Output Power Fluctuations Research Articles

A simplified model and its parameters optimization methodology of LCC‐S WPT compensation network under dual‐side‐detuned conditions

AbstractWireless power transfer (WPT) systems typically operate under broad coupling conditions. In response to the issue of significant fluctuations in output power due to changes in the coupling coefficient when the coupling coils are offset, this paper proposes a parameter design method for the LCC‐S topology that remains applicable under dual‐side‐detuned conditions. Presented the design principles of the dual‐side‐detuned circuit, and an iterative approach is employed to guide the parameter design process. It also introduced a method for selecting the rated coupling coefficient to minimize power fluctuations within the expected range. Experimental validation demonstrates that the robustness and resistance to coupling coefficient fluctuations of the proposed dual‐side‐detuned LCC‐S topology surpass those of other candidate schemes. Within a coupling variation range from 0.23 to 0.35, the maximum fluctuation rate of the output power remains below 6% while maintaining acceptable efficiency. This design has relevance to typical application scenarios.

Decentralized Power Sharing with Frequency Decoupling for a Fuel Cell-Battery DC Shipboard Power System

The maritime industry is under increasing pressure to reduce its carbon footprint by adopting new energy generation and storage technologies in shipboard power systems (SPS). Fuel cells (FCs) show great potential as primary power sources when hybridized with energy storage systems (ESS). Integrating different technologies in future SPS requires the coordination of power generation and storage modules, which can be facilitated by DC technology with power electronics interfaces. However, studies on FC integration have primarily focused on small-scale applications with centralized control architectures. There has been little research on the modular control of multiple FC and battery modules in SPS. This study proposes a decentralized droop-based power sharing approach with load frequency decoupling to efficiently utilize power system modules based on their dynamic capabilities. The proposed strategy further incorporates decentralized voltage regulation and state-of-charge (SoC) management functions. The methodology was applied to a short-sea cargo vessel with an FC-battery DC power system. The results indicate that the mission load profile can be satisfied while limiting fluctuations in the FC output power. Moreover, the proposed strategy achieves the same voltage regulation performance as a centralized proportional-integral (PI) controller and can be easily tuned to achieve load frequency decoupling with the desired time constant. Finally, a comparative analysis shows how the trade-off between the dynamic operation of the FC and the discharge depth of the ESS is affected by the choice of time constant.

Intermittent power smoothing control for grid connected hybrid wind/PV system using battery-EDLC storage devices

Wind and solar radiation are intermittent with stochastic fluctuations, which can influence the stability of operation of the hybrid system in the grid integrated mode of operation. In this research work, a smoothing control method for mitigating output power variations for a grid integrated wind/PV hybrid system using a battery and electric double layer capacitor (EDLC) is investigated. The power fluctuations of the hybrid system are absorbed by a battery and EDLC during wide variations in power generated from the solar and wind system, subsequently, the power supplied to the grid is smoothened. This makes higher penetration and incorporation of renewable energy resources to the utility system possible. The control strategy of the inverter is realized to inject the power to the utility system with the unity power factor and a constant DC bus voltage. Both photovoltaic (PV) and wind systems are controlled for extracting maximum output power. In order to observe the performance of the hybrid system under practical situations in smoothing the output power fluctuations, one-day practical site wind velocity and irradiation data are considered. The dynamic modeling and effectiveness of this control method are verified in the MATLAB/Simulink environment. The simulation results show that the output power variations of the hybrid wind/PV system can be significantly mitigated using the combination of battery and EDLC based storage systems. The power smoothing controller proposed for the hybrid storage devices is advantageous as compared to the control technique which uses either battery or ultracapacitor used for smoothing the fluctuating power

Improving power output wind turbine in micro-grids assisted virtual wind speed prediction

