Optimal Modulation for Meeting Grid Harmonic Limits Under Bounded Voltage Disturbances

Abstract

The output current and voltage of grid-connected converters must comply with grid standards. This becomes particularly challenging under non-ideal grid conditions, where harmonics - introduced by other converters connected to the point of common coupling (PCC) - act as disturbances. Even though the profile of such harmonics may be known, suggesting the possibility of mitigation, variations in the impedance between these converters and the PCC result in disturbances with uncertain (but bounded) magnitude and phase. To deal with such uncertainties and fulfill grid standards while achieving the highest possible current quality, this paper proposes a robust harmonic-constrained optimization framework for computing optimized pulse patterns (OPPs). Numerical results demonstrate the superior performance of the proposed OPPs in meeting harmonic grid standards compared to established modulation methods, despite the disturbance profile being only partially known during the OPP computation process.