Unit Partition Method for the Resonance Research in the Dc-link Busbar of Back-to-back Converter

The dc-link capacitor current harmonics in a back to back type wind turbine power converter may get deteriorated due to the resonance in the busbar impedance network. The unexpected capacitor current and thermal issues are even worse when laminated busbar is not used due to the low cost consideration. Corresponding analysis and design guide for these dc-link busbar issued are missing. The main challenge lays in the accurate analysis of resonance in the high-order and multi-port dc-link network. In this paper, a unit partition method is proposed and successfully estimated the inherent resonance frequency and the accompanied frequency. Then the resonance frequencies adjustment and harmonic current depression is achieved following the proposed method. It is shown that the RMS value of dc-link capacitor current gets reduced by 24.5%.