Black start control method and controller

Abstract

The black-start control method and the controller are applied to the field of off-grid power systems, an energy storage unit is started, the energy storage unit is connected to a low-voltage bus, a step-down transformer and a load are connected at the same time, and the load capacity of the load is controlled to be matched with the power supply capacity of the energy storage unit; triggering a step-up transformer at the grid side of the low-voltage bus, and connecting the recovered grid frame to the medium-voltage bus; connecting other non-black-start power supplies to the medium-voltage bus to establish a main bus voltage; and connecting the renewable energy generator set to the main bus until all loads are recovered. Distributed access of the energy storage unit is adopted, power supply instability of a single starting power supply is reduced, meanwhile, the risk of overvoltage in the power grid recovery process is effectively reduced by controlling charging and discharging of the energy storage unit, the error-tolerant rate in the black-start process is greatly increased through cooperation of the renewable energy generator set and the energy storage unit, and the black-start efficiency is improved. And the stability of the system in the black start process is improved.

Description

Technical Field

[0001] The invention relates to the field of off-grid power systems, and in particular to a black start control method and a controller. Background Art

[0002] Black start technology is the process of gradually restoring power supply through the system's internal energy management control strategy or generators with self-starting capabilities after a large-scale power outage without the support of a large power grid. In modern power systems, the black start process usually includes three stages: black start, grid reconstruction, and load recovery. The black start stage is the first step in the entire recovery process. The key lies in selecting the appropriate black start power source, the started unit, and the optimal recovery path. Its selection directly affects the success rate and effect of the black start solution. The selection of black start power sources usually includes hydropower units, gas units, and new energy power sources, such as wind power and photovoltaic power generation. The latter can also serve as an effective black start power source after being equipped with a certain capacity of energy storage system; black start path planning is a key factor in determining the system recovery speed. It is necessary to restore the main power plant of the regional power grid as soon as possible, reduce the length of the start path and the conversion of different voltage levels. In the black start stage, a certain load is connected in time to ensure the frequency and voltage level of the system and maintain power balance.

[0003] However, the intermittent and instability of renewable energy generation such as wind power and photovoltaic power makes it difficult for them to serve as stable black start power sources when the system is first started or after a power outage. At the same time, off-grid systems cannot rely on the support of the large power grid, which will further aggravate the intermittent and instability of renewable energy generation.

[0004] Therefore, it can be seen that people in this field urgently need to solve the instability problem of renewable energy power generation during black start. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a black start control method and controller. The instability problem of renewable energy power generation during black start is solved. The specific scheme is as follows:

[0006] In a first aspect, the present application provides a black start control method, which is applied to a black start control device, wherein the black start control device includes a plurality of groups of renewable energy generator sets, wherein the plurality of groups of the renewable energy generator sets are connected to a bus, and a group of the renewable energy generator sets includes a plurality of renewable energy generators and energy storage units corresponding to each of the renewable energy generators, wherein the method includes:

[0007] Starting each of the energy storage units, and connecting each of the energy storage units to a low-voltage bus, and simultaneously connecting a step-down transformer and a load, and controlling the load to match the power supply capacity of each of the energy storage units;

[0008] After the low-voltage bus is successfully restored, the step-up transformer on the grid side of the low-voltage bus is triggered to connect the restored grid to the medium-voltage bus;

[0009] After the medium voltage bus is successfully restored, other non-black start power supplies are connected to the medium voltage bus to establish a main bus voltage;

[0010] After the main bus voltage is successfully established, the renewable energy generator set is connected to the main bus until all loads are restored.

[0011] Optionally, connecting each of the energy storage units to a low-voltage bus includes:

[0012] Obtaining the SOC of the energy storage unit;

[0013] Determining a relationship between the SOC of the energy storage unit and a first threshold;

[0014] When the SOC of the energy storage unit is less than the first threshold, the energy storage unit is charged to restore the function of the energy storage unit and connected to the low-voltage bus.

