Inter‐harmonics monitoring method based on PMUs

An Interharmonic Phasor and Frequency Estimator for Subsynchronous Oscillation Identification and Monitoring

“…Accordingly, the zeroth-order phasor derivatives are the interharmonic phasors and raw fundamental phasor estimates, and the fundamental phasor can be obtained according to (3). According to [22], the subsynchronous interharmonic frequency can be estimated based on the phasor derivative estimates, which is given by (9) where Im{•} denotes the operation of picking the imaginary part of its argument; and * denotes the conjugate operator. Similarly, supersynchronous interharmonic and fundamental frequencies can be estimated like (9).…”

“…According to [22], the subsynchronous interharmonic frequency can be estimated based on the phasor derivative estimates, which is given by (9) where Im{•} denotes the operation of picking the imaginary part of its argument; and * denotes the conjugate operator. Similarly, supersynchronous interharmonic and fundamental frequencies can be estimated like (9). Fundamental rate of change of frequency (ROCOF) can be estimated by [22] (10)…”

“…At first, the initial model frequencies are used to generate matrix Ψ and get phasor derivative estimates. Then, these phasor derivative estimates are used to estimate frequencies according to (9). Finally, model frequencies are set equal to these frequency estimates and generate matrix Ψ. Iterations of the last two steps are needed to get accurate model frequency estimates.…”

“…In China, PMU is also expected to play an important role in SSO identification and monitoring, i.e., measuring interharmonics within [10,40] and [60,90] Hz [8]. This is because most interharmonics caused by SSOs have frequencies within these two bands [9]. Concerning SSO identification and monitoring, the key is to obtain sub-and supersynchronous interharmonic phasors and frequencies for mitigation equipment operation [10].…”

“…There are two kinds of sub-/supersynchronous interharmonic parameter estimation methods in literature: 1) fundamental phasor estimates-based methods and 2) signal field data-based methods. As for 1), two typical methods were proposed in [9] and [10] to identify SSOs. Nevertheless, they have an extremely long latency due to the long observation window, which reaches 1 s. [6] proposed a method to estimate SSO frequencies based on the fundamental phasor estimates.…”