Search

The paper presents the performance enhancement of band-pass filter-based M-class phasor estimation. The performance of the M-class phasor estimation using a band-pass FIR filter is enhanced with a magnitude correction factor for the off-nominal frequency range. The band-pass filter is implemented for the phasor estimation with various window functions Tukey, Rife Vincent class-I order-2 (RV2), Hamming, Hanning, Blackman, and Flat-top (FT) and its performance are evaluated under the steady and dynamic state tests prescribed by the standard. A rigorous performance analysis of enhanced phasor estimation using band-pass FIR filter with various window functions is presented with the accuracy indices of total vector error (TVE), frequency error (FE), and rate of change of frequency error (RFE). The result analysis reveals that the performance enhanced phasor estimation using band-pass FIR filter offers significantly less error than reported work at the low sampling rate. The design and performance analysis of the phasor estimation using the band-pass FIR filter is performed in the MATLAB platform. [ABSTRACT FROM AUTHOR]

Introduction: Phasor measurement is crucial for the monitoring and management of power grids. Traditional hardware-based phasor measurement units (PMUs) are effective but often complex and expensive. This paper introduces a software-based phasor measurement method that utilizes soft synchronization with temporal pulse signals from GPS and mobile communication stations, offering a simpler and cost-effective alternative.Methods: The proposed method synchronizes the local oscillator with Pulse Per Second (PPS) signals from GPS and primary synchronization signals from mobile communication bases. Raw data affected by the local oscillator’s instability are transformed into calibrated data using B-Spline interpolation to emulate an ideal sampling rate. The calibrated data are then subjected to a Recursive Discrete Fourier Transform (RDFT) algorithm for synchronized phasor measurement.Results: The method’s performance was assessed in compliance with the C37.118.1 standard. Key performance indicators, such as frequency, phase, and Total Vector Error (TVE), were evaluated. The proposed software-based approach demonstrated high accuracy in synchronized phasor measurements.Discussion: The results confirm that the proposed method can serve as a highly accurate and simpler alternative to conventional hardware-based solutions. Its application promises to advance synchronized phasor measurement practices in power grid monitoring, enhancing reliability and reducing complexity and costs.

Synchrophasor estimation was mostly used in transmission systems in the past, and it is difficult to directly apply an existing synchrophasor algorithm to a distribution system with a more complex structure and environment. A synchrophasor estimation algorithm with a high accuracy and fast response speed is required to complete the calculation of the phasor in the face of the complex and changeable power signal of a distribution network. Therefore, an enhanced all-phase discrete Fourier transform (e-apDFT) algorithm is proposed for a distribution system in this paper, and the algorithm is deployed in a phasor measurement unit (PMU) prototype based on digital signal processing (DSP). Aiming to solve the problem of the accuracy of the traditional apDFT being reduced when the response speed is fast due to the influence of a dense spectrum, the existing algorithm is improved through iteratively compensating the spectral interferences to the main bin produced by adjacent bins. The experimental results show that the e-apDFT algorithm still has a fast response speed and that its estimation accuracy is much better than that of the traditional apDFTs in the presence of adjacent harmonic components. The proposed algorithm also complies with the IEEE standards for P-class PMUs. [ABSTRACT FROM AUTHOR]

This paper presents a suite of analytics that are proposed to be embedded in next-generation smart sensors in electric power grids. The proposed analytics take the electrical signals as the input and unlock the full potential in signal processing and machine learning for real-time event detection and classification. Meanwhile, a robust synchrophasor estimation mechanism is housed within the proposed sensor technology that will be triggered following a detected event and guides on the adaptive selection of the best-fit (most accurate) synchrophasor estimation algorithms at all times. Embedding such analytics within the sensor and closer to where the waveforms are captured, the proposed distributed intelligence solution technology mitigates the potential risks to communication failures and latencies as well as malicious cyber threats. Our experiments demonstrate that the introduced scheme achieves improved quality of measurements with a promising event detection and classification accuracy, collectively resulting in enhanced online situational awareness in modern power grids. [ABSTRACT FROM AUTHOR]

