Method of parametric analysis of reciprocating electric generators with permanent magnets

A method for the parametric analysis of electric generators of reciprocating motion with permanent magnets has been developed, which allows revealing the values of the parameters of the magnetic circuit (cross-sectional area) and the working winding (number of turns) at a given value of the efficiency, providing a minimum specific gravity of the generator. The method of parametric analysis of electric generators of reciprocating motion with permanent magnets consists of three stages. The first and second stages are the electromagnetic calculation of the generator: at the first stage, the main geometric dimensions of the magnetic system and the parameters of the working winding of the generator are determined; at the second stage, the verification of the electromagnetic calculation of the generator, calculation of the nominal mode, calculation of the efficiency and assessment of the thermal state of the generator are fulfilled. At the third stage, a parametric analysis of electric generators of reciprocating motion with permanent magnets with specified constraints is carried out, as well as the refinement of the geometric dimensions and configuration of the magnetic system of the generator using a two-dimensional finite element model of the magnetic field. As a result, to ensure better use of the electrical steel of the magnetic circuit of the generator and thereby reduce its mass, the most saturated areas and areas, which are characterized by low values of the magnetic field strength, are determined. Distinctive features of the proposed technique are: the use of a minimum specific gravity of electric generators of reciprocating motion with longitudinal, transverse or combined changes in the magnetic flux passing through the working winding as an objective function; combined approach to electromagnetic calculation; taking into account the influence of the operating temperature on the parameters of the permanent magnet, as well as overheating of individual parts of the generator.

Design and selection of a belt drive for an electric generator

The issue of the selection of mechanical drive for medium size power generators was raised in the work. The issue begins with the analysis of the propulsion system in the hydroelectric power plant, in which the turbines were selected for the amount of water flowing and for these turbines electric generators. An overview of the available drive solutions pointed to belt transmissions, which must meet the task of transferring torque from the turbine to the generator. The solution must be durable, which is why the authors conducted a deep analysis of material issues and pointed to modern polymer strips that can meet the challenges posed.

The Thyristor Switched Parallel Capacitors (TSPC) Converter for Power Factor Correction in Wind Power Systems

This paper presents a novel power factor correction circuit suitable for low-speed electric generators usually used in direct drive wind turbines. The Thyristor Switched Parallel Capacitors (TSPC) circuit belongs to the Controlled Series Capacitor (CSC) circuits. Those circuits have been used in power transmission lines to correct the power factor and improve the performance of the electrical system. Such a circuit can be used in wind power systems to improve and maximize the efficiency of a wind turbine. A typical direct-drive wind power system employs variable speed electric generators, but the downside is that systems like that suffer from high and variable inductive reactance. In order to correct the power factor and to improve the efficiency of the system, the inductive reactance of the generator must become equal in value to the capacitive reactance. A TSPC circuit uses a set of capacitors, connected in series with anti-parallel thyristors. In every cycle, a controller triggers the appropriate thyristors, allowing the current to pass from the capacitor which then provides the system with the capacitive reactance that matches the generator’s inductor reactance. Therefore, the TSPC circuit is able to counteract for any reactive losses and improve the power factor, as well as, the efficiency. This paper introduces this novel power factor correction circuit that employs capacitors in parallel configuration. This circuit was simulated in PSPICE and was implemented and tested in the lab. Based on the simulation and implementation results, we discuss the benefits as well as the drawbacks of the proposed circuit

Variable Speed Diesel Electric Generators: Technologies, Benefits, Limitations, Impact on Greenhouse Gases Emissions and Fuel Efficiency

A substantial share of the electric energy is generated with synchronous generators that provide sustained alternating current (AC) voltage and frequency energy to regional and national power systems, which subsequently transport and distribute it to diverse users. In an attempt to reduce environmental effects, electric energy markets have recently become more open, resulting in more flexible distributed electric power systems. In such distributed systems, stability, quick and efficient delivery, and control of electric power require some degree of power electronics control to allow for lower power in the electric generators to tap the primary fuel energy potential better and increase efficiency and stability. This is how variable-speed electric generators (VSEG) recently came into play, up to the 400-megavolt ampere (MVA)/ unit size, and which have been at work since 1996. This paper provides coverage of variable-speed electric diesel generators (VSDEG) in distributed generation and their impacts on fuel efficiency and greenhouse gases (GHG). It discusses permanent-magnet-(PM) synchronous generators, solutions based on power electronics such as diesel-driven wound-rotor-induction generator, doubly-fed-induction generator (DFIG), rotating stator generator, and the application of continuously variable transmission to a VSEG. The benefits and limitations of the selected technologies are also presented. The list of references given at the end of the paper should offer aids for students and researchers working in this field.

