Averaging Technique for the Modeling of STATCOM and Active Filters

This paper introduces average circuit models for switch mode shunt converters coupled with power systems such as active filters and static compensators (STATCOM). These devices absorb or deliver reactive power to the utility network by employing either a fixed or a variable switching frequency (e.g., pulsewidth modulation voltage control or hysteresis current control). Analysis and simulation of these exact devices could be complex under transient and steady state conditions. Ongoing investigations on design of a practical STATCOM show that performing these kind of simulations (e.g., with PSpice) are very sluggish. Here both the fixed and variable switching frequency shunt devices are modeled using an averaging approach, by deriving their state-space equations. An average operator is defined, and applied to the state equation to get averaged mathematical models. Expansion of these models will eventually lead us to average circuit models. Further, the ripple is approximated to provide a correction to the average model. The resulting models produce much faster simulations than their exact devices. Theoretical considerations show that the averaged models agree well with the original system, and this is confirmed by PSPICE and MATLAB simulations. Additionally, experimental results are presented to validate the developed models.