As a new element of the new power system, energy storage has been widely concerned
As the country blows the horn of the “double carbon” goal, the construction of a new power system has become the primary goal. A high proportion of new energy will lead to fundamental changes in the power grid. The problems of power electronics, low moment of inertia, and weak controllability of wind and solar power generation make the safe and reliable operation of the power grid face challenges. Energy storage has been recognized by industry experts and is the key to supporting the construction of a new power system. The National Development and Reform Commission and the National Energy Administration have successively issued the Guiding Opinions on Accelerating the Development of New Energy Storage and the Implementation Plan for the Development of New Energy Storage during the “Fourteenth Five Year Plan”. All localities have actively responded to the introduction of corresponding policies. Experts in the industry have actively carried out technical research around energy storage, and the energy storage industry has shown a hot development trend.
Energy storage application faces many practical problems
At present, although energy storage has made some progress in technology research and development, project construction, business model exploration, etc., there are still many practical problems in the actual construction process.
First of all, objectively speaking, the existing energy storage is faced with the problem of high construction costs. Considering the service life, number of uses, maintenance cycle, use environment requirements, especially the capacity degradation of electrochemical energy storage, the later stage also involves battery replacement, which is a huge investment cost. The existing investment subjects can be divided into power generation enterprise investment, power grid investment, user investment and other business subjects’ investment. According to the overall accounting, the general energy storage construction cost is in the tens of millions of dollars, and the energy storage cost has always been high. The relevant market-oriented mechanism, investment return mechanism and cost dredging mechanism are not perfect, which leads to the energy storage investment subject to flinch.
Secondly, although energy storage can play a huge role in system frequency modulation, voltage regulation, peak shifting and valley filling, arbitrage of peak valley price difference for large users, delaying the upgrading and transformation of transmission equipment, system black start, improving output characteristics by bundling with new energy, and being used as emergency power supply and auxiliary service, its essence is to rely on the storage capacity and power of energy storage for regulation. According to the ratio of energy storage power and capacity, energy storage can be divided into power type, energy type and capacity type. Capacitive energy storage generally needs to meet the requirements of continuous charging and discharging for a long time. Power energy storage batteries need to achieve rapid charging and discharging in the second level period. Energy energy storage is between the two. Each type of energy storage has its own application requirements, so it is unrealistic to talk about the role of energy storage without considering the specific type, capacity and power of energy storage. Moreover, in practice, the application scenarios of various energy storage technologies are not clearly defined, which will lead to a large deviation from the planning and operation to the actual benefits.
In addition, what role will energy storage play and how to participate in power grid dispatching after construction? In the case of unclear implementation plans, the enthusiasm of new energy enterprises to actively invest in energy storage is generally low. There is no clear mechanism for who will conduct the regulation and maintenance after the construction of energy storage, which has not been effectively implemented to the responsible subject, and the relevant standard system has yet to be formed. Therefore, the commercialization and scale of energy storage are still in the exploration stage. To truly enable energy storage to play its role in supporting the construction of new power systems, we need to jointly promote technology and systems.
At present, Yunnan Power Grid Corporation has mainly carried out technical research on the planning, dispatching and control of “new energy + energy storage”.
Research on energy storage configuration method of new energy stations and key technologies of grid connection regulation
(1) Energy storage optimization allocation technology considering the active support capability and technical economy of new energy stations
As the randomness, intermittency and fluctuation of wind power and photovoltaic power generation will cause a series of problems such as grid frequency voltage, etc., the “new energy+energy storage” coordination is used to mitigate related problems, and a new energy station energy storage optimization configuration method is proposed to comprehensively consider multiple functional orientations such as stabilizing the fluctuation of new energy output, improving power supply capacity, promoting the consumption of new energy, and supporting the stable operation of the grid.
On the basis of mainly considering the demand of suppressing the fluctuation of new energy output, promoting the consumption of new energy, meeting the peak shaving demand of provincial power grid, supporting voltage and frequency regulation, and improving technical economy, etc., according to the network conditions, resource characteristics, energy storage characteristics and technical economy, research the energy storage configuration boundary under multiple functional orientations such as peak shaving, frequency modulation, voltage regulation, multi time scales, and coordination between stations, and propose the target scenario of energy storage configuration. Considering the differential operation characteristics and stable operation requirements of the system under different new energy power generation proportions in the future, the functional orientation and technical economy of energy storage configuration of new energy stations are analyzed from multiple aspects such as the frequency and voltage recovery of new energy stations actively supporting disturbances, the stabilization of power fluctuation of new energy stations, peak shifting and valley filling, and the compensation of power prediction deviation, so as to form the guiding principles of energy storage configuration of new energy stations under various typical scenarios, The technical and economic evaluation is also carried out, which is expected to provide guidance for energy storage configuration of new energy stations.
(2) Optimal dispatching model and method strategy of new energy+energy storage
Considering the cooperative regulation capacity of energy storage and new energy, the dispatching algorithm is designed around the uncertainty of new energy power generation, power and electricity balance of the grid, grid security, peak shaving, frequency regulation and voltage regulation and other grid demands, and the characteristics of new energy and multi type energy storage are fully considered in combination with the characteristics of rapid regulation and regulation space of energy storage, generation output and load prediction, new energy output characteristics, etc, According to the actual situation of new energy stations, the mathematical model of “new energy+energy storage” dispatching object applicable to power grid analysis can be arbitrarily combined, and the optimized dispatching function of “new energy+energy storage” that flexibly matches the needs of power grid operation can be built.
In view of typical scenarios with different proportions of new energy power generation, define the functional positioning and system requirements of energy storage in terms of frequency and voltage support capability in large disturbance events, comprehensively consider the coordination with conventional units and new energy power generation’s frequency and voltage regulation capability, establish a techno economic optimal allocation model of energy storage capacity, and study the frequency regulation subsidy The relationship between the allocation of energy storage capacity and the comprehensive income of new energy stations is to build a model of “new energy+energy storage” for middle note and local power dispatching, which adapts to different levels of new energy output fluctuation and meets the requirements of frequency, voltage and safety support, to achieve an orderly and hierarchical management of multi-level energy storage dispatching mode, based on the changes in grid operation mode, maintenance arrangements, and new energy prediction results, Realize the dispatching strategy to meet the power supply demand in the next three days.
(3) “New energy+energy storage” integrated active support control technology to improve system stability
Focusing on the inertia support, frequency control and voltage control requirements of new energy power plants, and aiming at the problems of large number of control objects, complex dynamic characteristics and difficult source storage coordination of new energy power plants equipped with energy storage, the “new energy+energy storage” integrated active support control technology has been developed to improve system stability.
The multi aggregation index system of new energy stations considering inertia, frequency modulation droop characteristics, voltage regulation droop characteristics and other factors shall be established; Aiming at the problems of imprecise parameters and output prediction of new energy stations, the construction method of active and reactive power control model driven by operation data under incomplete parameters is proposed.