Hydropower station black start method and system based on hybrid energy storage

Abstract

The invention discloses a hydropower station black start method and system based on hybrid energy storage, and the method comprises the steps: monitoring that a power plant meets a black start condition through a monitoring system, and transmitting a black start instruction; controlling the energy storage converter to be converted from a standby mode to an isolated network operation mode through the energy storage energy management system based on the instruction; the energy storage system is controlled through the energy storage converter to enable the auxiliary system for black start of the hydropower station to recover work; the auxiliary system controls the hydroelectric generating set to operate; the hydroelectric generating set is monitored and controlled to be merged into the isolated network, the output is gradually reduced by controlling the energy storage system, the output is gradually increased by controlling the hydroelectric generating set until all auxiliary power loads are transferred to the hydroelectric generating set, and the hydroelectric generating set is controlled by the auxiliary system to serve as a power supply to supply power to the outside. Therefore, the black start process can be shortened, the time delay can be reduced, and the stability of the isolated network can be maintained.

Description

Technical Field

[0001] This application relates to the field of power system technology, and in particular to a black start method and system for hydropower stations based on hybrid energy storage. Background Technology

[0002] In recent years, numerous large-scale power system collapses worldwide have severely challenged the safety and stability of power grids. These sudden, widespread blackouts have not only resulted in enormous economic losses but also had a profound impact on social order and public safety. Despite significant advancements in power system safety and stability control theories and technologies, the risk of major power outages has not been completely eliminated, especially under conditions of system-level failures caused by extreme weather, natural disasters, or human factors.

[0003] As the cornerstone of the national energy structure and a key node in the power grid, the ability of hydropower stations to quickly restore power after large-scale power outages is crucial to the safe and stable operation of the overall power system. However, black start relies on diesel generators, and the black start time of hydropower stations is relatively long. Summary of the Invention

[0004] This application provides a method and system for black start of a hydropower station based on hybrid energy storage, which can shorten the black start process, reduce time delays, and maintain the stability of the isolated grid.

[0005] In a first aspect, embodiments of this application provide a black start method for a hydropower station based on hybrid energy storage, including: Once the monitoring system detects that the power plant meets the black start conditions, it sends a black start command to the energy storage management system. The energy storage management system controls the energy storage converter in the energy storage system to switch from standby mode to islanded operation mode based on the black start command; The circuit breaker between the energy storage system and the target bus is closed by controlling the energy storage converter so that the battery in the energy storage system can supply power to the target bus. The power on the target bus is then transmitted to the plant bus via the plant transformer so that the auxiliary system for black start of the hydropower station can be restored to power supply. The auxiliary system controls the operation of the hydropower unit, and synchronizes the frequency and phase of the hydropower unit with the isolated grid. The monitoring system controls the hydropower unit to connect to the isolated grid, the energy storage management system controls the energy storage system to gradually reduce its output, and the auxiliary system controls the hydropower unit to gradually increase its output until all plant power load is transferred to the hydropower unit. The energy storage management system controls the energy storage converter to switch to standby mode, and the auxiliary system controls the hydropower unit to supply power to the outside world.

[0006] Secondly, this application provides a black start system for a hydropower station based on hybrid energy storage, including: a monitoring system, an energy storage management system, an energy storage system, a plant transformer, an auxiliary system, and a hydropower unit; the energy storage system includes an energy storage converter and a battery; The monitoring system is used to detect when the power plant meets the black start conditions and send a black start command to the energy storage management system. The energy storage management system is used to control the energy storage converter in the energy storage system to switch from standby mode to islanded operation mode based on the black start command; The energy storage converter is used to control the closing of the circuit breaker between the energy storage system and the target bus, so as to use the battery in the energy storage system to supply power to the target bus; The plant service transformer is used to transmit electrical energy from the target bus to the plant service bus so that the auxiliary system for black start of the hydropower station can resume operation. The auxiliary system is used to control the operation of the hydropower unit and to synchronize the frequency and phase of the hydropower unit with the isolated grid. The monitoring system is also used to control the hydropower unit to connect to the isolated grid; The energy storage management system is also used to control the energy storage system to gradually reduce its output; The auxiliary system is also used to control the hydropower unit to gradually increase its output until all the plant's power load is transferred to the hydropower unit. The energy storage management system is also used to control the energy storage converter to switch to standby mode; The auxiliary system is also used to control the hydropower unit to supply power to the outside world as the power source for the isolated grid.

