As a widely used display terminal, the uniformity of Light-emitting Diode(LED) display screen brightness has a significant impact on its display effect. To improve the brightness uniformity of LED display screens, the Charge-coupled Device(CCD) image method is often used. This method uses a CCD camera to obtain the display image of the LED display screen, obtains the LED brightness through the image, and obtains the correction coefficient from it. In practice, it is necessary to determine the coordinates of the light points in the image. To address this issue, the relationship between the position of the light points in the LED display and the coordinates in the image was analyzed, and a formula for calculating the brightness of the light points was derived. And an internal circuit of Field Programmable Gate Array(FPGA)for brightness correction was designed. Through experiments, the non-uniformity of LED display screens has been reduced from 6.506 to 2.923. The results show that this method is efficient, time-saving, and can significantly improve the brightness uniformity of LED display screens.
In this paper, the electrochemical energy storage converter based on 3L-ANPC topology is taken as the research object, and the sliding mode controller(SMC) with disturbance observation is introduced. Firstly, a nonlinear SMC based on Gaussian reaching law is designed to control the grid current and inject the required active power and reactive power into the network. Then a Kalman observer is established for parameter mismatch and model uncertainty, and the stability of the disturbance observer is analyzed when there are errors in the parameters of the induction filter. Then, the neutral point voltage is balanced by zero vector injection carrier modulation. Finally, the effectiveness of the proposed method is verified by simulation.
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