scholarly journals Investigating the Impact of Power-Take-Off System Parameters and Control Law on a Rotational Wave Energy Converter’s Peak-to-Average Power Ratio Reduction

2020 ◽  
Author(s):  
H. Bora Karayaka ◽  
Yi-Hsiang Yu ◽  
Nathan Tom ◽  
Eduard Muljadi
Keyword(s):  
Wave Energy ◽  
High Speed ◽  
High Efficiency ◽  
Average Power ◽  
Gear Ratio ◽  
Irregular Waves ◽  
Strong Impact ◽  
Power Ratio ◽  
Hardware In The Loop ◽  
The Impact

Abstract Due to the irregular nature of real waves, the power captured in a wave energy converter (WEC) system is highly variable. This is an important barrier to the effective use of WECs. To address this challenge, this study focuses on a rotational WEC power-take-off system in which high-speed and high-efficiency generators along with a torque/power smoothing inertia element can be effectively utilized. In the first phase of this study, the U.S. Department of Energy’s reference model 3 (WEC-Sim RM3; two-body point absorber), along with a slider-crank WEC, were integrated for linear to rotational conversion. Relative motion between the float and spar in RM3 was the driving force for this slider-crank WEC, which is connected to a motor/generator set through a gearbox. RM3 geometry was scaled down by 25 times to work within the limits of the physical motor/generator set used in the experimentation. Once the integration in a hardware-in-the-loop simulation environment was successfully completed, data on the peak-to-average power ratio was collected for various wave conditions including regular and irregular waves. The control algorithm designed to keep the system in resonance with waves was able to maintain relatively high speed depending on the specific gear ratio and wave period. Initial results with hardware-in-the-loop simulations reveal that gear ratio and crank radius have a strong impact on the peak-to-average power ratio. In addition, it was found that output power from the generator was maximized at a larger gear ratio, as the crank radius was increased.

scholarly journals A Novel Hybrid Precoding-Companding Technique for Peak-to-Average Power Ratio Reduction in 5G and beyond

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1410
Author(s):  
Mohamed Mounir ◽  
Mohamed B. El_Mashade ◽  
Salah Berra ◽  
Gurjot Singh Gaba ◽  
Mehedi Masud
Keyword(s):  
Computational Complexity ◽  
Orthogonal Frequency Division Multiplexing ◽  
High Speed ◽  
Average Power ◽  
Papr Reduction ◽  
Power Ratio ◽  
Error Vector Magnitude ◽  
Hybrid Precoding ◽  
High Power Amplifier ◽  
Reduction Techniques

Several high-speed wireless systems use Orthogonal Frequency Division Multiplexing (OFDM) due to its advantages. 5G has adopted OFDM and is expected to be considered beyond 5G (B5G). Meanwhile, OFDM has a high Peak-to-Average Power Ratio (PAPR) problem. Hybridization between two PAPR reduction techniques gains the two techniques’ advantages. Hybrid precoding-companding techniques are attractive as they require small computational complexity to achieve high PAPR reduction gain. Many precoding-companding techniques were introduced to increasing the PAPR reduction gain. However, reducing Bit Error Rate (BER) and out-of-band (OOB) radiation are more significant than increasing PAPR reduction gain. This paper proposes a new precoding-companding technique to better reduce the BER and OOB radiation than previous precoding-companding techniques. Results showed that the proposed technique outperforms all previous precoding-companding techniques in BER enhancement and OOB radiation reduction. The proposed technique reduces the Error Vector Magnitude (EVM) by 15 dB compared with 10 dB for the best previous technique. Additionally, the proposed technique increases high power amplifier efficiency (HPA) by 11.4%, while the best previous technique increased HPA efficiency by 9.8%. Moreover, our proposal achieves PAPR reduction gain better than the most known powerful PAPR reduction technique with a 99% reduction in required computational complexity.

scholarly journals Advantages of Spectrally Efficient Frequency Division Multiplexing Over Orthogonal Frequency Division Multiplexing

2020 ◽  
Vol 9 (8) ◽  
pp. 238-244
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Average Power ◽  
Frequency Division Multiplexing ◽  
Power Ratio ◽  
Frequency Division ◽  
Sphere Decoder ◽  
Symbol Rate ◽  
Transmission Length ◽  
Spectrally Efficient ◽  
The Impact

