On the Sequential Control of ITER Poloidal Field Converters for Reactive Power Reduction

Self Cite

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.

“…The non-linearity of reactors and distortion of line voltages may cause some non-characteristic harmonics. These are reasons for the deviation between the theory and practice [17].…”

Section: Comparison and Analysis Of Resultsmentioning

confidence: 99%

“…The maximum output current is the rated current ±55 kA. The whole operation time is 30 s [15][16][17].…”

Section: Simulation Modelingmentioning

confidence: 99%

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

Wang¹,

Xu²,

Fu³

et al. 2017

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“…The maximum short-circuit current can reach hundreds of kilo-amperes. Compared with conventional highpower converters, both the structure and design parameters have higher technical challenges [9][10][11]. Three-phase bridge rectifier circuit is used for the CRAFT converter because of the wide application and reliable technology.…”

Section: High Power Converter Topologymentioning

confidence: 99%

Preliminary design of high power magnet converter for CRAFT

Wang

Huang

et al. 2020

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In order to test the superconducting magnet performance for the Comprehensive Research Facility for Fusion Technology (CRAFT) project of China, a power supply converter needs to be designed. In this paper, short circuits upstream and downstream of the direct current (DC) reactor are analyzed, and the thyristor style and the parallel number are determined by the limit analysis of junction temperature and fault current I 2 t. On this basis, the over current and voltage verification of fast fuse are finished to protect the thyristor at fault cases by considering the short circuit of the bridge arm. Then, the resistor and capacitor parameters of thyristor snubber are committed to decreasing the reverse over voltage. These analysis results will be used as the preliminary design of high power magnet converter for CRAFT.

“…Based on formula (15), the effective value of the primary current (I A ) can be calculated by formula (16).…”

Section: Analysis Of the Power Factor Of A 12-pulse Convertermentioning

confidence: 99%

“…So it is necessary to minimize the electrical energy loss during AC/DC conversion. In recent years, sequential control has been used for multi-series converters to reduce reactive power consumption [14][15][16]. Although reactive power was saved to some degree and the power factor was partially improved by this technique, the converter's current distortion becomes more serious.…”

Section: Introductionmentioning

confidence: 99%

Control strategy optimization for energy efficiency and harmonic mitigation in multi-series converters

Ronglin¹,

Fu²,

Zhu³

et al. 2019

Self Cite

To provide electrical power for the Research System of Superconducting Magnets (RSSMs) including the background field superconducting magnet and the tested superconducting objects, the high power phase-controlled converter will be used to develop the power supply system. However, because of its inner nonlinear feature, the current harmonics and the reactive power are injected into the AC power supply system. To improve the quality of the power supply system for RSSMs, an improved synchronous control strategy is suggested for the superconducting magnet power supply system, which comprises four series-connected six-pulse converters fed by a phase-shifting transformer, respectively. According to the proposed control strategy, the basic unit is two 12-pulse converters and the control method will be changed in terms of load fluctuations which are represented by the per unit value of converter output voltage. As a result, harmonic is greatly reduced but the power factor is also high.