Optimal Efficiency Point Research Articles

Optimal efficiency point membership incorporating fuzzy logic and automatic control of various charging stages for electric vehicles

Introduction: The rapid development of electric vehicle technology in the field of renewable energy has brought significant challenges to wireless charging systems. The efficiency of these systems is crucial for improving availability and sustainability. The main focus of the research is to develop an intelligent charging strategy that utilizes fuzzy logic to optimize the efficiency of wireless charging systems for electric vehicles.Method: Introduce a model that combines fuzzy logic algorithm with automatic control system to improve the wireless charging process of electric vehicles. The model adopts dynamic tracking and adaptive control methods by analyzing the characteristics of static wireless charging systems. Utilizing primary phase shift control and secondary controllable rectifier regulation, combined with optimized fuzzy control algorithm.Result and discussion: The experimental results show that when the secondary coil is stable, the model maintains a stable duty cycle of about 75.6% and a stable current of 5A. It was observed that when the mutual inductance values were set to 10, 15, and 20 uH, the efficiency of the primary coil before applying control decreased with increasing resistance.Conclusion: The proposed system has shown great potential for application in real-world electric vehicle charging systems, demonstrating good applicability and feasibility in controlling the charging process and tracking the optimal efficiency point. The integration of fuzzy logic enhances the system’s ability to adapt to different operating conditions, which may lead to wider implementation and improved operational efficiency.

The impact of hump characteristics on variable speed pumped storage units under pump mode and improvement measures

The input power of variable speed pumped storage units (VSPSUs) under pump mode is adjustable, which effectively increases the units' frequency regulation capacity and ability during low demand periods in the power system, providing strong support for the stable operation of the grid. However, the operation of the VSPSU under pump mode is affected by the hump characteristics, which limits the regulation capability of the unit. Therefore, this paper analyzes the mechanism of the impact of the hump characteristics on VSPSUs and proposes an effective improvement measure. Firstly, on the basis of the pump on-cam curves, a simple and effective efficiency optimization method of the VSPSU under pump mode is proposed. Then, based on the characteristics of the hump region, the relationship between the optimal efficiency points and the hump characteristics is obtained, revealing that the hump characteristics affect the operating conditions of the variable speed units under any head. Subsequently, a novel nonlinear model of the pump-turbine is proposed based on the basic characteristic curves of various openings under pump mode to solve the multi-value phenomenon, and the influence mechanism of hump characteristics on pump mode of VSPSU from a control perspective is obtained. Finally, an improvement measure is proposed to modify the optimal efficiency points by setting operating safety margins, and the sub-optimal efficiency point that is not affected by the hump characteristic at the same input power is used to replace the optimal efficiency point that is affected by the hump characteristic to avoid the impact of the hump characteristic. Compared to the method of setting hump characteristic limit, the adjustment range of the VSPSU under pump mode is greatly increased.

FPP'DEN CPP'YE DÖNÜŞTÜRÜLEN BİR PERVANENİN HİDRODİNAMİK PERFORMANSININ SAYISAL İNCELENMESİ

Present paper investigates the hydrodynamics of a Controllable Pitch Propeller (CPP) which is generated by geometrical modifications applied on a benchmark propeller designed as a fixed pitch propeller (FPP). The aim of the study is to examine the practical feasibility of converting a propeller model designed as a FPP to a new one operating with CPP principles. The flow around propeller models is solved via computational fluid dynamics and the results of the new generated model are presented in comparison with its parent geometry. The well-known KP505 propeller model is chosen as test case. The primary results show that the effect of the geometrical modifications on the propeller efficiency mainly depends on the propeller load and the blade pitch angle. The optimum efficiency point is determined as J=0.8, for the new design model. For the J values below this point, negative pitch angle changes improve the efficiency compared to FPP model. If the J exceeds the above mentioned value, positive pitch angle changes are needed to gain efficiency increase. The results led us to conclude that, it’s possible to convert a FPP to a CPP, but the blade pitch angle should be carefully controlled, for efficient operation

Efficiency optimization for phase‐shifted full‐bridge converter with variable frequency control

