The Experts below are selected from a list of 17259 Experts worldwide ranked by ideXlab platform
Grzegorz Wiczyński - One of the best experts on this subject based on the ideXlab platform.
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Determining location of Voltage Fluctuation source in radial power grid
Electric Power Systems Research, 2020Co-Authors: Grzegorz WiczyńskiAbstract:Abstract The effects of Voltage Fluctuation are a common reason for complaints about low power quality. Voltage Fluctuations in power grids are usually caused by changes in states of loads. In order to counteract this problem, it is required to determine the location of the source of Voltage Fluctuations as well as their parameters. The paper presents examples of locating disturbance loads which cause symmetric and asymmetric Voltage Fluctuation in LV radial power grid. In the process, the results of Voltage Fluctuation indices’ measurements have been used. The results of location process have been used to describe the propagation of Voltage Fluctuation in an example power grid. In addition, the current variation which causes the observed Voltage Fluctuation has also been determined.
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An example of converting Voltage Fluctuation indices into Pst indicator
2018 18th International Conference on Harmonics and Quality of Power (ICHQP), 2018Co-Authors: Mateusz Michalski, Grzegorz WiczyńskiAbstract:A set of power quality measures includes Pst indicator and Voltage Fluctuation indices. Both of the measures describe Voltage variation. They however differ in their properties. This results, among others, in different diagnostic capabilities. Because of that the power quality assessment should make use of both of the measures. One of the consequences of taking such an approach is the matter of possible recalculation of Voltage Fluctuation indices into Pst indicator. This paper presents an example of such recalculation. During the process a results of measurements recorded in LV power grid were used. The chosen example presents the case where the quality of Pst indicator restoration is only moderate. It is shown that the results of calculations are basically similar to real Pst indicator values. To give wider insight into the example, also maximal and minimal rms Voltage values were used along Voltage Fluctuation indices and Pst indicator.
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Estimation of $\boldsymbol {P}_{st}$ Indicator Values on the Basis of Voltage Fluctuation Indices
IEEE Transactions on Instrumentation and Measurement, 2017Co-Authors: Grzegorz WiczyńskiAbstract:Power quality is described by Voltage Fluctuation measures. Voltage Fluctuation is understood as “a series of Voltage changes or a continuous variation of the rms or peak value of the Voltage.” Voltage variation is most often manifested by flicker, which might become obnoxious at a high enough intensity. One of the standard measures of Voltage Fluctuation is $\boldsymbol {P}_{st}$ indicator. One of its major flaws is its limited diagnostic capabilities. Voltage Fluctuation indices are the measure, which provides much bigger range of diagnostic capabilities. However, it has not been acknowledged as a standard measure. The initial part of this paper includes the description of the accepted method of reproducing Voltage variation. It also presents general characteristics of the $\boldsymbol {P}_{st}$ indicator and Voltage Fluctuation indices. The next part of this paper describes the methods of converting Voltage Fluctuation indices into $\boldsymbol {P}_{st}$ indicator and vice versa. The capability of estimating the $\boldsymbol {P}_{st}$ indicator on the basis of the indices has been confirmed. Three examples of measurement results of both these measures in low-Voltage (LV) power grids have been presented. These results have proved the connection between the estimated values (on the basis of Voltage Fluctuation indices) and the results of the $\boldsymbol {P}_{st}$ indicator measurements.
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Estimation of Pst indicator values on the basis of Voltage Fluctuation indices
IEEE Transactions on Instrumentation and Measurement, 2017Co-Authors: Grzegorz WiczyńskiAbstract:Power quality is described by Voltage Fluctuation measures. Voltage Fluctuation is understood as “a series of Voltage changes or a continuous variation of the rms or peak value of the Voltage.” Voltage variation is most often manifested by flicker, which might become obnoxious at a high enough intensity. One of the standard measures of Voltage Fluctuation is Pst indicator. One of its major flaws is its limited diagnostic capabilities. Voltage Fluctuation indices are the measure, which provides much bigger range of diagnostic capabilities. However, it has not been acknowledged as a standard measure. The initial part of this paper includes the description of the accepted method of reproducing Voltage variation. It also presents general characteristics of the Pst indicator and Voltage Fluctuation indices. The next part of this paper describes the methods of converting Voltage Fluctuation indices into Pst indicator and vice versa. The capability of estimating the Pst indicator on the basis of the indices has been confirmed. Three examples of measurement results of both these measures in low-Voltage (LV) power grids have been presented. These results have proved the connection between the estimated values (on the basis of Voltage Fluctuation indices) and the results of the Pst indicator measurements.
