Voltage Generator Research Articles

Small‐signal modelling and analysis of microgrids with synchronous and virtual synchronous generators

AbstractIn autonomous alternating current microgrids, the grid‐forming virtual synchronous generators can cooperate with the conventional synchronous generators to improve system inertia and frequency regulation capability. However, undesired active power oscillations between the synchronous generators and grid‐forming virtual synchronous generators may trigger their overcurrent protection and even result in a blackout. To explicitly reveal the oscillatory modes over all frequency bands, a high‐fidelity full‐order state‐space model is first developed. A potentially destabilising sub‐synchronous oscillation mode resulting from the interaction between grid‐forming virtual synchronous generators voltage controller and synchronous generators q‐axis damper winding is identified. Other modes reflecting the low‐frequency oscillation and frequency restoration dynamics are also assessed. Subsequently, to make a reasonable trade‐off between the accuracy and simplicity of system modelling, an enhanced quasi‐stationary model dedicated to low‐frequency oscillation evaluation is simplified from the full‐order type. The enhanced quasi‐stationary model features simplicity and low‐order benefits, which makes it more practical for multi‐generator system analysis. Moreover, by considering the dynamics of synchronous generators field winding and excitation system, the enhanced quasi‐stationary model significantly improves the low‐frequency oscillation characterisation accuracy compared with the existing quasi‐stationary model. The two developed models are comprehensively compared with the existing small‐signal models. Real‐time simulations based on RT‐LAB are conducted to verify the correctness of the theoretical analysis and the accuracy of the proposed small‐signal models.

Use of a Pair of Pulse-Charged Grounded Metal Nets as an Electrostatic Soil Cover for Eradicating Weed Seedlings

An electrostatic technique was developed to generate a simple physical method to eradicate weeds in crop fields. The proposed apparatus consisted of double-expanded metal nets connected to a pulse-charging type negative voltage generator and a grounded line. The two metal nets were arranged in parallel at an interval (6 mm) that caused no arc (spark) discharge between the negatively charged metal net (NC-MN) and the grounded metal net (G-MN). The paired nets were used as a soil cover to zap weed seedlings emerging from the ground. As plant seedlings are biological conductors, the seedling was subjected to an arc discharge from the upper metal net (NC-MN) when it emerged from the soil and passed through the lower net (G-MN). The discharge was strong enough to destroy the seedling with a single exposure. The arc treatment was highly effective for eradicating successively emerging mono- and dicotyledonous weed seedlings, regardless of the number of coexisting weeds or the area of the netted field. Thus, the present study provides a simple and reliable weed eradication method that could be integrated into a sustainable crop production system.

Heat management technology for solid‐state high voltage and high repetitive pulse generators: Towards better effects and reliability

AbstractSolid‐state high voltage high repetitive pulse generators have a broad prospect in various applications. The high power and high‐frequency operation of the pulse generator suffer from the massive heat dissipation problem, which limits the improvement of the output parameters and even affects the lifetime. This article focuses on heat management technology for high voltage high repetitive pulse generators. Firstly, the typical circuit topology of the high repetitive pulse generators was summarised. From the perspective of different application requirements, the demands of the heat management design were concluded. Moreover, the heat generation characteristics and difficulties of solid‐state high voltage high repetitive pulse generators were analysed. Then, the different state‐of‐art cooling techniques were reviewed, and their applicability and limitations for the high voltage high repetitive generators were discussed. Finally, a flow chart for heat management design was given.

Optimizing Large-Scale PV Systems with Machine Learning: A Neuro-Fuzzy MPPT Control for PSCs with Uncertainties

The article proposes a new approach to maximum power point tracking (MPPT) for photovoltaic (PV) systems operating under partial shading conditions (PSCs) that improves upon the limitations of traditional methods in identifying the global maximum power (GMP), resulting in reduced system efficiency. The proposed approach uses a two-stage MPPT method that employs machine learning (ML) and terminal sliding mode control (TSMC). In the first stage, a neuro fuzzy network (NFN) is used to improve the accuracy of the reference voltage generation for MPPT, while in the second stage, a TSMC is used to track the MPP voltage using a non-inverting DC—DC buck-boost converter. The proposed method has been validated through numerical simulations and experiments, demonstrating significant enhancements in MPPT performance even under challenging scenarios. A comprehensive comparison study was conducted with two traditional MPPT algorithms, PID and P&O, which demonstrated the superiority of the proposed method in generating higher power and less control time. The proposed method generates the least power loss in both steady and dynamic states and exhibits an 8.2% higher average power and 60% less control time compared to traditional methods, indicating its superior performance. The proposed method was also found to perform well under real-world conditions and load variations, resulting in 56.1% less variability and only 2–3 W standard deviation at the GMPP.

