| EPE 2023 - DS2e: Grid Connected Converters |
| You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2023 ECCE Europe - Conference > EPE 2023 - Topic 02: Power Converter Topologies and Design > EPE 2023 - DS2e: Grid Connected Converters |
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 | A COMMON GROUND (CG) SWITCHED CAPACITOR MULTILEVEL INVERTER (SCMLI) WITH AN ADDITIONAL CHARGE PUMP CELL FITTED FOR PHOTOVOLTAICS - SUPPLIED ENERGY SYSTEMS
By Jiandong ZHANG, Xueyong LI, Jia YAO, Qinsong QIAN, Adrian IOINOVICI | [View]
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Abstract: A CG - SCMLI with an additional charge pump cell is proposed. This cell, supplied often by the source, frequently recharges the other capacitors or replaces them in transferring energy to the load. Thus, all the capacitors are recharged with a high frequency. The input source keeps pumping energy continuously. As a result, (a) the capacitors continuous discharging time intervals are greatly reduced, allowing for a design with very small value (µF) capacitances; and (b) the input current becomes continuous. The common input source - load ground effectively annihilates the solar cells leakage current. The above characteristics are perfect for PV applications. A prototype of 240 W, 7-levels inverter, of small size and low weight was built and tested. The measured nominal efficiency is 97.7\%.
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| | A Comparative Study of Three-Phase Inverter Topologies for Common Mode Voltage Reduction in Photovoltaic Applications
By Jamil HASSAN, Victor MINAMBRES-MARCOS, Fermin BARRERO-GONZALEZ, Anas Abdullah ALVI, Mariusz MALINOWSKI, Luis MARTINEZ-CABALLERO | [View]
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Abstract: The popularity of photovoltaic (PV) systems has increased as the demand for renewable energy sources has risen in recent years. The inverter is an important component and has a significant impact on the overall performance of a PV system. Therefore, its topology must be chosen carefully based on the application. This paper presents a study and comparison of different inverter topologies for PV applications. The paper begins by discussing the traditional three-phase H6 inverter topology for PV systems and then reviews various inverter topologies derived from this structure for leakage current reduction. Three topologies are chosen and compared their potential for PV applications considering leakage currents and total harmonic distortions using the MATLAB/Simulink simulation model.
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| | A modified Control Strategy of Neutral-Point Clamped Converter-Fed PMSM Drives with Engergy Storage Systems
By Jun XIE, Ying LI, Yalesromulo DENOVAES, Martin SUBERSKI, Dustin HENNEBERG, Juergen PETZOLDT, Alan WATSON | [View]
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Abstract: This paper proposes a modified control strategy for three-phase three-level neutral point clamped (NPC) converter-fed Permanent Magnet Synchronous Motor (PMSM) drive in the application of Energy Storage Systems (ESS) using single-carrier modulation. The increasing demands in renewable energy (RE) sources has attracts many research interests in recent years. The integration of different types of distributed DC systems has become a challenge for high power application. In this study, the NPC converter is employed for DC-AC conversion, with two ESS units serving as individual DC power supplies. The main focus is on simplification of the control and modulation technique for the NPC converter, which operates with individual ESS units having imbalanced SOC and voltages. The aim is to achieve balanced SOC between the ESS units and maintain high-quality AC output. Additionally, utilizing single-carrier modulation reduces the complexity of the control when a digital signal processor (DSP)-based platform is employed. Simulation results verifies effectiveness of the proposed method.
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| | A New Hybrid-Modular Multi-level Inverter with Fault-Tolerant Capability
By Babak ROOHOLAHI, Saeed PEYGHAMI, Amir Sajjad BAHMAN | [View]
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Abstract: This paper proposes a new single-phase hybridmodular multi-level inverter (H-MMI) topology.The proposed H-MMI can ensure fault-tolerance under different faulty scenarios. The H-MMIarchitecture utilizes a series connection of DC sources and power switches to generate multiplevoltage levels, but this arrangement also increases the system's vulnerability to failures. To address this challenge, a fault-tolerant technique is proposed for the H-MMI inverter, ensuring reliable operation even in the presence of component failures. Furthermore, the proposed control method can be utilized to compensate any voltage drop of the dc-link caused by the aging of the input capacitors. The eleven-level form of the proposed H-MMI is simulated in PLECS program. The results show that the inverter output current effectively tracks the reference current, maintaining stable operation even during faulty scenarios.
