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Direct loading test are the general test method to obtain running performance of induction motors. However, direct loading test is difficult to test cryogenic induction motors for submerged liquefied natural gas (-162°C, LNG) pumps because the motors are installed inside the LNG pumps and share the shaft with the pump. This paper presents a semi-static methodology that can successfully predict the running performance of a 15kW cryogenic induction motor for LNG pumps. The methodology combines a static double-frequency test with a rotating no-load test, based on a Г-equivalent circuit model, to calculate the running performance of the 15kW motor in liquid nitrogen (-196°C, LN). Experimental validation of the methodology is provided by direct loading test in LN. Finally, the methodology is used to predict the performance of the motor in LNG.

When tidal current energy generation is connected to the grid with distributed energy or directly applied to the equipment, it is necessary to detect the power quality of tidal current energy to avoid grid operation failure or damage to precision equipment. In this paper, the principle of tidal current energy generation is introduced, and the problem of power quality is analyzed based on Hilbert Huang transform(HHT). The Hilbert spectrum is obtained by Empirical Mode Decomposition(EMD) and Hilbert transform. The results show that HHT can detect the harmonic and other power quality problems in power system, which is of great significance in the further analysis of quality detection of tidal current energy.

This paper reports on a method for the analysis of a cryogenic induction motor for submerged liquefied natural gas (-162°C, LNG) pumps by coupled electromagnetic and thermal models in commercial software, MotorCAD. Examples using a 15kW cryogenic prototype in LN illustrate the method is an available tool for analyzing the cryogenic motor. Furthermore, the motor performance in LNG is investigated by this tool. This paper will be useful to scholars and engineers interested in cryogenic motors.

Focus on the torque balance control of dual-motor driven system (DMDS), this paper proposes an equivalent switching variable structure sliding mode control (VSSMC) algorithm, which can improve the response speed and anti-interference performance of the system. Comparing with the traditional PI control algorithm, the equivalent switching VSSMC can eliminate the steady-state tracking error completely. Based on two control strategies proposed in the previous study, the simulation analysis of the two algorithms is carried out respectively by using MATLAB in this paper, and the effectiveness of equivalent switching VSSMC algorithm is further verified by the simulation results.