Emergency Power Supply Switching Strategy for Distribution Areas Based on Converged Terminals and Shared Energy Storage Systems

Abstract

This invention proposes an emergency power supply switching strategy for transformer substations based on integrated terminals and shared energy storage systems. Electrical connections between shared energy storage units are achieved via DC interconnection cables between substations. The voltage drop on the common DC side caused by the grid connection of the energy storage converter in the emergency power supply substation is utilized. Power transfer between shared energy storage units is achieved through DC voltage droop control. Emergency power supply startup is executed according to the switching strategy: by controlling the PCS to switch to V / f off-grid operation, the energy from the energy storage battery is inverted and reversed to supply power to the AC bus, providing short-term emergency power to critical loads; or emergency power supply restoration is executed by switching the PCS of the emergency power supply substation to P / Q control mode and activating the P / Q control mode of other substation PCS, restoring the shared energy storage power mutual assistance function.

Description

Technical Field

[0001] This invention relates to the field of intelligent control technology for distribution transformer areas, and in particular to an emergency power supply switching strategy for distribution transformer areas based on a converged terminal and a shared energy storage system. Background Technology

[0002] With the large-scale integration of high-proportion distributed photovoltaic (PV) power grids into distribution substations, substation-side energy storage has also been put into operation for PV consumption. To improve inter-regional PV consumption capacity, existing technologies interconnect energy storage devices in various substations via DC buses or DC cables to form a shared substation energy storage system. This system allows for the sharing of battery capacity and power across multiple substations, thereby achieving greater capacity with relatively small investments. As a new generation of substation-side intelligent devices, the substation intelligent fusion terminal possesses application functions such as high-frequency data acquisition, IoT access, and edge computing. It can serve as the core for accessing substation-side intelligent resource devices and conduct edge computing analysis applications.

[0003] Because critical loads such as hospitals and schools in Class A+ and Class A power supply areas have extremely high requirements for power supply reliability, the economics of independently configuring substation-side energy storage are poor, and the control methods are limited. Existing technologies lack the function of achieving emergency power supply through shared energy storage, resulting in insufficient support for emergency power supply of critical loads by substation-shared energy storage systems. Summary of the Invention

[0004] This invention addresses the shortcomings and deficiencies of existing technologies by proposing a distribution area emergency power supply switching strategy based on a converged terminal and a shared energy storage system. The strategy achieves electrical connection of shared energy storage units through DC interconnection cables between distribution areas. It utilizes the voltage drop on the common DC side caused by the grid connection of the energy storage converter in the emergency power supply area, and controls the power transfer between shared energy storage units based on DC voltage droop. The emergency power supply switching strategy executes two stages: emergency power supply initiation and emergency power supply restoration. By controlling the PCS to switch to V / f off-grid operation, the energy from the energy storage battery is inverted and reversed to supply power to the AC bus, achieving short-term emergency power supply for critical loads.

[0005] The corresponding system includes an intelligent converged terminal, a communication gateway, an energy storage grid-connected switch, a shared energy storage unit, and DC interconnection cables. The shared energy storage unit includes: a power storage converter (PCS), a DC / DC converter, energy storage batteries, a communication mid-level unit, and a communication UPS device. The intelligent converged terminal has a built-in supercapacitor, enabling it to support at least 3 minutes of analysis, calculation, and control command interaction in the event of a power outage.

[0006] The present invention specifically adopts the following technical solution:

[0007] An emergency power supply switching strategy for transformer substations based on integrated terminals and shared energy storage systems

[0008] The electrical connection of the shared energy storage units is achieved through the DC interconnection cable between the substations. The voltage drop on the common DC side caused by the grid connection of the emergency protection substation energy storage converter is utilized. Based on the DC voltage droop control, the power transfer between the shared energy storage units is realized.

[0009] According to the emergency power supply switching strategy of the distribution area, the emergency power supply is activated: by controlling the PCS to switch to V / f off-grid operation, the energy storage battery power is inverted and reversed to supply power to the AC bus, so as to realize the short-term emergency power supply for important loads; or the emergency power supply is restored by switching the PCS of the emergency power supply distribution area to P / Q control mode and putting the P / Q control mode of other distribution area PCS into operation, so as to restore the shared energy storage power mutual assistance function.

[0010] Furthermore, the converged terminal in the distribution area is equipped with a supercapacitor to support at least 3 minutes of analysis, calculation, and control command interaction in the event of a power outage.

