Feedback Current Control Techniques for a Single-Phase Grid-Connected Photovoltaic System

The modeling and control of 1-Φ grid-tied voltage source inverter is discussed in this paper for solar photovoltaic (PV) applications. The grid-connected inverters are commonly used to inject the current from the PV system to the utility grid. Generally, the grid-connected inverters are operated with the pulse width modulation technique which results harmonics in grid-current. A third-order LCL filter is used to eliminate these harmonics. However, the use of LCL filter leads the high complexity of the overall system and affects its stability. In order to maintain unity power factor and power quality of the grid-current, a proper current controller is highly essentials for a grid-tied PV system. A review on the single-loop grid-current control techniques for the inverter is discussed here by taking current feedback from grid-side inductor and inverter side inductor. Commonly used proportional-integral (PI) controllers are used in both the cases. In this paper, the step-by-step design procedures of the grid-current loop and its comparison in terms of its steady state performance are discussed. The steady state performances of both the controllers are evaluated on the basis of total harmonic distortion (THD). Finally, the best possible current control scheme is suggested by using experimental results.