Fundamental Frequency Voltage Research Articles

Detection of flexibly bound adsorbate using the nonlinear response of quartz crystal resonator driven at high oscillation amplitude

Flexibly bound heavy adsorbates as antibodies, biomarkers, microbeads, bacteria do not produce response at quartz resonators accounted by their mass alone, which complicates their acoustic detection. To resolve this problem, an anharmonic detection technique (ADT) has been developed. It generates higher harmonics by applying a high voltage (0.7–10V) fundamental frequency excitation to 14.3MHz AT-cut quartz crystal. Due to non-linearity the parameters of generated oscillations depend on the amplitude A of the applied signal, being proportional to A2 for the fundamental resonance frequency and mainly to A3 for the amplitude of generated 3rd harmonics. The coefficients of proportionality depend on number of attached particles, but not on their mass and can be calculated from the phenomenological model based on Duffing equation with damping. The model was tested in liquids of various viscosity, on composite layer including polymer film with deposited gold nanoparticles and in electrochemical mode for E.-coli adsorption.

The third harmonic generated voltage by salient-pole synchronous generator during 3-phase-to-ground fault

Summary Conducted experiment proves that third harmonic (TH) component of salient-pole synchronous generator behaves differently compared with fundamental frequency component in terms of generated voltage. Fundamental frequency-generated voltage depends on the excitation system, and the generated voltages before and during fault are almost the same. However, TH-generated voltage is independent of the excitation system. In other words, variation of the excitation current does not affect the generation of TH voltage as much as it affects the generation of fundamental frequency voltage. On top of that, the generation of TH voltage before and during fault varies significantly. Hence, a typical method to solve fault analysis for 3-phase–to–ground fault is not applicable in TH domain. Therefore, in this article, a method to find TH-generated voltage is proposed. The TH-generated voltage during 3-phase–to–ground fault is presented in terms of percentage called the harmonic fundamental ratio, which is the ratio of TH zero-sequence–generated voltage to fundamental frequency–positive sequence-generated voltage during fault. The harmonic fundamental ratio is obtained by short circuiting the generator terminal prior to the application in the system. It turns out that the generated TH voltage by synchronous generator depends on the zero-sequence TH impedance of the TH fault current path. Lastly, the proposed method to obtain TH-generated voltage by salient-pole synchronous generator is validated by comparing the calculated TH fault current with the actual TH fault current obtained from experiment.

Harmonic Load Mitigation Using the Optimal Double Tuned Passive Filter Technique

Harmonic is one of the power quality disturbances customarily imminent in an unbalanced electrical system. Harmonic represents as the multiple integral of fundamental frequency of voltage and current inflicting towards the shifting in system frequency causing to a disruptive operation of electrical devices. This paper investigates on the performance of passive filter intrinsically by utilizing the inductor and capacitor electrical components to mitigate harmonic problem emanating from an unbalanced electrical system. In particular, explication in this paper will focus on the optimal parameters specification for the double tuned passive filter that used to overcome the phenomenon of harmonic issue. The two case studies constituting with different number of harmonic orders injected in a system were introduced to distinguish effectiveness of double tuned passive filter in solving the aforesaid problems. The parameters configuration of the passive filter are automatically tuned by the MATLAB® software to reduce the total harmonic distortion incurred in a system designed under the Simulink® software.

A Demodulation-Based Technique for Robust Estimation of Single-Phase Grid Voltage Fundamental Parameters

This paper proposes a robust technique for the single-phase grid voltage fundamental amplitude, frequency, and phase angle estimation under distorted grid conditions. It is based on a demodulation method tuned at a fixed frequency. It does not have stability issue due to an open-loop structure, does not require real-time evaluation of trigonometric and inverse trigonometric functions, and also avoids the use of look-up table. It can provide accurate estimation of the single-phase grid voltage fundamental parameters under dc offset and harmonics. When compared with a frequency adaptive demodulation technique, the proposed one is less affected by dc offset, can provide faster frequency estimation, and also avoids interdependent loop, trigonometric, and inverse trigonometric functions operation. Simulation and experimental results are presented to verify the performance of the proposed technique.

Accurate Estimation of Single-Phase Grid Voltage Fundamental Amplitude and Frequency by Using a Frequency Adaptive Linear Kalman Filter

This paper reports the performance of a linear Kalman filter (LKF)-based technique to estimate the single-phase grid voltage fundamental amplitude and frequency under distorted grid conditions. An enhanced frequency-locked loop is combined with the LKF to obtain the frequency adaptive capability of the technique. A frequency domain analysis is presented to show the effect of tuning the parameters of the LKF. When compared with a non-LKF, such as the extended KF, the technique is linear and computationally efficient, as it does not contain derivative operations and nonlinear terms. The technique is less affected by dc offset and harmonics, and also shows improved convergence property as compared with an extended complex KF. Simulation and experimental results are provided to validate the performance of the technique.

