Research On Photovoltaic Source Access Capacity And Permeability Of Rural Distribution Network Considering Power Quality Constraints

In recent years,with the strong support of national policies,the photovoltaic(PV)industry has developed rapidly.However,the PV output power has strong randomness due to natural factors such as irradiance and ambient temperature,leading to the power that PV injects system is also a random variable.At the same time,the PV power supply who contains a certain amount of power electronic devices injects a large amount of harmonics into the system during the working process.As the penetration rate of PV power supply in the power grid increases,the impact on the distribution network is becoming more and more intense,especially the impact on power quality indicators.From the perspective of probability,this thesis evaluates the probability of voltage deviation,harmonic voltage distortion rate and three phase unbalance of distribution network with PV power supply,and uses the probabilistic assessment results as constraints to study calculation method of limit access capacity of PV power supply in distribution network.Firstly,to avoid the calculation of limit access capacity of PV power supply is incorrect due to the consideration of the occurrence of a small probability event,this thesis proposes a method that is based on the chance constraints of voltage deviation and taking into account the randomness of PV power and load to calculate the limit access capacity of PV power supply.This thesis regards the maximum access capacity of PV power supply as the objective function,and regards the voltage deviation as the chance constrained condition to establish the calculation model of limit access capacity of PV.Then this thesis uses the probabilistic load flow(PLF)that is based on Latin hypercube sampling(LHS)to obtain the statistical properties of node voltage,then uses calculation results of PLF and quantum genetic algorithm to solve the model.The effectiveness and feasibility of the proposed method are demonstrated by the simulation of IEEE-34 node and the actual rural distribution network in a county in Gansu Province.Secondly,this thesis that is based on considering the randomness of the harmonic amplitude of PV power supply uses chance constrained programming to calculate the limit access capacity of PV power.This thesis regards the maximum access capacity of PV power supply as the objective function,regards the voltage deviation and the total harmonic distortion of voltage as the chance constrained condition to establish calculation model of limit access capacity of PV.Finally uses the particle swarm optimization(PSO)algorithm and the calculation results of harmonicPLF that is based on LHS to solve the model.By comparing the results of optimization with deterministic programming in IEEE-34 bus system,the validity of the proposed method are verified.Thirdly,aiming at the influence of single phase PV power supply on the three phase unbalance of the system,this thesis comprehensively considers the three main power quality indicators that are voltage deviation,harmonic voltage distortion rate and three phase unbalance and regards the maximum access capacity of PV power supply as the objective function,regards the comprehensive power quality indicators as the chance constrained condition to establish calculation model of limit access capacity of PV,then uses PSO algorithm and three phase PLF that is based on LHS to solve the model.The effectiveness and feasibility of the proposed method are verified by simulation calculations in IEEE-36 node examples,this method provides theoretical basis and scientific guidance for calculating the limit access capacity of PV power supply in rural distribution network considering power quality constraints.