Three Steps to Unlocking the Potential of High-Power Wind Turbines

This is a guest article by Daniel Gerber, Senior Vice President, Global Product Group Manager Wind, System Drives, ABB.

The critical role of wind in the world’s future energy needs is clear: the Ocean Renewable Energy Coalition states that 1,400 gigawatt (GW) of offshore wind power will sustain one tenth of global electricity demand by 2050. Key to achieving this is the upward power rating of wind turbines, which we anticipate will reach an individual turbine capacity of 20 GW within the next five years.

But increasing demand does create challenges. Namely, the infrastructure needed to supply wind power effectively needs to be modernized and scaled up. Yet government subsidies have been reduced, putting pressure on wind farm operators and turbine manufacturers to come up with cost-effective ways to bring about this change. Equally, they cannot compromise on performance, reliability and energy efficiency; they must ensure that both increasing demand and return on investment (ROI) expectations can be met.

A further critical element to the success of this upscaling is compliance with regional grid specifications. This is particularly important from a cost point of view – retrofits to account for grid code changes are expensive. What this means is that manufacturers must conduct large amounts of testing under simulated grid conditions.

Overall, there are three core steps that must be completed to determine the effectiveness of the coming generation of high-power turbines.

Converters are a critical element in the wind turbine’s electrical drivetrain. They regulate the voltage and frequency output of the generator to suit the local grid. When choosing them there are two main options: low (LV) or medium voltage (MV). Years of experience in applying converters in industrial applications has established that low voltage (LV) converters are more cost-effective when running at low power levels, whereas MVs are more effective at high power levels. This also applies to wind turbines.

However, different wind farms will have different requirements, so choosing between LV or MV is not necessarily so simple. Many factors – such as turbine size, power requirements and location (onshore or offshore) – must be taken into account. Existing turbine projects that have been successfully using LV converters often stick with them. Manufacturers have responded to this need and the maximum voltage for new LV converters has risen from 690 V to 990 V.

The result is an overlap between both converter types when the requirement band is between 6 and 12 MW. But as the power output of turbines increases beyond 12 MW the case for switching to MV converters becomes more clear-cut.

For example, MV converters use fewer components and therefore have a smaller footprint than their LV counterparts. This means that MVs are also more cost-effective in terms of material and installation costs. Additionally, the reduced component count means a reduced risk of failure.

MV converters are based on the three-level Neutral Point Clamped (NPC) converter topology in conjunction with integrated gate-commutated thyristor (IGCT) technology. As well as having fewer components, the use of IGCT technology also translates into a high level of reliability.

The transition to MV converters is leading to a decrease in levelized cost of energy (LCOE) based on increased efficiency, improved performance and reliability and lower installation costs.

Major wind energy projects are now using MV converters. For example, GE Renewable Energy’s Dogger Bank Wind Farm in the UK recently took delivery of ABB 95 MV converters. These converters will be fitted to GE’s Haliade-X 13 MW wind turbines.

To test the turbines of the future, facilities must be capable of handling their increased outputs. But 15 MW is beyond most facilities and procedures in use today. That is why the Fraunhofer Institute for Wind Energy Systems (IWES) in Germany is producing a mobile grid simulator designed for high power. It will allow for effective testing of high-power wind turbines rated up to 20 MW.

The simulator is set to begin operations in 2023 and, with a power rating of up to 28 megavolt ampere (MVA) and 80 MVA in the short term, will be the largest of its kind in the world. To make the simulator more flexible, it will be capable of splitting off into two separate units rated at 14 MVA each.

Not only will this allow for the testing of entire wind farms, but it can also test the energy efficiency of the equipment used – a key factor in grid code compliance. Additionally, its modular structure gives it the advantage of near-endless configurations. Whether testing in the field or on test benches, this technology is versatile enough to simulate dynamic, steady-state and fault grid conditions. This flexibility means the simulator will be an ideal proving ground for “grid-of-the-future” scenario research and development.

Wind turbines typically have a lifespan in excess of 20 years and will need to perform at peak capacity throughout. To maximize output over this time, maintenance to both prevent and address breakdown will be essential.

The best way to deliver consistently high performance is to use data-driven digital solutions. This can be achieved by using intelligent sensors installed within the equipment. These sensors enable operators to not only remotely diagnose issues, but also to measure energy usage and accurately forecast any future problems. Since this approach does not require an on-site presence, overall safety and incident response time are both increased.

Essentially, this is allowing for the creation of the wind turbine system’s digital “twin”. This means that any planned alterations to turbines (in terms of capacity, placement of new farms etc.) can be simulated under multiple conditions before a decision is made. When this is connected to the industrial internet of things (IIoT), the software can be constantly updated from any location to accommodate new functionalities and enable further improvements to turbine infrastructure.

In terms of electrical power, there is perhaps no theoretical limit to the power rating of offshore wind turbines. They are, however, limited by real-world mechanical factors such as size, weight and rotation speed. As a result, considerable effort in design and testing is essential to ensure that offshore turbines can be made larger and more powerful, with no compromise in reliability.

The three steps outlined here, especially the adoption of MV converters will be instrumental to the success of the new generation of high-power wind turbines.