Research On Characteristics And Protection Of Four-winding Induction Filter Transformer

Aiming at the rapid development of power electronic devices and their wide application in various fields,the resulting harmonic pollution also brings a series of safety hazard problems such as abnormal stress on transformer windings,serious heat generation in transmission lines and serious interference in communication control systems.The four-winding induction filter power transformer(FWIFT)is a transformer application scenario suitable for such multi-port harmonic inflow of 220 kV substation with severe harmonic pollution,which can realize local sup pression and reactive power compensation of harmonic components.The paper analyzes and studies the four-winding induction filter transformer.Firstly,according to the analysis of the zero-impedance design principle of the winding,a prototype of the engineering principle is designed according to the principle.The equivalent circuit is deduced and filtered by the zero-impedance design feature.The effects were analyzed in depth and related models were established.Correlation analysis and solution were carried out for coupled inductance parameters and induction filtering techniques.The action equations of relay protection were derived and relevant action criteria were established.Finally,the paper was proved by experiments and simulations.The correctness of theoretical research.This paper has carried out a series of theoretical research work on FWIFT.The main innovations achieved are mainly reflected in the following aspects:1?Theoretically reveals the relevant characteristics of the zero-impedance design of the winding.Firstly,the principle of the core zero-impedance design of the inductive filtering technology is expounded,and the special requirement of zero-impedance design between multiple windings is needed for the four-winding induction filter transformer.The design concept of winding zero impedance in the case of multi-winding is demonstrated in detail..At the same time,according to the zero-impedance design concept,the characteristic relationship under the short-circuit impedance parameter form and the coupled inductance parameter form is solved.At the same time,in order to visualize the necessity of the short-circuit impedance characteristic of zeroimpedance design for harmonic suppression,by analyzing the harmonic suppression mechanism of the four-winding induction filter transformer,the harmonic current equation of the grid-side winding is established,and the zero-impedance design is demonstrated for the transformer.The necessity and effectiveness of harmonic suppression.Finally,based on the designed zero-impedance design of the winding,a prototype of the four-winding induction filter transformer was developed,and the relevant experimental platform was built.2 ? Established a mathematical model of four-winding induction filter transformer based on inductance decouplingIn order to solve the problem that the number of windings of the four-winding induction filter transformer increases,the electrical qua ntities of the windings are coupled with each other,which leads to a complicated and difficult modeling problem.In this paper,based on the fully coupled circuit of the four-winding induction filter transformer,combined with the various winding coupling methods,the basic mathematical model and the fully decoupled equivalent circuit of the inductor are established by the method of inductance decoupling.At the same time,according to the different grounding methods of the neutral point of the transformer and the particularity of the filtering device,the corresponding node expansion model and the branch equivalent model are derived.3?A FWIFT relay protection action equation and its protection criterion are proposed.In order to ensure that FWIFT can be safely connected to the grid,it can better serve the power system.Based on the electromagnetic coupling equation of transformer,the flux linkage parameters are transformed into corresponding self-inductance mutual inductance parameters,and the basic cri teria of relay protection of FWIFT are determined by analyzing the constant nature of inductance parameters.Based on this,the protection action equation is gradually derived,and the protection criterion for identifying the internal fault of the transfor mer is determined.