Polaris Transmission and Distribution Network: Overcoming difficulties and being solid and reliable | SUN.KING Technology sets the standard for "domestic products" of DC link capacitor for flexible DC

Date: 2022-09-19

Source: Polaris Transmission and Distribution Network

Under the "dual carbon" goal, as new energy continues to move towards the main power source, large-scale new energy base long-distance transmission has become a top priority in the transformation of the national energy structure. The characteristics of the power grid at the sending and receiving ends determine that the use of flexible transmissiontechnology is essential.

Autonomy and controllability | Breaking through the barriers and breaking the monopoly of foreign capital

The high-quality development of new energy has brought huge market space for flexible power transmission. In the flexible direct current transmission technology, the key equipment such as the flexible direct current converter valve, the power electronic devices are highly dependent on imported products. There are still problems such as core technology being controlled by others and low localization rate, and the development of national localization is slow.

Take the DC link capacitor for the flexible DC converter valve as an example. As one of the key components, the DC link capacitor for the flexible DC converter directly determines the fluctuation range of the capacitor voltage and will also affect the pressure-bearing level of the power module devices. It has very high technical content and reliability requirements. Usually, most of these products are provided by foreign manufacturers.

The DC link capacitor for flexible DC transmission is also called DC-LINK capacitor. It provides support for DC voltage and absorbs ripple current to achieve the function of stabilizing voltage and current, thereby providing safety guarantee for the stable operation of the system.

To accelerate the localization and industrialization of DC link capacitor for flexible DC transmission and improve the industry's production capacity and technical level. In September 2021, the first drafting working group meeting of the energy industry standard "DC link capacitor for flexible DC transmission converter valves" was held, with more than 60 representatives from 44 units attending the meeting.Key topics such as discharge test, durability test, destruction test, self-healing test, and constant humidity and heat test were discussed.

At the above-mentioned standard drafting working group meeting,SUN.KING TechnologyGroup Co., Ltd. (hereinafter referred to as "SUN.KING Technology") proposed to add the partial discharge test between the terminal and the shell as a routine and type test item for DC link capacitor, and suggested that the durability test conditions be changed to AC and DC voltage superposition assessment in reference to the actual operating conditions of flexible DC. Added suggestions such as the extreme withstand voltage test at high temperature to assess the withstand voltage level of capacitor under extreme conditions, which did a lot of work for the drafting of the standard and promoted the process of formulating the standard.

According to the person in charge of R&D of Jiashan SUN.KING Capacitor, in the process of developing flexible DC link capacitor, the control of partial discharge between the terminal and the shell was once a difficult point. Partial discharge will lose energy in the form of heat, light, sound, etc., and also generate a large number of active chemical groups to react with the insulating medium, resulting in the continuous reduction of the performance of the insulating medium, which is a huge test for the insulation of high-voltage power equipment. SUN.KING Technology has continuously tried and improved the process, and finally summarized a set of process parameters that can optimize partial discharge, so that the partial discharge of the capacitor is always controlled at an excellent level. At present, the company has obtained a total of 6 patents for flexible DC link capacitor.

He further stated, "After the DC link capacitor for flexible DC converters are localized, it will not only break the monopoly of foreign products, but also allow product prices to return to a reasonable level, which will help reduce project costs and save national investment. ”

Solid and reliable | National production helps new energy power generation

In June 2022, the National Development and Reform Commission, the National Energy Administration and other nine departments jointly issued the "14th Five-Year Plan for Renewable Energy Development". The plan proposes to carry out deep-sea offshore wind power planning, and also plans to promote offshore large-scale development and deep-sea demonstration development.

As soon as this plan came out, coastal wind power development ushered in new market opportunities. According to statistics, the coastal provinces' planned offshore wind power development targets for the 14th Five-Year Plan exceed 50 million kilowatts, among which Guangdong, Zhejiang, Jiangsu and Shandong provinces have larger planned volumes, reaching 17GW, 5GW, 12.12GW and 8GW respectively. Excluding the 14.48 million kilowatts of newly installed capacity in 2021, there is still more than 35 million kilowatts of new space.

