The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Xiaoming Yuan - One of the best experts on this subject based on the ideXlab platform.

  • modeling and analyzing the effect of frequency variation on weak grid connected vsc system stability in Dc Voltage control timescale
    Energies, 2019
    Co-Authors: Hui Yang, Xiaoming Yuan
    Abstract:

    The effect of frequency variation on system stability becomes crucial when a Voltage source converter (VSC) is connected to a weak grid. However, previous studies lack enough mechanism cognitions of this effect, especially on the stability issues in Dc Voltage control (DVC) timescale (around 100 ms). Hence, this paper presented a thorough analysis of the effect mechanism of frequency variation on the weak grid-connected VSC system stability in a DVC timescale. Firstly, based on instantaneous power theory, a novel method in which the active/reactive powers are calculated with the time-varying frequency of Voltage vectors was proposed. This method could intuitively reflect the effect of frequency variation on the active/reactive powers and could also help reduce the system order to a certain extent. Then, a small-signal model was established based on the motion equation concept, to depict the effect of frequency variation on the weak grid-connected VSC system dynamics. Furthermore, an analytical method was utilized to quantify the effect of frequency variation on the system’s small-signal stability. The quantitative analysis considered the interactions between the Dc Voltage control, the terminal Voltage control, phase-locked loop, and the power network. Finally, case studies were conducted, and simulation results supported the analytical analyses.

  • modeling of vscs considering input and output active power dynamics for multi terminal hvDc interaction analysis in Dc Voltage control timescale
    IEEE Transactions on Energy Conversion, 2019
    Co-Authors: Wanning Zheng, Xiaoming Yuan
    Abstract:

    Multi-terminal high-Voltage direct current (MTDc) systems based on Voltage source converters (VSCs) are increasingly utilized. In such a case, dynamic interactions among different VSCs of each terminal become one of the leading problems for the ac/Dc interconnected system. This paper presents a frequency-domain small-signal model of MTDc-linked VSCs in Dc Voltage control (DVC) timescale based on the motion equation concept. Control schemes, including two typical Dc Voltage-droop control, phase-locked loop, and vector control in DVC timescale are taken into account adequately. By considering the dynamics of both input and output active powers across the Dc capacitor, the proposed model aims to describe the external characteristics of MTDc-linked VSCs independent of grid conditions, which makes it easy to extend in various types of MTDc systems. Interaction analysis of a typical four-terminal HVDc system was conducted to validate the feasibility of the presented model.

Feel-soon Kang - One of the best experts on this subject based on the ideXlab platform.

  • seven level pwm inverter employing series connected capacitors paralleled to a single Dc Voltage source
    IEEE Transactions on Industrial Electronics, 2015
    Co-Authors: Jinsung Choi, Feel-soon Kang
    Abstract:

    This paper presents an effective circuit configuration of a multilevel inverter that can increase the number of output Voltage levels with a reduced number of circuit components. The proposed seven-level pulsewidth-modulation inverter consists of a single Dc Voltage source with a series of capacitors, diodes, active switches for synthesizing output Voltage levels, and an H-bridge cell. After theoretical analysis, we carry out computer-aided simulations and experiments to verify the validity of the proposed approach. Here, we also introduce a modified switching strategy to solve the capacitor Voltage unbalancing that occurs in series-connected capacitors.

  • unification of buck boost and flyback converter for driving cascaded h bridge multilevel inverter with single independent Dc Voltage source
    International Conference on Electrical Machines and Systems, 2013
    Co-Authors: Jinsoo Park, Feel-soon Kang
    Abstract:

    It presents a unification of buck-boost and flyback converter for driving a cascaded H-bridge multilevel inverter with a single independent Dc Voltage source. Cascaded H-bridge multilevel inverter is useful to make many output Voltage levels for sinusoidal waveform by combining two or more H-bridge modules. However, each H-bridge module needs an independent Dc Voltage source to generate multi levels in an output Voltage. This topological characteristic brings a demerit of increasing the number of independent Dc Voltage sources when it needs to increase the number of output Voltage levels. To solve this problem, we propose a converter combining a buck-boost converter with a flyback converter. The proposed converter provides independent Dc Voltage sources at back-end two H-bridge modules. After analyzing theoretical operation of the circuit topology, the validity of the proposed approach is verified by computer-aided simulations using PSIM and experiments.

