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Using a single-point sensor, non-intrusive load monitoring (NILM) discerns the individual electrical appliances of a residential or commercial building by disaggregating the accumulated energy consumption data without accessing to the individual components. To classify devices, potential features need to be extracted from the electrical signatures. In this article, a novel features extraction method based on current shapelets is proposed. Time-series current shapelets are determined from the normalized current data recorded from different devices. In general, shapelets can be defined as the subsequences constituting the most distinguished shapes of a time-series sequence from a particular class and can be used to discern the class among many subsequences from different classes. In this work, current envelopes are determined from the original current data by locating and connecting the peak points for each sample. Then, a unique approach is proposed to extract shapelets from the starting phase (device is turned on) of the time-series current envelopes. Subsequences windowed from the starting moment to a few seconds of stable device operation are taken into account. Based on these shapelets, a multi-class classification model consisting of five different supervised algorithms is developed. The performance evaluations corroborate the efficacy of the proposed framework.

This article presents an efficient design architecture of an islanded and scalable DC microgrid comprising several power management units (PMUs) and a time slot-based control interface. There are two primary sections in this manuscript-performance analysis of a microgrid design with phase shift modulation (PSM)-controlled dual active bridge (DAB) converter-based PMUs to charge Li-ion battery energy systems and design of a time slot-based control scheme to regulate the operation of PMUs for future applications. The batteries can act as the power sources in home energy management systems, transactive energy systems and so on. The PMUs are connected in parallel to a capacitive bus, which is supplied power by a photovoltaic (PV) energy source. There is a maximum power point tracking (MPPT) control block, which is constituted by a perturb and observe (P & O) algorithm and boost converter average model. For performance evaluations, the DAB-based microgrid design is developed and tested in MATLAB/Simulink [textregistered]. In the second section, the control interface design is illustrated and explained with the constituent algorithms.

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Numerical simulations have been carried out to examine the performance and flow parameters of forced rotating vaneless diffuser obtained by the extension of impeller disks of a low-pressure ratio shrouded type centrifugal compressor stage with diffuser diameter ratio 1.40. Four different levels of shroud extensions (i.e., impeller disks alone) forming the rotating vaneless diffusers are analyzed at four different flow coefficients. The extension of impeller disks alone by 40% of impeller exit diameter leads to a fully forced rotating vaneless diffuser thereby replacing the existing stationary vaneless diffuser. The comparative studies are performed using the same impeller with a stationary vaneless diffuser also having a diffuser diameter ratio of 1.40. Static pressure rise in ES40 is found to be higher than SVD by around 9.84% at design flow coefficient and also at above off-design flow rates. Energy coefficient is highest for ES40, followed by ES30 compared to SVD. For ES40, the static pressure recovery coefficient also is higher compared to SVD. The efficiency of ES40 is lesser by around 5.40% to 3.43% compared to SVD, at design as well as at above off-design flow coefficients. The stagnation pressure losses for ES40 drastically reduced compared to SVD. The comparison of stagnation pressure contours and absolute velocity contours near the hub and shroud walls of ES40 and SVD configurations shows that the rotating diffuser walls as in ES40 causes further addition of energy to the fluid. This adds up the kinetic energy level of the fluid which due to better diffusion, results in gain of static pressure rise. Moreover, there is a net increase in stagnation pressure distribution at the exit of diffuser due to rotating vaneless diffuser. Also, the presence of a fully rotating vaneless diffuser (ES40) smooth out the distorted entry flow profiles, thereby improving the performance of the centrifugal compressor stage.

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