Showing papers on "Rectifier published in 1999"

Hybrid multilevel power conversion system: a competitive solution for high power applications

Abstract: Use of multilevel inverters is becoming popular in recent years for high power applications. Various topologies and modulation strategies have been investigated for utility and drive applications in literature. Trends in power semiconductor technology indicate a trade-off in the selection of power devices in terms of switching frequency and voltage sustaining capability. New power converter topologies permit modular realization of multilevel inverters using a hybrid approach involving integrated gate commutated thyristors (IGCT) and insulated gate bipolar transistors (IGBT) operating in synergism. This paper is devoted to the investigation of a hybrid multilevel power conversion system typically suitable for high performance, high power applications. This system designed for 4.16 kV, /spl ges/100 hp load comprises of a hybrid seven-level inverter, a diode bridge rectifier and an IGBT rectifier per phase. The IGBT rectifier is used on the utility side as a real power flow regulator to the low voltage converter and as a harmonic compensator for the high voltage converter. The hybrid seven-level inverter on the load side consists of a high voltage, slow switching IGCT inverter and a low voltage, fast switching IGBT inverter. By employing different devices under different operating conditions, it is shown that one can optimize the power conversion capability of entire system. A detailed analysis of a novel hybrid modulation technique for the inverter, which incorporates stepped synthesis in conjunction with variable pulse width of the consecutive steps is included. In addition, performance of a multilevel current regulated delta modulator as applied to the single phase full bridge IGBT rectifier is discussed. Detailed computer simulations accompanied with experimental verification are presented in the paper.

Circuit and method for controlling a synchronous rectifier converter

Abstract: A rectifier having an input and an output and a method of controlling the rectifier. The rectifier comprises: (1) switching circuitry coupled between the input and the output, the switching circuitry adapted to operate in selected one of (a) an active bidirectional mode of operation and (b) an inactive unidirectional mode of operation to rectify substantially alternating current at the input to produce substantially direct current at the output and (2) control circuitry coupled between the rectifier output and a control input of the switching circuitry, the control circuitry capable of sensing an output current level of the rectifier and transitioning the switching circuitry between the active bidirectional mode and the inactive unidirectional mode as a function of the output current level thereby to prevent substantial reverse power flow through the rectifier. The rectifier is particularly useful in power systems having a plurality of rectifiers operating in parallel to prevent one rectifier from driving the other.

Uninterruptible power supply

Abstract: An electronic circuit, such as a UPS, interfaces a main ac power source and at least one secondary power source to a load. The secondary power source(s) may include one or more auxiliary generators, a flywheel motor generator or microturbine with high speed motor generator, and/or any of a variety of dc storage devices. The electronic circuit includes a dc bus, a first uncontrolled rectifier in combination with a first filter for coupling the main ac power supply to the dc bus, one or more additional uncontrolled rectifier(s) and filter(s) for coupling the auxiliary generator(s) to the dc bus, and a dc-to-ac inverter (between the dc bus and the load) for providing ac output power to the load. The advantages of reduced parts count, increased compatibility between the generator(s) and the electronic circuit, and a simpler method for paralleling many storage and generation devices with a very high power factor to the sources, regardless of the load power factor, are provided.

Status of the techniques of three-phase rectifier systems with low effects on the mains

Abstract: Based on a comprehensive study of the literature, concepts of three-phase rectifier systems with low effects on the mains are classified. Such systems are unidirectional and bidirectional self-commutated power converters with impressed output voltage or output current and line-commutated rectification in connection with passive and active filtering. Selected circuit concepts are analyzed concerning the operational behavior and the obtainable quality of the mains current. Furthermore, an evaluation of the rectifier concepts concerning utilization of the power semiconductors, rated power of the inductive and capacitive components and of the realization effort in general is given. Finally, problems of the practical application of high switching frequency PWM rectifier systems and topics of further research are discussed.

Universal distributed-resource interface

Abstract: An electronic interface couples a combination of generation and storage devices with a power grid and/or a load. The interface comprises a DC bus; a DC storage device coupled to the DC bus; a first DC-to-AC inverter (N1) having a DC port operatively coupled to the DC bus, and an AC port; a second DC-to-AC inverter (N2) having a DC port operatively coupled to the DC bus, and an AC port; a switch (S4) for electrically coupling the AC port of the second DC-to-AC inverter to a first generator or an AC storage device; a first rectifier (D1) for coupling an AC output of the first generator to the DC bus; and a second rectifier (D2) for coupling an AC output of the AC storage device to the DC bus. The electronic interface provides an efficient mechanism for integrating a variety of storage and generation devices to produce high quality power and reliability to a load as well as to facilitate interfacing of the storage and generation devices to the power grid for purposes of energy control, load leveling, and peak shaving.

