Pivotal Technology Research Of High Step-up DC-DC Converter

The lack of traditional energy sources,the intensification of environmental pollution and the increase of electricity demand make the development of green energy become an important choice for the sustainable development strategy.The step-up DC-DC converters play an important role in applications where green energy is the primary energy source,like distributed generation systems,new energy vehicles,LED lamp drivers and active power factor correction etc.Conventional Boost converter has been widely applied due to its simple structure,but the voltage gain is not high enough.There are many ways to increase the voltage gain,but the topology innovation will improve the voltage gain of the DC-DC converter under low cost condition.In this paper,basing on the current step-up technology of DC-DC converter,several new high step up DC-DC converters are proposed from the perspective of topology innovation.Firstly,the paper takes advantage of coupled inductor,a novel high-gain soft-switching DC-DC converter based on coupled inductors is proposed.In this paper,the topologies of the converters,the operating modes and the selection of parameters in the circuit are analyzed in detail.Converter performance comparison is also completed.The results show that the converter has several advantages:(1)The converter achieves the voltage gain from multi-degree-of-freedom including the coupling inductance turns ratio and duty cycle,which breaks principle of the traditional boost converter regulating voltage gain only by the duty cycle;(2)Voltage stress of all the switching devices is lower than the output voltage;(3)The power switch can be turned on softly,the diode can be turned off under zero-current state,which greatly alleviate the reverse recovery problem of the output diode,hence circuit loss are reduced.Secondly,the paper utilizes the Z-source technology,a Z-source network based DC-DC converter with high-gain and low-stress is proposed.In this paper,the topology,working principle and steady-state performance of the proposed converter are discussed and performance is compared with other converters.The results show that the converter has several advantages:(1)The converter uses the Z-source network to further improve the voltage gain and avoid the duty cycle working close to 1;(2)The structure of the converter makes the voltage stress on the power switch is greatly reduced;(3)The capacitive ripple on the Z-source network can cancel each other out,which helps to reduce the ripple in the circuit.Thirdly,the paper combines with switched capacitor,a high-gain Boost converter based on the inductor-capacitor structure is proposed.The topology of the converter and its working principle in continuous conduction mode and discontinuous conduction mode are introduced.The performance comparison between different converters and the parameters involved in this converter are also presented.The results show that the converter has several advantages:(1)The converter increases the voltage across the inductor-capacitor structure through the switched capacitor technology,and the inductors and capacitors are charged in series and discharged in parallel,hence the voltage gain of the converter is greatly improved,This way can reduce the working duty cycle of the proposed converter;(2)With the duty cycle are reduced,the current ripple on the switch are decreased correspondingly,therefore,the circuit loss is reduced.The novel DC-DC converters proposed in this paper have the characteristics of high gain and low stress,which makes it suitable for low-voltage new energy generation system and other low voltage applications.