Rotating Vector Holder for Wide-Band-Gap Based Inverters Switching at Very High Frequency

The performances of the current controllers are strongly affected by a low ratio between the electrical time constant and the sampling period, that introduces a distortion in the current waveform. A similar effect can be observed also in the case of a low ratio between the fundamental electric period and the sampling one. Often, a multi-rate current controller is used in these cases, i.e. the control voltage is applied at a switching frequency higher than the sampling one. In this paper the multi-rate feature is exploited to introduce a rotating vector holder to overcome the distortion issue. The discrete-time model for a three-phase RL load supplied with the proposed holder is derived. The direct design of discrete current controller is revised accordingly. Simulations and experiments are presented to prove the advantages of the proposed solution.