WEI Y F, ZOU J K, WANG P,et al.New power flow method for flexible DC systems based on seventh-order NR method and Broyden method[J].Journal of Henan Polytechnic University(Natural Science) ,2024,43(4):141-151.

doi:10.16186/j.cnki.1673-9787.2022030044

Received:2022/03/16

Revised:2023/04/11

Published:2024/07/05

New power flow method for flexible DC systems based on seventh-order NR method and Broyden method

WEI Yanfang1,2, ZOU Jiankai1,3, WANG Peng4, ZENG Zhihui1

1.School of Electrical Engineering and Automation，Henan Polytechnic University，Jiaozuo  454000，Henan，China;2.Henan Key Laboratory of Intelligent Detection and Control of Coal Mine Equipment，Jiaozuo  454000，Henan，China;3.State Grid Anyang Power Supply Company，Anyang  455000，Henan，China;4.Electric Power Research Institute，State Grid Henan Electric Power Company，Zhengzhou  450052，Henan，China

Abstract: Objectives  To solve the problem of low solving efficiency of power flow algorithm for flexible DC transmission systems， Methods  firstly，a power flow algorithm based on the seventh-order NR method was proposed.Compared with the traditional power flow algorithm，this algorithm had a higher convergence order，which could effectively reduce the number of iterations and improve the efficiency of the algorithm.Then， an improved algorithm based on the seventh-order NR method with Broyden was proposed for the problem that the seventh-order NR method was computationally intensive in a single step iteration.It took advantage of the outstanding convergence characteristics of the seventh-order NR method to reduce the number of iterations， while retaining the advantage of the lower computational cost of the single-step iteration of the Broyden method to avoid the waste of computational power，resulting in a large improvement in computational efficiency.Further，a rule of thumb was proposed to determine the number of iterations of the high order NR method in the modified algorithm. Results  The modified IEEE standard examples were simulated and tested by the classical and improved methods，and the results showed that，compared with the classical NR method，the maximum error of AC and DC power flow results was 1×10-8 and 2×10-8.In terms of average computing time，the calculation time of the improved algorithm was reduced by about 61% compared with that of the classical NR method under four example systems as IEEE-14，IEEE-30，IEEE-57，IEEE-118.When the example system changed from double-ended to triple-ended and double-fed，the number of iterations of the improved algorithm remained unchanged，and the calculation time increased by 0.352 ms and 0.636 ms，respectively.In the case of heavy load，the improved algorithm had the highest computational efficiency and the preset number of iterations were simple.When the load value reached 2.992，the calculation time was only 60% of that of the classical NR method. Conclusions  The improved algorithm in this paper had the same accuracy as the classical NR method，but had more advantages in computing speed，and was more conducive to the application in extreme cases such as heavy loads.

Key words:voltage source converter;high voltage direct current;seventh-order NR method;Broyden method;power flow calculation