Equation
Lieutenant General
He didn't have to say "I'm telling ya in Britain we're doomed..." because they have been "doomed' since the USA took them over about a century ago before. And course soon to be China as the next super power.
News on China's scientific and technological development.
- Thread starter Quickie
- Start date
He didn't have to say "I'm telling ya in Britain we're doomed..." because they have been "doomed' since the USA took them over about a century ago before. And course soon to be China as the next super power.
Jura The idiot
General
now noticed the tweet
China's first bullet train that allows for the compartments to be rearranged is ready to be rolled off the factory floor on Feb 22. It is an upgrade of existing one which has 8 or 16 fixed compartments. The new "transformer-like" train increase the seating capacity by 70%.
China's first bullet train that allows for the compartments to be rearranged is ready to be rolled off the factory floor on Feb 22. It is an upgrade of existing one which has 8 or 16 fixed compartments. The new "transformer-like" train increase the seating capacity by 70%.
Jura The idiot
General
antiterror13
Brigadier
China contributes most to global greenery expansion
China is the source of a quarter of global increase in green leaf area between 2000 and 2017, ranking the first in the world regarding the contribution rate, said a recent study by the US National Aeronautics and Space Administration (NASA).
In recent 20 years, China’s forest area and stock volume kept growing, making China a country of the world’s largest increase in forest resources, according to the country’s National Forestry and Grassland Administration.
China forest area stands at 208 million hectares and the forest stock volume 15.137 billion cubic meters. 21.63 percent of the country’s territory is covered by forests, according to the eighth national investigation on forest inventory.
China saw a rapid rise of forests and grasslands in the recent two decades. It thoroughly implemented key projects, conducted voluntary tree-planting campaign among the citizens, promoted forestation in both governmental departments and the society, and enhanced efforts in grassland ecological protection.
As a result, the coverage of China’s man-made forest has reached 786,667 square kilometers, topping other countries around the world. In addition, China has nearly 4 million square kilometers of natural grasslands, with a grassland comprehensive vegetation coverage reaching 55.3 percent.
Key forestation projects played a significant role in making China greener. China has created 298,000 square kilometers of forest since the Grain for Green Program was launched in 1999, raising the forest coverage rate in project areas by 3.6 percentage points. In addition, 1.296 million square kilometers of natural forests were well preserved in the past 20 years thanks to the Natural Forest Protection Project.
China has launched a series of major projects to restore ecology, including the treatment project of desertification in the source area of the sand and dust endangering Beijing and Tianjin, and wetland restoration programs. By doing so, forest coverage in those areas steadily increased and desertification was effectively curbed, and ecological situation substantially improved.
The coverage of China’s desertification and sandy land showed a descending trend over three consecutive monitoring periods. In late 1990s, China’s total sandy land was expanding by 3,436 square kilometers on a yearly basis, but now it is shrinking by an average of 1,980 square kilometers per year. It is a historical change from “sand advancing and people retreating” to “green advancing and sand retreating.”
To date, China has built more than 11,000 natural protection areas including nature reserves, forest parks, wetland parks, scenic spots, geological parks and special marine protection areas or marine parks, protecting 90 percent of terrestrial ecosystem types, 85 percent of wildlife species, 65 percent of higher plant communities and 50.3 percent of natural wetlands.
China is the source of a quarter of global increase in green leaf area between 2000 and 2017, ranking the first in the world regarding the contribution rate, said a recent study by the US National Aeronautics and Space Administration (NASA).
In recent 20 years, China’s forest area and stock volume kept growing, making China a country of the world’s largest increase in forest resources, according to the country’s National Forestry and Grassland Administration.
China forest area stands at 208 million hectares and the forest stock volume 15.137 billion cubic meters. 21.63 percent of the country’s territory is covered by forests, according to the eighth national investigation on forest inventory.
China saw a rapid rise of forests and grasslands in the recent two decades. It thoroughly implemented key projects, conducted voluntary tree-planting campaign among the citizens, promoted forestation in both governmental departments and the society, and enhanced efforts in grassland ecological protection.
