Design Of A Bidirectional Mobile Power Management System

From vehicle charging to emergency power,mobile power management and inverter are inseparable.This thesis mainly studies the 48 V lithium battery management system and single-phase bidirectional inverter circuit,and proposes a new mobile power management system.The topology of the balance circuit and voltage sampling circuit in low-voltage lithium battery management system has been improved,the parameter design and control method of the single-phase bidirectional switching power supply have been optimized,and simulation and testing have been completed.The circuit and control strategy of the mobile power management system proposed in this paper is simple and efficient,and it is highly expandable.The main design content of this article is divided into three parts: lithium battery management system,bidirectional AC-DC inverter and bidirectional LLC.First of all,starting from the existing lithium-ion battery management systems on the market,a cascaded lithium battery management system was proposed using equalization circuit and voltage sampling circuit multiplexing technology.By cascading the lithium battery component group and AFE,the two-stage low-voltage AFE management design of the 48 V lithium battery group is realized;the control path is made more compact by multiplexing the equalization circuit and the voltage sampling circuit,and the MCU’s response to the battery voltage is accelerated,More timely protection and higher equilibrium efficiency.The voltage sampling function and equalization function was tested on the prototype.The voltage sampling inaccuracy of most batteries was less than 10 m V,and the voltage range between the batteries was not higher than 160 m V after equalization.Secondly,a dual Boost bridgeless PFC structure is used to implement bidirectional AC-DC inverter,and the forward PFC and reverse inverter share the main circuit.The forward PFC operation adopts a one-cycle control strategy.The control loop is simple,no multiplier is required,and the MCU’s calculation pressure is reduced.The feedback amount only needs to collect the DC output voltage and the voltage on the sense resistor,which reduces the cost of current waveform detection.Matlab / Simulink was used to simulate the one-cycle control forward PFC.The PF value at 250 W power was 0.98,and the PF value at 800 W power was 0.995.The input current following characteristics are good.Third,the reverse inverter circuit structure is equivalent to a full-bridge inverter,and a dual voltage loop control strategy is adopted,which only collects AC voltage,implements outer loop compensation via the instantaneous inner loop,and outputs a PWM signal to control the switch;Polarity SPWM converts DC to AC.Matlab / Simulink was used to simulate the circuit.The THD value was 7.03% at 250 W and 5.37% at 1000 W.It can meet the design requirements when there is no grid connection.In summary,the latter stage of this design optimizes the parameters of the bidirectional LLC structure,and is designed to adapt to the mainstream MCU resonant frequency,which can achieve bidirectional voltage transformation of 400 V and 50 V at 10 k Hz,and the overall system stability.The Cadence simulation results verify the correctness and feasibility of the design.