Research On Electrical Characteristic Of Novel Balance Transformer In Electrified Railway

Traction load has the characteristics of nonlinear, asymmetry and large power in electrified railway, the three-phase power supply system is transported to the zero sequence current and negative sequence current of when is run time through the traction transformer, resulting in asymmetric operation and energy loss. According to the problem of the zero sequence current and negative sequence current, the transformer winding connection equations, output-port voltage equations, magneto-motive force balance equations, voltage transfer equations and the method of symmetrical components of power system are used, a novel balance transformer is designed, the circuit characteristics and winding structure of novel balance transformer are researched. The novel balance transformer system of the 3 single phase based on Matlab/Simulink simulation platform is established, the electrical characteristics of novel balance transformer is analyzed. The combined dynamic simulation system of the traction load and novel balance transformer is established, the electrical characteristics of the cycling operation and double car operation condition are researched. Research shows that, the performance of balance transformation and natural decoupling of the novel balance transformer are satisfied, and has the function of eliminate zero sequence current and reduce negative sequence current. The fundamental research contents and achievement are as follows:(1) The current various balance transformer is systematically analyzed(the impedance match balance traction transformer, YNvd connection balance traction transformer, asymmetrical connection three-phase to two-phase balance traction transformer and novel impedance match three-phase to four-phase balance traction transformer), the operation electrical characteristics of various balance transformer are derived and compared, and the performance of various balance transformer are summarized.(2) A novel balance transformer is designed, the wiring scheme and the iron core winding structure of the novel balance transformer are given. Between the windings of the balance conditions, current matrix, short circuit impedance of winding, two-phase decoupling condition, performance of balance transformation and characteristics of current unbalance degree of the novel balance transformer are researched. Theoretical study shows that: the novel balance transformer has the windings and iron core structure simple, symmetrical of winding structure, winding less, relationship of winding short circuit impedance simple. The performance of balance transformation and natural decoupling condition are satisfied, and has the function of eliminate zero sequence current and reduce negative sequence current, and high material utilization rate.(3) The novel balance transformer system of the 3 single phase based on Matlab/Simulink simulation platform is established. The no-load experiment, the symmetry experiment, the short-circuit experiment and the load experiment are carried out. The experimental results show that: the novel balance transformer has the function of the three-phase power system can be converted into two symmetrical traction power supply system. When the traction side one phase short circuit or with load balancing, the primary side current is symmetry and the negative sequence current and zero sequence current are approximately 0. When the traction side two-phase short circuit, with unbalanced load or load changes, the negative sequence current is relatively small and the zero sequence current is approximately 0, and the traction operation will not affect the normal operation of the other. That is: the performance of balance transformation and two-phase decoupling of the novel balance transformer are satisfied, and has the advantage of natural decoupling and the function of eliminate zero sequence current and reduce negative sequence current. On the based, the operation control strategy of novel balance transformer under different load case are presented.(4) The combined dynamic simulation system of the traction load and novel balance transformer is established, the electrical characteristics of the cycling operation and double car operation condition are researched. The experimental results show that: the difference of reaches the minimum of the positive sequence current and negative sequence current under cycling operation condition, and the current unbalanced degree is approximately 1 of the traction load changes before and after. The negative sequence current of reaches the minimum under double car operation, the positive sequence current has been increased, and the current unbalanced degree is approximately 0 of the traction load changes before and after. To elimination the zero sequence current and the decrease of negative sequence current.