Improved Sample Value Adjustment for Synchrophasor Estimation at Off-Nominal Power System Conditions
The phasor measurement unit (PMU) commonly implements enhanced discrete Fourier transformation (EDFT) to compensate leakage and signal discontinuity errors at offnominal frequencies. However, EDFT results in a high total vector error (TVE) at large offnominal frequency and worsens with harmonics in power signals. Although the sample value adjustment (SVA) technique addressed such demerits, it generates an asymmetrical TVE profile. In addition, the frequency estimator was not taken into account in the previous publication on SVA. This paper proposes an improved sample value adjustment (ISVA) as a pre-DFT technique to further enhance the phasor estimation. The ISVA generates a symmetrical TVE profile and performed better than EDFT, SVA, and Taylor weighted least-square method at steady-state conditions. Subsequently, the ISVA is integrated with a recursive least-square frequency estimator, which enabled it to track dynamic signals as well. The algorithm is validated in MATLAB simulation and in a prototyped PMU. Static and dynamic test signals are based on the IEEE C37.118.1a-2014 standard.