A new soft-switched quasi-single-stage (QSS) bi-directional inverter/charger

Abstract: A new soft-switched quasi single-stage (QSS) bidirectional inverter/charger topology is proposed in this paper. It realizes seamless four-quadrant operation in inverter mode, and rectifier operation with unity power factor in charger mode. Single stage power conversion, standard half-bridge connection of devices, soft-switching for all the power devices, low conduction loss, simple center-aligned PWM control, and high efficiency are among the salient features. The principles of circuit operation, PWM control and synthesis, and topological extension are discussed in this paper. The experimental results on a 3 kVA prototype (12 V DC to and from 110 V AC) are also presented.

DC ripple current reduction on a single-phase PWM voltage source rectifier

Abstract: A novel topology of single-phase pulsewidth modulation (PWM) voltage-source rectifier capable of achieving not only a sinusoidal input current, but also a zero-ripple output current, is presented. The rectifier consists of a conventional single-phase PWM voltage-source rectifier, a pair of additional switches and an inductor. Hence, the proposed rectifier requires neither a large DC capacitor nor a passive L-C resonant circuit. The input current control is achieved by the conventional PWM current control technique. However, DC ripple current reduction control is difficult because one of the switching legs in the DC ripple current reduction circuit is shared with the PWM rectifier circuit. Two control methods, referred to here as the DC C inductor method and the AC inductor method, are proposed for DC ripple reduction, and the characteristics of these control methods are discussed. These control methods are implemented using a microprocessor, and the effectiveness of the circuit is confirmed experimentally. This rectifier has useful applications in uninterruptible power systems and DC power supplies, especially for cases in which the batteries are connected in parallel to the DC line.

Novel zero-voltage and zero-current-switching full-bridge PWM converter using a simple auxiliary circuit

Abstract: A novel zero-voltage and zero-current-switching (ZVZCS) full-bridge pulsewidth modulation converter is presented to simplify the circuits of the previously presented ZVSCS converters. A simple auxiliary circuit, which consists of one small capacitor and two small diodes, is added in the secondary to provide ZVZCS conditions to primary switches, as well as to clamp secondary rectifier voltage. The additional clamp circuit for the secondary rectifier is not necessary. The auxiliary circuit includes neither lossy components nor additional active switches, which makes the proposed converter efficient and cost effective. The principle of operation, features, and design considerations are illustrated and verified on a 2.5 kW 100 kHz insulated-gate-bipolar-transistor-based experimental circuit.

Barrier inhomogeneities and electrical characteristics of Ti/4H-SiC Schottky rectifiers

Abstract: Forward density-voltage (J-V) measurements of titanium/4H-SiC Schottky rectifiers are presented in a large temperature range. While some of the devices present a behavior in accordance with the thermionic current theory, others present an excess forward current at low voltage level. This anomaly appears more or less depending on the rectifier and on the temperature. A model based on two parallel Schottky rectifiers with different barrier heights is presented. The characteristics show good agreement. It is shown that the excess current at low voltage can be explained by a lowering of the Schottky barrier in localized regions. A proposal for the physical origin of these low barrier height areas is given.

An RC load model of parallel and series-parallel resonant DC-DC converters with capacitive output filter

Abstract: A novel analytical methodology is proposed and applied to investigate the steady-state processes in voltage-fed parallel and series-parallel resonant DC-DC power converters with a capacitive output filter. In this methodology, the rectifier, output capacitor and load are replaced by an equivalent circuit which includes a capacitor and resistor connected in parallel. Excellent agreement was obtained when comparing numerical values calculated by the proposed model to cycle-by-cycle SPICE simulation and to the numerical results of earlier studies.

Minimum-loss strategy for three-phase PWM rectifier

Abstract: In this paper, the conduction and switching losses of a voltage-fed three-phase pulsewidth modulation (PWM) rectifier are analyzed for various PWM schemes. On the basis of this result, a novel PWM strategy which minimizes the loss of a three-phase PWM rectifier is developed. This minimization result is derived from the following two factors: (1) less switching frequency ratio; and (2) the absence of switching in the vicinity of peak input current. As a result, it is anticipated that the switching loss of the rectifier is reduced by 46%, compared with continuous space-vector PWM rectifiers, and 20% compared with conventional discontinuous space-vector PWM rectifiers. Moreover, the proposed PWM scheme can produce the highest available output voltage because it is based on the concept of the voltage space vector. The effectiveness of the proposed PWM strategy is verified by experiments.

