1,721,137 research outputs found
Implementation Issues of a Fuzzy-Logic-Based Three-Phase Active Rectifier Employing only Voltage Sensors
No full textSwitch-mode rectifiers are becoming more and more
interesting in those applications where bidirectional power flow,
power-factor correction, and electromagnetic interference re-
duction are required. Typical active rectifiers include current or
voltage sensors, however, in order to obtain low-cost systems, their
number should be reduced. In this paper, a current-sensorless
active rectifier with feedforward fuzzy logic control is presented
and discussed. The mathematical description of the system and the
design of the fuzzy logic controller are introduced and analyzed;
moreover the implementation on a SH7047 microcontroller is
presented with emphasis on the most significant implementation
issues. Experimental results are reported and discussed
A novel three-phase single-stage distributed power inverter
No full textIn this paper, a novel three-phase, dc/ac converter suitable for distributed power applications is proposed. The system consists of three dc/dc boost converters with a common point and operating as a three-phase inverter with intrinsic step-up capability. The converter obtained can invert, amplify and, where possible, regenerate bidirectional power sources such as fuel-cells, small gas turbines, and photovoltaic arrays. There are two main advantages to the system: the use of only six insulated gate bipolar transistors and small passive elements, and the fact that it does not need reverse voltage blocking capability. Simulation and experimental results show the effectiveness of the proposed system during both steady-state and dynamic operations
A Novel Three-phase Single-stage Distributed Power Inverter
No full textIn this paper, a novel three-phase, dc/ac converter suitable for distributed power applications is proposed. The system consists of three dc/dc boost converters with a common point and operating as a three-phase inverter with intrinsic step-up capability. The converter obtained can invert, amplify and, where
possible, regenerate bidirectional power sources such as fuel-cells,
small gas turbines, and photovoltaic arrays. There are two main advantages to the system: the use of only six insulated gate bipolar
transistors and small passive elements, and the fact that it does not need reverse voltage blocking capability. Simulation and experimental results show the effectiveness of the proposed system during both steady-state and dynamic operations
Control of H-bridge based multilevel converters
No full textMultilevel converters are suitable for high voltage and high power applications. Among them H-bridge ones have encountered good success due to their simpler layout and the reduced number of components over the counterparts. H-bridge multilevel converters used as active rectifiers represent an attractive solution in traction systems due to the possibility to reduce the ac filter size and to boost the dc voltage. Moreover they can feed many dc loads at the price of considerable difficulties in ensuring stability of the overall system. The Passivity Based Theory seems suitable to address and solve such a kind of problem. The main idea is to design a non-linear controller which function is to shape systems energy aiming to obtain the desired behavior. A comparison is made between a control technique using classical PI controllers and a Passivity based control
Design of a harmonic free three-phase UPS
No full textIn this paper a novel three phase, step-up, converter for industrial UPS applications is proposed. The system basically consists of three, star-connected, boost-type DC/DC converters working together like a three-phase voltage source inverter, but with intrinsic step-up capability. The main advantages of the system are the smaller dimensions of the passive components and the reduced number of switching devices that do not need reverse voltage blocking capability. Test results show the effectiveness of the proposed system both during steady state and dynamic operations as well
A passivity-based multilevel active rectifier with adaptive compensation for traction applications
No full textThe control of a single-phase multilevel H-bridge rectifier suitable for traction applications is considered. Such a converter often presents instability problems making difficult its design and uncertain its behavior. In this paper the use of a passivity-based controller is experimentally investigated. Such a controller achieves stability, unity power factor, good balancing between the two dc links, and satisfactory behavior even in the presence of load changes. A right choice of the damping parameters allows the fulfilling of system requirements in terms of dc-link voltage error and grid current distortion
Design of H-bridge Multilevel Active Rectifier for Traction Systems
No full textThis paper is focused on the design of the controller for a high voltage-high power single phase front-end rectifier stage, for a large electric drive designed for, but not limited to, traction field applications. The rectifier should absorb current with low harmonic content to eliminate disturbances on the communication equipments and more generally to reduce environment electromagnetic pollution. Additional specification is the elimination of the heavy and bulky transformer to reduce encumbrances and cost. A multilevel H-bridge single phase configuration has been chosen. In this paper, the design has been fully investigated with the help of theoretical analysis and simulations
A fuzzy-logic-based controller for active rectifier
No full textThis paper presents a current-sensorless active rectifier specifically designed for low-cost applications. Both the control and the modulation use fuzzy logic. A simple model of the system is given in order to explain the current feedforward control using fuzzy logic and the fuzzy-logic-based modulation, then, the new algorithm is. analyzed looking for high performance even using small passive elements and low switching frequency. Performance are compared with those of a closed-loop proportional-plus-integral (PI)-based rectifier with space-vector modulation (SVM). This comparison has been carried out either considering the whole systems or a combination of their components (PI control + fuzzy modulation or fuzzy feedforward control + SVM). The results show that even without current sensors, the low-frequency distortion of the line currents and the dc voltage oscillations produced by the proposed system are very limited, ensuring performance similar to those of PI-based closed loop active rectifiers
Design of a Multilevel Front-End Stage for Traction System with the Passivity Theory
No full textThis work addresses the control of a high voltage, high power single phase rectifier suitable for traction applications. A multilevel H-bridge single phase configuration has been considered. Such a converter often presents instability problems making difficult its design and uncertain its behaviour. This paper proposes a new controller based on the passivity-based approach. Such a controller allows stability, unity-power factor, good balancing of the two DC links and a satisfactory transient behaviour even in presence of sudden load changes. A different choice of the damping parameters allows fulfilling the system requirements in terms of reduced DC link voltage error or low grid current distortion or to find an optimum trade-off between them. The better performance in comparison with a PI are demonstrated
An energy-based control for an n-H-bridges multilevel active rectifier
No full textThis paper deals with the control of a multilevel n-H-bridges front-end rectifier. This topology allows n distinct dc buses to be fed by the same ac source offering a high loading flexibility suitable for traction applications as well as for industrial automation plants. However, this flexibility can lead the system to instability if the dc buses operate at different voltage levels and with unbalanced loads. Thus, linear controllers, designed on the basis of the small-signal linearization, are not effective any longer and stability can not be ensured as large-signal disturbances occur. The use of a passivity-based control (PBC) designed via energy considerations and without small-signal linearization properly fits stability problems related to this type of converter. The system has been split into n subsystems via energy considerations in order to achieve the separate control of each dc bus and its stability in case of load changes or disturbances generated by other buses. Then, a set of n passivity-based controllers (one for each subsystem) is adopted: the controllers are linked using dynamical parameters computed through energy balance equations. Hence, the system dc buses are independent and stable as experimental results demonstrate
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