Research on Three-Dimensional Stress Distribution of Reactor Core

Gapped iron-core reactors can obtain larger inductance, but they make larger vibration and noise than other kinds of reactors. On vibration dampers, many researchers kept their eyes on vibration isolation structures or vibration isolation materials. However, they did not compute reactor core vibration under fundamental frequency voltage or harmonic one. Because stress is the inherent reason of vibration and noise, this paper proposes a finite-element model for reactor core stress calculation based on the Maxwell stress theory. The model can handle reactor exciting currents, not only fundamental frequency but also superposition of fundamental frequency with different harmonics. Because core materials have different magnetic characteristics under different excitation conditions, this paper tested multigroup H-B curves to support the simulation. Then, the finite-element method is used to calculate the magnetic field and Maxwell stress distribution. Finally, the frequency spectrum of the stress is analyzed to provide a theory basis for further analysis of vibration and noise reduction in gapped iron-core reactors.

An Analysis of Modified Demodulation-Based Grid Voltage Parameter Estimator

The estimation of the grid voltage fundamental parameters, i.e., the phase, frequency, and amplitude, is required for a wide variety of applications, particularly for synchronization and control of grid-connected converters and for monitoring and protection purposes in power systems. To accomplish this task, many approaches have been proposed in the literature. Recently, a modified demodulation-based technique (MDT) has been presented, which aims to accurately extract the grid voltage fundamental parameters under harmonically distorted and frequency-varying conditions. In this letter, it is shown that the MDT is actually a phase-locked loop. The MDT small-signal modeling and stability analysis are then conducted, and some modifications to enhance its performance are suggested. The effectiveness of these modifications is finally confirmed using numerical results.

Single-Phase Grid Voltage Frequency Estimation Using Teager Energy Operator-Based Technique

This paper reports the performance of a technique for the estimation of single-phase grid voltage fundamental frequency under distorted grid conditions. The technique combines a Teager energy operator (TEO) with a frequency adaptive bandpass filter (BPF). The TEO is based on three consecutive samples and is used to estimate the fundamental frequency. The BPF relies on a recursive discrete Fourier transform (RDFT) and an inverse RDFT, and is used to extract the normalized amplitude of the grid voltage fundamental component. The technique is computationally efficient and can also reject the negative effects caused by dc offset and harmonics. It requires less computational effort, can provide faster estimation, and is also less affected by harmonics as compared with a technique relying on the RDFT-based decomposition of the single-phase system into orthogonal components. The performance of the technique is verified using both simulation and experimental results.

Using disturbance records to automate the diagnosis of faults and operational procedures in power generators

Nowadays, it is a common practice in power generation utilities to monitor the generation units using digital fault recorders. As the disturbance records are generally analysed and stored at a central office or control centre, it has become difficult for engineers to analyse all this data. Some of the main steps in developing automated diagnosis tools to help in this task are the segmentation and feature extraction of the recorded signals and decision making. This study presents a methodology to extract meaningful information from each segment of a disturbance signal. In the approach described in this study, the segmentation is performed by an extended complex Kalman filter. The main features extracted from each segment are symmetrical components at fundamental frequency of voltage and current signals. Feature extraction uses root-mean-square values to obtain the symmetrical components of the three phase quantities. This methodology focuses on offline analysis of fault recorder data of power generators and it is developed not only to fault analysis, but also to verify normal operational procedures, from which result most of the disturbance records. This study also describes an expert system that can be used to automatically classify each record into known categories, focusing the engineer's attention to the most relevant occurrences.

Control of ion energy distributions using phase shifting in multi-frequency capacitively coupled plasmas

Control of ion energy distributions (IEDs) onto the surface of wafers is an ongoing challenge in microelectronics fabrication. The use of capacitively coupled plasmas (CCPs) using multiple radio frequency (rf) power sources provides many opportunities to customize IEDs. In dual-frequency CCPs using a fundamental frequency and its second harmonic, varying the relative voltages, powers, and phases between the fundamental and second harmonic biases have demonstrated potential as control mechanisms for the shape of the IEDs. In this paper, we report on computational and experimental investigations of IED control in dual-frequency and triple-frequency CCPs where the phase between the fundamental and second harmonic frequency voltage waveform is used as a control variable. The operating conditions were 5–40 mTorr (0.67–5.33 Pa) in Ar and Ar/CF4/O2 gas mixtures. By changing the phase between the applied rf frequency and its second harmonic, the Electrical Asymmetric Effects was significant and not only shifted the dc self-bias but also affected plasma uniformity. When changing phases of higher harmonics, the energies and widths of the IEDs could be controlled. With the addition of a 3rd high-frequency source, the plasma density increased and uniformity improved. Computed results for IEDs were compared with experimental results using an ion energy analyzer in systems using rf phase locked power supplies.

