©　2018　by　the　authors.　This　study　aims　to　present　a　novel　proportional-integral-derivative-resonant　law-based　sliding　mode　current　control　strategy　with　online　inductance　estimator　(PIDR-SMCC-OIE)　for　voltage　source　converter　medium　voltage　direct　current　(VSC-MVDC)　system　converter　stations　under　unbalanced　grid　voltage　conditions.　A　generalized　current　reference　calculation　method,　by　which　the　ratio　of　the　amplitude　of　the　active　power　ripple　to　that　of　the　reactive　power　ripple　can　be　continuously　controlled　without　current　distortion　is　presented.　A　dynamic　model　of　the　current　control　errors　in　the　positive　sequence　synchronous　reference　frame　is　developed,　and　a　PIDR　law-based　sliding　mode　current　controller　is　designed,　where　derivatives　of　the　current　references　are　obtained　by　simple　algebraic　operations.　An　OIE　adopting　the　dynamic　filtering　method　and　gradient　algorithm　is　proposed　to　further　improve　system　robustness.　In　this　OIE,　the　converter　pole　voltages　are　obtained　by　computation　utilizing　the　gate　signals　of　the　switching　devices　and　the　DC　bus　voltage,　so　that　no　additional　voltage　sensors　are　needed.　To　verify　effectiveness　of　the　PIDR-SMCC-OIE　strategy,　simulation　studies　on　a　two-terminal　VSC-MVDC　system　are　conducted　in　PSCAD/EMTDC.　The　results　show　it　can　provide　satisfactory　performance　over　a　wide　range　of　operating　conditions.