Development of Refined Electromagnetic Models of Reciprocating Electric Generators with Permanent Magnets

The analysis of scientific papers devoted to the mathematical description of electric generators of reciprocating motion with permanent magnets demonstrated that the proposed mathematical models of this type of generators are based on the theory of magnetic circuits. Such mathematical models are based on a simplified representation of the magnetic system and the magnetic field in the form of a magnetic circuit with corresponding magnetic conductivities. However, unlike traditional rotary type electric machines, electric generators of reciprocating motion have a number of features, the omission of which in mathematical modeling causes the increase of the cost of their creation (due to the duration of the design and experimental refinement of the generators). Therefore, at the initial stages of electromagnetic calculation and solving optimization problems, it is necessary to use adequate mathematical models to improve the accuracy of calculations of the parameters of these generators. For this purpose, a mathematical model based on field theory can be used; however, its main drawback is the complexity of its application for solving optimization problems. In this regard, to improve the accuracy of calculations of the parameters of electric generators of reciprocating motion with permanent magnets, it is proposed to use refining coefficients (coefficients of scattering and buckling of the magnetic flux) in mathematical models based on the theory of magnetic circuits. The authors have developed refined electromagnetic models of electric generators of reciprocating motion with permanent magnets, which make it possible to obtain the main parameters of generators at the initial stages of electromagnetic calculation and when solving optimization problems with acceptable accuracy. A distinctive feature of the refined electromagnetic models of generators is the consideration of the scattering and buckling coefficients of the magnetic flux in the magnetic system that change during the simulation.

Efficiency of wave energy conversion into electric power: calculation results

Object and purpose of research. The object of the study is the wave energy converters (WEC) into electric power. The purpose of the study is to draw up a differential equation describing the operation of the WEC, its solution and determination for the design parameters influence of the WEC on the efficiency of energy conversion. Materials and methods. The theoretical methods adopted in ship mechanics and theory are used to study the operation of complex mechanisms and dynamics of marine objects. The data on the characteristics of electric generators are used. Main results. The differential equation describing the operation of the WEC on regular wave is compiled. The equation relates the characteristics of waves to the design parameters of the WEC. Generalized characteristics of electric generators are obtained. Systematic calculations are carried out; they show the influence of the WEC design parameters on the efficiency of wave energy conversion into electric power. Conclusion. The results can be used in design of the WEC. The resulting differential equation makes it possible to investigate the operation of the WEC in various marine conditions and to evaluate the influence of design parameters on the efficiency of energy conversion. The generalized characteristics of electric generators can be used in design of wave power structures and wind power plants.

A Comparative Performance Analysis of Counter-Rotating Dual-Rotor Wind Turbines with Speed-Adding Increasers

Increasing the efficiency of wind power conversion into electricity poses major challenges to researchers and developers of wind turbines, who are striving for new solutions that can ensure better use of local wind potential in terms of both feasibility and affordability. The paper proposes a novel concept of wind systems with counter-rotating wind rotors that can integrate either conventional or counter-rotating electric generators, by means of the same differential planetary speed increaser, aiming at providing a comparative analysis of the energy performance of counter-rotating wind turbines with counter-rotating vs. conventional electric generators. To this end, a generalized analytical model for angular speeds and torques has been developed, which can be customized for both system configurations. Three numerical simulation scenarios have been contrasted: (a) a scenario with identical wind rotors in both systems, (b) a scenario with the secondary wind rotors being identical in the two applications, but different from the primary rotors, and (c) a scenario with different secondary rotors in the two wind turbines. The results have shown that the wind systems with counter-rotating generator are more efficient and have a higher amplification ratio, compared to systems with conventional generators. In addition, the analyzed wind system with a counter-rotating generator displays better energy performance with low values for output power and ratio of input speeds, whereas the wind turbine with a conventional generator proves to be more efficient in the high-value range of the above-mentioned parameters.