Showing papers on "PWM rectifier published in 2005"

Comparative evaluation of three-phase high-power-factor AC-DC converter concepts for application in future More Electric Aircraft

Abstract: A passive 12-pulse rectifier system, a two-level, and a three-level active three-phase pulsewidth-modulation (PWM) rectifier system are analyzed for supplying the dc-voltage link of a 5-kW variable-speed hydraulic pump drive of an electro-hydrostatic actuator to be employed in future More Electric Aircraft. Weight, volume, and efficiency of the concepts are compared for an input phase voltage range of 98-132 V and an input frequency range of 400-800 Hz. The 12-pulse system shows advantages concerning volume, efficiency, and complexity but is characterized by a high system weight. Accordingly, the three-level PWM rectifier is identified as the most advantageous solution. Finally, a novel extension of the 12-pulse rectifier system by turn-off power semiconductors is proposed which allows a control of the output voltage and, therefore, eliminates the dependency on the mains and load condition which constitutes a main drawback of the passive concept.

An improved robust predictive current regulation algorithm

Abstract: Current regulation techniques for pulsewidth-modulated (PWM) voltage source inverters (VSIs) can be classified as either linear or nonlinear. Linear techniques consist principally of either a proportional-integral (PI) or a predictive current control strategy, while nonlinear schemes are usually based on a hysteresis strategy. Of the two linear strategies, predictive current control offers the advantages of precise current tracking with minimal distortion and can also be fully implemented on a digital platform. However, the conventional implementation of the predictive current regulation (PCR) algorithm is sensitive to noise and errors in the load inductance estimate, particularly when the back EMF is also estimated. This paper presents an improved PCR algorithm that retains all the benefits associated with PCR while achieving significantly increased robustness to load parameter mismatch and reduced zero current clamped oscillation effects. It is also relatively insensitive to noise in the sampled current measurements. The algorithm is equally applicable to variable fundamental frequency applications such as variable speed drives and to fixed fundamental frequency applications such as PWM rectifier systems or active filters. Simulation and experimental results are presented to confirm the improved robustness of the new algorithm.

Active damping control of a high-power PWM current-source rectifier for line-current THD reduction

Abstract: The use of active damping to reduce the total harmonic distortion (THD) of the line current for medium-voltage (2.3-7.2 kV) high-power pulsewidth-modulation (PWM) current-source rectifiers is investigated. The rectifier requires an LC filter connected at its input terminals, which constitutes an LC resonant mode. The lightly damped LC filter is prone to series and parallel resonances when tuned to a system harmonic either from the utility or from the PWM rectifier. These issues are traditionally addressed at the design stage by properly choosing the filter resonant frequency. This approach may result in a limited performance since the LC resonant frequency is a function of the power system impedance, which usually varies with power system operating conditions. In this paper, an active damping control method is proposed for the reduction in line current THD of high-power current-source rectifiers operating at a switching frequency of only 540 Hz. Two types of LC resonances are investigated: the parallel resonance excited by harmonic currents drawn by the rectifier and the series resonance caused by harmonic pollution in the source voltage. It is demonstrated through simulation and experiments that the proposed active damping control can effectively reduce the line-current THD caused by both parallel and series resonances.

Active filtering function of three-phase PWM boost rectifier under different line voltage conditions

Abstract: Slight hardware and algorithm modifications as well as a higher power ratio of a three-phase pulsewidth-modulation (PWM) rectifier make compensation of neighboring nonlinear power load possible. The active filtering function enlarges the functionality of PWM rectifiers, which decreases the cost of additional installation of compensating equipment. It gives a chance to fulfill both shunt active filter (SAF) and PWM rectifier tasks in a multidrive system by one advanced converter. Thanks to the idea of virtual flux, the direct power control space-vector-modulated (DPC-SVM) and new synchronous double reference frame phase-locked loop approach, the control system is resistant to a majority of line voltage disturbances. This assures proper operation of the system for abnormal and failure grid conditions. Simulation and experimental results have proven excellent performance and verify the validity of the proposed system.

