Research On Supercapacitor Pressure Equalization Technology

With the continuous progress of society and rapid development of economy, the demand for energy increases gradually. Therefore, it becomes particularly important to find optimal energy storage. In the current power electronic literature, it becomes a heated topic to improve energy efficiency. Supercapacitor is a new type of energy storage element with high energy density, high energy-storage rate, and short charge and discharge time. It is widely used in electric vehicles and electric power industry. Due to different demand on voltage and capacitance from different electric fields, quantity of supercapacitors in an energy supply system is not the same. Also, voltage is not distributed evenly when supercapacitor in series and parallels, which will reduce overall efficiency. So equalizing-voltage technology of supercapacitor plays an important role in improving energy efficiency.The paper first introduces background of supercapacitor development. The RC series connection model is elaborated as simulation model, where math model of several kinds of supercapacitors are analyzed and compared. Through analysis on arrays of supercapacitors in series and parallel circuits, the “parallel series model” is chosen because it enhances reliability of the whole system. To find the best fit model in different situations, advantages and disadvantages are discussed after comparative analysis on several methods of equalizing-voltage.Secondly, the paper focuses on typical methods of equalizing-voltage control of energy transfer, namely more flying capacity method. Based on operating principle analysis and mathematical models, the paper analyzed the improving voltage equalization. This method using flying capacitors replaced by inductors, and make appropriate control methods. By introduction the working principle and analyzing the simulation waveforms, superiority and feasibility of equalizing-voltage are proved.Thirdly, in order to tackle the voltage imbalance issue, I combined the above mentioned methods to form two hierarchical equalizing-voltage control systems, namely group of capacitor with inductance and improved voltage balance with flying capacitor. Using hierarchical control, the paper establishes the whole operational flow chart according to axiom and hierarchical control. The two systems under different ways of equalizing-voltage can transmit energy fleetly between supercapacitor device by controlling switch and output of impulse signal. As a result, system voltage consistency is achieved.Finally, I build simulation models of two hierarchical equalizing-voltagecontrol systems according to different frequency and duty cycle in Matlab. The mathematical analysis on all simulation data proves the superiority and high efficiency of this new system under equalizing-voltage.