Robust frequency-estimation method for distorted and imbalanced three-phase systems using discrete filters

Differentiation filter‐based technique for robust estimation of single‐phase grid voltage frequency under distorted conditions

“…generation) and demand (i.e. loads) [6][7][8][9][10][11][12][13][14]. The larger variations of fundamental frequency are much more likely to occur, when the loads are supplied by a generator isolated from the grid [13].…”

Power System Frequency Estimation by Using a Newton-Type Technique for Smart Meters

“…Therefore, many international grid codes are introduced, where a range of frequency variation is specified within which the DG should stay connected with the grid while ensuring stable operation [25], [26]. The International Electrotechnical Commission (IEC) standard 61727 describes that a photovoltaic system has to be disconnected from the grid when the grid frequency exceeds ±1 Hz of the rated frequency [27], [28]. In the case of a microgrid, the frequency is required to be monitored and controlled to maintain the active power balance [28].…”

“…The International Electrotechnical Commission (IEC) standard 61727 describes that a photovoltaic system has to be disconnected from the grid when the grid frequency exceeds ±1 Hz of the rated frequency [27], [28]. In the case of a microgrid, the frequency is required to be monitored and controlled to maintain the active power balance [28]. The frequency control of a microgrid is also important during the transitions between grid-connected and islanding modes, where a high deviation of frequency can occur.…”

“…The frequency control of a microgrid is also important during the transitions between grid-connected and islanding modes, where a high deviation of frequency can occur. The IEEE standard 1547 defines that the frequency of a microgrid cannot differ from the grid frequency more than 0.1% during the reconnection with the grid [28], [29]. The frequency estimation by using the SMs demands sparing some of the processing power and memory at the software implementation level, because they will be installed once over their lifespan [14]- [16].…”

“…The grid voltage fundamental frequency can be estimated using various DSP techniques such as the discrete-Fourier transform (DFT) [30]- [34], Kalman filter (KF) [35], [36], zero crossing detection (ZCD) [37], [38], phase-locked loop (PLL) [39]- [42], frequency-locked loop (FLL) [43]- [45], finite-impulse-response (FIR) filter [28], [46]- [48], least-squares (LS) [49], [50], and Newton-type algorithm (NTA) [51]- [56]. The DFT is the basic technique for spectral analysis of a stationary waveform but shows spectral leakage property during nonperiodic cases [30], [31].…”