RoCoF calculation using low-cost hardware in the loop: multi-area Nordic power system

This research paper presents a rate of change of frequency (RoCoF) implementation using low-cost hardware in the loop (HIL) with application to Nordic Power System (NPS). Two methods to calculate the RoCoF are presented: Incremental difference one step and moving window (MW) or rolling window. HIL) approach is used to reach natural noise levels found in the frequency signal obtained from real power devices. The low-cost HIL implementation is based on two Arduinos ® in the loop. An Arduino ® working as standalone is used to generate an analogue signal representative of one area of the NPS, a second Arduino ® in the loop contains the RoCoF calculation methods and filters. This paper analyses the effect of including lowpass filters (LPFs) because the noise of the frequency affects the RoCoF calculation. Three cases are implemented in the Arduino ® and compared with Simulink ® /MTALAB™ simulations: Base Case: no filter and noise signal, Case I: LPF applied to the input frequency signal, Case II: LPF at the frequency signal and LFP at the output of the RoCoF (smoothing). Results demonstrate that RoCoF calculation methods worked correctly in the HIL and using two LPFs clean the signal from the noise produced by the Arduino ® .