Switched mode power supplies, inverters.
|A Novel Control Concept for Reliable Operation of a Three-Phase Three-Switch
Buck-Type Unity Power Factor Rectifier with Integrated Boost Output Stage
under Heavily Unbalanced Mains Condition|
In this paper the reliable operation of a three-phase three-switch buck-type PWM unity power factor rectifier with integrated boost output stage under heavily unbalanced mains, i.e. mains voltage unbalance, loss of one phase, short circuit of two phases or earth fault of one phase is investigated theoretically and experimentally. The analytical calculation of the relative on-times of the active switching states and of the DC link current reference value is treated in detail for active and deactivated boost output stage. Based on the theoretical considerations a control scheme which allows to control the system for any mains condition without change-over of the control structure is described. Furthermore, digital simulations as well as experimental results are shown which confirm the proposed control concept for different mains failure conditions and for the transition from balanced mains to a failure condition and vice versa. The experimental results are derived from a 5kW prototype (input voltage range (208 . . . 480)Vrms line-to-line, output voltage 400VDC of the rectifier system, where the control is realized by a 32-bit digital signal processor.
|SMALL-SIGNAL MODELING USING TIME-DOMAIN MODELS|
The objective of this paper is to identify the small-signal transfer function by means of a Fourier analysis of time-domain responses. Small-signal modeling is the identification of the time-domain response of a converter for small-signal excitations. It gives a Linear Time Invariant (LTl) model of a Linear Time Variant (LTV) converter. The new method is based on a time-domain model. During simulation of this time-domain model a perturbation is performed on the model. The resulting response is measured and transformed to the frequency-domain. The small-signal transfer functions are calculated from the frequency-domain representations of the input and output of the SMPS. The small-signal analysis by modeling and simulation is similar to a measurement on a real SMPS in a laboratory test. This makes the small-signal analysis based on a time-domain perturbation useful for any type of SMPS and has special value for SMPS which are difficult to analyze and model with existing methods like resonant converters, converters with current programmed control or pulse frequency modulated converters. The new method is also applicable to three phase AC and drive systems. Examples will be given for impedance measurement, a buck converter, where the Bode Diagram of the input-output transfer function is calculated beyond the switching frequency and a Zero-Current resonant converter.
|Thermal Simulation of Power Electronics|
In many electronic appliances, Power Electronics is used to supply the electronics. Due to miniaturization of the appliances, such as mobile telephones, small drives in automotive industry, etc., thermal overload becomes are serious challenge for the Power Electronics Engineer. He can not only design his system for the worst case scenario, but has to optimize his design for both efficiency as well as transient response. Nowadays, engineering thermal design methods are not suitable for the distributed designs containing more than one semiconductor. Therefore a coupled modeling/identification/simulation method is developed where 3D thermal designs can be taken into consideration in the total Power Electronics design optimization.Keywords
Thermal, Power Electronics, ANSYS/MULTIPHYSICS, CASPOC
|An Averaged Switch Model Including Conduction Losses for Boundary Conduction Mode Dc-to-Dc Converters|
In this paper, following the averaged switch approach, an averaged model, including conduction losses for the switch network of the pulse width modulated (PWM) dc-to-dc converters operating at the boundary between continuous conduction mode (CCM) and discontinuous inductor current mode (DICM) is developed. The model is verified through PSpice and CASPOC simulation for the boost converter. The averaged model is general, and can be applied to different dc-to-dc converters, without deriving a different averaged switch network model for each converter configuration.Keywords
Conduction losses, boundary conduction mode, dc-dc converters, averaged models, discontinuous inductor current mode, power electronics.
|Hopf Bifurcation in a Discontinuous Capacitor Voltage Mode Ćuk Dcdc
In this paper a simple closed-loop dc-dc Ćuk converter operating in Discontinuous Capacitor Voltage Mode (DCVM) is studied. Analysis of the state equations shows that the system loses stability via Hopf bifurcation. The results are verified through CASPOC simulation.Keywords
Hopf bifurcation, chaos, Ćuk converter, dc-dc converters, averaged models, Discontinuous Capacitor Voltage Mode, power electronics.
|An Improved Integration-Reset Controlled Power Factor
Correction Sepic Rectifier with Lower Distortion|
An improved control integration method for a CCM operated Sepic converter as a power factor correction (PFC) circuit is proposed in the paper. By adding a ripple compensation network consisting of a simple resistive divider and two integrators with reset, the total harmonic distortion (THD) coefficient of the input current is effectively reduced. The proposed method is easy to implement based on the general PWM modulator concept and is very suitable for IC fabrication. Theoretical analysis is provided in detail while simulation results based on the CASPOC package confirmed the theoretical expectations.Keywords
Sepic converter, power factor correction, integration control, general pulse-width modulator.
|State-Space Control Structures for Buck Converters with/without Input Filter|
Power supplies normally provide a constant output voltage. In most of the applications a DC/DCconverter is controlled by a voltage mode or a current mode controller . These controller types are well known and there are a lot of PWM controller ICs on the market. The controllers are often combined with feedforward techniques of the input voltage or output current, because these variables are disturbance variables. In this paper three state-space control structures are introduced. Based on the state-space representation an easy controller is designed first. The second one is improved as it works with an inner one-cycle controller and an outer I-controller for improving robustness. The third controller is designed for a buck converter with an input filter. The advantages of state-space controllers are pole placement and easy implementation. The input filter requires no resistor for damping and the filter elements can be much smaller. For each of the three controllers an example will be shown with controller design, simulation and results. Experimental results are shown for the state-space controller with inner one-cycle controller and outer I-controller.Keywords
Converter control, Simulation, Switched-mode power supply
|CAD/CAE Software Aids Converter Disign|
Typically, power supply disign involves electronic and magnetic components. Using a flyback converter example, let's see how CAD/CAE tools aid the engineer in both areas, reducing prototyping costs and providiing insight into system perfomance.