Showing papers on "PWM rectifier published in 2004"

A novel three-phase three-port UPS employing a single high-frequency isolation transformer

Abstract: A three-phase PWM rectifier and a three-phase PWM inverter are coupled via two four-quadrant full-bridge converter cells and a high-frequency isolation transformer. By employing a third transformer winding and further full-bridge cell battery energy storage is incorporated into the power transfer between rectifier and inverter resulting in a three-port UPS concept. The phase shift control of the power flow between the ports is analyzed for square-wave operation of the full-bridge cells. Furthermore, the utilization of the degrees of freedom of the system control, i.e. the extension to duty cycle control for optimizing the system behavior is discussed and control laws ensuring minimum overall system losses are derived. Finally, a control-oriented converter model is proposed and the decoupled control of the power flow of the ports is treated briefly. All theoretical considerations are verified by simulations using PSIM.

Optimization of the DC ripple energy compensating circuit on a single-phase voltage source PWM rectifier

Abstract: This paper presents parameter optimization of the compensating circuit for the reduction of the DC ripple energy on a single-phase voltage source PWM rectifier. In the single-phase PWM rectifier, it is well known that a power pulsation with twice the utility frequency is contained in the output power. In a conventional PWM rectifier, electrolytic capacitors with large capacitance have been used in order to smooth the DC voltage. However, lifetime of those capacitors is shortened by the power pulsation with twice utility frequency. The authors have been studied two kinds of DC ripple compensation circuits, such the authors call an inductive storage method and a capacitive storage method, those enable to transfer the ripple energy appeared on the output DC capacitors into the energy in an additional inductor and additional small capacitors. Hence, extension of the lifetime of the converter can be expected because the small film capacitor substitutes for the large electrolytic capacitors. Moreover, the inductance and capacitance region in which the DC ripple energy can be compensated completely and the overall dimensions of the energy storage devices are shown. Finally, experimental results of compensation characteristics on both the steady state and transient state are discussed.

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.

Comparative evaluation of three-phase high power factor AC-DC converter concepts for application in future more electric aircrafts

Abstract: A passive 12-pulse rectifier system, a two-level, and a three-level active three-phase 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 aircrafts. Weight, volume and efficiency of the concepts are compared for an input phase voltage range of 98 V to 132 V and an input frequency range of 400 Hz to 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 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.

Analysis of loss and junction temperature in power semiconductors of the matrix converter using simple simulation methods

Abstract: In this paper, simple simulation methods to calculate power semiconductor loss and instantaneous junction - case temperature difference in a power module of a matrix converter are proposed. The validity of the proposed simulation method for loss calculation is confirmed through experiment using a 22 kW test set-up of the matrix converter. By using the simulation method for temperature calculating, the influence of the output frequency on the junction - case temperature difference is investigated. Moreover, the effect of using a novel IGBT (RB-IGBT) that has reverse blocking capability is discussed. It is shown that the efficiency of a matrix converter using the RB-IGBT is higher by 1.3 points than that of a conventional PWM rectifier and inverter system.

Improved control of an active-front-end adjustable speed drive with a small de-link capacitor under real grid conditions

Abstract: Active front-end topologies are widely used in the future and among them especially the two-level PWM rectifier, due to the need to improve the quality of the input currents and the robustness against grid disturbances of adjustable speed drives (ASDs). Another expectation is that electrolytic capacitors are replaced by film capacitors in order to increase the ASD lifetime, but as this has lower energy density, the dc-link capacitance is expected to decrease. In these circumstances, operation under unbalanced and distorted supply voltage as well as high dynamic operation of the ASD makes the control task more challenging. This paper discusses problems related to the ASD DC-link both in respect to its stability (under regeneration as well as in the case of constant power absorbed by the inverter stage) both also in respect to the dc voltage ripple generated by the grid unbalance and made more severe due to the small DC-link storage. To mitigate the latter problem it is proposed to recompensate the DC-link voltage reference signal considering the real grid voltage. Experiments show that the system handles successfully unbalance situation even with a small DC-link capacitor.

