Research On The Control Strategy Of Voltage Quality Compensation In Micro-grid

With the continuous development of new energy power generation technology,new energy power generation has brought some negative effects on power quality.Therefore,as an effective way to solve the problem,microgrid has been widely studied.As a new type of power generation system,the microgrid can not only solve the problem of power supply in remote areas and emergency situations,but also solve the problem of power shortage in the majority of customers through grid-connected operation.The access of the nonlinear and unbalanced load makes the voltage quality of PCC point poor,in the case of island operation,which will cause fever and damage of local equipment;In case of grid-connected operation,which cause interference on the power grid,leading to power fluctuations and instability.This paper research voltage unbalance and harmonic compensation control method,which based on the distributed hierarchical control method in the two-phase stationary coordinate system,and compensate the voltage quality of the PCC point together with the local controller and the secondary controller.In order to solve the problem of voltage frequency and reactive power deviation in local control level,based on distributed hierarchical control strategy,the secondary controller was designed to control the deviation of the voltage,frequency and reactive power.Finally,the simulation result is carried out that frequency and reactive power could be well eliminated by the secondary controller.Considering the problem of voltage unbalance,the voltage quality problem is studied based on the distributed hierarchical control strategy.In the secondary controller,the voltage unbalanced compensator is designed to calculate the voltage unbalance compensation value of the PCC point,which is sent to local controller to compensate the voltage of the PCC point.Finally,the validity of the proposed control strategy is verified by simulation.For voltage unbalance and harmonic conditions,the voltage quality of the PCC point is studied.When the PCC voltage is unbalanced and harmonic,the harmonic detection and extraction module based on SOGI-DSC is utilized to extract harmonic component,and calculate the harmonic distortion and voltage unbalance,so as to obtain the harmonic compensation value and voltage unbalance compensation value for compensating voltage quality on PCC point;if the DG itself is not able to compensate fully,this APF will be use to carry out voltage and current compensation.Finally,the proposed control strategy is verified by simulation.