As a result, the coverage of China’s man-made forest has reached 786,667 square kilometers, topping other countries around the world. In addition, China has nearly 4 million square kilometers of natural grasslands, with a grassland comprehensive vegetation coverage reaching 55.3 percent.
Key forestation projects played a significant role in making China greener. China has created 298,000 square kilometers of forest since the Grain for Green Program was launched in 1999, raising the forest coverage rate in project areas by 3.6 percentage points. In addition, 1.296 million square kilometers of natural forests were well preserved in the past 20 years thanks to the Natural Forest Protection Project.
China has launched a series of major projects to restore ecology, including the treatment project of desertification in the source area of the sand and dust endangering Beijing and Tianjin, and wetland restoration programs. By doing so, forest coverage in those areas steadily increased and desertification was effectively curbed, and ecological situation substantially improved.
The coverage of China’s desertification and sandy land showed a descending trend over three consecutive monitoring periods. In late 1990s, China’s total sandy land was expanding by 3,436 square kilometers on a yearly basis, but now it is shrinking by an average of 1,980 square kilometers per year. It is a historical change from “sand advancing and people retreating” to “green advancing and sand retreating.”
To date, China has built more than 11,000 natural protection areas including nature reserves, forest parks, wetland parks, scenic spots, geological parks and special marine protection areas or marine parks, protecting 90 percent of terrestrial ecosystem types, 85 percent of wildlife species, 65 percent of higher plant communities and 50.3 percent of natural wetlands.
Jura The idiot
General
now noticed the tweet
Chinese scientists are exploring the possibility of setting up a space-based solar power station, which is expected to reduce pollution back on Earth and mitigate energy shortfalls. Researchers have begun designs on a testing facility in Chongqing, local media reported.
Chinese scientists are exploring the possibility of setting up a space-based solar power station, which is expected to reduce pollution back on Earth and mitigate energy shortfalls. Researchers have begun designs on a testing facility in Chongqing, local media reported.
Jura The idiot
General
now noticed the tweet
The lander of China’s Chang’e-4 probe awoke at 7:52 am (GMT+8) on Friday to start working on its 3rd lunar day on the moon. The moon rover Yutu-2 had woken up earlier on February 28 and is in normal operation.
The lander of China’s Chang’e-4 probe awoke at 7:52 am (GMT+8) on Friday to start working on its 3rd lunar day on the moon. The moon rover Yutu-2 had woken up earlier on February 28 and is in normal operation.
Jura The idiot
General
now noticed the tweet
A recent scientific breakthrough made jointly by scientists in China and the United States will enable mammals to see in the dark, and also serve as the basis for fixing human beings color blindness. The achievement was published on Friday on the journal Cell.
***
adding
A recent scientific breakthrough made jointly by scientists in China and the United States will enable mammals to see in the dark, and also serve as the basis for fixing human beings color blindness. The achievement was published on Friday on the journal Cell.
***
adding
You can smell the American primordial fear when and where China is at the forefront.
"Even as State Grid irons out the kinks in its UHV grids, the company is pushing its equipment and expertise abroad. It has led the creation of nine UHV standards through the International Electrotechnical Commission and the IEEE—a move that researchers at Argonne National Laboratory, in Illinois, warned would help Chinese suppliers “crowd others out of the global market” [PDF]."
China’s Ambitious Plan to Build the World’s Biggest Supergrid
A massive expansion leads to the first ultrahigh-voltage AC-DC power grid
By Peter Fairley
Wind rips across an isolated utility station in northwestern China’s desolate Gansu Corridor. More than 2,000 years ago, Silk Road traders from Central Asia and Europe crossed this arid, narrow plain, threading between forbidding mountains to the south and the Gobi Desert to the north, bearing precious cargo bound for Imperial Beijing. Today the corridor carries a distinctly modern commodity: gigawatts of electricity destined for the megacities of eastern China. One waypoint on that journey is this ultrahigh-voltage (UHV) converter station outside the city of Jiuquan, in Gansu province.
