As the energy crisis and environmental pollution continue to be a gradual threat, the energy saving of transmission systems has become the focus of railway vehicle research and design. Due to their high-power density and efficiency features, permanent magnet synchronous motors (PMSM) have been gradually applied in railway vehicles. To improve the efficiency of the transmission system of diesel railway vehicles, it is a good option to use PMSM as both a generator and traction motor to construct a full permanent magnet transmission system (FPMTS). Due to the application of the new FPMTS, some of the original control strategies for diesel railway vehicle transmission systems are no longer applicable. Therefore, it is necessary to adjust and improve the control strategies to meet the needs of FPMTS. We studied several key issues that affect the reliability and comfort of the vehicles. As such, this paper introduced the FPMTS control strategy, including the coordinated control strategy of the diesel and the traction motor, the two degrees of freedom (2DOF) decoupling current regulator, the maximum torque control of the standardized unit current, the wheel slip protection control, and the fault protection strategy. The experiment was carried out on the test platform and the test run of the diesel shunting locomotive equipped with the FPMTS. The results showed that the control strategy described in this paper met the operation characteristics of the FPMTS and that the control performance was superior. The study of FPMTS lays the foundation for the subsequent application of permanent magnet motors in high-powered diesel locomotives and high-speed diesel multi-units.

Due to the unchangeable air-gap flux density, the voltage output by permanent magnet synchronous generator (PMSG) will have a variation when the load changes. In order to reduce the voltage variation when PMSGs provide power for the rectifier load in diesel railway vehicles, an optimal method is presented to design a 9-phase PMSG. This optimal method not only ensures the open-circuit voltage of the generator equals the rated voltage of the load, but also it guarantees the PMSG has a low voltage change rate at the same time. In this paper, the saliency ratio range and the relationship between resistance of load and the induction of d-axis are derived according to the two-axis theory, when the PMSG has the negative or zero voltage change rate. Then based on the result of the derivation, by adding the I-shaped permanent magnet (PM) to the d-axis magnetic circuit of V-shaped interior PM rotor, a V-I-shaped PMSG is formed. After that, the Kriging method and the finite-element method (FEM) are used to establish a multi-objective function model. By calculating the minimum value of the multi-objective function, the construct dimension of the I-shaped PM is obtained. After the optimal design results are verified by the FEM, a 520 kVA 9-phase PMSG is manufactured to validate the effectiveness of the proposed methods.