Harmonic compliance is necessary for obtaining energization (EON), interim (ION), and finale (FON), operational notifications, for grid-connection of the inverter-based resources (IBR) plants to the distribution and transmission grids. Generally, the harmonic compliance shall be proven by simulation studies using harmonic impedance envelopes representing various operation regimes of the grid and provided by the grid operator. The harmonic impedance envelopes may range from tens ohms up to several thousand ohms with a step by one ohm for each relevant integer harmonic and interharmonic order. The grid operator may request the simulation results for the impedance envelopes with 1-ohm resolution.

Conventional, commercially available methods conduct load-flow (LF) followed by (HLF) harmonic load-flow simulations in each point of the impedance envelope for each harmonic order that is very accurate but extremely time consuming.

This presentation presents a fast simulation method for assessing harmonic compliance of inverter-based resource (IBR) plants at high accuracy. The method identifies a couple of critical points within the envelope and interpolates the solution within the entire impedance envelopes without execution of LF and HLF. High accuracy of the method is achieved by an approach that resamples of solving optimization functions and demonstrated by direct comparison to the solution by LF and HLF simulations. The demonstration is for real-life, anonymized cases.

The method applies for the IEC (balanced) and the Phase-Correct (unbalanced) harmonic assessments at high accuracy, both magnitudes and phase angles for the Phase-Correct simulations, and with an execution speed that is up to hundred times faster than conventional methods.

The motivation behind development of the method is that the compliance studies shall be fully completed and approved by the grid operator prior to granting operational notifications.