Efficient approach to characterising harmonic currents generated by a cluster of three-phase AC/DC converters

An efficient approach to characterising harmonic currents generated by a cluster of parallel-operated AC/DC converters in the steady state is presented. The approach is carried out in the time domain and the interactions between converters are considered. In calculating harmonic currents generated by a single converter, the Poincare map-based approach is applied to increase the computational efficiency. A solution procedure that is sequentially solving a single-converter problem with detailed model in the time domain, while the others are fixed as equivalent AC current sources, is proposed to find the overall source-side harmonic currents. The computed AC-side harmonic components of each converter current are then extracted via FFT. Solutions obtained by the proposed method are compared with those obtained by using a brute-force time-domain simulation tool, Simulink. It is shown that the AC-side harmonic currents determined by the proposed approach agree well with those obtained by the time-domain simulation tool, but the solution time is significantly reduced. Therefore, the proposed approach is useful for quantifying harmonic currents generated by a cluster of AC/DC converters and to facilitate the harmonic mitigation implementations, such as passive and active harmonic filter designs, for complying with harmonic standards such as IEC 61000-3-4 and IEEE-519. In addition, the proposed approach is suitable for characterising harmonic currents generated by other types of power-electronic devices, such as AC and/or DC drives, operated in parallel simultaneously. The solution algorithm can also be integrated into a harmonic power flow program for penetration studies to provide a fast quantification of the impact of multiple harmonic sources on the power system