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This paper reviews major use cases for blockchain architectures relevant to the energy sector and continues with a critical review of issues to study in future research work including as related to energy consumption of blockchain architectures and ensuring a reliable distribution network and security of supply. It also reviews what is happening in the market with relation to smart contracts.

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The increasing interest in Hybrid Electric Vehicles led to the study of new powertrain structures. In particular, it was demonstrated in the technical literature how series architecture can be more efficient, compared to parallel one, if supercapacitors are used as storage system. Since supercapacitors are characterized by high efficiency and high power density, but have low specific energy, storage sizing is a critical point with this technology. In this study, a detailed analysis on the effect of supercapacitor storage sizing on series architecture was carried out. In particular, in series architecture, supercapacitor storage sizing influences both engine number of starts and the energy that can be stored during regenerative braking. The first aspect affects the comfort, whereas the second aspect directly influences powertrain efficiency. Vehicle model and Energy Management System were studied and simulations were carried out for different storage energy, in order to define the optimal sizing.

In this paper, a high output voltage power converter working at variable input DC-link voltage is presented. The variable DC link voltage opens to very interesting solution at system level. However, those solutions will be the subject of futures papers. Only the main power converter structure is presented here. After an evaluation of the most promising converter topologies for the required high voltage and power, eventually an LCC resonant converter with phase shift control has been chosen. The resonant converter is followed by a double secondary high frequency transformer with a two diode voltage doublers. The system has been fully analysed from the theoretical point of view, designed, built and tested. The control system has been fully digital implemented making use of a TI DSP microcontroller, TMS320X28335.

A distorted grid voltage or nonlinear behavior in the current control loop can cause low frequency current harmonics in a grid-connected voltage source inverter (VSI). Many efforts have been made to mitigate such phenomena, including hardware and/or control structure improvements. A well-known suitable strategy to reduce current harmonics in a selective manner is to apply a Proportional Multi-Resonant (PMR) current controller. Inverter-grid stability is another common issue when dealing with grid-connected VSI. Stability is influenced by the inverter impedance, which depends on the controller parameters. This paper presents a simplified tuning strategy for the PMR controller, taking into consideration the inverter-grid stability issue. The obtained controller was implemented and tested in a 10 kW three-phase inverter with a passively damped LCL filter. A significant reduction of current harmonics emission from the inverter up to 650 Hz was achieved without any hardware modification. The limits of PMR controllers to mitigate current harmonics were studied, and the influence of the grid impedance was verified.

Abstract-Within the context of microgrids optimal voltage control, most schemes proposed in the literature either rely on (i) droop-control methods or (ii) methods involving the computation of explicit nodal power set-points as a solution to a given optimization problem. The first category of approaches is in general suboptimal as it relies on locally sensed measurements. The second category guarantees some level of optimality but requires an accurate and up-to-date model of the network that is, in general, not always available in low voltage grids. To overcome the aforementioned limitations, in this work we propose a methodology suitable for voltage control in generic low voltage 3-phase unbalanced grids. It can be used for the computation of either explicit power set-points or to define the droops of local voltage regulators. Its main characteristic is that it does not rely on the knowledge of the system model and its state. In particular, the goal is to compute linearized dependencies between voltage magnitude and nodal power injections, i.e., voltage sensitivity coefficients. The proposed method assumes availability of a monitoring infrastructure and the computation of the desired sensitivities involves the solution of an over-determined system of linear equations constructed solely using available measurements of nodal power injections and voltage magnitudes. The proposed method is also capable to account for the measurement errors and their time correlation. The performance evaluation of the proposed method is carried out using real measurements coming from a real low voltage feeder located in Switzerland equipped with an appropriate metering infrastructure.