  We compute the $\mathcal{N}=2$ SUSY algebra of the massive Grassmannian sigma
model in 2+1 dimensions. We first rederive the action of the model by using the
Scherk-Schwarz dimensional reduction from $\mathcal{N}=1$ theory in 3+1
dimensions. Then, we perform the canonical quantization by using the Dirac
method. We find that a particular choice of the operator ordering yields the
quantum SUSY algebra of the $Q$-lumps with cental extension.
