Flexible direct current interconnection device

Abstract

The utility model discloses a flexible direct current interconnection device, which comprises a plurality of transformer areas, a seamless change-over switch, an energy storage device, a power conversion unit and conversion devices, each transformer area is connected with one conversion device, and the seamless change-over switch, the energy storage device and the power conversion unit are arranged between one transformer area and the conversion device. In the implementation process of the utility model, through the flexible direct-current interconnection device, an alternating-current and direct-current micro-grid in which the direct-current sides of the two transformers are interconnected is constructed, so that power balance between different transformers in a factory area and efficient consumption of green power are realized, heavy overload of the transformers is prevented, and the problem of power imbalance caused by a load power utilization time sequence is solved; voltage sag treatment and emergency guarantee functions are provided for key loads through the grid-connected and off-grid seamless change-over switch, the energy storage device and the power conversion unit.

Description

Technical Field

[0001] This utility model belongs to the field of power distribution network technology, specifically a flexible DC interconnection device. Background Technology

[0002] The grid connection of large-scale distributed photovoltaic power and the widespread adoption of new loads, such as electric vehicle charging stations, directly impact the power quality and operation control of existing distribution substations. Large-scale, unregulated grid connection will also lead to insufficient capacity in distribution substations and power lines, requiring substantial investment in capacity expansion. On the other hand, inconsistent economic structures within the same region result in significant load disparities among substations. With the advancement of the dual-carbon strategy, the capacity of connected public transformers is gradually increasing, creating risks of overload and overvoltage in some substations that are difficult to address through capacity expansion investments. Conversely, some substations in the same region have lighter loads but are not fully utilizing their capacity. Therefore, flexible DC interconnection technology between multiple substations in the same region can improve load balancing and energy optimization capabilities to some extent, alleviating the pressure of grid upgrading and transformation. Summary of the Invention

[0003] In view of the above situation and to overcome the defects of the prior art, this utility model provides a flexible DC interconnection device, which effectively solves the problems in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a flexible DC interconnection device, comprising multiple transformer substations, a seamless switching switch, an energy storage device, a power conversion unit, and a conversion device. Each transformer substation is connected to a conversion device, and a seamless switching switch, an energy storage device, and a power conversion unit are also provided between one transformer substation and the conversion device.

[0005] Preferably, the multiple transformer substations include substation 1, substation 2, and substation 3. Substation 1 is connected to a seamless transfer switch, an energy storage device, and a power conversion unit. Substation 2 and substation 3 are each connected to a conversion device. Substation 1 is connected to the mains power.

[0006] Preferably, the conversion device is an AC / DC conversion device or a DC / DC conversion device.

[0007] Compared with the prior art, the beneficial effects of this utility model are:

[0008] Flexible DC interconnection technology can improve the load balancing and energy optimization capabilities between distribution stations to a certain extent, and alleviate the pressure of power grid upgrading and transformation.

[0009] By using flexible DC interconnection devices, an AC / DC microgrid is constructed with the DC sides of two transformers interconnected, achieving power balance among different transformers within the plant area, efficient consumption of green electricity, prevention of transformer overload, and resolution of power imbalance caused by load timing. Through seamless grid-connected / off-grid switching switches, energy storage devices, and power conversion units, voltage sag mitigation and emergency backup functions are provided for critical loads.

[0010] The constructed distributed photovoltaic system is connected to a DC 750V DC bus via a DC / DC converter to achieve efficient grid connection and balanced power distribution.

[0011] The DC bus connects to energy storage batteries and new energy vehicles through DC-DC power conversion devices, and interacts with photovoltaic power generation through strategic adjustments, providing voltage disturbance management and emergency power supply support for the system.

[0012] Intelligent operation and maintenance (O&M) is based on fully digital management, reducing manpower and improving the predictability of the system. It elevates traditional O&M to the O&M of green, digital, and smart microgrids for photovoltaics, energy storage, and charging piles under new power systems. This enhances the operational safety and intelligence level of projects. Attached Figure Description

[0013] The accompanying drawings are provided to further illustrate the present invention and form part of the specification. They are used together with the embodiments of the present invention to explain the present invention, but do not constitute a limitation thereof. In the drawings:

[0014] Figure 1 This is a schematic diagram of the overall structure of this utility model. Detailed Implementation

[0015] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the protection scope of the present utility model.

