C.P. Dick

Active damping of LCL resonance with minimum sensor effort by means of a digital infinite impulse response filter

This paper presents a concept for active damping of an LCL filter connecting a digitally controlled PWM converter to the grid. Active damping is performed by means of a digital Infinite Impulse Response (IIR) filter. Digital filters, being well known in digital signal analysis, can easily be implemented when using digital controllers and require very low computational effort. In contrast to active damping solutions found in literature, no extra quantities except the controlled current must be sensed. This functionality is proven via experimental results. After a short introduction of the problem and an overview of solutions found in literature, the implemented fundamental procedure for active damping is described. Subsequently, the main idea of using an IIR filter for active damping, being an approximation to a derivative function, is qualified and the design procedure is presented. In this paper it is stated that with this method the sensors are minimized and that due to the approximation of the derivative function the damping performance is lower compared to solutions found in literature. However, the damping effect by using an IIR filter is proven. The use of IIR filters and the reduction of sensor effort for active damping of EMI filters with multiple passives looks promising also for other applications with a known load.

A high-efficient LLCC series-parallel resonant converter

A high efficient LLCC-type resonant dc-dc converter is discussed in this paper for a low-power photovoltaic application. Emphasis is put on the different design mechanisms of the resonant tank. At the same time soft switching of the inverter as well as the rectifier bridge are regarded. Concerning the design rules, a new challenge is solved in designing a LLCC-converter with voltage-source output. Instead of the resonant elements, ratios of them, e.g. the ratio of inductances Ls/Lp is considered as design parameters first. Furthermore, the derived design rule for the transformer-inductor device fits directly into the overall LLCC-design. Due to the nature of transformers, i.e. the relation of the inductances Ls/Lp is only a function of geometry, this design parameter is directly considered by geometry. Experimental results demonstrate the high efficiency.

Comparison of Three-Phase DC-DC Converters vs. Single-Phase DC-DC Converters

In this paper a comparison of common single-phase and three-phase DC-DC resonant and non- resonant converter bridges on application level is carried out. Device stresses and efficiencies are qualified at constant transferred power and constant terminal voltages. As a result, this paper presents the predominance of three-phase topologies when talking about switching losses in silicon devices of non-resonant solutions. Subsequently transformer efficiency is discussed in detail for specific core geometries. Finally the stress on the input capacitors is qualified. Concerning losses and charge to be buffered the predominance of the three-phase topology is shown.

Control of a medium-voltage test generator

This paper describes the design of a digital control for a 3.3 kV, 1 MVA three-level PWM converter operating as test generator for disturbances in medium-voltage grids according to standards like IEC 61000, EN 50160, and IEEE 1547. The proposed control combines state-feedback with additional dynamic output feedback. It is designed fully in the stationary reference frame to avoid processing of complex transformations into different rotating reference frames. Resonant controllers provide zero steady-state error for up to ten harmonics. A DSP platform is used for implementing the control. It replaces the control unit of a commercial converter. Experimental results of a downscaled breadboard construction verify the functionality of the control.

Sensorless direct instantaneous torque control for switched reluctance machines

This paper presents a position-sensorless torque controller for switched reluctance machines (SRMs) based on direct instantaneous torque control (DITC). An indirect position estimation to eliminate the need of the position encoder is developed based on current-flux-linkage method. The current-flux-linkage method has advantages of simplicity and requires less computation time. Therefore, the controller can be implemented with a high control bandwidth. The accuracy of position estimation and effects of estimation errors are studied. The functionality of the developed controller and its performance are investigated and verified by experiments over a wide operating range

Unified Control Strategy Covering CCM and DCM for a Synchronous Buck Converter

In general, transfer functions of switch-mode converters are treated differently when operating in continuous-conduction mode (CCM) or discontinuous-conduction mode (DCM). This complicates the development of a control algorithm for a converter operating in both operating modes. To solve this problem, a control algorithm is developed, which is applicable for CCM and DCM. Since the developed control algorithm is based on linear equations instead of differential equations, it is easy to implement and its calculation effort is minor. It is based on equating the volt-seconds across the inductor for both operating modes and adjusting the duty cycle d. All necessary equations are derived and the functionality of the developed algorithm is shown by means of simulation and measurements.

A Dynamic Boost Converter Input Stage for a Double 120° Flattop Modulation Based Three-Phase Inverter

This paper presents a dynamic boost converter as input stage for a high efficient double 120deg flattop modulation based three-phase inverter. The boost converter can be regulated with hysteresis control or predictive PWM. The objective of the input stage is to provide a dynamic and accurate current into a pulsating DC-link. The algorithms are verified with simulations and experiments using a prototype. Both results show that the designed input stage can provide the required dynamics and accuracy for the three-phase inverter operating with double 120deg flattop modulation.

Design of a contactless rotary energy transmission for an industrial application

Till now, the common practice of transferring energy from a stationary to a rotating plane is realized via slip rings. These systems exhibit a small mechanical size but limit the achievable rotational speed. Due to abrasion, the lifetime of slip rings is limited. Contactless rotary energy transmissions can overcome these problems. They are not affected by fouling and are theoretically maintenance-free. This paper deals with the development of a contactless energy transmission for a drilling tool. The developed energy transmission transfers up to 200 W. The transferred energy is used to drive a piezoelectric actuator, which in turn controls the position of the cutting edge of the drilling tool. First, the mechanical constraints of this application are given and the consequences for the energy transmission are derived. Afterwards, the topology most suitable for this application is selected. Subsequently, the different methods to solve the difficulties, which arise from the mechanical constraints, with their advantages and disadvantages are compared and their influence on the design of the components is shown. At the same time, it is determined which degree of mechanical dislocation is allowed before the system will trip.

Sensorless Direct Instantaneous Torque Control for Switched Reluctance Machines

Abstract This paper presents a position-sensorless torque controller for Switched Reluctance Machines (SRMs) based on Direct Instantaneous Torque Control (DITC). An indirect position estimation is developed based on a current-flux-linkage method to eliminate the need of the position encoder. The current-flux-linkage method has advantages of simplicity and requires a relatively short computation time. Therefore, the controller can be implemented with a high control bandwidth. The accuracy of position estimation and influences of estimation errors are studied. The functionality of the developed controller and its performance are investigated and verified by experiments over a wide operating range.

Novel high frequency transformer configurations - amorphous metal vs. ferrites

In this paper a novel configuration of anamorphous metal tape transformer, with the flux being closed within the magnetically anisotropic tape plane, is introduced. After characterization of the metal tape in both tape plane directions, the configuration and basic mechanical and chemical processing steps of the transformer construction are presented.