Electricity from the region’s wind turbines, solar farms, and coal-fired power plants arrives at the station as alternating current. Two dozen 500-metric-ton transformers feed the AC into a cavernous hall, where AC-DC converter circuits hang from the 28-meter-high ceiling, emitting a penetrating, incessant buzz. Within each circuit, solid-state switches known as thyristors chew up the AC and spit it out as DC flowing at 800 kilovolts.
From here, the transmission line traverses three more provinces before terminating at a sister station in Hunan province, more than 2,300 kilometers away. There, the DC is converted back to AC, to be fed onto the regional power grid. Since it opened in mid-2017, the 26.2 billion yuan (US $3.9 billion) Gansu–Hunan transmission line has moved about 24 terawatt-hours.
The sheer scale of the new line and the advanced grid technology that’s been developed to support it dwarf anything going on in pretty much any other country. And yet, here in China, it’s just one of 22 such ultrahigh-voltage megaprojects that grid operators have built over the past decade. In the northwestern region of Xinjiang, China recently switched on its largest UHV link: a 1,100-kV DC circuit that cost over 40.7 billion yuan. The new line’s taller transmission towers and beefier wires parallel the Gansu–Hunan line through the Gansu Corridor, before diverting to Anhui province in the east.
The result of all this effort is an emerging nationwide supergrid that will interconnect China’s six regional grids and rectify the huge geographic mismatch between where China produces its cleanest power (in the north and west) and where power is consumed (in the densely populated east). By using higher voltages of direct current, which flows through conductors more uniformly than does alternating current, the new transmission lines dramatically reduce the amount of power that’s lost along the way.
But even as China celebrates the completion of more than 30,000 km of UHV lines, power engineers are struggling to master the resulting hybrid AC-DC transmission system. They must ensure that the new long-haul DC lines don’t destabilize China’s regional AC grids. For example, if the 8-gigawatt DC line from Gansu were to unexpectedly go off line, the power shock could cause widespread blackouts in Hunan and beyond.
To minimize the threat, the State Grid Corp. of China, a state-owned company that runs most of China’s transmission and distribution grids, intentionally limits the line’s throughput to no more than 4.5 GW. In practice, the line has carried less than one-quarter of its design capacity on average. That’s one reason why over one-third of Gansu province’s theoretical wind output and one-fifth of its solar potential went unused in 2017. Other UHV lines in neighboring regions have similarly operated below capacity. And eastern provinces don’t have sufficient incentive to import the cleaner power that the UHV lines offer.
The ultimate solution to both issues, according to State Grid engineers, is to double down on UHV. They argue that the country must move far more energy via UHV DC to maximize the use of renewable energy while slashing reliance on coal. State Grid is also building a world-leading set of ultrahigh-voltage AC lines, to help eastern China’s regional AC grids absorb the output from those massive lines.
“The UHV AC power grid is like a deep-water port, and the UHV DC is like a 10,000-ton ship. Only the deep-water port can support the 10,000-ton ship,” says Qin Xiaohui, vice director of power system planning with State Grid’s China Electric Power Research Institute, in Beijing.
Meanwhile, power authorities everywhere are watching. Gregory Reed, a DC transmission expert who runs the University of Pittsburgh’s Center for Energy, says China’s UHV grid puts it far ahead of the rest of the world. “They’re investing significantly, and they’ve gone right to the highest levels of technology capability from day one. There’s no comparison anywhere else in the world. It’s like we’re all still pedaling our bicycles, while the Formula 1 race car goes flying by.”
China’s UHV movement was born of a limo ride. It was late 2004, and Liu Zhenya, then president of State Grid, was sharing a car with Ma Kai, minister of the National Development and Reform Commission (NDRC), the powerful state body that regulates China’s growth and major investments. As Chinese policy expert Yi-chong Xu describes in her 2017 book Sinews of Power (Oxford University Press), Ma complained of the crippling power shortages of the day. Liu blamed “weak and fragmented” grids, ones ill-equipped to exchange bulk power. And he proposed a bold solution: massive cross-country power lines utilizing the most advanced UHV technologies.
