Voltage Margin Research Articles

Predictive Trajectory Control Strategy for Permanent Magnet Synchronous Motor Drives Based on Deadbeat Predictive Flux Linkage Control Method

Deadbeat predictive controller features a two-sample step response with the existence of one-sampling-period digital delay in a motor drive. However, voltage deficiency is common during abrupt torque change and it inevitably degrades the dynamic performance. In this article, a novel predictive trajectory control strategy with improved dynamic performance is presented for permanent magnet synchronous motor drives. The predictive trajectory controller is developed based on a deadbeat predictive flux linkage controller, and it aims to achieve fast current transient response considering the voltage and current constraint. With the control scheme, deadbeat response is achieved for the case of sufficient voltage margin, and transient performance is optimized for the case of insufficient voltage margin. Solution of the optimization problem is visualized with a geometrical description and analyzed in different spaces. In addition, the trajectory optimization is combined with dynamic overmodulation algorithm to simplify the computation and save the code execution time. Experimental results are finally provided to validate the excellent performance and low computational cost of the proposed control scheme.

The impact of DC-bus impedance on the switching performance of low-voltage silicon power MOSFETs

Typical DC-bus stabilization for low-voltage power circuits consists primarily of ceramic capacitors due to the capacity density and low equivalent series resistance (ESR) resulting in low conduction losses. Particularly in hard-switching and hard-commutation operation, the low ESR and high equivalent series inductance (ESL) of the capacitors in the commutation path restrict the damping of the switch node voltage overshoot and introduce high-frequency ringing, reducing the voltage margin of the transistor. Therefore, this paper analyzes the impact of the DC-bus impedance and proposes a DC-bus snubber based on an RC network to form the DC-bus impedance’s characteristic, which minimizes the overshoot voltage. A comprehensive simulation using measurement-derived component models is shown, which is verified by an in-situ measurement on a test PCB. Furthermore, transient measurements using a double pulse test setup show the effectiveness of the proposed approach.

Temperature rise effects on static characteristics of complementary FETs with Si and Ge nanosheets

We simulate the static behavior of Ge-p/Si-n nanosheet complementary FETs (CFETs), where p-type FETs containing Ge nanosheet channels are stacked on top of n-type FETs containing Si nanosheet channels, and we investigate its relation to temperature while comparing it with that of Si-p/Si-n nanosheet CFETs, whose p-type FETs contain Si nanosheet channels. It is found that temperature rise has similar effects on the static characteristics of the two CFETs operating as inverters, although the variations in threshold voltage and noise margin with rising temperature are slightly smaller in the Ge-p/Si-n CFET inverter than in the Si-p/Si-n CFET inverter. The temperature rise effects are fully explained by the temperature dependence of material and carrier properties of Ge and Si.

Electrical and optical properties of electro chemical luminescence device with quasi solid electrolyte and ZnO/TiO2 electrode

In this work, a quasi-solid electrolyte process that can be simply manufactured for an electrochemical luminescence (ECL) device with a ZnO/TiO2 electrode was proposed, and the electro-optical characteristics of the fabricated ECL cells were investigated. The electrolyte was prepared by adding poly (vinylidene fluoride-co-hexa-fluoropropylen) with the Ru(bpy)3(PF6)2 as a luminescence material in 1:4 weigh ratio in 1 g of Acetonitrile (ACN). The ZnO/TiO2 films as an electrode were prepared by RF sputtering system. The ZnO and TiO2 targets were set up in co-sputtered system and FTO glass size 2 × 2 cm2 was used as a substrate. Argon gas flow rating as the working gas was fixed at 30 sccm. First, the ZnO layer is deposited on the FTO substrate at 100 W of RF power and at 10 mTorr of Argon gas pressure. TiO2 layer is deposited on the ZnO layer while increasing the sputtering time by 10 min. The morphological and optical properties of the thin films as electrode were confirmed using scanning electron microscope (SEM, Hitachi Su70), X-ray diffraction (XRD, Rigaku D/max 2100H) and UV–vis spectrometer (DH-2000-BAL Ocean Optics). The performance of proposed ECL devices were evaluated by varying operation voltage of 0.5 V from 2 V to 5 V. As the result, we can achieve high performance of device having a wide operating voltage margin and improved luminance intensity.

