Research On Multi-modes Constant Power Control Of Resonant Capacitor Charging Power Supply Based On State Plane Model

Pulsed power technology is widely used in the basic scientific research,industrial production,medical treatment,environmental protection and other fields.The storage capacitors are its important energy source.After the capacitor discharges and releases the energy,it needs to be quickly charged to the rated voltage by the capacitor charging power supply(CCPS)to meet the repeated operation requirements of the system.Therefore,it is of great significance to research the circuit topology and charging control technology of CCPS.The resonant CCPS has attracted much attention because it can make full use of the parasitic parameters,realize the soft switching easily,and has the advantages of high efficiency and high power density.With the continuous development of pulsed power technology towards miniaturization,re-frequency,and diversified applications,resonant CCPS also faces two major challenges.On the one hand,the load changes greatly and the dynamic process is rapid during the capacitor charging process,so it is difficult to control.The present control methods are relatively few and have many limitations such as slow charging speed,large device stress,and low input power utilization.On the other hand,the resonant converter is highly nonlinear and has many different working modes with complex resonant process,so the modeling and analysis of the resonant converter is complicated.So far the modeling and analysis methods have a large contradiction between accuracy and convenience,which makes the design and control of the resonant converter less efficient.In order to solve the above problems,this thesis adopts the state plane analysis method to model the resonant converter.The analytical output expressions of the LC series resonant circuit and the LCC series-parallel resonant circuit are derived successfully.On this basis and due to the shortcomings of traditional constant current control and the single mode charging control of resonant CCPS,a new multi-modes constant power control strategy is proposed,which can significantly accelerate the charging speed without increasing the stress of the switching devices.The research on modeling analysis method and the charging control strategy in this thesis is beneficial to the rapid and accurate engineering design and application of resonant CCPS,and it shows good theoretical value and practical significance.In terms of circuit modeling and analysis,the state-plane analytical model of the two-elements LC series resonant converter is derived by geometric mathematical analysis of its operation trajectory.However,the state plane analysis is difficult to describe the operation trajectories of the high-order resonant converters in the two-dimensional plane,since the independent state variables increase.Hence the application of this method is limited.To solve this problem and based on the modeling of LC series resonant circuit,this thesis proposes to use the equivalent resonant capacitor as a reference,and adopts two sets of normalization rules.Then the operation trajectories of LCC series-parallel resonant circuit are successfully expressed in a two-dimensional coordinate system.And the analytical expression of the output relationship in each mode is obtained.The state plane method can convert the analysis of the complex resonant process into a solution of the geometric mathematical relationship,and can obtain an analytical model with high accuracy and easy application,which provides the good foundation for the design and control of the resonant CCPS.In terms of charging control strategies,this thesis first systematically compares the output characteristics of the two resonant converters in different operation modes and summarizes their similarities and differences.Based on this,the thesis proposes a new multimodes constant power control method and designs an intuitive and flexible control trajectory according to the state plane analytical model.It contains four working modes.In the early charging stage,the resonant circuit works in continuous conduction mode(CCM)to improve the charging speed without increasing the device stress.In the later stage,discontinuous conduction mode(DCM)is used to avoid the turn-off loss and electromagnetic interference of the high-frequency CCM and ensure the charging efficiency and reliability.This control strategy comprehensively utilizes the relatively complementary output characteristics of the resonant circuit in DCM and CCM to realize the optimization of the entire charging process.Finally,the simulation of resonant CCPS is carried out and an experimental prototype is built.And the results of the comparative experiments show that the multi-modes constant power control can save 34.6% of the charging time under the same voltage and current stress,which verifies the accuracy of the state plane modeling results and the effectiveness of the charging control strategy and shows good engineering application value.