Search

Mixed mode TCAD simulations are used to show the effects of guard bands and high density well contacts in maintaining the well potential after a single event strike and thus reduce the width of long transients in a 130-nm CMOS process. Experimental verification of the effectiveness in mitigating long transients was achieved by measuring the distribution of SET pulse widths produced by heavy ions for circuits with isolated contacts and for circuits with guard bands combined with larger contacts in a 130-nm process using an autonomous characterization technique. Heavy-ion test results indicate that controlling the well potential by using guard bands, along with high density well contacts, helps eliminate > 70 % of SETs longer than 1 ns. Index Terms--CMOS, guard band, parasitic bipolar, pulse width, single event transient (SET), single event upset (SEU), soft error, well contact.

This paper discusses the potential of a transformerless STATic synchronous COMpensator (STATCOM) intended for installation on the 6.6-kV industrial and utility distribution systems. The STATCOM consists of a five-level diode-clamped pulsewidth-modulation converter rated at 1 MVA and a voltage-balancing circuit rated at 6 kVA. Moreover, this paper designs, constructs, and tests a 200-V 10-kVA STATCOM based on a five-level converter with a carrier frequency of 3 kHz and a voltage-balancing circuit with a switching frequency of 3 kHz. The STATCOM and its experimental waveforms verify the viability and effectiveness of the 6.6-kV transformerless STATCOM. Index Terms--Multilevel converter, reactive power, split dc capacitors, static synchronous compensator (STATCOM), voltage-balancing circuit.

The use of the controller area network communication protocol for H-bridge multilevel (HBML) inverters, and localized pulsewidth modulation generation and automated voltage regulation is proposed in this paper. It is shown that the performance and reliability of conventional distributed controllers for HBML inverters can be improved with less communication hardware requirements, when using the proposed method. It is also shown that the expansion and modularization capability of the HBML inverter is improved since individual inverter modules operate more independently. The proposed hardware is described in detail and the validity of the proposed system is verified experimentally on a 6600-V 1400-kW induction motor drive. Index Terms--Controller area network (CAN), H-bridge multilevel (HBML) inverter, pulsewidth modulation (PWM) phase-shift, PWM synchronization, serial communication.

An autotuning system, which takes into account the self-compatibility of power converters, is proposed in this paper. It is based on a startup routine and a self-disturbance evaluation board, which selects the optimal switching frequencies for the power converter in order to decrease the internal disturbances in terms of electromagnetic interference between the power section and the control one. The entire test and tuning system does not require any field or current sensor but just digital comparators and counters. This configuration allows achieving a robust and low-cost autotuning system for internal compatibility of power converters. Index Terms--DC/DC converters, electromagnetic compatibility (EMC), electromagnetic interference (EMI), pulsewidth modulation (PWM) converters, self-compatibility.

In this paper, a CLL resonant tank fed by an asymmetrical pulsewidth-modulated (APWM) drive train is presented as an attractive option for low-power point-of-use power supplies used in telecom applications. This configuration can guarantee zero-voltage switching (ZVS) for an extended input voltage range of 35-75 V, while significantly reducing the associated conduction loss present in existing topologies. Proper resonant tank design will ensure efficient operation over the entire working range by maintaining ZVS for all line and load conditions, as well as minimizing the conduction loss by decreasing the circulating-current commensurate with load. Analysis of the converter topology is conducted, and a design procedure is presented. Experimental results from a 25-W 48-V/2.5-V proof-of-concept prototype are presented to validate the analysis and simulation results and to highlight the merits of the proposed topology. The proposed converter is shown to provide a 7%-14% efficiency improvement over a reference topology. Index Terms--DC-DC power conversion, pulsewidth modulation (PWM), resonant power conversion.

This paper aims to achieve good performance for both the dc boost and the ac output voltage control of the Z-source inverter (ZSI). The algorithm to control linearly the capacitor voltage is suggested in order to improve the transient response for dc boost control of the ZSI. The peak value of the ac output voltage is used to control exactly the ac output voltage to its desired level. A modified space vector pulsewidth modulation scheme is applied to control the shoot-through time for boosting dc voltage. The proposed algorithms are verified with simulation and experiment with a 32-bit digital signal processor. Index Terms--AC output voltage control, dc boost control, modified space vector pulsewidth modulation (MSVPWM), Z-source inverter (ZSI).