Optimal energy management and spinning reservation system in independent microgrids considering practical constraints and demand response

Programming for supplying electricity in these regions is performed by developing the global electricity system and using islanded microgrids (MGs). Herein, a probabilistic model for simultaneous programming of energy and reserve of an islanded MG is proposed by considering demand-response (DR) programs and security constraints using a developed water wave search algorithm. Since the above problem has many nonlinear constraints, in order to avoid early convergence and not be located in local points, an additional operator is provided to improve the search performance in the feasible space of the problem. In the proposed method, the weak waves are eliminated, and the waves that are close to the optimal answer are strengthened; so that the unworthy answers are removed from the population and worthy answers are created in their place. The objective function aims to maximize the MG operator's profit by considering several security-related and operational constraints, e.g., voltage and frequencies. In the proposed method, the conditional value at risk (CVaR) method is adopted to evaluate and manage the risk of problem uncertainties. An effort is made to coordinate the variables of the problem, such that their generation capacity can be determined based on the created scenarios. In this method, the operator's profit sensitivity and the safety margins of the MG with and without the participation of responsive loads are evaluated concerning the risk index. This method enables the operators to select the proper risk coefficient, maximize their profit and improve the safety margin, voltage, and frequency of the MG. Finally, the proposed method and model have been discussed and investigated on the studied system on different scenarios. The numerical results show that with the participation of customers in the DR program, the expected profit of the operator and the security margin of voltage and frequency increase. In periods of low load, production units have more free capacity. Therefore, even at a low-risk factor, the operator has purchased enough storage capacity, and as a result, the frequency deviation in these hours is low in both cases with and without DR.

Time Series Optimal Capacity Determination Model of Regional Comprehensive Energy Considering Multi Energy Complementarity and Load Flexibility

In order to improve the voltage stability margin and convergence speed of the power grid, a regional comprehensive energy time series optimization capacity model is established under the condition of fully considering the multi energy complementarity and load flexibility. The multi energy complementary optimal operation model of regional comprehensive energy system is established, the load flexibility and multi energy complementary characteristics are analyzed, and the robust optimal capacity target of regional comprehensive energy system is set on the basis of considering the load flexibility. From the perspective of time series, an optimized capacity model is constructed, and genetic algorithm is improved to solve the multi-objective optimization model of regional comprehensive energy time series capacity. The experimental results show that this method has good optimization effect, improves the stability margin and convergence speed of power grid voltage, and can find the optimal solution for the established objective function, which effectively improves the effect of capacity determination.

Ionic liquid gated unipolar inverters with tunable switching voltage and excellent noise margin

Solution-processable organic semiconductor-based ambient-stable and flexible-compatible ionic liquid-gated inverter with a gain >10 and noise margin ≈60% paves the way for the integration of ionic liquid-gated logic components into circuits.

Ripple Excitation-Based Adaptive Sensorless Control of IPMSM in Full Speed Range

This paper proposes an adaptive sensorless finite-control-set model predictive control (FCS-MPC) method for the interior permanent magnet synchronous motor (IPMSM). The method is feasible in the full speed range from zero speed to the flux-weakening region above rated speed, without the method transition between the low and the high speeds. A ripple excitation-based position estimation method is proposed to extract the rotor-saliency-based position information from the inherent voltage ripples of the FCS-MPC. Therefore, the additional voltage margin consumption, the special sampling timing, or the interference in the fundamental control are all avoided. Furthermore, to alleviate the parameter dependency, an adaptive predictive model with the online estimation of the lumped voltage terms and the equivalent dynamic susceptances is proposed. In this way, the main machine parameters and the unmodeled disturbances in the d-q voltage equations of the IPMSM are all considered. The position deviation due to the cross-coupling effect is also analyzed, and a compensation method is proposed. Finally, the effectiveness of the proposed method is validated by the experimental results and the comparison with existing methods.

Electrical Phenomena on Fully Airborne Vertical Electric Antennas in Extreme Weather Conditions

This is a conference extension of the paper ‘Investigation on the mature storm cloud’s electric field using long airborne antennas’. The use of vertical antennas (including the VEDs—Vertical Electric Dipoles), lifted up by aerostats to high altitudes without being anchored to the ground, presents numerous advantages in comparison with large terrestrial VLF (Very Low Frequency) antenna structures. A slow-moving floating-earth conductor—a vertical wire antenna—is subjected to intense electrification mechanisms in the atmosphere and inside the cloud layers, producing additional risks for the transmitter and the flight train itself. The electrical potential achieved in this process is, therefore, compared with the flashover voltages over the antenna’s upper fixing point, defining the voltage margins at which the VLF transmitter is able to operate. The electrification processes are also compared to the model based on experimental data on the occurrence of corona discharges over a long, vertical wire traversing a storm cloud layer. The external electric field strength (around the antenna wire) is calculated and compared with older experimental data for storm clouds for various locations, showing the correctness of the proposed analytical electrification model, and, therefore, expanding it with the loss of the electric charge via corona.

