A new hybrid filter based on differential current control method for low-order harmonic suppression in Tokamak power system

Abstract

SummaryWith high-power, high-parameter operation of Tokamak device, not only characteristic harmonics but also much noncharacteristic harmonics, especially below the third-order harmonics, present in its power supply system. These low-order harmonics, which further amplified by the capacitive impedance in system, will endanger the reliable operation of Tokamak device and the power supply. Although Tokamak devices have taken some filtering measures, the resonance of low-order harmonics could not be completely prevented. In this paper, a hybrid filter based on differential current control method is proposed, which can effectively increase the filtering capability. The hybrid filter was mainly analyzed and validated in EAST power supply system. The results show that it can restrain the resonance and suppress low-order harmonics in the system and can be extended to large-capacity occasions.KEYWORDS differential current control, hybrid filter, low-order harmonic suppression, Tokamak power system 1 | INTRODUCTION Tokamak, which uses strong magnetic field to confine plasma in the shape of a torus achieving a stable plasma equilibrium, may be the ultimate solution on the energy crisis. The Tokamak devices such as EAST, KSTAR, ASDEX-U and others aim to reach higher plasma current and longer plasma sustaining time under high performance operation (H-mode) during experiments. To achieve such high performance of plasmas, extreme high demand of the power, usually at the order of hundreds of MVA, is required for the power supplies system, as well as the fast transients. 1 Thyristor-based converters are widely selected for the majority of the Tokamak power supplies due to the high current rating and the DC voltage/current characteristics. However, such complex operation mode will directly lead to the asymmetry of the converter firing angles, sharp fluctuations of current amplitude and phase in the AC system, direct current bias of transformer and dynamic harmonic coupling between AC and DC network. 2 These will usually stimulate low-order harmonic in the AC side, for instance, second, third, or even inter harmonics. 3 The power suppliers will draw large reactive power pulses from the grid, and reactive power control is necessary for voltage stabilization and compensation together with filters to eliminate harmonics generated by the power converters. The improper design of the filters will result in the harmonic application in the low frequency (75-135 Hz) domain. These low-order harmonics can jeopardize Tokamak system operation and the security of the grid.

RETRACTED: Harmonics mitigation in hybrid shunt active power filter connected renewable energy source using an intelligent controller

“…Instances of harmonics-making loads include static volt ampere reactive compensators, inverters, direct current converters, switch-mode power supplies, alternating current or direct current motor drives, electric arc furnaces, capacitor switching and lightning strikes (Biswas et al, 2017; Yang et al, 2018). These disturbances bring about malfunctions, decreased lifetime and disappointment of electrical equipment (Lu et al, 2017). The majority of researchers used the various innovations for the harmonics mitigation, for instance, recursive least square, differential evolution algorithm, etc.…”

Hybrid Kalman Filtering Algorithm With Stochastic Nonlinearities and Multiple Missing Measurements

“…By applying Lemma 6, the parameter H can be calculated by formula (26), as shown at the top of the next page. Therefore, the equations (17), (19) and (21) can be obtained by (23)- (26). By using the equations (14), (23) and E { k − } = 0, E {ν k+1 } = 0, it can be easily deduced that…”

“…In order to solving the estimation problem for this kind of systems, the hybrid filters were proposed by applying the different filtering approaches [14]- [18]. To mention just a few, in [19], a hybrid filter, which can effectively increase the filtering capability, was proposed by using the differential current control method and the hybrid filter was mainly analyzed and validated in EAST power supply system. An unscented Kalman-particle hybrid filter was designed in [20] for recursive Bayesian estimation of space objects, where the hybrid filtering scheme provided accurate and consistent estimates when measurements were sparse without incurring a large computational cost.…”

An overview of power quality enhancement techniques applied to distributed generation in electrical distribution networks

“…Hybrid active power filters offer a method to overcome the physical limits of tuned passive filters and at the same time, reduce cost of using an expensive high capactiy active power filter [91][92][93]. The main categories of hybrid filters are shunt active series passive filters [67,[94][95][96][97][98][99][100][101], shunt active shunt passive filters [26], and series active shunt passive filters [96,97].…”