When faced with the task of developing a new current control method, it was soon realised that there was not a consistent way to prove that a newly developed current control method had made improvements over existing methods. Thus the focus of this thesis turned towards investigating what aspects a ect the delity (i.e. quality of control) of current control methods for the given voltage source inverter (VSI ) topology. The main purpose of such research would be to develop a set of criteria to justify any improvements of the new current control method over existing current control methods and also identify which particular aspects might show potential for improvement in control delity. Both aspects require a way of measuring the capabilities of present methods and therefore necessitates the establishment of desirable performance criteria. This e ectively leads to a "benchmark" approach to investigating the performance of existing current control methods. The highlights from carrying out this investigation are as follows: Phase-shift between the current output versus the reference current was observed to be proportional to the target switching frequency of the considered current control methods, which indicates an aspect of predictability that may have compensation potential. The results also showed a proportional relationship between phase-shift and blanking time, which would justify using appropriate compensation methods. Feedback delay was shown to contribute additional low-order harmonic content and thus such delays should be minimised whenever possible. A control method that performs well independent of DC bus variation will make it easier to design for, since it would be su fcient to just design the DC bus level to meet a certain controllability margin (where this margin will ensure that the system remains controllable even under transients and non-ideal assumptions).
|Publication status||Unpublished - 2010|