As an important puzzle of new power system, nanrui power assisted DC power distribution system has been successfully demonstrated and applied

2022-04-30 0 By

On January 18th, the demonstration project of “Key Technology and Application of Medium and low voltage DC Power Distribution System”, which nangrui Group participated in, passed the acceptance of the Ministry of Industry and Information Technology of the People’s Republic of China.On January 18th, the demonstration project of “Key Technology and Application of Medium and low voltage DC Power Distribution System”, which nangrui Group participated in, passed the acceptance of the Ministry of Industry and Information Technology of the People’s Republic of China.This is the dc power distribution system with the most abundant application scenarios, the most types of source charges and the latest technical equipment built at home and abroad.By adopting dc power distribution mode, the energy utilization rate of the project is 3% higher than that of the AC system with the same voltage level, and the medium voltage DC transformer technology fills the gap in the industry.In daily life of Jiuli Central Station built by Nangrui Group, 220 VOLTS AC is a well-known power supply voltage.But in fact, most household appliances are using DIRECT current or including DC link, through the internal “AC – DC – AC” electrical energy conversion, to achieve flexible control of various electrical appliances.At one end is the AC power distribution system, and at the other end is the DC power supply and DC load. Their connection requires more power electronic equipment for AC-DC conversion, which increases the power loss and the difficulty of power grid regulation and reduces the energy utilization efficiency.As the clean energy transition continues to accelerate, wind power, photovoltaic and other new energy sources are connected to the grid on a large scale. Meanwhile, DC loads represented by electric vehicles are developing rapidly, and DC power distribution systems are gradually developing.Compared with ac power distribution system, DC power distribution system does not need AC-DC conversion, and has the advantages of larger power supply capacity, longer power supply radius, and higher operating efficiency.Therefore, the construction of high efficiency, low consumption and reliable DC power distribution system has become the development trend of future power grid, and has become an important support for the construction of new power system under the background of “double carbon”.Low voltage dc with electricity system in suzhou “key technology and application” special demonstration project is the national key research and development plan, covering 10 kv and 750 v, 375 v dc voltage grade three, realized the full given area distributed new energy 100% and dc load plug and play, the strong support of suzhou city energy Internet tongli demonstration area construction,Provide “Jiangsu model” for global energy reform and construction of new power system, and help achieve China’s “carbon peak, carbon neutral” strategic goal.Two 10kV DC central stations were built in the demonstration project, namely Pangdong Central Station and Jiuli Central Station, which are the two “main hearts” of the demonstration project.Relying on the sound industrial chain, Nanrui Group has gathered its advantages in RESEARCH and development, design, equipment and system integration and engineering services, and completed the development of dc transformer in the “Main heart” and EPC general contract construction of jiuli Central Station new project.The company also undertakes the supply of complete sets of converter valve equipment and secondary protection device, medium and low voltage DC power distribution coordination control system, DC monitoring system, intelligent auxiliary system, series of low voltage DC switchgear equipment and other key equipment.Breaking through key technologies, the ±10kV/2MW DC transformer used in the “governor” of DC distribution network in Pundong Central Station was successfully developed by the Power Electronics R&D Center of Nanrui Research Institute relying on the State Grid Corporation’s science and technology project “Key Technology Research on HVDC Transformer with Fault Isolation Capability”.It can realize the functions of medium and low voltage DC voltage conversion, power flow control and electrical isolation, etc. It is the core equipment supporting the demonstration project to achieve medium and low voltage DC voltage level conversion.In DC power distribution network, different levels of voltage coexist, the dc power distribution network with higher voltage is suitable for the construction of the backbone network and constitutes the “highway” of electricity.The dc distribution network with low voltage is used for the construction of new energy generation and power consumption system, constituting the “street path” of direct electricity to users.The DC transformer technology is the “governor” of power voltage regulation and shift, which makes power shuttle freely in high voltage and low voltage DC distribution network.Efficiency and reliability are very important in the process of power voltage regulation in DC distribution network.As an important highlight of the demonstration project, the efficiency optimization technology of Nanrui Research Institute shows how to improve the efficiency of equipment, reduce the power loss of DC system, and achieve low carbon distribution network, which is one of the key problems to be solved in DC transformer technology.The research and development team of Nanrui Group proposed the series resonant double active bridge technology based on optimization target decoupling and the optimized control strategy of phase shift frequency conversion. The application of soft switch technology with wide load range greatly improved the high frequency conversion efficiency of the equipment. Considering all additional losses of cooling and control and protection system, the efficiency of the whole machine reached 97.89%.High efficiency conversion of voltage ratio from ±10kV to 750V is realized.For DC distribution network, fault isolation technology has always been a key technical factor restricting its further development.Different from AC power distribution network, the fault current of DC power distribution network has no zero crossing, so the method of ac system fault isolation cannot be used.When the DC distribution network fails, the system will overcurrent seriously in a few milliseconds, threatening the safety of the power network.Therefore, the development of ultra-high speed fault identification and economical and reliable fault opening is an urgent problem to realize medium-voltage DC fault crossing.South group which r&d team thorough analysis of medium voltage dc fault characteristics, innovation in medium voltage fault in the fast and reliable locking technology, low voltage through technology, rapid detection of low pressure short circuit and reliable locking technology, fast back after fault recovery technology, and other key core technology research, can block the fault current within 160 microseconds,15 milliseconds after the fault is cleared, the stable operation state is achieved, and the medium-voltage bipolar short circuit fault is controllable and traversable.A fault segmentation online identification method based on bus voltage characteristics and a feed-forward closed-loop control strategy introduced with fault