A method for arranging a regional local area network for distributed photovoltaic systems without supporting access

Abstract

The present invention relates to a method for arranging a regional local area network for distributed photovoltaics without supporting access. When the regional local area network provides access to a large number of distributed photovoltaics without supporting access, the regional local area network provides packaged regulation functions such as AC / DC conversion, voltage stabilization, frequency regulation, active and reactive coordination, harmonic control, and three-phase voltage imbalance regulation, thereby realizing plug-and-play and unconditional access of distributed photovoltaic power generation components. The regional local area network arrangement method is equipped with a shared energy storage device that shares multiple voltage levels; a principle for the coordinated arrangement of quantitative electrochemical energy storage and reactive power generation equipment is proposed; and the arrangement capacity and type of reactive power generation equipment are planned under the premise of the frequency modulation time and capacity response of the quantitative electrochemical energy storage; and a logic for the coordinated arrangement and collaborative work of electrochemical energy storage and reactive power generation equipment under the frequency control function of energy storage is proposed.

Description

Technical Field

[0001] The present invention relates to the field of regional power grid construction, and in particular to a method for arranging a regional local area network without supporting access for distributed photovoltaics. Background Art

[0002] China has made a solemn "30·60" commitment to the world, proposing to meet total carbon emissions targets by 2030. To support its energy transition, China has proposed accelerating the construction of a new power system dominated by renewable energy, aiming for at least 1.2 billion kilowatts of wind and photovoltaic power installed capacity nationwide by 2030. Currently, centralized photovoltaic project construction is rapidly advancing in central and eastern my country, and distributed photovoltaic projects are also nearing capacity expansion. Technical challenges facing the rapid development of distributed photovoltaics include clarifying relevant policy requirements, addressing the impact of large-scale distributed photovoltaic integration on medium and low voltage distribution networks, and ensuring stable power quality in regional power grids. Furthermore, addressing the need for layered reactive power devices when multiple power sources are connected and proposing solutions for the coordinated configuration and coordinated operation of layered reactive power devices and energy storage, based on the large-scale application of electrochemical energy storage, to improve the economic efficiency and safety of local area network operations. Summary of the Invention

[0003] In order to solve the above technical problems, the primary purpose of the present invention is to provide a method for arranging a regional local area network without supporting access for distributed photovoltaics.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for arranging a local area network (LAN) for distributed photovoltaic systems without supporting access. The equipment in the LAN includes distributed photovoltaic power generation components, circuit breakers, a junction station, an inverter with frequency regulation capability, a harmonics suppressor, a layered reactive power compensation device, and multi-voltage shared energy storage. An isolating switch tube, an AC / DC converter module, an isolation transformer, and an energy storage converter are provided before the transformer at the multi-voltage shared energy storage access point.

[0006] By arranging an inverter with frequency regulation capability in front of the confluence station, the frequency in front of the confluence station is regulated; by arranging the layered reactive power compensation device in front of the confluence station and working together with the multi-voltage shared energy storage device, the reactive power in front of the confluence station and the grid connection point is regulated, thereby adjusting the frequency and stabilizing the voltage; when a large number of distributed photovoltaic power generation components are not connected in a supporting manner, the local area network provides the functions of AC / DC conversion, voltage stabilization, frequency regulation, active and reactive power coordination, harmonic control, and three-phase voltage imbalance regulation, thereby realizing plug-and-play and unconditional access of distributed photovoltaic power generation components.

[0007] Furthermore, the multi-voltage shared energy storage is a shared energy storage device that shares multiple voltage levels.

[0008] Furthermore, the layout method proposes a principle for coordinated layout of quantitative electrochemical energy storage and reactive power generation equipment, and plans the layout capacity and type of reactive power generation equipment under the premise of frequency modulation time and capacity response of quantitative electrochemical energy storage.

[0009] Furthermore, the arrangement method forms a coordinated arrangement and collaborative working logic of electrochemical energy storage and reactive power generation equipment based on the multi-voltage shared energy storage frequency control function, specifically including:

[0010] (1) First, frequency adjustment is performed at the inverter before the confluence station;

[0011] (2) After being merged into the merging station, the layered reactive power compensation device will first be activated;

[0012] (3) If the grid voltage does not meet the requirements, the control device of the multi-voltage shared energy storage starts to start and perform primary and secondary frequency compensation until the grid voltage meets the requirements.

[0013] Furthermore, the isolating switch tube is used to physically isolate the shared energy storage device from the transformer, the AC / DC conversion module is used to convert the DC to AC power of the shared energy storage device, and the isolation transformer is used to switch between different voltage levels; the energy storage converter realizes the switching of power between active and reactive power.

