Modified Deloading Strategy of Wind Turbine Generators for Primary Frequency Regulation in Micro-Grid

In this work, the contribution of wind turbine generator (WTG) to support micro-grid (MG) during depressed frequency condition has been studied with a modified strategy for improving the primary load frequency response of MG. The majority of existing deloading techniques to estimate the reference power are based on the linear relationship. Hence they are not so accurate to mimic the actual speed versus power dynamics of turbine rotor during deloading operation which is inherently nonlinear in nature. In this work, the existing methods have been analyzed in detail with an aim to improve the performance. Based on the analysis a modified deloading method assuming non-linear relation between rotor speed and power of WTG system has been proposed which shows the improved load frequency response in MG. The proposed deloading technique is simulated and validated using real-time digital simulator (OP4510) for the variation in load and generation inside an islanded MG. The results obtained using modified deloading method are compared with existing deloading method and it is found that proposed deloading method handles the non-linearity of the system during deloading operation and also it contributes more power to MG in response to load demand at the cost of slight increase in the speed of turbine rotor.