Position Sensorless Control of IPMSM Using Adjustable Frequency Setting Square-Wave Voltage Injection

Position sensorless control of interior permanent magnet synchronous motors (IPMSMs) is of great importance for the sake of the cost reduction and robustness improvement. An improved position sensorless method based on adjustable high-frequency (HF) square-wave voltage injection has been proposed for the IPMSM drive under zero- and low-speed regions. The general detection method of position from positive- and negative-sequence HF current response has been developed by the simple algebraic operations of data at some adjacent sampling instants. In addition, the proposed method not only can retain the advantage of the removal of low-pass filters in current feedback but also can increase the voltage margin of inverter with adjustable frequency setting of HF signal compared with existing square-wave voltage injection methods. Comprehensive experimental results have been given to verify the proposed theoretical analysis.

A High-Level Approach for Energy Efficiency Improvement of FPGAs by Voltage Trimming

Chip manufacturers define voltage margins on top of the “best-case” operational voltage of their chips to ensure reliable functioning in the worst-case settings. The margins guarantee correctness of operation, but at the cost of performance and power efficiency. Violating the margins is tempting to save energy, but might lead to timing errors. This article proposes an algorithmic solution that enables reliable removal of the margins by detecting errors on the fly. In contrast to previous approaches that require special hardware to detect timing errors, the proposed method is fully implementable using high-level synthesis tools without reliance on additional hardware. The approach is demonstrated using a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$32 \times 32$ </tex-math></inline-formula> matrix-matrix multiplication and a simple multilayer neural network implemented on two Xilinx ZC702 field-programmable gate array (FPGA) System-on-Chip (SoC) platforms, showcasing its utility in detecting errors that may originate from different sources of logic circuits, clock tree, or memory. Results show that the energy dissipation is halved, while the implementation is clocked at 2.5x faster than specified by the design tool of the vendor.

12-kV 1-kA Breaking Capable Modular Power Electronic Interrupter With Staged Turn-off Strategy for Medium-Voltage DC Hybrid Circuit Breaker

The dc circuit breaker plays an important protection role in the dc distribution systems. Hybrid dc circuit breaker (HCB) offers low conduction losses and reasonably fast response times. In this article, a high power density, modular, and scalable power electronic interrupter (PEI) design is introduced for medium-voltage (MV) HCB platforms. Following this concept, the single low-voltage module is first investigated in terms of the high pulse current ratio and the voltage clamping circuit. After the comparison and test among different devices, a compact module with 1.7-kV discrete IGBTs are selected as main switches. While the voltage clamping circuit is carefully designed to guarantee no tail current bump and sufficient turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> voltage margin. Next the whole system with series modules is optimized on the aspects of the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> strategy, power supply structure, and layout of modules. An improved staged turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> scheme is proposed, which can not only reduce the peak current and total metal oxide varistor (MOV) energy, but also help balance the MOV energy distribution. A 12-kV and 1-kV breaking capable PEI was demonstrated based on the proposed PEI design, achieving a peak power density of 7.4 kW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , much higher than the IGBT module-based solution. The breaking capability and effectiveness of the modular PEI is demonstrated in a 6-kV MVDC HCB device.

Design for Reliability of SiC-MOSFET-Based 1500-V PV Inverters With Variable Gate Resistance

1500-V photovoltaic (PV) configuration is the standard design in the solar PV industry. Extending the maximum dc voltage from 1000 to 1500 V can reduce the installation cost of the entire power plant. However, it may affect the reliability of the corresponding 1500-V PV inverters, due to the increased loading stresses, i.e., voltage stress and thermal loading of power devices. In this context, this article proposes a solution to the reliability enhancement of silicon carbide- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> -based 1500-V PV inverters with variable gate resistance. This solution offers a possibility to adaptively adjust the switching speed to make a compromise between the switching power loss and voltage overshoot during commutation, thus enhancing the reliability. The evaluation results based on the mission profile of a 125-kW 1500-V PV system installed in Denmark indicate that the PV inverter with the proposed design, i.e., variable gate resistance, can improve reliability performance compared to the fixed gate resistance solution while ensuring a safer operating voltage margin.

Mechanism of Degradation of Capacity and Charge/Discharge Voltages of High‐Ni Cathode During Fast Long‐Term Cycling Without Voltage Margin (Adv. Energy Mater. 29/2022)

High-Nickel Cathodes In article number 2201151, Seung Min Kim, Wonyoung Chang and co-workers show that constant-voltage step following constant-current charging to high voltage (4.3 V) entails a periodic cation-mixed state in high-nickel cathode materials, which leads to significant deterioration in electrochemical performance. Only with constant-current charging, does the cathode material maintain its original structure with a non-periodic cation-mixed state. Thus, constant-voltage step should be avoided unless a sufficient voltage margin is maintained for high-nickel cathode materials.

