Showing papers on "Rectifier published in 1995"

VSI-PWM rectifier/inverter system with a reduced switch count

Abstract: A current-controlled VSI-PWM rectifier and inverter with capacitor DC link is regarded as one of the most important structures for three-phase to three-phase power conversion. This type of power converter normally requires twelve switches for the rectifier and an inverter composed of self turnoff switch such as a bipolar transistor or an IGBT with an anti-parallel diode. In this paper, a new three-phase to three-phase AC/AC power converter for AC motor drives is proposed. The proposed power converter employs only eight switches and has the capability of delivering sinusoidal input currents with unity power factor and bidirectional power flow. This paper describes the feasibility and the operational limitations of the proposed structure. A mathematical model of the system is derived using the generalized modulation theory and experimental results for steady-state and dynamic behavior are presented to verify the developed model.

Nonlinear-carrier control for high power factor boost rectifiers

Abstract: Novel nonlinear-carrier (NLC) controllers are proposed for high-power-factor boost rectifiers. In the NLC controllers, the switch duty ratio is determined by comparing a signal derived from the main switch current with a periodic, nonlinear carrier waveform. As a result, the average input current follows the input line voltage. The technique is suitable for boost power converters operating in the continuous conduction mode. Input voltage sensing, the error amplifier in the current-shaping loop, and the multiplier/divider circuitry in the voltage feedback loop are eliminated. The current-shaping is based on switch (as opposed to inductor) current sensing. The NLC controllers offer comparable or improved performance over existing schemes, and are well-suited for simple integrated-circuit implementation. Experimental verification on a 240 W rectifier is described. >

Performance investigation of a current-controlled voltage-regulated PWM rectifier in rotating and stationary frames

Abstract: Active front-end rectifiers with reduced input current harmonics and high input power factor will be required in the near future for utility interfaced applications. In order to meet the new and more stringent regulations with force-commutated switches, the voltage source inverter approach is superior to the conventional current source approach, in terms of number of components and control options. However, the straightforward power angle control of the rectifier is characterized by a slow response and potential stability problems. This paper proposes a current-controlled PWM rectifier as an alternative. It provides near sinusoidal input currents with unity power factor and a low output voltage ripple. Moreover, it produces a well-defined input current harmonic spectrum, exhibits fast transient response to load voltage variations, and is capable of regenerative operation. PWM pattern generation is based on a carrier technique and the current controller is implemented in the: (a) stationary (abc) frame; and (b) rotating (dqo) frame. The design and the performance of the two controller options are investigated and compared. >

A novel on-line UPS with universal filtering capabilities

Abstract: A novel line-interactive uninterruptible power supply (UPS) is proposed that offers the characteristics of an "on-line" or "inverter-preferred" UPS (which incorporates a pulse-width modulation (PWM) rectifier) at a reduced cost. This new UPS is based on the combination of two full-bridge VSI converters: one in series with the input and the other in parallel with the load. The UPS acts as a line conditioner and output-voltage stabilizer in the presence of input power while charging the battery at a controlled rate. In case of loss of input power, the UPS can make a seamless transition to backup mode while supplying the load with a controlled sinusoidal voltage, drawing power from the battery. The series converter sees only a small percentage of the input voltage (typically, 10%-20%) while carrying the input current and therefore has a small kilovoltampere rating. The parallel converter supplies the load during blackout and hence determines the total kilovoltampere rating of the UPS. The reduced kilovoltampere rating of the series converter results in reduced system cost compared to conventional on-line systems without sacrificing any desirable characteristics. A laboratory version of the proposed UPS has been built to demonstrate the claimed capabilities, and both simulation and experimental results are included in the paper.

Integrated cranking inverter and boost converter for a series hybrid drive system

Abstract: An electric continuously variable drive system includes an ac motor, an alternator for supplying electrical power to the ac motor via a rectifier and an inverter, a heat engine for driving the alternator, an energy storage device for providing electrical energy to the electric continuously variable drive system, and a combination cranking inverter and boost converter. The combination cranking inverter and boost converter is coupled in series between the alternator and the energy storage device and coupled substantially in parallel with the rectifier in a series hybrid drive.

