Research On PV Grid-connected Control Strategy With Active Power Filter Function

With the introduction of the concept of sustainable development, China graduallyattaches great importance to the research on new energy to ease the energy crisis andenvironmental problems. At the present stage, the solar energy has been widely used as a newnon-polluting-renewable energy source in various countries in the emerging field ofphotovoltaic power generation. Solar power generation can not only save energy, protect theenvironment, but also improve the efficiency of the entire grid system by the use of activepower filter technology. It is of great significance for sustainable development of the nationaleconomy.The equivalent circuit model and equivalent mathematical model of photovoltaic cellsfor engineering applications have been summarized and analyzed. Thus the working principleof MPPT on photovoltaic cell and its three kinds of common algorithm have been introduced.The design principle of photovoltaic cells has been analyzed, that is, the output voltage andcurrent have been increased by the eries-parallel connection of photovoltaic battery to achievethe interconnection requirements. In order to better research the control strategy. Themathematical and physical model of grid-connected PV system has been analyzed detailedly,and the dynamic frequency, low frequency and control model in the dq and β coordinatesystem is established in this paper. This paper mainly analyzed the design principle of filterparameter value in three kinds of applications, which laid the foundation for the simulationmodel and experimental study of simulation.The working principle of grid-connected PV system and active power filter (ActivePower Filter, APF) have been analyzed, both of them have a single function, which led to alow utilization rate and high cost of the inverter. In order to compare and analysis thesimilarities between the circuit and control method, this paper proposed grid-connected PVsystem with APF function. Based on the original circuit structure of grid-connected PVsystem, its functions is extended, which has double functions of PV grid connected powergeneration and suppression of harmonics and reactive current, this feature greatly improvesthe utilization rate of equipment, thus the cost has been saved.The control strategy for grid-connected PV system in dq coordinate has also been studiedin this paper. In this control strategy, the decoupled voltage and current have been tracked andcontrolled in the circuit, through tracking control of system. And the current type of SVPWMmodulation had been used to achieve grid connection. PV grid-connected with APF functionhas been Studied on the basis of instantaneous power theory, this control strategy takes thelargest active current component, which is transformed from the maximum active power of PV issued, and the harmonic reactive current, which is measured by the instantaneousharmonic detection module sum, as the reference of current, and grid connected by way ofcomparison hysteresis loop. Then studying of PV grid-connected with APF function in dqcoordinate, this control strategy takes the d-axis and grid-connected current component,which is transformed from the maximum active power of PV issued, and the d-axis and q-axiscurrent component, which is measured by the instantaneous harmonic detection modulecorresponding sum, as a reference current to control inverter.Finally, This paper established engineering equivalent model of photovoltaic cells in theMATLAB/SIMULINK platform, according to the model and the parameters of each part ofthe circuit to determine in advance, the simulation model of the above three kinds of thecorresponding control strategy is also established, and the correctness and feasibility of thecontrol strategy have been verified, and it is also proved that it has grid waveform and theability to compensate harmonic and reactive current.