Research On The Bidirectional DC/DC Converter And The Battery Energy Management System

The new energy develops in a large scale currently. The energy storage system oflarge capacity and large scale plays an important role in improving the reliability andquality of the power. The Battery Energy Storage System which is made up of an AC/DCconverter and a DC/DC converter has been widely used all over the world. The researchfocus of this paper is the DC/DC converter which is used in the Power Conversion System.The mathematical model, work principle of the machine, the State of Charge (SOC)detection technology and how to design to controller have been analyzed in detail.The topology of the DC/DC converter has been introduced and a detail description ofhow it works has been given. Small signal model was derived with the help of the statespace average method.The DC/DC converter used in the PCS was responsible for the battery charge anddischarge control. Constant current charging and discharging was achieved through thecurrent closed-loop control and the constant voltage charging was achieved through thevoltage closed-loop and current closed-loop control. The PI controller is designed with thefrequency domain method. In order to verify the correctness of the controller, thesimulation model was established with the help of the Matlab.In order to facilitate energy management and battery charge and discharge control, theSOC was detected in a method which contains the Ampere-hour method and theOpen-circuit-voltage method. The Open-circuit-voltage versus SOC curve has beendetected with the experiment, and it would be used to calculate the initial SOC. Manyfactors which will affect the detection of the SOC have been analyzed and the factor ofcurrent rate has been modified with the Peukert equation when the Ampere-hour method isused.A bidirectional DC/DC converter experimental platform was accomplished. Thedevices type has been selected. The parameters have been calculated and the driving circuithas been designed. DSP and the host computer were used for the management of batterycharge and discharge control. The C language was used to write the control program andthe VB language was used to write the host computer program. Communication between the DSP and the host computer was realized with the Serial Communication Interface.Many experiments such as constant current charge, constant voltage charge andconstant current discharge have been accomplished. The experiment results show that thecontrol strategy adopted in this converter can work well and the converter has excellentsteady and dynamic performance. In conclusion, the bidirectional DC/DC converter and thecontrol strategy can be applied in two-stage PCS.