Single Voltage Research Articles

A 34.16–39.6 GHz low phase noise VCO for frequency‐modulated continuous‐wave radar in a 28‐nm CMOS

AbstractA dual‐core voltage‐controlled oscillator (VCO) using harmonic resonance is presented in this letter. Without an additional switch capacitor bank, harmonic resonance implemented in VCO is realized by only a single control voltage, satisfying the requirement of frequency‐modulated continuous‐wave radar. Two pairs of varactors are added to the transformer‐based tank, which ensures a constant ratio between the two resonant frequencies of the tank in the entire tuning range. Robustly single‐frequency oscillation is obtained by increasing the coupling coefficient of the transformer and the coupling capacitor's capacitance. Implemented in a 28‐nm complementary metal–oxide–semiconductor, the VCO shows a 14.75% frequency tuning range covering 34.16–39.6 GHz. The measured results show it exhibits −102.13 dBc/Hz phase noise at a 1 MHz offset from the 34.16 GHz. The oscillator core draws 21–28 mA from a 0.9 V supply.

Investigation of Humid Air on Corona Onset Voltage in Wire-Plane Electrodes Under AC–DC Composite Voltages via Test and Modeling

Detailed characteristics of corona onset voltage under AC-DC composite voltages in wire-to-plane electrodes at various humidity were investigated both experimentally and numerically in this paper. The humidity experiments under AC-DC composite voltages were carried out in the artificial climate chamber. The experimental results indicate that both the corona onset voltage and corona onset electric field strength of positive DC-AC and negative DC-AC decreased with the increase of humidity under composite voltages. Meanwhile, a fluid-hydrodynamic corona model considering humidity and photoionization was established to investigate the influence of humidity on space charge distribution. The numerical results state clearly that compared with the corona under single voltage, the corona under composite voltages was more intense and generated more space charges. Secondly, the higher the humidity was, the higher the concentration of positive ions, electrons and negative ions would be. Finally, the increase of humidity promotes the increase of net ionization coefficient, photoionization rate and net electron generation rate. Under the same humidity and AC voltage, the photoionization rate and net electron generation rate of negative DC-AC was faster than positive DC-AC.

Substitution Method for the Analysis of Systems Based on Two Nonlinear Resonators

Circuits containing two nonlinear resonators have recently been proposed for nonreciprocal isolators, robust wireless power transfer, and sensors. A fundamental characteristic is the presence of hysteresis, associated with points of infinite slope in the solution curves. However, the prediction of hysteresis in the presence of the two distinct resonators is not possible in default harmonic balance (HB) and the additional use of continuation techniques may not be exhaustive enough. Here, we present a novel substitution method, based on the use of two auxiliary generators (AGs), that enables the system control through a single excitation voltage. A simple condition is also provided to obtain all the existing loci of infinite-slope points. The methods, which are compatible with commercial HB, will be illustrated through their application to a Lorentzian–Fano nonlinear isolator.

Effective Multivector-Operated Predictive Current Control of PMSM Drive With Reduced Torque and Flux Ripple

Model predictive current control (MPCC) is a frequently used method for the control of permanent magnet synchronous motor (PMSM). It has faster execution on modern digital platform than the previous generation micro-controllers. Conventional MPCC fails to provide satisfactory steady-state performance as a single voltage vector (VV) is applied during every sampling interval. This article proposes two novel multi-vector operated MPCC methods for reducing torque and flux ripples, as well as the computational burden. The first proposed method uses one active and one null VV; whereas, the second method uses two active and one null VV to further improve the steady-state performance. Proposed methods determine required change in stator-flux (CSF) to reduce/eliminate error in statorcurrent during every sample and VVs nearer to CSF vector are chosen as optimal VVs. The durations of optimal VVs are calculated using the components of CSF along optimal VVs. CSF, obtained using calculated durations of optimal VVs, significantly reduces torque and flux ripples. The proposed methods are effective and less complex compared to other multi-vector operated methods. The proposed methods are compared with existing two-VV and three-VV based MPCC methods and their effectiveness is experimentally verified for decreased torque and stator-flux ripple in addition to a small rise in switching frequency.

