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Power Electronics, IEEE Transactions on

Issue 1 • Date Jan. 2003

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Displaying Results 1 - 24 of 24
  • Foreword special issue on digital control in power electronics

    Page(s): 293
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    Freely Available from IEEE
  • Fast estimation techniques for digital control of resonant converters

    Page(s): 365 - 372
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (537 KB) |  | HTML iconHTML  

    Series resonant converters based on a transistor inverter, a transformer, a series capacitor and a rectifier with buffer capacitor find widespread application today. They provide soft switching and are thus of interest when low EMI and reduced switching losses are required. Due to the high quality factor of the corresponding resonant circuit, formed by the leakage inductance of the transformer and the series capacitor, the operation point of a converter strongly depends on the ratio of the control frequency to the resonant frequency. This may cause problems for the control if the resonant frequency changes. The problem can be solved by a fast control algorithm presented in this paper. It estimates the unknown or variable resonant frequency of a series resonant converter by successive measurement of the converter current at certain time instants within a conduction period. As a result the converter frequency can continuously follow the resonant frequency of the system, which leads to a perfect matching (sinusoidal current and ZCS). The algorithm has been implemented in a DSP (TMS320LF2407) and successfully proved experimentally. Furthermore, it is shown how the estimation principle can be adapted for a low speed DSP and for a simple 8-b μC. View full abstract»

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  • Control and filter design of three-phase inverters for high power quality grid connection

    Page(s): 373 - 380
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    The trend toward using inverters in distributed generation systems and micro-grids has raised the importance of achieving low-distortion, high-quality power export from inverters. Both switching frequency effects and pre-existing grid voltage distortion can contribute to poor power quality. A well designed filter can attenuate switching frequency components but has an impact on the control bandwidth and the impedance presented to grid distortion. This paper describes a filter designed to incorporate an isolating transformer and the design of a complementary controller that rejects grid disturbance, maintains good waveform quality and achieves real and reactive power control. A realistic discrete time implementation is discussed and validated with experimental results. View full abstract»

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  • A discrete-time predictive current control for PMSM

    Page(s): 464 - 472
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    In this paper, a new predictive current controller for a permanent magnet synchronous motor (PMSM) considering delays is presented. In a full digital current control system for a PMSM, there are inevitable delays in calculating and applying the inverter output voltages to the motor terminals. A predictive current controller implemented in a full digital system has serious problems such as the oscillation and large overshoot. A discussion of compensation methods to cope with the nonlinearities of the real system is also presented. The proposed current controller has been analyzed, and the experimental results are shown to prove the feasibility and effectiveness of the proposed predictive current controller using a prototype 750 W PMSM servo drive system. View full abstract»

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  • A controller architecture for high bandwidth active power filters

    Page(s): 317 - 325
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    This paper presents a novel architecture for a unit-delay digital deadbeat current controller for a shunt active power filter (APF). The APF is based on a fixed frequency pulsewidth modulated voltage-sourced converter (VSC). The proposed controller increases the APF current-tracking bandwidth without increasing the VSC switching frequency. Previous APF digital deadbeat controllers have a current-tracking delay of two or more sample-periods. One delay is due to current controller computation, a second sample delay represents VSC actuation time. The paper presents a new controller architecture employing both asynchronous programmable logic and a small microprocessor. Current-tracking feedback control calculations are executed in asynchronous programmable logic to effectively eliminate the controller computation delay. The microprocessor executes fundamental frequency disturbance rejection computations and all other supervisory functions. The proposed architecture retains all high-level functions in the microprocessor to minimize controller development time without compromising APF performance. View full abstract»

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  • Predictive digital current programmed control

    Page(s): 411 - 419
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    This paper explores predictive digital current programmed control for valley, peak or average current. The control laws are derived for the three basic converters: buck, boost, and buck-boost. It is found that for each variable of interest (valley, peak or average current) there is a choice of the appropriate pulse-width modulation method to achieve predictive digital current control without oscillation problems. The proposed digital control techniques can be used in a range of power conversion applications, including rectifiers with power factor correction (PFC). Very low current distortion meeting strict avionics requirements (400-800 Hz line frequency) is experimentally demonstrated on a digitally controlled boost PFC employing predictive average current programmed control. View full abstract»

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  • Development of a digital controller using a novel complex modulation method for the metal halide lamp ballast

