Analysis Of Deviation Of Real-time Measured Phase Angle Under Dynamic Condition

Real-time and accurate measured data of voltage phase angle is very important to power system’s monitoring and analysis. With the development of Global Position System and information communication technology, power system phase angle monitoring device based on Wide Area Measurement System becomes much more matured. Power flow can be directly obtained through the monitoring device if monitoring device is allocated properly in power system. Power flow computation speed can be accelerated even if monitoring devices are not so enough.Phase angle measuring methods used in present measuring devices are all required to be under steady condition. However, with the increasing proportion of new energy generators in power system and new kinds of non-linear loads connected to the grid, the power system is disturbed more often now. Nowadays power system is more under the dynamic operation condition than steady state, thus the phase angle measuring methods based on steady condition could have some error.The real complex power system is simulated by a simple circuit to analyze the components of voltage signal in dynamic state. It is achieved from the analysis that voltage signal also contains lots of damping components besides sinusoidal signal. Fourier Transform method is used in this paper to analyze the error of phase angle caused by damping components. Furthermore the impact of different characteristic roots and their corresponding residues on the error of voltage phase angle measuring is discussed. Finally the existence of phase angle’s maximum deflection angle is also verified.Since the beginning of the dynamic procedure cannot be always synchronized with the onset time of sampling period. This paper discusses the case that only a part of sampling value is contained with dynamic information during the sampling period, and gives out the analytic describe of the phase angle’s components.By analysis above, it is pointed out that there is a deviation angle between the real-time measurement voltage phase angle and ideal phase angle if the voltage signal contains some damping components. The deviation angle reflects the function of exponential damping component. The deviation angle will get bigger when the exponential damping components take more proportion. And the deviation angle will make the real-time measurement value bias and reduce the accuracy of the grid’s analysis and monitoring.