Abstract: 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.

Abstract: 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.

Abstract: Four control techniques for pulse-width modulation (PWM) rectifiers in AC adjustable speed drives are presented. In particular, the so-called virtual-flux oriented control (VFOC) and virtual-flux based direct power control (VF-DPC) schemes are described and compared with their voltage based counterparts. These are the voltage oriented control (VOC) and voltage-based direct power control (V-DPC) techniques. Theoretical background is provided, and results of computer simulations and laboratory experiments are given, documenting advantages and disadvantages of the individual control strategies.

Abstract: This paper introduces a new control method and proportional PWM modulation of the cascaded H-bridge multilevel converter for grid-connected photovoltaic systems. This control makes each H-bridge module supply different power levels, allowing therefore for each module an independent maximum power point tracking of the corresponding photovoltaic array.

Abstract: Method and system are disclosed for compensating for color variations due to thermal differences in LED based lighting systems The method and system involves characterizing the LEDs to determine what PWM (pulse-width modulation) is needed at various operating temperatures to achieve a desired resultant color The characterization data is then stored in the microprocessor either in the form of a correction factor or as actual data When an operating temperature that is different from a calibration temperature is detected, the characterization data is used to adjust the PWM of the LEDs to restores the LEDs to the desired resultant color

Abstract: A novel technique for efficiently extracting the maximum output power from a solar panel under varying meteorological conditions is presented. The methodology is based on connecting a pulse-width-modulated (PWM) DC/DC SEPIC or Cuk converter between a solar panel and a load or battery bus. The converter operates in discontinuous capacitor voltage mode whilst its input current is continuous. By modulating a small-signal sinusoidal perturbation into the duty cycle of the main switch and comparing the maximum variation in the input voltage and the voltage stress of the main switch, the maximum power point (MPP) of the panel can be located. The nominal duty cycle of the main switch in the converter is adjusted to a value, so that the input resistance of the converter is equal to the equivalent output resistance of the solar panel at the MPP. This approach ensures maximum power transfer under all conditions without using microprocessors for calculation. Detailed mathematical derivations of the MPP tracking technique are included. The tracking capability of the proposed technique has been verified experimentally with a 10-W solar panel at different insolation (incident solar radiation) levels and under large-signal insolation level changes.

Abstract: Nonlinear differential-geometric techniques are proposed for the design of a feedback controller for three-phase voltage-source pulsewidth modulation (PWM) AC/DC boost converters under a cascade control structure. The input-output linearizability of the system modeled in d-q synchronous reference frames is examined. The results lead to a decoupled d-q current control scheme. For the internal DC-bus voltage dynamics (zero dynamics), by considering the d-axis current command as control input and using a square transform on DC-bus voltage, it is shown that this remaining system contains an input memoryless nonlinearity of conic sector type and satisfies the conditions for a Lur'e plant. This suggests a new outer-loop control strategy to control the square of the DC output voltage, rather than DC output voltage itself, utilizing a simple proportional plus integral (PI) controller cascaded to the d-axis current loop. Since most results do not consider the control of zero dynamics, the strategy for the control of zero dynamics via cascade control structure may provide valuable insight for the design of input-output linearized systems in which zero dynamics contain some desired control variables. The absolute tracking concept for Lur'e plants is introduced to prove the global tracking capability with zero steady-state error of the voltage loop. The controlled PWM AC/DC converter has the features of global stability, fast (exponential) tracking of DC-bus voltage command with zero steady-state error, asymptotic rejection of load disturbance, robustness against parameter uncertainties and decoupled dynamical responses between d and q current loops. Also, measurement of load current is not required. All these features are confirmed via laboratory experiments on a 1.5 kVA PC-based controlled prototype.

Abstract: A full-bridge converter which employs a coupled inductor to achieve zero-voltage switching of the primary switches in the entire line and load range is described. Because the coupled inductor does not appear as a series inductance in the load current path, it does not cause a loss of duty cycle or severe voltage ringing across the output rectifier. The operation and performance of the proposed converter is verified on a 670 W prototype.

Abstract: 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.

Abstract: This paper presents a new active common-mode electromagnetic interference (EMI) filter for the pulse-width modulation (PWM) inverter application. The proposed filter is based on the current sensing and compensation circuit and it utilizes a fast transistor amplifier for the current compensation. The amplifier utilizes an isolated low-voltage DC power supply for its biasing and it is possible to construct the active filter independent of the source voltage of the equipment. Thus the proposed active filter can be used in any application regardless of its working voltage. The effectiveness of the proposed circuit has been verified by experimental results.