A Meshed MMC-Based MTDC System with Improved Voltage Margin Control for Robustness Towards Disturbances

A Meshed MMC-Based MTDC System with Improved Voltage Margin Control for Robustness Towards Disturbances

Mechanism of Degradation of Capacity and Charge/Discharge Voltages of High‐Ni Cathode During Fast Long‐Term Cycling Without Voltage Margin

AbstractThe authors reveal the mechanisms of degradation of capacity, charge voltage, and discharge voltage of commercially‐available high‐nickel cathode material when it is cycled without a voltage margin by two different charge protocols: constant‐current charging and constant‐current, constant‐voltage charging. With repeated constant‐current charging, the cathode material changes to a non‐periodic cation‐mixed state, which causes a relatively low voltage degradation, whereas during constant‐current, constant‐voltage charging, the cathode material changes from a layered structure to a periodic cation‐mixed spinel‐like phase, with consequent severe voltage decay. This decay results from a reduction in the equilibrium electrode potential and an increase of overpotential which are aggravated in a periodic cation‐mixed state. The findings provide insights into the use of excess Li without charge‐voltage margin in high‐Ni cathode materials.

Flux-Weakening Control for Variable Flux Reluctance Machine Considering the Second Order Harmonic in Phase Voltage

Due to the second order harmonic in the phase voltage, the voltage peak value is much higher than the amplitude of its fundamental component in the 6/4 variable flux reluctance machines (VFRMs). Conventionally, the amplitude of the fundamental component in the phase voltage is used to calculate the voltage constraint in flux-weakening control, which results in a large voltage margin and reduces the DC link voltage utilization. To deal with this problem in the VFRMs, the flux-weakening control considering the second order harmonic of the phase voltage is proposed in this paper. In this method, the voltage peak value is used to calculate the current operating points, by using which the maximum voltage utilization in flux-weakening region can be achieved. It shows by using the proposed method a wider the constant torque region owing to the lower voltage margin in the VFRMs, which exhibits higher power output in flux-weakening region. Finally, the method is verified by the test results in the VFRM.

A 15 Gb/s Non-Return-to-Zero Transmitter With 1-Tap Pre-Emphasis Feed-Forward Equalizer for Low-Power Ground Terminated Memory Interfaces

This brief presents a 1-tap pre-emphasis transmitter (TX) for a single-ended ground-terminated memory interface with 28 nm complementary metal-oxide-semiconductor (CMOS) technology. By employing a charge pump scheme, a voltage level below ground was used to remove inter-symbol interference (ISI). Encoded with the unit interval (UI) delayed data, the proposed equalization technique increases the vertical voltage margin for the receiver (RX) compared to conventional feed-forward equalization (FFE). In addition, the short current after equalization was removed, and impedance matching for reflection was facilitated. The data rate of the proposed work is 15 Gb/s, and the data path power dissipation for the entire design is 20.3 mW. The measured energy efficiency is 1.35 pJ/bit, and the total area occupation is 0.008 mm².

P-GaN Gate HEMTs With 10.6 V Maximum Gate Drive Voltages by Mg Doping Engineering

We present a novel p-gallium nitride (GaN) gate HEMT structure with reduced hole concentration near the Schottky interface by doping engineering in metal-organic chemical vapor deposition (MOCVD), which aims at lowering the electric field across the gate. By employing the additional unintentionally doped GaN (u-GaN) layer, the gate leakage current is suppressed and the gate breakdown voltage is boosted from 10.6 to 14.6 V with negligible influence on the threshold voltage and ON-resistance. A reduced Mg concentration in the u-GaN layer was confirmed by secondary-ion mass spectrometry. Time-dependent gate breakdown measurements reveal that the maximum gate drive voltage increases from 6.2 to 10.6 V for a ten-year lifetime with a 1&#x0025; gate failure rate, which effectively expands the operating voltage margin of the p-GaN gate HEMTs without any other additional process step.

Quantitative Analysis of System Operating Margin With the High Penetration of Distributed Generators in Distribution Networks

With the integration of distributed generators (DGs) and multiple types of loads, it is increasingly difficult to cope with the uncertainties of DGs, which brings challenges to the secure operation of distribution networks (DNs). Source and load cannot obtain the power balance locally, which may cause operational problems such as line power overload and node voltage violation. However, the methods for quantitatively analyzing the operating status of DNs have not yet formed a unified standard. For which reason, the concept of operating margin is proposed in this study, to represent the distance from the operating point to the boundary. In this study, to generally evaluate the operating status of DNs, the concept of node power margin is proposed first. Then the evaluation indexes including line power margin (LPM) and node voltage margin (NVM) are introduced. The quantitative calculation method for system operating margin (SOM) is further elaborated, which is supposed to be the evaluation indexes on system level. After that, the analysis process of evaluation methods for SOM is discussed. Finally, case studies are performed on the modified IEEE 33-node system to evaluate the operating margin of DNs and verify the enhancement brought by the energy storage system (ESS) and soft open point (SOP) through the flexible adjustment of power flow. The simulation results show that the distance between the DN and the security boundary is effectively quantified through the proposed method, the value can be easily calculated, and the change can be clearly reflected.