Indirect digital control of three-phase DC/AC inverter

Abstract

This paper presents an analytical design method of indirect full digital controller with a simple structure for three-phase inverter system. Most of conventional researches on the analytical design of controller have been studied about the structure of continuous-time controller, and so the final implementation of full digital controller for industrial application was complicate and anyway based on the trial and error methods for gain tuning. So firstly, two axes model of synchronous reference frame is derived to adopt a linear controller in s-domain. During this process, two decoupling terms are generated and the system is to be MIMO. Before eliminating the coupling term to make the system be SISO, the effects of two coupling terms are analyzed by RGA and simulation. And then, the controller of two-parameter structure which has no additional zero in the transfer function is designed by the CRA method and the pole-placement method in s-domain to meet the time response specification depending on the system response. To make a digital controller, the designed controller of twoparameter structure is manipulated and minimally realized. The indirect full digital controller is simulated by PSiM DLL and experimented by TMS320VC33 without any conversion of program. The simulation and experiment results show the good performance of tracking and regulation.Index Terms--Three phase inverter, digital controller design, coefficient ratio assignment (CRA) method