Analysis of linear and nonlinear control of a three-phase/level PWM DC-AC neutral point clamped converter

This paper introduces two control methods for multilevel PWM voltage source power converter (VSC). The first approach consists of a traditional cascaded linear PI regulator while the second presents a fast voltage control scheme applying a nonlinear input-output feedback linearization (IOFL). The system modeling is obtained with the state space model of the VSC in order to meet a constant dc-bus voltage and keep the input power at unity. By IOFL, the system is linearized and decoupled without leading any zero dynamics, and then a feedforward law is derived to account for model error. Simulation results demonstrate the effectiveness response of the two designed issues in steady state and prove that with nonlinear structures, output signal responses become faster than those in cascaded control schemes.