Showing papers in "IEEE Transactions on Industry Applications in 2001"

A closed-loop selective harmonic compensation for active filters

Abstract: This paper proposes a control algorithm for parallel active power filters, based on current-controlled pulsewidth-modulated converters, which allows precise compensation of selected harmonic currents produced by distorting loads. The approach is based on the measurement of line currents and performs the compensation of the selected harmonics using closed-loop synchronous frame controllers. Thanks to the closed-loop operation, full compensation of the desired harmonics is achieved even in the presence of a significant delay in the current control. Thanks to the selective approach, active filter interactions with possible dynamic components of the load are minimized. Moreover, the complexity of the synchronous frame controllers is overcome using equivalent stationary frame controllers. Experimental results confirm the theoretical expectations.

A novel current-tracking method for active filters based on a sinusoidal internal model [for PWM invertors]

Abstract: A new current control method based on the internal model principle in control theory is proposed. It introduces a sinusoidal internal model into the control system. It does not use any coordinate transformations. The method can be used for tracking an arbitrary number of harmonics: a DC component or fundamental frequency component signal. It is applied to a single-phase pulsewidth modulation inverter and active filter. The validity is confirmed by simulation and experimental results.

Industry application of zero-speed sensorless control techniques for PM synchronous motors

Abstract: This paper presents the state of the art in the area of industrial applications of sensorless control for permanent-magnet synchronous motor (PMSM) drives. A new emerging technology is becoming mature to come to the market, based on high-frequency signal injection, that makes it possible to achieve zero-speed operation without increasing the complexity and the cost of the system. After an overview of major theoretical principles of sensorless control of PMSMs, the paper focuses on the practical implementation of one of the previously described high-frequency injection techniques in both salient and nonsalient PM machines. Experimental results are presented, including useful hints for practical implementation.

Synchronous-frame harmonic control for high-performance AC power supplies

Abstract: In order to achieve the reduction of voltage distortion in AC power supplies (ACPSs), this paper describes an implementation of synchronous-frame control for selected frequencies in the output voltage. The regulation of the fundamental output voltage, as well as that of some low-order harmonics, is achieved using a synchronous-frame controller for each selected frequency in addition to a conventional control. The conventional part conserves good dynamic performance under load changes, while rotating-frame controllers allow a slow, but very precise compensation of the residual errors within the assumption that the harmonics produced by distorting load are slowly varying. Moreover, motivated by a fixed-point implementation, a set of refinements and modifications of the original scheme is proposed, allowing a reduction of signal processing requirements and a new control algorithm structure less sensitive to quantization and rounding errors. This solution is particularly effective for high-power fully digitally controlled ACPSs, where the voltage loop bandwidth is usually not large enough to provide regulation at harmonic frequencies. The proposed control scheme has been implemented using a fixed-point single-chip digital signal processor (ADMC401 by Analog Devices). Experimental results on a 3-kVA three-phase converter prototype show the effectiveness of the proposed approach.

Dynamic voltage restorer based on voltage-space-vector PWM control

Abstract: A dynamic voltage restorer (DVR) based on the voltage-space-vector pulsewidth-modulation algorithm is presented. Phase-jump compensation is achieved using a software phase-locked loop and a lead-acid battery energy store. A battery-charging control technique using the DVR itself is also described. To validate the control of the DVR, a three-phase prototype with a power rating of 10 kVA has been successfully developed. Simulation and experimental results are shown to validate the control methods.

Uninterruptible power supply multiloop control employing digital predictive voltage and current regulators

Abstract: A digital control technique for the inverter stage of uninterruptible power supplies (UPSs) is described, which is based on voltage and current predictive regulators. Its aim is to achieve a deadbeat dynamic response for the controlled variables (output voltage and inverter current). The controller maintains the advantageous conventional multiloop structure and is capable of guaranteeing a high-quality dynamic performance. Moreover, its design is extremely simple and requires only a reasonably accurate knowledge of the output filter parameters. Finally, the only sensed variables are the output voltage and the converter output current. The validity of the proposed strategy is demonstrated by means of simulation and experimental results referring to a single-phase UPS laboratory prototype (1 kVA).

