A nonlinear control strategy for a grid-tie inverter that injects instantaneous complex power to the grid

A nonlinear controller for a VSC injecting power to the grid is designed. The design is based on instantaneous complex power definition. The proposed strategy results in a complex nonlinear controller where both the real part and imaginary part of the instantaneous complex power track a desired reference. It is assumed that a constant power source feeds the VSC. The input power value is needed for calculating the control law, but in this work a nonlinear observer is used for obtaining estimates of input power value and its time derivatives. In this way, the number of sensors is reduced, improving the reliability. Simulation results showing the good performance of the proposed controller are presented.