We present two improvements to the subspace-based phasor measurement unit (PMU) algorithms based on ESPRIT frequency estimation. The first is a dynamic, real-time thresholding method to determine the size of the signal subspace. This allows for accurate ESPRIT-based frequency estimates of the nominal system frequency and the frequencies of any out-of-band interference or harmonic frequencies. Since other frequencies are included in the least squares (LS) estimate, the interference from frequencies other than nominal can be excluded. This results in a near flat estimation error over changes in: 1) nominal system frequency; 2) harmonic distortion; and 3) out-of-band interference. We also reduce the computational burden of ESPRIT and demonstrate the proposed algorithm running in real time on resource-constrained platforms. The accuracy of this algorithm is evaluated using the IEEE standard for synchrophasor estimation, IEC/IEEE 60255-118-1, and compared with another state-of-the-art PMU algorithm. [ABSTRACT FROM AUTHOR]

Synchronized phasor and frequency measurements are key tools for the monitoring and management of modern power systems. Under dynamic conditions, it is vital to define algorithms that allow accurately measuring time-varying signals with short latencies and high reporting rates. A dynamic phasor model can help the design of these algorithms and, in particular, of those based on the Kalman filter approach. This article proposes a three-phase synchrophasor estimator based on the extended Kalman filter; state variables are obtained from Taylor expansions of amplitudes and phase angles. The underlying dynamic model considers the inherent relationship among the phases and includes harmonics in an effective way. The process noise covariance matrix that allows representing the uncertainty introduced by the dynamic model has been written by considering that practical ac power systems are nearly three-phase symmetric during typical operation. This a priori information allows improving noise rejection and increasing accuracy in the presence of amplitude modulation, as highlighted by the reported simulation results. [ABSTRACT FROM AUTHOR]

Space vector (SV)-based estimation algorithms represent attractive methods for synchronized phasor, frequency, and rate of change of frequency measurements in three-phase ac power systems. Recently, a phase-locked-loop (PLL) solution for improving the demodulation of the SV signal has been proposed. In this article, the potentialities of the SV-PLL approach are investigated in order to optimize accuracy and computational load. First, the impact of the PLL update rate on achieved performance is analyzed. Then, a novel two-step SV-PLL algorithm is presented so that the accuracy of a fast PLL execution frequency can be matched with a considerably lower computational cost. The behavior in the case of fast phase angle variations has been also significantly improved. The proposed synchrophasor estimation technique has been validated through simulations; exemplary dynamic performance suggests that it is particularly suitable for grid control applications. Experimental tests carried out on a real-time implementation confirm simulation results. [ABSTRACT FROM AUTHOR]

The next-future extensive diffusion of distributed generation and the increasing energy demands due to new components (e.g. electrical vehicles, energy storages) are changing the characteristics of the power grid at the distribution level, which makes it inevitable to introduce the synchrophasor measurement technology into the distribution network. This study analyses the power spectrum for the background noise of the field measured voltage signal of 0.4 kV in one electrical vehicle charging station. The coloured filter model is established using the autoregressive moving average process, which leads to the conclusion that the coloured noise spectrum is generally concave. The impact of background noise for the phasor estimation is evaluated in the steady state and dynamic state referring to IEEE Std C37.118.1™-2011.

Synchronized phasor and frequency measurements are key tools for the monitoring and management of modern power systems. Under dynamic conditions, it is vital to define algorithms that allow accurately measuring time-varying signals with short latencies and high reporting rates. A dynamic phasor model can help the design of these algorithms and, in particular, of those based on the Kalman filter approach. This article proposes a three-phase synchrophasor estimator based on the extended Kalman filter; state variables are obtained from Taylor expansions of amplitudes and phase angles. The underlying dynamic model considers the inherent relationship among the phases and includes harmonics in an effective way. The process noise covariance matrix that allows representing the uncertainty introduced by the dynamic model has been written by considering that practical ac power systems are nearly three-phase symmetric during typical operation. This a priori information allows improving noise rejection and increasing accuracy in the presence of amplitude modulation, as highlighted by the reported simulation results. [ABSTRACT FROM AUTHOR]

