Improving the Accuracy of the Output Voltage of the Converter by Changing the Load Parameters

In the article on the basis of the theory of invariance the increase of accuracy of work of system with the converter for nuclear magnetic logging under condition of change of parameters of loading is considered. Based on the proposed functional scheme of two-channel control, formulas are given to determine the structural relationships and internal influences on the parameters of the control system components to reduce the impact of disturbances that occur both by changing load parameters and by changing the supply voltage. To maintain the required value of the carrier voltage amplitude, it is necessary to increase the reference voltage or decrease the amplitude of the sawtooth voltage, which is equivalent to increasing the gain of the feedback circuit. In this case, if you increase the gain of the feedback circuit, you must ensure that the stability of the system is maintained. The implementation of these proposals gives a more accurate formation of the bypass probing signal. The given functional scheme provides realization of regulation and stabilization of amplitude. The paper considers various options for reducing the effect of power supply perturbation on the output parameters of the converter. By changing the period of operation of the sawtooth voltage generator, which is determined by the frequency of the voltage-controlled generator and depends on the output frequency of the inverter, which varies depending on the parameters and properties of the rock during logging, the accuracy of stabilizing the amplitude of the probe signal increases. In the proposed two-channel control system, the first channel provides regulation and stabilization of the amplitude of the output voltage in accordance with the reference voltage. The second channel provides a change in the frequency of the sawtooth voltage generator by determining the period of the voltage-controlled generator from the phase detector, which determines the deviation of the real frequency from the frequency of the reference generator. The application of the above techniques allows to build circuit implementations of the system with transducers for nuclear magnetic logging, which meet the requirements for the accuracy of the formation of the bypass probing signal.

3.48-nW 58.4ppm/∘C Sub-threshold CVR with Four Transistors and Two Resistors

In this paper, an ultra-low power CMOS voltage reference capable of operating at sub-1[Formula: see text]V input supply is proposed. Four transistors biased in weak inversion are used to generate the required complementary-to-absolute-temperature (CTAT) and proportional-to-absolute-temperature (PTAT) voltages of the proposed circuit. Self-biasing of nature of the proposed configuration in the form of operational amplifier (opamp)-free ensure nano-power operation and eliminate the need for lateral bipolar junction transistors (BJTs) and offset cancelation techniques. A prototype of the circuit is designed and simulated in a standard 0.18-[Formula: see text]m CMOS process. Post-layout simulation results show that the circuit generates a reference voltage of 494[Formula: see text]mV with temperature coefficient (TC) of 58.4[Formula: see text]ppm/∘C across [Formula: see text]C to 85∘C; while the consuming power is lowered to 3.48[Formula: see text]nW at the minimum supply of 0.8[Formula: see text]V. The line sensitivity is 0.7%/V for the supply voltages from 0.8[Formula: see text]V to 1.8[Formula: see text]V, whereas the power supply ripple rejection (PSRR) is [Formula: see text]49.06[Formula: see text]dB at 1[Formula: see text]Hz. Monte Carlo simulation results of the voltage reference show a mean value of 497.2[Formula: see text]mV with [Formula: see text]/[Formula: see text] of 1.7%, demonstrating the robustness of the generated reference voltage against the process variations and mismatch.

Optimal Operation and Control Design of DC Arrester for Renewable Energy Transmission

The trip probability of transmission line under lightning stroke is rapidly increasing under complex weather conditions when large-scale renewable energy is intergrated with modern power grid. Line arrester plays a critical role in reducing lightning damage and economic losses, in which DC reference voltage is a critical parameter to evaluate line arresters. Hence, a set of on-site DC test system of transmission line arresters is developed to realize the DC reference voltage test in this article. The output DC voltage of the test system is continuously adjustable (0–200 kV), while its rated power and the maximum output current are set to 400 W and 2 mA, respectively. Furthermore, the system is powered by a lithium battery instead of a 220/380 V AC energy source. It employs split design and integrating assembly on-site that reduces the total weight by 36.7%, which considerably decreases the demand for the space of test site. Besides, the weights of control cabinet, multiplying cylinder, and energy source are reduced by 60, 54.55, and 33.33%, respectively. Meanwhile, the Bluetooth remote control module is used to effectively ensure the safety of test personnel. This system accomplishes DC reference voltage tests without removing line arresters on site, which can effectively enhance maintenance efficiency and economic benefits.