[0011] Furthermore, the integrated terminal of the designated emergency protection station area is the main control integrated terminal, and the communication connection between stations is realized through the communication connection of the gateway.

[0012] Furthermore, the emergency power supply activation process includes the following steps:

[0013] Step S1: The integrated terminal of the emergency protection radio area collects the AC electrical quantities of the access point in real time, including at least three-phase voltage and three-phase current, and collects the opening and closing signals of the low-voltage main switch, energy storage grid-connected switch and load switch in real time.

[0014] Step S2: The main control fusion terminal determines whether the three-phase voltage and current collected by the emergency protection radio station area suddenly become 0. If both are 0, then proceed to step S3; if they are not 0, then proceed to step S9.

[0015] Step S3: The main control fusion terminal determines that the low-voltage main switch is in the open position. If it is in the open position, then execute step S4; if it is in the closed position, then execute step S9.

[0016] Step S4: The main control fusion terminal communicates with the low-voltage main switch and interactively obtains the reason for the low-voltage main switch tripping;

[0017] Step S5: The main control fusion terminal determines that the tripping cause is undervoltage protection tripping. If it is undervoltage protection tripping, then proceed to step S6; otherwise, proceed to step S9.

[0018] Step S6: The main control fusion terminal determines whether the energy storage grid connection switch and the load switch are in the closed position. If both are in the closed position, then proceed to step S71; otherwise, proceed to step S72.

[0019] Step S71: The main control fusion terminal communicates with the PCS through the intermediate unit to determine the enable status of the emergency power supply function of the PCS. If it is enabled, then execute step S8; otherwise, execute step S9.

[0020] Step S72: The main control fusion terminal controls the closing of the energy storage grid-connected switch and the load switch;

[0021] Step S8: The main control fusion terminal enters the emergency power supply start-up mode and completes the following sequential operations within 3 minutes of the low-voltage main circuit breaker tripping:

[0022] 1) Issue PCS emergency power supply function instructions;

[0023] 2) Broadcast the emergency power supply mode signal to the subordinate fusion terminal;

[0024] 3) The subordinate fusion terminal controls the shutdown of the PCS in this area, controls the disconnection of the grid-connected energy storage switch in this area, and takes over the control of the master fusion terminal;

[0025] 4) The subordinate fusion terminal will switch the PCS of the emergency power supply area to V / f off-grid operation and generate electricity on the grid according to the rated power to complete the short-term power supply for emergency power supply;

[0026] Step S9: The main control fusion terminal sends a message to the PCS to disable emergency power supply and refuse to enter the emergency power supply mode;

[0027] Step S10: The main control fusion terminal will report the fault information, including the adjustment of the low-voltage main switch of the emergency protection radio area, to the main station.

[0028] Furthermore, emergency power restoration includes the following steps:

[0029] Step R1: Power is restored to the main control fusion terminal of the emergency backup radio area;

[0030] Step R2: The main control fusion terminal issues a PCS shutdown command;

[0031] Step R3: The main control fusion terminal determines that there is no voltage at the output of the emergency protection radio station area PCS and that there is a rated 380V voltage at the upper end of the low voltage main switch. If the conditions are met, proceed to step R41; otherwise, proceed to step R42.

[0032] Step R41: The main control fusion terminal controls the low-voltage main switch opening and closing;

[0033] Step R42: Wait 10 seconds, then repeat step R3;

[0034] Step R5: The main control fusion terminal broadcasts the shutdown of the emergency power supply mode, switches the PCS of the emergency power supply area to P / Q control mode, controls the closing of the grid-connected energy storage switches of other areas, and puts the P / Q control mode of the PCS of other areas into operation, restoring the shared energy storage power mutual assistance function.

[0035] And, a shared energy storage system for transformer substations, used to execute the above-mentioned emergency power supply switching strategy for transformer substations;

[0036] It includes a converged terminal, a communication gateway, an energy storage grid-connected switch, a shared energy storage unit, and a DC interconnection cable; the shared energy storage unit includes at least: an energy storage converter PCS, a DC / DC converter, an energy storage battery, a communication midpoint computer, and a communication UPS device;

[0037] The fusion terminal is equipped with a supercapacitor, which can support at least 3 minutes of analysis, calculation and control command interaction in the event of a power outage.