An analysis on Spectrally Efficient Frequency Division Multiplexing (SEFDM) is contrast with Orthogonal Frequency Division Multiplexing (OFDM) considering the impact on Peak to Average Power Ratio (PAPR) and nonlinearities within fibre. With respect to OFDM the sub-carriers in SEFDM signals are compressed adjacent to each other at a rate of frequency lesser than the symbol rate. At the receiver end we have utilized the Sphere Decoder which is used to recover the data to remunerate the Interference created by the compressed signals (ICI) faced in the system. This research shows the advantages by using SEFDM and evaluates its achievement. PAPR. when compared with OFDM, while effects of non-linear fibres are considered. The use of various formats of modulation going from 4-QAM to 32-QAM, shows that the SEFDM signals have a noteworthy increment in the transmission length with respect to ordinary signals.

scholarly journals MEASUREMENTSBASEDEVALUATION OF PATHLOSSEXPONENTS IN URBAN OUTDOORENVIRONMENTS

2021 ◽  
Vol 9 (03) ◽  
pp. 72-79
Author(s):  
Akohoule Alex ◽  
◽  
Bamba Aliou ◽  
Kamagate Aladji ◽  
Konate Adama ◽  
...  
Keyword(s):  
Mobile Networks ◽  
Average Power ◽  
Path Loss ◽  
Wireless Channel ◽  
Propagation Model ◽  
Strong Impact ◽  
Efficient Design ◽  
Path Loss Exponent ◽  
Outdoor Environments ◽  
The Impact

In wireless networks, propagation models are used to assess the received power signal and estimate the propagation channel. These models depend on the pathloss exponent (PLE) which is one of the main parameters to characterize the propagation environment. Indeed, in the wireless channel, the path loss exponent has a strong impact on the quality of the links and must therefore be estimated with precision for an efficient design and operation of the wireless network. This paper addresses the issue of path loss exponents estimation for mobile networks in four outdoor environments. This study is based on measurements carried out in four outdoor environments at the frequency of 2600 MHz within a bandwidth of 70 MHz. It evaluates the path loss exponent, and the impact of obstacles present in the environments. The parameters of the propagation model determined from the measurements show that the average power of the received signal decreases logarithmically with the distance. We obtained path loss exponents values of 4.8, 3.53, 3.6 and 3.99 for the site 1, site 2, site 3 and site 4, respectively. Clearly the density of the obstacles has an impact on the path loss exponents and our study shows that the received signal decrease faster as the transmitter and receiver separation in the dense environments.

scholarly journals Monitoring and characterization of vibration and shock conditions aboard high-performance marine craft

2018 ◽  
Vol 233 (4) ◽  
pp. 1068-1081
Author(s):  
Manudul Pahansen de Alwis ◽  
Karl Garme
Keyword(s):  
Real Time ◽  
High Speed ◽  
High Performance ◽  
Severity Index ◽  
Irregular Waves ◽  
Vibration Exposure ◽  
Data Set ◽  
Real Time Analysis ◽  
Impact Acceleration ◽  
The Impact

The stochastic environmental conditions together with craft design and operational characteristics make it difficult to predict the vibration environments aboard high-performance marine craft, particularly the risk of impact acceleration events and the shock component of the exposure often being associated with structural failure and human injuries. The different timescales and the magnitudes involved complicate the real-time analysis of vibration and shock conditions aboard these craft. The article introduces a new measure, severity index, indicating the risk of severe impact acceleration, and proposes a method for real-time feedback on the severity of impact exposure together with accumulated vibration exposure. The method analyzes the immediate 60 s of vibration exposure history and computes the severity of impact exposure as for the present state based on severity index. The severity index probes the characteristic of the present acceleration stochastic process, that is, the risk of an upcoming heavy impact, and serves as an alert to the crew. The accumulated vibration exposure, important for mapping and logging the crew exposure, is determined by the ISO 2631:1997 vibration dose value. The severity due to the impact and accumulated vibration exposure is communicated to the crew every second as a color-coded indicator: green, yellow and red, representing low, medium and high, based on defined impact and dose limits. The severity index and feedback method are developed and validated by a data set of 27 three-hour simulations of a planning craft in irregular waves and verified for its feasibility in real-world applications by full-scale acceleration data recorded aboard high-speed planing craft in operation.

