Civil Engineering Reference
In-Depth Information
To remedy the instability problem indicated above, the stand-alone induc-
tion generator must always have some minimum load, dummy if necessary,
permanently connected to its terminals.
12.4
Hybrid System
12.4.1 Hybrid with Diesel
The certainty of meeting load demands at all times is greatly enhanced by
the hybrid system using more than one power source. Most hybrids use
diesel generator with pv or wind, since diesel provides more predictable
power on demand. In some hybrids, batteries are used in addition to the
diesel generator. The batteries meet the daily load fluctuation, and the diesel
generator takes care of the long-term fluctuations. For example, the diesel
generator is used in the worst case weather condition, such as extended
overcasts or windless days or weeks.
Figure 12-6
is one of the largest pv-diesel hybrid systems installed in
California. The project was part of the Environmental Protection Agency's
PV-Diesel Program.
Figure 12-7
is a schematic layout of the wind/diesel/battery hybrid sys-
tem. The power connection and control unit (PCCU) provides a central place
to make organized connections of most system components. In addition, the
PCCU houses the following components:
•
battery charge and discharge regulators.
•
transfer switches and protection circuit breakers.
•
power flow meters.
•
mode controller.
Figure 12-8
is a commercially available PCCU for hybrid power systems.
The transient analysis of the integrated wind-pv-diesel requires an exten-
sive model that takes the necessary input data and event definitions for
computer simulation.
3
12.4.2
Hybrid with Fuel Cell
In stand-alone renewable power systems of hybrid designs, the fuel cell has
the potential to replace the diesel engine in urban areas. In these applications,
the diesel engine would be undesirables due to its environmental negatives.
The airborne emission of fuel cell power plant is 25 grams per MWh delivered.
