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The modular multilevel converter (MMC) has become the most promising converter technology for high power applications. However, to get more number of levels in the output voltage, a conventional MMC requires large number of submodules. The main technical challenges of an MMC, with a large number of submodules, are the requirement of large number of semiconductor switches, submodule capacitors and...
In this paper, three configurations of three-phase ac-dc cascaded converters are presented. They are referred as basic configurations, and are composed by two three-phase bridges, where the second bridge is cascaded to the first by means of a three-phase injection transformer. Basic configurations have one bidirectional option (composed only by IGBT switches), and two unidirectional ones (composed...
Magnetic Core Characterization is returning as a critical area of research. This is due in part to the rise of wide bandgap semiconductors that have enabled new applications, new converter topologies and system designs that are pushing the limits of passive components. Similarly, new core materials are opening design spaces previously unfilled by legacy cores. With all of these new opportunities,...
This paper presents a case study of different control approaches for a single phase Dual Active Bridge (DAB) based MVDC Shipboard power system (SPS). The Line Regulating Converters (LRCs) are based on DAB topology and the load side converters or Point of Load Converters (POLs) are based on buck topology. The tightly controlled POLs exhibit a constant power load (CPL) behaviour, which has a destabilising...
A novel virtual voltage control strategy is proposed for modular multilevel converter in order to reduce the quantity of voltage sensors at the terminal. The output voltage of the inverter is obtained through the upper and lower arm currents of the converter and used to trace the reference active and reactive power, respectively. According to the Routh-Hurwitz criterion, the root trajectory of the...
Dual active bridge (DAB) with input-series output-parallel (ISOP) structure is capable to interconnect low voltage DC micro grid with medium/high voltage DC distribution grid, named as DC solid state transformer (DCSST). This paper presents a combined decoupling control strategy for the DCSST, which aims to achieve input voltage sharing among sub-modules and enhance voltage control of the parallel...
This paper presents a novel control strategy for isolated multilevel inverters. This converter has been chosen due to the autonomy of each full bridge. Other advantage is the feasibility of handling the power by cell when there are changes in the batteries state of charge (SOC). In order to take advantage of these benefits, a control strategy has been developed. The main goal of the proposed solution...
In this study, a new multilevel inverter topology using modified H bridge with reduced number of switches has been proposed which can be operated in “symmetric” or “asymmetric” modes. Higher number of levels leads to generation of a high quality with low Total Harmonic Distortion (THD) output voltage waveform. To increase number of voltage levels, for determination of magnitude of DC voltage sources...
This paper discusses the design and analysis of a 380/12 V DC-DC high efficient LLC converter having a power output of 750W. The ripple in output voltage is brought down to 0.09V. It works with an efficiency of 96.1 percent at full load, 97.2 percent efficiency at 50 percent load and 91.2 percent efficiency at 10 percent load. Since zero voltage and zero current switching are used, losses are reduced...
This paper proposes the modeling and control of a Solid-State Transformer built using a three stage conversion topology. First, a rectification stage is used, where a three-phase high-voltage AC signal is converted to a DC level; this stage is then followed by a DC-DC converter, and finally an inverter is used to convert the DC into a three-phase low-voltage AC signal. The adopted topology is modeled...
This paper proposes a new methodology of firing to increase the number of levels in the output voltage of a conventional seven-level inverter. In a conventional 7-level cascaded H bridge (CHB), by employing a new firing scheme with unequal DC sources, an output waveform of 21-levels has been generated. Thus near sinusoidal waveform has been achieved with the same number of switches. The simulation...
This paper investigates a three-level three-phase Dual Active Bridge (DAB) dc-dc converter with a star-delta connected transformer. The soft-switching region is analyzed for two and three-level operation, using symmetrical voltage waveforms, showing an increased ZVS range for three-level operation. A large number of switching modes are identified and are modeled with piecewise-linear equations. To...
This paper investigates a nine-switch converter topology for STATCOM (Static Synchronous Compensator) application as well as the developed controller and the modulation strategy. The focus of the paper is to study the grid code compliance of a wind farm integrated into the grid while using the aforementioned converter topology. A numerical example is also given so as to examine the dynamic range of...
In this paper, two types of new submodule (SM) circuits are proposed for modular multilevel current source converter (MMCSC) with dc fault ride through capability, namely, type I diagonal bridge SM (DBSM) and type II DBSM. The topologies and possible operation states of the two types of DBSMs are presented. Each type of DBSM is capable of providing bipolar voltages in unidirectional current. Replacing...
A semi-dual-bridge resonant converter derived from the popular dual-bridge resonant converter (DBRC) topology is proposed in this paper for applications requiring only unidirectional power flow such as various types of DC power supplies, battery chargers in electric vehicles and dc-dc stage of different types of photovoltaic inverters. Based on the similarity of topology to the DBRC converter, the...
This paper presents a control strategy of modular multilevel converter which produces variable DC output from a three phase AC source. With this proposed strategy the output DC voltage of the converter can be bidirectional (i.e. both positive and negative) and can be varied to a value higher than the peak input voltage (boost), or to a value lower than the peak input voltage (buck). A simple synchronous...
This paper proposes an elementary super lift boost converter to achieve high voltage transfer gains, high conversion ratio in addition with isolated full bridge boost converter are used in high voltage applications. The proposed circuit eliminates some of the drawbacks in the conventional full bridge boost converter such as voltage and current stresses through the power converter devices, possibility...
Solar is a kind of new energy, and photovoltaic power generation is an important way of distributed generation; FREEDM system is a kind of Energy Internet model, which is presented by Professor Alex Q. Huang from North Carolina State University in 2008. Combining the advantages of photovoltaic power generation and FREEDM system, this paper proposes a kind of grid-connected photovoltaic power generation...
Transformer-less string PV inverter is getting more and more widely utilized due to its higher efficiency, smaller volume and weight. However, without the galvanic isolation, the leakage current limitation and operation safety became the key issues of transformer-less inverters. This paper simplifies the leakage current generation circuit model and presents a leakage current estimation method both...
Multipulse rectifiers are one of the solutions for current harmonics mitigation. In this paper, a novel 20-pulse full-wave AC-DC converter based in two three-to-five phases delta/zigzag transformers connected in series is proposed. A theoretical investigation of the proposed rectifier operation is presented. Afterwards this structure is simulated to obtain more real operation results. A prototype...
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