Study Of The Damping Controller Considering Signals Transmission Delay For Power System

Inter-regional connection is an important characteristic of modern power system. As the power grid develop,the increasingly serious low-frequency oscillations problems has become quite prominent. Though there are lots of references concentrating on the low-frequency oscillations problem, many problems have not been yet well solved. Among these problems, the signal transmision delay is a significant problem. A long time delay may be a detriment to system stability and degrade system robustness.The basic function of. a power system stabilizer(PSS)is to add damping to the generator rotor oscillations. PSS based on shaft speed signal has been used successfully on generator unit. However, the low-frequency oscillation still happened even some PSS were installed in generator unit. The new principles of controller design should be study so as to increase damping ratio to the local oscillation mode and inhibit the low frequency oscillation.The input signals of the conventional PSS come from local generator, can damp the local mode oscillations well, but not the inter-area mode oscillations. Wide-area Measurement System can retrieval the real time dynamic and static information of the large scale power system under the same time reference, helping to resolve the problems of the dynamic analysis and control for an interconnected power system, especially the low-frequency oscillation. However, communication delay is a non-ignorable factor for the stability of wide-area control.To improve the existing methods, the damping controller including the power system stabilizer,the governor damping controller and the wide area damping controller considering signals transmission delay for power system is presented for the first time in the dissertation. The main works presented in the dissertation contain:1. The Pade approximation method is used to express time delay, Analysis of the influence of the signal transmission delay on the power system stabilizer, and calculate the delay margin to maintain the system asymptotic stability. Research shows that the second-order Pade approximation has better accuracy. The power system stabilizer considering signals transmission delay is proposed for generators excitation controllers, Simulations in a single-machine infinite bus test system are given to demonstrate the advantages of the proposed.2. The principle of the governor damping control is discussed. The governor damping controller considering signals transmission delay is designed. Simulations in a single-machine infinite bus test system are given to demonstrate the advantages of the governor damping controller.3. The principle of the wide area damping control is discussed, The second-order Pade approximation method is used to express time delay. The equivalent damping ratio conception based on the Routh algorithm is proposed,Simulations in a 4-machine test system are given to demonstrate the dvantages of the wide area damping controller.The theoretical results proposed in the dissertation establishes the control theory and engineering application foundation for the low-frequency oscillations. The economical efficiency can be improved on the promise of safe operation of power grid.