Voltage saturation anti-windup for harmonic controllers in multiple reference frames

The output voltage references in grid connected Voltage Source Converters must be limited according to the available dc voltage to avoid over-modulation and windup of the current controllers. This may be especially critical for Active Power Filters (APFs), since uncontrolled over-modulation can cause unintended harmonics in the output voltage and interfere with the harmonic compensation. This paper presents an anti-windup mechanism for harmonic current controllers in Multiple Reference Frames (MFRs), which prevents controller windup. The proposed method extends the harmonic compensation capability by allowing operation of each harmonic controller into the non-linear modulation region. This is achieved by selective conditional integration of the errors in each reference frame. Simulation results are presented to demonstrate the effectiveness of the proposed anti-windup mechanism.