Research

18 pages, 5466 KiB

Open AccessArticle

Reconfiguration of a Multilevel Inverter with Trapezoidal Pulse Width Modulation

by Nataraj Prabaharan, V. Arun, Padmanaban Sanjeevikumar, Lucian Mihet-Popa and Frede Blaabjerg

Energies 2018, 11(8), 2148; https://doi.org/10.3390/en11082148 - 17 Aug 2018

Cited by 8 | Viewed by 3134

This paper presents different multi-carrier unipolar trapezoidal pulse width modulation strategies for a reduced switch asymmetrical multilevel inverter. The different strategies are phase disposition, alternative phase opposition and disposition, and carrier overlapping and variable frequency that involve triangular waves as carriers with a [...] Read more.

This paper presents different multi-carrier unipolar trapezoidal pulse width modulation strategies for a reduced switch asymmetrical multilevel inverter. The different strategies are phase disposition, alternative phase opposition and disposition, and carrier overlapping and variable frequency that involve triangular waves as carriers with a unipolar trapezoidal wave as a reference. The reduced switch, asymmetrical multilevel inverter operation was examined for generating the seven-level output voltage using Matlab/Simulink 2009b and the results were verified with a real-time laboratory-based experimental setup using a field-programmable gate array. Different parameter analyses, such as total harmonic distortion, fundamental root mean square voltage, and distortion factor, were analyzed with different modulation indices to investigate the performance of the selected topology. Unipolar trapezoidal pulse width modulation provides a higher root mean square voltage value. Full article

(This article belongs to the Special Issue Advanced Control Techniques for Power Converters)

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21 pages, 7719 KiB

Open AccessArticle

A Transformerless Single-Phase Current Source Inverter Topology and Control for Photovoltaic Applications

by Jorge Cardoso, Nimrod Vazquez, Claudia Hernandez and Joaquin Vaquero

Energies 2018, 11(8), 2011; https://doi.org/10.3390/en11082011 - 02 Aug 2018

Cited by 4 | Viewed by 3948

Abstract

Low power grid-tied photovoltaic (PV) generation systems increasingly use transformerless inverters. The elimination of the transformer allows smaller, lighter and cheaper systems, and improves the total efficiency. However, a leakage current may appear, flowing from the grid to the PV panels through the [...] Read more.

Low power grid-tied photovoltaic (PV) generation systems increasingly use transformerless inverters. The elimination of the transformer allows smaller, lighter and cheaper systems, and improves the total efficiency. However, a leakage current may appear, flowing from the grid to the PV panels through the existing parasitic capacitance between them, since there is no galvanic isolation. As a result, electromagnetic interferences and security issues arise. This paper presents a novel transformerless single-phase Current Source Inverter (CSI) topology with a reduced inductor, compared to conventional CSIs. This topology directly connects the neutral line of the grid to the negative terminal of the PV system, referred as common mode configuration, eliminating this way, theoretically, the possibility of any leakage current through this terminal. The switches control is based on a hysteresis current controller together with a combinational logic circuitry and it is implemented in a digital platform based on National Instruments Technology. Results that validate the proposal, based on both simulations and tests of a low voltage low power prototype, are presented. Full article

(This article belongs to the Special Issue Advanced Control Techniques for Power Converters)

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18 pages, 6847 KiB

Open AccessArticle

Multi Objective Optimization in Charge Management of Micro Grid Based Multistory Carpark

by Lukáš Prokop, Tomáš Vantuch and Stanislav Mišák

Energies 2018, 11(7), 1791; https://doi.org/10.3390/en11071791 - 08 Jul 2018

Cited by 11 | Viewed by 2653

Abstract

Distributed power supply with the use of renewable energy sources and intelligent energy flow management has undoubtedly become one of the pressing trends in modern power engineering, which also inspired researchers from other fields to contribute to the topic. There are several kinds [...] Read more.