Integrating reduced graphene oxides and PPy nanoparticles for enhanced electricity from water evaporation

ABSTRACT Developing high-performance nanostructured materials is key to deliver the potential of hydrovoltaic technology into practical applications. As single-component materials have approached its limit in generating hydrovoltaic electricity, the development of multi-component hydrovoltaic materials has been necessary in continuously boosting the electricity output. Here, we report a hydrovoltaic material by integrating reduced graphene oxides and polypyrrole nanoparticles (rGO/PPy), where the rGO contributes improved conductivity and large specific surface area while PPy nanoparticles enable enhanced interaction with water. The device fabricated with this material generates a short-circuit current of 6 μA as well as a maximum power density of over 1 μW/cm3 from natural evaporation of water. And the substantial ion–PPy interaction enables robust voltage generation from evaporation of various salt solutions. Moreover, an outstanding scaling ability is demonstrated by connecting 10 devices in series that generate a sustainable voltage of up to ~2.5 V, sufficing to power many commercial devices, e.g. LED bulb and LCD screen

A Multilevel Inverter for Grid-Connected Photovoltaic Systems Optimized by Genetic Algorithm

This article introduces a grid-connected photovoltaic (PV) source combined with a multi-level inverter. A converter five-level neutral point (NPC) can be used to integrate the PV power into the power grid with minimum harmonic distortions and high power capacity. If the output voltage of the PV generator varies significantly with solar radiation, the output voltage of the ripple must be fixed. For this reason, a regulation loop was used. In this study, we used a classical PI regulator. It is difficult to determine the PI controller transaction values, so Genetic Algorithm was used to optimize the PI controller parameters. The Matlab/Simulink simulation results show the better performance and efficiency of the PI controller optimized by the GA, in comparison to the stand-alone PI controller, regarding stability and accuracy, and the reduction of Total Harmonic Distortions (THD) of the current injected into the grid for any difference in solar radiation.

Analysis of using capacitors in 3-phase induction generators to get constant voltage

Induction machine is one of the machines that can be applied as an alternative power plant and also as a new renewable energy system. Giving reactive power at the terminal in the form of a capacitor, the induction machine can be used as an induction generator. Reactive power is also needed as a voltage generation process. Because one of the weaknesses of the induction generator is that the voltage generated is very fluctuating when the load being served changes. To overcome this, several capacitors with different values are used. Identify the value of the voltage generated by the induction generator when loading occurs by setting the required capacitor value. Setting the capacitor value is done by using a simulation of the simulink circuit in the MATLAB software. Based on the simulation of loading an induction generator of 6800 watt – 7500 watt different capacitor values are needed starting from 112 uF - 140 uF and to get a constant voltage value.

Self-Powered Wearable Breath Sensor Cum Nanogenerator Using AuNR-rGO-PVDF Nanocomposite

Breathing is the most important function of living being. It is well known that breath contains 90% humidity along with various gases and volatile organic compounds (VOCs). These gases are released during various metabolic activities in the body. These gases present in the breath can act as biomarkers to showcase healthiness or abnormalities in the body. Therefore, breath sensors are the need of time to detect diseases at early stages and in noninvasive way. Herein, we report, simple breath sensor using Au nanorods (AuNRs) and its nanocomposite with reduced graphene oxide (rGO) and polyvinylidene fluoride (PVDF). The nanocomposites system is designed in such a way that each component has its advantages for breath sensing. Here, AuNR being a good humidity sensitive material detects the breath efficiently. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> phased PVDF being a very good ferroelectric material, contributes for voltage generation during sensing and enables the device to be self powered. The highly conducting rGO increases the sensitivity and voltage generation by facilitating the electron transport in the nanocomposite system. The nanocomposite was optimized with respect to PVDF, rGO and Au concentration. The as-synthesized materials were characterized by physiochemical characterization techniques such as field emission scanning electron microscopy (FESEM), X-ray diffraction analysis (XRD), UV-Visible spectroscopy, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> phase formation of the PVDF was confirmed from the XRD peak at 20.41°. SEM results revealed that AuNR have length 15–20 nm and aspect ratio <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim $ </tex-math></inline-formula> 3–4. Breath sensing tests were carried out for as synthesized nanocomposite material. The nanocomposite exhibited high sensitivity towards breath and generated the voltage of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim $ </tex-math></inline-formula> 0.7 V within 0.8 s.

