Research On Voltage Characteristics Of Photovoltaic Power Sources Accessing Active Distribution Network

With the increasing depletion of conventional energy and the increasingly serious of environmental pollution,it has been a trend to use renewable energy instead of traditional energy.The distributed photovoltaic power is connected to the distribution network,which has relieved the problem of energy crisis and environmental pollution.But it brings a series of power quality problems,especially the voltage problem.The conversion of the PV output from DC to AC power is based on PWM control,which can easily cause voltage deviation.Therefore,this paper analyses and studies the voltage characteristics of distribution network when the distributed photovoltaic power supply is connected to the active distribution network.Firstly,this paper sets up the basic model of photovoltaic power supply and active distribution network in MATLAB/Simulink environment,including photovoltaic power supply,maximum power tracking,inverter control,transformer model,load model,transmission line model,and verify its PV output.The correctness of the characteristic curve.Secondly,it discusses the mechanism of the voltage deviation in the distribution network and the influence of the photovoltaic power supply on the voltage deviation when it is connected to the active distribution network.To use MATLAB/Simulink simulation software to verify the influence of photovoltaic power supply on the active distribution network under the conditions of large capacity,small capacity,contact position and power factor,and elaborate on the access location when the photovoltaic power supply is separately connected.The effect on the voltage magnitude between the on-load tap change transformer and the bus,the end of the feed line,the load side of the line regulator,and the individual user side is different,and different influencing factors produce different voltage changes to the voltage.Finally,the mechanism of voltage over-limit formation when PV power is described is connected to the active distribution network.Based on the increase of the photovoltaic power supply of energy storage devices,the active power limit strategy and the active/reactive power collaborative control strategy for PV inverters are proposed.Both control strategies can be prevented by the simulation software MATLAB/Simulink.The active limit requires limiting the inverter's capacity,power factor,and ampacity,which can add to the cost of the inverter and make it difficult to control.First Active/reactive cooperative control is to reduce the active output when the voltage threshold is low,then the excess energy stored in the energy storage device;adjusted the active power when the limit value is relatively large,and using the inverter to absorb Excess reactive power,active and reactive power control can reduce the voltage at the grid point.It can not only prevent the voltage from exceeding the limit,but also does not need to increase the capacity of the inverter,which can improve the grid connection capability of the active power,and further ensure a good power supply quality.