Taylor–Fourier (TF) filters represent a powerful tool to design phasor measurement unit (PMU) algorithms able to estimate synchrophasor, frequency, and rate of change of frequency (ROCOF). The resulting techniques are based on dynamic representations of the synchrophasor, and hence, they are particularly suitable to track the evolution of its parameters during time-varying conditions. Electrical quantities in power systems are typically three-phase and weakly unbalanced, but most PMU measurement techniques are developed by considering them as a set of three single-phase signals; on the contrary, this peculiarity can be favorably exploited to improve accuracy and reduce the computational cost. In this respect, this paper proposes to directly perform the TF expansion of the space vector (SV) samples obtained from three-phase measurements. A new paradigm allows to independently estimate positive and negative sequence synchrophasors along with system frequency and ROCOF, leveraging the three-phase characteristics. The performance of the proposed technique is assessed by using test signals inspired by the standard IEEE C37.118.1-2011, including noise as well as magnitude and phase unbalance. Achieved results highlight the flexibility of the enhanced SV-based approach, which is capable to combine excellent dynamic performance together with an accurate estimation of both positive and negative sequence components. [ABSTRACT FROM AUTHOR]

Power oscillating signals are analyzed with the Discrete Taylor–Fourier Transform (DTFT). This is implemented by modulating the impulse responses of its low-pass differentiators, defined by a family of O-splines. This implementation reduces its computational complexity since in practice only a small subset of filters is applied. The estimated parameters provide richer dynamic information than the traditional methods, in particular, a space representation for each dynamic component, and detection of frequency modulated events. Their estimation performance is assessed through the new proposed Total Phasor Error. To illustrate its application, and its progressive accuracy, this technique is applied to observe the synchrophasor estimates of voltages and to separate the electromechanical modes of an oscillation in a real power system. In conclusion, this multiresolution technique provides a series of increasingly precise solutions for time-frequency separation of oscillations with fluctuating frequency. [ABSTRACT FROM AUTHOR]

In the recent years, the scientific community is paying great attention to the development of phasor measurement units (PMU) and, particularly, to novel digital signal processing algorithms for these instruments. While the performance of estimation algorithms is usually evaluated through simulations on a PC, the overall PMU accuracy depends on measurement hardware as well (e.g., transducers, data converters, and synchronization circuitry). However, the relationship between estimation algorithms accuracy and metrological characteristics of hardware equipment is very difficult to predict or to simulate. Therefore, the performance of different algorithms can be hardly compared when they are actually implemented in real instruments and used in the field. This paper attempts to address this problem by presenting an open testbed for PMU estimation algorithms. The key distinctive feature of the testbed is its ability to evaluate and to compare algorithm accuracy under experimental conditions that include not only the disturbances specified in the IEEE Standard C37.118.1-2011 and its Amendment IEEE C37.118.1a-2014, but also the effects of given uncertainty contributions due to different hardware components. A thorough metrological characterization of the testbed, properly supported by a noise propagation model, is performed in order to quantify such uncertainty contributions and their impact on the estimates of synchrophasor magnitude, phase, fundamental frequency, and rate of change of frequency returned by different algorithms under test. As a case study, three state-of-the-art estimation algorithms are tested in a variety of conditions. [ABSTRACT FROM AUTHOR]

In the future, phasor measurement units are expected to be applied in distribution networks (DNs) for their control and monitoring. Because of the widely used power electronic devices in DNs, harmonics are widely present in a voltage/current signal. Particularly, second harmonics have the most significant uncertainty contributions to synchrophasor estimation, which is especially true when a short cycle observation window is used for a fast response. Based on the interpolated dynamic discrete Fourier transform (IpD²FT), this paper introduces an enhanced IpD²FT (e-IpD²FT) synchrophasor estimator that considers second harmonic interferences. First, the adaptive equivalent filters of the IpD²FT are given. Based on these, the optimal frequencies where the IpD²FT has the least second harmonic interferences are then searched using an enumeration method, and the e-IpD²FT synchrophasor estimator is accordingly proposed. Instantaneous frequency responses and several simulation tests show that the e-IpD²FT performs much better than the IpD²FT in second harmonic suppression, and can meet the P-class response time requirements and most of the M-class accuracy requirements of the IEEE standard C37.118.1 only over a three-cycle window. [ABSTRACT FROM AUTHOR]