[0007] The technical solution provided in this application embodiment involves: monitoring the power plant to detect that it meets the black start conditions and sending a black start command to the energy storage management system; controlling the energy storage converter to switch from standby mode to islanded operation mode through the energy storage management system; controlling the circuit breaker between the energy storage system and the target bus to close through the energy storage converter, so that the target bus is powered by the batteries in the energy storage system to create an islanded network through the energy storage system, and transmitting the power on the target bus to the plant service bus through the plant service transformer to restore the auxiliary system for black start of the hydropower station; controlling the operation of the hydropower units through the auxiliary system, and controlling the frequency and phase of the hydropower units to synchronize with the islanded network; controlling the hydropower units to connect to the islanded network through the auxiliary system; controlling the energy storage system to gradually reduce the output of the energy storage system and gradually increase the output of the hydropower units through the auxiliary system until all plant service load is transferred to the hydropower units; controlling the energy storage converter to switch to standby mode through the energy storage management system; and controlling the hydropower units to supply power externally through the monitoring system. This application describes a method that uses an energy storage management system to control the energy storage system to create an isolated grid at the beginning and to restore the auxiliary system for black start of the hydropower station. The auxiliary system controls the operation of the turbine units, and the energy storage management system controls the energy storage system to gradually reduce its output while the auxiliary system controls the turbine units to gradually increase their output until the turbine units can supply power to the outside world. Compared with the existing technology where the black start of hydropower stations relies on diesel generators, this method can shorten the black start process, reduce time delays, and maintain the stability of the isolated grid. Attached Figure Description

[0008] Figure 1 A flowchart of a black start method for a hydropower station based on hybrid energy storage is provided for embodiments of this application; Figure 2 This is a schematic diagram of a black start system for a hydropower station based on hybrid energy storage, provided as an embodiment of this application. Detailed Implementation

[0009] Figure 1 This is a flowchart illustrating a black start method for a hydropower station based on hybrid energy storage, provided in an embodiment of this application. The method can be executed by a black start system for a hydropower station based on hybrid energy storage. Figure 1 As shown, the method may include the following steps: S110: The monitoring system detects that the power plant meets the black start conditions and sends a black start command to the energy storage management system.

[0010] In this embodiment, the energy storage system can remain in a hot standby state before sending the black-start command. The state of charge of the batteries in the energy storage system can be maintained above 80%. The energy storage management system (EMS) can communicate with the monitoring system to monitor the hydropower station's status in real time. In the event of a large-scale power outage on the external power grid, the hydropower station's outgoing line switches trip, resulting in the loss of auxiliary power. The hydropower station's DC system / UPS immediately activates to ensure uninterrupted power supply to control, protection, and communication equipment. Specifically, the monitoring system automatically detects that the power plant meets the black-start conditions (e.g., loss of voltage on the main transformer's high-voltage side, loss of auxiliary power), and automatically or manually issues a "black-start" command, which is then sent to the energy storage management system.

[0011] S120: The energy storage system controls the energy storage converter in the energy storage system to switch from standby mode to islanded operation mode based on the black start command.

[0012] In this embodiment, the energy storage management system controls the energy storage converter to switch from standby mode to V / f islanded operation mode. The energy storage converter is the core device in the energy storage system, controlling the charging and discharging process of the batteries and performing AC / DC conversion.

[0013] S130: The circuit breaker between the energy storage system and the target bus is closed by controlling the energy storage converter, so that the target bus is powered by the battery in the energy storage system, and the power on the target bus is transmitted to the plant bus through the plant service transformer so that the auxiliary system of the hydropower station black start can resume operation.

