Page 246 - Modern Control of DC-Based Power Systems

210 Modern Control of DC-Based Power Systems

Figure 5.71 ISPS I L15L25L3 virtual distribution sliding mode for ideal CPL and
30.9-53.4 MW.

5.9 SUMMARY
Throughout this chapter several control approaches were presented:
First their theoretical foundation and then their application on MVDC
ISPS.
This chapter started with the LSF which follows the idea of compen-
sating the nonlinearity so that a linear system is created on which linear
control theory can be applied. This control relies on the measurement of
all states and an exact load model. The synthesis procedure is straightfor-
ward. A decentralized application does not seem to be feasible as perfect
knowledge of the system is needed for appropriate nonlinearity
cancelation.
The second approach was the synergetic control which is a nonlinear
control design method that includes the switching characteristic of a sys-
tem into the design. The synergetic control law seems from the central-
ized design procedure very complex, especially if several converters in
parallel have to be coordinated. While the parameter tuning for the LSF
is mainly a matter of pole placement the selection for the appropriate syn-
ergetic control parameters is coupled to multiple algebraic restrictions, as
not only disturbance rejection is influenced through them but also current
sharing modes. A decentralized variation of the synergetic control is in
the context of the virtual disturbance also possible. The third approach
was nonlinear Immersion and Invariance controller, which has the