Step Changes In Wind Speed Research Articles

Frequency Support Studies of a Diesel–Wind Generation System Using Snake Optimizer-Oriented PID with UC and RFB

The present paper discusses the modeling and analysis of a diesel–wind generating system capable enough to cater to the electrical power requirements of a small consumer group or society. Due to high variations of the load demand or due to changes in the wind speed, the frequency of the diesel–wind system will be highly disturbed, and hence to regulate the frequency and power deviations of the wind turbine system, an effective controller design is a necessary requirement, and therefore this paper proposes a novel controller design based on PID scheme. The parameters of this controller is effectively optimized through a new snake optimizer (SO) in an offline manner to minimize frequency and power deviations of an isolated diesel–wind system. The performance of SO-PID for the diesel–wind system is evaluated by considering the integral of time multiplied absolute error (ITAE), integral absolute error (IAE), and integral of time multiplied square error (ITSE). The results were calculated for a step change in load, step change in wind speed, load change at different instants of time with diverse magnitude, and for random load patterns, and they were compared with some of the recently published results under similar working conditions. In addition, the effect of an ultracapacitor (UC) and redox flow battery (RFB) on SO-PID was investigated for the considered system, and the application results demonstrated the advantages of our proposal over other studied designs.

Application of a Novel Synergetic Control for Optimal Power Extraction of a Small-Scale Wind Generation System with Variable Loads and Wind Speeds

The synergetic control technique (SCT) has the solution for understanding the symmetry inherent in the non-linear properties of wind turbines (WTs); therefore, they achieve excellent performance and enhance the operation of the WT. Small-scale WTs are efficient and cost-effective; they are usually installed close to where the generated electricity is used. This technology is gaining popularity worldwide for off-grid electricity generation, such as in rural homes, farms, small factories, and commercial properties. To enhance the efficiency of the WT, it is vital to operate the WT at its maximum power. This work proposes an efficient and fast maximum power point tracking (MPPT) technique based on the SCT to eradicate the drawbacks of the conventional methods and enhance the operation of the WT at the MPP regardless of wind speed and load changes. The SCT has advantages, such as robustness, simplified design, fast response, no requirement for knowledge of WT characteristics, no need for wind sensors or intricate power electronics, and straightforward implementation. Furthermore, it improves speed convergence with minimal steady-state oscillations at the MPP. The investigated configuration involves a wind-driven permanent magnet synchronous generator (PMSG), uncontrolled rectifier, boost converter, and variable load. The two converters are used to integrate the PMSG with the load. Three scenarios (step changes in wind speed, stochastic changes in wind speed, and variable electrical load) are studied to assess the SCT. The results prove a high performance of the suggested MPPT control method for a fast convergence speed, boosted WT efficacy, low oscillation levels, and applicability under a variety of environmental situations. This work used the MATLAB/Simulink program and was then implemented on a dSPACE 1104 control board to assess the efficacy of the SCT. Furthermore, experimental validation on a 1 kW Darrieus-type WT driving a PMSG was performed.

Two novel approaches to capture the maximum power from variable speed wind turbines using optimal fractional high-order fast terminal sliding mode control

In this paper, two nonlinear control approaches using optimal fractional high-order fast terminal sliding mode (FHOFTSM) control are proposed to maximize the captured wind energy and minimize the mechanical loads in the variable speed wind turbines (VSWTs). The optimal condition of the system which uses the presented approaches is achieved by creating a compromise between maximizing the energy extraction and minimizing the control input. So, the mechanical stress on the drive-train is reduced by minimizing the control input. To achieve this compromise, the behavior of the wind turbine system should be precisely modeled. Fractional calculus theory is an effective method for modeling the VSWT, which provides a more accurate description of the system performance compared with integer-order modeling. Based on the fractional-order modeling of the system, the optimal approach is designed by calculating the error dynamics of the system and defining two types of performance indexes, integer-order and fractional-order performance indexes. Hence, the design procedure of an optimal FHOFTSM control for each performance index requires two-stages process. At first phase, an optimal controller is presented for the system nominal error to minimize the quadratic performance index. Then a switching controller is offered in the second phase that is obtained by defining the fractional high-order sliding manifold and fractional nonsingular fast terminal sliding manifold to overcome the unknown disturbance. Hence, the order of the controllers is smaller than the second order. The optimal strategy is applied to minimize the control input, whereas the FHOFTSM method is used to obtain the maximum wind power extraction, reduce mechanical loads, attenuate the chattering, and achieve fast finite-time convergence. The closed-loop stability of the control system is approved by the fractional Lyapunov direct method and the Mittag-Leffler stability theorem. To illustrate the effectiveness of the proposed approaches, the proposed controllers are compared with some already existing controllers. The performance of controllers is verified through three scenarios, i.e., random variation of wind speed, step change of wind speed, and robustness against parameter uncertainties, in which the simulation results confirm the effectiveness of the proposed controllers.