    Page(s): 390 - 400
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    This paper presents a digital controller using a novel complex modulation method for the metal halide lamp ballast. The proposed controller has an ability to prevent acoustic resonance more effectively than the conventional modulation controller. Furthermore, the proposed controller includes some useful functions such as soft starting, lamp fault protection, power control for dimming, overload protection, real-time acoustic resonance detection, and so on. To accommodate future application-specific integrated circuits (ASICs), the proposed controller has been designed with erasable programmable logic devices (EPLDs). In this paper, detailed complex modulation algorithms and digital control schemes are described, and experimental results of the prototype 150-W metal halide lamp ballast with the proposed digital controller are finally discussed. View full abstract»

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  • High-fidelity PWM inverter for digital audio amplification: Spectral analysis, real-time DSP implementation, and results

    Page(s): 473 - 485
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    A complete digital audio amplifier has been developed, implemented and tested. The process is entirely computational, and the output load and filter are the only analog components in the system. The process makes use of digital signal processing and a switching power stage to provide both high fidelity and high efficiency, beginning with a digital audio data stream. The advantages of naturally-sampled pulse-width modulation (PWM) are discussed in depth, including spectral analysis and comparisons to uniformly-sampled PWM. It is shown that natural PWM does not introduce audible distortion at switching frequencies consistent with power electronics practice. Interpolation methods for sample data conversion to natural PWM are discussed, and error analysis is presented based on Lagrange's Expansion Theorem. Noise-shaping processes are used to support high fidelity with practical values of time resolution. A counter conversion process enforces switching dead time in the inverter gate signals. The experimental full-bridge inverter implementation demonstrates that miniaturization is possible. A complete test system delivered more than 50 W into an 8 Ω load with an efficiency of 80% and total harmonic distortion plus noise of 0.02%. View full abstract»

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  • Restructuring of first courses in power electronics and electric drives that integrates digital control

    Page(s): 429 - 437
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (863 KB) |  | HTML iconHTML  

    Since 1994, the University of Minnesota has been undertaking a long overdue restructuring of power electronics and electric machines/drives courses. This restructuring allows digital control to be integrated into first courses, thereby teaching students what they need to learn, making these courses appealing, and providing a seamless continuity to advanced courses. By a concise presentation in just two undergraduate courses, this restructuring motivates students to take related courses in programmable logic controllers, microcontrollers and digital signal processor applications. This ensures a first-rate education that is meaningful in the workplace as well as in graduate education leading to a research and development oriented career. This restructuring has several components to it. Outdated topics that waste time and mislead students are deleted. To integrate control in the first courses, unique approaches are developed to convey information more effectively. In the first course in power electronics, a building block is identified in commonly used power converter topologies in order to unify their analysis. In the field of electric drives, the use of space vectors is introduced on a physical basis to describe operation of ac machines in steady state in the first course, and to discuss their optimum control under dynamic conditions in the advanced course. Appropriate simulation software and software-reconfigurable hardware laboratories using a DSP-based rapid prototyping tool are used to support the analytical discussion. View full abstract»

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  • Digitally-controlled single-phase single-stage AC/DC PWM converter

    Page(s): 326 - 333
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB) |  | HTML iconHTML  

    The paper presents the implementation of a fully digital controller for a boost integrated AC/DC PWM converter. The considered converter has the following basic features: high power factor, full control of the DC output voltage, high-frequency line filter inductor and insulation transformer. Its main advantage is the complete integration of a rectifier and an inverter stage, requiring only four IGBTs and six diodes. The converter is described in detail and the structural limitations of its operation are highlighted. The paper focuses on the converter control strategy describing in detail the implementation, by means of the TMS320F240 digital signal processor, of a fully digital, predictive, input current control technique. An application specific modulation strategy is also developed that allows simultaneous input current and output voltage control. The control system is finally tested on a 0.5 kW laboratory converter prototype. The presented results validate the design procedure and illustrate the achievable converter performance. View full abstract»

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  • A fixed-frequency quasi-sliding control algorithm: application to power inverters design by means of FPGA implementation

    Page(s): 344 - 355
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    In this paper, a fixed-frequency quasi-sliding control algorithm based on switching surface zero averaged dynamics (ZAD) is reported. This algorithm is applied to the design of a buck-based inverter, and implemented in a laboratory prototype by means of a field programmable gate array (FPGA), taking into account processing speed versus computational complexity trade-off. Three control laws, namely sliding control (SC), fixed-frequency quasi-sliding ZAD and PWM-based control have been experimentally tested to highlight the features of the proposed algorithm. According to the experimental results presented in the paper, the ZAD algorithm fulfills the requirement of fixed switching frequency and exhibits similar robustness properties in the presence of perturbations to those of sliding control mode. View full abstract»

