LQ control of sinusoidal current PWM rectifiers

A new design method based on linear quadratic control theory is developed for the design of PWM rectifiers with sinusoidal input current. PWM rectifiers are promising because they can supply DC power while keeping a sinusoidal current with unity in the fundamental power factor. There are two types, a voltage-fed rectifier and a current-fed rectifier. The former is required to simultaneously control both the fundamental power factor and direct voltage, while the latter does so for both the fundamental power factor and direct current. State feedback control is essentially suited for multi-input and multi-output systems such as these. Here a discrete-time optimal regulator is applied to their control because it provides a microprocessor-based robust feedback system without steady-state errors in response to a step reference and/or disturbance change. The regulator is implemented using a digital signal processor. Experimental results demonstrate the validity.