Maximum Power Load Research Articles

Twin-rotor hover performance examination using overlap tests

PurposeThe aim of this paper was to experimentally examine twin-rotor hover performance for different rotor overlap ratios at practical rotor loading.Design/methodology/approachThe methodology was formed based on data measurements for a designed twin-rotor test model and development of hover performance mathematical models. Thus, measurements were made using a central composite test plan, and then mathematical models for thrust power required power loading (PL) and figure of merit (FM) as functions of collective pitch tip speed; rotor overlap ratio was obtained. In the present paper, the test model consisted of two three-bladed rotors with a diameter of 220 mm and a blade aspect ratio of 16.05. The blades were of a rectangular planform with NACA 0012 cross sections and had no twist or taper. The model was built such that the rear rotor was fixed on the fuselage, and the front rotor could move longitudinally for tests up to about 40 per cent overlap ratio in hover.FindingsThe best hover aerodynamic efficiency (maximum PL of 14.6 kg/kW) was achieved for non-overlapped rotors at a low value of disc loading (DL) and also at FM of 0.6 at that DL. This result was in agreement with blade element momentum theory predictions.Practical implicationsResults for the twin-rotor test model can be generalized for actual tandem helicopters through the Reynolds number transformation technique and also some modifications.Originality/valueDesign and construction of the twin-rotor test model and experimental measurements of hover performance based on an optimal test plan were performed for the first time.

Modeling and Experimental Verification of an Electromagnetic and Piezoelectric Hybrid Energy Harvester

This paper describes mathematical models of an electromagnetic and piezoelectric hybrid energy harvesting system and provides an analysis of the relationship between the resonance frequency and the configuration parameters of the system. An electromagnetic and piezoelectric energy harvesting device was designed and the experimental results showed good agreement with the analytical results. The maximum load power of the hybrid energy harvesting system achieved 4.25 mW at a resonant frequency of 18 Hz when the acceleration was 0.7 g, which is an increase of 15% compared with the 3.62 mW achieved by a single electromagnetic technique.

Energy conversion by ‘T-shaped’ cantilever type electromagnetic vibration based micro power generator from low frequency vibration sources

The design, development, and analyses of low-frequency vibration based T-shaped cantilever type electromagnetic micro power generators (EVMPGs) are presented in this paper. Four different configurations (Configurations A to D) of EVMPGs were designed and fabricated and subsequently characterized using detailed experimental and limited analytical techniques. Configuration A and B consisted of a single and a double cylindrical moving magnets (NdFeB), respectively, while Configuration C consisted of four rectangular moving magnets with respect to a fixed copper coil. In contrast, Configuration D used a moving coil between four rectangular magnets with a back-iron bar. The open circuit RMS voltage output was observed to be a maximum from Configuration D (98.2mV at 6.29Hz) with a base vibration acceleration of 0.8ms−2. Therefore, Configuration D was selected for further experimental investigations, which included changing the back-iron bar thickness, changing the base acceleration level, and changing the air gap separation between the magnets in order to optimize this configuration. The maximum load RMS voltage and power outputs of Configuration D were 105.4mV and 1.35mW at 6.29Hz for load resistance 8.2Ω and a base acceleration of 0.8ms−2 with a 4.2mm back-iron bar when the air gap between the magnets was 20mm. Finally, a small portable EVMPG prototype was developed based on the Configuration D and was tested at different human movement conditions (i.e., walking, quick walking, and running). The developed EVMPG prototype was capable of harvesting 35.2mV and 0.22mW at 7Hz with load resistance 5.6Ω for a base acceleration of 0.8ms−2.

General Top/Bottom-Plate Charge Recycling Technique for Integrated Switched Capacitor DC-DC Converters

Energy loss due to top/bottom plate parasitic capacitances is one of the factors determining the efficiency of integrated switched capacitor DC/DC converters. This loss is particularly significant when MOS gate or deep trench capacitors are used. We propose a technique for top/bottom-plate charge recycling that can be applied with low overhead independently of the converter architecture. Two examples of application of the technique are presented. First, it is shown how the technique can be applied to any converter by transforming it to an interleaved implementation. This approach is demonstrated in a series-parallel 1/3 down converter achieving a maximum load power of 240 μW. Simulation results show an improvement of 7% in the efficiency by decreasing the top/bottom-plate parasitic capacitance losses by 52%. The second example considers an architecture where the proposed technique can be directly applied without additional transformations of the converter implementation. It is a ring modular architecture converter, which was fabricated in a 130 nm CMOS process. An efficiency improvement of up to 4% was achieved in measurements by reducing the top/bottom plate losses by 70%, thus reaching an outstanding efficiency of 80.6% at a conversion ratio of 2/3 and a maximum load power of 2.2 mW.

