Research On Three-phase Unbalanced Comprehensive Treatment Device In Rural Distribution Network

With the development of the social economy and the improvement of people's living standards,a large number of power electronic equipment and high-power loads are entering the ordinary households.It's is making the unbalance of the power distribution area more and more prominent.On the other hand,power users are increasingly demanding power quality.Today's power quality conditions have not met the needs of customers.For these reasons,this dissertation proposed a comprehensive management device to improve system power factor,reduce current unbalance and harmonic content.Firstly,this dissertation proposed the topology of the pure passive form of the three-phase three-wire system,including the passive compensator and the passive filter.The working principle of passive compensator for reducing current unbalance and reactive power content was analyzed in detail,and the calculation formula of three-phase compensation admittance was derived.The relationship was established between compensation admittance and firing angle.Aiming at the harmonic problem generated by passive compensator in the working process,this dissertation proposed a new type of passive filter,which generates harmonic voltage by mutual inductance principle to achieve the purpose of filtering target harmonics.The detailed formula derivation and parameter design method were simulated and analyzed by Simulink.The simulation results verified the feasibility of the design method.Secondly,the current detection algorithm based on instantaneous reactive power theory was used and improved his deficiencies.An i_p-i_q detection algorithm based on second-order generalized integrator was proposed to realize accurate detection under voltage imbalance.It got a more accurate compensation effect.The Simulink simulation model of passive compensator and new passive filter was established,which proved the correctness of the compensation algorithm described in this dissertation.Finally,this dissertation designed a complete set of devices with TMS320F28335 as the control core,including the main circuit and controller.The hardware circuit of the controller included a signal acquisition circuit,a signal trigger circuit,a BOD protection circuit,and other peripheral circuits.At the same time,the parameter design method of thyristor,capacitor and reactor in the main circuit was given.The experimental verification was carried out under the existing conditions of the laboratory.The results showed that the design scheme can reduce the three-phase unbalance of the system,improve the power factor,reduce the harmonic content rate,improve the power quality.The result proved that it had practical engineering application value.