| Nordex N29/250 further improves the clean image of King Island.
Following a successful tender application, the Hydro-Electric
Corporation a subsidiary of Tasmania’s government, Australia’s most southerly
state, Sterling Wind Pty Ltd, Nordex Balke Dürrs, Australian agents, were contracted to
supply and erect 3 X N29 250 kW. Nordex Balcke-Dürr Wind Turbines on 30 m. tubular towers
for King Island, a 64 kilometre by 27 kilometre remote Island 80 kilometres from the
Australian south coast.
King Island is a popular tourist destination, and its well known for
its fresh produce, being beef, dairy products, fishing and special bottled rain waters.
The three Windturbines have now added to King Island’s clean environment image, and
become the latest tourist attraction on the Island.
Because of the Islands remoteness and fragile environment, it was
extremely important that strict control over environmental standards was maintained by the
Hydro Electric Corporation and Sterling Wind during construction, the H.E.C. have been
carefully planing the Windturbine site to ensure the Windturbines visually would blend
into the landscape and minimise the disturbance and impact of the environment.
The Windturbines were manufactured by Nordex Balcke-Dürr GmbH in
Denmark, they were shipped from Europe to Melbourne in five 40-foot containers and one
20-foot containers.
In Melbourne the containers were loaded on to semitrailers and had
to be ferried to the Island, via mainland Tasmania. including a 100 tonne Demag mobile
crane for unloading, assembly and erection of the equipment
The time schedule was very tight as the mobile crane and the
semitrailers with the containers had to be ready for return shipping to Melbourne within
six days, which allowed only two days for unloading, assembly and erection of each
Windturbine.
Due to the remoteness and the harsh wind conditions on the island
the working conditions, were very difficult with sand storm where the soil had been
disturbed, However, the three Windturbines were all pre-assembled on the ground, ready for
erection five days after the equipment’s arrival to the island, on the sixth day all
three windturbines were erected.
Finally, the Windturbines were successfully commissioned on the
January 23rd 1998 after the Christmas and New Year holidays. After three (3)
months of operating the Windturbines have been running remarkably well and generated over
500,000 kW/h. in total.
The PLC controlled SCR. triggered Wind/Diesel control including a
special Dump load system was designed by Sterling Wind and T~Tech and manufactured by
T~Tech, an Australian Consulting and Engineering a company specialising in Power
Electronic and diesel power generation controls.
The dumpload is connected to the low voltage part of the Wind Farm
feeder:
The dumpload consists of four heating elements ( 35 kW. - 70 kW- 140
kW - 280 kW.) mounted in a cabinet, cooled by fans. The dumpload can be controlled in
steps of 35 kW from 0 to 525 kW.
The heating elements are switched on/off by solid state switches at
zero crossing. This enables the dumpload to change it’s load very fast (once every 20
m/sec). As the solid state switches are fully electronic, their lifetime is much longer
than any mechanical moving device.
The solid state switches are controlled via digital outputs of a
dedicated PLC. communicating with the Diesel Power Station Controller providing optimal
power level from the Wind Farm. The same PLC will turn On and Off Windturbines as required
for regulation.
The control system is expandable up to 100% of wind power generation
using the same strategy and equipment with future additions of more Windturbines where the
system can run with all Diesel power shut down, with this existing system it has been
proved during commissioning that the system can operate with at least 85% of the energy
from wind power, with the system still being stabile, including Voltage and Frequency.
The active power output from the wind park is controlled by
start/stop of one or more wind turbines and by switching heating elements in the dumpload
on/off. The dumpload can be controlled in steps of 35 kW. from 0 to 525 kW.
The set point for the primary (relatively slow) controller in the
cascade control loop for active power can be either:-
1. A maximum wind park output, set by the diesel power plant
operator, or
2. Calculated on the basis of a percentage of penetration, set by
the diesel power plant operator, or
3. Calculated on the basis of a percentage minimum load on the
diesel(s) in operation, set by the diesel power plant operator. This method has been used
successfully in previously, or
4. Calculated in a mathematical model, based upon more of the above
parameters.
The set point for the secondary (fast) controller will be the
present wind park output. This will largely minimise the consequence of fluctuating wind
power.
When the dumpload is unable to keep the output down at the set
point, a wind turbine is stopped. The turbine to be stopped will always be the one with
the highest number of hours in operation.
When the start wind is achieved at more than one Windturbines at the
same time, the control system sends the start signals to the turbines with a delay of one
minute between each start.
An operator initiated stop (chosen from the power plant control
system) overrules the wind park control system and must be reset from the diesel power
plant before the turbines can be started.
When the active power is controlled as suggested above, utilisation
of the available wind power can be pushed to a high limit without endangering the
integrity and power quality of the grid.
It should be noted that especially on small, weak grids, stall
controlled wind turbines with dumpload control are superior to pitch controlled turbines.
1. The dumpload control is much faster than the pitch control and
therefore, able to ease the influence of fluctuating wind conditions when using a stall
regulated Windturbine.
The PLC is connected to the diesel power plant’s PC. though
optical fibre serial communication link.
Control of the relevant digital signals (circuit breaker status,
etc.) from the diesel power plant (via digital inputs or RS 232C).
The control system is expandable for more than 100% future
additions.
CONTROL SYSTEM SOFTWARE
The software is divided into the following three groups:-
PLC Logic Control Software.
1.The software is s programmed in logic ladder program. It controls
the dumpload unit.
2.Start/stop of the wind turbines.
3.Monitoring various grid feeder and Diesel Station Load.
The control systems enables the fully automatic operation of the
Windturbines in parallel with the Hydros existing diesel power station, which was build
and commissioned in 1985 and is well maintained in excellent operating condition and
appearance. It is fully automatic, capable of operating unattended for periods up to 48
hours.
Existing Diesel Power Station And Facilities.
Four (4) X 1200 kW. diesel generators with unit transformers,
operating at 1500 rpm. And in parallel connection to the Diesel Power Station’s 11
kV. Bus. Varying demands result in operating loads ranging from a night time minimum of
850 kW. to a day time maximum of 2700 kW. controls are fully programmable and logic
schedules as follows:
System Load: Operating Generators:
Load < 1100 kW. 1200 kW. (1 X 1200)
1100 < Load < 2200 kW. 2400 kW. (2 X 1200)
Load > 2200 kW. 3600 kW. (3 X 1200)
With the average annual wind speed of 9.5 m/Sec. the site is exposed
to the "roaring 40s" that are predominantly westerly winds making King Island
one of the best wind regime areas in Australia.
Estimated power generated by this project of 3,000,000 kW/h.
annually, enabling savings in diesel costs of A$500,000.00 per year.
Further reduction in maintenance and overhaul cost of diesel
generators are achieved by reduced operating hours, where at times one diesel generator
can be shut down due to high generation from the wind farm.
The wind farm will supply 20% of the Islands power needs, and it is
expected that further equipment will be required from the H.E.C. to increase the size of
wind farm for further reduction in diesel fuel consumption.
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