Power conditioning system for grid-connected photovoltaic system

• A photovoltaic system with integrated active power filter is designed.
• The grid current, not output current, is shaped to be a sinusoidal current.
• A repetitive controller is designed for current control loop.
• Non-active components analysis for acting as active power filter is not necessary.
• Only one sensor for current detection plus two voltage sensors are required.

This study develops a new control strategy for an expandable grid-connected photovoltaic (PV) system. The proposed system performs dual functions of a PV generation and an active power filter, or either one. To this end, the grid current, instead of output current of the converter, is shaped to be a sinusoidal current in phase (or opposite phase) with the grid voltage. Furthermore, its reference current is generated in multiplying the voltage loop controller output by the grid voltage waveform, and therefore non-active components analysis for harmonics elimination and reactive power compensation in the conventional design is not necessary. As a result, the algorithm is simple and easy to implement, and only one sensor for current detection plus two voltage sensors are required. Experimental results verified the effectiveness of the proposed method.