Showing papers on "PWM rectifier published in 2010"

Predictive Direct Power Control of Three-Phase Pulsewidth Modulation (PWM) Rectifier Using Space-Vector Modulation (SVM)

Abstract: In this paper, we present a direct power control (DPC) of three-phase pulsewidth modulation rectifier with constant switching frequency using space-vector modulation (SVM). The developed DPC scheme is based on the predictive control strategy to achieve direct control of instantaneous active and reactive power of the converter. For this purpose, at the beginning of each switching period, the required rectifier average voltage vector allowing the cancellation of active and reactive power tracking errors, at the end of the switching period, is calculated by means of predictive control algorithm in the sense of deadbeat control. The main advantages of the proposed control, compared to the works published in this subject, are that no need to use predefined switching table and voltage vector or virtual flux position, PI-based active and reactive power control loops are not necessary and constant-switching frequency. The proposed predictive direct power control was tested both in simulations and experimentally and compared with DPC using switching table. Results have proved excellent performance, and verify the validity of the proposed DPC scheme, which is much better than conventional DPC using switching table.

A high power density single phase PWM rectifier with active ripple energy storage

Abstract: It is well known that there exist second-order harmonic current and corresponding ripple voltage on dc bus for single phase PWM rectifiers. The low frequency harmonic current is normally filtered using a bulk capacitor in the bus which results in low power density. This paper proposed an active ripple energy storage method that can effectively reduce the energy storage capacitance. The feed-forward control method and design considerations are provided. Simulation and 15kW experimental results are provided for verification purposes.

Design of a Plug-In Repetitive Control Scheme for Eliminating Supply-Side Current Harmonics of Three-Phase PWM Boost Rectifiers Under Generalized Supply Voltage Conditions

Abstract: This paper presents a digital repetitive control (RC) scheme to minimize the even-order harmonics at the dc link voltage and odd-order harmonics in the line-side currents under distorted and unbalanced supply voltage conditions. The proposed current control scheme consists of a conventional PI and a plug-in repetitive controller. On the basis of the mathematical model of the three-phase pulsewidth-modulated (PWM) boost rectifier under the generalized supply voltage conditions, the control task is divided into: 1) dc-link voltage harmonics control and 2) line-side current harmonics control . In the voltage harmonics control scheme, a reference current calculation algorithm has been derived accordingly to ensure that the dc link voltage is maintained constant at the demanded value and the supply-side power factor is kept close to unity. In the line-side current harmonics control scheme, a plug-in repetitive controller is designed to achieve low total harmonic distortion (THD) line-side currents of the three-phase PWM boost rectifier. The experimental test results obtained from a 1.6-kVA laboratory-based PWM rectifier confirm that the proposed control scheme can reduce the line-side current THD from 16.63% to 4.70%, and improve the dc-link voltage tracking accuracy substantially over the conventional PI-based controller.

Control of Three-Phase Boost-Type PWM Rectifier in Stationary Frame Under Unbalanced Input Voltage

Abstract: In the last decade, many methods for control of three-phase boost-type pulsewidth modulation (PWM) rectifier under unbalanced input voltage conditions have been studied and presented. These methods use the sequential components of input voltages, pole voltages, and input currents of the rectifier to analyze and control the instantaneous powers, of which dual (positive-sequence and negative-sequence rotating) frame control is the most common structure. Anyway, this paper analyzes the instantaneous powers of the PWM rectifier in two-phase stationary frame. Based on this analysis, the input-power-control, input-output-power-control, and output-power-control methods for PWM rectifier under unbalanced voltage conditions are proposed in single stationary frame. Compared with the existing methods, simplicity may be the major advantage of the method in this paper. Rotating transformation and phase detection of the input voltages are both eliminated. Moreover, sequential component extraction of the control variables is also not necessary, leading to much reduced time delay to the control system. Experimental results on a 9-kVA PWM rectifier show validity and effectiveness of the proposed methods.

Three-Phase Multilevel PWM Rectifiers Based on Conventional Bidirectional Converters

Abstract: Almost two decades of research on unidirectional three-phase multilevel boost-type pulsewidth modulation (PWM) rectifiers have shown the benefits of employing this technology to comply with power quality standards while assuring high efficiency and low volume and weight. However, the unidirectional topologies directly derived from the conventional three-level bidirectional converters, such as the neutral point clamped (NPC), the flying capacitor and the cascaded H-bridge converters have not been properly analyzed. This letter introduces some of the unidirectional topologies that arise from the inspection of the widespread conventional bidirectional converters. Special emphasis is put in the analysis of the NPC-based three-phase/-level PWM rectifier operating as power factor corrector.

