Showing papers on "Rectifier published in 1993"

A space vector-based rectifier regulator for AC/DC/AC converters

Abstract: A voltage-sourced rectifier control scheme for use with AC/DC/AC variable speed drives is presented. A control scheme is derived that directly calculates the duration of time spent on the zero state and on each switching state adjacent to the reference vector, over a constant switching interval, in order to drive the line current vector to the reference vector. In addition, under transient conditions, when deadbeat control is not possible, a control scheme is presented that ensures that the line current vector is driven in the direction of the reference current vector. The current reference for the rectifier controller is derived from the bus voltage error and a feedforward term based on the estimated converter output power. The proposed space vector-based rectifier regulator is shown to exhibit improved harmonic and transient performance over existing per-phase duty cycle prediction methods, especially at modulation indices near unity. The deadbeat control of the rectifier input current is accomplished every half-cycle with constant switching frequency while still symmetrically distributing the zero state within the half-cycle period. >

High frequency inverter with power-line-controlled frequency modulation

Abstract: An electronic high frequency supply, such as a lamp ballast, having a full-wave rectifier, a storage capacitor charged to a voltage greater than the peak of the rectifier output, and an isolating diode between the rectifier and the storage capacitor. An inverter is connected to the storage capacitor, and has a high frequency inductive load circuit connected between the inverter output and a junction between the isolating diode and the bridge rectifier. A capacitor, connected to the junction in parallel with a series circuit formed by the isolating diode and storage capacitor, forms a high frequency resonance circuit with the inductive load circuit. Current is drawn from the rectifier only as a series of pulses at the inverter frequency. To minimize variation in the high frequency load current, the inverter frequency is varied linearly with but oppositely to the instantaneous value of the rectifier output voltage.

Force commutated three level boost type rectifier

Abstract: A new force commutated three level boost type rectifier is proposed in this paper. The rectifier has the characteristics of drawing nearly sinusoidal current from utility with unity fundamental power factor. High reliability is possible due to its shoot-through free structure. A doubled dc bus voltage compared to a normal two-level rectifier is also possible because of the neutral point clamping. The operating principle, steady state analysis, input current and neutral point voltage control schemes, as well as detailed experimental results are presented in this paper.

Circuit topologies for single-phase voltage-doubler boost rectifiers

Abstract: A new family of single-phase voltage-doubler PWM (pulse width modulated) boost rectifiers is presented. By examining the switching states of several standard single-phase boost rectifier circuits, three characteristic PWM voltage switching patterns are identified: unipolar PWM; bipolar PWM; and phase-adjusted unipolar PWM. From this analysis, an equivalent family of voltage-doubler rectifiers is derived. When high output voltages are required, voltage-doubler rectifiers are shown to be able to generate AC line currents with the lowest current distortion. The circuits presented are examined using circuit simulators and experimental results. >

A new approach to improve power factor and reduce harmonics in a three phase diode rectifier type utility interface

Abstract: A novel approach to improving power factor and reducing harmonics generated by a three-phase diode-rectifier-type utility interface is proposed. This approach is passive and consists of a novel interconnection of a star/delta power transformer between the AC and DC sides of the diode rectifier topology. This interconnection, in combination with the 120 degrees conduction intervals of each diode, is shown to generate a circulating third-harmonic current between the AC and DC side of the rectifier bridge. This current is shown to drastically improve the performance of the diode-rectifier-type interface. The resulting input current is near-sinusoidal, with significant reduction in line current harmonics. The proposed system can be viewed as a cost-effective retrofit to the existing diode rectifier utility interface applications. A design example illustrates the sizing of the necessary passive components. Selected results were verified experimentally on a laboratory prototype system. >

Expandable multiterminal DC systems based on voltage droop

Abstract: This paper introduces a decentralized control scheme for the parallel connection of multiple rectifiers feeding a DC network with numerous inverters. The coordination of multiple HVDC power systems without explicit communication is accomplished by the use of DC-side voltages as a "droop" mechanism. The DC side voltage serves the role of frequency in an ordinary AC system. The approach is most suitable to superconducting DC systems and to DC systems that span small distances and where voltage is relatively uniform throughout the DC system. This paper presents the concept in the context of a high capacity superconducting 10 kV urban infeed. >