[0015] Optionally, when the SOC of the energy storage unit is less than the first threshold, charging the energy storage unit to restore the function of the energy storage unit and connecting it to the low-voltage bus includes:

[0016] Calculate the ratio of the number of energy storage units in the same group whose SOC is less than the first threshold to the total number of energy storage units;

[0017] determining a relationship between the ratio and a second threshold;

[0018] When the ratio is less than the second threshold, the normally working energy storage unit in the same group as the renewable energy generator set is charged to restore the function of the energy storage unit and connect to the low-voltage bus.

[0019] Optionally, when the SOC of the energy storage unit is less than the first threshold, charging the energy storage unit to restore the function of the energy storage unit and connecting it to the low-voltage bus includes:

[0020] Calculate the ratio of the number of energy storage units in the same group whose SOC is less than the first threshold to the total number of energy storage units;

[0021] determining a relationship between the ratio and a second threshold;

[0022] When the ratio is greater than the second threshold, the other renewable energy generating sets are ordered to charge the energy storage unit to restore the function of the energy storage unit and connect it to the low-voltage bus.

[0023] Optionally, when the SOC of the energy storage unit is less than the first threshold, charging the energy storage unit to restore the function of the energy storage unit and connecting it to the low-voltage bus includes:

[0024] When the SOCs of the energy storage units are all less than the first threshold, the diesel generator is enabled to charge the energy storage units to restore the functions of the energy storage units and connect them to the low-voltage bus.

[0025] Optionally, connecting the renewable energy generator set to the main bus until all loads are restored includes:

[0026] Obtaining the maximum power parameter of the renewable energy generator set;

[0027] The renewable energy generator set is configured to be connected to the main bus under the maximum power parameter state until the load is fully restored.

[0028] Optionally, connecting the renewable energy generator set to the main bus until all loads are restored further includes:

[0029] Real-time monitoring of the power generation of the renewable energy power generation unit and the load of the load;

[0030] Determine the relationship between the power generation of the renewable energy power generation set and the load;

[0031] When the power generation of the renewable energy generator set is greater than the minimum load requirement of the load, the active power output of the energy storage unit is controlled to be zero; when the power generation of the renewable energy generator set is less than the minimum load requirement of the load, the energy storage unit is controlled to output active power.

[0032] Optionally, also include:

[0033] When the SOC of the energy storage unit is less than a third threshold, the energy storage unit stops discharging.

[0034] Optionally, also include:

[0035] Real-time monitoring of bus voltage value;

[0036] When the voltage fluctuation of the bus is greater than a threshold fluctuation range, an auxiliary power supply is connected to supply power to the bus.

[0037] In a second aspect, the present application provides a black start controller for controlling the startup and connection of various components to implement the above-mentioned black start control method.

[0038] It can be seen that the present application starts the energy storage unit, and connects the energy storage unit to the low-voltage bus, and simultaneously connects the step-down transformer and the load, and controls the load to match the power supply capacity of the energy storage unit; after successfully restoring the low-voltage bus, triggers the step-up transformer on the grid side of the low-voltage bus, and connects the restored grid to the medium-voltage bus; after successfully restoring the medium-voltage bus, connects other non-black start power supplies to the medium-voltage bus to establish the main bus voltage; after successfully establishing the main bus voltage, connects the renewable energy generator set to the main bus until all the loads are restored. The present application adopts distributed access of energy storage units, which reduces the unstable power supply of a single starting power supply, and at the same time effectively reduces the risk of overvoltage during the power grid recovery process by controlling the charging and discharging of the energy storage unit. The coordinated cooperation between the renewable energy generator set and the energy storage unit also greatly increases the fault tolerance rate during the black start process, and improves the stability of the system during the black start process. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0040] Figure 1 A flow chart of a black start control method disclosed in this application;

[0041] Figure 2 A diagram of a black start control device disclosed in this application;

[0042] Figure 3 This is a voltage level monitoring data diagram at different stages of a black start system disclosed in this application. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] The core of this application is to provide a black start control method.