Wind energy is an alternative form of energy easily obtainable in the landscape. However, the main challenge is to extract electrical power from varying wind speeds. Wind energy can be a significant production resource for power electronics technologies, converters, and electrical generators. Due to their dependence on wind speed, the output power from wind turbines experiences severe fluctuations with the change in wind speed, and ripples increase the output power from the wind turbine. Therefore, the engineers’ critical research prediction will smooth these extraction fluctuations. Several speed prediction methods have been used to reduce the changes in the output power of wind turbines. One of these wind speed prediction methods is a fast energy storage system that can be charged and discharged in seconds. Applying wind speed prediction to overcome the slowness of the wind source will be the primary approach considered in this article. Also, a wind turbine with a nominal power of 50 kW and an ultra-capacitor storage system are determined, and these sources are made in MATLAB/SIMULINK softwareIn this study, the control signal for adjusting the turbine pitch angle is derived from both actual and predicted data. The signal from actual data undergoes a multiplication by 0.8, while the signal from predicted data is multiplied by 0.2. This approach serves two purposes: firstly, it helps prevent overshooting of turbine power at the initial stages, ensuring a smoother transition. Secondly, it aids in maintaining a consistent power output of 50 kW during subsequent moments. By combining actual and predicted data in this weighted manner, the control system achieves a balanced response, effectively managing turbine power dynamics. Finally, the results show that utilizing wind speed prediction to improve output wind turbine in Micro-grids (MGs) will reduce fluctuations in the wind source's output power and the ultra-capacitor storage.

Research on wind turbine variable pitch control based on wind speed estimation

With the continuous promotion of the “double carbon” strategy, the capacity of wind turbines is increasing, and the dimensions of key parts such as the diameter of the wind turbine wheel, the height of the tower, and the radius of the tower tube are also increasing. Large wind turbines have a large inertia, so the execution time of the pitch actuator and the response time of the pitch action are usually longer, which leads to large fluctuations in the output power of the wind turbine when the wind speed changes rapidly under the working conditions above the rated wind speed and leads to complex loading problems. Therefore, in this paper, the design of pitch control is carried out by estimating the effective wind speed at the wind turbine surface and using the inverse system method to transform the nonlinear wind turbine system into a linear decoupled form. This method improves the pitch response speed, reduces the output power fluctuation, and better suppresses the load of the turbine to ensure the safe and stable operation of the turbine

A Method Based on Vector-Summing of Reduce Output Power Fluctuation for EV-DWPT System with the Passive LC Network

A Method Based on Vector-Summing of Reduce Output Power Fluctuation for EV-DWPT System with the Passive LC Network

Predictable Local Polarization inside Electrodes By Three-Dimensional Multi-Scale Model in Flow Batteries

Redox flow batteries (RFBs) are regarded as one of the most promising grid-scale energy storage technologies, which can improve the applicability of wind and solar energy by leveling their fluctuating power output. In RFBs, the gas side reactions including hydrogen evolution reaction and oxygen evolution reaction reduce the efficiency and capacity of the batteries and the gas produced may even cause safety problems. Even if the voltage is controlled in practical applications to restrict the gas side reactions, it is still inevitable due to flow dead zones or insufficient reactants locally inside the electrode. Gas side reactions are usually caused by too high local overpotential, i.e., local over polarization. Therefore, in this work, we propose a multi-scale model that allows the rapid prediction of local polarization to limit and manage the gas side reactions. The multi-scale model contains a deep neural network, a pore network model, and a three-dimensional continuum model with the advantages of both accuracy and extensibility. By learning from the sample data provided by the cell-scale model and the pore-scale model, the deep neural network can quickly predict the local polarization under different operating conditions and give the distribution map of the entire electrode. Compared with conventional models, multi-scale models can take into account the geometry of electrode fibers and are suitable for electrode design and modification. Due to the calculation superiority of the pore network model, the multi-scale model can realize three-dimensional local polarization prediction, which enables a more accurate analysis of the internal uniformity of the electrode. Through the developed model, we explore the effects of the interdigitated flow field, flow rate, initial concentration and voltage on local polarization. It is shown that the multi-scale model can accurately predict local polarization. However, the promotion of flow rate cannot completely eliminate the occurrence of local over polarization.

