Single Phase Grid-tie Inverter Design Using PLL and MPPTTechniques

Abstract

This paper focuses on designing and implementing a grid-tie inverter, which can convert DC voltage from the PV systems into an AC voltage using pulse width modulation technique. The proposed inverter is synchronized with the local grid to provide an alternate solution for the energy generation. To obtain the maximum power from the inverter maximum power point tracking technology is used. Using MPPT, approximately 95% power efficiency was achieved. Boost converter is designed to boost the voltage from solar panels to 240V. Phase locked loop circuit is utilized to synchronize the output frequency of the inverter with that of the local utility grid. Phase locked loop circuit uses phase detector to detect the phase difference between the reference (utility grid) frequency and the quiescent (required) frequency set in Voltage Controlled Oscillator. This quiescent frequency is converted to match with the reference frequency. This converted or synchronized frequency is then used as a reference for pulse width modulation controller to generate Pulse Width Modulation waveform. Using PLL, phase or frequency matching between utility grid’s electricity and inverter’s electricity was achieved in just 0.6 seconds. In the end, filtering system is designed using LMS filter and KALMAN filter to remove the noise from inverter output. A total of -22.63 dB total harmonic distortion was achieved using Kalman filter and were proved to be better than LMS filter. The simulation results provided in this report show the efficacy of the proposed grid-tie inverter.