AbstractIn this paper, a control method combined with variable frequency and phase shifting is proposed, the primary purpose of which is to optimize the operating efficiency of the phase‐shift full‐bridge (PSFB) DC‐DC converter. By modeling the losses of the PSFB converter, the optimal switching frequency related to the load conditions is found. A neural network aided variable frequency controller that can work linearly is built to achieve the proposed method. At the same time, the voltage control loop is retained to ensure the stability of the output voltage and the necessary dynamic response of the converter. This paper builds an experimental platform for a 2 kW PSFB DC‐DC converter to verify the effectiveness of the proposed control method. With the control method proposed in this paper, the PSFB converter can always work at the optimum efficiency point under different load conditions. In addition, this paper also analyzes the influence of variable frequency control on PSFB operating states, such as zero‐voltage‐switching (ZVS) constraints, continuous conduction mode (CCM) operating states, and power density, which have an impact on its operating conditions.

Optimizing Energy Efficiency for Connected and Autonomous Electric Vehicles in the Context of Vehicle-Traffic Interaction

The operational efficiency of connected and automated electric vehicles (CAEVs) is significantly impacted by the interplay between vehicle dynamics and traffic conditions. This study presents an energy-conscious optimization (ECO) approach aimed at enhancing the energy efficiency of CAEVs. This is achieved by addressing the dynamic constraints of the traffic environment and the vehicle's powertrain limitations within a unified framework. To develop the ECO approach, a novel bias deep compensative estimator is introduced to determine the parameters of the vehicle dynamics model. Utilizing these identified parameters, the traffic environment's constraints are translated into corresponding powertrain constraints for CAEVs. In the pursuit of optimal energy efficiency while adhering to powertrain limitations, a fresh velocity-torque coordinate system is established to normalize the constraints. Additionally, an iterative neighborhood search algorithm is proposed to systematically explore the coordinate system and identify the optimal efficiency point. With this newfound optimal efficiency point, a torque tracking control strategy is formulated. This strategy serves to guide the electric powertrain, ensuring its operation within the high-efficiency region. Real-world experiments are conducted to validate the effectiveness of the proposed approach, with a direct comparison against two prevailing state-of-the-art methods.

Efficiency improvement of dual active bridge converter using simple graphical optimization method

SummaryAiming to the problems of high circulating current and low efficiency caused by the traditional strategy of dual active bridge (DAB) converter under light load, in this paper, simple graphical optimization method (GSO) is proposed to improve the efficiency of dual active bridge converter. Through the contour plot of transmission power and current stress, optimal efficiency point can be obtained by tangent of contour map under condition of constant power, and heavily calculation or complex iterations of existing conventional control strategies are avoided. Moreover, analysis of proposed graphical current stress optimization is addressed, and controller design of proposed method is given and described. Efficiency comparison between traditional modulation strategy and GSO is given to show the advantage of proposed mothed. An experimental prototype is built to verify the analysis.

Critical decision making for rehabilitation of hydroelectric power plants

ABSTRACT Due to their diminishing performance, reliability, and maintenance requirements, there has been a rise in the demand for the restoration and renovation of old hydroelectric power facilities in recent decades. Prior to initiating a rehabilitation program, it is crucial to establish a comprehensive understanding of the power plant’s current state. Failure to do so may result in unnecessary expenses with minimal or no improvements. This article presents a systematic rehabilitation methodology specifically tailored for Francis turbines, encompassing a methodological approach for condition assessment, performance testing, and evaluation of rehabilitation potential using site measurements and CFD analysis, and a comprehensive decision-making process. To evaluate the off-design performance of the turbines, a series of simulations are conducted for 40 different flow rate and head combinations, generating a hill chart for comprehensive evaluation. Various parameters that significantly impact the critical decision-making process are thoroughly investigated. The validity of the reverse engineering-based CFD methodology is verified, demonstrating a minor difference of 0.41% and 0.40% in efficiency and power, respectively, between the RE runner and actual runner CFD results. The optimal efficiency point is determined at a flow rate of 35.035 m3/s, achieving an efficiency of 94.07%, while the design point exhibits an efficiency of 93.27% with a flow rate of 38.6 m3/s. Cavitation is observed in the turbine runner, occupying 27% of the blade suction area at 110% loading. The developed rehabilitation methodology equips decision-makers with essential information to prioritize key issues and determine whether a full-scale or component-based rehabilitation program is necessary. By following this systematic approach, hydroelectric power plants can efficiently address the challenges associated with aging Francis turbines and optimize their rehabilitation efforts.