Power System Frequency Estimation by Using a Newton-Type Technique for Smart Meters

This paper proposes a single-phase grid voltage fundamental frequency estimation technique for smart meters. The technique relies on a nonlinear Newton-type algorithm and a recursive differentiation filter (NTA–DF). It can reject the negative effects caused by dc offset, harmonics, notches, and spikes. When compared with a NTA technique based on least-squares (NTA–LS), the proposed one reduces matrix dimensions, avoids matrix inversion, and is computationally efficient, thus requiring less hardware and associated cost for real-time implementation. Moreover, unlike the NTA–LS technique, the NTA–DF shows less sensitivity to the presence of harmonics. Simulation and experimental results are presented to verify the performance of the proposed technique.

Identifying Defects in the Transmission Lines by Neural Networks

The paper presents a new technique for the identification of defects in transmission lines using artificial neural networks. The technique uses the amplitude at the fundamental frequency voltage and current signals to one end of the line. A study is conducted to evaluate the performance of the fault identifier.

Robust technique for accurate estimation of single‐phase grid voltage fundamental frequency and amplitude

This study proposes a robust technique for accurate estimation of single-phase grid voltage fundamental amplitude and frequency. The technique relies on a quadrature signal generator (QSG) based on a fixed frequency tuned second-order generalised integrator (SOGI) and an infinite-impulse-response differentiation filter (DF). The DF is used to estimate the fundamental frequency from the instantaneous phase angle obtained from the generated orthogonal voltage waveforms. The estimation technique is robust and offers an easy tuning process as there is no interdependent loop between the orthogonal voltage system and the frequency estimation. Additionally, the technique is computationally efficient and can also reject the negative effects caused by the direct current offset and harmonics. Furthermore, the frequency estimation is less sensitive to harmonics when compared with a similar technique relying on the QSG based on the fixed frequency tuned SOGI and least-squares method. Simulation and real-time experimental results are provided to validate the robustness of the proposed technique.

High speed directional relaying algorithm based on the fundamental frequency positive sequence superimposed components

The conventional travelling wave protection is susceptible to the high frequency transient quantities, which can reduce the protection reliability. A directional-relay algorithm based on positive sequence superimposed components is proposed in this study. In microprocessor relays, the extraction of fundamental frequency voltages and currents is, conventionally, provided by phasor estimation methods such as the Fourier algorithm. The common required time for fault detection in these relays is approximately one to two cycles. This study presents a high-speed algorithm for the extraction of fundamental frequency positive sequence voltages and currents superimposed components based on Park transformation. In the meantime, specially designed high speed algorithms to solve the difficult problems that exist in a real system are proposed. Extensive simulations are performed to evaluate the performance of the proposed algorithm. The results show that the algorithm is fast and reliable for power transmission line protections. Also it is immune to fault resistances and system condition.

Accurate Estimation of Single-Phase Grid Voltage Parameters Under Distorted Conditions

This paper presents an accurate technique for the estimation of single-phase grid voltage fundamental amplitude and frequency. The technique consists of a quadrature signal generator (QSG) and a discrete Fourier transform (DFT). The frequency information required by the QSG based on a second-order generalized integrator (SOGI) is estimated using the spectral leakage property of the DFT. The presented DFT operation does not require real-time evaluation of trigonometric functions. The frequency estimation is less affected by the presence of harmonics when compared to similar techniques based on QSG-SOGI such as the phase-locked loop and the frequency-locked loop. Moreover, unlike these techniques, the DFT-based QSG-SOGI (DFT-SOGI) technique does not create any interdependent loops, thus increasing the overall stability and easing the tuning process. The effectiveness of the proposed technique has been validated on a real-time experimental setup.

Differentiation filter‐based technique for robust estimation of single‐phase grid voltage frequency under distorted conditions

This study proposes a robust estimation technique for the single-phase grid voltage fundamental frequency under grid disturbances. The technique relies on a demodulation method and a finite-impulse-response-based differentiation filter (DF). A frequency domain analysis for designing the DF is presented and is used to estimate the time-varying fundamental frequency from the instantaneous phase angle obtained by the demodulation method. The technique can reject the negative effects caused by the presence of DC offset and harmonics. The proposed DF shows less sensitivity to the presence of oscillations caused by the demodulation method when compared to a similar finite-impulse-response-based DF. Simulation and experimental results are provided to verify the performance of the proposed technique.

