Output Load Research Articles

Dynamic Stabilization of DC Microgrids Using ANN-Based Model Predictive Control

Over the past decade, the high penetration of renewable-based distributed generation (DG) units has witnessed a considerable rise in electrical networks. In this context, direct current (DC) microgrids based on DGs are being preferred due to having less complexity for the establishment and control. At the same time, they offer higher efficiency and reliability compared to their alternating current (AC) counterparts. This paper proposes a new model predictive control (MPC)-trained artificial neural network (ANN) control strategy being an ANN-MPC instead of conventional cascaded-proportional-integral (PI)-trained ANN control for dynamic damping of photovoltaic (PV)-battery-based grid-connected DC microgrids. Unlike traditional controllers, the proposed control approach more rapidly attains generation-load power balancing under variable climate input (meteorological sensor data) and output (load demand), hence achieving quick DC-bus voltage damping. The proposed ANN-MPC scheme is examined under different operating conditions, and the results are compared with the ANN-based conventional PI controller. The results show the proposed control strategy's efficacy to lessen the instability issues and achieve effective attenuation of oscillations in DC microgrids.

ZVS Analysis and Design for Half Bridge Bidirectional LLC-DCX Converter With Consideration of Nonlinear Capacitance and Different Load Under Synchronous Turn-On and Turn-Off Modulation

In the application of bidirectional LLC -DCX converter, synchronous turn-on and turn-off modulation can be adopted to simplify the control. In view of zero-voltage switching (ZVS) performance, conventionally, the magnetizing inductance is regarded as a current source to discharge output capacitance of primary switches, neglecting the effect of secondary output capacitance and load, which leads to insufficient accuracy and non-ZVS. This article presents the ZVS analysis and design for half-bridge LLC -DCX converter with consideration of nonlinear capacitance and different load values under the synchronous turn-on and turn-off modulation. With consideration of nonlinear capacitance and different load values, the charging and discharging process of the output capacitance during the dead time is analyzed in detail. The analysis indicates that the ZVS conditions are not only affected by the dead time and magnetizing inductance as in the previous study but also related to the load and other parameters. Based on in-depth analysis, more precise ZVS conditions on the magnetizing inductance, dead time, load, and resonant parameters are revealed. In addition, based on the obtained ZVS conditions, the guidance for parameters design is given to achieve full-load-range ZVS. Finally, the effectiveness of the proposed solution has been verified through experimental results.

Control strategy of DC/DC converter for photovoltaic-storage-DC microgrid based on improved LADRC

Aiming at the problem that the DC bus voltage is easily affected by nonlinear noise of the converter, photovoltaic output power and load disturbance, a bidirectional DC/DC converter control strategy based on the improved Linear Active Disturbance Rejection Control is designed. Firstly, establish the mathematical model of the bidirectional DC/DC converter, and analysis of existing problems in traditional LADRC. On this basis, a new state variable is introduced to observe the differential of the total disturbance to improve its rapidity; Then a lead-lag correction link is connected on the total disturbance observation channel to suppress the problem of high-frequency noise amplification. Finally, the Bode diagram is used to analyze the performance indicators of the improved LADRC. The simulation results show that, compared with the traditional LADRC, the control strategy in this paper reduces the bus voltage amplitude fluctuation by 63%, the adjustment time by 59%, and the inductor current ripple by 66%, which is more superior to suppressing the DC bus voltage fluctuation.

Future pem fuel cell system renewable energy systems based on hydrogen equipment for microgrid networks

The simulation results of a modest 6 KW fuel cell energy system employing technical control are presented in this study. Technical control and fuzzy logic the performance of the controller used for maximum power point tracking (MPPT) can improve the efficiency of the FC system when Particle Swarm Optimization (PSO) and the system Boost DC/DC Converter power converter that steps up voltage (while stepping down current) from its input (supply) to its output (load) are compared. An electrolyzer with a proton exchange membrane fuel cell (PEMFC). This paper presents dynamic modeling of various components of a small isolated system. The dynamic modeling of this nonlinear 45 Vdc energy system is done with Simulink. The simulation findings are analyzed, as well as the constraints of a fuel cell energy system. The hydrogen produced is used by the third operating subsystem (the fuel cell stack), which generates electricity to power the DC bus. The global system is modeled, and the results are presented and analyzed. Due to its better efficiency, clean operation, and cost-effective supply of power sought by consumers, fuel cell (FC) technology has attracted substantial attention as an alternative to traditional power units among the numerous renewable energy sources. In the SIMULINK environment, the proposed model is implemented. The simulation outcomes are examined.

