Showing papers on "PWM rectifier published in 2007"

PWM Converter Power Density Barriers

Abstract: Power density of power electronic converters in different applications has roughly doubled every 10 years since 1970. Behind this trajectory was the continuous advancement of power semiconductor device technology allowing an increase of converter switching frequencies by a factor of 10 every decade. However, today's cooling concepts, and passive components and wire bond interconnection technologies could be major barriers for a continuation of this trend. For identifying and quantifying such technological barriers this paper investigates the volume of the cooling system and of the main passive components for the basic forms of power electronics energy conversion in dependency of the switching frequency and determines switching frequencies minimizing the total volume. The analysis is for 5 kW rated output power, high performance air cooling, advanced power semiconductors, and single systems in all cases. A power density limit of 28 kW/dm3@300 kHz is calculated for an isolated DC-DC converter considering only transformer, output inductor and heat sink volume. For single-phase AC-DC conversion a general limit of 35 kW/dm3 results from the DC link capacitor required for buffering the power fluctuating with twice the mains frequency. For a three-phase unity power factor PWM rectifier the limit is 45 kW/dm3@810 kHz just taking into account EMI filter and cooling system. For the sparse matrix converter the limiting components are the input EMI filter and the common mode output inductor; the power density limit is 71 kW/dm3@50 kHz when not considering the cooling system. The calculated power density limits highlight the major importance of broadening the scope of research in power electronics from traditional areas like converter topologies, and modulation and control concepts to cooling systems, high frequency electromagnetics, interconnection technology, multi-functional integration, packaging and multi-domain modeling and simulation to ensure further advancement of the field along the power density trajectory.

Control of Single-Phase-to-Three-Phase AC/DC/AC PWM Converters for Induction Motor Drives

Abstract: This paper proposes a novel control scheme of single-phase-to-three-phase pulsewidth-modulation (PWM) converters for low-power three-phase induction motor drives, where a single-phase half-bridge PWM rectifier and a two-leg inverter are used. With this converter topology, the number of switching devices is reduced to six from ten in the case of full-bridge rectifier and three-leg inverter systems. In addition, the source voltage sensor is eliminated with a state observer, which controls the deviation between the model current and the system current to be zero. A simple scalar voltage modulation method is used for a two-leg inverter, and a new technique to eliminate the effect of the dc-link voltage ripple on the inverter output current is proposed. Although the converter topology itself is of lower cost than the conventional one, it retains the same functions such as sinusoidal input current, unity power factor, dc-link voltage control, bidirectional power flow, and variable-voltage and variable-frequency output voltage. The experimental results for the V/f control of 3-hp induction motor drives controlled by a digital signal processor TMS320C31 chip have verified the effectiveness of the proposed scheme

Comprehensive Design of a Three-Phase Three-Switch Buck-Type PWM Rectifier

Abstract: A three-phase three-switch buck-type pulsewidth modulation rectifier is designed for telecom applications in this paper. The rectifier features a constant 400-V output voltage and 5-kW output power at the three-phase 400-V mains. The principle of operation and the calculation of the relative on-times of the power transistors are described. Based on analytical relationships the stresses of the active and passive components are determined and the accuracy of the given calculations is verified by digital simulations. Exemplarily, a 5-kW power converter is then designed based on the analytical expressions and on switching loss measurements from a hardware prototype constructed with insulated gate bipolar transistor/diode power modules. The loss distribution of the components, the total efficiency, and the junction temperatures of the semiconductors are then evaluated in dependency on the operating point. Finally, the trade-off between the selected switching frequency and the admissible power range for the realized design is shown and a total efficiency of 95.0% is measured on the hardware prototype, where an excellent agreement with the theoretically evaluated efficiency is shown

A novel nine-switch PWM rectifier-inverter topology for three-phase UPS applications

Abstract: A novel three-phase PWM rectifier-inverter topology for UPS applications is proposed in this paper. The topology uses only nine IGBT devices for AC/AC conversion through a quasi DC link circuit. This converter topology features sinusoidal inputs and outputs, unity input power factor, and more importantly, low manufacturing cost. The operating principle of the converter is elaborated and a novel modulation scheme is presented. The performance of the proposed converter is verified by experiments on a 5 kVA prototyping UPS system.

