In this paper, a methodology for the control design and low-cost HIL simulation of a multivariable interconnected Smartgrid is proposed. For this purpose, kalman filtering is implemented to obtain the gain to minimize the quadratic error. A discrete-time linear quadratic optimal controller is proposed for the multivariable system, where the controller is computed in real time for the discrete state space model of the interconnected smartgrid. The proposed controller is evaluated in a low-cost real time (hardware-in-the-loop) HIL structure by considering two microcontrollers, the first one is the Texas Instruments C2000 and the second one is the Arduino DUE. Two evaluations are performed: the system simulated in Matlab and the system implemented in real time on microcontrollers which have external disturbances. As a result, effective regulation of the closed-loop system is observed, in which the reference is effectively tracked.