The LPRT is only started when the wind turbine transformation is under way

The recent Jiuquan is very lively, even as hot as when bidding three years ago. Only this time, the focus is on the transformation of the low-voltage ride-through capability of wind turbines.

Huang Yuanyan, an engineer at Goldwind's grid-connected technology department, has been busy since April of this year and has started to upgrade low-voltage traversing wind turbines. Because the task of the National Energy Administration is that it must be completed within one year. The Goldwind is considering whether or not it can compress the time and strive to complete the relevant upgrade work before the strong wind season arrives. It also promised that “for all direct-drive permanent magnet units in operation, the latest low voltage ride through will be completed by the end of the year, and the associated costs will be borne by Goldwind Technology”.

It is not Goldwind that considers the customers so. Sinovel, Dongqi, Xiangdian, NORDEX, VESTAS and other companies all stated that they have started the transformation project of low voltage ride through. The Jiuquan Gansu Wind Power Base, which has attracted much attention due to the occurrence of several wind turbine off-grids, has become a place where these engineering teams get together.

“As of the end of June 2011, the area has completed the reconstruction of nearly a thousand turbines, accounting for 48.24% of the total. Due to the different installed quantities of wind turbine companies, 128 gold winds have been completed, and Huarui completed 472 units. Completed 267 units. According to schedule, the crews of Goldwind and Huarui will complete the transformation before the end of the year, and Dongqi will basically complete the transformation by the end of July.” Zuo Yuxi, deputy director of the Northwest Division of State Grid, said that this progress has been very optimistic.

However, things are not that simple. “Some domestic units cannot be reformed at all. Not to mention that the hardware is not designed, even the space for placing hardware is not reserved, and such units are not rare.” Emerson Network Power Co., Ltd. Greater China Wind Energy Cui Yibin, vice president of the industry line, complained to the Energy magazine reporter.

The rectification of the wind blows to the country this time the rectification was blown from the Jiuquan. A few months ago, many wind farms including Jiuquan had a number of fan off-grid accidents in a short period of time, which greatly stimulated the nerves of the competent authorities.

Wang Yuling, chief engineer of the National Electric Dispatching and Communication Center, and her team counted out a set of authoritative data: As of the end of June this year, the wind power grid connection in the national grid system reached 37.21 million kilowatts, an increase of 70.3% over the same period last year. The proportion of large- and medium-sized wind farms with a maximum share of 10,000 kilovolts was 166, accounting for 74.8%, and the total capacity was higher than that of wind power developed countries such as Spain. In the first half of this year alone, the total number of fans in the system was off-net 35 times, and off-grid fans were 3,848 units/time. Large accident 6 times. Among them, 4.35 million kilowatts were lost in the 4.25 accident in the northwest, and 1,278 off-grid units were installed.

Wang Yuling explained that the mismatch between the wind turbine control system's network protection setting and the fan's fault ride-through capability is one of the reasons for the loss of the network. 60% of accidents are caused by equipment failures. Among the 3848 wind turbines, 57.8% were due to the lack of low voltage ride through, and 26.6% were due to the lack of high voltage ride through.

According to the State Grid Corporation of China, for wind turbines with a lack of low voltage ride through capability, wind farms are required to operate within 0.9-1.1 times rated voltage, and wind turbines can operate normally. The problem now is that a considerable number of units are off-grid within 1.1 times of the rated voltage within 100 milliseconds, and rectification is completed within the specified time without this capability. Also have the necessary high voltage ride through capability. Their reason is that in countries with more developed wind power, there are requirements for more than 1.1 times the voltage, and the strictest is 1.3 times to run for 60 milliseconds.

The failure of the grid was originally unavoidable. Why is this issue of low voltage ride through so important?

Wu Nan, Director of Electrical Department of NORDEX, was concise and clear. “If the fan has no low-voltage ride-through function, once the grid has a small fault, the fan will be automatically disconnected for self-protection, which will enlarge the fault of the power grid. After the low-voltage ride-through function, it can be ensured that the fault will not be magnified because of the fan. After the fan is the main power source, this problem will be highlighted and must be resolved."

As Wang Weisheng, head of the New Energy Institute of the Chinese Academy of Electric Power, put it, many people believe that the issue of low-voltage ride-through has been magnified in off-line accidents. In fact, this view is wrong, because of the lack of follow-up problems caused by low-voltage traversing. More tricky.

When all parties realized that the problem was serious, they faced a lot of calm in the face of this rectification.

