Prof. Dr. Joachim Holtz
Editor-in-Chief
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Prof. Dr. Joachim Holtz |
Special Section on High Power Factor Rectifiers - Part I
- Guest Editorial: High Power Factor Rectifiers
by Ivo Barbi
- A Robust Three Phase Active Power Factor Correction and Harmonic Reduction Scheme for High Power
by Bang S. Lee, Jaehong Hahn, Prasad Enjeti, Ira J. Pitel
Abstract - This paper proposes a robust three-phase active power factor correction and harmonic reduction scheme suitable for higher power applications. The proposed system is a unique combination of a low kVA 12-pulse rectifier system with a single-phase boost PFC scheme to shape the input current to near sinusoidal waveshape. The VA rating of the active PFC converter is 0.05 pu and is not exposed to line transients under varying load conditions. The proposed system is suitable for utility interface of higher power rectifiers employed in power supplies and adjustable speed drive systems which demand clean input power characteristics in the range of 1 to 500kW. The proposed system is rugged and in the event the active control were to fail the system reverts to 12-pulse operation with 5th and 7th harmonic cancellation. Analysis and design of the system is examined in detail, simulation and experimental results on a 10kVA prototype are shown.
- Design and Evaluation of a Cellular Rectifier System with Distributed Control
by David Perreault, John G. Kassakian
Abstract - This paper presents the design and experimental evaluation of a six-cell, six-kilowatt cellular (parallel) rectifier system which operates at nearly unity power factor. The cellular rectifier system implements both distributed load sharing and distributed ripple cancellation, eliminating the need for any centralized control. The implemented system mitigates some of the major drawbacks of its single-converter counterpart, and achieves performance levels that cannot be achieved with an equivalent single converter.
- Integrated Active Rectifier and Power Quality Compensator with Reduced Current Measurement
by A. D. le Roux, J. A. du Toit, J. H. R. Enslin
Abstract - This paper describes a 3-phase integrated active rectifier and shunt power quality compensator (IPQC). The measurement of only 3 currents is required and the control algorithm can be implemented using a low-cost controller. The IPQC improves the harmonic content of the supply current, displacement power factor, supply current balance and can serve as a four-quadrant active rectifier for motor drives and other dc-link loads. The operation of the IPQC is experimentally verified using a conventional 3-phase IGBT voltage source inverter. A low-cost fixed-point digital signal processor (DSP) based controller with fixed band hysteresis current regulation is used for the implementation of the control algorithms.
- A Novel Simplified Space-Vector Modulated Control Scheme for Three-Phase Switch-Mode Rectifier
by Chern-Lin Chen, Che-Ming Lee, Rong-Jie Tu, Guo-Kiang Horng
Abstract - A novel simplified control scheme for three-phase switch-mode rectifier is proposed in this paper. The proposed control scheme is based upon a load-conductance rectifier controller, in which reference current signals are obtained. The goal to follow the reference current is converted to follow a reference voltage. A simplified control scheme utilizing space-vector modulation is developed to calculate the duty ratio required to synthesize the reference voltage. The proposed scheme has the advantage of space-vector modulation with fast dynamic response, and being simple enough to be implemented in a single-chip microprocessor 80196MC.
- Minimum-Loss Strategy for 3-Phase PWM Recifier
by Dae-Woong Chung, Seung-Ki Sul
Abstract - In this paper, the conduction and switching losses of voltage-fed 3-phase PWM rectifier are analyzed for various PWM(Pulse Width Modulation) schemes. On the basis of this result, a novel PWM strategy which minimizes the loss of 3-phase PWM rectifier is developed. This minimization result is derived from the following two factors: less switching frequency ratio and the absence of switching in the vicinity of peak input current. As a result, it is anticipated that switching loss of the rectifier is reduced by 46% compared with continuous space vector PWMs, 20% compared with conventional discontinuous space vector PWMs. Moreover, proposed PWM scheme can produce the highest available output voltage because it is based on the concept of voltage space vector. The effectiveness of the proposed PWM strategy is verified by experiments.
