The detection of composite insulator defects in substations still relies on manual inspection. In this paper, we propose a detection method for insulator crack shape features by improving the RCNN convolution kernel. The method can meet the premise of insufficient training sample data, but also can get better CNN training effect, and finally achieve accurate crack recognition. In the training phase, the RGB three-channel decomposition method is used to expand the training data set; the median filtering method is used to remove the noise; the improved convolutional kernel is used to train the CNN; in the test phase, the images are decomposed by RGB three-channel decomposition and input to CNN to get the exact crack center coordinates and length; the NMS algorithm is used to de-weight the images to get the final crack recognition results. The example analysis shows that the method in this paper can still achieve good recognition accuracy and accurately identify the specific location of cracks under the premise of insufficient training samples.
Electrically assisted manufacturing (EAM) is a promising and rapidly developing metal processing method. The power supply is a key sub-system for EAM, which needs to be designed properly. This paper proposes the model-based design of a low-voltage high-current pulse power supply used for EAM based on converter-level electro-thermal modeling. The thermal stress of key components is obtained by converter-level finite element simulations. A simplified thermal modeling method is proposed to reduce the computation burden of the FEM simulation to obtain the dynamic thermal profile under pulse current operation. The impact of the duration of the current pulse on the maximum temperature and temperature variations of MOSFETs is investigated based on the thermal model. A case study of a 10V/500A pulse power supply is presented to demonstrate the theoretical analyses and verification. The outcomes contribute to the design optimization and virtual prototyping of pulse power supplies for EAM applications.
When the permanent magnet assisted synchronous reluctance motor(PMaSynRM)runs at high-speed with flux-weakening control,the DC bus voltage utilization is not high,and the efficiency and torque output capacity of the motor are low. Therefore,a flux-weakening control strategy of permanent magnet assisted synchronous reluctance motor based on hexagonal trajectory was proposed. Firstly,based on the d-q axis equivalent circuit of the permanent magnet assisted synchronous reluctance motor,the voltage and current constraints of the flux-weakening process were derived,and the root cause of the flux-weakening control to improve the speed regulation ability of the motor was proved. Secondly,in order to give full play to the advantages of high-power density under high-speed operation of permanent magnet assisted synchronous reluctance motor,the over-modulation algorithm was derived. It was applied to the flux-weakening operation of permanent magnet assisted synchronous reluctance motor to achieve higher DC bus voltage utilization. Finally,the effectiveness of the proposed method was verified by simulation.
Aiming at the problem of imbalance load of feeder lines and reverse photovoltaic power flow in distribution network, the flexible interconnection scheme based on full-power converter is the key to realize intelligent control of distribution network. In this paper, a power control strategy for flexible interconnection system is proposed, which including heavy-load limiting control for the rational power distribution when some feeder lines are heavy-loaded, and power balance control for that all feeders are heavy-loaded to relieve the power supply pressure of flexible interconnection devices (FIDs). Case study based on real load data verifies that the proposed strategy can cope with different seasonal distribution network scenarios with different load characteristics and different degrees of reverse photovoltaic power flow. The proposed can suppress forward and reverse heavy load flow, and improve the power supply safety and efficiency of the distribution network.
In order to improve the sensorless control performance of permanent magnet synchronous linear motor, a sensorless control method based upon disturbance compensated flux observer was studied. The rotor flux observer studied in this paper combines the disturbance observer and the feedback compensation, which can suppress the initialization errors of dc bias and integration, and the parameter debugging is simple. In addition, the studied observer will not bring errors in the amplitude and phase of the flux linkage. The position and speed are estimated by a phase-locked loop to ensure the observation accuracy of the observer. Finally, the simulation verifies the correctness and effectiveness of this method.
