Analysis and Design of Controllers for Four-leg Three-Phase Inverters to decouple d and q Channels

摘要

An averange model of the three-phase four leg inverter in the synchronous referential dq0 presents a coupling between the channels d and q that produces a negative influence on the performance of the system. In this work a model averaged in discrete time is obtained to analyze the coupling and establish guidelines for the design of an internal loop of current control that allows to attenuate the coupling between channels d and q. A robustness analysis allows to verify that the system is stable for a variation of the parameters of the filter comprised from 20% to 180% of its nominal values. An external voltage control loop is designed considering channels d and q as independent SISO systems and its performance is satisfactorily verified by simulations, for different load conditions, verifying that the decoupling achieved by the internal loop was adequate.