Static Voltage Stability Analysis And Reactive Power Optimization Of AC/DC System Considering Wind Power

With the rapid development of new energy,wind energy has been widely used due to its widely distributed,clean and environmentally friendly characteristics.Due to the randomness and uncertainty of wind power,it is an urgent problem that how to ensure the stable operation of the static voltage of the power system under the wind power connection.In addition,with the rapid construction of AC/DC system,the physical form and operation mode of power grid have changed significantly.It is of great significance to comprehensively consider the impact of new energy and DC part on the voltage stability of power grid.Based on the risk assessment,this paper analyzes the voltage stability of VSC-HVDC System with wind power access.It proposes comprehensive voltage stability risk indicators,analyzes the influence of different factors on voltage stability,establishes system weaknesses,and further develops a multi-objective reactive power optimization strategy based on system weaknesses.This paper focuses on the voltage stability of AC/DC systems considering wind power.The main research contents include the following aspects:The mathematical model of VSC-HVDC AC/DC system is established,and the commonly used VSC control method,AC/DC power flow calculation method and static voltage stability analysis method are introduced.Based on the traditional continuous power flow algorithm,considering the wind power access characteristics and load characteristics,in order to accurately and quickly draw the PV curve,a method using a combination of linear prediction and non-linear prediction in the prediction link is given.The selection of the control step size lays the foundation for evaluating the voltage stability.Based on the risk assessment theory,a voltage stability risk index considering wind power access is proposed.This index comprehensively considers the changes in node voltage and system load margin,which can more comprehensively evaluate the risk status of system nodes.By establishing different wind power access scenarios,adjusting VSC control methods and control parameters,and using Latin hypercube sampling to select the operating status of the system for system risk assessment,the weak areas of the system are determined.The simulation examples show that the risk index proposed in this paper can effectively determine the node’s weakness and system risk,and reasonable consideration of load characteristics,wind power access location and VSC control parameters can reduce the risk of voltage stability of the wind power access system.A multi-objective reactive power optimization model considering system risks,voltage fluctuations,and system economic costs is established for the weak areas of the system identified after wind power is connected to the grid.The Elitist Non-dominated Sorting Genetic Algorithm with Elite Strategy is used to solve the problem.For the Pareto solution set obtained by the NSGA-II algorithm,this paper considers the preferences of dispatchers and actual engineering requirements.The method of obtaining the compromise solution from the Pareto solution set was introduced.Finally,through improved 10-node and IEEE39-node system simulations,the results verify the effectiveness of the proposed reactive power optimization strategy,and achieve reactive power optimization and compensation in the weak areas after wind power is connected to the grid,so as to maximize the voltage stability of the AC/DC system.