The Research On A Novel Power Flow Control System Of High-Speed Electrified Railway And Its Control Strategy

With the wide application of AC drive electric locomotives in railway networks, the negative sequence current and neutral section increase significantly, the co-phase power supply system with railway power flow control system (RPFCS) is an effective solution.Compared to traditional DC electric locomotive, AC electric locomotive’s traction power is bigger, its power factor is higher(it is usually unit power factor) and the harmonic content is less, so the problems of negative sequence and passing netural section in AC electrical locomotive’s traction supply system is particularly prominent. In order to reduce the capacity of inverter part in RPFCS, decrease the one-time cost of the cophase supply system and improve its reliability, a noval hybrid railway power flow control system (H-RPFCS) suitable for high-speed electrical railway is put forward in this paper, based on analyzing the structure of traction power supply system and the principle of RPFCS. The main work and innovation points are as follows:At first, the composition of the traction power supply system are introduced, the co-phase power supply system with RPFCS is detailed analyzed. And the disadvatange and advantage of cophase power supply system and Interphase power supply system is compared. On this basis, this paper introduce the structure and windings scheme of cophase power supply system based on V/v traction transformer.it is focus anysis that the principle of RPFCS and its current and power relations.Then, In order to reduce the operation voltage and capacity of inverter part in RPFCS, a noval H-RPFCS suitable for high-speed electrical railway is put forward in this paper. This paper analyze its principle of this system, operation voltage characteristic of its inverter part and compared it with RPFCS. Based on it, the key parameters of H-RPFCS is designed and the design procedure of key parameters is given in this section. Then, the capacity of RPFCS and H-RPFCS were compared in theory. The theoretical analysis shows that the capacity of inverter part in H-RPFCS is much lower than that in RPFCS in completing same compensational task, so the total cost and loss of the system are reduced, as a result, the reliability of the H-RPFCS is improved.Next, directive extraction algorithms are introduced, then, this paper built the instruction current extraction algorithm of H-RPFCS and the direct current control strategy for compensated side closed loop with compensation current instruction (denoted as CCI-CSCL direct current control), the deficiency of the CCI-CSCL control strategy is analyzed, based on it, a noval no compensation current instruction (NCCI) control strategy is proposed. By analyzing the internal system equilibrium principle of active energy, the possibility of NCCI control strategy is demonstrated. Direct current control strategy for compensated side closed loop with NCCI (NCCI-CSCI) of H-RPFCS and direct current control strategy for power side closed loop with NCCI (NCCI-PSCL) of H-RPFCS are built. Compared to CCI-CSCL direct current control, The proposed NCCI-PSPL direct current control strategy doesn’t need compensation current detection calculation according to locomotive current, so it reduce the burden of the controller, at the same time, it also save a high-power current transformer, reduce the cost of the control system and improve its reliability and accuracy.Finally, the simulational model of H-RPFCS is set up in Simulink. The compensation effect of H-RPFCS and RPFCS is compared under the condition of steady and transient state, at the same time, the direct current control strategy of NCCI-PSPL of H-RPFCS is aslo validated. The results of simulation analysis show that the correctness and rationality of the proposed system structure and NCCI-PSPL direct current control strategy.