Single-stage buck–boost inverter with feedforward control

The off-grid inverter with the inverter side voltage as the feedback parameter has the advantages of a single voltage loop, simple control parameter design, and low cost. But the output voltage accuracy is not enough. A single-stage off-grid inverter with feedforward control is recommended to improve the output voltage accuracy. It has a higher voltage regulation rate compared to the proportional–integral (PI) control and it can track a given AC signal at any frequency compared to the proportional-resonant (PR) control. Bus capacitors can employ thin-film capacitors for improved reliability and higher power density and the voltage stress on power devices can be decreased by controlling the intermediate bus voltage to a non-constant value. The working principle is explained. The design principles of the parameters are provided and the external characteristics and stability of the system are analyzed. A simulation model was built to verify the control strategy for improving voltage accuracy and decreasing voltage stress.

Consensus based phase connectivity identification for distribution network with limited observability

The mitigation of distribution network (DN) unbalance and the use of single-phase flexibility for congestion mitigation requires accurate phase connection information, which is often not available. For a large DN, the naïve phase identification proposed in the majority of the prior works using a single voltage reference, this does not scale well for a multi-feeder DN. We present a consensus algorithm-based phase identification mechanism which uses multiple three-phase reference points to improve the prediction of phases. Due to the absence of real measurements for a real-suburban German DN, the algorithms are developed and evaluated over synthetic data using a digital twin. To utilize strongly correlated measurements, the DN is clustered into zones. We observe those reference measurements located in the same zone as the single-phase consumer, with unknown phase connectivity, leads to accurate prediction of DN phases. Four consensus algorithms are developed and compared. Using numerical results, we recommend the most robust phase identification mechanism. In our evaluation, measurement error, and the impact of the neutral conductor are also assessed. We assume limited DN observability and apply our findings to a German DN without smart meters, but only less than 8% of nodes have measurement boxes along with single-phase consumers with a home energy management system. Voltage time series for 1 month (hourly sampled) is utilized. The numerical results indicate that for 1% accuracy class measurement, the phase connectivity of 308 out of 313 single-phase consumers in a German DN can be identified. Further, we also propose metrics quantifying the goodness of the phase identification. The phase identification framework based on consensus algorithms for DN zones is scalable for large DN and robust towards measurement errors as the estimation is not dependent on a single measurement point.

Vanadium redox flow batteries real-time State of Charge and State of Health estimation under electrolyte imbalance condition

This paper presents a novel observer architecture capable to estimate online the concentrations of the four vanadium species present in a vanadium redox flow battery (VRFB). The proposed architecture comprises three main stages: (1) a high-gain observer, to estimate the output voltage and its derivatives; (2) a dynamic inverter, to obtain a set of concentration candidate solutions; and (3) a static selector, to determine the actual concentrations. The methodology does not rely on the classic assumption of balanced electrolytes, thus significantly widening the application range in comparison with most of the literature previous studies. Furthermore, to perform the estimation, only a single voltage and current measurements are required, which eliminates the need of including complex and costly additional sensors.To validate the proposal, comprehensive simulation tests are conducted. These tests take into account typical side reactions that cause imbalance in VRFB systems, such as vanadium crossover and V2+ oxidation. The observer shows a remarkable performance when dealing with these realistic conditions, allowing to estimate with high accuracy and robustness the four vanadium concentrations, the State of Charge and the State of Health with a relative error below 2%.