A study of dead-time of PWM rectifier of voltage- source inverter without DC link components and its operating characteristics of induction motor

Abstract: A voltage source inverter without DC link components is an AC-to-AC converter having dual bridges such as a PWM rectifier and a PWM inverter without DC link components, therefore, a PWM rectifier and a PWM inverter can be controlled independently. Conventional matrix converters have disadvantages such as a complicated commutation scheme and necessity of a large sized clamp circuit, but commutation and protection of this inverter can be implemented easily. In order to control the PWM rectifier and the PWM inverter independently, snubber circuits for the PWM rectifier are required to assure the path of load current during dead time. In this paper, analytical method of a snubber circuit and operating characteristics of an induction motor are described when a 0.75 kW induction motor driven by this inverter.

Differential mode EMC input filter design for a three-phase buck-type unity power factor PWM rectifier

Abstract: For a three-phase buck-type PWM rectifier input stage of a high-power telecommunications power supply module a differential mode EMC filter is designed which ensures compliance to EN 55022 class B. The design is based on a harmonic analysis of the converter input current and a mathematical model of the measurement procedure including the LISN and the test receiver. Guidelines for a successful filter design are given and components for a 5 kW prototype of the rectifier system are selected. There, the damping of filter resonance is optimized for given attenuation in order to facilitate a higher stability margin for the system control. Furthermore, the dependency of the filter input and output impedances and attenuation characteristic on the inner mains impedance is discussed. Finally, the theoretical considerations are verified by conducted emission measurements and the high quality sinusoidal shape of the resulting mains current is demonstrated.

A novel carrier-based PWM strategy for hybrid multilevel inverters

Abstract: The hybrid multilevel power conversion has achieved attention in resent years for minimizing the cascaded cells number for given output voltage levels. However, the equipment complexity is not really decreased due to the adopting of PWM rectifier and this restrains its industry utilization. In order to avoid using controlled rectifier, the hybrid frequency carrier-based PWM (HFPWM) control strategy adapted to hybrid power cells is presented in this paper. In comparison with the general scheme, this proposed strategy is able to make each cell of the hybrid inverter participate PWM modulation and have the same output voltage polarity. Thus the reverse current of the low-voltage cell is not present and this power cell can also be fed by diode rectifier. The hybrid multiply connecting approach of the transformer secondary windings feed for the three-phase diode rectifiers with different input voltages is illustrated in this paper. The driving approach of each power cell is derived from this strategy and realized on the hybrid seven-level adjustable-speed drive laboratory system. This control strategy will benefit the energy saving applications such as speed control of pumps and blowers.

A simplified algorithm for space vector modulation of three-phase voltage source PWM rectifier

Abstract: A simplified algorithm is proposed in this paper for space-vector modulation (SVM) of three-phase voltage source PWM rectifier. The transfer function and control loop design of the rectifier are detail described. For three-phase voltage source PWM rectifier, the space-vector modulation scheme has excellent features such as increased utilized voltage, easy implementation via microprocessor etc. In this paper the duty cycles of space voltage vectors are calculated directly to track the reference voltage vector in each sector of the space vector plane. It avoids the look-up tables of sine and/or arctangent and complex calculations needed in the conventional methods. Based on experimental platform for Power Electronics "PE-PRO / VC33", the experimental results demonstrated that the proposed system also has the advantages including unity input power factor and greatly reduced input line current harmonic distortion due to nearly sinusoidal input line current attainable with controlled rectifiers.

