Constant Resistive Load Research Articles

Influence of Wind and Rainfall on the Performance of a Photovoltaic Module in a Dusty Environment

This study presents an analysis of the influence of weather conditions on the performance of a multicrystalline silicon photovoltaic module, which operates under constant resistive load and is situated near a limestone quarry. The quarry is a significant source of dust, and hence the focus of the study is on the weather factors influencing the presence of soiling on the module’s surface. The analysis encompasses a three-week period, during which the global horizontal irradiance and wind speed were recorded at 10-min intervals by an on-site weather station. The current, voltage, and back temperature of the module were also measured. Supplementary weather data were obtained from the Copernicus Atmosphere Monitoring Service and the NASA POWER databases. The primary objective is to assess whether any influence of the observed weather conditions on the presence of soiling can be inferred from the recorded data. The contribution is in part intended to test how different techniques can be used to extract useful information on the weather-related effects from somewhat limited data, assembled from various sources, while dealing with the underlying uncertainties. The analysis indicates a persistent deterioration of the module’s performance because of soiling and its subsequent improvement due to a favourable weather event.

A long-horizon move-blocking based direct power model predictive control for dynamic enhancement of DC microgrids

This research paper presents a novel long-horizon move-blocking based direct power model predictive control (DPMPC) strategy, uniquely designed to enhance the dynamic performance of boost converters in the grid-connected mode within DC microgrids. A precise dynamic model is developed considering a boost converter connected to a DC-link supplying constant power and resistive loads. To predict the system's dynamic behavior over an extended interval and enhance its performance in the presence of constant power loads, the long-horizon based finite control set model predictive control (FCS-MPC) method is introduced. To address the computational complexity associated with the conventional long-horizon DPMPC approach, a move-blocking (MB) strategy is incorporated into FCS-MPC, reducing the computational burden while improving the dynamic performance of the boost converter. Unlike recent studies that utilize DPMPC with short prediction interval, this paper presents evidence that a longer prediction interval is crucial for maintaining system stable and enhancing the dynamic response and also utilizing MB to make the control implementable in the real-time. The simulation results conducted using MATLAB/Simulink demonstrate the effective performance of the proposed strategy across various operating conditions of the boost converter. Experimental results further validate the strategy's capability to enhance the dynamic performance of the boost converter. Importantly, the experimental findings confirm the feasibility of implementing the proposed long-horizon move-blocking DPMPC strategy in real-time applications.

Fast Charging Control Method for Electric Vehicle-to-Vehicle Energy Interaction Devices

In order to reduce energy consumption and alleviate environmental pollution, the number of electric vehicles is increasing. But people are still worried about the choice of electric vehicles because of the problems of battery charging and duration. Therefore, a vehicle-to-vehicle energy interaction converter device is proposed in this paper, which has the characteristics of high-power, high-gain and small-volume. Based on the characteristics of this device, this paper uses modularized boost converter (MBC) to design this device. However, the electric vehicle battery can be divided into constant resistance loads and constant power loads (CPLs). Therein, the CPLs are very easy to cause the instability of the charging device. Therefore, a nonlinear controller combining an external nonlinear disturbance observer and an adaptive backstepping algorithm is proposed in this paper. In the first place, the high order MBC model is reduced to Brunovsky’s canonical form by using accurate feedback linearization technology in this paper. Afterwards, a nonlinear disturbance observer is designed to speed up the dynamic response of the system. At the same time, an adaptive backstepping controller is designed to ensure the stability of the output voltage in the sense of large signal by using the output of nonlinear disturbance observer. In the end, simulation and experiment results illustrate the correctness and feasibility of the converter device.

Evaluation and Suppression of Oscillations in Inductive Power Transfer Systems With Constant Voltage Load and Pulse Skipping Modulation

This paper identifies how Constant Voltage Load (CVL) characteristics cause Inductive Power Transfer (IPT) systems to exhibit a poorly damped oscillation mode. When operated with pulse skipping strategies such as Pulse Density Modulation (PDM), the skipped voltage pulses can excite this mode and cause severe oscillations that do not appear in systems with a constant resistance load (CRL). The critical mode is identified from a linearized state-space model of the system and two control approaches are proposed for attenuating the oscillations in current amplitude and power flow. Firstly, the influence of the operating frequency on the critical eigenvalue is analyzed and it is shown how slightly off-resonant operation can increase the damping of the oscillation mode. Secondly, an active damping method based on sending current feedback control is studied. The active damping is based on Phase Shift Modulation (PSM) with limited phase shift angles applied to the PDM signal when oscillations are detected. The effectiveness and feasibility of the proposed methods are validated by simulations and experimental results from a small-scale laboratory prototype.

