Selective Harmonic Compensation in SPC Grid-Forming Converters for Improving Power Quality in Weak Grid

Abstract

The expansion of renewable energy sources highly increased the number of grid-connected converters associated to PV and wind in power plants as well as in residential areas. The appearance of voltage harmonics, which are typically generated by a large number of devices, is a common issue in weak grid environments and it is transitioning to the main utility grid. This harmonic distortion is significantly increasing due to the interaction between electronic power converters and the network, which not only contribute to damage other equipment connected to the same point of common connection (PCC), but also increase the losses and saturation of the transformers in the line. While previous studies have extensively addressed this issue for grid-following power converters, the harmonic control in parallel grid-forming converters, particularly those based on virtual synchronous emulation, remains underexplored. This paper intends to provide a solution focused on providing a selective harmonic control for synchronous power controller (SPC) based power converters. The proposed solution enables the parallelization of power converters to naturally share the harmonics attenuation effect at the PCC. The methodology is presented and validated through real-time simulations as well as experimental tests conducted in a 200 kVA microgrid testbed.