A current error space phasor based simple hysteresis controller is proposed in this paper to control the switching frequency variation in two-level pulsewidth-modulation (PWM) inverter-fed induction motor (IM) drives. A parabolic boundary for the current error space phasor is suggested for the first time to obtain the switching frequency spectrum for output voltage with hysteresis controller similar to the constant switching frequency voltage-controlled space vector PWM-based IM drive. A novel concept of online variation of this parabolic boundary, which depends on the operating speed of motor, is presented. A generalized technique that determines the set of unique parabolic boundaries for a two-level inverter feeding any given induction motor is described. The sector change logic is self-adaptive and is capable of taking the drive up to the six-step mode if needed. Steady-state and transient performance of proposed controller is experimentally verified on a 3.7-kW IM drive in the entire speed range. Close resemblance of the simulation and experimental results is shown. Index Terms--Current error space phasor, hysteresis controller, parabolic boundary, switching frequency variation control.

This paper calculates and compares the efficiency and loss distribution in the three most popular state-of-the-art types of large motor drive systems: 1) current-source drive with active front-end rectifier; 2) current-source drive with 18-pulse thyristor rectifier; and 3) three-level voltage-source drive with 12-pulse/24-pulse diode rectifier. For converter systems with efficiencies better than 90%, it is suggested to calculate or measure the losses of all the components separately and add them up to calculate the total efficiency. A simple and accurate method of calculating switching losses for a current-source and voltage-source converter is proposed. Through the calculation and simulation of each loss factor such as switching losses, conduction losses, and snubber and filter losses, the three-level voltage-source drive system has been found to have the highest efficiency of 98.77% under the rated load of 1.6 MW. Index Terms--AC motor drives, multilevel systems, pulsewidth-modulated inverters, solid-state rectifiers.

A considerable number of nonlinear industrial loads employ three-phase inductive filters to reduce their peak currents and mitigate the conduction of harmonic currents into the supply system. In modeling and analysis of this kind of filter, the fact that--for reasons of economy--they consist of a single block where the three electrical phases share the same magnetic core instead of having three single-phase reactors is often overlooked. Since the three windings are coiled in the same plane, the central magnetic limb of the core has a lower magnetic reluctance than do the lateral limbs. Moreover, this undesired effect is increased by the existence of internal magnetic couplings. The above phenomenon, which might, at first sight, be considered negligible, will become noticeable in real electrical facilities because of the particular operating conditions of three-phase inductive filters. The aim of this paper is, thus, to present a new model for three-limb core three-phase inductive filters that includes all the above parasitic effects and to describe its practical application in order to assess the magnitude of the errors produced by traditional models when estimating real filter behavior. Index Terms--Filter modeling, inductive filter, pulsewidth modulation (PWM) adjustable speed drives (ASDs), structural asymmetry, voltage unbalance.

Voltage unbalance in a three-phase system caused performance deterioration of a pulsewidth modulation (PWM) converter by producing the 120-Hz voltage ripples in the dc link and by increasing the reactive power. To eliminate the dc-link voltage ripple and the dc component of the reactive power, both positive- and negative-sequence currents should be controlled simultaneously, according to the paper by Rioual et al. We used two synchronous reference frames: a positive-sequence current regulated by a proportional integral (PI) controller in a positive synchronous reference frame (SRF), and a negative-sequence current regulated by a PI controller in a negative SRF. In the positive SRF, which rotates counterclockwise, the positive sequence appears as dc, while the negative sequence appears as 120Hz. In contrast, in the negative SRF, which rotates clockwise, the negative sequence appears as dc, while the positive sequence appears as 120 Hz. By deleting 120-Hz components using a notch filter in each SRF, one can measure positive- and negative-sequence currents separately, and use them for constructing two feedback controllers. Since the negative-sequence current is also controlled in its own SRF by a dc command, this approach yields better performance without increasing the control gain. Note that, since the controller is implemented by a software routine in the digital signal processor chip, using two SRF's does not require additional hardware. We demonstrated the effectiveness of the proposed control scheme by using computer simulation and experiments. Index Terms: Current control, dual control scheme, pulsewidth modulation power converters, rectifiers, symmetrical components, synchronous frame control scheme, voltage unbalance.

With the increased availability of power MOSFET's and insulated gate bipolar transistors, a new generation of simple choppers for ac inductive loads is foreseen. These new power semiconductors ease the use of forced commutations of thyristor switches to improve the supply power factor, even with highly inductive loads. The ac controllers with thyristor technology can be replaced by pulsewidth modulation (PWM) ac chopper controllers which have important advantages. In this paper, a symmetrical PWM ac chopper designed to operate with single-phase inductive loads with a reduced number of controlled switches is described. The operation as a variable voltage source of this converter is evaluated. This includes the conversion characteristics, harmonic generation, harmonic distortion factor, and input power factor. By digital simulation, these characteristics are investigated theoretically, and to correlate the measurements with theory, an experimental setup is presented to confirm the analytical analysis. Index Terms: AC chopper, duty cycle, harmonic distortion, switching function, symmetrical pulsewidth modulation, voltage controller

A review of the existing methods to determine the output currents in a pulsewidth modulation voltage-source (PWM-VS) inverter using a single current sensor in the dc link is presented, and a novel solution is proposed. The unique arrangement of the dc link allows full protection of the inverter from short circuits and overloads. Also, a new method of sampling the dc-link current is described that produces true values of the output currents at the centers of switching intervals. Results of investigation of an experimental setup have shown that full protection of the inverter has been accomplished and the output currents can accurately be determined within the whole operating area. Index Terms - AC drives, current sampling, modulation, sensor reduction.

