Photovoltaic inverter without phase-locked loop

Do three-phase inverters need grid voltage phase detection?

Abstract: Three-phase inverters for grid-connected applications typically require some form of grid voltage phase detection in order to properly synchronize to the grid and control real and reactive power. This phase detection is usually based upon some type of grid voltage sensing.

Can grid-following inverters regulate power exchange with the grid?

Abstract: This paper proposes a power-synchronized control strategy for grid-following inverters (GFLIs) to regulate their power exchange with the grid without any need for sensing/regulating the point of connection voltage.

Is there a phase-locked loop in a grid current-control scheme?

However, in this work, a method is proposed, whereby the phase angle of the grid can be accurately identified solely via the grid current feedback. In the proposed current-control scheme, the only measurement is the output inverter current, and no phase-locked loop (PLL) exists within the scheme.

What is a phase-locked loop (PLL) in a current-control scheme?

In the proposed current-control scheme, the only measurement is the output inverter current, and no phase-locked loop (PLL) exists within the scheme. This phase observer is incorporated into a current controller, which can manage the injected power to the grid.

How does a closed-loop control system work?

To summarize, this scheme archives current control for a grid-connected inverter using only current feedback. In comparison, traditional methods require voltage and current feedback along with a PLL to synchronize with the grid creating a cascaded closed-loop control system.