Contents lists available at ScienceDirect Electrical Power and Energy Systems journal homepage: www.elsevier.com/locate/ijepes Flexible arc-suppression method based on improved distributed commutations modulation for distribution networks Ze-Yin Zheng a,b , Mou-Fa Guo a, ⁎ , Nien-Che Yang b,c, ⁎ , Tao Jin a, ⁎ a Department of Electrical Engineering and Automation, Fuzhou University, Fuzhou 350116, China b Department of Electrical Engineering, Yuan Ze University, 135, Yuan-Tung Road, Chung-Li, Taoyuan 32003, Taiwan c Department of Electrical Engineering, National Taiwan University of Science and Technology, 43, Keelung Road, Section 4, Taipei 10607, Taiwan ARTICLE INFO Keywords: Distribution networks Single-phase-to-ground fault Flexible arc suppression Improved distributed commutations modulation ABSTRACT Because of the hazard of single-phase-to-ground faults on distribution networks for human security and device insulation, it is important for the ground-fault current to be eliminated by an arc-suppression device. However, owing to their shortcomings, passive arc-suppression devices cannot compensate the ground-fault current fully. Therefore, active arc-suppression devices have been studied. The flexible arc-suppression device (FASD) with a cascaded H-bridge (HB) topology is one type of active arc-suppression device. An FASD connected to a bus bar of distribution networks is applied to mitigate the ground-fault current. Owing to the high voltage and large current during the ground fault, a large number of HBs are required for the FASD. To modulate the HBs, an improved distributed commutations modulation method, which is combined with the flexible arc-suppression method, is proposed. The proposed modulation strategy aims to minimise the error between the reference signal and the tracking signal during each sampling period. Finally, the proposed strategy is validated via simulations and experiments to confirm its effectiveness for the FASD. 1. Introduction W. Petersen invented the arc-suppression coil in 1916. The tradi- tional arc-suppression coil represented by the Petersen coil can com- pensate the capacitive component of a ground-fault current [1,2]. However, with the popularity of cable lines (CLs) and the expansion of the size of distribution networks, the current of ground capacitance has gradually increased [3]. This may result in an increased ground-fault current when a single-phase-to-ground fault occurs. Therefore, the grade-adjustable arc-suppression coil has been developed. Its inductor is adjusted for adapting to the change of the ground parameters. Nevertheless, the single-phase-to-ground fault is always accompanied by the arc. The harmonics of the ground-fault current cannot be ig- nored. Thus, a series of new arc-suppression coils represented by the active arc-suppression method have been intensively studied. To achieve full current compensation, the novel arc-suppression device composed of power electronic components eliminates the different components of the ground-fault current. To increase the performance of ground-fault arc suppression, researchers have focused on the active arc-suppression methods in distribution networks. B. Chen [4] presented a two-stage magnetically controlled reactor (MCR) based on the traditional MCR to eliminate the reactive component and the third-order harmonic. In [5,6], a Petersen coil connected in parallel to a single-phase active inverter and an inductor was proposed to eliminate the harmonic components and active com- ponent, including the reactive component of the ground-fault current. X. Zeng [7,8] proposed a new Petersen coil connected in series to a single-phase active inverter and a zigzag transformer to compensate the ground-fault current via voltage and current double closed-loop pro- portional–integral (PI) control. The electromagnetic hybrid Petersen coil (EHPC) proposed in [9] is composed of an active power compen- sator (APC) and an MCR. The EHPC is based on compound control method and mitigates the power frequency component and harmonic components of the ground-fault current. However, the aforementioned arc-suppression methods require a large-capacity zigzag transformer or reactor and increase the volume of the arc-suppression device. For reducing the volume of the arc-suppression device and in- creasing the control flexibility, M. Guo [10] presented a flexible arc- suppression device (FASD) with a cascaded H-bridge (CHB) topology to mitigate the ground-fault current. However, when a single-phase-to- ground fault occurs, the FASD can be adversely affected by the over- voltage of the distribution networks. To limit the voltage stress of each cell to its individual rating, the CHB topology has been applied to in- crease the voltage rating of the FASD beyond the capacity of an https://doi.org/10.1016/j.ijepes.2019.105580 Received 4 November 2017; Received in revised form 25 June 2019; Accepted 26 September 2019 ⁎ Corresponding authors. E-mail addresses: gmf@fzu.edu.cn (M.-F. Guo), ncyang@mail.ntust.edu.tw (N.-C. Yang), jintly@fzu.edu.cn (T. Jin). Electrical Power and Energy Systems 116 (2020) 105580 Available online 03 October 2019 0142-0615/ © 2019 Elsevier Ltd. All rights reserved. T