Common-mode Components Research Articles

A Multi-Point Joint Prediction Model for High-Arch Dam Deformation Considering Spatial and Temporal Correlation

Deformation monitoring for mass concrete structures such as high-arch dams is crucial to their safe operation. However, structure deformations are influenced by many complex factors, and deformations at different positions tend to have spatiotemporal correlation and variability, increasing the difficulty of deformation monitoring. A novel deep learning-based monitoring model for high-arch dams considering multifactor influences and spatiotemporal data correlations is proposed in this paper. First, the measurement points are clustered to capture the spatial relationship. Successive multivariate mode decomposition is applied to extract the common mode components among the correlated points as spatial influencing factors. Second, the relationship between various factors and deformation components is extracted using factor screening. Finally, a deep learning prediction model is constructed with stacked components to obtain the final prediction. The model is validated based on practical engineering. In nearly one year of high-arch dam deformation prediction, the root mean square error is 0.344 and the R2 is 0.998, showing that the modules within the framework positively contribute to enhancing prediction performance. The prediction results of different measurement points as well as the comparison results with benchmark models show its superiority and generality, providing an advancing and practical approach for engineering structural health monitoring, particularly for high-arch dams.

A Mathematical Structural Modulation Method for Neutral-Point Potential Balancing of Three-Level Neutral-Point-Clamped Converters

To achieve the fast neutral-point potential balance of three-level neutral-point-clamped (3L-NPC) converters, a mathematical structural modulation method is presented in this paper, featuring fast balance capability, low computation, and easy implementation. In this method, the duty cycle is decomposed into the differential-mode component (DMC) and the common-mode component (CMC). The CMC is used to synthesize the AC output voltage while the DMC is adopted to control the neutral-point potential. Based on the fractional-order sliding-mode control theory, the DMC is constructed. As a result, neutral-point potential balancing in a pre-calculated time is achieved. Finally, the effectiveness of the proposed method is verified by experimental results.

Spatiotemporal variability at seasonal and interannual scales of terrestrial water variation over Tibetan Plateau from geodetic observations

ABSTRACT In the context of ongoing global climate warming, researchers have observed an intricate relationship between the variability of Terrestrial Water Storage (TWS) on the Tibetan Plateau (TP) and climate anomalies. In this study, we utilize a combination of Global Navigation Satellite System (GNSS), Gravity Recovery and Climate Experiment (GRACE), and precipitation data to investigate the response of TWS on the TP to extreme climate changes, with a focus on seasonal and interannual variations. Our findings reveal that the first Common Mode Component (1st CMC) extracted from GNSS coordinate time series exhibits strong interannual fluctuations. Additionally, both GNSS and GRACE-inferred TWS demonstrate noticeable anomalous changes during the 2015/2016 period. The estimated periods of the 1st CMC of GNSS and GRACE-inferred TWS are approximately 5 and 7 years, respectively. Both reach a minimum during the extreme climate event in 2015/2016. Furthermore, we investigate the spatial variation of summer precipitation before and after the extreme drought event on the TP. It reveals that the inflection point of TWS occurs approximately 1 year prior to the drought event, suggesting a consistent spatial propagation process between precipitation and TWS. This indicates that the changes of TWS during this drought event were primarily influenced by precipitation. Finally, we evaluate the response of 12 sub-basins on the TP to the drought event that occurred in 2015/2016. The regions experiencing significant abnormal fluctuations in TWS are mainly located in inner and northeastern plateau. These regions show rapid upward changes in the TWS and demonstrate a strong spatial consistency with summer precipitation.

