Generalized Voltage-based State-Space Modelling of Modular Multilevel
Converters with Constant Equilibrium in Steady-State
(2017)cite arxiv:1706.04959.Аннотация
This paper demonstrates that the sum and difference of the upper and lower
arm voltages are suitable variables for deriving a generalized state-space
model of an MMC which settles at a constant equilibrium in steady-state
operation, while including the internal voltage and current dynamics. The
presented modelling approach allows for separating the multiple frequency
components appearing within the MMC as a first step of the model derivation, to
avoid variables containing multiple frequency components in steady-state. On
this basis, it is shown that Park transformations at three different
frequencies ($+ømega$, $-2ømega$ and $+3ømega$) can be applied for deriving
a model formulation where all state-variables will settle at constant values in
steady-state, corresponding to an equilibrium point of the model. The resulting
model is accurately capturing the internal current and voltage dynamics of a
three-phase MMC, independently from how the control system is implemented. The
main advantage of this model formulation is that it can be linearised, allowing
for eigenvalue-based analysis of the MMC dynamics. Furthermore, the model can
be utilized for control system design by multi-variable methods requiring any
stable equilibrium to be defined by a fixed operating point. Time-domain
simulations in comparison to an established average model of the MMC, as well
as results from a detailed simulation model of an MMC with 400 sub-modules per
arm, are presented as verification of the validity and accuracy of the
developed model.
Описание
Generalized Voltage-based State-Space Modelling of Modular Multilevel
Converters with Constant Equilibrium in Steady-State