Fast dynamics and transient events are becoming more and more frequent in power systems, due to the high penetration of renewable energy sources and the consequent lack of inertia. In this scenario, Phasor Measurement Units (PMUs) are expected to track the monitored quantities. Such functionality is related not only to the PMU accuracy (as per the IEC/IEEE 60255-118-1 standard) but also to the PMU reporting rate (RR). High RRs allow tracking fast dynamics, but produce many redundant measurement data in normal conditions. In view of an effective tradeoff, the present paper proposes an adaptive RR mechanism based on a real-time selection of the measurements, with the target of preserving the information content while reducing the data rate. The proposed method has been tested considering real-world datasets and applied to four different PMU algorithms. The results prove the method effectiveness in reducing the average data throughput as well as its scalability at PMU concentrator or storage level. • Phasor Measurement Unit (PMU) • Synchrophasor, frequency and ROCOF tracking error metrics. • Adaptive reporting rate for PMU. • Data throughput optimisation. • Measurement accuracy. [ABSTRACT FROM AUTHOR]

Next-generation phasor measurement units (PMUs) are expected to play a key role for monitoring the behavior of future smart grids. While most of the PMUs used nowadays in transmission networks rely on static phasor models, more sophisticated representations and stricter accuracy requirements are needed to track amplitude, phase, and frequency changes of power waveforms in strongly dynamic scenarios as those expected in future distribution systems. In this paper, a discrete Fourier transform (DFT)-based algorithm based on a dynamic phasor model (referred to as interpolated dynamic DFT-based synchrophasor estimator) is used to estimate not only amplitude and phase of the collected waveforms, but also their frequency and rate of change of frequency. The performances of the proposed method are evaluated through multiple simulations in different steady-state and transient conditions described in the Standard IEEE C37.118.1-2011. [ABSTRACT FROM PUBLISHER]

In this paper, a simple synchrophasor estimation algorithm has been proposed considering power system steady state, dynamic conditions, and protection requirements. The new IEEE Standard C37.118.1-2011 for synchrophasor measurements includes the dynamic performance requirements for the phasor measurement units. It is shown that the proposed method satisfies all the steady state and dynamic requirements of the new IEEE Standard. Presently, synchrophasors are mainly used for wide area monitoring. Increasingly, synchrophasors are being considered for protection applications in smart grids. Protection applications require shorter response times and lower overshoot/undershoot values for estimated phasors during large disturbances. It is shown that the proposed method performs satisfactorily during system faults, which is an important requirement for protection applications. A detailed performance comparison with the existing phasor estimation algorithms has also been presented. [ABSTRACT FROM PUBLISHER]

Transient amplitude or phase changes in current or voltage waveforms may seriously affect synchrophasor estimator's accuracy and responsiveness. The IEEE Standard C37.118.1-2011 specifies test conditions as well as accuracy and response delay limits for different types of disturbances. In this paper, the performances of three state-of-the-art techniques based on phasor Taylor's series expansion specifically conceived to track phasors in dynamic conditions are analyzed and compared with the one-cycle discrete Fourier transform estimator under the effect of amplitude step changes, phase step changes, and linear frequency variations. Several simulation results show that the total vector error (TVE) tends to increase linearly with the step size. However, the peak TVE increments for a given step size are quite similar for all the considered techniques and are dominated by amplitude or phase errors, depending on whether the step affects the waveform amplitude or its phase, respectively. In this paper, the response times of the considered estimators for two different TVE thresholds are also analyzed and compared as a function of the step size, to assess their compliance to the requirements of the standard. Further simulation results show that in the case of linear frequency variations, responsiveness is not an issue and the TVE values of all estimators lie within the same worst case boundaries as those related to the case of static off-nominal frequency offsets. [ABSTRACT FROM AUTHOR]

