Research On Coordinated Control Of Photovoltaic DC Boost And Collection System

In recent years,under the strong support of national policies,photovoltaic power generation industry is developing rapidly.How to achieve more efficient grid connected photovoltaic transmission has become a key issue.Compared with the traditional AC grid connection,large scale photovoltaic power generation will bring great economic benefits by using DC collection and grid connection,which is because PV itself is a DC component and can be efficiently imported into the DC busbar by step-up transformation.And in terms of transmission performance and cost,the DC power grid has a great advantage.In this paper the principle and typical mode of planning and design of large scale photovoltaic power plant,voltage level,DC/DC collection and photovoltaic system interconnection,DC system coordinated control and protection technology,key equipment,structure parameters and control design technique,research on HVDC under grid friendly technology,put forward principles and application methods of PV technology flexible DC collection and based on internet.This paper first analyzes the basic principles for establishing the DC voltage level,the constraints set of voltage level,through the study of our current existing engineering case,and the voltage level of empirical formula,combined with the specific circumstances of the DC power system in China,the voltage sequence of photovoltaic DC boost exchange set.Then,based on the collection of the photovoltaic DC unit is analyzed for accurate modeling and related properties,focus on photovoltaic cells,isolated boost full bridge converter modular multilevel converter analysis.The IBFBC unit adopts PWM control to adjust duty ratio to achieve maximum power point tracking and photovoltaic cell boost.The unit adopts constant DC voltage control to stabilize DC bus voltage,and a PWM control algorithm is adopted in the voltage sharing mode.After that,a real-time power weighting hierarchical control strategy is proposed for single photovoltaic plants,which solves the problem of partial module voltage exceeding the rated operation range due to different lighting conditions in photovoltaic power plants.Finally,this paper proposes a coordinated control strategy of DC boost for multi photovoltaic power plants,so that modules of each PV power station operate in the rated voltage range,achieving stable operation of the system.And the power of the whole system is distributed flexibly through droop control.In this paper,the PV DC pooled grid system is modeled,and the system characteristics of the PV power station under typical conditions are simulated and verified.