Study On Droop Control Of Distributed Power Supply Of Low Voltage Optical Storage AC Microgrid

With the increasing demand for electric energy and the increasing awareness of environmental protection,the increasing use of clean energy has become an irresistible trend.However,the time variability and uncertainty of most clean energy,such as wind energy and light energy,bring many adverse interference to the large power grid and electrical equipment.Moreover,the traditional distributed power supply also imposes a huge burden on the power grid due to its access characteristics.Therefore,research on clean energy and/or off-grid access technology can help improve the utilization of clean energy.The increasing use of solar water heaters,wind-powered street lamps and other clean energy devices in people's lives provide an indispensable source of electricity for the local micro-grid.Therefore,microgrid technology has become a hot topic for scholars around the world.Aiming at the fact that the line impedance is resistive when the photovoltaic micro-source is connected to the low-voltage micro-grid,this paper analyzes the influence of line impedance on the inverter control method,and proposes a new sag control method for the low-voltage ac micro-grid system in optical storage combined with the traditional sag control method.The simulation platform is built by analyzing the characteristics and working principles of each component.By using the improved droop control method on the simulation platform,the load switching simulation experiment proves that the improved control technology can more accurately meet the demand of supply load power.It make the ac bus voltage more stable than the traditional droop control.First,according to the working characteristics of photovoltaic cells,a universal photovoltaic cell model is built.The disturbance observation method is adopted to control the duty cycle of boost circuit,so that the photovoltaic cell can keep working at the maximum power output point and realize the efficient utilization of clean energy.And through the two-way dc-dc control circuit access battery,solve the photovoltaic cell output voltage change by the external environment,so that the inverter DC side input voltage remains stable.Secondly,the inverter simulation model is built.The voltage and current feedforward decoupling control technology is introduced into the voltage and current double closed-loop feedback control device to enable the control system to accurately output the required voltage and current.Through the comparison test,it is proved that the tracking ability of the system can be greatly improved by introducing the voltage and current double closed loop control.Then,the influence of line impedance on droop control is analyzed,and the droop control method is improved in view of the fact that the line impedance is resistive when the user's low voltage side(PCC node)accesses the ac bus.The improved droop control model is built in the system model.Through load switching experiment,it is proved that the improved droop control method can meet the demand of load variation by adjusting the amplitude and frequency of inverter output voltage.Finally,the parallel experiment of inverter is carried out according to the fact that the line impedance is deviated in practice.The results of load switching and inverter switching experiments show that when two inverters are parallel,the voltage stability on ac bus is not affected when the line impedance error is small.Meanwhile,the inverter can be "plug and play" with high accuracy.