Academic literature on the topic 'Four leg three phase inverter'

Three-phase four-leg voltage source inverters (VSIs) are widely used in distributed power generation applications, three-phase UPS systems and fault-mode operation of a balanced three-phase system where the balanced three-phase voltage output is required when the loads are unbalanced. A three-dimensional space vector modulation (3-D SVM) switching scheme, which is proved to be compatible with modern DSP implementation for a four-leg VSI, has the advantage of higher DC link utilization, less harmonic contents and less switching losses compared with sinusoidal PWM. Therefore it is the first choice of switching schemes for a four-leg inverter. Electromagnetic interference (EMI) which is associated with common-mode switching for a high voltage level power system can degrade the equipment performance and cause communication problems. The conventional 3-D SVM switching scheme exhibits high common-mode voltage (CMV) characteristics which may result in problems in high power applications. The 3-D SVM has the drawback of being complex which could become a software burden in computationally intense real-time control applications. Attempts to reduce the complexity of the 3-D SVM have been made by many researchers and new switching schemes such as carrier-based PWM proved to have the same performance. This thesis presents a switching scheme called near-state 3-D SVM that can reduce the CMV voltage level of a four-leg inverter by avoiding the use of the two zero switching states of the inverter. A laboratory test bench has been built to validate the proposed switching scheme. An in-depth analysis has been carried out for a four-leg inverter in terms of total harmonic distortion (THD) factor, current harmonic distortion factor, conduction losses and switching losses. The proposed switching scheme is analyzed and compared with the conventional 3-D SVM using the analysis method. Additionally, a simplified switching scheme which is still based on space vector theory is proposed. This simplified switching scheme remains compatible with vector control. Experimental results show that the simplified switching scheme has the same performance as 3-D SVM, with reduced program execution time. Abstract iii An output voltage control loop with current feed-forward term in d-q-0 coordinate, which is designed in the discrete-time domain, proves to be most compatible with a DSP-based control system. Experimental results demonstrate the performance of the control loop in both steady state and transient operation.

A method for high performance output voltage control of a four-leg inverter based three-phase transformerless UPS is proposed. Voltage control loop is employed and the method employs stationary frame resonant filter controllers for the fundamental and harmonic frequency components. A capacitor current feedback loop provides active damping and enhances the output voltage dynamic performance. The controller design and implementation details are given. Linear and nonlinear loads for balanced and unbalanced load operating conditions are considered. The steadystate and dynamic performance of the UPS are investigated in detail. A scalar PWM method with implementation simplicity and high performance is proposed and implemented. The control and PWM methods are proven by means of theory, simulations, and experiments.