Techniques for minimizing the input current distortion of current-controlled single-phase boost rectifiers

Abstract: Techniques for minimizing the input current distortion of current-controlled single-phase boost rectifiers are described. The switching patterns of several boost rectifiers are examined to identify the nature of their input current waveforms. This analysis is used to examine the low-frequency current distortion levels, and hence the power quality, associated with the rectifiers. A PWM (pulse width modulation) strategy that selectively switches between positive unipolar PWM and negative unipolar PWM, called phase-adjusted unipolar PWM, is shown to produce the lowest current distortion levels. A novel two-switch asymmetrical half-bridge rectifier is presented that draws an input current at a unity fundamental power factor and with the same low distortion as obtained with the four-switch H-bridge rectifier. The operation of the various rectifiers is examined with reference to theoretical predictions, circuit simulations, and experimental results. This analysis is used to compare the performances of the various rectifier switching patterns. >

A high performance single phase AC to DC rectifier with input power factor correction

Abstract: A high performance single phase AC to DC rectifier with input power factor correction is proposed. The proposed approach has many advantages which include fewer semiconductor components, simplified control, high performance features and satisfaction of IEC 555 harmonic current standards. Simulation and experimental results obtained on a laboratory prototype are discussed. >

Blue LEDs, UV photodiodes and high-temperature rectifiers in 6H-SiC

Abstract: Single junction devices in silicon carbide have been developed for use as blue LEDs, UV photodiodes and high- temperature rectifiers. As a light emitter, 6H-SiC junctions can be tailored to emit light across the visible spectrum. The most widely commercialized device is the blue LED. Over the past two years, the quantum efficiency of the Cree blue LED has increased significantly. The devices emit light with a peak wavelength of 470 nm with a spectral halfwidth of ∼70 nm. The optical power output is typically between 12 and 18 μW for a forward current of 20 mA at 3 V. This represents a power efficiency of ∼0.02–0.03%. In addition to blue emission, the energy bandgap of ∼3.0 eV allows for inherently low dark currents and high quantum efficiencies for ultraviolet photodiode detectors made in 6H-SiC, even at high temperatures. These devices typically exhibit a quantum efficiency of 80–100% and peak response of ∼250–280 nm. These characteristics are maintained to at least 623 K. The dark current density at -1.0 V and 473 K is ∼10-11 A/cm2. This corresponds to an extrapolated room temperature current density of ∼2 × 10-17 A/cm2 at -1.0 V. Rectifiers with blocking voltages as high as ∼1400 V and a forward current rating of 400 mA at ∼3.0 V have been fabricated. For a 710 V rectifier, the reverse bias leakage current density at 200 V is shown to increase from ∼10-9 to ∼10-7 A/cm2 from 300 to 673 K, respectively. The reverse bias breakdown appears to occur via avalanche multiplication processes exhibiting a sharp knee at breakdown. For a ∼1400 V rectifier, the reverse bias leakage current at 1375 V is less than 1 μA at room temperature.

Unity PF current-source rectifier based on dynamic trilogic PWM

Abstract: One remaining step in perfecting the stand-alone, unity power factor, regulated current-source pulse-width-modulated (PWM) rectifier is to reduce cost, by bringing the twelve-valve converter (consisting of three single-phase full bridges that operate with two-level or bilogic PWM) to the six-valve bridge. However, the six-valve topology requires a three-level or trilogic PWM strategy that can handle feedback signals. A general method of translating three-phase biologic PWM signals into three-phase trilogic PWM signals is presented. The method of translation retains the characteristics of the bilogic PWM, including the frequency bandwidth. Experiments show that the trilogic PWM signals produced by the method can handle not only stabilizing feedback signals but also signals for active filtering. >

A new control algorithm for three-phase PWM buck rectifier with input displacement factor compensation

Abstract: A new control algorithm for the three-phase buck rectifier with an input filter is developed. The algorithm employs a separate control loop for compensation of the input current displacement factor in steady-state, in addition to the standard output voltage regulation loop. The algorithm allows separate design of the input filter and of closed loop output voltage control. The design procedure is explained and illustrated on an example. The algorithm is verified experimentally on an 1-kW, 100-kHz, three-phase isolated buck power converter. >

