Prediction of the Average Value of State Variables for Modulated Power Converters Considering the Modulation and Measuring Method

A method is developed to predict, at every sampling instant, the average value of the system variables in a power converter. To achieve this, a model of the converter is used, incorporating the modulation method and the type of analog-to-digital converter, either a conventional sample-and-hold or a sigma-delta converter. The measurement given by the analog-to-digital converter is used to predict the time progress of the system variables during the present switching period and then to evaluate its average value, even before the period is completed. The method allows us to obtain simultaneously the average value for currents and voltages, to get rid of the delay introduced by filtering, and to avoid aliasing in the measurement. An example is given based on the buck converter. It is also shown experimentally how different types of measuring methods influence the performance of the closed-loop control.