A major disadvantage of existing condition monitoring methods is the need for additional sensors and measuring equipment. In this work, this disadvantage is eliminated by completely avoiding additional hardware. Instead, software-based methods from the field of machine learning are used. Therefore, measurement signals and control output variables are utilized which are acquired and processed in any power electronic system for the purpose of converter control. The publication focuses on two main converter components: power semiconductors and DC link capacitor. For each component, the aging mechanisms that have been studied in the literature are explained. Based on the aging mechanisms, the degradation indicators are identified. Then, a converter model is built that allows the variation of degradation indicators in order to analyze their effects on the available data set. These findings form the basis for mathematical models, which detect future failure mechanisms of this type during converter operation. The test setup must offer the possibility of generating reproducible failure cases in various components with the aid of additional failure equipment. Finally, failure mechanisms are intentionally introduced at the test bench in order to validate the methodology of the developed approach.

In power electronics, the modular multilevel converter (MMC) is an easily scalable topology with an high output voltage quality. It is suitable for the transmission of large amounts of electrical power over long distances, which supports the realization of the ongoing energy transition. State-of-the-art methods require a comparatively large total cell capacitance in the system for energy pulsations during operation. In the present paper, in order to minimize this total capacitance, first a new method is developed to model the system, and second, by help of this model, optimal current trajectories are calculated. These currents are used for control to reduce the energy pulsation over the complete operating range, and thus, to better utilize the hardware. The new method independent on the Clarke transformations is implemented on a laboratory scale setup, and measurement results are presented which validate the new method. Furthermore, the new method is compared to the state-of-the-art method of the compensation of the 2nd harmonic and outperforms the latter significantly. This applies to the entire operating range for different power factors. A total reduction of up to 44\% of the energy pulsations is achieved.

More demanding harmonic limits of future grid standards are likely to aggravate the disadvantages associated with the use of passive filters in high-power converters. For this reason, active filters are an increasingly attractive alternative for reducing converter-induced harmonics, however their performance is often subject to a limited frequency range and a frequency-dependent attenuation. To further improve the potential of active filters for use with grid-connected power converters, this paper presents a novel control scheme for a parallel voltage-source active filter integrated into a high-power main converter. A detailed converter analysis shows that, due to the advantageous converter configuration, the active filter requires only fundamental frequency current control to mitigate converter-induced current harmonics. In contrast to conventional active filter applications, this avoids tuning to specific frequencies, identification of individual harmonics, measurement of high-frequency current ripple and high control bandwidth. As shown by simulation results, the active filter thus allows the mitigation of harmonics up to frequencies above the switching frequency of the main converter at only a small share of the total power and with small passive components. Finally, the effectiveness of the presented control scheme is verified experimentally using a silicon carbide demonstrator.

The ongoing transformation of power supply is leading to an increasing penetration of electrical grids with power converters, which are used in high-volume applications such as grid integration of renewable energy sources, energy storage systems, charging infrastructure for electric vehicles, and industrial electric drives. This results in significant and novel challenges for power quality and supply stability, which will likely result in further increasing demands on the converters used in the aforementioned applications. To address these challenges, this article presents a novel multilevel converter system for high-power grid applications, which is characterized by high output power and voltage quality, low energy pulsation, and high scalability and modularity. These characteristics are achieved by a novel concept of operation for the combination of a high-power main converter and a low-power cascaded H-bridge converter, which is derived based on the modeling and control design carried out for the proposed converter system. Simulation and experimental results verify the potential of the multilevel converter system and show that, compared to full-power multilevel converters, it allows high output voltage quality at high output power while maintaining low current load and low energy pulsation within the cells of the cascaded H-bridge converter.

Three integrated battery charger concepts based on six-phase electrical machines (EMs) are presented in this article. State-of-the-art topologies for galvanically isolated integrated chargers are reviewed as a basis for a novel integrated charger using the electrical drive (e-drive) as an isolated dc/dc converter, while the rotor is kept at standstill. Efficiency levels up to 88% and a cost breakdown are reported. Furthermore, the well-known reconfigurations of three-phase machines are reviewed and proposed as a basis for novel series-connected boost–buck converters, in which each stage is represented by one of the two three-phase machine windings and power electronic converters. The efficiency analysis of a 144-kW e-drive under this 6.6-kW dc biased battery charging condition is presented. The EM iron losses are calculated with finite-element method (FEM) using new Steinmetz parameters based on ring core measurements reflecting charging conditions. In addition, the dc and ac copper losses are analytically calculated. Moreover, inverter losses are analyzed based on their own switching loss measurements. The calculated efficiency of the integrated charger is compared with measurement results. The difference in efficiency between both remains within ±1% and efficiency levels up to 93% are reported. Finally, silicon carbide technology shows enhanced efficiencies.