LCL grid-connected inverter is good at suppressing the high frequency current, but the inherent resonance frequency of the filter will lead to the resonance peak. Therefore, the active damping is commonly used to suppress the resonance effect. Since the weighted average current control can provide better bandwidth for the system with high frequency and has the characteristics of system reduction, it is often used to replace the traditional dual-loop current control in the application of LCL grid-connected inverter. However, the reduction of current resonance peak at the grid side by the weighted average current control is limited, so it is necessary to combine the grid voltage and capacitor current feedback loop to achieve the ideal results. In weak grid, the newly added feedback path would easily lead to the loss of system reduction, which results in the existence of transient variables in the transfer function affecting the stability of the control strategy. To solve this technical problem, this paper addresses a new control method of LCL grid-connected inverter based on weighted average current control. By adding a capacitor current feedback path, pole-zero cancellation of the control system is realised as to reduce the systematic order and improve the robustness of the controller under the time-varying weak grid.
With the rapid development of materials technology, insulating materials are widely used in spacecraft construction with its excellent electrical and mechanical properties. However, compared to the Earth's surface environment, the insulating materials in vacuum are prone to electrostatic discharge -flashover along the surface. In this paper, we will introduce the formation, characteristics and mechanism of flashover in vacuum environment, and provide a theoretical basis for the targeted protection of spacecraft in the development process. In the meantime, this paper summarizes the research progress and the difficulties of the vacuum flashover at home and abroad, and clears the thought for the study of the vacuum surface flashover in the future.
Abstract. With the continuous development of science and technology, the convenience spacecraft brought to us has been everywhere. During the orbit operation, the spacecraft interacts with the complex space environment, which makes the surface and internal materials appear charging and discharging phenomenon, and thus may lead to shortened its life or cannot work properly, or even scrapped and so on. The surface charge and the medium charge of the spacecraft during orbital operation are discussed in depth. It has certain reference value for the system to study the spacecraft charged and the protection design of spacecraft charge and discharge.
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