New control strategy to allow the photovoltaic systems operation under grid faults

This paper presents a new control strategy that allows the photovoltaic system operation under grid faults without overcurrent and assuring grid sinusoidal currents. The current limiter is made indirectly by using an active power limiter that is calculated dynamically based on the grid positive-sequence voltage. The paper also shows that the classic control strategies used in the PV systems cause harmonic current injections on the electrical grid and dangerous overcurrents when voltage sags occur. The strategy presented here overcomes these drawbacks and allows the inverter operation under any unbalanced condition. The control is made on stationary reference frame using Proportional-Resonant current control. This new control strategy is compared to the classic strategy through simulations in PSCAD/EMTDC and the experimental results prove its effectiveness.