Accuracy Analysis of the Zero-Order Hold Model for Digital Pulse Width Modulation

This paper analyzes the accuracy of the zero-order hold (ZOH) model for the digital pulse width modulator (DPWM) in the s-domain. The s-domain model and the exact z-domain model for the current control of a single-phase inverter with an L-type filter are elaborated for quantifying the deviation of the ZOH model for the DPWM. The influences of the different computational delay and duty-cycle update modes on this deviation is analyzed in detail. The compensation method for this deviation of the ZOH model is proposed for accurately predicting the stability region of the control system in the s-domain. Simulations and experimental tests are executed to verify the effectiveness and correctness of the theoretical analysis.