A Nonadaptive Window-Based PLL for Single-Phase Applications

The rectangular window filter, typically known as the moving average filter (MAF), is a quasi-ideal low-pass filter that has found wide application in designing advanced single-phase phase-locked loops (PLLs). Most often, the MAF is employed as an in-loop filter within the control loop of the single-phase PLL. The in-loop MAF, however, causes a large phase delay and, hence, makes the PLL dynamic response slow. Recently, using MAFs as a prefilter/quadrature signal generator (QSG) before the PLL input has been suggested. As the MAFs are outside the PLL control loop, the problem of slow dynamic response is avoided. Nevertheless, the PLL implementation complexity considerably increases as MAFs are frequency-adaptive and, therefore, they require an additional frequency detector for estimating the grid frequency. To reduce the implementation complexity while maintaining a good performance, using a nonadaptive MAF-based QSG with some error compensators is suggested in this letter. The effectiveness of the resultant PLL, which is briefly called the nonadaptive MAF-based PLL, is verified using experimental results.