[0038] Furthermore, the shared energy storage unit is powered by a communication UPS for its internal equipment, and is connected to the gateway, energy storage converter PCS, and DC / DC converter via a communication intermediate unit, and is connected to the AC bus of the integrated distribution box of the emergency protection station area through an energy storage grid-connected switch.

[0039] Furthermore, a DC interconnect cable connects the PCS of the two shared energy storage units to the common DC side of the DC / DC converter.

[0040] The present invention and its preferred embodiment rely on the edge computing capabilities of the integrated terminal and the electrical energy of the shared energy storage to achieve emergency power supply for critical loads. Attached Figure Description

[0041] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0042] Figure 1 This is a schematic diagram of the structure of the emergency power supply system for transformer substations provided in an embodiment of the present invention.

[0043] Figure 2 This is a schematic diagram of the activation process of the emergency power supply switching strategy for transformer substations provided in an embodiment of the present invention.

[0044] Figure 3 This is a schematic diagram of the restoration process of the emergency power supply switching strategy for transformer substations provided in an embodiment of the present invention. Detailed Implementation

[0045] In the following, specific embodiments of this application will be described in detail with reference to the accompanying drawings. Based on these detailed descriptions, those skilled in the art will be able to clearly understand and implement this application. Without departing from the principles of this application, features from various embodiments can be combined to obtain new implementations, or certain features from some embodiments can be substituted to obtain other preferred implementations.

[0046] To make the features and advantages of this patent more apparent and understandable, specific embodiments are provided below, along with accompanying drawings, for detailed explanation:

[0047] like Figure 1 As shown, this embodiment first adjusts and improves upon the existing shared energy storage system in the transformer substation area, including an intelligent fusion terminal, a communication gateway, an energy storage grid-connected switch, shared energy storage units, and DC interconnection cables. The shared energy storage unit includes: a power storage converter (PCS), a DC / DC converter, an energy storage battery, a communication mid-level unit, and a communication UPS device. The intelligent fusion terminal has a built-in supercapacitor, which can support at least 3 minutes of analysis, calculation, and control command interaction in the event of a power outage.

[0048] In this embodiment, the electrical connection of the shared energy storage unit is achieved through the DC interconnection cable between the substations, and short-term power and energy supply support is provided.

[0049] The designated emergency protection station area uses a fusion terminal as the main control fusion terminal, and communication between stations is achieved through a communication connection of "fusion terminal (main) - gateway 1 - gateway 2 - fusion terminal (slave)".

[0050] The shared energy storage unit is powered by a communication UPS for its internal equipment. It is connected to the gateway, energy storage converter PCS, and DC / DC converter via a communication intermediate unit, and is connected to the AC bus of the integrated distribution box of the emergency protection station through an energy storage grid-connected switch.

[0051] A DC interconnect cable connects the PCS of the two shared energy storage units to the common DC side of the DC / DC converter. Power transfer between the shared energy storage units is achieved by utilizing the voltage drop on the common DC side caused by the grid connection of the emergency backup power storage converter and controlling the DC voltage droop.

[0052] The emergency power supply switching strategy for the transformer substation includes two stages: emergency power supply activation and emergency power supply restoration.

[0053] like Figure 2 As shown, the emergency power supply startup process provided in this embodiment includes the following steps:

[0054] Step S1: The integrated terminal of the emergency protection radio area collects the AC electrical quantities of the access point in real time, including three-phase voltage, three-phase current, etc., and collects the opening and closing signals of the low-voltage main switch, energy storage grid-connected switch and load switch in real time.

[0055] Step S2: The fusion terminal (main) determines whether the three-phase voltage and current collected by the emergency protection radio station area suddenly become 0. If both are 0, then proceed to step S3; if they are not 0, then proceed to step S9.

[0056] Step S3: The fusion terminal (main) determines that the low-voltage main switch is in the open position. If it is in the open position, then proceed to step S4; if it is in the closed position, then proceed to step S9.

[0057] Step S4: The fusion terminal (main) communicates with the low-voltage main switch and interactively obtains the reason for the low-voltage main switch tripping.

[0058] Step S5: The fusion terminal (master) determines that the tripping cause is undervoltage protection tripping. If it is undervoltage protection tripping, then proceed to step S6; otherwise, proceed to step S9.