Interannual hydrological variability in the Mississippi River Basin based on contemporary geodetic measurements and land surface models

The impact of climate change on terrestrial water storage (TWS) is critical for understanding the global hydrological process. The Global Positioning System (GPS) measurements, Gravity Recovery and Climate Experiment (GRACE), and GRACE Follow-On (GFO) data were used to measure the processes involved in the hydrological process in the Mississippi River Basin (MRB) from 2002 to 2021. The common-mode component (CMC) of the GPS network in the MRB obtained using principal component analysis (PCA) was utilized to study the hydrological loading deformation. The data from GRACE/GFO and hydrological models revealed a long-term trend of reduction in the TWS and obvious depletion of the groundwater storage (GWS) in the southwestern part of the MRB. Both GRACE/GFO and the GPS can accurately detect elastic land deformations in the MRB due to hydrological anomalies caused by El Niño/ Southern Oscillation (ENSO), while the sensitivity of GPS in Tennessee regions to net precipitation around 2016 is higher than that of GRACE/GFO. Furthermore, numerous interannual fluctuations and long-term periodic signals observed in both GPS and GRACE/GFO measurements are found to be intimately connected with hydrological processes and ENSO. The findings demonstrate that modern geodetic methods are useful in monitoring the impacts of climate change on hydrological process.

Design of a Common-Mode Rejection Filter Using Dumbbell-Shaped Defected Ground Structures Based on Equivalent Circuit Models

An efficient design method is proposed for a compact common-mode rejection (CMR) filter utilizing dumbbell-shaped defected ground (DS-DG) structures and gap-coupled stub (GCS) resonators. A CMR filter for differential lines helps to improve the signal integrity of high-speed digital signals on printed circuit boards. The proposed CMR filter design is based on the equivalent circuit models, while the previous designs depended heavily on the DS-DG structure optimization using the EM simulations. The proposed CMR filter effectively rejects the common-mode components while minimally affecting the differential signals. To prove the simplified design approach, a fifth-order Chebyshev band-stop filter is designed with three DS-DG structures and two GCS resonators. From the simulated and measured results, it is found that the proposed CMR filter provides ~90% fractional frequency bandwidth with more than 20 dB of common-mode rejection ratio and less than 0.6 dB of insertion loss of the differential signal.

A common-mode suppression structure for absolute optical encoders

In traditional absolute optical encoders, the DC levels of the absolute code output signals are easily influenced by factors such as light intensity and temperature, leading to fluctuations in the duty cycles and errors in reading absolute code information. This paper presents a novel common-mode suppression structure for the readout of absolute code signals. By eliminating the common-mode component of the signals, the structure effectively suppresses common-mode interference and ensures that the duty cycles of the output signals remain close to the ideal value of 50%. To verify the effectiveness of the proposed common-mode suppression structure for absolute optical encoders, a photonic readout chip based on a 0.35μm CMOS process was designed, and good common-mode suppression effects can be achieved by combining the differential-distributed code disk. Test results show that when the LED’s normal operating current is 3.5 mA, the output duty cycle error is less than ±4%, which reduces 50% compared to the traditional structure. Under a variation of ±1 mA in LED operating current, the corresponding changes in output duty cycles remain within 5%. Similarly, when the temperature shifts from 25 °C to 125 °C, the changes in output duty cycles are contained within 3% It can be seen that this structure can suppress most of the common-mode interference caused by external factors, ensuring the stability of the output signals and reducing the bit error rate of the absolute code signals.

A Flexible and Decoupled Space Vector Modulation Scheme With Carrier-Based Implementation for Multilevel Converters

This article proposes a novel space vector pulse width modulation (SVPWM) scheme for multilevel converters in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">abc</i> coordinate system, in which the reference vector is decomposed into an offset vector and a remainder vector that can be synthesized using two-level SVPWM. The switching state satisfying a specific relationship is first selected as the offset vector such that the common-mode components are eliminated and therefore the phase voltages are decoupled. A dynamic reference point mechanism establishes a one-to-one correspondence between all available vector combinations and one unique variable, i.e., the number of level shifts. This feature further facilitates a general approach to determining the optimum switching states to satisfy different control objectives, such as common-mode voltage rejection. Besides, phase decoupling enables the introduction of carrier-based modulation to simplify implementation, where the duty cycle of the zero vector can be flexibly adjusted while the non-zero vectors remain the same to generate an equivalent output. Consequently, two-level SVPWM-based method and carrier-based PWM are combined to exploit their respective strengths. The proposed scheme achieves overmodulation operation, and provides more flexibility, i.e., redundant switching states and adjustable duty cycles, to optimize switching patterns. Simulation and experimental results validate the proposed algorithm.

