Research On Compound Control Of Interleaved Parallel Boost Converter With Constant Power Load

Boost converters are commonly used as power conversion modules for fuel cells and solar energy in microgrids,however,the output of traditional Boost converters is limited by the system power,which is difficult to meet the requirements of high current output and high power density.In addition,when the distributed energy in DC Microgrids(DCMs)is connected to the DC bus after conversion by the Boost converter,the Constant Power Load(CPL)in the DCMs system has negative impedance characteristics,which will cause bus voltage oscillation.In order to solve the above problem,this paper investigates the stability control of the bus voltage of DCMs with CPL by taking the interleaved parallel Boost converter as the research object.To suppress the effect of negative impedance characteristics in CPL on the output of the interleaved parallel Boost converter.Firstly,a cascade Proportional-Integral(PI)controller is established in combination with the average current control to ensure the current balance of each phase of the interleaved parallel converter.Secondly,on the basis of the cascade control structure,the inverse dynamics system can be linearly represented by the flat outputs by using the differential flat theory for the feedforward design of the inner and outer loops respectively,replacing the PI controller,and by selecting the inner and outer loop outputs that conform to the flat characteristics.Finally,the error feedback design is carried out using a linearized feedback method,and the cascade flat controller is proposed as a result.For the negative effects of circuit parameter perturbation on the system in the interleaved parallel Boost converter,an inner-loop Differential Flatness Baesd Control(DFBC),outer-loop Global Fast Terminal Sliding Mode Control(GFTSMC)composite control strategy.Firstly,the terminal sliding mode controller is designed based on the dynamic model of the external capacitive energy loop,and the terminal sliding mode control is introduced with the terminal convergence law in order to weaken the shaking effect of the sliding mode control.Secondly,the convergence of the external loop sliding mode controller is analyzed by using Lyapunov stability theory.Finally,it is verified by simulation that the system under the composite control strategy has strong robustness to circuit parameter perturbation,and has excellent stability performance and equalization effect when subjected to load disturbance.In order to overcome the insufficiency of the system output subject to a wide range of external disturbances,a composite control strategy based on Nonlinear Disturbance Observer(NDO)is proposed.Firstly,the NDO of the interleaved parallel Boost converter system is designed and the observed values are fed back to the composite control law to further the effect of external disturbances.Secondly,the stability analysis of the NDO is carried out by Lyapunov stability theory,and the basis for the selection of the observer gain parameters is obtained.Finally,the stability and finite convergence of the external loop controller after NDO compensation are demonstrated.It is verified by simulation that the observer can track the external disturbance quickly and accurately,and the system has good transient performance when subjected to external disturbance.