Voltage Oscillations Research Articles

An improved secondary voltage control method for half-wavelength transmission system

The half-wavelength transmission has the potential application to transmit bulk power through very long distances. In this paper, an improved secondary voltage control method is proposed for half-wavelength transmission system without dependency on remote control signal communication. At first, quantitative relationships between terminal voltages of half-wavelength line and transmission power are deduced based on the distributed parameter model. Then, three main improvements are proposed in secondary voltage control level. Reactive power transmission restriction of half-wavelength line is introduced as another control objective except for pilot bus voltage regulation. Variable pilot bus voltage reference setting method is given according to the voltage/active power correlation considering load fluctuation. Specific voltage control activation conditions are deployed to avoid control direction error or voltage oscillations. After that, simulation results demonstrate that the proposed voltage control method can trace variable voltage reference accurately and flat voltage profiles along half-wavelength line effectively in different disturbance conditions.

Primer to Voltage Imaging With ANNINE Dyes and Two-Photon Microscopy.

ANNINE-6 and ANNINE-6plus are voltage-sensitive dyes that when combined with two-photon microscopy are ideal for recording of neuronal voltages in vivo, in both bulk loaded tissue and the dendrites of single neurons. Here, we describe in detail but for a broad audience the voltage sensing mechanism of fast voltage-sensitive dyes, with a focus on ANNINE dyes, and how voltage imaging can be optimized with one-photon and two-photon excitation. Under optimized imaging conditions the key strengths of ANNINE dyes are their high sensitivity (0.5%/mV), neglectable bleaching and phototoxicity, a linear response to membrane potential, and a temporal resolution which is faster than the optical imaging devices currently used in neurobiology (order of nanoseconds). ANNINE dyes in combination with two-photon microscopy allow depth-resolved voltage imaging in bulk loaded tissue to study average membrane voltage oscillations and sensory responses. Alternatively, if ANNINE-6plus is applied internally, supra and sub threshold voltage changes can be recorded from dendrites of single neurons in awake animals. Interestingly, in our experience ANNINE-6plus labeling is impressively stable in vivo, such that voltage imaging from single Purkinje neuron dendrites can be performed for 2 weeks after a single electroporation of the neuron. Finally, to maximize their potential for neuroscience studies, voltage imaging with ANNINE dyes and two-photon microscopy can be combined with electrophysiological recording, calcium imaging, and/or pharmacology, even in awake animals.

Multimode Smooth Switching Strategy for Eliminating the Operational Dead Zone in Noninverting Buck–Boost Converter

The existence of operational dead zone during mode switching in noninverting buck–boost converter results in oscillation of the output voltage and instability of the system during high power operation. The mechanism and effect of the operational dead zone are analyzed, the conditions that need to be met when eliminating the operational dead zone are researched, and a multimode smooth switching control strategy which can completely eliminate the operational dead zone is proposed. The converter works with three operating modes, the method of theoretical analysis combined with experimental correction is used to set the mode switching parameters, to ensure that the actual voltage gains of the converter on both sides of the mode switching points are equal. A single-degree-of-freedom buck–boost mode is designed to replace the pass-through mode to maintain the converter's stable output. And the converter's operating power level and overall power transmission efficiency can be improved, when the control parameters are designed to reduce the interval length of the boost mode and the single-degree-of-freedom buck–boost mode. Finally, a 700-W experimental prototype is built to verify the effectiveness of the proposed solution.

High Precision Compensation for a Total Reflection Prism Laser Gyro Bias in Consideration of High Frequency Oscillator Voltage.

Traditional compensation methods based on temperature-related parameters are not effective for complex total reflection prism laser gyro (TRPLG) bias variation. Because the high frequency oscillator voltage (UHFO) fundamentally affects the TRPLG bias, and the UHFO has a stronger correlation with the TRPLG bias when compared with the temperature, an introduction of UHFO into the TRPLG bias compensation can be evaluated. In consideration of the limitations of least squares (LS) regression and multivariate stepwise regression, we proposed a compensation method for TRPLG bias based on iterative re-weighted least squares support vector machine (IR-LSSVM) and compared with LS regression, stepwise regression, and LSSVM algorithm in large temperature cycling experiments. When temperature, slope of temperature variation, and UHFO were selected as inputs, the IR-LSSVM based on myriad weight function improved the TRPLG bias stability by 61.19% to reach the maximum and eliminated TRPLG bias drift. In addition, the UHFO proved to be the most important parameter in the process of TRPLG bias compensation; accordingly, it can alleviate the shortcomings of traditional compensation based on temperature-related parameters and can greatly improve the TRPLG bias stability.

