Archives 2000-2003

1. Study of Power Quality at BNL (Brookhaven National Lab.)

Harmonic distortion is a major power quality concern. Simulations will provide LIPA and BNL with a tool for harmonic evaluation procedure at the 69/13.8 kV distribution system. Harmonic modeling and simulation of a 69/13.8 kV distribution system using two types of approach: a frequency-domain method and a time-domain method. Two software packages were selected: the EDSA Electrical Power System Design Software and the Power System Blockset (PSB) of the Matlab/Simulink package. The purpose of the power quality at the BNL was to check the voltage and current harmonic limits according to IEEE 519-1992 Std. at the 69 kV Bus1 which is the point of common coupling (PCC) between LIPA and BNL and to identify the source of current harmonics.

2. Voltage Collapse in Electric Systems

Voltage collapse means that the system can no longer maintain voltage at the load site In practice, the system operator determines the system status by observing the decline in voltage levels at the command control Second criterion is offered by monitoring the phase-angle between voltage vectors at the sending and receiving ends

3. Cold-Load Pickup of Distribution Systems

The re-energization of a large electric secondary-network distribution-system poses a server problem for a utility. Because of the network size, there is no practical way to control customer's appliance usage. Therefore, the utility must be prepared for the worst startup condition. A re-energization requires two to five times the normal power demand. At the instant of startup, high inrush currents will depress voltage to a value that may be below equipment's minimum starting voltage. Under this condition, the load will continue to draw locked-rotor or high inrush current that will keep the voltage depressed. Equipment may sustain permanent damage if exposed to an extended period of abnormally high current. In order to protect both customer and utility equipment, it is necessary to know the network re-energization process in detail.

4. Load Model under Varying Voltage Conditions

The main purpose of this project is to develop a customer load profile function that will estimate the customer demand when given a voltage level and the nominal demand. The customer load profile function will be, in some sense, a best fit of commercial or residential functions that are developed during the course of the project. In addition, the project will tabulate the error between this single customer load file function and the commercial or residential functions that are developed during the course of the project and also the error for the constant kVA representation.

5. Computer Aided Site-Specific Load Model

The goal of the project is to provide Con Edison with a stand-alone computer program to study individual load types as well as small combined loads for power, reactive power, current, power factor and impedance as a function of voltage at steady-state. It will allow the utility to predict whether a reduction in the power consumption, as a function of voltage drop, is feasible; i.e., whether or not the load current will change in a reasonable way, or will increase excessively as a result of the voltage reduction.

6. Hypervelocity Linear Induction Launcher

EM launcher (railgun, coilgun, and ETC) is a device that accelerates a projectile by means of a magnetic field (w/o propelling the fuel) to hypervelocity levels. In LIL (coilgun), the barrel coils are energized by polyphase currents that set up a traveling magnetic field which induces currents in the conductive projectile-sleeve. The interaction B x I generates an accelerating force

7. Resonance Power Supply for ES Precipitator

Develop a phase-controlled series-parallel resonant converter operating at 20KHz as the power supply for the electrostatic precipitator, which is to be used in environment industries. The converter is to be digitally controlled with a DSP. For the controller design purpose, the converter model has been developed and a scale-down closed-loop system has been built and tested.

8. Selected Harmonic Elimination for Electric Drives

In recent ten years, there has been a greatly increased demand for applying pulse-width modulation (PWM) technique to power electronics converters. Performance characteristics of a rectifier/ inverter power conversion scheme largely depend on the choice of the particular PWM strategy. In this project, we research the new optimal algorithm to calculate the programmed PWM problem. This new method is easy to realize; can control low-order harmonics and has optimal output waveform. At the end use this method in microprocessor to control MOSFET inverter.

9. Control of Bi-Directional DC/DC Converter

The bidirectional dc-dc converters find many applications in dc uninterruptible power supplies, battery charges, battery charger/discharger for satellites, photovoltanic applications, back-fire applications, auxiliary power supplies and many more. The input to these converters is often unregulated line voltage with fluctuations. There are also load variations. The main function of the feedback control is to convert the unregulated voltages to a desired dc output. The controller must have robust characteristics and should perform perfect tracking of the reference voltage (zero steady-state error).