Wideband Series Harmonic Voltage Compensator Using Look-Ahead State Trajectory Prediction for Network Stability Enhancement and Condition Monitoring

A wideband series harmonic voltage compensator (WSHVC) with an operating bandwidth of 10 kHz for microgrids with a plurality of grid-connected inverters (GCIs) is proposed. It generates a voltage to compensate for high-frequency harmonic voltage at the point of common coupling (PCC), resulting in a virtually zero high-frequency impedance at the aggregate output of the GCIs and, thus improving system stability. The generation of the harmonic voltage is based on predicting the state trajectory of the WSHVC after a switching period per half-switching cycle to determine the moment at which the switches in the WSHVC change their states. The PCC impedance and the equivalent impedance of the GCI network are extracted by analyzing the system response after injecting the entire system with particle-swarm-optimization (PSO) optimized multisine power disturbances. Therefore, system stability is predicted. The condition of passive components in the WSHVC is also monitored by estimating their values with the sampled state variables. A 500 VA, 1 MHz, FPGA-controlled, GaN-based prototype is evaluated on a 6.5 kVA testbed that consists of three commercial GCIs, nonlinear load, and adjustable grid impedance. A comparative study of the system performance with and without the WSHVC is conducted. Experimental results are favorably compared with theoretical predictions.

An Enhanced Predictive Current Control Scheme for Common Mode Voltage Alleviation and Improvement of Torque Response of PMSM Drive

Predictive current control (PCC) is an effective control scheme with provisions to handle multiple objectives and nonlinear constraints. In the conventional PCC (CPCC) scheme, the application of a zero-voltage vector (ZVV) leads to the generation of large common-mode voltage (CMV), which gradually leads to bearing damage. However, disregarding ZVV can suppress CMV at the expense of large distortions in stator current. To avoid this, the present work deploys synthesized voltage vectors (SVVs) obtained from adjacent active vectors (AAVs) for permanent magnet synchronous motor (PMSM) drive control. In this article, two techniques are proposed for alleviating the CMV. Two AAVs are applied for a fixed duration in the first proposed method. Thus, the effect of neglection of ZVV can be circumvented with the application of two AAVs. In the second method, multivectors are applied to ensure CMV suppression and improvement of the steady-state torque response. Furthermore, an effective voltage vector (VV) preselection scheme using the complex-plane concept is introduced. Unlike the conventional CMV reduction schemes, the proposed VV-preselection evades tangent inverse angle determination and complex transformations. This offers the advantage of reduced computational burden with improved steady-state torque performance. The effectiveness of the proposed schemes is validated by comparing them with CPCC and existing literature.

Maximum power point tracking method based on impedance matching for a micro hydropower generator

An innovative maximum power point tracking method based on impedance matching is proposed and applied in a micro hydropower generator. The micro hydropower generator exploits the water head which is derived from the repeated diving of the marine animal to power the marine telemetry tag. The output voltage of the micro generator is intermittent and changes very fast. The present maximum power point tracking methods can’t deal with this type of intermittent and fast changing voltage of the generator. Hence, to track the optimum operation point and improve the energy efficiency, a new MPPT method which tracks the optimum operation point by directly matching the virtual load impedance of the generator to its internal resistance is proposed. The impedance matching law is developed based on the mathematical model. The experiment of the MPPT hardware is conducted, and the experiment result is used to validate the simulation model. Based on the validated model, the analysis results show that under the fluid pressure from 2 MPa to 8 MPa, the energy efficiency of the generator that uses the MPPT method increase to 1.8 to 2.7 times the one with the direct charging method. The results indicates the effectiveness and advantage of the MPPT method in tracking the optimum operation point and improving the energy efficiency in the context of intermittent and fast changing voltage.