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 an application requiring regenerative capability, each power cell must be constructed with a three- or single-phase pulsewidth-modulation (PWM) rectifier as 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 straightforward This paper proposes the use of higher order resonant controllers in the classical control structure of the single-phase PWM rectifier This ensures 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

Improved switching table for direct power control of three-phase PWM rectifier

Abstract: The switching table based direct power control (ST-DPC) of three-phase PWM rectifier is analysed and an improved switching table (IST-DPC) is presented. The proposed switching schedule improves the quality of line current and results in better dynamic performances. In addition, the predictive direct power control (PDPC) of three-phase boost rectifier is presented and simulation results (in MATLAB/SIMULINK environment) are compared with those generated by ST-DPC and ISD-DPC approaches. Advantages and limitations of each control scheme are highlighted and conclusions regarding applications, quality of current waveforms and burden of calculations are presented.

Comparison of 3-Phase Wide Output Voltage Range PWM Rectifiers

Abstract: A three-phase buck boost pulsewidth modulation (PWM) rectifier with a three-switch buck-type rectifier input stage and an integrated dc/dc boost converter output stage, and a three-phase boost buck PWM rectifier system formed by series connection of a boost-type rectifier input stage (Vienna Rectifier) and a dc/dc buck converter output stage are presented and comparatively evaluated. Both systems are characterized by sinusoidal input current and wide output voltage control range. The comparison is for 6 kW rated output power at 400 Vrms line-to-line input and variable output voltage 200 V 600 V and identifies the buck boost approach as significantly superior regarding the overall efficiency, the volume and weight of the passive power components, and the overall system complexity.

PWM rectifier with LCL-filter using different current control structures

Abstract: The control of a PWM rectifier with LCL-filter using a minimum number of sensors is analyzed In addition to the DC-link voltage either the converter or line current is measured Two different ways of current control are shown, analyzed and compared by simulations as well as experimental investigations Main focus is spent on active damping of the LCL filter resonance and on robustness against line inductance variations

Space Vector Modulation Applied to Three-Phase Three-Switch Two-Level Unidirectional PWM Rectifier

Abstract: This work presents a methodology to apply space vector modulation to a three-phase three-switch two-level Y-connected unidirectional pulsewidth modulation (PWM) rectifier. Converter switching stages are analyzed to determine switch control signals for space vector modulation. A switching sequence is proposed in order to minimize the number of switch commutations and to reduce the switching losses. Duty cycle functions are determined and the desired switching sequences are performed by a simple PWM modulator with no need of to determine the present sector of vector. For this propose is just necessary to impose the desired current sectors from input voltage references. The vector control structure used with the proposed modulation technique is also described. In order to validate the proposed modulation technique, experimental results are presented for a 20 kW prototype.

Sensorless Operation of a PWM Rectifier for a Distributed Generation

Abstract: This paper presents a power converter configuration interfaced with the distributed ac power generation system to regulate the dc bus voltage. It is composed of a pulsewidth modulation (PWM) rectifier directly tied to the generator's terminals without ac reactors. Hence terminal voltages are not useful due to the switched pulse of the PWM rectifier and also it is not the terminal voltages, but the generator's electromagnetic field voltages that are required for a synchronous angle of the PWM rectifier. This paper proposes a method for estimating the synchronous angle through only the measurement of the ac line currents, and is thus called the voltage sensorless control strategy. For a smooth startup of the PWM rectifier, a technique of setting the integrators' initial values in the proposed estimator is described. In this paper a commercial engine generator set is used as the distributed generation system. The feasibility of the overall system and algorithms has been verified by the experimental results

