Dynamic Harmonic Phasor Measurement Through Coordinated Modal Subspace and Pole State Estimation

Changes in modal order alter the predictor dimension, pole-label swaps disrupt frequency continuity, and time-varying envelopes affect phasor magnitude and phase. Estimating these quantities independently can propagate errors across successive processing stages. A coordinated estimator is developed for the modal subspace, pole states, and regression parameters. An order confidence index combines the spectral gap, cumulative energy, and noise separation to select the model order and reconstruct the signal in one low-rank subspace. Variable-order recursive prediction and frequency–damping state association then form continuous pole trajectories, followed by adaptive smoothing and class-dependent unit-circle projection. The associated oscillatory and decaying direct-current (DC) poles update the Maclaurin regression atoms. Finite-window coupling is handled by either modal initialization followed by Gram iteration or a direct joint regularized solution, avoiding repeated leakage compensation. Tests with modal-order changes, frequency dynamics, modal crossings, amplitude modulation, and decaying DC show that the coordinated parameter chain preserves pole identity and improves dynamic phasor measurement. In the main dynamic test case, the mean and 95th-percentile total vector errors (TVEs) are 3.2082% and 6.0672%; the 95% paired confidence interval for the mean-TVE difference between the proposed method and estimation of signal parameters via rotational invariance techniques (ESPRIT) remains below zero. A separate RK3568 bare-metal test of the standalone three-tone Prony kernel completed 800 frames without a processing failure. Its mean processing time was 18.621 ms per frame, with observed values from 18.537 to 19.070 ms.