Virtual-sensor-based control of PWM current source rectifiers

High performance control strategies applied to pulse-width modulated current source rectifiers (PWM-CSR) require sensing of the supply currents, the input capacitor voltages, and synchronization with the AC supply voltage in addition to the DC voltage and current sensors used for protection purposes. For instance, control strategies developed to provide the necessary input line current damping-thus avoiding the need for damping resistors-and decoupled control of the active and reactive instantaneous powers, require the sensing of the supply currents and input capacitor voltages. As a result, a large number of sensors is needed and the over all reliability is therefore reduced. This paper proposes a technique based on virtual sensors to provide the required AC current and voltage values without actually sensing the electrical variables. The technique takes into account the nonlinear model of the PWM-CSR by using the information from the DC current and DC voltage sensors in combination with a linear state observer and a linear parameter identification algorithm. As a result, at least four sensors can be eliminated, while the features of the control strategy are preserved. The paper includes a complete formulation of the virtual sensor based algorithm and its application to the control of active and reactive instantaneous powers in a PWM-CSR. Results are presented to confirm the validity of the theoretical considerations.