•Reactive power control in DFIG-based wind turbine to provide ancillary services.•Use EGRPS-based wireless communication to DFIG reactive power management.•Constant monitoring of busbar voltages in ...electrical systems.•Co-simulation of telecommunications and Power Systems.•Solution for operation planning of modern power systems in smart grid environments.
This paper presents an alternative topology analysis for reactive power control in wind farms with wireless communication link integration. The co-simulation environment with telecommunication, machine control, and power system demonstrate in this analysis, that it can be an useful solution for planning the operation of modern power systems and their ancillary services in a smart grid scenario. A low cost and easy implementation EGPRS standard wireless link was adopted to perform the communication from the smart grid operator and the wind farm with the objective of maintain the voltage levels under established limits. The wireless communication was used to send the value of measured voltage of one critical bar to the operator and to return the reactive power reference to the wind farm. The studied scenario is represented by a seven bar power system model connected to a DFIG wind farm. The results obtained by this co-simulation endorse this original proposal and show its operability.
This paper proposes a novel non-linear filter applied to wireless-transmitted reference signals in a deadbeat control strategy of a doubly-fed induction wind turbines. These signals are likely to be ...corrupted by spikes intrinsically imposed by the wireless channel. This impulsive noise is traditionally mitigated using classical error-correction schemes, and the proposed filter is an alternative that is simpler and has lower computational cost. The proposed technique, hereby designated as Functionally-Weighted Moving Average (FWMA) filter, is based on a non-conventional weighting of the signal samples, which is carried out by a rectangular function. The filter realization is as straight as any linear technique. The generator control scheme, which includes the filter, is embedded in a microprocessor locally placed at the generator site, where it acts on the reference signals at the receiving end of the channel. The performance of both the filter and the control system are verified by simulations that include the wind turbine dynamics and the communication channel. The proposed technique is compared with a morphological filter, previously suggested for the same purpose. The results endorse the FWMA filter efficacy to clean out impulsive interferences with minor delays.
•A nonlinear filter for impulse noise is proposed.•The filter is based on a rectangular function to weight signal samples.•The filter is applied to clean wireless transmitted signals.•The wireless transmitted signals control wind turbines.
In a renewable energy power system inside a smart grid environment, the use of wireless technologies for remote transmitting control information to the wind turbines requires modern techniques to ...improve the overall generated power quality and prevent damage to the turbines and converters. In this work, a robust wireless control system for a squirrel cage induction wind turbine connected to the power grid is proposed. The system employs convolutional coding and morphological filtering jointly to enhance the generated power quality by improving the robustness of the control system to the errors caused by the radio propagation channel. The performance is investigated in terms of total harmonic distortion and overall system response to verify the power quality delivered by the wind turbine to the grid. The satisfactory results endorse the operability and advantages of the proposed wireless control system.
•A morphological filter for SCIG wind turbine applications is proposed.•The wireless transmitted signals control wind turbines.•The filter is applied to clean wireless transmitted signals.•An important power quality enhancement is observed.
Smart grids treat energy in a much more efficient manner than it is done currently by conventional power systems. One important aspect in the design and analysis of smart grids is to take into ...account some real characteristics of the power system and its loads. In this context, we propose a dynamic load model for residential applications based on a non-homogeneous Poisson process, whose parameters depend on the electrical characteristics of the loads and their time-varying power profiles. Some of the advantages of this model are its flexibility to represent any specific energetic scenario found in different regions of the globe and the possibility to independently control individual low-voltage loads of the evaluated system by modifying the activation function of the corresponding load model. This last characteristic is fundamental to represent adequately and analyze the behavior of smart grids. To demonstrate the accuracy and effectiveness of the proposed strategy, several load curves were generated with the aid of the proposed model and compared against real measurements.
Wind energy is the major driver to obtain an optimized and efficient use of renewable energy in smart grids. To provide balanced supply, demand, and storage of energy in a much more efficient manner ...than is done today, smart grids require the employment of an advanced communication infrastructure associated to a robust power control and real-time monitoring systems.
Towards this objective, we present a wireless-coded power control scheme for doubly fed induction generators operating at variable speed. The proposed system employs adaptive neuro-fuzzy control, quaternary phase shift-keying modulation, and low-density parity check coding techniques to improve the system robustness and reliability in different propagation conditions for remotely transmitting the power control references from the control center to a given aerogenerator.