  • cascaded h bridge multilevel inverter employing front end flyback converter with single independent Dc Voltage source
    International Conference on Electrical Machines and Systems, 2013
    Co-Authors: Feel-soon Kang
    Abstract:

    Abstract – Cascaded H-bridge multilevel inverter requires independent Dc Voltage sources to produce multi output Voltage levels. When it needs to generate more levels in the output Voltage wave, the number of independent Dc Voltage sources usually limits its extension. To solve this problem, we propose a cascaded H-bridge multilevel inverter employing a front-end flyback converter for unifying input Dc Voltage sources. After theoretical analysis of the proposed circuit, we verify the validity of the proposed inverter using computer-aided simulations and experiments. Keywords: Cascaded H-bridge Multilevel Inverter, Flyback Converter, Transformer, Inverters, Multilevel systems 1. Introduction notCascaded H-bridge multilevel inverter has been studied for high Voltage applications since it has merits in high reliability, modularity, and number of components [1]-[8]. Usually multilevel inverter is focusing on a generation of a high Voltage using lower Voltage rating devices connected in series. Also it has a potential advantage to get a high quality output Voltage by producing multi levels in the output Voltage wave. However, it increases the number of independent Dc Voltage sources and switching components resulted in the increase of complexity problem and system cost. To solve this problem, many researchers have been studied to reduce the number of components. However, it generally focuses on reducing the number of switching components [4]-[8]. In this paper, we present a cascaded H-bridge multilevel inverter adopting a front-end flyback converter to unify independent Dc Voltage sources. The flyback converter employs a transformer operated in high switching frequency, and it has one primary winding and two secondary windings. The secondary of the transformer in the general flyback converter consists of one diode and an output capacitor. In the proposed method, the diode is substituted for an active switch to control the output Voltage in a constant value. Most of all, we can obtain our goal that is to drive the cascaded H-bridge multilevel inverter with a single independent Dc Voltage source. Because the transformer is operated in high switching frequency, it does increase size and volume of the system. After theoretical analysis, the validity of the proposed approach is proved by computer-aided simulations and experiments.

Hirotaka Koizumi - One of the best experts on this subject based on the ideXlab platform.

  • a single phase multilevel inverter using switched series parallel Dc Voltage sources
    IEEE Transactions on Industrial Electronics, 2010
    Co-Authors: Youhei Hinago, Hirotaka Koizumi
    Abstract:

    A novel multilevel inverter with a small number of switching devices is proposed. It consists of an H-bridge and an inverter which outputs multilevel Voltage by switching the Dc Voltage sources in series and in parallel. The proposed inverter can output more numbers of Voltage levels in the same number of switching devices by using this conversion. The number of gate driving circuits is reduced, which leads to the reduction of the size and power consumption in the driving circuits. The total harmonic of the output waveform is also reduced. The proposed inverter is driven by the hybrid modulation method. In this paper, the circuit configuration, theoretical operation, Fourier analysis, simulation results with MATLAB/SIMULINK, and experimental results are shown. The experimental results accorded with the simulation results.

  • a single phase multilevel inverter using switched series parallel Dc Voltage sources
    Energy Conversion Congress and Exposition, 2009
    Co-Authors: Youhei Hinago, Hirotaka Koizumi
    Abstract:

    A novel multilevel inverter with a small number of switching devices is proposed. It consists of an H-bridge and an inverter which outputs multilevel Voltage by switching the Dc Voltage sources in series and in parallel. The proposed inverter can output more number of Voltage levels in the same number of the switching devices by using this conversion. The number of gate driving circuits is reduced, which leads to the reduction of the size and power consumption in the driving circuits. The total harmonic of the output waveform is also reduced. The proposed inverter is driven by the hybrid modulation (HM) method. In this paper, the circuit configuration, the theoretical operation, Fourier analysis, simulation results with MATLAB/ SIMULINK and the experimental results are shown. The experimental results accorded with the simulation results.

Ronnie Belmans - One of the best experts on this subject based on the ideXlab platform.

  • Modeling of multi-terminal vsc hvDc systems with distributed Dc Voltage control
    IEEE Transactions on Power Systems, 2014
    Co-Authors: Jef Beerten, Stijn Cole, Ronnie Belmans
    Abstract:

    This paper discusses the extension of electromechanical stability models of Voltage source converter high Voltage direct current (VSC HVDc) to multi-terminal (MTDc) systems. The paper introduces a control model with a cascaded Dc Voltage control at every converter that allows a two-terminal VSC HVDc system to cope with converter outages. When extended to an MTDc system, the model naturally evolves into a master-slave set-up with converters taking over the Dc Voltage control in case the Dc Voltage controlling converter fails. It is shown that the model can be used to include a Voltage droop control to share the power imbalance after a contingency in the Dc system amongst the converters in the system. Finally, the paper discusses two possible model reductions, in line with the assumptions made in transient stability modeling. The control algorithms and VSC HVDc systems have been implemented using both MatDyn, an open source MATLAB transient stability program, as well as the commercial power system simulation package EUROSTAG.

