A Divide-by-Difference-Filter Based Algorithm for Estimation of Generator Rotor Angle Utilizing Synchrophasor Measurements

This paper investigates the possibility of using a nonlinear estimator for estimating the internal variables of a synchronous generator, such as the rotor angle, from the data acquired from phasor measurement units (PMUs). A divide-by-difference filter (DDF) has been used for accurate estimation of the rotor angle of the generator. The proposed rotor angle estimator utilizes the measurements of the terminal voltage, active power output, and field voltage of the generator. These measured quantities and the reference mechanical torque are utilized by the nonlinear state estimator to estimate the generator rotor angle. The measurement update for the DDF has been carried out every 20 ms. The measurement error used in the design and implementation of the filter is assumed to be white Gaussian noise. The effectiveness of the method has been tested on a single machine infinite bus system, a nine-bus system, and a 68-bus New England-New York interconnected system. The simulation results show that the proposed method provides more accurate estimation of the rotor angle of a generator.