Grid operators are turning to technology to ensure grid stability and efficiency. With the ever-increasing incorporation of power generation and renewable energy, STATCOM technologies can help operators adapt and prepare for the future energy transformation.
By Stephen Ballard
Transmission grids are undergoing fundamental changes in terms of power generation. With the high penetration of renewable generation and ever-growing demand, power quality, and dynamic grid stability are at risk due to the lack of synchronous power generation.
This forces grid operators to look for technology solutions to help them stabilize the grid and ensure that the electricity keeps flowing. One answer to this is static synchronous compensators, a regulating device used on alternating current electricity transmission networks. It is based on a power electronics voltage-source converter and can act as either a source or sink of reactive AC power to an electricity network.
It is a technology that Siemens Energy has been deploying for some time, and in late June 2019, in Germany, it celebrated the installation of its 100th STATCOM. These devices are particularly relevant today, with the ever-increasing incorporation of inverter-connected generators tied to wind and solar power.
German energy transition
The energy transformation in Germany, widely known as the Energiewende, is the country's planned transition to a low-carbon, nuclear-free economy. Initially, Siemens Energy built grids with the generation as close as possible to the consumer. Those were the days of coal and nuclear plants within the region of the cities where people would have the most use for that energy. Now and for the future, the challenge is to limit carbon dioxide emissions.
Renewable energy is the answer, but this is usually not available near the urban centers that need electricity. One of the places where the wind is strongest is offshore. The difficulty for grid operators was how to get this energy to the people who needed it. In this case, grid access solutions, such as high-voltage direct-current (HVDC), ensured that power was delivered to shore with minimal loss.
Another element of the energy transition is the move away from nuclear power. Germany will cease the use of nuclear power by 2022. Nuclear plants are mostly located in the southern part of the country, where there is a significant electricity demand. In the future, renewable power will have to be transmitted from the North to the South's load centers. The transmission system was never designed to carry such heavy loads over long distances. One solution has been the addition of volt-ampere reactive (VAR) compensators to ensure power supply from the north to the southernmost parts of the country. A similar situation exists in California, where there is a lot of renewable generation, a vast grid, huge distances, and fewer people. In California, grid operators have overcome these problems by using STATCOM.
The challenge for grid operators is that energy production is volatile. When operating overhead lines with high load and low load, operators need VAR compensation. Reactive power can be inductive or capacitive in a considerable amount. Those differences get magnified because the transmission distances are increasing.
"The challenge is that we even have to modernize our existing grid. Electricity demand is increasing, so control software and hardware have to be updated. We see that we will have an increasing demand for VAR compensators, as well as increasing electronics to get the grid really working well."Ludger Meier, Head of Operations and Engineering at the German grid operator Amprion
Transmission networks worldwide
Germany has a very dense population that lives in a very narrow country. The country has learned to react over short distances to ensure the stability of the grid and therefore suffer no outages. However, there are different challenges in other parts of the world. One thing remains constant, and that is how to get a stable voltage level and power supply. In the United States, there are quite different ideas on how to do this. In Texas, they have exceptionally low density, while in New England, the networks can be very dense and convoluted.
In Brazil, most people live on the coasts, while power generation is in the rain forests. The power is generated in the north, far away from where it needs to be moved to the cities. In Chile, they also have long distances, along with high altitude. The generation is in the far North, and far South, so the population lives in-between.
Whereas India has an enormous population, but some do not have access to electricity. It is much easier to stabilize the existing network than build a new line because it is crowded. Every country has a different situation, but we all need stabilization.
Opportunities and challenges from digitalization and electrification
The challenge the energy sector faces is the need to modernize existing grids. The demand for electricity is increasing, so control software and hardware have to be updated. One of the main focuses of electrification is the rise in electric vehicles (EVs), but that is more of a concern for the grid's distribution level than transmission operators.
The more fundamental challenge for transmission grid operators is how to keep it affordable to run the grid. How much investment is needed, and how to drive an increase in use. How to forecast the patterns and how to react quickly.
Future gazing
Moving forward, the trend of urbanization is expected to continue with rising populations in all the cities around the world. Coupled with this is a greater public resistance for building new infrastructure and a reduction of investment to keep electricity affordable. The third driver is that the growing penetration of renewable resources makes it harder for grid operators to forecast generation. This is where power electronics come to the fore by allowing operators to adapt more effectively to generation fluctuations. For Siemens Energy, this means that looking to the future, we expect to see an increasing demand for VAR compensators and increased use of electronics to ensure that the grid continues to perform optimally whatever challenges it faces.
Download the brochure on the latest innovation in STATCOM tech
While grids are undergoing fundamental changes in terms of power generation, renewable infeed and ever-growing demand, power quality and dynamic grid stability are at risk due to less synchronous power generation. With SVC PLUS frequency stabilizer, Siemens Energy further enhanced the capabilities of a STATCOM with modular multilevel converter technology to also support fast frequency response. Whenever your applications require a highly dynamic solution for voltage regulation and fast frequency support, the SVC PLUS FS is the first choice.
Stephen Ballard is a freelance technical author based in London.
Combined picture credits: Siemens Energy, Getty images