Co-simulation and hardware realization of PMSG–WECS based on current source inverter for grid synchronization

Buck boost converter and current source inverter based Permanent Magnet Synchronous Generator (PMSG) for the Wind Energy Conversion System (WECS) is proposed in the system. The Synchronous Reference Frame (SRF) theory controller with hysteresis band for the pulse generation is used as the control algorithm to synchronize with the grid. The maximum power conversion is achieved by using the PI based closed loop controller in the buck boost converter. The validation of the proposed system is done in co-simulation of MATLAB and LabVIEW with Simulation Interface Toolkit (SIT) server through transmission control protocol/internet protocol communication network. The proposed system is analyzed with constant wind speed, the step change in wind speed, frequent change in wind speed. The results proved that the system could produce power at all operating conditions and able to deliver constant power to the grid and loads. The hardware realization of the model is performed using FPGA-based controllers.

Modeling and Control Design of an Autonomous Hybrid Wind/Energy Storage Generation Unit

The purpose of the present paper is to investigate a controller design and simulations of autonomous hybrid wind turbine system with variable-speed permanent magnet synchronous generator (PMSG) and a system for storing energy. The proposed system is mainly composed of a wind turbine drives permanent magnet synchronous generator, uncontrolled rectifier, DC/DC converter, DC/AC inverter and static loads. Furthermore, the mathematical model of the studied sub-systems and two control loops are considered. The first one is the controller which needed to preserve the DC-link voltage fixed at its desired value. The second one is the controller which needed to regulate the charge/discharge modes of the storage battery. The suggested hybrid wind/energy storage power generation model is considered and analyzed in case of without controller firstly. Then, the considered hybrid wind/energy storage power generation unit with the proposed controller is examined through a step change in wind speed. Digital simulation results show that the power desired by the linked loads may be successfully supplied and transported by the presented hybrid wind turbine and energy storage power generation system based on proportional-integral-derivative (PID) controller. Also, the emulation results show that there a good foretelling of the electrical variable waveforms and good achievement in case of the presented controller emulated with the case of without controller as maintaining the load voltage fixed at its reference values

Modeling and Analysis of Maximum Power Tracking of a 600 kW Hydraulic Energy Storage Wind Turbine Test Rig

An innovative wind turbine with a particular hydraulic transmission and energy storage system is proposed in this paper. The purpose of applying the hydraulic transmission is to remove the gearbox and power converter of traditional wind turbine and cooperate on wind resource storing with the energy storage system. To overcome the volatility and intermittence shortcomings of wind and improve the output power quality, hydraulic accumulators are used as the energy storage device for wind energy regulation. The original gearbox and generator in the nacelle of a Micon 600 wind turbine were removed and replaced with a hydraulic pump to make a test rig for the investigation into maximum power point tracking (MPPT) of this hydraulic wind turbine concept. The mathematical model of the entire test system is established according to the four function modules. The MPPT control strategy based on the tip speed ratio (TSR) is adopted and a control system containing three closed-loop controls is designed to achieve maximum wind power extracting and produce constant frequency power generation. Ultimately, the dynamic response of rotor speed control is revealed under step change of wind speed and the maximum power tracking performance of the 600 kW hydraulic energy storage wind turbine test bench is simulated and analysed by subjecting to turbulent speed condition. The simulation results demonstrate that the rotor of the wind turbine can run at the expected optimal speed depending on wind speed, and the wind power utilization coefficient of the unit is stabilized at about the maximum value.

