E. Olias

New Power Factor Correction AC-DC Converter With Reduced Storage Capacitor Voltage

Most of single-stage power factor correction (PFC) ac-dc converters usually present a high voltage swing on the storage capacitor. That means, high size and cost of the storage capacitor is obtained. The Series Inductance Interval (SII) PFC converters allow reducing cost and size of the storage capacitor since the capacitor voltage is lower than the output voltage and, therefore, the voltage swing is significantly reduced. In this paper, the novel single-stage SII-B-2D PFC converter is presented. In addition, this topology provides input current harmonics under EN61000-3-2 Class D limits and advantageous component count

The fast response double buck DC-DC converter (FRDB): operation and output filter influence

The fast response double buck (FRDB) dc-dc converter was presented like a low output voltage dc-dc converter with fast transient response, in order to feed devices such as microprocessors and digital signal processors (DSPs). The topology of the FRDB is composed of two buck converters connected in parallel, each one of them with different features and aims, and controlled by means of the novel linear-non-linear (LnL) control. In this paper, the topology, the control strategy and the operation principle are shown. Finally, experimental results in different prototypes are presented to show both, the transient response and the recovery time when these prototypes are subjected to load current steps, and the influence of the output filter on these parameters.

Theoretical study and implementation of a fast transient response hybrid power supply

This paper presents a theoretical and experimental study of the hybrid sources capabilities to improve both the dynamic response and the stability of switching power supplies. The hybrid sources are composed by both, a linear and a switching source connected in parallel. The reached improvements have been possible without affecting, significantly, the efficiency of the whole circuit. This solution is checked in low voltage sources. The obtained experimental results show that these power supplies present high dynamical performance, and therefore they can be used to feed digital signal processors and microprocessors.

Transformer modeling for FRA techniques

Transformers are one of the main devices in the utility grids. Reliability, power quality, economic cost and even the company image are influenced by the transformers health. For this reason, advanced techniques have been developed in order to improve the transformer life assessment. FRA (frequency response analysis) techniques are nowadays widely used by the electric utilities as one of these advanced techniques. They are specially appreciated to detect winding displacements inside the transformer. The main problem about FRA techniques is to interpret the observed evolution of the frequency response in order to identify both failures and failures tendencies in the transformer. In order to solve this problem a modeling tool is proposed in this work using the frequency response measured at the transformer.

Linear-non-linear control (LnLc) for DC-DC buck converters: stability and transient response analysis

Power supplies for last generation of microprocessors and DSPs must present low output voltage and fast transient response. The linear-non-linear control (LnLc control) was presented as a solution to improve the transient response in DC-DC buck converters. However, once the LnLc control has been analyzed, other important performances have been found such as, improving the stability of the system, improving the efficiency, reducing of the recovery time, making independent the bandwidth and the switching frequency; reaching all these performances with an easy implementation. In this paper, the features of the linear-non-linear control are described. It will be shown, how the LnLc improves the stability of a DC-DC buck converter modifying the open loop gain and phase as a function of the load current steps. To show this behavior the control transfer function (G/sub LnLc/) has been deduced. Several experimental results have been obtained in a synchronous rectifier buck converter to check its behavior. Thus, the novel LnLc control has been compared with the conventional voltage control under different conditions. Finally, the control transfer function has been obtained experimentally.

Fast transient response with combined linear-non-linear control applied to buck converters

Nowadays, one of the main challenges for power supplies designers is to feed the latest generation of microprocessors and DSPs, since they require high current slew rates together with low output voltage. In this paper, a novel control technique is presented to help the designers to comply with the current requirements. The proposed combined linear-nonlinear control (LnLC) scheme increases significantly the capability of conventional linear control to reduce the recovery time of the output voltage drop produced when a load current step occurs. Experimental results have been obtained for two cases: a synchronous rectifier buck converter, with a conventional voltage loop and the same converter with the novel LnLC. The comparison of these experimental results shows that, with the new control, the recovery time of the output voltage is reduced.

New DC/DC converter with low output voltage and fast transient response

A new alternative to get fast transient response DC/DC switching converters is presented in order to feed devices such as microprocessors and DSPs. The topology of the switching power supply is composed of two buck converters connected in parallel, each one of them with different aims, controlled by means of the linear-nonlinear control. In this paper, the LNL control is reviewed and applied to the proposed power supply (fast response double buck, FRDB). Also, experimental results are obtained to show the main features of the proposed converter and to compare them with the features of some other solution.

New power factor correction AC/DC converter with reduced storage capacitor voltage

Single-stage power factor correction (PFC) AC/DC converters usually present a high storage capacitor voltage stress and voltage variation. The series inductance interval (SII) PFC converters allow obtaining a bulk capacitor voltage lower than the peak value of the line voltage and even lower than output voltage. In this paper the novel single-stage SII-B-2D PFC converter is presented. This topology combines as three main advantages a low value and not much variable storage capacitor voltage, input current harmonics under EN61000-3-2 Class D limits, and an advantageous component count.

DC Current Injection Into the Network from PV Grid Inverters

The present paper is focused on the study of the DC current injection for low voltage small grid-connected PV systems, which is one power quality requirements by the utility companies. For this aim, the existing status of guidelines and regulations in six selected countries where the development in the grid PV sector has evolved rapidly over the last decade, (Japan, Germany, USA, Australia, Spain and United Kingdom) has been viewed, according to the DC current injection into the grid. Furthermore, a grid-connected system installed in Spain has been used to perform measures about their possible DC current injection into the grid. Thus, twelve single-phase inverters (according to the transformer options: 50 Hz LF transformers, HF transformers or transformer-less) from the European market have been tested. Many groups of measurements were made, under different conditions. The results show that in all cases there is any DC current injection, even if a LF transformer inverter is used

PWM-PD multiple output DC/DC converters: operation and control-loop modeling

In this paper, PWM-PD multiple output dc/dc converters are presented. Operation analysis and power block design are shown. Furthermore, a small-signal model is developed for the PWM-PD multiple output dc/dc converters working in continuous conduction mode. The control-block is presented and the closed-loop circuit performances, such as the line, load and cross regulation, are obtained analytically. Finally, experimental results for a PWM-PD converter, with three fully regulated outputs and with transformer, are shown.