Multivariable integral linear quadratic Gaussian robust control of islanded microgrid to mitigate voltage oscillation for improving transient response

AbstractA novel robust integral linear quadratic Gaussian (ILQG) controller is presented in this paper to control the voltage of islanded microgrid and improves its transient response. Microgrid is a small grid that consists of number of distributed generator units, power‐electronic components with inductor‐capacitor (LC) filters and loads. The loads are parametrically uncertain and unknown that produces the voltage or power oscillation. The ILQG controller is capable to compensate for the voltage oscillation and exhibits the tracking of grid voltage against the different load dynamics. The design of ILQG controller is carried out by augmenting the plant dynamics with an integrator. The robustness of the ILQG controller is studied by considering a number of uncertainties within the plant model. The performance of ILQG controller is compared with linear quadratic regulator (LQR) and linear quadratic Gaussian (LQG) controller in terms of rise time, settling time, bandwidth and tracking error. The comparison results ensure the high bandwidth and tracking performance of ILQG controller as compared to other controllers.

An Improved Adjustable Modulation Strategy for Three-Level NPC Inverters Considering Dynamic Loading Applications

Three-level neutral-point-clamped (NPC) inverters are being widely adopted in low-voltage low-power applications. For an intended application, the modulation strategy and the operating conditions are the two key factors that highly influence the major performance indices of the NPC inverter, such as efficiency, harmonic distortion, and voltage oscillations at neutral point (NP). Considering dynamic loading applications where the operating point varies significantly, this paper proposes an improved adjustable pulsewidth modulation (PWM) strategy for a three-level NPC inverter that can alter its modulation pattern to meet desired performance objectives for the full operation range. It has been shown that by varying two control parameters namely discontinuity control parameter and bias control parameter, the proposed modulation strategy changes its pattern between the most efficient generalized discontinuous PWM to NP oscillations-free partial dipolar PWM strategy. Additionally, to obtain a tradeoff between the performance parameters-efficiency, NP oscillations, and waveform quality-The proposed strategy has the ability to settle at the intermediate modulation patterns by transforming into a hybrid modulation signal. Furthermore, considering NP voltage unbalance mitigation as major technical challenge in adjustable modulation strategy, a voltage unbalance compensator that exhibits satisfactory balancing performance for the entire variations of modulation patterns and operating conditions has also been presented. The performance of the proposed modulation strategy in conjunction with voltage unbalance compensator has been evaluated in simulation by widely varying the speed and load of induction motor, and verified in experimentation.

Real-Time Local Volt/Var Control Under External Disturbances With High PV Penetration

Volt/var control (VVC) of smart PV inverter is becoming one of the most popular solutions to address the voltage challenges associated with high PV penetration. This work focuses on the local droop VVC recommended by the grid integration standards IEEE1547, rule21 and addresses their major challenges i.e. appropriate parameters selection under changing conditions, and the control being vulnerable to instability (or voltage oscillations) and significant steady state error (SSE). This is achieved by proposing a two-layer local real-time adaptive VVC that has two major features i.e. a) it is able to ensure both low SSE and control stability simultaneously without compromising either, and b) it dynamically adapts its parameters to ensure good performance in a wide range of external disturbances such as sudden cloud cover, cloud intermittency, and substation voltage changes. A theoretical analysis and convergence proof of the proposed control is also discussed. The proposed control is implementation friendly as it fits well within the integration standard framework and depends only on the local bus information. The performance is compared with the existing droop VVC methods in several scenarios on a large unbalanced 3-phase feeder with detailed secondary side modeling.

Actuator Placement for Enhanced Grid Dynamic Performance: A Machine Learning Approach

This paper proposes a machine learning approach for placing control actuators to enhance dynamic performance in power systems with high penetration of renewable energy. The method transforms the placement problem into a classification problem by studying the relationship between system topological, physical and operational features, and dynamic performance related labels. The proposed framework includes four stages: power system setup; dataset creation; feature extraction and analytical model generation, and creating guidelines for system planners. Test results in the IEEE 39-bus system and the IEEE 118-bus system determine the most significant features including inertia, topological, and impedance distributions. This paper also contributes to providing general criteria and guidance for system planners to place the control resources for improving oscillation damping, voltage, and transient stability issues.

