Research On Static Stability Of Diversified Devices Of New-energy Power Generation Base Under Weak Grid

In response to major problems such as the energy crisis and environmental pollution caused by the traditional power generation industry,my country is doing its best to develop renewable energy power generation technologies.At the same time,my country’s abundant wind and solar resources are located in the "Three North" area far from the load center,and most of the new energy power generation bases operate under weak grid conditions.Different from traditional power systems,a lot of power electronic equipment is used in the process of connecting new energy power generation bases to the grid.Among them,the grid-connected converter is the main grid-connected interface,which is widely used in the grid-connected wind power and photovoltaic power generation,and its stable operation is very important.In the actual operation of the new energy power generation base,multiple grid-connected converters are required to operate in parallel,and supporting equipment such as synchronous generators and reactive power compensation devices are required.Under weak power grid conditions,the various parts of the system are coupled,and stability problems continue to arise.Static stability research can determine the power limit that can be transmitted by new energy power generation bases,and can provide theoretical support for system planning and operation.This article focuses on the static stability of a single and two voltage source grid-connected converters and the static stability of the grid-connected converter in parallel operation with other equipment.The specific content is divided into the following aspects:(1)The mathematical model of the grid-connected converter under the DC voltage time scale is established.Aiming at the AC side output active power characteristics of the gridconnected converter under the closed-loop control of the output current,the grid-connected converter is regarded as a current source,and the fundamental frequency equivalent circuit of the grid-connected converter stand-alone infinity system is established,and the output active power is obtained.Power characteristics.Combining the mathematical model under the DC voltage time scale of the grid-connected converter and the output active power characteristics of the AC side,the static stability criterion of the grid-connected converter is proposed.(2)Aiming at the more complex infinity system of dual grid-connected converters,the static stability of the system is analyzed based on the establishment of the state space equation and the eigenvalue analysis of the single infinity system.The grid-connected converter operating at unity power factor is equivalent to a negative resistance,and the basic frequency equivalent circuit of the infinite-bus system of the dual grid-connected converter is established to obtain the output active power characteristics.Based on the output active power characteristics,a linearized dual grid-connected converter connected in parallel to the infinitebus system state development space equation is established,and the static stability criterion and static stable working area of the system are obtained by the eigenvalue analysis method.(3)Aiming at the scenario where the grid-connected converter and the synchronous generator are connected in parallel to the infinite power grid,based on the state space equations of the synchronous generator and the grid-connected converter,the characteristic root analysis method is used to study the scenario The static stability problem.At the same time,the influence of various equipment parameters and line factors on static stability in this scene is deeply explored.(4)After considering the compensation of SVG on the basis of the single infinite bus system of the grid-connected converter,the static stability of the grid-connected converter and SVG in parallel operation is studied.After deriving the output active power characteristics of the grid-connected converter in this scenario,combined with the mathematical model under the DC voltage time scale,the static stability is obtained.