Showing papers in "IEEE Transactions on Power Electronics in 1993"

Small-signal modeling of average current-mode control

Abstract: A recently proposed average current-mode control method is analyzed. A complete small-signal model for the control scheme is developed. The model is accurate up to half the switching frequency. This control scheme is suitable for applications where the average inductor current needs to be controlled, as in power factor correction circuits and battery charger dischargers. The subharmonic oscillation, commonly found in peak current-mode control, also exists in this method. This subharmonic oscillation can be eliminated by properly choosing the proper gain of the compensation network in the current loop. Model predictions are confirmed experimentally. >

On continuous control of PWM inverters in the overmodulation range including the six-step mode

Abstract: The power output and the dynamic performance of PWM (pulse width modulated) controlled AC motor drives can be improved by increasing the inverter output voltage through overmodulation. Two different solutions are proposed to increase the output voltage in a continuously controllable fashion up to maximum possible value, which is reached in the six-step mode. The solutions differ in their approaches. A space vector strategy is used for high dynamic performance, high switching frequency drives, while a field-oriented PWM method is used for low switching frequency, high power inverters. Experimental results are presented. >

A space vector-based rectifier regulator for AC/DC/AC converters

Abstract: A voltage-sourced rectifier control scheme for use with AC/DC/AC variable speed drives is presented. A control scheme is derived that directly calculates the duration of time spent on the zero state and on each switching state adjacent to the reference vector, over a constant switching interval, in order to drive the line current vector to the reference vector. In addition, under transient conditions, when deadbeat control is not possible, a control scheme is presented that ensures that the line current vector is driven in the direction of the reference current vector. The current reference for the rectifier controller is derived from the bus voltage error and a feedforward term based on the estimated converter output power. The proposed space vector-based rectifier regulator is shown to exhibit improved harmonic and transient performance over existing per-phase duty cycle prediction methods, especially at modulation indices near unity. The deadbeat control of the rectifier input current is accomplished every half-cycle with constant switching frequency while still symmetrically distributing the zero state within the half-cycle period. >

Electronic ballast for fluorescent lamps

Abstract: A frequency-domain analysis is given for a Class D voltage-switching power inverter with a load resistance connected in parallel with a resonant capacitor Using the fundamental component approximation, design equations are derived to provide easy-to-use design tools The inverter is inherently short-circuit-proof, but cannot operate safely with an open circuit at the resonant frequency Safe operation with an open circuit can be achieved if the operating frequency is sufficiently lower or higher than the resonant frequency Experimental results are given for two F40 fluorescent lamps connected in series, using MTP5N40 MOSFETs The operating frequency was 50 kHz at full power and 70 kHz at 20% of full power At full power, the efficiency of the Class D inverter was 956% and the efficiency of the power factor corrector was 93% The overall efficiency of the ballast was 894% at full power >

Use of ESR for deterioration diagnosis of electrolytic capacitor

Abstract: A new deterioration diagnosis method for the electrolytic capacitor is proposed for a forward-type converter and a buck-boost converter. It was observed that the ESR (equivalent series resistance) of the electrolytic capacitor increases as it deteriorates, and the knowledge that ripple varies proportionally to the ESR increase was used. With this method, the electrolytic capacitor life-cycle aging rate can be projected for the active circuit over the system life. This approach to deterioration is valid for any load condition, no matter whether the circuit has feedback control or not. >

Circuit topologies for single-phase voltage-doubler boost rectifiers

Abstract: A new family of single-phase voltage-doubler PWM (pulse width modulated) boost rectifiers is presented. By examining the switching states of several standard single-phase boost rectifier circuits, three characteristic PWM voltage switching patterns are identified: unipolar PWM; bipolar PWM; and phase-adjusted unipolar PWM. From this analysis, an equivalent family of voltage-doubler rectifiers is derived. When high output voltages are required, voltage-doubler rectifiers are shown to be able to generate AC line currents with the lowest current distortion. The circuits presented are examined using circuit simulators and experimental results. >

The three-level ZVS-PWM DC-to-DC converter

Abstract: A novel high-frequency DC-to-DC power converter for high voltage and high power is introduced which features zero voltage switching (ZVS), operation at constant frequency, regulation by pulse width modulation (PWM), and low RMS current stress upon power switches. Its greatest attribute, in comparison with the full-bridge (FB-ZVS-PWM) converter, is that the voltage across the switches is half of the input voltage, This property is achieved due to the use of a three-level leg in place of the conventional two-switch leg. Operation, analysis, design procedure and example, and simulation are presented. A prototype operating at 100 kHz, rated at 600 V input voltage, and 1.5 kW output power and 25 A output current has been fabricated and successfully tested in the laboratory. The measured efficiency at full load was 93%. >