[0014] It can be seen from the above technical solution that the beneficial effects of the present invention are:

[0015] The present invention provides a local layout method for a large number of distributed photovoltaics without supporting access, realizing plug-and-play and unconditional access of distributed photovoltaics; it is equipped with shared energy storage equipment with multiple voltage levels, and the energy storage equipment can be shared by multiple voltage levels; the present invention proposes a principle for the coordinated layout of quantitative electrochemical energy storage and reactive power generation equipment, and plans the layout capacity and type of reactive power equipment under the premise of frequency modulation time and capacity response of quantitative energy storage; the present invention proposes the coordinated layout and collaborative working logic of electrochemical energy storage and reactive power generation equipment under the frequency control function of energy storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a regional local area network configuration diagram for distributed photovoltaic without supporting access of the present invention.

[0017] Figure 2 This is a logical diagram of the coordinated arrangement and collaborative operation of the electrochemical energy storage and reactive power generation equipment of the present invention. DETAILED DESCRIPTION

[0018] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0019] The regional local area network of the present invention provides a large number of distributed photovoltaic power generation components without supporting access. The regional local area network provides packaged adjustment functions such as AC / DC conversion, voltage stabilization, frequency regulation, active and reactive coordination, harmonic control, and three-phase voltage imbalance regulation, thereby realizing plug-and-play and unconditional access of distributed photovoltaic power generation components.

[0020] like Figure 1 As shown, the distributed photovoltaic system without supporting access to a local area network of the present invention includes distributed photovoltaic power generation components, circuit breakers, a junction station, an inverter with frequency regulation capability, a harmonics suppressor, a layered reactive power compensation device, and a multi-voltage shared energy storage device. The multi-voltage shared energy storage device is a shared energy storage device equipped with multiple voltage levels, that is, the energy storage device can be shared by multiple voltage levels.

[0021] Before the shared energy storage device is connected to the grid-connected transformer, an isolating switch tube, an AC / DC direct-to-alternating conversion module, an isolation transformer, and an energy storage converter are provided. The isolating switch tube is mainly used to physically isolate the multi-voltage shared energy storage device from the isolation transformer. The AC / DC direct-to-alternating conversion module is used for the DC-to-AC conversion of the electric energy of the multi-voltage shared energy storage device. The isolation transformer is used for switching between different voltage levels, which include three voltage levels: 220 / 380V, 10KV, and 35KV. The energy storage converter can realize the switching between active and reactive power, and can be converted into inductive reactive power, capacitive reactive power, and active power.

[0022] Among them, the regional local area network layout method of the present invention is provided with a multi-stage frequency adjustment device, wherein an inverter with frequency adjustment capability is provided in front of the confluence station to adjust the frequency in front of the confluence station; a layered reactive power compensation device is provided before the confluence station and the grid connection point, which works together with the multi-voltage shared energy storage device to adjust the reactive power before the confluence station and the grid connection point, thereby playing a role in adjusting the frequency and stabilizing the voltage.

[0023] This invention proposes a principle for the coordinated placement of quantitative electrochemical energy storage and reactive power generation equipment. The capacity and type of reactive power generation equipment are planned based on the frequency modulation time and capacity response of the quantitative electrochemical energy storage. During the project planning phase, the utility of electrochemical energy storage in the reactive power sector is calculated and some reactive power generation devices are replaced. Regarding the selection of reactive power generation devices, based on the principle of maximizing economic efficiency, a combination of physical reactive power generation equipment and power electronic regulation devices is adopted, sequentially employing shunt capacitors, series reactors, static reactive power compensation devices, and dynamic reactive power compensation devices.

[0024] Assume the grid frequency deviation dead zone percentage (+c%, -c%), the total installed capacity of all distributed photovoltaic power generation components A, the energy storage ratio a%, and the energy storage completion time B1 and the completion time B2-B3, where B2 is the minimum time for the secondary frequency regulation and B3 is the maximum time for the secondary frequency regulation. The power change rate per minute is d%, then:

[0025] The primary frequency regulation capacity of a certain capacity energy storage is Q1 = (2·A·a%·B1) / (1-2·A·c%);

[0026] The secondary frequency regulation capacity of a certain capacity energy storage is Q2 = [2·A·d%·B3·(B3-B2)] / (1-2·A·c%);

[0027] The sum of the primary and secondary frequency regulation capacities of a certain capacity energy storage is Q3:

[0028] Q3=Q1+Q2=(2·A·a%·B1) / (1-2·A·c%)+[2·A·d%·B3·(B3-B2)] / (1-2·A·c%)

[0029] After planning the role of energy storage in frequency regulation, the remaining reactive power required by the grid is provided by static reactive power generation equipment. The reactive capacity required for 220kV and below grids is:

