Teaching older grids new tricks: How power electronics make our grids fit for the energy transition

Power gaps in the grid, faults and fluctuating voltage – the shift to green energy has caused a major upheaval for both transmission system operators and industries, and over the past decade they’ve been turning to an economic power electronic solution for speed, stability and flexibility.

 

By Blas Ulibarri

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Today, if you could pull out a map detailing the transmission systems worldwide, you would find 100 installations of the fastest dynamic voltage stabilizer shoring up power grids on every continent but ice-covered, bleak Antarctica where the population of researchers and staff dwindles down to a cool grand in winter.

 

Let your finger run down to the jungles and plateaus in the Americas or back up to the clover-strewn prairies and there you will find them – power electronic solutions for the grid – even in unlikely regions where weather or geological conditions would seem too severe for even the most robust power electronic solutions: in the hot desert climate of Medina where temperatures can sizzle up to 50 degrees and in the arctic conditions of Alberta where temperatures can plunge so far below zero it turns car tires square.

Better brains and bigger muscle

In the past, simple mechanically switched capacitators were used for reactive power compensation to stabilize voltage in power grids, but response time and control accuracy were limited. The introduction of power electronics has since massively boosted Static Var Compensation (SVC) and Static Synchronous Compensator (STATCOM) technologies. SVC PLUS is Siemens’ advanced STATCOM solution. The power electronics it uses are the powerful muscle that moves the heavy loads of reactive power for dynamic stability. And it’s guided by a proprietary control system or brain that allows for more rapid response times and even subtler modulations during load compensation.

Energy’s abnormal EKG: sags, spikes and blackouts

The popularity and necessity of SVC PLUS among transmission and distribution system operators has grown hand in hand in the last ten years with the popularity and necessity of renewables like wind and solar. And the reason is easy to understand. From coast to coast and pylon to pylon, most of the transmission systems delivering our electricity were built for an all but bygone energy era of large, centralized power plants that delivered a constant supply of power and acted as shock absorbers as large loads tripped in and out of the grid. The systems were neither designed nor built for a large-scale shift to intermittent power sources like wind and solar.

 

Intermittent power sources can cut in and out, can suddenly spike, can suddenly sag, like the display of an abnormal heartbeat on an electrocardiogram (EKG). And these voltage excursions along with line malfunctions and damages can lead to faults that cause your lights to flicker – or worse: go out for good. Think of the India blackout a few years ago that left half the country without electricity or any of the ten major blackouts last year. 

“Investments in SVC PLUS systems have added flexibility to the grid.”
I.S. Jha, former Chairman and Managing Director of PGCIL

The safety net for India’s massive energy transition

Reactive power solutions help operators avoid blackouts caused by excessive loads and surges or insufficient voltage, or blackouts caused by natural catastrophes that might take out one or more parts of the grid. They act as a safety net for all these challenges, especially as power companies transition to renewables. In India, for example, where they have ambitious plans to integrate 175 gigawatts of renewables into the grid, they have also placed the largest SVC PLUS order to date. I.S. Jha, the former Chairman and Managing Director of Power Grid Corporation India Limited (PGCIL) who has now been appointed to the country’s Central Electricity Regulatory Commission (CERC), says that, “these investments have added flexibility to the grid.”

 

Since its first application nearly a decade ago at Thanet Wind Farm off the coast of England (at the time the largest offshore wind farm in the world), SVC PLUS has been supplying grid operators with a flexible, modular solution for grid code compliance, increased power quality and dynamic load compensation. The solution uses modular multilevel convertor (MMC) technology that reduces harmonics and allows it to be built into stackable containers with only a few durable components. It takes up little space on a wind farm like Thanet and responds to voltage fluctuations in a record-breaking 30 milliseconds.

Stand and deliver: the tropics and the Kaikoura quake 

The durability of its components was put to a live test two years ago in Christchurch, New Zealand, where the country’s grid operator Transpower had been using SVC PLUS to increase the amount of power they could transfer and add dynamic voltage support without having to go through a costly and time-consuming investment in new lines. And when the region was struck by an earthquake with a whopping magnitude of 7.8 – damaging bridges and rail lines, collapsing houses and causing landslides that closed down major roads – the SVC PLUS system delivered support at all times.

In that case the solution had been customized beforehand to withstand seismic stress and shows how versatile the system can be to meet the needs and demands of customers. The same goes for the system being used by the Brazilian utility Rio Branco Transmissora de Energia in Rio Branco. There Siemens erected an SVC PLUS system in the thick of the Amazon rainforest where usually metal-damaging humidity can run up to 88 percent and 100 inches of rain can fall per year. “Before SVC PLUS,” says the utility, “Rio Branco suffered blackouts daily due to transmission line power oscillation. It’s truly unprecedented work, and the installation secured power stability.” 

“When the last storm hit, our lights came on faster.”
David Roop, Director of Electric Transmission at Dominion

A solution built for speed in the USA and Germany

In the United States the utility Dominion Energy had a unique request. They already had Siemens SVC PLUS solutions in service for load compensation and “when the last storm hit,” says David Roop, Director of Electric Transmission at Dominion, “our lights came on faster.” But this time they wanted a solution that could be moved around in emergencies for rapid restoration. In other words: They wanted a solution with wheels. So together with Dominion, Siemens developed an SVC PLUS that fits into three easily maneuverable plug-and-play containers. The first of these new mobile reactive power compensators went into operation in the summer of 2018.

 

And wheels aren’t the only thing SVC PLUS is getting. In Germany, the system for grid operator Amprion will be equipped with a newly developed Siemens Active Filter that works like a noise reducer, sifting out background harmonics to provide a clearer voltage. Amprion will use the system to incorporate more renewables into the existing grid and maintain a stable energy transmission when older plants are shut down. This is the first SVC PLUS installation in Germany, with two more currently under construction, and has been running successfully in test operation since last December. The Siemens Active Filter is one more step in creating grids that can adapt to the future.

2019-06-27

Blas Ulibarri is a freelance journalist based in Switzerland.

Combined picture and video credits: independent Medien Design & Yagi Studio DigitalVision via Getty Images

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