STATIC MAGNETIC FIELD IMPACT ON SEMICONDUCTOR DEVICES AND CENTRIFUGAL PUMPS AT ITER

An astounding number of components belonging to subsystems of different nature are installed in the ITER Tokamak building and all of those subjected to a constant or slowly variable magnetic field, an environmental condition unusual for other standard applications. Indeed, the magnetic field generated by ITER magnets can reach 70 mT in the crane hall of the Tokamak building, with a maximum derivative of 10 mT/s. Among these components, there are a few which are critical in the correct operation of the overall system and on which extremely few data are available regarding their interaction with a strong External Static Magnetic Field (ESMF). In particular, power semiconductor devices and pumps stand out as key elements in the electrical distribution network supplying the magnets and in all cooling applications respectively. Naturally, these two groups of components are not the only one potentially greatly affected by the ESMF, but the current phase of the plant design and construction requires an immediate action in gathering information on how the operation of these two very different devices is affected by the magnetic field. Unfortunately, a very limited number of work is available both regarding the countermeasures that must be taken in designing power electronic systems and cooling pumps operating in the environment described above. Besides, no information is available concerning the magnetic compatibility of standard components normally installed nowadays in industrial applications. In order to identify the operational limits of many other components such as low power electronic, low voltage circuit breakers, sensors, contactors logical controllers and other control electronic devices, ITER in collaboration with external contractors put in place a set of experimental test in the last two decades, the main results were described in some papers and internal reports. In particular, a large amount of operational malfunctioning and failure were observed, for instance; electromechanical relays would open or close with a certain delay, or they even would not close or open at all, depending on many factors such as their orientation with respect to the magnetic field direction. Usual active current transducers (LEM) might experience a 0.5% zero offset drift at 10 mT, typical pulse transformers work properly only up to 50 mT, switch mode power supply might generate some acoustic noise, increase the peak current in switching transistors and may even be destroyed in a DC induction higher than 30 mT, etc. All the components which underwent the DC magnetic field immunity tests could be grouped into 3 main categories: \u2022 Components whose operation relies on some ferro-magnetic nucleum (i.e. transformers, inductors, mechanical relays etc.). \u2022 Sensors whose physical principle which they are based on relies on magnetic field measurements (Hall effect sensors). \u2022 Semiconductor devices, specifically the power semiconductor devices. Although the physical mechanisms and interactions between a static magnetic field and the first two categories of components are clear and commonly known (they basically come down to iron saturation and the distortion of the hall voltage), it is still unclear how a DC magnetic fields interacts with solid state device. Therefore, thrusted by the results (sometimes worrying) of previous test campaigns, ITER is currently moving towards the preparation of further experimental analysis, with a particular focus on power semiconductor devices (IGBTs, Thyristors, IGCTs etc.), pumps and electric motors. While some internal studies have already been made on the latter subject, no analysis has been carried out yet on pumps and power semiconductor devices. Thus, it is exactly in this framework that this study places itself into, particularly persuing two main goals of this study can be considered to be dual: 1. Provide a theoretical/simulation analysis useful for the interpretation of the results of future tests. 2. Provide fundamental insights and criteria to design devices specifically immunes to the presence of an ESMF (information which can difficultly be drawn from experimental tests), especially needed when no shielding is feasible. As regards the analysis of the semiconductor devices, the aims are first to analyze the documents available in the scientific literature concerning the interaction between an ESMF and solid state devices. Secondly, due to the current lack at ITER of dedicated software licenses able to conduct this sort of compatibility analysis, to develop a simulation tool in MATLAB able to quantify, after some approximation and simplifications, the impact of a static magnetic field on solid state technology. Given the degree of approximation in this case, the results are only to be interpreted as an indication of the order of magnitude of the considered phenomenon and as an indication of the potentially critical operating conditions to target for monitoring during the experimental tests. On the other hand, as regards the analysis of centrifugal pumps, the magnetic analysis is carried out through the ANSYS/Maxwell software, allowing to obtain significantly more accurate results predictions

Electrical-Loss Analysis of Power-Split Hybrid Electric Vehicles

The growing development of hybrid electric vehicles (HEVs) has seen the spread of architectures with transmission based on planetary gear train, realized thanks to two electric machines. This architecture, by continuously regulating the transmission ratio, allows the internal combustion engine (ICE) to work in optimal conditions. On the one hand, the average ICE efficiency is increased thanks to better loading situations, while, on the other hand, electrical losses are introduced due to the power circulation between the two electrical machines mentioned above. The aim of this study is then to accurately evaluate electrical losses and the average ICE efficiency in various operating conditions and over different road missions. The models used in this study are presented for both the Continuously Variable Transmission (CVT) architecture and the Discontinuously Variable Transmission (DVT) architecture. In addition, efficiency maps of the main components are shown. Finally, the simulation results are presented to point out strengths and weaknesses of the CVT architecture