[0045] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0046] Black start technology is the process of gradually restoring power supply through the system's internal energy management control strategy or generators with self-starting capabilities after a large-scale power outage without the support of a large power grid. In modern power systems, the black start process usually includes three stages: black start, grid reconstruction, and load recovery. The black start stage is the first step in the entire recovery process. The key lies in selecting the appropriate black start power source, the started unit, and the optimal recovery path. Its selection directly affects the success rate and effect of the black start solution. The selection of black start power sources usually includes hydropower units, gas units, and new energy power sources, such as wind power and photovoltaic power generation. The latter can also serve as an effective black start power source after being equipped with a certain capacity of energy storage system; black start path planning is a key factor in determining the system recovery speed. It is necessary to restore the main power plant of the regional power grid as soon as possible, reduce the length of the start path and the conversion of different voltage levels. In the black start stage, a certain load is connected in time to ensure the frequency and voltage level of the system and maintain power balance.

[0047] However, the intermittent and instability of renewable energy generation such as wind power and photovoltaic power makes it difficult for them to serve as stable black start power sources when the system is first started or after a power outage. At the same time, off-grid systems cannot rely on the support of the large power grid, which will further aggravate the intermittent and instability of renewable energy generation.

[0048] Therefore, it can be seen that people in this field urgently need to solve the instability problem of renewable energy power generation during black start.

[0049] See also Figure 1 As shown, this embodiment discloses a black start control method, which may include:

[0050] Step S11, start each energy storage unit, and connect each energy storage unit to the low-voltage bus, and simultaneously connect the step-down transformer and the load, and control the load to match the power supply capacity of each energy storage unit.

[0051] In this embodiment, the intermittent and unstable nature of renewable energy generation such as wind power and photovoltaic power makes it difficult for them to serve as a stable black start power source when the system is first started or after a power outage. Therefore, in the initial stage of black start, a stable power supply energy source can be connected as the first black start power source, such as the energy storage unit of the generator set to improve the startup success rate, wherein the energy storage unit is a distributed energy storage, so that when an individual energy storage unit fails, it will not affect the black start process of the system. The specific connection method can be that the energy storage unit is connected to the input end of the low-voltage bus, the output end of the low-voltage bus is connected to the primary winding of the step-down transformer, and the secondary winding output of the step-down transformer is then connected to the load.

[0052] In a specific implementation, it may include: obtaining the SOC of the energy storage unit; determining the relationship between the SOC of the energy storage unit and the first threshold; when the SOC of the energy storage unit is less than the first threshold, charging the energy storage unit to restore the function of the energy storage unit and connect to the low-voltage bus. It is understandable that the first threshold is a criterion for determining whether the energy storage unit can work normally. When the SOC of the energy storage unit is less than the first threshold, after successfully restoring the low-voltage bus, the adjacent energy storage unit may be called to charge the energy storage unit with the low SOC and connect to the low-voltage bus.

[0053] At the same time, the system adopts a load-following source control method, that is, in the self-starting stage of the black start power supply, the step-down transformer and the load are connected so that the load can automatically respond to the output change of the black start power supply; that is, before the black start power supply is started, the load is guaranteed to be in a state of being put into use. In the subsequent recovery stage, there is no need to put the load into use, so as to reduce the excessive impact of the put-in load on the restored system, and can assist the black start power supply to form a stable black start recovery initial system.

[0054] Step S12: After the low-voltage bus is successfully restored, the step-up transformer on the grid side of the low-voltage bus is triggered to connect the restored grid to the medium-voltage bus.

[0055] In a specific implementation method, the recovery of bus voltage is a gradual process. The insulation level of low-voltage equipment is relatively low and the ability to withstand voltage is limited. First access to the low-voltage bus, whose lower voltage level can reduce the voltage stress faced by the equipment when starting, reduce the probability of equipment insulation breakdown and other faults, and improve the success rate and safety of equipment startup. After the low-voltage bus is successfully connected and stably operated to power key low-voltage equipment, access to the medium-voltage bus can further expand the power supply range and provide power for more medium-voltage equipment, such as some medium-voltage motors and transformers. The startup and operation of these medium-voltage equipment help to restore some important functions of the system, further enhance the operating capacity and stability of the system, and lay the foundation for the comprehensive recovery of the entire system. At the same time, the voltage level of the medium-voltage bus is between the low voltage and the main bus voltage. First access to the medium-voltage bus can achieve a gradual increase and matching of the voltage. When the black start power supply supplies power to the medium-voltage equipment through the medium-voltage bus, it can improve the efficiency and economy of power transmission to a certain extent, reduce the energy loss and equipment damage risk caused by voltage mismatch, and also provide a transition for the subsequent voltage regulation and stability when the main bus is connected.