Within a year, Ma’s NDRC had approved an ambitious and comprehensive plan that embraced Liu’s vision. It combined UHV DC lines, which excel at moving bulk power from one spot to another over long distances, and a UHV AC backbone to reliably distribute that power to consumers. State Grid would lead the engineering and ensure that domestic suppliers would manufacture 90 percent of the UHV equipment, thus building up a new high-tech export sector for China.
Over the next decade, Liu delivered. He put some 2,000 State Grid engineers on the project and funded more than 300 professors and 1,000 graduate students at Chinese universities to conduct power-grid-related R&D. State Grid expanded and refocused its research centers to attack specific UHV issues, including how to safely handle the higher electromagnetic fields and the more potent impulses during switching and faults.
In January 2009, State Grid energized its first UHV demonstration line—a 650-km, 1,000-kV UHV AC transmission line that linked the North China and Central China regional grids. Ten years on, State Grid has completed 19 of 30 proposed UHV lines.
That aggressive build-out has helped fast-growing urban centers such as Shanghai stave off power shortages despite delays in the expansion of China’s nuclear power capacity and constraints on local coal power due to air-quality concerns. The new UHV grid is also helping the country lead the global transition to renewable generation, moving 161.5 terawatt-hours of hydro, wind, and solar energy in 2017 alone.
ABB, Siemens, and other international power-technology companies have been instrumental in developing and validating key components of the Chinese UHV grid. But State Grid has insisted on sharing the intellectual property for the technologies developed at its behest.
"Even as State Grid irons out the kinks in its UHV grids, the company is pushing its equipment and expertise abroad. It has led the creation of nine UHV standards through the International Electrotechnical Commission and the IEEE—a move that researchers at Argonne National Laboratory, in Illinois, warned would help Chinese suppliers “crowd others out of the global market” [PDF]."
China’s Ambitious Plan to Build the World’s Biggest Supergrid
A massive expansion leads to the first ultrahigh-voltage AC-DC power grid
By Peter Fairley
Wind rips across an isolated utility station in northwestern China’s desolate Gansu Corridor. More than 2,000 years ago, Silk Road traders from Central Asia and Europe crossed this arid, narrow plain, threading between forbidding mountains to the south and the Gobi Desert to the north, bearing precious cargo bound for Imperial Beijing. Today the corridor carries a distinctly modern commodity: gigawatts of electricity destined for the megacities of eastern China. One waypoint on that journey is this ultrahigh-voltage (UHV) converter station outside the city of Jiuquan, in Gansu province.
Electricity from the region’s wind turbines, solar farms, and coal-fired power plants arrives at the station as alternating current. Two dozen 500-metric-ton transformers feed the AC into a cavernous hall, where AC-DC converter circuits hang from the 28-meter-high ceiling, emitting a penetrating, incessant buzz. Within each circuit, solid-state switches known as thyristors chew up the AC and spit it out as DC flowing at 800 kilovolts.
From here, the transmission line traverses three more provinces before terminating at a sister station in Hunan province, more than 2,300 kilometers away. There, the DC is converted back to AC, to be fed onto the regional power grid. Since it opened in mid-2017, the 26.2 billion yuan (US $3.9 billion) Gansu–Hunan transmission line has moved about 24 terawatt-hours.
The sheer scale of the new line and the advanced grid technology that’s been developed to support it dwarf anything going on in pretty much any other country. And yet, here in China, it’s just one of 22 such ultrahigh-voltage megaprojects that grid operators have built over the past decade. In the northwestern region of Xinjiang, China recently switched on its largest UHV link: a 1,100-kV DC circuit that cost over 40.7 billion yuan. The new line’s taller transmission towers and beefier wires parallel the Gansu–Hunan line through the Gansu Corridor, before diverting to Anhui province in the east.
