Research On Structure Design And Voltage Control Of Multi-port Energy Router

With the wide application of distributed energy generation and new energy,the diversified development of power supply forms and energy flow,the traditional power system can not meet the needs of the diversity and complexity of power control,so the concept of energy Internet comes into being.As the core equipment of energy Internet,energy router can adjust the flow of energy and carry out real-time information transmission,so it has important research value.Combined with the characteristics of multi-energy and multi-load access,this paper chooses the structure of multi-port energy router,and studies the coordination and stability of the system under the condition of multi-energy access and multi-direction energy flow.Aiming at various energy access and power distribution requirements,the main topology of distributed single DC bus energy router is adopted,and combined with the characteristics of energy transmission,the circuit parameters of photovoltaic,energy storage,power grid and ACDC load interface converter are designed.Based on the control objectives such as DC bus voltage stability,maximum power point tracking and AC grid-connection,modeling and analysis of photovoltaic units,energy storage units and AC-DC conversion units of the energy router are carried out to study the energy characteristics of each interface unit and the control methods of corresponding converters.Through the establishment of the battery model of energy storage unit,the working characteristics of the battery were analyzed,and the method of controlling the charge and discharge of energy storage unit was designed.Through the establishment of photovoltaic module model,the influence of light intensity and temperature on photovoltaic maximum power point is analyzed.The maximum power point tracking method is obtained by piecewise incremental conductance method,and the maximum power point tracking and constant voltage control method of photovoltaic power generation unit are designed.By establishing the mathematical model of three-phase full-bridge converter in the dq coordinate system,the multi-objective control method of DC voltage stabilization and power control of DC/AC converter is studied.By building an energy router simulation model in Matlab/Simulink,the energy storage unit charge and discharge control,photovoltaic unit constant voltage control and MPPT control,AC/DC conversion unit bus voltage control were simulated.The simulation results show that the energy storage unit can run stably in the state of constant voltage discharge,constant voltage and constant current charging.The photovoltaic unit constant voltage control can better stabilize the voltage of the DC bus,MPPT control can quickly track the new MPP under the condition of light intensity change,stable and dynamic performance is good.The grid-connected current can be well traced to the grid voltage under the control of the busbar voltage of AC-DC conversion unit.The total harmonic distortion rate of grid-connected current is 2.16%,which is lower than the requirement of 5% of the national standard grid-connected harmonic.The simulation results show that the control methods selected in this paper can effectively achieve the control objectives,and verify the effectiveness of the proposed control methods.Compared with the traditional coordination control method,based on the research of energy access and converter control methods of each functional unit,on the basis of hierarchical control and master-slave control,a coordinated control method combining the two is proposed.The system is divided into the bottom control layer and the central management layer.The bottom control layer introduces sagging control to control each unit converter.The control method is determined by the central management,which analyzes the status of each interface unit and issues control instructions.The converters coordinate with each other under different operating conditions to maintain the voltage stability of the DC bus and the power balance of the system.The hardware platform of the energy router was designed and built.TMS320C6747 was the main control chip,FPGA was the auxiliary chip,and TMS320C6747 was used for algorithm implementation.FPGA completed ADC acquisition,PWM signal output and other functions.The main control program of the software part uses cycle and interrupt to realize each control objective,and the SVPWM algorithm and PI control algorithm are designed for each port.Experiments of off-grid operation mode and grid-connected operation mode of the energy router system are carried out on the hardware platform.The experimental results show that the energy storage unit can stably carry out charge and discharge control under off-grid operation,and the photovoltaic unit can timely track the new MPPS according to the changes of the environment.The stability and dynamics of the system meet the design requirements.In the grid-connected operation state,5k VA power operation test is carried out.The frequency and phase of grid-connected current are basically the same as the grid voltage,and the total harmonic distortion rate of grid-connected current is 4.32%,which meets the national standard.The effective output voltage is 220.1V,the power is 4.62 KW,and the system conversion efficiency is 95.3%,which meets the design requirements.The voltage overthrow and regulation time of the DC bus can be improved significantly after the sagging control is introduced.The experimental results show that the proposed converter control methods and voltage stabilizer coordinated control strategies can maintain the voltage stability of the bus and the power balance of the system.