Mechanism and Mitigation Strategy of Sub-synchronous Oscillation Caused by Grid-connected DFIG with Series Compensation

Power systems are at risk of sub-synchronous oscillation (SSO) when connecting doubly-fed induction generator (DFIG)-based wind turbines to transmission lines with series compensation. This paper focuses on the mechanism and mitigation strategy of SSO. Firstly, the mechanism of SSO is studied from two aspects: induction generator effect (IGE) and sub-synchronous control interaction (SSCI). An equivalent circuit is developed to illustrate the negative resistance effect. Based on the result of the analysis, the SSO mitigation strategy using notch filter and virtual resistance control is proposed. In order to verify the result of analysis and the effectiveness of mitigation strategy, time-domain simulations are carried out based on PowerFactory DIgSILENT.

Frequency Scan–Based Mitigation Approach of Subsynchronous Control Interaction in Type-3 Wind Turbines

Integration of wind energy resources into the grid creates several challenges for power system dynamics. More specifically, Type-3 wind turbines are susceptible to subsynchronous control interactions (SSCIs) when they become radially connected to a series-compensated transmission line. SSCIs can cause disruptions in power generation and can result in significant damage to wind farm (WF) components and equipment. This paper proposes an approach to mitigate SSCIs using an online frequency scan, with optimized phase angles of voltage harmonic injection to maintain steady-state operation, to modify the controllers or the operating conditions of the wind turbine. The proposed strategy is simulated in PSCAD/EMTDC software on the IEEE second benchmark model for subsynchronous resonance. Simulation results demonstrate the effectiveness of this strategy by ensuring oscillations do not grow.

Multimedia technology-assisted stereo geometry teaching

Multimedia technology makes our life more stereoscopic and intuitive. Graphic images and animations are the most important part of multimedia information expression. It makes our visual effects of three-dimensional representation of things more vivid, like the plane and three-dimensional we usually see. As with the picture, modern multimedia technology transforms our lives into three dimensions, integration, control, interaction and interaction. For the vivid three-dimensional representation of three-dimensional geometric figures in teaching, not only is it limited to the geometric composition of a piece of chalk, but more with the wide application of multimedia technology, multimedia-assisted teaching, especially multimedia-assisted three-dimensional geometric figure teaching is playing more and more The important role, through the aid of multimedia, has cultivated students’ spatial abstract thinking ability and ability to understand graphics and theorems. As multimedia becomes more and more concerned by the education community, this paper is about the question of why multimedia technology should be used to assist the teaching and application of solid geometry applications, and how to apply multimedia technology to achieve the maximum value of the teaching effect of stereo geometry. A lot of experimental research has been carried out. Through experiments, we have built a more complete multimedia assistant teaching system, which is beneficial for students to acquire new knowledge on the Internet. The multimedia technology-assisted three-dimensional geometric method is more conducive to mobilizing the enthusiasm and initiative of students than the traditional method. The biggest innovation of this paper is to use the indispensable advantages of traditional teaching to discount the media to the network platform. To some extent, the research in this paper enhances the guiding significance of interactive research to the actual development work.