Design Of Multi-port Energy Router Topology And Energy Management Strategy

With the continuous increase in user load demand and the large-scale access of distributed energy,the complexity of power grid structure is constantly increasing.Energy routers have outstanding advantages in dealing with the multiplicity and complexity of electric energy control,so studying multi-port energy routers is of great significance.This paper focuses on a photovoltaic power generation,lithium batteries,supercapacitors as energy ports in a microgrid system aimed at stabilizing DC bus voltage.The research includes maximum power tracking control for photovoltaic power generation,topology design for energy router,threelevel pulse width modulation rectifier and energy management strategy for energy router.For different energy demands,theoretical analysis and mathematical modeling are conducted on photovoltaic power generation,lithium batteries,supercapacitors and gridconnected inverters;topologies and parameters for each port converter are designed and verified using simulation software.In terms of maximum power tracking control for photovoltaic power generation,a nonlinear control method based on the sine perturbation method is proposed to improve anti-interference ability by using current sine perturbation to achieve stable and efficient operation at the PV source port.To solve the problem that existing droop control cannot achieve uniform distribution of energy in grid-connected inverters due to differences in line impedance causing uneven voltage offset,a third-order filtering system is used along with virtual impedance reference to improve voltage offset,and thus solve the problem of unequal distribution caused by differences in line impedance.Based on three-level pulse width modulation rectifier,the modulation model is derived by solving four basic variables to reduce calculation time,and a modulation strategy considering neutral point voltage balance is proposed.In terms of topology design for an energy router,a modular multi-level converter integrated with supercapacitor storage system was designed which can be applied to different voltage levels;also introduced was a modular multi-level converter scheme applicable to medium-voltage hybrid distribution networks integrating battery storage systems.Through its internally integrated supercapacitor storage system,input and output power decoupling is achieved.In terms of energy router management strategy,the limiting conditions of the energy router are analyzed and upper and lower control strategies for off-grid and grid-connected modes are designed.A droop control method based on hybrid energy storage DC bus voltage is used,and the stability of the system under each mode is analyzed.The proposed nonlinear control method based on sine perturbation method for maximum power point tracking and energy router management strategy based on droop control using hybrid energy storage DC bus voltage were experimentally verified on a test platform,with experimental results confirming their effectiveness.