Software method for harmonic content evaluation of grid connected converters from distributed power generation systems

This paper is deals with the implementation of a software control method for harmonic content evaluation in the dq synchronous rotating reference frame for grid side VSIs (Voltage Source Inverters) used in DPGS (distributed power generation systems) applications. In order to verify the performance of the proposed approach, in experiments a DC voltage source (playing the role of a generic renewable energy source) is connected to the grid using a two-level inverter. Additionally, the control structure of the grid side converter is presented the possibility of low order harmonics compensation is also discussed. A comparative study in terms of current harmonic distortion between two different proportional gain values of the PI controller running in steady state condition is made, through simulations and experiments. The comparative study is performed to demonstrate the stability and effectiveness of the PI control algorithm across a wide range of operating conditions with the software method. The analyzed structure was simulated using Simulink software and then implemented and tested at laboratory level using a dSPACE setup. The experimental and simulation results confirm that the proposed software control method achieves good current tracking, thus satisfying grid-connection harmonics standards.