The paper presents the results of testing and research of the characteristics of a controlled autonomous magnetoelectric synchronous generator with a magnetic shunt. Structurally, the studied generator is a modified asynchronous machine in which the rotor is made with permanent magnets and an additional system in the form of a magnetic shunt. By adjusting the winding current of the magnetic shunt, the output voltage of the generator is regulated. The following characteristics were investigated: the no-load characteristic during operation with permanent magnets and when the winding current of the magnetic shunt changes with forward and reverse polarity. Also, the external characteristic for active and active-inductive loads; the control characteristic when the load current changes at a constant generator voltage. Analysis of the obtained characteristics makes it possible to determine the limits of regulation of the external characteristic, which is ≈40 % relative to the main magnetic flux. The obtained regulation depth allows maintaining the stability of the external characteristic for power factors not exceeding 0.9, which is the usual passport value for autonomous power plants based on synchronous generators. Comparison of the data of research conducted on the experimental setup shows sufficient convergence for engineering and practical tasks. The maximum quantitative difference is 9.3 %, which suggests the adequacy of the previously developed mathematical model. The control characteristic, constructed experimentally at constant generator voltage, is the control law of the magnetic shunt winding for the studied generator. The investigated version of a synchronous generator with a magnetic shunt should be used for autonomous power plants, renewable energy systems, and autonomous power supply systems.
mous power systems. Wind power engineering is developing particularly rapidly. Hundreds of thousands of small wind plants and thousands of large wind turbines are currently in operation worldwide. The electric generator with permanent magnets has a series of significant drawbacks. Existing generators need to be improved to overcome these deficiencies, resulting in additional investment. That could improve efficiency of such generators, but would also increase their cost and compromise their reliability. New high-performance magnetoelectric generators on permanent magnets could contribute to solve a given task.A relevant scientific and practical field is the development of new types of generators with permanent magnets. Underlying such designs is a conventional cylindrical electric
The object of this research is electromechanical processes in a generator with an axial magnetic flux and a double stator and an additional non-contact excitation winding operating as part of autonomous electric power systems. The power of the additional excitation system is about 2 % of the generator power. The presence of an additional non-contact winding, which is powered by direct current, makes it possible to control the generator voltage by changing the excitation current. This resolves the task to stabilize the output voltage of the generator with permanent magnets when the load and shaft speed change. This paper reports the construction of a three-dimensional field axisymmetric mathematical model of the generator under study, which has made it possible to calculate and investigate its characteristics and parameters, in particular the magnitude of magnetic induction in all structural elements. The model built takes into account the influence of finite effects, magnetic scattering fields, and the radial-axial nature of the closure of the main magnetic flux and the magnetic flux of the additional excitation winding. The use of a structure with a double stator makes it possible to more efficiently utilize the usable volume of the generator and to increase its power. A mathematical model of the generator in the d-q coordinate system was built, which has made it possible to synthesize algorithms for controlling the automatic voltage stabilization system of the generator voltage under conditions of change in load and shaft speed. Control algorithms were developed on the basis of the concept of inverse dynamics problems in combination with minimizing local functionalities of instantaneous energy values, which ensures that the system is robust when changing generator parameters and that regulators are implemented in a simple way, due to the lack of differentiation operations. Based on the models built and algorithms developed, the quality of control of the generator's output voltage when the load and frequency of the generator change was investigated by modeling in the MATLAB/Simulink environment. When setting a jump in the rated load and changing the rotational speed within ±15 % of the rated value, the automatic stabilization system provides astatic voltage control at a given level of 48 V. The results can be practically used in the design of autonomous electric power systems with high energy conversion efficiency, in particular wind turbines and hydraulic units
Purpose. Development of a mathematical model of an autonomous wind power plant based on an end-generator with a double stator and combined excitation to evaluate methods for improving the efficiency of conversion of mechanical wind energy into electricity. Methodology. The research used methods of general theory of wind power plants, methods of mathematical modeling, which are based on the numerical solution of nonlinear differential equations to evaluate methods for correcting the output power in Matlab-Simulink by modifying standard units. Findings. A numerical simulation mathematical model of an autonomous wind power plant consisting of a magnetoelectric generator with an axial magnetic flux with combined excitation and a double stator has been developed. The model was created to study the parameters and characteristics of the installation, as well as to evaluate methods and means to improve the efficiency of conversion of wind energy into electricity. According to the research, it is established that a more effective method for regulating the output power of the generator in the wind turbine is the use of additional winding for magnetization, compared with the use of additional capacity. The latter provides up to 716% increase in output power, while using the magnetizing winding can increase the output power to 3235%. The results obtained by the authors allow further developing a number of methods to increase the efficiency of conversion of mechanical energy of the wind turbine rotor into electrical energy. Originality. The mathematical model developed for the first time, in contrast to the existing ones, takes into account the presence of a double stator, an additional winding for magnetization of the magnetic system and the axial nature of the circuit of the main and additional magnetic flux. The developed model also takes into account the change in the parameters of the electric generator with axial magnetic flux when changing the parameters of the wind, the rotor of the wind turbine and the load. The model is designed to analyze the possibility of adjusting the output power of the generator when the wind speed changes. Practical value. The simulation results indicate the prospects of industrial implementation of wind power plant based on magnetoelectric generator for their use as autonomous electrical installations and as part of shunting power systems.
The object of this study is electromechanical processes in an autonomous wind power plant with a magnetoelectrical generator. Under actual conditions, the wind speed is constantly changing. The wind turbine works as efficiently as possible only at the rated value of wind speed. When the wind speed changes, the efficiency of converting mechanical wind energy into electrical energy decreases. Controlling the power of the electric generator when the wind speed changes is a relevant scientific and technical task. A maximum power selection control system based on the parameters of an experimental sample of a synchronous magnetoelectric generator has been designed and investigated. A feature of the synthesized control system is that it was developed on the basis of the concept of inverse dynamics problems in combination with minimization of local functionals of instantaneous energy values. The control law provides weak sensitivity to parametric perturbations of the object and carries out dynamic decomposition of the interdependent nonlinear system, which predetermines its practical implementation. Transient processes of the power, voltage, and current of the stator, as well as the voltage and excitation current were established when the wind speed changes from 3 to 8 m/s, as well as when the active electrical resistance of the load changes. The results of this study confirm the effectiveness of the maximum power take-off control system when wind speed and load change. When the wind speed changes within 3–8 m/s and the load by 50 %, the efficiency of converting mechanical wind energy into electrical energy increases by 15–40 % compared to the traditional magnetoelectric system. The findings of the current study are recommended for practical use in autonomous power plants based on wind turbines with generators with permanent magnets.
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