- Optimal Regulator Based Control of NPC Boost Rectifiers for Unity Power Factor and Reduced Neutral Point Potential Variations
by Shoji Fukuda, Yasumasa Matsumoto, Akira Sagawa
Abstract - Neutral-point-clamped boost rectifiers (NPCR) are suitable for high voltage systems because of their circuit structure. The NPCRs, however, have a problem that the neutral point potential (NPP) varies when the current flows into or out of the neutral point. The variations cause voltage deviations in the input waveforms as well as unbalanced voltage stress on the devices. This paper describes a controlling method for NPCRs based on a state space model. There are three control objectives; to keep the power factor (PF) at unity, to keep the DC link voltage at a reference value, and to keep the neutral point potential at zero volts. The neutral point current is treated as one of the inputs. The controller is designed based on the optimal regulator theory in order to achieve the three objectives simultaneously. The validity of the proposed method is demonstrated by experimental results.
- Analysis and Design of Three-Phase AC-to-DC Converters with High Power Factor and Near-Optimum Feedforward
by Ming-Tsung Tsai, W. I. Tsai
Abstract - This paper presents a three-phase pulse-width modulated (PWM) ac-to-dc converter with unity power factor and near-optimum dynamic regulation. A general mathematical model of the converter has been established to lead to a comprehensive analysis. The averaged small signal technique is used to obtain the near-optimum feedforward compensator, thus resulting in the output impedance and the audio susceptibility become zero. That is, the output voltage of the converter presented in this paper is independent of variations of the dc load current and the utility voltage. The proposed procedure of analysis is simple and effective, it is also easy to implement. Finally, the theoretical formulations are verified both by simulated and experimental results in a 5 KW laboratory prototype system.
- A Novel Current Control Method for Three-Phase PWM AC/DC Voltage Source Converters
by Hasan Kömürcügil, Osman Kükrer
Abstract - This paper presents a novel current-control based control strategy, obtained in stationary frame, for a three-phase PWM ac/dc voltage-source converter. In this control strategy, an error voltage is produced from the comparison of the output dc voltage with a dc reference voltage. This error voltage is then utilized by a PI controller to generate a command signal for the input line current amplitude and is automatically controlled to the desired value. Therefore, there is no need to measure the input line currents. Stability analysis of the closed-loop system is made and the stability region for proportional and integral gains which makes the operating point stable is also found. The resulting closed-loop system not only exhibits good transient response, but also provides sinusoidal line currents and unity power factor both in the rectifying and regenerating modes. Experimental results are presented and compared with simulations.
- AC-DC Converter with Parametric Reactive Power Compensation
by Kuno Janson, Jaan Järvik
Abstract - Resonant converters of 50(60) Hz AC-DC are described, where each half- cycle of network voltage the capacitor and inductor of an oscillatory circuit are switched from series into parallel and vice versa. The duration of series and parallel connection and also the transformer ratio are parametrically dependent on load. In case of short circuit only the parallel oscillating circuit operates. This restricts sharply the output current. The reactive power of the capacitor and the inductor compensate with each other both in case of series and parallel connection. Therefore the power factor is very high from no-load to short-circuit. This converter fits very well to supply arc furnaces. Then there is no need for the costly and fast reactive power compensator and filter circuits. The operating principle of the converter, design principles and a real operating converter rated 8.4 MW supplying steel-melting arc furnace are described.
- Improving Dynamic Response of Power Factor Correctors by using Series-Switching Post-Regulator
by Marta M. Hernando, J. Sebastian, P. Villegas, S. Ollero
Abstract - A new method to improve the dynamic response of Power Factor Correctors (PFC) is described in this paper. The method is based on the use of a new very highly efficient post-regulator, called a Series-Switching Post-regulator. This new Post-regulator exhibits very high efficiency due to the fact that only a part of the total power undergoes a power conversion process. The proposed Post-regulator can be used with any PFC topology (either with or without a transformer) with no modifications in the topology, and can be easily protected against short-circuits.
