Shashank Krishnamurthy

Bio: Shashank Krishnamurthy is an academic researcher from Goodrich Corporation. The author has contributed to research in topics: Control theory & Inverter. The author has an hindex of 11, co-authored 48 publications receiving 494 citations. Previous affiliations of Shashank Krishnamurthy include Raytheon & Cape Peninsula University of Technology.

The operation of diesel gensets in a CERTS microgrid

Abstract: In this paper the operation of diesel engine-driven wound-field synchronous generator sets as distributed generators (DGpsilas) is studied. The objective of this work is to develop the modeling and control framework for such gensets to enable their operation in a distribution system that contains multiple DGpsilas including inverter-based sources. The paper presents experimental results for the interaction of conventional gensets with inverter-based sources in a microgrid test system. From the test results it is observed that there is significant circulating reactive power between the sources as well as frequency oscillations caused by the response of the conventional genset controller. A new controller for the genset is proposed that alleviates these issues and enables the various sources to share power and maintain power quality within the system. The operation of the new controller is demonstrated using simulation results.

Analytical Wideband Model of a Common-Mode Choke

Abstract: This paper presents an analytical model of a common-mode choke suitable for accurate calculation of the choke impedance over a wide frequency range. The model consists of lumped parameters (resistances, inductances, and capacitances) related to individual turns of the coils wound on the core. It takes into account the mutual interactions between the turns and the core with respect to their inductive and capacitive links. The variation of the core permeability and losses with frequency up to 100 MHz is also included. The open-mode impedance characteristic calculated analytically for a VAC 6123x425 single-phase common-mode choke shows very good agreement with the 3-D finite-element model and the measured characteristic from 150 kHz up to 30 MHz, thus confirming the accuracy of the model over a wide frequency range.

A high temperature, double-sided cooling SiC power electronics module

Abstract: A high temperature, wire-bondless power electronics module with a double-sided cooling capability is proposed and successfully fabricated. In this module, a low-temperature co-fired ceramic (LTCC) substrate was used as the dielectric and chip carrier. Conducting vias were created on the LTCC carrier to realize the interconnection. The absent of a base plate reduced the overall thermal resistance and also improved the fatigue life by eliminating a large-area solder layer. Nano silver paste was used to attach power devices to the DBC substrate as well as to pattern the gate connection. Finite element simulations were used to compare the thermal performance to several reported double-sided power modules. Electrical measurements of a SiC MOSFET and SiC diode switching position demonstrated the functionality of the module.

Impact of price penalty factors on the solution of the combined economic emission dispatch problem using cubic criterion functions

Abstract: Thermal power plants play a major role in power production. The impacts of the various pollutants such as sulphur dioxide (SO2), Nitrogen oxide (NOx) and carbon dioxide (CO2) affects the environmental issues. The fuel cost of the generator in an economic dispatch problem can be presented by any order polynomial. The literature review reported that most of the papers consider the single pollutant using the second order polynomial function. The paper formulates the dispatch problem using a cubic function for both fuel cost and emission values. The impacts of various pollutants and price penalty factors such as Max-Max, MinMax, Average, and Common are considered in the multi-objective dispatch problem. The dispatch problem is solved using Lagrange's method and the simulation results are provided for IEEE 30 bus system. It concludes that Min-Max Price penalty factor provides minimum fuel cost and minimum emission values in comparison to the other price penalty factors.

Simplified loss analysis for high speed SiC MOSFET inverter

Abstract: SiC devices provide significant performance improvement compared to traditional Si devices, such as lower conduction loss and higher switching speed. The ability to accurately predict converter loss is essential for converter design. This paper provides a simplified loss model, which enables users to calculate converter loss based on datasheet values. Also, it provides insight to major switching loss contributors.