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| | A Novel Single-phase Common-grounded Rectifier Without Electrolytic Capacitor
By Yuhao YUAN, Weimin WU, Koutroulis EFTYCHIOS, Ning GAO, Henry CHUNG, Frede BLAABJERG, Lixun ZHU, Min HUANG | [View]
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Abstract: This paper presents a novel non-isolated single phase power factor correction (PFC) rectifier with active decoupling capability. Firstly, the power decoupling principle is derived and the operating principle of the proposed power decoupling circuit is analyzed. A small DC film capacitor is employed to replace the conventional bulky electrolytic capacitor, while the proposed common-ground structure eliminates leakage current. Furthermore, the implementation of deadbeat control streamlines the control procedure and guarantees the optimal circuit performance. Finally, simulation results are provided to validate the feasibility of the proposed rectifier.
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| | A Study on Simplification of Commutation Methods for Three-Phase Direct Matrix Converters
By Jun XIE, Martin SUBERSKI, Dustin HENNEBERG, Uwe RÄDEL, Juergen PETZOLDT | [View]
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Abstract: This paper presents a simplified one-step commutation method for Direct Matrix Converter (DMC). A comprehensive study on commutation strategies of three-phase to three-phase DMC in a three-wire system is conducted, starting from the most commonly employed four-step commutation strategy. By considering the input voltages and the direction of the output currents, the commutation method can be simplified into three-step or two-step commutation methods. The input voltages are divided into six sectors. Through the constant holding of two switches within each sector, the proposed simplified one-step commutation method is achieved, which significantly contributes to the reduction of control complexity. The principle of the proposed strategy is explained in detail. Simulation results are used to verify effectiveness and performance of this proposed strategy.
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| | An Enhanced Current Controller for Grid-Connected Inverters based on Capacitor Current Feedback Active Damping and Capacitor Voltage Decoupling
By Amiron SERRA, Luiz RIBEIRO, José Gomes MATOS | [View]
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Abstract: This paper proposes a new control strategy for LCL-filtered grid-connected inverters, based on capacitor current feedback active damping and capacitor voltage decoupling. The results show that this control strategy can mitigate the resonance frequency effect and improve the disturbance rejection of the system by diminish the grid voltage harmonics influence over the injected current.
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| | An Optimized Third-Harmonic Injection Reduces DC-Link Voltage Ripple in Cascaded H-Bridge Converters up to 50\% for all Power Factors
By Roland UNRUH, Joachim BÖCKER, Frank SCHAFMEISTER | [View]
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Abstract: Star-connected cascaded H-bridge Converters require large DC-link capacitors to buffer the second-order harmonic voltage ripple. First, it is analytically proven that the DC-link voltage ripple is proportional to the apparent converter power and does not depend on the power factor for nominal operation with sinusoidal reference arm voltages and currents. A third-harmonic zero-sequence voltage injection with an optimal amplitude and phase angle transforms the 2nd harmonic to a 4thharmonic DC-link voltage ripple. This reduces the voltage ripple by exactly 50\% for all power factors at steady-state at balanced conditions. However, this requires 54\% additional modules for unity power factor operation and even 100\% for pure reactive power operation to account for the increased reference arm voltages due to the large amplitude of the optimal third-harmonic injection. If notenough modules are available, an adaptive discontinuous PWM is utilized to still minimize the voltage ripple for the given number of modules and power factor. With a very limited number of modules (modulation index is 1.15), the proposed method still reduces the DC-link voltage ripple by 24.4\% for unity power factor operation. It requires the same number of modules as the commonlyutilized 3rd harmonic injection with 1/6 of the grid voltage amplitude and achieves superior results. Simulations of a 10kV/1MVA system confirm the analysis.
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| | Analysis of using MMC topologies for the direct integration of renewable generationwith modular electrolyzers
By Eduardo RAUSELL NAVARRO, Gustavo NAVARRO SORIANO, Marcos LAFOZ PASTOR, Santiago ARNALTES GÓMEZ, José Luis RODRÍGUEZ AMENEDO, Marcos BLANCO AGUADO, Jorge NÁJERA ÁLVAREZ | [View]
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Abstract: This paper analyzes the use of MMC topologyfor integrating directly renewable generation withmodular electrolyzers in order to increase the efficiency,and to favor the use of additional energy storage andthe increase of capacity factor. The study focuses onthe performance of the MMC in different operationalscenarios. The results demonstrate the proper behavior ofthe converter when the consumption of the electrolyzersis equal in each submodule of the MMC.
