Research On The Design And Key Technologies Of Multi-Module Output Series High Voltage Capacitor Charger

With the rapid development of pulse power,capacitor energy storage,which is mature in technology,simple to implement,and low cost,is widely used in pulse power equipment,and capacitor charger has therefore become an important research topic that draws the attention of a large number of scholars.The current mainstream high-voltage capacitor charging solution is using a single customized charger,which has relatively low applicability and flexibility and cannot be easily transplanted and expanded.In this paper,a constant current high voltage capacitor charger scheme with multiple modules output series is proposed,besides,the current sharing problem of the interleaving parallel branches in single module and the voltage sharing problem of the multi-module output series are studied.Firstly,in order to achieve the demands in principle,a charging scheme with 16 modules output series is designed,in which every single module adopts a four-phase interleaved buck converter.The scheme proposed avoids the high voltage danger for each module,and can be expanded flexibly.Each module can be designed and produced in a unified way,which is convenient for debugging and reduces the cost.Based on the design scheme,the working principle of single module is described in detail by means of modal analysis.And then,The hardware parameters of single module are designed.Secondly,from the perspective of single module,the current of four phase branches tend to be unbalanced due to the mismatch of parameters.To address this problem,the mechanism of current imbalance is analyzed.The result shows that the main reason of current imbalance is the parasitic resistance mismatch of the continuation loop.Then,the four-phase interleaved buck converter is modeled,and a control strategy with branches decoupling,which can avoid the unbalance and steady state error of the inductance current,is proposed according to the model.Simulation results show that the proposed strategy can achieve the ideal effect of current sharing.Thirdly,from the perspective of multi-module,the modules can not be completely unified,there are sampling error,control error and output filter capacitance tolerance in practice,so that the output voltage is usually unbalanced.To solve this problem,this thesis analyzes the mechanism of voltage imbalance under multi-module output series and concludes that the mismatch of module current and output filter capacitance are the main causes of output voltage imbalance.Then,a voltage balancing strategy with output voltage feedback is proposed,which adjusts the module current to an equilibrium current through feedback compensation of the module output voltage,and thus balances the output voltage.Finally,a 1.2 kW low-power experimental platform containing three modules is designed.The proposed current-sharing control strategy with branch decoupling,voltage feedback voltage sharing strategy and the proposed overall scheme of modular high-voltage capacitor charger are experimentally verified.The experimental results show that the proposed currentsharing control strategy with branch decoupling can effectively balance branch current and achieve accurate control of charging current in four-phase interleaved buck converter;The proposed voltage feedback voltage sharing strategy can significantly improve the voltage equalization of multi-module output series system;The proposed modular high voltage capacitor charger scheme can meet the actual charging requirements and is feasible for application.