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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Submodule Capacitor Reduction for a 1 MVA SiC-Based Modular Multilevel Converter Motor Drive using High Frequency Common-Mode Voltage Injection

This paper describes a strategy to reduce the size of submodule capacitors of a 1 MVA, 0-1 kHz, 7-level modular multilevel converter (MMC) based medium voltage variable speed drive (MVVSD) using 1.7 kV SiC MOSFETs. Hardware designs of submodules to withstand high dv/dt and capacitor selection based on common mode voltage injection have been presented in literature. The issue with injection is the error in tracking of injected circulation current which results in fundamental frequency fluctuations in the submodule capacitor voltage. This paper presents a strategy for higher frequency sinusoidal common mode voltage based on more accurate tracking of the circulating current; realized through an improved control strategy combined with a higher switching frequency. Using the methods presented in this paper, a smaller submodule capacitance and reduced output current THD of the motor drive is achieved. A loss analysis model is proposed to evaluate the effect of the proposed strategy on the MMC efficiency. This helps balance the reduction in the capacitor against the increase in the losses as a result of increased switching frequency. Simulations and a down-scaled experimental setup are used to demonstrate this concept.

Potty, Karun↗
DOE OSTI2024

Electronics module with raceway and submodules

Systems and methods for providing an electronics module including a raceway for mounting submodules and establishing electrical communication with said submodules. The raceway comprises a base structure and a conductive trace formed by a conductive plating process. Connection pads on the raceway are configured to receive connection nodes of the submodules for providing a continuous electrical connection between the raceway and the submodules for electrical communication and power transmission.

Eickbush, Ryan J.↗
DOE OSTI2019

Optimal Submodule Capacitor Sizing for Modular Multilevel Converters with Common Mode Voltage Injection and Circulating Current Control

Abstract - Modular multilevel converters (MMCs), with the filterless and transformer-less features, are considered as a promising topology for high-efficiency medium voltage (MV) high voltage (HV) drive systems. However, at low frequencies (< 30 Hz), a large current ripple flowing through the capacitors of each submodule will cause significant capacitor voltage fluctuation. This paper proposes an optimal submodule capacitor selection based on the common mode voltage injection. The proposed sizing model includes two functions: a) accurately estimating the capacitor voltage ripple based on the drive system parameters; and b) identifying the minimum capacitance of the submodule capacitors based on the allowed maximum capacitor voltage fluctuations. Simulation and hardware-in-the-loop (HIL) test results show that the error between the actual and estimated values of the voltage fluctuation is within 3% using the proposed model.

Capacitor Sizing↗
NASA NTRS1966

Solar cell submodule design facilitates assembly of lightweight arrays

Solar cell submodules with bus bars that leave tabs along one end of the submodule and wires with raised portions along the other end are assembled by interlocking the tabs and wires of adjacent submodules. This structural design is lightweight and reliable and requires no metallic substructure.

Yasui, R. K.↗
DOE OSTI2019

Single-Submodule Open-Circuit Fault Diagnosis for a Modular Multi-level Converter Using Artificial Intelligent-based Techniques

Modular multi-level converters (MMCs) are one of the promising topologies in recent years for medium or high voltage applications. They are considered as the next generation DC/AC converters for medium/high voltage (MV/HV) motor drive applications due to their transform-less structures, high efficiency and modularity. Reliability is one of the most important challenges in MMCs, since a large number of power switching devices are used and each of these devices can be considered as a potential failure point. It is significant to detect and locate the fault accurately and apply appropriate protections in a timely manner. This paper investigates the behavior of the failure submodules and healthy submodules and use artificial neural network (ANN) classification algorithms for singlesubmodule open-circuit fault diagnosis. The ANN algorithm is implemented in field programmable gate array (FPGA) and the ANN parameters training is completed offline in Matlab. Experimental results of the proposed fault diagnosis for a singlemodule open-circuit fault are presented in this paper.

artificial intelligent↗
DOE OSTI2019

A Novel Discharging Control Strategy for Modular Multilevel Converter Submodules without Using External Circuit

A novel discharging control strategy is proposed and implemented for submodules in modular multilevel converters (MMCs). By sequentially controlling the arm currents of a MMC to the arm resistors, all submodule capacitors are discharged safely and rapidly without adding additional devices and circuits, resulting in improved performance and reduced cost. Both open- and closed-loop control methods are evaluated for effectiveness of the new control strategy. Simulation and experimental results are provided to validate the new control strategy.

Modular multilevel converter, discharging method, ↗
DOE OSTI2020

Modular Multilevel Converter (MMC) Modeling Considering Submodule Voltage Sensor Noise

The modular multilevel converter (MMC) is a popular topology in medium- and high-voltage applications, and many efforts have been spent on MMC modeling. However, the impact of submodule voltage sensor noise (SVSN), which becomes more severe due to increasing switching speed of power semiconductors and compact submodule design, has not been considered in conventional models. In this letter, the SVSN is introduced by coupling capacitances between the sensor and power stage in an MMC switching model. Furthermore, the SVSN impact is considered in an MMC average model based on derivation of the relationship between the SVSN and the duty cycle. Here, the proposed MMC switching model and average model considering the SVSN are validated by comparing simulations with experimental results in an MMC prototype using 10-kV SiC MOSFETS.

