The Research Of Complex Dynamical Behavior In One-Cycle Controlled Power Converters

Power converters are highly nonlinear systems, which means they may exhibit nonlinear phenomena, such as bifurcation and chaos. The nonlinear phenomena jeopardize performance of the converters, so it is necessary to thoroughly analyze these phenomena. Over the last two decades, many works have been done to study the nonlinear dynamics in traditional linear controlled power converters. Little is known about nonlinear dynamics in nonlinear controlled power converters, which may exhibit nonlinear dynamics different from linear controlled converters, due to the different control methods. Therefore, study of nonlinear dynamics in nonlinear controlled power converters is important. One-cycle control is one of the most widely used nonlinear control methods, and this dissertation focuses on nonlinear dynamics in several basic One-cycle controlled power converters.One-cycle controlled Buck converter and Boost converter are two basic topologies. In this dissertation, sampled-data model of One-cycle controlled Buck converter is derived. Analysis of the model indicates that, when the reference voltage is less than the input voltage, the One-cycle controlled Buck converter is always stable. In One-cycle controlled Boost converter, bifurcation due to variation of the reference voltage and the load resistance is analyzed by using the sampled-data model. Averaged model of the One-cycle controlled Boost converter is derived to confirm the result from the analysis of the sampled-data model. Based on the averaged model, a washout filter is proposed to control the bifurcation in the One-cycle controlled Boost converter. Routh-Hurwitz criterion is applied to select the parameters of the washout filter. The sampled-data model of the One-cycle controlled Cuk converter is derived, and the bifurcation in the input stage of the converter under variations of the reference voltage and the load resistor is analyzed using the model. A washout filter is proposed to control the bifurcation in the input stage by taking the input capacitor voltage as its input. The sampled-data model of the One-cycle controlled Cuk converter with the washout filter is derived. The effect of the parameters of the washout filter on the stability of the converter is analyzed. The characteristics of the washout filter aided method used in power converters are discussed by using the sampled model.Slow-scale bifurcation in the One-cycle controlled Boost Power Factor Correction (PFC) converter is studied. The averaged model of the converter is derived through the first averaging, which averages all state variables within one switching cycle. After adopting the second averaging and harmonic balance method, the DC component model, the first- and the second-order harmonic component averaged model are derived to describe the dynamics of the converter. The equilibria of these models are calculated. Based on the signal transfer function, the stability boundaries of the circuit parameters are derived. The stability boundaries of some main parameters are discussed.A washout filter is proposed to control the slow-scale bifurcation in the average current mode controlled Boost PFC. Two cases of the Boost PFC are studied, i.e., the Boost pre-regulator and the complete two-stage Boost PFC. The DC component model, the first- and the second-order harmonic component averaged model are derived from the averaged model of the Boost pre-regulator to study its dynamics. After reasonable assumption of the steady state of the DC component and the second-order harmonic component, the dynamics of the converter is decided by a linear system. A washout filter may be used to stabilize the linear system. The effect of circuit parameters of the washout filter on the dynamics of the converter is studied in detail. The response under variation of parameters in the converter is analyzed. The average model of the complete two-stage Boost PFC converter is derived, and the DC component model, the first- and the second-order harmonic component averaged model are derived from the averaged model to study the effect of the washout filter aided method. A comparison between the effects of the washout filter method on the two cases is given.Slow-scale bifurcation in the One-cycle controlled Cuk PFC converter is analyzed. Based on the average model, the approximate resolution of the state variables is obtained by adopting harmonic balance method. The stability boundaries of some circuit parameters are presented and are discussed.