Fault Characteristics Analysis Of Distribu-Tion System With Inverter-interfaced Distributed Generation Considering Low Voltage Ride Through

As the global energy situation becomes more and more severe and much attention has been paid to the protection of the environment,Inverter-interfaced Distributed Generators(IIDG)represented by photovoltaic power and wind power have been widely used in world.With the increasing capacity of IIDG access distribution system,the control strategy of IIDG needs to meet IIDG’s low voltage ride through(LVRT)requirement and ensure the power quality of the distribution system.A large number of IIDGs’ access makes the fault analysis method of distribution system more complex,and the short-circuit voltage and current of original distribution system change.Thus,in view of the above problems,the LVRT control strategy of IIDG,the fault analysis method of distribution system with IIDG and the influence of the IIDGs’ access on the fault characteristics of the distribution system are studied in this thesis.A new LVRT control strategy based on positive and negative sequence double current loop control and the IIDG’ LVRT requirements,considering the constraint of the maximum short-circuit current flowing through the IIDG inverter,is proposed in this thesis.The strategy can suppress the negative sequence components of IIDG output current to ensure the three-phase balance of current,and make IIDG output different reactive power according to the drop degree of Point of Common Coupling(PCC)voltage,so as to support system voltage.The feasibility of the LVRT control strategy mentioned in this thesis is verified by a simulation of fault in a distribution system with IIDG carried out in PSCAD simulation software.The IIDG’s equivalent current source model controlled by the PCC positive-sequence voltage,based on the LVRT control strategy,is established in this thesis.A fault analysis method of distribution system with single or two and more IIDGs under different fault locations and fault types is proposed in this thesis.The factors that affect the fault characteristics of distribution system with IIDG which adopts the LVRT control strategy mentioned in this thesis are proposed,and the rules of the PCC voltage and each branch short-circuit current of the distribution system with I IDG changed with different factors are analyzed and summarized.According to the above fault analysis method,the correctness of the variation rules of PCC voltage and each branch short-circuit current along with the variation of different factors is verified by MATLAB.