Input-state feedback control of a shunt active power filter

A new nonlinear control technique of a three-phase three-wire voltage source inverter used as a shunt active filter is considered in this paper. The exact state space model of the active filter is elaborated in the synchronous 'dq' frame. The model obtained is a nonlinear multi-input multi-output (MIMO) system. It involves two inputs and three outputs which are the state variables of the system. These variables are namely two AC inductor current signals and one DC capacitor voltage signal. The nonlinear multivariable system is highly interconnected; therefore the control of every state variable separately is a difficult task. Based on the nonlinear MIMO model, an input-state feedback linearizing control is derived using an additional third auxiliary input. Hence, the resulting linear model is a decoupled linear system equations. Therefore, a pole placement control strategy is then designed.