Rate of Change of Frequency Estimation for Power Systems Using Interpolated DFT and Kalman Filter

Abstract

This paper presents a new method for estimating rate of change of frequency (RoCoF) of voltage or current signals measured using instrument transformers. The method is demonstrably superior to currently available methods in literature, in terms of estimation-latency and estimation-error. The estimation is performed in two steps. In the first step, the analog voltage or current signal obtained from an instrument transformer is statistically processed using interpolated discrete Fourier transform in order to obtain the means and variances of the signal parameters. These means and variances are then given as inputs to the second step, in which Kalman filtering is used to find the final RoCoF estimate. Accurate mathematical expressions for the means and variances of signal parameters have been derived and used in the second step, which is the main reason behind the superior performance of the method. The applicability of the method has been demonstrated on a benchmark power system model.

FAPI Controller for Frequency Support in Low-Inertia Power Systems

“…-Estimation of RoCoF as an input signal can help the performance of the frequency derivative-based FAPI controller. This can be confidently done by using emerging approaches, like the Kalman filter-based method [44].…”

Roles of Dynamic State Estimation in Power System Modeling, Monitoring and Operation

“…On the other hand, ROCoF has been utilized as an important parameter for system protection, especially for the inverter-based generations. By treating it as a dynamic state instead of an algebraic variable, an accurate estimation of it can be achieved [20]. The measurements are always subject to noise and even large errors caused by communications, instrument transformer saturation, cyber-attacks, etc.…”

Dynamic State Estimation for Power System Control and Protection

“…Based on this idea, a hybrid decentralized control is proposed in which RoCoF estimation is used to infer if a large disturbance has occurred. To do this, the DSE-based RoCoF estimate obtained using [34] is multiplied with the machine's inertia to get a switching signal: if the absolute value of this signal is greater than a predefined value (say 0.5 p.u.) for two AC cycles, then the control is switched to the nonlinear control given in [30].…”