Converter used as a battery charger and a motor speed controller in an industrial truck

Abstract: This paper presents a bi-directional power converter used on one hand as a battery charger and on the other hand as a motor speed controller. Different possibilities are presented and a comparison of these structures is carried out. In battery charger mode, the power converter has to absorb a sinusoidal current with a unit power factor. According to the power range, two possibilities are presented: the isolated CUK converter with a 1.5 kW DC motor and a pulse width modulation (P.W.M.) inverter/rectifier to supply a 6 kW induction machine

Modelling and control of three-phase/switch/level fixed-frequency PWM rectifier: state-space averaged model

Abstract: A new and simple state model of a three-phase, three-switch, three-level, fixed-frequency pulse-width-modulated rectifier is presented. The modelling approach uses the state-space averaging technique in continuous current mode. The averaging process is applied on two time intervals: the switching period for average current evaluation, and the mains period for average voltage computation. A basic mathematical model of the converter is first established. A simplified time-invariant model is then deduced using the rotating Park transformation. The steady-state regime is analysed on the basis of the model obtained, and converter design criteria consequently discussed. The proposed modelling approach is then verified numerically through a digital implementation of the converter in the Matlab/Simulink framework, using the switching function approach. The numerical results show the reliability of the proposed model that would be then easily applied to the design of suitable duty-cycle-based control schemes.

Pulse width modulation (PWM) rectifier with variable switching frequency

Abstract: A method for controlling a device including a plurality of switching devices operated in accordance with a pulse width modulation technique includes receiving a reference voltage signal associated with a first pair of the switching devices. A switching signal is generated. The first pair of switching devices are controlled based on the reference voltage signal and the switching signal in accordance with the pulse width modulation technique. A frequency of the switching signal is varied based on the value of the reference voltage signal.

A UPF power conditioner with maximum power point tracker for grid connected variable speed wind energy conversion system

Abstract: In this paper, a UPF power conditioner for an optimal extraction of output power from grid connected variable speed wind energy conversion system (VSWECS) is presented. The system consists of a variable speed wind turbine coupled to a permanent magnet synchronous generator (PMSG) through a gear box, two PWM power converters and a maximum power point tracker (MPPT). Output power from PMSG is first converted into DC, inverted and then it is fed to the grid. Both the power conversions are performed at unity power factor and the DC link voltage is maintained constant. PWM rectifier is controlled based on the principle to shape the phase current as phase voltage and PWM inverter is controlled by a hysteresis current controller. The control algorithm is implemented on TMS320F243 DSP and the viability of the scheme is confirmed through experimental studies. The complete system has been simulated for various wind velocities. Typical simulation and experimental results are presented.

A high performance DSP controller for three-phase PWM rectifiers with ultra low input current THD under unbalanced and distorted input voltage

Abstract: Although in recent years three-phase PWM rectifiers have become increasingly popular, in most practical cases the line unbalance and/or the presence of distortion can seriously affect their performances. Line unbalance and distortion add unwanted low frequency harmonics to the input current, leading to an increase in the total harmonic distortion (THD). At high power level, the switching frequency is restricted to a few kilo hertz and therefore an LC filter is needed to eliminate the switching ripple of the current. The resulting structure is an LCL filter that causes instabilities and oscillations. This paper details how to implement a high performance multi-loop digital controller suitable for a boost type PWM rectifier, leading to an extremely low THD content even with non-ideal input voltage conditions. The multi-loop method uses only two capacitor filter voltages and inverter currents to estimate the line voltages and currents. Positive and negative sequence controllers are used to regulate the fundamental currents while resonant controllers tuned to each harmonic from third to thirteenth remove the low frequency components due to input voltage unbalance and/or distortion. The proposed approach is implemented on a 16-bit fixed point DSP (ADMC401) and tested on a three-phase 20 kW IGBT-based PWM rectifier.

Method and apparatus for estimating line inductance for PWM rectifier control

Abstract: A rectifier includes a switching circuit and a controller. The switching circuit is coupled between positive and negative buses and a plurality of input voltage sources. The switching circuit includes a plurality of pairs of switching devices. Each pair is associated with one of the input voltage sources. The controller includes first and second control loops operable to generate control signals for operating the pairs of switching devices to generate a potential across the positive and negative buses. The controller is further operable to estimate a line inductance seen by the rectifier based on at least one of the control signals and generate an inductance compensation gain factor for applying to the control loops based on the estimated line inductance.

