Wide Area Control through Aggregation of Power Systems

The power systems are operating closer to their capacity limits to improve the efficiency of the system operation. This has increased the risk of system failures in the event of possible contingencies. The electricity supply industries need tools for dealing with system-wide disturbances that can cause widespread blackouts in power networks. When a major disturbance occurs in the system, the protection and controlling systems play the greatest role to prevent further degradation of the system, restore the system to a normal state, and minimize the impact of the disturbance. Synchronized phasor measurement units (PMU) can be installed in the network to improve the performance of the power systems in the event of faults by wide-area monitoring and control systems. Due to the complexity of power systems and large number of dynamic states, the conventional control designs based on wide-area measurements require extensive computational effort which is not practical for dealing with large disturbances in the network. In order to reduce the complexity of the power system, unimportant dynamics and states can be excluded for the control design by obtaining a reduced dynamic model containing major system states that have higher effect on the system stability. In this research, a feasible wide-area control approach based on dynamic reduction and aggregation of power systems is presented to improve the performance of the system in the event of severe faults. The model reduction is an important part of this research which is performed on the entire network to obtain a reduced model with measurements. The nonlinear reduced model is first obtained based on the available model of the power system and a Kalman filter is applied to estimate the iv Wide Area Control through Aggregation of Power Systems reduced system states using measurements. The reduction process relies on identification of the coherent generators in the network. This is addressed in this research by developing a method to find the coherent generators and areas which stay coherent for a wide range of operating conditions. A more general dynamic reduction approach is achieved by identifying the parameters of the nonlinear reduced model by online processing of the data obtained from phasor measurement units. The reduced model is integrated with a nonlinear Kalman filter to estimate the angles and frequencies of the equivalent areas which represent the inter-area oscillations of the power system. The main goal of this research is achieved by integrating the developed reduction …