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  • Direct current control-a new current regulation principle

    Page(s): 495 - 503
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    In this paper, two novel methods for current regulation are proposed. Both methods follow the synchronized on-off principle. In the classical approach, transistors are switched depending on the sign of the current error, which in turn is sampled at equal time intervals. In the first method, the current vector at the end of the interval is predicted for two possible cases when either the active voltage vector pointing toward current error or the zero voltage vector is applied. The one producing the smaller current error at the end of the sampling interval is chosen, thus obtaining drastic reduction of the switching frequency. In the second method, the best fitting active voltage vector succeeds the zero vector during the same time interval. A simple algorithm is used to calculate the duty cycle thus gaining the smallest possible current error. The method is compared with the CRPWM. Both methods were simulated and tested on a laboratory model with passive load. In the last part of the paper, the behavior of the second method is tested for erroneously estimated load parameters. The two methods show very small degradation of performance even when a rather high parameter error is introduced. View full abstract»

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  • Architecture and IC implementation of a digital VRM controller

    Page(s): 356 - 364
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    This paper develops the architecture of a digital PWM controller for application in multiphase voltage regulation modules (VRMs). In this context, passive current sharing and VRM transient response with nonzero controller delay are analyzed. A scheme for sensing a combination of the VRM output voltage and output current with a single low-resolution window analog-to-digital converter (ADC) is proposed. The architecture and IC implementation of a digital PWM (DPWM) generation module, using a ring-oscillator-multiplexer scheme, is discussed. Experimental results from a prototype VRM and a partial controller IC implementation are presented. View full abstract»

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  • Design of FPGA-based emulator for series multicell converters using co-simulation tools

    Page(s): 455 - 463
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    When high dynamic performances are desired, multicell converters are an option, but they may require extra control loops. However, cost reduction does not allow using additional sensors, and low cost estimators and observers have to be developed. Field-programmable gates arrays (FPGAs) with high sampling frequency seem to be able to perform such functions. The aim of this paper is to show how co-simulation helps designing such estimators and predicting their performances. View full abstract»

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  • Concurrent and simple digital controller of an AC/DC converter with power factor correction based on an FPGA

    Page(s): 334 - 343
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    Nowadays, most digital controls for power converters are based on DSPs. This paper presents a field programmable gate array (FPGA) based digital control for a power factor correction (PFC) flyback AC/DC converter. The main difference from DSP-based solutions is that FPGAs allow concurrent operation (simultaneous execution of all control procedures), enabling high performance and novel control methods. The control algorithm has been developed using a hardware description language (VHDL), which provides great flexibility and technology independence. The controller has been designed as simple as possible while maintaining good accuracy and dynamic response. Simulations and experimental results show the feasibility of the method, opening interesting possibilities in power converters control. View full abstract»

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  • Digital repetitive controlled three-phase PWM rectifier

    Page(s): 309 - 316
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (787 KB) |  | HTML iconHTML  

    In this paper, a digital repetitive control (RC) strategy is proposed to achieve zero tracking error for constant-voltage constant-frequency (CVCF) pulse width modulation (PWM) converters. The proposed control scheme is of "plug-in" structure: a plug-in digital repetitive controller plus a conventional controller (e.g., PD controller). The design of the plug-in repetitive learning controller is systematically developed. The stability analysis of overall system is discussed. A repetitive controlled three-phase reversible PWM rectifier is given as an application example. Near unity power factor and constant output DC voltage are ensured under parameter uncertainties and load disturbances. Simulation and experimental results are provided to testify the effectiveness of the proposed control scheme. View full abstract»

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  • Bilinear discrete-time modeling for enhanced stability prediction and digital control design

    Page(s): 381 - 389
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    This paper presents a new bilinear discrete-time modeling method for switching power converter circuits. The method utilizes a new approximation of the matrix exponential involved in the exact discrete-time models. Compared to the conventional bilinear discrete-time models or to the continuous-time averaged models, the new bilinear models provide a means for more reliable and accurate stability and transient response prediction. They also lend themselves better to digital control design than do the exact discrete-time models due to their simplicity. The modeling method is validated by several example converters, for which traditional averaged models and conventional bilinear discrete-time models fail to predict the stability characteristics correctly. View full abstract»

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  • Self-tuning digitally controlled low-harmonic rectifier having fast dynamic response

    Page(s): 420 - 428
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (755 KB) |  | HTML iconHTML  

