Study On Transient Voltage Stability Analysis And Reactive Power Allocation Control Of AC/DC Terminal Power Grid

In recent years,high voltage direct current transmission project has been developed by great-leap-forward development for the advantages such as long distance transmission,large capacity.The large receiving-end power system with multi-infeed direct current had been formed in load centers like East-China Grid and Guangdong Grid.For the reason that interaction of AC/DC and the electrical distance of each DC infeed point are small in receiving-end power system,which poses severe challenges to the transient voltage stability of receiving-end power system.Therefore,the research of this thesis on transient voltage stability analysis and control of AC/DC high voltage power system is important theoretical significance and practical value.The main contributions of this paper are summarized below.(1)Firstly,the factors that affect transient voltage stability of AC/DC power system are analyzed.The reactive voltage characteristics of HVDC transmission which are controlled by the change of DC control mode and transient voltage and asynchronous motor are analyzed.The influence of interaction between HVDC transmission,parallel capacitor compensation asynchronous motor load on the transient voltage stability of MIDC receiving-end power system is analyzed comprehensively,which provides a theoretical basis for subsequent control.(2)Secondly,a new transient voltage stability margin index(TVSM)on power grid side using transient voltage trace data is proposed.The transient voltage stability criteria and the derived evaluation indexes are introduced.By combining voltage stability requirements,limiting transient minimum voltage and steady state recovery voltage level after failure,the multiple-two-element notation that representing the characterization of acceptable is proposed based on the thought that different weights for different dropping degree to solve the problem of low distinction with existing indexes.Simulation results with the actual power system proving the applicability and effectiveness of the index assessing transient voltage stability.(3)A configuration method for dynamic reactive power compensators according to sensitivity of the TVSM index.Dynamic reactive power compensator is connected in each node step by step and the optimal access nodes are determined by the result of quantitative assessment of transient voltage stability.Reasonable allocation plan of dynamic VAR can be proposed by combining with actual power systems.And combined with DC modulation,the transient voltage stability of the receiving-end power system under various faults can be effectively improved.