Novel control technique of single-phase PWM rectifier by compensating output ripple voltage

Abstract: Novel control technique of single-phase PWM rectifier by compensating output ripple voltage is presented. Output ripple voltage is cancelled before feeding to voltage controller in order to increase system bandwidth while supply current is still nearly sinusoidal and maintains unity power factor. Output ripple voltage estimator is calculated by the information of peak value of supply voltage and current. Peak value estimator of sinusoidal signal is introduced with the help of a simple trigonometric rule. Additionally, feed forward current controller is also presented so as to improve tracking performance of supply current. The proposed scheme is simulated in order to compare with conventional scheme. The simulation results show that the proposed scheme is working effectively both in rectifying mode and regenerating mode

Design and experimental analysis of a DC to 1 MHz closed loop magnetoresistive current sensor

Abstract: This paper presents the improvement of a commercially available current sensor based on the anisotropic magneto-resistive effect for applications requiring high bandwidth current measurement such as high switching frequency single-phase and three-phase unity power factor PWM rectifier systems The sensor concept is of special interest as it could be packaged into compact power processing units and integrated power electronic modules In this paper the anisotropic magneto-resistive effect, as well as the analog interface electronic for signal conditioning for integrated current sensing are discussed The sensor functional principle, the advantages and limitations are shown in detail The measured sensor characteristics are also shown Finally, improvements are discussed which involves further reduction of the size and the offset calibration procedure

Zero steady-state error input current controller for regenerative multilevel converters based on single-phase cells

Abstract: Multicell converters are one of the alternative topologies for medium voltage industrial drives. For application requiring regenerative capability each power cell must be constructed with a three- or single-phase PWM rectifier as a front end. The choice of single-phase PWM rectifiers for the input of the cells results in a reduced number of power switches and a simpler input transformer than the three-phase equivalent. However, its control is not as straight forward. This paper proposes the use of higher order resonant controllers in the classical control structure of the single-phase PWM rectifier. This ensures a zero steady-state tracking error of the reference current at fundamental frequency. A detailed description of the design criteria for the position of the zeros and poles of the controller is given. Experimental results showing the good performance of the single-phase input cells and its proposed control are included

The research of decoupled state variable feedback linearization control method of three-phase voltage source pwm rectifier

Abstract: Based on the feedback linearization theory of differential geometry theory, an affine nonlinear mode of three phase voltage source PWM rectifier in the rotating frame d-q is set up by applying impulse mode integral method. The feedback linear model of three phase voltage source PWM rectifier is obtained and decoupled reactive and active power control strategies of three phase voltage source PFC rectifiers are proposed. Research shows that this proposed control scheme can realize decoupled control of three phase PWM PFC rectifiers with perfect dynamic characteristics. The theory is verified by the simulation and experiment.

A new direct power control strategy of three phase boost type pwm rectifiers

Abstract: This paper analysies the principle and properties of the direct power control (DPC) system for present three phase boost type PWM rectifiers based on its mathematical model. Switching table in power loop of DPC system controls instantaneous active power and reactive power ,leading to the fluctuation of power and DC voltage in temporary state and DC dynamic voltage drop during load current disturbance. This paper presents a new direct power control strategy based on alternate use of instantaneous active power and reactive power switching tables. Good control properties are achieved by the new control strategy. Meanwhile, DC dynamic voltage drop during load current disturbance is decreased and stable voltage drop is eliminated by the duty cycle of square wave to control double switching table based on load current feedback. The new control strategy is proved feasible by simulink and experiment.

Novel Direct-Power-Control Strategy of Current-Source PWM Rectifier

Abstract: This paper describes a novel control strategy of a current-source PWM rectifier, which is based on relay control of instantaneous active and reactive power, and presents its experimentally examined operation characteristics, followed by a theoretical derivation of the control algorithm The most important feature of this strategy is a direct selection of switching modes of the PWM rectifier to restrict errors between the feedback values and the command values of the active and reactive power Therefore, a theoretical analysis on relationship between the instantaneous power and the switching modes of the PWM rectifier is deeply investigated, which is essential to compose a switching mode table in the controller Feasibility of the proposed strategy is experimentally verified, using a prototype setup As a result, 927-% maximum efficiency and 999-% maximum total power factor are confirmed through the experimental tests

The Research on Characteristics of Electronic Power Transformer for Distribution System

Abstract: The 3-phase and 4-wire distribution electronic power transformer (D-EPT) is composed of the input three phase PWM rectifier, medium frequency transformer and output single phase inverters. In this paper, the operation principle of D-EPT is analyzed and its control scheme is designed. For the PWM rectifier, an outer loop control of the DC voltage and an inner loop control of AC current are adopted. Then, a dual-loop control is implemented for the output inverters based on the RMS value and instantaneous value of output voltage respectively. The simulation results show that D-EPT has good steady-state and dynamic load characteristics under the proposed control scheme