Vector Control of a Modular Multilevel Matrix Converter Operating Over the Full Output-Frequency Range

The modular multilevel matrix converter (M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C) is an ac-to-ac converter topology suitable for the control of high-power variable-speed drives. The control of this converter is complex, particularly when the two ac system frequencies are similar or identical because large voltage oscillations can be produced in the floating capacitors within the M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C. This paper proposes a new vector control system based on nested controllers to regulate the M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C over the full range of frequencies. The proposed control scheme is especially useful to mitigate or eliminate the oscillations that arise when the frequencies are similar. An extensive discussion of the model and control of the M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C is presented in this work. The effectiveness of the proposed vector control system is demonstrated through simulation studies and experimental validation tests conducted with a 27-cell-5kW M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C prototype.

Onboard Charging DC/DC Converter of Electric Vehicle Based on Synchronous Rectification and Characteristic Analysis

The DC/DC converter is the core part of the two-stage electric vehicle Onboard Charger. At present, the phase-shifted full-bridge soft-switching DC/DC converter has problems such as difficulty in commutation of the lagging leg, voltage fluctuation on the secondary side of the transformer, and low efficiency. A full-bridge DC/DC converter with two clamp diodes and synchronous rectification is proposed in this paper. Clamping diodes are used to suppress the voltage oscillation of the secondary side of the transformer and provide the commutating energy of the lagging leg. Synchronous rectification reduces the loss of the switching device. The operating principle and control method of the DC/DC converter are analyzed, and the switching device loss is calculated. The simulation and experimental results show that, compared with the traditional DC/DC converter, the voltage impulse of the secondary side of the transformer is smaller, the efficiency is higher, and the soft switch can be realized in a wide load range, which satisfies the requirement of fast charging of vehicle-mounted batteries.

Zero‐voltage‐switching full‐bridge converter with low filter requirement and voltage oscillation amplitude

This article presents a new full-bridge converter with three-winding coupled inductor. The proposed converter can solve the drawbacks of traditional full-bridge converter, such as narrow zero-voltage-switching range, serious voltage oscillation, and large primary circulating current. By introducing a coupled inductor into the full-bridge converter, the currents of leading-leg and lagging-leg are optimised and a wide zero-voltage-switching range can be achieved. In the proposed converter, the secondary voltage oscillation occurs only when the rectified voltage is low. Thus, the amplitude of voltage oscillation and the voltage stress of rectified diodes are well suppressed. Furthermore, the primary power can be continually transferred to the output side during the whole switching period, resulting in reduced circulating current and low filter requirement. Finally, the theoretical analysis is verified on a laboratory prototype. Experimental results show the effectiveness of the proposed converter.

Isolated Series-Capacitor-Based Full-Bridge Converter With Reduced Circulating Losses and Wide Soft Switching Range

Aiming at the limitations of traditional full-bridge dc/dc converters, such as, narrow soft switching range, large circulating loss during the freewheeling period, and voltage oscillation on the rectifier diodes, in this paper, a series capacitor-based full-bridge dc/dc converter is presented to reduce the voltage stress of power switches to half of input voltage, and by introducing the asymmetric pulsewidth modulated (APWM) scheme to the proposed converter, zero-voltage switching for all the switches in the proposed converter can be obtained. Moreover, due to the reduced voltage turned-OFF stress for switches, the energy of commutation process for switches is reduced and turned-OFF switching losses can be decreased. Therefore, wide soft switching range for the proposed converter could be achieved on the condition of variable input voltage and load power. Furthermore, a simple auxiliary circuit on the secondary side of the transformer is utilized to clamp the voltage stress of rectifier diodes and voltage oscillation is eliminated. Moreover, during the freewheeling period, the current through the primary side of the transformer can be decay to zero; circulating losses are eliminated and zero current switching for the lagging switches could be achieved. The circuit configuration, operating principle, and relevant analysis results of the proposed converter are analyzed, and a design example is given in this paper. Finally, experimental results from a 400-W 300–380-V/42-V prototype are presented to verify the analysis of the proposed converter.

Flexible PCB-Based 3-D Integrated SiC Half-Bridge Power Module With Three-Sided Cooling Using Ultralow Inductive Hybrid Packaging Structure

