Research On A Novel Multi-port Power Router With Full-bridge Submodul

With the shortage of energy and the increasingly serious environmental problems,a large number of distributed new energy represented by photovoltaics and wind energy and energy storage equipment have been connected to the distribution network,and the power supply form and power control have become more complex,the distribution network and equipment cannot meet such complex power control requirements.In order to solve the above problems,the energy Internet,which can realize the efficient consumption of energy was born.Power router(PR)has the advantages of multidirectional power flow,active power flow control,multiple AC and DC access ports,etc.,and is a key core device in the energy Internet.In addition,DC side fault protection is a key problem that needs to be solved urgently in the development process of voltage source AC-DC hybrid transmission and distribution system.Therefore,it is necessary to study the topology of power routers with DC fault ride-through capability in the context of energy Internet applications.First,a new multi-port PR topology with full-bridge sub-modules is proposed,which consists of high-voltage stage,isolation stage and low-voltage stage.In order to realize DC side fault protection based on the converter’s own control,the high-voltagelevel Modular Multilevel Converter(MMC)sub-module adopts a full-bridge submodule structure.Furthermore,the high-voltage stage has two AC ports of 10 k V and20 k V,and adopts three-phase four-arm MMC and three-phase six-arm MMC structures respectively,which can realize the interconnection of 10 k V and 20 k V distribution networks.In addition,the third phase of the traditional three-phase four-arm MMC is composed of capacitors in series,and in order to avoid the discharge of the series capacitor in the case of a short-circuit fault on the DC side,the third phase adopts a half-bridge module structure.The isolation stage adopts a series resonant DC/DC converter structure,and the low-voltage stage adopts a full-bridge inverter structure.Further,the control methods of the high-voltage stage,isolation stage and low-voltage stage of the proposed topology are analyzed in detail.Secondly,for the proposed new multi-port PR topology,the fault characteristics of the HVDC side short-circuit fault are studied.Through the analysis,it can be seen that when the HVDC side short-circuit fault occurs,the sub-module capacitor will discharge,resulting in a large short-circuit fault current in the loop.The fault current loop after the power switch device is blocked is analyzed,and it is found that the module capacitor of the full-bridge sub-module in the fault loop will provide a back electromotive force,and when the back electromotive force is greater than the amplitude of the AC line voltage,the reverse blocking of the diode can block the fault short-circuit current and realize the DC fault protection of the new multi-port PR.Finally,according to the proposed new multi-port PR topology,its redundant backup configuration scheme and the control method under fault-tolerant operation state are studied.A new multi-port PR redundant configuration scheme based on hot standby is proposed,and the control method of the isolation stage under fault-tolerant operation,the control method of the capacitor voltage of the high-voltage stage MMC sub-module and the corresponding modulation strategy are studied.For the new multi-port PR topology and control algorithm proposed in this paper,a simulation model is built in MALAB/Simulink software.The simulation results verify the effectiveness of the proposed new multi-port PR topology,control algorithm,fault protection method and redundant fault-tolerant control method.