Design, optimization and test of an electromagnetic vibration energy harvester for industrial wireless sensor networks

To scavenge vibration energy from industrial application environments and supply power to wireless sensor networks, this paper proposes an electromagnetic vibration energy harvester (VEH) using an optimized transducer. The VEH consists of a planar spring, an axially magnetized magnet assembly, a coil assembly and an outer casing. An analytical model is proposed to analyze and optimize the electromagnetic transducer and improve its energy harvesting performance. Finite element analysis is then used to verify the model. An optimized prototype is manufactured and fabricated, and finally tested by experiment. The experimental results indicate that an open-circuit voltage of 2.2 V can be achieved when the VEH is excited by the vibration with a resonant frequency of 22.4 Hz and an acceleration amplitude of 100 mg. When the optimal resistor of 200 Ω is connected to the coil assembly, its maximum load power of 0.29 mW can be achieved, which can meet the needs of many industrial sensors as well as wireless communication modules and guarantee their intermittent work at least.

Jump Squat is More Related to Sprinting and Jumping Abilities than Olympic Push Press.

The aim of this study was to test the relationships between jump squat (JS) and Olympic push press (OPP) power outputs and performance in sprint, squat jump (SJ), countermovement jump (CMJ) and change of direction (COD) speed tests in elite soccer players. 27 athletes performed a maximum power load test to determine their bar mean propulsive power (MPP) and bar mean propulsive velocity (MPV) in the JS and OPP exercises. Magnitude-based inference was used to compare the exercises. The MPV was almost certainly higher in the OPP than in the JS. The MPP relative to body mass (MPP REL) was possibly higher in the OPP. Only the JS MPP REL presented very large correlations with linear speed (r>0.7, for speed in 5, 10, 20 and 30 m) and vertical jumping abilities (r>0.8, for SJ and CMJ), and moderate correlation with COD speed (r=0.45). Although significant (except for COD), the associations between OPP outcomes and field-based measurements (speed, SJ and CMJ) were all moderate, ranging from 0.40 to 0.48. In a group composed of elite soccer players, the JS exercise is more associated with jumping and sprinting abilities than the OPP. Longitudinal studies are needed to confirm if these strong relationships imply superior training effects in favor of the JS exercise.

Generalized Models on Self-Decoupled Dual Pick-up Coils for Large Lateral Tolerance

Self-decoupled dual pick-up coils for large lateral tolerance and low electromagnetic field for pedestrians are proposed. Analytical models are developed that are applicable to any self-decoupled coils, regardless the coil types such as single/dual pick-ups and core/coreless coils. An optimum decoupling distance between adjacent pick-up coils is determined and found to be independent of the existence of a core plate. Maximum load power over a large lateral tolerance is obtained for the optimum decoupling distance. The proposed models are so general that they can be applied to any self-decoupled pick-up coils for stationary charging and dynamic charging systems. Moreover, the self-decoupled coils are compatible with any compensation method such as serial, parallel, and serial–parallel. A prototype system of 1.5 kW and $Q = 60$ for roadway powered electrical vehicles was implemented and showed fairly good agreements with the theoretical models and simulations. The measured lateral tolerance was 90 cm, which is about 1.5 times of the coil width.

