Jan Abraham Ferreira’s research while affiliated with Delft University of Technology and other places

There exists two well known types of power transfer ac or dc. Power transfer at multiple frequencies has not yet gained much attention. This paper aims at bringing out such topologies, which are capable of integrating different electrical power sources (ac or dc) irrespective of its frequency of generation, form a multi-frequency bus, transmit power over a single line and extract/convert them at the load side. This leads to the definition of unified utility/grid concept. For this, the paper presents more insight into three possible multi-frequency converter topologies with renewable energy sources (RESs)/battery integration. The proposed topologies work on the principle of orthogonal power transfer. Furthermore, power transfer at multiple frequencies shows an effective way of decoupling the individual sources of the system. Finally, the feasibility of transferring power at multiple frequencies is validated experimentally and the results are discussed herein along with its potential benefits.

In this paper, a coupled-inductor based LCC resonant converter with the primary-parallel-secondary-series (PPSS) configuration is proposed to achieve output-voltage sharing ability for the HV generator applications. The PPSS configuration of the LCC resonant converter with voltage multipliers is introduced to achieve high output-voltage and increase the output-power level. However, the variations of the magnetizing inductance, leakage inductance and winding capacitance of the HV transformer and voltage multiplier impact on the output-voltage sharing. Subsequently, the resonant inductors in the primary side of the conventional LCC resonant converters with the PPSS configuration are coupled to achieve the output-voltage sharing without any additional circuits and control efforts. Furthermore, an analytical equivalent circuit model considering the magnetizing inductor of the HV transformer is derived to analyze the output-voltage sharing ability. Moreover, the design method for the coupled inductors considering the output-voltage sharing affected by the leakage inductance of the coupled inductors is presented. Finally, the output-voltage sharing of the proposed coupled-inductor based LCC resonant converter with the PPSS configuration is validated by the experimental results of a 50V input, 5kV output 100W prototype. The experimental results show that the unbalance voltage degree decreases from 67.7% to 8.5% with the utilization of the coupled-inductor.

In this paper, a unified equivalent circuit model which can simplify the design and analysis of a family of high voltage (HV) generation architectures based on the series-parallel (LCC) resonant converter is proposed. Firstly, four HV generation architectures are reviewed in terms of the modularization level of HV transformers and rectifiers. Next, the unified equivalent resistor and capacitor (RC) model which can be easily embedded into the resonant tank to replace the complex HV transformers and rectifiers is derived. The generic model can be applied to different architectures, voltage multiplier topologies, stage and polarities number. Further analysis of the power factor of the resonant tank, the voltage gain and electrical stresses of power components is achieved with the derived equivalent circuit model. Subsequently, a comprehensive design methodology considering the power factor, conduction angle and quality factor is presented, which leads to low electrical stresses on the components and high efficiency. Furthermore, the parameter selection constraint based on the power factor, conduction angle and quality factor is derived. Finally, the proposed unified equivalent model and design methodology are validated by the experimental results of a 250V input, 20kV output 500W HV generator hardware prototype with distributed transformers and voltage multipliers.

This paper describes the behavior of voltage weak DC distribution systems. These systems have relatively small system capacitance. The size of system capacitance, which stores energy, has a considerable effect on the value of fault currents, control complexity, and system reliability. A number of potential definitions of voltage weak DC distribution systems are proposed. These definitions address the main characteristics of voltage weak systems. A small signal model of a general voltage weak DC distribution system is developed in order to observe sufficient conditions for system stability. This is achieved by analyzing the dominant poles. The source converters are modeled as droop-controlled current sources in parallel with their respective terminal capacitors. As constant power loads have incremental negative impedances, which affect the system stability, especially, in voltage weak system, ideal constant power loads with their terminal capacitors are included in the small signal model. A three-node voltage weak DC distribution grid is analyzed, as a case study, by implementing the developed small signal model. The effects on system stability by the values of system capacitance, cable inductance, and cable resistance are investigated using dominant pole placement. Likewise, the influence of proportional-integral regulators and droop coefficients of source converters on the stability of the system is examined. Finally, the three node DC distribution grid is developed in MATLAB/Simulink in order to demonstrate the influence of small capacitance on system stability. Moreover, effect of the rate of change of constant power loads on the system stability is simulated. These results are further compared and verified on a voltage weak DC experimental test bench with a 350 VDC bus voltage.

This paper deals with a generic methodology to evaluate the magnetic parameters of contactless power transfer systems. Neumann’s integral has been used to create a matrix method that can model the magnetics of single coils (circle, square, rectangle). The principle of superposition has been utilized to extend the theory to multi-coil geometries, such as double circular, double rectangle and double rectangle quadrature. Numerical and experimental validation has been performed to validate the analytical models developed. A rigorous application of the analysis has been carried out to study misalignment and hence the efficacy of various geometries to misalignment tolerance. The comparison of single-coil and multi-coil inductive power transfer systems (MCIPT) considering coupling variation with misalignment, power transferred and maximum efficiency is carried out.