Frequency-division decimation of RDFT for selective harmonic suppression of 100kHz SAPF

The recursive discrete Fourier transform (RDFT) can extract the frequency components of periodic signals quickly and accurately, which makes the shunt active power filter (SAPF) capable of selective harmonic suppression. However, with the increase of SAPF switching frequency, digital signal processor (DSP) needs to complete 6l±1(l is a positive integer) characteristic harmonic current operation within 50th in a shorter switching cycle. When the switching frequency reaches 100kHz, DSP cannot complete all specified harmonic operations in each switching cycle. In order to make DSP complete as many harmonic suppression as possible, the influence of different sampling frequency on the calculation of harmonic suppression instructions is analyzed firstly, and the minimum allowable sampling frequency is determined. Then, the RDFT harmonic instructions in DSP program are processed by frequency division extraction operation to shorten the calculation amount of harmonic instructions in each switching cycle of DSP, so more specified harmonic suppression is realized. Finally, the strategy is verified on an SAPF with a switching frequency of 100kHz and a capacity of 10KVA. The experimental results show that the strategy improves the suppression ability of high-frequency SAPF significantly.