Research on building a new power system framework with new energy as the main body

Third, traditional security problems persist for a long time. In the future for a long time, the power system will still be dominated by AC synchronous network. However, with a large number of new energy sources replacing conventional power supplies, the fundamental elements of maintaining the security and stability of the AC power system are weakened, and the stability problem of the traditional AC power grid is aggravated. For example, rotating equipment is replaced by stationary equipment, system inertia no longer increases with scale or even decreases, and the frequency control of power grid is more difficult; The voltage regulation ability is decreased, the voltage control in the high proportion of new energy access areas is difficult, and the dynamic reactive power support capacity in the high proportion of power receiving areas is insufficient. The electromagnetic transient process of power electronic equipment has a profound effect on the rotor motion of synchronous motor, and the power Angle stability problem is more complicated.

Fourth, the power system with a high proportion of power electronics and a high proportion of new energy (" double high ") faces new problems. In the near future, new energy units have the common vulnerability of power electronic equipment. In the face of frequency and voltage fluctuations, it is easy to go off-grid, and the fault evolution process is more complicated, which is superimposed with the further expansion of long-distance transmission scale, resulting in an increase in the risk of large-scale power outage. The decrease in the proportion of synchronous power supply and the lack of support capacity of power electronic equipment lead to new stability problems such as broadband oscillation, and the power system presents complex characteristics of multi-instability mode coupling. In the long term, a higher proportion of new energy or even all-power electronic systems will bring new stability problems.

(4) Overall power supply cost

New energy parity online is not equal to parity utilization. In addition to the cost of the new energy station, the cost of new energy utilization also includes system costs such as flexible power supply investment, system adjustment operation cost, large power grid expansion and reinforcement investment, network connection and distribution network investment. Research at home and abroad shows that after the penetration rate of new energy power exceeds 10%~15%, the system cost will enter the critical point of rapid growth, and the future cost reduction of new energy stations is difficult to fully offset the system cost increase of new energy. With the gradual increase of the penetration rate of new energy generation, the system cost increases significantly and the dredging is difficult, which will inevitably affect the power supply cost of the whole society.

Fourth, the connotation, construction principles and ideas of the new power system

To cope with the problems and challenges faced by the power system, a new type of power system should be constructed scientifically to ensure the implementation of the national energy transformation strategy. To build a new type of power system with new energy as the main body, we must adhere to the system thinking, follow the technical characteristics and objective laws of the power system, make full use of mature technologies, stock systems and further tap the potential, "open and inclusive" support the development of new technologies, and actively, steadily and step by step to realize the transformation.

(1) The connotation of the new power system

The new power system takes new energy as the main supply, meets the growing demand for clean electricity, and has a high degree of safety, openness and adaptability.

In terms of security, the coordinated development of power grids at all levels in the new power system, the integration of various power grid technologies, and the optimization of wide-area resource allocation capabilities have been significantly improved; The power grid security and stability level is controllable, controllable and in control, effectively carrying a high proportion of new energy, DC and other power electronic equipment access, to meet the needs of national energy security, reliable power supply, and safe operation of the power grid.

In terms of openness, the grid of the new power system is highly diverse, open and inclusive, compatible with all kinds of new power technologies, and supports the convenient access needs of all kinds of new equipment. It supports the interactive transformation of various energy sources and the two-way interaction of new loads, and becomes a hub for the organic interconnection of various energy networks.

In terms of adaptability, the various links of the source network, load and storage of the new power system are closely connected and coordinated, and through the application of advanced technology and the expansion of the control resource pool, strong flexible adjustment ability and highly intelligent operation control ability are achieved, and the application scenario of extensive access and intensive interaction of massive heterogeneous resources is adapted to.