Konrad Woronowicz

Design and Development of an Efficient Multilevel DC/AC Traction Inverter for Railway Transportation Electrification

This paper presents a new trend in the transportation industry to adopt the multilevel inverter-based propulsion systems and gives the design procedure of a new DC/AC three-phase six-level inverter for powering the rail metro cars. The proposed inverter is based on the multilevel converter as it possesses much lower component voltage stress compared with the pulsewidth-modulated (PWM) topologies. Space vector pulsewidth modulation (SVPWM) with back-to-back clamped diode voltage modulation operation is used to achieve voltage regulation and high efficiency at any loading condition. Zero-current-switching operation is achieved without using an auxiliary circuit, which leads to minimum switching losses. The novelty of the proposed inverter lies within the proposed control methodology, which uses a new switching pattern that guarantees a modified SVPWM to eliminate the unwanted harmonics from the output voltage. The new algorithm is developed using numerical iterative solution using the Newton-Raphson technique that was downloaded to the processor using digital signal processing developed code. The mathematical model is simple but proven to be effective. As a result, a higher operating efficiency at full load of 98.5% is achieved as compared to previous efficiency of 97%. Analytical, simulation, and experimental results of a 1500 Vdc/700 Vac 400-kW converter are presented to offer the proof of concept. The converter provides real estate savings for the train under floor layout, higher operating efficiency as well as better cost price than the conventional two-level PWM hard-switched converters.

A practical approach to inductive power transfer systems for transportation applications using boucherot bridge method

A practical method for analysis and design of inductive power transfer (IPT) systems is presented. A generalized frequency-domain analysis for steady-state operation of the system is provided. The proposed analytical method facilitates understanding of IPT systems through a systematic approach to designing a practical power transfer solution.

A Novel Linear Induction Motor Equivalent-Circuit With Optimized End Effect Model

A new method to model the end effect for single-sided short-primary linear induction motors (LIMs) is developed by considering the effect of nonzero leakage inductance of the secondary. The well-established equivalent circuit model-introduced by Duncan in the 1980s-is improved by taking nonzero leakage inductance into account. This new approach closes the gap between predictions and test results of a transit LIM. It also allows for reliable model utilization in engineering practice. The analytical predictions are verified with the field test data collected from a full-scale LIM designed for public transit systems.

Reactive power compensation in three phase high output inductive power transfer

Inductive power transfer becomes increasingly more popular as a method for contact less charging of high power loads. Enabled by the rapid progress in power electronics components and controls, the power transfer solutions cross the previously unattainable boundaries of power levels and cost limits. Because of the high frequencies necessary for voltage induction in the secondary parts of the transformers and because of a rather low magnetic coupling, the system would have to constantly supply high levels of the reactive power, generating very high losses and limiting the available output power. Various tuning techniques have developed to tune-out the reactive power. In this paper a systematic approach to tuning of a high power three phase coupled transformer is presented and arithmetical calculations backed by simulation utilizing its values from the electromagnetic FEA analysis. The approach is based on the fundamental frequency approximation neglecting the higher order harmonics which is valid for tuning the system at the fundamental harmonics of the switching frequency.

A general approach to tuning of a dual secondary winding transformer for wireless power transfer

The concept of multi secondary transformer is well known in electrical engineering. Extending that concept to wireless power transfer transformers brings advantages such as the possibility of supplying power to independent subsystems or to increase primary to secondary misalignment tolerances. An example of such transformer is a long primary multiple car charging system or multi secondary rail vehicle. In this paper an analysis of a WPT transformer with dual load output is provided. A systematic approach is used to specify a sufficient condition for decoupling the secondaries to achieve load independent compensation and tuning. It is further shown that the proposed decoupling condition is applicable to an arbitrary number of secondaries.

