Implementation of Low Cost FPGA Based Digital Modulation Techniques for the Suppression of EMI and Improvement of Power Factor for Three-Phase Grid Connected P-V Inverters

Direct-Sequence Spread-Spectrum (DSSS) modulation techniques are proposed, for the suppression of EMI and improvement of power factor in a three-phase grid connected Photo-Voltaic (PV) inverter. Under DSSS modulation, Binary Phase Shift Keying (BPSK) and Quadrature Phase Shift Keying (QPSK) modulation techniques are proposed for the first time for such an application. These digital modulation techniques are implemented through a compact low-cost SPARTAN Field Programmable Gate Array (FPGA), by developing a suitable VHDL coding for producing the required switching pulses. An extensive comparative analysis is presented between the proposed modulation techniques and bit-stream modulation technique with the conventional Sinusoidal Pulse width modulation (SPWM) technique. It is inferred from the implementation of DSSS modulation techniques, the EMI and Total Harmonic Distortion are reduced and power factor is improved significantly in comparison with bit-stream modulation and SPWM techniques.