Currently, asynchronous electric drive on the basis of semiconductor frequency converters is widespread because of the relative simplicity and reliability of the design, the use of digital control systems, providing the accuracy and flexibility of process control, which allows for a significant increase in product quality, reduction in energy consumption and improvement of the enterprise profitability. In spite of these advantages, the problem of ensuring high energy efficiency of the drive in wide range of its operational modes is still not solved in full scale. The paper is devoted to the reduction of losses in the asynchronous drive on the basis of en-ergy-saving control algorithms that aim to ensure the desired mode of the driven mechanism while minimizing losses in copper and steel of the motor. On the basis of the motor model, taking into account magnetic losses, dependences of losses in the copper and steel, as well as the total loss from the absolute slip have been derived for different operating points of the drive. The optimal values of the absolute slip for different speeds of the rotor have been obtained for use in the con-trollers ensuring operation of the drive at maximum efficiency, highest power factor and minimum of the stator current. For minimizing the losses in the drive when changing the motor parameters it has been offered the combined method based on the method of loss model and iterative method of searching the minimum of power consumption. The effectiveness of the proposed control system using fuzzy logic is confirmed by comparing the graphs of losses and efficiency, obtained at using a traditional control law and the optimal control law.
In the face of energy lack and rising energy prices one of the priorities of current researches is to improve energy efficiency of electric drives, which are widely used in modern industrial plants. Existing methods of minimizing losses are mainly designed for stationary regimes. At the same time, the development of algorithms for reducing losses in transient and in particular starting conditions is given little attention. Due to the high complexity of the description of the multivari-ate dynamic processes determining the optimal control laws is advantageously to be carried out us-ing stochastic optimization methods. The work seeks to substantiate the optimal starting character-istics of an asynchronous drive based on a genetic algorithm. A feature of the proposed method of optimization is the use of multiple simulation experiments to find start-up characteristics which provide a minimum energy loss. Automation of the search is performed using the developed pro-gram, which includes a module of a genetic algorithm and a module for interfacing with the elec-tric model in the MATLAB/Simulink environment. The program allows choosing the parameters of the genetic algorithm along with controlling the process of optimization. Application of the proposed method allowed obtaining the optimal starting characteristics «voltage – frequency» in a tabular form with consequent linear approximation of the data. Increase in efficiency due to the proposed start up law has been confirmed by comparing the simulation re-sults under conditions of using a traditional linear characteristic and derived optimal law. The es-timation of losses reduction has been carried out at the drive load of different kind in a wide range of its variation.
