Passivity-based control with dual lagrangian model of four-wire three-level three-phase NPC voltage-source rectifier

This paper presents the EL modeling of the four-wire 3-level 3-phase NPC voltage source rectifier (VSR). The load current of the four-wire 3-level 3-phase 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. So that two EL models will be obtained for four-wire 3-level 3-phase NPC voltage source rectifier. The models are completely in accordance with Kirchoffs circuit theory and superposition law of course. One of the rules is utilized to control the voltage of C₁ and the other is used to control the voltage of C₂. Transforming the EL model from the abc reference frame to dq reference model will completely retain the energy dissipative properties of two models. Having drived the EL models, the control method combined with the techniques of the energy shaping and damping injection applied to the dq frame EL models of the converter. To study the output regulation problem of C₁ and C₂, the voltage indirect control method has been applied to the passivity based controller. To regulate the internal dynamics of the output voltages of C₁ and C₂ an outer loop that consisting PI controller is added to both controller models. To verify the ability of the proposed control method different simulations have been carried out by MATLAM/SIMULINK software. The simulation results clarify the abilities of the new method such as: very low THD, unity power factor, decoupled current loop dynamics, low oscillation in the neutral point potential (NPP).