Improved analysis of a bearingless switched reluctance motor

Abstract: Bearingless switched reluctance motors, which can control rotor radial positions with magnetic force, have been proposed. Bearingless switched reluctance motors have combined characteristics of switched reluctance motors and magnetic bearings. Production of radial force for rotor shaft magnetic suspension is explained with differential stator windings. Mathematical relations between motor currents and radial force are derived by considering cross coupling and fringing fluxes. Theoretical relationships are verified with experimental results at partial overlap positions.

A new space-vector-based control method for UPS systems powering nonlinear and unbalanced loads

Abstract: In this paper, a new real-time space-vector-based control strategy is presented for three-phase uninterruptible power supply systems powering nonlinear and unbalanced loads The proposed control strategy generates the inverter reference and gating signals in closed loop and guarantees high-quality output voltages at the load terminals The approach, which is implemented on a digital signal processor, adapts to a wide variation of nonlinear and unbalanced load conditions without specific knowledge of the output filter (L-C) component values Analysis and experimental results on a 10-kVA prototype are presented The results show that the output voltage is restored at heavy nonlinear and unbalanced load

Wavelet and neural structure: a new tool for diagnostic of power system disturbances

Abstract: The Fourier transform can be used for the analysis of nonstationary signals, but the Fourier spectrum does not provide any time-domain information about the signal. When the time localization of the spectral components is needed, a wavelet transform giving the time-frequency representation of the signal must be used. In this paper, using wavelet analysis and neural systems as a new tool for the analysis of power system disturbances, disturbances are automatically detected, compacted and classified. An example showing the potential of these techniques for diagnosis of actual power system disturbances is presented.

Partial discharge theory and technologies related to medium-voltage electrical equipment

Abstract: Partial discharge (PD) monitoring is an effective online predictive maintenance test for medium-voltage (MV) motors, MV generators, and MV switchgear at 4160 V and above, as well as other electrical distribution equipment. The benefits of online testing allow for equipment analysis and diagnostics during normal production. Corrective actions can be planned and implemented, resulting in reduced unscheduled downtime. An understanding of the theory related to PD, and the relationship to early detection of insulation deterioration is required to properly evaluate this predictive maintenance tool. This paper presents a theory to promote the understanding of PD technology, as well as various implementation and measurement techniques that have evolved in the industry. Data interpretation, corrective actions, and application to electrical distribution equipment is also reviewed.

Application of a sliding-mode observer for position and speed estimation in switched reluctance motor drives

Abstract: A sliding-mode observer is applied toward the operation of a switched reluctance motor (SRM) drive. The sliding-mode observer estimates rotor position and velocity to control the conduction angles of the machine. Conventional on-off control with hysteresis current control is included with the position estimation scheme. The particular case of an automotive brake system motor is considered in detail where the conduction angles are modified with velocity feedback to provide optimum time response to brake system commands. Nonlinear modeling of a SRM is described and a computer simulation is developed based on data from an experimental SRM system. The sliding-mode observer is implemented with fixed-point and floating-point digital signal processors (DSPs) and the discrete-time implementations first examined under locked-rotor conditions. A comparison is also made between the implementation in two different types of DSPs. After confirming the accuracy of the computer simulation with experimental data, the design considerations in selecting observer coefficients with regard to sampling time, convergence rate, and transient stability are discussed. In conclusion, the effects of flux estimation errors on the system time response during a startup transient are examined.

Freewheeling diode reverse-recovery failure modes in IGBT applications

Abstract: In this paper, reverse-recovery failure modes in modern fast power diodes are investigated. By the aid of semiconductor device simulation tools, a better view is obtained for the physical process, and operating conditions at which both diode snappy recovery and dynamic avalanching occur during the recovery period in modern high-frequency power electronic applications. The work presented here confirms that the reverse-recovery process can by expressed by means of diode capacitance effects which influence the reverse-recovery characteristics. The paper also shows that the control of the carrier gradient and the remaining stored charge in the drift region during the recovery phase influence both failure modes and determine if the diode exhibits soft, snappy, or dynamic avalanche recovery characteristics.