Large-Strain Consolidation of Sludge in Multiple-Drainage Geotextile Tubes

This paper presents a profound solution for a novel method of dewatering dredged sludge using a combined geotextile tube and vacuum-assisted prefabricated horizontal drains. Firstly, an analytical model was proposed to provide a basis for the design of the proposed approach. This two-dimensional plane-strain consolidation model was based on Gibson’s large-strain theory, incorporating the horizontal and vertical flows with consideration of the self-weight, nonlinear compressibility, and hydraulic conductivity of soil. Secondly, the numerical solution obtained using the alternative direction implicit method was compared with the existing one-dimensional model for verification. Thirdly, a field trial was carried out to evaluate the performance of the proposed approach and analytical model. Finally, the effects of various major design parameters on the consolidation efficiency of the tube system were also investigated through a parametric study to establish an optimal design. This study showed that a higher consolidation efficiency and an earlier optimal efficiency point could be achieved when decreasing the horizontal drain interval and increasing the tube height. Furthermore, surcharge preloading induces a more significant effective stress increment in soil than vacuum preloading of the same magnitude.

Prediction of hydrodynamic noise in ducted propeller using flow field-acoustic field coupled simulation technique based on novel vortex sound theory

As one of the primary noise sources of underwater-robots, the hydrodynamic-noise of the ducted-propeller (DP) originates from various unsteady flows in the flow-field. To investigate the coupling-mechanism between the flow-field and the acoustic-field of DP, this paper establishes a three-dimensional flow field-acoustic field coupling numerical calculation model based on the vortex-acoustic equation. It combines simulation and experimental research to investigate the unsteady flow-field of the DP. The mechanism of acoustic-wave generation and the distribution characteristics of the acoustic field are studied, and the DP's propagation law of hydrodynamic-noise is analyzed based on the field-synergy theory. The results show that the DP domain's vortex structure is mainly influenced by the tensile-distortion and Coriolis-force term. However, hydrodynamic-noise generation is closely related to the vortex, turbulent pulsation, and other unstable flows in the flow-field. The radiated noise of the propeller decreases and then increases with the increase of the inlet velocity-coefficient (IVC) and is smallest at the optimal efficiency point (J = 0.6). With the increase of IVC, the synergy of the propeller flow field-acoustic field is enhanced, the energy-loss of acoustic transmission increases, and the far-field radiation noise decreases. This paper provides a theoretical reference for suppressing the hydrodynamic-noise of the DP and acoustic-optimization design of the underwater-robots.

Study on the blade squealer tip affecting tip leakage flow and performance of a multiphase pump

Tip clearance is the distance required between the blade tip and the pump body wall of an impeller in a helicon-axial multiphase pump, which tends to induce tip leakage flow. The tip leakage vortex formed by the interaction of tip leakage flow with the mainstream can seriously affect the performance of the multiphase pump. To minimize the adverse effects of tip leakage flow in the multiphase pump, a method to design a squealer tip on the impeller blade is proposed in this paper. The effect of the squealer tip on external characteristics, tip clearance flow characteristics, and energy dissipation of the multiphase pump is analyzed. Research results indicate that the blade squealer tip can effectively improve hydraulic efficiency of the multiphase pump. At the optimal efficiency point, the head and hydraulic efficiency of the multiphase pump with a squealer tip increased by 3.62% and 4.15%, respectively, compared with the original model. The influence of tip leakage flow in the axial rear half passage of the multiphase pump impeller is far greater than that in the axial forward half passage, especially on the back position in the middle of the impeller passage. The squealer tip can restrain the reverse of leakage flow from the pressure side to the suction side of the impeller blade, and the clearance leakage flow of the model with a squealer tip is smaller than that of the original model. The squealer tip on blade will reduce the energy dissipation caused by unsteady flow in the mainstream. The research results in this paper can provide theoretical support for effectively restraining the influence of the tip leakage vortex on the mainstream of the helicon-axial multiphase pump and contribute to engineering practice value of improving the performance of the multiphase pump.