47 OTHER INSTRUMENTATION↗
DOE OSTI2026

Submodule-Level Decentralized Control for Cascaded Quadruple Active Bridge-Based Medium-Voltage Converters

High-power, low-voltage DC (LVDC) loads, such as AI data centers, electric vehicle fast-charging hubs, and hydrogen electrolyzers, are accelerating the deployment of solid-state transformers (SSTs) that directly interface medium-voltage AC (MVAC) to LVDC, streamlining power delivery. This paper proposes a submodule-level decentralized control strategy for an SST comprising a cascaded H-bridge (CHB) active rectifier on the MVAC side and per-module quadruple-active-bridge (QAB) converters on the LVDC side with local controllers. The proposed strategy eliminates the need for high-fidelity, real-time cross-isolation communication by synchronizing all active bridges to a common heartbeat signal and enabling the primary- and secondary-side controllers to generate independent local control signals (phase shifts). The resultant phase shifts naturally govern average and double-line frequency power transfer between active bridges, enabling each side to meet its control objectives using only local measurements. Detailed controller design considerations are presented based on a stability analysis. Comprehensive electromagnetic-transient simulations demonstrate tight DC-link voltage regulation, high-quality grid currents, and robust operation under load transients and grid disturbances, without real-time communication among the submodule controllers. These results indicate that the proposed scheme can significantly enhance the reliability, scalability, and flexibility of cascaded bridge-based medium-voltage converters.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2026

Submodule-Level Decentralized Control for Cascaded Quadruple Active Bridge-Based Medium-Voltage Converters: Preprint

High-power, low-voltage DC (LVDC) loads, such as AI data centers, electric vehicle fast-charging hubs, and hydrogen electrolyzers, are accelerating the deployment of solid-state transformers (SSTs) that directly interface medium-voltage AC (MVAC) to LVDC, streamlining power delivery. This paper proposes a submodule-level decentralized control strategy for an SST comprising a cascaded H-bridge (CHB) active rectifier on the MVAC side and per-module quadruple-active-bridge (QAB) converters on the LVDC side with local controllers. The proposed strategy eliminates the need for high-fidelity, real-time cross-isolation communication by synchronizing all active bridges to a common heartbeat signal and enabling the primary- and secondary-side controllers to generate independent local control signals (phase shifts). The resultant phase shifts naturally govern average and double-line frequency power transfer between active bridges, enabling each side to meet its control objectives using only local measurements. Detailed controller design considerations are presented based on a stability analysis. Comprehensive electromagnetic-transient simulations demonstrate tight DC-link voltage regulation, high-quality grid currents, and robust operation under load transients and grid disturbances, without real-time communication among the submodule controllers. These results indicate that the proposed scheme can significantly enhance the reliability, scalability, and flexibility of cascaded bridge-based medium-voltage converters.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2022

Open-circuit submodule fault diagnosis in MMCs using support vector machines

Series connection of semiconductor submodules (SM) in a modular multilevel converter (MMC) makes the MMC prone to open-circuit (OC) IGBT failures inside SMs. If left undetected, these faults degrade the operation of the MMC and lead to its instability. This article proposes a method to detect, localise, and classify single OC SM faults in an MMC using support vector machines (SVM) trained with data obtained from the capacitor voltage balancing block of the MMC control system. The proposed method relies on data extracted from the sorted capacitor voltage arrays of the upper and lower phase arms. Therefore, it does not require extra measurements and hardware. Additionally, it offers a fixed time for detecting and localising OC SM faults. This method is easy to implement as SVM has a simple decision function. Time-domain simulation case studies are performed on a three-phase nine-level MMC to evaluate the performance of the proposed method.

42 ENGINEERING↗
NASA NTRS1985

Interconnect resistance of photovoltaic submodules

Small area amorphous silicon solar cells generally have higher efficiencies than large interconnected submodules. Among the reasons for the differences in performance are the lack of large area uniformity, the effect of nonzero tin oxide sheet resistance, and possibly pinholes in the various layers. Another and usually small effect that can contribute to reduced performance of interconnected cells is the resistance of the interconnection i.e., the series resistance introduced by the metal to tin oxide contact through silicon. Proper processing problems to avoid poor contacts are discussed.

