York Yih Sun

Adaptive Harmonic Control in PWM Inverters with Fluctuating Input Voltage

New techniques of harmonic reduction and voltage regulation in PWM inverters with fluctuating input voltage are described. A novel selective harmonic reduction technique is also developed for three-phase full-bridge inverters to reduce the number of switchings per output cycle. For keeping the fundamental load voltage at the present value and suppressing the generation of low-order harmonics when the input voltage fluctuates, the conventional sinusoidal reference of the triangulation method is replaced by a quasi-sinewave whose magnitude varies inversely with the input voltage to keep the product of the reference voltage and the input voltage sinusoidal. Harmonic analysis of the W-type modulation and M-type modulation is given to show that the load voltage spectra of the output waveforms generated with the proposed methods are insensitive to the source voltage fluctuation and load variation. Experimental results confirm the theoretical analysis.

Waveform synthesis via inverse Walsh transform

The dominant-term concept in representing arbitrary functions using Walsh series is described. To verify dominant-term concept, a Fast Walsh Transform/Inverse Fast Walsh Transform (FWT/1FWT) subroutine following Browns algorithm and an Approximato IFWT (AIFWT) subroutine have been written in FORTRAN IV and applied to various functions. The results obtained aro quito satisfactory. Based upon the dominant-torm concept, an inexpensive, fully digital, programmable waveform synthesizer lias beon designed and implemented. The various waveforms obtained from the aynthesiier coincide with the results obtaind from computer simulation.

Digital modelling and robust digital redesign of sampled-data uncertain systems via the interval tuning bilinear approximation method☆

Abstract Based on the bilinear approximation method, we present an interval tuning bilinear approximation method to do the digital model conversion and digital redesign of sampled-data uncertain systems. The tuning bilinear method together with interval arithmetic operation is employed to obtain the approximate discrete-time model and the digital robust control law from the continuous-time uncertain state equation and the given continuous-time robust control law, respectively. The proposed digitally tuning redesigned control law with one parameter can be adjusted so that the resulting dynamic states of the digitally controlled sampled-data uncertain system are able to closely match those of the original continuous-time well-designed uncertain system for a relatively longer sampling period.

Digital modeling and hybrid control of sampled-data uncertain system with input time delay using the law of mean

Abstract This paper utilizes an interval Pade approximate method together with interval arithmetic operation to convert a continuous-time uncertain system with input time-delay to an equivalent discrete-time interval model and transforms the robust control law of a continuous-time uncertain system with input time delay into an equivalent one of a sampled-data uncertain system with input time delay. The developed discrete-time interval model tightly encloses the exact discrete-time uncertain system with input time delay. Based on the law of mean and inclusion theory, a perturbed digital control law of input time-delay sampled-data uncertain system is newly presented, so that the states of the digitally controlled sample-data uncertain system closely match those of the originally well-designed continuous-time uncertain system.

Transformations of a class of non-linear multivariable control systems to block companion forms and their applications

The problem of transforming a class of multivariable non-linear systems to the controller and observer block companion forms is considered for pole assignment and observer design. Solving non-linear partial differential equations is needed for finding the transformations and the conditions for the existence of such transforms are stated.

A new SPWM inverter with minimum filter requirement

Abstract A new sinusoidal pulsewidth modulation (SPWM) control technique for simplifying the implementation of the SPWM method and minimizing the requirement of the voltampere rating of the inverter input filter is described and analysed. With the proposed modulation scheme, the regeneration of low-order harmonics caused by the input voltage fluctuation can be suppressed and the peak fundamental output voltage can be regulated rapidly and precisely by the dual voltage feedback control. Only a minimum voltampere rating of the inverter input filter is required for avoiding overmodulation. The theoretical results of the proposed approach with open-loop self-regulating property are discussed and experimentally verified.

Novel sinusoidal pulsewidth modulation schemes for voltage-source inverters with fluctuating input voltage

The optimum waveform parameters of pulse position and pulse widths for voltage-source inverters with fluctuating input voltage are proposed. Eight types of modulation schemes are described for synthesizing the optimum low-distortion output waveforms, of which the harmonic spectra and the peak fundamental-value are almost insensitive to the input-voltage fluctuation, with a minimum voltampere rating of inverter input filter. For fluctuating inverter input voltage with insufficient filtering, the type-VII and the alternative type-III modulation schemes are found to be especially suitable for practical implementation. Detailed descriptions of the suggested circuits with dual-feedback control for implementing two such modulation schemes are given. A peak-value detector that can rapidly produce the peak value of the inverter output voltage with a minimum time constant is also proposed. The theoretical results of the proposed approaches with one-loop self-regulating property are experimentally verified and compared with the conventional method. >

An H-soft-switched cell for single-switch nonisolated DC-to-DC converters

An H-soft-switched cell is proposed in this paper for obtaining soft switching in single-switch nonisolated DC-to-DC power converters. The proposed H-soft-switched cell provides constant-frequency lossless switching. The H-soft-switching cell may be regarded as a switch whose control circuit is the same as the ones used in conventional PWM power converters. The voltage stresses of the switching elements are the same as the ones of the conventional PWM converters and the current stress of the switching elements can be designed a little greater than the ones of the conventional hard-switched PWM converters. Moreover, an average method for steady state analysis is proposed in this paper. An equivalent effective duty is submitted for simplifying the output voltage. Experimental results of an H-soft-switched buck converter are presented for verifying the proposed topologies and the analytical methods.<<ETX>>

A new soft switching transition PWM boost converter for power factor correction using parallel resonant tank

A new topology of PWM boost power converter for power factor correction, by inserting a parallel resonant tank between the boost switch is proposed in this paper. The soft switching transition pulse width modulation (SST-PWM) technique is proposed in this topology for obtaining zero turn-on and zero turn-off losses of all switches. A variable delay method used for generating the drive signals of the main switch is proposed to minimize the circulating loss during soft switching transition. This method can also be used in novel zero voltage transition pulse width modulation (ZVT-PWM) power converters. An experimental 3 kW converter is built to verify the proposed topology and method. The results show that the proposed topology and method are very suitable for high power applications.<<ETX>>

On a reliable data communication broadcast system

This paper describes the design and implementation of a 3 KHz band HF data broadcast communication system, using a quantized frequency modulation, adaptive lattice equalizer together with forward error correcting code (FEC) to obtain a high link reliability and low error rate. A frequency diversity approach is also used in the selection of the timely best carrier frequency, and a microcomputer is implemented into the system for automatic best carrier acquisition, data transmission and clock synchronization, with minimum operators attention. Extensive field experiments were conducted and experimental results indicate that the system can achieve, for daytime operation, a link reliability of 87–98%, with a probability of error between 10−4 to 10−5, depending upon data rate (50, 75bps) and FECs used. For night time operation, the link reliability reduces to from 65–93% with a probability of error down in the order of 10−3.