Application of a sinusoidal internal model to current control of three-phase utility-interface converters

Three-phase voltage-source converters are used as utility interfaces. In such a case, the converter line currents are required to track sinusoidal references synchronized with the utility grid without a steady-state error. In this paper a current control method based on a sinusoidal internal model is employed. The method uses a sine transfer function with a specified resonant frequency, which is called an S regulator. The combination of a conventional proportional-integral, (PI) regulator and an S regulator is called a PIS regulator. The PIS regulator ensures that the steady-state error in response to any step changes in a reference signal at the resonant frequency and 0 Hz reduces to zero. An experiment was carried out using a 1-kVA prototype of three utility-interface converters, a voltage-source rectifier, an active power filter, and static synchronous compensator. Almost perfect current-tracking performance could be observed.