Circuit topologies for PWM boost rectifiers operated from 1-phase and 3-phase AC supplies and using either single or split DC rail voltage outputs

Abstract: This paper provides a survey of PWM boost rectifier circuit topologies for controlling a nonisolated DC-rail voltage whilst drawing supply currents at a unity fundamental power factor and with a low total harmonic distortion. Rectifier-leg topologies are classified by the number of switches and by the PWM waveforms generated. Complete rectifier circuit topologies are described for operation off 1-phase and 3-phase AC supplies. Circuit analogies are made between rectifiers for 1 and 3 phases, rectifiers using either a single or a split DC-rail and between rectifiers using either AC or DC side inductors. The performances of the various circuits are assessed with reference to factors such as conduction losses, efficiency, switch count, semiconductor voltage stresses, 3-level and 2-level PWM voltage waveforms and, finally, bi-directional power conversion. >

Combined deadbeat control of a series-parallel converter combination used as a universal power filter

Abstract: This paper presents the notion of combined control of a system of interconnected power electronic converters. The concept is demonstrated using a three-phase series-parallel active power filter as an example. The described active power filter consists of a series-parallel combination of two full bridge VSIs capable of arbitrarily controlling the input current and the output voltage. The proposed control scheme treats the converter combination as a single unit and uses the inverse system model to generate deadbeat control response for both input current and output voltage. A full order predictive state observer is used to reduce the number of sensors. Simulation results show the excellent disturbance rejection characteristics of the proposed control when compared to the separately controlled converter scheme. >

A zero-voltage switched, three-phase isolated PWM buck rectifier

Abstract: A novel three-phase, single-stage, isolated PWM rectifier is proposed, which is capable of achieving unity power factor, and low harmonic distortion of input currents, and at the same time realizing zero-voltage switching for all power semiconductor devices. Operation of the proposed circuit is thoroughly analyzed. Design equations and trade-offs are provided. The performance of the proposed circuit is demonstrated through a 2 kW, 100 kHz, digital signal processor controlled prototype. The conversion efficiency is around 93%. >

A current-type PWM rectifier with active damping function

Abstract: A new control method for current-type pulse-width modulation (PWM) rectifiers which can provide active damping function is presented. This damping function is effective only on the harmonic components of AC input current selectively. Thus steady-state waveform distortion and transient oscillation of the input current are reduced by the active damping effects. The active damping function can be realized by feedback control of an LC filter connected to the AC side of the rectifier, and it does not require any additional components in the main circuits, permitting a simple circuit configuration. The control system of the proposed PWM rectifier is analyzed by using a simple block diagram developed in the present paper. From the analytical results, the influence of the circuit parameters and control delay on the active damping effects and the stability of the operation are clarified to establish the design method. To confirm the effectiveness of the active damping function, some results of basic experiments are included. As an example of application of the active damping function, the proposed rectifier is applied to reduce the harmonic currents generated by conventional rectifiers operating in parallel with the proposed rectifier. Some experimental results in this application are also included.

A current-source inverter fed induction motor drive system with reduced losses

Abstract: Standard low- and medium-power induction motor drives are based on the pulse width modulation (PWM) voltage-source inverter (VSI) fed from a diode rectifier. The dual topology, based on the current-source inverter/rectifier structure is used in medium- and high-power applications. This paper analyzes the existing motor drives based on current-source topologies and proposes a control strategy that addresses some of the drawbacks of this approach compared to the voltage-source approach. The proposed strategy features the following: (1) an online operated PWM CSI, using instantaneous output capacitor voltage control based on space-vector modulation; and (2) an additional inverter modulation index control loop, ensuring constant inverter modulation index and minimum DC-link current operation. The resulting additional advantages include the following: (1) fixed and reduced motor voltage distortion; (2) minimized DC-bus inductor losses; (3) minimized switch conduction losses; and (4) elimination of motor circuit resonances. Experimental results based on a DSP implementation are given.

Electronic ballast with interface circuitry for phase angle dimming control

Abstract: A gas discharge lamp dimming ballast has a two wire input for connection to the hot dimmed and neutral leads of a phase control dimmer The ballast has an improved topology in which a pre-conditioner supplies a substantially constant DC voltage to a ballast stage including an inverter, a resonant tank output and a control circuit A dimming interface circuit derives a dimming signal having a voltage equal to the average value of the rectified output voltage of a full-bridge rectifier feeding the pre-conditioner circuit The dim signal is independent of the DC rail voltage and, in combination with the maintenance of a substantially constant DC rail voltage, permits of improved dimming control while providing the ease of installation of a two wire ballast The response time of the interface circuit relative to the pre-conditioner is selected to avoid power imbalances The ballast also includes an EMI filter and circuitry to prevent capacitive hold-up by the EMI filter of the rectified voltage to preserve the conduction angle for the interface circuit