A Compact Ultra-Broadband RF Rectifier Using Dickson Charge Pump

In this letter, an ultra-broadband rectifier is proposed and tested to get more RF energy from ambient. The rectifier using the Dickson charge pump increases the bandwidth and improves the dc voltage of the output load. The upper branch uses an inductor in series to counteract the capacitance of the imaginary parts of the diode and at the same time acts as a booster circuit to increase the output voltage. A shunt open-circuit stub acts as part of the matching network, tuning the imaginary part of the input impedance of the high frequency to realize the impedance matching of the ultra-broadband rectifier. The manufactured rectifier is measured and the result shows a fractional bandwidth of 145.5% (0.6-3.8 GHz) with an RF-to-dc power conversion efficiency (PCE) exceeding 40% at 8 dBm input power. And the measured efficiency remains over 50% across the frequency range from 1.6 to 3.4 GHz (including GSM1800, GSM2100, and WiFi). In addition, the rectifier made a maximum conversion efficiency of 66.6%.

On-line monitoring of steel ball stamping by mechatronics cold heading equipment based on PVDF polymer sensing material

Abstract In order to explore the influence of cold heading equipment based on polyvinylidene fluoride (PVDF) polymer sensing material on steel ball stamping, a new method was proposed to reflect the defects of cold heading forming of steel ball by load signal. PVDF piezoelectric film is used as the sensor design of force and support structure of steel ball cold heading electromechanical sensor model. PVDF piezoelectric thin film force sensor is used for the structural optimization and simulation. The structural parameters affecting the natural frequency are numerically analyzed by MATLAB software. The mapping relationship between the external load and the output load of the sensor is obtained by using ANSYS software, and the simulation curve of the natural frequency of the sensor is compared with the theoretical curve to verify the factors affecting the natural frequency. The results show that the nonlinear error of sensors refers to the measured curve and the maximum deviation between the fitting line and the percentage of full-scale output.

Quantification of 3D spatiotemporal inhomogeneity for wake characteristics with validations from field measurement and wind tunnel test

To further understand the spatiotemporal inhomogeneity characteristics of wake profile caused by the inflow change of upstream wind turbine and reduce the influence of wake expansion on the power output and fatigue load of downstream wind turbine, a three-dimensional full wake model (3DJGF model) and a three-dimensional temporal wake model (3DJGF-T model) are proposed and verified in this paper. Assuming that the downstream wake distribution of wind turbine is double-Gaussian distribution, a new 3DJGF model is derived based on the law of conservation of mass and considering the wind shear effect. Based on the 3DJGF model, the time variable is introduced to calculate the delay time, and the 3DJGF-T model of the whole flow field is obtained. The accuracy of the proposed 3DJGF model and 3DJGF-T model is verified by wind field measurement and wind tunnel test, and the relative error of the 3DJGF-T model is analyzed: under the time-varying characteristics of different incoming wind speeds, the error of the newly proposed 3DJGF-T model is basically within 4%. The results show that the 3DJGF-T model can effectively describe the spatiotemporal inhomogeneity distribution and expansion characteristics of wake, which can provide a reference for the dynamic load analysis of downstream wind turbine considering the dynamic adjustment process of wind turbine control strategy, further improve the wake model and optimize the control strategy of wind turbine.

Design of a maximum power point tracking-based PID controller for DC converter of stand-alone PV system

Stand-alone photovoltaic system (PV) produces a variance in the output voltage under variable irradiation and temperature, and variable load conditions, resulting in control challenges. The research scope is to maintain a constant output load voltage despite variations in input voltage or load. The use of a DC converter ensures that the output voltage of such systems remains constant regardless of changes in the production voltage and load. The control on a DC boost converter is employed to solve this problem. This paper presents the design of a maximum power point tracking-based (MPPT) DC converter controller for such a system. The MPPT-based PID has been proposed as a control approach and implemented to the system DC converter. Incremental Conductance (IC) algorithm has been employed as an MPPT in association with an optimized PID. The Particle Swarm optimization technique (PSO) has been used to optimize the proposed PID through selected cost function. The PV system with the loaded converter is modeled and simulated using the MATLAB/Simulink environment. The system performance is displayed using a family of curves under different operating conditions and disturbances.

