A New Dual Lagrangian Model and Input/Output Feedback Linearization Control of 3-Phase/Level NPC Voltage-Source Rectifier

An input/output feedback linearization control strategy is developed for control of three-level three-phase neutral-point-clamped rectifier using its dual Lagrangian modeling. The load current of the rectifier can be given in two forms: (i) the load current involving the current of capacitor C1 (ii) the load current involving the current of capacitor C2. Applying the obtained load current to the Euler-Lagrange parameters of the rectifier, two nonlinear models of the system are derived. The models are based on the superposition law of the load current and the Euler-Lagrange description of the rectifier. Also, the two power-balance equations between the input and output sides are obtained by considering the effects of two load currents separately. Then, the two nonlinear models and power-balance equations are linearized using input-output feedback linearization, and the state feedback law controlled inputs are completed by pole placement. With the definition of outputs of the feedback linearization law, the zero dynamics of the system are avoided and a fast output voltages control scheme is designed. Finally, some integrators are added to robust control against parasitic elements. The proposed nonlinear controller is compared to the PI controller and the MATLAB/SIMULINK results verify the proposed control strategy.