10. Radio-Frequency DC/DC Converter for Communication

An RF (radio frequency) dc-dc converter has been devleoped to demonstrate using a flyback configuration at 63 Mhz. The "hard switching" 1-Watt converter achieves 60 to 70 percent efficiency, while operating with a wide range of input and output voltages. Such a converter can be used as a power supply for more efficient power amplifiers for wireless communication transmitters, by following the envelope of the signal.

11. Analog and DSP Implementation of Controllers

An H 8 Controller for use in a bi-directional flyback converter was designed and tested. Earlier work has shown that the H infinity controller is superior to that of a traditional reference-to-output frequency-compensated controller. The design of the H 8 controller was verified in open and closed loop simulation's and on-going experimentation.

12. Design of VLSI Controllers for RF Converters

RF Power converters can be used to reduce energy in Mobile Computing and Communications devices as an envelope following power supplies for more efficient power amplifiers for wireless transmitters or as a Dynamic Voltage Scaling power supply for variable voltage/speed processors. Both applications require fast converters which in turn require even faster controllers (GHz) that translate a desired output voltage to a pulse with a duty ratio which will cause the converter to have that voltage. The current design employ Analogue CMOS VLSI techniques such as high speed Current Conveyors.

Archives 80's-90's

1. Electromagnetic coil accelerator work, supported by the Department of Defense, 1986 to 1994, has resulted in the development of a multi-section linear induction launcher. This has attained wide recognition: in the US , England , Russia , and France : those places where related studies have been done. Lately, it is unfortunately true that the level of praise has not been matched by the level of support, which will soon be terminated by the de-emphasis on defense-related projects. (An evaluation study of non-US electromagnetic R&D was recently completed for SAIC (Science Applications International Corporation of McLean , VA ). A current unfunded joint effort with the US Army Benét Laboratory in Watervliet , NY , involves the construction of a hybrid gas/electric gun, where a launcher, to be mounted at the muzzle end of a “conventional” cannon, is to be used to further accelerate the emerging shell.

2. A study concerned with the generation of unwanted harmonics in power systems, resulting from the proliferation of non-linear loads, has been financially supported by KeySpan (called LILCO -- Long Island Lighting Company), 1992 to 1995, as well as by ESEERCO (Empire State Energy Research and Development Agency), ERDA ( New York State Energy Research and Development Agency). Consolidated Edison of New York is a strong participant, offering in-kind help, and open-handed availability of information from their systems.

3. A new simple ac/dc static power supply that provides a smooth dc output while presenting a linear load impedance to the utility (a clear sine-wave at near-unity power factor) was awarded a research grant by KeySpan Energy (LILCO), 1994 to 1998.

4. For Consolidated Edison of NYC, a cold-start simulation model was developed, which, since its completion, has been continuously in use by the company. Confidence in this model was obtained during a severe outage in midtown Manhattan , where the utility was able to restore power, using the model, days earlier than had been publicly announced, under conditions of great political pressure. This study was funded from 1980-1984, and the model has been adapted by PTI (Power Technologies Inc.) for their load-flow program. From 1987-1988, the utility funded the development of a dead feeder detector for possible field use. Without question, the helpfulness now exhibited by Consolidated Edison in our present harmonic study, and their donation of money toward our newly-refurbished machinery laboratory, is based on the help that the utility obtained in the past from the Polytechnic.

5. For the FRA (Federal Railroad Administration) of the US Department of Transportation, studies on linear propulsion, levitation and guidance systems were supported from 1973-1980. In a joint venture with the General Electric Company (GE) , a linear synchronous motor intended to power a train was designed by the Polytechnic, and a full scale unit was built by GE as a large-diameter rotating wheel, which was successfully tested at Schenectady , NY .

6. For Ebasco, primary contractor for the Princeton Tokomak (a thermonuclear fusion test reactor), the group participated in the development of the 1.2 GW pulsed-power supply. The original design concept that emerged resulted in quite substantial savings in its construction; perhaps millions of dollars. This took place 1976-1979.

7. For the US Department of Energy (DOE), Prof. Levi (on leave) served as full-time Senior Technical Advisor to the MHD division, where he was in charge of power conditioning, for two years, from 1976-1978. Work by the Group on power take-off in MHD generators, supported by the DOE from 1979-1983 , resulted in the invention of a pulse-width-modulated power consolidation scheme for Faraday and diagonal channels.