Reference frames fit for controlling PWM rectifiers

Abstract: The authors argue that one should keep things simple when controlling bidirectional pulsewidth modulation rectifiers by considering the utility grid as a virtual electric machine. The advantage is that the air-gap flux of this big machine can be directly measured in a straightforward way. Therefore, as shown in this paper, principles of field orientation can be applied to control the power flow, yielding high-dynamic performance.

High power factor rectifier with reduced conduction and commutation losses

Abstract: This paper presents a high power factor rectifier with reduced conduction and commutation losses for telecommunication applications. The reduced conduction losses are obtained through the use of a single converter, instead of the conventional configuration, composed of a four-diode front-end rectifier followed by a boost converter. A nondissipative snubber is responsible for the reduction in the commutation losses. A prototype rated at 1.6 kW, operating at 25 kHz with IGBTs has been implemented in laboratory.

An analysis of three-phase low-harmonic rectifiers applying the third-harmonic current injection

Abstract: An analysis of the three-phase low-harmonic rectifiers applying passive third-harmonic current injection networks is presented in this paper Optimal amplitude of the injected current to minimize the input current total-harmonic distortion (THD) is derived as a function of the injected current phase displacement Power aspects of the third-harmonic current injection are analyzed, and it is shown that improvement in the input current THD could be obtained at the expense of the power taken by the current injection network In the case of optimal current injection, the power taken by the current injection network is shown to be equal to 8571% of the input power, resulting in the input current THD of 5125% Effects of unwanted higher order harmonics in the injected currents are studied for two previously proposed passive current injection networks The current injection networks are compared under the constraint that volt-ampere ratings of applied components are the same Analytically obtained results are experimentally verified

A simple wind power generating system with permanent magnet type synchronous generator

Abstract: The authors propose an inexpensive wind power generating system in this paper. Existing wind power generating systems are mostly of large capacity (over 100 kW) and high-priced (about 1000 USS/kW). Because of the erratic changes of wind power and of smoothing peak power, an AC/DC converter-fed battery system is recommended. Thus, one requires the exact rotating speed of generators (especially in the case of synchronous generators) to use AC/DC converters with high quality. These factors are increasing the cost of such systems. The authors adopt a compact permanent magnet type synchronous generator, which doesn't need exciting current, and a step-up/down buck-boost chopper to wind power generating system of a few kW output without position or speed sensor. In addition, they employ an inexpensive rectifier circuit using a diode bridge instead of an AC/DC power converter with PWM method. Using these methods, they achieve a simple and inexpensive wind power generating system.

Transcutaneous energy transmission system with full wave class e rectifier

Abstract: This inventions is a transcutaneous energy transmission system (TETS) (10) including a Class E full wave low dv/dt rectifier in the implanted receiver circuit (14). The TETS provides power for any kind of an implanted device (26) requiring a source of DC power for operation. The Class E full wave low dv/dt rectifier provides efficient conversion of radio frequency power to direct current power. Another embodiment of a TETS includes a Class E full wave low dv/dt rectifier with circuitry for synchronous rectification. A receiver circuit (34) including a Class E full wave low dv/dt rectifier configured for use with a transmitter circuit, is also disclosed.

Forward-flyback converter with current-doubler rectifier: analysis, design, and evaluation results

Abstract: Complete design-oriented steady-state analysis of the forward-flyback converter, with the current-doubler rectifier is provided. Advantages and disadvantages of this topology compared to the conventional forward converter are discussed. In particular, the transformer-secondary copper losses are evaluated. In addition, a step-by-step design procedure is given, Finally, experimental evaluation results obtained on a 3.3 V/50 A DC/DC converter prototype for the 40-60 V input-voltage range are presented.

Control of a three-phase PWM rectifier using estimated AC-side and DC-side voltages

Abstract: A new control method of a pulsewidth modulation (PWM) rectifier without measuring AC- and DC-side voltages is proposed. As information about these voltages is necessary for the controller, all required voltage values are estimated from the measured line currents and the calculated values of the input reactor voltage during switching of the rectifier circuit. The input reactor voltage can be obtained by using a differentiator that produces the derivative of the line current or by detecting the voltage induced in a secondary winding wound on the input reactor. The secondary winding creates the electric isolation between the main circuit and the controller. The proposed method is verified by experiment. This paper describes the estimation method, gives the configuration of the controller, and discusses steady-state and transient performances of the rectifier.

