Stan Atcitty

Performance Indices for the Dynamic Performance of FACTS and FACTS with Energy Storage

The integration of energy storage into flexible AC transmission systems (FACTS) devices leads to increased controller flexibility by providing decentralized active power capabilities. Combined FACTS/energy storage systems (ESS) can improve power flow control, oscillation damping, and voltage control. This article presents performance indices that have been developed for quantifying the active power, reactive power, and voltage performance enhancement of different FACTS combinations. The dynamic responses of a shunt (StatCom), a StatCom/battery energy storage system (BESS), a synchronous series compensator (SSSC), a SSSC/BESS, and a unified power flow controller (UPFC) are presented to support the validity of the developed indices.

Slow Detrapping Transients due to Gate and Drain Bias Stress in High Breakdown Voltage AlGaN/GaN HEMTs

Charge trapping and slow (from 10 s to >; 1000 s) detrapping in AlGaN/GaN high electron mobility transistors (HEMTs) designed for high breakdown voltages ( >; 1500 V) is studied through a combination of electrical, thermal, and optical methods to identify the impact of Al molefraction and passivation on trapping. Trapping due to 5-10 V drain bias stress in the on-state (Vgs = 0) is found to have significantly slower recovery, compared with trapping in the off-state (Vgs <; Vth, Vds = 0). Two different trapping components, i.e., TG1 (Ea = 0.6 eV) and TG2 (with negligible temperature dependence), in AlGaN dominate under gate bias stress in the off-state. Al0.15Ga0.85N shows much more vulnerability to trapping under gate stress in the absence of passivation than does AlGaN with a higher Al mole fraction. Under large drain bias, trapping is dominated by a much deeper trap TD. Detrapping under monochromatic light shows TD to have Ea 1.65 eV. Carbon doping in the buffer is shown to introduce threshold voltage shifts, unlike any of the other traps.

Role of barrier structure in current collapse of AlGaN/GaN high electron mobility transistors

Simultaneous measurements of surface potential by Kelvin force microscopy and drain current detrapping transients in AlGaN/GaN high electron mobility transistors are performed on devices with two different epitaxial structures to understand if the trapped charges are predominantly in the AlGaN bulk, at the AlGaN surface, or in the GaN buffer. The results show that the predominant location of charge trapping is affected more strongly by the design of the device and the operating voltages than by surface passivation or buffer defects. The experiments also show that the dominant component of current collapse in devices with thick AlGaN barrier layers comes from AlGaN traps.

Integration of a StatCom and battery energy storage

Summary form only given as follows. The integration of an energy storage system, such as battery energy storage (BESS), into a FACTS device can provide dynamic decentralized active power capabilities and much needed flexibility for mitigating transmission level power flow problems. This paper introduces an integrated StatCom/BESS for the improvement of dynamic and transient stability and transmission capability; compare the performance of the different FACTS/BESS combinations, and provide experimental verification of the proposed controls on a scaled StatCom/BESS system.

Battery Energy Storage System

This chapter discusses the various technical components of battery energy storage systems for utility-scale energy storage and how these technical components are interrelated. The introduction lists the basic types of large-scale storage and how storage can be used to mitigate the variability associated with renewable generation. It also provides an overview of how to define storage applications as primarily “power” or “energy” based. A basic description of how battery energy storage works is provided with several examples to illustrate how battery energy storage can be used in large-scale applications. A brief discussion of the various battery chemistries that are suited to large-scale applications is provided, as well as guidance on what factors to look for when trying to select an appropriate chemistry for a given application. An overview of how the storage system’s power electronics work is followed by a more detailed description of possible power electronic topologies and power electronic controls that are used to ensure that the system can be properly integrated with the generation source and, if necessary, the load. Battery management and battery monitoring via the power electronic controls is discussed briefly. This chapter concludes with a detailed example of battery energy storage system integration that is summarized with data obtained in the field.

Sub-bandgap light-induced carrier generation at room temperature in 4H-SiC metal oxide semiconductor capacitors

Carrier generation characteristics in n-type substrate silicon carbide (SiC) metal oxide semiconductor capacitors induced by sub-bandgap energy light are reported. The generation rate is high enough to create an inversion layer in approximately 20 min with monochromatic front side illumination of energy 2.1 eV in 4H-SiC for electric fields less than 1 MV/cm. Generation and recovery results strongly indicate involvement of a metastable defect whose efficiency as a generation center increases under hole-rich and decreases under electron-rich conditions. The generation dependence on bias history and light energy shows the defect to have properties consistent with the metastable silicon vacancy/carbon vacancy-antisite complex (VSi/Vc–CSi).