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

Three phase voltage-source converters are used as a utility interface. 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 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 zero hertz reduces to zero. Experiment was carried out using a 1kVA prototype of three utility-interface-converters, a voltage source rectifier, an active power filter, and STATCOM. Almost perfect current tracking performance can be observed.