Design and Comparative Evaluation of Three-Phase Buck+Boost and Boost+Buck Unity Power Factor PWM Rectifier Systems for Supplying Variable DC Voltage Link Converters

Abstract: A three-phase boost+buck PWM rectifier system formed by series connection of a boost-type rectifier input stage and a DC/DC buck converter output stage and a three- phase buck+boost PWM rectifier system comprising a three- switch rectifier input stage with integrated DC/DC boost converter output stage are presented and comparatively evaluated. Both systems are characterized by sinusoidal in- put current and wide output voltage control range. Analyti- cal expressions for the calculation of the current stresses on the power components and results of transistor switching loss measurements are provided as guidelines for the system design. Furthermore, the overall efficiency, the loss contri- butions and the volume and weight of the main components are given for 6kW rated system output power at 400Vrms line-to-line input. In combination with an assessment of the realization effort this provides a basis for the selection of the appropriate topology for an industry application.

Controller of power converter

Abstract: PROBLEM TO BE SOLVED: To provide a controller of a power converter in which the distortion of an output voltage and an adverse affect to a load are prevented by reducing an output voltage error. SOLUTION: The controller of a power converter composed of a PWM rectifier 1 and an inverter 2 comprises a means 202 for performing the two-phase modulation of the inverter 2, a means 204 for operating the compensation amount of the output voltage error at the time of two-phase modulation, an inverter PWM patterning means 203, a rectifier PWM patterning means 101, a means 400 for detecting the switching of the PWM rectifier 1, a means 500 for detecting voltages of a maximum phase, an intermediate phase and a minimum phase from the input voltage of each phase, and a means 300 for determining the polarity of a load current. The compensation amount operating means 204 operates the compensation amount using outputs from the voltage detecting means 500, the polarity determination means 300 and the switching detecting means 400, and the frequency and the dead time of the inverter 2. COPYRIGHT: (C)2006,JPO&NCIPI

Novel sensorless direct power and torque control of space vector modulated ac/dc/ac converter

Abstract: A novel control strategy for PWM rectifier-inverter system is proposed. Fast controls strategies such as line voltage sensorless virtual flux (VF) based direct power-control with space vector modulator (DPC-SVM) for rectifier and direct torque control with space vector modulator (DTC-SVM) for inverter side are used. These strategies lead to good dynamic and static behaviour of the proposed control system- direct power and torque control- space vector modulated (DPT-SVM). The results obtained in simulations and experiment show good performance of the proposed system. Additional power loop from motor to PWM rectifier side improved dynamic behaviors of the power flow control. As result, better input-output energy matching allows decreasing the size of the dc-link capacitor.

Pump characteristic based optimization of a direct water cooling system for a 10 kW/500 kHz Vienna rectifier

Abstract: A high power density 10 kW/500 kHz three-phase PWM rectifier (Vienna Rectifier) is under development. Due to preliminary measurements and numerical simulations the total efficiency is assumed to be 95% at full load, resulting in power losses of up to 150 W in each multi-chip power module realizing a bridge leg of the rectifier. In order to keep the power density of the system high direct water cooling is employed where water is in direct contact with the module base plate. Based on the measured characteristic of the water pump (pressure drop dependent on water flow) the geometry of different water channel structures below the module base plate is systematically optimized based on analytical expressions which are formulated based on the well-established theory of fluid dynamics. The design optimization is constrained by the desire to keep the geometry of the water channels in a range that allows simple and low-cost manufacturing. The aim is to find a channel structure resulting in a minimum thermal resistance of the power module for a given pump characteristic. In this paper a very simple slot channel is investigated. The dependency of the thermal resistance on the cooling system is calculated in dependency on the height of the slot channel, and an optimized channel height is found under the side condition of simple manufacturability. Discussing the shortcomings of the simple slot structure, a novel metallic inlay structure is introduced and optimized resulting in a reduction of the thermal resistance of the direct water cooling scheme as compared to the slot channel system. All theoretical considerations are verified via experimental measurements. The general optimization scheme introduced in this paper can easily be adapted to other cooling problems.