Abstract: 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.

Abstract: A method for controlling an active power filter using neural networks is presented. Currently, there is an increase of voltage and current harmonics in power systems, caused by nonlinear loads. The active power filters (APFs) are used to compensate the generated harmonics and to correct the load power factor. The proposed control design is a pulse width modulation control (PWM) with two blocks that include neural networks. Adaptive networks estimate the reference compensation currents. On the other hand, a multilayer perceptron feedforward network (trained by a backpropagation algorithm) that works as a hysteresis band comparator is used. Two practical cases with Matlab-Simulink are presented to check the proposed control performance.

Abstract: This paper presents complete design, simulation, and experimental investigations on a 3-phase shunt active power filter to compensate harmonics and the reactive power requirement of nonlinear loads. The paper describes the complete design aspects of power circuit elements and control circuit parameters. The compensation process is based on sensing line currents only, an approach different from conventional methods that require the harmonics and reactive volt-ampere requirement of the load. Various simulation results are presented to study the performance during steady-state and transient conditions to validate the design. A laboratory prototype has been developed to verify the simulation results. The control scheme is realized on a dedicated micro-controller-based system. PWM pattern generation is based on carrierless hysteresis-based current control to obtain the switching signals. Based on simulation and experimental results it can be concluded that the compensation process is simple and easy to impleme...

Abstract: 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 /spl Omega/ load with an efficiency of 80% and total harmonic distortion plus noise of 0.02%.

Abstract: A PFC-PWM controller with a power saving means is disclosed. A built-in current synthesizer generates a bias current in response to feedback voltages sampled from the PWM circuit and the PFC circuit. The bias current modulates the oscillation frequency to further reduce the switching frequencies of the PWM signal and the PFC signal under light-load and zero-load conditions. Thus, power consumption is greatly reduced. The PFC and the PWM switching signals interleave each other, so that power can be transferred more smoothly from the PFC circuit to the PWM circuit. The saturation of the switching components can be avoided by limiting the maximum on-time of the PWM signal. Further, an external resistor is used to start up the PFC-PWM controller and to provide an AC template signal for PFC control.

Abstract: A power circuit configuration to realise three-level inversion is proposed. Three-level inversion is realised by connecting two two-level inverters in cascade, in the proposed configuration. An isolated DC power supply is used to supply each inverter in this power circuit. Each DC-link voltage is equal to half of the DC-link voltage in a conventional NPC (neutral point clamped) three-level inverter topology. Neutral point fluctuations are absent, and fast recovery neutral clamping diodes are not needed. The proposed inverter scheme produces 64 space-vector combinations distributed over 19 space-vector locations as compared to 27 combinations in a conventional three-level topology. The present power circuit can be operated as a two-level inverter in the range of lower modulation, by clamping one inverter to a zero state and by switching the other inverter. When compared to the H-bridge topology, this circuit needs one power supply less. A space vector based PWM scheme is used for the experimental verification of the proposed topology.

Abstract: A modified voltage space vector pulse-width modulated (PWM) algorithm for a four-wire dynamic voltage restorer (DVR) is described The switching strategy based on a three-dimensional (3-D) /spl alpha//spl beta/O voltage space is applicable to the control of three-phase four-wire inverter systems such as the split-capacitor PWM inverter and the four-leg PWM inverter In contrast to the conventional voltage space vector PWM method, it controls positive, negative and zero sequence components of the terminal voltages instantaneously Three 3-D modulation schemes are analyzed with respect to total harmonic distortion (THD), weighted total harmonic distortion (WTHD), neutral line ripple and switching loss over the whole range of the modulation index when the DVR experiences both balanced and unbalanced sags with phase angle jumps Experimental results from a 9 kW DVR system using a split-capacitor PWM inverter are presented to validate the simulation results

Abstract: The three-level neutral-point-clamped voltage source inverter is widely used in high power, medium voltage applications. This paper studies continuous and discontinuous PWM for this inverter. Detailed analysis of discontinuous modulation shows that the average switching frequency is not directly proportional to the carrier or sampling frequency, since additional switching transitions occur between different regions of discontinuity. At typical switching frequencies for high power applications (up to 2 kHz) these additional transitions contribute significantly to the inverter's total losses, so that a proper comparison of the harmonic performance can only be carried out under constant loss conditions with varying carrier frequency. This comparison is performed for a typical industrial medium voltage inverter. The paper then considers the major issues of neutral-point voltage balancing and loss distribution within the inverter, for the identified optimal modulation schemes.

