Research On Equalizer Based On Voltage Multiplier Rectifier

At present,energy storage system such as energy storage batteries and supercapacitors have been widely used in photovoltaics,electric vehicles and other fields.Because the cell voltage of the energy storage battery and the super capacitor(for the convenience of description,the following analysis is collectively referred to as the energy storage system)is low,it cannot be directly applied to high-voltage occasions,so a large number of cells need to be connected in series to meet the high-voltage output demand.However,there are differences in electrochemical properties of different cellrs,and the charge and discharge during use will increase their differences,which will eventually lead to overcharge and overdischarge of some cells,thereby reducing the available capacity of the energy storage system and shortening its service life.Therefore,for the safe and reliable operation of the energy storage system,the introduction of equalization technology is essential.Equalization circuits can be divided into lossy equalization circuits and non-lossy equalization circuits.Although the lossy equalization circuit has a simple structure and convenient control,it has large loss and low efficiency,and is usually used in low-power applications.At present,scholars at home and abroad mainly study non-lossy equalization circuits.Most non-lossy equalization circuits are based on multi-winding transformers or a large number of switching devices to achieve the equalization of energy storage system,and the number of them increases with the increase of the number of cells.The equalization circuit based on Half Wave Voltage Multiplier(HW-VM)can effectively reduce the number of switches,and does not need to use a multi-winding transformer,and has the advantages of simple structure and good scalability.However,the critical voltage difference of the equalization circuit based on HW-VM is large,which leads to slow equalization speed and large loss of the equalization circuit.Aiming at the problems existing in the equalization circuit based on HW-VM,this paper proposes and studies a Buck-S-HW-VM equalization circuit based on Symmetrical Half Wave Voltage Multiplier(S-HW-VM).The equalization circuit can effectively reduce the critical voltage difference of the cells and improve the equalization speed of the equalization circuit.In some cases,the equalization circuit needs to realize the equalization between the modules of the energy storage system and the cells in the module at the same time.In this paper,an Improved Hybrid Half Wave Voltage Multiplier(Improved H-HW-VM)is proposed and studied.The Improved H-HW-VM circuit realizes the hybrid balance of the cells/modules of the energy storage system with any number of cells by changing the connection method of the rear-stage diode-capacitor network,and reduces the influence of the internal resistance of the cells on the equalization accuracy,improving the equalization speed,reducing equalization loss.The equalization circuit based on HW-VM can achieve effective equalization only in half a switching cycle,which makes the equalization circuit slow and lossy,and the equalization accuracy is greatly affected by the internal resistance of the cell.Aiming at the shortcomings of the equalization circuit based on HW-VM,this paper proposes and studies the Tap Inductor Hybrid Full-Wave Voltage Multiplier(TI H-FW-VM)equalization circuit.The TI H-FW-VM circuit can achieve efficient cell/module hybrid equalization.Compared with the Improved H-HW-VM circuit,it has the advantages of fast equalization speed and high equalization accuracy.Finally,a simulation and experimental platform is built in this paper,and the simulation analysis and experimental results verify the feasibility and effectiveness of the proposed equalization circuits.