| With the mining and excavation of human beings,the production of coal has become less and less.At this time,the development of new energy has become a general trend.Solar energy is widely used due to its features of environmental protection and abundant resources.Among them,photovoltaic power generation is an important area for the effective use of solar energy.This paper mainly focuses on the research of two-stage grid-connected grid in three-phase photovoltaic grid-connected grids.It analyzes and studies some problems in the boosting circuit controlled by MPPT and the grid-connected inverter in the next stage.First,the photovoltaic power generation system was introduced.By comparing and analyzing the characteristics,applications and scales of off-grid and grid-connected systems,the grid-connected power generation system was selected in terms of long-term development and market value.Then the schedulable and unschedulable of the grid-connected system are analyzed.Because of the environmental pollution of the battery and the complexity of the system,the unschedulable is chosen as the research object.Then,the single-stage,two-stage,and multi-stage grid-connected systems were analyzed,and the two-stage type was easy to operate,simple,and practical.Therefore,a two-stage grid-connected system was selected,thus confirming the overall design scheme.Next,the research on the photovoltaic components of the core components has been conducted.Due to the different semiconductor materials and different efficiencies,the current research on photovoltaic semiconductor materials is extensive.In this paper,the working principle and circuit model of photovoltaic cell are deeply studied.By using MATLAB to simulate the light intensity and temperature in the actual environment,the variation law of the output power of the battery is obtained.In order to improve the solar energy utilization efficiency,the paper further studies the photovoltaic maximum power point tracking method.Boost circuit is used in the previous stage,and some common MPPT methods are analyzed and compared.Conducting simulation studies on the conductance increment method,perturbation observation method,and hysteresis comparison method,it is found that MPPT has the problems of slow tracking speed and misjudgment.Aiming at the existing problems,an adaptive fuzzy PID method was proposed.Through the MATLAB simulation software,the traditional fuzzy control and the improved control were simulated and compared.The effectiveness of the improved algorithm was obtained and applied to an independent power generation system.Finally,the paper introduced the after-stage inverter control circuit.In order to achieve the grid-connected inverter control,the space vector pulse modulation method(SVPWM)was chosen in this paper.Due to the multivariable coupling and time-varying problems of photovoltaic inverters,the inverter controller simplifies the equivalent transformation ofα-β/d-q.The α-β/d-q adopts the idea of coordinate transformation.In the process of DC change into alternating current in the later stage,harmonics are easily generated in the system.Therefore,the system incorporates the LCL grid-connected inverter controller to achieve inversion and filtering.Since the load is required to be connected to the power grid,a phase shift phenomenon occurs and the power quality of the power grid is reduced.For this reason,a parallel static reactive power compensator is proposed in this paper,and the feed forward link is added and inverted.The current is connected to the power grid using a three-phase,four-wire system to reduce the impact.Finally,an overall three-phase power system simulation model was built,the three-phase output current voltage and the distortion rate were analyzed,and applied to the smart grid.Through a practical case,the feasibility of the three-phase power generation system was further verified. |
PDF Full Text Request