Smart Distribution: Coupled Microgrids

Abstract: The distribution system provides major opportunities for smart grid concepts. One way to approach distribution system problems is to rethinking our distribution system to include the integration of high levels of distributed energy resources, using microgrid concepts. Basic objectives are improved reliability, promote high penetration of renewable sources, dynamic islanding, and improved generation efficiencies through the use of waste heat. Managing significant levels of distributed energy resources (DERs) with a wide and dynamic set of resources and control points can become overwhelming. The best way to manage such a system is to break the distribution system down into small clusters or microgrids, with distributed optimizing controls coordinating multimicrogrids. The Consortium for Electric Reliability Technology Solutions (CERTSs) concept views clustered generation and associated loads as a grid resource or a “microgrid.” The clustered sources and loads can operate in parallel to the grid or as an island. This grid resource can disconnect from the utility during events (i.e., faults, voltage collapses), but may also intentionally disconnect when the quality of power from the grid falls below certain standards. This paper focuses on DER-based distribution, the basics of microgrids, possibility of smart distribution systems using coupled microgrid and the current state of autonomous microgrid technology.

Microgrids research: A review of experimental microgrids and test systems

Abstract: A microgrid is particularly a portion of the power distribution system that comprises distributed generation, energy storage and loads. To be capable of operating in parallel to the grid, as an autonomous power island and in transition modes, microgrids must be robust in controlling the local voltage and frequency, and protecting the network and equipment connected to the microgrid. It also needs to facilitate demand side management and resynchronization. This paper presents a review of existing microgrid test networks around the world (North America, Europe and Asia) and some significantly different microgrid simulation networks present in the literature. Paper is focused on the test systems and available microgrid control options. A summary table comparing and contrasting the existing test systems is presented. The paper is concluded highlighting the worthy findings and possible areas of research that would enhance practical use of microgrid facilities.

CERTS Microgrid Laboratory Test Bed

Abstract: The CERTS Microgrid concept captures the emerging potential of distributed generation using a system approach. CERTS views generation and associated loads as a subsystem or a “microgrid.” The sources can operate in parallel to the grid or can operate in island, providing uninterruptible power-supply services. The system can disconnect from the utility during large events (i.e., faults, voltage collapses), but may also intentionally disconnect when the quality of power from the grid falls below certain standards. CERTS Microgrid concepts were demonstrated at a full-scale test bed built near Columbus, OH, and operated by American Electric Power. The testing fully confirmed earlier research that had been conducted initially through analytical simulations, then through laboratory emulations, and finally through factory acceptance testing of individual microgrid components. The islanding and resynchronization method met all Institute of Electrical and Electronics Engineers Standard 1547 and power-quality requirements. The electrical protection system was able to distinguish between normal and faulted operation. The controls were found to be robust under all conditions, including difficult motor starts and high impedance faults.

Some Aspects of Stability in Microgrids

Abstract: This paper investigates some aspects of stability in microgrids. There are different types of microgrid applications. The system structure and the control topology vary depending on the application and so does the aspect of stability in a microgrid. This paper briefly encompasses the stability aspects of remote, utility connected and facility microgrids depending on the modes of operation, control topology, types of micro sources and network parameters. The small signal, transient and the voltage stability aspects in each type of the microgrid are discussed along with scope of improvements. With a brief review of the existing microgrid control methods in the literature and different industry solutions, this paper sets up an initial platform for different types of microgrids stability assessment. Various generalized stability improvement methods are demonstrated for different types of microgrids. The conventional stability study of microgrids presented in this paper facilitates an organized way to plan the micro source operation, microgrid controller design, islanding procedure, frequency control and the load shedding criteria. The stability investigations are presented with different control methods, eigen value analysis and time domain simulations to justify different claims.

Prototyping versus specifying: A multiproject experiment.

Abstract: In this experiment, seven software teams developed versions of the same small-size (2000-4000 source instruction) application software product. Four teams used the Specifying approach. Three teams used the Prototyping approach. The main results of the experiment were the following. 1) Prototyping yielded products with roughly equivalent performance, but with about 40 percent less code and 45 percent less effort. 2) The prototyped products rated somewhat lower on functionality and robustness, but higher on ease of use and ease of learning. 3) Specifying produced more coherent designs and software that was easier to integrate. The paper presents the experimental data supporting these and a number of additional conclusions.