The result of all this effort is an emerging nationwide supergrid that will interconnect China’s six regional grids and rectify the huge geographic mismatch between where China produces its cleanest power (in the north and west) and where power is consumed (in the densely populated east). By using higher voltages of direct current, which flows through conductors more uniformly than does alternating current, the new transmission lines dramatically reduce the amount of power that’s lost along the way.
But even as China celebrates the completion of more than 30,000 km of UHV lines, power engineers are struggling to master the resulting hybrid AC-DC transmission system. They must ensure that the new long-haul DC lines don’t destabilize China’s regional AC grids. For example, if the 8-gigawatt DC line from Gansu were to unexpectedly go off line, the power shock could cause widespread blackouts in Hunan and beyond.
To minimize the threat, the State Grid Corp. of China, a state-owned company that runs most of China’s transmission and distribution grids, intentionally limits the line’s throughput to no more than 4.5 GW. In practice, the line has carried less than one-quarter of its design capacity on average. That’s one reason why over one-third of Gansu province’s theoretical wind output and one-fifth of its solar potential went unused in 2017. Other UHV lines in neighboring regions have similarly operated below capacity. And eastern provinces don’t have sufficient incentive to import the cleaner power that the UHV lines offer.
The ultimate solution to both issues, according to State Grid engineers, is to double down on UHV. They argue that the country must move far more energy via UHV DC to maximize the use of renewable energy while slashing reliance on coal. State Grid is also building a world-leading set of ultrahigh-voltage AC lines, to help eastern China’s regional AC grids absorb the output from those massive lines.
“The UHV AC power grid is like a deep-water port, and the UHV DC is like a 10,000-ton ship. Only the deep-water port can support the 10,000-ton ship,” says Qin Xiaohui, vice director of power system planning with State Grid’s China Electric Power Research Institute, in Beijing.
Meanwhile, power authorities everywhere are watching. Gregory Reed, a DC transmission expert who runs the University of Pittsburgh’s Center for Energy, says China’s UHV grid puts it far ahead of the rest of the world. “They’re investing significantly, and they’ve gone right to the highest levels of technology capability from day one. There’s no comparison anywhere else in the world. It’s like we’re all still pedaling our bicycles, while the Formula 1 race car goes flying by.”
China’s UHV movement was born of a limo ride. It was late 2004, and Liu Zhenya, then president of State Grid, was sharing a car with Ma Kai, minister of the National Development and Reform Commission (NDRC), the powerful state body that regulates China’s growth and major investments. As Chinese policy expert Yi-chong Xu describes in her 2017 book Sinews of Power (Oxford University Press), Ma complained of the crippling power shortages of the day. Liu blamed “weak and fragmented” grids, ones ill-equipped to exchange bulk power. And he proposed a bold solution: massive cross-country power lines utilizing the most advanced UHV technologies.
Within a year, Ma’s NDRC had approved an ambitious and comprehensive plan that embraced Liu’s vision. It combined UHV DC lines, which excel at moving bulk power from one spot to another over long distances, and a UHV AC backbone to reliably distribute that power to consumers. State Grid would lead the engineering and ensure that domestic suppliers would manufacture 90 percent of the UHV equipment, thus building up a new high-tech export sector for China.
Over the next decade, Liu delivered. He put some 2,000 State Grid engineers on the project and funded more than 300 professors and 1,000 graduate students at Chinese universities to conduct power-grid-related R&D. State Grid expanded and refocused its research centers to attack specific UHV issues, including how to safely handle the higher electromagnetic fields and the more potent impulses during switching and faults.
In January 2009, State Grid energized its first UHV demonstration line—a 650-km, 1,000-kV UHV AC transmission line that linked the North China and Central China regional grids. Ten years on, State Grid has completed 19 of 30 proposed UHV lines.
That aggressive build-out has helped fast-growing urban centers such as Shanghai stave off power shortages despite delays in the expansion of China’s nuclear power capacity and constraints on local coal power due to air-quality concerns. The new UHV grid is also helping the country lead the global transition to renewable generation, moving 161.5 terawatt-hours of hydro, wind, and solar energy in 2017 alone.