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| | Comparative Evaluation of Grid Connected Current Source and Voltage Source Inverters for Wind Turbines
By Junye CHEN, Michael SCHÜTT, Hans-Günter ECKEL | [View]
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Abstract: Voltage source inverters (VSIs) are currently the predominant inverters in power systems. In the context of renewable energy, grid connected VSIs are designed with LC filter to minimize inductive components. However, the remaining inductors still constitute a significant portion of the system's size and cost. In contrast, current source inverters (CSIs) employ a C filter, reducing the number of filter inductors but necessitating an inductor on the DC link. To perform an economic evaluation, it is essential to compare the inductive energy storage of VSIs and CSIs. This paper presents a comparison of system configurations, control schemes, inductance energy, and dynamic performance between VSIs and CSIs, using a 5 MW wind turbine as an example. The study demonstrates that CSIs are economically viable, and may even be superior, for this application.
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| | Comparison of Modular Multilevel Converter and Neutral Point Clamped Converter Topologies for MVDC applications
By Adriana CAMPOS, Juan PAEZ, Piotr DWORAKOWSKI | [View]
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Abstract: The utility grid is experiencing a shift from a top-down architecture to a decentralized system with a hybrid AC and DC network. This includes MVDC networks. The AC-DC power converter is a key technology for this transition. This article presents a comparison between the 3-Level NPC and MMC topologies in terms of size, power losses and DC fault response for MVDC networks. It was found that the 3L-NPC has lower costs related to semiconductor devices. In terms of efficiency, the MMC converter has a better performance, namely thanks to its reduced switching losses. Regarding passive elements, both topologies seem to be comparable. Finally, the MMC offers more flexibility in DC fault handling, namely thanks to the use of bypass thyristor.
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| | Comprehensive comparison of efficiency in the three-phase active rectifier and TNPC with SiC MOSFET for the electric vehicle charger
By Xinyue LI, Lin MA | [View]
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Abstract: This paper compares the losses and efficiency of three-phase two-level rectifier and TNPC for the application of electric vehicle charger. The emerging SiC MOSFETs with superior switching characteristics expands the applications of power switches in various systems. In this paper, the efficiency of the most applied state-of-art AC/DC converter, i.e. three-phase active rectifier, has been evaluated based on commercially available power switches, both with Si IGBT and SiC MOSFET. Their loss distribution and efficiency are compared in our work. Moreover, thanks to the higher efficiency and lower total harmonic distortion, T-type neutral point clamped (TNPC) converter is considered as a promising alternative to its two-level counterpart. We also investigated the efficiency of two types of TNPC, namely the hybrid TNPC and SiC MOSFET-based TNPC. The simulation results are summarized and compared.
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| | Controller Stability and Low Frequency Interaction Analysis of Railway Train-Network Systems
By Rui KONG, Subham SAHOO, Xiaoqin LYU, Frede BLAABJERG, Xiaoru WANG | [View]
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Abstract: In electrified railways, low-frequency oscillations (LFO) are commonly observed as a result of thewidespread implementation of electric trains incorporating power electronic converters. Whilethe impedance method has been employed in current stability studies for train-network systems, there is a requirement to extend stability modeling and analysis studies for the train network system considering multiple trains having different control strategies. Hence, this paper establishes a unified impedance model in the dq-frame for the aforementioned system. Subsequently, an improved stability criterion, namely the dominant eigenvalue frequency response criterion (DEFRC), is proposed to assess system stability and unveil the mechanism of LFO. Furthermore, the interaction betweendifferent trains is clarified by analysis and case studies. Finally, the theoretical analysis is verifiedfor accuracy based on time domain simulations.
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| | Current Limitation for Angle Control of Grid-Side Converters
By Magdalena GIERSCHNER, Hans-Günter ECKEL | [View]
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Abstract: A converter-control structure for novel Angle Control is presented. Converters are now controlled as voltage sources with a defined stiff grid voltage of 50Hz. A highly efficient current limitation is shown, preventing over currents in grid fault situations.
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| | Design and Implementation of the Space Vector Modulation for a Hexaphase Indirect Matrix Converter
By Chabi Salomon D. SANNI, Augustin MPANDA MABWE, Ahmed EL HAJJAJI | [View]
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Abstract: This work is a continuation of our research on high-performance (6-phase) permanent-magnet faulttolerant synchronous generator (HPHSG). It focuses on interfacing the HPHSG source to the electrical distribution network via a matrix converter (MC) whose indirect topology (IMC) has six phases on the generator side and three phases on the grid side. In the literature, the most common MCs are three-phase and publication on multi-input converters with (Nsup.3) are quite rare. Themain objective of this paper is to develop a hexaphase IMC structure and its corresponding SVM control law. A closed-loop simulation of the system feeding a 1.35MW inductive load is carried out, and provides an overall evaluation of the system's performance.
