Benjamin Sahan

A Single-Stage PV Module Integrated Converter Based on a Low-Power Current-Source Inverter

This paper presents a transformerless three-phase inverter designed for the integration into a special type of a photovoltaic (PV) module, which is capable of providing an output voltage of several hundred volts. The chosen topology, a current-source inverter, features a single-stage power conversion system that directly feeds into the grid. The principle operation and control is described, and a modified modulation strategy is proposed to attenuate common-mode currents. A robust and highly efficient laboratory prototype of a 250-W module integrated converter has been implemented and tested. Its compact and flat design allows the direct attachment to the PV module.

LCL filter design for grid-connected NPC inverters in offshore wind turbines

This paper deals with the analysis, design and optimization of a LCL filter topology to connect a 7MW NPC inverter to the grid. Following the requirements based on the IEEE 519-1992 recommendation and the German Guideline VDEW, simulation results were evaluated in order to access the performance of the proposed filter and the quality of the current injected into the grid.

Comparative Evaluation of Three-Phase Current Source Inverters for Grid Interfacing of Distributed and Renewable Energy Systems

Despite the rapid growth of self-commutated inverter technology, the well-known current source inverter (CSI) has not achieved significant practical application so far. This raised the question regarding the fundamental criteria that could either prevent or promote the use of such inverters, especially considering emerging fields of application such as grid integration of renewable sources. This paper will, thus, focus on a systematic comparison between circuits based on the CSI and voltage source inverter (VSI). For such purpose, dimensionless benchmark factors were derived. The pulse width-modulated CSI with its inherent step-up capability alongside the indirect CSI (ICSI) with only two high-frequency switches features very interesting characteristics in terms of low switching losses and high inductor power density. However, both topologies show constraints with respect to the provision of reactive power. Two experimental setups have been implemented demonstrating the technical feasibility of different CSI solutions as a grid interface.

Novel grid-connected non-isolated converters for photovoltaic systems with grounded generator

In the photovoltaic branch, transformerless inverters are nowadays the majority of the systems installed in Europe, mainly because of the higher level of efficiency and reduced cost and weight when compared with their counterparts with transformer, whether this concerns low- frequency or high-frequency models. Nevertheless, some limitations arise for the operation of such systems, mainly regarding the fact that normally the panel output cannot be grounded, what is, for example not allowed in USA. Non- grounded operation of panels composed of some new cells technologies can bring undesired effects like cell aging and efficiency reduction. In addition, security matters regarding leakage current due to the panel parasitic capacitance are also a common problem in such systems. In order to address such matters, this paper proposes a novel DC-DC converter for the application in transformerless photovoltaic systems. As main characteristic, it allows the grounding of the negative output of the photovoltaic array and provides a bipolar output voltage. Following the proposition of the circuit, the analysis and evaluation will be performed. A prototype was built and the experimental results are presented in the end.

Analysis and proposition of a PV module integrated converter with high voltage gain capability in a non-isolated topology

Usually considered as one of the future solutions for grid connection of photovoltaic systems, module integrated converters were already the focus of several researches and projects. Most of the proposed approaches relied so far on the use of high frequency step-up transformers either in isolated operation or integrated in isolated dc-dc topologies. This paper analyses the possibility of using non-isolated topologies to achieve the necessary high-voltage gain for grid connection. Several circuits were analyzed and the best suited one for the current application was evaluated and optimized. Experimental results are presented in the final section.

Development of a single-stage three-phase PV module integrated converter

A transformerless three-phase power conditioning unit interfacing with a high voltage (>200 V) photovoltaic module is presented. The chosen topology, a Current Source Inverter, features a single-stage power conversion system that feeds directly into the grid. A robust and highly efficient laboratory prototype of a Module Integrated Converter has been implemented and demonstrated by experimental results.

Evaluation of a NPC1 phase leg built from three standard IGBT modules for 1500 VDC photovoltaic central inverters up to 800 kVA

This paper presents the concept and characterization of a NPC1 phase leg built up out of three PrimePACK™ 2 power modules with .XT and 1200 V IGBT5. The target application of such a topology is 1500 V solar central inverter. After a short description of the cosmic ray reliability issues leading to the NPC1 approach, different design concepts will be discussed. Double pulse measurements have been used to characterize the overvoltage during the long commutation in reactive power mode. The moderate stray inductance of the long commutation path within the design of the PrimePACK™ 2 NPC1 phase leg allows a safe turn-off without the need of clamping diodes in the driver. Furthermore the power conversion efficiency as well as the maximum power rating of a solar central inverter using the presented concept has been investigated by feeding the measured switching energies into simulations. It turns out that a power rating of more than 800 kVA can be reached due to the higher power density and more efficient switching thanks to the .XT and IGBT5 technology.

Application of SiC Normally-On JFETs in Photovoltaic Power Converters: Suitable Circuits and Potentials

Photovoltaic systems have been considered as one of most promising fields of application for SiC semiconductors mainly due to the requirements for very high efficiency values. Several other system aspects like volume and cost may also profit from the interesting characteristics of such innovative devices. One promising example is the vertical JFET, mainly due to its relative structural simplicity. Nevertheless, its inherent normally-on characteristic calls for especially tailored topologies, as some suitable applications for photovoltaic systems will be presented.