Switched reluctance motoring and generating operation in single pulse, current chopping and voltage PWM modes

Switched reluctance motoring and generating operation in single pulse, current chopping and voltage PWM modes

High Step-Up Gain Converter Based on Two-Phase Interleaved Coupled Inductor Without Right-Hand Plane Zero

This paper proposed a novel two-phase interleaved Coupled Inductor (CI) based high step-up gain converter without Right Half Plane (RHP) zeros for a wide operating range of duty cycle. A coupled inductor between input and output is used in the proposed converter to eliminate RHP zero. The energy of CI is transferred to output capacitor when switch is ON to eliminate RHP zero. Furthermore, the converter has a wide operating range to eliminate RHP zero with a coefficient coupling of CI near one. Thus, the converter achieves higher bandwidth and a wide range of control over output voltage. The small-signal model of proposed converter is derived to verify the proposed claim. The single loop voltage control is sufficient to regulate output voltage of the converter with a good stability margin and faster dynamic response for a wide range of load changes. In addition, proposed converter has a high voltage step-up gain and low voltage stress on switching devices compared to the boost converter. Moreover, interleaved operation at input side reduces ripple and increases power density. All theoretical findings are verified by simulation and experimental results. Experimental results are provided from implemented laboratory prototype of input voltage of 24 V to output voltage of 100 V and 200 W power.

Novel nanoarchitecture of 3D ion transfer channel containing nanocomposite solid polymer electrolyte membrane based on holey graphene oxide and chitosan biopolymer

In the arena of three-dimensional (3D) nanoarchitecture, holey graphene oxide (HGO)—a class of two-dimensional (2D) graphene oxide porous nanosheet, has emerged as a promising choice of additive material to design advanced 3D nanocomposite for energy and environmental applications. With a facile and cost-effective solution-casting technique, we fabricated here a flexible, wearable, free-standing, and super-thin (∼0.08 mm) solid polymer electrolyte membrane (SPEM) consisting of 2D-HGO, lithium bis(trifluromethanesulfonyl)imide (LiTFSI) salt, polyvinylpyrrolidone (PVP) polymer binder, and chitosan (CH) biopolymer. SPEM exhibited impressive ionic conductivity of 2.76 × 10-3 S⋅cm−1 at room temperature (RT = 23 °C) which is comparable to liquid electrolytes. Robust mechanical property (5.87 MPa) and easy lithium-ion diffusion capability of SPEM were identified by the ultra-low activation energy (Ea) of 0.089 eV, which is one of the best values among the reported solid polymer electrolytes. Good lithium-ion transference number (tLi+= 0.76) and wide electrochemical stability window (ESW = 4.4) indicated single ion conduction and stable battery operation voltage capability of SPEM. Moreover, fast ion transfer mechanism of SPEM was proposed according to the comprehensive characterizations; mostly relating to uniform and strong interconnecting novel 3D ion transferring routes. Temperature and frequency responsive charge carrier mobility trend were also investigated with an in-depth dielectric study. Promising RT galvanostatic Li plating-stripping performance was observed at 5 mA⋅cm−2 with a hybrid symmetric cell. Using Li metal as anode, SPEM, and LiCoO2 as cathode in the full cell, a good RT specific discharge capacity of 142.8 mA⋅h⋅g−1 was achieved at 0.1 C rate.

Experimental Demonstration of Beam Scanning of Dual-Metasurface Antenna

Beam-scanning antennas are employed in a wide range of applications, such as in satellite communications and 5G networks. Current commercial solutions rely mostly on electronically reconfigurable phased arrays, which require complex feeding networks and are affected by high losses, high costs, and are often power-hungry. In this paper, a novel beam scanning architecture employing a pair of planar metasurfaces, for use in thin reconfigurable antennas, is presented and experimentally demonstrated. The structure consisted of a radiative passive (non-reconfigurable) modulated metasurface, and a second metasurface that controls beam pointing, operating as a variable-impedance ground plane. Unlike other existing approaches, surface impedance variation was obtained by on-plane varactor diodes, no vias and a single voltage bias. This paper presents a design procedure based on an approximate theoretical model and simulation verification; a prototype of the designed antenna was fabricated for operation in X band, and a good agreement between measured results and simulations was observed. In the presented simple embodiment of the concept, the angular scanning range was limited to 10°; this limitation is discussed in view of future applications.

