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Single-source cascaded transformers multilevel inverter with reduced number of switches

IET POWER ELECTRONICS 2012年第9期5卷 1748-1753页

作者： Banaei, M. R. Khounjahan, H. Salary, E. Azarbaijan Shahid Madani Univ Fac Engn Dept Elect Engn Tabriz Iran

This study presents a novel topology for multilevel inverters so called cascaded transformer reduced switches inverter (CTRSI). This topology consists of one DC source and several single-phase transformers. Each single-phase transformers generates three levels with two semiconductor switches and only two switches for all transformers alter the direction of single DC source. Whereas each single-phase transformers in conventional cascaded transformer multilevel inverter includes four switches. Hence, CTRSI has the advantage of a reduced number of components compared with conventional cascaded transformer multilevel inverter. simulation results carried out by matlab/simulink and a low-power experimental setup was planned to test the converter in practice. The results show that the proposed inverter topology is able to reach high-quality output voltages. Using switches with higher rating current than conventional topology is main disadvantage of CTRSI.

关键词： high-quality output voltage semiconductor switch single DC source Semiconductor devices matlab-simulink simulation low-power experimental setup CTRSI power convertors Relays and switches Inductors and transformers DC transformers single-source cascaded transformer multilevel inverter topology semiconductor switches single-phase transformer Power electronics, supply and supervisory circuits converter

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Dual active bridge synchronous chopper control strategy in electronic power transformer

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IET ELECTRIC POWER APPLICATIONS 2014年第3期8卷 89-97页

作者： Zhang, Rui Wang, Dan Mao, Chengxiong Lu, Jiming Yang, Jiawei Yi, Yang Chen, Xun Zhang, Junfeng Huazhong Univ Sci & Technol State Key Lab Adv Electromagnet Engn & Technol Wuhan 430074 Peoples R China Guangdong Power Grid Corp Power Syst Div Elect Power Res Inst Guangzhou Guangdong Peoples R China

The electronic power transformer (EPT) is a novel transmission and transformation device, which consists of a series connection of two voltage-source H-bridge converters and a DC-DC converter with high-frequency isolation transformer. When applied to microgrids, EPT will not only deliver energy to loads from the utility grid but also inject some amount of excess power into the utility grid. Hence, the capability of bidirectional power flow is important for EPT, which depends on the DC-link stage. The traditional synchronous chopper control for a dual active bridge (DAB) converter has some limitations in the application of bidirectional power flow area. This study proposes a novel synchronous chopper control strategy for the DAB converter to implement bi-direction power flow, details the basic principle and steady-state operation and presents the mathematical derivations. A three-phase three-stage circuit configuration of 10 kV/400 V bi-direction EPT system based on the novel control DAB converter is designed, and corresponding control schemes for the system are discussed. The performance of this EPT system is validated by the matlab/simulink-based simulations and the laboratory prototype experiments.

关键词： choppers (circuits) DC-DC power convertors distributed power generation load flow control power transformers dual-active bridge synchronous chopper control strategy electronic power transformer transformation device transmission device voltage-source H-bridge converters DC-DC converter high-frequency isolation transformer microgrids utility grid bidirectional power flow capability DC-link stage traditional synchronous chopper control dual active bridge converter DAB converter bidirectional power flow steady-state operation mathematical derivation three-phase three-stage circuit configuration bidirection EPT system matlab-simulink simulation

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Harmonic distortion-based island detection technique for inverter-based distributed generation

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IET RENEWABLE POWER GENERATION 2009年第4期3卷 493-507页

作者： Massoud, A. M. Ahmed, K. H. Finney, S. J. Williams, B. W. Texas A&M Univ Qatar Dept Elect Doha Qatar Univ Strathclyde Dept Elect Glasgow Lanark Scotland

A harmonic distortion-based island detection technique for inverter-based distributed generation (IBDG) is proposed. The proposed technique is classified as an active island detection technique and it is based on the voltage change at the point of common coupling (PCC) that occurs in islanding. To avoid island detection failure in case of a close matching between IBDG-generated power and load power, an active power-voltage locus is introduced to shift the reference active power for PCC voltage change, therefore breaking the IBDG-load power balance and transferring the operating point outside the non-detection zone. A new harmonic performance index, named harmonic amplification factor, is introduced to detect the island. This factor amplifies each harmonic component by its order. Besides the ability of detecting short circuit, the proposed technique can discriminate between islanding and other disturbances, as load change, grid voltage distortion and unbalance, and capacitor bank switching. The proposed technique is validated by matlab/simulink simulation and practically as well.

