs on power system stability, operational challenges associated with large amounts of distributed IBR generation, and modern power system simulation trends driven by IBR characteristics. [ABSTRACT FROM AUTHOR]

With increased penetration of the converter dominated renewables, the overall inertial response and frequency stability of the power grid has been reduced. Low inertia contributes to maximum frequency deviations with higher rate of change of frequency that undermines the reliability of the power system. In the case of type-4 grid connected wind turbines, the kinetic energy of the rotor cannot be directly used to mitigate frequency excursions in the AC grid since fully-rated converters decouple the grid from the turbine rotor. Nonetheless, by designing an adequate control system for full converters, emulated inertia of the rotor can be propagated to the grid. In this paper, we present inertia emulation control strategy based on second order differential equation analogous to the swing equation of classical synchronous machines employed in machine side converter of the permanent magnet synchronous generator wind turbines. The proposed control allows the management of virtual inertia, damping and reactance. The performance of the proposed controller is verified through time-domain simulations and eigenvalue analysis performed in MATLAB Simulink. • The proposed control emulates SMs' behaviour and renders inertia support to the grid. • Unlike typical inertia controllers, proposed scheme does not rely on derivative term. • Enables power oscillation damping without affecting the steady state of the frequency. • Offers better RoCoF mitigation, and nadir improvement over PD-based controllers. • Its features include simple control design, easily scalable, efficient, and reliable. [ABSTRACT FROM AUTHOR]

• Extensive review of the tools and techniques used in DC microgrid protection. • Critical overview of fault current limiting and interrupting devices. • Standards in DC microgrid systems. • Faults and power electronic converters. • Future research opportunities in DC microgrid. The technological escalation in DC power generation from renewable energy sources has attracted the attention of researchers to the concept of DC microgrids (DCMGs). However, the design and development of tailor-made schemes to fulfil the complete protection requirements in a DCMG remain a challenge. Practical inexperience, lack of standards, and differences in the behaviour of the DC system compared to AC aggravate the issue. This paper throws light on the latest advancements and research prospects in DCMG protection by traversing through the developments in DC protection standards, fault detecting and locating techniques, the impact of faults on the power electronic converters, the role of converters in fault handling, and DC circuit breaking. [ABSTRACT FROM AUTHOR]

Capacitors are an important component of power conversion systems because they affect the cost, size, performance, and range of such systems. However, capacitors have the highest degradation and failure rates of any power converter component. Therefore, condition monitoring is an important process for assessing the condition of capacitors and providing predictive maintenance to ensure the operational stability of power conversion systems. When using Equivalent Series Resistance (ESR) as a primary indicator for condition monitoring the error varies with a minimum error of 1.2 % and a maximum error of 10 % in literature. On the other hand, the error range for determining the capacitance of a capacitor is between 0.18 % and 7.2 %. Capacitor Equivalent Series Resistance (ESR) and Capacitance are two widely-used parameters for assessing the condition of a capacitor. This paper reviews critically previous research on the condition monitoring techniques of capacitors with the said parameters and gives a better understanding of condition monitoring of capacitors used in the power electronic system. • Reviews of studies relating to the operational stability monitoring of capacitors • Identified the two most commonly used parameters for capacitor failure prediction • Estimation of capacitance and series resistance indicates accurate results. • Percentage of errors of various existing methods have been compared. • Data Driven Methods gives promising results in condition monitoring of capacitors. [ABSTRACT FROM AUTHOR]

Several factors can affect performance of an ultrasound system such as quality of excitation signal and ultrasound transducer behaviour. Nonlinearity of piezoelectric ultrasound transducers is a key determinant in designing a proper driving power supply. Although, the nonlinearity of piezoelectric transducer impedance has been discussed in different literatures, the trend of the nonlinearity at different frequencies with respect to excitation voltage variations has not been clearly investigated in practice. In this paper, to demonstrate how the nonlinearity behaves, a sandwich piezoceramic transducer was excited at different frequencies. Different excitation signals were generated using a linear power amplifier and a multilevel converter within a range of 30–200 V. Empirical relation was developed to express the resistance of the piezoelectric transducer as a nonlinear function of both excitation voltage and resonance frequency. The impedance measurements revealed that at higher voltage ranges, the piezoelectric transducer can be easily saturated. Also, it was shown that for the developed ultrasound system composed of two transducers (one transmitter and one receiver), the output voltage measured across receiver is a function of a voltage across the resistor in the RLC branches and is related to the resonance frequencies of the ultrasound transducer. [ABSTRACT FROM AUTHOR]

Switched power electronic converters involve different control actions for different system events. A local control strategy may be developed which reacts only to some local information available to each component without any communication between the different system components located far away in real time. The purpose of this paper is to present a low cost memory based control strategy in a dc–dc boost converter. The control employed in this work is based on a sliding-mode hysteretic control strategy where the sliding manifold is derived a priori and stored as a look-up table in digital memory hardware. The proposed control implementation strategy is low cost and offers a robust dynamic response that is used to mitigate many disturbances in the system. [ABSTRACT FROM AUTHOR]

