DC-Link Capacitor Sizing Considerations for HEV/EV e-Drive Systems

Paper #:
  • 2017-01-1234

  • 2017-03-28
Dc-link capacitor sizing considerations are discussed for HEV/EV e-Drive systems. The capacitance value of the dc-link in HEV/EV e-Drive systems affects numerous factors. For example, some of the most significant are the system stability and the maximum tolerable dc-bus transient voltage with operating point change or with worst-case energy dump into the capacitor. Also to be paid attention is the equivalent series resistance and inductance of the capacitor module, because they affect thermal behavior of the capacitor module and voltage spikes occurring across a power semiconductor switch with its every turning-off instant, respectively. In addition, these factors are cross-coupled with other power-stage component parameters, control structures and controller gains. Furthermore such effects and cross-couplings are operating point dependent. This makes the dc-link capacitor sizing for HEV/EV e-Drive systems a complex task and it looks as if this is done primarily by empirical manner with possibly more than enough safety margin. It appears accordingly that no systematic step-by-step methodology for the capacitor sizing has been discussed in public domain. In this paper, a list of the items to be considered for such a systematic dc-link capacitor sizing is presented and a detailed description follows for each item. The above-mentioned cross-coupled matters and the resulting trade-offs are also discussed. Potential issues caused by the use of emerging wide-bandgap semiconductors are briefly accounted as well. Taken as an example is an HEV e-Drive system consisting of two electric machine drive inverters and a dc-dc converter interfacing a high-voltage battery and the dc-link.
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