characteristics were proposed to realize low voltage crossing under different conditions of medium voltage side voltage and large disturbance, ensuring the power supply reliability of dc power distribution system.”In order to solve the problem of losing pulse when bipolar short-circuit, we have carried out more than 100 ±10kV bipolar short-circuit fault tests in one day. Each test our equipment can achieve fast protection and re-casting, which also indirectly verified the safety and reliability of the equipment.”Nanrui Research Institute power Electronics RESEARCH and development Center technology director introduced.On November 23, 2020, Nanrui Group’s ±10kV/2MW DC transformer successfully passed all factory tests and third-party tests.All the tests not only pass at one time, but also a number of test results greatly exceed expectations, especially in the aspects of fault handling and the efficiency of the whole machine. It is one of the few products in the industry that can meet the latest technical specifications of medium-voltage voltage sag and bipolar short circuit and meet the highest requirements of fault crossing.Due to its advanced technology, nanrui R&D team was invited to participate in the drafting of IEEE P2892 medium voltage DC transformer standard, which is the world’s first international standard in the field of DC transformers.Play the overall advantages, to provide comprehensive support for engineering service center construction in the process, in the nine south group which give full play to the design optimization of leading role, from engineering design, complete sets of equipment, control system, the integrated application of various aspects to provide clients with complete EPC solution, ensure to achieve quality and efficiency of the overall project requirements.Distribution company staff is cooperating with debugging to low voltage dc switchgear in addition to + 10 kv / 2 mw dc transformer outside the “weapon”, the south group which also delve into the dc distribution operation control technology, innovation developed in the low voltage dc with coordinated control system, dc series low voltage dc switchgear equipment monitoring system, and other key equipment.Coordinated control system in the low voltage dc with electricity as support demonstration project to run one of the “brain”, for ac/dc module library integrated graphics services, rich functions such as man-machine interface, real-time database, collaborate with dc monitoring system, implementation based on the multi-scale numerical weather prediction ac/dc power distribution network, load forecast,Energy scheduling based on power prediction and demand response can also be used for advanced applications such as load and storage coordination control, combined loop operation control, power control and power flow control of AC and DC source networks.As an “eye”, dc monitoring system can monitor and control the operation of converter station, DC switch station and DC power distribution room.Serialized low-voltage DC switchgear complete sets of equipment with perfect protection, measurement, measurement, control and monitoring functions, DC protection sampling frequency up to 40kHz, protection group time less than 10 milliseconds.All the above equipments are applied in the demonstration project as the first set of equipments and run well at present.In order to ensure the demonstration of the project, to achieve the goal of construction, in the design stage, it is necessary to plan the engineering practice transformation of each new technological achievement.To this end, we organized various professional and equipment teams to conduct a full demonstration and scheme comparison to ensure the advancement, reliability, economy and applicability of the design scheme.”Jiuli central station design director introduced to.The Jiuli Central Station, located in a corner of Tongli Town, looks like an ordinary three-story building with ingenious interior designs.Jiuli Central Station integrates converter station, opening and closing station and power distribution room. The multi-station construction scheme saves land use, reduces investment and facilitates operation, maintenance and maintenance.Combined with the characteristics of the project, the construction structure of the two ends of the ring grid is adopted to reduce the length of the cable and the incidence of failure.The converter valve adopts half bridge, except the converter valve outlet adopts circuit breaker, and the subordinate switches adopt load switches. By optimizing the switch configuration scheme, the project cost is reduced by nearly 30 million yuan.In the station, ac and DC power supply is adopted, and batteries are added as backup power supply, which not only ensures power quality and high reliability of power supply, but also fully embodies the significance of project demonstration.The project management personnel of the design company carry out quality inspection of construction parts. While constantly optimizing and adjusting the design scheme, the project management and control is also the focus of Nanrui Group.Safety, quality, schedule and technical management should not be lax.Jiuli Central Station has a steel structure volume of more than 1200 tons. Optimizing and improving the progress of the main steel structure is the key to ensure the progress of the whole project.The nanrui project team carefully prepared the lifting scheme and adopted measures such as regional lifting, which reduced the lifting period by one third.There was no precedent for dc equipment commissioning, so the project team consulted data, organized arguments, and completed the commissioning in a third of the time using conventional stations.On June 18, 2021, the new project of Jiuli Central Station was awarded “Jiangsu Provincial Standard Star Construction Site”.On June 21, 2021, State Grid Suzhou Power Supply Company sent a letter of appreciation to Nanrui Group for its work on safety, quality, schedule management and other aspects of EPC general contracting project.On September 29, 2021, the expert group of the Ministry of Industry and Information Technology carried out the performance evaluation and acceptance of the demonstration project, and gave a high evaluation to the construction and operation of jiuli Central Station.Nine central station in new project named “the standardization of construction in jiangsu province” star site support suzhou “in the low voltage dc electrical system with key technology and application” demonstration project put into operation, the southern group which stick to “one four wings” development layout, based on the core technology advantages, to support the new construction of electric power system, power “double carbon” a miniature of the goal.In the next step, Nanrui Group will closely follow the needs of power grid development, speed up basic theory research, core technology research and key equipment development, hold high the banner, shoulder the responsibility, seek progress while maintaining stability, move forward bravely, comprehensively support the construction of new power system, and make more positive contributions to the realization of the goal of “dual carbon”.Disclaimer: the above content is reproduced from China Energy net, the content does not represent the position of this platform.National Energy Information Platform Tel: 010-65367702, email: hz@people-energy.com.cn, Address: People’s Daily, No.2 Jintai West Road, Chaoyang District, Beijing