| Voltage control is a technology originated from the French EHV power system.Its main purpose is to respond to load changes and ensure that the voltage of each bus of the power system is within a reasonable range as much as possible.Traditional voltage control is mainly composed of network partition,zonal pilot bus selection,secondary voltage control.Its core idea is to divide the power system into several mutually decoupled sub-regions,and select a pilot bus in each sub-region to reflect the region.Then,by adjusting the reference value of the generator terminal voltage to ensure that the pilot bus voltage is within a reasonable range,the voltage of each sub-region is controlled,and then the voltage of the entire network is controlled.However,traditional voltage control methods also have many problems.For example,traditional grid partitioning methods have problems such as difficulty in measuring partition quality and long running time,while secondary voltage control based on pilot buses is difficult to find the optimal combination of pilot buses.At the same time,as more and more photovoltaics are connected to the grid,their operation mode is mostly active-reactive power injection,which is different from traditional generators.This makes photovoltaic generators unable to participate in voltage control and makes the power system vulnerable to load changes.In order to solve the above problems,the main research contents of this paper are as follows:1)A fast network partition method based on modularity and community detection algorithm is proposed.This method can obtain better partition results in a short time,that is,it can result in decent decoupling between regions and coupling within regions.The feasibility and effectiveness of the method are verified through the test of IEEE39 node standard example and the comparison with existing methods;2)An optimal regional pilot bus selection method based on surrogate optimization is proposed.This method has the ability to find a better pilot bus combination within an acceptable time,so that the effects of secondary voltage control based on the pilot bus combination are improved.The feasibility and effectiveness of the method are verified by simulation verification in IEEE 39-bus,118-bus and 123-bus systems,as well as comparison with the method;3)The application of the proposed fast network partition method and regional pilot bus selection method in the practical Tibet power grid is studied.First,a program to read the power flow data of the PSD-BPA software of the China Electric Power Research Institute was developed.By considering the bus types,the data of the practical power grid was converted into the MATPOWER data format to make the conversion result more accurate;then the photovoltaic generators in the Tibet power grid run at voltage-controlled mode,making it able to participate in voltage control.Based on the two points above,the ability of the proposed method to deal with load changes is tested in the Tibet power grid,and the voltage control effect of voltage control with and without solar generators is compared.The results show that photovoltaic participation in voltage control is more conducive to the recovery of bus voltages after disturbance.The above research contents show that the power grid partition method based on modularity and community search algorithm and the regional pilot bus selection method based on surrogate optimization proposed in this paper are feasible,and the effect is better than the existing methods,and these methods are also suitable for realworld networks with photovoltaic generators.The proposed method is also conducive to improving the security and stability of the power grid. |
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