Analysis Of Voltage Stability For Multi-infeed HVDC Terminal

Global energy development faces severe challenges,such as shortage of resources,environmental pollution,climate change,uneven development and so on.This poses a serious threat to human survival and development,the fundamental way out is to speed up the clean development and promote the transformation of energy transformation.In the context of the global energy Internet,clean energy has been widely exploited and utilized worldwide.The backbone of the HVDC power transmission project is the backbone of the global energy Internet,which is the basic platform for the large-scale development,transportation and use of clean energy in the world.Since the establishment of the global energy Internet development cooperation organization of China's national Power Grid Corp in March 2016,China has increased the development of renewable energy to an important position,and gradually realized the strategic adjustment of the energy structure.The basic national conditions of the unbalanced development of energy and productivity in China have made electricity have to be transported to a large area of large quantity of electricity in the East.With the development of the west east power supply,China has been fed into the Yangtze River Delta and the Pearl River Delta region with multiple DC densely fed into the Yangtze River Delta.More and more multi-infeed AC/DC projects bring severe tests to the stability of the entire power system.It is very necessary to analyze the safety and stability of multi-infeed HVDC systems.This paper introduces the distribution of DC projects at home and abroad,as well as the interconnection status of all continents in the world.The development of multi-infeed UHVDC transmission projects in China is mainly introduced.The research status of voltage stability in DC multi-infeed transmission system is discussed,and the identification criterion of static voltage stability of DC multi-infeed transmission system is emphatically analyzed.Among them,the multiple infeed short circuit ratio index is widely accepted and widely used in the engineering field.However,the relationship between the multi-infeed short circuit ratio and the static voltage stability of multi-infeed system is relatively clear compared with the single infeed short-circuit ratio.The physical meaning is not very clear.When it is used to evaluate the stability of the multiple terminal feedforward system,it can only qualitatively analyze the voltage stability.This paper focuses on the study of this problem,based on the traditional simplified model by multi-infeed Thevenin end system through to the exchange by the end of the node impedance matrix diagonalization to obtain the characteristic value,put forward multi-infeed receiving system decoupling model,analyzes the physical meaning of receiving end system impedance matrix eigenvalue,and that special case in the uncoupled model single infeed system is multi-infeed system.Put forward a new evaluation index of static voltage stability of multi-infeed system based on decoupling of multi-infeed system model,and based on the maximum power curve method,the critical value of the new index was calculated with the typical parameters of DC system.In this paper,a simple three feed in system is built by BPA software.The value of the new index of the decoupling model is set up by example simulation,and the fault is set up to verify the voltage stability of the new index to the DC multi-infeed end system.Finally,based on the data of the typical multi-infeed system in Shanghai,the simulation of the new parameters of the decoupling model to the planning of the large power grid is illustrated.