Stable electrospray signal on a microfabricated glass chip with three-dimensional open edge and tiered depth geometries

This paper presents the microfabrication and performance of a three-dimensional electrospray ionization (ESI) emitter tip made from glass, which achieves stable current signals important for chemical analysis. Our novel microfabrication process and custom-built signal conditioning hardware provides the advantage of providing accurate features and steady signals. The fabrication process relies on standard microfabrication techniques (i.e., deposition, photolithography, and wet etching). This fabrication method involves the novel application of two layers of positive and negative photoresists in addition to Parafilm® wax tape. Open edge and tiered depth details were successfully created from a multilayer planar mask. This is a benefit for integrated miniaturized and microfluidic systems that often require micro features for their functionality but relatively large millimeter size features for their physical periphery. We demonstrate the fundamental performance of electrospray with this microfluidic chip. The emitter tip was fixed on a linear axis stage with high resolution (10 μm) to finely control the tip distance from a metal counter electrode plate. A custom printed circuit board system was built to safely control four voltages applied to the microchip ports from a single high voltage power supply. To readily form the electrospray, non-aqueous solvents were used for their low viscosity and a constant voltage of +2.7 kV was applied to the sheath electrospray microchannel. The liquid being sprayed was 80/20 (v/v) methanol/acetonitrile with 0.1% acetic acid in the sheath microchannel and with ammonium acetate (10–40 mM) in its remaining microchannels. The electrospray signal was measured in response to varying the distance (1.4 to 1.6 mm) between the electrospray emitter tip and a metal counter electrode plate in addition to the varying concentration of the background electrolyte, ammonium acetate. Stable and repeatable electrospray signal showed linear relationships with emitter tip distance and concentration (r2 ≥ 0.95).

Multimodal analysis of generic cantilever-based piezoelectric nanogenerators with offset-proof mass

The present work investigates analytically and experimentally the multimodal performance analysis of piezoelectric (PZT-5A) based generic nanogenerators. The present nanogenerators consider both uni-morph and bimorph with offset-proof mass subjected to sinusoidal base excitation. The finite element-based multi-mode electromechanical coupled dynamics governing equations are derived to formulate the analytical expressions of uni-morph, and bimorph nano-harvesters for frequency responses function of output voltage, current, and power, respectively. The impact of base excitation, load resistance, thickness, length, and mass of offset-proof mass on the output voltage and harvested energy is investigated by considering multi-mode vibration bodies. PZT-5A is evenly distributed over the substructure for the single voltage output. Interestingly, we noticed that a uni-morph cantilever with offset-proof mass is the best among all the investigated configurations, showing the maximum power at different load conditions. Analytical solutions are in good agreement with nearly no error for the first few vibration modes as compared to what was obtained using numerical simulation. The experimental realization for a single mode of vibration has been explored, and results showed that the fundamental mode swings very similar behaviors in voltage and power output, mostly in pre-and post-resonance conditions as compared to analytical results, and the difference between these two results is about nearly 5%. Thus, the present work depicts an effectual correlation between analytical development, numerical results using COMSOL 2D, and experimental realization for analyzing energy harvesting devices. These results may be helpful for the experimentalists to design efficient nanogenerators.

Performance evaluation of isolated three-phase voltage source inverter with LC filter adopting different MPC methods under various types of load

