Research On Single-Phase Photovoltaic Grid-Connected Micro-Inverter With Reactive Power Regulation Function

With the requirements of social sustainable development,the acceleration of scientific and technological progress and the strengthening of government support,renewable energy will be the largest source of global energy growth.Among them,solar energy is the most powerful part of renewable energy development.Solar photovoltaic power generation will get unprecedented rapid development.the micro inverter has strong adaptability to the unsatisfactory light conditions,and can ensure that each PV module can capture the maximum power point without barrel short board effect.At present,with the rapid development of micro inverter technology and fierce market competition,micro inverter can achieve intelligent regulation according to different grid requirements.In the future,micro inverter will be more secure,more efficient,more intelligent,small size,easy to install and so on.This paper focuses on the design and control method of micro inverter which can meet the requirements of grid reactive power control.First of all,through the comparative analysis of the topology structure,select the appropriate topology scheme.A two-stage topology is adopted,and the forward and reverse converter topology is adopted in the former DC-DC part.Based on the discontinuous current mode(DCM),the zero voltage on(ZVS)control mode is realized by controlling the bottom position of the drain source voltage resonance valley of the switch tube,optimizing the parameters of the forward and flyback transformer to achieve the goal of wide input,high gain and high efficiency.The latter stage DC-AC adopts the critical peak current control mode to realize the reactive power regulation function.Compared with the advantages and disadvantages of single bipolar control,the bipolar control scheme is optimized.The critical peak current control method is adopted.The switching mode near zero crossing point is optimized to realize the control of switching frequency range by combining the software calculation of switch on time and hardware current reset mode,so as to realize the high-efficiency bipolar DC-AC full bridge inverter control.Secondly,the control strategy and working principle of two-stage micro inverter are analyzed and discussed in detail,and the effects of power devices,transformer parameters,switching frequency and other factors on efficiency are analyzed and explained.On this basis,the designed circuit is simulated and verified by PSIM circuit simulation software.Thirdly,the reactive power regulation method and control strategy of two-stage micro inverter are further discussed.Finally,the design scheme of 300 W two-stage reactive power regulation micro inverter system is given,and the experimental prototype of the two-stage topology scheme is built.The experimental results verify the feasibility and correctness of the theoretical analysis.