Modeling Analysis and Control of a Current Source Inverter-Based STATCOM

This article presents a new approach for the dynamic control of a current source inverter (CSI)-based STATCOM. The dq-frame model and the steady-state characteristic of the CSI STATCOM are proposed as a basis for control design. Use of traditional PI controllers leads to a poorly damped high-frequency oscillation between the inductance and capacitance of the CSI output filter. The new approach includes a fast ac current control inner loop and a slower dc current control outer loop. The inner loop, which is a combination of multivariable full state feedback and integral control, allows for rapid nonoscillatory dynamics of the ac current without overshoot or steady-state error. Experimental tests on a 5 kVA laboratory CSI STATCOM setup validate the proposed control design as well as the simulation results.