A cascaded hybrid inverter with improved dc-link voltage control for grid connected systems
- Authors: Wanjekeche, T. , Jimoh, A. A. , Nicolae, Dan-Valentin
- Date: 2012
- Subjects: Voltage-frequency converters , Converters , Electronic circuits
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/17312 , uj:15870 , ISBN: 9781467301589 , Ciatation: Wanjekeche, T.,Jimoh, A.A. & Nicolae, D.V. 2012. A cascaded hybrid inventer with improved dc-link voltage control for grid connected systems IEEE – ISIE 2012, 28–31 May, Hangzhou, China:1950-1956. DOI:10:1109/ISIE.2012.6237391
- Description: Abstract: This paper presents investigation of a new Phase shifted PWM technique with improved harmonic suppression. A novel balance circuit for DC – link voltage balance of two three level legs connected back – to back is designed and tested. Combined with the individual voltage control, a complete voltage controller is developed for a cascaded nine level hybrid model with two cells. Robustness of the proposed algorithm under varying operating conditions and modulation indices is verified by simulation.
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A cascaded NPC/H-bridge inverter with simplifiied control strategy and minimum component count
- Authors: Wanjekeche, T. , Nicolae, Dan-Valentin , Jimoh, A. A.
- Date: 2009
- Subjects: Electric inverters , Harmonics (Electric waves) , Power electronics
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/22319 , uj:16188 , ISBN: 978-1-4244-3919-5 , Citation: Wanjekeche, T., Nicolae, D.V. & Jimoh, A.A. 2009. A cascaded NPC/H-bridge inverter with simplifiied control strategy and minimum component count. Proceedings of IEEE-Africon, 23-25 September, 2009, Kenya. DOI: 10.1109/AFRCON.2009.5308551
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A novel 9-level multilevel inverter based on 3-level NPC/H-bridge topology for photovoltaic applications
- Authors: Wanjekeche, T. , Jimoh, A. A. , Nicolae, Dan-Valentin
- Date: 2009
- Subjects: Harmonics , Photovoltaic power generation , Electric power generation
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/21278 , uj:16136 , Citation: Wanjekeche, T, Jimoh, A.A. & Nicolae, D.V. 2009. A novel 9-level multilevel inverter based on 3-level NPC/H-bridge topology for photovoltaic applications. International Review of Electrical Engineering, 4(5):769-777. , ISSN: 1827-6660
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Analysis, modeling and control of cascaded NPC/H bridge inverter for high power quality grid connection
- Authors: Wanjekeche, T. , Nicolae, Dan-Valentin , Jimoh, A. A.
- Date: 2010
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/18314 , uj:15983 , Citation: Wanjekeche, T., Nicolae, D.V. & Jimoh, A.A. 2010. Analysis, modelling and control of cascaded NPC/HNPC/H bridge inverter for high power quality grid connection. In: Proceedings of the IASTED AsiaPes 2010, Thailand, Nov. 2010:74-79
- Description: Abstract: The cascaded NPC/H- bridge inverter is first analyzed by establishing a new switching model based on a derived control law. From the developed switching model, a general model is obtained using state space technique. A new and accurate average model is developed using abc to dqo transformation technique. Finally small signal model is obtained by linearizing all the state variables around their quiescent operating points. The small signal model is used to study the effects of various control feedback variables on the dynamic performance of the Grid connected system. Feedback control scheme is designed to improve the dynamic response of the system. The system with the proposed control technique also achieves sinusoidal grid voltage and current output with low THD which is a preferred characteristic for any power injected to the grid. Simulation results are provided to validate the analytical models
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Comparative analysis of third harmonic injection PWM and SPWM control techniques for UPS inverter
- Authors: Wanjekeche, T. , Nicolae, Dan-Valentin , Jimoh, A. A.
- Date: 2008
- Subjects: Uninterruptible power supply , Pulse width modulation
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/20338 , uj:16086 , Citation: Wanjekeche, T., Nicolae, D. V. & Jimoh, A. A. 2008. Comparative analysis of third harmonic injection PWM and SPWM control techniques for UPS inverter. Proceedings of The IASTED International Conference on Power and Energy Systems, 8-10 September 2008, Gaborone, Botswana.
- Description: Abstract Pulse Width Modulation (PWM) techniques has been researched for three decades but there are no explicit guidelines on how one can choose the desired technique for particular application especially in power processing devices. Thus choosing a particular PWM technique for UPS application remains a challenging task since UPS operate under varying load conditions. All the techniques appear to give superior performance as well as short-comings when it comes to control of UPS inverter. This paper presents analytical and simulated results that demonstrate the equivalence between the two types of PWM control techniques and the superior performance when considering high conversion factor (C.F.) and Total Harmonic Distortion (THD) for UPS application.
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Complete analysis of a multilevel inverter based on 3 level NPC/H- bridge topology for photovoltaic application
- Authors: Wanjekeche, T. , Nicolae, Dan-Valentin , Jimoh, A. A.
- Subjects: Bridge circuits , Capacitance meters , Electric power measurement
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/18262 , uj:15978 , Citation: Wanjekeche, T., Nicolae, D.V. & Jimoh, A.A. 2010 Complete analysis of a multilevel inverter based on 3 level NPC/H- bridge topology for photovoltaic application. IEEE
- Description: Abstract: The cascaded NPC/H- bridge inverter is first analyzed by establishing a new switching model based on a derived control law, then using the model a general model using state space technique is obtained. A new and accurate average model is developed using abc to dqo transformation technique. A small signal model is developed by linearizing all the state variables around their quiescent operating points. The small signal model is used to study the effects of various control feedback variables on the dynamic performance of the PV- Grid system. Based on the transfer function developed feedback control loop is developed to improve the dynamic response of the system as well as voltage balancing of the DC link. Simulation results are provided to validate the analytical models.
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Modeling and control of a cascaded NPC/H-bridge inverter with LCL filter in PV- grid application
- Authors: Wanjekeche, T. , Nicolae, Dan-Valentin , Jimoh A. A.
- Date: 2010
- Subjects: Technological photography , Photo-optics
- Language: English
- Type: Conference proceedings
- Identifier: http://ujcontent.uj.ac.za8080/10210/365713 , http://hdl.handle.net/10210/18523 , uj:16009 , ISBN: 9781424473984 , Citation: Wanjekeche, T.,Nicolae, D.V.& Jimoh, A.A. 2010. A modeling and control of a cascaded NPC/H-bridge inverter with LCL filter in PV- grid application, The 9th International Conference on Power and Energy (IPEC 2010), 27-29 October, 2010, Singapore:334-339. DOI:10.1109/IPECON.2010.5697154
- Description: Abstract: The output voltage and current of renewable energy sources such as Photo- voltaic are not controlled. Consequently PV- Grid interface system is employed condition output voltage and current into the grid. This call for efficient and well designed control strategies to ensure reliability, stability and quality power output. This paper proposes nine- level cascaded NPC/H-bridge inverter as the PV- Grid interface. Cascaded NPC/H-Bridge inverter is modeled and a control law for realizing nine- level output with reduced harmonic content is developed. Modeling is easily achieved by considering the whole inverter as having four cascaded three level legs, two positive and two negative. Then a mathematical model is formulated for LCL filters assuming that the resistances associated with the inductances have negligible effect on the system steady state variables. Finally a control technique is developed for the whole system and its robustness tested by carrying out several simulations tests in MATLAB under different operating conditions.
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