O-Linearization Based Current Decoupling Control of Modular Multilevel
Cascade Converters
Abstract
A generic current control system for modular multilevel cascade
converters (MMCCs) is proposed. It is based on (i)
input/output-linearization (I/O-linearization), (ii) feedforward
disturbance compensation and (iii) parallelized
proportional-integral-resonant controllers to compensate for arbitrarily
many harmonics (including positive and negative sequence). The
controller design is performed in state space. It is generic and
flexible and combines pole placement and LQR tuning. Moreover, it allows
to take all system parameters such as cluster or output (grid)
inductances or resistances individually into account during controller
design and tuning. Moreover, the typically imposed simplifying
assumptions on system dynamics (e.g., identical parameters) or operating
conditions (e.g., balanced loading) can be overcome. The proposed
control system is validated for a dual-star bridge-cell MMCC. The
simulation results illustrate its excellent control performance under
ideal but also non-ideal conditions, where conventional approaches
usually fail.