[0016] Depend on Figure 1 The present invention discloses a flexible DC interconnection device, characterized in that it includes multiple transformer substations, a seamless switching switch, an energy storage device, a power conversion unit, and a conversion device. Each transformer substation is connected to a conversion device, and a seamless switching switch, an energy storage device, and a power conversion unit are also provided between one transformer substation and the conversion device.

[0017] The system includes multiple transformer substations, namely Substation 1, Substation 2, and Substation 3. Substation 1 is connected to a seamless transfer switch, an energy storage device, and a power conversion unit. Substations 2 and 3 are each connected to a conversion device. Substation 1 is connected to the mains power supply.

[0018] The conversion device is an AC / DC conversion device or a DC / DC conversion device.

[0019] The seamless switching switch is model STS-M(100K∽500K)-FA380 energy storage grid-connected switching device.

[0020] The energy storage device is a three-wire PCS-M100K-TA380 energy storage converter module.

[0021] The converter is model DCDC-M60K.

[0022] As one specific implementation method:

[0023] The system consists of three 200kVA bidirectional AC / DC converter cabinets, one of which is an AC / DC bidirectional converter (conversion device) with automatic grid connection and disconnection functions, consisting of an STS seamless switching module + PCS three-wire module (energy storage device) + Yn-D isolation transformer + power change unit, as well as intelligent management and other units.

[0024] The system operates as follows: Upon grid connection, the AC / DC bidirectional converter in transformer area 3 establishes a DC bus voltage of 750Vdc (this system) → DC voltage regulation mode is activated → the AC / DC bidirectional converters in transformer areas 2 and 1 are activated to control energy flow → AC loads are activated for power output. During this process, the energy control level can be manually set on the local monitoring and management system display screen. Both the bidirectional AC / DC converter cabinets in transformer areas 2 and 3 can support the bus and can also be used for power control.

[0025] If the AC / DC bidirectional converter in transformer area 1 is in DC regulated operation mode to support the bus voltage, when the mains power in transformer area 1 is abnormal, the DC bus is regulated by other AC / DC bidirectional converters. After the DC bus is taken over, the DC bus voltage range is between 730 and 770 Vdc. The original set value of AC active power becomes invalid. At this time, the AC / DC bidirectional converter in transformer area 1 switches from AC voltage source mode to load inverter power supply (seamless off-grid). At the same time, the local control terminal will compare the load rate and select the AC / DC bidirectional converter on the grid side of the transformer area with a lighter load rate as a backup voltage source to support the DC bus voltage.

[0026] If the AC / DC converter #3 is operating in DC regulated mode to support the bus voltage, when the mains power in area 3 is abnormal, the DC bus will be regulated by other AC / DC bidirectional converters (such as area 1, which was originally in current source PQ mode). After the takeover, the bus voltage range will be between 730 and 770 Vdc, and the original set value of AC active power will become invalid. At this time, the AC / DC bidirectional converter in area 3 will switch to off-grid mode and be in standby mode. After the mains power is restored, it will automatically switch to grid-connected current source mode; at the same time, the EMS will compare the load rate and select the AC / DC converter on the grid side of the area with the lighter load rate as the backup voltage source to support the DC bus voltage.

[0027] If the ACDC2# converter is in DC regulated operation mode, the control logic is the same as above.

[0028] When all three main power supplies in the distribution area fail, all ACDC converters will be in standby mode.

[0029] When the mains power (grid) fails and the energy storage device establishes an AC power source, the device completes the mode switch, with a power transfer time in the order of seconds. When AC power fluctuations (voltage and frequency exceeding limits) are caused by impulsive load input and photovoltaic power generation fluctuations, triggering the AC-DC converter protection threshold, the corresponding flexible interconnection device enters standby mode.

[0030] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0031] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A flexible DC interconnection arrangement, characterized by: The power supply system comprises a plurality of districts, seamless switching switches, energy storage devices, power conversion units and conversion devices, each district is connected with a conversion device, and one district is further provided with a seamless switching switch, an energy storage device and a power conversion unit between the district and the conversion device.

2. The flexible DC interconnection arrangement of claim 1, characterized in that: The plurality of districts comprise a district 1, a district 2 and a district 3, the district 1 is connected with the seamless switching switch, the energy storage device and the power conversion unit, the district 2 and the district 3 are respectively connected with a conversion device, and the district 1 is connected with the commercial power.

3. The flexible DC interconnection device of claim 1, wherein: The conversion device is an AC / DC conversion device or a DC / DC conversion device.

Images