In this paper, a new power control system for wind turbines based on a squirrel cage induction generator linked to the mains by means of a back-to-back converter for smart grid applications is ...proposed. The wireless system employs orthogonal frequency division multiplexing, convolutional coding, and functionally weighted moving average filtering to improve the system performance against the errors due to the propagation channel in the transmitted power references. Hence, the system avoids damages in turbines and converters and also increases the power quality of the power injected into the grid. Hence, the reactive power injection can be helpful in ancillary services. The system was analyzed regarding the total harmonic distortion for SCIGs’ currents and the system response to verifying the delivered power quality by the generator to the mains. The simulated results validate the proposed wireless-coded control system.
A low concentration of nitric oxide associated with a high concentration of asymmetric dimethylarginine (ADMA) can explain the lack of ischemic cardioprotection observed in the presence of ...hypercholesterolemia. The objective of the present study was to evaluate the effect of hypercholesterolemia on ischemic pre- and postconditioning and its correlation with plasma concentrations of ADMA. Male Wistar rats (6-8 weeks old) fed a 2% cholesterol diet (n = 21) for 8 weeks were compared to controls (n = 25) and were subjected to experimental myocardial infarction and reperfusion, with ischemic pre- and postconditioning. Total cholesterol and ADMA were measured in plasma before the experimental infarct and the infarct area was quantified. Weight, total cholesterol and plasma ADMA (means ± SE; 1.20 ± 0.06, 1.27 ± 0.08 and 1.20 ± 0.08 vs 0.97 ± 0.04, 0.93 ± 0.05 and 0.97 ± 0.04 µM) were higher in animals on the hypercholesterolemic diet than in controls, respectively. Cardioprotection did not reduce infarct size in the hypercholesterolemic animals (pre: 13.55% and post: 8% compared to 7.95% observed in the group subjected only to ischemia and reperfusion), whereas infarct size was reduced in the animals on a normocholesterolemic diet (pre: 8.25% and post: 6.10% compared to 12.31%). Hypercholesterolemia elevated ADMA and eliminated the cardioprotective effects of ischemic pre- and postconditioning in rats.
•Power control.•Predictive control.•Renewable energy.•Smart grid and wireless communication.
As the smart grid structure interconnects renewable energy sources and operators, it is inevitably ...influenced by the conversion technology and communication system. Investigating the effects of both aspects jointly is an intricate task due to its multifaceted characteristic. In this paper, it is proposed a wireless coded predictive direct power control for a general renewable energy system connected to the grid for smart grid environment. The predictive direct power control processes the received power references that are sent through the wireless channel, and selects the optimal voltage vector to be supplied by the three-phase inverter using the power errors. The wireless communication system, which connects the smart grid operator to the energy systems, is based on Low Density Parity Check and Orthogonal Frequency Division Multiplexing, and in this work, it was used, as a reference of performance, a system that employs Convolutional Coding. The behavior of the proposed power control is evaluated experimentally presenting an operational condition with satisfactory performance.
•A DTC technique for a DFIG was proposed to testing the reactive power and the electromagnetic torque step changes according to the grid conditions using the wireless references signals.•Simulations ...were done to evaluate the behavior of the control technique via GPRS-CS1, EGPRS-MCS1 and EGPRS-MCS5, showing that the better option was the EGPRS-MCS5.•Fuzzy-tuned PI controller applied to a DTC was proposed for optimizing the calculation of the proportional and the integral gains.
Wireless communication applications for smart grids are a novel trend in renewable energy solutions. However, the problem of interference in the channel must be considered. The GPRS/EGPRS standards could be used to transmit the reference signals to the wind power system. A Direct Torque Control technique for a DFIG was proposed to testing the reactive power and the electromagnetic torque step changes according to the grid conditions using the wireless references signals. A Fuzzy-tuned PI controller was included to optimize the calculation of its proportional and the integral gains. Simulations were done in Matlab/Simulink to evaluate the behavior of the control technique via GPRS-CS1, EGPRS-MCS1 and EGPRS-MCS5 standards. The total harmonic distortion for the stator currents injected to the grid is also evaluated.
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