Optimization Design And Operation Strategies Study Of Gaoling Back-to-Back HVDC Project

With the rapid development of China's economy,the load of electricity in the middle eastern regions of our country has been increasing year by year,the energy distribution and economic development of our country,however,showed a imbalance.Under this circumstance,the significance of the interconnection of regional power grid is more obvious in the area of integrating power resources,optimizing energy allocation and promoting energy strategy construction.Gaoling DC Back-to-Back(BTB)project,the energy hub connecting the northeast power grid and the north China power grid,is of important strategic significance in power structure.As a traditional DC project,Gaoling DC has technical shortcomings,which reflected in the "commutation failure" risk of LCC-HVDC DC transmission technology.Since the project was put into operation in 2008,the "commutation failure" has occurred many times,and this posed a serious threat to the safe operation of large power grids in both regions.In this paper,we introduced the reason of "commutation failure" from the operating principle of the traditional LCC-HVDC technology,and pointed out the existing shortcomings and operational risks of this project.We also came up with a program to optimize the design with LCC-VSC hybrid DC transmission technology.Based on the analysis of the operating data of the Baoling DC project,we determined reformation direction of the converter station,and it was selected according to the equipment parameters such as the topology of the main circuit,the commutation valve,the converter transformer and the sub-module topology of the actual project.Besides,the control strategy of the optimized DC project was designed in this paper.In order to realize the respective advantages of LCC and VSC converter stations,an optimal control scheme is selected from five applicative operation strategies.The optimal one not only meets the need of hybrid HVDC transmission project,but also has strong capability of failure crossing,which is of great significance to the safe and stable operation of optimized HVDC project.The optimization design and control strategy proposed in this paper are all based on the practice of Gaoling DC project and have strong practicality.So the optimized Gaoling DC project will play a greater role in the regional power grid.In the longer term,the optimization scheme designed in this paper will provide a reference example for the optimization and improvement of more traditional DC projects.