Research On The Non-isolated Three-wingding Coupled Inductor High-step-up DC/DC Converter

The high step-up DC-DC converters are widely used in green renewable energy conversion systems like photovoltaic,fuel cell,uninterrupted power supplies and electric vehicles.The fundamental boost converter can not suitable to provide a high-voltage gain in practical applications due to the parasitic parameters of the devices.Furthermore,the extreme duty cycle opertion may result in the low conversion efficiency of the fundamental boost converter owing to large conduction losses,high switching losses and serious reverse-recovery problems.Therefore,it is of great significance to study the high-gain and high-efficiency DC-DC converters.In order to effectively improve the voltage gain of the converter,baesd on the three-winding coupled inductor and switched-capacitor technology,a nonisolated single-switch three-winding coupled inductor Boost converter with switched capacitors?SSCI-Boost?is proposed,which overcomes the shortcomings of the fundamental boost converter in high step-up applications.The SSCI-Boost converter achieves the high step-up voltage gain,avoding the occurrence of the large duty ratio in the high gain fields.The control of the SSCI-Boost converter is simple because of increasing the control degrees of freedom of the system.The voltage stress of the switch is depressed.Thus,the low-voltage-rated diode with low R_DS?on?can be adapted,which can reduce the conduction losses.By introducing the passive clamp circuit to the SSCI-Boost converter,the voltage spike caused the leakage inductance of the coupled inductor can be reduced and the energy of the leakage inductance can be transferred losslessly.The current of the diode is controlled by the leakage inductance of the coupled inductor,which alleviates the diode reverse-recovery problem.By introducing cross-coupling technique to the conventional interleaved boost converter,a nonisolated dual-stiwch three-winding coupled inductor Boost converter?DSCI-Boost?is presented in this paper.The DSCI-Boost converter not only retians the advantages of the SSCI-Boost converter,such as the large voltage conversion ratio,the flexible system control and the low voltage stress of switching devices,but also further improves the operating characteristics and performance of the SSCI-Boost converter.The operating principles and the steady-state analyses of the SSCI-Boost converter and DSCI-Boost converter are discussed in details.The simulation platforms are implemented for performance verification.The small-signal model using the state space average method is established for the SSCI-Boost converter and its stability is studied by the frequency analysis.The closed-loop loop compensation controller is designed.Finally,two prototype converters with the high speed processor TMS320F2812 as the core controller are designed in order to verify the theoretical analysis of the SSCI-Boost converter and DSCI-Boost converter.The correctness of the closed loop control of the SSCI-Boost converter and DSCI-Boost converter is verified.