Grid Connected Photovoltaic Power System with Active Power Filtering

Abstract

The solar energy become a popular and environmental friendly solution for meeting demand of the increasing demand for electric power. The photovoltaic system has now become grid connected system from stand-alone system as it was previously. Now feed in tariff (FIT) has made it a distributed energy (DG) sources in many countries around the world.
The power quality of the grid is being degenerated by the injection of the current by the grid connected PV system with the converters used for DC to AC conversion or the inverter functioning unaware of the harmonics injected by it. Additionally the voltage harmonics is also introduced by the current injected with filtering. Especially the increasing penetration of the DGs in low voltage networks which uses the PV energy as source has had worsened the situation. The rising use of non-linear load has resulted in excessive harmonic pollution resulting in losing of reliability and power quality of the system. Active power filtering can be performed by following various theories one such popular theory is the one using instantaneous power theory proposed and cross vector theory. Other theories like power balance theory and Synchronous reference frame is also effective in APF for distorted and unbalanced supply along with power injection from PV source.
Combining the PV system and APF through a single three phase voltage sourced inverter (VSI) thus making the full utilization of the switching devices at all times is the objective achieved. The PV power is used for the DC voltage regulation and the surplus power from the PV source is also fed through the voltage source inverter (VSI) to the load or the grid. For improving the efficiency single stage conversion is used. Current control is used with reference current generated for both the filtering of harmonics and the MPPT of PV panel and the DC voltage regulation. P&O algorithm with variable perturbation size was used for the efficient tracking of the MPP.