Experimental investigation of longevity and temperature of a lithium-ion battery cell using phase change material based battery thermal management system

Nowadays, conventional lead acid batteries are being replaced by Lithium-ion batteries due to their high energy density, low cost, and high electric capacities. But when subjected to high discharge conditions, these batteries undergo a rapid increase in temperature which can make them unstable and change their internal chemistry to the point of fire or explosion due to thermal runaway and reduce their working life (electrical capacity). To prevent this, battery thermal management systems need to be used. The current work is focused on investigating the performance of a phase change material-based thermal battery management system for controlling battery temperature and battery life. In this experimental study, RT-47 Paraffin phase change material is wrapped around a 1.2Ah, 3.7 V lithium-ion battery cell with a thickness of 4 mm. The results of temperature and electrical current were recorded for 1200 s during which the battery was discharged at a constant resistance load. It was found that using a phase change material based thermal management system the temperature of the battery cell was better maintained and it lasted approximately double the time as compared to a bare battery cell under the same loading conditions.

Enhanced Distributed Non-Linear Voltage Regulation and Power Apportion Technique for an Islanded DC Microgrid

There is a growing focus on exploring direct current (DC) microgrids in traditional power grids. A key challenge in operating these microgrids is ensuring proper current distribution among converters. While conventional droop control has been used to address this issue, it requires compensating for voltage deviations in the DC bus. This paper introduces an innovative distributed secondary control approach that effectively addresses both voltage restoration and current sharing challenges within a standalone DC microgrid. The distributed secondary control proposed in this study is integrated into the microgrid’s cyber layer, enabling information sharing between controllers. This distributed approach ensures reliability, even in the event of partial communication connection failures. The controller employs a fuzzy logic control approach to dynamically determine the parameters of the secondary control, resulting in an enhanced control response. Additionally, the proposed approach can handle constant power and resistive loads without specific requirements. Employing the Lyapunov method, we have derived adequate stability conditions for the proposed controller. The performance of the controller has been assessed using MATLAB/Simulink® models and validated with real-time experimental testing performed with a SpeedgoatTM real-time machine, considering five different test cases. The results indicated that the proposed control system is robust in achieving its control objectives within a DC microgrid, exhibiting fast response and minimal oscillations.

Nonlinear charge-voltage relationships in electric double layer capacitors performing under constant load resistance

Nonlinear charge-voltage relationships in electrochemical double layer capacitors (EDLCs) performing under constant load resistance, are analyzed. Three commercial EDLCs with nominal capacitances in the range from 0.1 to 1 F and maximum voltage 5 V, are selected. The time evolution of the electric current obtained during the discharge through a resistor of an EDLC, which is initially charged at a constant potential, is gathered and the electric charge is determined from the area of the current-time curve. Evolution with the electric potential of the stationary charge stored in the EDLCs is interpreted by means of a fitting which leads to a polynomial model for the capacitance. The study of the nonlinear dependence with voltage of the charge allows us to deepen in understanding the differences between integral and differential capacitances of an EDLC, as well as consider the role played by the capacitance at the zero-voltage limit. The model is validated by means of the simulation of the equivalent circuit constituted by the series combination of the equivalent series resistance (ESR) and the differential capacitance in the PSpice® program, and the theoretical and experimental comparison of the charge-voltage curves obtained during the transient discharge of the different EDLCs.

Passivity-Based Control of Buck-Boost Converter for Different Loads Research

Normally, the buck-boost converter adopts single or double closed-loop control, and there are differences in control and parameters for different working modes and loads. In this study, a unified control method, the passivity-based control (PBC), is applied to a buck-boost converter for different loads, including constant resistance load (CRL), constant power load (CPL), and battery load. The PBC is a nonlinear control based on energy dissipation principle, and it has strong robustness to parameter interference and external disturbance, and it also has the advantages of simple design and simple implementation. Although many research studies have been conducted before, the voltage and current-related power losses are considered, and different load models are also compared in this research. The detailed mathematical model, control principle, and controller design of the buck-boost converter are thoroughly analysed. In addition, SIMULINK-based simulation results and experimental verification results of different loads are also given in the paper. Also, the PBC has smaller current overshot and smaller current ripples compared with PI control in different loads condition.