DC zonal micro-grid architecture and control

Abstract: DC micro-gird architecture and its control have been proposed in this paper. A bidirectional PWM rectifier is used as a backup for DC micro-grid to balance the power when the management ability of the local micro-grid is limited. A power management algorithm is also proposed based on this configuration. The DC zonal micro-grid proposed here has the advantage of maximum utilization of local distributed resource and smooth transition among different modes. Simulation results are given to verify the effectiveness of the theory.

Practical methods for tuning PI controllers in the DC-link voltage loop in Back-to-Back power converters

Abstract: This paper provides two options for the design of the Proportional + Integral (PI) controller for the DC-link voltage loop, which is found in several topologies, such as AC/DC voltage source converters and Back-to-Back converters among others. The proposed methods are based in the bandwidth approach. For the design of the DC-link voltage loop, the Back-to-Back topology is used and two cases the studies are analyzed. In the first case the converter controls the power transfer between the mains and the load; in the second it controls the active and reactive power as a PWM Rectifier with active filter function (PWM-VSR-C). In both cases the dq reference frame is used for the design of the controllers. The proposed methods are practical and clearly explained. The designs are validated with simulations and experimental results.

Design of high-temperature SiC three-phase AC-DC converter for >100°C ambient temperature

Abstract: High temperature (HT) converters have become more and more important in industrial applications where the converters will operate in a harsh environment. These environments require the converter to have not only high-temperature semiconductor devices (SiC, GaN) but also high-temperature control electronics. This paper describes a design process for a three-phase PWM rectifier. The SiC JFET planar structure is used for the main semiconductor devices. Other high-temperature components, including the passive components, silicon-on-insulator chips and the auxiliary components are studied and summarized. Finally, a 1.4 kW lab prototype is fabricated and tested for verification.

Systems and methods of powering a refrigeration unit of a hybrid vehicle

Abstract: Systems and methods for providing power to a refrigeration unit or an air conditioner used on a hybrid vehicle. The system includes an accumulation choke, a PWM rectifier, and a frequency inverter. The accumulation choke is configured to receive a first AC power, a second AC power, and a DC power. The accumulation choke and PWM rectifier convert the received power into an intermediate DC power having a peak voltage. The PWM rectifier provides the intermediate DC power to the frequency inverter. The frequency inverter converts the intermediate DC power to an output AC power. The frequency inverter provides the output AC power to the refrigeration unit.

Modular energy feedback type traction power set and control method

Abstract: The invention relates to a modularized energy feedback traction power supply device and a control method thereof, wherein, the device comprises a multi-winding transformer, a plurality of PWM rectifier units and a central controller, wherein, the multi-winding transformer is provided with a primary winding and a plurality of secondary windings, and all of the secondary windings have the same connecting mode; each secondary winding of the transformer is connected with a PWM rectifier unit; the direct-current outputs of all the PWM rectifier units are connected to a direct-current bus of the general power supply device in serials. Double closed-loop control of voltage and current is adopted; an outer loop of direct-current voltage is arranged on the central controller and an inner loop based on synchronous rotating frame is arranged on each PWM rectifier unit. The power supply device is remarkably characterized by easy modularization, large capacity, bipolar energy transmission, high power factor, small current harmonic wave and stable direct-current voltage.

EMI filter design for high switching frequency three-phase/level PWM rectifier systems

Abstract: The actual attenuation characteristic of EMI filters in practice often differs from theoretical predictions and minor changes could result in a significant performance improvement. Whereas the performance of the differential-mode (DM) filter stage usually can be well predicted, the common-mode (CM) behavior is more difficult to handle. This is especially true for three-phase PWM rectifier systems, which show a large high-frequency CM voltage at the rectifier output. In this work the possible CM noise current paths of a three-phase/level PWM rectifier are analyzed where parasitic capacitances to the heat sink and to earth are considered. Additionally, a concept to significantly reduce CM emissions is discussed in detail. Based on the proposed models an EMI filter design for a system with 1 MHz switching frequency is shown. Experimental verification of the designed EMI filter is presented by impedance and conducted emission (CE) measurements taken from a 10 kW hardware prototype. Several practical aspects of filter realization like component arrangement, shielding layers, magnetic coupling etc. are discussed and verified by measurements.

