Research On The Topology Structure And Control Method Of Remote Power Supply For Ocean Observation Network

The remote power supply of the ocean observation network is the "energy supply heart" of the cabled ocean observation network.It is the core equipment to realize the high reliability and stable power supply of advanced marine engineering equipment.It is of great significance to carry out research on the remote power supply of ocean observation networks for marine scientific research,undersea resource exploration and hydroacoustic communication.The remote power supply of the ocean observation network contains shore-based power supply(SPS)and underwater power supply(UPS).The photoelectric composite submarine cable connecting the SPS and the UPS has high resistivity and large voltage drop,so the SPS needs to provide a wide range and continuous smooth output voltage to achieve smooth start-up of the UPS,and the UPS needs to achieve high reliability and stable power supply within a wide input voltage range.Resonant converters have the advantages of low switching losses and high power density,and are suitable for underwater power applications.The analysis,operation and design of existing resonant converters do not take into account the full range of switching frequency and duty cycle variation due to the difficulty of calculating accurate electrical parameters and the complexity of resonant network state variation.The SPS is difficult to meet the smooth start-up requirements of the UPS,and the UPS requires high reliability of voltage insulation of the sub-module and the control system,and high voltage start-up is difficult.Therefore,there is an urgent need to carry out research work on the topology and control methods of remote power supply for ocean observation networks.This thesis is funded by Guangdong Introducing Innovative and Enterpreneurial Teams,Science and technology innovation plan project in Hunan Province“Development of Key Technologies and Major Equipment for High Power Ocean Communication Electro-acoustic Transducer Systems”,National Natural Science Foundation of China “Research on Key Issues of Modular Combined DC Converter for DC Distribution of Submarine Observation Network”,and also supported by National Energy Conversion and Control Engineering Technology Research Center.It focuses on the research on the topological structure and control method of modular UPSs,highgain wide-output range SPSs,and natural voltage sharing(NVS)UPSs.The main work and innovation are reflected in the following four aspects:(1)Aiming at the problem of difficult calculation of precise electrical parameters of resonant converter and complicated change of resonant network state,a resonant converter time-frequency unified model is proposed to provide a theoretical basis for the analysis and optimal operation of resonant converters considering the full range variation of switching frequency and duty cycle.According to the equivalent "T" network,the switching states of the power switches and the diodes,all the states of the resonant converter in one switching cycle are analyzed,and the state trajectory of the resonant converter in one switching cycle is obtained.On this basis,an optimal operation method of the resonant converter is proposed.The optimal switching frequency and duty cycle of the resonant converter are obtained.The experimental results show that the proposed optimal operation control method can achieve the same voltage gain adjustment as the variable frequency control in a narrower frequency range,and has a wider voltage gain adjustment capability in the same frequency range.(2)In view of the problem that the design process of the resonant converter depends on the engineering design experience,the design results have a certain deviation,and multiple iterative calculations and simulations are required,the function fitting of peak gain and peak power is performed directly.This avoids the repeated iterative process in the design method based on the peak gain in the time domain.A multi-operating electrical parameter optimization design method is proposed under the condition that the switching frequency and duty cycle vary in the full range.Compared with the existing time domain peak gain design,the resonant voltage and current stress of the resonant converter designed by the proposed electrical parameter optimization design method under the same operating conditions is greatly reduced.(3)Aiming at the requirement of a continuous,smooth and wide output range of the front-stage SPS,a topology is proposed in which the cascaded synchronous Buck(CSB)converter is used to achieve a wide output range,and high-gain post-stage SPS based on resonant switched capacitor voltage doubling rectification(Re SCVDR).As for the front-stage SPS,the equivalent model of cascaded synchronous Buck converters is analyzed.Using the Lagrange multiplier method and the Karush-Kuhn-Tucker(KKT)condition,the phase shift angle of the front and rear stages to minimize the ripple of the intermediate capacitor is obtained.As for the post-stage SPS,the equivalent output resistance of the Re SCVDR is derived.The switching characteristics of the Re SCVDR considering parasitic parameters are analyzed.A solution of using an auxiliary inductor to realize soft switching is proposed.The experimental results show that the proposed method does not require online optimization and additional voltage and current sensors,and it greatly reduces the loss of intermediate capacitors.The experimental results also show that the proposed Re SCVDR can use low-cost silicon fast recovery diodes(SiFRDs),and has the characteristics of high efficiency,high switching frequency and high gain.(4)Aiming at the problems that the UPS has high requirements on the reliability of the SM insulation and control system,and the difficulty in high-voltage startup.The topological structure and control method of UPS with NVS are proposed,which greatly reduces the insulation requirements of the SMs and the difficulty of input voltage sharing(IVS).The power flow of the modular combined power supply is analyzed,and the contradictory relationship between the insulation requirements of the SMs and the power transfer is pointed out.The insulation design of the SM,the difficulty of IVS,and the difficulty of the startup are comprehensively considered.The topology featured“end to end” is constructed.The risk of SM input voltage divergence is eliminated.The resonant converters are taken as SMs to analyze the NVS of the UPS in a wide load variation range.The switching process of SMs considering parasitic capacitance and dead time is analyzed.A piecewise linear waveform calculation method is established.An optimized combination of switching frequency and dead time is proposed and the soft-switching of power switches is achieved in full range.The experimental results show that the proposed UPS with NVS does not require high insulation.IVS is naturally achieved,and the UPS can be applied for the startup process.Based on the above research and analysis,the engineering design of the remote power supply for the ocean observation network consisting of a 15 k W SPS and a 1 k W low-power node UPS is carried out.The selection of components is carried out in detail.The schematic design,printed circuit board(PCB)design and the structural design are drawn.The experimental prototype of a 10 k V/15 k W SPS and a 10 k V/1 k W lowpower node UPS was produced.Finally,the experimental prototypes of the 15 k W SPS and the 1 k W low-power node UPS are tested and verified.