Maximum efficiency tracking design of wireless power transmission system based on machine learning

For the typical magnetically coupled wireless power transmission system, power consumption is often caused by the impedance effect of the primary and secondary sides, the loss and heat generation of the actual semiconductor devices and the change of the coupling coefficient caused by distance. The uncertainty of frequency tracking efficiency caused by high enough coil transmission with low load receiving efficiency and load impedance changes makes it difficult to stabilize the output of the optimal efficiency point of the system. In order to solve this problem, a wireless power transmission system is proposed based on the traditional wireless power transmission system a wireless power transmission system is proposed to predict and stabilize the variable impedance, so as to stably track the efficiency of the system in the resonant frequency range. It is not affected by load jitter, actual circuit parameters and environmental disturbance. The test results show that the transmission efficiency of tracking frequency and predicting impedance can be realized at a certain distance, and the difference between the prediction error and the actual efficiency is about 1%–3%.

Comparative evaluation of the pump mode and turbine mode performance of a large vaned-voluted centrifugal pump

Large vaned-voluted centrifugal pump is a general machine used for large-scale water diversion. As a vane-type hydraulic machinery, it also has the ability of reversible operation. With the introduction of policies to reduce carbon emissions, the proportion of unstable new energy use has increased. The existing large centrifugal pump unit can realize the function of reverse power transfer. For peak shaving and valley filling of power grid, it has high feasibility and economy. In this paper, a large vaned-voluted centrifugal pump is simulated numerically, it is external characteristics and flow state under positive and negative rotation are obtained, its performance is predicted by best efficiency point method, and it is found that pump reversal can run at the optimum efficiency point with higher flow rate and head. Error analysis is carried out for different formulas. The flow energy dissipation (FED) of different flow rates under positive and negative rotation is analyzed. It is found that the main energy loss locates on suction side of blade, inlet and outlet part of blade and tail part of guide blade head. By comparing the flow energy dissipation distribution under the same flow conditions with positive and reverse rotation, it is found that the high energy loss area of blade mainly exists in inlet and outlet part of blade in pump mode. The high energy loss area of the blades in turbine mode mainly exists in the inlet part of the blades. This study is of great significance to the operation of low-carbon power grid assisted by existing reservoirs and hydraulic machinery.

A Novel Torque Matching Strategy for Dual Motor-Based All-Wheel-Driving Electric Vehicles

The market for electric vehicles is growing rapidly. Among them, the demand for a dual motor type 4 WD (Four -Wheel Driving) system is increasing. In this paper, we present the Torque Matching Strategy (TMS) method to select the optimal torque distribution ratio for dual motors. The TMS controller operates to set the optimal efficiency point by linearizing the drive efficiency combination of the two motors. Driving simulation and testing were performed through five drive cycles in the driver model interworking environment implemented in MATLAB and Carsim. The optimal distribution ratio was derived according to the front and rear gear ratios under the load condition, and the driving was verified by comparing it with the TMS control method. The efficiency was numerically verified by comparing the power loss of the driving motor. It reduced up to 34% in Urban Dynamometer Driving Schedule and up to 56.3% in Highway fuel efficiency test. The effectiveness of the TMS control method was demonstrated through the distribution rate trend based on the operation cycle and power loss.

Research of Particle Motion in a Two-Stage Slurry Transport Pump for Deep-Ocean Mining by the CFD-DEM Method

The slurry transport pump is the key equipment of deep-ocean mining systems. The motion law of coarse particles in the pump is not clear enough. In this paper, a hydraulic model of a laboratory-scale two-stage slurry transport pump is constructed, and the motion characteristics of coarse particles in the pump are numerically studied by using the computational fluid dynamics–discrete element method (CFD-DEM) method. The performance curve of the pump is obtained by experimental measurement, and the reliability of the calculated results is verified. Due to the application of the amplification flow rate design method, the optimum efficiency point of the pump is shifted to the large flow rate condition. Differences in particle swarm within two stages are compared. The position distribution, velocity variation and trajectory of particles in the impeller and bowl diffuser are studied in detail. The velocity of particles leaving the impeller depends on whether they collide with the impeller blade. The motion of particles in the bowl diffuser is divided into three periods. Collision between particles and blades in the bowl diffuser not only leads to energy loss but also gradually transforms the circumferential velocity of particles into axial velocity in the second period. This work can provide a reference for the study of wear and blockage prevention of slurry transport pumps.

