Showing papers on "PWM rectifier published in 1994"

A novel three-phase utility interface minimizing line current harmonics of high-power telecommunications rectifier modules

Abstract: Based on the combination of a three-phase diode bridge and DC/DC boost converter a new three-phase three-switch three-level PWM rectifier system is developed. It can be characterized by sinusoidal mains current consumption, controlled output voltage and low blocking voltage stress on the power transistors. The application could be, e.g., for feeding the DC link of a telecommunications power supply module. The stationary operational behavior, the control of the mains currents and of the output voltage are analyzed. Finally, the stresses on the system components are determined by digital simulation and compared to the stresses in a conventional PWM rectifier system. >

A complete DC and AC analysis of three-phase controlled-current PWM rectifier using circuit D-Q transformation

Abstract: A recently proposed circuit P-Q transformation is used to analyze a three-phase controlled-current PWM rectifier. The DC operating point and AC transfer functions are completely determined. Most features of the power converter are clearly interpreted. They are: (1) the output voltage can be controlled from zero to maximum; (2) the system is equivalently an ideal current source in the steady state; (3) the system can be described as linear circuits; and (4) the input power factor can be arbitrarily controlled within a certain control range. >

Digital-signal-processor-based control of three-phase space vector modulated converters

Abstract: The paper presents the implementation of a DSP-based controller for three-phase, space-vector modulated converters. The implementation is illustrated for the control of a 2 kW, ZVS matrix power converter-based three-phase PWM rectifier. The controller features very high data processing speed (converter switching frequency of 100 kHz), and provides high-quality, low-distortion power converter input currents and output voltages. The controller can be implemented using only a few standard integrated circuits, providing high reliability and low cost. >

Fast-response high-quality rectifier with sliding mode control

Abstract: A PWM rectifier including an uncontrolled rectifier and a Cuk converter stage driven by a sliding mode controller is described. Like other high-quality rectifiers, this solution allows low-distorted and in-phase line current. Moreover, due to the sliding mode control, fast and stable response is achieved, in spite of the large output filter. Control complexity is the same as that of standard current-mode controls. Converter analysis, design criteria, and experimental results are reported. >

A three-phase regulated PWM rectifier with on-line feedforward input unbalance correction

Abstract: The analysis and design of a direct six-switch three-phase PWM rectifier, capable of correcting input unbalance, is presented. Based on the input source positive and negative sequence components, an unbalanced transfer matrix in terms of input phase voltages is derived. An online method is used to implement the transfer matrix function and generate the switch gating signals. As compared to other unbalance correction methods, the proposed approach is very simple to implement. It uses only a few discrete analog and digital components. The algorithm of the proposed approach is described in this paper, and results are verified from a 1 kVA breadboard set-up. >

Non linear control of PWM rectifier by state feedback linearization and exact PWM control

Abstract: This paper describes two nonlinear studies concerning a PWM rectifier. A nonlinear control scheme using state feedback linearization is presented, followed by an exact compensation method for the nonlinear switching effects of PWM. The two control laws developed in this paper show higher performance than traditional cascade control methods. >

Pole-placement control of voltage-regulated PWM rectifiers through real-time multiprocessing

Abstract: The voltage-regulated pulsewidth-modulated (PWM) rectifier is prone to instability. The system can be stabilized by proportional-plus-integral feedback control, but its transient response is slow. This paper describes results of a study of digital control to improve the system dynamic response by pole placement through state feedback. The control algorithm is implemented for real-time operation by using a custom designed system of three high-speed microprocessors. Results from an experimental study with a 1 kW hardware laboratory model of the PWM rectifier shows that the dynamic response can be significantly improved even when the DC link capacitor is substantially reduced. >

Unity-power-factor PWM rectifier with DC ripple compensation

Abstract: This paper presents a new topology of PWM rectifier which can achieve unity-power-factor on the AC supply side and ripple-reduction on the DC output side. The main circuit of this rectifier is accomplished by adding only a pair of switches to a conventional PWM rectifier. And it does not need the large DC capacitor or passive L-C resonant circuit. These additional switches and PWM rectifier are controlled not only to make a unity power factor but also to reduce the ripple current. The effectiveness of this circuit is confirmed by the experiments and analysis. This rectifier is useful for UPS and DC power supply, especially in case that the batteries are connected to the DC line. >

