Electromagnetic Capability Research Articles

Разработка и исследование усовершенствованных алгоритмов ШИМ активных выпрямителей с целью улучшения качества электроэнергии во внутризаводских электрических сетях 6–35 кВ

Currently, application of frequency converters with active front end rectifiers (FC-AFE) has become a standard solution for powerful adjustable AC drives with frequent dynamic modes. The advantages of these converters include the possibility of recuperation of braking energy to the supply network, as well as the best electromagnetic compatibility of electromagnetic capability (EMC) with the supply network as stated by the manufacturers of converter technology. This statement is only partly true, since FC-AFE manufacturers do not consider possible resonant phenomena in the 6–35 kV intra-factory distribution network caused by the interaction of reactive elements of the power supply system. When significant harmonics of the FC-AFE current are superimposed on the resonant region, dangerous voltage distortions of 6–35 kV may occur. Traditional methods of providing electromagnetic capability of FC-AFE in this case may not have the desired effect. Therefore, it is relevant to develop alternative technical solutions to ensure an acceptable level of electromagnetic capability of FC-AFE. One such solution is the use of advanced PWM algorithms in the FC-AFE adapting to resonant phenomena in the 6–35 kV intra-factory network. The materials for the study are the oscillograms of the currents and voltages at the input of the FC-AFE obtained experimentally and using mathematical modeling. Experimental data have been obtained on operating equipment with FC-AFE and on a special laboratory setup. When developing improved PWM algorithm of AFE, a well-known mathematical apparatus is used. It describes the dependence of individual harmonics on the number of switching and switching angles. The results obtained show the effectiveness of improved PWM algorithms in terms of reducing the effect of FC-AFE on the supply network and improving the quality of electricity in intra-factory networks of 6–35 kV. The results of the study are implemented at a number of metallurgical enterprises, thanks to which it is possible to reduce voltage distortions of 6–35 kV and increase the stability of the operation of sensitive electrical receivers. The developed improved PWM algorithm of FC-AFE can significantly improve the quality of electricity in the in-house electrical networks of 6–35 kV without additional capital costs and installation of additional equipment. Based on the results obtained, it is recommended to use the developed PWM algorithms on the operating equipment with FC-AFE of industrial enterprises.

High Dimensional Electromagnetic Interference Signal Clustering Based On SOM Neural Network

In this paper, we study the spectral characteristics and global representations of strongly nonlinear, non-stationary electromagnetic interferences (EMI), which is of great significance in analysing the mathematical modelling of electromagnetic capability (EMC) for a large scale integrated system. We firstly propose to use Self-Organizing Feature Map Neural Network (SOM) to cluster EMI signals. To tackle with the high dimensionality of EMI signals, we combine the dimension reduction and clustering approaches, and find out the global features of different interference factors, in order to finally provide precise mathematical simulation models for EMC design, analysis, forecasting and evaluation. Experimental results have demonstrated the validity and effectiveness of the proposed method.

Using d–q Transformation to Vary the Switching Frequency for Interior Permanent Magnet Synchronous Motor Drive Systems

The switching frequency is one of the most important control parameters of the dc/ac inverter. In most motor drives for transportation, it is set as a constant value at some specific torque or speed. The variable switching frequency pulse width modulation (VSFPWM), which changes the switching frequency cycle to cycle based on a current ripple prediction method, has been proposed in previous literatures and realized in resistance—inductance (RL) loads and induction motors (IMs). It proves effective to increase the overall system efficiency and improve electromagnetic interference (EMI) performance. However, the previous current ripple prediction method encounters difficulty in dealing with more complex motors, e.g., interior permanent magnet (IPM) motors, which is widely used in electric vehicles. As a result, the benefits of VSFPWM cannot be fully utilized for IPM drive systems. This paper proposed a new current ripple prediction method using the d–q transformation instead of the conventional Thevenin equivalent circuit method and successfully implemented VSFPWM to IPM drives. Simulation and experiments on a 400-V IPM test bench validated the effectiveness of the method, which will vary the switching frequency from cycle to cycle in order to 1) restrain the three-phase current ripples; 2) increase the overall system efficiency; and 3) enhance the system electromagnetic capability (EMC).