The analysis and design of a modular three-phase ac to dc converter using single-phase CUK rectifier modules is discussed based on power balance control technique. The control strategy consists of single output voltage loop control and three-inductor current calculator. The main objective of the proposed system is to reduce the number of stages and improve dynamic response of dc bus voltage for distributed power system. The proposed scheme offers simple control strategy, flexibility in either 3-phase delta or star-connected and simpler design. The simulation and experimental results indicate that the proposed control system offers the fast transient response and power factor closed to unity.
In this paper a novel AC/DC rectifier topology is proposed. It operates in continuous current and PFC modes. This topology is close from the "VIENNA" one. By involving two coils, it permits to get a "Double Boost Effect", thus improves the rectifier features. Indeed, it exhibits the following advantages: (a) a Boost and a Buck-Boost effects operate and permit to transmit the energy to the DC capacitors even if the mains voltage is positive or negative, (b) for given capacitor values, the DC ripples decrease, (c) the mains current is under control of a self-oscillating controller which accurately tracks its reference. Furthermore, the "VIENNA I" rectifier power cell is not able to transmit the energy to both DC capacitors during the positive or negative half-period of the mains. The proposed rectifier can do it. The disadvantage of the investigated topology is to implement two coils. But if the sum of the "Double Boost Effect" topology coil inductance values equals the "VIENNA I" coil inductance one, the AC/DC "Double Boost Effect" rectification works better in term of DC ripple amplitudes. Then, it could be possible to reduce the "Double Boost Effect" rectifier capacitor values. In the proposed work, the operating of this new rectifier is studied and verified. Equations are given in order to depict all of the topology states. Simulations and experimental tests confirm the analysis results.
This paper presents a practical injection-based method for continuous monitoring of the crossover frequency and phase margin in digitally controlled switched-mode power supplies (SMPS). The proposed approach is derived from Middlebrook's loop-gain measurement technique, adapted to a digital controller implementation. A digital square-wave signal is injected into the feedback loop and the injection signal frequency is adjusted while monitoring loop signals to obtain the system crossover frequency and phase margin online, i.e., during normal closed loop SMPS operation. The approach does not require open loop or steady-state SMPS operation and is capable of convergence in the presence of load transients or other disturbances. A method for designing the stability margin monitor, based on small-signal models derived using an envelope modeling approach, is also presented. Experimental results are given for multiple power stage configurations demonstrating close matches between monitored and expected crossover frequencies and phase margins.
The utilization of inverters for the interconnection of distributed generators to the grid requires application of control systems capable of regulating the active and reactive output current, ensuring high power quality levels and achieving relative immunity to grid perturbations. This paper proposes a simple current control scheme, based on the combination of deadbeat and PI control, for a three-phase voltage source inverter connected to the grid via an LCL filter. The control system is analyzed in the frequency domain and an analytical expression for the harmonic content of the output current is derived. Theoretical analysis and computer simulation results validate the stability, fast transient response and robustness of the proposed system to network disturbances and variations in filter parameters.
Virtual and distance laboratories extend the application area of the web. This leads to an openly integrated environment which facilitates the sharing of not only educational material, but also hardware and software resources. This paper investigates distance learning with particular attention to experimental work. PEMCWebLab provides the user with a practical experience in Power Electronic education. It was designed based on leading ideas and had clear targets.