A novel load current control method for a leading power factor voltage source PWM rectifier

Abstract: A novel PWM voltage source rectifier, controlled by the load DC current instead of the DC voltage, has been developed. Its main characteristics are: (a) there is neither input current sensors nor DC voltage sensor; (b) it works with an unchangeable and predefined PWM pattern; (c) it presents a very strong stability; (d) its stability does not depend on the size of the DC capacitor; (e) it can work at leading power factor for all load conditions; and (f) it can also work with zero regulation for all load conditions. Digital simulations, analyses, and experiments confirm all these characteristics of the control method. >

A three-phase current-source type PWM rectifier with feed-forward compensation of input displacement factor

Abstract: Three-phase current-source type PWM rectifiers are often used as the front-end power converter unit in utility-interfaced systems. Due to the input filter (needed for current harmonic suppression), the input displacement factor is less than unity. It varies with the rectifier operating point and may result in unacceptable low values. In this paper, a new control method is proposed to achieve unity displacement factor independent of the load conditions. The proposed method controls the phase shift of the input currents in a feedforward fashion. The modulating signals are phase shifted according to the rectifier operating point to always result in near unity input displacement factor. The compensation scheme makes use of a DC current loop and the standard DC voltage regulation loop to produce the modulating signals with the required phase shift. As a result, the control circuitry does not require additional sensors. The PWM pattern is generated online, which results in fast response to transients. The rectifier is analyzed and design equations are derived. A design example is given and theoretical considerations are verified through simulation and by experimental results obtained on a 1 kVA laboratory prototype. >

Reliable 3-phase PWM boost rectifiers employing a series-connected dual boost converter sub-topology

Abstract: This paper describes circuit topologies for 3-phase PWM boost rectifiers that operate with a unity fundamental power factor and a low line-current distortion. Overlap delays between the switching of the upper and lower devices in a PWM rectifier leg are not critical and diodes eliminate the possibility of the DC-link capacitor discharging into short circuits and shoot-through fault conditions. The rectifiers are operated using a "series connected dual boost converter cell" sub-topology that rotates connections every 60/spl deg/ of the mains cycle and can be used in two current control modes. The dual current control mode shapes two line currents and can achieve current distortion levels below 5%. The single current control mode controls one line current and can achieve current distortion levels close to 5% with the output DC voltage operated at the standard rectified mains voltage level. The per-unit current ratings of the active 3-phase switching networks are around 15-20% of the input RMS line current as compared to 70% for a standard 3-phase PWM rectifier. Circuit simulations and experimental results are used to demonstrate the performance and feasibility of the rectifiers described. >

An on-line operated near unity power factor PWM rectifier with minimum control requirements

Abstract: Most PWM rectifiers use online PWM patterns which results in slow transient response. Damping resistors must be provided to avoid amplification of harmonics and current oscillations, especially during transient conditions. This results in reduced efficiency. In this paper, a current-source type PWM rectifier with online pattern generation and inherent pattern synchronization with the AC mains is proposed. The voltages across the input filter capacitors are chosen as the modulating signals. This results in a very fast starting and a much improved transient response. Also, the need of the damping resistors is eliminated due to the effective damping provided through the modulating of the capacitor voltages. Moreover, an additional phase-shifting circuit is added to the control scheme to achieve near unity power factor independent of the load variations. The paper includes analysis, design guidelines and experimental results on a 1 kVA laboratory prototype to confirm the theoretical considerations. >

A new three-phase series resonant active power filter

Abstract: In this paper a new three-phase series resonant active power filter is presented. The proposed approach employs a series resonant LC tank tuned to a high frequency along with a PWM rectifier topology to cancel lower order (5,7,11,13) harmonics generated by nonlinear loads. The PWM control of the active filter allows for independent control of several lower order (5,7,11,13) harmonics, both in amplitude and in phase, to effectively cancel load generated harmonics under varying load conditions. The LC resonant frequency is chosen to be high, thus resulting in smaller sizes of passive components. Further, a zero voltage switching strategy with capacitive snubbers is explored to minimize the switching losses. The simulation and preliminary experimental results presented verify the concept of the proposed system. >

