Harmonic Mitigation in Traction Supply Substation Using Cascaded H-Bridge Converter

Abstract

<span lang="EN-US">The conventional three-level inverter has been proposed to act as a recuperating converter in Traction Supply Substation. This converter is mainly used to feed back the regenerative braking energy to the grid. However, passive filter is desired to mitigate the current and voltage harmonics. Therefore, this paper investigates the possibility to use a seven-level Cascaded H-Bridge (CHB) converter as the recuperating converter without additional filtering. The proposed converter is modeled with MATLAB/Simulink simulation software. It is then simulated with two potential modulation schemes, namely Phase-Shifted PWM (PS-PWM) and Phase-Disposition PWM (PD-PWM). The quality of AC waveforms produced by these two modulation methods is compared and studied. The results show that PS-PWM technique is preferable for this application as it offered a clean AC current waveform with less than 5% harmonic distortion. However, a twenty-one-level CHB was predicted to comply with the 8% voltage harmonic requirement.</span>

Comparative study of two potential recuperating converters in DC railway electrification system for harmonic mitigation

“…The common modulation techniques used in these converters can be classified as carrier-based modulation techniques, Space-Vector-Modulation (SVM) methods, and Selective Harmonic Elimination (SHE) [16,18,20]. Carrier-based modulation is simple for implementation but this method introduce high switching losses.…”

“…In addition, the AC grid and rectifier transformer are modeled as RL-load configured in Y-connection. The load parameters are fixed according to [16]. Table 1 presents the simulation parameters.…”

“…Figure 2 shows the proposed configuration of a multilevel converter which used to restore the regenerative energy back to the utility grid. In [16], a 17-level Cascaded H-Bridge (CHB) converter which is modulated with Level-Shifted Pulse-Width-Modulation (LS-PWM) technique manages to keep the voltage distortion as low as 8%. Conversely, the configuration of the power circuit is complex by involving approximately 96 units of power semiconductors.…”