ABB, Siemens, and other international power-technology companies have been instrumental in developing and validating key components of the Chinese UHV grid. But State Grid has insisted on sharing the intellectual property for the technologies developed at its behest.
continued ...
In a 2014 interview, Executive Vice President Liu Zehong described one tense episode in 2006 when State Grid asked international suppliers to help develop 6-inch-diameter thyristors capable of handling more current than 5-inch thyristors could. The suppliers initially balked, said Liu, but ultimately relented because of State Grid’s “determined attitude” and the “huge market opportunities” of the Chinese market. Two years later, Chinese firms were manufacturing the resulting 6-inch switches.
For all of State Grid’s progress, its UHV deployment remains uneven and incomplete. China could end up with just half of the 89,000 km of UHV lines that its plans called for by 2020 and none of the anticipated UHV links to Kazakhstan, Mongolia, and Russia. Many proposed projects—particularly for the UHV AC backbone—have failed to gain the NDRC’s blessing. As a result, many areas still have no UHV AC lines, and both types of UHV are delivering well below expectations.
What has blocked full implementation is an intense debate over the future of UHV. Some Chinese grid experts question the hundreds of billions of yuan spent on UHV projects and what they see as State Grid’s monopolization of grid engineering and manufacturing. Provincial officials have chafed at the centralization of grid planning and operation that UHV requires.
Some experts have also criticized Liu’s ultimate goal for the UHV AC backbone—linking up and synchronizing China’s regional grids—as far too risky. Han Yingduo, a member of the prestigious Chinese Academy of Engineering and a professor at Tsinghua University, in Beijing, has warned that unifying China’s grid would make it far more vulnerable to cascading blackouts, like the one in 2003 that knocked out power in the northeastern United States and Canada.
Because no other country has ever built a hybrid UHV AC-DC grid, State Grid engineers are having to feel their way along. In a traditional lower-voltage network, the grid operator typically reserves emergency power to cover the sudden loss of the grid’s largest asset. That may mean keeping a gigawatt or two of extra power generation at the ready.
Now add multiple UHV lines to your network, each carrying 8 to 12 GW, and your requirements for reserve power rise dramatically.
Maintaining the ideal voltage on a UHV grid is also enormously challenging. Thyristor-based UHV converters consume what’s known as reactive power—found in AC systems in which the current and voltage are out of phase. (By contrast, active, or real, power is the power that’s actually consumed by the grid’s loads; its current and voltage waves are aligned.) By consuming reactive power, the UHV converters tend to pull down the voltage of surrounding AC lines, so converter stations have equipment to supply reactive power and prop up the AC voltage.
But if an AC line’s voltage sags, nearby converters will consume even more reactive power, pulling voltage down further. A voltage sag can also disrupt the thyristors’ ability to switch from one current path to another, a process known as commutation. A severe commutation failure [PDF] will cause the converter to shut down, deepening the AC voltage drop and starting a potentially destructive feedback loop that could end in a blackout. “Successive DC commutation failures will trigger a chain reaction,” says Qin, the system planning expert at State Grid’s Beijing research institute.
The resulting blackout could travel far and fast, notes Zhang Fang, a system operator in State Grid’s National Electric Power Dispatching and Control Center, in Beijing. When a UHV DC circuit goes off line unexpectedly, it creates a power surge hundreds or thousands of kilometers away, on the AC grid that feeds it. “The UHV DC line is actually acting as an amplifier. A small AC disturbance in the receiving end can become a large AC disturbance in the sending-end grid,” says Zhang.
To minimize the risk of multiple converter failures and cascading blackouts, engineers for State Grid’s East China regional grid have deployed a fiber-optic control network that automatically rebalances supply and demand. If necessary, it can boost line voltage within 200 milliseconds of a voltage drop, using a set of fault responses that have been built into the East China grid’s AC-DC converters. As soon as the fiber-optic network flags an outage on a UHV DC line, the converters pull up to 10 percent more power over the remaining DC lines to keep the grid operational. The optical control scheme can also restore balance by releasing power from pumped hydro plants, which store energy by pushing water uphill. And it can trigger small controlled blackouts, shutting off some distribution feeders to reduce demand while sparing hospitals and other essential loads.
