Compensating Nonlinearities in Voltage Transformers for Enhanced Harmonic Measurements: The Simplified Volterra Approach

Toscani, Sergio; Faifer, Marco; Ferrero, Alessandro; Laurano, Christian; Ottoboni, R.; Zanoni, Michele

doi:10.1109/tpwrd.2020.2978668

Cited by 31 publications

(27 citation statements)

References 42 publications

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“…Therefore, one may neglect the first kind of terms in the summation: it corresponds to consider the HD produced by the fundamental as the only nonlinear effect, thus assuming that there is no interaction (intermodulation) between different spectral components in the primary voltage. Scientific papers confirm that Harmonic Distortion (HD) is the strongest nonlinear phenomenon jeopardizing the measurement of low-order, odd harmonics [17], [19], which are the most affected by nonlinearity. Introducing this simplification, after some passages we obtain:…”

Section: Nonlinearity Compensation Techniquesmentioning

confidence: 99%

Theory and Experimental Validation of Two Techniques for Compensating VT Nonlinearities

D’Avanzo

Faifer

Landi

et al. 2022

IEEE Trans. Instrum. Meas.

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Inductive Instrument Transformers (ITs) are still the most used voltage and current sensors in power systems. Among the numerous applications that require their use, one of the most important is surely represented by harmonics measurement. In this case, the recent literature shows that, since they suffer from both a filtering behavior due to their dynamics and from nonlinear effects produced by their iron core, they can introduce errors up to some percent. This paper wants to deeply investigate, in the very same experimental conditions, about the performance of two digital signal processing techniques, recently introduced for the improvement of harmonics measurements performed through ITs, namely SINDICOMP and compensation of Harmonic Distortion through Polynomial modeling in the frequency domain (PHD). These methods have been applied to two different voltage transformers, having different specifications, by using two measurement setups based on different architectures. The impact of the voltage generator employed during the identification on the achieved accuracy is theoretically and experimentally evaluated. Modified versions of SINDICOMP and PHD compensation, which are more robust against non-idealities of the measurement setup, are presented. The performances of the techniques are evaluated by adopting voltage waveforms similar to those that can be encountered during the normal operation in a real distribution grid.

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Section: Nonlinearity Compensation Techniquesmentioning

confidence: 99%

Theory and Experimental Validation of Two Techniques for Compensating VT Nonlinearities

D’Avanzo

Faifer

Landi

et al. 2022

IEEE Trans. Instrum. Meas.

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“…This enables a thorough characterization of VTs: linear and nonlinear effects can be separated, nonlinearities can be classified, and their individual impact on the overall metrological performance can be studied. Furthermore, identifying the inverse model permits a very precise reconstruction of the primary voltage harmonics from the secondary side, thus compensating most of the nonlinearities other than the filtering behavior [ 27 ].…”

Section: Introductionmentioning

confidence: 99%

A Simple Method for Compensating Harmonic Distortion in Current Transformers: Experimental Validation

Laurano

Toscani

Zanoni

2021

Sensors

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Conventional current transformers (CTs) suffer from nonlinearities due to their ferromagnetic cores. On one hand, it is well-known that severe core saturation may occur because of large overcurrents or unidirectional transient components: this may substantially impact the operation of relays. On the other hand, weaker nonlinear effects are also present during regular working conditions. In particular, the spectral content of typical current waveforms is characterized by a strong fundamental term responsible for harmonic distortion affecting the frequency components at the secondary side. In turn, this has a significant impact on the accuracy that can be reached as long as current harmonics must be monitored. The target of this work is implementing a simple signal processing technique that allows compensating for this effect. The method, characterized by extremely low computational complexity, is first introduced and validated using numerical simulations. After this, it was tested experimentally to improve the harmonic measurement capability of inductive CTs. The achieved results highlight a noticeable reduction of errors at low-order harmonics over a wide range of primary current amplitudes. It is worth noting that the black-box approach makes the technique suitable also for compensating nonlinearities introduced by current transducers based on different operating principles. Thanks to this peculiarity and to the low computational complexity, the proposed method is suitable to be employed in power quality analyzers and merging units. In this way, high-accuracy monitoring of current harmonics in power systems can be achieved, opening the way to advanced power quality management and to the location of disturbing users.

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“…In this paper the determined characteristic of voltage ratio error at harmonics with frequency for a given medium voltage inductive instrument transformer is used to predict the value of the slow-front overvoltage in its secondary circuit. The nonlinearity of the magnetization characteristics of the magnetic core of the inductive VTs causes the need for accurate evaluation of the values of ratio error and phase displacement at harmonics of the rated primary voltage; this is required during the test [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ]. There are many methods and measuring systems that enable evaluation of the values of ratio error at harmonics of inductive VT.…”

Section: Introductionmentioning

confidence: 99%

“…There are many methods and measuring systems that enable evaluation of the values of ratio error at harmonics of inductive VT. The most recent solutions from a given group of authors are referenced as [ 17 , 18 , 25 ]. However, the resonance frequencies and the measured values of ratio error and phase displacement do not change with the value of the applied voltage.…”

Section: Introductionmentioning

confidence: 99%

Transformation of Transient Overvoltages by Inductive Voltage Transformers

Kaczmarek

Brodecki

2021

Sensors

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Overvoltage transients occur after any type of switching activity in a power network, such as breaker operation, fault occurrence/clearance and rapid load change. This distortion of voltage is transformed to the secondary circuit of a voltage transformer. The maximum values of such impulses may many times exceed the rated value of its secondary voltage. This can lead to malfunction of measuring or protection devices connected to the secondary circuit of a voltage transformer and even their damage. The paper presents the application of determined values of ratio error at harmonics of the inductive voltage of the transformer to predict the value of transformed slow-front transient overvoltage to their secondary circuits. This will help to prevent malfunction of measuring or protection devices connected to the secondary side of the voltage transformer and increase their safety of operation. The inductive voltage transformer equivalent circuit for transformation of higher frequency components of distorted voltage must be extended with internal capacitances of windings. This is caused by the fact that the resonance phenomenon of the slow-front transient overvoltage results from leakage inductance and capacitance of primary winding, not from the magnetic core. Therefore, this behaviour is independent from the value of the applied voltage.

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Compensating Nonlinearities in Voltage Transformers for Enhanced Harmonic Measurements: The Simplified Volterra Approach

Cited by 31 publications

References 42 publications

Theory and Experimental Validation of Two Techniques for Compensating VT Nonlinearities

Theory and Experimental Validation of Two Techniques for Compensating VT Nonlinearities

A Simple Method for Compensating Harmonic Distortion in Current Transformers: Experimental Validation

Transformation of Transient Overvoltages by Inductive Voltage Transformers

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