Journal of Electrical Engineering & Technology

In modern electrical traction drives, a variable dc-link voltage can be applied to increase efficiency in partial load. A dc-dc converter can supply a variable dc-link voltage and transfer energy between the battery and the dc-link. Hybrid cars combine the advantages of long driving ranges with the partial zero-emission operation. In series-hybrid drive trains, a switched reluctance machine can be used as a generator for the range extender unit. This paper presents at first the mechanism of energy transfer between the battery and the dc-link. Further, a control parameter analysis of an inverter topology for a switched reluctance machine, which combines the dc-dc converter for the power transfer between the battery and the dc-link with the inverter for the generator, is investigated. For this analysis, the control parameters turn-on, freewheeling and turn-off angle are varied to test the controllability of the energy transfer between these two components. The simulation results of the presented analysis are finally validated with measurements on the test bench.

The equilibrium degree of transmission lines in the multi-objective planning of power grid is studied in this paper. The main purpose of the study is to ensure the economy and improve the balanced distribution of active power flow of transmission lines, furthermore increase the adaptability of transmission lines in the future power grid. The problem is mainly focus on the single-level of line load rate, in researching on the distribution balance of active power flow in transmission lines. Three indexed, which are line load rate power flow entropy, active loss rate power flow entropy and transmission efficiency power flow entropy, are defined in this paper. The weighted sum of the three indexes is defined as the balance factor of active power flow distribution in transmission lines. This factor is used in transmission network planning to improve the overall balance of active power flow distribution in transmission lines. On this basis, a multi-objective programming model with minimum economic cost and maximum equilibrium factor of transmission network is established. The model is solved by using multi-objective bacterial colony chemotactic algorithm (BCC) and optimal compromise solution method. The results verify the superiority and rationality of the proposed method and model.

A compact dual-mode balun bandpass filter with improved out-of-band performance is proposed based on a ring resonator. In order to excite the two degenerate modes and obtain filtering balun performance, three parallel-coupled lines are placed at three excitation ports along the ring resonator. By properly arranging the angles between the excitation arms, four transmission zeros can be realized to improve stopband performance. Finally, a prototype of the designed balun bandpass filter is implemented and fabricated. The measured results show a good agreement with those obtained from the simulation, thus verifying our proposal with good in-band filtering and out-of-band performance.

In order to improve the control performance of state-of-charge (SOC) balance control and expand the application scenarios of SOC balance control, in this paper, an SOC-based switching functions double-layer hierarchical control is proposed for distributed energy storage systems in DC microgrids. Firstly, the switching functions in the primary layer of double-layer hierarchical control, which is defined as droop coefficient in the droop control, is divided into two SOC-related functions. The first one in the switching functions is a composite exponential function with power function and nonlinear function. The second one in the switching functions is a nonlinear function with a capacity balance factor. Since the composite function is very sensitive to the change of SOC, it can speed up the time of SOC balance. It plays a positive role in solving the rapid SOC balance problem between energy storage units. In addition, the nonlinear function with a capacity balance factor is designed to reduce the steady state deviation of SOC. Capacity balance factor is a weighting coefficient related to capacity, under which this control can ignore the limitation of capacity problem on SOC balance to expand the application scenarios. Secondly, a voltage restoration controller is introduced in the second layer of double-layer hierarchical control. The voltage restoration controller can compensate the voltage deviation caused by the primary layer, therefore, the bus voltage can maintain at the normal value. Finally, simulation results show the effectiveness and feasibility of the proposed scheme.

In order to overcome the weakness of dc line protection under high impedance fault, a traveling wave similarity based pilot protection method is proposed using improved Hausdorff Distance algorithm. The issue of asynchronous data, noise and anomalies are solved with the improved Hausdorff Distance algorithm. The instantaneous frequency based wave head detection method is used to overcome the problem of delay in protection start-up. Based on this protection scheme, external fault can be distinguished from internal faults regardless of fault impedance, fault location and fault type. Moreover, the faulty pole and fault direction are recognized via ratio of transient energy at line terminals. Taking the Zhangbei high voltage dc transmission project as an example, a four-terminal ring type dc grid model is developed in PSCAD/EMTDC platform for fault simulation and the data processing is performed in MATLAB platform. Based on the theoretical analysis and simulation study, the proposed pilot protection is verified with excellent fault impedance withstanding ability and robustness against noise, abnormal data and asynchronous data.

Các lệnh định hình bật-tắt được đề xuất nhằm giảm bớt dao động dư trong các hệ thống linh hoạt không bị giảm chấn với các bộ chấp hành bậc hai có độ trễ bất đối xứng, đây là một vấn đề phổ biến trong các ứng dụng công nghiệp. Các bộ chấp hành bậc hai có độ trễ bất đối xứng có thể tạo ra dao động dư lớn trong các hệ thống linh hoạt không bị giảm chấn trong các hoạt động chuyển động từ trạng thái nghỉ. Do đó, một giải pháp chính xác cho các lệnh định hình bật-tắt đã được phát triển bằng phương pháp vector pha và hàm phản ứng theo bước của hệ thống bậc hai. Hơn nữa, một phương pháp để thu được các lệnh định hình bật-tắt ổn định được trình bày với công thức tối ưu hóa tham số nhằm bù đắp cho các không chắc chắn trong mô hình dưới các bộ chấp hành bậc hai có độ trễ bất đối xứng. Hiệu suất điều khiển của cả hai phương pháp được phân tích liên quan đến các tham số thiết kế lệnh, dao động dư và độ nhạy, và được so sánh với các bộ định hình đầu vào thông thường. Các lệnh định hình đầu vào bật-tắt được đề xuất đã được đánh giá bằng số với một hệ thống đơn mô-đun không giảm chấn, và chúng đã được xác thực thực nghiệm với một cần trục minibridge.

Based on the deep learning BP neural network algorithm, we establish the electromagnetic torque and loss prediction analysis model of permanent magnet synchronous motor to provide new design ideas and methods for optimizing motor structure design. In this paper, four-rotor structure parameters which are Rib, Air Gap, Magnet Thickness and Magnet Width, motor electromagnetic torque, and motor losses of the “V” type Interior Permanent Magnet Synchronous Motor are selected as the research object. The BP neural network structure prediction model with 2 visible layers and 2 hidden layers was built by 256 groups of sample data calculated by Maxwell transient electromagnetic simulation. 226 out of 256 randomly selected data samples were used to train the prediction model, and 30 groups were used to test the accuracy and generalization ability of the prediction model. and the prediction results data were compared with the deep learning prediction model through finite element simulation data. The results show that the BP neural network small-sample data prediction model has high prediction accuracy in the loss prediction of the vehicle permanent magnet synchronous motor, and verifies the feasibility of the motor torque and loss prediction model based on the deep learning algorithm.