Distributed power supply with the use of renewable energy sources and intelligent energy flow management has undoubtedly become one of the pressing trends in modern power engineering, which also inspired researchers from other fields to contribute to the topic. There are several kinds of micro grid platforms, each facing its own challenges and thus making the problem purely multi objective. In this paper, an evolutionary driven algorithm is applied and evaluated on a real platform represented by a private multistory carpark equipped with photovoltaic solar panels and several battery packs. The algorithm works as a core of an adaptive charge management system based on predicted conditions represented by estimated electric load and production in the future hours. The outcome of the paper is a comparison of the optimized and unoptimized charge management on three different battery setups proving that optimization may often outperform a battery setup with larger capacity in several criteria. Full article

(This article belongs to the Special Issue Advanced Control Techniques for Power Converters)

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21 pages, 4508 KiB

Open AccessArticle

Model-Based Current Sharing Approach for DCM Interleaved Flyback Micro-Inverter

by Mi Dong, Xiaoyu Tian, Li Li, Dongran Song, Lina Wang and Miao Zhao

Energies 2018, 11(7), 1685; https://doi.org/10.3390/en11071685 - 27 Jun 2018

Cited by 8 | Viewed by 3821

Abstract

Current sharing control is a challenge for a discontinuous conduction mode (DCM) micro-inverter based on interleaved flyback topology. To solve this problem, this study proposes a novel and systemic model-based approach. Firstly, an accurate fourth-order model is presented for the interleaved flyback circuit, [...] Read more.

Current sharing control is a challenge for a discontinuous conduction mode (DCM) micro-inverter based on interleaved flyback topology. To solve this problem, this study proposes a novel and systemic model-based approach. Firstly, an accurate fourth-order model is presented for the interleaved flyback circuit, which takes the two flybacks’ parameter mismatch and coupling into account. Secondly, based on the presented model, a continuous time sliding mode current controller is proposed to tackle the output imbalance caused by parameter mismatch, coupling and disturbance. The proposed controller is derived from the Lyapunov function without switching conditions. Finally, the effectiveness of the proposed model and control method is validated by simulation tests using MATLAB/SIMULINK. Simulation results show that the proposed approach improves the current sharing for the interleaved flyback micro-inverter when compared to the conventional current sharing approach. Full article

(This article belongs to the Special Issue Advanced Control Techniques for Power Converters)

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23 pages, 8569 KiB

Open AccessArticle

Low-Frequency Oscillation Suppression of the Vehicle–Grid System in High-Speed Railways Based on H∞ Control

by Zhaozhao Geng, Zhigang Liu, Xinxuan Hu and Jing Liu

Energies 2018, 11(6), 1594; https://doi.org/10.3390/en11061594 - 18 Jun 2018

Cited by 14 | Viewed by 4393

Abstract

Recently, a traction blockade in the depots of numerous electric multiple units (EMUs) of high-speed railways has occured and resulted in some accidents in train operation. The traction blockade is caused by the low-frequency oscillation (LFO) of the vehicle–grid (EMUs–traction network) system. To [...] Read more.

Recently, a traction blockade in the depots of numerous electric multiple units (EMUs) of high-speed railways has occured and resulted in some accidents in train operation. The traction blockade is caused by the low-frequency oscillation (LFO) of the vehicle–grid (EMUs–traction network) system. To suppress the LFO, a scheme of EMUs line-side converter based on the H∞ control is proposed in this paper. First, the mathematical model of the four-quadrant converter in EMUs is presented. Second, the state variables are determined and the weighting functions are selected. Then, an H∞ controller based on the dq coordinate is designed. Moreover, compared with the simulation results of traditional proportional integral (PI) control, auto-disturbance rejection control (ADRC) and multivariable control (MC) based on Matlab/Simulink and the RT-LAB platform, the simulation results of the proposed H∞ control confirm that the H∞ controller applied in EMUs of China Railway High-Speed 3 has better dynamic and static performances. Finally, a whole cascade system model of EMUs and a traction network is built, in which a reduced-order model of a traction network is adopted. The experimental results of multi-EMUs accessed in the traction network indicate that the H∞ controller has good suppression performance for the LFO of the vehicle–grid system. In addition, through the analysis of sensitivity of the H∞ controller and the traditional PI controller, it is indicated that the H∞ controller has better robustness. Full article

(This article belongs to the Special Issue Advanced Control Techniques for Power Converters)

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21 pages, 5608 KiB

Open AccessArticle

Enhanced Control for Improving the Operation of Grid-Connected Power Converters under Faulty and Saturated Conditions

by Mahdi Shahparasti, Pedro Catalán, Nurul Fazlin Roslan, Joan Rocabert, Raúl-Santiago Muñoz-Aguilar and Alvaro Luna

Energies 2018, 11(3), 525; https://doi.org/10.3390/en11030525 - 28 Feb 2018

Cited by 8 | Viewed by 4048

Abstract

In renewable energy based systems Grid-Connected Voltage Source Converters (GC-VSC) are used in many applications as grid-feeding converters, which transfer the power coming from the renewable energy sources to the grid. In some cases, the operation of GC-VSC may become unstable or uncontrollable [...] Read more.

