Research On The Control Method Of High Fidelity Digital Power Amplifier

The ocean contains abundant mineral resources,power resources,biological resources and chemical resources,which is the cradle of all life on earth,and is closely related to the survival and development of human beings.Therefore,marine exploration has become an important topic in the research of human science and technology in the world.Ocean communication technology is one of the key technologies in the field of ocean exploration,in which the main way to realize deep-water long-distance ocean communication is to rely on the high-power acoustic signal from the electroacoustic transducer.Digital power amplifier(DPA)is the core equipment to drive the electroacoustic transducer to emit sound waves.Its output fidelity,operation reliability and other technical indicators directly affect the performance of underwater acoustic communication system.Several key problems,such as high anti-interference control,low complexity control,open-circuit fault diagnosis and seamless fault tolerance of the DPA,are analyzed and discussed in this dissertation.Some corresponding solutions to achieve high-fidelity output,improve reliability and extend service life are also put forward.The research of this dissertation can provide technical support for the development of submarine navigation,underwater acoustic ranging,marine acoustic tomography and other technologies.This dissertation is funded by the National Natural Science Foundation of China(NSFC)project "Research on high power electro acoustic high efficiency energy conversion mechanism and control method" [51837005] and the NSFC project "Research on topology,passive current sharing mechanism and control technolog y of coupled resonant network type multi-channel resonant converter" [51977069].With the support of National Energy Conversion and Control Engineering Technology Research Center,high anti-interference control,low complexity control,open-circuit fault diagnosis technology and seamless fault tolerance of the high fidelity DPA are studied.The main work and innovation of this dissertation are are as follows:(1)A robust model predictive control(MPC)based on disturbance observation is proposed to solve the problem of output voltage waveform distortion caused by filter parameter mismatch of single module digital power amplifier(SMDPA).The circuit topology of SMDPA and its operation mechanism in different modes are analyzed,which reveals the different effects of different switching states on the internal and external characteristics of the SMDPA.The discrete model represented by the rated parameters of the filter is established,and the reason of the output waveform distortion caused by the mismatches of the filter parameters is clarified.On this basis,a disturbance observer based on Kalman filter(KF)is proposed,and the stability of the disturbance observer is proved.The finite set model predictive control of the SMDPA is designed,which realizes the voltage output tracking and DC capacitor voltage balancing at the same time.SMDPA experiments are carried out to verify the proposed method.The results show that the proposed method can achieve high fidelity voltage output and improve the system robust ness under the condition that the filter parameters have ±50% perturbations without load current sensor configuration.(2)A simplified MPC based on hierarchical structure is proposed to solve the problem that the controller of multi module cascaded digita l power amplifier(MMCDPA)needs too much computation due to too many switching states.The circuit topology of MMCDPA is analyzed,and a discrete predictive model with the output level as the control option is established,so that the output current track ing is linear with the control option.A multilayer MPC including upper,middle and lower layers is proposed,which significantly reduces the calculation of the controller.In the upper layer control,the control objective which is linear with the control option are centralized to avoid repeated prediction and evaluation of the cost function.In the middle layer control,the output level is allocated to achieve the capacitor voltage balance.In the lower layer control,the switching state of each submodule is determined,and the switching action times are reduced.MMCDPA experiments are carried out,and the results show that the proposed method can reduce the operation time of the control algorithm from 3.76 ms to 7.3μs.(3)A parallel open-circuit fault diagnosis method(POFDM)is proposed to solve the problem that it is difficult to diagnose multiple open-circuit fault components in MMCDPA.The abnormal change rule of the submodule capacitor voltage caused by IGBT open-circuit fault in the positive and negat ive direction of the output current is analyzed,and the fault characteristics of the open-circuit fault diagnosis are summarized.The extraction method of the abnormal change of the capacitor voltage is deduced to avoid the adverse effect caused by the low frequency fluctuation of the DC power supply voltage of the submodule.The POFDM is proposed,which makes the fault diagnosis of different submodules independent of each other.The feasibility of the proposed method to diagnose the inner switch fault and the outer switch fault at the same time is analyzed.The influence of measurement noise on the proposed method is revealed,and the misdiagnosis caused by measurement noise is avoided.The experimental results show that the proposed method can diagnose al l the faulty devices in parallel in a single sine wave period under the condition that the open-circuit faults occur at different positions of the three submodules of the experimental prototype.(4)A seamless fault tolerance method(SFTM)based on redundant submodule autonomous control is proposed to solve the problem of the output current waveform distortion caused by device failure in MMCDPA.The control requirements of maintaining output waveform fidelity in different operation stages are analyzed.In the normal operation stage,a bypass method of the redundant submodule outputing 0level is proposed to speed up the input speed of the redundant submodule.In the fault diagnosis stage,an autonomous control method of the redundant submodule is proposed to compensate the output current tracking error.In the fault reconfiguration stage,the redundant submodule is proposed to replace the fault submodule to ensure the full capacity of the reconstructed MMCDPA.The selection method of the fault detection threshold based on current tracking error is analyzed to avoid misoperation during normal operation.The longest time of waveform recovery is estimated,and the feasibility of seamless fault tolerance is proved quantitatively.Experimental results show that the output current waveform of the MMCDPA is seriously distorted due to the device failures,and the cumulative tracking error is up to 29.4%.After adopting the proposed SFTM,the waveform distortion and tracking error are significantly reduced,and the high fidelity current output is realized under fault conditions.(5)An experimental prototype of high fidelity DPA with rated power of 10 k W is developed.The main circuit parameters of the DC/DC and DC/AC part in the submodule are derived,and the power switch device selections and control circuit design of the two parts are carried out.A MMCDPA experimental prototype with five submodules cascaded is built,and the main controller and extended controller of the prototype are designed.Finally,the performance of the designed experimental prototype is tested,and the results show that the designed prototype achieves high fidelity output,good reliability,and meets the design requirements.