A DQ Synchronous Reference Frame Current Control for Grid Connected Photovoltaic Systems using Single Phase Cascaded H Bridge Multilevel Inverter

Abstract

This paper projects a high performance decoupled current control using a dq synchronous reference frame for single-phase inverter. For the three-phase inverter the conversion from AC to DC with Proportional Integral controller grants to obtain steady state error for AC Voltages and currents but has a few challenges with the single-phase systems. Hence, an orthogonal pair (β) is created by shifting the phase by one quarter cycle with respect to the real component (α) which is needed for the transformation from stationary to rotating frame. The synchronous reference frame control theory helps in controlling the AC voltage by using DC signal as the reference with the proportional integrator controllers. The implementation of the control is done with two-stage converter with LCL filter for a single-phase photovoltaic system. A modified MPPT Incremental conductance algorithm along with decoupled current control helps in regulating the active and reactive power infused into the grid where the power factor is improved, the efficiency of the system is increased above 95% and total harmonic distortion for current is also reduced to3%. The results have been validated using MATLAB.