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.