Vehicle Sensor Self-Powered Technology Research Based on Piezoelectric

As a result of the electric vehicles popularity and the development of vehicles intelligent, the number of vehicle sensors surge, meanwhile, many defects of traditional energy supply are increasingly prominent, such as pollution and maintenance difficulties. Taking into account the vehicle vibration exist everywhere, we use the piezoelectric technology to collect vibration energy, and designs a piezoelectric vibration energy harvesting system to be used to solve the energy problem of micro-power sensor. In this paper, the system structure and the theoretical model are analyzed, and the mathematical model of the system vibration frequency and the piezoelectric output have been put forward, then a piezoelectric energy harvesting device is designed on the basis of simulation analysis. Experiments have been done to test the performance of its power generation in the case of resonance. The results showed that the theoretical model proposed in this paper can be a good predictor of the output characteristics of the system. As the resonance frequency is 16.5 Hz, acceleration is 0.5g, the maximum open circuit voltage of the system obtained is 3.5 volts, the optimum load resistance is 425kΩ, and the vibration energy collection device maximum load power is 14 uW. Conclusion: Greater energy could be caught to meet the vehicle sensor power supply needs with the use of super capacitor.

Vehicle Sensor Self-Powered Technology Research Based on Piezoelectric

As a result of the electric vehicles popularity and the development of vehicles intelligent, the number of vehicle sensors surge, meanwhile, many defects of traditional energy supply are increasingly prominent, such as pollution and maintenance difficulties. Taking into account the vehicle vibration exist everywhere, we use the piezoelectric technology to collect vibration energy, and designs a piezoelectric vibration energy harvesting system to be used to solve the energy problem of micro-power sensor. In this paper, the system structure and the theoretical model are analyzed, and the mathematical model of the system vibration frequency and the piezoelectric output have been put forward, then a piezoelectric energy harvesting device is designed on the basis of simulation analysis. Experiments have been done to test the performance of its power generation in the case of resonance. The results showed that the theoretical model proposed in this paper can be a good predictor of the output characteristics of the system. As the resonance frequency is 16.5 Hz, acceleration is 0.5g, the maximum open circuit voltage of the system obtained is 3.5 volts, the optimum load resistance is 425kΩ, and the vibration energy collection device maximum load power is 14 uW. Conclusion: Greater energy could be caught to meet the vehicle sensor power supply needs with the use of super capacitor.

Maximum power output and load matching of a phosphoric acid fuel cell-thermoelectric generator hybrid system

Based on the current models of phosphoric acid fuel cells (PAFCs) and thermoelectric generators (TGs), a new hybrid system is proposed, in which the effects of multi-irreversibilities resulting from the activation, concentration, and ohmic overpotentials in the PAFC, Joule heat and heat leak in the TG, finite-rate heat transfer between the TG and the heat reservoirs, and heat leak from the PAFC to the environment are taken into account. Expressions for the power output and efficiency of the PAFC, TG, and hybrid system are analytically derived and directly used to discuss the performance characteristics of the hybrid system. The optimal relationship between the electric currents in the PAFC and TG is obtained. The maximum power output is numerically calculated. It is found that the maximum power output density of the hybrid system will increase about 150 Wm−2, compared with that of a single PAFC. The problem how to optimally match the load resistances of two subsystems is discussed. Some significant results for practical hybrid systems are obtained.

Urban Saturated Power Load Analysis Based on a Novel Combined Forecasting Model

Analysis of urban saturated power loads is helpful to coordinate urban power grid construction and economic social development. There are two different kinds of forecasting models: the logistic curve model focuses on the growth law of the data itself, while the multi-dimensional forecasting model considers several influencing factors as the input variables. To improve forecasting performance, a novel combined forecasting model for saturated power load analysis was proposed in this paper, which combined the above two models. Meanwhile, the weights of these two models in the combined forecasting model were optimized by employing a fruit fly optimization algorithm. Using Hubei Province as the example, the effectiveness of the proposed combined forecasting model was verified, demonstrating a higher forecasting accuracy. The analysis result shows that the power load of Hubei Province will reach saturation in 2039, and the annual maximum power load will reach about 78,630 MW. The results obtained from this proposed hybrid urban saturated power load analysis model can serve as a reference for sustainable development for urban power grids, regional economies, and society at large.

Composite piezoelectric spinal fusion implant: Effects of stacked generators.

