Harmonics analysis of the ITER poloidal field converter based on a piecewise method

Poloidal field (PF) converters provide controlled DC voltage and current to PF coils.The many harmonics generated by the PF converter flow into the power grid and seriously affect power systems and electric equipment.Due to the complexity of the system,the traditional integral operation in Fourier analysis is complicated and inaccurate.This paper presents a piecewise method to calculate the harmonics of the ITER PF converter.The relationship between the grid input current and the DC output current of the ITER PF converter is deduced.The grid current is decomposed into the sum of some simple functions.By calculating simple function harmonics based on the piecewise method,the harmonics of the PF converter under different operation modes are obtained.In order to examine the validity of the method,a simulation model is established based on Matlab/ Simulink and a relevant experiment is implemented in the ITER PF integration test platform.Comparative results are given.The calculated results are found to be consistent with simulation and experiment.The piecewise method is proved correct and valid for calculating the system harmonics.