It must be pointed out that this time the wind turbines with more than 1 MW must be rectified. However, there are no rigid regulations for the “750” and “850” models of wind turbines with long domestic operating hours.

Then, how should this part of the wind turbine be reformed? Who should pay for the cost?

Goldwind has launched two gearboxes in recent years: the "750-kilowatt" gearbox unit and the "1.5-megawatt" direct-drive permanent magnet unit. At present, the 750-kilowatt wind turbine unit has basically stopped production, and all models have turned to megawatts. Direct-drive permanent magnet machine. For the direct-drive permanent magnet unit, Cui Xinwei, chief engineer of Goldwind Technology, frankly stated that the hardware has been taken into consideration when the line is down, but the software part is being rebuilt, and each station can be completed in 2 hours; for the gearbox unit “750 kilowatts” Models require a lot of effort, not only software, but also hardware components. Since this part of the unit was sold, the market did not mention the low-voltage ride-through function, so for this part of the transformation of the unit, Goldwind said The plan has been prepared for the owner to choose.

indeed so. Qin Ming, director of the State Power Cooperative Wind Power Equipment Technology Research Institute, said that it is reasonable for the equipment manufacturer to bear the cost of this modification in the contracted wind field. However, it is not appropriate for the equipment manufacturer to bear the responsibility for the equipment that was put into operation in previous years and the contract is not clearly required because the wind power low-voltage ride-through function is a new technology. Past policies and users have not made similar requirements.

“Once a new national standard is introduced, then the newly-produced wind turbines must have a low-voltage ride-through function, and this part of the cost will be absorbed by the fan companies. However, all units newly produced by Goldwind will come with the latest version of low voltage. Through the function." Cui Xinwei said.

This also makes this national wind turbine big rectification not only the wind turbine manufacturing enterprise one side is busy, but from the wind farm to the power grid, then the wind turbine enterprise all participates. The power grid issued the final subpoena for the wind farm. If it is not reformed, it cannot be connected to the grid. The wind farm can only requisition the turbine and the wind turbine enterprise to complete the transformation.

“The Huaneng Jiuquan 300,000 kilowatt wind farm has been completed and is waiting for testing. We also call on the Electric Power Institute to speed up testing and not waste resources.” Zhang Shaohong, Vice Minister of Planning and Development of Huaneng Group, has talked about remodeling topics more than once, but It has become an indisputable fact that the rectified wind farms are waiting in line for testing. China's testing department is only one of the Institute of Electrical Engineering, and it is not enough to face so many wind farms. As a result, the nationwide queuing inspection became a new topic for wind power companies.

Restructuring problems and deriving new markets have rationalized the question of who will bear the cost of transformation. The remaining challenge is to transform the technology.

Wu Nan believes that low-voltage ride-through is a very mature technology. It has been operating in Europe for many years. NORDEX has also implemented it for several years. As an option, it is placed on the quotation list of Chinese customers. The owner freely chooses, even if it was not selected at that time. It can be bought later, and it can be completed in a day or two. "I don't think this is a new technology. It was only started in China two years ago."

Yao Yu, director of public affairs of Goldwind Technology, also repeatedly stated that two years ago, when hearing some problems in the power grid, Goldwind's wind turbines had already demonstrated the features of low voltage ride through. This is because direct-drive permanent magnets use Permanent magnet motors and full-power converters support low-voltage ride-through on the technology route, not that they were evaluated in 2010 to be able to do this.

“For us, whether it is the software transformation of the 1.5 MW wind turbine or the hardware and software transformation of the 750 kW wind turbine, it can be completed as long as there is demand.”

However, not all wind turbines can be planned in advance like NORDEX and VESTAS. Nor are all wind turbines claiming that their wind turbines can be retrofitted like Goldwind and Xiangdian.

“Some wind turbines are really impossible to transform. Not only did the hardware modules not be designed, but the space used to install the hardware was not reserved. The life span of the wind turbine is 20 years. These should be considered early. Some domestic companies only consider 3 years. It is irresponsible to take money away after three years, and it is also the reason why a group of wind turbine companies declare bankruptcy. So what do these wind turbines do?” Cui Yibin asked.

Can these wind turbines be transformed by existing wind turbine manufacturing companies? VESTAS sales personnel have been shaking their heads when they hear this question. “This is not something that has been done with a single module. It was the low-voltage ride through when the wind turbine was designed. The concept has been put in and it is in line with the entire wind turbine."

Wu Nan of NORDEX also expressed negative opinions. He said: “Each family has its own design and the technical route is different. It cannot be used on other wind turbines. The general cost of our wind turbines is about 300,000 yuan, I think domestic Fan companies will not be lower than this cost."

