Yin Minghui

Investigating instability of the wind turbine simulator with the conventional inertia emulation scheme

In order to pre-validate control strategies of wind energy conversion system (WECS), wind turbine simulators (WTS) are usually adopted to simulate the output characteristic of field wind turbines (WT) in the laboratory. Since the moment inertia of WTS is smaller than that of a practical WT, an inertia emulation scheme has been applied in WTS to replicate the dynamic behavior of real WT. In this paper, an instability phenomenon of the WTS with the inertia emulation scheme is investigated. By modeling of torque compensation loop based on discrete difference equations and analyzing its time-domain response, the instability of the WTS is interpreted and the stability condition of the system is proposed and theoretically proved. Finally, the simulations as well as experimental results verify the stability condition.

Research on the influence of fault current limiters on commutation failure and transient stability in AC/DC power system

In this paper, the method of installing fault current limiters (FCLs) near DC converter station is proposed, which is aimed at the commutation failure caused by short circuit fault of the DC inverter side in AC/DC power system. Influence mechanism of FCLs on suppressing commutation failure is analyzed. Whats more, effects of FCLs in different locations on commutation failure are compared. In addition, theoretical analysis of transient stability on multiple high voltage direct current (HVDC) commutation failure system with FCLs is discussed using the extended equal area criterion (EEAC) theory. Finally, simulation is carried out based on an actual power grid. Theoretical and simulation results show that, the action of FCLs can not only limit the short-circuit current, but also effectively suppress commutation failure and alleviate the power imbalance and the transferred system flow caused by the concurrent commutation failures, which can significantly decrease the power impact of the regional section and improve the transient stability of the system.

Two new upper bounds of the solution for the continuous algebraic Riccati equation and their application

In this paper, for the solution of the continuous algebraic Riccati equation (CARE), we derived two new upper matrix bounds. Compared with the existing results, the newly obtained bounds are less conservative and more practical, which means that the condition for the existence of the upper bounds derived here is much weaker. The advantage of the results is shown by theoretical analysis and numerical examples. Moreover, in redundant optimal control, when we increase the columns of the input matrix, some sufficient conditions are presented to strictly decrease the largest singular value of the feedback matrix by utilizing these upper bounds. We also give some examples to illustrate the effectiveness of these sufficient conditions.