Page 10 - Industrial Technology July 2021

INDUSTRY

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Improving wind power quality

THE CHOICE OF GENERATOR PLAYS A KEY ROLE IN CONSISTENT WIND POWER OUTPUT

he Danish government recently made history reliability for consumers. For wind to be upscaled for winds,” says Bruckner. “In such scenarios, it is not
with the commission of the world’s first energy widespread use – as is the case with Denmark’s energy possible to control the generator output in the same way
island. The island will house 200 giant wind island – the inconsistent, unpredictable input needs to be due to the high rotor voltage.
Tturbines to power three million households converted into a consistent, reliable output. “If high voltages aren’t appropriately managed, they
across Denmark, and could support neighbouring nations This is where generator choice plays a huge role in can lead to high currents and amplified voltage
such as Germany and the UK. Although wind is maximising the wind power capture of a turbine, which in transients, which in turn can destroy elements of
abundant, ensuring a consistent, high-quality power turn determines its ability to produce a high-quality generator systems such as the converter diodes.
output can be challenging. power output as cost-effectively as possible. “Consistency Therefore, preventing high rotor voltages is essential to
With COP26, the latest United Nations climate is key,” says Bruckner. “Wind turbine generators have an avoiding equipment failure and power outage on the
change summit, on the horizon, many countries are operational range – the minimum and maximum wind grid.”
recognising the urgent need to effectively reduce speeds at which the generator connects to the power To protect DFIGs, a crowbar circuit is used. If the
emissions from their power sectors. The International grid. Maximising this range to include the widest scope of rotor current reaches its upper limit, crowbar resistors,
Renewable Energy Agency (IRENA) has recognised that speeds possible is essential to providing a reliable power which are connected directly to the rotor windings of a
scaling up wind power will play an essential role in output.” DFIG, prevent damage to the generator by disconnecting
decarbonising power generation. One of the most common generator types is the the convertor. Crowbar resistors are designed with a low
Simone Bruckner, managing director of power resistor doubly fed induction generator (DFIG), which enables inductance to reduce the impact of high transient
manufacturer Cressall Resistors, says: “Wind is in wind turbines to operate at variable speeds. The stator frequencies, and can withstand high currents while
plentiful global supply with no geographical limitations, windings of the DFIG are integrated directly into the remaining operational.
meaning that all nations can tap into this valuable power grid, while the rotor windings are connected to a “Commissioning large wind turbine projects, such as
resource. However, when it comes to power generation, convertor via slip rings. The advantage of this system is the Danish energy island, is essential to increasing the
its inconsistency can present a problem. Wind speed that the rotor frequency, which directly correlates to wind renewable input of our power grids,” Bruckner concludes.
constantly fluctuates depending on atmospheric pressure, speed, can freely differ from the grid frequency, which in “However, increasing the quantity of turbines alone will
which results in a variable power input for wind turbines. the UK is 50 Hertz (Hz). not allow us to reach renewable power targets. Using
While everywhere can use wind, it’s difficult to guarantee The converter separates the input and output of the electrical components, like DFIGs, which are specifically
its availability and secure a consistent power supply on a generator, allowing for a consistent output of power from designed with the challenges of wind power in mind,
day-to-day basis.” the stator into the grid, regardless of the input speed into allows for high-quality power generation that could secure
With a rising proportion of the grid coming from the generator from the wind turbine. “One challenge to the renewable grid for the sustainable future of our
variable renewable sources like wind power, there needs DFIG function arises if the rotor speed exceeds the planet.
to be adequate measures to ensure grid stability and operational range of the system due to extremely high MORE INFORMATION: www.cressall.com

10 INDUSTRIAL TECHNOLOGY • July 2021