[0059] Step S6: The fusion terminal (main) determines whether the energy storage grid connection switch and the load switch are in the closed position. If both are in the closed position, then proceed to step S71; otherwise, proceed to step S72.

[0060] Step S71: The fusion terminal (master) communicates with the PCS through the intermediate unit to determine the enable status of the emergency power supply function of the PCS. If it is enabled, then execute step S8; otherwise, execute step S9.

[0061] Step S72: The integrated terminal (main) controls the closing of the energy storage grid-connected switch and the load switch;

[0062] Step S8: The fusion terminal (main) enters the emergency power supply start-up mode and completes the following sequential operations within 3 minutes of the low-voltage main circuit breaker tripping:

[0063] 1) Issue PCS emergency power supply function instructions;

[0064] 2) Broadcast emergency power supply mode signal to the fusion terminal (from);

[0065] 3) The fusion terminal (slave) controls the shutdown of the PCS in this area, controls the disconnection of the grid-connected energy storage switch in this area, and takes over the control of the fusion terminal (master);

[0066] 4) The integrated terminal (from) switches the PCS of the emergency power supply area to V / f off-grid operation and generates electricity on the grid according to the rated power to complete the short-term power supply for emergency power supply;

[0067] Step S9: The fusion terminal (master) issues a PCS emergency power supply de-enablement command and refuses to enter the emergency power supply mode;

[0068] Step S10: The fusion terminal (main) reports fault information such as the adjustment of the low-voltage main switch in the emergency protection radio area to the main station, which then pushes the fault information to the management personnel to arrange on-site troubleshooting and handling.

[0069] like Figure 3 As shown, the emergency power restoration provided in this embodiment includes the following steps:

[0070] Step R1: Power is restored to the fusion terminal (main) of the emergency backup radio area;

[0071] Step R2: The converged terminal (master) issues a PCS shutdown command;

[0072] Step R3: The fusion terminal (main) determines that there is no voltage at the output of the emergency protection radio area PCS and that there is a rated 380V voltage at the upper end of the low voltage main switch. If the conditions are met, proceed to step R41; otherwise, proceed to step R42.

[0073] Step R41: The fusion terminal (main) controls the low-voltage main switch opening and closing;

[0074] Step R42: Wait 10 seconds, then repeat step R3;

[0075] Step R5: The fusion terminal (main) broadcasts the shutdown of the emergency power supply mode, switches the PCS of the emergency power supply area to P / Q control mode, controls the closing of the grid-connected energy storage switches of other areas, and puts the P / Q control mode of the PCS of other areas into operation, restoring the shared energy storage power mutual assistance function.

[0076] The above description is a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

[0077] This patent is not limited to the above-described preferred embodiments. Anyone can derive other forms of emergency power supply switching strategies for transformer substations based on integrated terminals and shared energy storage systems under the guidance of this patent. All equivalent changes and modifications made within the scope of this patent application shall fall within the scope of this patent.

