A few days ago, the Zhejiang Provincial Energy Bureau officially issued the first provincial implementation guidelines for the entire county to promote distributed photovoltaic development pilot work "Zhejiang Province's entire county (cities, districts) to promote rooftop distributed photovoltaic development work guidelines". The document clearly states that all pilot counties (cities, districts) should determine the distributed photovoltaic construction goals in accordance with the local "14th Five-Year Plan" renewable energy development goals, and the new photovoltaic power generation scale shall not be less than 100MW during the "14th Five-Year Plan" period. The cumulative installed capacity of photovoltaic power generation shall not be less than 15% of the maximum load of the local "14th Five-Year Plan" power plan.
  With the advancement of the construction of a new power system with new energy as the main body, more and more distributed photovoltaics are connected to the rural power grid. Under the guidance of the national "dual carbon" goal, my country's rural distributed photovoltaic power generation will continue to grow significantly year by year. The large-scale development of distributed photovoltaic power generation in rural areas will inevitably bring challenges and far-reaching effects to traditional rural power grids, and then reconstruct the development model of rural power grids. It is imminent to promote the construction of a new type of rural power grid that meets the "dual carbon" goal.
  

       "Hurricane Advancement" of Zhejiang Distributed Photovoltaic

       Taking Zhejiang as an example, Zhejiang belongs to the third category of photovoltaic resource areas, and photovoltaic resources are relatively scarce. However, the Zhejiang government actively implements the development concept of "green water and green mountains are golden mountains and silver mountains", and vigorously supports the development of the entire photovoltaic industry chain, especially the distribution Type photovoltaic, both the installed capacity of distributed photovoltaic and the installed capacity have long been in the forefront of all provinces in the country. As of June 2021, the total installed capacity of photovoltaic power generation in the province reached 16.216 million kilowatts, an increase of 884% compared to the end of 2015. The installed capacity has exceeded hydropower and is the second largest power source in the province after thermal power. Among them, the installed capacity of distributed photovoltaic power generation projects was 11.374 million kilowatts, and the number of grid-connected projects reached 242,000.
       In May of this year, Zhejiang Province issued the "Fourteenth Five-Year Plan for Renewable Energy Development" to vigorously develop wind power and photovoltaics, and implement the "Wind-Wind Multiplying Plan"; The Pilot Work Plan for Large-scale Photovoltaic Development requires all 26 counties in the mountainous areas of the province to participate in the pilot and encourages the districts and counties with high enthusiasm and heavy daytime load to participate in the pilot. During the "14th Five-Year Plan" period, Zhejiang Province plans to add 13 million kilowatts of photovoltaic installed capacity, of which the actual installed capacity of distributed photovoltaics will exceed 20 million kilowatts.
  In response to the development of large-scale distributed photovoltaics, State Grid Zhejiang Electric Power Co., Ltd. (hereinafter referred to as “State Grid Zhejiang Electric Power”) has taken multiple measures to improve rural power grids. First, increase the photovoltaic carrying capacity of rural power grids. Make overall plans to meet the needs of photovoltaic grid connection, make overall plans to promote the construction of rural distribution networks, promote the deployment of appropriate energy storage devices, and optimize the management of supporting project plans. Promote rural electrification to improve the level of local consumption. Carry out the construction of digital and intelligent power supply stations, promote the improvement of both the management and service capabilities of the power supply stations, and serve the development of distributed photovoltaics. Formulate the "Three-year Action Plan for the Construction of Digital Intelligent Power Supply Stations", build a digitally intelligent power supply station management platform, promote the "Internet +" and electronic channels of power supply stations, and provide more convenient and accurate services for distributed photovoltaic grid connection. Second, explore the demonstration of friendly access to distributed power sources. At the same time, State Grid Zhejiang Electric actively improved the distributed photovoltaic management system and innovated the distributed photovoltaic service model.
  As Zhejiang takes the lead in developing clean energy in rural areas, power grid companies and governments at all levels have unified thinking, smooth communication, and effective measures to ensure that all kinds of new energy power generation are smoothly connected to rural power grids, and there is no abandonment of wind or light. At present, the adverse effects of the development of distributed photovoltaic in Zhejiang Province on the operation of rural power grids are still within a controllable range. However, with the continuous access to large-scale distributed photovoltaics and a variety of distributed clean energy in the future, the rural power grids in Zhejiang Province will also It is bound to be further upgraded and transformed into a new rural power grid that adapts to the "dual carbon" goal.
