The Study On Voltage Difference Analysis And Voltage Control Of Cascade STATCOM Capacitor

With the increasing demand for power quality in production and life, it is becoming more and more important to ensure the reliability of power supply and high power quality.H bridge scries static synchronous compensator (STATCOM) as an important reactive compensation device, because ot its advantages of simple structure, easy modularization design, good harmonic characteristics, has the research value and wide application prospect.In recent years,the research on H bridge series STATCOM is becoming more and more in-depth, in which the H bridge series STATCOM DC side capacitor voltage balance control has become one of the research hotspots.In this paper, according to the domestic and international development situation of Cascade STATCOM, the topological structure is determined, which is connected by Y type and 5 H bridges are connected in series.In addition, through various methods of modulation strategy and control compared with STATCOM chain, to determine the control method of the uni polarity phase shifted carrier modulation method and self excitation of single variable.In order to solve the problem of unbalance of DC capacitor voltage, the influence of various factors on DC voltage is analyzed by establishing mathematical model and formula derivation.In order to solve the problem of unbalanced DC voltage, the balance control method of active voltage vector superposition is adopted.Through the establishment of Simulink simulation model and STATCOM experimental prototype, the balance control method of active voltage vector superposition and the control range of the derived control method are verified.The simulation results and experimental results show that the control method in whatever conditions can make the DC capacitor voltage balance, the steady-state performance and dynamic performance, and according to the scope of regulation principle of this control method is also correct.