PCSMC design of permanent magnetic synchronous generator for maximum power point tracking

This study develops a perturbation compensation based sliding-mode control (PCSMC) strategy of a permanent magnetic synchronous generator (PMSG) for optimal extraction of wind energy. Firstly, PMSG non-linearities, uncertain parameters, unmodelled dynamics, and stochastic wind speed variations are aggregated into a perturbation. Then, it is estimated by a sliding-mode state and perturbation observer in the real time. Further, the perturbation estimate is fully cancelled by sliding-mode controller (SMC) for global control consistency, together with considerable robustness thanks to the sliding-mode mechanism. In addition, the upper bound of perturbation is replaced by its real-time estimate; thus more proper control costs could be achieved without over-conservativeness. Moreover, PCSMC does not require an accurate PMSG model while only the measurement of d-axis current and mechanical rotation speed is required. Four case studies are carried out, e.g. step change of wind speed, low-turbulence stochastic wind speed, high-turbulence stochastic wind speed, and PMSG parameter uncertainties. Simulation results demonstrate that PCSMC can rapidly extract higher power under different wind speed profiles against vector control and SMC. Lastly, a dSpace-based hardware-in-the-loop experiment is undertaken which validates its implementation feasibility.

Torque and pitch angle control of a wind turbine using multiple adaptive neuro-fuzzy control

This article presents a multiple adaptive neuro-fuzzy inference system-based control scheme for operation of the wind energy conversion system above the rated wind speed. By controlling the pitch angle and generator torque concurrently, the generator power and speed fluctuation can be reduced and also turbine blade stress can be minimized. The proposed neuro-fuzzy-based adaptive controller is composed of both the Takagi–Sugeno fuzzy inference system and neural network. First, a step change in wind speed and then a simulated wind speed are considered in the proposed adaptive control design. A MATLAB/Simulink model of the wind turbine system is prepared, and simulations are carried out by applying the proportional integral, fuzzy-proportional integral and the proposed adaptive controller. From the obtained results, the effectiveness of the proposed adaptive controller approach is confirmed.

Passivity‐based linear feedback control of permanent magnetic synchronous generator‐based wind energy conversion system: design and analysis

This study designs a passivity-based linear feedback control scheme of a permanent magnetic synchronous generator-based wind energy conversion system, which attempts to achieve a maximum power point tracking (MPPT) at generator-side voltage source converter (VSC) and enhance fault ride-through (FRT) capability at grid-side VSC simultaneously. A storage function is constructed based on the passivity theory, in which the actual role of each term is meticulously investigated while the beneficial ones are remained so as to significantly improve the transient responses. Then, an auxiliary input is employed in the form of linear feedback control to ensure a desired tracking error convergence. Moreover, the closed-loop system stability is thoroughly analysed, together with a detailed physical interpretation of the storage function. Three case studies are undertaken including step change of wind speed, stochastic wind speed variation, and FRT. Simulation results verify that the proposed approach can effectively achieve MPPT and dramatically improve the FRT capability under various operation conditions against that of vector control and feedback linearisation control.

Sensorless Strategy of a Two-Level MPPT for Permanent Magnet Wind Generation System Using SRF-PLL

This paper presents the optimization of the wind power in a variable speed Wind Energy Conversion System (WECS) using a sensorless Maximum Power Point Tracking (MPPT) strategy that avoids mechanical measurement of the wind speed. The proposed system consists of a turbine, a direct-drive Permanent Magnet Synchronous Generator (PMSG) controlled by a Field Oriented Control (FOC) through a three phase controlled rectifier connected to a DC load. The choice of the FOC is justified by a power maximization analysis. The generator rotor speed and position required by the FOC and the sensorless MPPT are estimated using a Synchronous Reference Frame Phase Locked Loop (SRF-PLL). The proposed technique is validated using both simulation in Matlab-Simulink and experimental work based on step changes in wind speed. Results are presented at the end of the paper showing that the estimated angle and speed by the SRF-PLL are approximatively the same as the real ones, also figure of the output power shows that it is maximized confirming the effectiveness of the adopted approach.

Democratic joint operations algorithm for optimal power extraction of PMSG based wind energy conversion system

This paper proposes a novel military philosophy inspired meta-heuristic algorithm called democratic joint operations algorithm (DJOA), which attempts to find the optimal parameters of proportional-integral-derivative (PID) controllers of permanent magnetic synchronous generator (PMSG) based wind energy conversion system (WECS), such that a maximum power point tracking (MPPT) under different wind speed profiles can be achieved. In order to realize a deeper optimum search, an additional deputy officer is introduced into the democratic defensive operations of each military unit, in which the soldiers can wisely seek a more optimal defensive position following the consensus/compromise of the officer and deputy officer. Furthermore, the shuffling strategy of shuffled frog leaping algorithm (SFLA) is employed for the shuffling regroup operations of DJOA, which effectively avoids the local optimum trapping by sharing the global position information among all the soldiers. Three case studies are carried out, e.g., step change of wind speed, low-turbulence stochastic wind speed variation, and high-turbulence stochastic wind speed variation, respectively. Simulation results verify that an improved optimal power extraction can be realized by DJOA compared with that of other five typical meta-heuristic algorithms.

