A Half-Cycle Fast Discrete Orthonormal S-Transform-Based Protection-Class μPMU

This article proposes a novel, fast discrete orthonormal Stockwell transform (FDOST)-based protection-class microphasor measurement unit (P-<inline-formula> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>PMU) algorithm. The proposed algorithm provides very fast and high-resolution measurements of the system state, which are then expected to serve various active distribution networks (ADNs) protection applications, e.g., islanding detection and fault detection. The phasors are estimated from FDOST, utilizing the half-cycle discrete Fourier transform (DFT). The two major concerns of the half-cycle FDOST with respect to the response in the presence of even harmonics and off-nominal frequency are handled using the even harmonics filtration (EHF) and half-cycle sample value adjustment (HC-SVA), respectively. Since both of these techniques, namely, EHF and HC-SVA, require system frequency as the input, a new peak and zero-crossing-based hybrid frequency estimator (PZC-HF_E) is also proposed in this article. The performance of the proposed methodology is evaluated for various simulated scenarios as per the IEEE Std. C37.118.1a-2014, as well as in the hardware setup. The results of the proposed P-<inline-formula> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>PMU algorithm are also compared with two other methodologies, i.e., the Hilbert transform and convolution based PMU (HTC-PMU) and two-cycle interpolated discrete Fourier transform-based PMU (IpDFT-PMU) using the hardware setup. The test results reveal the superiority of the proposed P-<inline-formula> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>PMU algorithm over the compared methods in terms of response time and the estimation accuracy.