关键词： distributed power generation active power-voltage locus IBDG harmonic amplification factor capacitor bank switching Power supply quality and harmonics inverter-based distributed generation invertors matlab-simulink simulation harmonic distortion power system harmonics harmonic distortion-based island detection technique Distribution networks

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Multilevel inverter topology based on series connected switched sources

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IET POWER ELECTRONICS 2013年第1期6卷 164-174页

作者： Gupta, Krishna Kumar Jain, Shailendra Maulana Azad Natl Inst Technol Dept Elect Engn Bhopal 462051 India

A new topology for multilevel DC-AC conversion is presented in this study. It consists of isolated symmetric input DC sources alternately connected in opposite polarities through power switches. The structure allows synthesis of multilevel waveform using reduced number of power switches as compared to the classical topologies. The working principle of the proposed topology is explained with the help of a single-phase five-level inverter. simulation studies are carried out in matlab/simulink environment and experimental validations are obtained on a laboratory prototype. An exhaustive comparison of the proposed topology against the classical cascaded H-bridge topology indicates reduction in number of power switches, losses, installation area and converter cost.

关键词： bridge circuits DC-AC power convertors invertors switching convertors multilevel inverter topology series connected switched sources multilevel DC–AC conversion isolated symmetric input DC sources power switches single-phase five-level inverter matlab-simulink simulation cascaded H-bridge topology installation area converter cost

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Multilevel voltage source inverter with optimised usage of bidirectional switches

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IET POWER ELECTRONICS 2015年第3期8卷 378-390页

作者： Jamaludin, Jafferi Abd Rahim, Nasrudin Ping, Hew Wooi Univ Malaya UM Power Energy Dedicated Adv Ctr UMPEDAC Kuala Lumpur 59990 Malaysia Univ Malaya Fac Engn Dept Elect Engn Kuala Lumpur 50603 Malaysia

This study presents a multilevel voltage source inverter that has been designed to reduce circuit complexity by optimising the use of bidirectional switches. The proposed inverter is built by adding an auxiliary circuit comprising an arrangement of bidirectional switches to the three-phase, six-switch, full-bridge configuration. Several bidirectional switches are made to function in the optimised mode in which their operations are divided among the three phases. The presence of the optimised mode considerably reduces the number of power switches as the number of levels in the line-to-line voltage waveform increases. A novel modulation scheme based on space vector concept with virtual vectors utilisation has also been developed. A detailed study of the proposed inverter is described through the example of a five-level structure. The performance of the proposed inverter is analysed through matlab/simulink simulation and verified via the practical tests conducted on a laboratory prototype with a DSP-based controller. A comparison is also made against classical multilevel inverters to complete the analysis.

关键词： invertors circuit complexity switches multilevel voltage source inverter bidirectional switches circuit complexity reduction auxiliary circuit full-bridge configuration six-switch configuration three-phase configuration power switches line-to-line voltage waveform space vector modulation scheme virtual vector utilisation five-level structure matlab-simulink simulation DSP-based controller

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Common-ground non-isolated high-gain DC/DC converter for low powerdistributed generation photovoltaic systems

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IET POWER ELECTRONICS 2020年第12期13卷 2589-2597页

作者： Nemati, Milad Hosseini, Seyed Hossein Sharifian, Mohammad Bagher Bannae Sabahi, Mehran Univ Tabriz Fac Elect & Comp Engn 29 Bahman Blvd Tabriz Iran Near East Univ Engn Fac Mersin 10 TR-99138 Nicosia 10 North Cyprus Turkey

A high step-up/high-efficiency converter is one of the essential requirements of a low power grid-connected photovoltaic system that provides the maximum power point tracking ability and injects the low voltage extracted power to AC or DC distribution network. This study presents a common-ground non-isolated high-gain DC/DC converter whit a naturally wide range of soft-switching conditions. The proposed converter has two resonant loops, and a new simple structure consists of an active switch, three diodes, two inductors and two capacitors, work in two useful operation modes. In the optimum operation mode (OOM), the switch turns on/off in zero current switching (ZCS)/zero voltage switching condition, and at the sub-OOM, the switch turns on in ZCS condition and turns off in hard switching condition. The mathematical analysis and matlab/simulink simulation results are described in detail. Also, a prototype 100 W converter is built and tested to validate the simulation analysis on a 100 W photovoltaic panel.

