Novel control of grid-tied solar PV for enhancing transient stability limit at zero and high penetration levels

Power grids globally are currently facing challenges in inter-connecting larger capacity solar farms due to their inadequate power transmission capacity. This work proposes a novel control of grid-tied photovoltaic (PV) solar farm to improve transient stability limit and therefore improved power transfer capability of the transmission line. When solar PV output suddenly goes to zero, this new control scheme makes the inverter perform similar a STATCOM-a flexible AC transmission system (FACTS) device, provides voltage regulation at the point of common coupling and improves stability and subsequently the power transfer limits. During the sunny time, solar PV farm inject real power in to the grid via inverter, this new control makes the solar farm inverter provide voltage control with the remaining inverter capacity and thus increases power transfer limits significantly. To validate the proposed control, a Matlab/Simulink based simulation study is presented in two scenarios (i) 3-phase fault is applied on the test system under various PV penetration levels (ii) When solar PV output suddenly goes to zero. Results of the simulation confirm that augmentation in transient stability limit is achieved using proposed control.