ENHANCING THE FREQUENCY RESPONSE OF ROGOWSKI COIL USING FEEDBACK PID COMPENSATOR WITH INTEGRATOR CIRCUIT

Summary

Rogowski coil is considered an electrical device used for the measurement of Alternating Current (AC) or
high-speed current pulses from other devices. It has gone through many stages of development towards
improving its performance and applications. It has been a challenging task to develop a Rogowski coil model
that maximizes the sensitivity and bandwidth of the coil simultaneously for current measurement based on the
arbitrary selection of the geometric factors. To address this challenge, an adaptive compensator for Rogowski
coil performance improvement using Proportional Integral and Derivative (PID) technique has been presented.
The mathematical models of Rogowski coil circuit have been developed, an integrator designed and a PID
compensator was developed. Then MATLAB/Simulink models including MATLAB programme were
developed for Rogowski coils whose output responses were improved with the addition of the PID controller.
In the first analysis, the Rogowski coils were evaluated in their conventional state and the frequency domain
analysis revealed that the first model has a gain of 13.3 dB at a frequency of 144 MHz and the second model
has a gain of 38 dB at a frequency of 27.4 MHz. Their phase margins (errors) were 103o
and 90.7o
respectively.
Thus, these results showed that the Rogowski coils band of frequencies from lower and upper limits were in
the tens of MHz. An integrator was added to the Rogowski coils and the simulation results indicated that the
frequencies of the coils were enhanced such that a frequency of 50/60 Hz can be measured or detected together
with frequencies in tens of MHz (up to 7 decades and more). Furthermore, the PID compensator was designed
and integrated with the individual Rogowski coils plus the integrator. The results revealed that the frequency
limits of the coils were further improved such that it is possible to measure and detect current for fast switching
transient and at the same time, retain the capacity to accurately measure currents of 50/60 Hz given that the
lower limit of the frequency band is 0.1 Hz. Generally, two Rogowski coil models were simulated with the
developed PID compensator and the results showed that the PID compensator provided similar results in the
frequency domain for both coils, which validates its adaptability to parameter variation.

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