  • Optimizing Dc Voltage Droop Settings for AC/Dc System Interactions
    IEEE Transactions on Power Delivery, 2014
    Co-Authors: Robert Eriksson, Jef Beerten, Mehrdad Ghandhari, Ronnie Belmans
    Abstract:

    In this paper, a methodology is presented to optimize the Dc Voltage droop settings in a multiterminal Voltage-source converter high-Voltage direct-current system with respect to the ac system stability. Implementing Dc Voltage droop control enables having multiple converters assisting the system in case of a converter outage. However, the abrupt power setpoint changes create additional stress in the ac system, especially when multiple converters are connected to the same interconnected ac system. This paper presents a methodology to determine optimized converter droop settings in order to not compromise the ac system stability, thereby taking into account the adverse effect the droop control actions have on the interconnected ac system. Developing a disturbance model of the interconnected ac/Dc system, the principal directions indicate the gain and directionality of the disturbances; from this, optimal droop settings are derived to minimize the disturbance gain.

  • A Distributed Dc Voltage Control Method for VSC MTDc Systems
    Electric Power Systems Research, 2012
    Co-Authors: Carlos Dierckxsens, Jef Beerten, Stijn Cole, Kailash Srivastava, Muhamad Reza, Ronnie Belmans
    Abstract:

    Abstract With the development of VSC HVDc transmission, the realization of the first VSC MTDc grid is coming within reach. An outstanding issue is Dc Voltage control in MTDc systems. The easiest way to maintain stable operation is to assign the task of Dc Voltage regulation to one converter. This paper discusses a control strategy for an extended VSC MTDc grid using a typical Dc Voltage control on one Dc bus, combined with a Dc Voltage droop characteristic on the other Dc buses. The impact of the proposed control structure on the stability of the AC and Dc grid is investigated by numeric simulations using the MatDyn software package.

  • vsc mtDc systems with a distributed Dc Voltage control a power flow approach
    IEEE PowerTech Conference, 2011
    Co-Authors: Jef Beerten, Dirk Van Hertem, Ronnie Belmans
    Abstract:

    In this paper, a power flow model is presented to include a Dc Voltage droop control or distributed Dc slack bus in a Multi-terminal Voltage Source Converter High Voltage Direct Current (VSC MTDc) grid. The available VSC MTDc models are often based on the extension of existing point-to-point connections and use a single Dc slack bus that adapts its active power injection to control the Dc Voltage. A distributed Dc Voltage control has significant advantages over its concentrated slack bus counterpart, since a numbers of converters can jointly control the Dc system Voltage. After a fault, a Voltage droop controlled Dc grid converges to a new working point, which impacts the power flows in both the Dc grid and the underlying AC grids. Whereas current day research is focussing on the dynamic behaviour of such a system, this paper introduces a power flow model to study the steady-state change of the combined AC/Dc system as a result of faults and transients in the Dc grid. The model allows to incorporate Dc grids in a N-1 contingency analysis, thereby including the effects of a distributed Voltage control on the power flows in both the AC and Dc systems.

Juan M. Carrasco - One of the best experts on this subject based on the ideXlab platform.

  • Dc Voltage ratio control strategy for multilevel cascaded converters fed with a single Dc source
    IEEE Transactions on Industrial Electronics, 2009
    Co-Authors: Sergio Vázquez, Jose I. Leon, Leopoldo Garcia Franquelo, J J Padilla, Juan M. Carrasco
    Abstract:

    Recently, a multilevel cascaded converter fed with a single Dc source has been presented. An analysis of the steady-state working limits of this type of converter is presented in this paper. Limits of the maximum output Voltage and the minimum and maximum loading conditions for stable operation of the converter are addressed. In this paper, a way to achieve any Dc Voltage ratio (inside the stable operation area of the converter) between the H-bridges of the single-Dc-source cascaded H-bridge converter is presented. The proposed Dc-Voltage-ratio control is based on a time-domain modulation strategy that avoids the use of inappropriate states to achieve the Dc-Voltage-ratio control. The proposed technique is a feedforward-modulation technique which takes into account the actual Dc Voltage of each H-bridge of the converter, leading to output waveforms with low distortion. In this way, the Dc Voltage of the floating H-bridge can be controlled while the output Voltage has low distortion independently of the desired Dc Voltage ratio. Experimental results from a two-cell cascaded converter are presented in order to validate the proposed Dc-Voltage-ratio control strategy and the introduced concepts.

  • Feed-forward space vector modulation for single-phase multilevel cascaded converters with any Dc Voltage ratio
    IEEE Transactions on Industrial Electronics, 2009
    Co-Authors: Jose I. Leon, Sergio Vázquez, Patrick W. Wheeler, Alan J. Watson, Leopoldo Garcia Franquelo, Juan M. Carrasco
    Abstract:

    Modulation techniques for multilevel converters can create distorted output Voltages and currents if the Dc-link Voltages are unbalanced. This situation can be avoided if the instantaneous Dc Voltage error is not taken into account in the modulation process. This paper proposes a feed-forward space vector modulation method for a single-phase multilevel cascade converter. Using this modulation technique, the modulated output Voltage of the power converter always generates the reference determined by the controller, even in worst case Voltage unbalance conditions. In addition, the possibility of optimizing the Dc Voltage ratio between the H-bridges of the power converter is introduced. Experimental results from a 5-kVA prototype are presented in order to validate the proposed modulation technique.