Coordinated frequency modulation strategy considering source-load uncertainty

Xiaohong Dong ^1* Dengxin Ai ^2* Shuo Wang ¹ Yang Ma ^1* Xiaodan Yu ^3*

• ¹ Hebei University of Technology, Beichen District, China
• ² State Grid Tianjin Electric Power Research Institute, Tianjin, Hebei Province, China
• ³ Tianjin University, Tianjin, Tianjin, China

Wind turbine generators (WTGs) and electric vehicles (EVs) are used as source-side and load-side resources, respectively. And the uncertainties of WTGs output and EVs charging load seriously affect the frequency stability of the power system. For the wind speed prediction error and the uncertainty of EV off-grid time, a cooperative frequency modulation (FM) strategy is proposed. Firstly, the wind speed interval is divided based on the operating characteristics of WTGs and the load reduction rate. On the basis, a load reduction operation strategy based on rotor speed control and pitch Angle control is proposed to enable WTGs to have bidirectional frequency modulation capability. The adjustable capacity of WTGs is determined based on the wind speed prediction error and the operation strategy of load reduction; Secondly, based on the controllable domain model of an EV considering the off-grid time uncertainty, the adjustable capacity of EV clusters is determined by state grouping of the state of charge (SOC) according to its charging urgency. By defining EV FM capability parameters and charging urgency parameters, the EV priority list for FM is determined and the power allocation strategy is proposed; Then, based on the urgency of EV charging and the economy of WTGs load reduction operation, a cooperative FM task assignment strategy is proposed. Finally, a numerical example is given to verify that the proposed cooperative FM strategy can not only increase the FM capability, but also improve the FM effect by 6.05% compared with the fixed proportion assignment of FM tasks and enhance the frequency stability of the power system from both source and load sides.