The Research On Harmonic Suppression And Reactive Power Compensation Of UHVDC Transmission System

With the continuous development of UHVDC transmission,power quality problem is becoming more and more highlighted.UHVDC transmission in the process of transmission,the converter station features a large amount of characteristic harmonics and non-characteristic harmonics.Power filter can improve power quality.At present,most filtering technology is used in active filter,passive filter,hybrid filter.In this paper,a new type of inductive filtering technology is studied.Application of the new induction filter in the UHVDC transmission system can increase the filtering effect and other superior performance.This paper mainly has carried out the research work of the following aspects:Firstly,according to the wiring scheme of the traditional 12-pulse converter transformer,this paper analyzes the characteristic harmonics of the Traditional UHVDC Converter Station on AC side.Given filtering and reactive compensation wiring to traditional HVDC transmission system and a comparative analysis obtained:under the traditional program,converter transformer itself can not eliminate harmonics in its interior.Established the harmonic model of the traditional converter transformer and its equivalent circuit.The results show that:changes in the system impedance parameters of the filter components and other factors will affect the passive filter effect.Secondly,this paper describes the basic principles of inductive filtering technology.It focuses on the induction type converter transformer.A unified equivalent-circuit model and the harmonic transfer model for the inductive filtering are established.Combined UHVDC transmission system,this paper based on existing induction filter technology solutions put forward innovatively a connection scheme of inductive filtering converter transformers with parallel filtering windings,that the new connection scheme of UHVDC transmission.A unified equivalent-circuit model are established to study the harmonic characteristics of the new UHVDC.Then this paper analysis and verify the advantage of the new type of UHVDC.connection scheme.Then,this paper proposes the designed method of AC filter,including traditional and new filter AC filter.Based on the principle of inductive filter filter design method,this paper focuses on the analysis of the new single-tuned harmonic filter and a new double-tuned harmonic filter and second-order high-pass filter calculation.A new design of the filter unit does not need to use partial tuning,then the difficulty of designing and manufacturing is greatly reduced.Finally,referring to the engineering parameters of the Jiuquan-Hunan ±800 kv UHVDC transmission project,the simulation models of the proposed harmonic filtering scheme and the traditional schemes are established respectively.Based on the comparative analysis of the currents at the grid and valve sides of the two models,it can comes to such a conclusion that the proposed harmonic suppression scheme has a better operational performance in contrast with the traditional one.