Stochastic optimal scheduling of wind power and pumped-storage hydropower complementary systems with multiple uncertainties

The joint operation of wind farms (WFs) and pumped-storage hydropower plants (PSHPs) is an effective way to smooth out the random fluctuations of wind power and improve its consumption rate. In this paper, a novel method to describe the multiple uncertainties of wind power outputs is proposed. A WFs-PSHP joint optimal scheduling model based on chance-constrained programming is then developed. The optimization model aims to maximize the total generation profit of the WFs-PSHP complementary system, and comprehensively considers the hydraulic constraints, unit operation constraints and system power balance constraint of the PSHP. To improve the model solving efficiency, this study converts the previous model with high-dimensional, non-convex, nonlinear and stochastic characteristics to the deterministic mixed integer linear programming (MILP) one. The optimization results demonstrate that the PSHP not only compensates for the fluctuations in wind power output, but also increases the total generation profit of this complementary system to 966.48 × 104 CNY, which is 17.56 % higher than that of independent operation.

A 77 GHz Power Amplifier with 19.1 dBm Peak Output Power in 130 nm SiGe Process.

This article reports a two-stage differential structure power amplifier based on a 130 nm SiGe process operating at 77 GHz. By introducing a tunable capacitor for amplitude and phase balance at the center tap of the secondary coil of the traditional Marchand balun, the balun achieves amplitude imbalance less than 0.5 dB and phase imbalance less than 1 degree within the operating frequency range of 70-85 GHz, which enables the power amplifier to exhibit comparable output power over a wide operating frequency band. The power amplifier, based on a designed 3-bit digital analog convertor (DAC)-controlled base bias current source, exhibits small signal gain fluctuation of less than 5 dB and saturation output power fluctuation of less than 2 dB near the 80 GHz frequency point when the ambient temperature varies in the range of -40 °C to 125 °C. Benefiting from the aforementioned design, the tested single-path differential power amplifier exhibits a small signal gain exceeding 16 dB, a saturation output power exceeding 18 dBm, and a peak saturation output power of 19.1 dBm in the frequency band of 70-85 GHz.

A Composite Super-Twisting Sliding Mode Approach for Platform Motion Suppression and Power Regulation of Floating Offshore Wind Turbine

The floating platform motion of an offshore wind turbine system can exacerbate output power fluctuations and increase fatigue loads. This paper proposes a new scheme based on a fast second-order sliding mode (SOSM) control and an adaptive super-twisting extended state observer to suppress the platform motion and power fluctuation. Firstly, an affine nonlinear model of the floating wind turbine pitch system is constructed. Then, a fast SOSM pitch control law is adopted to adjust the blade pitch angle, and a new adaptive super-twisting extended state observer is constructed to achieve total disturbance observation. Finally, simulations are conducted under two cases of wind and wave conditions based on FAST (fatigue, aerodynamics, structures, and turbulence) and MATLAB/Simulink. Compared with the traditional proportional integral (PI) control scheme and standard super-twisting control scheme, the platform roll under the proposed scheme is reduced by 13% and 4%, and pitch is reduced by 16% and 3% in Case 1. Correspondingly, the roll is reduced by 9% and 15%, and pitch is reduced by 7% and 1% in Case 2. For the tower top pitch and yaw moment, load reductions of 7% and 3% or more are achievable compared with those under the PI control scheme. It is indicated that the proposed scheme is more effective in suppressing floating platform motion, stabilizing output power of the wind turbine system, and reducing tower loads.

A New Simultaneous Wireless Power and Information Transfer System With Integrated Signal Magnetic Coupler