Ultra Compact Three-phase PWM Rectifier

Abstract: An increasing number of telecom, data server and aircraft power supply applications require high power, highly efficient, compact, sinusoidal input current rectifiers The design and experimental performance of an 85 kW/liter (139 W/in3), 3-phase PWM rectifier with a power output of 10 kW is presented The high power density is achieved by increasing the switching frequency up to 400 kHz, which results in smaller EMI filters and boost inductors, while still maintaining a high efficiency over 95% To minimize the switching losses, a combination of a CoolMOS and SiC diode are used in a custom power module The module together with an optimized forced air cooled heat sink, optimized EMI filter, and a fully digital controller are used to obtain the high power density of the rectifier

An Analytical Modelling of Three-Phase Four-Switch PWM Rectifier Under Unbalanced Supply Conditions

Abstract: A new description of the three-phase four-switch converter aimed at compensating reactive power in the general case of unbalanced source voltages is proposed. A mixed p-z approach based on integral transformations (the Laplace and modified Z-transform) is suggested for obtaining solution in a closed form. The analytical procedure is verified by experimental results to confirm the effectiveness of the proposed control scheme.

PWM rectifier in power cell of cascaded H-bridge multilevel converter

Abstract: This paper proposes to use PWM rectifier to replace the diode rectifier in the cascaded H-bridge multilevel converter in order to regenerate the power from the load to the grid. The rectifier in this paper employs the leakage reactance of the secondary windings of the input transformer instead of physical reactor because of the large number of the reactors needed by the PWM rectifier in a cascaded H-bridge multilevel converter. Voltage oriented control (VOC) is used to obtain the good performance of the control system.

The virtual flux oriented control of three-level neutral point clamped PWM rectifier

Abstract: This paper presents a new control strategy for three-level neutral point clamped (NPC) pulse width modulated (PWM) rectifier without power source voltage sensors. Virtual flux is estimated and served as the oriented vector for the control of PWM rectifier. Theoretical principles of this method are presented and the neutral point potential balance control of the rectifier is also discussed. A digital-signal-processor-based experimental system was developed, and several experiments were conducted to examine the controllability. As a result, it is confirmed that unity power factor can be realized and the system exhibits several advantages, such as the low cost, high reliability, low harmonics and low voltage stress of power switches compared with conventional two-level rectifier.

A Novel Algorithm of SVPWM Harmonic Analysis Based on PWM Rectifier

Abstract: According to the operational principle of SVPWM and considering the characteristics of digital implement, a novel algorithm of SVPWM harmonic analysis based on PWM rectifier is proposed. This algorithm gives the expression of phase voltage harmonics through Fourier analysis, which provides the guidance for the design of grid side inductance. Since the harmonic spectrum of ac-side phase voltage of PWM rectifier is influenced not only by pulse modulation style, but also by the parameters of close-loop adjustors, a three-phase voltage source inverter controlled by TMS320F2812 has been built to obtain the harmonics purely generated by SVPWM and verify the algorithm. Power analyzer PZ4000 has been adopted to acquire experimental results. The good agreements between experimental results and those obtained in calculation demonstrate the accuracy of this algorithm.

Control Strategy of Combined PWM Rectifier/Inverter for a High Speed Generator Power System

Abstract: Recently more attention has been paid to the distributed power systems due to their high flexibility and reliability. The high speed permanent magnet (PM) generator driven by micro-turbine has been widely investigated since it has small size, high efficiency and power density. The output high frequency AC power of the high speed PM generator needs to be converted into the AC power with constant frequency and voltage using AC/DC/AC converter. The normal AC/DC conversion through diode rectifier will generate harmonic currents in the generator winding which will cause additional losses and increase temperature rise of the generator. To reduce the current harmonics of high speed generator, the structure and control strategy of a combined PWM rectifier/inverter are introduced in this paper. The converter is first utilized as a PWM inverter to drive the generator for the micro-turbine starting, and then operates as a PWM rectifier during the normal power conversion. The double closed loops (current loop and voltage loop) are adopted. The simulation and experimental results show the feasibility of the proposed design structure and control strategy.

