Fast self-synchronization between low-voltage micro grid and inverter using virtual synchronous converter

Abstract EN

In this paper, a fast self-synchronization known as virtual synchronous converter (VSCon) between single-phase microgrid and inverter in low-voltage microgrid, has been developed in Matlab/Simulink.

The idea is to any phase locked loop (PLL) circuit for inverter-microgrid synchronization in order to improve the synchronization time.

As known, it is difficult and lengthy process to tune the PLL gain parameters to reach suitable performance for synchronizing among the voltage, phase-angle and frequency between them.

Due to this problem, a fast self synchronization technique is needed in order to minimize the time losses at the microgrid connection.

Therefore, the VSCon has been developed which is based on the synchronous generator mathematical model but in virtual environment representation.

It has been applied in the inverter control for generating switching pattern to the inverter switches in order to respond to the grid voltage for improve the synchronization.

For a prove of concept, several simulation tests in MATLAB models have been conducted, in order to see the effectiveness of this VSCon.

First test has been conducted, when a 240V, 50Hz frequency grid source is used for observing the self-synchronization the system with the power flows output.

Furthermore, the next test is conducted when the grid frequency is changed from the rated frequency at 50Hz to 51Hz and the result shows the VSCon in inverter control takes nearly 40ms to synchronize to this new frequency value.

The test on grid phase-angle delay also been tested when ac grid voltage has 150 phase delay.

As from all the results, the improved inverter control with VSCon structure is able to have fast and self-synchronized between the invertergrid connection before the power from the inverter can be transferred.