- Average Current Mode Control of Two-Input Buck Post-Regulators used in Power Factor Correctors
by Javier Sebastián, P. J. Villegas, M. M. Hernando, F. Nuno, F. Linera
Abstract - The use of the Average Current Mode Control in the recently introduced Two-Input Buck post-regulator is studied in this paper. Using this type of control, the attenuation of the input voltage ripple (100-120 Hz) increases in relation to the one obtained when a conventional Voltage Mode Control (with or without feedforward) is used and, therefore, lower bulk capacitors can be used to obtain a very low voltage ripple at the output, which is very important when a battery is connected at the output. This is very common in distributed power supply systems.
- Interaction between EMI Filters and Power Factor Preregulators with Average Current Control: Analysis and Design Considerations
by Giorgio Spiazzi, José Antenor Pomilio
Abstract - The effects of a non negligible source impedance, due to the presence of an input EMI filter, on the stability of Power Factor Preregulators (PFP) with average current control are analyzed by using a State Space Averaged model. Differently from previous approaches, it allows to derive a simple expression for the loop gain in terms of the converter current loop gain. The overall system stability was studied for boost, Cuk and SEPIC PFP topologies. Based on this model, a simple modification of the standard current control loop is proposed which increases the converter robustness against instabilities. Comparison between model forecasts and experimental measurements was carried out using two prototype: one based on the boost topology and the other based on the SEPIC topology both rated at 600W. Finally, the model accuracy was investigated with measurements at different current loop bandwidths.
- Modeling of Single-Stage Converters with High Power Factor and Fast Regulations
by Tsai-Fu Wu, Yu-Kai Chen
Abstract - This paper presents an approach to systematically modeling single-stage dc/dc converters operated in discontinuous conduction mode (DCM) based on the graft scheme. With the graft scheme, the converters whose active switches are with a common node and operating in unison can be integrated to form a single-stage converter (SSC). The small signal models of SSC can be, therefore, derived by combining those of its originally separate converters. Using the proposed approach can help to yield highly related dynamic models of the converters in a family, and in addition, physical insights between the converters can be readily identified. Moreover, the expressions of the small signal models for the SSCs operated in DCM can be extended to those in continuous conduction mode (CCM) operation. These have made the proposed modeling method be valuable and viable. Experimental measurements have demonstrated that the small signal model of an SSC derived with the proposed approach is relatively accurate.
- Sliding Mode Control of Boost Type Unity Power Factor PWM Rectifier
by José Fernando Silva
Abstract - A robust sliding mode controller, suitable for the output voltage control of voltage sourced, unity power factor three phase PWM rectifiers, presenting no steady state errors, is described. This "Just In Time" switching controller, controls the output voltage and the line input currents, while providing bi-directional power flow, near unity power factor operation, low harmonic content, fast dynamic response of the output voltage, and minimum switching frequency due to a new a-b space vector current regulator. The voltage controller performances are compared with the behaviour of the conventional Proportional Integral (PI) output voltage control, aided by PWM current mode modulators, and with the non robust fast and slow manifold sliding mode approach. The comparison shows that the proposed controller confers faster dynamics and does not present steady state errors. Test results confirm that the performance of the controller is independent of system parameters and load, and exceeds the performance of existing hysteretic current mode control systems.
- Sliding Mode Control Design of a High Power Factor Buck-Boost Rectifier
by Oscar Lopez, Luis García de Vicuna, Miguel Castilla, José Matas, Mariano López
Abstract - This paper presents multi-input sliding mode control schemes for unity-power factor rectifiers based on buck-boost converters. The proposed controllers can effectively improve the tracking performance of the line current and the output voltage regulation. The sliding surfaces are designed by imposing a desired dynamic behavior on the system, which allows us to determine the main parameters in designing the sliding mode controller. This results in fast controllers which provide both robustness, with regard to external disturbances, and a good dynamic response of the output voltage.
