Showing papers presented at "European Conference on Power Electronics and Applications in 2003"

A diagnostic method for on-line fault detection and localization in vsi-fed ac drives

Abstract: This paper describes a novel approach to the detection and localization of semiconductor faults in VSI-fed AC drives. We use the DC-to-fundamental motor current ratio as the diagnostic variable. The method has proved to reliably detect true faults, while not issuing false alarms under transient conditions. The method has been validated by both simulation and experiment.

Current capability and power density of supercapacitors: considerations on energy efficiency

Abstract: Supercapacitors are components for energy storage. Due to their series resistors, the energy efficiency of supercapacitors can be low. In this paper, the unloading of supercapacitors with constant current and power are studied, to identify and take into account the energy efficiency and the power density of supercapacitors.

Experimental Identification of an Electronic Throttle Body

Abstract: Detailed off-line experimental identification of an automotive electronic throttle body (ETB) servo drive is carried out with the aim to aid design of a high-performance electronic throttle control strategy. The linear and nonlinear parts of the ETB model are conveniently identified separately. Identification of ETB linear dynamics includes a multi-step identification method based on the physical ETB model form, and single-step methods based on the black-box continuous-time and discrete-time ETB model forms. The nonlinear effects identified include static and dynamic friction effects, and distinctive limp-home nonlinearity.

Power-Electronic Interface for a Supercapacitor-Based Energy-Storage Substation in DC-Transportation Networks

Abstract: A Power-electronic interface for supercapacitive-storage based substation in DC-transportation networks is proposed, which allows to feed as a current-source in any voltage conditions of the line. The system has been designed as a compensation-substation to be placed at weak points like end-of-line stations, and can replace supplementary feeding substations. A dedicated power-electronic converter with associated control system is proposed, for the stabilization of the voltage level at the point of coupling. Practical results are also presented, which have been recorded from a reduced scale prototype.

Voltage Control and Load Sharing in DC Distribution Systems

Abstract: This paper addresses voltage control and load sharing in DC distribution systems. At present, DC distribution systems are utilised in, for example, telecommunication systems. Future applications could also involve distributed power systems based on renewable energy sources. The dynamic and stationary properties of voltage droop control and its load sharing abilities are investigated. The DC bus voltage droop controller gain is selected so that the loading of each source converter is equal in per unit. Both experimental and simulation results verify the operation. Experimental results regarding fault detection in DC distribution systems are also presented.

FPGA-based current control of PWM voltage source inverters

Abstract: In this paper, a single-phase deadbeat digital current control algorithm using voltage source inverters for grid-connected applications is presented. The controller is designed directly in the digital domain using the method of Ragazzini. The line voltage is estimated by bandpass filtering the current error. The development of a robust fast prototyping platform, consisting of a Field Programmable Gate Array (FPGA) and a Digital Signal Processor (DSP), is discussed. The current control algorithm is implemented on a Digital Signal Processer, while the Pulse Width Modulation (PWM) algorithm and additional protection blocks are implemented in the FPGA. Both the simulations and the experimental results validate the results of the theoretical analysis. Specific advantages of the proposed current control algorithm include the fast and accurate deadbeat response, the robust operation and the avoidance of the use of a line voltage sensor. Introduction Current controlled Pulse Width Modulated Voltage source Inverters have a wide range of applications in variable speed drives, distributed generation and power conditioning systems, such as active power filters. Various modulation strategies and control algorithms have been developed [1]-[3]. The various techniques to control the current in a voltage source inverter can be roughly classified as hysteresis, ramp comparison and predictive current controllers. While hysteresis control is traditionally implemented using analog components, enabling fast response and high bandwidths, predictive controllers have mostly been implemented digitally. Microprocessors and Digital Signal Processors (DSPs) have been widely adopted for the design of digital current controllers. Field-Programmable Gate Arrays (FPGAs) allow rapid prototyping of digital systems. The FPGA realization of PWM current control strategies provides advantages such as fast prototyping, simple hardware and software design, higher switching frequency and reduction of the computational load of the DSP. Recently, it has been shown that through increasing the sampling frequency it is even possible to implement Hysteresis Current Control digitally, by using a FPGA [4]. 1

A low cost solution for laboratory experiments in induction motor control

Abstract: In this paper we present a controller suitable for educational activities in electric drives. A prototype has been designed specifically to meet the requirement of low cost and it contains all of the active functions required to implement the open loop control of an induction motor. In this way, the prototype allows the easy assimilation of important concepts and enables the understanding of the enclosed subsystems. Some experiments that highlight the quality of the proposed approach are presented.

Non-Equilibrium State Capacitor Voltage Stabilization in a Hybrid Asymmetric Nine-Level Inverter: Non-Linear Model-Predictive Control

Abstract: Hybrid asymmetric multi-level inverters promise significant improvements for medium-voltage industrial drives. Floating sub inverters without feeding allow increased efficiency, but can only supply reactive power. An on-line non-linear model-predictive controller stabilizes their intermediate-circuit capacitor voltages in steady-state and during transients, as demonstrated by simulations and measurements.

Power Cycling Test Circuit for Thermal Fatigue Resistance Analysis of Solder Joints in IGBT

Abstract: The paper will give a detailed presentation of an active power cycling test bench in high temperature conditions developed to ageing the solder between the Direct Copper Bonding (DCB) and the base of IGBT devices. The average junction temperature measurement protocol, the temperature regulation of the base plate, the acquisition of all the electrical signals, and the performance of the test circuit will be presented and discussed. Moreover, a thermal modelling presentation has been used to define the power cycling test parameters. The paper will present results of long time power cycling tests in server working conditions in the case of a base plate temperature equal to 90 °C, for a power injection of 300 W/cm2 during 10 s.