关键词： inductors diodes power grids distributed power generation zero voltage switching photovoltaic power systems maximum power point trackers switching convertors zero current switching mathematical analysis solar cell arrays power system simulation power capacitors low power grid-connected photovoltaic system maximum power point tracking hard switching condition common-ground nonisolated high-gain DC-DC converter low power distributed generation photovoltaic systems high step-up-high-efficiency converter AC distribution network DC distribution network soft-switching conditions resonant loops active switch diodes inductors capacitors optimum operation mode zero current switching ZCS condition zero voltage switching condition mathematical analysis matlab-simulink simulation photovoltaic panel power 100.0 W

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Modelling and analysis of modular multilevel converter for solar photovoltaic applications to improve power quality

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IET RENEWABLE POWER GENERATION 2015年第1期9卷 78-88页

作者： Alexander, Albert Thathan, Manigandan Kongu Engn Coll Dept EEE Perundurai 638052 Tamil Nadu India PA Coll Engn & Technol Dept EEE Pollachi 642002 Tamil Nadu India

The design of control circuit for a solar fed cascaded multilevel inverter to reduce the number of semiconductor switches is presented in this study. The design includes binary', trinary' and modified multilevel connection' (MMC)-based topologies suitable for varying input sources from solar photovoltaic's (PV). In binary mode, 2(s)(N) (+1) - 1 output voltage levels are obtained where N-s is the number of individual inverters. This is achieved by digital logic functions which includes counters, flip-flops and logic gates. In trinary mode, 3(Ns) levels are achieved by corresponding look-up table. MMC intends design in both control and power circuits to provide corresponding output voltage levels by appropriate switching sequences. Hence to obtain a 15-level inverter, the conventional method requires 28 switches and in binary mode 12 switches are needed. In trinary mode with the same 12 switches, 27 levels can be obtained whereas in MMC only 7 switches are employed to achieve 15 levels. The advantage of these three designs is in the reduction of total harmonic distortion by increasing the levels. simulations are carried out in matlab/simulink and comparisons were made. All the three topologies are experimentally investigated for a 3 kWp solar PV plant and power quality indices were measured.

关键词： power convertors photovoltaic power systems solar power stations power supply quality logic gates flip-flops counting circuits table lookup switchgear harmonic distortion power system harmonics power semiconductor switches modular multilevel converter solar photovoltaic application power quality control circuit design solar fed cascaded multilevel inverter semiconductor switch modified multilevel connection MMC binary multilevel connection trinary multilevel connection digital logic function counter flip-flop logic gate look-up table 15-level inverter total harmonic distortion reduction matlab-simulink simulation solar PV plant

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Pulse width modulation schemes enabling single DC power source driven dual two-level voltage source inverter with single voltage source inverter switching

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IET POWER ELECTRONICS 2014年第5期7卷 1181-1191页

作者： Srinivas, Srirama Kalaiselvi, Jeyaraman Indian Inst Technol Dept Elect Engn Chennai 600036 Tamil Nadu India

Three-level voltage space phasor can be obtained using a dual two-level voltage source inverter (VSI). Two zero sequence voltage elimination pulse width modulation (PWM) switching variants are proposed in this paper for complete elimination of zero sequence voltage (ZSV) in the dual-VSI scheme. Both the PWM variants are designed in such a way that only one inverter is switched at any instant of time;to ensure that switching power losses in the dual-VSI is limited to one inverter only at any instant of time. Analytical expressions for the dwell times of the dual-VSI are developed and presented that successfully forces the ZSV in the dual-VSI to zero;at all instants of time. As a result, both the PWMs facilitate the dual-VSI to be driven from a single DC power source only. The implementation of the proposed PWM algorithms is greatly simplified and involves just the use of instantaneous magnitudes of the reference space vector. The implementation of PWMs totally avoids the time consuming task of sector identification and do not use look up tables. The PWMs proposed in this paper are first analysed, simulated using matlab/simulink and then verified experimentally to validate the proposed PWMs.