Trench MOS Barrier Schottky (TMBS) rectifier: A Schottky rectifier with higher than parallel plane breakdown voltage

Abstract: A new rectifier structure, called Trench MOS Barrier Schottky (TMBS) rectifier, is proposed and demonstrated by modeling and fabrication to have excellent characteristics. Two-dimensional numerical simulations have demonstrated coupling between the charge in the N − drift region and the metal on the trench sidewalls resulting in an improved electric field distribution. For epitaxial layer doping of 1 × 10 17 cm −3 , simulations show that break-down voltages of three times the plane parallel breakdown can be achieved with low leakage current. The measured on-state voltage drops for the devices fabricated using 0.5 μm technology at 60 and 300 A/cm 2 were 0.2 and 0.28 V, respectively. Due to smaller drift region resistances, TMBS rectifiers can be operated at large current densities (∼ 300 A/cm 2 ) resulting in small evice sizes.

Universal-input, high-power-factor, boost doubler rectifiers

Abstract: This paper describes new universal-input high-power-factor boost doubler rectifiers (BDR). The new rectifiers can be configured for low-line (90-130 V RMS) or high-line (180-260 V RMS) operation such that component stresses and the rectifier efficiency are approximately the same for both the high-line and the low-line input. As a result, significant efficiency and size improvements can be obtained compared to the conventional boost rectifier designed for universal-input operation. Results are experimentally verified on a 220 W prototype. >

Dual output synchronous-induction starting/generating system

Abstract: An electric power starter generator system comprises a synchronous generator and an induction motor/generator mutually coupled to a shaft being driven to an external prime mover. The synchronous generator and the induction motor/generator are driven by the shaft at the same speed. The system includes a rectifier/inverter having ac terminals coupled to the output of the induction motor/generator, and dc terminals coupled to a dc bus. This rectifier/inverter allows bi-directional power flow to effectuate both power generation as well as electric start of the prime mover. The synchronous generator is excited by a commonly driven permanent magnet generator and a modulated exciter field control. The induction motor/generator is self-exciting through the rectifier/inverter once a voltage is established on the dc bus. The establishment of this voltage may be accomplished by a battery, or by connection of the synchronous generator's output to the input of the rectifier/inverter through a poly-phase contactor. This contactor also allows cross connection of either machine to either distribution bus if one of the machines were to fail, or if the loading on that particular bus became excessive.

Voltage balanced multilevel voltage source converter system

Abstract: A voltage balanced multilevel converter for high power AC applications such as adjustable speed motor drives and back-to-back DC intertie of adjacent power systems. This converter provides a multilevel rectifier, a multilevel inverter, and a DC link between the rectifier and the inverter allowing voltage balancing between each of the voltage levels within the multilevel converter. The rectifier is equipped with at least one phase leg and a source input node for each of the phases. The rectifier is further equipped with a plurality of rectifier DC output nodes. The inverter is equipped with at least one phase leg and a load output node for each of the phases. The inverter is further equipped with a plurality of inverter DC input nodes. The DC link is equipped with a plurality of rectifier charging means and a plurality of inverter discharging means. The plurality of rectifier charging means are connected in series with one of the rectifier charging means disposed between and connected in an operable relationship with each adjacent pair of rectifier DC output nodes. The plurality of inverter discharging means are connected in series with one of the inverter discharging means disposed between and connected in an operable relationship with each adjacent pair of inverter DC input nodes. Each of said rectifier DC output nodes are individually electrically connected to the respective inverter DC input nodes. By this means, each of the rectifier DC output nodes and each of the inverter DC input nodes are voltage balanced by the respective charging and discharging of the rectifier charging means and the inverter discharging means.

Ballast circuit for fluorescent lamp

Abstract: An improved ballast circuit for use with a compact fluorescent lamp includes an EMI filter, a rectifier and voltage amplification stage, an active resonant circuit and power factor correction stage which is connected in parallel to a lamp load. The ballast circuit includes a feedback capacitor which provides a feedback path for a portion of the high frequency current to the rectifier and voltage amplification stage. The feedback capacitor of the improved ballast circuit reduces the non-linear characteristics of the diode, thus providing almost a linear load on the input power supply and therefore achieving an improved power factor, on the order of 0.95 or greater. The improved ballast circuit may also include a dimming stage which works with the active resonant circuit to vary the amount of power that is supplied to the lamp load. The dimming stage does not require the addition of parasitic active stages and thus provides a lamp with high electrical efficiency.