Rapid Evaluation Method for Modular Converter Topologies

The success of modular multilevel converters (MMCs) in high-voltage direct current (HVDC) applications has fueled the research on modular converter topologies. New modular converter topologies are often proposed, discussed, and sometimes applied in HVDC, as well as other industrial application such as STATCOMs, DC/DC HVDC, medium-voltage direct current (MVDC), etc. The performance evaluation of new modular converter topologies is a complex and time-consuming process that typically involves dynamic simulations and the design of a control system for the new converter topology. Sadly, many topologies do not progress to the implementation stage. This paper proposes a set of key performance indicators (KPIs) related to the cost and footprint of the converter and a procedure designed to rapidly evaluate these indicators for new converter topologies. The proposed methodology eliminates the need for dynamic simulations and control-system design, and is capable of identifying whether a particular converter is worth considering or not for further studies of a specific application, depending on the operating requirements. Thanks to the method outlined in this work and via the key parameters quantifying the “relevance” of the analyzed converters, promising topologies were easily identified, while the others could be rapidly discarded, resulting in saving valuable time in the study of the solutions that have a real potential. The proposed method is first described from a general point of view and then applied to a case study of the new converter topology—Open-Delta CLSC—and its application in two use cases

Rapid Evaluation Method for Modular Converter Topologies

The success of modular multilevel converters (MMCs) in high-voltage direct current (HVDC) applications has fueled the research on modular converter topologies. New modular converter topologies are often proposed, discussed, and sometimes applied in HVDC, as well as other industrial application such as STATCOMs, DC/DC HVDC, medium-voltage direct current (MVDC), etc. The performance evaluation of new modular converter topologies is a complex and time-consuming process that typically involves dynamic simulations and the design of a control system for the new converter topology. Sadly, many topologies do not progress to the implementation stage. This paper proposes a set of key performance indicators (KPIs) related to the cost and footprint of the converter and a procedure designed to rapidly evaluate these indicators for new converter topologies. The proposed methodology eliminates the need for dynamic simulations and control-system design, and is capable of identifying whether a particular converter is worth considering or not for further studies of a specific application, depending on the operating requirements. Thanks to the method outlined in this work and via the key parameters quantifying the “relevance” of the analyzed converters, promising topologies were easily identified, while the others could be rapidly discarded, resulting in saving valuable time in the study of the solutions that have a real potential. The proposed method is first described from a general point of view and then applied to a case study of the new converter topology—Open-Delta CLSC—and its application in two use cases

Conceptual design upgrade on hybrid powertrains resulting from electrics improvements

Hybrid vehicles have experienced a great boom in recent years thanks to the increasing spread of \u201cparallel\u201d architectures, often realized by a planetary gear train (HSD). At the same time, an enhancement of electrical and electronic components has been experienced; these improvements especially concern reliability and efficiency. Particularly the possibility of using supercapacitors with increasing storage performances, makes possible to manage higher power flows together with a superior efficiency. These innovations may challenge the architecture used nowadays on medium size cars. The hybrid series architecture, which allows the optimal management of the combustion engine, has been disadvantaged until now by the electric powertrain efficiency. In the current scenario, this architecture could benefit from the above mentioned technology, becoming a competitive alternative to the actual powertrain configurations. The aim of this paper is the efficiency analysis, in order to evaluate the operational energy efficiency achievable thanks to this configuration. This analysis will be carried out considering all the possible working conditions of the different powertrains

Advantages of Using Supercapacitors and Silicon Carbide on Hybrid Vehicle Series Architecture

In recent years enormous growth has taken place in the hybrid vehicle sector; parallel architecture is the most widespread configuration regarding medium size cars. At the same time, storage systems and power electronics have experienced some important innovations. The development of supercapacitors has permitted management of high power with elevated efficiency. Moreover, the availability on the market of silicon carbide components has allowed a significant reduction of power electronic losses. These improvements may challenge the hybrid architecture used in medium size cars nowadays. On one hand, series architecture would relevantly benefit from an electric powertrain efficiency increase, on the other hand, these innovations would generate low benefits in parallel architectures. The aim of this paper is to evaluate electric component average efficiency over different road missions, in order to estimate fuel economy over various working conditions and finally to establish which hybrid configuration is most efficient in vehicle applications

Open-Delta SBC: a New Converter Topology with Low Number of Sub-Modules for MV applications

International audienceMedium voltage direct current (MVDC) technology has been experiencing a great boom of interest in recent years. This paper aims at giving a contribution to this field by proposing a new converter topology for MVDC applications. This topology is characterized by a low number of sub-modules (SMs) which is strongly related to the converter footprint and complexity. The new topology sizing is compared to the modular multilevel converter (MMC) for the same requirements to highlight advantages and disadvantages of the proposed solution

Open-Delta SBC: a New Converter Topology with Low Number of Sub-Modules for MV applications

International audienceMedium voltage direct current (MVDC) technology has been experiencing a great boom of interest in recent years. This paper aims at giving a contribution to this field by proposing a new converter topology for MVDC applications. This topology is characterized by a low number of sub-modules (SMs) which is strongly related to the converter footprint and complexity. The new topology sizing is compared to the modular multilevel converter (MMC) for the same requirements to highlight advantages and disadvantages of the proposed solution

A Sliding Mode Control Approach for Gas Turbine Power Generators

Gas Turbines are raising nowadays growing interest in the power generation industry. Being able to regulate their power production faster than any other form of conventional source, they are extremely valuable in compensating stochastic power fluctuations deriving from renewable energy sources in large scale electrical grids, preserving grid stability, etc. In this context, gas turbines dynamical performance plays a key role as it needs to be enhanced compatibly with preserving the machine lifetime. Nonlinear model based control systems can effectively deal with this problem, exploiting the system structure to obtain optimal dynamical performance. Therefore, this paper aims at developing a Sliding Mode model based control for gas turbines and at comparing the results obtained by its application on a heavy duty Ansaldo Gas Turbine model (AE94.3A) with the ones obtained thanks to the traditional controls employed in these applications