High frequency grid impedance analysis with three-phase converter and FPGA based tolerance band controller

Abstract

The electrical grid features show a frequency dependent impedance. To know their value in the frequency range between grid fundamental frequency and up to frequency's in the kHz-range is very useful. It contributes to optimize energy feed in as well as from decentralized converter equipped renewable sources. This paper presents an advanced frequency dependent impedance measurement system for the energized grid with a high frequency range. For these grid impedance measurements a fast switching three-phase high frequency converter with a fast and robust control is required. Control is carried out by a FPGA based tolerance band or hysteresis control. The power circuit for high frequency (up to 10 kHz) measuring current is presented and measurements are shown and analyzed.