A new zero-voltage transition, three-phase PWM rectifier/inverter circuit

Abstract: A switching rectifier/inverter technique that combines the conventional three-phase, six-stepped pulse-width modulated (PWM) rectifier/inverter with a simple commutation circuit to provide zero-voltage turn-on for the switches and soft turn-off for the diodes is presented. The commutation circuit is active only during a short period of the switching cycle, thus it consumes minimum power and does not impair the normal constant frequency PWM control. The addition of the commutation circuit does not result in increased component current and voltage stresses compared to the conventional PWM converter. >

Phase-controlled series-parallel resonant converter

Abstract: A constant-frequency, phase-controlled, series-parallel resonant DC-DC converter is introduced, analyzed in the frequency domain, and experimentally verified. To obtain the DC-DC converter, two identical series-parallel resonant inverters are paralleled and the resulting phase-controlled resonant inverter is loaded by a voltage-driven rectifier. The converter can regulate the output voltage at a constant switching frequency in the range of load resistance from full-load resistance to infinity while maintaining good part-load efficiency. The efficiency of the converter is almost independent of the input voltage. For switching frequencies slightly above the resonant frequency, power switches are always inductively loaded, which is very advantageous if MOSFETs are used as switches. Experimentally results are given for a converter with a center-tapped rectifier at an output power of 52 W and a switching frequency of 127 kHz. The measured current imbalance between the two inverters was as low as 1.2:1. >

A fully software-controlled PWM rectifier with current link

Abstract: A fully-software-controlled pulse-width-modulated (PWM) rectifier with a current link is presented. The rectifier uses six switches to connect the three-phase source of the load directly. Line power factor is controlled while maintaining DC current. The input filter of the rectifier is analyzed, showing that unity power factor is achieved by the lagging of the input current of the rectifier with respect to the source voltage. The PWM technique is developed using a space vector modulation, and its implementation is carried out with a minimal control hardware structure based on a 16 b single-chip microcomputer. It is shown experimentally that the scheme gives good performance. >

PWM-rectifier/voltage-source inverter without DC link components for induction motor drive

Abstract: Voltage-source inverters are normally equipped with an electrolyte capacitor in their DC link. A voltage-source inverter without DC link components is proposed to eliminate the electrolytic capacitor which has a short life compared with an AC capacitor (metalised polyester film, etc.). This inverter system requires an AC filter composed of L and C in the AC source side. In this case, the most important problem is the reduction of AC filter capacity. To achieve this reduction, the rectifier section is operated by PWM control. The waveform of the AC source current is also improved. Steady-state analysis, the calculated characteristics of the AC filter capacity and the waveforms of voltage and current are described for a 0.75 kW induction motor driven by the system. The AC filter capacity is reduced to about 38% of the rectifier without PWM. Measured waveforms are presented for a motor slip of 4%. The stability with, and without, DC link components, is also discussed.

Zero-voltage-transition pulse-width-modulated converters

Abstract: To date, soft-switching techniques applied to the PWM converters, with the exception of a few isolated cases, are subjected to either high switch voltage stresses or high switch current stresses, or both. This invention presents a new class of zero-voltage-transition PWM converters, where both the transistor and the rectifier operate with zero-voltage switching, and are subjected to minimum voltage and current stresses. Breadboarded converters are constructed to verify the novelty of the proposed new family of converters.

An industrial power distribution system featuring UPS properties

Abstract: A high power quality DC power distribution system for industrial applications is described. The distribution system incorporates uninterruptible power supply (UPS) properties and can supply larger loads than conventional UPSs. Certain high power applications are very sensitive to power quality problems. The scheme described has two rectifier terminals supplying a DC ring bus system capable supplying a large number of parallel inverters. The DC system incorporates energy storage systems to ride through an AC system outage until a backup generator is brought online. The scheme described utilizes superconductors on the DC bus, but the same basic scheme will work with ordinary conductors following some modification of the converter control. >

Audio frequency power amplifiers

Abstract: An audio frequency amplifier having a switching converter comprising source and sink rectifiers configured for sourcing and sinking current, in which the source and sink supply voltages of the rectifiers track the audio frequency signal being amplified. The amplifier has a circuit or element for discharging the output capacitors of the source and sink rectifier as necessary to prevent floating of the source and sink supply voltages. The discharging element can be a locking capacitor or one or more Zener diodes connected across the source and sink supply voltages. The discharge circuit can be one or more switching transistors connected across the freewheeling diodes of the source and sink rectifiers to actively pull the source and sink voltages down to discharge the output capacitors and thereby prevent floating. Low voltage rated parts can be used in the output stage amplifier, and in certain configurations a high voltage low current preamplifier stage can be eliminated.

