Photovoltaic (PV) generation is widely used to solve energy shortage and environment problem. Since the output current of the solar cell will change with the sunlight irradiation, the power of the solar cells are not stable, so there is a need of a storage equipment connected to the PV system. With the characteristics of high efficient energy storage and quick response of the power exchange, the superconducting magnetic energy storage (SMES) can be used to meet the balance between the grid and the PV. A SMES and PV subsystem are connected together with the DC bus, which have less power electronics elements and can control power quality efficiently than linked with the AC bus. This hybrid system is composed of a DC/AC converter on the grid side, a DC/DC converter with the PV arrays, and a DC chopper with the superconducting magnet. A detailed model of the hybrid system is built with MATLAB/SIMULINK. Simulation results with and without SMES connected to the grid-connected photovoltaic system are presented, compared, and analyzed. The results of simulation demonstrate that the SMES system can maintain the DC bus as a constant value which can contribute to the stability and reliability of the grid-connected PV system.
J-TEXT, formerly known as TEXT-U, has been reconstructed since 2004. The 100 MVA pulse generator system is the main power supply of J-TEXT, including the toroidal coil, the ohmic heat coil and the divertor coil and high-voltage power supply for Electron Cyclotron Resonance Heating. The pulse generator system was designed in USA with a 60 Hz grid so that the maximum rotation speed of the flywheel was 713 rpm and the maximum stored energy was 185 MJ. Now in China the grid is 50 Hz, in asynchronous mode the maximum rotation speed of the flywheel is 598 rpm and maximum stored energy is 128 MJ. To reach the designed maximum rotation speed of the pulse generator system, a doubled-fed unit is designed to ensure the tokamak operates with high parameters. This paper presents the design procedure of the double-fed unit: including the stator field oriented control of the double-fed induction motor, voltage oriented control of the AC-DC rectifier and the structure of the control system. The experiment results show the feasibility of the unit.
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