  How to solve the problem?
  In the future, as the grid will be connected to a large number of distributed photovoltaics and a variety of new energy sources, the rural power distribution system will change from the original radial passive network to an active network with a large number of distributed power sources, and the physical characteristics of the grid will undergo major changes. Therefore, the traditional rural power grid will inevitably not be able to adapt to the widespread access of large-scale intermittent distributed power sources. In the future, rural power grids will also face new challenges.
   One is the insufficient capacity of rural power grids. Zhejiang Power Grid has a large load base, and the overall consumption of new energy in Zhejiang Power Grid is relatively good. So far, there has been no abandonment of wind or light. However, in some areas dominated by rural power grids, because the regional load characteristics do not match the output characteristics of photovoltaic, wind power and other power sources, it is difficult to absorb them, and it is necessary to upgrade or increase substation capacity. The second is to affect the power quality of the power grid. As the grid connection capacity increases, the voltage deviation will show a "U-shaped" change that first decreases and then increases, and in extreme cases it may even exceed the upper limit of the voltage requirement. The third is to affect the automation of the distribution network and the actions of relay protection. Traditional rural power distribution networks generally do not consider double-sided or multi-sided power supplies, and most of the configuration current protection is non-directional overcurrent protection. After a large number of distributed photovoltaics are connected, both the system and photovoltaics provide short-circuit current to the fault point when the system fails, which changes the current flowing through the protection, which may cause the relay protection device to malfunction or refuse to operate. At the same time, there is the risk of incorrect operation of protections such as standby automatic switching and reclosing, which will further expand the scope of power grid accidents. The fourth is the influence and harm of harmonics. When distributed photovoltaics are connected in a high proportion, power electronic components such as inverters are connected to the grid on a large scale, and some inverters are of poor quality, which may cause serious harmonic pollution of the grid to exceed the standard. The harm of power grid harmonics is multifaceted, which will lead to increased power grid loss, relay protection malfunction, inaccurate meter measurement, etc., which reduces the reliability of power supply and power quality. Fifth, it is more difficult for county-level power grids to peak load. A high proportion of intermittent non-peak-shaving power sources such as photovoltaics are connected to county-level rural power grids, and the dispatchable peak-shaving resources of the grid are prominently insufficient. Because traditional rural power grids do not have energy storage equipment, it will cause the misalignment of photovoltaic power generation peaks and power peaks in some areas. The power grid peak shaving is more difficult, especially during holidays.
       To cope with the above-mentioned challenges, grid companies should pay attention to the following tasks: carry out the investigation and evaluation of the distributed photovoltaic access capability of the county distribution network; carry out research on the impact of large-scale distributed photovoltaic access on the distribution network and load-side voltage; Harmonic test of photovoltaic power generation with different capacities connected to low-voltage distribution network; carry out research on the impact of distributed photovoltaic grid-connected on rural power grid relay protection; carry out investigation and evaluation of the local and nearby consumption of photovoltaic power generation; carry out adaptive distribution Research on related technologies of energy storage devices for integrated photovoltaics. Among them, on the energy storage side, it is necessary to explore a combination of centralized and distributed energy storage supporting schemes, give full play to the multi-dimensional support capacity of energy storage for the power grid, and effectively solve the problem of uneven and asymmetric source and load development in mountainous counties. Promote the introduction of a "quota system" energy storage construction model to solve the dilemma of energy storage device construction that "power generation companies do not want to invest, grid companies cannot invest, and social capital does not want to invest".
  From the perspective of the government, the first is to carry out research on new rural power grid planning and improve rural power distribution grid standards. The second is to vigorously cultivate the rural electricity market, and absorb photovoltaic power generation on the spot. The third is to promote the establishment of policies and regulations to promote the development of new rural power grids (power systems). The fourth is to raise awareness of the importance of building a new rural power grid for the consumption of large-scale distributed clean energy and achieving my country’s “dual carbon” goals in the local party committee and government and the whole society, and establish a leading group for the construction of a new rural power grid at the government department level. , To formulate phased construction plans and plans to vigorously promote the construction of new rural power grids.