Development and performance evaluation of a wheel-type cantilevered piezoelectric rotational energy harvester via an unfixed exciting magnet

A wheel-type cantilevered piezoelectric rotational energy harvester (wheel-type PREH) via an unfixed exciting magnet was presented to harvest energy from rotational motion without or far away from a fixed support. To verify the structural feasibility and figure out the effect of rolling exciting magnet and excited magnet on the dynamic characteristics and power generation performance of the wheel-type PREH, the theoretical analysis, simulation, fabrication and experimental testing were performed. The results showed that the performance of the wheel-type PREH depended on the rotary speeds, proof mass and piezo-cantilever mass, number of exciting magnets, cylindrical sleeve materials and so on. When other parameters were constant, there were multiple optimal rotary speeds for the maximal amplitude-ratio, output voltage, electrical energy and output power to achieve peak. Besides, the total number of voltage crests per second did not change with rotary speed. There was a constant optimal resistance load for the wheel-type PREH at different rotary speeds to achieve maximal power. The PREH prototype could yield a maximum output power of 0.74 mW at 767 r/min with optimal load resistance of 215 kΩ and 40 different color LEDs in parallel and a low power light strip could be lighted by wheel-type PREH.

Modelling, Analysis and Performance of a Low Inertia AC-DC Microgrid

In a world where the energy crisis is becoming overwhelming, demand for integrating renewable energy sources is increasing and forming microgrids is becoming an essential solution. The new microgrid systems, which depend mainly on renewable energy sources instead of conventional synchronous generators, come with a low inertia concern. This paper proposes a virtual inertia controller based on a high-pass filter (HPF) to support the frequency of the AC microgrid while maintaining the DC voltage of the DC microgrid within the nominal ranges in cases of contingencies. The proposed system encounters an AC-DC microgrid with a renewable energy source on the DC microgrid alongside constant power load and resistive loads, while on the AC microgrid side, a synchronous generator is used to present the low inertia of the grid with dynamic loads and static loads. The state-space linearized model of the system is developed and verified using Matlab Simulink. The dynamic response of the proposed controller is compared to the low-pas filter (LPF)-based controller. Moreover, the effect of changing the system’s parameters on eigenvalues is investigated.

Multivariable-Feedback Sliding-Mode Control of Bidirectional DC/DC Converter in DC Microgrid for Improved Stability with Dynamic Constant Power Load

In order to mitigate the influence of negative impedance characteristics on the stability of a DC microgrid with a constant power load, and the influence of nonlinear characteristics of a bidirectional converter on DC bus voltage, a control method of a bidirectional converter based on a multivariable-feedback sliding-mode control is proposed. The traditional control method usually uses the DC bus voltage error as a single controlled variable to optimize the design of the control law, which will lead to the lack of global coordination of each state variable. In this paper, the multi-state process variables-feedback sliding-mode control of a bidirectional DC/DC converter is designed, which can effectively improve the stability of the DC bus voltage, despite dynamic power disturbances. Firstly, the model of a bidirectional DC/DC converter, as well as the state equations of a converter with constant power load and resistive load, are analyzed. Secondly, to express various dynamic characteristics of the DC bus voltage fluctuation process, the output voltage error, the inductor current error and its integral are defined as the controlled state variables. Then, the multivariable weight combination-based sliding-mode surface is defined, and the sliding-mode controller is derived from a fast exponential power reaching law. Thirdly, the existence and stability of the multivariable-feedback sliding-mode control and the choice of control law parameters are discussed. Finally, MATLAB / Simulink software is used to simulate the proposed controller. Compared with PI and intelligent PID controllers, the proposed controller has the fastest response speed, the smallest steady-state voltage deviation and the best adjustment performance.

The active and reactive power characteristic analysis and decoupling control of current source PWM rectifier

The current source PWM converter has the advantages of continuous and adjustable DC current and strong ability to limit short circuit current, and it is suitable for DC ice melting application of transmission line. In this paper, the mathematical model of current source PWM converter is established, the active and reactive power characteristics of constant current load and constant resistance load are analyzed thoroughly, the double closed-loop controller of active and reactive power decoupling is designed, and the simulation research is carried out in Simulink. The results show that the proposed method can realize active and reactive powers decoupling control. When the system voltage drops, it can also output stable DC current.

