The paper proposes a novel PV power generation system, through employing the quasi-Z source inverter with battery, to balance the stochastic fluctuations of PV power, and smooth the power injected to the grid/ load. The analytical model is built to analyze the power and current relationships among the PV panel, battery, and the inverter output. The capacitor voltage outer loop with a battery current inner loop ensures a constant dc link peak voltage for a wide range of PV voltage, an incremental load based maximum power tracking achieves the PV panels operating at the maximum power point, even for a wide variation of solar irradiation and temperature. The simulated and experimental results verify the proposed novel PV interface inverter and its control principle.
In this paper, a unique 100kHz sampling and switching frequency shunt active power filter (SAPF), which is based on a dual-core DSP TMS320F28377D, is designed to achieve high control bandwidth for the potential market of wide frequency range harmonic suppression and resonance damping in future more electric aircraft (MEA) or high-speed railway power grid. By rearranging different computation segments, such as analog-to-digital conversion, recursive discrete Fourier transform (RDFT), inner-loop current and outer-loop voltage control, the traditional single pipeline code structure in DSP can be reformed as two parallel running groups. This multitasking strategy provides the proposed SAPF with huge advantages on higher frequency harmonic suppression compared to the mostly commercial SAPF with 10~20kHz switching frequency. Detailed parameter design of LCL filter, DC-side capacitor and deadtime are also presented. A 10kVA prototype utilizing CREE SiC power module CCS050M12CM2 is set up to verify the effectiveness of the proposed SAPF. The results show that the total harmonic distortion can be limited within 5%, which complies with the IEEE power quality standard 519-2014.
Feature plays an important role in pedestrian detection, and considerable progress has been made on shape-based descriptors. However, color cues have barely been devoted to detection tasks, seemingly due to the variable appearance of pedestrians. In this paper, Color Maximal-Dissimilarity Pattern (CMDP) is proposed to encode color cues by two core operations, i.e., oriented filtering and max-pooling, which emulate the functions of primary visual cortex (V1). The extensively experimental results reveal that the biologically-explainable encoding scheme increases the invariance of color cues, and outperforms the state-of-the-art color descriptor in terms of both accuracy and speed.
Tracking humans that are interacting with the other subjects or environment remains unsolved in visual tracking, because the visibility of the human of interests in videos is unknown and might vary over time. In particular, it is still difficult for state-of-the-art human trackers to recover complete human trajectories in crowded scenes with frequent human interactions. In this work, we consider the visibility status of a subject as a fluent variable, whose change is mostly attributed to the subject's interaction with the surrounding, e.g., crossing behind another object, entering a building, or getting into a vehicle, etc. We introduce a Causal And-Or Graph (C-AOG) to represent the causal-effect relations between an object's visibility fluent and its activities, and develop a probabilistic graph model to jointly reason the visibility fluent change (e.g., from visible to invisible) and track humans in videos. We formulate this joint task as an iterative search of a feasible causal graph structure that enables fast search algorithm, e.g., dynamic programming method. We apply the proposed method on challenging video sequences to evaluate its capabilities of estimating visibility fluent changes of subjects and tracking subjects of interests over time. Results with comparisons demonstrate that our method outperforms the alternative trackers and can recover complete trajectories of humans in complicated scenarios with frequent human interactions.
This paper introduces a new MMC topology, in which each phase leg consists of four arms. Two of the arms consists of cascaded connected submodules and are just like single phase leg in traditional MMC topology. Another two arms are formed by series switches such as high voltage IGBT, which are only activated when the ac voltage changes polarity. And then three phase legs are series connected in vertical direction to support the DC bus voltage. The major advantage of proposed topology are as follows: (1) The total number of required submodules are reduced to 1/3 compared with traditional MMC topology. (2) The energy ripple in each arm is calculated to be smaller than the traditional 3-phase MMC. Therefore, the total capacitor size can be reduced. A detailed 20 MW simulation has been conducted and the related results of proposed topology have been presented. What's more, The SM prototype and preliminary experiments are also demonstrated and analyzed.
The methodology for the synthesis of fluorene-based atropisomers was developed via the strategy of aromatic ring formation. By this strategy, an efficient benzannulation of indene-based diene with benzoylacetonitrile divergently promoted by DABCO and a chiral organocatalyst was established, and various atropisomeric fluorene-based skeletons were generated in good yields, which not only provide a new strategy for the construction of atropisomeric biaryls but also offer a new member to the atropisomeric family.
Traditional voltage-source PWM rectifier (VSR) is a boost converter and traditional current-source PWM rectifier (CSR) is a buck converter. A dc-dc converter is requested to use with them to implement buck-boost capability. Also CSR can only provide unidirectional power flow. To overcome these limitations, voltage-fed Z-source PWM rectifier and current-fed Z-source PWM rectifier have been proposed. They can buck and boost the ac voltage with only six active switches. In addition, current-fed Z-source PWM rectifier has its own merits because it can provide bidirectional power flow without replacing the diode in Z network with an active switch which is required in voltage-fed Z-source PWM rectifier. However, CSRs are less investigated because the switches have to be reverse blocking. Recently developed reverse blocking IGBT (RB-IGBT) makes the CSRs and current-fed Z-source rectifiers more attractive and realizable. This paper describes the operating principle of this current-fed Z-source PWM rectifier, analyzes the circuit and characteristics, and discuss the PWM control strategy. A RB-IGBT based current-fed Z-source PWM rectifier has been developed in laboratory. Both simulation and experimental results are shown to verify the operation and theoretical analysis.
We propose a novel approach for tracking an arbitrary object in video sequences for visual surveillance. The first contribution of this work is an automatic feature extraction method that is able to extract compact discriminative features from a feature pool before computing the region covariance descriptor. As the feature extraction method is adaptive to a specific object of interest, we refer to the region covariance descriptor computed using the extracted features as the adaptive covariance descriptor. The second contribution is to propose a weakly supervised method for updating the object appearance model during tracking. The method performs a mean-shift clustering procedure among the tracking result samples accumulated during a period of time and selects a group of reliable samples for updating the object appearance model. As such, the object appearance model is kept up-to-date and is prevented from contamination even in case of tracking mistakes. We conducted comparing experiments on real-world video sequences, which confirmed the effectiveness of the proposed approaches. The tracking system that integrates the adaptive covariance descriptor and the clustering-based model updating method accomplished stable object tracking on challenging video sequences.
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