Research On The Controlling System For Balanced Charging Of Battery On Electric Car Based On DSP

With the sustained and rapid development of the economic society,people are increasingly demanding transportation.As the mainstream of new energy vehicles,electric vehicles have great potential and are frequently seen in major cities.However,the problems that the number of charging piles is so small and the technology on battery is not mature enough and so forth have become a bottleneck restricting the further development and popularization of electric vehicles.The technology on battery is an important part of today's electric vehicle technology,and it is the basic guarantee for the development of smart cars in the future.Battery management technology directly affects battery performance and battery life.A good charge and discharge management solution can make full use of electrical energy,minimize charging time,extend battery life and increase single cruising range.Traditional electric vehicle power battery charging systems often have some problems.This paper mainly changes the following two aspects to solve related problems.First,most of the electric vehicle power battery charging systems are powered by commercial power,using Boost circuit and Buck circuit as APFC converter,Boost adopts current and voltage double PI control loop,and Buck adopts conventional PI single loop control,two circuits.Simultaneously with the control loop,it can output a relatively stable DC power,and can provide a stable power supply for the segmented charging of the constant current and constant voltage of the battery.In the process of APFC conversion in Boost circuit,due to the phase difference between inductance and current voltage,the input current is distorted after zero-crossing.This distortion is called zero-crossing distortion.Based on the circuit structure,according to the control principle,The input current rise rate at zero crossing is analyzed to find the root cause of zero-crossing distortion.Aiming at the reason that the input current lags the input voltage,the phase compensation method of changing the tracking target is given.In the control loop,the input current follows the leading voltage waveform,thereby compensating for the phase difference between the current and voltage.For the reason of the large inductance,the reason is given.The interleaved parallel control technology,the parallel branches are alternately turned on and off,equivalently reducing the inductance,while not affecting the stability of the supply current as much as possible.Combining the two methods significantly reduces the zero-crossing distortion and reduces the total harmonic distortion to less than 5%.Second,the electric vehicle battery charging is carried out in a series structure,but due to the process error,there is always a slight difference in the performance parameters of each unit.As the charging time goes on,the error accumulates,eventually resulting in a part of thebattery having a smaller capacity.It is damaged and damaged,and some of the batteries with large capacity are undercharged and it is difficult to perform their performance.In order to solve this problem,this paper presents a method of equalization of series-parallel structure recombination.At the beginning of charging,the terminal voltage of each monomer is collected in real time,the monomers with the largest and smallest terminal voltages of all the monomers are connected in parallel,and then the remaining terminals of the monomers are connected in parallel with the maximum and minimum voltages,and so on.All parallel combinations are connected in series.In the charging process,the terminal voltage of each unit is collected in real time and the recombination module and the peripheral switch are controlled,and all the monomers are dynamically connected and combined in the above manner in real time to achieve the purpose of low-loss and fast balanced charging of the battery pack.The simulation results show that the method can make the terminal voltage difference among the batteries less than 1mV at the end of charging.Because the calculation data amount,calculation speed,communication speed and control real-time requirements in the control process of the equalization charging method are relatively high,this paper uses DSP as the control chip,mainly using its superior calculation speed,rich internal resources and fast Communication speed.In addition,this paper adopts high and low level control for the new equalization method,and reduces the switching loss as much as possible on the basis of receiving good equalization effect.