A Single-Phase High-Power-Factor Neutral-pointer Clamped Multilevel Rectifier

Abstract: A single-phase rectifier based on neutral-clamped converter (NPC) is proposed to achieve high power factor, lower current distortion and low voltage stress of power semiconductors. The principle of single-phase three-level PWM rectifier is introduced. Neutral-point balance problem is an inherent problem of three-level converter, so a bangbang control method is schemed to control the capacities' voltage. A dual close-loop control is used to make the rectifier have favorable dynamic and steady state performance, sinusoidal input current and unity power factor. Finally, the feasibility and validity of the proposed control scheme and neutral-point voltage control scheme are verified through the simulation using MATLAB.

Multi-Level Current-Source PWM Rectifier Based on Direct Power Control

Abstract: This paper describes a novel control strategy of a multi-level current-source PWM rectifier, which is based on relay control of instantaneous active and reactive power. The key of this strategy is direct selection of switching states on the basis of instantaneous control 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 states of the PWM rectifier is investigated, which is essential to select current vectors. In addition, this paper discusses DC bus current control to balance the multiple PWM rectifiers. Several computer simulations are conducted and their results prove feasibility of the proposed technique of controlling the multi-level current-source PWM rectifier.

Power conversion device with sets arranged in parallel

Abstract: PROBLEM TO BE SOLVED: To make it possible to perform interrupting operation at high speed when any anomaly occurs in the direct-current voltage and the zero-phase current of a power converter and perform stable operation with very small influence of electromagnetic interference and the like SOLUTION: A power conversion device with sets arranged in parallel includes: power converters each having a PWM rectifier 3 and an inverter 4; a PWM rectifier-side arithmetic processing unit that carries out processing for the PWM rectifiers 3; and an inverter-side arithmetic processing unit that carries out processing for the inverters 4 The PWM rectifiers 3 and the inverters 4 are driven by the arithmetic processing units mounted on different control boards 6, 7 When one arithmetic processing unit detects any anomaly in the power conversion device, it transmits an anomaly detection signal to the other arithmetic processing unit through a relay 11 or a photocoupler COPYRIGHT: (C)2009,JPO&INPIT

Specific Harmonic Power Suppression of Drector-Power-Controlled Current-Source PWM Rectifier

Abstract: This paper focuses on specific harmonic active power suppression of a direct-power-controlled (DPC) PWM current-source rectifier (CSR) in order to achieve low distortion of the input line currents Total input power factor of the DPC-based PWMCSR becomes worse as the load gets lower due to the low-order harmonics in the line currents, especially the fifth and the seventh Since the dominant low-order harmonic currents cause an oscillation in the active power at frequency of sixth, suppression of the sixth-order harmonic active power is essential to improve the total power factor particularly in the low-load range The paper describes a theoretical aspect and a suppression technique of the harmonic active power, followed by basic configuration and operation of the DPC-based PWMCSR Effectiveness of the proposed technique is confirmed through computer simulations and experimental tests, using a 2-kW prototype As a result, the total harmonic distortion of the line currents is effectively reduced by 10 %, which results in approximately 20-% improvement of the total input power factor at a 350-W load condition

Unity Power Factor Operation of Three-Phase PWM Rectifier Based on Direct Power Control

Abstract: In this paper, direct power control (DPC) of three-phase PWM rectifiers is presented, without line voltage sensors. The controller builds upon the ideas of the well known direct torque control (DTC) for induction motors. In our case, the active and reactive powers replace the torque and flux amplitude used as controlled output in DTC. The instantaneous active and reactive powers, directly controlled by selecting the optimum state of the converter, are used as the PWM control variables instead of the phase line currents being used. The controller ensures a good regulation of the output voltage, and guarantees the power factor close to one. The proposed controller was tested both in simulation and experimentally. The results show the excellent performance of the proposed system such as a good dynamic behavior, a good rejection of impact load disturbance.

