Reduce Power Fluctuations Research Articles

Advanced microgrid and its multi‐objective regulation strategy for shore supply

This study presents a new microgrid paradigm for the shore-side power supply system. The shore supply microgrid is developed for container and cruise harbours to further improve the capability of energy saving and emission reduction. The typical structure and operation modes are designed based on the requirements of shore supply systems. A multi-objective regulation strategy is devised for energy management system. The strategy aims to reduce power fluctuation and to implement the microgrid self-supply at ports. A parallel optimisation model is built to solve the regulation problem. A study case of four different ship-berthing scenarios is utilised to validate the effectiveness of the designed microgrid and its regulation strategy.

Overview of energy storage in renewable energy systems

This paper presents an overview of energy storage in renewable energy systems. In fact, energy storage is a dominant factor in the integration of renewable sources, playing a significant role in maintaining a robust and reliable modern electricity system. It can reduce power fluctuations, enhances the electric system flexibility, and enables the storage and dispatching of the electricity generated by variable renewable energy sources such as wind and solar. Different storage technologies are used in electric power systems. They can be chemical, electrochemical, mechanical, electrical or thermal. Energy storage facility is comprised of a storage medium, a power conversion system and a balance of plant. This work focuses on hydrogen, batteries and flywheel storage used in renewable energy systems such as photovoltaic and wind power plants, it includes the study of some economic aspects of different storage technologies. Finally, the behavior of battery and flywheel storage systems in photovoltaic and wind energy applications is studied under Matlab/Simulink and some obtained results are presented.

Compensation of a distorted N-fold orbital angular momentum multicasting link using adaptive optics.

By using an adaptive feedback correction technique, we experimentally demonstrate turbulence compensation for free-space four-fold and eight-fold 16-ary quadrature amplitude modulation (16-QAM) carrying orbital angular momentum (OAM) multicasting links. The performance of multicasted OAM beams through emulated atmospheric turbulence and adaptive optics assisted compensation loop is investigated. The experimental results show that the scheme can efficiently compensate for the atmospheric turbulence induced distortions, i.e., reducing power fluctuation of multicasted OAM channels, suppressing inter-channel crosstalk, and improving the bit-error rate (BER) performance.

Field Oriented Control of DFIG Based Wind Energy System Using Battery Energy Storage System

Wind power is the fastest growing source of electrical energy in the world today due to the increasing awareness of the environmental problems together with the rapid increase in the fuel cost and the power demand. Wind energy conversion using Doubly Fed Induction Generator (DFIG) is one of the most important types of renewable energy generations. The wind farm power output has large fluctuations due to sudden wind speed changes. Fluctuate power can often cause the violation of voltage and frequency limits in the weak system. It can be severe problem for the system stability also. The control system in the proposed arrangement of DFIG is able to reduce power fluctuation with the help of Battery Energy Storage System (BESS). In order to decouple the active and reactive powers generated by the machine, field oriented control is applied. As a result, high performance control of power can be achieved. The developed method has been tested through modelling a DFIG based wind energy system with BESS using SimPower System tools of MATLAB and simulated for operation as a grid connected system. The performance of DFIG based wind energy system demonstrates satisfactory performance under different wind speed conditions.

Methods of reducing power fluctuations in wave energy parks

One of the major challenges in constructing effective and economically viable wave energy parks is to reduce the large fluctuations in power output. In this paper, we study different methods of reducing the fluctuations and improve the output power quality. The parameters studied include the number of devices, the separating distance between units, the global and local geometries of the array, sea state and incoming wave direction, and the impact of including buoys of different radii in an array. Our results show that, e.g., the fluctuations as well as power per device decrease strictly with the number of interacting units, when the separating distance is kept constant. However, including more devices in a park with fixed area will not necessarily result in lowered power fluctuations. We also show that varying the distance between units affects the power fluctuations to a much larger extent than it affects the magnitude of the absorbed power. The fluctuations are slightly lower in more realistic, randomized geometries where the buoys tend to drift slightly off their mean positions, and significantly lower in semi-circular geometries as opposed to rectangular geometries.