In renewable energy based systems Grid-Connected Voltage Source Converters (GC-VSC) are used in many applications as grid-feeding converters, which transfer the power coming from the renewable energy sources to the grid. In some cases, the operation of GC-VSC may become unstable or uncontrollable due to, among others: a grid fault or an inappropriate current-power reference, that give rise to fast electrical transients or a saturation of the controller. In this paper, an improved control scheme is proposed to enhance the controllability of GC-VSC in all these situations. This solution consists of two parts, on the one hand a new Proportional-Resonant (PR) controller with anti-windup capability to be used as current controller, and secondly a new current/power reference modifier, which defines the suitable reactive current/power reference to keep the system stable. It is worth to mention that the proposed scheme does not need information about the grid parameters as it only uses the converter current, and the voltage at the capacitors of Inductor-Capacitor (LC) output filter. Full article

(This article belongs to the Special Issue Advanced Control Techniques for Power Converters)

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16 pages, 7750 KiB

Open AccessArticle

Performance Improvement for Reduction of Resonance in a Grid-Connected Inverter System Using an Improved DPWM Method

by Jin-Hyuk Park and Kyo-Beum Lee

Energies 2018, 11(1), 113; https://doi.org/10.3390/en11010113 - 03 Jan 2018

Cited by 9 | Viewed by 4314

Abstract

This paper proposes discontinuous pulse width modulation (DPWM) for a grid-connected inverter system using an LCL-filter which consists of two inductors and a capacitor that is connected in parallel per phase. The modulation signal is discontinuously changed, and the harmonic voltages are generated [...] Read more.

This paper proposes discontinuous pulse width modulation (DPWM) for a grid-connected inverter system using an LCL-filter which consists of two inductors and a capacitor that is connected in parallel per phase. The modulation signal is discontinuously changed, and the harmonic voltages are generated in the wide frequency range at the output terminal of the inverter when the conventional DPWM is used. If these harmonic voltages are present in the resonance frequency band by an LCL-filter, then the resonance problem of the grid current occurs. To suppress the resonance problem, the proposed DPWM injects the sixth harmonic to the modulation signal. Therefore, in the improved DPWM, harmonic voltages at the output terminal of the inverter are sufficiently reduced because the discontinuous change of the modulation signal disappears. The proposed DPWM method is verified by a Powersim (PSIM) simulation (Powersim Inc., Rockville, MD, USA) and experiments with a 3-kW neutral-point clamped (NPC)-type grid-connected inverter system. Full article

(This article belongs to the Special Issue Advanced Control Techniques for Power Converters)

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6529 KiB

Open AccessArticle

An Improved Modulation Strategy Combining Phase Shifted PWM and Phase Disposition PWM for Cascaded H-Bridge Inverters

by Muxuan Xiao, Qianming Xu and Honglin Ouyang

Energies 2017, 10(9), 1327; https://doi.org/10.3390/en10091327 - 02 Sep 2017

Cited by 15 | Viewed by 4589

Abstract

Abstract: Multilevel modulation strategy is an important factor affecting the output performance of multilevel converters. In this paper, the relationship between phase-shifted pulse width modulation (PWM) and phase disposition PWM is analyzed, and then an improved hybrid modulation strategy is proposed for cascaded [...] Read more.

Abstract: Multilevel modulation strategy is an important factor affecting the output performance of multilevel converters. In this paper, the relationship between phase-shifted pulse width modulation (PWM) and phase disposition PWM is analyzed, and then an improved hybrid modulation strategy is proposed for cascaded H-bridge. In addition, the implementation method of multilevel discontinuous modulation for an improved modulation strategy is described. The new modulation strategy is optimized to increase the DC link voltage utilization and further improvement in output harmonics by the injection of a common voltage into the reference. Simulation and experiment verify the effectiveness of the proposed modulation strategy. Full article

(This article belongs to the Special Issue Advanced Control Techniques for Power Converters)

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