Research On UPFC's Optimal Configuration And Related Control Strategy

With the increasing load of modern power grid,the contradiction between the demand of improving power flow distribution and the scarcity of power construction land is becoming increasingly prominent.In order to maximize the power supply capacity of the power grid itself,more and more Unified Power Flow Controller(UPFC)projects have been built and put into operation in China.In this paper,the problem of location selection and implementation of UPFC demonstration project in UHV level in actual power grid planning is studied,mainly aiming at the application scenario where the existing transmission capacity of the section is limited by the uneven distribution of power flow.Firstly,the concept of proportional coefficient of unit capacity regulation of UPFC is studied to quantify 500 kV UPFC scenarios of.Based on the analysis of UPFC typical application scenarios,the control effect of UPFC is represented by the ratio of the transverse transmission power increase to the installed capacity of UPFC.According to the reliability cost/benefit analysis,the proportional coefficient of unit capacity regulation is standardized to make it suitable for the horizontal comparison of UPFC distribution points in the whole country.Next,a three-step research method of "overall configuration-precise location-capacity optimization" is established for UPFC location and capacity optimization.Considering the energy distribution and power demand in China,the overall allocation principle,that is give priority to interconnection section and important transmission section in provinces,to maximize the comprehensive benefit of UPFC.The specific selection principle of UPFC is studied from two aspects of installation purpose and installation effect,and these principles are prioritized to avoid a large number of blind calculations in large-scale actual power grids.A method of calculating the optimal capacity of UPFC based on the proportional coefficient of unit capacity regulation is proposed,considering both the control effect and economic benefit of UPFC.Then the UPFC selection process at the technical level is put forward,and the UPFC selection scheme of UHV network in China is studied.Based on 2-3 years rolling calculation data of the whole network,through preliminary comparison,simulation analysis and horizontal comparison of the distribution points,the suggestions for priority development of UPFC demonstration project are obtained.The results show that the method proposed in this paper is feasible with certain guiding significance for the UPFC layout screening and demonstration project implementation on UHV level,and can provide technical support for the formulation of UPFC related technical standards.Finally,aiming at the operation of UPFC demonstration project,a system-level control strategy of UPFC based on section load balance is established.The standard deviation of line load rate in section is used to measure the uniformity of power flow distribution.Considering the adaptability of power grid to external environment,the optimal objective value of UPFC power flow control is obtained by establishing and solving optimization model.Taking the 500 kV UPFC project in Jiangsu as an example,the paper proposes control methods of UPFC in three cases,three phases permanent N-1 fault,steady state operation and DC latch.The simulation results show that the UPFC control method based on the index can achieve the purpose of improving the transmission capacity and tidal current distribution of the section,and improve the safety and stability of the power grid.