Three-phase grids imbalance causes serious alternating input current distortion in three-phase pulsewidth modulation (PWM) rectifiers where the conventional control scheme is employed. In this article, a generalized Clarke transformation is proposed to convert three-phase unbalanced sinusoidal quantities to two orthogonal sinusoidal quantities with equal amplitudes. Then, these two orthogonal sinusoidal quantities could be converted to two direct quantities by the Park transformation. Furthermore, based on the generalized Clarke transformation, an enhanced dual-loop control (EDLC) scheme is proposed to control the three-phase PWM rectifier in the synchronous rotating frame. Finally, a 5-kW Vienna-type rectifier prototype was built to verify the proposed generalized Clarke transformation and the proposed EDLC control scheme. Experimental results show that, by using the proposed EDLC scheme, the low current total harmonic distortion is achieved even both the amplitude and phase of the utility grid voltages are unbalanced.

This paper develops an improved non dominated sorting genetic algorithm II (NSGA-II) based on objective importance vector γ, abbreviated as γ-NSGA-II. Different importance levels for the multiple objectives are incorporated in the objective importance vector, which is applied to determine the individual selection of sorting individuals in the critical layer. And such an individual selection strategy is developed to the NSGA-II algorithm in order to obtain the optimized solution for a task which has multiple objectives with different importance. The differences between the γ-NSGA-II algorithm and the traditional NSGA-II algorithm are discussed in detail. A notch filter is designed for the conducted emission suppression of a transformer rectifier unit (TRU) used in C919 flight testing, and then the parameters optimization design of a notch filter is discussed and conducted based on the γ-NSGA-II algorithm. The non-linear relationship between the filter’s parameters and the suppression effect of the conducted emission is also discussed with the help of an electromagnetic compatibility (EMC) evaluation model based on a back propagation (BP) neural network. The experimental results show that the optimized design of the notch filter is effective and the improved γ-NSGA-II algorithm be more specific.

As time series data with internal correlation, networks traffic data can be used for abnormal detection using Recurrent Neural Network (RNN) and its variants, but existing models are difficult to calculate in parallel, and gradient explosion or vanishing easily occurs. To address this problem, we propose a Bidirectional Independent Recurrent Neural Network (BiIndRNN) with parallel computation and adjustable gradient, which can extract the bidirectional structural features of networks traffic by forward and backward input and capture the spatial influence in the data flow. To establish the dependencies on the forward and backward moments of networks traffic, a model combining Global Attention (GA) with BiIndRNN is proposed to pay more attention to the moments containing essential information. Taking the UNSW-NB15 dataset as the object, the GA expression of the packets feature vector of the networks is derived, feature fusion, as well as loss calculation, is performed for multiple fully connected layers. The experimental results show that, compared with traditional deep and shallow machine learning and other state-of-the-art technologies, our GA-BiIndRNN model converges faster, the accuracy, precision, and F1 scores are all above 99%, and the false positive rate (FPR) is close to 0.36%, which can effectively identify normal and malicious network activities. These results provide a theoretical basis for the rapid implementation of protective measures.

A dual-input dual-buck inverter (DIDBI) with integrated Boost converters (IBCs) is proposed for grid-connected applications. The proposed DIDBI is composed of two Buck-type inverter-legs and two IBCs. Two renewable DC sources with independent MPPT can be realized with the DIDBI. The IBCs are used to provide a constant and stable DC-Bus voltage for the inverter-legs, enabling the inverter to operate well, even when the DC source voltage varies widely and is lower than the peak amplitude of the grid voltage. Unlike a conventional two-stage DC-AC inverter, only a small ratio of the input power needs to be processed by the IBCs. The other part of the input power is directly fed to the grid through the inverter-legs; therefore,the conversion stages of the DIDBI, power rating, and losses of the IBCs are all reduced. Switching loss can be reduced as well because of the multi voltage-level characteristics of the proposed DIDBI. As a result, higher efficiency is achieved. Modulation and control strategies are proposed to realize independent regulation of the two DC inputs. Operation principles and characteristics of the proposed DIDBI are analyzed in detail. Experimental results have been provided to verify the effectiveness and advantages of the proposed method.

Torque ripples caused by the particular doubly salient structure of the doubly salient electromagnetic machine (DSEM) restrict its application in the field requiring high performance. This paper employs the current given function (CGF) to propose a torque ripple reduction strategy for DSEM to enhance the torque capability. The optimal current profile for minimizing the copper loss is obtained based on the theoretical analysis. It is found that the obtained three-phase currents are distributed according to the phase torque coefficient that represents the torque capability of each phase. Then, to minimize the torque ripple and copper loss, four CGFs are proposed to distribute the reference current of each phase according to the torque characteristics of DSEM. Finally, the influence of overlap angle on the proposed strategy is analyzed to select the reasonable CGF and overlap angle under different operating conditions through simulation, improving the current tracking performance and torque-ampere ratio. The simulation and experimental results demonstrate the effectiveness of the proposed strategy in suppressing torque ripple and improving the torque-ampere ratio.

A method to derive topologies of four-quadrant dual-dc-port dual-buck inverter (DDP-DBI) is proposed in this article. A new family of DDP-DBIs is obtained by replacing one of the switching legs in a four-quadrant dual-buck half-bridge switching cell with a dual-input buck type switching leg. With the proposed DDP-DBIs, both the low voltage dc source and the high voltage intermediate dc-bus can be used as the inputs of the inverter. Therefore, in comparison with the conventional two-stage dc-ac power system, a semi-two-stage dc-ac power conversion system with reduced power losses and enhanced conversion efficiency is achieved. A unipolar sinusoidal pulse width-modulation strategy is presented for the DDP-DBI. In each line cycle, all the power devices and filter inductors only operate within half line cycle, and only one active switch is operated at high frequency. Moreover, no freewheeling current flows through the body diodes of the active switches. As a result, the conversion efficiency of the overall dc-ac power conversion system is improved. Operation principles, characteristics, modulation and control strategies of one of the proposed DDP-DBI are analyzed in detail. Effectiveness and feasibility of the proposed DDP-DBI are verified with experimental results.