A Comparative Study on Variable-Speed Operations of a Wind Generation System using Vector Control

Abstract: This paper presents a comparison study among three control methods based on vector control for maximising the output power and improving the performance of a small-scale wind generation system (WGS). The three control methods are a hysteresis-band current controller (HBCC), a PI current controller (PICC) and an improved PI current controller (IPICC) which is based on particle swarm optimisation (PSO). The WGS investigated in this research consists of a permanent magnet synchronous generator (PMSG) directly driven by a vertical-axis wind turbine (VAWT), a current controlled PWM rectifier, and a stand-alone DC load. The principle of maximum power point tracking (MPPT) is to adjust the rotational speed of a wind turbine at optimal speeds that ensures optimal tip-speed ratios (TSR) and maximum power coefficients over a wide range of wind speeds. Simulations are based on actual parameters which are obtained experimentally from a real wind turbine generator system. The simulation results show the effectiveness of the IPICC method compared with the HBCC and PICC methods due to its satisfactory dynamic responses with fast MPPT under wind speed variations.

High-density system integration for medium power applications

Abstract: Over the past ten years, there has been increased incorporation of electronic power processing into alternative, sustainable, and distributed energy sources, as well as energy storage systems, cars, airplanes, ships, homes, data centers, and the power grid. The goals have been to reduce the size, weight, and maintenance and operational costs of these power systems, while increasing overall energy efficiency, safety, and reliability. This paper summarizes some of the authors' research efforts in the last four years on the improvements in power density and physical integration of power converters, mostly for vehicular applications. Several approaches to integration of active components into high-temperature modules are presented together with examples of the evaluation and modeling of 1.2 kV SiC JFET and MOSFET. Possible improvements in the power density through hybrid passive and active integration of an EMI filter and of an energy storage capacitor in single-phase PWM rectifier are also shown. Examples of converter integration for a 10 kW motor drive with active front-end using SiC devices operating at 250 °C, and for paralleling three-phase boost rectifiers with interleaved PWM are presented.

Common mode modelling and filter design for a three-phase buck-type pulse width modulated rectifier system

Abstract: The EMC input filter design for a three-phase pulse width modulated (PWM) rectifier is usually separated into the design of the differential mode (DM) and common mode (CM) stages. While for the DM filter design rules and procedures are well known and easier to predict, the CM filter design is often based on trial-and-error methods and/or on the experience of the designer. In the present study, a comprehensive design procedure for a CM EMC input filter is performed for a three-phase three-switch buck-type PWM rectifier. A model of the CM noise propagation is developed and the relevant parasitic impedances are identified. A capacitive connection from the star-point of the DM input filter to the capacitive centre point of the rectifier output voltage is proposed and the effect of this measure-concerning CM is verified. Finally, a two-stage CM filter is designed and compliance to the conducted emission (CE) requirements of CISPR 22 Class B is verified through measurements on a 5 kW prototype.

Control Strategy for Three Phase Voltage Source PWM Rectifier Based on the Space Vector Modulation

Abstract: This paper proposes the space vector pulse width modulation (SVPWM) control scheme for three-phase voltage source PWM rectifier. The control system based on SVPWM includes two PI contr ...

Line-frequency rectifier dc-bus voltage instability analysis and mitigation

Abstract: Use of small dc bus capacitors is desirable in variable-speed drives and distributed power systems as it can reduce the size and improve reliability of the system. However, small dc bus capacitors may lead to instability of the dc bus voltage. Such voltage stability problem can occur when the bus is fed from a PWM rectifier or a line-frequency rectifier. This paper considers the case when a line-frequency rectifier is used and presents a method for the analysis of dc bus voltage instability in such systems. Small-signal input impedance of multipulse line-frequency rectifiers is used in conjunction with the ac source output impedance to detect possible instability on the dc bus. Stabilization of the dc bus voltage by a passive damping is presented and compared to other stabilization methods such as increasing dc bus capacitance or placing the damper at the ac input of the rectifier. Experimental results from a 12-pulse rectifier feeding an electronic load that is programmed to emulate constant-power load behavior typical of DPS and variable-speed drives are presented to validate the analysis and design approach.

Compensation of control delay and discrete control error in predictive direct power control for three-level PWM rectifier

Abstract: In three-level pulse width modulation (PWM) rectifier, the performances of the conventional predictive direct power control (PDPC) method are seriously degraded by the one-control-period delay and the discrete error of control variables. This paper investigates the problem by evaluating the influences of the control delay and the discrete control error on the performances of the system, and proposes a novel three-level PDPC method with compensation of control delay and discrete control error. An instantaneous power predictor is designed to compensate the control delay. Optimized prediction and control equations are deduced considering the variations of grid voltages during one control period in order to improve the control precision. Simulation and experimental results prove that the proposed three-level PDPC strategy achieves excellent steady-state and dynamic performances.