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Methods of representing the results of Voltage Fluctuation indices measurements
2016 17th International Conference on Harmonics and Quality of Power (ICHQP), 2016Co-Authors: Grzegorz WiczyńskiAbstract:Voltage variation in power grids is usually described with the use of several measures. One of them is the group of Voltage Fluctuation indices which concern the δU magnitude and the f rate. Other measures include the maximum and minimum rms Voltage values. The paper describes selected methods of representing the results of Voltage Fluctuation indices measurements. An magnitude-rate chart has been presented which provides the information about magnitude and rates of Voltage Fluctuations and makes it possible to assess the obnoxiousness of Voltage Fluctuations. The paper underlines the fact that such a method of evaluating the obnoxiousness is unique among similar measures as it enables the user to estimate the obnoxiousness of Voltage Fluctuations for different types of powered loads. The next part of the paper includes the representation of measurement results of the Voltage Fluctuation indices with the use of time plots of δU = f (t) magnitude and f = f (t) rate. It has been shown that the analysis of the Voltage Fluctuation indices can be supported with the Umax maximum and Umin minimum rms Voltage values. Analysis of time plots revealed periods of time important from the diagnostic point of view. For these periods obnoxiousness of Voltage Fluctuations has been assessed and δV values along with its rate has been delimited. On the basis of the f = f (δV) histograms, the Voltage changes have been grouped within the selected ranges of the δV values. Finally, the rate of δV occurring has been derived for Voltage changes grouped in this manner.
Yang Yihan - One of the best experts on this subject based on the ideXlab platform.
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Voltage Fluctuation and flicker caused by wind power generation
Power system technology, 2003Co-Authors: Yang YihanAbstract:During the continuous operation and the switching-option of wind turbines connected to the power grid, the Voltage Fluctuation and flicker occur and affect the power quality in the local power network. Starting from the Fluctuation of the power output of wind turbines, the main reasons causing the Voltage Fluctuation and flicker by wind power generation are analyzed, then the IEC Standard 61400-21 for the power quality of grid-connected wind turbines is introduced. The calculation formulae for flicker and relative Voltage change which occurs during the continuous operation and the switching-option of wind turbines are given. The research achievements in the calculation methods and the influencing factors of the Voltage Fluctuation and flicker caused by wind power generation is summarized. Finally, the research area and the key problems to be researched in the future are viewed.
Longya Xu - One of the best experts on this subject based on the ideXlab platform.
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Capacitor Voltage Fluctuation Minimization for Four-Level Hybrid Clamped Converter Using Improved Common-Mode Voltage Injection
IEEE Transactions on Power Electronics, 2020Co-Authors: Yong Yang, Longya XuAbstract:When a four-level hybrid clamped converter (4L-HCC) operates at low frequencies, the high load current causes significant Voltage Fluctuations among the capacitors in the dc link. A mathematical model is developed to clarify the mechanism of excessive capacitor Voltage Fluctuations. An improved common-mode Voltage injection algorithm is proposed and integrated to the overall control method. With the applied algorithm, the Voltage Fluctuation minimization of the dc-link capacitors and the dynamic Voltage balancing capability are investigated. Both simulation and experimental results validate the effectiveness of the proposed algorithm, with a Voltage Fluctuation reduction over 50%. The 4L-HCC with the proposed algorithm achieves much faster dynamic response to converge the unbalanced capacitor Voltages and the reduced output current harmonics compared with the conventional common-mode Voltage injection algorithm.
Dianguo Xu - One of the best experts on this subject based on the ideXlab platform.
