Doubly salient electromagnetic machine (DSEM) can constitute a competitive rugged starter generator (SG) system. But under the traditional startup control method, the field current is set to the rated value regardless of speed or load torque conditions, and the phase currents are controlled with standard angle commutation, bringing in large power loss as well as non‐negligible torque ripple. To overcome these shortcomings, based on the established DSEM power loss calculation model, a currents distribution strategy is proposed according to the obtained quantitative relationship between DSEM power loss and field current under multiple speed and load torque conditions. Then, to identify the load torque for practical implementation, a novel torque observer is designed based on back propagation (BP) neural network algorithm. Afterwards, to further improve the startup torque performance, currents distribution with advanced angle commutation (AAC) strategy is put forward, where the optimal advanced angle is selected from a 3‐D lookup table to achieve the minimal commutation torque ripple. Under the proposed control strategies, DSEM power loss as well as the output torque ripple are desired to be decreased, the simulation and experimental results on a 12/8‐pole DSEM prototype verify the correctness and feasibility of the proposed strategies under multiple operating conditions.

To supply the cathode voltage for the two gyrotrons (140GHz/2MW/3s) of the electron cyclotron resonant heating(ECRH) system on HL-2A, a high voltage power supply (HVPS) based on pulse step modulator(PSM) with rated output of 80kV/200A has been built. It is found that storing energy of the PSM HVPS is very lower than traditional HVPS. It's beneficial to load protection. In the HVPS, there are 8 dry-type multi-winding transformers and each transformer has 14 secondary windings. The electrical insulation level between the primary side and the secondary side of the multi-windings transformer reach to 150kV. There are 112 switch power supplies in the HVPS, the output voltage can be regulated from 0 to 80kV by modulating their delay time and pulse widths. To realize two gyrotrons parallel operating and respective quick protection, solid-state high voltage modulators(SSHVM) based on IGBT are also applied in the power supply. The over-current and over-voltage protection are executed by turning off the HVPS and the SSHVM. The protection time is less than 10μs. A fully digital controller based on digital signal processor and field programmable gate arrays has been developed to ensure the stability of output voltage of the HVPS. The design circuit and elements are described, and test results of the HVPS of the gyrotrons are given.

In order to verify the feasibility of OH power supply design, simulation study based on Simulink is carried out. The simulation model includes 300MVA six-phase motor generator, transformers, converters, crowbar, cable and load. The models of transformers, converters and the control system are built in detail. The impedance of AC side includes the one of generator, transformers and cables are estimated. The inductance of interphase reactor is calculated and selected to ensure the current balance in parallel mode and restrain circulating current in circulating current mode. The normal operation and protection strategy of possible faults are discussed. The simulation and analysis results show that the circuit topology is feasible. Output curve is reasonable through optimizing control and circuit parameters.