[0056] Step S13: After the medium voltage bus is successfully restored, other non-black start power sources are connected to the medium voltage bus to establish the main bus voltage.

[0057] In this embodiment, the main bus is the core part of the power system, connecting the main equipment in various links such as power generation, transmission and distribution. After the low-voltage bus and medium-voltage bus are successfully connected and operate stably, the main bus connects the black start power supply to the main network of the entire power system, thereby achieving full recovery and normal operation of the entire power system. After access to the main bus, the system can reconstruct and optimize the power grid according to the topological structure and operation requirements of the power grid. Provide these high-voltage devices with appropriate voltage and sufficient starting power, and gradually start the high-voltage loads according to the predetermined order and requirements, so that power can be transmitted to a wider area and power supply to various users can be restored.

[0058] As the grid restoration process progresses, the load in the system will gradually increase. Relying solely on black start power supplies may not be able to meet the growing load demand. Therefore, starting other non-black start power supplies at this time can provide more power supply, ensure the balance of power supply and demand in the restoration area, and maintain the stable operation of the grid. Black start power supplies usually refer to power supplies that have the ability to start themselves without external grid power supply, such as wind turbines. When the wind speed reaches a certain cut-in wind speed, the lift generated by the wind acting on the blades overcomes the resistance torque of the wind wheel, causing the wind wheel to start rotating. The hub of the wind wheel is connected to the generator. After the wind wheel starts to rotate, this mechanical connection transmits the rotational motion to the generator. Non-black start power supplies usually have thermal power units and do not have self-starting capabilities. The startup of non-black start power supplies requires a large number of auxiliary equipment, such as coal feeders, blowers, induced draft fans, etc. These equipment usually require external power supply to work. In the absence of external grid power supply, these auxiliary equipment cannot operate, and the thermal power unit cannot start. Therefore, the non-black start power supply can only be connected after the medium voltage bus is successfully restored.

[0059] Step S14: After the main bus voltage is successfully established, the renewable energy generator set is connected to the main bus until all loads are restored.

[0060] The main bus is the core part of the power system. Accessing the main bus means connecting the black start power supply to the main network of the entire power system, enabling the power generation equipment to deliver a large amount of electricity to the grid to meet the power needs of various high-voltage and large-capacity equipment in the system. At this time, the power supply of the energy storage unit alone is difficult to sustain.

[0061] Therefore, after the main bus voltage is successfully established, the renewable energy generator set is connected to the main bus. In order to accelerate the black start process, this embodiment provides a black start control method, which may include: obtaining the maximum power parameter of the renewable energy generator set; configuring the renewable energy generator set to be connected to the main bus under the maximum power parameter state until the load is fully restored. That is, by gradually increasing the power output, the load input amount is increased, and finally the full recovery of the load is achieved.

[0062] It can be seen that the present application starts the energy storage unit, and connects the energy storage unit to the low-voltage bus, and simultaneously connects the step-down transformer and the load, and controls the load to match the power supply capacity of the energy storage unit; after successfully restoring the low-voltage bus, trigger the step-up transformer on the grid side of the low-voltage bus, and connect the restored grid to the medium-voltage bus; after successfully restoring the medium-voltage bus, connect other non-black start power supplies to the medium-voltage bus to establish the main bus voltage; after successfully establishing the main bus voltage, connect the renewable energy generator set to the main bus until all loads are restored. The distributed access of the energy storage unit is adopted in the present application, which reduces the unstable power supply of a single starting power supply, and at the same time effectively reduces the risk of overvoltage during the power grid restoration process by controlling the charging and discharging of the energy storage unit. The coordinated cooperation between the renewable energy generator set and the energy storage unit also greatly increases the fault tolerance rate during the black start process, and improves the stability of the system during the black start process.