These measures have enabled a trio of UHV DC lines that deliver hydropower from the Southwest China grid to operate continuously at their combined 21.6-GW design capacity. The result is an electrical trifecta: Greater Shanghai, China’s most densely urbanized and industrialized region, gets more clean power; the Yangtze River Delta’s megadams spill less excess water during flood season; and State Grid earns more revenue from its UHV investment. Even so, Shanghai still runs short of power for several weeks each summer, forcing State Grid to pay big customers to idle their factories. Keeping pace with growth may require tripling Shanghai’s electricity imports within a decade.
At the national control center, in Beijing, mounting pressure to push more clean power through State Grid’s UHV lines is hard to miss. The main screen displays the status of the AC and DC trunk lines, providing a real-time view of the entire system. Dominating the left wall are warning lights tracking renewable energy curtailment in each of 25 provinces—and who should be fixing it. Green lights mean that all of the potential solar and wind power is being used. Blue, yellow, and orange lights indicate renewable energy waste, which State Grid’s provincial, regional, or national controllers, respectively, must try to stop.
“We are determined to consume the renewable energy to the maximum extent. That’s our job,” says Zhang. Controllers may reroute power from a province with low electricity demand to another where demand is higher. Or they may steer electricity to one of State Grid’s 21 pumped hydro plants, which collectively can soak up 19 GW.
In theory, Chinese law has long required grid operators to prioritize renewable energy. But in practice, each province has its own plans and priorities, which tend to favor electricity generated locally. For instance, in Zhejiang province, south of Shanghai, significant opposition to importing electricity has hampered the operation of an 8-GW UHV DC line from Ningxia province, according to analysts at Bloomberg New Energy Finance.
On the windy, sunny day when I visited Gansu’s DC converter station last year, its UHV line was carrying just 3 GW of its 8-GW capacity. That was the cumulative output from several renewable plants. But the province also has an additional 15 GW of solar and wind that’s connected to the new line but not yet authorized to feed power into it.
In a 2014 interview, Executive Vice President Liu Zehong described one tense episode in 2006 when State Grid asked international suppliers to help develop 6-inch-diameter thyristors capable of handling more current than 5-inch thyristors could. The suppliers initially balked, said Liu, but ultimately relented because of State Grid’s “determined attitude” and the “huge market opportunities” of the Chinese market. Two years later, Chinese firms were manufacturing the resulting 6-inch switches.
For all of State Grid’s progress, its UHV deployment remains uneven and incomplete. China could end up with just half of the 89,000 km of UHV lines that its plans called for by 2020 and none of the anticipated UHV links to Kazakhstan, Mongolia, and Russia. Many proposed projects—particularly for the UHV AC backbone—have failed to gain the NDRC’s blessing. As a result, many areas still have no UHV AC lines, and both types of UHV are delivering well below expectations.
What has blocked full implementation is an intense debate over the future of UHV. Some Chinese grid experts question the hundreds of billions of yuan spent on UHV projects and what they see as State Grid’s monopolization of grid engineering and manufacturing. Provincial officials have chafed at the centralization of grid planning and operation that UHV requires.
Some experts have also criticized Liu’s ultimate goal for the UHV AC backbone—linking up and synchronizing China’s regional grids—as far too risky. Han Yingduo, a member of the prestigious Chinese Academy of Engineering and a professor at Tsinghua University, in Beijing, has warned that unifying China’s grid would make it far more vulnerable to cascading blackouts, like the one in 2003 that knocked out power in the northeastern United States and Canada.
Because no other country has ever built a hybrid UHV AC-DC grid, State Grid engineers are having to feel their way along. In a traditional lower-voltage network, the grid operator typically reserves emergency power to cover the sudden loss of the grid’s largest asset. That may mean keeping a gigawatt or two of extra power generation at the ready.
Now add multiple UHV lines to your network, each carrying 8 to 12 GW, and your requirements for reserve power rise dramatically.