For a reliable and controllable wireless power transfer (WPT) system, the simultaneous wireless power and information transfer (SWPIT) technology has recently attracted special consideration to achieve real-time information exchange between the transmitter and receiver. In this article, a novel SWPIT system with an integrated signal magnetic coupler is proposed for wireless charging applications. The signal detection coil integrated with the receiver coil is designed to utilize the existing ferrite cores of the magnetic coupler, reducing the overall cost and obtaining a more compact design. Meanwhile, the deviation frequency enlargement effect (DFEE) principle and the frequency shift keying (FSK) technology are used to realize SWPIT in a wireless charger. The equivalent circuit of the proposed system is modeled and analyzed considering the cross-couplings between the integrated signal coil and the main coils. The finite element analysis (FEA) is presented through Ansys Maxwell software to select the optimal ferrite core structure and eliminate these unwanted cross-couplings. Finally, a 70- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$W$</tex-math></inline-formula> power experimental prototype is established, and comprehensive experimental results are given to verify the feasibility and effectiveness of the proposed SWPIT system. Furthermore, the experimental results demonstrate that the measured output power fluctuation is below 0.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> during information transmission, the transmission rate is up to 9.6 kbps, and the system efficiency can be maintained at 88.76 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> .

Fluctuation characteristics induced by energetic coherent structures in air-core vortex: The most complex vortex in the tidal power station intake system

The air-core vortex is the most complex vortex in the intake system of tidal power stations. Nearly all power plants prohibit the operation of units with air-core vortices, as these vortices not only contain air but also induce significant inflow fluctuations that can potentially lead to significant damage to the units. The current understanding of the fluctuation characteristics and mechanisms induced by energetic coherent structures in the air-core vortex flow is very limited. To address this, the coupled level-set and volume-of-fluid large-eddy simulations are conducted to investigate the energetic coherent structures that cause power output fluctuations. Two critical frequencies have been identified in the energy spectra of the velocity field: the air-core vortex meandering frequency and the shear vortex shedding frequency. The level and trend of the spectrum density at low frequencies are determined by the large-scale energy structure represented by the air-core vortex. The shear vortices are initially formed from a shear separation layer that eventually evolves into streamwise vortices downstream. When the air-core vortex enters the pipe, it breaks up and merges with the near-wall coherent structures. The enhanced velocity and pressure fluctuations, induced by air-core vortices and coherence structures, are analyzed using the turbulent kinetic energy transport equation, revealing that the production term dominates the development of turbulent kinetic energy. Moreover, the diffusion term is responsible for transferring energy through the evolution of turbulent structures. The energy loss induced by fluctuations is investigated using the entropy production method. We find that the direct dissipation of entropy production is mainly induced by air-core vortices, while the side-wall coherent structures in the pipe contribute to the turbulent dissipation.

Blue LD-pumped continuous wave a-cut Pr3+:LiYF4 near-infrared laser at 868 nm

We reported an 868 nm Pr3+:LiYF4 (Pr:YLF) laser pumped by an InGaN blue laser diode (LD) for the first time. The maximum power of the laser was 641 mW and the beam quality Mx2 and My2 factors were ∼2.66 in the x-direction and ∼2.32 in the y-direction, respectively. The output power fluctuation was stable within ±2 %. The 868 nm laser was successfully realized in Pr:YLF crystal by designing and optimizing the laser resonant cavity and optical thin films. In addition, we theoretically simulated the nonlinear relationship between the laser output power and the absorbed pump power, and the theoretical simulation results were in agreement with the experimental data. The first realization of the 868 nm Pr:YLF laser further expands the near-infrared lasers.

Coordinated planning method considering flexible resources of active distribution network and soft open point integrated with energy storage system

AbstractFaced with the uncertainty of wind and photovoltaic power output and load fluctuation caused by the increase of new energy penetration in active distribution network, the demand for operational flexibility and the construction demand for flexible resources of distribution network are gradually increasing. The flexible operation of active distribution network can be realized by coordinated planning of the soft open point integrated with energy storage system (ESOP) and flexible resources. Firstly, the flexibility resource adjustability evaluation and margin indicators are proposed for the response model of typical flexibility resources. Secondly, a two‐stage distributionally robust coordinated planning model considering the coordination planning scheme of distributed generation, flexibility resource, and ESOP as well as the comprehensive norm uncertainty of wind power and photovoltaic outputs multi‐operation scenarios is established with the distribution network construction cost, annual operation cost, and annual power sales revenue as the objective functions meanwhile the investment and flexibility resource operation as constraints. Finally, the column constraint generation algorithm is used to solve the problem, and the effectiveness of the proposed model is verified by the modified IEEE33 node system.