[0063] According to the above embodiment, this embodiment provides a specific solution. Under normal circumstances, all energy storage units are in normal working state. After confirming the SOC of each energy storage unit, the energy storage units work together to establish a low-voltage bus voltage. However, when the energy storage unit cannot work normally due to the low energy storage SOC (State of Charge, SOC), it is necessary to remediate the energy storage unit with low SOC, and different response plans are required for the working conditions of energy storage units with low SOC in different ranges.

[0064] In a specific implementation, it may include: calculating the ratio of the number of energy storage units with SOC less than the first threshold in the same group to the total number of energy storage units; judging the relationship between the ratio and the second threshold; when the ratio is less than the second threshold, charging the energy storage units in the same group of the renewable energy generator set that can work normally to restore the function of the energy storage units and connect to the low-voltage bus. It can be understood that the second threshold is a range determination standard for energy storage units with low SOC in the same power generation group. When the ratio of the number of energy storage units with SOC less than the first threshold in the same group to the total number of energy storage units is less than the second threshold, it means that the energy storage units in the same group are still capable of charging the energy storage units with low SOC. Therefore, after successfully restoring the low-voltage bus, the energy storage units in the same group that can work normally are mobilized to charge the energy storage units with low SOC to restore the function of the energy storage units with low SOC and then connect the restored energy storage units with low SOC to the low-voltage bus.

[0065] In another specific implementation, it may include: calculating the ratio of the number of energy storage units with SOC less than the first threshold in the same group to the total number of energy storage units; judging the relationship between the ratio and the second threshold; when the ratio is greater than the second threshold, instructing other renewable energy generator sets to charge the energy storage units to restore the function of the energy storage units and connect to the low-voltage bus. When the ratio of the number of energy storage units with SOC less than the first threshold in the same group to the total number of energy storage units is greater than the second threshold, it means that the energy storage units in the same group no longer have the ability to charge the energy storage units with low SOC. Therefore, after successfully restoring the low-voltage bus, the energy storage units that can work normally in other renewable energy generator sets are mobilized to charge the energy storage units with low SOC to restore the function of the energy storage units with low SOC, and then the restored energy storage units with low SOC are connected to the low-voltage bus.

[0066] In a third specific implementation, it may include: when the SOC of the energy storage units are all less than the first threshold, the diesel generator is enabled to charge the energy storage units to restore the functions of the energy storage units and connect to the low-voltage bus. In the most extreme case, when all energy storage units fail to work, the system will rely on the diesel generator as a backup power source. The diesel generator will first charge the energy storage unit with a low SOC to restore the function of the energy storage unit with a low SOC, and then connect the restored energy storage unit with a low SOC to the low-voltage bus.

[0067] It can be seen that in this embodiment, different implementation methods are adopted to deal with and solve different working conditions of low SOC of the energy storage unit. In order to ensure that the establishment of the low-voltage bus is not affected, after the energy storage unit with low SOC is found, except for the most extreme situation where all energy storage units cannot work, the energy storage units that can work normally are first connected to the low-voltage bus to restore the normal operation of the low-voltage bus. After the low-voltage bus is successfully restored, the normally working energy storage units are used to charge the energy storage units with low SOC and connect them to the low-voltage bus, ensuring the safety and efficiency of the black start process.

[0068] The energy storage unit plays a key role in the black start process. It can provide key initial power when there is no large power grid support or when it is started for the first time, help the generator set with self-starting capability to start, and then drive other units to resume operation. Therefore, the output of the energy storage unit is controlled according to the power generation of the renewable energy generator set. This embodiment provides a black start control method, which may include: real-time monitoring of the power generation of the renewable energy generator set and the load; judging the size relationship between the power generation of the renewable energy generator set and the load; when the power generation of the renewable energy generator set is greater than the minimum load requirement of the load, the active power output of the energy storage unit is controlled to be zero; when the power generation of the renewable energy generator set is less than the minimum load requirement of the load, the energy storage unit is controlled to output active power. It can be understood that when the SOC of the energy storage unit is less than the third threshold, the energy storage unit stops discharging. In order to ensure the natural power consumption of the wind turbine or photovoltaic removal under short-circuit conditions, and considering the healthy life of the energy storage unit, part of the battery capacity of the energy storage unit should be reserved as a temporary charge margin, and the lower limit of the battery discharge of the energy storage unit should be set. This is based on ensuring the black start power supply demand of the wind turbine and considering the self-discharge of the battery itself.

