Search

Increasing penetration level of renewable energy results in unprecedented operational challenges of AC grids due to generation uncertainty and reduced inertia. In grid emergencies, Fast active Power output Reduction (FPR) is demanded to drop wind turbine generator (WTG) power outputs faster than usual. However, the power mismatch between WTG mechanical power input and reduced electrical power output resulted from FPR can lead to rotor overspeed, which cannot be timely nullified by slow‐responding pitch control. Therefore, this paper proposes a novel FPR scheme for doubly‐fed induction generator (DFIG)‐based WTG through coordinated control of DC chopper and pitch angle. Specifically, the FPR command is executed by DFIG rotor‐side converter control, while rotor overspeed is restricted by triggering the DC chopper to dissipate the mismatched power. The pitch angle is actuated at a maximal rate to eliminate the mismatched power and switch off the DC chopper. The effectiveness of the proposed FPR scheme is verified through comparative simulation studies under FPR command execution and a grid fault. It shows the proposed scheme can achieve FPR in tens of milliseconds, avoid rotor overspeed and provide low‐voltage ride‐through capability in a fully‐controlled manner. [ABSTRACT FROM AUTHOR]

In this article, a series of novel semi‐interpenetrating polymer networks (s‐IPNs) based on linear polyimide (PI) and crosslinked epoxy (EP) were firstly prepared aiming at controlling violent vibration and noise originating from operation of the machine. The damping, thermal, and mechanical performances of s‐IPNs films were systematically investigated in terms of the structure of polyimide (the molar ratios of diamines) and the component ratios of PI/EP. The results indicate that PI/EP s‐IPNs films exhibit prominent damping properties, and the effective damping temperature range can reach up to 58.8 °C when molar ratio of diamines is 1:3 within PI and component ratio of PI/EP is 70:30. Meanwhile, all the PI/EP s‐IPNs films show good thermal stability compared to cured EP and certain mechanical behaviors due to the formation of semi‐interpenetrated structure. Meaningfully, the prepared novel PI/EP s‐IPNs will be used as effective damping materials and have a potential application in damping fields. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48032. [ABSTRACT FROM AUTHOR]