| High-power digital amplifier can be widely used in sonar,underwater acoust ic communicat ion where requiring high voltage and large capacit y.The high-power digital amplifier has developed rapidly at home.A series of power amplifier products has been developed in recent years in China.However,it is behind western developed countries,as represented by U.S.,in terms of voltage level,waveform distort ion,bandwidth o f output voltage and reliabilit y of the amplifier.Therefore,it is of great significance to develop a new t ype of high-voltage and high-power digital power amplifier.This thesis is funded by the key project of the Nat ional Natural Science Foundat ion of China "Research on the Mechanis m and Control Method of High-Power Electroacoust ic Efficient Energy Conversio n" [51837005],supported by the Nat ional Power Conversion and Control Engineering Technology Research Center.A new modular cascaded mult ilevel digital power amplifier wit h the ad vantages of wide band,low distort ion,mult i-load adaptabilit y,high voltage and high reliabilit y is proposed according to the specific requirements of power amplifier.Moreover,the control methods and modulat ion strategies of modular cascaded mult ilevel digital power amplifier(MCM-DPA)are studied.The main work and innovat ion are as follows :(1)For the contradiction between stability and dynamics of digital control system of DC/DC converter in modular cascaded multilevel digital power amplifier,a predictive deadbeat average model control method is proposed.Taking the phase-shifted full-bridge converter as the research carrier,a multi-point sampling deadbeat control average model is established.The traditional single-point sampling control is transformed into multi-point average control,which overcame the problem that the stability of the controller declined due to the interference of single-point sampling.Furthermore,the control value of the next beat is predicted by the prediction method on the established deadbeat control average model,which improved the dynamic performance of the controller.At the same time,the stability of this method in Z domain is analyzed,and the range of inductance parameters keeping the system in stable is given.In addition,feedforward compensation is made for the duty cycle loss of phase-shifted full-bridge converter,which further improves the steady-state tracking and dynamic performance of digital control system.In the end,the effectiveness of the proposed control method in improving the anti-interference performance and dynamic performance of digital control system is verified by simulation and experiment.(2)For the problem that space vector pulse width modulation(SVPWM)is difficult to be applied in modular cascaded multilevel digital power amplifier due to its complicated calculation,a carrier-based multilevel SVPWM modulation strategy is proposed.In this thesis,the concept of equivalent carrier is introduced to analyze the essential reasons of the difference in output voltage between phase shift pulse width modulation(PS-PWM)and phase disposition pulse width modulation(PD-PWM)modulation strategy Then,by adjusting the carriers,the advantages of the two modulation strategies are integrated,and a multi-level SVPWM modulation strategy based on carrier is proposed.The power balance characteristics between power units of the proposed strategy is analyzed theoretically,and the conclusion that the power balance of carrier-based multilevel SVPWM modulation strategy is realized is obtained.By calculating and comparing the time required by conventional SVPWM and the proposed strategy,it is proved that the proposed strategy can greatly optimize the computational complexity of the algorithm,and the time of computation will not increase with the increase of the number of levels,which is convenient for expansion to any level.In the end,simulation and experiment verify the effectiveness of the proposed modulation strategy in decreasing the computational complexity of the algorithm,improving the utilization of DC voltage and reducing the total harmonic distortion of the output voltage(3)A unified PS-PWM and PD-PWM equivalent output modulation strategy is proposed for the multi-mode operation of modular cascaded multilevel digital power amplifier.The mathematical relationship between switching combination and output voltage of power amplifier is established,and a multilevel modulation strategy based on switching combination rotation is proposed.In the strategy,multilevel voltage is divided into platform voltage and pulse voltage by switching combination,and the on and off signals of bridge arm are controlled under the constraint of switching combination sequence,thus realizing the switching frequency balance of bridge arm and the power balance between power units.Based on the switching combination rotation strategy and the concept of equivalent carrier,the implementation method of PS-PWM and PD-PWM modulation strategies is unified,which reduces the complexity of control system and provides technical support for low harmonic output and reliable application of power amplifier in multi-mode.Finally,the effectiveness of the proposed strategy is verified by simulation and experiment.(4)For the problems of sub-optimal harmonic performance and large common-mode voltage under low modulation in traditional PS-PWM discontinuous modulation,two improved multilevel discontinuous modulation methods DPWMMAX and DPWMMIN based on switching combination rotation strategy are proposed.Through simulation analysis,this thesis reveals the mechanism of excessive common-mode voltage under low modulation of PS-PWM discontinuous modulation strategy,and deduces the process of realizing discontinuous modulation based on switching combination rotation by injecting zero-sequence voltage into pulse votage part.Finally,the effectiveness of the proposed method in optimizing the harmonic performance of output voltage and decreasing the common-mode voltage is verified by simulation and experiment.(5)The 5k V/30 A cascaded multilevel high-power amplifier is developed and implemented.This thesis elaborates the power circuits,control circuits,software design,thermal design,mechanical structure and other design principles of the cascaded multi-level high-power amplifier in details.During the process of thermal design,a practical calculation method for evaluating the thermal resistance and temperature rise of heatsink quickly and conveniently is given by empirical method.Finally,the functionality and performance of the device are verified effectively by comprehensive tests. |
PDF Full Text Request