[0014] In this embodiment, the circuit breaker between the energy storage system and the target busbar is closed by controlling the energy storage converter. The target busbar can be a 10kV busbar. By closing the circuit breaker, the 10kV busbar is powered by the battery, which can quickly establish an isolated grid with extremely stable voltage and frequency (e.g., 10.5kV, 50.00Hz) on the 10kV busbar. The plant service busbar can be 400V. Through the plant service transformer, the power from the 10kV busbar can be sent to the 400V plant service busbar. All auxiliary systems required for black start of the hydropower station immediately obtain a stable and reliable power supply. The auxiliary systems can include speed control systems, excitation systems, etc. With the power supply of the energy storage system, the speed control system, excitation system, etc., resume normal operation. The auxiliary systems can be started by operators or by automatic programs.

[0015] S140: Control the operation of the hydropower unit through the auxiliary system, and control the frequency and phase of the hydropower unit to synchronize with the isolated grid.

[0016] In this embodiment, the hydropower unit includes a turbine and a generator. The turbine is started by a monitoring system, the guide vanes are opened, and the turbine begins to rotate. The speed of the turbine is controlled by a speed regulation system. When the speed approaches the rated value, the excitation system is activated, and the voltage at the generator terminals begins to rise. The frequency and phase are adjusted by an automatic synchronizing device to make it completely synchronized with the isolated grid established by the energy storage system.

[0017] S150: The monitoring system controls the hydropower unit to connect to the isolated grid, the energy storage system gradually reduces its output through the energy storage management system, and the auxiliary system gradually increases the output of the hydropower unit until all plant power load is transferred to the hydropower unit. The energy storage management system controls the energy storage converter to switch to standby mode, and the auxiliary system controls the hydropower unit to supply power to the outside.

[0018] In this embodiment, the monitoring system can control the closing of the circuit breaker at the outlet of the hydropower unit, allowing the hydropower unit to connect to the isolated grid. The energy storage management system controls the gradual reduction of the energy storage system's output, while the auxiliary system controls the gradual increase of the hydropower unit's output, smoothly transferring all plant power load to the hydropower unit. The energy storage converter switches to standby mode, and finally, the hydropower unit acts as a power source for external power supply. Specifically, the external power supply process can involve sequentially supplying power to unloaded lines, substations, and other power plants along the black start path, gradually expanding the system recovery range. The process is consistent with the traditional black start process for hydropower stations. During the initial voltage build-up of the hydropower unit, the frequency and voltage of the isolated grid are prone to fluctuations. The energy storage system can provide instantaneous power support, maintaining the stability of the isolated grid's frequency and voltage.

[0019] In this embodiment, optionally, controlling the energy storage system to gradually reduce its output through the energy storage management system and controlling the hydropower unit to gradually increase its output through the auxiliary system includes: controlling the energy storage system to linearly reduce its output through the energy storage management system and controlling the hydropower unit to linearly increase its output through the auxiliary system. The rate at which the energy storage system linearly reduces its output can be determined based on actual needs, i.e., the required time for the hydropower station's black start. By controlling both the linear reduction and increase of the energy storage system's output, control complexity can be reduced, control efficiency improved, and the black start process made more stable.

[0020] In this embodiment, optionally, when the hydropower unit is operating and is used as a power source, the energy storage management system obtains the actual islanded frequency and the state of charge (SBC) of the battery, and controls the power output of the energy storage system based on the actual islanded frequency and the SBC. Specifically, in islanded mode, when the SBC is greater than a preset threshold and the actual islanded frequency is less than a preset frequency, the energy storage system is controlled to output power.

[0021] In this embodiment, after the black start of the hydropower station, the following may also be included: in islanded mode, the target power output of the energy storage system is determined by the energy storage management system based on the primary frequency regulation frequency, the system rated frequency, the rated power of the hydropower station, the droop rate of the primary frequency regulation of the hydropower station, the initial value of active power at the moment of frequency overrun, and the actual islanded frequency.

[0022] Specifically, in islanded grid mode, the primary frequency regulation function of the hydropower unit is deactivated, and the energy storage system is controlled by the energy storage management system to activate the primary frequency regulation function, automatically adjusting the power according to changes in the grid frequency. The specific calculation method is shown in the following formula: ; in, f d The frequency of the first frequency modulation is Hz; f n The system's rated frequency is 50Hz. P n δ% represents the rated power of the hydropower station (MW); δ% represents the primary frequency regulation droop rate of the hydropower station. P 0 Let MW be the initial value of active power at the instant of frequency crossover. P The target power output of the energy storage system; f This refers to the actual isolated network frequency.