Supply-side Current Harmonics Control of Three Phase PWM Boost Rectifiers Under Distorted and Unbalanced Supply Voltage Conditions

Abstract: This paper presents a hybrid current control scheme to minimize the even order harmonics at the dc link voltage and odd order harmonics in the line currents under the distorted and unbalanced supply voltage conditions. The hybrid current control scheme consists of a conventional PI and a repetitive controller (RC). Based on the mathematical model of the three-phase PWM boost rectifier in the positive and negative synchronous rotating frames, the influence of the distorted supply voltages on the line side currents has been investigated from the analytical point of view. The control task is divided into: (a) dc-link voltage harmonics control and (b) line side current harmonics control. In voltage harmonics control, a reference current calculation algorithm has been derived accordingly to ensure that the dc link voltage is maintained constant and the supply side power factor is kept close to unity. In current harmonics control, a plug-in repetitive controller is designed to achieve low THD line currents of the three phase PWM boost rectifier. The proposed analysis and hybrid current control scheme have been validated by experimental test results on a 1.6 kVA laboratory based PWM rectifier. Test results obtained confirm that the proposed control scheme enhances the performance of the PWM rectifier over the conventional one.

A Carrier-Based Unipolar PWM Current Controller That Minimizes the PWM-Cycle Average Current-Error Using Internal Feedback of the PWM Signals

Abstract: A carrier-based unipolar pulsewidth modulation (PWM) current controller is described using a one-phase PWM rectifier bridge as a test circuit. The controller PWM signal generator uses a sawtooth carrier signal to obtain both synchronized PWM waveforms and a constant switching frequency. A current-error signal and an amplitude modulation depth signal are used to create the input reference signal to the PWM signal generator. The amplitude modulation depth signal is obtained from the PWM-cycle average of the PWM signal generator output signals. This internal feedback is illustrated using a second-order low pass Butterworth filter. With an appropriately designed low-pass filter, the current-error signal is forced to be centered on zero over a PWM cycle. The maximum peak-peak magnitude of the current-error signal is used as a design guideline for deciding an appropriate gain constant in the controller current feedback loop. The low pass filter design is examined to determine a suitable gain and 20-dB attenuation frequency to minimize the current-error signal. The steady-state and transient operation of the proposed current controller is compared with a proportional-integral controller and an average current-error controller. SPICE simulations and experimental results are used to demonstrate the characteristics of the controller.

Three-phase multi-level PWM rectifier multi-carrier discontinuous voltage modulation strategy

Abstract: Multi-level PWM rectifier requires fewer semiconductor switches compared with its bidirectional multi-level converter counterpart Though three-level (multi-level) PWM rectifiers are known for more than 10 years, no multi-level PWM rectifier carrier based voltage modulation strategies were reported so far After multi-level PWM rectifier topologies introduction and classification, the paper presents a three-phase multi-level PWM rectifier phase shifted multi-carrier voltage modulation strategy based on appropriate discontinuous voltage commands transformation Suggested formalism naturally allows derivation of a multi-level PWM rectifier voltage amplitude (modulation index) vs voltage-current phase angle operation envelope without making use of space vector calculus PWM rectifier operation envelope becomes less restrictive with levels count increase and full utilization Suggested approach is not limited to a three-phase case and is applicable to a general multi-phase case

A Three-Phase Space-Vector Based PWM Rectifier with Power Factor Control

Abstract: A three-phase space-vector based PWM rectifier with power factor control has been proposed in this paper. The three-phase phase locked loop (PLL) is designed to detect the phase angle of utility voltage, which is used to create three-phase reference currents. The proposed scheme is simple and practical to be implemented on a fixed-point digital signal process based controller. It also does not require any system parameters. According to experimental results, the dc output voltage is successfully controlled while the unity power factor is accomplished.