Control-oriented modeling and robust control of a three-phase buck+boost PWM rectifier (VRX-4)

Abstract: The modeling and control of a three-phase, three-switch buck-type rectifier system with integrated boost output stage (VRX-4) is analyzed in this paper. A cascaded multi-loop control structure is presented that has the following features: constant output voltage for a wide input voltage range and step-wise changes of load; sinusoidal input currents in phase with the mains voltages that also remain sinusoidal in case of asymmetric mains conditions; and active damping of the input filter resonance. For the control design an equivalent DC-DC small-signal model of the converter is derived and verified by simulations and measurements. Based on this and the identification of the critical operating point the controllers for the inner DC current and outer voltage control loops are selected The stability of the closed loop system is discussed and the robust operation of the system is verified by measurements on a 5 kW prototype.

Sensorless control of 3-Phase PWM rectifier

Abstract: This paper presents a simple sensorless voltage oriented control strategy for PWM rectifier and a phase voltage tracking method is presented. The experimental tests show the advantages of the proposed phase tracking method. The control method is applicable to PWM drive converters without hardware changes whether they use space vector modulation method or hysteresis based modulation.

A novel control strategy for high-frequency AC-link AC/AC direct converter based on virtual converter system

Abstract: This paper proposes a simple control strategy for a high-frequency AC-link AC/AC direct converter The proposed control strategy is based on the virtual converter system that consists of a PWM rectifier part, a high-frequency AC-link part and an inverter part The proposed method realizes wide control range, high performances and low snubber loss The validity of the proposed method is confirmed through the simulation and experimental results

A PWM rectifier control technique for three-phase double conversion UPS under unbalanced load

Abstract: PWM rectifiers are widely used in three-phase ac-dc-ac systems due to its capability in dc voltage boost and regulation, input power factor correction, and input current harmonic control. However, with the conventional rectifier control technique, the input current tends to be unbalanced under unbalanced inverter load, which contaminates input power source and is therefore undesirable. In this paper, the cause of the unbalancing is disclosed by evaluating the spectra of the switching functions of the full bridge three-phase inverter analytically using Bessel function under standard space vector PWM switching scheme, which relates the dc link current and voltage ripples to the inverter load balancing. The analysis shows that the dc link voltage contains significant second order harmonic component which affects the voltage loop of the rectifier controller, especially when the control gain is high. A notch filter based voltage control loop is proposed to eliminate the second harmonic component in the dc-link voltage feedback signal and achieve balanced three-phase input currents. Simulation and experimental results are presented to demonstrate the effectiveness of the proposed control technique in decoupling the rectifier and the inverter under unbalanced load.

A discrete current control for PWM rectifier

Abstract: Applications of PWM rectifiers are very promising, since they are able to supply DC power while keeping a sinusoidal current with unity in the fundamental power factor simultaneously. Another important application for PWM rectifiers is as static VAR compensators, where they supply reactive power to compensate inductive loads connected on grid. In this paper, a microprocessor-based regulator is proposed for voltage-fed PWM rectifiers with sinusoidal input current to control both the fundamental power factor and direct voltage. The grid current is controlled through a discrete-time feed-forward regulator and a state feedback control, which provide a fast response without steady-state errors. A outer DC voltage loop is composed by a PI regulator. Simulation results are presented for load variations and reactive power control.

Novel estimator of distorted and unbalanced electromotive force of the grid for control system of PWM rectifier with active filtering

Abstract: Control of PWM rectifier with active filtering is realized by fast and precise shaping of its AC currents. In the paper the control system with predictive algorithms of both set currents calculation and currents control is proposed. These algorithms provide very high accuracy and dynamics of AC currents shaping which is limited only by parameters of the power circuits. In both algorithms calculations are based on precise information about present and future samples of in general distorted and unbalanced equivalent electromotive force (emf) of the grid. For this purpose the novel, grid voltages sensorless, precise estimator and predictor of grid emf is proposed. This robust algorithm is based on digital signal processing techniques and requires relatively low computational effort. In this paper the simulations and experimental results are presented which show the performance of proposed estimator and predictor of grid emf and its influence on operation of the control system of PWM rectifier with active filtering

Grid voltages sensorless control system of the PWM rectifier with active filtering function

