Three-level Static Synchronous Compensator Integrated With Distribution Transformer

With the great development of the power electronics and the digital control technology,the theory, method and achieve means of the static reactive power compensation technologyhave made great progress. Besides, the application of the Static Synchronous Compensator(STATCOM) is more and more wide. It has played an important part in the aspects ofdynamic reactive power compensation, harmonics restraint and improving the systemstability in power system. For the present, the application of the STATCOM in thedistribution network is mature. However, there are many questions in the aspects of thetopology of the main circuit, the join up method and the control technology in STATCOMthat are worth studying.The three-level DT-STATCOM joined up from the distributiontransformer tap and its control panel proposed in this paper has got some achievement inthe aspects of lowering the access voltage of the STATCOM, improving the compensationratio and increasing the expansibility of the complicate control function.The basic theory of the reactive power compensation of DT-STATCOM is studied first.According to the distribution transformer of Yyn type and Dyn type, integration structuresof single-tap and multi-tap are designed respectively. he problem of the how to choose thevoltage of the transformer tap that connecting the STATCOM to make a more satisfactoryreactive power compensation ability without the overload in the high-voltage winding isstudied.On the basis of the analysis of the main circuit of DT-STATCOM and its workingprinciple, the efficient controller based on DSP and FPGA is designed. The total designscheme is introduced. The design principle, function configuration and the design schemeof the hardware and software are explained systematically.The reactive current detectionalgorithm, common control strategy and SPWM modulation method in DT-STATCOM areanalyzed in this paper. On that basis, the program achievement and software design of thecontrol strategy and modulation method that adopted by the scheme is illustrated accordingto the actual development of the controller of D-STATCOM.The dynamic simulation test platform of DT-STATCOM system is designed and developed. The dynamic simulation test scheme of tap-inserted DT-STATCOM system isdesigned. The tap-inserted compensation ability of the distribution transformer-STATCOMintegrated compensation system is tested by the dynamic simulation. The results verifiedthat DT-STATCOM has a good performance in reactive power compensation.