Current Control of AC/DC Thyristor Converter with Model Reference Adaptive Control

Abstract

In current control systems of AC/DC thyristor converters, digital PI controllers are usually used. But in case of lacking the knowledge about the parameters of the systems, it is difficult to choose appropriate values of gains. Moreover, the control characteristic of a PI controller will change when the input signal reaches its upper or lower bound. This paper presents a new controller by using MRAC (Model Reference Adaptive Control) theory. First, the unified discrete-time model for the full range of the control angle is derived. Next, based on the strict model and the approximate one respectively, two design methods of the MRAC controller are proposed. With the approximate model, the number of the identified parameters can be reduced and the convergence speed of the patameters is high. Finally, the results of computer simulation and experiment show that the MRAC controller is stable, and it's dynamic characteristic is much better than that of PI controllers.