Research On Low-frequency Oscillation Suppression Of Pulse Train Controlled Cuk Converter

Cuk converter has the advantages of wide input voltage range,output step-up or step-down,and simple implement of the driving circuit.It is a switching converter with excellent performance,which has been widely used in photovoltaic inverter,rectifier,power factor corrector,reactive power compensation and other fields.In order to improve the load transient performance of the Cuk converter,a pulse train(PT)controlled Cuk converter is presented in this paper.There exists low-frequency oscillation when the PT controlled Cuk converter operates in continuous conduction mode(CCM),which seriously affects its steady-state and transient performance.Therefore,it is of great significance to study the low-frequency oscillation suppression of PT controlled CCM Cuk converter.Firstly,this paper takes PT controlled Cuk converter as the research object,the working principle of PT controlled Cuk converter operating in discontinuous conduction mode(DCM)and CCM are analyzed in detail.When equivalent series resistance(ESR)of output capacitor is considered alone,and when ESRs of intermediate capacitor and output capacitor are both considered,the energy models of PT controlled Cuk converter are established respectively according to the law of energy conservation.The essence of low-frequency oscillation in PT controlled Cuk converter is revealed by combining CCM,DCM,ESR of intermediate capacitor and ESR of output capacitor.The results show that the low-frequency oscillation of PT controlled CCM Cuk converter is not only related to the ESR of output capacitor,but also closely related to the ESR of intermediate capacitor.It shows that increasing the ESR of output capacitor alone can’t effectively suppress the low-frequency oscillation of Cuk converter,increment of the ESR of intermediate capacitor should be considered at the same time.Secondly,the PT controlled DCM-CCM Cuk converter is proposed,and its working principle and characteristics are analyzed.Considering the influence of ESR of output capacitor and ESR of intermediate capacitor,the non-ideal energy model of PT controlled DCM-CCM Cuk converter is established.On this basis,the inherent mechanism of PT controlled DCM-CCM Cuk converter to effectively suppress low-frequency oscillation is explored,and the extended topology of the scheme in other high-order converters is given.The critical expression of DCM-CCM is derived,which provides theoretical basis for the design of circuit parameters.The results show that PT controlled DCM-CCM Cuk converter can effectively suppress the low-frequency oscillation.Compared with PT controlled CCM Cuk converter,PT controlled DCM-CCM Cuk converter has better load transient performance,higher steady-state accuracy and higher work efficiency.The correctness of the theoretical analysis is verified by experiments.Finally,in order to suppress the low-frequency oscillation of PT controlled CCM Cuk converter,a PT controlled Cuk converter operating in discontinuous capacitor voltage mode(DCVM)is proposed.The working principle of PT controlled DCVM Cuk converter,the internal mechanism of suppressing low frequency oscillation,the characteristics of energy progressive transmission and output voltage ripple are analyzed.The results show that compared with the PT controlled CCM Cuk converter,the PT controlled DCVM Cuk converter can effectively suppress the low-frequency oscillation,and has better load transient performance.In addition,the output voltage ripple of PT controlled DCVM Cuk converter is small,which is negatively related to the number of pulse cycles and directly proportional to the change of output capacitor voltage in a single switching cycle.The correctness of the theoretical analysis is verified by experiments.