A Modified Demodulation Technique for Single-Phase Grid Voltage Fundamental Parameters Estimation

This paper proposes a modified demodulation technique to provide accurate estimation of the single-phase grid voltage fundamental amplitude, frequency, and phase angle under distorted grid conditions. A quadrature oscillator is combined with a demodulation technique for rejecting oscillations at second harmonic generated by the demodulation of the fundamental voltage component; thus, it can provide more accurate estimation, as compared to a conventional one, using same-order and cutoff-frequency-based infinite-impulse-response low-pass filters after the demodulation stage. It also does not require a separate frequency estimation algorithm for adaptive demodulation as the frequency is obtained from the estimated initial phase by using a differentiation operation and an integral controller. The technique is relatively simple and can also reject the negative effects caused by harmonics under a wide range of fundamental frequency variation as specified by the standard requirements. When compared with a quadrature phase-locked loop technique, the proposed one provides improved estimation of the fundamental voltage parameters. The performance of the proposed technique is verified using both simulation and experimental results.

Electric Field Calculation Software for Epoxy Resin Casting Dry-Type Transformer Based on the VB

In the paper, combining the advantages of interface design of VB and secondary design of ANSYS, the electric calculating software for epoxy resin casting dry-type transformer was designed. In the procedure of designing transformer, designers only need to input the structure parameters and electrical parameters of the transformer, which would be transferred to ANSYS Parametric Design Language (APDL) program automatically. Then, the different loading conditions and post-procedure programs can be selected. Furthermore, VB calls ANSYS from the background program and reads the APDL file to calculate electric field distribution. Finally, the case analysis verifies that the software can establish the finite element model automatically and calculate the electrical field distribution under any fundamental frequency voltage and lighting surge.

Hybrid power filter for advanced power quality in industrial systems

The paper presents the structure and control strategy of the hybrid power filter (HPF) with a split passive part. Its impedance is divided into two parts tuned to 50Hz and 250Hz.The HPF topology is very efficient to mitigate harmonic currents. The fundamental frequency voltage at the converter terminals is remarkably small in comparison with the grid voltage at the same moment. The HPF functionality is only negligibly influenced by the grid inductance changes.The HPF characteristics were compared with those for standard HPF topologies and the classical passive compensation by means of simulations done in the Matlab/Simulink environment. The voltage and current responses and their harmonic spectra were also measured in an industrial plant under different conditions.

A Dynamic Filter for Removal DC - Offset In Current and Voltage Waveforms

Abstract— In power systems, protective relays must filter their inputs to remove undesirable quantities and retain signal quantities of interest. This job must be performed accurate and fast. A new method for filtering the undesirable components such as DC and harmonic components associated with the fundamental system signals. The method is s based on a dynamic filtering algorithm. The filtering algorithm has many advantages over some other classical methods. It can be used as dynamic on-line filter without the need of parameters readjusting as in the case of classic filters. The proposed filter is tested using different signals. Effects of number of samples and sampling window size are discussed. Results obtained are presented and discussed to show the algorithm capabilities. Keywords — Protection, DC-offset, Dynamic Filter, Estimation. I. I NTRODUCTION N power system protection, the fundamental frequency voltage or current signals must be decomposed by relays to enable fast response. One of important protection applications is distance protection. In such protection system, to locate the fault accurately and fast the fundamental voltage and current signals must be extracted on-line. Therefore digital filtering in distance relays includes some form of signal parameter estimation algorithm. The resistance-inductance behavior of the power system produces dc- offset components in the fault current which are exponentially decaying. It is known that distance relays have the tendency to overreach in the presence of dc- offset component in the faulted current waveform. A number of techniques has been proposed to remove the dc-offsets from the fault currents. Digital filters, which eliminate the effect of an exponentially decaying component, were proposed in many references. Some of these filters are based on static and dynamic techniques [1], [2], [3]. Sachdev et-al [1] proposed the application of the well known least error square estimation technique. For decomposing the fault current and removing the dc off-set components [1]. The least error squares is an accurate estimation technique but in case of the data set is contaminated with bad measurements, the solution may not be accurate unless extra filters are used for detecting the bad measurements. A digital mimic filter for the removal of DC-offset current waveforms is presented in reference 2. The proposed filter in this reference is used in conjunction with other classic estimators such as least error square to detect the whole system signals components for relaying purposes. Reference 3 proposed the use of Kalman filtering