Johann Minibock

Comparative evaluation of three-phase high-power-factor AC-DC converter concepts for application in future More Electric Aircraft

A passive 12-pulse rectifier system, a two-level, and a three-level active three-phase pulsewidth-modulation (PWM) rectifier system are analyzed for supplying the dc-voltage link of a 5-kW variable-speed hydraulic pump drive of an electro-hydrostatic actuator to be employed in future More Electric Aircraft. Weight, volume, and efficiency of the concepts are compared for an input phase voltage range of 98-132 V and an input frequency range of 400-800 Hz. The 12-pulse system shows advantages concerning volume, efficiency, and complexity but is characterized by a high system weight. Accordingly, the three-level PWM rectifier is identified as the most advantageous solution. Finally, a novel extension of the 12-pulse rectifier system by turn-off power semiconductors is proposed which allows a control of the output voltage and, therefore, eliminates the dependency on the mains and load condition which constitutes a main drawback of the passive concept.

Towards a 99% Efficient Three-Phase Buck-Type PFC Rectifier for 400-V DC Distribution Systems

In telecom applications, the vision for a total power conversion efficiency from the mains to the output of point-of-load (PoL) converters of 95% demands optimization of every conversion step, i.e., the power factor correction (PFC) rectifier front-end should show an outstanding efficiency in the range of 99%. For recently discussed 400-V dc distribution bus voltages, a buck-type PFC rectifier is a logical solution. In this paper, an efficiency-optimized, 98.8% efficient, 5-kW three-phase buck-type PFC rectifier with 400-V output is presented. Methods for calculating losses of all components are described and are used to optimize the converter design for efficiency at full load. Special attention is paid to semiconductor losses, which are shown to be dominant, with the parasitic device capacitance losses being a significant component. The calculation of these parasitic capacitance losses is treated in detail, and the charge-balance approach used is verified. A prototype of the proposed rectifier is constructed which verifies the accuracy of the models used for loss calculation and optimization.

Exploring the pareto front of multi-objective single-phase PFC rectifier design optimization - 99.2% efficiency vs. 7kW/din 3 power density

Up to now, in the development of power electronics systems, the reduction of the initial costs or the increase of the power density have been of primary concern. However, with increasing energy costs also the power conversion efficiency is gaining higher and higher importance. Accordingly, while maintaining high power density, an efficiency as high as possible must be obtained. In this paper the maximum attainable efficiency and the dependency of the efficiency limit on technological parameters is determined for single-phase PFC boost rectifiers. In a first step basic PFC boost rectifier topologies are briefly compared with regard to high efficiency and a dual-boost PFC rectifier with integral common-mode filtering is selected as basis for the investigations. Next, simple approximations of the technological limits of the system performance are calculated in the efficiencypower density plane. With this, the Feasible Performance Space and the reduction in power density which has to be accepted for increasing the efficiency are clarified, and the trade-off limit curve (Pareto Front) of a multi-objective, i.e. efficiency and power density design optimization is determined. Furthermore, a comprehensive numerical efficiency optimization is carried out which identifies an efficiency limit of 99.2% for a 3.2kW system. The theoretical considerations are verified by experimental results from a laboratory prototype of the ultra-high efficiency system achieving 99.1% efficiency at a power density of 1.1kW/din3, as well as those firom an ultra-compact dual-boost PFC rectifier (95.8%, 5.5kW/dn3) and a very low switching freluency (3kHz) conventional PFC boost rectifier (96.7%, 2kW/din3). Finally, the sensitivity of the efficiency optimum with regard to various technological parameters is analyzed and an outlook on the further course of the research is given.

Novel concept for mains voltage proportional input current shaping of a VIENNA rectifier eliminating controller multipliers

This paper proposes a novel mains voltage proportional input current control concept eliminating the multiplication of the output voltage controller output and the mains ac phase voltages for the derivation of mains phase current reference values of a three-phase/level/switch pulsewidth-modulated (VIENNA) rectifier system. Furthermore, the concept features low input current ripple amplitude as, e.g., achieved for space-vector modulation, a low amplitude of the third harmonic of the current flowing into the output voltage center point, and a wide range of modulation. The practical realization of the analog control concept as well as experimental results for application with a 5-kW prototype of the pulsewidth-modulated rectifier are presented. Furthermore, a control scheme which relies only on the absolute values of the input phase currents and a modified control scheme which does not require information about the mains phase voltages are presented.