Small-signal modeling of soft-switched asymmetrical half-bridge DC/DC converter

Abstract: A small-signal model of soft-switched asymmetrical half-bridge DC/DC converter operating in a continuous inductor conduction mode is proposed. The analysis of this model is applicable to converters with any type of output rectifier (full-wave or half-wave). Based on the proposed model, the feedback compensation network for a prototype converter was designed. An open loop frequency response and voltage ripple attenuation of the converter with closed feedback loop were calculated. The experimental results validated all theoretical predictions. >

Bridge rectifier circuit having active switches and an active control circuit

Abstract: A bridge rectifier circuit uses active switches for at least two of its four rectifying elements, and employs an active control circuit to control the state of the active switches. The active control circuit receives its input from the AC input to the bridge rectifier circuit, is powered by the DC output of the bridge rectifier circuit, and provides control outputs to the active switches. In this manner, a bridge rectifier circuit having improved performance and decreased power dissipation is achieved.

Adjustable speed drive for residential applications

Abstract: This paper describes a demonstration of an adjustable speed drive suitable for use in residential applications such as compressors and fans in heat pumps, air conditioners, and refrigerators. The adjustable speed drive uses only a four-diode rectifier and a six-transistor six-diode inverter and does not require a source-frequency filter inductor or capacitor. Motor speed is adjusted with source-frequency phase control eliminating the switching loss and electromagnetic interference caused by the more commonly used high-frequency pulse-width modulation. Low source-current distortion and high power factor are obtained at a full-load operating point which is found using a parametric analysis.

Telephone ringing signal detector

Abstract: An integrated ringing signal detector sufficiently small for implementation on a single PCMCIA card. The detector has a DC-blocking capacitor 28 disposed between the telephone line and a bridge rectifier 27. The output 29 of the rectifier 27 connects to a voltage detector 23 which detects when the ringing signal exceeds a predetermined voltage. Output 30 of the voltage detector 23 triggers thyristor switch 24 into conduction. Switch 24 remains conductive until current flowing therein falls below the holding current of the thyristor switch 24. Current limiter 25 limits the current flowing therein to a substantially fixed predetermined amount of current, sufficient for the adequate operation of the LED in the opto-coupler transducer 22. The transducer 22 is shown here as an opto-coupler having an LED transmitter and a phototransistor receiver to provide galvanic (high-voltage) isolation between the telephone line and the utilization device, here a modem.

Current-mode rectifier with improved precision

Abstract: A modified bridge bias arrangement is described for a precision current-mode rectifier that avoids the adjustment sensitivity of a previously reported scheme by directly defining diode bias current. In addition, an analysis of current-mode bridge rectification is presented, along with performance enhancements due to the introduction of a current summing output stage.

High performance ripple feedback for the buck unity-power-factor rectifier

Abstract: The buck unity-power-factor rectifier has harmonic-free input current with complete load regulation down to zero output voltage. A new "nonlinear ripple feedback" is proposed which exactly cancels the spoiling effect of DC-side current ripple on the low-distortion AC line current waveforms, even for large amounts of ripple. This cancellation is independent of operating point and readily implemented with analog hardware, thereby permitting economies in the design of the DC filter while maintaining harmonic-free operation. Both large-signal and incremental analyses of the rectifier are given. Confirming experimental results from a 1 kW 48 V isolated battery charger operating with current-ripple levels ranging from 50% to discontinuous-conduction-mode operation are given. >

Multi-resonant boost high power factor circuit

Abstract: A multi-resonant boost power factor correction circuit includes a full-wave rectifier; a high frequency filter capacitance coupled across the input terminals of the full-wave rectifier; a series half-bridge converter; a diode connected between the output of the rectifier and the dc bus voltage such that its cathode is connected to a dc bus; a capacitance coupled between the output of the rectifier and the junction between the series-connected switching devices of the half-bridge converter; a resonant load circuit connected to the junction between the switching devices, including a resonant inductor, a resonant capacitor and a load, such as a fluorescent discharge lamp; and a driver circuit for alternately switching the switching devices via a dead time control for selecting a dead time after one of the devices switches off and the other device switches on. The multi-resonant boost high power factor circuit meets the IEC standard for low harmonic content on input current, thus operating with a very high power factor, and operates with a minimal number of circuit components. In addition, the circuit meets lamp current crest factor specifications for fluorescent discharge lamp ballasts and requires lower voltage power devices.