High performance adaptive maximum power point tracking technique for off-grid photovoltaic systems

Solar photovoltaic (PV) energy has met great attention in the electrical power generation field for its many advantages in both on and off-grid applications. The requirement for higher proficiency from the PV system to reap the energy requires maximum power point tracking techniques (MPPT). This paper presents an adaptive MPPT of a stand-alone PV system using an updated PI controller optimized by harmony search (HS). A lookup table is formed for the temperature and irradiance with the corresponding voltage at MPP (VMPP). This voltage is considered as the updated reference voltage required for MPP at each temperature and irradiance. The difference between this updated reference voltage at MPP and the variable PV voltage due to changing the environmental conditions is used to stimulate PI controller optimized by HS to update the duty cycle (D) of the DC–DC converter. The temperature, irradiance, and corresponding duty cycle at MPP are utilized to convert this MPP technique into an adaptive one without the PI controllers' need. An experimental implementation of the proposed adaptive MPPT is introduced to test the simulation results' validity at different irradiance and temperature levels.

Ideal Gas Reference for Association and Dissociation Reactions: II. Kinetic Reference Potentials and Concentration Bias in Electrolysis

The ideal gas reference for association and dissociation reactions, developed in the first part of this series, is applied to electrochemical reactions. We obtain an ideal Nernst equation that quantifies the unspecific voltage contribution arising from an imbalance between the reactant and product concentrations of an electrochemical reaction for the given conditions. Subtracting this concentration bias from the equilibrium voltage/potential, we define the "kinetic reference voltage/potential" where the reactant and product states are "aligned" within the potential energy landscape of the system. The kinetic reference voltage/potential is a fundamental descriptor for a given electrochemical reaction, providing an intrinsic reference point which is most relevant in cases where the (standard) equilibrium voltage/potential is biased by large concentration differences between the reactant and product side. This is most dramatic for the case of water electrolysis, where the gaseous H₂ and O₂ product concentrations are several orders of magnitude smaller than the liquid water reactant concentration. The respective equilibrium voltage is strongly biased by the low H₂ and O₂ concentrations, although the latter do not directly influence the forward water splitting rate. The unbiased kinetic reference voltage agrees remarkably well with the experimentally observed onset of macroscopic water splitting rates. We further extend our analysis to the kinetic reference potentials of the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and lattice oxygen evolution reaction (LOER), providing an unconventional perspective on pH-dependent overpotentials, anticipated electrocatalysis improvements, and kinetic stabilization of electrocatalyst materials.

Influence of the switching frequency of the switch and the amplitude of the reference voltage of a pulsed voltage regulator of the lowering type on its stability

On the basis of classical stability criteria, using the expressions of the transfer function, according to the block diagram, the stability of the impulse controller with feedback is estimated. The influence of the switching frequency of the switch and the amplitude of the reference voltage on the stability of a pulsed voltage regulator of a lowering type with deterministic parameters of the system is analyzed. In accordance with the Nyquist criterion for the transfer function of an open-loop system, both stability and phase stability margins for a closed-loop system can be estimated. When simulating the operation of the device, the phase stability margin was obtained, according to the Nyquist criterion, which is с = Н = 7. An increase in the sawtooth voltage is not a desirable phenomenon, which, although it increases the margin of stability, however, reduces stability. Moreover, the dependence of the ripple, affecting the stability of operation, on the amplitude of the sawtooth voltage is not a predictable value and takes on a random value.

Characterization of Atrial Propagation Patterns and Fibrotic Substrate With a Modified Omnipolar Electrogram Strategy in Multi-Electrode Arrays

Introduction: The omnipolar electrogram method was recently proposed to try to generate orientation-independent electrograms. It estimates the electric field from the bipolar electrograms of a clique, under the assumption of locally plane and homogeneous propagation. The local electric field evolution over time describes a loop trajectory from which omnipolar signals in the propagation direction, substrate and propagation features, are derived. In this work, we propose substrate and conduction velocity mapping modalities based on a modified version of the omnipolar electrogram method, which aims to reduce orientation-dependent residual components in the standard approach.Methods: A simulated electrical propagation in 2D, with a tissue including a circular patch of diffuse fibrosis, was used for validation. Unipolar electrograms were calculated in a multi-electrode array, also deriving bipolar electrograms along the two main directions of the grid. Simulated bipolar electrograms were also contaminated with real noise, to assess the robustness of the mapping strategies against noise. The performance of the maps in identifying fibrosis and in reproducing unipolar reference voltage maps was evaluated. Bipolar voltage maps were also considered for performance comparison.Results: Results show that the modified omnipolar mapping strategies are more accurate and robust against noise than bipolar and standard omnipolar maps in fibrosis detection (accuracies higher than 85 vs. 80% and 70%, respectively). They present better correlation with unipolar reference voltage maps than bipolar and original omnipolar maps (Pearson's correlations higher than 0.75 vs. 0.60 and 0.70, respectively).Conclusion: The modified omnipolar method improves fibrosis detection, characterization of substrate and propagation, also reducing the residual sensitivity to directionality over the standard approach and improving robustness against noise. Nevertheless, studies with real electrograms will elucidate its impact in catheter ablation interventions.