The Study On Static Var Generator Of Cascaded H-Bridge

Application of cascaded H-bridge STATCOM(Static Synchronous Compensator) will be very popular in the condition of high voltgage and high power, but the balance problem of DC side voltage of cascaded H-bridge STATCOM is one of the key technical problem for the application of that In this thesis, an improved H-Bridge DC side voltage control method is presented, it is based on the cause analysis of DC side unbalance voltage. By adjusting tiny phase angle and tiny modulation index at the same time, it controls the DC side voltage of H-Bridge, among them, adjusting the tiny phase angle and the tiny modulation index are based on the method of mean difference Through the simulation experiment, it shows that this method can find the adjusted range of the tiny phase shift angle quickly and reduce the number of tests significantly, which reduce the difficult of the former adjustment about the tiny value and change the basic condition of a long time and a lot of trial and error. The simulation experiment is carried out under the conditions of parallel loss and mixed loss, ultimately the simulation results show that the DC side voltage of H-Bridge is balanced.After the improved control method for DC side of the cascaded H-bridge STATCOM, the simulation model of eight H-bridge STATCOM is built in this thesis, the main structure of the simulation platform is formed by eight cascaded H-bridge, such the output voltage wave of high-voltage H-bridge STATCOM is seventeen level voltage wave This simulation platform control method is the state decoupling feedback control based on PARK transformation. By decoupling the load reactive current feedback value and the load active current feedback value, it can generate the initial control parameters which is constituted by modulation index and phase shift angle Then it integrates the intial control parameters and the tiny modulation index and the tiny phase shift angle and thus generates the sine modulation wave that is needed by unipolar dual-frequency CPS-SPWM(Carrier Phase-Shifted Sinusoidal Pulse-Width Modulation).Finally, the switch devices of each H-bridge is controlled by unipolar dual-frequency CPS-SPWM. When the eight H-bridge STATCOM is operated in the lOkV power system which contain the 600kVar reactive power, the simulation experiment obtains the compensation effect and the compensated simulation parameter values on each module of compensation device.