Sampled-Time-Domain Analysis of a Digitally Implemented Current Controlled Inverter.

This paper presents a sampled-time-domain analysis to investigate the sampling effect on instantaneous switching frequency of a digitally implemented hysteresis current control (HCC) in a voltage source inverter (VSI). The generalized expression of the instantaneous switching frequency with the consideration of sampling frequency has been derived. The effect of variation in sampling frequency on effective hysteresis band and switching frequency has been analyzed. The difference between maximum to minimum switching frequency of a fixed-band HCC VSI depends on the sampling frequency of the digital controller. The sampling also generates a steady-state tracking error exceeding the fixed-band limit at the fundamental frequency for fixed hysteresis band operation. The analysis has been done to achieve fixed switching frequency with variable hysteresis band and with varying sampling period. The frequency spectrum of the load current is presented to show the effect of a digital controller. The sampling effect on the switching performance has been demonstrated for a single-phase VSI under different loading conditions. To verify the analytical results, the simulation and experimental results are obtained with the current controller implemented on a field programmable gate array-based digital controller. [ABSTRACT FROM PUBLISHER]