Spinal fusion surgeries have a high failure rate for difficult-to-fuse patients. A piezoelectric spinal fusion implant was developed to overcome the issues with other adjunct therapies. Stacked generators were used to improve power generation at low electrical load resistances. The effects of the number of layers on average maximum power and the optimal electrical load resistance were characterized. The effects of mechanical preload, load frequency, and amplitude on maximum power and optimal electrical load resistance were also characterized. Increasing the number of layers from one to nine was found to lower the optimal electrical load resistance from 1.00 GΩ to 16.78 MΩ while maintaining maximum power generation. Mechanical preload did not have a significant effect on power output or optimal electrical load resistance. Increases in mechanical loading frequency increased average maximum power, while decreasing the optimal electrical load resistance. Increases in mechanical loading amplitude increased average maximum power output without affecting the optimal electrical load resistance.

Design, Simulation, and Optimization of a Frequency-Tunable Vibration Energy Harvester That Uses a Magnetorheological Elastomer

This study focuses on the design, simulation, and load power optimization for the development of a novel frequency-tunable electromagnetic vibrational energy harvester. The unique characteristic of a magnetorheological elastomer (MRE) is utilized, that the shear modulus can be varied by changing the strength of an applied magnetic field. The electromagnetic energy harvester is fabricated, the external electric circuit is connected, and the performance is evaluated through a series of experiments. The resonant frequencies and the parasitic damping constant are measured experimentally for different tuning magnet gap distances, which validate the application of the MRE to the development of a frequency-tunable energy harvesting system. The harvested energy of the system is measured by the voltage across the load resistor. The maximum load power is attained by optimizing the external circuit connected to the coil system. The analysis results are presented for harvesting the maximum load power in terms of the coil parameters and external circuit resistance. The optimality of the load resistance is validated by comparing the analytical results with experimental results. The optimal load resistances under various resonance frequencies are also found for the design and composition of the optimal energy harvesting circuit of the energy harvester system.

COMPARATIVE STUDY OF DIFFERENT KALMAN FILTER IMPLEMENTATIONS IN POWER SYSTEM STABILITY

Voltage stability and voltage collapse issues have in recent years begun to constitute an unpleasant warning to the operational security of power systems. Many techniques have been investigated in order to predict the point of voltage collapse. However, there are still several restrictions due to the insufficiency of current system state information. Accompanied by the commencement of the Phasor Measurement Units (PMUs) evolving technology, it donates a solution to enhance the existing power system state estimation. In consequence, the significances to develop preferable methods that would provide a preliminary warning before the voltage collapse had grabbed the attention. This study covers the forming of real-time system monitoring methods that able to provide a timely warning in the power system. The algorithms used to estimate the points of collapse are according to the theory that voltage instability is approximately linked to the maximum load ability of a transmission network. As a result, the critical operating conditions (peak of maximum deliverable power) come when the system Thevenin impedance is equal to the load impedance. This study focuses specifically on research about the motivation and the application of different Kalman filter implementations such as Discrete Kalman Filter (DKF), Extended Kalman Filter (EKF) and Unscented Kalman Filter (UKF) are used to track the Thevenin parameters. Therefore, the implications of this research paper are to determine the robustness and reliability of the proposed tracking methods. As compared to previous studies, the tracking process is just mainly focused on DKF method only, while the novelty throughout this study is to compare the performances and efficiencies of different Kalman filters in determining the maximum load ability on the 2 different types of test systems. Accompanying, the parameters are utilized in real-time voltage instability estimator to discover the current system’s condition. In this study, the effectiveness of the proposed algorithms is assessed under a large number of random operating conditions on the Malaysia’s power system 132 kV, 2-bus and 10-bus systems. Eventually, the results are differentiated by using the early-warning index of voltage collapse. All through the test cases, EKF method shows the best ability to track the Thevenin parameters as compared to DKF and UKF. Last but not least, the early-warning index acted as a pioneer implication in estimating the maximum load power ability of the power system right before load shedding methods are being executed.

Adaptive overcurrent relay coordination for off-peak loading in interconnected power system

Due to the substation automation, the supervisory control and data acquisition (SCADA) system is spreading that the protective relay settings can be modified through the network automatically. This work presents an overcurrent relay coordination decision for switching the relay settings to adaptive the off-peak loading in interconnected power system. Overcurrent relays (OCR) including directional and non-directional protective relays are widely applied in power system as main protective devices as they are reliable, cost effective and selective. Usually, the OCR protective coordination is coordinated at the time of maximum load and normal power supply, which may not be adaptive, as generating and load power are decreased significantly during the off-peak period of time compare to peak load that insufficient currents caused cascade lagging to activate OCRs. An example of single-ring interconnected power system was tested to demonstrate the coordination and confirm that the proposed approach method is practical during the off-peak time.