The real-time high-accuracy measurement of waveform phasors is one of the many open challenges that need to be addressed in future smart grids. In this paper, the accuracy of four recently proposed synchrophasor estimators is analyzed and compared with the well-known one-cycle discrete Fourier transform estimator under the effect of static frequency offsets, amplitude modulation, phase modulation, harmonic distortion, and wideband noise. Two of the considered techniques track the phasor variations through finite-difference equations that estimate the first- and second-order derivatives of the phasor itself. The other two methods are instead based on a least squares estimation of the coefficients of the phasor Taylor's series expansion. The analysis reported in this paper covers the main scenarios described in the Standard IEEE C37.118.1-2011. In particular, the influence of different signal parameters on the total vector error (TVE) values is quantified and used to determine the maximum TVE increments associated with distinct parameters and the corresponding upper bounds. [ABSTRACT FROM AUTHOR]

Synchrophasor estimation accuracy is a well-known critical issue in systems for smart grid monitoring and control. This paper deals with an in-depth analysis of the effect of both steady-state and dynamic disturbances on single-cycle and multicycle windowed discrete Fourier transform (DFT)-based synchrophasor estimators. Unlike other qualitative or simulation-based results found in the literature, this work provides two accurate and easy-to-use analytical expressions that can be used to determine the worst case range of variation of the total vector error (TVE) due to off-nominal frequency deviations. In such conditions, estimation accuracy is limited by two factors, i.e., the infiltration caused by the input signal image frequency and the scalloping loss associated with the spectrum main lobe of the chosen window. Starting from the aforementioned general analysis, a new two-term window minimizing the detrimental effects of image frequency tone is proposed. The accuracy of the related DFT-based synchrophasor estimator is evaluated under both static and dynamic conditions, which is the most interesting scenario for future smart grids. Moreover, the effect of waveform frequency measurement uncertainty on scalloping loss compensation is quantified. Several simulation results (including the effects of noise, harmonic distortion, and amplitude and phase modulation) confirm that the proposed window can significantly improve the accuracy achievable with a simple single-cycle DFT estimator. Indeed, TVE values much smaller than 1% can be achieved even in the worst case conditions reported in the standard IEEE C37.118.1-2011, when the frequency waveform deviations are within ±4% of the nominal value. In addition, the proposed solution could be useful to improve the performance of more complex dynamic phasor estimators, e.g., those in which the first- and second-order terms of the phasor Taylor series expansion result from the differences of consecutive DFT-based phasor estimates. [ABSTRACT FROM AUTHOR]

• Phasor Measurement Unit (PMU) for protection and measurement applications. • Iterative interpolated modulated sliding Discrete Fourier Transform (DFT). • Field Programmable Gate Array (FPGA) based design. • Experimental validation: synchrophasor accuracy and measurement reporting latency. • P and M performance class compliance. Low-inertia grids are characterized by high shares of harmonic and inter-harmonic distortion, produced by the inverters that interface non-conventional generation assets to the electrical grid. These interfering tones largely compromise synchrophasor estimation and may jeopardize protection and control strategies based on Phasor Measurement Units (PMU). Indeed, the IEEE Std. C37.118 does not require resiliency against inter-harmonic tones for protection PMUs. In view of increasing synchrophasor technology reliability, the paper presents the design and the experimental validation of a PMU that is simultaneously compliant with both protection (P) and measurement (M) class of PMU performance defined in the IEEE Std. C37.118. The synchrophasor estimator is based on the interpolated DFT and iteratively estimates and compensates the effects of the spectral interference produced by a generic interfering tone and the negative image of the fundamental tone. The proposed hardware architecture is based on a Field Programmable Gate Array (FPGA). [ABSTRACT FROM AUTHOR]