As the variety of loads in microgrids continues to grow rapidly, the drawbacks of using conventional voltage and current double closed-loop PI control are becoming increasingly intolerable. These disadvantages include poor static tracking of the output and the need for complicated tuning of optimal PI control parameters. Model predictive control (MPC) is widely studied in recent years and gradually applied to the inverter as a modern control strategy. Currently, the research on MPC mainly focuses on reducing the computational burden of algorithms and improving computing skills. In this paper, the control theory of continuous-control-set model predictive control (CCS-MPC), optimal switching vector model predictive control (OSV-MPC), quasi-sliding mode model predictive control (QS-MPC) and optimal switching sequence model predictive control (OSS-MPC) are elaborated. Also, the disadvantages of adopting conventional voltage and current double closed-loop PI control on microgrids are clarified. Moreover, aiming at evaluating the influence of connecting and/or removing the common loads, such as electric vehicles to the microgrid on the output performance of microgrids in practical engineering applications, single three-phase voltage source inverter with LC filter system with two-phase pure resistance load, three-phase diode rectifier bridge nonlinear load, constant power load and constant current source load applying four different MPC methods, are simulated. The simulation results show that under different types of load, system with nonlinear load applying OSV-MPC method has the biggest value of total harmonic distortion (THD) of the output voltage and the biggest steady state root mean square (RMS) tracking error of the output voltage, which are 1.33% and 2.1 V, respectively. The performances of the output voltage of the system adopting MPC are generally improved compared to the system using conventional voltage and current double close-loop PI control. Regarding the output voltage performance of a system under load step change, a system using the OSS-MPC method with a nonlinear load exhibits the smallest overshoot of the output voltage and the smallest root mean square value of the tracking error (RMSE) between the output voltage and the reference value within 20ms after the load step change. Specifically, the overshoot and RMSE are 2.804 V and 0.810 V, respectively. The simulation results provide valuable guidance for selecting the appropriate model predictive control strategy for microgrid integrating complex loads, such as electric vehicles in practical applications.

Fuzzy-Based Fifteen-Level VSC for STATCOM Operations with Single DC-Link Voltage

A static synchronous compensator (STATCOM) is a powerful mechanism for balancing reactive power and uplift voltage stability in a transmission system. Nowadays, the desire to save energy by reducing losses is prioritized as an essential target instead of increasing the power generation for the sustainability of any nation’s growth plans. As a result, power-electronics-based converters are more significant for power savings in transmission systems. STATCOM based on voltage source converters (VSC) are operated to improve on stable performance conditions as well as to minimize the harmonic distortions in a power system. Hence, this paper explores low harmonic distortions of fifteen-level VSC structured STACOM using only one DC-link voltage to balance the reactive power and to manage the voltage profile in large power transmission systems. STATCOM consisting of H-bridge type VSCs and binary weighted transformers was utilized to maintain an AC system voltage at 132 kV, 50 Hz. The three stages of VSCs were operated with meticulous firing angles based on converter levels for controlling THD (total harmonic distortion) and providing system improvement. The proposed model of the fifteen-level H-bridge type voltage source converters with fuzzy logic decoupled control algorithm based STATCOM can be used for large power range applications with a small number of switches. This model attained stable operation of the system with a low harmonic deviation at any dynamical conditions. The simulation results using MATLAB showed that the system’s operation was enhanced, with a smoother response and improved steady state performance.

Diffusion-aware voltage source: An equivalent circuit network to resolve lithium concentration gradients in active particles

Traditional equivalent circuit models (ECMs) have difficulties in estimating battery internal states due to the lack of relevant physics, such as the lithium diffusion in active particles. Here we configure a circuit network to describe the lithium diffusion and define it as a new high-level circuit element called diffusion-aware voltage source. The circuit representation is proven equivalent to the discretized diffusion equation. The new voltage source gives the electrode potential as a function of the surface concentration and thus automatically incorporates the diffusion overpotential. We show that an ECM with the proposed diffusion-aware voltage sources (called “shell ECM”) can reproduce the single particle model simulation results, making it a trustworthy easy-to-implement substitute. Furthermore, the simplest shell ECM consisting of a single diffusion-aware voltage source and a resistor is validated against experimental constant-current discharges at various rates. The diffusion-aware voltage source can be used to measure diffusivity by fitting the diffusion resistance against experimental data. The viability of the shell ECM for onboard usage is confirmed by implementation into a battery management system of WAE Technologies. By tracking the internal concentration states, the shell ECM demonstrates robustness to dynamic applied-current profiles.

