Variable-Structure Generalized Delayed Signal Cancellation PLL to Improve Convergence Time

This paper shows a scheme for improving the detection performance of the fundamental-frequency positive-sequence (FFPS) space vector through the generalized delayed signal cancellation phase-locked loop (GDSC-PLL). We implemented a variable-structure scheme in order to reduce the convergence time by changing the traditional datapath whenever even harmonics are not present in the input signal. If this condition is not true, the performances of the variable-structure GDSC-PLL and the traditional GDSC-PLL for detecting the FFPS space vector will be similar. Therefore, the variable-structure GDSC-PLL does not require a previous knowledge about the harmonic components of the three-phase signal. Furthermore, we improved the frequency-adaptive scheme. The performances of the original and proposed schemes were compared through transient test cases based on IEC 61000 and typical electrical events. The new approach led to a reduction of up to 62% in the convergence time.