From November 5th to 6th ,2024, China International Industrial and Commercial Energy Storage Conference (BRICS Energy Storage Forum) was held in Shenzhen Convention and Exhibition Center with the theme of "Focus on High Quality and Lead New Development" jointly hosted by China Wind, Solar and Energy Storage Network, China Charging Pile Network and Solar Storage and Charging Industry Alliance. The forum integrates "main forum + 4 sub-forums + new product launch + brand selection", making it a significant event for the industry to explore the future energy development trend and the innovation of shared charging and swapping technology.

Technical Director Yuan Yuan from Shenzhen Yunt Digital Power Co., Ltd. gave a speech on the topic of "Exploration of Industrial and Commercial Energy Storage Network Applications".

        The theme report shared by Yunt Digital Power is "Exploration of Industrial and Commercial Energy Storage Grid-building Application". The reason why we say exploration is that Grid-building is a concept proposed under the emerging power system, and industrial and commercial applications are still being explored. The following are some of Yunt Digital Power's explorations and achievements in industrial and commercial applications of grid-building.

1.The significance of the research on Grid-building technology

Under the new power system, the proportion of new energy is getting higher and higher, and the problems it brings are becoming more and more obvious. New energy power generation has the characteristics of intermittent, volatile, nonlinear and uncertain, which makes the imbalance between power generation and power consumption large and the grid regulation difficult. Renewable energy power generation is accompanied by strong daily periodicity and temporal and spatial distribution. Power is transmitted from west to east, and the geographical distribution of power generation and consumption is uneven, resulting in long transmission lines and fragile grid structures. Wind and solar power grid connection technology has a non-synchronous nature, does not have the inherent angle of attack stability of synchronous machines, and cannot effectively provide grid inertia. In the "double high" system, due to insufficient system inertia, the grid's ability to resist the imbalance between power generation and power consumption is degraded, resulting in an increase in the probability of frequency collapse of the grid during accidents.

In the current solution: "Energy storage + phase regulator", energy storage is mainly used for active regulation, frequency regulation and peak regulation; phase regulators mainly support voltage stability, but the equipment cost is high and maintenance is complicated.

In the new power system, the new solution is to adopt a new grid construction technology, with the converter as the carrier and the grid construction control as the core, to build a synchronous power supply, provide inertia and support voltage. The converter can be a power electronic conversion device such as photovoltaic, wind power, SVG, PCS, etc.

Grid-building control is to adjust the active and reactive power output by changing the output voltage phase and amplitude of the converter, thereby providing frequency and voltage support for the system, simulating the voltage source characteristics of the synchronous generator, and keeping the internal potential constant during transient response. Grid-building control achieves synchronization with the help of power synchronization strategy, does not rely on external grid phase information, and can work in both isolated and grid-connected modes.

In the new power system, grid construction is mainly applied in weak power grids. Its main functions are:

(1) Supporting the grid voltage, possessing voltage source characteristics, and actively providing grid potential;

(2) Supporting the inertia of the grid, possessing angle of attack stability, and autonomously providing grid inertia;

(3) Fault ride-through capability, which can continuously connect to the grid under grid faults

(4) Damping controllability, which can smooth the output of new energy and avoid vibration.

In industrial and commercial application scenarios, off-grid power supply applications of energy storage systems, diesel generator power supply applications, substation microgrid applications, etc. can all be regarded as "weak power grid" application scenarios, and grid construction technology will play a great role in these application scenarios. 

2.Industrial and commercial energy storage applications of grid-building technology                     

The basic application scenarios of industrial and commercial energy storage are shown in the figure below

    With the continuous development of industrial and commercial energy storage, there are more and more large industrial users, and the demand for industrial and commercial storage networking has arrived. Grid construction technology can help large industrial users transform into low-carbon. With the help of grid-building technology, Yunt Digital Power enables industrial and commercial storage to adapt to and improve the power grid, have the ability to start in black and maintain power off the grid. Through flexible multi-machine paralleling strategies, flexible expansion is achieved while supporting distributed applications. Yunt’s PCS module can achieve megawatt-level expansion, effectively responding to the dynamic capacity expansion and off-grid power protection needs of large industrial users.

    Yunt has made many scene applications in diesel storage paralleling with the help of grid-building technology. We support single/multiple PCS paralleling and parallel with diesel generators to power the load. Energy storage can not only increase the capacity of diesel generators, but also support the frequency and voltage of diesel generators, and provide stable power supply voltage for loads.

    The substation microgrid is a regional island power grid built based on "source-grid-load-storage". It has all the links of generation, transmission, distribution and use, and has the characteristics of isolated grid operation. It can independently power large industrial production loads.

    Large machine and small grid, high requirements for industrial load production process and power quality, low safety and stability margin of power system; 

    New energy installations gradually squeeze synchronous power capacity, intermittent output, volatility and device fragility make the safety and stability of enterprise microgrids more prominent and power balance more difficult. 

Higher requirements are also put forward for the control strategy of microgrid in the substation area:    

1) New energy is dominant, lack of the foundation for self-synchronous stable operation, and needs to be built by itself;

2) The output of new energy with a high proportion is unstable, and it is necessary to coordinate the "source, grid, load and storage" to participate in the regulation;

3) Primary frequency regulation and voltage regulation need to be interfered, and power grid fluctuations need to be quickly coordinated and controlled to smooth out;

4) Rapidly coordinate control and dispatching system, stable system linkage.

The energy router cabinet independently developed by Yunt Digital Power provides an integrated microgrid system solution. The micro-grid hybrid cabinet provides a variety of AC and DC interfaces. The AC end can be connected to loads, power grids, diesel generators, charging piles, new energy power generation equipment, etc.; the DC end can be connected to photovoltaic, batteries, charging piles and other equipment. The energy router cabinet integrates EMS functions, has efficient energy management strategies, flexible parallel expansion, supports diesel and storage integration, has strong grid adaptability, and strong load capacity.