COMPARISON ON STUDY OF LITHIUM ION SERIES AND LEAD ACID SERIES CHARGING AND DISCHARGING CHARACTERISTICS

Lead acid batteries are strings of 2 volt cells connected in series, commonly 2, 3, 4 or 6 cells per battery. Strings of lead acid batteries, up to 48 volts and higher, may be charged in series safely and efficiently. However, as the number of batteries in series increases, so does the possibility of slight differences in capacity. These differences can result from age, storage history, temperature variations or abuse .Fully charged batteries should never be mixed with discharged batteries when charging batteries in series. The discharged batteries should be charged before connection .When a single constant voltage charger is connected across an entire high voltage string, the same current flows through all cells in the string. Depending on the characteristics of the individual batteries , some may overcharge while other remain in a slightly undercharged condition .To minimize the effect of individual battery differences , use batteries of the same age , manufacturer , amp hour , and history and , if possible ,charge in strings of no greater than 24 or 48 volts . On the other hand it is highly recommended to charge lithium batteries in series with a multi-bank charger. This means each battery is charged at the same time but completely independent of the other. Charging properly a lithium-ion battery requires 2 steps: Constant Current (CC) followed by Constant Voltage (CV) charging. A CC charge is first applied to bring the voltage up to the end-of-charge voltage level. One might even decide to reduce the target voltage to preserve the electrode. Li-ion does not need to be fully charged as is the case with lead acid, nor is it desirable to do so. In fact, it is better not to fully charge because a high voltage stresses the battery. In a lithium-ion battery, overcharging can create unstable conditions inside the battery, increase pressure, and cause thermal runaway. Lithium-ion battery packs are required to have a protection circuit to prevent excessive pressure build- up and cut off the flow of ions when the temperature is too high. A partial charge and discharge will reduce stress and prolong battery life. It is recommended to avoid full cycles and stay between 100% and 50% DOD (0-50% SoC).

Investigation of Single-Phase, Single Voltage Source Multilevel Inverter with Voltage Boosting Gain Based on Different Sinusoidal Pulse Width Modulation Approach

Investigation of Single-Phase, Single Voltage Source Multilevel Inverter with Voltage Boosting Gain Based on Different Sinusoidal Pulse Width Modulation Approach

An active damping control strategy with improved transient performance for high‐frequency AC power distribution in intelligent vehicles

SummaryHigh‐frequency AC (HFAC) LCLC resonant inverter has recently received more and more attention in power distribution system (PDS) of intelligent vehicles. However, LCLC resonance complicates the design of a current control loop and can even threaten the stability and transient performance of PDS. Active damping (AD) strategies based on the feedback of a single filter voltage or current have been shown to be effective and cost‐efficient method for attenuating resonant spikes. In this paper, a notch filter‐based AD (NFAD) control strategy is proposed to improve the stability and transient performance of PDS for intelligent vehicles. By sensing and feeding back the output resonance current of LCLC resonant inverter, the NFAD control strategy is then formulated to emulate a virtual impedance in order to improve the system phase margin and crossover frequency. Hence, the proposed control strategy can not only suppress the LCLC double resonance peaks but also effectively improve the transient performance of resonant inverter while guaranteeing the stability of the system. Finally, an experimental prototype was established and tested to verify the effectiveness of the proposed control strategy with a rated output power of 130 W, an operation frequency of 25 kHz, and a sinusoidal output voltage of 28 V (rms).

A Power Control Scheme for a Wind Turbine/Fuel Cell Hybrid Power System with DFIG-DC Link Topology

This study discusses performance of the power control strategy for a Wind Turbine/Fuel Cell Hybrid System with a Doubly Fed Induction Generator (DFIG)-Direct Current (DC) link configuration. To overcome high cost and the complex structure of the previous paper, a new DFIG-DC link configuration is proposed that uses a single Voltage Source Inverter (VSI) and a diode rectifier to connect the stator and rotor to the DC-link, respectively. Also, the DFIG-DC system is modeled and a Stator Field-Oriented Control (SFOC) is adopted to control the VSI to extract the maximum power generated by the wind turbine. The model and the control of the DC-DC boost converter used to connect the hydrogen fuel cell to the DC-link are established. To achieve better performance of the proposed DFIG-DC system, the power control strategy has been tested by using the dSpace DS1104 processor board and the experimental results show the performance of the control strategy in terms of parameters regulation under a different scenario.