Improving frequency regulation ability for a wind-thermal power system by multi-objective optimized sliding mode control design

Abstract

Enhancing the frequency response ability of the wind-thermal coordinated load frequency control system is an effective means to maintain the stability of the grid frequency and improve the flexibility of the new power system. Thus, this paper designs a cascaded extended state observer sliding mode control (CE-SMC) method based on the osprey-dung beetle fusion optimization algorithm and applies it to the wind-thermal coordinated system to improve the frequency regulation performance of the system. Firstly, cascaded extended state observers are utilized to accurately estimate the combined effects of parameter uncertainties and internal and external disturbances in the system and compensated by sliding mode controller in real time, which helps the system to achieve fast frequency regulation. Secondly, the osprey-dung beetle fusion optimization algorithm is employed to optimize the parameters of CE-SMC. Moreover, a multi-objective function including the frequency regulation performance, thermal power unit output smoothness, carbon emission and economy is constructed to guide the power system to operate at the utopian point of flexibility, economy and low carbon. The control scheme effectively combines the features of fast frequency response, robust immunity and accurate parameter tuning. Finally, simulations are carried out in different load disturbances and various wind power penetration rates. Results show that the CE-SMC scheme can effectively improve the frequency response ability of the system while taking into account energy saving and emission reduction. Compared with integral sliding mode control, the frequency regulation performance is improved by 20.99 %, the output stability of thermal power unit is improved by 19.31 %, the power generation cost is reduced by 1.88 % and the carbon emission is reduced by 2.16 % in single load perturbation. As such, the CE-SMC algorithm provides a practical reference for the flexible, low-carbon and economic operation of new power system.