Direct Power Control in Constant Switching Frequency for PWM Rectifier Under Unbalanced Grid Voltage Conditions

Abstract: Constant switching frequency direct power control(CSF-DPC) strategy has the advantages of fixed switching frequency,good dynamic performance and low system sampling frequency requirementIn this paper,a developed CSF-DPC strategy was proposed to solve the problems in pulse width modulation(PWM) rectifiers,such as current harmonics,significantly fluctuating active power and performance deterioration,caused by unbalanced grid voltageThe positive and negative sequence components of grid voltages and currents were calculated to obtain instantaneous power in two revolving coordinates,which rotate at positive and negative synchronous angular velocity respectivelyThe errors between reference values and calculated values of power were regulated to build the output voltage space vectorThe duty cycle of rectifier was calculated by SVM methodThe proposed strategy was finally verified by simulation and experimental resultsIt is proved to be effective on reducing input current harmonics and reactive power DC components,stabilizing output active power

Line-frequency rectifier dc-bus voltage instability analysis and mitigation

Abstract: Use of small dc bus capacitors is desirable in variable-speed drives and distributed power systems as it can reduce the size and improve reliability of the system. However, small dc bus capacitors may lead to instability of the dc bus voltage. Such voltage stability problem can occur when the bus is fed from a PWM rectifier or a line-frequency rectifier. This paper considers the case when a line-frequency rectifier is used and presents a method for the analysis of dc bus voltage instability in such systems. Small-signal input impedance of multipulse line-frequency rectifiers is used in conjunction with the ac source output impedance to detect possible instability on the dc bus. Stabilization of the dc bus voltage by a passive damping is presented and compared to other stabilization methods such as increasing dc bus capacitance or placing the damper at the ac input of the rectifier. Experimental results from a 12-pulse rectifier feeding an electronic load that is programmed to emulate constant-power load behavior typical of DPS and variable-speed drives are presented to validate the analysis and design approach.

Input impedance modeling of multipulse rectifiers by double-fourier series method

Abstract: Rectifier input impedance models are required for stability analysis of ac power systems with significant amount of rectification loads. Such stability analysis is particularly important for mobile and autonomous systems, such as aircraft and ship power systems, where high-power, multipulse rectifiers often dominates the loads. Averaging techniques can be applied to develop input impedance models for PWM rectifiers. To model the input impedance of line-frequency rectifiers, a direct linearization technique was developed recently and has been applied to model direct multipulse rectifiers without using inter-phase transformers. This paper extends the previous work and uses double-Fourier series method to develop describing (mapping) functions for the rectifier bridge. The double-Fourier method overcomes the limitations of conventional Fourier analysis which requires the perturbation frequency to be commensurable with the line fundamental frequency. The method is also applied to model the input impedance of multipulse rectifiers with interphase transformers. Analytical input impedance models are presented and validated by numerical simulation and experimental results.

The optimized strategy for input current harmonic of low switching frequency PWM rectifier

Abstract: The industry application of High-power medium-voltage drives converter is an appealing spot in Power electronics technology in recent years. This paper presents an optimized control strategy for input current harmonic of rectifier of three-level NPC back-to-back converter under low switching frequency conditions. A modified P-N SVPWM method includes asymmetrical regular sampling, even-order harmonic elimination and natural DC bus balancing is applied for optimize the THD performance of input currents. And a modified proportional sinusoidal signal integrator method based on control scheme in two phase stationary reference frame which is different from ordinary direct-quadrature (DQ) rotating reference frame is proposed. It provides a specific input current harmonic elimination performance especially considerable in low switching frequency circumstance. Simulation and experimental results based on a rectifier of a 75kVA three-level NPC back-to-back converter prototype with a 400Hz device switching frequency constraint show satisfactory performance.

Modeling and Simulation of Three-phase Rectifier Based on SVPWM

Abstract: The mathematical and simulation model of three-phase voltage source rectifier (VSR) used in aircraft is introduced in this paper. Based on the model, the principle of the seven-segment space vector pulse-with modulation (SVPWM) control strategy is presented. The double closed-loop control method is applied in the PWM rectifier. The rectifier can realize unity power factor by adopting the fixed switching frequency SVPWM current control method to realize that the current signal track voltage. The simulation results show that the mathematical model is accurate, and the SVPWM current control method can administer to improve the dynamic performance of three-phase rectifier obviously.

Direct power control of PWM rectifiers based on virtual flux

Abstract: In this paper, direct power control based on the virtual flux (VF-DPC) of the three-phase voltage-type PWM rectifier is presented and the formation mechanism of the switching table is analyzed. In Matlab / simulink environment the model of the VF-DPC system is established. The simulink results show that the system has good dynamic response and a good way to achieve active power and reactive power control, while ensuring the input side of the unity power factor control. Compared with the existing current control strategy, VF-DPC system without complicated algorithms and PWM modulation block can achieve higher power factor and low harmonic disturbance (THD).