[0023] in, f d It can be 0.1Hz. f n The frequency is set to 50Hz, and δ% can be above 5%. Therefore, by controlling the power output of the energy storage system through the primary frequency regulation, the system's rated frequency, the hydropower station's rated power, the hydropower station's primary frequency regulation droop rate, the initial value of active power at the moment of frequency overshoot, and the actual islanded grid frequency, the grid frequency can be more stably regulated.

[0024] The technical solution provided in this application embodiment monitors the power plant to ensure it meets the black-start conditions and sends a black-start command to the energy storage management system. The energy storage management system controls the energy storage converter to switch from standby mode to islanded operation mode. The energy storage converter controls the circuit breaker between the energy storage system and the target bus to close, allowing the batteries in the energy storage system to supply power to the target bus, thus creating an islanded network. The power from the target bus is then transferred to the plant service bus via the plant service transformer to restore the auxiliary system for black-starting the hydropower station. The auxiliary system controls the operation of the hydropower units, synchronizing their frequency and phase with the islanded network. The monitoring system controls the hydropower units to connect to the islanded network. The energy storage management system gradually reduces the output of the energy storage system, and the auxiliary system gradually increases the output of the hydropower units until all plant service load is transferred to the hydropower units. The energy storage management system switches the energy storage converter to standby mode, and the auxiliary system controls the hydropower units to supply power externally. This application utilizes an energy storage management system to control the energy storage system to create an isolated grid at the start, and to restore the auxiliary system for black start of the hydropower station. The auxiliary system controls the operation of the turbine units, and the energy storage management system controls the energy storage system to gradually reduce its output while the auxiliary system controls the turbine units to gradually increase their output until the turbine units can supply power to the outside world. Compared with the existing technology where black start of hydropower stations relies on diesel generators, this application eliminates the need to wait for the diesel generators to start and warm up, shortens the black start process, reduces human error, reduces time delays, and maintains the stability of the isolated grid.

[0025] Based on the above embodiments, the technical solution provided in this application may further include, when the hydropower unit is operating and is used as a power source, if the output power of the hydropower unit is detected to be less than a preset power, controlling the energy storage system to output power through the energy storage management system so that the sum of the output power of the energy storage system and the output power of the hydropower unit equals the preset power. Since the output power of the hydropower unit may be unstable due to its inherent characteristics, if the output power of the hydropower unit is detected to be less than the preset power, the energy storage system can be controlled to output power to provide power support. Thus, the energy storage system can provide assurance for the frequency and voltage stability of the power grid. Furthermore, the energy storage system can also participate in ancillary services such as power grid frequency regulation, peak shaving, and backup, generating economic benefits.

[0026] Based on the above embodiments, the technical solution provided in this application may further include: when the hydropower unit is operating and is used as a power source, controlling the power output of the energy storage system based on time periods through an energy storage management system. Specifically, during peak electricity consumption periods, the output power of the hydropower unit may sometimes be insufficient to fully meet electricity demand; therefore, controlling the power output of the energy storage system can ensure normal power consumption for the load.

[0027] Figure 2 This application provides a schematic diagram of a black start system structure for a hydropower station based on hybrid energy storage, as shown in the embodiment of the present application. Figure 2 As shown, the system includes a computer monitoring system, an energy storage management system, an energy storage system, a plant transformer, and an auxiliary system; the energy storage system includes an energy storage converter and a battery.

