Optimal use of kinetic energy for the inertial support from variable speed wind turbines

The use of kinetic energy, stored in the rotational masses of Variable Speed Wind Turbines (VSWT), for inertial support is well established. The idea is to employ the fast control response of the VSWT to inject additional power for the short duration following the disturbance. However, the variable speed operation of the VSWT poses a great challenge in successfully designing an appropriate control approach, applicable for wide operating ranges, capable of minimizing the effects of energy regain by the Wind Turbine (WT) after the support period. To address this issue, this paper proposes a modified inertia-emulation scheme, based on Step Over-Production (SOP) approach. Further, to enable optimum energy transfer and to handle the problem of variable Stored Kinetic Energy (SKE), the shaping parameters of the proposed scheme are optimized using the Particle Swarm Optimization (PSO) algorithm. The results show that the proposed approach can limit the fall of frequency while reducing post disturbances across the entire operating range of the WT. In addition, the quantitative analysis reveals that the proposed method can easily satisfy the stringent grid code requirements for the inertia emulation and provides a better alternative to the conventional inertia control architectures.