Microgrid is divided into off grid microgrid and grid connected microgrid. The off grid microgrid is generally used to solve the power supply demand of remote areas or island areas. In terms of technical economy, it is the inevitable choice for the extension of the main network, and its development is inevitable. The grid connected microgrid is different, it is only a solution for the local power supply mode, not the only solution. Therefore, compared with off grid microgrid, how to develop grid connected microgrid is more worthy of consideration. The following discussion refers to the grid connected microgrid, referred to as microgrid.
Grid connected microgrid has the main technical characteristics of micro, clean, self balancing and isolated grid operation. In recent years, both guidance documents and demonstration projects are encouraging the commercial development of grid connected microgrid, but the actual effect is not satisfactory. There is a consensus in the industry that the main reason why microgrid is in trouble is that the reform of monopoly system and market mechanism is not in place, the cost advantage of nearby power supply and sales of microgrid can not be brought into play, and the flexibility advantage of support system. However, the industry also believes that as long as there is an appropriate market mechanism in the future, there will be broad space for the development of microgrid. However, the essence of market mechanism is the scarcity and necessity of resources. If microgrid resources are not needed in the future power system, the market mechanism that is conducive to the commercial development of microgrid may never come.
The trend of power system pattern in the 14th five year plan will have a crucial impact on the development of microgrid. The growth rate of power load in the 14th five year plan is likely to slow down further than in the past. Under the background of load growth, if we still only pay attention to traditional power solutions such as large-scale power stations and grid construction, it is worth pondering whether and how to develop micro grid.
1、 From a technical point of view, do we need a microgrid
From the analysis of the technical characteristics of the grid connected microgrid, it can establish a direct power supply relationship with users through the distribution facilities, improve the consumption ratio and utilization efficiency of distributed clean energy; reduce the impact of the high proportion of local distributed clean energy on the grid by effectively managing the distributed clean energy in local areas; and improve the operation capacity of large power grid through the isolated grid Through the collaborative response of “source network load storage”, the support ability of active power and reactive power of external power grid can be improved.
From the above point of view, microgrid is a very advanced solution for the future power system, we seem to need microgrid. However, the above analysis is based on these assumptions:
（1） There is a big gap between the installed capacity of main power sources (including new energy power stations) and the load development, and the gap is mainly solved by the development of distributed clean energy;
（2） The system is relatively weak, and it is difficult to withstand the fluctuation of large-scale distributed clean energy grid connection;
（3） The reliability of power grid is poor, so users need to improve the reliability of power supply and ensure the economy through a technical innovation;
（4） Due to the shortage of peak load regulation, frequency regulation and reactive power resources, more flexible resources are needed to maintain the security and stability of the system.
When “assumption (1)” is not satisfied, from the perspective of macro development and power balance, distributed clean energy will not have the basis for large-scale development, so the microgrid born to solve the problem of large-scale distributed clean energy consumption and management will not have broad market space.
When the “assumption (2)” is not satisfied, even if the distributed clean energy can be developed on a large scale, because the system resources (including grid capacity resources and auxiliary service resources) are strong enough, there is no need to reduce the impact of distributed clean energy on the grid through microgrid.
When the “assumption (3)” is not satisfied and the power supply reliability has met the basic needs of users, it is difficult for users to pay for the technical cost of seamless switching from “grid connected” to “isolated” microgrid.
When the “assumption (4)” is not satisfied, the demand for the auxiliary service capacity of the microgrid is not strong. The flexible resources enhanced by the unified control means of microgrid “source network load storage” are difficult to play the market value because of the scarcity of resources.
In fact, through the rapid construction of power system in recent decades, the power supply in most areas of China is sufficient and the power grid is relatively strong, which is also the most essential reason for the low application value of micro grid.
2、 The future power system pattern determines the development space of microgrid
Does the future power system need micro grid? The development of power load shows that the power gap will eventually appear, which means that the system will meet the demand of power supply security and reliability of new load, and also means that the system will have more demand for auxiliary service capacity. So these gaps and demands are solved through the construction of large power supply, long-distance transmission and strengthening the redundancy of power grid? Or should it be solved by vigorously developing distributed energy to supply power nearby and strengthening the collaborative management of “source network, load and storage” in local areas? Two different development ideas determine the real market space and value of microgrid in the future.
A very simple logic is that the active development of distribution network represented by microgrid and the strong development of transmission network are mutually exclusive. The higher the active degree of the distribution network, the smaller the construction scale of the transmission network; on the contrary, the larger the transmission capacity planning of the transmission network, the less the access power capacity of the distribution network. Is the fund used for the construction of traditional power facilities such as transmission network and large power sources, or for the construction of new power facilities such as distributed generation and Microgrid? The redundant result of the simultaneous development of the two is either that there is no economy in the investment of both, or that the cost of electricity consumption is pushed up.