Realisation and HIL testing of wind turbine emulator based on DTC squirrel cage induction motor drive

Direct torque control (DTC) is known to produce the fastest torque response in AC drives. In this paper, a wind turbine emulation (WTE) system using a squirrel cage induction motor (SCIM) working in a DTC mode is designed, implemented, and tested experimentally using Hardware-in-loop (HIL). The flux estimation is based on the current model where two stator currents and the rotor speed are measured. The DTC is realised using a space vector modulator to avoid variable switching frequency associated with the DTC switching tables. dSPACE MicroLabBox is used to handle the real-time control programmed in SIMULINK. Typhoon HIL402 is used to emulate the inverter, the machine, the connected mechanical load, and the feedback sensors of the current dc link voltage and speed. Thanks to the great flexibility offered by the HIL technique, a variety of tests has been conducted to validate the overall system performance. The tests include step change of load, step change of wind speed, operation under stochastic wind spe...

Realisation and HIL testing of wind turbine emulator based on DTC squirrel cage induction motor drive

Direct torque control (DTC) is known to produce the fastest torque response in AC drives. In this paper, a wind turbine emulation (WTE) system using a squirrel cage induction motor (SCIM) working in a DTC mode is designed, implemented, and tested experimentally using Hardware-in-loop (HIL). The flux estimation is based on the current model where two stator currents and the rotor speed are measured. The DTC is realised using a space vector modulator to avoid variable switching frequency associated with the DTC switching tables. dSPACE MicroLabBox is used to handle the real-time control programmed in SIMULINK. Typhoon HIL402 is used to emulate the inverter, the machine, the connected mechanical load, and the feedback sensors of the current dc link voltage and speed. Thanks to the great flexibility offered by the HIL technique, a variety of tests has been conducted to validate the overall system performance. The tests include step change of load, step change of wind speed, operation under stochastic wind speed variation and torque-speed characteristics' of the emulated wind turbine at different feeds of wind speeds and coupled mechanical loads. Testing results verified the perfect fit of DTC in WTE application and the effectiveness of the HIL testing technique.

Passivity-based sliding-mode control design for optimal power extraction of a PMSG based variable speed wind turbine

Abstract This paper proposes a novel passivity-based sliding-mode control (PB-SMC) scheme of permanent magnetic synchronous generator (PMSG) for maximum power point tracking (MPPT). A storage function is constructed based on the passivity theory at first, in which the beneficial system nonlinearities, e.g., which can make the derivative of storage function to be more negative, are carefully remained so as to improve the system damping while all the other system nonlinearities are fully removed. Then, an additional input is used to lead the closed-loop system to be output strictly passive via energy reshaping, meanwhile a sliding-mode control (SMC) is incorporated to greatly enhance the system robustness against various uncertainties of PMSG. Hence, PB-SMC can simultaneously own the promising merits of improved system damping and significant robustness, together with a globally consistent control performance under various operation conditions. Case studies including step change of wind speed, stochastic wind speed variation, pitch angle variation, and generator parameter uncertainties, are undertaken which verify the effectiveness and superiority of PB-SMC compared to that of other typical controllers. Lastly, a dSpace based hardware-in-loop (HIL) test is carried out to validate the implementation feasibility of PB-SMC.

DC grid/bus tied DFIG based wind energy system

This paper presents a novel configuration of Doubly Fed Induction Generator (DFIG) based wind energy systems (WESs) to improve the reliability of power systems. In the proposed configuration, rotor and stator sides of DFIG are connected to Direct Current (DC) grid/bus through converter and 12-pulse diode bridge rectifier, respectively, while loads are connected with the Alternating Current (AC) bus. Furthermore, the rotor current amplitude and frequency have been utilized to regulate the voltage of stator AC bus. The RMS detection of load/stator voltage method is used to calculate the reference rotor currents. The control pulses for rotor side converter are supplied by the hysteresis current controller, operated on the error signal, calculated between actual and reference rotor currents. Also, a comparative study between the speed-sensorless control and speed-sensor control techniques is presented for the rotor side converter of the proposed configuration. Furthermore, three possible cases, namely, ‘step change in reference input voltage’, ‘step change in wind speed or wind gust’, and load switching are simulated in MATLAB® for2 MVA DFIG based WESs connected to DC grid/bus to evaluate the proficiency of the proposed configuration. Also, proposed configuration is tested on experimental set-up to reveal its efficacy in real environment.

