Search results

This paper aims to establish the wideband model of a sub-module in a modular multilevel converter (MMC) and analyze the switch transients of the sub-module.

The paper builds an MMC sub-module test circuit and conducts dynamic tests both with and without the bypass thyristor. Then, it builds the wideband model of the MMC sub-module and extracts the model parameters. Finally, based on the wideband model, it simulates the switch transients and analyzes the oscillation mechanism.

The dynamic testing shows the bypass thyristor will add oscillations during switch transients, especially during the turn-on process. The thyristor acts like a small capacitor and reduces the total capacitor in the turn-on circuit loop, thus causing under-damped oscillations.

This paper found that the bypass thyristor will influence the MMC sub-module switch transients under certain circumstances. This paper proposes a partial inductance extraction procedure for the MMC sub-module and builds a wideband model of the sub-module. The wideband model is used to analyze and explain the switch transients, and can be further used for insulated gate bipolar transistor switch oscillation inhibition and sub-module design optimization.

The present work aims to explain how the nonlinear average model can be used in power electronic integration design as a behavioral model.

The nonlinear average model is used in power electronic integration design as a behavioral model, where it is applied to a voltage source inverter based on IGBTs. This model was chosen because it takes into account the nonlinearity of the power semiconductor components and the wiring circuit effects, which can be formalized by the virtual delay concept. In addition, the nonlinear average model cannot distinguish between slow and quick variables and this is an important feature of the model convergence.

The paper studies extensively the construction of the nonlinear average model algorithm theoretically. Detailed explanations of the application of this model to voltage source inverter design are provided. The study demonstrates how this model illustrates the effect of the nonlinearity of the power semiconductor components' characteristics on dynamic electrical quantities. It also predicts the effects due to wiring in the inverter circuit.

More simulations and experimental analysis are still necessary to improve the model's accuracy, by using other static characteristic approaches, and to validate the applicability of the model to different converter topologies.

The paper formulates a simple nonlinear average model algorithm, discussing each step. This model was described by VHDL‐AMS. On the one hand, it will assist theoretical and practical research on different topologies of power electronic converters, particularly in power integration systems design such as the integrated power electronics modules (IPEM). On the other hand, it will give designers a more precise behavioral model with a simpler design process.

The nonlinear average model used in power electronic integration design as behavioral model is a novel approach. This model reduces computational costs significantly, takes physical effects into account and is easy to implement.

This study aims to explore capability upgrading of EMNE’s subsidiaries in developed countries and how the parent-subsidiary relationship influences such upgrading.

The study adopts an interdisciplinary approach to capability upgrading of EMNEs subsidiaries in developed countries. It employs a single case study to explore this under-research area.

The analysis challenges the orthodox view and suggests broad-based capability upgrading has taken place in the EMNE-acquired subsidiaries ranging from product, process, functional to intersectoral. In addition, the capability upgrading was contingent on the degree of subsidiary autonomy and subsidiary mandates.

This study represents one of the first to examine capability upgrading and parent-subsidiary relationship in the context of EMNEs’ internationalisation activities.

The paper aims to focus on the semiconductor temperature prediction in the multichip modules by using a simplified 1D model, easy to implement in the electronic simulation tools.

Accurate prediction of temperature variation of power semiconductor devices in power electronic circuits is important for obtaining optimum designs and estimating reliability levels. Temperature estimation of power electronic devices has generally been performed using transient thermal equivalent circuits. This paper has studied the thermal behaviour of the power modules. The study leads to correcting the junction temperature values estimated from the transient thermal impedance of each component operating alone. The corrections depend on multidimensional thermal phenomena in the structure.

The classic analysis of thermal phenomena in the multichip structures, independently of powers’ dissipated magnitude and boundary conditions, is not correct. An advanced 1D thermal model based on the finite element method is proposed. It takes into account the effect of the heat‐spreading angle of the different devices in the module.

The paper focuses on mathematical model of the thermal behaviour in the power module. The study leads to a correction of the junction temperature values estimated from the transient thermal impedance of each component given by manufacturers. The proposed model gives a good trade‐off between accuracy, efficiency and simulation cost.

Power modules including the insulated gate bipolar transistor (IGBT) are widely used in the applications of motor drivers. The thermal behavior of these modules makes it important to choose the optimum design of cooling system. The purpose of this paper is to propose an RC thermal model of the dynamic electro‐thermal behavior of IGBT pulse width modulation inverter modules.

The electrothermal model has been implemented and simulated with a MATLAB simulator and takes into account the thermal influence between the different module chips based on the technique of superposition.

This study has led to a correction of the junction temperature values estimated from the transient thermal impedance of each component operating alone.

In this paper, an experimental technique of a thermal influence evaluation is presented.

The paper presents the findings of an R&D project connected to the development of 50 kW auxiliary power supply for the high‐voltage DC‐fed commuter trains. The aim was to introduce a new generation power converter utilizing high‐voltage insulated gate bibolar transistor (IGBT) modules, which can outpace the predecessors in terms of efficiency and power density, i.e. to provide more power for smaller volumetric space.

For development of the proposed converter, mathematical analysis and computer simulations were used. The software intended for simulations is Ansoft Simplorer, which is a mixed‐technology simulator for electrical, electromechanical, power electronic systems and drive applications. For the verification of theoretical results the full‐scale laboratory prototype of the proposed converter was developed and tested.

Thanks to increased switching frequency and current‐doubler rectifier (CDR) implemented in the proposed converter, the power dissipation of the isolation transformer was reduced by 30 percent as compared to earlier designs. Moreover, the 27 and 24 percent reductions in rectifier and inductor losses, respectively, led to approximately 1 percent efficiency rise of the proposed converter in comparison with its predecessors. Also, the proposed three‐level topology outpaces the two‐level one by more than 20 percent in terms of power density.

