Simple controller for STATCOM-based var generators

A STATCOM-based Var generator for medium power applications, utilising one-cycle control is proposed here. The control structure employs an integrator with a reset as its core component to control the pulse width of the converter devices so that the current drawn from the source is a precisely controlled reactive current leading or lagging the utility voltages as demanded by the system. Moreover, one-cycle control makes the switching frequency of the devices constant. This simplifies the process of design of passive filters to eliminate higher-order switching frequency harmonics. The semiconductor devices are operated with a switching frequency of 1 kHz so that GTOs or high-power IGBTs can be used for medium power applications. The effectiveness of the scheme is verified through detailed simulation studies. To confirm the viability of the scheme, detailed experimental studies are carried out on a scaled-down laboratory prototype developed for the purpose.