Low noise amplifier design with enhanced noise and gain performance using transformer boosting method for millimeter‐wave applications

AbstractIn low noise amplifier (LNA) design, achieving minimum noise figure (NF) and enhanced gain is equally important in the field of communication. The major aim of this design with previous methods are those having implemented in the topology of design like metal oxide semiconductor field effect transistor at common source connection topology, pole‐based transformer boosting, and dual feedback technique. However, these methods fail to reach the desired performance due to their low NF and low gain. In order to overcome these failures and their causes, this article presented a topology in LNA design using a transformer as boosting component to improve the performance of NF and gain for millimeter‐wave applications. It has three common gate stages connected in cascode form, and three transformers are acquired to link the drain to the input signal. Transformers permit radio frequency feeding signal from drain to source, and output from the previous stage is connected to the input of the next stage. This connection increases the gain of the circuit and an enlarged coupling coefficient of value “1,” which minimizes noise. The unilateral coefficient remains to be 1, to make the circuit stable throughout execution. NF value can be minimized by properly selecting conductance coefficient and S‐parameter values. Since the transformer is used to provide feedback in this circuit, stability condition has to be analyzed carefully. Output load value is selected optimum as it creates an impact on the stability of LNA. This topology implemented in LNA design helps to increase the gain by boosting the signal input, and hence, in turn, it increases overall gain performance. Similarly, while executing this optimal LNA design using transformer boosting technique in CADENCE software, this LNA exhibits a minimum NF of 3 dB at 30 GHz and power gain of 12.2 dB at 50 GHz in measurement. Comparatively, the proposed LNA design overruns conventional methods and consumes a power supply of 1.1 V.

Shared energy storage system for prosumers in a community: Investment decision, economic operation, and benefits allocation under a cost-effective way

With the rapid development of distributed renewable energy, energy storage system plays an increasingly prominent role in ensuring efficient operation of power system in local communities. However, high investment cost and long payback period make it impossible for prosumers to own the storage system. In this context, considering the complementarity of power generation and consumption behavior among different prosumers, this paper proposes an energy storage sharing framework towards a community, to analyze the investment behavior for shared storage system at the design phase and energy interaction among participants at the operation phase. Therefore, under the sharing mode that the operator invests and virtualizes physical storage system to provide virtual storage services for prosumers, this paper first establishes a two-stage optimization model. Based on a new storage sharing contribution rate index and asymmetric Nash bargaining model, a profit-allocation mechanism is designed. Then, combined with alternating direction method of multipliers, to achieve a mutual benefit and win-win situation. Finally, the above model is simulated by three buildings' realistic data, and the effectiveness of shared energy storage system is analyzed by using different technical and economic performance indexes. Additionally, the influence of battery cost, carbon tax, electricity price, and the uncertainties of renewable energy output power and load on shared storage system planning are also discussed. Numerical results show that, compared with personal energy storage scenario, the proposed storage sharing mechanism can achieve 6.09% cost savings, the self-consumption rate and self-sufficiency rate of renewable energy respectively increase by 5.01% and 5.21%, and all financial evaluation indexes have improved. In short, this paper can give practical guidelines for investors and prosumers to reasonably plan and share energy storage system, and provide realistic references for the government to effectively implement the shared energy storage.

Analysis and Design of a T/S Compensated IPT System for AGV Maintaining Stable Output Current Versus Air Gap and Load Variations

Inductive power transfer (IPT) technology for automatic guided vehicles wireless charging has widely drawn attention. The displacement of the air gap is inevitable due to tire pressure and spring deformation when vehicles are loaded with various weights. It can degrade the performance of the IPT system because the loosely coupled transformer parameters (self-inductances and mutual inductance) deviate from the designed values due to the position deviation of both sides’ ferrite cores. In this article, a parameter design method based on T-series (T/S) topology is proposed to maintain stable output current versus air gap and load variation. Then, the parameter design process of the T/S topology to improve air gap misalignment performance is elaborated. Finally, a 20 A/1 kW experimental setup was built to verify the validity. Experimental results show that the output current fluctuation is within 4.71% when the load varies from 1.2 to 2.4 Ω and the air gap decreases from 90 to 30 mm (primary self-inductance, secondary self-inductance, and mutual inductance increase by 4.71%, 30.22%, and 121.52%, respectively). Moreover, the overall output current fluctuation is less than 6% when the secondary side moves along the track with the air gap varying from 30 to 90 mm.