Techniques for minimizing the input current distortion of current-controlled single-phase boost rectifiers

Abstract: Techniques for minimizing the input current distortion of current-controlled single-phase boost rectifiers are described. The switching patterns of several boost rectifiers are examined to identify the nature of their input current waveforms. This analysis is used to examine the low-frequency current distortion levels, and hence the power quality, associated with the rectifiers. A PWM (pulse width modulation) strategy that selectively switches between positive unipolar PWM and negative unipolar PWM, called phase-adjusted unipolar PWM, is shown to produce the lowest current distortion levels. A novel two-switch asymmetrical half-bridge rectifier is presented that draws an input current at a unity fundamental power factor and with the same low distortion as obtained with the four-switch H-bridge rectifier. The operation of the various rectifiers is examined with reference to theoretical predictions, circuit simulations, and experimental results. This analysis is used to compare the performances of the various rectifier switching patterns. >

An improved full-bridge zero-voltage-switched PWM converter using a saturable inductor

Abstract: The saturable inductor is employed in the full-bridge (FB) zero voltage switched (ZVS) pulse width modulated (PWM) power converter to improve its performance. The current and voltage stresses of the switches as well as parasitic oscillations are significantly reduced compared to those of the conventional FB-ZVS-PWM power converter. The qualitative analysis is presented and is verified on a 500 kHz, 5 V/40 A converter. >

Lumped equivalent circuits of magnetic components: the gyrator-capacitor approach

Abstract: In place of the conventional reluctance-resistance analogy for forming lumped equivalent circuits of inductive components, a permeance-capacitance analogy is advocated. In this approach, magnetic paths are modeled by capacitive circuits and windings are represented by gyrator two-ports. The technique is applied to the integrated magnetics of a zero-ripple isolated Cuk DC-DC converter allowing its electrical and magnetic circuits to be simultaneously simulated with SPICE. >

Simulating the dynamic electrothermal behavior of power electronic circuits and systems

Abstract: The simulator solves for the temperature distribution within the semiconductor devices, packages, and heat sinks (thermal network) as well as the currents and voltages within the electrical network. The thermal network is coupled to the electrical network through the electrothermal models for the semiconductor devices. The electrothermal semiconductor device models calculate the electrical characteristics based on the instantaneous value of the device silicon chip surface temperature and calculate the instantaneous power dissipated as heat within the device. The thermal network describes the flow of heat from the chip surface through the package and heat sink and thus determines the evolution of the chip surface temperature used by the semiconductor device models. The thermal component models for the device silicon chip, packages, and heat sinks are developed by discretizing the nonlinear heat diffusion equation and are represented in component form so that the thermal component models for various packages and heat sinks can be readily connected to one another to form the thermal network. >

A pulsewidth-modulated inverter with parallel connected transistors using current-sharing reactors

Abstract: A technique for parallel connection of transistors by using current-sharing reactors for the pulse-width-modulated (PWM) transistor inverter is reported. The technique not only increases current capacity, but also decreases the output harmonic contents. The output voltage waveforms of the proposed inverter have certain voltage levels during their half cycles, and thus it is anticipated that it will be difficult to analyze the output harmonics. For such waveforms, a frequency analysis approach is described, and its results are verified by experiments. >

Unity PF current-source rectifier based on dynamic trilogic PWM

Abstract: One remaining step in perfecting the stand-alone, unity power factor, regulated current-source pulse-width-modulated (PWM) rectifier is to reduce cost, by bringing the twelve-valve converter (consisting of three single-phase full bridges that operate with two-level or bilogic PWM) to the six-valve bridge. However, the six-valve topology requires a three-level or trilogic PWM strategy that can handle feedback signals. A general method of translating three-phase biologic PWM signals into three-phase trilogic PWM signals is presented. The method of translation retains the characteristics of the bilogic PWM, including the frequency bandwidth. Experiments show that the trilogic PWM signals produced by the method can handle not only stabilizing feedback signals but also signals for active filtering. >

Analysis and design of a series-parallel resonant converter

Abstract: A high-frequency link series-parallel resonant power converter is analyzed using the state-space approach. Analysis is presented for both the continuous capacitor voltage mode and the discontinuous capacitor voltage mode. Steady-state solutions are derived. Design curves for the converter gain and other component stresses are obtained. A method of optimizing the converter under certain constraints is presented and a simple design procedure is illustrated by a design example. Experimental results are presented to verify the theory. >

A new Walsh domain technique of harmonic elimination and voltage control in pulse-width modulated inverters