Large-eddy simulations of turbulent flows in arrays of helical- and straight-bladed vertical-axis wind turbines

Effects of helical-shaped blades on the flow characteristics and power production of finite-length wind farms composed of vertical-axis wind turbines (VAWTs) are studied numerically using large-eddy simulation (LES). Two helical-bladed VAWTs (with opposite blade twist angles) are studied against one straight-bladed VAWT in different array configurations with coarse, intermediate, and tight spacings. Statistical analysis of the LES data shows that the helical-bladed VAWTs can improve the mean power production in the fully developed region of the array by about 4.94%–7.33% compared with the corresponding straight-bladed VAWT cases. The helical-bladed VAWTs also cover the azimuth angle more smoothly during the rotation, resulting in about 47.6%–60.1% reduction in the temporal fluctuation of the VAWT power output. Using the helical-bladed VAWTs also reduces the fatigue load on the structure by significantly reducing the spanwise bending moment (relative to the bottom base), which may improve the longevity of the VAWT system to reduce the long-term maintenance cost.

Application of energy storage allocation model in the context of mitigating new energy source power fluctuation

To address the impact of new energy source power fluctuations on the power grid, research has been conducted on energy storage allocation applied to mitigate the power fluctuations of new energy source. Firstly, based on the first-order low-pass filtering algorithm and discrete Fourier transform algorithm, the original power data of new energy sources were preprocessed to achieve the reconstruction of power signal. Subsequently, a more secure and reliable energy storage allocation model is constructed by taking into account the boundary conditions of energy storage charging and discharging efficiency, energy balance, state of charge, and target power output fluctuation. Then, a comprehensive Life-Cycle-Cost model for energy storage systems was developed and applied to economic evaluation of energy storage under two algorithms. Finally, the calculation case study analysis shows that the energy storage allocation model effectively improves the power fluctuations of new energy sources, represented by wind power, and ensure the safe and stable operation of energy storage system throughout the entire cycle, thus verifying the effectiveness and feasibility of the energy storage configuration model. Under fluctuation rate constraints of 10%, 15%, and 20%, the rated power required for the first-order low-pass filtering algorithm is 8.795 MW, 6.485 MW, and 4.022 MW, respectively, representing 18.32%, 13.51%, and 8.38% of the new energy source rated power(48 MW). The corresponding rated capacity required is 7.763 MWh, 3.675 MWh, and 1.123 MWh. In contrast, for the discrete fourier transform algorithm, the rated power required is 9.159 MW, 8.84 MW, and 5.78 MW, respectively, representing 19.08%, 18.42%, and 12.04% of the new energy source rated power. The corresponding rated capacity required is 2.01 MWh, 0.97 MWh, and 0.5 MWh. Form an economic feasibility perspective, the economic efficiency of energy storage allocation by discrete fourier transform algorithm is significantly better than allocated by the first-order low-pass filtering algorithm. For instance, when U10minup= 10%, the cost difference reaches a maximum of 1256 million ¥.

Stochastic dynamics of a semiconductor laser with delayed optoelectronic feedback and noise

Semiconductor lasers(SLs), versatile tools in communication, medicine, and scientific research, demand close examination of their dynamic behavior. With their unique geometric forms and diminutive sizes, these lasers possess a heightened sensitivity to noise. In this paper, we delve into time-delay semiconductor laser systems, noise included, honing in on time-delays’ effects on noisy laser equations. Carrier density (N) and laser intensity (I) constitute the core parameters that define the performance of these lasers, and we scrutinize their dynamic trajectories. A cutting-edge method fusing stochastic center manifold theory with the stochastic averaging method enables us to probe the stochastic dynamical attributes of semiconductor laser equations. We uncover that the time-delay parameter (τ 1) produces varied consequences on the laser system’s stability under both positive and negative optical feedback conditions. The negative feedback typically bolsters laser performance, fostering increased stability, whereas the positive counterpart could incite instability. By deftly managing the time-delay parameter, one can fine-tune the dynamic performance of semiconductor lasers, mitigating output power fluctuations and tightening linewidths, thereby augmenting stability and spectral purity. Moreover, in the realm of positive optical feedback scenarios, adroitly modifying the time-delay parameter can quell instability to a degree, paving the way for a novel regulatory approach to optimize laser performance. This lays the groundwork for further enhancement of semiconductor laser performance, as well as curbing the detrimental effects of noise on their operation.