Experimental Analyses of EMI Noise Separator for CISPR25

In energy transmission systems, devices must be able to work safely with each other. Therefore, electromagnetic emission and susceptibility of the converting systems are expected to be in a certain range. electromagnetic propagation, especially by radiation and conduction, cannot be neglected in power electronics such as electric vehicle, microgrid, aerospace technologies. In order to examine and reduce the noise emitted by the devices, the noise should be separated into common mode and difference mode components. In this study, Shou Wang modeling, which is used to separate the noise components into related components, has been examined in order to analyze the noise components within the framework of the CISPR25 standard used for electric vehicles and redesigned. Circuit simulation and design were done and the results were compared. Thanks to these results, it has been seen that the circuit works efficiently up to 90MHz and gives 8dB S11 reflection parameter at the 108MHz threshold level. In addition, the separator circuit was used in a bidirectional DC-DC converter with a known EMI level of 1KW and the noise components obtained were compared with the components of the converter. As a result, it has been seen that the results obtained using the noise separator circuit are almost the same as the real results. In the 18 - 42 MHz range, only the results obtained with the noise separator are up to 8dBuV higher than the real results, other than that the results are exactly the same.

Dual, Three-Level, Quasi-Z-Source, Indirect Matrix Converter for Motors With Open-Ended Windings

In this paper, a novel variable-voltage, variable-frequency, dual, three-level, quasi-Z-source, indirect matrix converter topology is proposed, including a detailed description of a modulation method and a control strategy for three-phase motors with open-ended windings. The proposed power drive system (PDS) supports bidirectional power flow and has a combined control of DC-link voltage and output AC voltage frequency. Experimentally validation was performed on a 4-kW PDS. For a given supply voltage amplitude and the same power switch voltage rating in the DC/AC converter, the proposed PDS can double the voltage output gain, thus being an interesting solution for high-power applications with motors designed for higher voltages. The proposed PDS topology, modulation method and motor control strategy can reduce the common-mode component, low-order harmonic content, peak values and d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</i> /d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> of the motor phase voltage, ultimately leading to lower winding insulation voltage stress at low-speed, low-voltage operation, lower harmonic losses in the motor, and ride-through capability over voltage sags in the mains, which are important advantages.

Interseismic Strain Accumulation between the Colorado Plateau and the Eastern California Shear Zone: Implications for the Seismic Hazard near Las Vegas, Nevada

ABSTRACTCrustal deformation in the central Basin and Range between the Colorado plateau and the Eastern California Shear Zone is active but slow, making it a challenge to assess how strain is distributed and crustal motion transferred. However, knowledge of strain rates is very important, particularly for addressing the seismic hazard for both the Las Vegas urban area and the site of the proposed Yucca Mountain nuclear waste repository, in southern Nevada. Global Positioning System (GPS) data provide important constraints, particularly now that the GPS network in the area has substantially expanded in recent years. However, because deformation is slow, it is important to mitigate any transient tectonic and nontectonic signals to obtain the most accurate long-term interseismic motion and robust estimation of strain rates. We use data from all GPS stations in the region including both long-running continuous and semicontinuous stations. We model and remove postseismic displacements at these stations using source parameters for 41 events, dating back to the 1700 Cascadia megathrust earthquake, which contribute significantly to the deformation field within the central Basin and Range. We also remove correlated noise from the time series with the common-mode component imaging technique. We find that removal of both the postseismic transients and common-mode noise substantially reduces the uncertainties and spatial variation in the velocities. We find east–west extension across the Las Vegas Valley of 0.5–0.6 mm/yr. The interseismic strain rate field, calculated with the final velocities, reveals higher strain rates through southern Nevada than in previous studies, with rates within Las Vegas Valley of 8.5±2.4×10−9 yr−1. Our results also confirm shear along the Pahranagat shear zone, but the estimated amplitude is strongly affected by postseismic relaxation.

