Modeling, analysis, and control of a current source inverter-based STATCOM

This paper presents a new approach for the dynamic control of a current source inverter (CSI)-based STATic synchronous COMpensator (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.