Fast harmonic analysis for PHIL experiments with decentralized real-time controllers

This paper proposes and implements, a harmonic analysis technique used in microgrids for inverter power control when measured voltage and current signals are passed over a communication link with considerable latency. Using frequency-shifting and filtering techniques, the measurement is converted to magnitude and phase information and passed over an asynchronous communication link to another controller, where the original waveform is recovered with delay compensation. The method allows accurate power calculations and grid synchronization over distributed prosumer controllers. The proposed method can work at different execution rates, depending on real time (RT) workload, and is shown to be robust against step changes, harmonics and communication delays. The method is demonstrated with two PHIL experiments at the CoSES, TU Munich lab in grid connected and island mode.