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Original scientific paperIn this manuscript, a novel sag and peak detector by means of a delta square operation for a single-phase is suggested. The established sag detector is from a single phase digital phase-locked loop (DPLL) that is founded on a d-q transformation employing an all-pass filter (APF). The d-q transformation is typically employed in the three-phase coordinate system. The APF produces a virtual phase with a 90• phase delay, but the virtual phase can not reproduce an abrupt variation of the grid voltage, at the moment in which the voltage sag transpires. As a consequence, the peak value is severely garbled, and settles down gradually. A modified APF produces the virtual q-axis voltage factor from the difference between the current and the former value of the d-axis voltage component in the stationary reference frame. Nevertheless, the amended APF cannot sense the voltage sag and peak value when the sag transpires around the zero crossing points such as 0• and 180 • since the difference voltage is not adequate to sense the voltage sag. The suggested algorithm is proficient to sense the sag voltage through all regions as well as the zero crossing voltage. Furthermore, the precise voltage drop can be obtained by computing the q-axis component, which is relational to the d-axis component. To authenticate the legitimacy of the suggested scheme, the orthodox and suggested approaches are contrasted by means of the simulations and investigational results.Key words: All pass filter, Digital phase locked loop, Sag, Swells, Single phase inverter system Novi gen algoritam za detekciju propada i poskoka napona na jednofaznom izmjenjivaču u mikromreži. U ovom radu je predložen novi detektor propada i poskoka napona korištenjem delta kvadratične operacije za jednu fazu. Predloženi detektor propada napona je u digitalnoj fazno-zatvorenoj petlji (DPLL) zasnovanoj na d-q transformaciji koja koristi svepropusni filtar (APF). D-q transformacija se tipično koristi u trofaznim koordinatnim sustavima. APF generira virtualnu fazu s 90• faznog kašnjenja, ali virtualna faza ne može reproducirati skokovitu promjenu napona mreže u trenutku u kojem se dogaa propad napona. Kao posljedica, detektirana vršna vrijednost se značajno izmijeni i smiruje se postepeno. Modificirani APF generira faktor napona virtualne q osi iz razlike izmeu struje i prošle vrijednosti komponente napona na d osi u stacionarnom koordinatnom sustavu. Meutim, izmijenjeni APF ne može detektirati propad i poskok napona kada se propad dogaa u okolini točaka presijecanja nule, kao što je 0• i 180 • s obzirom da diferencijski napon nije prikladan za detekciju propada napona. Predloženi algoritam je prilagoen detekciji propada napona u cijelom radnom području, uključujući i napon prelaska nule. Nadalje, precizni propad napona može se dobiti izračunom komponente napona na q osi, koja je u odnosu s obzirom na komponentu d osi. Za validaciju predloženih metoda provedena je njihova usporedba s konvencionalnim metodama u simulacijskom i eksperimentalnom okruženju.

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