Chernikov P. Optimal control of electric ships` propelling electric plants during maneuvres.

The dissertation is devoted to the search for optimal parameters of control signals for propelling electric plant, which provide the best manoeuvring quality of electric ship with an indivisible ship electric power system. A specified mathematical model of transient regimes of electric ship’s propulsion complex is developed. It includes heat engines, synchronous generators, electric power converters, propulsion motors, propellers, rudder, ship’s hull. The model is universal. It covers the vast majority of modern and promising electric ships with a traditional type of propulsors. It allows calculating the current values of the basic regime indices and assessing the quality indices of maneuvering. The model is made in relative units. Dimensionless parameters of the complex are obtained. It is these parameters that influence the main maneuvering quality indices. The adequacy of the suggested specified mathematical model and the developed computation method based on it were confirmed. To do this, the results of mathematical modeling for a real electric ship were compared with the data obtained in the course of field experiments conducted by other researchers. The mathematical description of a generator unit, as an integral part of an indivisible ship’s propulsion complex, makes it possible to calculate the dynamic operation modes of electric power sources during electric vessels’ maneuvering. There is an opportunity to design the electric ships’ propulsion power plant according to the final result – according to the indices characterizing the vessel and its maneuvering properties. The use of a system of dimensionless units provides a generality to the results obtained. Electric ships with equal values of dimensionless parameters will have correspondingly the same values (in relative units) of maneuvering quality indices. Numerical calculations of transient regimes of propelling electric plant at maneuvers and the processing of their results allowed us to analyze the influence of changing the values of the electric ships' parameters on selected quality indices. The parameters with significant influence were identified on the basis of the analysis results. The degree of influence of each parameter on the corresponding quality index is represented by polynomial dependencies with contributions to each parameter. The influence of other parameters is unessential and they can be assumed to be invariable in the future. Significant parameters, among all the parameters influencing the quality indices of electric ships' propelling electric plant, were revealed. This enables us to identify the objective laws of the processes under consideration, and in the future to reduce the amount of computing work. The proposed analytical dependences show the ways to improve the quality of transient processes of propelling electric plant at the earliest stages of design. The parameters of the complexes that significantly affect the optimality criteria are revealed. Optimization calculations have been carried out and the optimal control signals of the propulsion motors during electric ships’ maneuvres have been found for various combinations of the values of these parameters. Optimization is carried out by the criterionof the minimum braking distance and by the criterion of minimum energy consumption. The results are presented in an analytical form and in a graphical form. The effectiveness of the proposed control signals is illustrated. The method of searching for the optimal control signals of the propulsion motors is constructed according to the system principle. This allows us to find the control signals of the propulsion motors by the final result – by the indices of electric ships’ maneuverability. The proposed recommendations cover a wide class of vessels with electric motion. The proposed optimal control for propulsion motors can be used in the operation of propulsion power plants. The best parameters of the control signal can be selected and incorporated into the control system for any particular electric ship of the considered class, depending on the quality of maneuvering. In particular, the optimal control signal for propulsion motors providing electric ship’s minimum braking distance or minimum energy consumption for maneuvering can be chosen. Keywords: propelling electric plants; maneuvering properties of electric ships; optimal control by ships` indices.