An adaptive neuro fuzzy inference system controlled space cector pulse width modulation based HVDC light transmission system under AC fault conditions

Abstract In HVDC Light transmission systems, converter control is one of the major fields of present day research works. In this paper, fuzzy logic controller is utilized for controlling both the converters of the space vector pulse width modulation (SVPWM) based HVDC Light transmission systems. Due to its complexity in the rule base formation, an intelligent controller known as adaptive neuro fuzzy inference system (ANFIS) controller is also introduced in this paper. The proposed ANFIS controller changes the PI gains automatically for different operating conditions. A hybrid learning method which combines and exploits the best features of both the back propagation algorithm and least square estimation method is used to train the 5-layer ANFIS controller. The performance of the proposed ANFIS controller is compared and validated with the fuzzy logic controller and also with the fixed gain conventional PI controller. The simulations are carried out in the MATLAB/SIMULINK environment. The results reveal that the proposed ANFIS controller is reducing power fluctuations at both the converters. It also improves the dynamic performance of the test power system effectively when tested for various ac fault conditions.

Experimental results from wave tank trials of a multi-axis wave energy converter

A 1/64th scale prototype of multi-axis wave energy converter (WEC) has been tested in the wave tank and the overall concept has been verified. It is shown that when multiple directions of motion are involved, the multi-axis WEC proves to be able to supply more power generation than a single axis one. Results demonstrated that the optimal resonant frequency for maximum power output under different damping values does not vary with wave climate. It is also shown that large overload capability of the system is critical, and indicated that, electric power system is essential to reduce power fluctuations.

Computationally Inexpensive Approach for Pitch Control of Offshore Wind Turbine on Barge Floating Platform

Offshore floating wind turbine (OFWT) has gained increasing attention during the past decade because of the offshore high-quality wind power and complex load environment. The control system is a tradeoff between power tracking and fatigue load reduction in the above-rated wind speed area. In allusion to the external disturbances and uncertain system parameters of OFWT due to the proximity to load centers and strong wave coupling, this paper proposes a computationally inexpensive robust adaptive control approach with memory-based compensation for blade pitch control. The method is tested and compared with a baseline controller and a conventional individual blade pitch controller with the “NREL offshore 5 MW baseline wind turbine” being mounted on a barge platform run on FAST and Matlab/Simulink, operating in the above-rated condition. It is shown that the advanced control approach is not only robust to complex wind and wave disturbances but adaptive to varying and uncertain system parameters as well. The simulation results demonstrate that the proposed method performs better in reducing power fluctuations, fatigue loads and platform vibration as compared to the conventional individual blade pitch control.

Reduction of Power Fluctuations of a Large-Scale Grid-Connected Offshore Wind Farm Using a Variable Frequency Transformer

This paper presents a novel control scheme using a variable frequency transformer (VFT) of 100 MW to effectively reduce power fluctuations of an equivalent 80-MW aggregated doubly-fed induction generator (DFIG)-based offshore wind farm (OWF) connected to an onshore 120-kV utility grid. The q-d axis equivalent-circuit model is employed to establish the mathematical models for the VFT and the OWF to derive the complete dynamic equations of the studied system under three-phase balanced conditions. A frequency-domain approach based on a linearized system model using eigen techniques and a time-domain scheme based on a nonlinear system model subject to disturbance conditions are both performed to examine the effectiveness of the proposed control scheme. It can be concluded from the simulation results that the proposed VFT is effective to smooth the fluctuating active power of the OWF injected into the power grid while the damping of the studied OWF can also be improved.

234 自然エネルギー電源の出力変動抑制におけるガスエンジンの利用

In order to increase the capacity of renewable energy in power systems, it is necessary to reduce power fluctuations. In this paper, the potential of gas engines (GEs) is evaluated by means of dynamic simulation. In this system, a hybrid generation system made up from GEs and photovoltaic cells (PV) supplies power to a large grid. Such a system is hoped. As a result of simulations, 9.9 kW GE is very useful to compensate PV power fluctuation. The efficient way using GEs to compensate scaled-up version of renewable energy is also discussed in this paper. In conclusion, the next three points are revealed to be effective. (1) Adding a larger scale GE to small scale GEs, (2) controlling preferentially the GE whose output variation speed is faster, and (3) decreasing lower limit of GE outputs.

