In　current　photovoltaic　transmission　systems,　low　voltage　ride-though　is　a　main　challenge　that　restricts　the　development　of　photovoltaic　power　generation.　In　this　study,　a　power　system　with　large　photovoltaic　(PV)　power　penetration　is　considered,　and　nonlinear　control　strategies　for　PV　power　stations　are　designed　to　guarantee　the　operation　of　PV　power　system　and　provide　enough　reactive　power　for　the　grid.　First,　the　dynamic　model　of　PV　stations　is　constructed,　and　the　control　objective　is　to　enhance　the　robustness　of　the　system　against　grid　faults.　Second,　the　state-dependent　Riccati　equation　(SDRE)　technique　is　used　to　solve　the　robust　control　problem.　The　SDRE　technique　reconstructs　a　nonlinear　system　to　a　linear-like　structure,　and　controls　the　system　through　solving　an　algebraic　Riccati　equation　(ARE)-like　approach　with　state-dependent　coefficient　(SDC)　matrices.　Comparisons　with　conventional　PI　controllers　are　performed,　and　better　control　performance　is　achieved　through　the　proposed　strategy.　©　2019　IEEE.