[0069] In a specific implementation, if the power generation of the renewable energy generator set exceeds the load's absorptive capacity, the load operates at maximum power, for example, the upper limit of the energy storage unit charge is set to 90% during normal operation; to ensure the black start power supply demand of the renewable energy generator set, and considering the self-discharge of the energy storage unit itself, for example, the monthly energy consumption of the energy storage unit is less than or equal to 5%, the lower limit of the energy storage unit discharge is set to 35%. If the SOC of the energy storage unit is less than 90%, the surplus power generation is used to charge the energy storage unit until the SOC of the energy storage unit group returns to 90% and then stops. If the available power on the source side is higher than the rated capacity of the load for a long time or the chargeable amount of the energy storage unit is insufficient, the output of the renewable energy generator set should be limited or some power supply equipment should be cut off in conjunction with the equipment renovation plan.

[0070] In another specific implementation, if the power generation of the renewable energy generator set does not exceed the load's absorptive capacity, but is higher than the load's minimum load requirement, a charging strategy should be formulated based on the current SOC of the energy storage unit. For example, when the energy storage unit SOC is greater than 35%, charging is not performed, and the system power generation is guaranteed to ensure load operation. If the energy storage unit SOC is less than 35%, part of the renewable energy power generation is used to charge the energy storage unit while ensuring the load's minimum load requirement, and the charging is stopped when the energy storage unit SOC is greater than 35%.

[0071] In the third specific implementation, if the power generation of the renewable energy generator set is less than the minimum load demand, the energy management system should discharge in combination with the current SOC of the energy storage unit. For example, if the SOC of the energy storage unit is greater than 35%, it will provide short-term power support for the system to ensure continuous operation of the load. If the SOC of the energy storage unit is less than 30%, it will stop discharging. At this time, the system will cut off part of the system load under the condition of minimum cost based on the available power and the minimum power demand of each load through the set objective function.

[0072] It can be seen that in this embodiment, when the power system is operating normally, in order to allow renewable energy power generation systems such as wind turbines and photovoltaics to directly supply as much power to the grid as possible to meet the load requirements of the system. When the power generation of the renewable energy generator set is greater than the minimum load requirement of the load, controlling the active power output of the energy storage unit to zero can maximize the use of wind and solar energy, thereby improving the sustainability of the entire power system. However, in the early stages of a black start, the energy storage unit can provide power to the grid to support the recovery and stability of the grid. Once the grid recovers to a certain extent, the energy storage system will be controlled again to not output power, allowing the wind turbines and photovoltaic systems to continue to undertake the task of power supply.

[0073] It is understandable that the bus voltage will fluctuate to a certain extent during the black start process. Therefore, according to the above embodiment, a black start control method is provided in this embodiment, which may also include: real-time monitoring of the bus voltage value; when the bus voltage fluctuation is greater than the threshold fluctuation range, connecting the auxiliary power supply to power the bus. Here, the auxiliary power supply mainly plays the role of regulating the bus voltage, which can cope with system emergencies and bear the power changes of the system in a short time. The stability of the bus voltage during the black start process is further guaranteed.

