Standalone hybrid generation system for the remote area of Thar, Pakistan
2.7.6. Mixed-coupled Hybrid Power Systems
In hybrid-coupled system as shown in Fig. 1.3, various DG sources are
connected to the dc or ac
buses of the hybrid system.
In this application, some energy sources
can be implemented directly
without the use of a power electronic interfacing system.
As a result,
the system can operate with
higher efficiency and reduced cost. However, control and energy
management can be more
complicated than with dc-coupled and ac-coupled systems..
Fig. 2.39: AC-coupled sources connected with DC-coupled sources or mixed HPSs.
A comparison of mixed, AC- and DC-coupled systems show that AC-coupled systems have numerous
advantages [29] such as standardized coupling of different components, off-the-shelf grid components
can be used, simplified design
and operation of island grids, compatibility
with existing grids,
reduction of system costs, increased reliability of electrical power supply as well as expandability.
DC integration in many cases involves high costs for engineering, hardware, repair and maintenance;
and more importantly power system expandability for covering needs of growing energy and power
demand is also difficult with DC integration [28].
Different coupling schemes have their own appropriate applications. If the major generation sources
generate dc power and there is a substantial dc load in the system, a dc-coupling system is preferable.
On the other hand, if the main power systems are ac with substantial ac loads, an ac-coupled system is
preferred. If the major power generation system is a
combination of ac and dc power,
then hybrid-
coupled system is the best.
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