Vehicle-mounted charger for electrical car

Abstract: PURPOSE:To reduce the weight and cost of parts mounted on an electrical car for charging a battery and those of the electrical car by allowing an inverter to also play a role of a charger. CONSTITUTION:The output of an inverter 3 is connected to an electric motor 5 by a double-throw switch 4 while an electrical car is in operation and a stator coil winding 6 of the electric motor 5 is connected so that primary connection (for example, star-connection) can be made and then the inverter 3 is allowed to be in charge of drive control of the electric motor 5 which is its original operation. When the electrical car is at halt and the charging battery 1 is to be charged, the output of the inverter 3 is connected to a commercial power supply via the stator coil winding 6 of the electric motor 5 by the double-throw switch 4 and then the stator coil winding 6 is operated as an AC reactor. Further, the inverter 3 is allowed to operate as a PWM rectifier, thus performing charging control of the charging battery 1. Therefore, the number of parts mounted on the electrical car for charging the battery 1 can be reduced and hence the weight and cost of the electric car can be reduced.

Unity-Power-Factor PWM Rectifier With DC Ripple Compensation

Abstract: This paper presents a new topology of PWM rectifier which can achieve unity-power-factor on the AC supply side and ripple-reduction on the DC output side. The main circuit of this rectifier is accomplished by adding only a pair of switches to a conventional PWM rectifier. And it does not need the large DC capacitor or passive L-C resonant circuit. These additional switches and PWM rectifier are controlled not only to make a unity power factor but also to reduce the ripple current. The effectiveness of this circuit is confirmed by the experiments and analysis. This rectifier is useful for UPS and DC power supply, especially in case that the batteries are connected to the DC line. >

Control of a single-switch three-phase rectifier operating in continuous conduction mode

Abstract: In many power electronics power supplies, power converters connected to the network are diodes or thyristors bridges, which cause a great deal of harmonic currents. The increasing number of power converters used today may lead to high harmonic levels on the network, which is deemed a potential problem for electricity supply quality and the proper operation of electrical equipment. This explains the appearance of standards aimed at reducing the harmonic emission of power supplies. In terms of the three-phase power converters which are typical of medium- and high-power applications, the PWM rectifier is a well-known and efficient way of obtaining a good power factor. It is expensive, however, and the challenge is now to find more economical devices which would help the spread of such nonpolluting power converters. In response, this paper thus describes a single-switch, three-phase PWM rectifier. This power converter operates in continuous conduction mode in order to avoid the voltage or current overloads which are inherent to discontinuous conduction mode operation.

A New Control Strategy to Improve AC Input Current Waveform of Parallel Connected Current Type PWM Rectifiers

Abstract: PWM rectifiers which can realize unity power factor and sinusoidal input current have been widely investigated to overcome problems of reactive power and harmonic current in electric power systems. However, in such PWM rectifiers, an LC filter which is necessary for absorption of carrier harmonics and for reduction of commutation spike voltage may cause waveform distortion and transient oscillation of the ac input current. As a solution to these problems, a new control method introducing state feedback control of the LC filter was proposed in our previous paper. To achieve stable operation in this method, the control frequency or carrier frequency of the PWM rectifier must be higher than 5 times the resonant frequency of the LC filter. So, a method to reduce the required carrier frequency is necessary to implement high power PWM rectifiers.In this paper, a parallel connection of two bridge circuits is introduced to reduce the required carrier frequency. A new control method for the parallel connected PWM rectifiers is proposed. The main circuit configuration and inter-bridge current between the two component bridge circuits are investigated. To achieve the reduction of the required carrier frequency without affecting the controllability, a new method of generating PWM pattern is developed. The effectiveness of the proposed control method is confirmed by some experimental results employing a test system.

An on-line operated unity power factor PWM rectifier for AC drive applications

Abstract: In order to minimize their impact on the AC supply, AC drives often require an input rectifier stage with low input current harmonics and high input power factor. High efficiency is also desirable. Drawbacks of the conventional off-line operated PWM rectifiers include slow transient response, load dependent input power factor and the need for damping resistors to avoid harmonic amplification and current oscillations, particularly under transient conditions. In this paper, an on-line operated PWM rectifier with inherent damping and pattern synchronization with the AC mains is proposed. Since the modulation scheme uses the voltages across the input filter capacitors as templates, faster transient response is achieved under normal and starting conditions and the need of the damping resistors is eliminated. Moreover, an additional phase-shifting circuit is used in the control scheme to achieve unity power factor, independently of the DC link current variations. The paper includes analysis and design guidelines for the rectifier control circuit. Experimental results on a 1 kVA laboratory prototype confirm the feasibility of the proposed control structure. >

