Sensitivity analysis of PI cascade control of power converter

Cascade PI control systems have been widely used in the control of two level power converters. In this control system configuration, the cascade control PI controllers are designed using synchronous-frame where in the inner-loop, two PI current controllers are used to control the d and q axis currents while in the outer-loop, a PI controller is used to regulate the voltage for load disturbance rejection. This paper proposes the model based PI controller design using the physical model parameters with specification on desired closed-loop bandwidth. Furthermore, the paper presents the the sensitivity functions in both inner and outer loops systems and discuss their association with respect to robust performance and harmonic attenuation.