However, offshore wind power construction is technically difficult, and the difficulty coefficient increases exponentially from offshore to deep sea. How to promote wind farms to deep sea through technological innovation has become a problem that the industry focuses on.

“As wind farms move further and further offshore, how can we minimize the transmission of electricity? ”

It is understood that the transmission distance of submarine cable power transmission is inversely proportional to the frequency used, 15 Hz transmission frequency can achieve a transmission distance of about 300km. Low-frequency transmission technology can effectively solve the problem of medium and long-distance offshore wind power transmission.

In response to the rapid development of offshore wind power, State Grid Corporation of China has also been actively exploring flexible low-frequency transmission technology in recent years. State Grid Zhejiang Company has also carried out demonstration project construction in Taizhou, Hangzhou and other places.

In May 2021, the Zhejiang Hangzhou Power Supply Company's 220 kV Zhongbu-Tingshan flexible low-frequency transmission demonstration project was officially launched, which will realize the first 500 kV asynchronous low-frequency interconnection of supply areas in Zhejiang Province, which is an international pioneering technology. It is reported that the project will build frequency conversion stations on both sides of the 13.2-kilometer 220 kV Tingzhong transmission line, and interconnect the two major load centers of Fuyang and southern Xiaoshan at a low frequency of 20Hz.

Polaris Power Grid learned that flexible low-frequency AC transmission technology is a new type of transmission technology that flexibly selects a 20 Hz frequency with the help of advanced power electronics technology. Similar to using power electronic devices to convert industrial frequency 50 Hz into DC 0 Hz, it can take into account the advantages of flexible networking of industrial frequency AC systems, voltage level conversion, and long-distance and large-capacity power transmission, while also having flexible control functions such as power control, dynamic voltage adjustment, and asynchronous grid interconnection.

The person in charge of technical research and development of Jiashan SUN.KING Capacitor said that the "14th Five-Year Plan" is a critical period for my country's new energy to achieve leapfrog development. The commissioning of the Hangzhou Flexible Low-frequency Transmission Demonstration Project has accumulated experience for the transmission and consumption of new energy, and has played a role in promoting the green and low-carbon transformation of energy and achieving the goals of carbon peak and carbon neutrality. The project used for the first time the domestically produced flexible DC link capacitor for direct current produced by Jiashan Capacitor, a subsidiary of SUN.KING Technology. The smooth implementation of the project has not only accumulated a lot of work experience for SUN.KING Technology in promoting the development of new energy, but will also promote the gradual complete localization of flexible DC link capacitor for direct current. ”

He further stated that the Hangzhou low-frequency transmission flexible DC capacitor project is not only the first large-scale delivery project of Jiashan capacitor under SUN.KING Technology, but also the first batch project of localization of DC link capacitor for flexible DC in my country. More than 1,000 DC link capacitor in the order have been delivered by the end of May 2022, and the electrical test pass rate is 100%. SUN.KING Technology is confident in overcoming technical difficulties and breaking technical barriers, helping my country's power industry get rid of its dependence on imported key components, and changing the situation where core technologies have been controlled by others for a long time.

A sword is sharpened by grinding, and the fragrance of plum blossoms comes from the bitter cold. With the completion and commissioning of a number of high-voltage flexible transmission projects such as Zhangbei, Kunliulong, Zhoushan and Nan'ao Island, my country has accumulated a lot of experience in engineering applications. Flexible transmission technology has moved from the laboratory to reality and is at the forefront internationally. In the future, as the "dual carbon" goals gradually deepen, new energy sources such as wind power and photovoltaics are connected to the grid on a large scale, the development space of flexible transmission technology will be broader, and domestic flexible transmission equipment manufacturers represented by SUN.KING Technology will surely gain greater market opportunities.

Label :

Return to List

News Center

Polaris Transmission and Distribution Network: Overcoming difficulties and being solid and reliable | SUN.KING Technology sets the standard for "domestic products" of DC link capacitor for flexible DC

Date: 2022-09-19