This thesis deals with control of three phase inverter as three phase sinusoidal voltage source for UPS application. Thesis is split to two parts, teoretical and practical. Teoretical part deals with three phase inverter topology analysis according requirement of neutral line wire and possibilities of generating sinusoidal PWM in depend of topology. There are also analysed properties of contorled system and designed 3 regulation methods with simulations. Second part of thesis deals with realisation of sinusoidal power source with inverter borrowed by Elcom company. To inverter control is used digital signal controler TMS320F28335 with implemented control algorithms. There are also presented the measurement results of the prototype of power source. In conclusion, simulation results are compared with measurements and achieved results are summarized.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2017-10-06T12:04:38Z No. of bitstreams: 2 Dissertação - Lázaro Rubens Araújo Pinto - 2017.pdf: 16272237 bytes, checksum: 9f3d1693d0282cbf28a35702c1a9cf17 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5)<br>Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-10-06T12:04:51Z (GMT) No. of bitstreams: 2 Dissertação - Lázaro Rubens Araújo Pinto - 2017.pdf: 16272237 bytes, checksum: 9f3d1693d0282cbf28a35702c1a9cf17 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5)<br>Made available in DSpace on 2017-10-06T12:04:52Z (GMT). No. of bitstreams: 2 Dissertação - Lázaro Rubens Araújo Pinto - 2017.pdf: 16272237 bytes, checksum: 9f3d1693d0282cbf28a35702c1a9cf17 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-08-07<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES<br>This work proposes an analysis of the closed-loop operation of a distributed generation system connected to a three-phase four-wire AC power system by a three-phase four-leg inverter. The modulation strategy adopted for this inverter is determined by the Model Predictive Control (MPC) method. Reasons for the use of this topology and the control method are discussed. The chosen structure for the MPC predictive control aims to supply of active and reactive power by the inverter in order to maximize the power factor measured by the four-wire AC source (Y-n). Four possible cases of operation are reported for the analysis of the proposal in the three-phase four-leg inverter and other two cases for a three-phase full-bridge inverter (3F) for comparison purposes. Based on the monitoring of the active powers involved and the other variables of interest, it was possible to exemplify the achievement of the proposed objectives and validate the adopted method, at least under modeling and software simulation level.<br>Este trabalho propõe uma análise da operação em malha fechada de um sistema de geração distribuída para conexão em um sistema trifásico a quatro fios, a partir do controle de um inversor trifásico a quatro braços. A estratégia de modulação adotada para este inversor é determinada pelo método de controle preditivo baseado em modelo (MPC - Model Predictive Control). Justificativas para a utilização dessa topologia e do método de controle são discutidas. A estrutura escolhida para o controle preditivo MPC objetiva o fornecimento de potência ativa e reativa pelo inversor tendo em vista a maximização do fator de potência medido a partir da fonte pela fonte CA a quatro fios (Y-n). Quatro casos são abordados para análise da proposta no inversor trifásico a quatro braços e dois casos para um inversor trifásico em ponte completa (3F) para efeito de comparação. Baseando-se no monitoramento das potências elétricas envolvidas e nas demais grandezas de interesse, foi possível concluir que os resultados de simulações exemplificam o alcance dos objetivos propostos e validam o método adotado, pelo menos em relação à modelagem matemática empregada e à simulação do sistema de geração proposto em ambiente computacional.

This dissertation studies modeling and control issues of parallel three-phase pulse-width modulated (PWM) converters. The converters include three-phase boost rectifiers, voltage source inverters, buck rectifiers and current source inverters. The averaging of the parallel converters is performed based on a generic functional switching unit, which is called a phase leg in boost rectifiers and voltage source inverters, and a rail arm in buck rectifiers and current source inverters. Based on phase-leg and rail-arm averaging, the developed models are not only equivalent to the conventional three-phase converter models that are based on phase-to-phase averaging, but they also preserve common-mode information, which is critical in the analysis of the parallel converters. The models reveal such parallel dynamics as reactive power circulation and small-signal interaction. A unique feature of the parallel three-phase converters is a zero-sequence circulating current. This work proposes a novel zero-sequence control concept that uses variable zero-vectors in the space-vector modulation (SVM) of the converters. The control can be implemented within an individual converter and is independent from the other control loops for the converter. Therefore, it greatly facilitates the design and expansion of a parallel system. Proper operation of the parallel converters requires an explicit load-sharing mechanism. In order to have a modular design, a droop method is recommended. Traditionally, however, a droop method has to compromise between voltage regulation and load sharing. After parametric analysis, a novel droop method using a gain-scheduling technique is proposed. The numeric analysis shows that the proposed droop method can achieve both good voltage regulation and good load sharing. An interleaving technique is often used in parallel converter systems in order to reduce current ripples. Because of its symmetrical circuit structure, the parallel three-phase converter system can reduce both differential-mode and common-mode noise with a center-aligned symmetrical SVM. Based on the concept that a symmetrical circuit can reduce common-mode dv/dt noise, a conventional three-phase, four-leg inverter is modified so that its fourth leg is symmetrical to the other three legs. The common-mode dv/dt noise can be practically eliminated with a new modulation strategy. Meanwhile, with a modified control design, the new four-leg inverter still can handle low-frequency common-mode components that occur due to unbalanced and nonlinear load.<br>Ph. D.

