The Development Of A Medium Voltage High Power Battery Testing Equipment

It’s due to its high energy density, light weight, no pollution, environmental protection, charging and discharging voltage stability and easy to control, Lithium-ion batteries are more and more widely used. In the field of large-capacity storage power plants, urban rail trains and hybrid EMU and other high power applications, the battery voltage level is raised to the level of 1500V. In order to ensure the reliable working condition, it is necessary to maintenan and test the battery through periodical charging and discharging. However, the output voltage of battery testing equipment is no more than 1000V, which can not meet the testing requirement of high voltage Li-ion battery. In such situation, a prototype of 300kW,1500V battery testing equipment is studied and developed.The medium voltage high power lithium battery testing equipment adopts two stage three level topology, in which NPC three level PWM rectifier is used as the input stage and a non-common grounded bidirectional DC-DC converter is used as the output stage. Hardware design, control strategy planning and control system implementating and experiment debugging is conducted during the research.In the aspect of hardware design, the principle of the main circuit is analyzed, and the parameters of the main circuit are calculated and simulated. In the system control strategy, research and analysis of the net-side SVPWM modulation method and grid voltage orientation control, and dual-loop of both net-side and battery side converter are studied. With double cascade converter model built in MATLAB, the fuction of constant voltage, constant current charge-discharge test is implemented, and which have varified the feasibility of the relevant control strategies.To solve the problem of three-level circuit neutral point potential unbalance, the unbalance reason of the dual cascade converter is anaylzed, using the method of neutral point potential control of front and rear stage circuit. Simulation and experiment validate the feasibility of both converter running individually or combined as a group.The control system is designed, which includes a desktop computer, a touch screen and the converter controller. The function of both touch screen and converter controller are especially analyzed and described.A 300kW prototype battery testing equipment experiment is developed and tested. The expriments of charge-discharge and power control is carried out, with visible waveforms and data. The feasibility of the control strategy and modulation method is verified by experimental result, and the designed battery testing equipment has fulfilled the design requirement.