Abstract: A PWM plus phase-shift control bidirectional DC/DC converter is proposed. In this converter, PWM control and phase-shift control are combined to reduce current stress and both conducting and switching loss, to expand ZVS range. The operation principle and analysis of the converter are explained, and ZVS condition is derived. A prototype of PWM plus phase-shift bidirectional DC/DC converter is built to verify analysis.

Abstract: This paper studies how to design the spectrum of a UWB signal in accordance with the FCC regulations and IEEE 802.15.3a recommendations. We show that the "conventional" UWB system with pulse-position modulation and time-hopping multiple access gives rise to spectral lines that violate the regulations. The impact of different modulation and multiple access schemes on the spectrum shaping is derived from the power spectral density of a non-linear and memoryless modulation. Detailed theoretical and simulation results stress the difficulties raised by the use of dithered pulse trains. We thus propose several solutions to achieve compliance with the FCC spectral masks.

Abstract: This Paper provides a demonstrative derivation of the effect of up and down chirp modulation on point and extended target signals. Analysis has been performed with respect to signal amplitude, signal extension, modulation rate and phase behavior. The suppression of "point target" range ambiguities is investigated for the a possible TerraSAR-X parameter setting. Extended targets have been simulated and filtered. A Range-Ambiguity Simulator is under development which is based on airborne X-band data from the Experimental SAR (E-SAR) of DLR. The simulator concept is presented.

Abstract: 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 V/sub RMS/, 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.

Abstract: An ultra-wideband pulse modulation apparatus, system and method is provided. The pulse modulation method increases the available bandwidth in an ultra-wideband, or impulse radio communications system. One embodiment of the present invention comprises a pulsed modulation system and method that employs a set of different pulse transmission, or emission rates to represent different groups of binary digits. The modulation and pulse transmission method of the present invention enables the simultaneous coexistence of the ultra-wideband pulses with conventional carrier-wave signals. The present invention may be used in wireless and wired communication networks such as CATV networks.

Abstract: An integrated boost switched-capacitor (SC) converter able to step-up the line by ten times is presented. It is formed by a SC-circuit containing three capacitors and a boost stage. The two power stages are not connected in cascade, but they are integrated for achieving an overall high efficiency. The SC-circuit allows for a steep voltage ratio; for efficiency's purpose, it is not regulated. The boost stage gives the line and load regulation, using a classical PWM control. The theoretical results based on an energy-balance approach and simulation using the exact cyclical differential equations of the converter are confirmed by the experimental results on a prototype of 35 W power.

Abstract: A disk drive is disclosed comprising a pulse width modulated (PWM) signal generator for generating PWM control signals applied to the driver switches of a voice coil motor (VCM). The PWM control signals comprise a PWM cycle time, a Tforward time interval of the PWM cycle time wherein a positive control voltage is applied to the VCM, a Treverse time interval of the PWM cycle time wherein a negative control voltage is applied to the VCM, and a Tdead time interval of the PWM cycle time wherein a substantially zero control voltage is applied to the VCM. The Tdead time interval is adjusted to control a magnitude of an actual ripple current flowing through the VCM.

Abstract: A disk drive is disclosed comprising a disk and a voice coil motor (VCM) having a voice coil for actuating a head over the disk. A VCM driver comprises an H-bridge driver having a plurality of driver switches for driving current through the voice coil to ground. A first pulse width modulated (PWM) signal controls a first voltage level driving the voice coil relative to a duty cycle of the first PWM signal, and a second PWM signal controls a second voltage level driving the voice coil relative to a duty cycle of the second PWM signal, wherein the first voltage level is greater than the second voltage level.

Abstract: In this paper, a new three-phase high-frequency link matrix converter is discussed and the topology of conventional matrix converter is modified with the addition of a transformer for a variable speed constant frequency (VSCF) application. The proposed approach accomplishes voltage transfer ratio more than unity, galvanic isolation between both voltage sources and higher power density by employing a high-frequency transformer into the intermediate stage of the dual bridge matrix converter. It has a bidirectional power flow capability, controllable displacement power factor and lower harmonic distortion at both variable speed source and fixed frequency utility. Further, asynchronous or synchronous PWM can be employed depending on the frequency modulation ratio in the primary side converter and it guarantees full input voltage utilization for DC-link and near symmetric square wave pulse trains applied to high frequency transformer regardless of varying input frequency. The proposed approach is a competitive solution for VSCF distributed generating application such as wind-turbine and micro-turbine application. Simulation results are shown to demonstrate the advantages of the proposed system. Experimental results on a 230V, 3kVA 400 Hz to 60 Hz VSCF system based on DSP controller are presented.