Civil Engineering Reference
In-Depth Information
11
Power Elect
ronics
The power electronic circuits in wind and photovoltaic power systems basi-
cally perform the following functions:
•
convert AC into DC.
•
convert DC into AC.
•
control voltage.
•
control frequency.
•
convert DC into DC.
These functions are performed by solid state semiconductor devices peri-
odically switched on and off at desired frequency. In terms of applications,
no other technology has brought greater change in power engineering, or
holds greater potential of bringing improvements in the future, than the
power electronic devices and circuits. In this chapter, we review the power
electronic circuits used in modern wind and photovoltaic power systems.
11.1
Basic Switching Devices
A great variety of solid state devices is available in the market. Some of the
more commonly used devices are as follows:
•
bipolar junction transistor (BJT).
•
metal-oxide semiconducting field effect transistor (MOSFET).
•
insulated gate bipolar transistor (IGBT).
•
silicon controlled rectifier (SCR), also known as the thyristor.
•
gate turn off thyristor (GTO).
For specific application, the choice depends on the power, voltage, current,
and the frequency requirement of the system. A common feature among
these devices is that all are three-terminal devices as shown in their generally
