  Real-time power dispatch (RTD) can coordinate wind farms, automatic
generation control (AGC) units and non AGC units. In RTD, the probable wind
power forecast errors (WPFE) should be appropriately formulated to ensure
system security with high probability and minimize operational cost. Previous
studies and our onsite tests show that Cauchy distribution (CD) effectively
fits the leptokurtic feature of small timescale WPFE distributions. In this
paper, we propose a chance-constrained real time dispatch (CCRTD) model with
the WPFE represented by CD. Since the CD is stable and has promising
mathematical characteristics, the proposed CCRTD model can be analytically
transformed to a convex optimization problem considering the dependence among
wind farms outputs. Moreover, the proposed model incorporates an affine control
strategy compatible with AGC systems. This strategy makes the CCRTD adaptively
take into account both the additional power ramping requirement and power
variation on transmission lines caused by WPFE in RTD stage. Numerical test
results show that the proposed method is reliable and effective. Meanwhile it
is very efficient and suitable for real-time application.