Stability of ideal thyristor and diode switching circuits

Abstract: This paper analyzes the stability of a general RLC circuit with ideal thyristors or diodes and periodic sources. Applications include high power thyristor controlled reactor and bridge rectifier circuits. The periodic steady states of the circuit are analyzed using a Poincare map and transversality conditions are given to guarantee the smoothness of the Poincare map. A simple and exact formula for the Jacobian of the Poincare map is proved. Account is taken of the varying state space dimension as diodes switch on and off. When the transversality conditions fail, switching times can jump or bifurcate. Examples show that these switching time bifurcations can cause instability of thyristor circuits and mode changes of diode circuits. The simplification of the Jacobian formula is used to explain why the switching time bifurcations occur and are not predicted by the eigenvalues of the Jacobian. Periodic orbits of ideal diode circuits are proved to be stable using Jacobian and incremental energy methods. A source of damping in switching circuits is identified. >

Portable computer having built-in AC adapter incorporating a space efficient electromagnetic interference filter

Abstract: An internal AC adapter which incorporates a space efficient EMI filter is positioned within a main chassis portion of a portable personal computer having at least one energy-demanding component also positioned within the main chassis portion. The internal AC adapter, which converts alternating current received from an alternating current main to direct current for transmission to the energy-demanding components, includes a first connector for electrically connecting the internal AC adapter to the alternating current main, a bridge rectifier circuit having an AC input side electrically connected to the first connector and a DC output side and a space efficient electromagnetic interference filter having an input side electrically connected to the DC output side of the bridge rectifier circuit and an output side. The bridge rectifier circuit converts alternating current received from the first connector to direct current for transmission to the electromagnetic interference filter. In turn, the electromagnetic interference filter includes at least one capacitative element for filtering noise from the direct current transmitted thereto by the bridge rectifier circuit. The filtered direct current is then transmitted to the energy-demanding components electrically connected to the output side of the electromagnetic interference filter. By placing the electromagnetic interference filter on the DC output side of the bridge rectifier circuit, reduced size capacitors such as a multilayer ceramic capacitor may be used as the capacitative element.

Power-factor correction in bridge and voltage-doubler rectifier circuits with inductors and capacitors

Abstract: To improve the power factor and to comply with line-harmonics regulations, a power-factor-correction/line-harmonics-reduction circuit must be added to the capacitively filtered bridge or voltage-doubler rectifier. Passive solutions (i.e. circuits using only inductors and capacitors) are simple, reliable, and generate no EMI. In this paper we discuss single-phase rectifier circuits employing an additional inductor and one or more additional capacitors for power-factor correction. >

Truly temperature independent current conveyor precision rectifier

Abstract: A current conveyor based rectifier circuit with very low temperature sensitivity is presented. The use of a current mirror arrangement to bias the rectifying diodes provides higher temperature stability than previously reported designs. The output offset voltage is easily adjustable to the desired optimum level.

HVDC convertor waveform distortion: a frequency-domain analysis

Abstract: A linear and direct method of determining the major components of noncharacteristic waveform distortion at the terminals of an HVDC convertor is presented. The method is a development of the frequency-domain transfer function technique, and relates the AC current and DC voltage to distortion in the firing angle, AC voltage and DC current. The consequential effects of the commutation period and its dynamic variation are included. It is demonstrated that the dynamic variation of the commutation period is an important factor. The model is validated for low-order frequencies by comparison with results obtained by dynamic simulation for a simple test case.

Third-Harmonic Modulated Power Electronics Interface with Three-phase Utility to Provide a Regulated DC Output and to Minimize

Abstract: A novel approach to achieve nearly sinusoidal line current rectification of three-phase utility voltages is presented. The scheme incorporates two step-up dc-dc converters to mod- ulate the dc-link currents at the third-harmonic frequency. The modulated currents are then circulated through the ac-side of the diode-bridge rectifier, using a zigzag autotransformer. Simulation results for a three-phase, 208-V (line-to-line), 1-kW system are presented. Results from experimental investigations on a labora- tory model are included, supporting the concept.