A boot-strap estimator for joint flux and parameters online identification for vector controlled induction motor drives

Abstract: This paper presents a new approach for joint rotor flux and electrical parameters on-line identification in vector controlled high-performance induction motor drives based on a boot-strap estimator that uses a reduced order extended Kalman filter for rotor flux components and rotor parameters estimation and a recursive prediction error method for stator parameters estimation. Within the prediction error method some approaches are used and compared that affect both the adaptation gain and the direction in which the updates of stator parameters are made. The induction motor model structures are described in the rotor reference frame in order to reduce the computational effort by using a higher sampling time interval.

Electric Machines and Drives for X-by-Wire Systems in Ground Vehicles

Abstract: The transition from conventional mechanical-hydraulic actuation systems to innovative "x-by-wire" solutions in the treatment and transmission of pilot's commands represents a new leading edge for the automotive industry. Relevant improvements are indeed expected from the introduction of electrical drives suitably controlled by hierarchical computer-based management systems interconnected through a field bus: better performances, greater overall safety and reliability, higher efficiency, lower emissions, reduced maintenance etc. Starting from the servo-systems presently adopted, this paper aims to presents an overview of the main issues and of the most interesting solutions proposed in the technical literature, particularly referring to the aspects regarding electric machines and drives. The potential benefits with respect to conventional systems are highlighted, and some orienting considerations are formulated referring both to conventional powertrain structures and to hybrid and electric vehicles. 1.- Fly-by-wire: the predecessor Since the end of the second world war, as the diffusion of air transportation led to the development of larger and heavier airplanes facing more and more stringent safety regulations, an increasing research effort was devoted from the avionic industry to the development of "fly -by-wire" solutions employing electro-hydraulic or purely electric systems as a replacement for the conventional mechanical and/or hydraulic structures previously used for the transmission of the pilot's commands to the actuated devices (flaps, injectors etc.). In fact, as a general rule the benefits correlated to the transition from mechanical to electric systems become more and more evident as the size of the system augments, in terms of both simplicity, flexibility, efficiency, performances and weight. Moreover, the adoption of active command leverages, equipped with suitably controlled actuators, permits to provide the pilot with a useful wrench feedback, allowing him to virtually sense the intensity of the effort required to execute his commands just as if a mechanical connection still exists. Finally, nowadays fly-by-wire systems have evolved from their original pure servo-system role, aimed to simply "amplify" the physical effort of the human pilot to allow him driving large airplanes, to a more critical role thanks to the introduction of computer -based supervision and management systems charged to reliably perform sophisticated functions such as stability control, route-tracking and so on. Under this point of view, the higher precision and better repeatability and dynamic performances of electric drives represent then the natural choice in the selection of servosystems. Consequently, nowadays only small tourism airplanes are still equipped with conventional systems, while modern large airplanes extensively employ fly-by-wire systems, although in many cases indirect hybrid electro-hydraulic configurations are still employed using electromagnetic servo-valves to regulate the operation of hydraulic actuators. Nevertheless, the direct employ of electric drives is steadily growing and all the main typologies are under careful evaluation (e.g. [1]), since they already proved to be able to provide reliability and robustness levels even higher than conventional solutions when suitable design criteria are adopted.

Large signal models of ZVS class E2 resonant converters

Abstract: This paper proposes a simple and systematic procedure for identifying averaged large-signal models of resonant converters. The nonlinear behaviour of the converter is modelled via Hammerstein models, i.e., the model is represented by a static nonlinearity, followed by a linear transfer function. The parameters of the approximating structure are identified from input-output noisy data, with the application of modulating functions method. PSpice simulations and experimental tests are run for an exhaustive and accurate validation of the proposed methodology. A relevant result is that the technique allows an easy modelling in the critical case of resonant converters, where traditional averaging techniques fail.

Common Mode Choke Charactérisation method and modelling for EMI filter in Power Electronics

Abstract: An equivalent circuit has been developed to model the linear electrical behaviour of any two windings common mode chokes. Its topology is independent of size and technology and a general method of characterization, exclusively based on external impedance measurements has been presented.

Active clamping of IGBT: capacitor replaces TRANSIL diodes

Abstract: Active clamping is one major security function of an IGBT driver. Transil diodes are commonly used. This paper details the investigation of an original solution without such diodes. A charged capacitor in series with a fast diode is used. Clamping voltage is continuously adjustable. Experimental results are presented.

Sampling Algorithm for Small Input Current Distortion in Digitally Controlled Boost PFC Converters

Abstract: After a short introduction to the digital control of boost power factor correction converters, the principle of operation of the alternating-edge-sampling algorithm is reviewed. The main features of this sampling algorithm are: switching noise immunity, straightforwardness, the need for only few extra processor cycles and accurate measurement of the averaged input current. However, to accomplish this last feature the timing of the sampling instants has to be tuned manually. Moreover, the “ideal” timing instants may slowly vary because of temperature effects and during the life-time of the converter. To annihilate these effects and to avoid manual tuning, the alternating-edge-sampling algorithm is extended with an autotuning feature for the timing of the sampling instants. The distortion caused by the sampling algorithm due to an inaccurate timing of the sampling instants is quantified to obtain an estimate for the timing error. This timing error is continuously monitored and intermittently used to adjust the timing of the sampling instants. As a result, the proposed sampling algorithm provides accurate measurements of the averaged inductor current without manual tuning, over a wide temperature range and during the operating life-time of the converter. Experimental verification using a digitally controlled boost converter demonstrates the feasibility of the proposed sampling algorithm and demonstrates that a small input current distortion can be achieved.