A 5G FR2 Power-Amplifier With an Integrated Power-Detector for Closed-Loop EIRP Control

A fifth-generation (5G) frequency range 2 (FR2) transmitter front end with a fully integrated power detector for enabling closed-loop power control is presented. The power detection path includes a miniature broad-side directional coupler, a sense pair, and a current-mode successive approximation analog-to-digital converter. The stacked power amplifier (PA) implemented in a 28-nm CMOS silicon on insulator (SOI) process delivers 12.5-dBm output power with a power-added efficiency of 10% and an error vector magnitude (EVM) lower than −25 dB with a CP-OFDM/64-QAM/400-MHz bandwidth signal. The PA supports 5G frequency bands n257/n258/n261 covering a frequency range from 24.25 to 29.5 GHz. With a matched output load, the power detector has less than ±0.15-dB error over a 15-dB power dynamic range and 85° temperature range.

High-Speed Searching of Optimum Switching Pattern for Digital Active Gate Drive to Adapt to Various Load Conditions

Digital active gate driving has been shown to effectively manage the switching performance for power devices with the adjustable driving waveforms. However, most of the studies are based on a dedicated test circuit rather than a practical inverter with the sinusoidal output current. In fact, it is the dependence on the load current that makes the design of the gate driving profiles a critical issue. To investigate the digital active gate driver in an inverter application, this article has applied optimal patterns adapting to time-varying output load current. Prior to the search of optimal patterns, the proper design of time slot is discussed with three different time resolutions. With the proper resolution determined for patterns, multiple optimizations are carried out for different current conditions. In this way, the search for optimal patterns can be completed in an efficient time. Next, a lookup table of optimal switching pattern in correspondence with each certain load current condition was built in advance. According to the output load current, the optimal pattern is selected based on the lookup table. Compared to conventional constant driving waveform, the power loss has been reduced by 7% with full optimal lookup table applied.

Performance Comparison of Silicon- and Gallium-Nitride-Based MOSFETs for a Power-Efficient, DC-to-DC Flyback Converter

Gallium Nitride (GaN)-based devices offer many advantages over conventional electronic devices, such as lower input/output capacitances, a higher switching speed, and a compact size, resulting in higher-density power outputs and reduced switching losses. This research investigates the power and switching efficiency of GaN-based FET in an active-clamp, DC-to-DC flyback converter for step-down application (24 V to 7 V) and compares it with silicon (Si)- based devices in the same circuit topology. The operation is analyzed under various input conditions and output loads such as R, RC, RL, and RLC. The proposed topology can achieve a maximum power-conversion efficiency of 99.6% and can operate at higher frequency values above 1 MHz. The presented GaN-based flyback model can replace conventional Si-based switches in power applications which require high power-efficiency and switching speed in a compact device.

Analysis and Design of Series-LC-Switch Capacitor Multistage High Gain DC-DC Boost Converter for Electric Vehicle Applications

Research into modern transportation systems is currently in progress in order to fully replace the traditional inter-combustible engine with a noiseless, fast, energy-efficient, and environmentally friendly electric vehicle. Electric vehicles depend on an electric motor and require highly efficient converter drive circuits. Among these converters, DC-DC boost converters play a major role in charging not only the battery banks but also in providing the DC-link excitation voltage in transformerless applications. However, the development of these converters, which have higher voltage and current gain with minimum components, minimum voltage, and current stress, is quite challenging. Therefore, this research work aims to address these issues and also to improve overall system performance. These aims are achieved by developing a series LC-based single-stage boost converter, and extending its gain through a multi-stage boost converter using switch capacitor phenomena. This article also presents a complete operating model in continuous conduction mode. The proposed converter is tested under various testing conditions, such as output loading, input voltage levels, and duty cycle ratio for a 50 W resistive load. The results are compared with existing models. The proposed converter is stated to have achieved the highest efficiency, i.e., 96.5%, along with extendable voltage gain with reduced voltage and current stresses, which is a major contribution to this research field.

Control Method for Improving Voltage Response and Ripple of Isolated DC-DC Converter

Affected by the abrupt changes of load and unregulated first-stage rectifiers, it is difficult for the output voltage of the isolated DC-DC converter with traditional proportional-integral (PI) control to meet the needs of industrial applications such as automotive electrophoretic painting. A voltage response improving the method based on a radial basis function neural network (RBFNN) is proposed in this study for the output voltage mutation of DC converter caused by load mutation. By detecting the output voltage deviation and load current value, the RBF model gives the compensation amount of the duty ratio to enhance the PI controller to speed up the voltage regulation and improve voltage response. For the six-pulse voltage ripple introduced by the unregulated rectifier in the previous stage, a delay link is adopted, where the compensation amount of the duty ratio and its delay time are reasonably designed to reduce the ripple value. The experimental test platform is built, and the proposed method is verified. The results show that the proposed method can effectively improve the output voltage response and ripple as well as improve the output voltage quality of the DC converter, which is of certain engineering application value.

