The Research On Theory And Applications Of New Balance Transformer And Harmonic Suppression Transformer

Focused on hot topics of negative sequence and harmonic in power system and based upon the principle and structure of transformers which are the essential components in power system, this article develops a series of theoretical and application researches to solve the negative sequence and harmonic problems by utilizing the transformer's potential. With its heavy theoretical significance and engineering value, this study gains a wide applications in engineering practice.This dissertation, together with key study project 102174 of Ministry of Education - new-style transforming device and its application as well as key science & technology project 05GK1001-2 of the Tenth Five Year Plan of Hunan Province -research & manufacture of new-style converter transformer in HVDC power transmitting system, makes numbers of studies in the following aspects.In this dissertation, negative sequence, harmonic and their suppression methods in power system are systematically analyzed, basic technical characteristics and application range of various types of existing balancing transformers as well as their application limitation are expounded. The main topological structures and their features of passive filter, active filter and compound filter are anatomized and meanwhile three technical keys in active filter application are listed.Inherent rules of the balancing transformer are explored. Operation principals of the existing balancing transformers, such as Scott-Teaser transformers, Le Blanc transformers, Wood Bridge transformers, impedance-matched balancing transformers, multi-function balancing transformers, YN/A balancing transformers, YN/> /~-V balancing transformers, four-phase four-leg transformers and etc, are systematically discussed. A more sound theory framework of balancing transformers is shaped as the theoretical benchmark for the analysis, calculation and operation of balancing transformers.In this dissertation, the theoretical assumptions of new-style balancing transformer are presented. Three connection models of new-style balancing transformers, i.e. star-double trapezia connection three-phase to four-phase or two-phase balancing transformer, star-trapezium connection three-phase to two-phase balancing transformer and star-delta connection three-phase to two-phase and three-phase balancing transformer, are invented. The connection schemes for these three models of new-style balancing transformer are proposed, the mathematical models of new-style balancing transformers are established and a more sound theoretical system of new-style balancing transformer is profiled. The conceits, taking short circuit impedance of winding as balance condition and decoupling condition, are provided and the corresponding equations that apply to short circuit impedance of winding are deducted. These fruits are theoretical guideline and foundation for the design, manufacturing and operation of new-style balancing transformers.The three models of new-style balancing transformers, which were pioneered by the author and characterized by simple structure, design and manufacturing easiness, excellent all-around performance and high utilization rate of material, can eliminate zero sequence currents, considerably suppress negative sequence currents and especially suit for the application that single phase load or two phase load is necessary. For star-double trapezia connection or star- trapezium connection balancing transformers which remain an infinite application potential, the utilization rate of material can be up to 100%. Already, the three models of new-style balancing transformers have applied for national invention patents.The general concept and topological structure of harmonic-suppressed transformers are indicated in this dissertation. The fundamental principals of inductive harmonic-suppressed transformers and auto-coupling harmonic-suppressed transformers are illustrated. Various harmonic-suppressed transformer structures relative to passive filters, active filters and compound filters are defined. The technical features of harmonic-suppressed transformers are specified. These theoretical achievements orientate the further researches in the future.The primary structures, technical characteristics, operation principles and applications of various practical harmonic-suppressed transformers like multi-function balancing transformers, harmonic-shielded transformers and new-style converter transformers are investigated. The test models of these three kinds of transformers were developed and passed the type-tests. The filter design methods for harmonic-suppressed transformers are offered, the design principals for filters with harmonic magnetic-potential ampere-turn balance are explained and the examples and data of filter design are given as well.Design works concerning the testing platform of DC power transmitting based on new-style converter transformers are concluded. The system architectures and combination principals are discussed. The functions and control characteristics of each part in control system are classified. The filtering methods, filter architectures and parameters are tabulated. This has concreted a solid theory foundation for the startup of the testing platform.The application and testing of harmonic-suppressed transformers are studied. The filtering methods and testing schemes for multi-function balancing transformers and harmonic-shielded transformers are delivered. Several operation conditions of on-site operation are simulated. A great number of test data are obtained. After being examined, the testing results show that the principals of harmonic-suppressed transformers are true and the filtering effects are excellent.A sample of multi-function balancing transformer is developed. Many key technical roadblocks in engineering practices of multi-function balancing transformers are swept away. The onsite networking between multi-function balancing transformer sample and its matching filter is carried out. The main functions of this transformer as well as auxiliary functions such as higher harmonic filtering, reactive compensation and supplying power for substation are realized. Based on the onsite testing data, various operation modes of this transformer are considered. The onsite testing results witnessed the operation principal and the filtering effect of this transformer. It gathered valuable onsite operation experiences for the extended application of this transformer. This achievement has passed the technical appraisement of Shanghai Railroad Bureau and was approved to be adopted in railroad system.The new-style balancing transformers and harmonic-suppressed transformers successfully met the imperative requirements of negative sequence and harmonic suppression. Bearing an infinite application potential, these transformers take various architectures, by means of balancing nature of transformer's magnetic potential, to match different fields, achieve comprehensive results by squeezing transformer's potentials and satisfy the basic requirements such as power saving, material efficiency and simple structure.