http://ieeexplore.ieee.org/iel5/5610941/5624686/05624745.pdf

Power electronics

The modular multilevel converter (MMC) has become the most promising converter technology for high-voltage direct current (HVDC) transmission systems. However, similar to any other voltage-sourced converter-based HVDC system, MMC-HVDC systems with the half-bridge submodules (SMs) lack the capability of handling dc-side short-circuit faults, which are of severe concern for overhead transmission lines. In this paper, two new SM circuit configurations as well as a hybrid design methodology to embed the dc-fault-handling capability in the MMC-HVDC systems are proposed. By combining the features of various SM configurations, the dc-fault current path through the freewheeling diodes is eliminated and the dc-fault current is enforced to zero. Several MMC configurations based on the proposed hybrid design method and various SM circuits, that is, the half-bridge, the full-bridge, the clamp-double, and the five-level cross-connected SMs, as well as the newly proposed unipolar-voltage full-bridge and three-level cross-connected SMs, are investigated and compared in terms of the dc-fault-handing capability, semiconductor power losses, and component requirements. The studies are carried out based on time-domain simulation in the PSCAD/EMTDC software environment for various SM configurations and dc-fault conditions. The reported study results demonstrate the proposed hybrid-designed MMC-HVDC system based on the combination of the half-bridge and the proposed SM circuits is the optimal design among all evaluated systems in terms of the dc-fault-handing capability, semiconductor power losses, and component requirements.

Hybrid Design of Modular Multilevel Converters for HVDC Systems Based on Various Submodule Circuits

To maximize the introduction of renewable energy, introducing grid energy storage systems are essential. Electrochemical energy storage system, i.e., battery system, exhibits high potential for grid energy storage application. A battery energy storage system is comprised of a battery module and a power conversion module. This paper starts by reviewing several potential battery systems, as well as an advanced aluminum-ion battery that currently has promising prospects in the electrochemical energy storage system. The characteristics of the batteries are reviewed and compared, including the materials, electrochemistry, performance and costs. The application prospect of the batteries is discussed. The paper summarizes the features of current and future grid energy storage battery, lists the advantages and disadvantages of different types of batteries, and points out that the performance and capacity of large-scale battery energy storage system depend on battery and power condition system (PCS). The power conversion system determines the operational condition of the entire energy storage system. The new generation wide bandgap semiconductor for power electronic technology is discussed from the perspective of performance, topology, model and non-linearity and is compared to the traditional silicon-based semiconductor. Finally, the application prospect of the new generation semiconductor technology in the energy storage system is indicated. This paper concludes the application status of the energy storage system in the renewable energy power generation and indicates the critical problems that need to be addressed during the construction and operation of the storage system.

Energy storage system: Current studies on batteries and power condition system

This paper proposes a nonunit protection scheme for DC microgrids (DC MGs) utilizing only local measurements. This scheme is developed based on the natural characteristics of DC current and its first and second derivatives under fault transients. Since it is based on local measurements, the problems associated with the communication delay are avoided. The selected protection scheme detects and discriminates the faults within a few microseconds of its inception. In this paper, a method to calculate the thresholds, used for the protection scheme, is also discussed. The proposed scheme is validated on a ring-type DC MG architecture under different fault scenarios and tested through MATLAB/Simulink simulations.

A Non-unit Protection Scheme for DC Microgrid Based on Local Measurements

Power switching devices based on wide bandgap semiconductor materials, such as silicon carbide (SiC) and gallium nitride (GaN) offer superior performance such as low switching and conduction losses, high voltage, high frequency, and high temperature operation. In this paper, a 600-V GaN switch and a 600-V GaN diode were tested in detail to understand the GaN device capabilities with respect to equivalent silicon-based devices such as IGBT and MOSFET. Detailed experimental loss models are developed and compared with datasheet models. Experimental setup of different power converters such as boost, buck-boost, and half-bridge inverter and associated comparative experimental results are presented. This paper also presents the investigations into the effectiveness of using GaN devices and higher switching frequencies in reducing the total size and cost of power conversion equipment such as an online UPS system.

Investigations of 600-V GaN HEMT and GaN Diode for Power Converter Applications

A new, smart distributed DC micro-grid suitable for high-penetration and that efficiently utilizes energy available from distributed, renewable generators is described. It is shown that energy saving in excess of 10% is feasible using the proposed DC power distribution system when compared to the current approach where inverters are used. This conclusion is substantiated by first-order calculations of a 50 kW solar photovoltaics (PV) array delivering power to DC-compatible electrical loads typically present in a household and/or commercial building. Further energy saving may be achieved by replacing state-of-the-art silicon-based DC-DC power converters with more-efficient emerging Gallium Nitride (GaN) FET converters at a reduced cost. The proposed DC micro-grid architecture is hybrid in nature and is easily scalable to other power levels. It is ideally suited for residential and commercial applications as well as for powering sustainable communities.

Smart DC micro-grid for efficient utilization of distributed renewable energy

Simple and accurate circuit simulation models for high-voltage silicon carbide power MOSFETs and Schottky barrier diodes are presented and validated. The models are physics-based and consist of minimal number of model parameters that can be easily extracted from simple static $I$ – $V$ and $C$ – $V$ measurements. The models are used in a buck-boost bidirectional dc-dc converter, with and without an antiparallel Schottky diode. The efficiency of the converter was analyzed for synchronous and nonsynchronous operation of the switches. An optimal selection of the antiparallel Schottky diode is proposed to minimize the cost of the converter without compromising its efficiency.

Simple and Accurate Circuit Simulation Model for SiC Power MOSFETs

Current Status and Emerging Trends in Wide Bandgap (WBG) Semiconductor Power Switching Devices

Simple and accurate circuit simulation model for gallium nitride (GaN) power field-effect transistors (FETs) is presented and validated in high-frequency low-voltage synchronous buck (SB) dc-dc power converters. For comparison, simulation results are also presented for the power converter based on silicon power metal-oxide semiconductor (MOS)FETs with similar voltage and current ratings. An improvement in power conversion efficiency of more than 4% is reported with GaN power FETs compared to the best commercially available silicon power MOSFETs in a 19 V/1.2 V, 7 W SB dc-dc power converter with excellent load regulation. A temperature- and frequency-dependent power inductor model is also reported and is shown to be necessary in order to accurately model the converter performance.

Simple and Accurate Circuit Simulation Model for Gallium Nitride Power Transistors

A smart sensor network that integrates latest advances in cognitive science and artificial intelligence with low- power wireless sensors is presented for emerging applications in energy, agriculture, environment, healthcare, medicine, transportation, and defense and space.

Krishna Shenai

Papers

Smart DC micro-grid for efficient utilization of distributed renewable energy

Simple and Accurate Circuit Simulation Model for SiC Power MOSFETs

Current Status and Emerging Trends in Wide Bandgap (WBG) Semiconductor Power Switching Devices

Simple and Accurate Circuit Simulation Model for Gallium Nitride Power Transistors

Cognitive sensor networks