Individual blade pitch control of floating offshore wind turbines

AbstractFloating wind turbines offer a feasible solution for going further offshore into deeper waters. However, using a floating platform introduces additional motions that must be taken into account in the design stage. Therefore, the control system becomes an important component in controlling these motions. Several controllers have been developed specifically for floating wind turbines. Some controllers were designed to avoid structural resonance, while others were used to regulate rotor speed and platform pitching. The development of a periodic state space controller that utilizes individual blade pitching to improve power output and reduce platform motions in above rated wind speed region is presented. Individual blade pitching creates asymmetric aerodynamic loads in addition to the symmetric loads created by collective blade pitching to increase the platform restoring moments. Simulation results using a high‐fidelity non‐linear turbine model show that the individual blade pitch controller reduces power fluctuations, platform rolling rate and platform pitching rate by 44%, 39% and 43%, respectively, relative to a baseline controller (gain scheduled proportional–integral blade pitch controller) developed specifically for floating wind turbine systems. Turbine fatigue loads were also reduced; tower side–side fatigue loads were reduced by 39%. Copyright © 2009 John Wiley & Sons, Ltd.

LVRT of Grid Interfaced Variable Speed Driven PMSG for WECS during Fault

- 392 - Abstract— Wind energy conversion systems have become a focal point in the research of renewable energy sources. This is in no small part due to the rapid advances in the size of wind generators as well as the development of power electronics and their applicability in wind energy extraction. The voltage of the direct driven permanent magnet wind generators (PMSG) is variable due to the intermittent nature of the wind energy. Fluctuating voltage and power is of major concern in the converter based grid connected wind generation systems. An inverter is essential for the interfacing of the wind source with the AC network. This paper discusses the interconnection issues of permanent magnet wind generators to local grid as per prevailing grid standards during healthy and fault conditions. The fault ride-through topology for PMSG has been demonstrated using MATLAB Simulink based simulation. Wind energy is a reliable, natural and renewable electrical power supply. The high installed capacity of today 's wind turbines and decreasing plant costs have shown that wind power can be competitive with conventional, more heavily polluting, fuels in the long term. Wind power growth with a 20% annual rate has experienced the fastest growth among all renewable energy sources science five years ago. It is predicted that by 2020 up to 12% of the world's electricity will have been supplied by wind power. Figure-1 shows the global cumulative installed capacity and global annual installed capacity. In terms of wind power generation technology, as a result of numerous technical benefits (higher energy yield, reducing power fluctuations and improving var supply) the modern MW-size wind turbines always use variable speed operation which is achieved by electrical converters .These converters are typically associated with individual generators and they contribute significantly to the costs of wind turbines. Between variable speed wind turbine generators doubly fed induction generators (DFIGs) and permanent magnet synchronous generators (PMSGs) with primary converters are emerging as the preferred technologies.

Experimental results from sea trials of an offshore wave energy system

A full-scale prototype of a wave power plant has been installed off the Swedish west coast and the overall wave energy converter concept has been verified. Initial results have been collected and significant insights discovered. Energy absorption dependency on load as well as output voltage and power is demonstrated. It is shown that great overload capability of the directly driven linear generator is critical, and indicated that, for resistive loads, optimal load does not vary with wave climate. Future grid supplying energy production would necessitate parks of wave power plants in order to reduce power fluctuations.

Power Stabilization of a Helium-Neon Laser Using the Zeeman Effect

The helium-neon laser is utilized in many applications today by scientists and engineers. These applications frequently require a visible amplitude-stable optical source. Helium-neon lasers have been shown to have amplitude fluctuations of typically ± 1%. Amplitude stabilization techniques have been previously concerned with mechanical improvements, discharge current regulation, and variable loss modulation. The Zeeman effect of a magnetic field will be shown to control the output power of a helium-neon laser. A servo feedback system was constructed to demonstrate the ability to stabilize the visible power by reducing power fluctuations from ± 1.0% to ± 0.05%. The Zeeman effect stabilizer overcomes the necessary insertion loss of the current regulation stabilizer. It is also independent of the negative impedance high voltage discharge system.