Research On Topology And Control Strategy Of Multi-port Building Power Supply Energy Router

With the ever-increasing growth of distributed energy sources and the continuous emergence of new types of loads,it is imperative to construct a new type of power system.Energy Router(ER)is the core equipment of the new power system,and its functionality and reliability have become an urgent problem to be solved in the development of a new power system.However,current research mainly tends to the application of energy routers in the d istribution network,and little attention is paid to the flexible distribution of electric energy in energy routers and the coordinated operation control between ports.To this end,this paper takes the building power supply energy router formed based on t he combination of three-level converters as the object,and studies the topology and control strategy of the multi-port energy router,including the topology selection of each level of converter and the design of corresponding control methods,T-type DC /DC converter research,DC bus voltage stability control strategy realization,energy router coordinated operation control method design.In order to make full use of the building roof area and renewable energy to generate electricity,and to realize the flexible access of various AC and DC loads,the topology and solid-state module functions of the three-level converter in the energy router are studied.Based on analysing of the shortcomings of the traditional DC microgrid in buildings,a building power supply energy router based on three-stage converter is proposed,and the topology of each stage o f the energy router is designed;the control method corresponding to each level of topology is studied,and the frequency domain method is used to analyze the perf ormance of the controller,and then the functional design of each controller in the solid-state module is realized.The simulation and experimental results show that the proposed three-level converter control method has good dynamic performance and low impulse voltage and current during mode switching.In order to reduce the return power and switch tube stress of the dual active bridge(Dual Active Bridge,DAB)in the electric energy conversion process,the control strategy of the T-type three-level DAB converter is studied.Analyzed the working principle of T-type DAB,studied the eight working modes in one cycle of T-type DAB according to the difference of inductor current slope,and obtained the quantitative relationship between transmission power and dut y cycle and shift ratio;by analyzing the transmission power characteristics of the T-type DAB,two control methods,phase-shift control and hybrid control,are proposed,and the conditions for the minimum return power when the hybrid control method is ado pted are given.Simulation and experimental results show that no matter whether the voltage gain ratio is equal to 1,the T-type DAB can achieve zero return power transmission;compared with the traditional two-level DAB,the stress of the two main switch tubes in the T-type bridge arm is reduced half.In order to improve the transient performance and steady-state performance of the energy router,the DC bus voltage stability control method of the energy router is studied.Analyzed the transient process of the DC bus voltage of the energy router,and established the energy transmission relationship between the three-level converters according to the energy balance,and then designed the 400 V and 750 V DC bus voltage control methods;according to the steady-state characteristics of the DC bus voltage of the energy router,the traditional voltage-power droop control method is studied and applied to the multi-DC bus system.By standardizing the two DC buses,the DAB control block diagram for realizing the power b alance of the energy router is obtained.The simulation results show that after adopting energy balance control,the impact caused by the DC bus voltage during the mode switching of the three-level converter is significantly reduced,and the transient tran sition time is greatly shortened;when the power grid and energy storage equipment do not participate in the power balance of the energy router,the DC bus voltage is stabilized by controlling the DAB to migrate the unbalanced power.In order to reduce the abandonment rate of building photovoltaics and realize the flexible flow and automatic management and control of energy at each port of the energy router,a partition control method for the building power supply energy router is proposed.Divide the operating mode of the energy router into four quadrants according to the magnitude of the two DC bus voltage per unit value;according to whether the power grid and energy storage equipment participate in the system power balance,19 working modes of the energy router are studied,and the working mode of the converter in each mode is analyzed.The simulation results show that the adopted coordinated control method can realize the steady-state distribution of the power of the energy router and the flexible flow o f energy in each port,and ensure the stable operation of the system.This paper comprehensively studies the topological form,control method and coordinated operation strategy of building power supply energy router,which is of great significance for realizing the full absorption of distributed photovoltaic,ensuring the continuous and stable power supply of various AC and DC loads in buildings,and finally realizing the efficient distribution and management of electric energy,energy saving and emission reduction.