Multi‐objective optimization design of the large‐scale high‐intensity homogeneous magnetic field coil system based on non‐dominated sorting genetic algorithm (NSGA‐II)

Abstract

With the development of modern tokamak devices, the magnetic interference problem has become increasingly serious. On considering the International Thermonuclear Experimental Reactor (ITER), for example, the stray magnetic field around the tokamak device will be over 200 mT. To ensure the reliable operation of the electrical and electronic equipment installed around the tokamak, the magnetic immunity test becomes a mandatory requirement. Generally, a set of coils is employed to realize the required test field. Since the coil power loss and conductor mass are proportional to the dimension and intensity of the test field, optimization design is of great significance. This paper presents the multi‐objective optimization design of a large‐scale high‐intensity homogeneous magnetic field coil system. The analytical model of the multi‐coil system is proposed, and the constrained multi‐objective optimization model is established based on the non‐dominated sorting genetic algorithm. Taking the ITER test coil as an example, the optimization design is performed and the Pareto‐front is figured out. The designed four‐coil system enables the magnetic field immunity tests for equipment within 1 m side‐length at a highest test level of 275 mT with a magnetic field inhomogeneity of 1.05. The validity of the proposed model is verified by the finite element analysis and experimental tests.

Fusion power supply advances by the J-TEXT engineering team

“…How to balance the weight and the power becomes the key point in the design of a large-scale test coil. A multi-object optimization method based on a non-dominated sorting genetic algorithm (NSGA-II) is proposed to solve this problem in [17]. In the proposed method, the weight and power are treated as the optimization object, the structure parameters are treated as the variables, the characteristic parameters of the test field are treated as the constraints, and a Pareto-front, as shown in figure 11, is obtained.…”

“…We have also designed a test coil for the ITER Organization for the qualification test, as shown in figure 12(c). The test zone size is 1 m, the field strength is 275 mT and the field inhomogeneity is 1.05 [17]. All three coils are cooled by water due to the high operating power.…”

“…At present, the magnetic field immunity test is the most efficient method to qualify the sensitive equipment under high SMF due to the lack of experience of MFI problems [8]. We proposed the optimization design method of the magnetic field generating coil [16], which is the key component of the test platform, and designed the test coils for J-TEXT and ITER, and also helped the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP) to complete the design of the test platform [17,18]. In addition, the exploration of the failure of electromagnetic actuators [19,20], which are the most sensitive to SMF, and their optimization [21] is briefly introduced.…”