Dual AC-drive system with a reduced switch count

Abstract: A dual current-regulated pulsewidth-modulated voltage-source inverter based on multiple two-phase PWM inverters, also called a B4 topology, requiring a dual AC-drive system with reduced switch count is proposed. The drive utilizes a total of only eight switches to produce two sets of three-phase or two-phase sinusoidal output currents that can be employed to feed three-phase or two-phase induction motors. A suitable control strategy of this new scheme is shown to minimize the single-phase current now through the DC-link capacitors, which is a common problem in reduced-switch-count topologies. In order to verify the performance of the motor drive system, an application on traction of an electric vehicle is carried out. Results show that the AC current through the DC link can be minimized, and when utilizing two-phase motors on the proposed dual drive, the reduced voltage gain problem, also common in B4 topologies feeding three-phase motors, can be solved.

Starting high-inertia loads

Abstract: Common methods used to start AC induction motors driving high-inertia loads include across-the-line starting and reduced-voltage starting by autotransformer, wye-delta, or resistor/reactor. Application of these methods is generally well documented and understood. However, with the increased use of electronic soft starters and variable-frequency drives, applications can be markedly different. This paper reviews the aforementioned methods and explains the benefits and limitations of each. The effect of high-inertia loads on both acceleration time and motor heating is examined. A case history of starting a centrifuge with an electronic soft starter is studied. Finally, a comparison of all of the methods is presented with recommendations on choosing the proper starter given.

Position-sensorless control of the transverse-laminated synchronous reluctance motor

Abstract: The sensorless control of the transverse-laminated synchronous reluctance motor is introduced, pointing out the negative effect of cross saturation. Then, an observer-based sensorless control scheme is proposed which solves this problem. Thus, a very good robustness against load variations is achieved. Moreover, the working speed is extended from zero to maximum speed, including the flux-weakening feature. This is obtained by a combined method of rotor position estimation, making use of both electromotive-force-based estimation and signal injection, without any need of additional voltage. A prototype drive has been assembled, making use of a commercial motor, and the obtained experimental results are given. A dynamic performance is achieved which is near to that of a sensored control, in the whole speed range. Moreover, position-sensorless position control is feasible.

Performance evaluation of a hybrid system comprising silent discharge plasma and manganese oxide catalysts for benzene decomposition

Abstract: A hybrid system comprising a silent discharge plasma reactor (SDR) and manganese oxide (MnO/sub 2/) catalyst was used for the decomposition of benzene in air. The benzene conversion was greatly enhanced by combining MnO/sub 2/ with the SDR in the latter part. The MnO/sub 2/ catalyst decomposed benzene by using ozone (O/sub 3/) that was formed in the SDR as the oxidant precursor. With an increase in the amount of water vapor in air, the benzene conversion was decreased, due to the deactivation of high-energy electrons, the diminished formation of O/sub 3/ in SDR, and decreased activity of MnO/sub 2/ for the benzene oxidation with O/sub 3/. The only products of the reaction were CO/sub 2/ and CO. The carbon mass balance was not perfect due to the deposition of intermediates on MnO/sub 2/ during the reaction. The intermediates were subsequently decomposed to CO/sub 2/ and CO by MnO/sub 2/ in the presence of O/sub 3/. In dry air, the selectivities to CO/sub 2/ and CO were 70% and 30%, respectively, and were almost independent of specific energy density. The CO/sub 2/ selectivity was improved to 90% by humidifying the background air.

Relative properties of the new combustion-resist vegetable-oil-based dielectric coolants for distribution and power transformers

Abstract: Electrical distribution transformer insulation systems are being reevaluated based on their total life-cycle cost from economical, safety, and environmental perspectives. Due to the inherently higher efficiency design offered by liquid-cooled transformers, development has focused on fluids having improved environmental and health properties while maintaining the fire-resistant properties of "less-flammable" fluids. This paper reports our findings from several years of research and development on alternative dielectric systems using both natural and synthetic esters. Because esters have lower inherent resistance to oxidation than conventional mineral oil, a novel insulation system was developed to overcome this potential handicap. Single- and three-phase prototype field installations using these new dielectric coolants are discussed.

