Research On Hierarchical Voltage Control For Large-Scale Wind Power Integration System

Due to the advantages of low carbon,environmental protection and sustainability,the penetration rate of renewable new energy represented by wind power in the power system is increasing.The instability of wind power output and low voltage inertia characteristics of power electronic devices lead to the great challenge to the voltage safety of large-scale wind power systems.But at the same time,the decoupling control characteristics of active power/reactive power of power electronic devices provide a new idea for the voltage management of the system.The weak reactive power control capability of many power generation units in the system can be used to aggregate the total reactive power resources from the equipment layer,the station layer to the regional layer from bottom to up,which can be allocated by the upper control center.The upper control center forms control strategies through the optimal allocation of reactive power resources,and then distributes control instructions from the regional layer,the station layer to the equipment level from top to bottom,so as to achieve the reasonable coordination of system economy and security,steady-state performance and transient performance.In the aspect of capability aggregation evaluation from bottom to up,a station layer reactive control capability aggregation evaluation method considering operational volatility is proposed.The method firstly quantifies the reactive power control capability of diversified equipment;Then the aggregation evaluation model of reactive power control capability from the equipment layer to the station layer and the on-line monitoring model for practical application are established;Finally,based on the optimal sensitivity theory,an efficient and fast algorithm is designed for the above models.This method mainly focuses on the coordination and interaction between equipment level and station level.In terms of the control instruction distribution from top to bottom,the regional layer voltage/reactive power coordination control method is proposed based on the reactive power control capability information summarized at the lower station level.In this method,the characteristics of reactive power control capability of the lower station layer are integrated firstly by considering the uncertain effect of wind power output,so as to solve the problem of the interaction between the lower layer aggregation and the upper layer control;Then,the regional layer voltage/reactive power coordination control model is established based on N-1 off-grid security constraint and active power auxiliary control strategy of wind farm;Finally,based on the requirement of transient fault crossing,the model is checked and modified to realize the reasonable coordination between steady-state performance and transient constraint.This method mainly focuses on the coordination and interaction between the station layer and the regional layer,and finally completes the task of voltage/reactive power control for the large-scale wind power system.