A CMOS Double-Demodulation Lock-In Amplifier for Stimulated Raman Scattering Signal Detection

In typical stimulated Raman scattering (SRS) signal extraction, the photodetector and lock-in amplifier are often based on separate platforms, rendering the system cumbersome and non-scalable. This paper proposes an SRS double-demodulation lock-in amplifier implemented with a complementary metal-oxide semiconductor (CMOS) image sensor technology that integrates two-stage 1/f noise and offset reduction circuits with a high-speed lateral electric field modulation (LEFM) photo-demodulator. A weak SRS signal is buried in a large offset with a ratio of 10−4 to 10−6; boosting such signals in a CMOS device requires an extremely high offset and noise reduction capability. The double-modulation two-stage lock-in amplifier demodulates at 40 MHz with a sampling frequency of 20 MHz, can suppress the laser and circuit’s 1/f noise to achieve higher detection sensitivity. A prototype chip fabricated using 0.11 μm CMOS image sensor technology is evaluated. Both simulation and measurement results are presented to verify the functionality and show that the differential readout structure can successfully reject laser common mode components while emphasizing its differences. The measurement results show that the double-modulation lock-in amplifier effectively suppresses the circuit’s 1/f noise by a factor of nearly two decades.

Decentralized Circulating Current Attenuation With Model Predictive Control for Distributed/Shunted Single/Three-Phase Grid-Tied Inverters

This letter proposed a decentralized control method to attenuate the circulating current among the grid-connected inverters without extra cost on the communication. Based on the combination of cascaded model predictive control (MPC) and modified <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$LCL$</tex-math></inline-formula> filter topologies, the developed method can locally limit the circulating current for different types of inverters, e.g., single/three-phase grid-connection, and various applications, e.g., shunted or distributed inverters with/without common dc bus, respectively. The merits of the proposed method include the following. 1) Decentralized circulating current control without the need of a central controller or the corresponding communication to collect the sampling and calculate the common mode components for leakage current attenuation among different inverters. 2) Generalized control method that can be applied to single/three-phase inverters for both shunted and distributed inverters with/without common dc bus applications. 3) No synchronization is needed for pulsewidth modulation signals among different inverters to attenuate the circulating current. 4) Cascaded MPC without the need of individual inverter’s grid side uncertain filter parameters for the attenuation of circulating current and system parametric modeling. 5) Better transient performance with the inner loop MPC. The experimental results verified the proposed method.

Analysis of High-Frequency Common Mode Component Characteristics of Common Mode Peak Voltage Suppression Method for Indirect Matrix Converter

A variety of modulation strategies for suppressing output common-mode voltage (CMV) of indirect matrix converters (IMC) have been proposed, but most of them mainly reduce the peak of CMV by 42.3%. The frequency-domain characteristics of CMV have not been deeply analyzed. In order to improve the theory of frequency-domain characteristics of output common-mode voltage of IMC, this paper proposed a common-mode frequency domain analysis of five common-mode voltage peak suppression modulation methods for IMC. The common-mode voltage spectrum corresponding to the five modulation methods is obtained by the triple Fourier series, and the variation laws of the output common-mode components of the five modulation methods under different modulation indexes are compared and analyzed. By comparing and analyzing the low-frequency amplitude characteristics and high-frequency amplitude characteristics of five modulation methods, the suppression performance of the five modulation methods is evaluated. Finally, experiments verify the correctness of the theoretical analysis of the frequency domain characteristics of the output common-mode voltage of the indirect matrix converter.

SPICE-Based Circuit Analysis of Power Flow Coupling Effect in Double-Input Cuk--Buck DC–DC Converters

An equivalent simulation program with integrated circuit emphasis (SPICE) based circuit is derived from the proposed small-signal averaged model of double-input Cuk--Buck dc–dc converter so that the power flow coupling effect amongst input/output ports is easy to be analyzed in terms of circuit theory rather than pure mathematics. Based on the equivalent SPICE-based circuit, common mode and differential mode power flow decomposition is presented to unveil the power flow coupling between three ports, and furthermore benefits frequency response analysis. It is shown that common mode perturbation analysis reveals the power flow coupling amongst input and output ports, whereas differential mode perturbation analysis does the power flow coupling between input ports. Meanwhile, the explanation of circuit knowledge is provided for power flow coupling effect. Particularly, it is found that the occurrence of the pseudo resonant phenomenon is the result of counteract effect of the common mode and differential mode components in power mismatched condition. Besides, the application of frequency-selective decoupling is proposed to weaken the power flow coupling between ports. Finally, theoretical analysis is verified by experimental ones. These results are useful to understand coupling effects in multiple-input converters and provide a guidance to the controller optimization and engineering application.

