Inertia emulation based sliding mode control of VSC HVDC system for transmission of power from onshore wind farms to AC grids

This paper proposes a novel control method for controlling voltage source converter (VSC) based high voltage direct current (HVDC) converters present in a network consisting of a Doubly Fed induction generator (DFIG) - wind farm (WF) connected to infinite bus via an HVDC line and a parallel tie line. A new idea has been presented where inertia emulation capability of capacitors present in HVDC network has been utilized with a nonlinear control such as sliding mode control method. In this method the DC voltage reference for the control is allowed to vary with the frequency deviations in the system for emulating the inertia characteristics of the DC link capacitance and thus controlling the power oscillations. The results of the proposed method are then compared with that of conventional PI control. The simulations results obtained in MATLAB proved the effectiveness in stabilizing the oscillations in case of various transient events such as fault and power reference variations of the DC link.