Therefore, from the perspective of development, the increment of future load provides an opportunity to reconstruct the pattern of power system. Although microgrid is a more efficient, greener and safer energy production and supply solution in the future, if the future power system pattern is not subversive development, then with the further development of power capacity, grid capacity and other alternative modes, it is difficult to have broad demand for grid connected microgrid in the future.
3、 The effect of power reform determines the possibility of micro grid breakthrough
Of course, whether in the future or now, the micro grid industry may not need to compete with the traditional mode. The idea of power system development focusing on large-scale development of distributed clean energy and local balance is indeed conducive to the large-scale application of microgrid. However, even if the power system pattern does not change subversively, the microgrid, as an effective supplement to the power system technology mode, has become an important tool for the development of microgrid industry There’s plenty of space.
In this case, what supports the development of microgrid is not the macro demand, but the micro solution that can be implemented. The main production and operation mode of microgrid is to sell distributed clean energy power to users nearby, which plays a positive role in improving the utilization rate of clean energy and reducing the cost of electricity. But whether this mode can run smoothly is the main problem of the development of micro grid. In short, the openness and inclusiveness of power rationing reform, the rationality and fairness of power market trading mechanism determine whether the microgrid solution can break through.
The Trial Measures for promoting the construction of grid connected microgrid (fgneng  No. 1339) defines the operation subject of grid connected microgrid as the second kind of power selling company with the right to operate the distribution network, and endows the microgrid with legal market subject identity. However, it is precisely this rigorous positioning that unexpectedly interweaves microgrid and incremental distribution reform. Therefore, in the case of incremental distribution project implementation is not smooth, micro grid project implementation is more difficult.
4、 Microgrid regulatory model can be more flexible
The original intention of microgrid is to manage large-scale grid connected distributed clean energy, and its development focus should also be to solve the local consumption and safety management of distributed clean energy, rather than the development of “scale competition” with the distribution network. For microgrid, the purpose of electricity supply and sale for users is not to solve the problem of distributed energy consumption and improve the efficiency of distributed energy utilization. Therefore, from this point of view, the micro grid regulatory model can be innovative and breakthrough, not to the power supply effect as its main regulatory goal, but to the distributed energy consumption effect and comprehensive energy efficiency improvement as the basis to support the existence of micro grid business.
On the one hand, for the large-scale microgrid, it can still be positioned as the second type of electricity selling company, but it needs innovative management and breakthrough in the regional division, repeated power supply and other problems encountered in the incremental distribution network. The necessity of microgrid existence and the legitimacy of obtaining the identity of business entity should focus on the matching of distributed clean energy, power supply facilities and user load, as well as the ability to act as a controllable response unit of power system from the electrical physical level, rather than the division of power supply area at the spatial level. The division of power supply objects based on the electrical physical level of distribution facilities has greater significance for the local consumption of distributed clean energy and the promotion of flexible resources, which is more in line with the original intention of the appearance of microgrid.
On the other hand, for smaller microgrid, it can be positioned as a technical supplement to the end link of public distribution network, serving the comprehensive energy service business of office buildings, commercial complexes and other power supply links. Using microgrid mode to give this kind of subject legal power supply status and optimize its power supply management can help solve the lack of legal service subject in China’s power supply link In addition, it can help the development of user side integrated energy services. At the same time, the unified management idea of “source network load storage” of microgrid is more conducive to the controllable response of such load aggregation units, and is more conducive to improving the flexibility of power system than the general sense of power transfer.
5、 The development of microgrid technology should focus on market demand
As mentioned above, only under specific conditions can microgrid with full technical characteristics be completely needed by the system. When the macro fundamentals of the system can not realize all the technical characteristics of microgrid, some of its technical requirements appear to be weak, such as the proportion requirement of renewable energy, and the technical requirements of self balancing operation ability and isolated grid operation ability.
The proportion of renewable energy depends more on resource conditions, site conditions, economic conditions and operation mode of microgrid; whether microgrid can balance itself in the final analysis depends on market demand. On the one hand, it is the technology and economy of internal power development; on the other hand, it is the transaction cost with external power market and the transmission and distribution fee settled with external power grid（ The technology cost of seamless switching from “grid connected” to “isolated network” is not low. Whether the revenue can be generated through isolated network operation is crucial, which depends on whether the user needs the project to provide isolated network operation service and is willing to pay for it, or whether the market can pay for the interruptible load capacity of the unit.
Therefore, in terms of encouraging the development of microgrid format, except for some basic technical requirements, it is not necessary to completely limit the technical form of microgrid projects with unified technical standards.
There is no doubt that microgrid is a more advanced, more efficient and more green energy production and consumption mode, but what supports its development is neither the technical advantages of castles in the air nor the encouragement of red head documents, but the real market demand. The market space of microgrid depends on the development pattern of power system in the future, the landing of microgrid depends on the effect of system and mechanism reform, and the market vitality of microgrid is related to the flexibility of supervision mode.
In short, although the microgrid is still in the pilot demonstration stage, it does not reflect much commercial investment value, but if only under the established track of power system capacity development and system and mechanism reform, the microgrid already faces the choice of whether to develop and how to develop.