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This paper presents a new structure of a power sharing controller for a modular based dual active bridge (DAB) DC/DC converter. The modular topology is based on input-series output-parallel (ISOP) connection of DAB modules suitable for a voltage step down application at medium voltage level. Since DAB has bi-directional power flow capability, this connection would act as its dual input-parallel output-series...
A novel sub-module circuit is proposed in this paper based on the controllability theory. At first, traditional full bridge sub-modules (FBSM) of the MMC is modeled as a switched linear system, then controllability of the switched linear system model of the sub-module circuit is studied. It is found that the sub-module circuit is state controllable with only four operation modes adopted in the model...
In three-phase dual-active-bridge (DAB) converter, the zero-voltage-switching (ZVS) range, DC capacitor ripple current and converter efficiency are significantly impacted by the selectable system parameters, including transformer turn ratio n, switching frequency f and leakage inductance Lk. The converter performance also varies with different operation conditions, i.e., input voltage, output voltage...
Cascaded multilevel inverter (MLI) topologies have received an attractive solution for grid connected PV system. In this paper, two-cascaded MLI topologies are presented for grid connected PV system. These are seven level cascaded H-bridge multilevel inverter and three phase cascaded voltage source multilevel inverter. In both presented MLI configurations, each PV module is connected to one DC-DC...
As the fluctuation of sub-module capacitance voltage when MMC operates at low frequency, the application of MMC in the field of motor drive has been limited. Therefore, this paper proposes a low frequency control method for the MMC with tuned filter circuit. Based on the theoretical analysis for this tuned filter, the circulating current of 2nd frequency could be suppressed effectively at rated frequency...
The modular multilevel converter (MMC), is widely adopted in high voltage applications because of its simplicity and modularity. However, the current and power flow is very complicated. As a result, methods proposed for capacitor reduction, which is required to stored line frequency related circulating energy, all went through complicated mathematical derivation. C. Li proposed a state plane analysis...
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...
For Smart Transformers (ST), reliability is one of the major problems when compared to the traditional low-frequency transformers. Modular ST with advanced control algorithms could increase the reliability compared to the non-modular solutions. This could be achieved by distributing differently the power among the cells depending on their aging. This unequal power transfer is a challenge for Cascaded...
Due to the increasing demands of safe and efficient renewable energy systems, isolated DC-DC converters became widely used in this field as the essential power conversion blocks. At the same time, such converters are demanded for wide input voltage range and fault tolerance as desirable features. This paper proposes a isolated boost full bridge DC-DC converter which features wide input range and resilient...
A full bridge modular multilevel converter (FBMMC) can work in buck and boost modes. It is thus suitable for grid-connected applications in which the dc link voltage varies over a wide range. In this work the emphasis is set on the steady-state analysis of the grid-connected FBMMC under different levels of the dc link voltage. Two control strategies for the dc capacitor voltage are considered and...
This paper presents a single-stage isolated softswitching tri-port converter for integrating a renewable resource like solar PV, and energy storage with single-phase AC grid through high-frequency galvanic isolation. The single-stage approach reduces the component count, and the full-range softswitching feature realizes higher efficiencies compared to the state-of-the-art methods. A significant advantage...
The modular multilevel cascaded converter (MMCC) has been considered as a promising solution for integrating the utility-grade renewables to the medium-voltage (MV) power system. However, the implementation becomes difficult with the centralized control architecture as the cascaded numbers increase. This paper presents a distributed control technique for the cascaded converter, which significantly...
Multi-megawatt scale isolated DC-DC converters are likely to become increasingly popular as means to interconnect the MVDC grids of different voltage levels. Three-phase dual active bridge DC-DC (3DAB) converters operating with the zero-voltage switching (ZVS) is a promising candidate for the target multi-megawatt application. This paper presents a systematic approach of the design considerations...
This paper presents a single-stage soft-switching high-frequency link isolated converter for bidirectional motor drive applications. The ‘minimal’ topology is based on the recently proposed soft-switching solid-state transformer (S4T) with a single current-source power conversion stage. This single stage approach reduces total switch rating, provides sinusoidal input and output voltages, and uses...
This paper proposes a 5-level single-phase multilevel inverter topology with reduced number of components. In order to validate the proposed structure, simulation and experimental results are presented. In addition, the proposed topology is compared with an existing counterpart structure in terms of number of levels and number of devices and value of power supply.
A battery-free power management circuit (PMC) for an impact-type piezoelectric energy harvester for micro wind is presented in this paper. As the energy generated by micro wind is intermittent, sleep mode is adopted for the PMC to save power. A new energy sensing circuit is designed to detect the energy level generated by the piezoelectric cantilever and then to control the operation modes, sleep...
A current-fed soft-switching three-phase dc-dc converter suitable for high-power high-voltage-gain applications is presented in this paper. Proposed converter consists of constant-current-fed three-phase inverting bridge with reverse-blocking switches, primary-Y-connected three-phase transformer and voltage-doubler rectifier modules at the output. The rectifier modules are connected in series at the...
As the penetration level of wind power increases, displacing conventional power generation with wind power will reduce the inertia of power system and decrease the frequency stability. Energy storage devices with only 5% energy storage of wind farm's rated capacity can produce the same virtual inertia as a same capacity synchronous generator. To reduce the additional costs of individual energy storage...
This paper presents theoretical and experimental discussions on low-voltage-ride-through (LVRT) operation of a modular multilevel single-delta bridge-cell (SDBC) inverter intended for utility-scale photovoltaic (PV) systems. As the penetration of distributed generation from renewable energy sources connected to medium- and high-voltage grids increases, grid-tied inverters progressively need to abide...
This paper presents a novel method for fault detection and location in modular five-level converters (MFLC) based on stacked sparse autoencoder (SSAE). SSAE is composed of multiple SAE and a softmax classifier. The capacitor voltage signals of all sub-modules (SMs) in the MFLC circuit are combined into a multi-channel signal. By moving window along the multi-channel signal, a set of signal segments...
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