The main objective of the control strategies applied at hybrid micro grid systems (wind/hydro/solar), that function based on maximum power point tracking (MPPT) techniques is to improve the ...conversion system's efficiency and to preserve the quality of the generated electrical energy (voltage and power factor). One of the main goals of maximum power point tracking strategy is to achieve the harvesting of the maximal possible energy within a certain time period. In order to implement the control strategies for micro grid, there are typically required specific transducers (sensor for wind speed, optical rotational transducers, etc.). In the technical literature, several variants of the MPPT techniques are presented and particularized at some applications (wind energy conversion systems, solar systems, hydro plants, micro grid hybrid systems). The maximum power point tracking implementations are mainly based on two-level architecture. The lower level controls the main variable and the superior level represents the MPPT control structure. The paper presents micro grid structures developed at Politehnica University Timisoara (PUT) within the frame of a research grant. The paper is focused on the application of MPPT strategies on hybrid micro grid systems. There are presented several structures and control strategies and are highlighted their advantages and disadvantages, together with practical implementation guidelines.
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
The main followed objectives within control strategies dedicated to hybrid micro grid systems (wind hydro solar), that operate based on maximum power point tracking (MPPT) techniques are to improve ...the conversion systems efficiency and to maintain the quality of the produced electrical energy (the voltage and power factor control). One of the main goals of maximum power point tracking strategy is to achieve the harvesting of the maximal possible energy within a pre-set time period. In order to implement the control strategies for micro grid systems that operate at time variable parameter, there are usually required specific transducers (anemometer for wind speed measurement, optical rotational transducers, taco generators, etc.). In the technical literature there are presented several variants of the MPPT techniques, which are particularized at several applications (wind energy conversion systems, solar systems, hydro plants and micro grid hybrid systems). The maximum power point tracking implementations are mainly based on two-level architecture. The inferior level controls the primary variables, while the superior level represents the MPPT control structure. In the paper, authors present some micro grid structures proposed at Politehnica University Timisoara within the frame of a research grant. The paper is focused on the application of MPPT strategies on hybrid micro grid systems. There are presented several structures and control strategies and are highlighted their advantages and disadvantages, together with practical implementation guidelines.
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.
The paper concerns a dual (double) split-wound three-phase stator windings induction generator having the same poles number (split-wound). The separate stator windings have distinct functions - ...excitation and, respectively, electric energy generation, that assures the physical decoupling of the excitation and of the load and their control simplification, There was considered 90 electrical degrees space displacement between the excitation and the load windings - orthogonality, that assures the mutual magnetic decoupling of the two windings. The paper presents, mainly, experimental results on load modes of operation, as well as on the problem of windings current harmonics due to the presence of different types rectifiers at generator ends.
The paper presents some issues regarding an online tuning procedure for a recursive last mean square (RLMS) parameter estimator embedded into an adaptive controller used to control the terminal ...voltage of a synchronous generator. The analysis is mainly focused on the problematic regarding the reinitialization of the covariance matrix within the RLMS algorithm. A study case for a dynamical model, with variable parameters (obtained through a linearization, around a functioning point, of a synchronous generator nonlinear model), is performed and some reinitialization rules are highlighted in order to improve the performance of the parameter estimator.
An adaptive self-tuning control solution is exposed in this paper. The control strategy is to minimize a cost function, which incorporates fluctuations of input, output and set point with the ...system-identified parameters. The designed control strategy proposes to remove the internal integrator component from the adaptive control law (which is inappropriate for some process due to control system instability) and using an external integrator loop, parallel connected with the self-tuning controller.
PDF
