2. Introduction
The usage of tidal energy conversion benefits
from the fact that tides can be predicted at a
higher level of accuracy compared to wind and
solar resources.
This is important in the context of smart grid
operation. To better understand the interaction of
tidal energy conversion systems (TECS) when
integrated in a smart grid, simulation can provide
a valuable resource for analysis.
3. Concept of Simulation of Power and
Energy
A tidal cycle lasts 12 hours and 25 minutes, thus,
ebb and flood occur once. Besides this cycle
other cycles exist, e.g. a 14-days cycle with high
spring tide and low neap tide as illustrated in
Figure.
4. The power available in the tidal stream with a tidal
current velocity v is determined by the water density ρ,
and the area A swept by the rotor blades
Ptide = (1 /2)*ρAv3
In order to identify the power generated by the TECS, the
power coefficient cp is to be included in figure. The
parameter cp determines the maximum power generation
for a specific tidal current velocity.
5. Due to available tide tables, good information concerning the power flow
from TECS exists. That can support significantly the design of the smart grid
operation strategy. For example, as seen from Figure 2, maximum power is
available every 14 days. This information is important for the dispatching of
all conventional and renewable power generators. In addition, it can help to
optimize the scheduling for maximum renewable power generation.
6. Concept Of Simulation Of Voltage And
Control
The tidal turbine is directly connected to the generator, which is a
permanent magnet synchronous generator (PMSG).
Due to the variable tidal current velocity the PMSG rotates with
variable speed. In order to connect the TECS to the grid, a
voltage source converter (VSC) is used. The VSC consists of a
generator side converter and a grid side converter. A filter
reduces the harmonics caused by the switching of the insulated
gate bipolar transistors (IGBTs) of the grid side converter. The
transformer increases the voltage to the grid voltage level.
7. A three-phase grid fault is applied at the point of
common coupling (PCC). The fault occurs at 1 s
and is cleared after 150 ms. The grid voltage
Vabc is zero during that time.
8. CONCLUSION
There two types of simulation concepts for a smart
grid with TECS are introduced.
First, the concept for simulation of power and energy
helps to schedule the generation units. By forecasting
the power generated by TECS, the operation of the
participating renewable and conventional generators
in a smart grid can be optimized.
Second, the concept for simulation of voltages and
currents is related to two important topics in power
systems: power quality issues and transients studies
9. Reference
EEA. Tracking progress towards Kyoto and 2020
targets in Europe. Technical Report 7/2010,
European Environment Agency, Copenhagen,
2010.
M. Grant Gross. Oceanography, a View of the
Earth. Prentice-Hall, Englewood Cliffs, New
Jersey, 1987.
J. Hardisty. The Analysis of Tidal Stream Power.
John Wiley & Sons, Chichester, West Sussex,
2009.
