New Type Booster Converter And Its Application In Photovoltaic Power Generation System

Inverter is the main equipment for energy conversion in photovoltaic power generation system.The performance of the system is playing the decisive role on the output power quality of the whole system.Based on the current researches about the topology of photovoltaic inverter,this paper studies and analyzes the topology structure and basic working principle of a new type of booster inverter.The corresponding modulation method and control strategy are designed for the characteristics of topological structure.And the system is finally applied to photovoltaic system.Firstly,after comparing and analyzing several inverter topologies which are mainly used in PV inverter system,the advantages and disadvantages of them are summarized.Based on this,a two-stage step-up inverter structure composed of the front stage booster circuit and the back-stage inverter circuit is proposed.Firstly,its circuit structure is relatively simple,and it has the capability of self-boosting,and no external booster transformer is required.Secondly,the structure can work in the direct mode,removing the influence of the dead zone.In addition,the pre-level input current of the structure can be kept continuously,avoiding the possibility of wasting the input power.Then the working states of the structure and the equivalent circuit are studied and analyzed,and the modulation method of the system is designed according to the working states of the system.In the case of system switching loss,the DPWM with fewer switching times is selected as the basis,and the direct vectors are added on it to obtain the modulation signal suitable for the system.Using this modulation method can effectively reduce the number of switch time per cycle than the traditional SVPWM,thus reducing system losses and improving system efficiency.At the same time,the corresponding control scheme is designed for the new booster inverter and its photovoltaic power generation system.For the photovoltaic part,the corresponding MPPT control algorithm is designed in the front stage booster circuit,so as to obtain the maximum output power of the photovoltaic panel.The rear stage is controlled by current closed-loop to ensure the overall quality of the system's output power.Finally,the hardware part and software part of the whole system are designed.The system requirement and the safety factors when actually used need to be integrated into account,and it is used to select and calculate the components of the system.A prototype system is used to validate the topology and the output waveform of the system is analyzed.Through the experimental results verify the effectiveness of the proposed new booster converter relative to the current commonly used photovoltaic inverter topology has certain advantages,and the output power quality also accords with the actual application needs.