Fault-tolerant grid frequency measurement algorithm during transients

An apparatus that determines in real time frequency of grid signals x(t) corresponding to an electrical grid comprising:

• a transient detector configured to:
• monitor a signal indicative of a grid signal x(k) from a voltage meter or current meter connected to the electrical grid, where the grid signal is expected to include a periodic signal with a nominal frequency fo and a sampling rate fs;
• produce, in real time and at the sampling rate of the monitored signal, a deviation signal Xdev indicative of whether or not the monitored signal includes the periodic signal;
• and
• determine, over one or more cycles, a measurement signal corresponding to the deviation signal;
• and
• a frequency estimator communicatively linked with the transient detector, the frequency estimator configured to:
• determine a frequency signal fe that corresponds to a frequency estimation of the monitored signal while values of the measurement signal are less than a deviation threshold;
• and
• maintain the frequency signal at a constant value while values of the measured signal equal or exceed the deviation threshold;
• where the transient detector is configured to transmit a flag to the frequency estimator indicating that the monitored signal:
• comprises a periodic signal when values of the measurement signal are less than a deviation threshold expressed as γ<thr, where γ comprises a measurement of the deviation signal and thr comprises the deviation threshold;
• and
• exhibits a transient when values of the measurement signal equal or exceed the deviation threshold expressed as γ≥thr.