Research On Stand-Alone Photovoltaic System With Storage

Now-a-days people are busy in finding the replacement for fossil fuels,because fossil fuels are at a stage of extinction.As the demand for energy requirement is high,the fossil fuels alone cannot meet the energy requirements.Some kind of clean,efficient,cheap and self-sustainable energy sources should be used,few of them are solar,wind,geothermal and hydro-power.As of now,it's a global mission to use the renewable energy sources,which can control the global warming and many other ecological imbalances.Many governments are encouraging and supporting for new researches in this field.Among all energy sources,solar energy is abundantly available on earth.Only 30% of solar radiation is reflected back to space,remaining 70% of radiation is absorbed by earth surface.In recent days,solar cells are manufactured with highly efficient materials which can generate large amount of currents.Solar array systems are modified to support low power and high power applications by controlling many parameters.In this research,a solar stand-alone system is built for residential use.The system involves a solar array,Boost converter,voltage control loop,PID controller,loads connected to DC bus.Maximum power point tracking system is designed in this system,which is mandatory for a solar array system to attain maximum power.Single-phase inverter is used to supply AC loads for residential use.Based on the analysis of the structure,modulation methods and control strategies of single-phase inverter,the research points out a new closed loop voltage control method using the RMS value of voltage.Meanwhile,simulation results verify its effectiveness,against the problem of steady-state error in traditional closed loop voltage control.Besides,the research uses the lead acid battery as storage device which is an indispensable part of stand-alone PV system,and studies its structure,theories and models.The research focuses on the analysis of bi-directional DC/DC converter,because it plays an important role in the stand-alone system,such as controlling the charge-discharge of battery.On the basis of topology of converter,the research builds the modeling of converter working in Buck mode and Boost mode,and controls the converter using one step MPC method and satisfactory optimal method.The simulation result confirms its obvious advantages comparing with traditional PWM modulation method.In the light of the PV arrays power and loads power,and SOC of the battery,the research designs the power management strategy of the system.The strategy grades the loads according to its importance,and sets five working mode,which improves the reliability of the system.Ultimately,the research sets up the whole system in MATLAB/SIMULINK and validates the effectiveness of proposed methods and power management strategy.