Chen Xiangyi

Wide-area PSS design considering the time-delay of feedback signals

Aimed at the inter-area low frequency oscillation in interconnected power system, the Wide-area PSS considering the time-delay of feedback signals is designed in this paper. The Wide-area PSS is composed with two-channel, the inputs of one channel are local signals without time-delay, the inputs of the other one are global signals with time-delay. Then the state equations of the closed-loop system including Wide-area PSS is presented, the sufficient condition of the time-delay system stability analyzed by Lyapunov function with LMI approach. The Multi-objective Adaptive Particle Swarm Optimization Algorithm (MAPSO) is proposed to design the parameters of Wide-area PSS, which takes the time-delay stability and the control effect of the controller as the optimization objects. At last the Wide-area PSS is applied to a practical system to control the poor damping inter-area low frequency oscillations. Simulation results indicate that the controller can provide good supplementary damping to the system and improve the robustness of time-delay.

On-line Transient Stability Assessment Using Hybrid Artificial Neural Network

On-line transient stability assessment of a power system is not yet feasible due to the intensive computation involved. Artificial neural network has been proposed as one of the approaches to this problem because of its ability to quickly map nonlinear relationships between the input data and the output. In this paper a hybrid neural network for TSA is proposed. The proposed hybrid neural network is composed of a Kohonen network and several radial-basis function (RBF) networks. It possesses properties of both kinds of networks. So, its ability of TSA is improved. The proposed hybrid neural network is applied for an actual power grid, the obtain results confirm the validity of the developed method. Also, a comparison between the proposed neural network and other ones is present, which indicates the efficiency of the proposed neural network.

Design a Wide-ara PSS for damping inter-area low-frequency oscillation

Based on the inter-area oscillation characteristics in interconnected power system, the machines participating in oscillation can be equivalent to a two-machine system according to their respective inertia center. This paper first deduces electromagnetic torque coefficient for the equivalent two-machine system, which lays the foundations of electromagnetic torque analysis of inter-area oscillation mode. On this basis a Wide-area PSS with two-channel feedback structure is presented, and the extended phase compensation method is adopts to coordinate mapping and conversion by a transfer function between wide-area and local feedback state variables, at last the mechanism of Wide-area PSS to damp inter-area oscillation is analyzed systematically. Simulation results show that it can not only damp inter-area mode effectively, but also improve small signal stability limit. Compared with other stabilizers, the proposed two-channel Wide-area PSS is helpful to make better the damping characteristic of the system.

Adjusting for the unblance of capacitor banks with H-bridge connection of power filter on UHVDC converter station

A method for adjusting the unbalance of the capacitor banks with H-bridge connection of the power filter on UHVDC converter station in this paper. Firstly, the concept of unbalance degree is proposed, and the expression of the unbalance degree is deduced, then the new method for adjusting the unbalance of the capacitor bank with H-bridge connection is put forward. The detection method is adopted to detect and adjust the unbalance of the capacitor with H-bridge connection. The test result shows that the proposed method could improve the work efficiency greatly, and the method is suitable for field commissioning test in UHVDC converter station.