Maintaining the ideal voltage on a UHV grid is also enormously challenging. Thyristor-based UHV converters consume what’s known as reactive power—found in AC systems in which the current and voltage are out of phase. (By contrast, active, or real, power is the power that’s actually consumed by the grid’s loads; its current and voltage waves are aligned.) By consuming reactive power, the UHV converters tend to pull down the voltage of surrounding AC lines, so converter stations have equipment to supply reactive power and prop up the AC voltage.
But if an AC line’s voltage sags, nearby converters will consume even more reactive power, pulling voltage down further. A voltage sag can also disrupt the thyristors’ ability to switch from one current path to another, a process known as commutation. A severe commutation failure [PDF] will cause the converter to shut down, deepening the AC voltage drop and starting a potentially destructive feedback loop that could end in a blackout. “Successive DC commutation failures will trigger a chain reaction,” says Qin, the system planning expert at State Grid’s Beijing research institute.
The resulting blackout could travel far and fast, notes Zhang Fang, a system operator in State Grid’s National Electric Power Dispatching and Control Center, in Beijing. When a UHV DC circuit goes off line unexpectedly, it creates a power surge hundreds or thousands of kilometers away, on the AC grid that feeds it. “The UHV DC line is actually acting as an amplifier. A small AC disturbance in the receiving end can become a large AC disturbance in the sending-end grid,” says Zhang.
To minimize the risk of multiple converter failures and cascading blackouts, engineers for State Grid’s East China regional grid have deployed a fiber-optic control network that automatically rebalances supply and demand. If necessary, it can boost line voltage within 200 milliseconds of a voltage drop, using a set of fault responses that have been built into the East China grid’s AC-DC converters. As soon as the fiber-optic network flags an outage on a UHV DC line, the converters pull up to 10 percent more power over the remaining DC lines to keep the grid operational. The optical control scheme can also restore balance by releasing power from pumped hydro plants, which store energy by pushing water uphill. And it can trigger small controlled blackouts, shutting off some distribution feeders to reduce demand while sparing hospitals and other essential loads.
These measures have enabled a trio of UHV DC lines that deliver hydropower from the Southwest China grid to operate continuously at their combined 21.6-GW design capacity. The result is an electrical trifecta: Greater Shanghai, China’s most densely urbanized and industrialized region, gets more clean power; the Yangtze River Delta’s megadams spill less excess water during flood season; and State Grid earns more revenue from its UHV investment. Even so, Shanghai still runs short of power for several weeks each summer, forcing State Grid to pay big customers to idle their factories. Keeping pace with growth may require tripling Shanghai’s electricity imports within a decade.
At the national control center, in Beijing, mounting pressure to push more clean power through State Grid’s UHV lines is hard to miss. The main screen displays the status of the AC and DC trunk lines, providing a real-time view of the entire system. Dominating the left wall are warning lights tracking renewable energy curtailment in each of 25 provinces—and who should be fixing it. Green lights mean that all of the potential solar and wind power is being used. Blue, yellow, and orange lights indicate renewable energy waste, which State Grid’s provincial, regional, or national controllers, respectively, must try to stop.
“We are determined to consume the renewable energy to the maximum extent. That’s our job,” says Zhang. Controllers may reroute power from a province with low electricity demand to another where demand is higher. Or they may steer electricity to one of State Grid’s 21 pumped hydro plants, which collectively can soak up 19 GW.
In theory, Chinese law has long required grid operators to prioritize renewable energy. But in practice, each province has its own plans and priorities, which tend to favor electricity generated locally. For instance, in Zhejiang province, south of Shanghai, significant opposition to importing electricity has hampered the operation of an 8-GW UHV DC line from Ningxia province, according to analysts at Bloomberg New Energy Finance.
On the windy, sunny day when I visited Gansu’s DC converter station last year, its UHV line was carrying just 3 GW of its 8-GW capacity. That was the cumulative output from several renewable plants. But the province also has an additional 15 GW of solar and wind that’s connected to the new line but not yet authorized to feed power into it.