Unified Coil and Compensation Network Design for Improving Wireless Power Transfer Efficiency Over Wide Output Load Variation Ranges

It is shown that compensation network and coil design collectively affect wireless power transfer efficiency. Based on this fact, a novel design approach of wireless power transfer (WPT) systems is proposed. Unlike majority of existing designs which aim at enhancing power transfer efficiency (PTE) at one rated operating point, the proposed design enhances the overall system PTE. This feature is essential for variable output loads such as batteries, where their internal impedance varies during charging period. To achieve this goal, improving time-weighted average efficiency of WPT system is set as the design criterion. Experimental studies of a 1.2 kW WPT system supplying constant resistive loads and battery loads verify that the proposed design enhances PTE both at rated output load and under wide output load variations.

Effect of resistive load characteristics on the performance of Organic Rankine cycle (ORC)

The effects of various organic Rankine cycle (ORC) components, such as evaporator, expander and condenser on the performance of the system have been extensively studied. However, only a handful of studies have focused on studying the influence of external load characteristics. A small-scale ORC test rig of 3 kWe was constructed to experimentally investigate the effect of resistive load on the performance of the system. In order to achieve this, the study combined the thermodynamic method with electrical analysis. The results showed that the increase in output power caused a simultaneous increase in rotational speed, torque and inlet pressure of the expander under constant load resistance conditions. However, the fluid mass flow rate only affected the expander's inlet pressure. The decrease in load resistance increased the expander's inlet pressure and torque, and reduced the superheating and rotational speed. The influences of load resistance on the isentropic efficiency and net efficiency were mainly thorough the expander's inlet pressure and superheating. The net efficiency also benefited from the ideal cycle efficiency due to that decreasing load resistance enlarged the enthalpy drop of expander. The effects of load resistance on performance parameters were restricted by the mass flow rate of the fluid.

An improved Newton-Raphson based linear power flow method for DC grids with dispatchable DGs and ZIP loads

PurposeThis study aims to provide a solution of the power flow calculation for the low-voltage ditrect current power grid. The direct current (DC) power grid is becoming a reliable and economic alternative to millions of residential loads. The power flow (PF) in the DC network has some similarities with the alternative current case, but there are important differences that deserve to be further concerned. Moreover, the dispatchable distributed generators (DGs) in DC network can realize the flexible voltage control based on droop-control or virtual impedance-based methods. Thus, DC PF problems are still required to further study, such as hosting all load types and different DGs.Design/methodology/approachThe DC power analysis was explored in this paper, and an improved Newton–Raphson based linear PF method has been proposed. Considering that constant impedance (CR), constant current (CI) and constant power (CP) (ZIP) loads can get close to the practical load level, ZIP load has been merged into the linear PF method. Moreover, DGs are much common and can be easily connected to the DC grid, so V nodes and the dispatchable DG units with droop control have been further taken into account in the proposed method.FindingsThe performance and advantages of the proposed method are investigated based on the results of the various test systems. The two existing linear models were used to compare with the proposed linear method. The numerical results demonstrate enough accuracy, strong robustness and high computational efficiency of the proposed linear method even in the heavily-loaded conditions and with 10 times the line resistances.Originality/valueThe conductance corresponding to each constant resistance load and the equivalent conductance for the dispatchable unit can be directly merged into the self-conductance (diagonal component) of the conductance matrix. The constant current loads and the injection powers from dispatchable DG units can be treated as the current sources in the proposed method. All of those make the PF model much clear and simple. It is capable of offering enough accuracy level, and it is suitable for applications in DC networks that require a large number of repeated PF calculations to optimize the energy flows under different scenarios.

Coulombic efficiency estimation technique for eco-routing in electric vehicles

<abstract> <p>A battery source is an indispensable component in electric vehicles and its efficient usage results in improvement of battery life. The amount of energy stored in batteries, including their state of charge and efficiency, are critical metrics for evaluating vehicle performance. This article presents an automated motor-generator linked technique for estimating battery-related parameters, which is an essential aspect of eco-routing in electric vehicles. This system enables discharging of a battery at various current rates by constant resistive loads which are electronically applied. The charging process however uses a charger attached to various sensors for estimating the current. The coulomb counting method has been used which provides information of State of Charge and Coulombic Efficiency of the test battery. Since battery behavior is dynamic; the energy source was charged and discharged over numerous cycles at various current rates. The experimental set-up uses sensors for accurate data acquisition. In addition to the experimental set-up, an electrical circuit battery model has also been simulated in this work. All simulation as well as post processing tasks have been done in the Arduino-MATLAB environment. The main highlight of this system is that the system is portable, easy to operate, low cost and can be used to test all types of batteries. The proposed system is simple and has yielded good results. The battery parameters obtained prove to be vital for range determination in eco-routing of electric vehicles among other applications.</p> </abstract>