Claims

1. A distribution area emergency power supply switching strategy based on integrated terminals and shared energy storage systems, characterized in that: The electrical connection of the shared energy storage units is achieved through the DC interconnection cable between the substations. The voltage drop on the common DC side caused by the grid connection of the emergency protection substation energy storage converter is utilized. Based on the DC voltage droop control, the power transfer between the shared energy storage units is realized. According to the emergency power supply switching strategy of the distribution area, the emergency power supply is activated: by controlling the PCS to switch to V / f off-grid operation, the energy storage battery power is inverted and reversed to supply power to the AC bus, so as to realize the short-term emergency power supply for important loads; or the emergency power supply is restored by switching the PCS of the emergency power supply distribution area to P / Q control mode and putting the P / Q control mode of other distribution area PCS into operation, so as to restore the shared energy storage power mutual assistance function. Emergency power supply activation includes the following steps: Step S1: The integrated terminal of the emergency protection radio area collects the AC electrical quantities of the access point in real time, including at least three-phase voltage and three-phase current, and collects the opening and closing signals of the low-voltage main switch, energy storage grid-connected switch and load switch in real time. Step S2: The main control fusion terminal determines whether the three-phase voltage and current collected by the emergency protection radio station area suddenly become 0. If both are 0, then proceed to step S3; if they are not 0, then proceed to step S9. Step S3: The main control fusion terminal determines that the low-voltage main switch is in the open position. If it is in the open position, then execute step S4; if it is in the closed position, then execute step S9. Step S4: The main control fusion terminal communicates with the low-voltage main switch and interactively obtains the reason for the low-voltage main switch tripping; Step S5: The main control fusion terminal determines that the tripping cause is undervoltage protection tripping. If it is undervoltage protection tripping, then proceed to step S6; otherwise, proceed to step S9. Step S6: The main control fusion terminal determines whether the energy storage grid connection switch and the load switch are in the closed position. If both are in the closed position, then proceed to step S71; otherwise, proceed to step S72. Step S71: The main control fusion terminal communicates with the PCS through the intermediate unit to determine the enable status of the emergency power supply function of the PCS. If it is enabled, then proceed to step S8; otherwise, proceed to step S9. Step S72: The main control fusion terminal controls the closing of the energy storage grid-connected switch and the load switch; Step S8: The main control fusion terminal enters the emergency power supply start-up mode and completes the following sequential operations within 3 minutes of the low-voltage main circuit breaker tripping: 1) Issue PCS emergency power supply function instructions; 2) Broadcast the emergency power supply mode signal to the subordinate fusion terminal; 3) The subordinate fusion terminal controls the shutdown of the PCS in this area, controls the disconnection of the grid-connected energy storage switch in this area, and takes over the control of the master fusion terminal; 4) The subordinate fusion terminal will switch the PCS of the emergency power supply area to V / f off-grid operation and generate electricity on the grid according to the rated power to complete the short-term power supply for emergency power supply; Step S9: The main control fusion terminal sends a message to the PCS to disable emergency power supply and refuse to enter the emergency power supply mode; Step S10: The main control fusion terminal will report the fault information, including the adjustment of the low-voltage main switch of the emergency protection radio area, to the main station.

2. The emergency power supply switching strategy for distribution areas based on converged terminals and shared energy storage systems according to claim 1, characterized in that: The converged terminal in the distribution area is equipped with a supercapacitor to support at least 3 minutes of analysis, calculation, and control command interaction in the event of a power outage.

3. The emergency power supply switching strategy for distribution areas based on converged terminals and shared energy storage systems according to claim 1, characterized in that: The designated emergency protection station area uses a converged terminal as the main control converged terminal, and communication between stations is achieved through the communication connection of the gateway.

4. The emergency power supply switching strategy for distribution areas based on converged terminals and shared energy storage systems according to claim 1, characterized in that: Emergency power restoration includes the following steps: Step R1: Power is restored to the main control fusion terminal of the emergency backup radio area; Step R2: The main control fusion terminal issues a PCS shutdown command; Step R3: The main control fusion terminal determines that there is no voltage at the output of the emergency protection radio station area PCS and that there is a rated 380V voltage at the upper end of the low voltage main switch. If the conditions are met, proceed to step R41; otherwise, proceed to step R42. Step R41: The main control fusion terminal controls the low-voltage main switch opening and closing; Step R42: Wait 10 seconds, then repeat step R3; Step R5: The main control fusion terminal broadcasts the shutdown of the emergency power supply mode, switches the PCS of the emergency power supply area to P / Q control mode, controls the closing of the grid-connected energy storage switches of other areas, and puts the P / Q control mode of the PCS of other areas into operation, restoring the shared energy storage power mutual assistance function.

5. A shared energy storage system for transformer substations, characterized in that, The emergency power supply switching strategy for distribution areas based on converged terminals and shared energy storage systems as described in any one of claims 1-4 is adopted. This includes converged terminals, communication gateways, energy storage grid-connected switches, shared energy storage units, and DC interconnect cables; The shared energy storage unit includes at least: an energy storage converter PCS, a DC / DC converter, an energy storage battery, a communication midpoint computer, and a communication UPS device; The fusion terminal is equipped with a supercapacitor, which can support at least 3 minutes of analysis, calculation and control command interaction in the event of a power outage.

6. The shared energy storage system for transformer substations according to claim 5 is characterized in that: The shared energy storage unit is powered by a communication UPS for its internal equipment. It is connected to the gateway, energy storage converter PCS, and DC / DC converter via a communication intermediate unit, and is connected to the AC bus of the integrated distribution box of the emergency protection station area through an energy storage grid-connected switch.

7. The shared energy storage system for transformer substations according to claim 6, characterized in that: A DC interconnect cable connects the PCS of the two shared energy storage units to the common DC side of the DC / DC converter.

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