Stability study and control methods for small-wattage high-intensity-discharge (HID) lamps

Abstract: The increasing speed of modern power electronics opens a way to study the stability of high-intensity-discharge lamps at very-high-frequency operation. In this paper, a lamp stability study based on a simplified theory on acoustic resonance frequency distribution in a small-wattage metal-halide (MH) lamp is presented. The frequency characteristic of a low-wattage MH lamp has been analyzed. Up to 700 kHz, extensive experiments using resonant-type electronic ballast have been conducted on 35-W MH lamps to investigate different control methods for avoiding acoustic resonance. The results indicate that a randomized switching scheme cannot always eliminate are instabilities caused by acoustic resonances in small-wattage MH lamps. The stability frequency regions should be identified. A stable arc can be obtained when the lamp is operated above the highest acoustic resonance frequency.

Towards ideal NO/sub x/ control technology using a plasma-chemical hybrid process

Abstract: The plasma-chemical hybrid process developed was extremely effective and economical in comparison with the conventional selective catalytic reduction (SCR) system and other technologies for NO/sub x/ removal from flue gas emissions. A series of experiments was performed to quantify all the reaction by-products such as N/sub 2/O, CO, HNO/sub 2/, HNO/sub 3/, and NO/sub 3//sup -/ and to evaluate NO/sub x/ removal efficiency. The optimum plasma reactor and its operating characteristics were investigated with regard to reaction by-products and NO/sub x/ removal efficiency using the ordinary ferroelectric packed-bed plasma reactor and the barrier-type packed-bed plasma reactor. The oxidation from NO to NO/sub 2/ without decreasing NO/sub x/ concentration (i.e., minimum reaction by-products) and with least power consumption is the key for the optimum reactor operating condition. The produced NO/sub 2/ was totally converted to N/sub 2/ and Na/sub 2/SO/sub 4/ with Na/sub 2/SO/sub 3/ scrubbing. The barrier-type packed-bed plasma reactor having 1.5 mm diameter electrode and 3 mm diameter BaTiO/sub 3/ pellets showed the superior NO oxidation without producing the by-products over the conventional packed-bed reactor. The barrier-type packed-bed plasma reactor followed by the chemical reactor showed extremely low operating costs (less than 1/6 of the SCR process) and achieved nearly 100% NO/sub x/ removal with less than 6 ppm of N/sub 2/O and 5 ppm of CO.

Encoderless position estimation for symmetric cage induction machines under loaded conditions

Abstract: This paper presents sensorless position estimation using a conventional or "symmetric" cage induction motor. The rotor position information is obtained by high-frequency injection and using the modulating effect of the rotor slots. This makes true sensorless position control possible. The deteriorating effect of saturation harmonies for operation at full flux and higher loads is suppressed by using a harmonic compensation scheme based on parameters obtained from an automated commissioning process. Experimental results are shown, demonstrating sensorless position estimation at full flux and high loads. Initial experimental results are presented for encoderless position control under full flux.

OH radical measurement in a pulsed arc discharge plasma observed by a LIF method

Abstract: Hydroxyl radicals generated by a pulsed arc discharge were measured by laser-induced fluorescence (LIF) with a tunable KrF excimer laser. It was shown that not only OH but excited O/sub 2/ (O/sub 2//sup */) and excited NO (NO/sup */) had absorption lines within a tunable range of the KrF laser, so that LIF signals of O/sub 2//sup */ and NO/sup */ were observed as well as OH signals. It was demonstrated that OH could be detected without disturbance by LIF signals of O/sub 2//sup */ or NO/sup */ through the A-X(3,0):P/sub 2/(8) excitation; OH density was measured under various conditions in the post-discharge region. The influences of humidity, discharge current, and O/sub 2/ concentration on OH density and OH decay rate were studied in H/sub 2/O/O/sub 2//N/sub 2/ mixture. The results provided some possible channels of OH production and reaction with other molecules in humid air. The absolute density of OH was estimated.

Input current shaper based on the series connection of a voltage source and a loss-free resistor

Abstract: A new input current shaper is proposed in this paper. The operating principle is based on the connection of a voltage source and a loss-free resistor (LFR) between the input rectifier and the bulk capacitor in a conventional switching mode power supply with no power-factor correction. Both the voltage source and the LFR are obtained as an additional output from the converter's transformer. This additional output is a forward-type one with one extra inductor. With the final topology, a good tradeoff between capacitor voltage, recycling energy, and harmonic content can be established in order to comply with IEC 1000-3-2 specifications.