Abstract: A method for selective harmonic elimination in pulse-width-modulated (PWM) inverter waveforms by the use of Walsh functions is presented. The Walsh operational matrix of PWM is introduced as a means of obtaining the Walsh spectral equations of PWM waveforms. The slope and intercept Fourier operational matrices of PWM are also introduced as a means of obtaining Fourier spectral equations of PWM waveforms. A noniterative algorithm that produces piecewise-linear, global solutions between angles and for the angles is proposed. The algorithm also produces the full range of variation of fundamental voltage for given harmonic elimination constraints. The set of systems of linear equations obtained replaces the system of nonlinear transcendental equations used in the Fourier series harmonic elimination approach. In general, the algorithm makes possible the synthesis of two-state PWM inverter waveforms with specified old harmonic content. >

The steady-state performance of a controlled current active filter

Abstract: An active filter that uses a high-frequency D-class asynchronous switching inverter for power system current distortion compensation is described. The distortion compensation technique involves deriving a signal corresponding to the distortion component of load current, inverting and amplifying this signal, and adding it to the supply current to cancel the load current distortion. A synthetic sinusoid is used to determine the distortion component in the time domain. Extensive computed and experimental results, illustrating the system's steady-state performance and ability to reduce the current harmonic distortion components are presented. An intelligent controller is proposed to maintain the active filter's performance at the optimal operating point under varying load conditions. >

Transient thermal response of power semiconductors to short power pulses

Abstract: Thermal response curves used to calculate the peak junction temperature of power semiconductors are normally derived by experimental identification of the parameters of a known model. Unfortunately the model, developed many years ago, is inappropriate for large surges of short time duration, as they are encountered in present day power conditioning systems. An alternative model is derived, the limits of its accuracy are estimated, and a correction factor is described. A verification of the accuracy of the two methods is also presented. For pulse widths shorter than the thermal transit time, which is in the order of 300 mu s, the peak junction temperature can be more accurately calculated with an expression derived in the present work, which takes into consideration the active volume in which the heat is generated, than with the transient thermal response curve. A correction factor, a function of the width of the pulse, inserted in this equation, further improves its accuracy. >

Commutation of SR motors

Abstract: Commutation schemes for most common types of switched reluctance (SR) motors are presented. Commutation can be achieved using two- or three-positions sensors and a simple commutation logic in a similar fashion to brushless electronically commutated motors. The commutation logic can be easily housed on a programmable logic array (PLA) or similar device. Two-quadrant operation, usually with two position sensors with variable phase shift and dwell angles, can be tuned up to achieve optimum efficiency at low cost. Four-quadrant operation with multimode commutation schemes, such as normal, boost, longdwell, and brake, which cover most of the SR drive applications, can be easily implemented with simple logic control and feedback from low-resolution position sensors. The speed range can be increased beyond the limit reachable with pulse-width modulation (PWM). A 100% increase in the speed range can be easily obtained by switching modes. >

Phase-controlled series-parallel resonant converter

Abstract: A constant-frequency, phase-controlled, series-parallel resonant DC-DC converter is introduced, analyzed in the frequency domain, and experimentally verified. To obtain the DC-DC converter, two identical series-parallel resonant inverters are paralleled and the resulting phase-controlled resonant inverter is loaded by a voltage-driven rectifier. The converter can regulate the output voltage at a constant switching frequency in the range of load resistance from full-load resistance to infinity while maintaining good part-load efficiency. The efficiency of the converter is almost independent of the input voltage. For switching frequencies slightly above the resonant frequency, power switches are always inductively loaded, which is very advantageous if MOSFETs are used as switches. Experimentally results are given for a converter with a center-tapped rectifier at an output power of 52 W and a switching frequency of 127 kHz. The measured current imbalance between the two inverters was as low as 1.2:1. >

400 MW SMES power conditioning system development and simulation

Abstract: A conceptual design for a 22 MWh superconducting magnetic energy storage (SMES) system engineering test model (ETM) was developed. The objectives of the SMES-ETM are to demonstrate the feasibility of using a SMES system to perform load-leveling and system stabilization for commercial utilities and to supply 400 MW power pulses for ground-based defense systems. The performance requirements and configuration of the proposed 22 MWh SMES-ETM and its power conditioning system are presented. The power conditioning system consists of a DC-DC chopper linked to a GTO-based voltage source converter interfacing the superconducting energy storage coil to the AC power system. The SMES system operation in the charging and discharging modes is described and the results of digital simulations demonstrating the feasibility of the proposed power conditioning system and exploring its overall behavior under normal and fault conditions are prevented. >