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| | Experimental validation of an isolated resonant converter for auxiliary systems in a train
By Joan GILES, Alberto RODRÍGUEZ, Marta M. HERNANDO, Javier SEBASTIÁN, Beñat ZELAA, Jon AGUIRRE, Ana CASTRO, Jose Manuel BERMEJO, David ORTEGA | [View]
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Abstract: This paper presents preliminary experimental results of a high-power resonant converter as a part of the auxiliary systems of a train. A series resonant converter is used developed and tested, since it has interesting characteristics for this type of applications, such as galvanic isolation, good power density and high efficiencies.
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| | Nine-level inverter based on NPC topology for high frequency operation
By Robert STALA | [View]
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Abstract: This paper presents the novel concept of an inverter with nine-level phase-to-phase voltage. A branch of the converter contains only one bidirectional switch more than the classic 3-level diode-clamped topology. However, such a modification allows to increase the levels of phase-to-phase voltage from five to nine. Furthermore, the proposed topology significantly reduces the value of the current passing through diodes of the NPC inverter and number of switching operations of diodes. The proposed topology allows to design high frequency, low voltage, low power NPC-based inverter with the use of MOSFET or GaN transistors. The distribution of losses in the components is much more uniform in the proposed converter than in the equivalent nine-level inverter diode-clamped. The topology of the proposed inverter is suitable for the use of GaN transistors with bi-directional blocking.
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| | Power Control and Voltage Balancing Strategies for a Five-Level T-Type Inverter
By Kevin ACADINE, Augustin MPANDA MABWE, Ahmed EL HAJJAJI | [View]
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Abstract: This paper presents the performance of a grid-tied five-level inverter (T5). Its structure requires fewer power components than the Neutral Point Clamped (NPC) and Flying Capacitor (FC) structures with equivalent voltage levels. The objective is to evaluate the PI, LMI (Linear Matrix Inequality) and SM (Sliding Mode) controllers for d- and q-axis current reference tracking. Each of these controllers is associated with a Space Vector Modulation technique (SVPWM) that provides DC-side capacitor voltage balancing. Efficiency and size are optimized as no additional components are required. The simulation of the complete system is performed on MATLAB/Simulink.
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| | Stability Analysis of Grid-Forming Inverter Considering Different Operating Points
By Yi XIAO, Hao LUO, Yinxiao ZHU, Yongheng YANG, Marta MOLINAS, Dehong XU | [View]
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Abstract: In recent years, the grid-forming (GFM) converters have been widely studied to integrate renewable energy sources (RESs). However, the stability of GFM inverters under various operating points exhibits distinct characteristics, and its mechanism remains unclear. It is thus investigated in this paper. In order to explore this issue, the full-order multiple-input multiple-output (MIMO) small-signal model of the three-phase GFM inverter is established. Based on this MIMO model, the stability of the system under different operation points is accordingly explored. The exploration has revealed that the influence of different active power operating points appears in the low-frequency range. Besides, the GFM inverter is apt to be unstable under low damping and large virtual inertia conditions, when the power increases. Finally, the analysis is verified by simulations and experimental tests.
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| | SVPWM-Based DC Voltage Balancing and Fault Diagnosis Method for a Cascaded H-Bridge Multilevel Converter
By Dong XIE, Chunxu LIN, Hongjian LIN, Thomas BASLER | [View]
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Abstract: In the DC voltage balancing control of a cascaded H-bridge multilevel converter, the frequently used PI controllers have complicated parameter tuning and cause the balancing ability to degrade under the switch fault condition. Regarding this, a space vector pulse width modulation-based DC voltage balancing method is presented to flexibly adjust the cell voltage levels and maintain the DC voltage balance between the power cells to the fullest degree. Furthermore, based on the voltage level changes under different switch faults, an active vector transition scheme is used to successively diagnose single or multiple open switch faults in one power cell or different power cells. The simulation and experimental results have shown the effectiveness of balancing algorithm under the normal and fault conditions, and the diagnosis validity for multiple faults.
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| | System Characteristics of Grid-Forming and Grid-Following Converter Systems
By Julian STRUWE, Holger WREDE, Hendrik VENNEGEERTS | [View]
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Abstract: Grid-forming converter controls have been observed to increase voltage stiffness and system strength. This work highlights the reasons for this behaviour, which is inherently fundamentally different from grid-following controls and, thus, why grid-following converters can notparticipate in the provision of virtual inertia. However, it shows that equipped with additional power-droops these controls can still benefit the grid.Therefore, based on the converter principle and additional support a new terminology that goes beyond the previously used terms 'grid-forming' and 'grid-following' is proposed. In simple black-box simulations it is proven how the different examples can be distinguished just by investigating their grid-behaviour. In addition to questions that are raised concerning the definition of system strength this work thus yields to a clear definition of grid-forming controls as well.
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