This paper provides a comprehensive and systematic review of robust control strategies in DC microgrids. Microgrids gain worldwide attention in decades regarding its effective and feasible integration of distributed generations (DGs). Getting rid of frequency synchronization and reactive power problem, the DC microgrid is superior to its ac counterparts in stability, flexibility and complexity. The recent efforts were mainly directed toward developing the feasibility of implementing DC microgrids on kinds of specific application scenarios. DC microgrids design-related aspects such as the system architecture and topology, voltage levels, operation and control framework, stability analysis method, and protection challenge have been studied in a deep degree. In this paper, operation and control framework in both grid-connected (grid-forming) mode and islanding (grid-following) mode will be focused, to provide the guideline where we currently stand on the migration path from the overwhelming fully AC microgrids to a more flexible DC microgrids. Besides, the impediments against stability and effectiveness of DC microgrids and representatively proposed solutions will be discussed. [ABSTRACT FROM AUTHOR]

This paper proposes a new short-circuit protection method for an IGBT. The proposed method is characterized by detecting not only gate charge but also gate voltage of the IGBT. This results in a shorter protection time, compared to the previous method that detects only the gate charge. A real-time monitoring system using an FPGA, A/D converters, and a D/A converter is used for the proposed protection method. Experimental results verify that the proposed method achieves a protection time of 390 ns, which is reduced by 68% compared to the previous method. [ABSTRACT FROM AUTHOR]

• The innovative technology for the production of amorphous 27-multi-gap cores. • The innovative three-phase amorphous harmonic filters 7,5kW/400 V/50 Hz. • Power losses in the amorphous filter are about 20% lower than those in Fe-Si filter. • For amorphous core the temperature rise after 1 h is lower about 13 °C. There is a permanent demand worldwide for the advanced low-losses soft magnetic materials intended for application in power electronics, including power electronic converters used to process various forms of the electrical energy into such that is best suited for the specific user loads or applications. This paper shows result of investigation of magnetic properties of amorphous multi-gap cores which were used to manufacture a prototype 27-multi-gaps core for the three-phase harmonic filter with a common yoke, with a rated power of 7.5 kW, operating voltage of 400 V and electric power frequency of 50 Hz. The main attention was focused on studying the effect of the chemical composition and core structure on the level of power losses in the core and temperature increase during operation for amorphous material in relation to the polycrystalline Fe-Si steel with 3 wt% Si core despite the low operating frequency of 50 Hz. [ABSTRACT FROM AUTHOR]

• Transient and steady state power electronic converter models are proposed. • Fault current contribution of converters is analysed with the proposed models. • Influence of grid code requirements on the converter's fault behaviour is assessed. • Negative sequence requirements have a major influence on the fault behaviour. Renewable energy sources primarily employ power electronic converters to deliver their energy to the grid. These converter-based distributed generators (CBDGs) have a fault behaviour different from conventional generators, capable of compromising the reliability of traditional protection schemes. This paper investigates the fault behaviour of CBDGs by presenting both an analytical steady state model and a numerical transient simulation model developed in MATLAB/Simulink. Using these models, the impact of grid code requirements regarding reactive current injection during faults is analyzed. The results underline that different modelling techniques can support the design of grid codes. [ABSTRACT FROM AUTHOR]

• The EMC assessment in multiconverter systems might be difficult. • Measuring difficulties result from low frequency envelopes of interference signals. • Theoretical considerations have been confirmed by measurements. • Measurements were made in a laboratory and at a 1 MW photovoltaic power plant. An assessment of electromagnetic compatibility is important from a technical as well as legal point of view. The harmonized standards should provide detailed guidelines enabling assessment of electromagnetic compatibility for the typical application of devices in systems. This paper presents the specific issues accompanying measurements of conducted electromagnetic interference in multiconverter systems. The theoretical considerations have been confirmed by experimental results obtained in a laboratory and in a real 1 MW photovoltaic power plant. The presented theoretical and experimental results might constitute the recommendations for practitioners dealing with conducted interference measurements, while the proposed approach can be used as a basis for the elaboration of reliable standards for electromagnetic compatibility assessment in multiconverter systems within the scope of the studied interference frequency range. [ABSTRACT FROM AUTHOR]

• Commonly used EMI measuring methods may lead to a wrong assessment of EMI • The paper shows the efficient spectrum aggregation method for proper EMI evaluation • The method enables selection of resolution and comparison of results • Spectrum harmonics are mapped linearly, and the spectrum RMS value does not change. However, the theoretical analyses as well as experimental results have indicated that ostensible reduction of the EMI level generated by random modulated converters results from the methodology of the EMI spectrum measurement, adopted in currently binding standards, rather than physical nature of interference generation phenomenon. The experimental investigations, presented in the paper, have shown that utilization of commonly used EMI measuring standards might lead to wrong conclusions in a case of assessment of electromagnetic compatibility of random modulated converters. The aim of this paper is to propose the novel, efficient method enabling objective evaluation of the EMI generated by random modulated converters. [ABSTRACT FROM AUTHOR]