A line and load independent constant-frequency zero-voltage-switching series resonant converter

Frequency modulation is often used in series resonant converters to gain output voltage regulation. Variable frequency however brings challenges for EMI filter and switch driver design and the desirable zero voltage switching cannot be maintained at light load conditions. This paper presents time-domain steady-state analysis of fixed-frequency series resonant converters with phase shift modulation. Three operation modes are identified and the mode boundaries are demonstrated. Based on this a passive robust auxiliary circuit is proposed to ensure the zero voltage switching of the converter in all three modes. The achievement of zero voltage switching is confirmed by experimental results.

Time-Domain Analysis of Voltage-Driven Series–Series Compensated Inductive Power Transfer Topology

This paper presents, initially, a systematic derivation of extended first harmonic approximation (FHA) analysis and, later, a comprehensive time-domain (T-D) analysis to study series–series compensated inductive power transfer (IPT) systems with a diode bridge rectifier. Further, the paper shows that both FHA and T-D methods predict four mutually exclusive and collectively exhaustive modes of operation. Explicit criteria for each operation mode and formulae for mode boundaries are derived and it is concluded that FHA can explain three of four modes. The proposed T-D analysis is capable of describing the quantitative behavior of the system in all four operation modes with closed-form equations for all the mode boundaries. This analysis provides an objective basis to assess the accuracy of FHA predictions under the entire operating conditions. Quantitative comparison of key variables revealed that the FHA results can be unacceptably inaccurate for certain operating points. It is shown that the T-D approach provides a comprehensive design base for series–series compensated IPT without a need to know the load value. The T-D predictions are validated by experiment. A mathematical design calculator tool is also provided to the reader to visualize the mode boundaries, all the waveforms and the numerical results from both methods.

Effects of parallel load-side compensation in wireless power transfer

High reliability and ever increasing cost-effectiveness of power electronics components and digital processors have resulted in high interests in inductive power transfer techniques. The interest is directed mostly at electric and hybrid passenger car battery charging, although the first solutions have already been conceptualized and turned into homologated products for much higher power levels for bus and light rail vehicles. Transformers used for automotive applications have a large air gap and relatively low coupling coefficients. High levels of output power require tuning techniques in order to eliminate or decrease the associated reactive power. In this paper a parallel load side compensation technique and its consequences are described. The analysis is done by utilizing a novel method based on Boucherot Bridge model for the wireless power transformer. The analytical results are confirmed by circuit simulation using the transformer parameters derived from finite element electromagnetic analysis.

Single-Phase Zero Reactive Power Wireless Power Transfer Topologies Based on Boucherot Bridge Circuit Concept

High reliability and cost effectiveness of power electronic components have resulted in high level of interest in wireless power transfer techniques among academic and industrial professionals. Since the major interest is directed toward automotive and rail industries for electromagnetically coupled fast battery charging systems, a special transformer with a large gap and relatively large leakage inductance is used. To achieve desired voltage and power levels with a reasonable compact-sized transformer, high frequencies in the order of 20-100 kHz are preferred, producing high levels of reactive power, which limit the amount of transferred power and efficiency if not compensated. There are four basic transformer compensation topologies reported in the literature, each being the combination of series and/or parallel compensations. This paper presents all four topologies and the associated input-to-output dependence based on a Boucherot bridge model of a transformer. Analytical modeling predictions are supported by finite-element analysis results to provide the proof of conceptual finding of this technology. Design procedures for each of the four configurations are presented in detail. A comparison study that highlights the merits and demerits of each configuration is given to help determine the appropriateness of each transformer configuration to a particular application.

A robust fixed-frequency soft switching series resonant converter for transportation applications

Frequency modulation is often used in series resonant converters to gain output voltage regulation. Variable frequency however brings challenges for EMI filter and switch driver design and the desirable zero voltage switching cannot be maintained at light load conditions. This paper presents time-domain steady-state analysis of fixed-frequency series resonant converters with phase shift modulation. Three operation modes are identified and the mode boundaries are demonstrated. Based on this a passive robust auxiliary circuit is proposed to ensure the zero voltage switching of the converter in all three modes. The achievement of zero voltage switching is confirmed by experimental results.