Develpoment Of Modularized DSTATCOM

Electric power plays a crucial role in the social industrial production and people's daily life,and the development of electric power industry is an important pillar of the national modernization construction and the improvement of economic level. At present,there is a long period of shortage of reactive power capacity in power system of our country,which not only increases the loss of power system,but also seriously affects the power quality of power users.Distribution static synchronous compensator(DSTATCOM) technology is a kind of power user technology,and is known as DFACTS by some scholars at home and abroad,which is the extension of FACTS technology in the distribution network.As a new generation of reactive power compensation device,DSTATCOM plays an important role in improving the power quality of the power grid.Firstly,the research background and significance of reactive power compensation device are introduced.The development and research status of STATCOM are summarized and the work principle of DSTATCOM is analyzed.The mathematical model of the system in three phase abc stationary coordinate system and two phase afi coordinate system both are established according to the topology structure of DSTATCOM system,laying the foundation for further analysis on direct power control(DPC).Secondly,the traditional direct power control based on voltage oriented (VO-DPC) is introduced and analysised.Due to hysteresis comparators are used in the power loop in the traditional DPC,the precision of the control system is low,and the switching frequency of the power device is not fixed.which causes difficulties in designing the filter in the AC side.A double loop predictive direct power control based on SPWM is proposed.DPC and predictive control is combined to get high controlquality in this control strategy.Meanwhile,SPWM is used instead of traditional logic switch table,solving the problem of switch frequency is not fixed.Three modulated wave optimization methods,which are simple and easy to implement in engineering,are studied and compared due to low utilization ratio of DC side voltage in traditional SPWM.Atilization ratio of DC side voltage is improved in these methods.The control strategy is verified by the simulation results.Thirdly,the design of the main circuitand the control system based on DSP+FPGA are presented,and the design ideas and working principles are described in detail.The practical engineering problems of DSTATCOM device are studied,including the mechanical design and heat dissipation design of the device.Experiments are carried out and the experimental results show that the proposed control method is feasible and effective.Lastly,the technology of parallel DSTATCOM is studied in the paper. Aiming at the disadvantage of low capacity utilization of single DSTATCOM in traditional parallel scheme,a DSTATCOM parallel control scheme based on redundancy control is proposed.The system can adjust the numbers of DSTATCOM according to the load,avoiding the low utilization rate of DSTATOM capacity.The circulating current in is analyzed parallel system.Aimed at switching frequency circulating current,a method based on carrier phase compensationis proposed.The simulation results shows the effectiveness of the proposed control strategy.