In the quest of improving the frequency response capability of wind turbines, control solutions trying to emulate synchronous machines have been proposed. While their performance in terms of frequency support is relatively good, they may trigger torsional oscillations, cause fatigue and damage in the drivetrain, and reduce its lifetime. In this paper, the torsional oscillations caused by a virtual synchronous machine (VSM)‐based frequency controller are illustrated, and methods for damping them are introduced. Two torsional oscillation damping methods are compared and combined to derive an improved method. Dynamic simulation results show better damping performance from the combined damping method.

Fast frequency response from wind turbines and plants has been playing an increasingly important role in our modern power system, which has a large share of wind energy integration. Frequency control from grid-following wind turbines and plants has been extensively investigated in the literature, whereas grid-forming frequency control methods have aroused people’s attention in recent years, with relatively little comparison available. This paper provides such a comparison, illustrating the differences between the two methods of providing frequency support in a power system. The comparison shows the superiority of grid-forming frequency control methods over grid-following ones, and gives a glance into power system frequency stability in the transition from grid-following to grid-forming frequency support supplied by wind power. The results are elaborated in a benchmark WSCC 9-bus system, which features detailed electromagnetic transient modeling of the components from a single converter, a wind turbine, and a wind plant to the whole power system.

Frequency support capability is becoming an important requirement for wind turbines, as wind power is increasingly integrated into power systems. In this paper, a frequency controller is implemented and validated. Such a controller allows wind turbines to help regulate the system frequency automatically and includes virtual inertia to help limit the rate of change of frequency. Compared with other methods, the controller achieves satisfactory frequency support capability with considerable simplicity. The controller is added to the grid-side converter controls, together with cascaded inner loops, which enables wind turbines to operate in grid-forming mode with overcurrent protection. The influence of the controller parameters on the frequency response is investigated.

This paper proposes a switching anti-windup design, which aims to enlarge the domain of attraction of the closed-loop system. Multiple anti-windup gains along with an index function that orchestrates the switching among these anti-windup gains are designed based on the min function of multiple quadratic Lyapunov functions. In comparison with the design of a non-switching anti-windup gain which maximizes a contractively invariant level set of a single quadratic Lyapunov function as a way to increase the size of the domain of attraction, the use of multiple Lyapunov functions and switching in the proposed design allows the union of the level sets of the multiple Lyapunov functions, each of which is not necessarily contractively invariant, to be contractively invariant and within the domain of attraction. As a result, the resulting domain of attraction is expected to be significantly larger than the one resulting from a single anti-windup gain and a single Lyapunov function. Indeed, simulation results demonstrate such a significant improvement.

Liang protocol (method, recipe) by Paul Snchz