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A novel battery energy storage system (BESS) based on an enhanced modular multilevel converter (M2C) with the ability to switch its modules in parallel is being presented. Compared to a full-bridge M2C equipped with batteries as energy storage elements on its submodules, the losses are reduced by 20%. The raise in efficiency is thoroughly explained as well as its reliability. Its high efficiency,...
Supplying 25 kV, 50 Hz railway systems is a challenging task due to the load characteristics of those systems. Hence, several approaches are developed to improve their grid integration with the static frequency converter based substations. However, this supply system can be further refined by the application of a dc grid. Hence, this paper presents and discusses one possible approach to enhance the...
Multilevel converters (MCs) are utilized in medium voltage (MV) high power applications due to its higher efficiency than two level converters. On the other hand, modular multilevel converters (MMCs) provide several advantages with regard to other MCs, such as higher scalability, reliability and no requirement of a common DC capacitor. Particularly, low switching frequency modulations, such as (2N+1)...
The use of a model predictive control algorithm to reduce the losses in a 3L-NPC inverter with SiC neutral point diodes was investigated. It considers the reduced switching losses associated with the commutations that involve a SiC diode. A loss reduction of 5% is achieved compared to a standard sine-triangle modulation.
For drive train efficiency estimation, three-level inverters are analyzed regarding different modulation techniques and switching frequencies. In this paper an optimized operating mode selector is proposed to choose a loss optimal modulation technique and switching frequency for each operating point. Energy savings due to the operating mode selector are validated on a driving cycle.
Efficient HV DC-DC converters are one key component of a future HVDC backbone grid. In this paper three promising MMC based HV DC-DC converter topologies, namely the front-to-front converter, the HVDC auto transformer and the modular multilevel DC converter are compared in terms of functionality, conversion efficiency and topology effort.
New standards and requirements for energy efficiency and power loss measurements for variable speed drives are presented. The power losses of typical variable speed drives with rated power of 22 kW are analyzed and alternatives to increase the drives efficiency together with system impact are investigated. An innovative motor drive with silicon carbide (SiC) devices and integrated LC filter is discussed...
Multi-level flying-capacitor converters are a promising topology for low-power applications. Conventional buck, 3- and 4-level converters have been modeled as a geometric program and optimized for loss and volume. Results show that 3- and 4-level converters are both smaller and more efficient over a wide range of design parameters.
The self-consumption of PV-systems can be increased with a battery. The proposed three-phase inverter provides three independent DC inputs that can each be connected to a battery or a PV-string. The innovative topology allows energy flow in each direction at a very high efficiency (> 98 % in each converter stage). The application of SiC transistors leads to a higher switching frequency (48 kHz)...
Recent studies show that Silicon Carbide and Gallium Nitride based power semiconductors promise better performance over conventional Silicon based devices. In this study, the performance analysis of a three level inverter based on SiC and GaN is discussed for photovoltaic applications. The converter can achieve 99.2% efficiency at 16kHz switching frequency and 1.4kW output power, and operate with...
Multilevel inverter topologies are an alternative for a wide range of low voltage electrical drives. They can reduce power semiconductor losses, voltage transients at the motor windings, harmonic losses in the cables and common mode disturbance currents. In the voltage range below 1000 V highly optimized switches with lower losses are available. The paper compares the component losses (power semiconductor...
An exhaustive study on the circulating currents and their consequences in modular multilevel converters for HVDC applications is presented. The first part is a review of an analytical study of the converter, aimed to minimize the capacitors voltage ripple. In the second part the effects on the system efficiency are presented.
The low voltage direct current (LVDC) distribution network is a promising solution to be considered in future smart grids. For facilitating the design of cost effective LVDC distribution networks, the total losses of the network with different configurations are evaluated and compared. The possibility to connect the customer loads asymmetrically, when the bipolar DC network is used and the fact that...
In this work different three-level topologies suitable for PV systems are analyzed. First the basic operation principles of the Neutral Point Clamped (NPC), Active Neutral Point Clamped (ANPC) and Mixed Voltage Neutral Point Clamped (MNPC) topologies are explained and the used PWM strategies are presented. All three topologies are realized in hardware on a modular test setup, so that it is possible...
For the upcoming need to transfer bulk power over long onshore distances, HVDC power transmission is the preferred choice. However, components like HVDC-DC converters and a protection concept for DC line faults present challenges, that still have to be solved. As up today, the sections of a segmented DC transmission corridor would still be linked via an AC connection, leading to high transformation...
Recent studies have pointed out the benefits of using Silicon Carbide (SiC) devices in photo-voltaic power conversion. In Particular, SiC Power MOSFET technology has greatly advanced over the last years and has presently reached sufficient maturity to stimulate a concrete interest in the development of power conversion circuits based entirely on this technology, in view of the clear potential advantages...
For the upcoming need to transfer bulk power over long onshore distances, HVDC power transmission is the preferred choice. However, components like HVDC-DC converters and a protection concept for DC line faults present challenges, that still have to be solved. As up today, the sections of a segmented DC transmission corridor would still be linked via an AC connection, leading to high transformation...
Due to new grid codes for grid connected photovoltaic power generation, since 2012 PV inverters have to be able to feed in reactive power down to a power factor of cos(ϕ) = 0.9 besides their normal operation with pure active power [1]. In this paper the influence of different semiconductors on the power losses as function of the power factor will be studied on the base of a three-level MNPC topology...
Nowadays, power electronic transformers (PETs) are under consideration in various applications since PETs offer several advantages over traditional low-frequency transformers, including reduced weight and energy saving. This paper describes the practical design and implementation of a modular PET demonstrator, which is to be installed in a test locomotive and to operate in the field. The experimental...
Presented here is a three level voltage source inverter for electric drives, uninterruptable power supplies and for mains feeds. Unlike the usual hard switching topologies, it is implemented as completely soft switching. A novel patented snubber circuit is added, which is structured very simply and consists of only a few passive components. This snubber circuit works in principle without any losses;...
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