180 nm FLASH ANALOG TO DIGITAL CONVERTOR

In this paper, Threshold Inverter Quantizer (TIQ) is a novel idea which can effectively replace the reference voltage generator, resistive/capacitive voltage divider network and array of differential comparators in a conventional flash Analog to Digital Converter (ADC) by an internal reference comparator array constructed of Complementary Metal Oxide Semiconductor (CMOS) inverters. The inverter threshold voltage serving as the reference voltage, this architecture claims large improvements in terms of silicon area, power consumption and operating speed. Perturbations due to sensitivity of the inverter threshold voltage to operating temperature/process variations pose impediments in such ADC designs and strongly demand a compensation scheme to such variations. This paper presents a TIQ based flash ADC, with inverter threshold voltage compensation. In this project 5 bit flash adc using TIQ Comparator is designed and simulated using TANNER EDA in 180nm technology. Key Words: flash, adc, tiq(threshold inverter quantization)

Production potential of cow dung for the generation of electric current using microbial fuel cell

Production potential of cow dung for the generation of electricity was investigated using microbial fuel cell (MFC). Cow dung was collected from FUTA farm and Ilesha Garage farm in Akure. Voltage and current was measured per day for 21 days and the electrode used for the set up are carbon-carbon and carbon-aluminium electrode. Proximate, physico-chemical and mineral composition were determined using standard methods. Isolation and identification of microorganisms present in the cow dung were determined before and after generation of voltage and current using microbiological techniques. The microorganisms isolated were Providencia alcalifaciens, P. rettgeri, P. stuartti, Escherichia coli, E. fergusonii, Morganella morganii, Staphylococcus haemolyticus, S. aureus, Micrococcus luteus, Fusarium solani, Saccharomyces cerevisiae and Mucor mucedo. The highest voltage 0.737±0 mV and electric current 1.265±0 mA were generated from FUTA cow dung. The pH ranged between 7.3 to 9.9 and the temperature ranged between 25 ˚C to 33 ˚C during generation of voltage and current. This study has shown that cow dung is a potential substrate for generation of electric current using fabricated double chamber MFC.

ANALYTICAL MODEL AND NUMERICAL FINITE ELEMENT MODEL FOR A SUBMERSIBLE SYNCHRONOUS HYDROGENERATOR

The main objective of the paper is to demonstrate the functionality and reliability of a hydrokinetic turbine system – a submersible electric generator, suitable for very low watercourses. To achieve this goal, it is necessary to design and build a prototype of a hydrokinetic turbine, coupled with an electric generator with excitation made with permanent magnets. This paper presents an analytical model and a finite element numerical model for estimating the electrical parameters of the generator (voltage, current, power, etc.). The two models were compared, and the results were extrapolated, in the analytical model, for several speed values.

The evolving paradigm of the subauroral geospace

An assessment of the status quo of fast subauroral flows—subauroral ion drifts (SAID) and subauroral polarization streams (SAPS), is presented. For a few decades, their development has been interpreted in terms of the voltage and current magnetospheric generators based largely on the drift motion of test particles. Recent multispacecraft observations revealed serious flaws in the generator paradigm and called for a new generation mechanism of fast-time subauroral flows and ring current (RC) injections. A novel model includes them in the overarching problem of the penetration of magnetotail plasma flow bursts (MPFs) into the plasmasphere and the substorm current wedge (SCW) development. SAID are created near the plasmapause, where inbound MPFs are short-circuited by the cold plasma. This stops the MPF’s electrons and forms the “dispersionless” plasma sheet (PS) boundary. The SAID electric field—the inherent part of the short-circuiting loop—stops the inward-moving MPF’s ions. In turn, SAPS are an integral part of the two-loop SCW system, or SCW2L, where the downward (R2) current emerges in response to the upward (R1) current in the SCW’s “head.” The meridional Pedersen current, which connects the R1 and R2 currents, leads to SAPS that ultimately drive the fast-time RC injections on the duskside.