关键词： losses PWM invertors PWM power convertors switching convertors pulse width modulation scheme single DC power source dual two-level voltage source inverter single voltage source inverter switching three-level voltage space phasor VSI zero sequence voltage elimination PWM switching ZSV switching power loss reference space vector look up table matlab-simulink simulation

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Comprehensive control strategy of virtual synchronous generator under unbalanced voltage conditions

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IET GENERATION TRANSMISSION & DISTRIBUTION 2018年第7期12卷 1621-1630页

作者： Zheng, Tianwen Chen, Laijun Guo, Yan Mei, Shengwei Tsinghua Univ Dept Elect Engn State Key Lab Power Syst Beijing 100084 Peoples R China

The virtual synchronous generator (VSG) is emerging as an effective approach for controlling converter to mimic the traditional synchronous generator (SG). VSG can provide virtual inertia, handle both reactive and active power, which is grid-friendly for integrating distributed generations. Generally, when grid voltage is unbalanced, the negative sequence voltage components will appear. Due to traditional VSG control strategy does not consider the negative sequence components and cannot eliminate them, thus it will lead to current unbalance and power oscillations. To address these problems, a comprehensive control strategy of VSG under unbalanced voltage conditions is proposed. Herein, the basic principle of VSG and inherent reasons for VSG current unbalance and power fluctuation are demonstrated with quantitative analysis. The cascaded control framework and design process of the comprehensive control strategy are presented, integrating the traditional VSG control algorithm, novel current reference generator and typical current regulator. Additionally, related critical issues such as sequence components extraction and control parameter design are discussed. The proposed control strategy can flexibly meet different operation demands, including current balancing and suppression of active power or reactive power oscillations. The validity and effectiveness of the proposed control strategy are verified with simulation and experimental results.

关键词： synchronous generators machine control control system synthesis electric current control comprehensive control strategy virtual synchronous generator power electronic converter control virtual inertia reactive power oscillation active power suppression distributed generation microgrid active distribution network grid voltage unbalancing negative sequence voltage component VSG control strategy cascaded control framework current reference generator current regulator matlab-simulink simulation

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Improved fault ride through strategy for doubly fed induction generator based wind turbines under both symmetrical and asymmetrical grid faults

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IET RENEWABLE POWER GENERATION 2016年第8期10卷 1114-1122页

作者： Mohammadi, Jafar Afsharnia, Saeed Vaez-Zadeh, Sadegh Farhangi, Shahrokh Univ Tehran Dept Elect & Comp Engn Coll Engn Tehran Iran

Due to the latest grid codes, wind turbines (WTs) are required to remain connected to grid under grid faults and supply reactive power into the grid. So, this paper proposes an improved fault ride through (FRT) strategy for doubly fed induction generators (DFIGs) under both symmetrical and asymmetrical grid faults. The proposed strategy is realized through active and passive FRT compensators. The active compensator is performed through control of the rotor- and grid-side converters of DFIGs to limit the stator and rotor over currents and inject reactive power into the grid to support the grid voltage recovery, respectively. The passive compensator is based on a three-phase rotor current limiter (RCL) resistor located in series with the rotor windings. It considerably reduces the rotor and stator overcurrent at the instants of grid faults occurrence and clearance. The proposed strategy decreases the stator and rotor over currents, electromagnetic torque oscillations and DC-link over voltage and also support grid voltage by supplying reactive power into the grid. In this way, the DFIG can fulfill the FRT requirements of the latest grid codes. simulation studies using matlab/simulink are conducted on a 1.5 MW DFIG-based WT to validate the effectiveness of the proposed FRT strategy.

关键词： power grids asynchronous generators wind turbines power generation faults reactive power rotors stators overcurrent protection overvoltage protection fault current limiters symmetrical grid fault asymmetrical grid fault doubly fed induction generator based wind turbine improved fault ride through strategy wind power penetration power system improved FRT strategy reactive power supply DFIG based WT passive FRT compensator active FRT compensator grid-side converter rotor-side converter reactive power injection three-phase rotor current limiter resistor grid voltage recovery rotor winding stator over current reduction rotor over current reduction electromagnetic torque oscillation DC-link over voltage matlab-simulink simulation power 1 5 MW

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