이중 변환 UPS의 병렬 운전 시 외란 저감 성능 향상을 위한 정지 좌표계 상의 전향 보상 기법 류효준1 , 윤영두✝, 모재성1 , 최승철1 , 우태겸1 Feed-Forward Compensation Technique in Stationary Reference Frame for the Enhanced Disturbance Rejection Performance in Parallel Operation of Double-Conversion UPSs

 이중 변환 UPS의 병렬 운전 시 외란 저감 성능 향상을 위한 정지 좌표계 상의 전향 보상 기법 류효준1 , 윤영두✝, 모재성1 , 최승철1 , 우태겸1

 Feed-Forward Compensation Technique in Stationary Reference Frame for the Enhanced Disturbance Rejection Performance in Parallel Operation of Double-Conversion UPSs 

By Hyo-Jun Ryu1 , Young-Doo Yoon✝, Jae-Sung Mo1 , Seung-Cheol Choi1 , and Tae-Gyeom Woo1 

Abstract 

Generally, a proportional-resonant controller is used to eliminate steady-state errors during the voltage– current control of a double-conversion uninterruptible power supply (UPS) in a stationary reference frame. Additionally, the feed-forward control compensating for the load current, which can be considered a disturbance of the voltage controller, can be used to improve the disturbance rejection performance. However, during the parallel operation of UPSs, circulating current can occur between UPS modules when performing both feed-forward control and droop control because feed-forward control reduces the circulating current impedance. This study proposes a feed-forward compensation technique that considers the impedance of circulating current. An additional feed-forward compensation technique is developed to enhance the disturbance rejection performance. The validity of the proposed feed-forward compensation technique is verified by the experiment results of the parallel operation of a 500 W double-conversion UPS module.

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A Comparative Review of Three Different Power Inverters for DC–AC Applications Ali Abdel-Aziz 1 , Mohamed A. Elgenedy 2,* and Barry Williams 1-25 October 2023

 A comparative review of three different power inverters for DC–AC applications

 Ali AbdelAziziMohamed ElgenedyBarry Williams25 October 2023DOI: 10.3390/EN16217254

 Abstract 

This paper presents a comparative review of three different widely used power inverters, namely the conventional six-switch inverter; the reduced switch count four-switch inverter; and the eight-switch inverter. The later inverter can be reconfigured as a neutral-point diode-clamped inverter at the failure of one inverter leg. The three power inverters are compared and discussed with respect to cost, complexity, losses, common mode voltage, and control techniques. The paper is intended to serve as a guide regarding selecting the appropriate inverter for each specific application. Simulation results are presented to demonstrate the performance of the three power inverters, followed by a comprehensive comparison between the three power inverters .

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不平衡负载下三相 UPS 逆变器的研究 Research on Three-phase UPS with Unbalanced Load-Ye Bincheng1 , Meng Chao1,2, Wei Wen1 1.PROTEK Electronic Technology Corporation（Xiamen, 361028. China）；2.School of Energy, Xiamen University（Xiamen, 361002, China）

 不平衡负载下三相 UPS 逆变器的研究 Research on Three-phase UPS with Unbalanced Load 要：三相电压的对称输出是衡量交流电源性能的一个重要指标。提出了一种新型的三相 UPS 逆变器系统，利用 Δ/Z0 型变 压器为三相不平衡负载造成的零序电流分量提供通路，再通过设计正、负序双 PI 控制器抑制不平衡负载中负序电压分量。从而 解决零序电压和负序电压造成的三相电压不平衡问题，使该三相 UPS 逆变电源系统可带三相不平衡负载。试制一台 60kVA 的三 相 UPS 样机，并给出实验结果。 关键词：三相 UPS 三相逆变器 不平衡负载 电压对称性 

Abstract: The balanced output of three-phase voltage is an important index to measure the function of alternating current .In order to obtain high-grade output voltage in the case where the load is out-off-balance, this paper analyzed the mechanism and result of threephase voltage caused by unbalanced load, and some existing solutions to solve this problem. A new three-phase UPS inverter system is also raised which use △ /ZO transformer to provide a current path for zero-sequence current that caused by three-phase unbalanced load. What’s more, it controlled the component of negative sequence voltage in the unbalanced load by designing the doubled PI controller (of positive and negative sequence). In these ways it could solve the imbalance of three-phase voltage caused by Zero-sequence voltage and， making the three-phase UPS inverter system able to load the three-phase unbalanced load. A 60kVA three-phase UPS prototypes was built and the results were given based on the experiments.