A Comparison of Selected Strategies for Adaptive Control of Wave Energy Converters

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Jørgen Hals ◽  
Johannes Falnes ◽  
Torgeir Moan
Keyword(s):  
Wave Energy ◽  
Reactive Power ◽  
Average Power ◽  
Volume Ratio ◽  
External Input ◽  
Irregular Waves ◽  
Optimal Velocity ◽  
Wave Energy Converters ◽  
Absorbed Power ◽  
Energy Converters

Wave-energy converters of the point-absorbing type (i.e., having small extension compared with the wavelength) are promising for achieving cost reductions and design improvements because of a high power-to-volume ratio and better possibilities for mass production of components and devices as compared with larger converter units. However, their frequency response tends to be narrow banded, which means that the performance in real seas (irregular waves) will be poor unless their motion is actively controlled. Only then the invested equipment can be fully exploited, bringing down the overall energy cost. In this work various control methods for point-absorbing devices are reviewed, and a representative selection of methods is investigated by numerical simulation in irregular waves, based on an idealized example of a heaving semisubmerged sphere. Methods include velocity-proportional control, approximate complex conjugated control, approximate optimal velocity tracking, phase control by latching and clutching, and model-predictive control, all assuming a wave pressure measurement as the only external input to the controller. The methods are applied for a single-degree-of-freedom heaving buoy. Suggestions are given on how to implement the controllers, including how to tune control parameters and handle amplitude constraints. Based on simulation results, comparisons are made on absorbed power, reactive power flow, peak-to-average power ratios, and implementation complexity. Identified strengths and weaknesses of each method are highlighted and explored. It is found that overall improvements in average absorbed power of about 100–330% are achieved for the investigated controllers as compared with a control strategy with velocity-proportional machinery force. One interesting finding is the low peak-to-average ratios resulting from clutching control for wave periods about 1.5 times the resonance period and above.

VARIABILITY OF THE SUSPENDED SEDIMENT DYNAMICS UNDER IRREGULAR WAVES

2017 ◽  
Author(s):  
Рубен Косян ◽  
Ruben Kosyan ◽  
Boris Divinsky ◽  
Boris Divinsky
Keyword(s):  
Bottom Sediment ◽  
Suspended Sediment ◽  
Frequency Distribution ◽  
Bottom Sediments ◽  
Wave Energy ◽  
Suspended Solids ◽  
Irregular Waves ◽  
Spectral Peak ◽  
Sediment Suspension ◽  
The Impact

The main objective of this paper is an analysis of the impact of the frequency distribution of wave energy on the dynamics of bottom sediment suspension as well as a study of the features of bottom sediments suspension during the passage of waves groups of varying shape and intensity. It is shown that the concentration of wave energy in the primary spectral peak promotes redistribution vertically suspended solids. Laws of suspension within the group are largely determined by the parameters of bottom roughness and the presence (absence) of ripples.

Research on Peak-to-Average Power Ratio for OFDM System

2013 ◽  
Vol 823 ◽  
pp. 366-369
Author(s):  
Hao Fang ◽  
Wan Hua Wei
Keyword(s):  
High Speed ◽  
Data Flow ◽  
Average Power ◽  
Power Ratio ◽  
Ofdm Systems ◽  
Ofdm System ◽  
Major Drawback ◽  
High Power Amplifier ◽  
Flow Through ◽  
Ofdm Signals

OFDM is a special multi-carrier modulation, its basic idea is to make high-speed transmission of data flow through the serial-parallel conversion and make it to be the low-speed transmission of data flow in a number of narrow-band orthogonal sub-channels. However, a major drawback of OFDM signals is their high Peak-to-Average Power Ratio (PAPR), which makes the inter modulation distortion occur due to the nonlinearity of the high power amplifier. The distortion severely deteriorates the performance of the OFDM systems. According the problems mentioned above, this dissertation focuses on the reducing the PAPR algorithms design for OFDM systems, such as SLM and PTS. In summary, this paper has completed the OFDM system simulation with Matlab and analyses the result.

scholarly journals Array modeling and testing of fixed OWC type Wave Energy Converters

2020 ◽  
Vol 3 (3) ◽  
pp. 137-143
Author(s):  
Bret Bosma ◽  
Ted Brekken ◽  
Pedro Lomonaco ◽  
Bryony DuPont ◽  
Chris Sharp ◽  
...  
Keyword(s):  
Numerical Model ◽  
Wave Energy ◽  
Average Power ◽  
Irregular Waves ◽  
Regular Waves ◽  
Wave Energy Converters ◽  
Phase Errors ◽  
Array Optimization ◽  
Tank Test ◽  
Energy Converters

If wave energy technology is to mature to commercial success, array optimization could play a key role in that process. This paper outlines physical and numerical modeling of an array of five oscillating water column wave energy converters. Numerical model simulations are compared with experimental tank test data for a non-optimal and optimal array layout. Results show a max increase of 12% in average power for regular waves, and 7% for irregular waves between the non-optimized and optimized layouts. The numerical model matches well under many conditions; however, improvement is needed to adjust for phase errors. This paper outlines the process of numerical and physical array testing, providing methodology and results helpful for researchers and developers working with wave energy converter arrays.

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