[0030] Q=K·P·1.15

[0031] Among them, K is the maximum natural reactive load factor of the power grid, and P is the maximum active load of the power grid;

[0032] The remaining reactive power generation device needs to provide equipment capacity:

[0033] Q4=Q-Q3=K·P·1.15-(2·A·a%·B1) / (1-2·A c%)+[2·A·d%·B3·(B3-B2)] / (1-2·A·c%)

[0034] In principle, static reactive power compensation equipment should be used for medium and low voltage reactive power generation. For transmission lines 220V and below, high and low voltage shunt reactors and capacitors should be used for compensation. Dynamic reactive power compensation equipment may be considered when there are a large number of junction stations for distributed photovoltaic power generation components. The configuration principle is: 10kV distribution lines should be equipped with high-voltage shunt capacitors, or low-voltage shunt reactors on the low-voltage side of the transformer. The installed capacitor capacity should be approximately 0.05%-0.1% of the line transformer capacity. The reactive power compensation capacity for connections at the 35kV voltage level should not exceed 12Mvar, and for connections at the 10kV voltage level should not exceed 8Mvar. The busbar voltage change caused by switching on or off the largest single reactive power compensation device should not exceed 2.5% of the rated voltage.

[0035] When energy storage and reactive power are operated in coordination, the criteria for determining the stable operation of the power grid include: (1) voltage qualification rate; (2) frequency deviation range; (3) three-phase voltage imbalance; and (4) harmonic ratio.

[0036] like Figure 2 As shown, the present invention proposes that when energy storage plays a frequency control function, a coordinated arrangement and collaborative working logic of electrochemical energy storage and reactive power generation equipment is formed, including:

[0037] (1) First, frequency adjustment is performed at the inverter before the confluence station;

[0038] (2) After being merged into the merging station, the layered reactive power compensation device will first be activated;

[0039] (3) If the grid voltage does not meet the requirements, the control device of the multi-voltage shared energy storage device starts to start and perform primary and secondary frequency compensation until the grid voltage meets the requirements.

[0040] In order to extend the service life of energy storage, take into account the economic efficiency of equipment configuration, avoid deep charging and discharging of energy storage, give priority to calling reactive power generation devices to work, and the insufficient frequency regulation is supplemented by energy storage.

[0041] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for arranging a regional local area network for distributed photovoltaic systems without supporting access, characterized by: Before the multi-voltage shared energy storage device is connected to the transformer at the grid connection point, an isolation switch tube, AC / DC direct-to-alternating conversion module, isolation transformer and energy storage converter are installed; By installing an inverter with frequency regulation capability before the confluence station, the frequency before the confluence station is adjusted; by installing a layered reactive power compensation device before the confluence station and the grid connection point, and working together with a multi-voltage shared energy storage device, the reactive power before the confluence station and the grid connection point is adjusted, thereby adjusting the frequency and stabilizing the voltage; when a large number of distributed photovoltaic power generation components are not connected with supporting equipment, the regional local area network provides the functions of AC / DC conversion, voltage stabilization, frequency regulation, active and reactive power coordination, harmonic control, and three-phase voltage imbalance regulation, realizing plug-and-play and unconditional access of distributed photovoltaic power generation components; The layout method proposes the principle of coordinated layout of quantitative electrochemical energy storage and reactive power generation equipment, and plans the layout capacity and type of reactive power generation equipment under the premise of frequency modulation time and capacity response of quantitative electrochemical energy storage; The arrangement method forms a coordinated arrangement and collaborative working logic of electrochemical energy storage and reactive power generation equipment based on the frequency control function of the multi-voltage shared energy storage device, specifically including: (1) First, frequency adjustment is performed at the inverter before the confluence station; (2) After being merged into the merging station, the layered reactive power compensation device will first be activated; (3) If the grid voltage does not meet the requirements, the control device of the multi-voltage shared energy storage device starts to start and perform primary and secondary frequency compensation until the grid voltage meets the requirements.

2. A method for arranging a regional local area network for distributed photovoltaic systems without supporting access according to claim 1, characterized in that: The multi-voltage shared energy storage device is a shared energy storage device that shares voltages at multiple voltage levels.

3. The method for arranging a regional local area network for distributed photovoltaic systems without supporting access according to claim 2, characterized in that: The isolating switch tube is used to physically isolate the multi-voltage shared energy storage device from the transformer, the AC / DC conversion module is used to convert the DC and AC power of the multi-voltage shared energy storage device, and the isolation transformer is used to switch between different voltage levels; the energy storage converter realizes the switching of power between active and reactive power.

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