Determining operating voltage of a given inverter subject input parameters variations for minimum output variations: Using standard deviation approach

Abstract

In this paper, it is shown that how using simple statistical measures like the standard deviations from target value can be used to determine the operating input voltage of a given inverter. The output voltage magnitude and its quality profile are a function of both the Input DC voltage and the firing angle. Any variation in these two factors, forces the output of the inverter to vary. This method is not to be used to make changes in the design of the inverter, but rather use the existing inverter at such a voltage level and firing angle, so that the output voltage variation per unit change in any input parameters is minimum. For practically implementing the proposed method, for deciding the input operating voltage, there is no need to know the mathematical model or the topology of the inverter, but the data for calculations is generated by subjecting the inverter to different input conditions of the allowable range of voltage and firing angle. In this paper the method has been demonstrated using Matlab simulations, to show how only meeting the output voltage conditions is not sufficient, and in some cases even the THD profile too can produce comparable results, making it difficult to decide amongst the probable choices of input voltage. Simulink analysis and other statistical tools have been used to authenticate the observations and conclusions.