Analysis of significant current tracking error and suppression of over-shoot current in grid-connected voltage source converter with abc frame control

This study proposes an analysis and specification of current loop tracking error in the grid-connected voltage source converter with direct current control. In practical applications, it is a common phenomenon that the current control loop sees a quite significant command-tracking error while the actual output current of the converter is still satisfactory, for example, for static var generators or parallel active power filters, it is exactly the reactive current and/or the harmonic current that are needed to compensate the load current. In this study, a detailed analysis is presented to investigate this confusing issue. Based on the obtained current loop transfer function, analytical expressions of the current tracking error are derived. The reasons why a significant current tracking error exists together with satisfactory compensation result are revealed subsequently. The current tracking error has a relationship with the source voltage. An over-shoot start current appears because of the current tracking error. Two new methods used to suppress the over-shoot current are also presented. Finally, the hardware experimental results verify the analysis and the methods of suppressing the over-shoot current.