Research On Distribution STATCOM And Its Output Filter

With the rapid development of power electronics technology, Static SynchronousCompensator (STATCOM) has become a hotspot in the filed of power quality because of itsfast dynamic response, good compensation performance and high quality in stabilizingsystem voltage. But the PWM inverter has harmonic problems; LCL filter is presented inthis paper to suppress the output current harmonic in low voltage distribution STATCOM.The principle of STATCOM is investigated first, and then its mathematical model isestablished in both of three phase static abc frame and dq synchronization reference frame.The matrixes used in the coordinate transformation are achived in detail. Detecting methodsof reactive current based on instantaneous reactive power theory and decoupling controlstrategy of STATCOM are explained.The design method of single L filter and LCL filter are emphasis introduced and thecharacters and performance of an LCL filter compared with the L filter are investigated.The variable relationship between LCL filter’s parameters and its performance are alsodiscussed in detail. Noted that LCL filter has better grid side current than L filter when theyhave the same inductance; in order to get the same quality of current in the grid side,smaller inductance is needed in LCL filter.Simulation model of STATCOM is built in PSIM. According to the model parameter,calculation example of filter and DC capacitor and its voltage are given. Performance of Lfilter and LCL filter are compared in simulation under two conditions: two filters have thesame inductance; STATCOM not operation under rated capacity. The simulation resultsaccord with the theoretical analysis; the reactive current diction, SPLL and control strategyare also verified by simulation.Finally, using TI’s digital signal processor TMS320F28335as the main control chip,write C language program, finished the system experiment. The experiment result validatedthe theoretical and simulation analysis.