Risk Reduction of SSO and Enhance the Stability in DFIG Control Systems Using Multi-Input Multi-Output State Space Methodology

Doubly-fed induction generators (DFIGs) have gained widespread acceptance in modern wind energy conversion systems. The stability and dynamics of power systems involving DFIGs have recently become salient issues. With the use of high power voltage source converters (VSCs) -based DFIG wind farms connected to series capacitors, sub-synchronous dynamics usually exist which reduces the overall damping and results in unstable dynamics. This paper investigates the sub-synchronous interactions (SSIs) by using eigenvalues and modal analysis tools, proposes sub-synchronous damping controller, which is integrated to the grid side converter as well as rotor side converter. Furthermore, this SSI damping controls are designed using multi-input multi-output (MIMO) approach. This provides greater flexibility in using several measurements and control inputs. Thus, this robust technique is able to properly damp the sub-synchronous resonance in a power system with series-compensated line.