Commutation strategies for brushless DC motors: influence on instant torque

Abstract: A solution to obtaining torque smoothness of a brushless DC drive within a wide speed range is presented. The voltage between the neural point of the inverter and the neutral point of the machine is not always zero. This voltage disturbs the phase currents during commutation. Since, in the case of real EMFs, the limited loop bandwidths of the current controller does not allow the currents to follow the adapted reference, a compensative and a predictive term have been added to the controller output. The robustness of the concept in the case of parameter variations is studied. >

Controlled power interface between solar cells and AC source

Abstract: A novel interface circuit between solar cells and a commercial AC source using Van Allen's multivibrator is presented. In this circuit, the AC source is used as a backup for solar cells, and the source and load power flow is automatically balanced by the circuit itself without any external phase control. Based on the analysis of the characteristics of solar cells and Van Allen's multivibrator, the authors describe a new method of controlling the DC power from solar cells according to the current load conditions, and a simple and fast optimization method for deriving the maximum solar power is discussed. >

Economic single-phase to three-phase converter topologies for fixed and variable frequency output

Abstract: Several component-minimized circuit topologies for single-phase to three-phase conversion are proposed. The topologies employ fewer semiconductor devices and generate high-quality output voltages. Suitable modification to achieve active input current shaping is illustrated in detail. Analysis and simulation of the proposed schemes are carried out to show the high-performance features. Suitable guidelines for the selection of filter components and for facilitating circuit design are presented. Selected results are verified experimentally on laboratory prototype converters. >

Analysis and design of a modified series resonant converter

Abstract: A modified series resonant converter (SRC) (also referred to as the LCL-type SRC) which overcomes the problems of the standard series resonant converter is presented. A state-space approach is used for the analysis. Analysis shows that the converter enters into three different modes. Converter gain and other component stresses are plotted with variation in the load current. Detailed experimental results obtained from a 500 W MOSFET converter are presented to verify the theory. With a proper selection of inductor ratio, only a narrow variation in switching frequency is required to regulate the output voltage for wide variation in the load current. It is shown that, by placing the parallel inductor on the secondary side, the parasitics of the high-frequency transformer can be used profitably. >

System design considerations for a high-power aerospace resonant link converter

Abstract: A novel variable-speed, constant-frequency (VSCF) 400 Hz aircraft generating system has been developed using an actively clamped resonant DC link converter. The design approach used to select the best configuration for the resonant converter power stage is described, including techniques for choosing power component values to meet key governing performance specifications. Interactions between the various converter components are discussed, suggesting approaches for selecting values which must meet multiple and sometimes conflicting system performance criteria. Verification is provided using a combination of simulation results and test data from a 60 kVA laboratory breadboard system. >

A guide to the application-oriented selection of AC/AC converter topologies

Abstract: A comprehensive review and a comparative evaluation of AC/AC converter topologies are presented. The aim is to provide guidelines for selecting an optimum technology for a given application. The topologies are discussed and evaluated based on the type of link they use. The essential features associated with the links are included. Mixed topologies, which are the focus of significant research activity, are also discussed. >

Robust control of multimodule current-mode controlled converters

Abstract: A robust controller for multimodule current-mode push-pull converters is presented First, the small-signal equivalent circuit and the transfer function model of the multimodule converter system are obtained Then, the selection of slope compensation and the model reduction are performed using the concept of dominant energy mode Based on the reduced converter model, a PI (proportional plus integral) controller is quantitatively designed according to the prescribed regulating specifications using a systematic design procedure A robust controller is proposed and augmented to improve the control performance when the parameter variations caused by system configuration change and operating point shift have occurred The performance of the converter and the effectiveness of the proposed controller are demonstrated by simulation and experimental results >

Three-loop control for multimodule converter systems

Abstract: A three-loop control scheme for multimodule power converter systems with a secondary LC filter is presented. In addition to output voltage and inductor current feedback, the control scheme employs feedback from the output capacitor of each module to improve the dynamic performance of the system, particularly the transient response in the event of failure of a module. The superiority of the three-loop control over the conventional two-loop current mode control is demonstrated by both small-signal analysis and large-signal simulations. >

Programmed pulsewidth modulated waveforms for electromagnetic interference mitigation in DC-DC converters

Abstract: The regular switching action of a pulse-width-modulated (PWM) circuit generates conducted and radiated electromagnetic interference (EMI) and may also generate acoustical disturbances. Programmed pulsewidth modulation techniques have been applied using various methods to control harmonics inherent in switched power circuits. A method for generating an optimal programmed switching waveform for a DC-DC converter is presented. This switching waveform is optimized to reduce the amplitude of harmonic peaks in the EMI generated by the converter. Experimental results, a brief discussion of sensitivity, and a practical implementation of a circuit to generate the PWM waveform are given. >