An Electrically Tunable Low Frequency Electromagnetic Energy Harvester

This paper reports the design, fabrication and experimental results of a low frequency electromagnetic energy harvester on FR4. The resonant frequency of the device is tuned electrically by using a generalized load (a capacitance in parallel with a resistance) instead of conventional resistive load. The device produces a maximum load power of 57μW across 3310Ω resistive load at 37.5Hz of untuned resonant frequency under 0.1g input acceleration. Later, the resonant frequency of the device is experimentally tuned up to 37Hz successfully by changing the load capacitance from 0 to 10μF. Though, this tuning comes with reduction in output power. It is observed that only 8.5% of the untuned maximum load power is obtained at the limit of the tuned range.

A Novel Approach for Nonstationary Time Series Analysis with Time-Invariant Correlation Coefficient

We will concentrate on the modeling and analysis of a class of nonstationary time series, called correlation coefficient stationary series, which commonly exists in practical engineering. First, the concept and scope of correlation coefficient stationary series are discussed to get a better understanding. Second, a theorem is proposed to determine standard deviation function for correlation coefficient stationary series. Third, we propose a moving multiple-point average method to determine the function forms for mean and standard deviation, which can help to improve the analysis precision, especially in the context of limited sample size. Fourth, the conditional likelihood approach is utilized to estimate the model parameters. In addition, we discuss the correlation coefficient stationarity test method, which can contribute to the verification of modeling validity. Monte Carlo simulation study illustrates the authentication of the theorem and the validity of the established method. Empirical study shows that the approach can satisfactorily explain the nonstationary behavior of many practical data sets, including stock returns, maximum power load, China money supply, and foreign currency exchange rate. The effectiveness of these processes is addressed by forecasting performance.

Saturated Electricity Power Analysis Based on Logistic Curve Model

Power load forecasting is the foundation of urban power grid planning, and saturated electricity power is a key indicator for determining the ultimate power grid scale when performing the urban power grid planning. Taken Hubei province as the empirical example, the saturated electricity power is studied by employing Logistic curve model in this paper. Firstly, the electricity power consumption and annual maximum power load of Hubei province are forecasted; then, the saturated time and scale are determined according to the judgment criteria of electricity power saturation. The calculation result shows the electricity power of Hubei province will reach saturation at 2042-2043, and the electricity power consumption and annual maximum power load will reach to 377.89 billion kWh and 66.2499 million kW, respectively.

Optimal shape design for divertors

Owing to the complex physics of the plasma edge, numerical simulation tools are indispensable for the evaluation of novel divertor concepts. Simulation-based divertor design is computationally extremely expensive, however, not in the least due to the large number of design variables. In this work, we show how shape optimisation methods can prove very valuable in partially automating the design process. We apply the continuous adjoint method to design divertor targets for maximum power load spreading. Shape sensitivities are derived using the material derivative approach. The resulting sensitivities depend on boundary data only, and can be computed very efficiently. Through numerical tests, we also prove that their accuracy is good. Next, the performance of two gradient-based optimisation algorithms and a so-called one-shot method is compared. Using the latter method, optimal solutions are obtained in a computational effort less than five times the time needed for a single analysis simulation.

Micro-electro-mechanical systems-based micro-electromagnetic vibration energy harvester

We developed a simple and efficient micro-electromagnetic energy harvester based on micro-electro-mechanical systems technology. For processes of electromagnetic vibration energy harvesters in the presence of the magnet, the compatibility with the micro-electro-mechanical systems processing is not good. Therefore, we have adopted a method of micro-assembly production energy harvester. The energy harvester mainly consists of a resonator chip processed by micro-electro-mechanical systems and a winding coil. The total volume of the energy harvesters is 0.95 cm3. Test results show that the energy harvester generated a maximum load power of 116.64 µW across 400 Ω load at 291.4 Hz for an acceleration of 0.5 g ( g = 9.8 m/s2) after the optimization of the parameters.