Sensorless control of PWM rectifier by distorted supply voltage

Abstract: A sensorless control strategy for three phase PWM power supply rectifiers, a "phase tracking" concept, was proposed on last PESC'03. This method proved to be robust to system parameters changes and provided line voltage estimation for line current control. Discussion after the PESC'03 presentation left concerns with respect to the control quality during line voltage fluctuations and under nonsymmetric line conditions. This paper reports the behaviour of the proposed "phase tracking" control method under distorted supply voltage. The following voltage distortions are tested: voltage unbalance, over-voltage and under-voltage. The control was performed on a rapid prototype system for power electronics control. Experimental results of the test are presented.

The investigation of PWM rectifier control method

Abstract: In general, power electric device is fed by AC/DC rectifier rather than by direct DC source and the inherent default of the rectifier has more bad influence on the power network. As a result, the PWM-rectifier has been paid more and more attention for unity input power factor, greatly reduced input line current harmonic distortion and bidirectional power flow capability. The paper present the topology of the main circuit, deduce the math model both in a-b-c and a - /spl beta/ reference frame, propose the direct current control scheme, get the current and voltage waveform and analyze the result of simulation which is processed by SIMULINK software on the base of math model.

Study of low voltage stress space vector pwm control for current source pwm rectifier

Abstract: To lower the voltage stress on switches of three phase Current Source PWM Rectifier (CSR), a new low voltage-stress SVPWM control method is developed in this paper based on the detailed analysis of the commutating process of power switches. By exchanging the sequence of the vectors composition, the power switches, could operate in natural commutation state, so the voltage-stresses of power switches are reduced greatly. Owning to the fact that the SVPWM control is of higher DC current utility-rate, low switching-looses and better transient performance. This new low voltage-stress SVPWM especially fits for high power three phase converter systems. The experimental results verify the theoretical analysis.

Sensorless direct power and torque control of PWM back-to-back converter-fed induction motor

Abstract: A novel control scheme for PWM rectifier-inverter system is proposed. Fast control strategies such as line voltage sensorless virtual flux (VF) based direct power control with space vector modulator (DPC-SVM) for PWM rectifier and direct torque control with space vector modulator (DTC-SVM) for PWM inverter side are used. These strategies lead to good dynamic and static behaviors of the proposed control system-direct power and torque control-space vector modulated (DPT-SVM). Simulations and experiment results obtained show good performances of the proposed system. Additional power feedforward loop from a motor to PWM rectifier control side improved dynamic behaviors of the power flow control. As a result, better input-output energy matching allows decreasing the size of the DC-link capacitor.

A hybrid current controller for a 1-phase PWM rectifier combining hysteresis and carrier-based schemes to achieve a zero current error and unipolar PWM waveforms

Abstract: A current controller is described for 1-phase PWM rectifiers that combines both the functionality of hysteresis-based and carrier based controllers. The development of this current controller is described with the aid of generic PWM controllers that use a sinusoidal modulating signal and a signal integrator. These controllers mimic the operation of the 1-phase PWM rectifier and are used to determine the optimal gain-constant associated the current-error feedback signal. The resultant current controller is relatively insensitive to variations in rectifier parameters such as the supply inductance and the dc link voltage magnitude. The controller combines the excellent current waveshaping ability of hysteresis-based controllers together with the constant switching frequency of carrier-based controllers. The main controller features include: real-time generation of the sinusoidal amplitude modulation signal from the PWM signal; elimination of phase-shifts caused by the limited rate-of-change of the rectifier current; a near zero current-error over a PWM half-cycle; no skewing effects in the current-error signal. Simulation results, using a per-unit system of values, are used to illustrate the step-by-step development of the current controller. A DSP-based controller is used, together with an IGBT rectifier, to demonstrate the experimental operation of the controller.

