RESEARCH OF A SQUIRREL-CAGE INDUCTION GENERATOR FOR RENEWABLE ENERGY WITH NON-STATIONARY CAPACITOR EXCITATION

Abstract

The relevance. The share of electricity generated by installations based on renewable energy is constantly growing, and therefore the need for the development of power supply systems and automatic control of electrical machines underlying wind and hydro generators is still relevant. As part of such alternating current generator sets, synchronous electric machines, induction generator with phase and squirrel-cage rotor are used. Frequency converters installed in the stator and rotor circuits of induction motor make it possible to control their excitation, however, to start generation, additional external power sources must be used. Due to the residual magnetization in the magnetic circuit, it is possible to ensure the process of guaranteed self-excitation of the induction generator by connecting the capacitor banks to the electrical circuit of its stator without using an additional external power source. The proposed method of non-stationary capacitor excitation makes it possible to ensure the adaptation of the generator set to the change in operating modes under conditions of decentralized power supply. The main aim of the research is to study the proposed voltage stabilization system of induction generator with a short-circuit rotor with variable capacitor excitation as part of a renewable energy source. Methods. To achieve the goal of the research, theoretical and experimental research methods were used. Theoretical research methods include the theory of differential equations, methods for the numerical solution of ordinary differential equations, the theory of electric drives, the theory of electrical machines, numerical methods for approximating data. The basis of experimental research is testing an induction generator with non-stationary capacitor excitation on a developed test bench in order to obtain load characteristics and oscillograms of voltages on the stator windings of an induction generator with a short-circuit rotor in different operating modes. Results. An original experimental setup with a unit imitating the operation of a turbine, an electromechanical energy converter in the form of an induction generator with a short circuit with non-stationary capacitor excitation has been developed and manufactured. The control system is made in the form of a galvanically isolated module integrated with the power unit in a moisture-resistant design using a wireless Bluetooth communication interface. A method for switching capacitor banks using thyristors as a controlled switch with two-way conduction is described and tested. The analysis of the obtained load characteristics shows the fundamental possibility of ensuring a guaranteed generation of electricity with voltage stabilization within the limits of load power variation. The system of automatic switching of capacitors with a capacitance varying depending on the power consumption applied as part of the experimental setup made it possible to provide an acceptable time for dynamic response to a disturbing effect under nonstationary load.

Keywords

• renewable energy sources
• induction generator
• squirrel-cage rotor
• non-stationary capacitor excitation
• decentralized power supply