DC-link capacitors are one of the components which fail the most in back-to-back converters (B2B) of wind turbine systems (WTS) with doubly-fed induction generators (DFIG). Due to its frequency and temperature dependent equivalent series resistance (ESR) additional low frequency current components, which have not been considered during the design stage of the converter, can cause significant additional losses which in turn lead to a decreasing lifetime of the capacitor. Unbalanced grid voltages in WTS with DFIG lead to low frequency components in the capacitor current's spectrum, which are caused by components from the grid-side converter as well as from the rotor-side converter because of the direct connection of the DFIG's stator to the grid. Therefore, in this paper, the study of impacts of unbalanced grid voltages on the hotspot temperature of DC-link capacitors in WTS with DFIG is proposed. A small scale laboratory demonstrator is presented and the measurement results are in accordance with the expectations based on analytical and simulations findings.