Single phase transformerless photovoltaic inverter with reactive power control

Abstract

The main objective of this paper is to understand the application of single phase grid tied photovoltaic inverter with reactive power control using three level voltage source inverter (VSI) configuration. For its implementation, a least complex grid synchronization approach was used for the generation of parallel and orthogonal components of the grid voltage in an efficient manner using various computing techniques to generate a synchronized current reference value in the current control loop. An improved H6 single-phase inverter topology ensures the elimination of the common-mode leakage current in the transformer-less photovoltaic grid-connected system. In addition this topology is also capable of withstanding the low input voltage similar to full-bridge inverter without causing any fault. The H6 inverter topology allows both unipolar Sinusoidal pulse width modulation (SINUSOIDAL PWM) as well as the bipolar (i.e. double frequency) SINUSOIDAL PWM control techniques for three-level output. Two additional switches are decoupled on the dc side for higher efficiency and convenient thermal design. Additionally, the unipolar-frequency SINUSOIDAL PWM facilitates higher frequency and low current ripples thereby reducing total harmonic distortion of the grid-connected current to a great extent.