Silicon carbide (SiC) devices are capable of high switching speeds and also enable high switching frequency in power electronic converters. However, this feature poses substantial challenges to packaging, especially limiting the loop inductance. The traditional wire-bonding packaged power module has large parasitic inductance, which will cause voltage overshoot, oscillation, parasitic turn-on, and EMI issues. In order to reduce the parasitic inductance, this paper proposes a flexible printed circuit board (FPCB) based full SiC half-bridge power module with a novel low inductive hybrid packaging structure and three-dimensional (3-D) integration method. This hybrid packaging structure has an ultrathin FPCB substrate stacked on a direct bonding copper (DBC) substrate, which forms a multilayer 3-D power loop. The SiC chips are soldered on the DBC substrate for good thermal dissipation through a cavity in the FPCB substrate. After power loop optimization, the power loop inductance of a 1200-V/120-A SiC power module is only 0.79 nH. The power module consists of three submodules, which are connected by the bendable FPCB substrate. The bendable power module enables maximum utilization of 3-D space. The gate drive, decoupling capacitors, and dc-link capacitors are also integrated and 3D-structured using rigid-flexible PCBs. Moreover, the cooling system is a high-efficiency three-sided cooling structure for the bendable power module. The simulation results show that the three-sided cooling structure reduces the heatsink volume by 50%. Applying this method, the converter can be designed as a system-in-package and a 3D-structured compact system. The power density of a 20-kW three-phase inverter will reach 19.3 kW/L based on this power module. In this paper, the 1200-V/120-A power module fabrication and assembly processes are given. Finally, the static and dynamic experimental comparisons are done for a commercial power module and the proposed power module. The experiment results show that the voltage overshoot of the proposed module reduces about 5.8 times and are consistent with the simulation results. Meanwhile, the proposed power module switching speed is 1.8 times faster than the commercial module under zero external gate resistors and the switching loss can reduce by about 60%.

Smart Transformer-Based Single Phase-To-Neutral Fault Management

The smart transformer (ST), with its high control capability, offers new features for optimizing the management of the distribution grid. The ST, by controlling the voltage in each phase independently, is able to manage the operations during grid faults, in particular in the single-phase ones. The ST, when a single-phase-to-ground fault occurs, can rapidly reduce the voltage in the phase under fault. Thus, it guarantees system safety and operates with the remaining two healthy phases to avoid unnecessary interruption in the healthy lines. However, the two-phase asymmetrical operation challenges the system performances due to the high power 2nd harmonic ripple in the dc voltage, that reduces the capacitors, lifespan and the high current flowing in the neutral conductor. These issues would force the grid operator to increase the ST maintenance, in order to avoid unplanned faults in the ST hardware, due to failure of aged capacitors. This paper presents a flexible-control strategy, based on the phase-shift angle control between two healthy-phase voltages, that reduces the impact of the power 2nd harmonic oscillation and thus can delay the maintenance intervention. The proposed strategy aims to improve system performances by avoiding neutral-line current overload and attenuating ac side active power (low voltage dc-link voltage) oscillation. Depending on the grid conditions (small dc link capacitance or low ampacity of neutral cable), the voltage angle can be adapted, minimizing the impact of the two-phase operation system in the ST-fed grid. The effectiveness and feasibility of the proposed approach have been validated experimentally with a simplified microgrid setup.

A Robust Control Scheme for Renewable-Based Distributed Generators Using Artificial Hydrocarbon Networks

Distributed generators (DGs) based on renewable energy systems such as wind turbines, solar panels, and storage systems, are key in transforming the current electric grid into a green and sustainable network. These DGs are called inverter-interfaced systems because they are integrated into the grid through power converters. However, inverter-interfaced systems lack inertia, deteriorating the stability of the grid as frequency and voltage oscillations emerge. Additionally, when DGs are connected to the grid, its robustness against unbalanced conditions must to be ensured. This paper presents a robust control scheme for power regulation in DGs, which includes inertia and operates under unbalanced conditions. The proposed scheme integrates a robust control algorithm to ensured power regulation, despite unbalanced voltages. The control algorithm is an artificial hydrocarbon network controller, which is a chemically-inspired technique, based on carbon networks, that provides stability, robustness, and accuracy. The robustness and stability of the proposed control scheme are tested using Lyapunov techniques. Simulation, considering one- and three-phase voltage sags, is executed to validate the performance of the control scheme.

Stepwise propagation of a guided streamer along a DBD helium plasma jet fed by biased oscillating voltage

A stepwise propagation of a guided streamer along a helium atmospheric pressure plasma jet driven by a dielectric barrier discharge was recorded. To feed the plasma jet, we used a power supply generating an output voltage signal consisting of a superposition of 41.6 kHz bipolar square pulses and 300 kHz oscillating signals. At a positive half a period of the output voltage signal, a step-by-step propagation was observed for the ionization wave along the plasma jet. The streamer head stops with the decrease in voltage in the first cycle of oscillations and then restarts its motion at the voltage front of the next cycle of a voltage oscillation. The streamer propagation velocity and plasma jet length are likely to be controlled by varying the gas flow rate, bias voltage, voltage rise rate, frequency of oscillations in the pulse, and other parameters.

