Design Of Power System Damping Controller Considering Singnal Transmission Delay

The cross-region interconnected power grid is the characteristic and development trend of modern power grid. Low frequency oscillation in the interconnected power grid not only limit the transmission capacity, but also have a impact on the system’s safe and stable operation. The traditional PSS, constitutes additional excitation feedback control by measuring the local information(e.g. power angle, angular velocity etc.), can damp local oscillation mode, but can not damp inter area oscillation mode effectively. Wide area damping control uses the global signals measured by wide area measurement system to design the controller, has a better effect to damp inter area oscillation mode. Time delay occurs when signals transfer in wide area power system, and the effect of delay on the controller’s performance and the system’s safe operation can’t be ignored, so the design of wide area damping controller should consider the time delay. Based on the wide area interconnected power system, the qualitative analysis about the composition of time delay in wide area damping control loop is finished, the problem about wide area damping control is studied for low frequency oscillation in this paper.A single delay wide area damping controller was designed for the low frequency oscillation problem. According to the delay dependent stability theory, derives single delay dependent sufficient condition of stability with all state variables have time delay. Design the controller based on the sufficient condition, and the simulation shows that the controller can significantly improve the two kinds of low frequency oscillation damping ratio and stabilizes the tie line power oscillations. Then design the controller only consider the delay of remote signals and ignore the local signals’ delay, the simulation verify the effectiveness of controller, and show that controller has damping effect with different time delays, but the control effect will become worse with the increase of time delay.A multiple delay wide area damping controller was designed for the low frequency oscillation problem, which can have damping effect under random time delay in a certain range. With all state variables have random time delay in a certain range, derive the multiple delay dependent sufficient condition of stability and design the controller. Small disturbance simulation verifies the effectiveness of controller and shows that the system finally converges to a certain range due to the random time delay changes in a certain range.A distributed damping controller was designed for the low frequency oscillation problem, which only uses the measurements from local and adjacent nodes as the input signals. Graph theory is adopted to describe the communication topology of the controller’s input signals. Taking the transmission delay of remote signals into account, the controller is designed under the time delay dependent sufficient condition of stability. Finally, the simulation results of a four-machine two-area system verified the designed controller can effectively improve the system’s damping and enhance the stability of system.