Photovoltaic inverter frequency locking

What is a phase-locked loop control strategy for a grid-connected photovoltaic inverter?

Based on that, a phase-locked loop control strategy for the grid-connected photovoltaic inverter is designed on the customized IP core technology of FPGA. The strategy realizes real-time tracking and adjustment of the phase difference between the photovoltaic inverter system and the grid.

How to synchronize an inverter with a grid?

To synchronize the inverter with a grid, the phase-locked loop plays a major role in the inverter control. Generally, a basic synchronous reference frame based phase-locked loop is used. The basic SRF phase-locked loop tracks the input signal phase and frequency using the closed-loop feedback control loop.

How do inverter controls work?

The inverter controls regulate the power delivered to the grid, the terminal voltage, and also maintain the microgrid frequency. The proposed control scheme uses a phase-locked loop (PLL) to establish the microgrid frequency at the inverter terminals, and to provide a phase reference that is local to the inverter.

How many control loops does a GFL inverter have?

GFL consists of two control loops, namely the slower voltage control loop and the faster inner current control loop . The GFL inverter is not able to regulate the voltage and frequency of the system directly and hence cannot operate when voltage or frequency instability occurs in the power system.

Why does switching frequency vary in a grid-connected photovoltaic system?

Because the rated power of inverters limits the choice of devices in filter design, the switching frequency also varies . In a grid-connected photovoltaic system, two distinctive topologies exist: the multi-string power station and the centralization power station.

Does phase lock ring affect grid-connected system in a weak grid environment?

In order to study the effect of phase lock ring on the grid-connected system in a weak grid environment, comparing the inverter output impedance bode diagram when considering and without phase lock ring, the inverter output impedance diagram in two cases is shown in Fig. 5.