Series resonant converter having a resonant snubber

Abstract: A fixed frequency, series resonant converter having a resonant snubber comprising an inductor and capacitor connected across a tank circuit of the converter. An optimum amount of inductance in the resonant snubber minimizes the degree of "shoot-thru," or conduction through a body-diode within a transistor switch of the converter caused by ringing, which allows for nearly sinusoidal current to be provided to a full bridge high voltage rectifier enabling the power converter to operate at a higher frequency. An alternate embodiment applies the resonant snubber only across a selected transistor switch.

Lamp ballast with frequency modulated lamp frequency

Abstract: An electronic high frequency supply, such as a lamp ballast, having a full-wave rectifier, a storage capacitor charged to a voltage greater than the peak of the rectifier output, and an isolating diode between the rectifier and the diode. An inverter is connected to the energy storage capacitor, and has a high frequency inductive load circuit connected between the inverter output and a junction between the isolating diode and the storage capacitor. A capacitor, connected to the junction in parallel with a series circuit formed by the isolating diode and storage capacitor, forms a high frequency resonance circuit with the inductive load circuit. Current is drawn from the rectifier only as a series of pulses at the inverter frequency. To minimize variation in the high frequency load current, the inverter frequency is varied according to a sensed parameter which varies during each cycle of the rectifier output.

Analysis and average-value modeling of dual line-commutated converter-6-phase synchronous machine systems

Abstract: Analytical relationships are established which can be used to predict the average value characteristics of a dual line-commutated power converter/6-phase synchronous machine system. In particular, basic relationships are established in which the average DC power converter voltages and the average q- and d-axis stator currents are related to the power converter firing delay angles. These relationships should be useful in the design and average value simulation of dual line-commutated power converter/6-phase synchronous machine systems. >

Modelling and analysis of a three phase PWM AC-DC convertor without current sensor

Abstract: The familiar state space averaging technique for DC-DC convertors is extended for modelling a three-phase AC-DC convertor without current sensor. The space vector representation technique is used to simplify greatly the modelling process without sacrificing the accuracy and valid frequency range. Both steady-state and small-signal analyses are made. The results show that for the proposed duty ratio control law the convertor can achieve an ideal property, namely, sinusoidal input current with unity power factor, zero output voltage ripple resulting from line frequency and fixed switching frequency. Moreover, the convertor also possesses the regenerative capability which is useful for many applications. Finally, some experimental results are presented for verification.< >

Electric power supply

Abstract: An electric power supply includes: a full-wave rectifier to rectify full-wave rectifying an ac input voltage; a switch for switching an output current of the rectifier; a signal generator for generating a target signal to force a dc output voltage to follow a reference voltage, and a controller for controlling a switching timing of the switch and for repeating the operations of turning off the switch when a current detection signal of the switch complies with the target signal and turning on the switch again after a predetermined short period of time.

Introduction of the harmonic distortion determining factor and its application to evaluating real time PWM inverters

Abstract: The harmonic distortion determining factor (HDDF), which represents the intrinsic spectral properties of pulse-width modulation (PWM) methods, is introduced. The HDDF is almost independent of the inverter operating conditions such as the switching frequencies or load parameters if the switching frequency is 40 times greater than the output frequency. Furthermore, it is closely related to the root mean square (RMS) values of the harmonic current and motor torque ripples for induction motor drives, or the RMS values of the harmonic current and DC voltage ripples for rectifier operation. Therefore, it is useful as a common quality index for the evaluation of PWM methods. Four typical analog PWM methods and four digital PWM methods are compared and evaluated based on HDDF values. It is shown that the harmonic injected PWM for analog PWM, or the digital PWM of type C has the best characteristics. >

