Page 44 - Modern Control of DC-Based Power Systems

Overview—Voltage Stabilization of Constant Power Loads 9

This book will present how some of those control concepts can be
applied to systems composed of multiple loads and multiple DC DC
converters connected to the same bus.

1.5 SUMMARY
This chapter presented an introduction to the so-called negative
incremental resistance and the resulting endangering of voltage stability.
Afterwards, a literature overview about several methods to compensate
CPLs was given. Those methods can be divided into two distinct families
depicted in Fig. 1.8.
The first one is a passive compensation approach: it relies on installing
a passive filter in front of the CPL. This method does not require modifi-
cation of the control system and is well suited to handle cases where nei-
ther the bus feeder control nor the CPL are modifiable.
Nevertheless, the use of such methods will increase the size (weight,
mass) of the system which may be very penalizing for some applications,
such as aeronautics or naval systems. In these cases, one might consider
the implementation of stabilizing controls on the system, which points to
the second approach.
The second approach is an active approach. It relies on control techni-
ques for compensating the CPL: depending on whether the DC bus will
be controlled or not, it can be further classified as being in load side con-
trol or generation side/feeder control.
The load side control relies on adapting CPL and its impact on the
stability of the network. Of course, this needs to have access to the con-
trol of the load. This method, if it is applied, must be considered during

Compensating Constant Power Loads (CPLs)

Passive Active

Compensation by Load side control Generation side control
intermediate or
circuit feeder control
Figure 1.8 Compensating Constant Power Loads.