- The Dynamics of a PWM Boost Converter with Resistive Input
by Sam Ben-Yaakov, Ilya Zeltser
Abstract - The Dynamics of a PWM Boost Converter with Resistive Input This study investigated the large and small signal response issues and in particular the inner loop gain and outer loop response of an indirect control method for Active Power Factor Correction. The control scheme is based on sensing the average inductor current and generating a DOFF (the complement of the switch duty cycle) which is proportional to the current. The method is demonstrated by considering the performance of a Boost type Active Power Factor Corrector (APFC) that does not need to sense the input voltage. Theoretical and experimental results confirm the validity of the approach and demonstrated that the proposed method can be useful in the design of robust APFC with low THD. The indirect control method investigated in this study is also compared to the classical direct APFC control method pointing to the differences between the two.
- Analysis Design and Resonant Current Control for a 1 MHz High Power Factor Rectifier
by S. V. Mollov, A. J. Forsyth
Abstract - Fundamental frequency analysis is used to examine the LCC series-parallel loaded resonant converter with a capacitive output filter when operating as a high power factor rectifier. Optimum values are identified for the Q factor and voltage conversion ratio such that zero voltage switching is just maintained whilst minimising the resonant circuit conduction losses. A simple resonant current control loop is shown to provide an effective mechanism of active control, achieving a high-quality input current waveform over a wide load range. Results are presented from a 1MHz, 160W prototype.
Letter to the Editor
- Reference Frames Fit for Controlling PWM Rectifiers
by Jorge L. Duarte, A. van Zwam, C. Wijnands, A. Vandenput
Abstract - Keep things simple when controlling bi-directional PWM rectifiers by considering the utility grid as a virtual electric machine. The advantage is that the air-gap flux of this big machine can be directly measured in a straightforward way.
The integration of the utility grid voltages with respect to time yields a virtual rotating magnetic-flux vector which can be chosen as a privileged reference frame to control the power flow in a bi-directional rectifier. The projection of the system equations onto this rotating frame leads to the separation of the line current into two orthogonal components. The component in quadrature with the virtual-flux vector imposes the instantaneous active-power exchange, while the direct-axis component gives the instantaneous reactive power between the phases.
As a consequence, decoupled and high-dynamic control is made possible, in complete similarity with well-known techniques commonly applied to perform field orientation in electrical machines.
Power Electronics
- A DC Current Transformer for Large Bandwidth and High Common Mode Rejection
by Luca Ghislanzoni, J. A. Carrasco
Abstract - At first a review of known magnetic coupled current sensing techniques is presented. Subsequently a novel technique is introduced, based on a configuration discussed in a previous work. The previous technique made use of a galvanomagnetic device (Hall effect sensor) to sense the magnetization of a current transformer core, so that the sum of the Hall voltage and the voltage across the secondary shunt resistor would yield a faithful copy of the input current. The technique described in this paper makes use of the same principle to obtain a high bandwidth (from DC to 1MHz) and very high Common Mode Rejection current transformer, without the need for a Hall effect probe. This is achieved by subtracting the high frequency components, detected across the secondary shunt resistor, from the voltage across a primary shunt resistor connected in series with the primary of the current transformer. The resulting signal is then an accurate image of the transformer magnetizing current, which is then transferred to the secondary side by means of low bandwidth isolation amplifier. The high frequency components are subsequently added, to the amplified and filtered low frequency components, by means of a third transformer winding whose number of turns is chosen to be equal to the gain of the low frequency amplifier.
- Using Power Diode Models for Circuit Simulations - A Comprehensive Review
by C. M. Tan, K. J. Tseng
Abstract - In recent years, a number of new models for the power diode have been proposed. The objectives of this paper are to provide the power electronics community with a comprehensive review and summary of recent power diode models. The models have been categorized systematically according to their modelling concepts with objective comparison of their status pertaining to the various modelling issues. A summary table has been created to aid power circuit design engineers and power rectifier device engineers in selecting appropriate models for their applications.