The proposed converter topology is aimed for the high‐voltage DC trains. With small modifications it also can be used in trams, trolleybuses as well as in some industrial applications.

The paper presents the novel DC/DC converter topology with 3.3 kV IGBT‐based three‐level neutral point clamped inverter, high‐frequency isolation transformer and the CDR.

In this paper, thermal analysis for a 1,200 A, 3.3 kV insulated gate bipolar transistor (IGBT) module was investigated and analysed using the three‐dimensional transmission line matrix (3D‐TLM) method. This paper also reviews the present status of the use of various thermal heat spreaders such as AlSiC MMC, Cu‐Mo and graphite‐Cu MMC and compares these with copper based heat spreaders and the use of aluminium nitride (AlN), diamond and BeO as substrates and their effect to dissipate the heat flux in heat sources localised in IGBT module design. The TLM method was found to be a versatile tool which is ideally suited to the modelling of many power electronic devices and which proved very useful in the study of transient thermal effects in a variety of device structures.

Multilevel inverter (MLI) is an established design approach for inverter applications in medium-voltage and high-voltage range of applications. An asymmetric design synthesizes multiple DC input voltage sources of unequal magnitudes to generate a high-quality staircase sinewave comprising a large number of steps or levels. However, the implications of using sources of unequal magnitudes results in the requirements of a large variety of inverter switches and higher magnitudes of the total blocking voltage (TBV) rating of the inverter, which increase the cost. The purpose of this study is to present a solution based on algorithms for establishing DC source magnitudes and other design parameters.

The approach used in this study is to develop algorithms that bring an asymmetric cascaded MLI (ACMLI) design close to symmetric design. This approach then reduces the variety of switch ratings and minimizes the TBV of the inverter. Thus, the benefits of both asymmetric design (generation of a large number of voltage levels in the output waveform) and symmetric design (modularity) are achieved. The proposed algorithms can be applied to a number of ACMLI topologies, including classical cascaded H-bridge (CHB). The effectiveness of the proposed algorithms is validated by simulation in Matlab-Simulink and experimental setup.

Two new algorithms are proposed that reduce the number of variety of switches to just three. The variety can further be reduced to two under a specified condition. The algorithms are compared with the existing ones, and the results are promising in minimizing the TBV rating of the inverter, which results in cost reduction as well. For a specific case of four CHBs, the proposed Algorithm-1 produced 27% and Algorithm-2 produced 53% higher levels. Moreover, the presented algorithms produced minimum values of the TBV and resulted in minimum cost of inverter.

The proposed algorithms are novel in structure and have achieved the targeted values of minimized switch variety and reduced TBV ratings. Due to less variety, the inverter achieves a near symmetric design, which enables to attain the added advantages of modularity and reduced difference of power sharing among the DC sources.

The purpose of this paper is to investigate how the dc-link voltage for the converter of a wind generator should be selected, i.e. to determine the losses in the generator and the converter when using various dc-link voltage levels.

To presents the efficiency evaluation of 5 MW wind turbine generating systems, two 5 MW surface mounted permanent magnet synchronous generators (PMSG) with medium and low rated voltage is designed. A two-level transistor converter is considered for ac/dc conversion. Three different dc-link voltage levels are used. By using these voltage levels the PMSG is utilized in slightly different ways.

It is found that the system with the lower voltage machine has slightly higher annual energy efficiency compare to the higher voltage system. Furthermore, it is shown that the best choice for the dc-link voltage level is a voltage between the minimum voltage which gives the desired torque and the voltage which gives Maximum Torque Per Ampere.

A procedure as well as investigations with quantified results on how to find the highest complete drive system efficiency for a wind turbine application. Based on two given PMSG, the most energy-efficient dc-link voltage has been established.

The lightning phenomenon is one of the main threats in photovoltaic (PV) applications. Suitable protection systems avoid major damages from direct strikes but also nearby strikes may induce overvoltage transients in the module itself and in the power conditioning circuitry, which can permanently damage the system. The effects on the PV system sensibly depend on the converter topology and on the adopted power switch. In the present study, a comparative analysis of the transient response due to a nearby lightning strike (LS) is carried out for three PV systems, each equipped with a different converter, namely, boost, buck and buck–boost, based on either silicon carbide metal oxide semiconductor field effect transistors (SiC MOSFET) or insulated gate bipolar transistors controlled power switch devices, allowing in this way an analysis at different switching frequencies. The purpose of this paper is to present the results of the numerical analysis to help the design of suited protection systems.

Using a recently introduced three-dimensional semi-analytical method to simulate the electromagnetic transients caused in PV modules by nearby LSs, we investigate numerically the effect of a LS on the electronic circuits connecting the module to the alternate current (AC) power systems. This study adopts numerical simulations because experimental analyses are not easy to perform and does not grant a sufficient coverage of all statistically relevant aspects. The approach was validated in a previous paper against available experimental data.

It is found that the load voltage is not severely interested by the strike effects, thanks to the low pass filters present at the converter output, whereas a relatively high overvoltage develops between the negative pin of the inner circuitry and the “ground” voltage reference. The overcurrent present in the active switches is hardly comparable because of the different topologies and working frequencies; however, the highest overcurrent is observed in the buck converter topology, with SiC MOSFET technology, although it shows the fastest decay.

This research proposes, to the best of the authors’ knowledge, a comprehensive comparison of the indirect lighting strike effects on the converter connected to PV panels. A proper design of the lightning and surge protection system should take into account such aspects to reduce the risk of induced overvoltage and overcurrent transients.