Current Issue : January - March Volume : 2013 Issue Number : 1 Articles : 5 Articles
Wide-input, low-voltage, and high-current applications are addressed. A single-ended isolated topology which improves the power\r\nefficiency, reduces both switching and conduction losses, and heavily lowers the system cost is presented. During each switching\r\ncycle, the transformer core reset is provided. The traditional tradeoff between the maximum allowable duty-cycle and the reset\r\nvoltage is avoided and the off-voltage of active switches is clamped to the input voltage. Therefore, the system cost is heavily reduced\r\nand the converter is well suited for wide-input applications. Zero-voltage switching is achieved for active switches, and the power\r\nefficiency is greatly improved. In the output mesh, an inductor is included making the converter suitable for high-current, lowvoltage\r\napplications. Since the active clamp forward converter is the closest competitor of the proposed converter, a comparison is\r\nprovided as well. In this paper, the steady-state and small-signal analysis of the proposed converter is presented. Design examples\r\nare provided for further applications. Simulation and experimental results are shown to validate the great advantages brought by\r\nthe proposed topology....
This paper deals with the use of triphase shunt active filter which is able to compensate current harmonics, reactive power, and\r\ncurrent unbalance produced by nonlinear loads. To performthe identification of disturbing currents, a very simple control method\r\nis introduced. It�s formed by a DC voltage regulator and a balance between the average power of load and the active power supplied\r\nby the grid. The output current of the voltage source inverter (VSI) must track the reference current. This is done by a neural\r\ncontroller based on a PI-Fuzzy adaptive system as reference corrector. Also to regulate the DC link capacitor voltage a fuzzy logic\r\nadaptive PI controller is used....
This paper is concerned with performance of the current shaping network in Average Current Mode (ACM) Active Power Factor\r\nCorrection (APFC) systems. Theoretical expressions for the ripple components are derived. Then, ripple interaction and impact on\r\nthe current loop reference signal are investigated. A modification of the controller network is suggested that results in an improved\r\nTotal Harmonic Distortion (THD). Design guidelines are suggested. The theoretical predictions were validated by simulation....
Power electronics are a core enabling technology for local area power networks and microgrids for renewable energy, telecom, data\r\ncenters, and many other applications. Unfortunately, the modeling, simulation, and control of power electronics in these systems\r\nare complicated when using traditional converter models in conjunction with the network nodal equations. This work proposes\r\na change of variables for the power electronic converter models from traditional voltage and currents to input conductance and\r\nstored energy. From this change of state, a universal point of load converter model can be utilized in the network nodal equations\r\nirrespective of the topology of the converter. The only impact the original converter topology has on the new model is the bounds\r\non the control and state variables, and the mapping back to the switching or duty cycle controls. The proposed approach greatly\r\nsimplifies the modeling of local area power networks and microgrids. This simpler model can be used to study stability and energy\r\nutilization and develop high-level control strategies that were not previously feasible....
This paper describes and demonstrates the principle and efficacy of a novel direct current fault interruption scheme using a reactor\r\nin series with a controlled rectifier and a conventional AC circuit breaker. The presence of the series reactor limits the capacitive\r\ndischarge current from the DC filter capacitor at the output terminals of the phase-controlled rectifier. In addition, the series\r\nreactor along with the filter capacitor forms an underdamped series RLC circuit which forces the fault current to oscillate about\r\nzero. This synthetic alternating current can then be interrupted using a conventional AC circuit breaker. The selection criteria for\r\nthe series reactor and overcurrent protection are presented as well. Using the proposed scheme for an example case, a DC fault\r\ncurrent magnitude is reduced from 56 kA to 14 kA, while the interruption time is reduced from 44 ms to 25 ms....
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