[0028] The monitoring system is used to detect when the power plant meets the black start conditions and send a black start command to the energy storage management system. The energy storage management system is used to control the energy storage converter in the energy storage system to switch from standby mode to islanded operation mode based on the black start command. The energy storage converter is used to control the circuit breaker between the energy storage system and the target bus to close, so that the target bus can be powered by the batteries in the energy storage system to create an islanded network. The plant service transformer is used to transmit the electrical energy from the target bus to the plant service bus to restore the auxiliary system for black start of the hydropower station. The auxiliary system is used to control the operation of the hydropower unit, synchronize the frequency and phase of the hydropower unit with the isolated grid, and control the hydropower unit to connect to the isolated grid through the monitoring system; the energy storage management system is also used to control the energy storage system to gradually reduce its output; the auxiliary system is also used to control the hydropower unit to gradually increase its output until all plant power load is transferred to the hydropower unit; the energy storage management system is also used to control the energy storage converter to switch to standby mode; the auxiliary system is also used to control the hydropower unit to supply power to the isolated grid.

[0029] Optionally, the energy storage system is always in a hot standby state.

[0030] Optionally, the computer monitoring system displays a control that triggers a black start command, which operators can manually trigger to send a black start command to the energy storage management system.

[0031] In this embodiment, the power (P) of the energy storage system primarily meets the maximum load requirements of the hydropower station's auxiliary power supply, while also considering a certain margin. It is necessary to calculate the total rated power of all critical equipment in the auxiliary system (governor oil pump, excitation system, technical water supply pump, main transformer cooler, target monitoring system, etc.) operating simultaneously during the black start process. Typically, the auxiliary power load of a medium-sized hydropower station ranges from several hundred kW to 1-2 MW. Therefore, a rated power of 1-3 MW is generally sufficient to meet the requirements. Regarding the capacity (E) of the energy storage system: it primarily meets the time requirements of the entire black start process. From the start of energy storage discharge to the successful grid connection and load takeover of the hydropower unit, the entire process is typically designed to take 0.5-2 hours. Therefore, the energy storage system's capacity can be configured to 1-4 MWh.

[0032] The calculation formula is: E(kWh) = P(kW) × T(h) × K (safety factor). For example, if the plant's power load is 800kW, expected to support it independently for 1.5 hours, and the safety factor is 1.2, then E = 800 × 1.5 × 1.2 = 1440kWh. In energy storage systems, lithium iron phosphate batteries are preferred due to their high safety, long cycle life, and mature technology, making them the mainstream choice for current energy storage systems.

[0033] Among them, the energy storage system can be connected to the 10kV busbar of the hydropower station, which is more efficient and has less impact on the power system. When the 10kV busbar remains unchanged, it can also be connected to the 400V busbar.

[0034] The energy storage system topology can be: battery cluster -> DC bus -> energy storage converter (PCS) -> step-up transformer -> 10kV bus of the power station.

[0035] The energy storage system is equipped with islanding protection, reverse power protection, and lockout protection strategies. Specifically, in islanding operation mode (V / f), the energy storage converter in the energy storage system needs to be configured with overvoltage / undervoltage and overfrequency / underfrequency protection to prevent damage to the equipment under abnormal conditions. Reverse power protection is required to prevent hydropower units from feeding power back to the energy storage system. Traditional protection is locked out; when supplying power to unloaded lines and transformers, the relevant protection settings must still be temporarily deactivated or adjusted according to the strategy. Islanding detection and anti-synchronization are required; the system must have a reliable mechanism to ensure that synchronous operation can only be performed within the islanded network established by the energy storage system, preventing asynchronous grid connection with external non-isolated power grids.

[0036] The descriptions of the various systems or devices in this embodiment can also refer to the descriptions in the above embodiments. It should be noted that... Figure 2 This is just a system example; the system's connection methods and internal devices are not fully illustrated.

[0037] This application controls the energy storage system to create an isolated grid at the beginning through an energy storage management system, and enables the auxiliary system for black start of the hydropower station to resume operation. The auxiliary system controls the operation of the turbine unit, and the energy storage management system controls the energy storage system to gradually reduce its output and the auxiliary system controls the turbine unit to gradually increase its output until the turbine unit can supply power to the outside. Compared with the existing technology where the black start of the hydropower station depends on the diesel generator, this application can shorten the start-up process, reduce time delays, and maintain the stability of the isolated grid.

