Ocean Wave Energy Harvesting 283
jn(t) 6-pulse diode
+ DC bus
C C C
FIGURE 4.63 Grid connection interface for applications using different generators.
using the generator voltage, grid voltage, and the voltage difference between these two.
After each phase–phase voltage comparison, the difference is processed for space vector
computation for use in the inverter switching controller.
A low-pass LC ﬁltering network is used in the fourth stage. The inductance and the
capacitance values for this ﬁlter network should be determined to suppress the higher
frequency components of the inverter output voltage. Thus, the cut-off frequency of the
ﬁlter should be a little bit higher than the grid frequency to avoid ﬁltering the fundamental
frequency component. After the ﬁltering stage, the output of the network is synchronized,
ﬁltered, and qualiﬁed for grid connection. This topology is suitable for applications with
linear generators and three-phase synchronous generators and squirrel cage induction
188.8.131.52 Grid Connection Interface for Induction Generator Applications
There might be several grid connection interfaces for the systems with induction generators
such as an induction generator with a shunt connected static synchronous compensator
(STATCOM), an induction generator in series with full converter, and a DFIG .
184.108.40.206.1 Induction Generator with Shunt-Connected STATCOM
An induction generator with a shunt-connected STATCOM is shown in Figure 4.64.
STATCOM is capable of injecting and absorbing reactive power to the network to over-
come voltage ﬂuctuations. STATCOM is a device with a bidirectional converter and a
capacitor connected to the DC side . The AC side of the STATCOM is used to com-
pensate for the voltage ﬂuctuations and low-voltage ride through (LVRT) . A larger
energy storage device can be employed at the DC side of the STATCOM for compensation
of active power ﬂuctuations originated by the natural behavior of wave power. The mag-
nitude and duration of the voltage drop or swell, generator, and grid parameters are used