Digital Controller Design and Implementation for AC and DC Side of 3ph qZSI

Abstract

This article presents the multi-loop digital controller design of a quasi-z-source inverter (qZSI). The qZSI is a single-stage power converter and can operate in buck and boost modes. The qZSI is an economical solution for distributed generation and eliminates the need for two-stage power conversion. This article proposes a detailed step-wise digital controller design using a multi-loop control method. The controllers of the AC and DC sides are designed separately. A proportional controller is used for the inner current control loop on both the AC and DC sides. In contrast, for outer voltage loop control, the proportional and resonant (PR) controller is used on the AC side, and the proportional and integral (PI) is used on the DC side. In designing the digital controllers, the effect of the sensor gain and low pass filter (LPF) in the feedback path is also considered. Furthermore, to mimic the behavior of the synchronous generator, the droop control is used to generate the reference voltage for the AC side of the controller. The time domain simulations are carried out to verify the designed controllers. Experimental results are also presented for the validation of the proposed controllers.