An adaptive distance protection back‐up scheme for transmission lines connected to doubly fed induction generator wind farms based on setting groups procedure

AbstractGenerally, wind speed alters continuously during a day and leads to fluctuating output power of a wind farm (WF). Connecting such a WF to the transmission line of grid causes a malfunction in the performance of the backup zone of the distance relays due to the random nature of generation and the number of connected wind turbines (WF penetration). In this study, a new adaptive setting groups‐based method has been proposed to set the second zone of the distance relay in the grid with a WF equipped with a doubly fed induction generator. In this method, the authors have also taken into account the uncertainty of wind fluctuations and the availability of WT. A Markov model is developed to implement these features. To determine the impedance setting of each of the set groups of the second zone in the distance relays of the remote bus, the obtained impedances are clustered in four clusters by using the combination of K‐means and particle swarm optimization algorithms. Finally, the details of the analysis results of this issue have been compared with other methods available in the literature. The validity and accuracy of the proposed approach also have been assayed and confirmed.

The Capacity Configuration of Energy Storage System in DC Microgrid with Source-storage Integration

The occurrence of a fault in a DC microgrid can significantly jeopardize the system’s safe operation, making it a critical area of research for scholars. One key focus of this research is on developing methods to suppress the fault current, which has become a research hotspot for many scholars. Each distributed power source is connected to DC microgrid through a battery storage system to form a source-storage integration DC microgrid structure, which can have good fault current control ability and obvious improvement effect on reducing the protection technology difficulty of DC microgrid and enhancing the flexibility of distribution network. Compared with the traditional DC microgrid structure, the source-storage integration DC microgrid, whose battery storage system is changed from centralized to distributed, will smooth fluctuations in distributed power output by modifying energy storage planning principles, and also maintain bus voltage and realize fault current control with distributed power sources. Capacity planning principles for energy storage systems proposed in this paper were studied for DC microgrids with source-storage integration, and the total energy storage capacity and power under two DC microgrid structures were compared and analyzed with a scenic complementary power station as an example. Although a DC microgrid with a changed grid structure would require less than a 20% increase in the overall capacity and power of the energy storage system, according to the calculation results, the operation of the microgrid can be significantly improved, the flexibility of power dispatching of the distribution network was enhanced, and the investment cost of fault protection was reduced. Research into the capacity configuration of energy storage systems has demonstrated that DC microgrids with integrated source and storage capabilities hold significant engineering application value and practical significance.

Missing interpolation model for wind power data based on the improved CEEMDAN method and generative adversarial interpolation network

Randomness and fluctuations in wind power output may cause changes in important parameters (e.g., grid frequency and voltage), which in turn affect the stable operation of a power system. However, owing to external factors (such as weather), there are often various anomalies in wind power data, such as missing numerical values and unreasonable data. This significantly affects the accuracy of wind power generation predictions and operational decisions. Therefore, developing and applying reliable wind power interpolation methods is important for promoting the sustainable development of the wind power industry. In this study, the causes of abnormal data in wind power generation were first analyzed from a practical perspective. Second, an improved complete ensemble empirical mode decomposition with adaptive noise (ICEEMDAN) method with a generative adversarial interpolation network (GAIN) network was proposed to preprocess wind power generation and interpolate missing wind power generation sub-components. Finally, a complete wind power generation time series was reconstructed. Compared to traditional methods, the proposed ICEEMDAN-GAIN combination interpolation model has a higher interpolation accuracy and can effectively reduce the error impact caused by wind power generation sequence fluctuations