Dual Lagrangian modeling and Lyapunov-based control of three-level three-phase NPC voltage-source rectifier

The load current of three level/phase neutral point clamped rectifier could be expressed in two forms: the load current involving the current of capacitor C1, and the load current involving the current of capacitor C2. Using the Euler-Lagrange model based on the superposition law and the obtained load current, a new dual Lagrangian model of the rectifier is founded in this paper and then the two obtained nonlinear state space models are developed in dq0 reference frame. According to the new model, two positive definite Lyapunov function candidates are defined and a Lyapunov-based control is applied to the rectifier. Each of the function is utilized to control its corresponding output voltage and also both functions are used to keep Neutral Point Potential (NPP) at 0 V. The MATLAB/SIMULINK results showed that: 1. the rectifier can be stabilized globally for handling large-signal disturbances. 2. The rectifier Exhibits good transient response in the rectifying modes. 3. Very low THD 4. The oscillation of the neutral point potential (NPP) is limited 5.Unity power factor.