[0038] The above embodiments are merely illustrative examples and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. A black start method for hydropower stations based on hybrid energy storage, characterized in that, include: Once the monitoring system detects that the power plant meets the black start conditions, it sends a black start command to the energy storage management system. The energy storage management system controls the energy storage converter in the energy storage system to switch from standby mode to islanded operation mode based on the black start command; The circuit breaker between the energy storage system and the target bus is closed by controlling the energy storage converter so that the battery in the energy storage system can supply power to the target bus. The power on the target bus is then transmitted to the plant bus via the plant transformer so that the auxiliary system for black start of the hydropower station can be restored to power supply. The auxiliary system controls the operation of the hydropower unit, and synchronizes the frequency and phase of the hydropower unit with the isolated grid. The monitoring system controls the hydropower unit to connect to the isolated grid, the energy storage management system controls the energy storage system to gradually reduce its output, and the auxiliary system controls the hydropower unit to gradually increase its output until all plant power load is transferred to the hydropower unit. The energy storage management system controls the energy storage converter to switch to standby mode, and the auxiliary system controls the hydropower unit to supply power to external systems.

2. The method according to claim 1, characterized in that, The energy storage system is gradually reduced in output by the energy storage management system, and the hydropower unit is gradually increased in output by the auxiliary system, including: The energy storage system is controlled by the energy storage management system to linearly reduce its output, and the hydropower unit is controlled by the auxiliary system to linearly increase its output.

3. The method according to claim 1, characterized in that, Also includes: The energy storage management system obtains the actual islanded grid frequency and the state of charge of the battery, and controls the energy storage system to output power based on the actual islanded grid frequency and the state of charge.

4. The method according to claim 3, characterized in that, The method of controlling the energy storage system to output power based on the actual islanded grid frequency and the state of charge includes: When the state of charge is greater than a preset threshold and the actual isolated grid frequency is less than a preset frequency, the energy storage system is controlled to output power.

5. The method according to claim 1, characterized in that, Also includes: In islanded operation mode, the target output power of the energy storage system is determined by the energy storage management system based on the primary frequency regulation frequency, the system rated frequency, the rated power of the hydropower station, the droop rate of the primary frequency regulation of the hydropower station, the initial value of active power at the moment of frequency overrun, and the actual islanded frequency.

6. The method according to claim 1, characterized in that, Also includes: When the hydropower unit is in operation and is used as a power source, if the output power of the hydropower unit is detected to be less than the preset power, the energy storage system is controlled by the energy storage management system to output power so that the sum of the output power of the energy storage system and the output power of the hydropower unit is equal to the preset power.

7. The method according to claim 1, characterized in that, Also includes: When the hydropower unit is in operation and is used as a power source, the energy storage management system controls the power output of the energy storage system based on time periods.

8. A black start system for a hydropower station based on hybrid energy storage, characterized in that, include: The system includes a monitoring system, an energy storage management system, an energy storage system, a plant transformer, an auxiliary system, and a hydroelectric generator; the energy storage system includes an energy storage converter and a battery. The monitoring system is used to detect when the power plant meets the black start conditions and send a black start command to the energy storage management system. The energy storage management system is used to control the energy storage converter in the energy storage system to switch from standby mode to islanded operation mode based on the black start command; The energy storage converter is used to control the closing of the circuit breaker between the energy storage system and the target bus, so as to use the battery in the energy storage system to supply power to the target bus; The plant service transformer is used to transmit electrical energy from the target bus to the plant service bus so that the auxiliary system for black start of the hydropower station can resume operation. The auxiliary system is used to control the operation of the hydropower unit and to synchronize the frequency and phase of the hydropower unit with the isolated grid. The monitoring system is also used to control the hydropower unit to connect to the isolated grid; The energy storage management system is also used to control the energy storage system to gradually reduce its output; The auxiliary system is also used to control the hydropower unit to gradually increase its output until all the plant's power load is transferred to the hydropower unit. The energy storage management system is also used to control the energy storage converter to switch to standby mode; The auxiliary system is also used to control the hydropower unit to supply power to the outside world as the power source for the isolated grid.

9. The system according to claim 8, characterized in that, The energy storage system is equipped with an islanding protection strategy, a reverse power protection strategy, and a lockout protection strategy.

10. The system according to claim 8, characterized in that, Before the energy storage management system receives the black start command, the energy storage system is in a hot standby state.

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