Achievability of Kinetic Energy Release in Wind Farm Active Power Control

Abstract

The frontier of research in wind farm active power control is moving toward exploring the potential of wind electric power systems (WEPSs) in realizing the full range of functionalities offered by conventional synchronous generators. In particular, much recent attention has been given to the topic of controlling the kinetic energy stored in WEPSs as a means to maintain transient frequency stability during a power imbalance. In this chapter, we look into this topic from a theoretical standpoint and ask the fundamental question of what can, and cannot, be achieved with kinetic energy release. We first show that the classic notion of wind farm capacity, conceived at a time when WEPSs always operated in the maximum power tracking mode, is inadequate to address this question. To overcome this issue, we introduce a new concept called achievability, which indicates whether a given quadruplet of initial state, final time, final state, and desired wind farm power output is achievable by releasing or storing kinetic energy in the wind farm. To promote this concept of achievability, we also discuss its practical implications, present an analytical method and a numerical method for characterizing it, and illustrate the numerical method via two examples.