22-05-2012, 11:40 AM
Application of a Large Capacity 3-level GCT Inverter to High-speed Compressor
Application of a Large Capacity 3-level.pdf (Size: 1.02 MB / Downloads: 151)
INTRODUCTION
Recently, power semiconductor devices have been
evolving to higher voltage, current, faster switching speed
and lower losses. Especially in the field of Oil and Gas
Industry, large and high speed AC motor drive system
has been introduced in many industries for helping
energy saving with high efficiency. The method of
driving the compressor changed as shown in Fig.1, and
the gas turbine drive method was used as traditional
methods in this industry. It is possible to design large
capacity Voltage Source Inverter (VSI) system because of
the development of advanced technologies for main
circuit along with the devices with high voltage and large
capacity in these days.
Overview of 3-level GCT inverter
the main circuit configuration of the 3-
level GCT VSI drive [3]. TMdriveTM-XL80 is connected
DC voltage with the input of power supply which is
isolated by a transformer, to diode rectifiers which are
connected in series. The input section of the VSI is a 24-
pulse diode rectifier. It decreases input harmonics by
shifting the phase of transformer secondary windings.
The output section of the VSI, supplying the power to the
motor, is a 3-level GCT inverter. The output phase
voltage is 3-level, and the line to line voltage is 5-level.
This inverter has a capacity of 15.8MVA at 3.8kV output
voltage. It is current drive type device GCT thyristor of
6000V-6000A ratings that enables to make in large
capacity. This GCT thyristor is a self turn off type device
that can do turnoff by applying the negative gate current.
Redundant control
In order to maintain the operating rate of the plant, the
reliability and a continuous driving are requested to the
inverter equipment that drives the motor and compressor.
In case of adopting redundant control, two of the same
unit control panels are installed. Only one of two unit
control panels operates the inverter. It is possible to drive
continuously without stopping the system when detecting
a fault and maintaining it with a redundant control
applied to this inverter. A restarting from the
instantaneous power failure