| Superconducting magnetic energy storage technology can realize rapid conversion of electrical energy and magnetic energy,realize millisecond-level response and instantaneous high-power release,can effectively improve power quality and system stability,and is an important direction for superconducting power technology to be practical.The superconducting magnet is the core component of the superconducting magnetic energy storage device,and its stability is an important issue related to the safe and stable operation of the entire device.For small and medium-sized superconducting energy storage magnets,thermal stability is the most critical factor affecting their safe operation.At present,the superconducting magnetic energy storage projects that have been completed or are being implemented at home and abroad have not considered the safety status and responsiveness of the energy storage magnets when executing commands.If the power grid is in some extreme working conditions,it may issue a response command to the energy storage system that exceeds the bearing capacity of the magnet,which will bring huge safety risks to the superconducting magnet,the core component of the energy storage system.The current quench protection methods for superconducting magnets belong to passive protection,and the damage to the magnets caused by quench cannot be avoided.In order to improve the safety and stability of superconducting energy storage magnets,this paper studies the state evaluation method and control strategy of superconducting energy storage magnets,and proposes an active protection method for superconducting energy storage magnets.The specific work content and results are as follows:(1)A "spoke-type" cold-conducting plate structure is proposed to improve the response efficiency of the energy storage magnet.Aiming at the problem of excessive eddy current loss of the copper cold-conducting plate,a "spoke-type" cold-conducting plate structure is designed in this paper.The position of the cold-conducting plate and the center of the coil is hollowed out,and the other positions are cut at equal intervals.By reducing the eddy current area,the eddy current loss of the cold-conducting plate is reduced by more than 90%.(2)A "dimension reduction-inversion" method is proposed,which solves the difficult problem of calculating the AC loss of toroidal superconducting magnets.The method calculates the coil magnetic field through the 3D constant conduction model,extracts the boundary magnetic field of the 3D model as the boundary condition of the air domain of the2 D model,and finally uses the 2D model to calculate the AC loss of the coil.Compared with the H equation method,the maximum instantaneous loss error of this method is 6.6%,and the average loss error is 10.9%,which meets the requirements of engineering calculation requirements.(3)A state evaluation method for superconducting energy storage magnets based on thermal stability is proposed,which solves the thermal quench problem that may occur due to excessive response power of energy storage magnets.This method uses an intelligent algorithm to predict the temperature rise of the energy storage magnet in the system command stage,comprehensively considers the magnet withstand voltage value,current energy storage and temperature rise,evaluates the response capability of the magnet,and avoids the magnet responding to commands beyond its own capability.active protection.(4)A coordinated control strategy based on temperature balance is proposed to solve the power allocation problem when the initial states of multiple SMES are different.This strategy allocates power according to the temperature of each magnet,the SMES with low magnet temperature undertakes the main power response task,and the SMES with high magnet temperature serves as the power supplement.Each SMES magnet will not exceed its temperature threshold during operation,which effectively improves the thermal stability of the energy storage magnet. |
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