Fault Ride Through with Conformance to Grid Voltage Limits in Photovoltaic Grid Connected Inverters.

Abstract

Short-duration voltage sags and swells are common in utility grids. This can activate the over-voltage/under-voltage protection relays in grid-connected solar inverters, thus disconnecting them from the main grid. This rapid separation might trigger a catastrophic voltage breakdown in utility networks with a substantial proportion of energy originating from solar power plants. Furthermore, the ensuing power imbalance might cause frequency or angular instability in the main grid. This paper presents a control technique capable of accomplishing both high voltage ride through (HVRT) and low voltage ride through (LVRT) in grid-connected solar inverters. When voltage sags occur, the provided control technique boosts the terminal voltage to meet the utility-regulated voltage restrictions. In the event of a voltage surge, the control technique decreases the terminal voltage to meet the utility's voltage limitations. The conformance to utility set voltage band can be achieved only in case of photovoltaic power plants with large power rating. The control given also decreases the voltage imbalance factor to the grid norms. This reduces the double frequency power flow oscillations in the inverter. The inverter's remaining power capacity is used to support the grid for real power. The inverter is used to its full apparent power capacity. These multiple fault ride through objectives are met while adhering to the inverter's maximum current capacity restriction. The control technique is evaluated for various voltage sags and swells in the Matlab/Simulink environment. This paper presents the findings.