Research on control strategy for AC side asymmetric fault of MMC-HVDC transmission system

When the Modular Multilevel Converter (MMC) fails on the AC side, the operating characteristics of MMC will be damaged. If the system wants to retain stable for a long time in the process of operation, it is obliged to design the control strategy in case of asymmetric fault. In this article, the control strategy based on feedback linearization principle is adopted to diminish the negative sequence current caused by breakdown, and a DC voltage controller is devised to suppress the fluctuation of the double frequency component under asymmetric fault conditions. The validity of the control strategy requires to be verified, the running results on PSCAD platform indicate this method is effective and feasible.

Study of a Four Rotor Aircraft Modeling

In order to design the four rotor aircraft attitude control system, take the hover state or low speed flight state as a benchmark, firstly, divide the aircraft model into linear motion model and the angular motion model and model it separately, the nonlinear mathematical model of aircraft can be obtained. And then use the small disturbance linearization principle to linear mathematical model for a simplified model. After substituting into the previous experimental data, the mathematical model which controller design needs is got.

ON THE COMPLEX GINZBURG–LANDAU EQUATION WITH A DELAYED FEEDBACK

We show how to stabilize the uniform oscillations of the complex Ginzburg–Landau equation with periodic boundary conditions by means of some global delayed feedback. The proof is based on an abstract pseudo-linearization principle and a careful study of the spectrum of the linearized operator.