A sliding mode control method based on improved reaching law for superbuck converter in photovoltaic system

Due to the influence of input voltage fluctuation, output load mutation, inductance and capacitance parameter perturbations, the DC bus voltage of photovoltaic power generation system will fluctuate accordingly. In order to maintain the stability of the bus voltage, a PID-type sliding mode control based on the improved reaching law is proposed. Using the saturation function sat(s), an improved fast reaching law is constructed to weaken the inherent chattering effect of sliding mode control, the finite time reachability property of the reaching law is verified, and the disturbance stability bound of closed-loop sliding mode control system in the presence of bounded disturbance is derived. Compared with PID control method and sliding mode control method based on power reaching law and exponential reaching law, the results show that the proposed control method weakens the influence of chattering, improves the dynamic response speed of the system by about 23% in the start-up stage. At the same time, the proposed control method has good dynamic performance and global robustness when subjected to external disturbances.

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.

Self-Powered Dual-Inductor MI-PSSHI-VDR Interface Circuit for Multi-PZTs Energy Harvesting

Vibration energy harvesting using multiple piezoelectric transducers (multi-PZTs) can increase its output power and environmental adaptability. At present, there are still few research articles on multi-input interface circuits for multi-PZTs, especially those using the parallel synchronized switching harvesting on inductor (PSSHI) technique. Therefore, this article presents a self-powered dual-inductor MI-PSSHI voltage doubler rectifier (VDR) interface circuit. It can process multi-PZT voltages with arbitrary phases input. The measurements demonstrate that the prototyped MI-PSSHI-VDR circuit can extract a peak power of 1.93 mW from four PZTs under an excitation of 1.5 g and 77.5 Hz. The energy integration efficiency and energy extraction efficiency of the prototyped circuit are 93.2% and 75.1%. Compared with a multi-input full-bridge rectifier, the proposed circuit can achieve 3.22× power improvement and 3.58× voltage improvement, which grasps a good balance between the indices of peak output power and load voltage range. Additionally, the MI-PSSHI-VDR circuit is easy to implement and shows a good scalability, which can be an alternative solution for multi-PZTs energy harvesting.

Analysis of the Spatial Distribution Characteristics of Livestock and Poultry Farming Pollution and Assessment of the Environmental Pollution Load in Anhui Province

Anhui Province is located in the eastern China, in the middle and lower reaches of the Yangtze River and Huaihe River, and contains three major basins, i.e., the Yangtze River, Huaihe River, and Xin’an River basins. Based on the statistical data of livestock and poultry quantity and farmland area in Anhui Province in 2019, ArcGIS was used to analyze the spatial distribution characteristics of the livestock and poultry excreta (LPE) pollutants in Anhui Province in order to explore the potential pollution risk posed by livestock and poultry farming to the farmland and the water environment in Anhui Province. The equivalent pollution load method was adopted to compare and assess the release of LPE pollutants in various cities and to analyze the causes. Through the calculation of the farmland carrying capacity load and early warning value of LPE and the water load of livestock and poultry pollutant release based on the equivalent pollution index method, a comprehensive assessment of the potential pollution risk posed by livestock and poultry farming on farmland and the water environment in Anhui Province was carried out. In this study, the spatial distribution of the livestock and poultry pollution in Anhui Province was analyzed, the effect of the pollution load of the livestock and poultry on the cultivated land and water environment was evaluated, and suggestions for environmental protection measures are provided. The results of this study revealed that the total pig equivalent of the livestock and poultry farming in Anhui Province was 55,068,400 and the LPE output was 47,778,600 t in 2019. The LPE pollutant output was 1,707,700 t, and the total release was 510,400 t. The release of pollutant chemical oxygen demand (COD) accounted for 71.67% of the total release. The average farmland load of the pig manure equivalent was 8.09 t/hm2 in the province. The average pollutant diffusion concentration of in the water was 31.63 mg/L. The average equivalent pollution index of LPE was 5.23, indicating a mild pollution impact on the water environment. Overall, the spatial distribution of the LPE pollutant output and pig manure equivalent farmland load in Anhui Province increased from south to north. Fuyang and Suzhou cities had a high risk of water environment pollution and should be the key regions for livestock and poultry pollution prevention and control measures. The optimization of the layout of livestock and poultry farming areas, smoothing the cycles of crop and livestock farming, and the vigorous promotion of the resource utilization of the LPE are proposed.