Harmonic minimization in a three-phase asymmetrical PWM rectifier

Abstract: A new pulse-width modulation (PWM) method for a three-phase bridge rectifier developed here gives minimized low order harmonics. As a PWM rectifier, it offers better input and output characteristics than phase-controlled rectifiers. It has inherited the characteristics of the PWM rectifier such as having high power factor at the input with low harmonic content of the input current and zero phase-shift of input voltage and current. The availability of power transistors at high power ratings enabled the implementation of PWM rectifiers much easily. The modulation method is applied to a DC motor drive system at 1 kW rating. A high speed microcontroller produces the switching pulses. >

A control method for improving ac input current waveform of current‐type PWM rectifiers

Abstract: Recently, PWM rectifiers which realize high-power factor and almost sinusoidal ac input current have been proposed and some of them have already been put into practice. In many cases the PWM rectifiers are of current type, that is, they have a smoothing reactor on the dc side. In such rectifiers, an LC filter has to be inserted on the ac side to reduce current harmonics due to the PWM operation. However, the LC filter may cause waveform distortion and transient oscillation of the ac side current. As a solution to this problem, a new control method is proposed introducing ac side current control by means of state feedback of the LC filter. In this case, both the dc output current and the ac input current controls should be achieved by the PWM operation of the rectifier. Furthermore, to obtain sufficient controllability regardless of the operating condition, the dc output and ac input current controls should be done independently. To meet these requirements, existing control methods for PWM rectifiers are not directly applicable. In this paper, a novel control circuit configuration and a method of generating a PWM pulse pattern suitable for the proposed control method are described in detail. From the viewpoint of stability, feedback coefficients and circuit parameters are investigated on the basis of root locus analysis. Some experimental results also are shown to confirm the effectiveness of the proposed control method and the validity of the analytical results. Improvement of the ac side current waveform and the stability of the transient response are demonstrated by these experimental results.

Current suppressing circuit for pwm control rectifier

Abstract: PURPOSE:To allow control of high surge current entering from an AC power supply upon start of a PWM rectifier by providing means for correcting deviation signals CONSTITUTION:Upon receiving current deviation values DELTAIU, DELTAIW, DELTAIV of respective phases from adders 11, 12, 13, a deviation signal correcting circuit 30 corrects deviation signals of respective phases such that an induction voltage corresponding to an AC power supply 2 is produced from a PWR4 rectifier 4 thus producing corrected current deviation values DELTAIUO, DELTAIVO DELTAIWO for respective phases A U phase comparator 22 delivers a PWM signal, obtained by comparing the corrected current deviation value DELTAIUO of U phase with a carrier signal, to a pulse distribution circuit 25 Similarly, V phase comparator 23 and W phase comparator 24 receive corrected current deviation values DELTAIVO, DELTAIWO and carrier signals, respectively, and deliver PWM signals to the pulse distribution circuit 25 This constitution avoids high input surge current at the time of starting

A unity power factor control for fully software-controlled three-phase PWM rectifier with voltage link

Abstract: A unity power factor control which is easy to implement with a single-chip microcontroller is proposed for a three-phase pulse width-modulated (PWM) rectifier with voltage link. When the conduction times of two adjacent space vectors are equally distributed at both sides in the middle of switching interval, the ripple of the sinusoidal waveform is reduced. Through steady state analysis, a condition for unity power factor is derived. DC output voltage and power factor are controlled by directly adjusting the phase of the rectifier input voltage. The proposed control scheme is easily implemented with a single-chip microcontroller. It is shown via experimental results that the proposed algorithms give good performance for the PWM rectifier with voltage link. >

A new digital control methodology for three-phase power factor correcting PWM rectifier

Abstract: This paper describes a digital control scheme for a three-phase power factor correcting rectifier using template modulated PWM signals. The control strategy is based on the notion that the three-phase line currents can be forced to trace a deterministic waveform such as a sinusoid by considering its implicit model in the controller structure. The modulating template waveform is shown to be based on segments of a tangent waveform and is generated using the line voltage, the rectifier output voltage and the load current. The paper provides the analysis and the design of the controller and presents simulation and preliminary implementation results to demonstrate its effectiveness. >