Volltrauer, H.↗
NASA NTRS1992

Software architecture for a distributed real-time system in Ada, with application to telerobotics

The architecture structure and software design methodology presented is described in the context of telerobotic application in Ada, specifically the Engineering Test Bed (ETB), which was developed to support the Flight Telerobotic Servicer (FTS) Program at GSFC. However, the nature of the architecture is such that it has applications to any multiprocessor distributed real-time system. The ETB architecture, which is a derivation of the NASA/NBS Standard Reference Model (NASREM), defines a hierarchy for representing a telerobot system. Within this hierarchy, a module is a logical entity consisting of the software associated with a set of related hardware components in the robot system. A module is comprised of submodules, which are cyclically executing processes that each perform a specific set of functions. The submodules in a module can run on separate processors. The submodules in the system communicate via command/status (C/S) interface channels, which are used to send commands down and relay status back up the system hierarchy. Submodules also communicate via setpoint data links, which are used to transfer control data from one submodule to another. A submodule invokes submodule algorithms (SMA's) to perform algorithmic operations. Data that describe or models a physical component of the system are stored as objects in the World Model (WM). The WM is a system-wide distributed database that is accessible to submodules in all modules of the system for creating, reading, and writing objects.

Olsen, Douglas R.↗
DOE OSTI2022

Proteome reallocation enables the selective de novo biosynthesis of non-linear, branched-chain acetate esters

The one-carbon recursive ketoacid elongation pathway is responsible for making various branched-chain amino acids, aldehydes, alcohols, and acetate esters in living cells. Controlling selective microbial biosynthesis of these target molecules at high efficiency is challenging due to enzyme promiscuity, regulation, and metabolic burden. In this study, we present a systematic modular design approach to control proteome reallocation for selective microbial biosynthesis of branched-chain acetate esters. Through pathway modularization, we partitioned the branched-chain ester pathways into four submodules including keto-isovalerate submodule for converting pyruvate to keto-isovalerate, ketoacid elongation submodule for producing longer carbon-chain keto-acids, ketoacid decarboxylase submodule for converting ketoacids to alcohols, and alcohol acyltransferase submodule for producing branched-chain acetate esters by condensing alcohols and acetyl-CoA. By systematic manipulation of pathway gene replication and transcription, enzyme specificity of the first committed steps of these submodules, and downstream competing pathways, we demonstrated selective microbial production of isoamyl acetate over isobutyl acetate. In this work, we found that the optimized isoamyl acetate pathway globally redistributed the amino acid fractions in the proteomes and required up to 23-31% proteome reallocation at the expense of other cellular resources, such as those required to generate precursor metabolites and energy for growth and amino acid biosynthesis. From glucose fed-batch fermentation, the engineered strains produced isoamyl acetate up to a titer of 8.8 g/L (> 0.25 g/L toxicity limit), a yield of 0.22 g/g (61% of maximal theoretical value), and 86% selectivity, achieving the highest titers, yields and selectivity of isoamyl acetate reported to date.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Multiscale Electrothermal Design of a Modular Multilevel Converter for Medium-Voltage Grid-Tied Applications

As a key feature of modular multilevel converters (MMCs), a large number of semiconductor devices are employed in the converter and distributed over a stack of submodules. Each submodule has a strict temperature limit that imposes constraints on the operating range of the converter. Different loading conditions/losses in the submodules lead to unavoidable temperature variations inside the MMC, which consequently affect the system-level performance and reliability. This paper is focused on the electrothermal analysis and design of a medium-voltage silicon carbide (SiC)-based MMC system, from submodule power semiconductors to the overall MMC system integration of multiple submodules, for grid-connected applications. Loss calculations are performed to estimate the cooling requirements and aid thermal design at different levels. The performance of a forced-air cooling approach is analyzed within a numerical modeling framework. Maximum temperature of the SiC power modules is predicted using numerical tools. Thermal design of the MMC cabinet with various arrangements of air inlet(s) and outlet(s) is investigated and compared from a cooling performance perspective. A fully resolved model of the arrangement that yields optimal results is developed to accurately predict the temperature profile of the essential components in the submodules.

computational fluid dynamics↗
DOE OSTI2021

Multiscale Electrothermal Design of a Modular Multilevel Converter for Grid-Tied Applications

As a key feature of modular multilevel converters (MMCs), a large number of semiconductor devices are employed in the converter and distributed over a stack of submodules. Each submodule has a strict temperature limit that imposes constraints on the operating range of the converter. Different loading conditions/losses in the submodules lead to unavoidable temperature variations inside the MMC, which consequently affect the system-level performance and reliability. This paper is focused on the electrothermal analysis and design of a medium-voltage silicon carbide (SiC)-based MMC system, from submodule power semiconductors to the overall MMC system integration of multiple submodules. Loss calculations are performed to estimate the cooling requirements and aid thermal design at different levels. The performance of forced-air cooling approach is analyzed within a numerical modeling framework. Maximum temperature of the SiC power modules is predicted using numerical tools. Thermal design of the MMC cabinet with various arrangement of air inlet(s) and outlet(s) is investigated and compared from a cooling performance perspective.

CFD↗