A novel indirect current control for single-phase PWM rectifier at low switching frequency

Abstract: This paper presents a novel indirect current control technique applied to a Single-Phase PWM rectifier to increase power factor and reduce harmonic current. It is applied to railway traction converters with low switching frequency, high voltage and high power. To get better stability and easier realization, indirect current control scheme is used in the inner loop control. Much computing such as extraction of square root and arc tangent affects the switching time of power devices and reduces the control accuracy. A new PWM control technique based on volt-seconds equalization is adopted. Simulation and experiment results proved the proposed scheme.

A bidirectional power converter for battery of plug-in hybrid electric vehicles

Abstract: A novel power converter for battery used in the Plug-in Hybrid Electric Vehicle (PHEV) is proposed, which could charge and discharge the battery effectively. The system is composed of two parts: a three phase full bridge PWM rectifier and a DC/DC converter. The PWM rectifier is utilized to rectify the three phase AC to DC voltage, which should be higher than the battery terminal voltage. The DC/DC converter is constructed by a buck-boost circuit, which is a buck circuit under charge mode and a boost circuit under discharge mode. The direct current control (DCC) algorithm is responsible for rectifying the AC output and diminishing the total harmonics distortion. The proportional-integral (PI) controller and bangbang controller is to control the charging current and voltage. The simulation and experiment results validate the effectiveness of proposed algorithm and the feasibility of system.

A Virtual Admittance Control Strategy of Three-Phase Voltage Source PWM Rectifier Under Unbalanced Input Voltage Conditions

Abstract: A virtual admittance control strategy is proposed for three-phase voltage source PWM rectifier by analysis on the time-domain relationship between three-phase AC current and three-phase AC voltage under unbalanced input voltage conditions. The strategy does not only simplify the control algorithm, but also realize wanted power factor by the Coordinate Transformation. With reduced computation and improved speediness, generalized integrator is also introduced to realize static error free tracking control of positive and negative sequence current on two-phase static frame. Extensive simulation and experimental results verify the correctness of the proposed control strategy.

Novel Quasi Direct Power Control Method for PWM Rectifier in Stationary Frame

Abstract: For most of the existing control methods for PWM rectifier,rotating frame is widely adopted. The underlying reason is that the control variables exist in DC form in steady state and the most popular PI controllers can be adopted to eliminate the steady state error. Unlike most of the existing schemes,this paper presented a novel quasi direct power control method for PWM rectifier in stationary frame based on instantaneous power theory. In the proposed method,unity power factor is obtained without the need of grid voltage phase detecting (such as phase lock loop),decoupling control or rotating transformation,which offers a simple control method for PWM rectifier. The parameters of the controllers were analyzed and the design algorithm was also presented. Computer simulations and experimental results on a 30 kVA PWM rectifier prototype show excellent performance of the proposed method.

A Novel Multi-level Medium Voltage Converter Designed for Medium Voltage Wind Power Generation System

Abstract: A novel back to back cascaded medium voltage converter is proposed for wind power generation. In the generator side, it is a H-bridge cascaded converter, which employs the vector control based on rotor flux orient to drive the medium induction generator. In the grid side, a series of two-level voltage source converters are used to support an isolated DC voltage for each H-bridge cell in the generator side, which is controlled by the PWM rectifier algorithm. With the novel converter, generators in the wind power can directly work in a 3~10 KV voltage system instead of the conventional 690 V system, which makes it impossible for a wind turbine to product a larger power such as 3 MW or 5 MW. The application not only improves the efficiency and the safety of the system, but also reduces the use of the cable and the cost greatly. To validate the fitness, some simulations are done in MATLAB/SIMULINK. The results are satisfactory.

An integrated control method for three-level NPC based PWM rectifier-inverter

Abstract: This paper presents a novel integrated control scheme for three-level neutral point clamped (NPC) based PWM rectifier-inverter. Two measures are taken to minimize the size of dc-bus capacitors which are expensive, bulky and have a lifetime limit. Firstly, the direct power control (DPC) for front-end three-level PWM rectifier is applied, which will provide better dynamic performance for the dc-link. Secondly, a power feed-forward control loop from inverter to rectifier side is introduced to reduce the response delay. Some experiments have been performed on an IGBT-based three-level PWM rectifier-inverter, and the results show that with the proposed scheme, the three-level NPC based rectifier-inverter exhibits excellent dynamic performance, and can minimize dc-bus voltage fluctuations remarkably.