Research On Hybrid Power Processing Half-Bridge Based On Silicon And Wide-band-gap Semiconductor Devices

In recent years,more stringent requirements on the cost,efficiency,reliability,and power capacity of power electronic converters are demanded in rail transportation,data centers,power grid systems,and other fields.The wide-band-gap semiconductor(WBG)power devices,such as silicon carbide(SiC)and gallium nitride(GaN),have broken through the performance limits of conventional Si-based devices and become the best candidate for high-frequency,highefficiency,and high power density power electronics.However,Some bottlenecks such as high cost,limited power rating,and poor device reliability hander the large-scale application of WBG devices nowadays.Based on this background,there is an urgent need to explore the theoretical and application methods of new converter design,to break the bottleneck limitations based on a single Si-based or WBG-based converter,and to investigate the low-cost and highperformance power electronic converter applicable to medium and high-power applications.Based on the application requirements of high-performance and low-cost converters,this thesis proposes a new converter design methodology named Si/WBG hybrid power processing(HPP)to relieve the bottlenecks of single Si-based and WBG-based converter technologies.Based on this methodology,Si/WBG hybrid half-bridge(HHB)is proposed as the basic application unit,and the key performance indicators,control strategy,power quality optimization,power loss optimization,and high-frequency application of the HHB and other related basic theories and engineering optimization challenges are investigated.The proposed solution gives new ideas for the design and application of high-performance and low-cost power electronics converters and forms a multi-scenario solution for Si/WBG hybrid highperformance low-cost converters.The research focus and achievements are mainly reflected in the following aspects:(1)Aiming at the difficulty in the synergistic improvement of cost and performance,a design methodology named Si/WBG hybrid power processing(HPP)is proposed for the first time.By using the large-capacity Si and small-capacity WBG devices to process the system power at different operating frequencies,and then restructured by the hybrid-frequency technique,the Si/WBG HPP can offer near the same performance as the full-WBG highfrequency design but with much-reduced cost.The proposed Si/WBG HHB methodology extends the application range of conventional partial power processing technologies and provides common theories and new methodology for the design of high-performance and lowcost converters.(2)To reduce the application complexity of Si/WBG HPP,a generalized Si/WBG hybrid half-bridge(HHB)structure is proposed.Firstly,the performance indicators in the HHB,including the current ripple,component cost,inductor selection,and capacitor RMS current,are analyzed.Secondly,a hybrid-frequency interleaving control strategy and sequential logic design are proposed to match the unique operation of the Si/WBG HHB,which not only realizes the power decoupling and free distribution between the base and partial power,but also achieves the cancellation of the low-frequency ripple.Finally,the comparative experiments between the Si/SiC HHB and the conventional all-SiC bidirectional DC-DC converter are carried out,and the results show that the cost of the HHB is reduced by 17% with similar efficiency performance while obtaining the twice higher spectrum performance and 33% reduction capacitor RMS current.The proposed Si/WBG HHB and hybrid-frequency interleaving control strategy can be regarded as the basic unit for applying Si/WBG HPP methodology,which can be easily extended to various converter topologies and provide the theoretical basis and technical support for the engineering and practical promotion.(3)Aiming at the problem of poor power quality affected by the uncompensable range,two power quality optimization solutions,the dynamically coordinated operation(software)and coupled inductor(hardware),are proposed.On one hand,The dynamic coordinated operation strategy regulates the operation mode and power distribution ratio according to different current magnitudes,which not only solves the power quality problem caused by the uncompensable range near the zero-crossing point,but also improves the light-load efficiency.Therefore,the dynamic coordinated operation strategy enables the Si/SiC TPBPFC to achieve the same power quality and full-load efficiency as the conventional two-phase all-SiC interleaved TBPFPC.On the other hand,by coupling the Si-phase and WBG-phase inductors at the optimal coupling coefficient,the coupled inductor solution not only solves uncompensable range in all operating range,but also simplifies the WBG-phase high-frequency control strategy.Therefore,this solution enables the Si/SiC hybrid TPBPFC to achieve the same ripple characteristics and power quality as the conventional full-SiC high-frequency design.(4)The influence mechanism of frequencies and power distribution ratio on the power loss of the Si/WBG HHB are analyzed,and two power loss optimization design methods based on the loss model(offline)and adaptive population intelligence algorithm(online)are proposed to solve the complex problem of optimal parameters design.The offline control method obtains the optimal parameters by establishing the power loss model of Si/WBG HHB,and then selects the pre-stored optimal parameters in the actual controller based on the operating conditions to achieve the optimization of power loss,which is suitable for DC or fixed operating conditions.Based on the particle swarm optimization algorithm,the online power loss optimization control method does not need to establish an accurate loss model,but only needs to iterate adaptively to search the optimal parameters under various operating conditions,which is suitable for AC or complex operating conditions.(5)A Si/GaN hybrid half-bridge boost PFC converter with 1MHz ultra-high effective frequency is proposed to demonstrate the potential of Si/WBG HHB at ultra-high effective frequency application.Under the high-frequency conditions,the simplification of the system model,and control strategy are analyzed,and a multi-threaded program and a low-stray highfrequency GaN-based power half-bridge module are designed.The experimental results show that the proposed Si/GaN hybrid PFC can achieve 98.04% peak efficiency and 0.99 power factor even with the MHz-frequency GaN phase,fully demonstrating the advantages of Si/WBG HHB in ultra-high frequency applications.