Harmonic Current Analysis of the PSM HVPS Modules under Voltage Distortion

To reduce the errors caused by current superposition with many power modules in Pulse-step modulation (PSM) high-voltage power supply (HVPS), it is necessary to establish more accurate current models of the PSM power modules that are supplied by different windings. The electrical models of power modules connected by different windings (wye and delta) are established, and the current mathematical models in windings are deduced, respectively. The "correlation function" is introduced to establish the relation of the harmonic voltage among two power modules connected to different windings when calculating the harmonic superposition. The current mathematical models in windings of two power modules are verified by simulation, and the performance of the two methods of the correlation function proposed is compared to the result of the simulation. The research shows that the current waveform generated by the power module in the winding under the distorted voltage can be obtained by the mathematical models, and the more accurate current superposition by the correlation function which establishes the relationship between the mathematical models in the two windings. Besides, the current in the AC side of power modules is significantly affected by the different harmonic ratio of voltage and its phases.