Decentralized STATCOM/ESS Control for Wind Generators

Wind energy has emerged as the fastest growing source of renewable energy and is expected to see continued strong growth in the immediate future. Wind power generation is required to provide a certain reliability of supply and a certain level of stability. Motivated by the above issues, many grid operators have started to introduce new grid-codes which treat wind power generation in a special manner. Most interconnection standards today require wind farms to have the ability to withstand severe faults, usually called the fault ride-through (FRT) capability or, in some cases, the low-voltage ride-through (LVRT) capability. The design and implementation of a new control scheme for reactive power compensation, voltage regulation and transient stability enhancement for wind turbines equipped with fixed-speed induction generators in large interconnected power systems is presented in this chapter. The low-voltage-ride-through (LVRT) capability is provided by extending range of the operation of the controlled system to include typical post-fault conditions. A systematic procedure is proposed to design decentralized multi-variable controllers for large interconnected power systems using minimax output-feedback control design method and the controller design procedure is formulated as an optimization problem involving rankconstrained linear matrix inequalities (LMIs). In this chapter it is shown that STATCOM with energy storage system (STATCOM/ESS), controlled via robust control technique, is an effective device for improving the LVRT capability of fixed-speed wind turbines.