Control Method For Parallel Operation Of STATCOM

The Advanced Static Var Generator (ASVG) has high adjustable speed and wide operation range. Because of the use of the technology of the multiformity, the multi-level or the PWM, it can greatly reduce the harmonic of the compensative current. As a new ASVG, STATCOM has become an important device of flexible AC transmission after twenty years development, and it will be an important device of reactive power compensation.The development of the ASVG is introduced, and the working principle of the STATCOM is studied. In face of the contradiction between the switching frequency and the capacity when STATCOM is used to compensate large capacity reactive power, a kind of non-interconnection parallel operation control method based on a set of current transformer is proposed after the discussion of the relative knowledge of the parallel control and modularization technology. Many modules are paralleled to grid independently, in which each can detect reactive current on ac side or the load side and distribute prorate the reactive current for each module as its reference.A simulation model of the system is established based on the proposed method. The simulation is achieved under the load stability, the load diversity and the removal of the breakdown module. The simulation results show that this method has good dynamic reactive compensation performance and can eliminate the influence of the breakdown module removal on system.A hardware system of two paralleled STATCOMs is designed. All the modules of the system are adjusted by single-variable control angleδ. The relative experiments of the system validate the correctness of the proposed method and realize parallel compensation to increase the STATCOM compensation capacity.