The renewable energy domain represents an important issue for the sustainable development of the mankind in the actual context of increasing demand for energy along with the increasing pollution that ...affect the environment. A significant quota of the clean energy is represented by the wind energy. As a consequence, the developing of wind energy conversion systems (WECS) in order to achieve high energetic performances (efficiency, stability, availability, competitive cost etc) represents a topic of permanent actuality. Testing and developing of an optimized control strategy for a WECS direct implemented on a real energetic site is quite difficult and not cost efficient. Thus a more convenient solution consists in a flexible laboratory setup which requires an experimental model of a WECS. Such approach would allow the simulation of various real conditions very similar with existing energetic sites. This paper presents a grid-connected wind turbine emulator. The wind turbine is implemented through a real-time Hardware-in-the-Loop (HIL) emulator, which will be analyzed extensively in the paper. The HIL system uses software implemented in the LabVIEW programming environment to control an ABB ACS800 electric drive. ACS800 has the task of driving an induction machine coupled to a permanent magnet synchronous generator. The power obtained from the synchronous generator is rectified, filtered and sent to the main grid through a controlled inverter. The control strategy is implemented on a NI CompactRIO (cRIO) platform.
The paper presents an extended structure for a minimum variance adaptive control system of an induction generator, which aims to improve its operating behavior under electrical short-circuit ...conditions. The basic design idea is to limit the control to physically achievable values, and thus increasing the robustness of the control system and avoiding an instability regime. A control limiting block is proposed and used for this purpose. Moreover, a short-circuit detector enables an on-line setting of the control penalty factor, improving the quality of the controlled output. All these additional customizations of the control system, implemented to keep the plant operational under and after a short-time short-circuit fault (acting as an abnormal perturbation), must also provide good performance in the normal operating mode. Index Terms--adaptive control, control engineering, generators, power system faults, short circuit currents
Starting from the target of the European Union (EU) to use renewable energy in the area that aims a binding target of 20% renewable energy in final energy consumption by 2020, this article ...illustrates the identification of risks for implementation of wind energy projects in Romania, which could lead to complex technical implications, social and administrative. In specific projects analyzed in this paper were identified critical bottlenecks in the future wind power supply chain and reasonable time periods that may arise. Renewable energy technologies have to face a number of constraints that delayed scaling-up their production process, their transport process, the equipment reliability, etc. so implementing these types of projects requiring complex specialized team, the coordination of which also involve specific risks. The research team applied an analytical risk approach to identify major risks encountered within a wind farm project developed in Romania in isolated regions with different particularities, configured for different geographical areas (hill and mountain locations in Romania). Identification of major risks was based on the conceptual model set up for the entire project implementation process. Throughout this conceptual model there were identified specific constraints of such process. Integration risks were examined by an empirical study based on the method HAZOP (Hazard and Operability). The discussion describes the analysis of our results implementation context of renewable energy projects in Romania and creates a framework for assessing energy supply to any entity from renewable sources.
In this paper is presented a mathematical model of the electric arc for an alternative current welding machine of low power. The electric arc model is based on dividing the voltage-current ...characteristic of the electric arc in many functioning zones. For the model of the entire welding machine are used real parameters as the ones of the proper welding machine. The voltage and current harmonics spectrum that is obtained during the welding process is presented. Also, the waveforms for the current and voltage of the electric arc plotted against time and the voltage-current characteristic of the electric arc are illustrated. The electric arc is considered as being supplied by alternative voltage from the electrical power network using a single phase transformer which has the output voltage of 80 volts. The model of the welding machine is developed in Simulink and the variations of some parameters of the electric arc are obtained by modifying of them in a Matlab function. Also, in this paper is presented the total harmonic distortion for the voltage and current of the electric arc obtained during simulation of the welding machine.
In the last years the usage of solar energy has grown considerably in Romania, as well as in Europe, stimulated by various factors as government programs, green pricing policies, decreasing of ...photovoltaic components cost etc. Also, the rising demand of using Solar Energy Conversion Systems (SECS) is driven by the desire of individuals or companies to obtain energy from a clean renewable source. In many applications, remote consumers far from other energetic grids can use solar systems more cost-effectively than extending the grid to reach the location. Usually the solar energy is measured or forecast on horizontal surface, but in SECS there is needed the total solar radiation incident on the collector surface, that is oriented in a position that maximize the harvested energy. There are many models that convert the solar radiation from horizontal surface to a tilted surface, but they use empirical coefficients and the accuracy is influenced by different facts as geographical location or sky conditions. Such models were used considering measured values for solar radiation on horizontal plane, in the western part of Romania. Hourly values measured for global solar irradiation on the horizontal plane, diffuse solar irradiation on the horizontal plane and reflected solar irradiation by ground are used to compute the total solar radiation incident on different tilted surfaces. The calculated incident radiation is then compared with the real radiation measured on tilted surface in order to evaluate the performance of the considered conversion models.
This paper represents a study on a recently developed turbine, namely an Archimedes spiral turbine, for use as a hydrokinetic turbine in a run-of-the-river configuration. This type of horizontal axis ...turbine has only been used in the wind power industry, where it shows great potential for extracting wind energy out of urban environments. Since it operates at low speeds with high efficiency, the Archimedes spiral turbine can be an excellent method of harnessing the kinetic energy from small rivers and streams. This turbine was modeled and simulated, the aerodynamic characteristics of the turbine were obtained and the torque and power outputs were analyzed.
This paper presents considerations of using wireless sensor networks for monitoring conditions within wind farms, taking into considerations the specific of such applications. In these scenarios, ...which are intended to cover a lot of ground or even operate in difficult radio environments with strong attenuation, the simple and direct communication between source and destination is not always possible, due to the distance restriction. To overcome these facts, there are required multi-hop algorithms considering the optimization of consumed energy, to enhance the network lifetime. In order to enhance overall network lifetime two methods were used, based on data aggregation and routing techniques.
This paper presents a self-tuning adaptive control structure designed through the minimization of a criteria function. It is described the computation methodology of the control law, being ...particularized for the case of a dual winding induction generator's excitation control. The parameter's estimator, integrated into the control system, is based on the on-line least mean square error algorithm. In order to validate the designed control structure and tuning, there are performed and presented several numerical simulation study cases.
There were conceived original methods that intend to optimize (maximize) the efficiency of variable speed fixed blade wind generators. These methods are based on mathematical models of fixed blades ...wind turbines windmills. This is the main reason that an important part of the paper is dedicated to the problematic of mathematical modeling of the wind turbine - focused mainly on the determination from experimental tunnels values of the required control values, by using different types of regression functions. From the values of the instantaneous generator's efficiency and the power supplied, by generator, while using the mathematical model of the turbine-generator group, the momentary value of the wind speed is determined. Also, by using the instantaneous value of the wind speed and the mathematical model of wind turbine's power, the optimum values of the operating rotation speed are computed for different wind speed values, in order to generate an off-line database table. The obtained optimum rotation speed values are further used in a look-up table for fast finding (through interpolation means) of the rotation speed, value that is prescribed to the rotation speed control loop. The main advantages of the proposed approach are the simplicity and robustness of the implementation.
This paper presents the implementation of a neural network-based fault detection for wireless sensor networks (WSNs). There are discussed two proposed approaches: both a centralized and respectively ...distributed fault detection. The methods are validated using a wireless sensor network that takes environmental measurements every 60 seconds. There were considered various fault scenarios that were detected and corrected by the implemented structure. Neural networks (NNs) are used to model the environmental parameter's dynamics. The physical measurement is compared against the predicted value and a given threshold of error to determine sensor fault.
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