An adaptive framework for mitigating current harmonics caused by distributed energy resources

When connected to distribution networks with distorted grid voltages, inverters can easily produce high levels of current harmonics. When these networks have high interface impedances, the control schemes designed to mitigate these harmonics can easily become destabilized. This paper demonstrates a multirate controller that can adapatively generate harmonic currents as needed at frequencies up to nearly half the sample rate. The controller is shown to be stable even with purely inductive grid impedances as high as 10% per unit. Both simulation and experimental results are presented.