Sliding-Mode Control of a Quadratic Buck Converter With Constant Power Load

This paper analyzes for the first time a two-loop sliding-mode control (SMC) of a high-order converter supplying a constant power load (CPL). The converter is a single-switch quadratic buck structure (QBC) interfacing a domestic 380 V DC bus to a CPL requiring a regulated voltage of 48 V DC. The converter is unstable in the absence of control and even after the insertion of an inner loop based on SMC of the input inductor current. The addition of an appropriate linear outer loop establishing the reference to the inner loop stabilizes the system and provides output voltage regulation. The regulated QBC shows a fast recovery of the output voltage with negligible overshoot in response to step-type changes of the output power or the input voltage. It is also shown that the implemented regulator for CPL supply can be used directly in the case of a constant current load (CCL) or a constant resistance load (CRL) resulting in similar performance to the CPL case. PSIM simulations and experimental results in a 400 W prototype are in good agreement with theoretical predictions.

An air insulated linear pulse transformer for electrodischarge technology

A linear pulse transformer with air insulation at atmospheric pressure was created and tested under both constant resistance and non linear loads. The maximum power of the transformer output pulse reached ∼500 MW at a matched load with a charge voltage 50 kV. The transformer transferred ∼60% of the stored energy to the load over a characteristic time of about 1 μs. The scalability the generator was studied by connecting two identical transformers in series which gave a power output of ∼850 MW with doubled output voltage and reduced current. The frequency mode of operation was studied using one and two transformers with a charge voltage of 50 kV and a load that was, close to matched. In both cases, the power maximum and jitter showed no significant changes at any of the frequencies tested (up to 5 Hz). These results mean that the use of this generator can be recommended for a wide field of applications due to its scalability and low internal impedance.

Intelligent Multiobjective NSBGA-II Control of Power Converters in DC Microgrids

In this article, we develop a novel multiobjective controller to regulate the power converters of a class of dc microgrids connected to nonlinear constant power loads and linear resistive loads. The suggested control approach uses the nondominating sorting binary genetic algorithm (NSBGA-II) to directly design the on/off switching signal of the converters without using the pulsewidth modulation technique. The multiobjective controller minimizes the tracking error of the dc bus voltage and at the same time tries to reduce the total number of switching actions. Thereby, the developed controller tracks the desired reference with a reduced converter switching action and power loss by using a proper Pareto solution. Moreover, by employing the NSBGA-II algorithm, it is feasible to involve the switching frequency in the design procedure to enhance the performance. Exploiting the binary genetic algorithm instead of the conventional genetic algorithm (GA) turns a continuous surface searching into a binary one, which not only makes it more compatible with the nature of the power converter control but also decreases the online computational burden. To illustrate the superiority of the proposed approach, real-time OPAL results are provided.

Power management and state of charge restoration of direct current microgrid with improved voltage-shifting controller

Recently, direct current (DC) microgrid is gaining increased importance due to large-scale utilization of different DC sources, such as photovoltaic (PV), fuel cell, DC loads, and high-level integration of energy storage devices and renewable energy. Additionally, unlike conventional alternating current (AC) system, DC microgrid does not require reactive power and frequency control. Nevertheless, DC microgrid control is a complex task due to the connection of several distributed generators, loads, energy storages, and renewable energy sources, such as PV, and wind, to the common DC bus. The control of DC bus voltage, effective power split among the energy storage devices, and state of charge (SOC) restorations are important in a DC microgrid. This paper proposes a new average voltage shifting-based strategy to split power-sharing between battery and supercapacitor. In the proposed approach, an average voltage shifting term derived from the battery and supercapacitor is introduced to reduce the DC link voltage deviation. As compared to the droop control, the addition of the voltage shifting term acts like a high pass filter and blocks the DC component which helps the DC bus voltage restoration process. The DC microgrid is composed of a hybrid energy storage system formed by battery and supercapacitor, AC utility grid interfaced with three-phase voltage source converter (VSC), constant power load, constant resistive load, and distributed generator. The SOC of the supercapacitor is automatically restored after any disturbances whereas the battery SOC is maintained by energy exchange with the distributed generator or grid. The real-time digital simulator (RTDS) and dSPACE-based control hardware-in-loop results show that the proposed approach is reliable, leading to improved DC bus voltage control while maintaining proper power flow and SOC within the microgrid. The comparative study is also conducted to show the superiority of the proposed strategy with the existing method.