Towards a 99% efficient three-phase buck-type PFC rectifier for 400 V DC distribution systems

In telecom applications, the vision for a total power conversion efficiency from the mains to the output of PoL converters of 95% demands for an optimization of every conversion step, i.e. the PFC rectifier front-end should show an outstanding efficiency in the range of 99%. For recently discussed 400 V DC distribution bus voltages a buck-type PFC rectifier is a logical solution. In this paper, an efficiency-optimized, nearly 99% efficient, 5 kW three-phase buck-type PFC rectifier with 400 V output is presented. Methods for calculating losses of all components are described, and are used to optimize the converter design for efficiency at full load. Special attention is paid to semiconductor losses, which are shown to be dominant, with the parasitic device capacitance losses being a significant component. A prototype of the proposed rectifier is constructed which verifies the accuracy of the models used for loss calculation and optimization.

Optimal design of a 5kW/dm 3 / 98.3% efficient TCM resonant transition single-phase PFC rectifier

In many applications single-phase PFC rectifiers should meet the demand for a high efficiency and a high power density at the same time. Depending on the weighting of these two design criteria, different topologies could be advantageous. As has been shown, with bridgeless PFC rectifiers an ultra high efficiency of 99.3% or a high power density of 5.6kW/dm3 could be realised. However, due to the hard switching operation it is not possible to achieve an exceptional efficiency and power density at the same time. Furthermore, SiC Schottky diodes are required for highly compact or highly efficient systems. Therefore, a triangular current mode (TCM), resonant-transition single phase PFC rectifier concept is presented in this paper, which overcomes both limitations. Besides a design procedure for optimising the chip area, also a simple and robust control concept, where a novel zero crossing detection concept is included, is explained and a prototype system as well as measurement results are presented for validating the concept and the design procedure.

Implementation of a novel control concept for reliable operation of a VIENNA rectifier under heavily unbalanced mains voltage conditions

The practical realization of a novel concept for output voltage control and mains voltage proportional guidance of the input currents of a three-phase/switch/level PWM (VIENNA) rectifier system being connected to a heavily unbalanced mains is presented. The control is investigated experimentally for a wide input voltage range 6.5 kW prototype of the VIENNA rectifier.

A new concept for reconstruction of the input phase currents of a three-phase/switch/level PWM (VIENNA) rectifier based on neutral point current measurement

A novel concept utilizing the neutral point current information which is gained by an AC current sense transformer or a shunt for observer-based continuous reconstruction of the input phase currents of a three-phase/switch/level boost-type PWM (VIENNA) rectifier system is proposed. The basic principle of operation and the dimensioning of the observer circuit which in modified form also could feature an output voltage earth fault detection are discussed in detail. Furthermore, results of a practical application of the system in connection with a highly dynamic ramp comparison mains current control of a 10 kW laboratory model of the VIENNA rectifier are given.

A new concept for minimizing high-frequency common-mode EMI of three-phase PWM rectifier systems keeping high utilization of the output voltage

Three-phase PWM rectifier systems in principle show a common-mode voltage with switching frequency between the mains neutral point and the center point of the output voltage. Without any counter-measures this leads to a high common-mode noise emission of the system and possibly to disturbances of the control unit of the converter being fed by the rectifier. In this paper a detailed discussion of the formation of the common-mode voltage for the VIENNA Rectifier I is given and a modified circuit topology which significantly reduces the switching frequency component of the common-mode voltage is given. The proposed circuit modification is applicable also to other three-phase PWM rectifier topologies. The filtering concept is analyzed by digital simulation and guidelines for the dimensioning of the filter components are given. The reduction of the common-mode noise is verified by EMI measurements taken from a 10 kW laboratory unit of a VIENNA Rectifier I. Finally, the advantages and drawbacks of the proposed filtering concept are compiled in the form of an overview.

A novel concept for mains voltage proportional input current shaping of a VIENNA rectifier eliminating controller multipliers. I. Basic theoretical considerations and experimental verification

Part I of this paper proposes a novel mains voltage proportional input current control concept eliminating the multiplication of the output voltage controller output and the mains AC phase voltages for the derivation of mains phase current reference values of a three phase/level/switch PWM (VIENNA) rectifier system. Furthermore, the concept features a low input current ripple amplitude as, e.g., achieved for space vector modulation, a low amplitude of the 3rd harmonic of the current flowing into the output voltage center point and a wide range of modulation. The practical realization of the analog control concept as well as experimental results for application with a 5 kW prototype of the PWM rectifier are presented. Furthermore, a control scheme which relies only on the absolute values of the input phase currents and a modified control scheme which does not require information about the mains phase voltages and therefore is ideally suited as a basis for the development of an integrated control circuit for three phase power factor correction is presented.