ABC Algorithm for Estimation of Dynamic Parameters in Radial Power System Transfer path

In this paper, the artificial bee colony algorithm (ABC) is used to predict the stability of the power system and is evaluated the aggregated machine reactance and inertias in the transfer path. The proposed method is used for estimating the dynamic parameters of the aggregated machines for each area utilising the amplitudes of voltage oscillations measured at any three intermediate points on the transfer path. Two types of voltage control equipment are considered, namely, a static var compensator (SVC) and a thyristor controlled series capacitor (TCSC) including the purpose of voltage support and reducing the disturbance in the system. The proposed methods employ bus voltage phasor data at several buses including the voltage control bus and the line currents on the power transfer path. Here, the three phase fault is applied in the power system. Based on the estimation, the dynamics of the power system is improved and the proposed strategy is utilised for improving the overall dynamic security. The proposed technique is implemented in MATLAB/simulink working platform and the output performance is evaluated and compared with the existing methods such as without facts devices, SVC based controller and genetic algorithm (GA) based TCSC controller respectively.

Failure Prediction of Submodule Capacitors in Modular Multilevel Converter by Monitoring the Intrinsic Capacitor Voltage Fluctuations

Modular multilevel converters (MMCs) are emerging as a promising topology for medium- and high-power applications. Aluminum electrolytic capacitors (AECs) are usually employed in MMCs as floating capacitors due to their high volumetric efficiency and low price. AECs gradually deteriorate over time due to electrolyte vaporization, and for this reason, they have been recognized as one of the most fragile components in the converter. As they continue to age, the AEC's capacitance decreases and its equivalent series resistance increases, which can result in an increase of submodule (SM) capacitor voltage ripple, power loss and could damage the operation of the MMC with prolonged use of aged capacitors. To prevent such damage, monitoring the health of capacitors is an important step to enhance the reliability of the MMC by predictive maintenance. This paper presents a failure prediction scheme for SM capacitors in the MMC by monitoring the SM capacitor voltage oscillations. Detailed simulation studies are carried out for a five-level MMC in the PLECS® platform and verified experimentally. The estimated capacitance through simulations and experiments is in close agreement to that value measured using the LCR meter.

Why pacing frequency affects the production of early afterdepolarizations in cardiomyocytes: An explanation revealed by slow-fast analysis of a minimal model

Early afterdepolarizations (EADs) are pathological voltage oscillations in cardiomyocytes that have been observed in response to a number of pharmacological agents and disease conditions. Phase-2 EADs consist of small voltage fluctuations during the plateau of an action potential, typically under conditions in which the action potential is elongated. Although a single-cell behavior, EADs can lead to tissue-level arrhythmias. Much is currently known about the biophysical mechanisms (i.e., the roles of ion channels and intracellular Ca^{2+} stores) for the various forms of EADs, due partially to the development and analysis of mathematical models. This includes the application of slow-fast analysis, which takes advantage of timescale separation inherent in the system to simplify its analysis. We take this further, using a minimal three-dimensional model to demonstrate that phase-2 EADs are canards formed in the neighborhood of a folded node singularity. This allows us to predict the number of EADs that can be produced for a given parameter set, and provides guidance on parameter changes that facilitate or inhibit EAD production. With this approach, we demonstrate why periodic stimulation, as occurs in intact heart, preferentially facilitates EAD production when applied at low frequencies. We also explain the origin of complex alternan dynamics that can occur with intermediate-frequency stimulation, in which varying numbers of EADs are produced with each pulse. These revelations fall out naturally from an understanding of folded node singularities, but are difficult to glean from knowledge of the biophysical mechanism for EADs alone. Therefore, understanding the canard mechanism is a useful complement to understanding of the biophysical mechanism that has been developed over years of experimental and computational investigations.

Functional Connectivity of Organic Neuromorphic Devices by Global Voltage Oscillations

Global oscillations in the brain synchronize neural populations and lead to dynamic binding between different regions. This functional connectivity reconfigures as needed for the architecture of the neural network, thereby transcending the limitations of its hardwired structure. Despite the fact that it underlies the versatility of biological computational systems, this concept is not captured in current neuromorphic device architectures. Herein, functional connectivity in an array of organic neuromorphic devices connected through an electrolyte is demonstrated. The output of these devices is shown to be synchronized by a global oscillatory input despite the fact that individual inputs are stochastic and independent. This temporal coupling is induced at a specific phase of the global oscillation in a way that is reminiscent of phase locking of neurons to brain oscillations. This demonstration provides a pathway toward new neuromorphic architectural paradigms, where dynamic binding transcends the limitations of structural connectivity, and could enable architectural concepts of hierarchical information flow.