Dual harmonic injection for reducing the sub-module capacitor voltage ripples of hybrid MMC

Reducing the capacitor voltage ripples of the half-bridge sub-modules (HBSM) and full-bridge sub-modules (FBSM) in a hybrid modular multilevel converter (MMC) is expected to reduce the capacitance, volume and costs. To address this issue, this paper proposes a dual harmonic injection method which injects the second harmonic circulating current and third order harmonic voltage into the conventional MMC control. Firstly, the mathematical model of the proposed control is established and analyzed. Then, the general strategy of determining the amplitude and phase angle of each injection component is proposed to suppress the fluctuations of the fundamental and double frequency instantaneous power. The proposed strategy can achieve the optimal power fluctuation suppression under various operating conditions, which also has the advantage of reducing the voltage fluctuation difference between HB and FB SMs. The correctness and effectiveness of the proposed strategy are verified in simulations in PSCAD/EMTDC

Modeling for complex modular power electronic transformers using parallel computing

The modular power electronic transformer (PET) faces difficulty carrying out microsecond-level electromagnetic transient (EMT) simulations. This paper provides a high-speed and high-precision simulation method capable of eliminating the internal nodes and reducing the order of the nodal admittance matrix. Meanwhile, the parallel computing is integrated into the whole solution process, which achieves a significant simulation speedup. A physical prototype is established to prove that the detailed model is sufficient to reflect the dynamics of physical devices. Moreover, simulations in PSCAD/EMTDC are carried out to compare the proposed method with the detailed model in terms of accuracy and time efficiency. Simulation results show that the proposed method is accurate to simulate the external and internal dynamics of PET with hundreds of times simulation speed acceleration

Accelerated electromagnetic transient (EMT) equivalent model of solid-state transformer

Accurate and efficient electromagnetic transient (EMT) simulation of various types of solid-state transformers (SST) is extremely time-consuming due to the complex module structure, flexible topology connections, large number of electrical nodes and simulation time-steps limited in the range of micro-seconds. Therefore, it is urgent to develop the EMT equivalent modelling and fast simulation of SSTs for system level studies. Taking the modular multilevel converter (MMC) based SST as an example, this paper proposes an accelerated EMT model which focuses on the equivalence of the dual active bridge (DAB) based high-frequency link (HFL) in the SST. Compared with the existing algorithms, two critical factors of the proposed method that contribute the most to the efficiency improvement are the preprocessing of the nodal admittance equation and the conversion of the short-circuit admittance parameters. The proposed model is verified in PSCAD/EMTDC by comparing it with the detailed EMT model. The results show that the accelerated model is one to two orders of magnitude faster than the detailed model without sacrificing the accuracy. The experiment validation also confirms the validity of the proposed model

Fast Lip Feature Extraction Using Psychologically Motivated Gabor Features

The extraction of relevant lip features is of continuing interest in the speech domain. Using end-to-end feature extraction can produce good results, but at the cost of the results being difficult for humans to comprehend and relate to. We present a new, lightweight feature extraction approach, motivated by glimpse based psychological research into racial barcodes. This allows for 3D geometric features to be produced using Gabor based image patches. This new approach can successfully extract lip features with a minimum of processing, with parameters that can be quickly adapted and used for detailed analysis, and with preliminary results showing successful feature extraction from a range of different speakers. These features can be generated online without the need for trained models, and are also robust and can recover from errors, making them suitable for real world speech analysis

A New Linear Relation for Estimating Surface Broadband Emissivity in Arid Regions Based on FTIR and MODIS Products

Broadband emissivity is a crucial parameter for calculating the radiation budget, still, it adopts a constant value in land surface models due to a lack of adequate observations. Arid regions have complex underlying surfaces and estimations of the broadband emissivity in such areas suffer from high spatial variation and uncertainty. Here, we propose a novel method for estimating broadband emissivity in the 8–14 µm range based on Fourier-transform infrared spectroscopy (FTIR) observations, moderate resolution imaging spectrometer (MODIS) emissivity, the leaf area index (LAI) and reflectance products. The proposed method exploits FTIR observations, MODIS single-channel emissivity, reflectance and the LAI to fit a linear regression of the broadband emissivity, so the optimal equation includes emissivity, reflectance and the LAI, with an R2 and root-mean-squared error of 0.942 and 0.08. Then we used the proposed method to generate a broadband emissivity map of Northwest of China, the broadband emissivity estimated by the method showed higher variations and finer distribution in arid areas and sparsely vegetated regions compared to data from the global land surface satellite and land model. An analysis of the relationship between the broadband emissivity, land-use type and soil moisture found an existing but not linear relationship, which indicated that the relationship was complicated under the inhomogeneous surface of wetness and vegetation. In conclusion, our results suggest that the proposed method can accurately estimate the broadband emissivity in arid regions. In future research, we will test the data in a land model

Genetic Analysis of Orf Virus (ORFV) Strains Isolated from Goats in China: Insights into Epidemiological Characteristics and Evolutionary Patterns

Contagious ecthyma (CE) is an acute infectious zoonosis caused by orf virus (ORFV) that mainly infects sheep and goats and causes obvious lesions and low market value of livestock, resulting in huge economic losses for farmers. In this study, two strains of ORFV were isolated from Shaanxi Province and Yunnan Province in China, named FX and LX. The two ORFVs were located in the major clades of domestic strains respectively, and exhibited distinct sequence homology. We analyzed the genetic data of core genes (B2L, F1L, VIR, ORF109) and variable genes (GIF, ORF125 and vIL-10) of ORFV to investigate its epidemiological and evolutionary characteristics. The sequences from 2007 to 2018 constituted the majority of the viral population, predominantly concentrated in India and China. Most genes were clustered into SA00-like type and IA82-like type, and the hotspots in East and South Asia were identified in the ORFV transmission trajectories. For these genes, VIR had the highest substitution rate of 4.85 × 10−4, both VIR and vIL-10 suffered the positive selection pressure during ORFV evolution. Many motifs associated with viral survival were distributed among ORFVs. In addition, some possible viral epitopes have been predicted, which still require validation in vivo and in vitro. This work gives more insight into the prevalence and phylogenetic relationships of existing orf viruses and facilitate better vaccine design