Solid-state transformer based on modular multilevel converters

A new highly compact topology for solid-state transformers is presented. It is based on modular multilevel converters and, therefore, has their usual advantages such as superior voltage shape, high reliability, and scalability. It utilises arm inductors for the isolated energy transfer between two converters and thereby allows for a more compact build compared to the design that uses separate transformers

Condition Monitoring of Power Electronic Systems through Data Analysis of Measurement Signals and Control Output Variables

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

Determination of Electromagnetic Material Properties of Ferromagnetic Stainless Steel Used in Domestic Induction Heating Cookware

Design-oriented modeling approaches, such as finite element analyses (FEA), rely on accurate material data for the modeled hardware. In the case of cookware used in domestic induction heating (IH) systems, manufacturers rarely provide the necessary data. Therefore, this contribution presents results for the electromagnetic material properties of ferromagnetic stainless steel, typically used in cookware for domestic IH. The magnetic material properties are modeled using Jiles-Atherton hysteresis model. With the used measurement method, less effort in preparation of suited material specimen is needed compared to conventional measurement methods. The presented results for the magnetic material properties are validated using Epstein frame measurements. It is shown that the hysteresis curves are similar to each other for both measurement methods. Regarding the specific electrical resistance, the results are validated using a microhmmeter. The values determined for the specific resistance show good accordance for the different measurement methods

High Efficient Maximum Power Point Tracking for Multiple Solar Strings with GaN-Based HiLEM Circuit

This paper discusses the potentials of string based Maximum Power Point Tracking (MPPT) in ground-mounted solar power plants using the HiLEM topology. First, the functionality of the HiLEM circuit is described, then the planned setup with the HiLEM topology is presented. Finally, the operating principle is illustrated by a simulated shading scenario

GaN-Based Modular Multilevel Converter for Low-Voltage Grid Enables High Efficiency

Gallium Nitride (GaN) semiconductors with low inductance packages enable low switching losses and high efficiency. In this paper we present a compact arm PCB design with low loop inductance, allowing for fast and efficient switching. The PCB includes four full-bridge cells for a 7 kW Modular Multilevel Converter (MMC) for low-voltage grid applications

Multi-Parameter Analysis and Measurement of Resonances in Grid-Connected Converters with LCL Filters

LCL filters offer high attenuation of grid current ripple, but are challenging from a control perspective due to the resonant peak in their transfer function. The influence of selected individual parameters has already been the studied in several papers. This paper builds on this existing body of work and provides a more comprehensive analysis of all relevant variables influencing the resonance. In addition, dependencies between the parameters are explored. Stability and resonances are evaluated using frequency responses and an impedance based approach. Finally, the analysis results are confirmed with measurements

Quasi-Two-Level Flying-Capacitor-Converter for Medium Voltage Grid Applications

Medium voltage converters are becoming more relevant in future grid applications. Especially more wind and PV generation systems will be have to added and integrated into the grid in order to achieve the required reduction in CO2 emissions. High power generation units will be integrated into the grid at medium voltage level. Furthermore meshed MV grids will require interties based on MV converter technology. Today\u27s standard medium voltage converters are either based on the MMC technology or us 3L/5L approaches operated at low switching frequencies and containing bulky filters. Both concepts still lead to relatively high costs and low efficiencies which are major reasons for the slow spread of power converters in medium voltage grid applications.. Future grid applications demand less distortion, higher reliability and lower costs for converter systems at each voltage level. The Quasi-Two-Level operation of the flying capacitor multilevel converter with silicone-carbide (SiC) based semiconductors is a method for achieving these requirements for medium voltage converters. This paper presents a new concept for minimizing capacitance and balancing the capacitors with fast switching semiconductors. Moreover, a novel approach for limiting the overvoltage stress caused by the Quasi-Two-Level modulation of a flying capacitor converter is presented

Hardware Prototype for the Quasi-Two-Level Operation of a Three-Phase Flying Capacitor Converter for Medium Voltage Applications

Today’s standard medium voltage converters are operated with low switching frequencies and contain bulky passive components. One concept to change this is the Quasi-Two-Level operation of a multilevel converter with SiC semiconductors. A three-phase hardware setup for a Quasi-Two-Level Flying Capacitor Converter with control and measurement results in a test setup are presented