Predictive Control of Power Converters and Electrical Drives

11.4 Examples

11.4.1 Switching Frequency Reduction

A predictive current control scheme with reduction of the switching frequency for a NPC inverter was presented in Chapter 5. In this scheme, the cost function presents a primary term for current reference tracking and a secondary term for reduction of the switching frequency:

11.2

The secondary term corresponds to the predicted number of switchings involved when changing from the present to the future switching state. Thus by increasing the associated weighting factor λ_sw it is expected that this term gains more importance in the cost function and forces a reduction in the switching frequency, an effect that can be clearly seen in Figure 11.2a. This figure has been obtained by performing several simulations, starting with λ_sw = 0 and gradually increasing this value after each simulation.

Figure 11.2 (a) Weighting factor influence on the current error and the device average switching frequency f_sw. (b) Results comparison for different weighting factors (load current and load voltage) (Cortes et al., 2009 © IEEE)

It can be observed in these results that a reduction in the switching frequency introduces higher distortion, affecting ...