A novel instantaneous power control strategy for a PWM rectifier under unbalanced input voltage conditions

Abstract: Instantaneous power regulation is an effective way to improve the performance of a PWM rectifier operating under unbalanced input voltage. By properly presetting current commands, this approach can maintain the desired performance features normally achieved only under ideal balanced operating conditions. These desirable performance features include sinusoidal input current at a near unity power factor, nearly constant DC output voltage with a small output capacitor and also fast dynamic response. However, the relationship between power and current in an AC to DC PWM rectifier is highly nonlinear under unbalanced operating conditions and it is not normally clear that a solution to the nonlinear system fulfilling all of the desirable requirements exists. The uniqueness and existence of a solution for such a nonlinear system is difficult to demonstrate. This paper presents a novel instantaneous power control strategy in which current commands are well regulated so as to distribute input power instantaneously and appropriately to the DC load and to the synchronous inductances while maintaining a constant DC voltage and sinusoidal input currents. A good feature of the proposed method is that the current commands are given by a set of simple equations, which can be easily implemented. Also, the simplicity of the equations avoids complex mathematical arguments for demonstrating uniqueness and existence of the solutions. It is shown also that near unity power factor operation can be achieved with the proposed scheme. Experimental results demonstrate that the scheme fulfils all the objectives of a high performance controller.

Four wire single-phase to three-phase system for rural distribution network

Abstract: This work presents the experimental development of a four-wire single-phase to three-phase static converter for rural distribution system. The converter topology is based on a front-end full-controlled PWM rectifier that handles the DC bus voltage regulation as well as improves the input power factor correction. In order to provide the three-phase four-wire system, a four-legged PWM voltage source inverter (VSI) is used at the output. The rectifier-inverter control strategy has been implemented in a digital processor (DSP), where a proposed PLL algorithm performs the rectifier synchronism. Component specification guidelines and control strategies are described. Complete models are implemented in an electromagnetic transient simulation package (PSCAD/EMTDC/spl trade/), where the converter is connected to a rural distribution network and is supplying three-phase and single-phase loads. Simulation results show that this converter can ride through a typical voltage sag condition that is very often in rural areas. The converter topology is composed of 12 IGBTs and can be implemented by two off-the-shelf three-phase PWM inverters. This availability can offer significant cost reduction. Experimental results are provided.

A novel concept for balancing of the phase modules of a three-phase unity power factor Y-rectifier

Abstract: The isolated star point of a three-phase star-connection of single-phase unity power factor PWM rectifier systems (Y-rectifier) results in a mutual coupling of the individual phase module outputs, i.e. the individual DC link voltage control loops. Starting from the theoretical analysis of a series connection of two DC-DC boost converters a control-oriented equivalent circuit of the three-phase Y-rectifier system is derived in analytically closed form. Based on this a robust multivariable control is designed which ensures constant DC link voltage levels for unsymmetric disturbances, i.e. step load changes of the phase modules, All theoretical findings are verified via numerical simulations.

Direct power constant switching frequency control of AC/DC/AC converter-fed induction motor

Abstract: A novel control scheme for PWM rectifier-inverter system is proposed. Fast control strategies such as line voltage sensorless virtual flux (VF) based direct power control with space vector modulator (DPC-SVM) for PWM rectifier and direct torque control with space vector modulator (DTC-SVM) for PWM inverter side are used. These strategies lead to good dynamic and static behaviors of the proposed control system-direct power and torque control-space vector modulated (DPT-SVM). Simulated and experimented results show good performances of the proposed system. Additional power feedforward (PF) loop from a motor to PWM rectifier control side improves dynamic of the power flow control. As a result, better input-output energy matching allows decreasing the size of the DC-link capacitor.

Single-phase static converters for rural distribution system

Abstract: This work presents the development of four-wire single-phase to three-phase static converters for rural distribution system. Component specification guidelines and control strategies of two proposed topologies are described. Both converters are based on a front-end half-controlled PWM rectifier that handles the DC bus voltage regulation as well as reduces the input current distortion. In order to provide three-phase four-wire system, two basic inverter topologies are considered: three-leg PWM-VSI with split DC link capacitors and four-leg PWM-VSI. Complete models are implemented in an electromagnetic transient simulation package (PSCAD/EMTDC ), where each converter is connected to a typical rural distribution network and supplies three-phase unbalanced loads. Performance analysis based on simulation results is carried out considering the occurrence of voltage sags.

