A Novel Frequency Estimation Method Based on Complex Bandpass Filters for P-Class PMUs With Short Reporting Latency

The measurement data of P-class phasor measurement units (PMUs) is used for protection and control applications. The reporting latency is critical for these applications. However, the data window of fundamental frequency estimation is commonly longer than that of phasor estimation, which introduces additional latency. In this paper, a novel frequency estimation method that uses sampling values rather than phase angles is proposed for P-class PMUs to reduce their reporting latency. This method uses two complex bandpass filters with different gains to extract the two positive fundamental components of the power signals. A one-to-one correspondence between the frequency and the ratio of the two positive fundamental components is established. By polynomial fitting this relationship, the frequency under static and dynamic conditions can be accurately estimated. In addition, to ensure the accuracy, the two applied complex bandpass filters are designed according to standard requirements, which can effectively suppress the negative fundamental component and harmonics. The simulation and experimental test results show that the proposed method achieves a frequency measurement accuracy that is 10 times higher than the standard requirements with a low computational burden and a data window of two cycles, indicating that the proposed method is suitable for P-class PMUs.