Drive Control
- Performance of Induction Motor with Free Rotating Magnets inside its Rotor
by Yoshiyuki Shibata, Nuio Tsuchida, Koji Imai
Abstract - We propose a new induction motor which has free rotating magnets inside the rotor. The magnets can revolve freely against the rotor with the shaft. In this motor, the air gap flux is provided by both rotating permanent magnets and the stator coil current. A prototype motor was fabricated by modifying the rotor of a conventional 3-phase 4-pole 400W squirrel-cage induction motor. In the experimental results of a prototype motor, the motor showed superior performances to conventional motors in terms of the power factor, efficiency and torque characteristics. The power factor can be controlled to be unity, leading or lagging by regulating the supply frequency, terminal voltage and/or flux of magnets. Efficiency of the motor, over a wide output power range, is remarkably higher than that of the same size conventional induction motor. The losses of the trial motor are about a half of the losses of a conventional motor of 400W. In particular, the efficiency is dramatically high under light load conditions. This is a distinct advantage over a conventional motor. A stalling torque increases and a high torque can be obtained in a high speed area. The unique induction motor may be used in the various fields, where speed and torque must be controlled or power factor must be adjusted with high efficiency over a wide output power range.
Robotics and Vision
- Viewing Corridors as Right Parallelepipeds for Vision-Based Vehicle Localization
by Zhi-Fang Yang, Wen-Hsiang Tsai
Abstract - An approach to vision-based vehicle localization by viewing corridors as a combination of right parallelepipeds is proposed. The objective is to derive the orientation and lateral position of a vehicle in a right parallelepiped corridor. These two kinds of information are all that is needed for vehicles to navigate safely in a right parallelepiped corridor. This approach requires low hardware cost and simple computation. Only one camera mounted on the vehicle is needed, and analytic formulas are derived for computing the vehicle location. The information source is the corridor ceiling. Two orthogonal sets of parallel lines on the corridor ceiling are used to detect the vanishing line of the ceiling. An equation is developed to derive the vehicle orientation by utilizing the detected vanishing line. Also, based on the observation of the variation of image line slopes when we move laterally, another equation is established to evaluate the relative lateral position of the vehicle by utilizing the line slope of the ceiling line pointing forward. Experiments have been conducted and acceptable vehicle localization results have been obtained to prove the feasibility of the proposed approach.
Letters to the Editor
- Recurrent Neural Network Based Implementation of a Programmable Cascaded Low-Pass Filter used in Stator Flux Synthesis of Vector-Controlled Induction Motor Drive
by Luiz E. B. da Silva, Bimal K. Bose, Joao O. P. Pinto
Abstract - The concept of programmable cascaded low-pass filter for stator flux vector synthesis by ideal integration of stator voltages at any frequency was introduced in the literature. A new form of implementation of this filter is being proposed here that uses a combination of recurrent neural network trained by Kalman Filter and a polynomial neural network. The proposed structure is simple, permits faster implementation by DSP, and gives improved performance.
- A Start-Up Control Algorithm for the Split-Link Converter for a Switched Reluctance Motor Drive
by Y. Liu, Pragasen Pillay
Abstract - This paper analyzes and presents the motor start-up problem when a split-link converter is used for switched reluctance motor drives. A new control algorithm to solve this problem is presented in this paper as well as the calculation of the split-link capacitance required during normal operation.
- A Decomposed Control Scheme for Vision Guided Manipulators Curve Tracking
by Jiang Ping, Hui-tang Chen, Yue-juan Wang, Jing Lin
Abstract - This paper presents a robot control algorithm for vision guided curve tracking using orthogonal decomposition control method. It was implemented in a glass cutting D.D. robot for the drawing curve input with high speed and smooth tracking performances.
- Comments on "A Passivity-Based Method for Induction Motor Control" by L. U. Gökdere and M. A. Simaan
by John Chiasson and Robert T. Novotnak
Abstract - A comparison is made between a passivity-based controller and an input-ouput linearization controller. We point out that this comparison is not valid as the same trajectory was not used for both controllers.
- Response to Comments on "A Passivity-Based Method for Induction Motor Control"
by Levent U. Gökdere and M. A. Simaan
Abstract - Contrary to the claims made in the above comment, there is experimental evidence demonstrating the benefits of the passivity-based controller developed for induction motors. These include closer tracking of the same mechanical trajectory, and less sensitivity to magnetic saturation, when compared with the input-output linearization controller.
