Research On Harmonic And Its Compensation Control Of High-Power Dc Electrically Driven System Designed For Mine Shafts

The efforts to improve the power factor in the power grid and reduce the ripple in the load side, in the dragging fields of high-power direct current motors in the mines result in the prevailing use of sequential control converters for DC motor power supplies. The advantage accruing from improvement in the grid power factor as a result of the application of sequence control, but the harmonic hazards caused on the grid can not be ignored.This paper provides an analysis of harmonic waves of the high-power DC dragging systems based on the sequence control in large-scale mines. The analysis shows that when the sequence of triggering angles in the two sets of bridge changes, there still exists the harmonic of 6 k±1 in the currents in the transformer network side, that is, the harmonic of the 5th,7th,17th,19th,…, and both amplitudes of the fundamental and the harmonic are related toΔα. The expression of harmonic currents has been derived and the relative curves between harmonic currents and the two trigger angle differenceΔα, that is, the curve of In = f(Δα) are given. The detection of harmonic currents in DC mine hoists with the power of 1250kW, the current of 2020A, depending on sequence control converters verifies the correctness of theoretical analysis.A new PWM topology of converters is used, that is, work styles of the hybrid energy storage in DC side and series resonant to form the new type of parallel active filters with reactive and active, and resistance characteristics is given of series resonance and reactive filters.Research is carried on parallel active filters with reactive and active which verifies the correctness of the topology.The PWM harmonic control strategy of the new active filter with reactive and active is discussed, a harmonic control strategy based on the Fourier transform is brought up to compensate for harmonic of the5th, 7th, 11th, 13th in three-phase power system. The simulation of control strategies by MATLAB and Pspice is described and thus the correctness of the control strategy is verified.The proposed control strategy is accomplished through TMS320F240 DSP.The corresponding input and output interface circuit of DSP is designed , the converter logic of PWM signals is given, the software blockset is drawn up to realize control strategies.In the laboratory, experimental prototypes are constructed to carry out experimental study. The study finds that with the real-time requirement of active power filter, the digital control strategy with DSP as the core achieves the digital control of active power filter, which verifies the effectiveness and its implementation.Errors produced by the two major restriction on compensation are estimated, The first restriction is the delayed compensation reference caused by digital signal processing equipment by sampling and processing process; the second one is the di/dt ability of the switching converters. Error models are deduced arising from these two restrictions. Experimental results show that the accurate determination of error impacts arising from these two restrictions on compensation can be achieved by the model which has been obtained in this paper.