The Research Of Power Quality To Electric Railway Base On Novel Transformer And Inductive Filtering Technology

The power quality comprehensive management of the traction substation has been a topic of concern. Based on the supportion of National Natural Science Fund Project "research of the negative sequence and harmonics unified management theories and methods of electrified railway based on the novel transformer "(Project No.51077044) and Hunan Provincial Natural Science Foundation "the negative sequence and harmonic suppression combined function traction transformer and its key technology research "(Project No.12JJ2034), the paper focuses on the traction substation power quality issues. The fundamental research and achievement are as follows:Several typical structure and the principle of balance transformers are analyzed firstly. Then the paper presents a novel asymmetrical connection balance transformer and has got a patent for this invention. The basic principle and connected scheme of the transformer are clarified. The mathematical model of the transformer is established. Based on this, the balance condition (i.e., the neutral current in primary side is zero) and the decoupling condition of the two-phase system are also obtained. What’s more, this paper clarifies the three-phase short-circuit impedance equal condition. The transformer has the advantage that the two-phase decoupling condition is naturally satisfied if the balance condition is matched. Compared with the typical balance transformer, which has a range of new features:Three-phase three-leg core is adopted and each phase has only two or three windings in this transformer. The transformer has a simple structure of iron and windings and has high material utilization ratio, while the two-phase system has a public point and a loop in which the third harmonic currents can flow. The transformer has good performance and may be utilized to two-phase or single power supply such as traction power supply in electric railway. A asymmetrical connection three-phase to four-phase balance transformer is also clarified in the paper. Its wiring scheme is elaborated and the mathematical model is analyzed, the transformer is suitable for electrified railway AT power supply and four-phase power transmission systems. Simulation results prove the correctness of the theoretical analysis about the above mentioned transformers.For a2kVA small-capacity transformer model, the design mothed is discussed. The design features of the new transformer is described and the electromagnetic design scheme is obtained. The wire with larger cross-sectional area is adapted in order to minimize the impact of the winding resistance. The principle of magnetic method and the principle of energy law are conducted to get the short-circuit impedance. Results from the two methods are consistent. The short-circuit impedance paremeters meet the design requirements. Using the design parameters, through the MATLAB simulation, the results proved the correctness about design of transformer modle and effectiveness to suppression negative current.A novel compensation system, based on novel V/v transformer and inductive filtering, is proposed in the paper. The structure of the system is discussed and the operation principle of the system is elaborated. The negative sequence current compensation principle is deduced and a novel reference current detection algorithm is obtained. The quasi proportional resonance is presented which has good current tracking effect even when fluctuation of the grid frequency. Simulation results show the correctness of the proposed system and control method.A novel integrated compensator based on multi-purpose balance transformer is proposed in this paper. The compensator consists of a three-phase voltage source converter (VSC) and two multi-groups thyristor switched capacitor (TSC). Firstly, the operation principle of the system is clarified. Then the reactive current distribution method is designed and the compensation algorithm based on balanced mmf using virtual current is deduced. Furthermore, the compensation equivalent circuit mode is established, the reference current detecting and the collaborative control strategy for TSC and VSC based on reactive power current abruption VSC are presented. Simulation results have shown the validity of the proposed system.A2kVA transformer model is developed. Many experimental studies have been carried out. The theoretical analysis and the design method of the new balance transformer is correct.