Analysis and design of a PWM rectifier using the DQ theory and a digital control based in a DSP

Abstract: This paper presents the application of DQ theory like a tool for the analysis operation and controller design of a PWM rectifier, which is able to regulate the DC load voltage, to maintain the power factor near to the unit and to reduce the harmonic distortion. This study stands out the conditions and limitations for the PWM rectifier operation, taking into account that system performance and transient response are directly related with physical parameters. The conditions and limitations exposed should be considered for the control law design. Analysis and modeling is presented, as well as simulation and experimental results validating the system operation.

Decoupled control and DSP implement of PWM rectifier

Abstract: On the basis of deducing and analyzing the mathematical model of PWM rectifier, a new method was put forward, which realized current decoupled control in d - q synchronous frame. The cascade control structure and the high performance space-vector pulse-width modulation (SVPWM) technique were adopted. A full digital PWM rectifier was implemented by using digital signal processor (DSP). With the full utilization of the inner resource and high-speed data processing ability of DSP, the rectifier fulfilled complex control algorithms and operation in real-time. Experiment result indicates that this control method has a good performance and is an ideal way for the implementation of PWM rectifier.

Secondary currents filtering by means of a properly sized winding in a multicoil traction transformer for high power applications to limit psophometric Currents

Abstract: In high power railway traction applications the modulation of traction converters, at low switching carriers, produces harmonic currents in the range of audio frequencies. To ensure correct operation modes of the signalling circuits, the interference magnitudes levels have to be reduced. Psophometric current (p.c.) gives an index of the interference level produced by traction equipments: it takes into account the harmonic content of the primary current waveform in the multiwinding transformer. To limit the p.c. in the feeding network, a method for filtering harmonic currents produced by the modulation of interlaced PWM rectifiers (V.S.R.) is described. A properly sized additional winding is considered on the multicoil transformer used to supply the traction equipment. In the paper the system is analysed by means of the mathematical model and some design guidelines are proposed.

A complete dc and ac analysis of three phase current source pwm rectifier using circuit d-q transformation

Abstract: The recently proposed circuit D-Q tramforniation is used to analyze a three phase current source PWM rectifier. DC operating point and AC transfer functions are conipletely determined. Most features of the converter are clearly interpreted. They are ( 1 ) the output voltage can be controlled from zero to nzmimum, ( 2 ) the system is equivaletitly 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.

Evaluations of two methods to clean utility line: PWM-voltage source rectifiers and active power filters

Abstract: Two methods to solve harmonic pollution problems caused by the diode rectifier are possible: one replacing the diode rectifier with a PWM rectifier and the other connecting an active power filter to the diode rectifier. Despite numerous publications for two converters, the features and evaluations between them have not been clearly explained. This paper, in detail, presents a theoretical analysis and a systematic comparison of the two converters, from the point of view of converter kVA ratings, DC bus voltage requirements, switch ratings, and reactive component designs.

Study on the Sensorless Current Control Strategy of Three-Phase Voltage-Source AC/DC PWM Rectifier

Abstract: Three-phase AC/DC PWM rectifier can improve power factor and decrease harmonic contami-nation.Bi-directional power flow is realized when this rectifier is used at the commutating side of an in-verter.The rectifier can be controlled by direct and indirect current control schemes.The former requires at least two current sensors with high capability.The latter is put forward to use current observer,which is cost-effective by improving the dynamic response compared with the phase and amplitude control in indirect scheme and eliminating the expensive current sensors.The current observer estimates the current by detect-ing phase voltage,DC output voltage of the rectifier and three-phase switch functions.Yet it is crucial to detect switch functions and estimate input currents.Its mathematical model is acquired by theoretical analysis and simplified expressions of currents observer are deduced under certain hypothesis.The value of the cur-rent observer is acquired by digital simulation in Matlab and compared with the actual current wave con-trolled by direct current control scheme.The experimental results are verified on power system PE-PRO.