Reactive power and unbalance compensation using STATCOM with dissipativity-based control

The paper investigates the use of dissipativity-based control for voltage sourced inverters (VSI) applied as reactive power and unbalance compensators, such as STATCOMs. The approach relies on a frequency domain modeling of system dynamics using both positive sequence and negative sequence dynamic components. The proposed approach can deal with unbalanced supply voltages and perform regulation of AC unbalanced currents, even for those VSI inverters where, due to switching frequency limitations, stationary frame regulators do not have enough bandwidth to cope with reference tracking. The passivity-based procedure is investigated in terms of adaptive terms, anti-wind-up limitations and decoupling between the DC link and AC current regulations, together with stability and convergence proofs. Finally, the paper explores a sequence of simplifications and adjustments that reduce the adaptive controller to PI structures with feedforward for positive and negative sequence components, thus establishing a downward compatibility with standard industrial practice.