Decoupling Capacitor Minimization of an MMC-Based Photovoltaic System With Three-Winding Power Channel

This article proposed a grid-connected photovoltaic (PV) converter based on modular multilevel converter (MMC), which can realize long-distance dc transmission while realizing the local consumption of PV. In addition to the advantage that there is no PV power mismatch between the upper and lower arms, the isolation transformer couples the two submodules of the upper and lower arms on a three-port transformer, and the differential-mode components of the capacitor voltage ripples in the upper and lower arms can be canceled between each other. Besides, through the double fundamental frequency circulating current control, the power exchange among MMC phase units can be realized, thereby eliminating the common-mode component of the capacitor voltage ripple. Through the combination of topology and control strategy, the low-frequency components of the voltage ripple can be completely canceled. Since the decoupling capacitance is reduced dozens of times, the volume and cost of the system are significantly reduced. Therefore, the life and reliability of the system are increased. Simulation and experimental results verify the effectiveness of the proposed topology and its control strategy.

The Interannual Fluctuations in Mass Changes and Hydrological Elasticity on the Tibetan Plateau from Geodetic Measurements

The mass balance of water storage on the Tibetan Plateau (TP) is a complex dynamic system that has responded to recent global warming due to the special regional characteristics and geographical environment on the TP. In this study, we present global positioning system (GPS), gravity recovery and climate experiment (GRACE) and follow-on (FO) observations obtained during the 2002–2020 period to identify hydrological changes on the TP. The spatial long-term trends in the GRACE/GRACE-FO data show continuous glacier mass losses around the Himalayas and accumulated mass on the inner TP due to the increased water mass in lakes. The singular spectrum analysis (SSA) was applied for interpolation of the data gap with GRACE/GRACE-FO. We evaluated the correlation between the vertical displacements obtained from 214 continuous GPS stations and GRACE/GRACE-FO-modeled water mass loads and found a high correlation, with spatial variabilities associated with the seasonal terrestrial water storage (TWS) pattern. The common-mode component obtained from continuous GPS coordinates was decomposed using principal component analysis (PCA) and presented different periodic signals related to interannual fluctuations in hydrology and the dynamics of the inner Earth. Moreover, the various characteristics of precipitation and temperature revealed similar interannual fluctuations to those of the El Niño/Southern Oscillation. We conclude that the GPS-inferred interannual fluctuations and the corresponding GRACE/GRACE-FO-modeled hydrological loads reflect climate responses. These findings shed light on the complex role of the spatiotemporal climate and water mass balance on the TP since the beginning of the 21st century.

Power Decoupling Control of MMC and Small-Signal Stability Analysis of AC/DC Distribution Network With Renewable Energy

AC/DC hybrid distribution network can realize the high penetration utilization of renewable energy and modular multilevel converter (MMC) is the key equipment to connect AC grid and DC grid. In this paper, the direct modulation based on the virtual resistor and the reference value of dc-bus voltage is adopted, and instantaneous-value model of three-phase half-bridge MMC is derived by introducing differential-mode and common-mode component representation. Then, the decoupling control of AC active power and reactive power is designed based on the linear active disturbance rejection control theory (LADRC). The total disturbances including the coupling term and capacitor voltage fluctuation can be estimated by extended state observer (ESO), and then cancelled exactly. Based on the simplified average-value model of MMC, the small signal stability analysis of three-terminal AC/DC distribution network with 26-level MMCs corresponding to the Tangjiawan-Jishan1-Jishan2 demonstration project is carried out by root locus and bode diagram method, which gives the guidance for the choice of the main circuit component and controller parameters, and shows that the virtual resistor greatly reduces the resonant peak of AC/DC distribution network. Simulation and experiment results verify the effectiveness of the power decoupling control strategy of MMC and the AC/DC distribution network can realize complex multi-directional power flow.

