An Adaptive Observer-Based Switched Methodology for the Identification of a Perturbed Sinusoidal Signal: Theory and Experiments

IEEE Trans. Power Electron.

et al. 2018

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Abstract-Parallel operation of multiple grid-connected power converters through LCL filters is known to have the potential problem of triggering oscillations in the ac mains. Such oscillatory frequencies are not integral multiples of the fundamental frequency and hence form a new source of interharmonics. Early detection of such oscillations is essential for the parallel power converters to move out of the unstable zone. This paper presents an online observer-based algorithm that can perform fast detection of interharmonics within a specified frequency band. The algorithm has been adopted in a specific and reduced form from an integral observer algorithm for detection of fundamental and interharmonic voltage components in the ac mains. A new method based on the kernel signal for fast interharmonic detection is proposed and practically verified. It has been implemented in a digital controller to detect oscillations such as those occurring between two grid-connected power converters. The practical results indicate that the algorithm can locate such frequency within the specific frequency band within 1 mains cycle.

Section: Fig 2 Schematic Of the Estimation Algorithmmentioning

confidence: 99%

Online Detection of Fundamental and Interharmonics in AC Mains for Parallel Operation of Multiple Grid-Connected Power Converters

IEEE Trans. Power Electron.

et al. 2018

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“…It worth noting that (9) is not well-defined at the time instants t in whichΩ(t) = 0. In spirit of the previous work by the authors on the estimation of a single sinusoidal signal [33], this limitation can be removed resorting to a suitable adaptive mechanism based on gradient method. More specifically, by defining the time-varying residual based on the equality (9):…”

Section: Remark 21mentioning

confidence: 99%

“…In the spirit of prior work by the authors on the single sinusoidal case (see the very recent paper [33]), a "dualmode" estimation scheme is proposed, which incorporates a switching algorithm depending on the instantaneous excitation level (concerning the excitation issues, a related contribution focusing on switching or hybridization to improve persistence of excitation can be found in [34]). In contrast with other methods that are either indirectly identifying the frequency contents or are characterized by local stability only, the present paper deals with a direct adaptation mechanism for the squares of the frequencies with semi-global stability based on the recent preliminary results presented in [35].…”

Section: Introductionmentioning

confidence: 99%

An Adaptive-Observer-Based Robust Estimator of Multi-sinusoidal Signals

IEEE Trans. Automat. Contr.

et al. 2018

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Abstract-This paper presents an adaptive observer-based robust estimation methodology of the amplitudes, frequencies and phases of biased multi-sinusoidal signals in presence of bounded perturbations on the measurement. The parameters of the sinusoidal components are estimated on-line and the update laws are individually controlled by an excitation-based switching logic enabling the update of a parameter only when the measured signal is sufficiently informative. This way doing, the algorithm is able to tackle the problem of over-parametrization (i.e., when the internal model accounts for a number of sinusoids that is larger than the true spectral content) or temporarily fading sinusoidal components. The stability analysis proves the existence of a tuning parameter set for which the estimator's dynamics are input-to-state stable with respect to bounded measurement disturbances. The performance of the proposed estimation approach is evaluated and compared with other existing tools by extensive simulation trials and real-time experiments.

“…Techniques based on adaptive observers have also been proposed in the recent literature (see [19,20,21,22,23,24]). In particular, [24] deals with a "dual-mode" estimation scheme, incorporating a switching algorithm (depending on the real-time excitation level) into an adaptive observer-based sinusoidal estimator.…”

Section: Introductionmentioning

confidence: 99%

“…In particular, [24] deals with a "dual-mode" estimation scheme, incorporating a switching algorithm (depending on the real-time excitation level) into an adaptive observer-based sinusoidal estimator. In the spirit of the preliminary results presented in [23], the robustness in presence of structured and unstructured uncertainties are addressed by Input-to-state stability (ISS) arguments.…”

Section: Introductionmentioning

confidence: 99%

A parallel prefiltering approach for the identification of a biased sinusoidal signal: Theory and experiments

Adaptive Control & Signal

et al. 2015

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SUMMARYThe problem of estimating the amplitude, frequency and phase of an unknown sinusoidal signal from a noisy biased measurement is addressed in this paper by a family of parallel pre-filtering schemes. The proposed methodology consists in using a pair of linear filters of specified order to generate a suitable number of auxiliary signals that are used to estimate -in an adaptive way -the frequency, the amplitude and the phase of the sinusoid. Increasing the order the pre-filters improves the noise immunity of the estimator, at the cost of an increase of the computational complexity. Among the whole family of estimators realizable by varying the order of the filters, the simple parallel pre-filters of order 2+2 and 3+3 are discussed in detail, being the most attractive from the implementability point of view. The behavior of the two algorithms with respect to bounded external disturbances is characterized by Input-to-State Stability arguments. Finally, the effectiveness of the proposed technique is shown both by comparative numerical simulations and by a real experiment addressing the estimation of the frequency of the electrical mains from a noisy voltage measurement.