Apparatus and method for control head unloading on power down in a disk drive

Abstract: Disclosed is a head loading/unloading type disk drive of retracting a head to a ramp by a reserve power supply upon power down of a main power supply. An unloading control system drives a VCM using a low-level voltage from the reserve power supply until the head reaches the ramp immediately upon power down of the main power supply. After the head reaches the ramp, the system applies a high-level voltage from the reserve power supply. The reserve power supply is made up of a rectifier for converting the back EMF of an SPM into a DC voltage. When a retract circuit detects power down of the main power supply, the DC voltage from the rectifier is limited to a low-level constant voltage by a constant voltage circuit, and applied to the VCM. When a ramp collision determining circuit determines collision of the head against the ramp, it controls the voltage applied to the VCM from the low-level voltage to a high-level voltage.

Harmonic-injection control technique for three-phase, discontinuous-conduction-mode, high-power-factor boost rectifiers with improved line-transient response

Abstract: A three-phase discontinuous-conduction-mode (DCM), pulse-width-modulated (PWM) boost rectifier using harmonic-injection control is provided with a feedforward path to vary the duty cycle of the PWM modulator according to the input voltage, so as to provide improved transient response. In one embodiment, the feedforward path provides to the PWM modulator a ramp voltage that has a slope proportional to the magnitude of the input line voltage. In one embodiment, the harmonic injection signal is summed with the error signal of an output feedback loop. In another embodiment, the harmonic injection signal is integrated and summed with the ramp voltage of the feedforward path. Moreover, by adding a nonlinear gain control circuit, the DC gain of the DCM boost rectifier at light load is adaptively reduced to achieve stability of the rectifier at light load.

Power conversion system

Abstract: A power conversion system always keeps a constant voltage level relative to the ground potential and shows an improved controllability for the noise compensation current. In the noise reduction circuit of the system, a rectified DC voltage is applied to the positive side output line and the negative side output line. The DC voltage is divided by a pair of capacitors connected in series with the intermediary point held to the ground potential. Thus, the positive side output line can always supply a positive voltage that is held to a constant level relative to the ground potential. Similarly, the negative side output line can always supply a negative voltage that is held to a constant level relative to the ground potential. Additionally, as the transistors are controlled for on/off operations by the amplifier, the noise compensation current flows through the noise reduction circuit between the input grounding terminal of the full-wave rectifier and the ground.

Single-stage input-current-shaping technique with voltage-doubler-rectifier front end

Abstract: In this paper, a new single-stage input-current-shaping (ICS) technique that integrates the voltage-doubler-rectifier front end with a DC/DC output stage is introduced. Due to the voltage-doubler-rectifier front end, the reduction of line-current harmonics can be achieved with a higher conversion efficiency compared to the corresponding single-stage ICS circuit with the conventional wide-range full-bridge rectifier. In addition, the proposed technique requires energy-storage capacitors with a lower voltage rating and smaller total capacitance than the conventional single-stage ICS counterpart, which reduces the size and cost of the power supply. The performance of the proposed technique is evaluated on a 100 W (5 V/20 A) experimental prototype circuit.

Analysis and average-value modeling of an inductorless synchronous machine load commutated converter system

Abstract: Synchronous machine fed load-commutated power converters (SMLCCs) are commonly used for DC power sources in marine and aircraft power systems. The focus of this paper is to set forth a model for SMLCCs for use in transient stability studies involving these systems. Although there has been considerable work in this area, much of this work has assumed the existence of a DC link inductor whereupon the DC link current is approximately constant. In practice, this filter is often eliminated, whereupon previous models are no longer valid. A new average-value model is set forth for SMLCCs in which there is no DC link filter inductor. The model is validated both experimentally and through the use of a detailed computer simulation.

Converter with a high power factor using a DC center point voltage

Abstract: Switching control is remarkably simplified and a DC voltage is boosted, and then, an input power factor is sufficiently improved and harmonics are reduced by connecting a full-wave rectifier circuit to an AC power source through a reactor, and connecting a smoothing capacitor and boosting capacitors, which are connected in series with each other, in parallel between the output terminals of the circuit. In addition, a switching device is connected between the input terminal of the circuit and the connecting point between the boosting capacitors, and a control device is provided to control the switching device so that the switching device can be switched at every half cycle of the power source voltage.