Common Mode Component and Its Potential Effect on GPS-Inferred Crustal Deformations in Greenland

The effective extraction and elimination of the Global Positioning System's (GPS) common mode error (CME) is of great significance to improving the signal-to-noise ratio of the coordinate time series and accurately estimating the characteristics of the crustal deformation. In this study, the principal component analysis (PCA), Karhunen–Loeve expansion (KLE) and stacking filtering methods are used to extract the CMEs of Greenland GPS station coordinates in the East-North-Up (ENU) directions. Their influence on GPS coordinate residuals and the relationship amongst the observations are also analyzed. The results show that the PCA, KLE and stacking filtering methods can effectively eliminate the common mode noise in the GPS station coordinate time series and reduce their uncertainty. The PCA method is better than KLE and stacking methods, and the filtering effect in the up (U) direction is better than those in the east (E) and north (N) directions. Then, as the CME can be detected periodically in the U direction, its physical mechanism is studied. On the one hand, the period of CME maximum power is 1 year but is not constant. On the other hand, the correlation between the GPS CME and GRACE ice loading deformation is 0.5. When the ice loading deformation is deduced by the GRACE method, the CME of the GPS network can be eliminated by 25.6%, which indicates that the ice loading deformation is part of the source of GPS CME in Greenland. Finally, the influence of the U direction CME on the station noise characteristics is analyzed using maximum likelihood estimation (MLE). The results show that the CME noise type is mainly WN + FN. Moreover, the estimated coordinate velocities and most of the annual amplitudes of the stations have an increasing trend after CME elimination, whereas the uncertainty has a decreasing trend. These findings are consistent with the trend of noise component change. The above results indicate that the CME elimination of the GPS stations cannot be ignored, as they can help to improve the estimation of station velocity and annual amplitude and reduce the uncertainty.

Differential and common-mode model-based controller for the double-dual buck transformerless inverter

This paper studies the double-dual DC-DC buck converter composed by two buck power stages in a double dual connection. This connection has been previously studied with the boost power stage in the well-known double dual boost converter. In contrast to the double dual boost, which can only be used as a dc-dc converter, the double dual buck can be used as an inverter. Furthermore, it has a non-pulsating voltage from the input terminals to the output terminals. This property is exploited to reduce the common-mode current, which is of special interest in transformer-less photovoltaic applications, among others. The study includes a model description of the system in terms of the differential and common-mode variables. A controller based on this model representation is proposed to alleviate the effects of the common-mode component of the inverter output voltage on the leakage ground current. The analysis shows that the double-dual buck based inverter in closed-loop with the proposed controller exhibits a considerably reduced leakage-ground current, i.e., an almost negligible common-mode current flowing through the ground-path. This natural benefit makes it an attractive option for applications such as grid-tied inverters for renewable energy systems and electric vehicles. An efficiency analysis is also provided considering a conventional modulation scheme. Finally, the system performance is evaluated in a 1 kW experimental setup.

Robust estimation of spatially varying common-mode components in GPS time-series

We present a new method to estimate common-mode components (CMC) in global positioning system (GPS) position time-series. The method (‘CMC Imaging’) is fully automated, relies entirely on robust statistics, and exploits the recent proliferation of GPS stations by allowing stations with relatively short time-series to be considered as filter stations as well. The spatial extent of the CMC is purposely defined as local as possible and constrained by the proximity of nearby GPS stations. Our approach also avoids the need for subjective assignment of filter stations; every station is considered and those stations that deviate significantly from the local CMC are flagged and excluded as filter stations. We study thousands of GPS position time-series in the intraplate area of western Europe, and we show that CMC Imaging method is superior to other approaches in terms of noise reduction: we obtain an RMS reduction of 50%, 44% and 39% in the residual time-series in vertical, east, and north components, respectively. We show the importance of using filter stations that are as local as possible, because of systematic lateral variations in inter-station correlations and indeed in CMC, particularly in the vertical component. Those spatial variations are largest for continental stations, particularly those around the Baltic Sea, and could be due to atmospheric and nontidal ocean loading. CMC filtering has a large influence on reducing the temporal trend variability and approximately doubles the trend accuracy (by comparing variability in short-term trends with the long-term estimate).