In this paper, a new technique for shaping the line current and reducing the total harmonic distortion in a three-phase bridge rectifier, feeding a capacitive load, is presented. Using the topology of a three-level three-switch pulsewidth modulated (PWM) rectifier, a new control technique has been implemented. The main objective here is to minimize the total harmonic distortion (THD) of the line current under different load conditions (20%-100% of full load). A review of the problems inherent in a bridge rectifier feeding a capacitive load and the possible solutions are first presented. Subsequently, the analysis of the new circuit and the control technique used are described, along with simulation results. Finally, the experimental results on a 1.6-kW prototype are presented. Index Terms - Modulation technique, power quality improvement, uncontrolled three-phase rectifier.

This paper examines ac motor shaft voltages and resulting bearing currents when operated under pulse width modulation (PWM) voltage source inverters. The paper reviews the electrical characteristics of bearings and motors that cause shaft voltages and bearing currents. A brief review of previous work is presented, including a system model for electrical analysis of bearing currents. Relying on the work of a companion paper, the propensity for electric discharge machining (EDM) is determined by a design equation that is a function of system components. Pertinent machine parameters and their formulas are presented and values calculated for machines from 5 to 1000 hp. The effects of system elements on shaft voltages and bearing currents are evaluated experimentally and the results compared to theory. Finally, the paper will present quantitative results for one solution to the shaft voltage and bearing current problem. Index Terms - Bearing capacitance ([C.sub.b]), bearing current ([I.sub.b]), bearing threshold voltage ([V.sub.th]), bearing voltage ratio (BVR), electric discharge machining (EDM), electrostatic shielded induction motor (ESIM), rotor shaft to ground voltage ([V.sub.rg]), stator to rotor capacitance ([C.sub.sr]).

Modern power inverters provide the industrial control industry with significant advantages. The faster switching devices have increased drive performance, but with some recently discovered disadvantages. One disadvantage, rotor shaft voltage and resulting bearing current, has become an industry concern. The oil film in a bearing acts as a capacitor and provides a charging mechanism for rotor shaft voltage buildup. Electrical breakdown of the film can damage the bearing. This paper examines the mechanical and electrical characteristics of the bearing and converts them into models. The mechanical model for the bearing contact area establishes an allowable bearing current density, which is used to estimate the electrical life of a mechanical bearing. The electrical model for the bearing provides a significant advancement, aids bearing design, and the analysis of electrically induced bearing damage. Finally, the paper presents quantitative results for one solution to the shaft voltage and bearing current problem. Index Terms - Bearing capacitance, bearing current, bearing current density, bearing threshold voltage, electric discharge machining, electrostatic shielded induction motor, rotor shaft-to-ground voltage, stator-to-rotor capacitance.

Pulse-width modulation is broadly used to control electric and electronic devices. The operation of many of these devices is based on the control of the output voltage of a passive filter. Their controllers are designed from the approximate linearization of the dynamics of the joint system, filter-pulse width modulation strategy, which is strongly nonlinear. Common linearization techniques work fine when the modulation frequency is much larger than the natural frequencies of the filter, but fail when that frequency is of the same order of magnitude or smaller than these filter frequencies, as happens in power electronic circuits. This paper develops a new linearization technique that allows a very precise control of these devices when small modulation frequencies have to be used. Our method permits the design of power electronic circuits with very fast output dynamic responses. An experimental circuit is developed to test this and results are reported. Index Terms--Computer control of electric circuits, linearization techniques, PWM control.

A magnetic bubble device (MBD) for revolution counters used for servomotors have been developed. This sensor was designed to count 32,487revolutions with only a 152bit memory. A magnetic garnet film was chosen so that a wide propagation margin was achieved. Thickness of the film was also optimized so that the bubbles were stretched at a high bias field. The thickness of Si[O.sub.2] was chosen to obtain a wide pulse width. The developed MBD achieved wide margins as follows: a propagation margin and a stretch margin were 25, 24Oe respectively in the bias field direction, and a pulse width margin was 5.6 [micro] sec. Index Terms -- encoder, magnetic bubble, revolution counter