Allocation Method And Optimization Design Of Reactive Compensating Devices For Multi-infeed HVDC System

The distribution of energy source and the unbalance of regional economic development make large scale and long distance transmission mode necessary. Owing to the fact that High Voltage Direct Current transmission has advantages in large capacity and long distance, HVDC has developed rapidly. With the extensive application of HVDC, the interaction between the parallel AC transmission system and the HVDC transmission lines in such configurations is very important to power system stability. The power grid in East China has formed the complex Multi-infeed Direct Current (MIDC) system with multiple DC infeed and this requires strong support by the end of the AC power grid. Allocation of dynamic reactive compensating devices is the best method to enhance the security for multi-infeed HVDC system. But how to perfectly make the dynamic reactive power devices effective and efficient is still an unsolved problem.The thesis introduces the problems that the multi-infeed direct current system in East China Area faces. Considering the relationship between reactive power and voltage control, this thesis confirms the voltage weak area of the system as the dynamic reactive power compensation area. The author put forward a concept of MIDC system’s reactive compensation pilot buses to decide optimal allocation sites learned from the concept of voltage pilot buses as well as taken the MIDC system’s features into consideration. The method considers the support effect that the AC system has to the DC system specially, and designed weighting factors using the multi-infeed short-circuits ratio to measure the importance of different DC system and it also considers the reactive compensation effect on other AC pitch point. And then a method of reactive power optimization of the capacity of the dynamic reactive compensation based on particle swarm algorithm is used. It was different from the traditional reactive power optimization. The method in the paper is based on the dynamic simulations, and uses the short-circuit capability as the indicator of the support capacity that AC system has to the DC system and also uses the compensation capacity as penalty function, considered the cost efficient of the dynamic reactive devices to make the optimize results effective and high efficient. Lastly, the example that transformed into a MIDC system from a IEEE30model is used to prove the effectiveness of the dynamic reactive devices optimization, besides the paper also make a simulation analysis on the reactive devices optimization of power grid in South Jiangsu Area which is proved that the method that put forward in this paper is effective and meaningful to a complex grid system.