Experimental Voltage Stabilization of a Variable Speed Wind Turbine Driving Synchronous Generator using STATCOM based on Genetic Algorithm

Abstract In this paper Static Synchronous Compensator (STATCOM) is used for improving the performance of the power grid with wind turbine that drives synchronous generator. The main feature of the STATCOM is that it has the ability to absorb or inject rapidly reactive power to grid. Therefore the voltage regulation of the power grid with STATCOM device is achieved. STATCOM also improves the stability of the power system after occurring severe disturbance such as faults, or suddenly step change in wind speed. The proposed STATCOM controller is a Proportional-Integral (PI) controller tuned by Genetic Algorithm (GA). An experimental model was built in Helwan University to the proposed system. The system is tested at different operating conditions. The experimental results prove the effectiveness of the proposed STATCOM controller in damping the power system oscillations and restoring the power system voltage and stability.

Advanced Control of Wind Electric Pumping System for Isolated Areas Application

The supply water in remote areas of windy region is one of most attractive application of wind energy conversion .This paper proposes an advanced controller suitable for wind-electric pump in isolated applications in order to have a desired debit from variation of reference speed of the pump also the control scheme of DC voltage of SIEG for feed the pump are presented under step change in wind speed. The simulation results showed a good performance of the global proposed control system.

Voltage and frequency control of an autonomous hybrid generation system based on linear model predictive control

This paper presents an adaptive control for voltage and frequency regulation of a stand-alone hybrid wind-diesel power system based on constrained linear model predictive control (MPC). The proposed system mainly consists of a wind turbine driving a self-excited induction generator (SEIG) connected via a DC link to a synchronous generator (SG) driven by a diesel engine. The SG is equipped with a voltage regulator and a static exciter. The wind generator and the synchronous generator together cater for the local load and power requirement. However, the load bus voltage and frequency are governed by the SG. To extract maximum available wind power, it is assumed that the wind generation system operates free without control. The control objective aims to control the load voltage and frequency. This is achievement via controlling the field voltage and rotational speed of the SG. The MPC controller is based on the minimization of a cost function of voltage and rotor speed errors while respecting the given constraints. The hybrid wind-diesel energy system with the proposed MPC has been tested through a turbulent and step change in wind speed and load impedance respectively. Simulation results show that accurate tracking performance of the system has been achieved.

NONLINEAR AUTOREGRESSIVE MOVING AVERAGE CONTROLLER FOR ISOLATED WIND GENERATION SYSTEM CONTROL

In this paper, the voltage and frequency control of an isolated selfexcited induction generator, driven by wind turbine, is developed with emphasis on nonlinear auto regressive moving average (NARMA-L2) based on neural networks approach. This has the advantage of maintaining constant terminal voltage and frequency irrespective of wind speed and load variations. Two NARMA L2 controllers are used. The first one is dedicated for regulating the terminal voltage of the induction generator to a set point by controlling the thyristor firing angle of a static reactive power compensator (SVAR). The second one is designed to control the mechanical input power to the generator via adjusting the blade pitch angle of the wind turbine. In this application, an indirect data-based technique is taken, where a model of the plant is identified on the basis of input-output data and then used in the model-based design of a neural network controller. The proposed system has the advantages of robustness against model uncertainties and external disturbances. The robustness of the wind-energy scheme has been certified through step change in wind speed. Moreover, the system is tested also during a step change in load impedance. Simulation results show that high dynamic performance of the proposed wind energy scheme has been achieved.

Transient response of sap flow to wind speed

Transient responses of sap flow to step changes in wind speed were experimentally investigated in a wind tunnel. A Granier-type sap flow sensor was calibrated and tested in a cylindrical tube for analysis of its transient time response. Then the sensor was used to measure the transient response of a well-watered Pachira macrocarpa plant to wind speed variations. The transient response of sap flow was described using the resistance–capacitance model. The steady sap flow rate increased as the wind speed increased at low wind speeds. Once the wind speed exceeded 8.0 m s−1, the steady sap flow rate did not increase further. The transpiration rate, measured gravimetrically, showed a similar trend. The response of nocturnal sap flow to wind speed variation was also measured and compared with the results in the daytime. Under the same wind speed, the steady sap flow rate was smaller than that in the daytime, indicating differences between diurnal and nocturnal hydraulic function, and incomplete stomatal closure at night. In addition, it was found that the temporal response of the Granier sensor is fast enough to resolve the transient behaviour of water flux in plant tissue.