Decoupled control of the active and reactive power in three-phase PWM rectifiers based on non-linear control strategies

Abstract: Pulse-width modulated (PWM) current-source and voltage-source rectifiers (CSRs and VSRs) present several advantages as compared to thyristor line commutated and diode bridge rectifiers, respectively. Indeed, low supply current harmonic distortion and displacement power factor control including unity displacement power factor operation, can be obtained. However, the models of the CSRs and VSRs are nonlinear, which involves their analysis and certainly their control. This complexity is somehow avoided when using direct line current control and relatively high switching frequencies (>1 kHz). Unfortunately, this approach does not guarantees the stability of the rectifier, results in a dynamic that is load dependant and covers low to medium power level applications. This paper proposes the application of a nonlinear control strategy in combination with a high performance low switching frequency space vector modulation technique. The approach can be used in high power applications and allows the independent control of the two supply current components (active and reactive), which admits the converter to either generate or absorb reactive power according to a given set point while operates as an independent DC power supply. The paper includes a complete formulation of the system equations and a controller design procedure. Simulated results confirm the validity of theoretical considerations.

Simplified control technique for high-power-factor flyback Cuk and Sepic rectifiers operating in CCM

Abstract: Control techniques for high-power-factor rectifiers which do not need input voltage sensing are gaining considerable attention due to their simpler implementation and inherently superior stability, as compared to conventional average or peak current mode control. Among these, the solutions based on the integration of a current signal (switch, diode, or inductor current) provide an inherent noise immunity, which makes them further appealing. This paper proposes a simple implementation of one such control technique for high-power-factor flyback, Cuk, or Sepic rectifiers, which, while still retaining a high power factor, further reduces the control complexity, thus making the solution very attractive for smart-power integration. A 200 W flyback rectifier with the proposed control technique was implemented and tested. The achieved results are in good agreement with the expected performance.

High-performance mobile power antennas

Abstract: An RFID tag's mobility can be increased and cost can be decreased by using high-performance mobile power antennas instead of battery powered tags. Disclosed are some power antennas that include a half wave rectifier, a full wave rectifier, and a voltage multiplier. These antennas can be cascaded to boost the power or voltage gain. Additionally, planar elements can be added to increase efficiency without decreasing mobility.

Performance improvement of half controlled three phase PWM boost rectifier

Abstract: The potential of the half-controlled three-phase pulse-width modulated (PWM) boost rectifier is investigated based on theoretical analysis, simulations and experiments. The main advantages of this rectifier are: (1) a simpler and economical system compared to a full controlled PWM rectifier (reduced controlled switch count, single power supply for gate drives, and shoot-through free leg structure); and (2) better performance compared to a diode rectifier (actively controllable DC link voltage and lower input current total harmonic distortion (THD)). In particular, it is shown in this paper that the input current THD of this rectifier can be reduced by intentionally introducing a lagging power factor current command. Several issues for further performance improvement are pointed out for future work.

A new control scheme for single-phase PWM multilevel rectifier with power-factor correction

Abstract: A new control scheme for a single-phase bridge rectifier with three-level pulsewidth modulation is proposed to achieve high power factor and low current distortion. The main circuit consists of a diode-bridge rectifier, a boost inductor, two AC power switches, and two capacitors. According to the proposed control scheme based on a voltage comparator and hysteresis current control technique, the output capacitor voltages are balanced and the line current will follow the supply current command. The supply current command is derived from a DC-link voltage regulator and an output power estimator. The major advantage of using a three-level rectifier is that the blocking voltage of each AC power device is clamping to half of the DC-link voltage and the generated harmonics of the three-level rectifier are less than those of the conventional two-level rectifier. There are five voltage levels (0, /spl plusmn/V/sub DC//2, /spl plusmn/V/sub DC/) on the AC side of the diode rectifier. The high power factor and low harmonic currents at the input of the rectifier are verified by software simulations and experimental tests.

Comparison of not synchronized sawtooth carrier and synchronized triangular carrier phase current control for the VIENNA rectifier I

Abstract: Integrated control circuits being available for the input current control of single-phase power factor correctors are frequently applied also for realizing a simple current control for each phase of a three-phase PWM rectifier system. There, the input currents are controlled independently although the three phases are mutually coupled, i.e., the sum of the phase currents is forced to zero for missing connections between the mains star point and the output voltage center point. However, ignoring of the coupling of the three phases results in increased amplitudes of harmonics with switching frequency and/or in a significantly higher ripple of the rectifier input current. This is shown in this paper by a detailed analysis of different current control concepts for a three-phase three-switch three-level boost-type PWM rectifier (VIENNA Rectifier I) with unity power factor. The theoretical considerations are verified by digital simulations and an experimental analysis of a laboratory prototype and are valid in general for three-phase boost-type voltage DC link PWM rectifier systems.