Research On Theory And Application Of Integrated Filtering Reactance Transformer And Its Filtering System

The widespread use of power electronic devices and other nonlinear loads leads to the increasingly serious problem of harmonious waves in power systems.Because of big harmonious content and limited floor space for electrical equipment,LC filter device is the most economical choice for power driven ships and urban power distribution network,and they need electric reactor in filter not only to be small in size but also with low noise.So the selection of filter reactor has become an engineering problem.According to the theory and application of integrated filter reactance transformer,this paper has accomplished the following researches:(1)A setting plan that building filter reactor integrated to transformer on the basis of nonorthogonal decoupling theory of transformer winding was put forward,and the decoupling theory between the filter reactor and the power winding of transformer,and between integrated filter reactors are detailed discussed,as well as the inductance value of each winding,coupling method and experimental verification.The characteristic of leakage reactance of integrated filter reactor was analyzed,and the calculation method of its inductance and the correlative equivalent model of integrated filter reactance transformer,the model of single-phase fundamental wave and harmonic circuit were made.The calculation method of inductance value and coupling coefficient by reducing the inductance matrix was put forward.By comparing the inductance value with the measured value of 5th electric reactor and7 th electric reactor,the error is within 5%,which is an allowable value in engineering.(2)In terms of the 10 kV box-type substation requiring small and compact equipment,this paper presented a scheme — integrated filter reactance 10 kV distribution transformer and its filter,including wiring and winding arrangement.Then according to the physical dimension parameters of distribution transformer,the three-dimensional finite element simulation model of the transformer is established in the electromagnetic simulation software.Then,according to the calculation method and mathematical model of inductance and coupling degree of the reduced order inductance matrix,the inductance matrix and coupling degree matrix of the integrated filter reactance 10 kV distribution transformer were calculated based on the established 3d finite element model of Ansoft/Maxwell.Finally,based on the theoryof integrated filter reactance transformer,a prototype of integrated filter reactance distribution transformer applied to a 10 kV box substation is developed.The inductance,linearity and coupling degree of the integrated filter reactor were tested by engineering prototype.The results of simulation and measurement showed that the proposed filter windings have good decoupling performance and inductance linearity.Next,according to the idea of field-circuit coupling,the field-circuit coupling simulation model of integrated filter reactance 10 kV distribution transformer and its filter was established.After using 5th and 7th integrated filters,the harmonic distortion rate at the side of 10 kV high-voltage network changed from11.41%--12.86% to 4.87%--6.45%.We put the sample machine into trial operation in residential area,and found that when 5th and 7th integrated filters were used,the harmonic distortion rate of the three-phase current on the side of 10 kV decreased from 7%-12% to 4%-7%,which showed its good filtering effect.This indicated that the filter branch formed by the integrated filter reactance winding and external capacitor worked well and had a good filtering effect.Moreover,it can realize harmonic shielding at the source,reducing the adverse effect of harmonics on the transformer body.So the correctness of integrated filtering reactance 10 kV distribution transformer scheme and model was verified.(3)In terms of the limited space for ship power system,this paper put forward the integrated filter reactance inductive filtering 6-pulse rectifier transformer and its filtering system.Because the commonly used circuit simulation software is lack of the accurate model of transformer,the traditional transformer model cannot reflect this kind of transformer internal electromagnetic relations,a new field-circuit coupling method is proposed,which made the inductance matrix as magnetic field and circuit coupling interface.According to this method,we use Ansoft software to build the transformer magnetic field model at first,and can obtain the inductance matrix of all windings(self-inductance and mutual inductance),calculate and analyze the coupling degree between the two windings.Then,we can write the winding state voltage equation with the inductance matrix as the core,get the electric quantity parameters under various port conditions,and get the short circuit impedance of the prototype.After comparing with the design value,we can know the error is very small.At last,with inductance matrix as the core and other components as peripheral circuits,a MATLAB software circuit simulation model was established.The current simulation waveform on the low-voltage side and the winding current waveform on the low-voltage side were basically consistent with the waveform deduced from thetheory,indicating that this simulation method is feasible and effective.The prototype of integrated filtering reactance inductive filtering 6-pulse rectifier transformer and its filtering system were constructed,and the inductance,volt-ampere characteristics of the 5th,7th and 11 th integrated reactors,as well as the coupling degree between the every two windings are measured.The harmonic current content,distortion rate,power factor,voltage and current phasor of the high voltage side were measured under the conditions of disconnecting and connecting to filter.When connecting to the filter,the harmonic distortion rate of the high voltage side decreased from 27.28% to 11.9%,and the power factor was greatly improved.Compared with the simulation results,the correctness of the magnetic field-circuit coupling calculation and simulation method with inductance matrix as the core was verified.(4)In view of the shortcomings of the traditional harmonic filtering scheme in the 12-pulse rectifier system for naval ships,a new integrated filtering reactance inductive filtering 12-pulse rectifier transformer and its filtering scheme was proposed.In this scheme,two triangular filtering windings were in parallel connection with 11 th filter and 13 th filter,in which 11 th and 13 th filters were integrated into the transformer.The topological structure,mathematical model,harmonic transfer characteristics,harmonic flow path in parallel filter winding circuit,harmonic suppression mechanism and electromagnetic induction process were analyzed in detail.Then,the field-circuit coupling model can be set up by using the finite element simulation software Ansys/Maxwell and circuit simulation software MTLAB,which verified that the system has good harmonic suppression effect.The prototype and its filtering platform were also built.The data tested on the YYD rectifier transformer side,YDD rectifier transformer side and the whole transformer side after the two current flow together under the following three working conditions respectively: the system without filtering measures,the system with filter winding in parallel connection and the system with filter winding connected in parallel with 11 th and 13 th integrated filters.The experimental results have shown the advantages of the new scheme.