Induction motor design for electric vehicle using a niching genetic algorithm

Abstract: In the case of the shape or structural optimization of induction motor design, it is necessary to identify multiple optimal profiles by locating local optima as well as global. Niching methods extend genetic algorithms to domains that require the location and maintenance of multiple solutions. In this paper, optimal design of an induction motor for an electric vehicle using a niching method adopting restricted competition selection is proposed. The evaluation criteria and the standards of the best design selection are also presented.

Instantaneous arcing-fault models developed for building system analysis

Abstract: An arcing fault is a dangerous form of short circuit that may have a low current magnitude. In the case of such faults, the magnitude of the current is limited by the resistance of the arc and may also be limited by the impedance of a ground path. This lower level fault current is often insufficient to immediately trip phase overcurrent devices, resulting in the escalation of the arcing fault, increased system damage, tremendous release of energy, and threat to human life. Despite modern advances in system protection and the adoption of National Electrical Code Section 230-95, people continue to be injured or killed from arcing faults, initiated by accidental physical contact or through a glow-to-arc transition. The initial phase of an arcing-fault research project was to review the historical evolution of arc modeling for low-voltage systems. A summary of the electrical aspects and the physics involved in arcing faults appeared in previous work. Today's better analytical tools facilitated the development of new instantaneous arc models with current-dependent arc voltages, which better represent the arcing phenomenon than the assumed arc voltage associated with previous instantaneous arc models. The arc currents in a typical medium-size building system are determined and harmonic analysis is performed.

A novel full-bridge DC-DC converter for battery charging using secondary-side control combines soft switching over the full load range and low magnetics requirement

Abstract: A novel full-bridge DC-DC configuration with a tapped transformer and secondary side control is proposed. It achieves zero-voltage switching for the primary side switches and zero-current switching for the secondary side switches, under all operating conditions. The conduction losses are significantly lower than those in the conventional soft-switching DC-DC converters. Due to superior filter waveforms, the filter requirements, both at the input and at the output, are significantly reduced. The features of the proposed converter are compared with those for the conventional phase-modulated full-bridge DC-DC converters. The proposed configuration is ideally suited for the AC-DC stage of high-power battery-charging applications with a power-factor-corrected preregulator. Analytical and experimental results on a 500 W/100 kHz prototype are presented.

Envelope simulation by SPICE-compatible models of linear electric circuits driven by modulated signals

Abstract: SPICE-compatible equivalent circuits were developed to facilitate the analysis and envelope simulation of electric circuits driven by modulated signals. The circuits are based on a novel complex phasor-domain transformation. The proposed method facilitates simulation of any general linear circuit driven by a modulated signal such as amplitude modulation, frequency modulation, or phase modulation. Simulation time by the proposed envelope simulation is much faster than the full cycle-by-cycle simulation of the original circuit and excitation.

Inherently decoupled magnetic suspension in homopolar-type bearingless motors

Abstract: The authors have proposed bearingless motors, that is, magnetic bearings combined with motors in the same stator. It is possible to reduce their shaft length compared with a conventional motor with magnetic bearings, and to achieve higher rotational speed. Bearingless motors generate radial force by adding n /spl plusmn/ 2-pole flux on n-pole motor flux to make the flux distribution unbalanced. Several types of bearingless motors have already been proposed, and most of them require variations of motor flux to be taken into account to maintain stable radial position control. In this paper, homopolar-type bearingless motors are proposed and their radial force is analyzed. The rotor of a homopolar motor has two cores with salient poles, and each core is magnetized in a single pole. The important characteristics that the radial force does not vary in accordance with the rotor angle or the motor torque current are derived from analysis. It is confirmed by experiments that the radial position can be controlled nearly independently from the rotational angle and torque.

Dynamic interaction analysis of HF ballasts and fluorescent lamps based on envelope simulation

Abstract: A SPICE-compatible simulation methodology for analyzing open- and closed-loop high-frequency electronic ballasts for a fluorescent lamp was developed. The proposed procedure applies envelope simulation and makes use of the SPICE-compatible model of a fluorescent lamp. Experimental results validate the reliability of proposed simulation method.