The Research On Harm Of Harmonics And Novel Project For Control In DC Transmission System

Considerable harmonics are generated by HVDC converter stations, which usually transfer a great deal of electric power. It's proved that these harmonics will do great harm to power grid. Harmonic and its elimination is one of the important issues in HVDC system. For implementing the industrialization of the patent of invention and the patent of utility model:"Self-coupled and Harmonic Suppression Converter Transformer", and supported by the key science & technology project 05GK1002-1 of the Tenth Five Year Plan and 06GK1003-1 of the Eleventh Five Year Plan of Hunan Province. Based on many literatures of China and foreign countries, comprehensive and thorough research has been made for harmonics in green power saving direct current electricity station. Some results in theories and practical engineering are given.This theoretical analytical system includes the following:1. Firstly, the paper introduces the concept of harmonics and its harm, and harmonic characteristics of HVDC, it also demonstrates the necessity of study harmonic.2. Secondly, to the question being in traditional converter transformer, there are stated of connected scheme of wine, mathematical model and possible types of structure. The vector relation between transformer windings'voltage is analyzed. And, the advantage and disadvantage have be analyzed for effect of filter, speed of vibration for transformer and commutation in the basic of novel direct current transmit electricity.3. The effect of harmonics is analyzed for hot wastage, induction electromotive force and pulse torque in dynamo. And in research object of 100KVA novel direct current transmit electricity back to back system, this article analyzes the loss and efficiency of generator cased by harmonics with filter and without filter in the novel DC transmission system. Finally, by using dynamic simulation experiment and analyzing the result, it indicates that the novel system has its unique advantage of reforming the quality for voltage and current in the fan-out of generator, improving rated export for generator.4. Finally, this paper analyses transformer's harmonic loss and calculation in detail. On the basis, a harmonic loss calculation method of transformer is presented. This method uses harmonic equivalent circuit of transformer and superposition principle and polynomial curve fitting to deduce the calculation formula of transformer's harmonic loss. The method is distinct and could be programmed easily. This paper researches the relationship between the electric harmonics'distortion rate and harmonic loss of transformer as well. At last, the curve of relationship between the electric harmonics'distortion rate and harmonic loss is gained.