Indeed, there are dozens of domestic wind turbine manufacturers, each with different technical routes, dual-feedback, direct-drive, and different models under the same technology route. The cost of retrofitting is certainly not the same.

What about the wind turbines that are not willing to be rebuilt by the whole machine business? An emerging market emerged. As Zhou Feng, director of Goldwind's strategy and global development, put it, some companies in Taiwan, Japan, and the United States have proposed low-voltage traversing transformations specifically for wind turbines, with quotes ranging from 300,000 to 890,000 yuan.

It is understood that by the end of 2010, the cumulative installed capacity of wind power in China has reached 42 million kilowatts, and the number of installed wind turbines has exceeded 20,000, and most of them have been put into operation between 2008 and 2010. Most installed fans do not have low voltage ride through capability. If the calculation is based on the renovation cost of 500,000 yuan per unit, domestic wind power companies and equipment manufacturers will pay more than 10 billion yuan for wind turbine reconstruction.

However, whether these newly emerged retrofit companies have questioned all models or whether they have been questioned, Li Shengmao stated, “Their practice is to uniformly add a big module, and many things in this big module are not necessary. It is a waste, and it is not practical, because the structure of each fan is different, not according to the design concept, but artificially adding a module, the effect is hard to say.”

The LPV limit is just beginning to “the new national standard will soon be introduced. We predict that this new national standard will be more stringent and that low voltage ride through is just the beginning.” Cui Yibin said that the Emerson Wind Turbine Converter team he heads predicted the next two Within three years, China’s requirements for wind turbines and key components are not the same as those mentioned so far. They will be more stringent and will continue to strengthen the requirements for reactive and other fluctuating and rapid response of the circuit. “So, we have completed the tests with NORDEX. Some domestic requirements that have not yet been enacted are made according to Spanish standards, which is also a relatively advanced European standard."

Perhaps the regulation of low voltage ride through is just the beginning. With the increasing proportion of wind power in China's power supply structure, some new requirements will be introduced to maintain the stability of the power grid.

For example, the wind power forecasting and forecasting mechanism has already begun. It is reported that the National Energy Administration issued relevant documents. “Energy” magazine reporter found out from this temporary management plan that all wind farms that have been connected to the grid are required to establish a wind power forecasting and forecasting system and a power generation plan application mechanism before January 1, 2012 and start trial operation, according to the requirements. The wind power forecast results are not established and cannot be connected to the network.

It also stipulates that the wind farm forecasting system will be officially launched from July 1, 2012.

The short four-page document clearly specifies various stringent requirements, for example, the wind power forecast forecast and the real-time forecast. The real-time forecast requires a time resolution of 15 minutes, that is, within 24 hours. 96 time nodes. This has stricter control over the accuracy rate, and the prediction error cannot be exceeded by 15%.

All indications are that the management of the wind power industry is bound to become increasingly stringent. Every wind power developer and wind turbine company that smells of odors is already working on it.

In 2009, China Electric Power Research Institute in Zhangbei made a test field, known as "the world's most advanced research and test center for wind power." It is reported that the project mainly includes wind power technology research capacity building, mobile detection capacity building and wind power test base construction. Only the first item includes wind power simulation research, wind power test database and data processing, wind energy resources and wind power prediction research and many other contents.

Ni Zhongren, Director of Engineering at NORDEX Wind Power Company, recalled that the first fan of Zhangbei Base came from his hand and was a 1.5 MW S77 model fan. It was customized according to the requirements of the Institute of Electrical Engineering and was added at the time. Advanced low voltage ride through modules.

Ni Zhongren said with a smile: “The wind turbine was sold for money. However, the Institute of Electric Power was a repeat customer and bought us a 2.5-megawatt N90. At that time, we were still asking why China’s demand for low voltage would be so fast? The relevant departments claimed that after three years, the European requirements were also a matter of recent years, and Europe’s first grid connection request was issued in 2000, but it did not happen that in less than three years it had moved from the exploration stage to the relatively mature stage. The demand is bound to increase."

In the past two or three years, some domestic companies that have gone out have also felt the pressure. Huang Yuanyan said that it is not possible to have low-voltage ride-through capability and that technology must be continuously upgraded. Recently, Goldwind passed the German Lloyd’s ship in Hami, Xinjiang. GL's Zero Voltage Pass-through field test and can provide reactive power to the grid. "From low voltage to zero voltage is only the first step. Our crew must be stricter than the national standard."