Fuzzy induced controller for optimal power quality improvement with PVA connected UPQC

Abstract The major power quality issues in grid are voltage fluctuations and harmonics. For better power quality of the power system during disturbances on the grid, the UPQC device is utilized to maintain voltage magnitude and reduced harmonics. At the DC link of UPQC along with the capacitor, a renewable PV source is connected which contributes in voltage compensation by the series VSC and harmonics compensation by the shunt VSC. For stable DC voltage generation from PV source a modified P&amp;O MPPT with DC reference is included controlling the boost converter connected to PV source. The controllers of VSCs are operated by feedback loop synchronized schematics with voltage reference generation in series VSC control and current reference generation in shunt VSC control. The shunt control is updated with hybrid Fuzzy-PI controller replacing the traditional PI controller further improving the power quality of the grid. The hybrid Fuzzy-PI varies the K p and K i gains as per the error generated by the DC voltage comparison concerning 25 rule-base for each gain. A comparative performance analysis is done with both the controllers in the shunt converter and the results are generated using MATLAB Simulink software.

A Direct Backstepping Super-Twisting Algorithm Controller MPPT for a Standalone Photovoltaic Storage System: Design and Real-Time Implementation

Abstract In this paper, we introduce a novel direct maximum power point tracking (MPPT) approach that combines the backstepping controller (BSC) and the super-twisting algorithm (STA). The direct backstepping super-twisting algorithm control (BSSTAC) MPPT was developed to extract the maximum power point (MPP) produced by a photovoltaic (PV) generator connected to the battery through a boost DC-DC converter. To reduce the number of sensors required for the BSSTAC implementation, a high gain observer (HGO) was proposed to estimate the value of the state of the PV storage system from measurements of the PV generator voltage and current. The suggested technique is based on the quadratic Lyapunov function and does not employ a standard MPPT algorithm. Results show that the suggested control scheme has good tracking performance with reduced overshoot, chattering, and settling time as compared to the prevalent MPPT tracking algorithms such as perturb and observe (P&amp;O), conventional sliding mode control (CSMC), BSC, and integral backstepping controller (IBSC). Finally, real-time findings using the dSPACE DS 1104 software indicate that the generator PV can accurately forecast the MPP, as well as the efficacy of the suggested MPPT technique. The provided approach’s effectiveness has been validated by a comprehensive comparison with different methods, resulting in the greatest efficiency of 99.88% for BSSTAC.

Voltage and frequency stabilization control strategy of virtual synchronous generator based on small signal model

Power system with large scale Inverter-based Resources (IBR) penetration is challenged with insufficient voltage and frequency support capacity. This paper restructures the control blocks of virtual synchronous generator (VSG) from the perspective of traditional synchronous generators’ control, the control path of the system over its active and reactive power output is clarified and simplified, which has facilitated the tuning of virtual inertia and damping parameters. Firstly, the small signal model of VSG control IBR is established, including instantaneous power calculation module, LC filter and power loop, voltage and current loops. In the meantime, the improved VSG voltage and frequency regulation control strategy is proposed based on the stability analysis of the small signal model. The stable operation range of the VSG control grid-connected inverter system is studied with the objective to improve the stability and robustness of the VSG-controlled grid-connected inverter system. Finally, MATLAB/Simulink simulation verifies the correctness of the proposed VSG’s dynamic model of power grid voltage and frequency regulation. The effectiveness of the restructures of VSG is verified as well. The results show that the control strategy not only improves the inertia of the system, but also enables the IBR to support the frequency and voltage of the system.

Development of Manganese-Coated Graphite Electrode in a Dual-Chambered Fuel Cell for Selenite Removal and Bio-Electricity Generation from Wastewater Effluent by Bacillus cereus

A manganese oxide-coated cylindrical graphite cathode with a zinc anode was developed to treat wastewater containing selenite in a dual-chambered microbial fuel cell. COD and selenite removal in the anodic chamber by Bacillus cereus with energy generation were evaluated in batch mode. A manganese dioxide-coated graphite cathode was tested for its surface morphology and chemical composition using scanning electron microscopy and dispersive energy analysis of X-rays. Compared to the non-coated graphite electrode, up to 69% enhancement was observed in the manganese dioxide-coated electrode voltage generation with 150 ppm selenite concentration. The fuel cell achieved a maximum power density of 1.29 W/m2 with 91% selenite reduction and up to 74% COD (initial COD of 120 mg/L) removal for an initial selenite concentration from 100 to 150 ppm. The current study demonstrated the possibility of a modified cathode in enhancing energy generation and the use of microbial fuel cell technology to treat wastewater containing selenite.

Self-Triggering Circuit for a Pulse Thyratron Switch in a Pulse Voltage Generator

Self-Triggering Circuit for a Pulse Thyratron Switch in a Pulse Voltage Generator