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analysis and design of an s sp compensated ipt system to minimize output Voltage Fluctuation versus coupling coefficient and load variation
IEEE Transactions on Vehicular Technology, 2018Co-Authors: Yijie Wang, Kaixing Lu, Dianguo XuAbstract:The capability of misalignment tolerance is vital for inductive power transfer (IPT) systems. S/SP compensation topology can provide a strong capability of misalignment tolerance if it is properly designed. This paper presents a detailed deduction process to acquire the optimal coupling coefficient, tuned at which the system can achieve minimum output Voltage Fluctuation. The impact of primary and secondary coupling inductance on output Voltage Fluctuation versus load variation was also analyzed. The output Voltage Fluctuation is not affected by the primary coupling inductance, but it decreases when the secondary coupling inductance is increased. Theoretical analysis was validated by both simulation and experiment. Three 200-W IPT prototypes were built. An overall efficiency of 94.1% was achieved when the coupling coefficient was 0.1733. The output Voltage Fluctuation was as low as 1.5% when the coupling coefficient increased by 34.5%, from 0.1288 to 0.1733. With a 900% rise in load resistance (from 80 to 800 Ω), the output Voltage Fluctuation decreased from 5.8% to 4.0% when the secondary coupling inductance increased from 136.3 to 250.0 μ H.
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Comparative Study of High-Frequency Injection Method and HMMC for Suppressing Capacitor Voltage Fluctuation of MMC
2018 21st International Conference on Electrical Machines and Systems (ICEMS), 2018Co-Authors: Jingkun Wang, Binbin Li, Shaoze Zhou, Dianguo XuAbstract:Modular multilevel converter (MMC) represents an interesting and emerging topology in medium-Voltage motor drive applications. The main challenge of using such a topology in variable-speed drives is the large Voltage Fluctuation of sub module capacitors at low speeds. The most widely used method of suppressing the Fluctuation of capacitor Voltage is high-frequency injection method. In addition, a novel hybrid modular multilevel converter (HMMC) topology has received extensive attention due to its inherent ability to reduce capacitor Voltage Fluctuation. In this paper, a comparative study of high-frequency injection method and HMMC in terms of converter loss, current stress and capacitance was conducted. The results show that the use of HMM C topology leads to lower loss and current stress at low frequency. The comparative study will guide the application of MMC in the field of motor drive.
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A Modified Modular Multilevel Converter With Reduced Capacitor Voltage Fluctuation
IEEE Transactions on Industrial Electronics, 2015Co-Authors: Binbin Li, Dianguo Xu, Yi Zhang, Gaolin Wang, Wei WangAbstract:The requirement of a large number of sizeable capacitors in traditional modular multilevel converter (MMC) submodules is seen as a major barrier hampering its widespread use in medium-Voltage applications. To reduce the value of capacitance, this paper presents a modified MMC (M-MMC) topology, which offers inherent alleviated capacitor Voltage Fluctuations compared with traditional MMC. Its operating principle, modulation, and capacitor Voltage balancing strategies are described in detail. Moreover, a novel capacitor Voltage Fluctuation suppression scheme is also proposed to further reduce the second-order capacitor Voltage ripples. Finally, both a three-phase prototype of M-MMC and traditional MMC have been built in the laboratory. The effectiveness of the proposed M-MMC topology and control methods is experimentally verified by comparing with the traditional MMC.
Yong Yang - One of the best experts on this subject based on the ideXlab platform.
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Capacitor Voltage Fluctuation Minimization for Four-Level Hybrid Clamped Converter Using Improved Common-Mode Voltage Injection
IEEE Transactions on Power Electronics, 2020Co-Authors: Yong Yang, Longya XuAbstract:When a four-level hybrid clamped converter (4L-HCC) operates at low frequencies, the high load current causes significant Voltage Fluctuations among the capacitors in the dc link. A mathematical model is developed to clarify the mechanism of excessive capacitor Voltage Fluctuations. An improved common-mode Voltage injection algorithm is proposed and integrated to the overall control method. With the applied algorithm, the Voltage Fluctuation minimization of the dc-link capacitors and the dynamic Voltage balancing capability are investigated. Both simulation and experimental results validate the effectiveness of the proposed algorithm, with a Voltage Fluctuation reduction over 50%. The 4L-HCC with the proposed algorithm achieves much faster dynamic response to converge the unbalanced capacitor Voltages and the reduced output current harmonics compared with the conventional common-mode Voltage injection algorithm.
