Vol 88, No 12 (2017)

The current state of the market of Stirling generators shows that high-technology engines that have been tuned in the process of cooperation or competition between powerful corporations are winning. The main advantages of Stirling engines are the ability to use various heat sources and combustion chambers meeting environmental requirements, a low level of noise and vibration; favorable characteristics for both vehicles and stationary electric generators, and good consistency with a linear electric machine. High cost and weight—size parameters, as well as limited aggregate capacity and useful life, are constraints on the development of Stirling generators. It is a feature of a Stirling engine that the pressure-circuit, generator, and combustion-chamber parameters need to be regulated. The control system should be intelligent to provide starting conditions. Power control of a free-piston Stirling engine is usually accomplished by changing the piston stroke, which is realized a linear generator electronic control unit. At the moment, due to the development of alternative energy and distributed power supply, a potential niche for the use of Stirling generators is growing.

A ship’s electric-power system (SEPS) provides reliable functioning of ship systems, as well as safety in navigation and the living conditions and work of the crew. SEPSs in large-displacement vessels can have a capacity of more than 100 MW and consist of thousands of interconnected components and subsystems. On ships with a propulsion system (PS), the SEPS powers both the PS, which consumes most of the power generated by a ship power plant, and numerous general consumers of power on the ship. The PS includes frequency converters with dc links; for a ship’s power plant, these converters are a high-power nonlinear load that causes significant voltage distortions in the ship’s network. When designing a vessel, at the stage of selecting the structure and components of the SEPS, electromagnetic compatibility between the PS and general vessel users needs to be provided. According to the requirements specified in the Russian Maritime Register of Shipping, the nonsinusoidal voltage in the ship’s electrical network must not exceed 10%. Computer simulation is the only effective tool for assessing the quality of ship-network voltage at the initial stages of design. In this paper, we present the results of estimating two alternative SEPS designs by means of the MATLAB Simulink package. It is shown that high-power transformers can be removed from the PS without significant deterioration of network-voltage quality, which makes it possible to reduce the cost, weight, and dimensions of electrical equipment.

Today, marine vehicles using environmentally friendly renewable-energy power plants are becoming increasingly widespread worldwide. Hydrogen—oxygen electrochemical generators (ECGs) with a solid polymer electrolyte are one such way to renew electric energy. The main advantages of such power plants are an absence of harmful emissions, low operating temperature, and wide power output range of the ECG depending on the load. However, the maximum efficiency of the system is achieved under the maximum power and the optimal temperature (of the order of 80°C). It should also be noted that, under a “cold” start, the battery does not generate full power. Thus, it is advisable to use a fuel-cell stack in a hybrid power plant, which also includes lithium-ion batteries and other power-storage devices to ensure the necessary maneuverability of marine vehicles. Thus, the problem of power control in hybrid power plants in the transient and steady modes of ship maneuvering is becoming important.

One of the main factors determining the efficiency of the operation of a modern vessel is the technical condition of electric machines used as drives for various mechanisms in the marine equipment. Evaluation of the current technical state of electric machines is a critical task in the general problem of process management in the system of marine-equipment maintenance and repair, the performance of which is connected with revealing partial malfunctions in the equipment and further operational failures. This article studies one of the algorithm options for processing the time series of the regulated parameters of the electric machines, which allows predicting the time frames for their maintenance according to their actual state in order to prevent a failure. The relevance of this approach is substantiated by the fact that switching to the technology of maintenance based on evaluation of the technical state of marine equipment, systematic observation, and operability prediction implemented using automated onboard measurement and regulation systems (among which are also diagnostic systems) is an efficient way of ensuring reliability of marine equipment.

Currently, power plants based on hydrogen—oxygen fuel cells are widely used. The advantages of such electrochemical generators are environmental friendliness, efficiency, and a wide power-output range. Some components of such engines are still being developed. One of these components is the working gasrecirculation system, which increases the efficiency of an installation. In addition, this system helps support the water balance in a fuel-cell stack by removing the water that occurs in the cavities of the membrane—electrode block as a result of the electrochemical reaction. With consideration of the complexity of the reactions that occur in an installation, an automatic control system (ACS) is necessary for the gas recirculation system. This article deals with the organization of an automatic control system based on a microprocessor controller, sensors, and actuators, which implements control algorithms for the components of the gas recirculation system.

Electrical engines are widespread in all areas of industry and technology. Electrical actuators are widely used as an actuating motor regulating the interconnected controls of different machines. Increased demands for precision in interconnected controls make it very important to consider dry friction in the executive mechanism. The consideration of dry friction in a mathematical model of an automatic system considerably complicates its analysis. In all known practical cases of research into such issues, the research is carried out by means of computing or analytically, but using a considerably simplified model of the dry-friction law. This simplified presentation does not allow one to uncover and understand the true (or apparent) reasons for loss of stability in a system accompanied by friction self-oscillations of different kinds (periodical, chaotic etc.). The decomposition method of parameter space presented in the current work allows investigation of nonautonomous nonlinear multivariable systems via basic subsystems (both linear and nonlinear) that have a lower-order state space and are amenable to strict analysis.

Planning electric-rolling-stock (ERS) maintenance in conditions of limited resources can be carried out based on the following criteria of efficiency of construction of the cycle diagram of the electric rolling stock: meeting the requirements of the railway-traffic safety provided by adjusting the planned movement time of the electric rolling stock for the purpose of not allowing an excessive lapse of time between the maintenance over that permissible and uniformity of maintenance. The solution of the set problem using the graph theory allows obtaining the whole set of the permissible values of maintenance and selecting a value that, on the one hand, corresponds to the planned train time schedule (PTTS) and, on the other hand, differs minimally from the optimal with respect to the selected criterion. This takes a significant amount of time. The problem can be quickly solved using a genetic algorithm. The introduction of a new criterion—total excess time lapse between maintenance works over the permissible interval—allows obtaining the solution with any initial data, which is not always achievable when using the uniform-maintenance criterion. The crossover and permutation algorithm implemented within the genetic algorithm is adapted taking into account considering the peculiarities of the agents engaged in solving the problem that has been set out. We have studied the possibility of using various types of crossover and permutation to construct the cycle diagrams and influence of the parameters of the genetic algorithm on the results. The obtained analytical results are tested for the conditions of the Moscow subway.

I consider the problem of determining the parameters of equivalent circuits of asynchronous motors with squirrel-cage and wound rotors by using catalog information to construct their mechanical characteristics. In known sources, determination of the parameters is carried out either by the selection method with variation of the ratio of the parameters, which can vary widely, or with some of the parameters being accepted equal to zero and expressions being simplified. The equivalent circuit of the asynchronous motor contains six unknown parameters of the resistance, of which only the nominal stator current and its active and reactive components are known, and so calculation of parameters is performed using well-known formulas describing the characteristics of the motor. In this work, by giving extreme values of the ratio nominal voltage to the EMF of the magnetization chain in the regime of perfect idling, which can vary within ±2.0%, the parameters of compliance with these coefficients are determined and, thus, the area of varying of the parameters of the equivalent circuit in conditions of their linearly interpolated dependence is determined. The calculation is done using equations of the second order based on the constancy of the power of electric motor, balance, and active and reactive power. Determination of the region of conformity of parameters allows making preliminary and, then, specific calculations, followed by assessment of the results of convergence solutions. This calculation method can be used in engineering practice not only for calculating parameters by means of catalog data, but also for determining the correspondence of parameters that are not defined in these data.