    This paper describes a completely digitally controlled high-performance low-harmonic rectifier. It is shown that the dynamics of the outer voltage loop can be significantly improved using a self-tuning digital comb filter. Low input current harmonics and fast voltage transient responses are experimentally verified on a 200 W universal-input boost rectifier operating at the switching frequency of 200 kHz. View full abstract»

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  • Comparison of digital control techniques with repetitive integral action for low cost PWM inverters

    Page(s): 401 - 410
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    This paper presents a comparison among digital control techniques with repetitive integral action applied to voltage-source PWM inverters. As a result of the repetitive integral action, these digital control schemes can reduce steady-state errors and distortions caused by unknown periodic disturbances, which usually result from the input source and output load. Moreover, these digital control schemes measure only the output voltage, decreasing the amount of sensors and the overall system cost. The control laws, stability analysis, common and distinguishing features of these control algorithms are discussed. Experimental results from a PWM inverter (110 VRMS, 1 kVA) controlled by a low cost microcontroller are presented to demonstrate the control techniques performance under different load conditions, output filters and command strategies. View full abstract»

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  • High-frequency digital PWM controller IC for DC-DC converters

    Page(s): 438 - 446
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (760 KB) |  | HTML iconHTML  

    This paper describes a complete digital PWM controller IC for high-frequency switching converters. Novel architecture and configurations of the key building blocks are A/D converter, compensator, and digital pulse-width modulator, are introduced to meet the requirements of tight output voltage regulation, high-speed dynamic response, and programmability without external passive components. The implementation techniques are experimentally verified on a prototype chip that takes less than 1 mm2 of silicon area in a standard 0.5 μ digital complementary metal oxide semiconductor (CMOS) process and operates at the switching frequency of 1 MHz. View full abstract»

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  • Delta operator digital filters for high performance inverter applications

    Page(s): 447 - 454
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    Most infinite impulse response (IIR) digital filter implementations in power electronic inverter applications are based on the time shift operator q and its associated z-transform. But for higher sampling frequencies where the sample period approaches zero for z-transform discrete systems, their dynamic response does not converge smoothly to the continuous counterpart, causing substantial implementation problems. In contrast, the response of filters based on the delta operator does converge to the continuous counterpart for smaller sample periods, and hence they are much better suited for digital control applications where sampling frequencies are much higher than the system poles. This paper describes the basis of the delta operator, its use for IIR digital filter systems, and shows how the technique can be used in power electronic inverter applications to achieve substantial performance benefits compared to equivalent shift-based implementations. A brief review of shift based IIR filtering is presented and the required conversions to the delta form given. The specific examples of an active filter and a P + Resonant current regulator are used to illustrate the improvements that can be expected. The superior performance of the delta operator for digital control of inverter applications has been verified in both simulation and experiment. View full abstract»

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  • Embedding DSP control algorithms in PSpice

    Page(s): 294 - 300
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    A new method is developed to embed DSP control algorithms into PSpice providing accurate time stamped simulation of real-time applications. The proposed method allows to build new PSpice models with an arbitrary number of external nodes using PSpice's Device Equation option. Sampled systems can be simulated including the effects of discrete sampling times as well as propagation delays caused by processors. Control code developed in C-language can be embedded into this PSpice control model prior to downloading into the real-time DSP environment. To verify the simulation approach, simulation results and experimental results of a shunt active filter for harmonic current compensation in a three-phase system are presented. View full abstract»

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  • Quantization resolution and limit cycling in digitally controlled PWM converters

    Page(s): 301 - 308
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    This paper discusses the presence of steady-state limit cycles in digitally controlled pulse-width modulation (PWM) converters, and suggests conditions on the control law and the quantization resolution for their elimination. It then introduces single-phase and multi-phase controlled digital dither as a means of increasing the effective resolution of digital PWM (DPWM) modules, allowing for the use of low resolution DPWM units in high regulation accuracy applications. Bounds on the number of bits of dither that can be used in a particular converter are derived. Finally, experimental results confirming the theoretical analysis are presented. View full abstract»

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  • A digitally controlled amplifier with ripple cancellation

    Page(s): 486 - 494
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    This paper describes a large-signal linear, multirate digital controller for, among other possible servomechanical applications, charging electric vehicle batteries. This controller permits the power amplifier to track and deliver a desired current trajectory for a wide range of loads while providing a unity-power-factor interface to the electric utility. A computationally inexpensive technique for implementing output ripple cancellation is also described and demonstrated on a prototype converter. View full abstract»

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Aims & Scope

IEEE Transactions on Power Electronics covers fundamental technologies used in the control and conversion of electric power.

Full Aims & Scope