Analysis and Experimental Validation of the Output Voltage and Input Current Performances in Three Phase PWM Boost Rectifiers Under Unbalanced and Distorted Supply Voltage Conditions

Abstract: This paper analyzes the dc output voltage and line side currents of the three phase PWM boost rectifier under unbalanced and distorted supply voltage conditions. Based on the mathematical model of the three-phase PWM boost rectifier in the positive and negative synchronous rotating frames, a detailed analytical expression for the dc link voltage has been derived and presented. It shows the presence of even order harmonic components in the dc output voltage caused by the negative sequence component of the supply voltages. The effect of the distorted supply voltage on the line side currents has been investigated from the analytical point of view and discussed in this paper. A simple cascaded PI current control scheme in the positive and negative synchronous rotating reference frames has been designed to ensure that the dc link voltage is maintained constant and the supply side power factor is kept close to unity under the unbalanced and distorted supply voltage operating conditions. Experimental test results with the proposed controller are provided on a 1.6 kVA laboratory based PWM rectifier. Test results obtained confirm that the performance of the proposed control scheme enhances the performance of the PWM rectifier over the conventional single reference frame based controller.

Power saving of PWM rectifier-VSI fed induction machines

Abstract: The inverter fed ac drives with transistorized grid rectifier are investigated from the point of view of steady-state power saving. It is shown that the optimal power saving control of frequency controlled induction motor drive provides saving about 0.5 to 3% of rated power by flux control less then the rated flux. This valid only for motor torques less than 50% of the rated load. In case of high modulation frequency about the same energy can be saved for both the inverter and sinusoidal operations. For the rated load some power saving (0.5-1.0%) is also possible but only by the increasing of the motor flux over the rated value. Generally, the energy saving control is economical only when the technology requires the frequency control.

Direct power control system of PWM rectifier based on synthetic voltage space vector

Abstract: The invention advances a resultant voltage space vector-based voltage type PWM rectifier direct power control system, synthesizing adjacent voltage space vectors into a resultant voltage space vector with an amplitude the same as those of other nonzero voltage space vectors to make the number of nonzero voltage space vectors up to 12. For further reducing power control errors, AC current harmonics and DC voltage fluctuation, it redivides input space into sectors. According to the new 12 voltage space vectors and divided sectors, it determines a new power control switch list. And computer simulation shows that it has good dynamic and static performances, making unit power factor, DC voltage fluctuation and AC current harmonics all reach national electric energy quality standard.

Simulation of Three-phase Voltage Source PWM Rectifier Based on Sliding-mode Control

Abstract: AC/DC/AC system in which three-phase voltage source PWM rectifier (VSR) is adopted as the front-end rectifier can hardly obtain good dynamic performance and robustness in four-quadrant operation due to the lag of PI regulator and the sensitiveness of its proportional and integral gains to system parameters. Considering the nonlinear characteristic of VSR, a sliding-mode control algorithm based on synchronous rotating reference frame was proposed. The whole system was modeled and simulated in MATLAB/SIMULINK to obtain comparison between sliding-mode and classical PI control. The results show that the sliding-mode control possesses preferable dynamic response compared with PI regulator.

Three-level Inverter Controlled by means of Vector Hysteresis Current Control. Application to Back to Back Structure

Abstract: The studied application is a back to back power electronic structure feeding a three-phase load. The line side converter is a two-level PWM rectifier controlled by a current hysteresis controller in the abc reference frame. It regulates the dc voltage and enables a unit power factor. The load side converter is a three-level voltage source inverter (VSI), which is controlled by means of a novel vector hysteresis current control (V.H.C.C). The proposed V.H.C.C, which is based on error square areas, controls the three-phase load AC currents. In addition, it regulates the neutral point voltage using the redundant inverter switching states. The three load current errors are gathered into a single space vector quantity. In this case, the magnitude of the error vector is limited within boundary areas of a square shape. The control scheme is based on the detection of areas and sectors, in which the vector tip of the current error can be located. Then it applies an appropriate voltage vector among the 27 voltage vectors. Simple look-up tables are required for the detection of areas and sectors, and also for the vector selection. The proposed V.H.C.C can be extended to further multilevel inverters.