Research On Topology Of Single Stage High Conversion Ratio Converter And Its One Cycle Control

With the increasing of the low voltage power utilization,such as LED driving and battery charging,and the low voltage generating equipments,like photovoltaic and fuel cell,the demanding of the high conversion ratio converter is becoming prominent increasingly.The high conversion ratio rectifiers need to convert the grid voltage to low device voltage while the power factor correction(PFC)function needs to be accomplished.Thus,the high conversion ratio rectifiers need to be studied deeply to make the rectifiers simple and cost-effective while realizing all the functions.Meanwhile,in renewable energy generation area,the high conversion ratio inverters need to be researched to maintain the simple structure and high efficiency while transferring the low voltage of PV and fuel cell to high gird voltage.This becomes one of the research hotspots in power electronics converters area.As a large signal and nonlinear control method,one cycle control has the merits of simple circuit implementation,good dynamic performance,and good anti-interference capability.Thus,it has been applied widely in power electronics and power system area and has attracted continuous attention by academic and industrial community.Therefore,researching on high conversion ratio converters topologies and their one cycle control will have important theoretical significance and practical value in engineering.In low output voltage PFC applications,the traditional two stage high conversion ratio PFC rectifiers use Boost converter to achieve PFC function and then another step-down converter to obtain the control of the output voltage.The two stage solution results in complicated circuits and high components counts.What's more,the components stress is high due to the step-up characteristics of the Boost converter.A single stage bridgeless high conversion ratio rectifier topology with bi-directional switch is proposed firstly.The proposed topology has simpler circuit and very low semiconductors count,only two switches and two diodes.The structure of bridgeless can decrease the conduction loss caused by the traditional diodes bridge.The high conversion voltage step-down is achieved by employing the tapped inductor.Meanwhile,the extreme duty ratio can be avoided when the output voltage is low.The two switches use the same driving signal and the reversed series connection makes the driving circuit simpler.The one cycle control is adopted as the control method,which can eliminate the input voltage sensor and the multiplier in the control loop that has to be used in the traditional PFC control methods.Therefore,the controller is simpler and cheaper.The feasibility of the proposed topology and its one cycle control is verified by the simulation and experiments.The results show that the proposed topology has the advantages of less components counts,less cost,and good PFC performance.What's more,a family of bridgeless high conversion ratio Buck-Boost PFC rectifier topologies is proposed by topology evolution.The topologies family can obtain similar but different circuit characteristics by variation of the circuit structure at gird side and output side,and meanwhile,maintain the advantages of low components counts and simple circuit.The feasibility of the proposed topologies family is verified by the simulation and good PFC performance is obtained by the simulation.Referring to single stage high conversion ratio inverters,the traditional two stage solution employs a stage of high gain DC-DC converter and another stage of traditional inverter,which results in complex circuit,more components counts,and high cost.The flyback type single stage topologies have to introduce the additional power decoupling circuit and will increase the components and decrease the efficiency.The traditional Boost type topologies can have easy power decoupling but are not suitable for high conversion ratio inverter application due to its limited voltage conversion ratio.A single stage high conversion ratio Buck-Boost inverter topology is proposed,which is derived from the bridgeless Buck-Boost PFC rectifier topology with bi-directional switch and has opposite power flow.The proposed topology has very less power components count,only four switches.The high conversion ratio is achieved by tapped inductor.The one cycle control is adopted as the inverter control method to obtain high quality sinusoidal output voltage and good anti-interference capability.The simulated results show that the operating principle is feasible and has the advantages of simpler circuit and low cost.Since the Buck-Boost type single stage high conversion ratio inverter still needs big power decoupling capacitors,a Boost type singe stage high conversion ratio inverter topology with tapped inductor is proposed then.The proposed topology is based on a full bridge inverter,and singe stage structure is achieved by sharing the lower switches for Boost voltage step-up.The high conversion ratio is obtained by employing the tapped inductor and therefore,the limited gain of the traditional Boost converter is solved.The proposed topology keeps the high voltage DC bus and makes the power decoupling easier and avoids the using of huge decoupling capacitors or additional power decoupling circuit in Buck-Boost type and flyback type singe stage inverter.In addition,the proposed topology has unique operation which makes the voltage step-up and inversion control independent,thus,can has the advantage of the traditional two stage topologies.Based on this topology,a single stage topology with higher voltage conversion ratio is proposed by introducing a charge pump.The charge pump only introduces two capacitors and two low voltage diodes but can increase the voltage conversion ratio largely and therefore,makes the proposed topology more suitable for higher voltage conversion ratio applications.At the same time,the charge pump structure can absorb the leakage energy caused by the tapped inductor,and eliminate the oscillation on the switches to improve the reliability of the inverter.The proposed two topologies adopt one cycle control as the inversion control method,which has the merits of simple and reliable control circuit,and good anti-interference capability.The feasibility of the proposed topologies is verified by the simulation and experiments.The results show that the proposed topologies can achieve high conversion ratio step-up inversion,and meanwhile have the features of less components,smaller decoupling capacitor,low cost and high efficiency.