A high density 48 V 200 A rectifier with power factor correction-an engineering overview

Abstract: In telecommunications installations it is desirable for power equipment to draw a balanced three phase current at unity power factor with zero neutral current. A compact 48 V, 200 A rectifier weighing 32 kg has been commercially developed for this need. The rectifier employs the power conversion techniques first reported at INTELEC 1989 by Dennis Chapman of Swichtec Power Systems (formerly Eltec Electronics), New Zealand. Powered from a three wire, three phase 400 V, 50-60 Hz supply the rectifier presents essentially a unity power factor to the line. The thermal layout adopted, combined with fan cooling, keeps the overall dimensions to 400 mm wide/spl times/178 mm high/spl times/460 mm deep (4U/spl times/19 inch rack module). Maximum continuous output power is 11.2 kW (56 V, 200 A) at an efficiency of 90%. The rectifier comprises three modules. Each module operates at 230 V AC and can supply up to 70 A at 56 V DC. The three modules are connected in a star or 'Y' configuration. The junction point of the three modules is maintained at the equivalent neutral point voltage by controlling the power processed by each module. >

Integrated thermoelectric system with full/half wave rectifier control

Abstract: A thermoelectric system which operates on AC input power without requiring external rectification or conditioning is provided The thermoelectric system includes a thermoelectric device with an integrated rectifier circuit The thermoelectric device includes a thermoelectric array which may function satisfactorily with 120 volt AC, 240 volt AC or any other desired input power A control circuit is also provided to allow switching the associated rectifier circuit of the thermoelectric system from full-wave rectification to half-wave rectification The thermoelectric system may use the control circuit to maintain the temperature of either the hot plate or the cold plate associated with the thermoelectric device at a desired value

Circuit for powering a fluorescent lamp having a transistor common to both inverter and the boost converter and method for operating such a circuit

Abstract: A circuit with a transistor common to both the inverter and the boost converter powers a gas discharge lamp. In a half-bridge inverter, a boost inductor is coupled between the rectifier and the junction between two switching circuits.

Reduced voltage/zero current transition boost power converter

Abstract: A reduced-voltage/zero-current transition (RV/ZC-T) PWM converter includes an added active resonant network shunting the active power switch to reduce the switching losses in both the active power and and passive rectifier switches. The active power switch turns-on under reduced-voltage while the rectifier diode turns-off under zero-current. A soft current turn-off of the rectifier makes this converter suitable for high voltage applications where the reverse recovery losses of the diode can be considerable. An auxiliary switch included in the resonant network also operates with zero-current- switching.

High-frequency isolation UPS with novel SMR

Abstract: This paper concerns a newly developed 2 to 5 kVA, high-frequency isolation type UPS (uninterruptible power system). This UPS features a novel SMR (switch mode rectifier) that is applied to the input converter section and a newly developed low-loss IGBT (insulated gate bipolar transistor) that is employed in both inverter and converter sections. The SMR, as a single converter, has functions for high-frequency isolation, enhancement of input power factor and stabilization of DC output voltage. In the case of a new type of DC-clamped SMR (DCC-SMR), the number of current flowing devices in the frequency changer has been reduced to 1/2 of those compared with systems using a conventional SMR, and simplification of the snubber discharge circuit has also been achieved. Owing to the above, this newly developed UPS not only has small volume and weight, about 1/2 of that of commercial frequency isolation type UPSs, but also provides high efficiency-at least equivalent to that of the latter UPS. >

Control equipment for high voltage direct current transmission system with equipment of self-commutated converter

Abstract: A high voltage dc transmission system uses equipment of self-commutated converters each of which comprises switching devices with a self-commutating (gate-turn-off) function A first control equipment associated with the rectifier comprises a constant reactive power (var) control circuit for holding constant the reactive power on the input side of the rectifier, and a constant dc voltage control circuit for holding constant the dc system voltage on the output side thereof A second control equipment associated with the inverter comprises a constant reactive power control circuit for holding constant the reactive power on the output side of the inverter, and a constant active power control circuit for holding constant the active power on the output side thereof The first control equipment and the second control equipment each have a current control circuit for making independent control of each component of a two-phase current resulted from transformation of a three-phase ac current