Comparison of harmonic detection methods applied in a photovoltaic inverter during harmonic current compensation

Traditional harmonic current detection methods track all harmonic contents of the load and the control tuning tends to be complex with low flexibility. However, several applications require a harmonic detector method able to track the higher load harmonic current. This work analyses harmonic detectors based on Discrete Fourier Transform (DFT): Fast Fourier Transform (FFT) and Iterative Discrete Fourier Transform (IDFT) and the detector based on Second Order Generalized Integrator (SOGI-PLL) structure. A comparison of the load harmonic current detection methods was done by variation in the load current and in the fluctuation of the grid frequency. Furthermore, the methods were applied in an adaptive current harmonic control strategy applied in multifunctional three-phase photovoltaic inverter. Simulation results showed that the DFT methods are faster and more accurate in the harmonic detection than the SOGI-PLL based method. However, SOGI-PLL structure is more robust during grid voltage frequency fluctuation.