Quasi-Omnidirectional Wireless Power Transfer for a Sensor System

The wireless sensor networks play a vital role in the field of monitoring, which can be powered by the wireless charging technology. In this paper, we reported a sensor node charging system via Omni-directional magnetic coupling resonant technology based on the application background of using the unmanned aerial vehicle (UAV) for wireless charging in a hazardous industrial environment. The system on the UAV can charge rapidly the battery on the wireless sensor nodes in the high-risk working environments when the battery capacity is below the threshold. The system can select two most suitable transmitter (TX) coils to charge for the sensor nodes by the feedback control circuit based on the sensor node location. Angle misalignment of the transmitter coils is a problem for many practical applications. Therefore, And we also models and analyzes the transmitter coil deviations to meet the angle misalignment during actual applications. The efficiency variation caused by the deflection of the transmitting coil and the offset of the optimal operating point are analyzed. The result shows that the optimal efficiency point will change as the coil is deflected. Controlling the UAV to the optimal efficiency point can reduce the influences of the non-orthogonal transmitter coil on the efficiency. Moreover, the experiments show that the system achieves a maximum output power of 12 W. Thus, this system can be a good candidate for the power supply of wireless sensor nodes working in a special environment.

Comparison of Basic Inductive Power Transfer Systems With Linear Control Achieving Optimized Efficiency

Inductive power transfer (IPT) systems with front-side and load-side converters are generally developed for better overall system efficiency than a single IPT converter by providing maximum efficiency tracking and output regulation against variations of coupling coefficient ( $k$ ) and load. The optimum efficiency point of an IPT converter is at a particular loading resistance, which varies with $k$ and is hard to measure directly for the purpose of control. Perturb and observe control is normally implemented to iteratively track the optimum efficiency point. However, this heuristic algorithm results in slow response to the variations of $k$ and load. Recently, a much faster linear control for optimum efficiency tracking has been developed for the series-series (SS) IPT system only. This paper proposes a general linear control scheme for all four basic IPT systems to track the optimum efficiency point. Unlike the SS IPT converter, it is found that additional control of either frequency or adaptive compensation is needed for the other three basic IPT converters to operate against the variation of $k$ . Different input to output transfer functions and their $k$ - and load-independent properties at optimum efficiency are identified for all four basic IPT systems. Thus, a general fast linear control can be applied in the front-side converter to achieve optimum efficiency, while the load-side converter regulates the output power independently. Furthermore, the maximum efficiencies of the IPT converters with these four basic compensations for an identical loosely-coupled transformer are compared theoretically and verified experimentally. The parallel–parallel IPT converter gives the best efficiency. Its additional frequency control in conjunction with the optimum efficiency tracking and the output power regulation is also experimentally validated.

The Evolving Value of Photovoltaic Module Efficiency

PV research is making efforts to create new cell and module efficiency records, while the manufacturing industry and the downstream project developers want to choose the optimal efficiency point where the best economics can be achieved at the system level. In this paper, we define representative system cost structurers for various applications in 2018 and quantify the value of greater module efficiency in lowering the levelized cost of electricity (LCOE). With the transparent methodology, we also extended the analysis into the future until 2025. As the value of module efficiency resides in non-module costs and the non-module costs will account for a higher percentage for a PV system in the future, industry will develop stronger motivation to adopt more efficient modules. Specifically, we examined the economics of bifacial modules and forecast that its market share would grow from 3% in 2018 to 40% in 2025.