碩士<br>中華大學<br>電機工程學系<br>106<br>Three-phase three-leg inverter has an inherent common mode voltage (CMV) problem.Therefore, three-phase four-leg inverter is proposed to mitigate the CMV. This study discusses the characteristics of multicarrier pulse width modulation (PWM) for three-phase four-leg inverter. The analysis of sinusoidal PWM and space vector PWM with multicarrier is presented. The simulation results are utilized to validate the performances of the proposed multicarrier PWM scheme.

碩士<br>中華大學<br>電機工程學系<br>106<br>The three-phase four-leg inverter is a system for mitigating common-mode voltages better than three-phase three-arm inverters. Therefore, for the common mode voltage (CMV), two techniques for three-phase four-arm inverters with multi-carrier pulse width modulation (PWM), sinusoidal PWM (SPWM) and space vector PWM (SVPWM) are proposed. To lower the CMV. This method is used to explore the impact on the system under load imbalance. Finally, the experimental and simulation software PSIM platform is used to analyze its system to verify the correctness of the proposed method.

碩士<br>清雲科技大學<br>電機工程研究所<br>96<br>Generally,the traditional three-phase three-leg DC-to-AC power inverter are used widely with three phase balanced loads. But, when the three-phase loads are unbalanced, that three phase voltage outputs can not be symmetrical. In this paper presents a three-phase four-leg DC-to-AC power inverter can be supply a midpoint to three phase unbalanced loads.So the three-phase four-leg DC-to-AC power inverter outputs three phase symmetrical voltages. Using symmetrical model analysises three-phase four-leg DC-to-AC power inverter how it suppresses the unbalanced loads. The mathematic model of three-phase four-leg DC-to-AC power inverter is established in different coordinates. Paper accomplishes the decoupling of the three-phase four-leg DC-to-AC power inverter. PI double loop controller based on synchronous frame is applied. The control circuit cosists of digital processor(DSP TMS320F2808PZA),which programmed in C language. The performance of system is simulated MATLAB SIMULINK. Experiments the three-phase four-leg DC-to-AC power inverter can output three-phase balanced AC voltage under the unbalanced loads conditions.

碩士<br>國立臺灣科技大學<br>電機工程系<br>97<br>The thesis is concerned with the analysis and development of six-leg three-phase inverter for permanent-magnet synchronous motor(PMSM) drives. The power circuit uses six-leg three-phase inverter. Connecting each winding to two separately controlling legs yields three phase dc-ac converter. The inverter control strategy uses unipolar voltage switching method to raise the utilization factor of dc-link voltage. When a winding of three-phase PMSM breaks down, the associated load may have to be reduced to retain continuous running and increase the reliability of the system. In the fault tolerance control strategy, the current of PMSM is used to determine which winding is broken, so that the other two winding currents can be corrected to result in a 60-degree angle difference, thereby reducing torque pulsation. In the proposed system, six Hall-effect sensors are used to measure the position and speed of the rotor to facilitate the coordinate transformation of feedback current to achieve d-q currents and speed closed-loop control. In this thesis, Matlab/Simulink is used to simulated the proposed PMSM system including six-leg three-phase inverter with unipolar voltage switching method control strategy, d-q current closed-loop control, speed closed-loop control and fault tolerance control strategy. The digital signal processor TMS320F2808 is adopted as the control core. A prototype of 100W six-leg three-phase inverter for PMSM drives is built. The speed is 170 rpm and the load is 4 N-m. When under the normal operation of the system, the total harmonic distortion of each phase-current is 14.67 %. While for two-winding operations of three different cases, the total harmonic distortions of three phase-currents for each case measured are 17.90%, 16.48% and 17.37%, respectively. The proposed system performance is thus verified experimentally.