Research Of Dual-Input Dual-Buck Inverters

Dual-Buck Inverter(DBI)is widely used in the fields of renewable energy,airborne/shipborne power supply system,military equipment,etc.In various DC/DC cascaded DC/AC two-stage inverter systems,multi-source complementary energy systems and other applications,by expanding the number of input ports of the DBI,it is possible to further optimize the system structure,improve the system power conversion efficiency,reduce the system volume and cost.In this paper,the topology and control strategy of Dual-Input Dual-Buck Inverter(DI-DBI)is studied in depth.Two types of DI-DBI topology derivation methodology are proposed.The first type of method separates pulsating voltage source cells from DBI,including two types: positive pulsating voltage source cells and negative pulsating voltage source cells.Then,based on dual-input DC/DC converter,positive and negtive dual-input pulsating voltage source cells are constructed.On this basis,a family of DI-DBI topologies are derived by replacing the single-input pulsating voltage source cells in the traditional DBI with dual-input pulsating voltage source cells,including two-quadrant,four-quadrant,non-isolated,and isolated type and so on.The second method divides the single-input DBI circuit topology into two parts: a single-input cell and an inverter cell.By replacing the single-input cell by a dual-input cell and cascading it with the inverter cell,another family of DI-DBI topologies are derived.The quasi-single-stage DC/AC system based on the DI-DBI is proposed.By connecting the two DC input ports of the proposed DI-DBI to a low-voltage DC source and a high-voltage DC bus,respectively,part of the power of the low-voltage DC input source can be directly transmitted to the DI-DBI without processing of the front-end DC/DC stage,thus single-stage conversion is achieved.Compared with the tranditional two-stage DC/AC system of Boost converter cascaded with DBI,the proposed quasi-single-stage architecture effectively reduces the power processing stages,and reduces the power capacity,loss,and volume of the front-end Boost converter.Thus,the overall efficiency of the quasi-single-stage DC/AC system is improved.Taking the proposed DB6 and DB5 as examples,the working principle and characteristics of the inverter in the quasi-single-stage architecture are analyzed in detail,and a carrier-stacked SPWM modulation strategy is proposed,the differences between the proposed DC/AC system and the tranditional two-stage DC/AC system are compared.The experimental results show the effectiveness of the proposed DI-DBI-based quasi-single-stage architecture in improving system efficiency.Compared with the two-quadrant DI-DBI,the four-quadrant DI-DBI’s working mode,characteristics,and modulation method are more complicated.A typical topology from the proposed four-quadrant DI-DBI,named DB8,is analyzed and tested,including it’s working principle and characteristics.The theoretical analysis and experimental results show that,the problem of reactive circulating current in the four-quadrant DI-DBI leads to increased voltage and current stress,increased loss,and reduced efficiency.To solve this problem,the four-quadrant DI-DBI is further optimizes and a new family of four-quadrant DI-DBI with less switches and without circulating current,named FQ-DB6,are proposed.On this basis,the quasi-single-stage DC/AC system based on the FQ-DB6 is studied in-depth,the working principle of the circuit is analyzed in detail,and the modulation and control strategy are designed,the influence of the four-quadrant DI-DBI’s unique energy feedback mode and load power factor angle on the single-stage power transmission ratio is analyed.The analysis result show that,the unique energy feedback mode of BI-DBI if help to further improve the system’s single-stage power transmission ratio.Finally,the correctness of the above theoretical analysis is proved by experimental tests.Applications such as distributed photovoltaic power generation require the inverter system to provide multiple DC input ports.By connecting the DI-PVSC of DI-DBI to different low-voltage DC sources,multi-input DBI can be derived.Take the single phase DI-DBI for example,by connecting the two DI-PVSC to two different low-voltage DC source,a multi-input DBI possess two low-voltage DC port and another high-voltage DC port is derived.Similarly,by connecting the three DI-PVSC to three different low-voltage DC source,a multi-input DBI possess three low-voltage DC port and another high –voltage DC port can be derived.The single-phase multi-input DBI is selected for analysis,the working principle,operating mode and characteristics of the converter are analyzed in detail,an adaptive modulation and control strategy is proposed to realize the independent control of the two low-voltage DC ports,stable operation and smooth switching between different operating modes are realized in each mode.Take two-input photovoltaic power generation system as an example,an experimental platform is builted and the experimental tests are carried out.The experimental results show that based on the proposed multi-input DBI topology,and the modulation and control strategy,independent maximum power tracking control of two-channel photovoltaic inputs is realized.