Experimental Investigation of Unsteady Characteristics in a Single-Channel Pump

Abstract Single-channel pumps are a specific type of centrifugal pump that is widely used in the sewage treatment of raw wastewater and effluent pumping applications. In single-channel pumps, the rotor–stator interactions may generate unbalanced pressures that change during one impeller revolution. A specific experiment rig was constructed to investigate the unsteady characteristics synchronously, including energy performance, head pulsation, pressure pulsation, and radial force. It was found that the difference between the maximum and minimum head was greater than 5 m under all flow rates during a rotation period. With the increase of the flow rate, the head reached its minimum value slowly and achieved its maximum value more quickly. The static pressure distribution at the impeller outlet was the most uniform at 1.0Qd. The high-pressure region located initially downstream of the tongue gradually moved toward the upstream end of the tongue with an increase in the flow rate. When the blade outlet goes through the tongue, the pressure pulsation appears at its peak at the eighth cross section of the volute. The peak position moves toward the upstream with the rotation of the impeller. In the single-channel pumps, the absolute pressure pulsation achieved its peak at the blade passing frequency, and the pressure pulsation amplitude for fBPF varied gradually with an increase in the flow rate. The radial force reached a minimum value near the optimal efficiency point and its direction was mostly downstream of the tongue. To meet the hydraulic balance of the impeller, it was suggested that a balance piece be adapted to counteract the radial force.

ASSESSMENT OF PUMP’S PERFORMANCE IN WATER SUPPLY SYSTEMS – DATA COLLECTED FROM MULTIPLE CASE STUDIES

This paper reports the evaluation of pump’s efficiencies and its optimization potential, in three water supply systems. The study surveyed 65 pumps groups, from 24 pumping stations, between 5 to 350 kW of absorbed power, with flow rates from 25 to 1500 m3/h. The performance of the pumps, was assessed by testing each pump group in different operational conditions. It was quantified, for each pump group, the specific consumption (kWh/m3) and cost (€/m3) as well as the difference between the optimum efficiency point, for the specific net head of each installation, and their actual operating point. The identified energy inefficiencies and proposed corrective measures for each pump group were compiled in order to improve their efficiency. Most problems identified are oversized groups, valve problems and inadequate operational working points. On average the surveyed pump’s efficiencies were 10 percentage points below their reference values. In order to reduce the gap several improvement measures were proposed, such as the refurbishment of the pumps, impeller adjustments, variable speed drive installation and the extension of the working periods with lower frequency regimes, where high efficiencies were identified. The implementation of these improvement measures has an energy saving potential of 331 MWh/year, which means 27.000 €/year.

Performance optimization of a regenerative Brayton heat engine coupled with a parabolic dish solar collector

In this study, a detailed thermodynamic analysis of a regenerative Brayton heat engine cycle coupled with a parabolic-dish solar collector is conducted. The analysis examines the thermal performance of the coupled system for power generation applications. Important non-dimensional parameters that govern the optimized performance of the coupled system are identified. The efficiency of the coupled system is expressed in terms of three parameters namely the Brayton cycle pressure ratio, the concentration ratio of the parabolic dish collector, and the maximum temperature ratio of the Brayton cycle. The efficiency of the coupled system is then optimized with respect to the aforementioned parameters by solving the resultant system of three coupled non-linear algebraic equations using a MATLAB(R) program. Optimal values for Brayton cycle pressure ratio, concentration ratio of the parabolic dish collector, and maximum temperature ratio of the Brayton cycle are obtained corresponding to the optimal efficiency of the coupled system. Effects of variation of heat exchanger efficiency, total concentrator error, rim angle and non-dimensional radiation flux parameter on the optimal performance of the coupled system are investigated. Impact of these parameters on the engine size is also presented. In addition, a procedure for preliminary design of the coupled system using performance charts is developed. Results are presented in the form of performance charts that display the effects of changing the heat exchanger efficiency, total concentrator error, rim angle and non-dimensional radiation flux parameter on the optimal efficiency of the coupled system. The analysis show that higher optimal efficiency of the coupled system is achieved for lower values of total concentrator error and higher values of the heat exchanger efficiency. It is also seen that a solar thermal power generation system using the regenerative Brayton cycle results in migration of the optimal efficiency point towards lower values of engine pressure ratio.