Известия Томского политехнического университета: Инжиниринг георесурсов (May 2019)
Research of magnetic transmission with variable gear ratio in a windhdriven generator for improving dynamic stability stoke
Abstract
The relevance of the research is caused by the fact that in Russia more than 2/3 of the territories is not provided with centralized power supply. There are small isolated energy systems, consisting of several loads of 1 to 15 MW. Unfortunately, the share of world production of small power stations is limited to 25 %. Another share falls on large turbine generators, power over 20 MW. One of the reasons for limited use of small power plants is their small stock of dynamic stability due to their low inertia. Let us mention that the dynamic stability is disturbed when sudden changes occur in load conditions or at short circuits. Single-phase circuits are observed in 70 % of the total number of disturbances that may cause disconnection of a load part or electric power generators in the system. This can result in asynchronous mode of the remaining generators. The paper introduces the method for maintaining a synchronous speed of a generator rotation by means of electromechanical complex based on magnetic transmission with variable gear ratio as a part of a low-power wind-driven generator. The main aim of the study is to increase the dynamic stability stock of power systems with distributed generation, having in its composition several low-power electric generators. The methods. The finite element method is used for geometry analysis of magnetic transmission with variable gear ratio on the basis of Maxwell 2D. The mathematical model based on magnetic fields equations was developed to determine the torque and its dependence on a rotor angular point. The results. The authors have obtained the mathematical model of magnetic transmission. It leads to the conclusion that there is the relationship of geometrical parameters and the magnitude of the maximum electromagnetic torque. The linear relationship was established between the transmission ratio and rotor control speed. The paper considers the analysis of the pole pair numbers ratio in the rotor magnetic transmission construction and their interconnection between the moments on slow and high-speed shafts. The author determined the dependence of the torque on the angular position of the high-speed link rotor and analyzed the magnetic fields of magnetic transmission to define the magnitude of losses in ferromagnetic yokes.