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https://core.ac.uk/download/323950531.pdf

“Performance Evaluation of a Proportional Integral with Proportional Derivative Feedforward Voltage Control for UPSs”-Tiago J. C. Sousa, Vítor Monteiro, Júlio S. Martins, J. C. Aparício Fernandes, João L. Afonso----ALGORITMI Research Centre – University of Minho Guimarães – Portugal

 Performance Evaluation of a Proportional-Integral with Proportional-Derivative Feedforward Voltage Control for UPSs 

Tiago J. C. Sousa, Vítor Monteiro, Júlio S. Martins, J. C. Aparício Fernandes, João L. Afonso ALGORITMI Research Centre – University of Minho Guimarães – Portugal 

 Abstract—This paper presents a performance evaluation of a proportional-integral (PI) with proportional-derivative (PD) feedforward control for the output voltage of a single-phase off-line uninterruptible power supply (UPS) without using additional sensors. The control system is explained and simulation results are presented to analyze the steady state and transient response of the implemented voltage control. A laboratorial prototype was developed, and acquired experimental results considering linear and nonlinear loads are presented and discussed, corroborating the obtained simulation results.

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https://core.ac.uk/download/185627388.pdf

Development of Magnetic Models to Assess Transformers’ Susceptibility to Geomagnetic Disturbances A thesis submitted to The University of Manchester for the degree of Doctor of Philosophy in the Faculty of Science and Engineering

 Development of Magnetic Models to Assess Transformers’ Susceptibility to Geomagnetic Disturbances A thesis submitted to The University of Manchester for the degree of Doctor of Philosophy in the Faculty of Science and Engineering 2018

 Yufan Ni 

School of Electrical and Electronic Engineering

 Abstract 

During the peak years of solar activity, the magnetic field held by the solar wind has an impact on the Earth’s magnetic field and induce an electric field on the Earth’s surface. The Geomagnetically Induced Current (GIC) is generated between two neutral points of transformers. The GIC can do severe harm to a power system, including to its transformers. The worst GIC event caused a power system blackout for several hours in Quebec in 1989. The research aims to build a representative model of core saturation and carry out simulation studies to understand the performance of transformer cores in the high flux density region. This in turn helps to identify the design features that need to be taken into account when assessing the capability of a transformer to withstand over-excitation. ATP is a kind of user-maintained software so it allows self-developed code to be added into the software package. The results simulated by the existing ATP models are inaccurate compared to the measured results. In addition, the existing models cannot provide flux distribution results, so it is difficult to understand the process of how the core is pushed into the deep saturation region by DC offset. A new model is developed to include the equivalent electric and magnetic circuit representations, taking flux leakage, in particular, into consideration. The flux leakage paths are composed of the oil gaps and tank in series. This model is validated by the consistency shown between the measured and simulated HV winding currents of a 5-limb transformer. The peaks of magnetising currents are identified with the peaks of magnetic flux which saturate the core. The model can identify the design features, such as the core structure, dimension of flux leakage paths and winding impedance that need to be taken into account when assessing the capability of a transformer to withstand over-excitation. A 3-limb model and a 5-limb core model are built to assess the susceptibility to GIC for different core types in high flux density region. The delta winding plays a role in holding the 3rd harmonics and unbalanced current generated by core saturation, and in delaying the core saturation. Lastly, Transformers are simulated under realistic GIC waveforms, for situations with and without load. The new model is expected to be coded into ATP to conduct a GIC study for a power system.

VIEW FULL TEXT: https://pure.manchester.ac.uk/ws/portalfiles/portal/139670403/FULL_TEXT.PDF