Abstract: The paper presents structure and experimental results of control system of the PWM rectifier with active filtering function. Proposed control system was designed for maximum filtering performance in steady state. This task is realized by predictive algorithms applied for both control as well as calculation of grid currents. Accuracy of these algorithms strongly depends on precise information about future samples of equivalent electromotive force of the grid, which is in general distorted and unbalanced. For this purpose, a novel estimator and predictor is proposed. The control of DC voltage is realized with application of variable gain PI controller. It ensures high dynamics in transient states and low gain for steady state oscillations of DC voltage. Proposed control system is AC voltages sensorless and has excellent active filtering performance, even at presence of grid voltage distortions. power quality, PWM rectifier, active filter, predictive control

High performance control of a boost AC-DC PWM rectifier-induction generator system

Abstract: This paper presents a control methodology for the dc voltage regulation of an induction generator/ac-dc boost rectifier system, in which the copper loss of the generator is minimized. With the aid of an input-output linearization technique, which linearizes and decouples the model equations in the synchronous reference frame, a rotor-flux-vector-control-type high performance is achieved. Steady-state analysis provides some insights into the operability regime of the generator. The effectiveness of the control scheme under different load conditions as well as varying rotor speeds has been demonstrated by computer simulations. Some experimental results have been included

A Three-Switch Current-Source PWM Rectifier with Active Filter Function

Abstract: Thyristor and diode converters are widely used in electric power systems. These nonlinear loads produce current harmonics which reduce power quality by distorting the supply network voltages. Nowadays, an increasingly popular trends is to compensate the harmonics by using six-switch active power filters. In this paper the capability of three-switch current-source PWM rectifier (3SW-CSR) to act as an active power filter and to compensate the harmonics caused by other converter is studied. It is shown by analysis, simulations and experimental tests that 3SW-CSR offers an effective and low-cost solution to improve the quality of electrical power in applications where group of three-phase rectifiers is used

A fast current control scheme for pwm rectifier

Abstract: In the control of voltage source PWM rectifier, direct current control and dual close loop control structure in d-q synchronous reference frame are widely adopted In this control method, the active and reactive current are separately controlled and synthetical consideration of two currents has been ignored; as a result, this scheme fails to track the reference current quickly and doesn’t obtain better control property By analyzing the factors which influence the fast transient response, this paper puts forward a new control scheme to improve current transient response rate by utilizing the reactive current in transient state Simulation results show that the proposed control scheme has satisfactory steady-state characteristics and fast transient response This control scheme possesses some practical values due to its simple implement

Control of a Three-Phase PWM Rectifier Based on a Dual Single-Input Single-Output Linear Model

Abstract: A state-space-averaged model of a three-phase boost-type PWM rectifier is available in literature. The model is complex with a multi-input multi-output (MIMO) non-linear structure and a non-minimum phase feature. However, such a MIMO non-linear system becomes a dual single-input single-output (SISO) linear system by ignoring certain dynamics and applying a simple feed-forward de-coupling controller. In addition, the non-minimum phase feature is also eliminated in the resultant model. Investigation into the dual SISO model shows that such a model is valid during both steady-state and transient operation provided the closed-loop bandwidth of voltage controller is much less than the corner frequency of the right half plane (RHP) zero which is the cause of the nonminimum phase feature. Thus, the paper presents the range of validity of the proposed dual SISO linear model. A cascaded controller is then implemented in a back-stepping style based on the proposed model. Simulation studies have been carried out to show the effectiveness of the proposed controller and also to illustrate how the non-minimum phase feature affects the behavior of rectifier. The simulation results verify the theoretical predictions

Experimental verification of a dual single-input single-output model of a three-phase boost-type PWM rectifier

Abstract: This paper proposes a simple dual SISO (single-input-single-output) model for a three-phase boost-type PWM rectifier under balanced line voltage conditions. In the proposed model, the q-axis model is a first order linear system determining the power factor regulation, whereas the d-axis model, which is shown to be similar to a traditional DC-DC boost converter, is a second-order non-linear system determining the power delivery. It is much easier to analyze and control a complex three-phase PWM rectifier using the proposed model. In addition, the complex non-minimum phase feature inherent in a AC-to-DC rectifier becomes a simple right half plane (RHP) zero appearing in the small-signal control-to-output transfer function of the proposed d-axis model. The knowledge of RHP zero's location is vital to the successful design of a stable controller for the rectifier, as the presence of the RHP zero imposes a strict limit on the achievable closed loop performance. The validity of the proposed model is verified through experimental Bode plot results obtained using a hardware prototype