[0074] Figure 2 This is a diagram of a black start control device disclosed in this application, which contains N wind turbine stations and N photovoltaic stations. The new energy power generation is sent to the load side through a series of power conversions, and the station is equipped with an emergency diesel power supply. Taking the No. 1 wind turbine and the No. 1 photovoltaic station as examples, T1 is a doubly fed active inverter, T2 and T4 are non-isolated bidirectional DC-DC converters, T3 is a NPPT (Non-PWM / PFM / Tracking) type bidirectional DC-DC converter, and T5 is an isolated bidirectional full-bridge (Dual ActiveBridge, DAB) converter. Figure 3The voltage level monitoring data table of the black start system at different stages corresponds to the following eight steps in combination with the specific circuit. The specific work flow is as follows: the first step is to start the wind turbine energy storage unit, power on the wind turbine converter, and establish a low-voltage DC bus voltage; the second step is to connect the wind turbine energy storage unit to the low-voltage DC bus; the third step is to start the photovoltaic energy storage unit, power on the photovoltaic converter, and establish a low-voltage DC bus voltage; the fourth step is to power on the photovoltaic side bidirectional DC transformer, and connect the photovoltaic energy storage unit to the DC main grid; the fifth step is to start the wind turbine, convert wind energy into mechanical energy, and start the permanent magnet synchronous motor; the sixth step is to power on the wind turbine side transformer, and the wind turbine output is put into the DC main grid to supply the load; the seventh step is to start the photovoltaic generator, connect it to the DC main grid, and gradually increase the photovoltaic output: the photovoltaic side is powered on, the photovoltaic output is put into the DC main grid to supply the load, and the photovoltaic output is gradually increased to improve the system load recovery; the eighth step is that the system black start is completed and the system voltage tends to be stable.

[0075] In this embodiment, since the wind turbine may require more initial power support during the startup process, and the energy storage system can provide such support, in addition, the startup of the wind turbine may have higher requirements for the stability of the power grid, the wind turbine is started first. The startup of the photovoltaic system is relatively simple and can be carried out after the grid voltage is stable. In a more specific implementation method, this order can be swapped, but it needs to be determined according to the specific situation of the power grid and the control strategy. When the capacity of the energy storage unit and the bearing capacity of the power grid are large enough, it is theoretically possible to support the simultaneous startup of the wind turbine and the photovoltaic system. In steps five, six, and seven, the startup order of the wind turbine and photovoltaic can be adjusted according to the actual power grid demand and resource conditions. For example, if the wind speed is low, it may be necessary to increase the photovoltaic output first to meet the power grid demand. On the contrary, if the lighting conditions are not good, it may be necessary to start the wind turbine first. In this way, the flexibility of the black start control method execution process is improved.

[0076] Furthermore, the present application also discloses a black start controller for controlling the startup and connection of various components to implement the aforementioned black start control method. The specific steps of the method can refer to the corresponding contents disclosed in the aforementioned embodiments, which will not be described in detail here.

[0077] The above is a detailed introduction to a black start control method and controller provided by the present application. The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can refer to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can refer to the method part description. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

[0078] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0079] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0080] The steps of the method or algorithm described in conjunction with the embodiments disclosed herein may be implemented directly using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0081] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0082] The technical solution provided by the present application is introduced in detail above. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea. At the same time, for general technical personnel in this field, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A black start control method, characterized in that: Applied to a black start control device, the black start control device comprises a plurality of groups of renewable energy generator sets, the plurality of groups of the renewable energy generator sets are connected to a bus, one group of the renewable energy generator sets comprises a plurality of renewable energy generators and energy storage units corresponding to each of the renewable energy generators, the method comprises: Starting each of the energy storage units, and connecting each of the energy storage units to a low-voltage bus, and simultaneously connecting a step-down transformer and a load, and controlling the load to match the power supply capacity of each of the energy storage units; After the low-voltage bus is successfully restored, the step-up transformer on the grid side of the low-voltage bus is triggered to connect the restored grid to the medium-voltage bus; After the medium voltage bus is successfully restored, other non-black start power supplies are connected to the medium voltage bus to establish a main bus voltage; After the main bus voltage is successfully established, the renewable energy generator set is connected to the main bus until all loads are restored.

2. The black start control method according to claim 1, characterized in that: Connecting each of the energy storage units to a low-voltage bus includes: Obtaining the SOC of the energy storage unit; Determining a relationship between the SOC of the energy storage unit and a first threshold; When the SOC of the energy storage unit is less than the first threshold, the energy storage unit is charged to restore the function of the energy storage unit and connected to the low-voltage bus.

3. The black start control method according to claim 2, characterized in that: When the SOC of the energy storage unit is less than the first threshold, charging the energy storage unit to restore the function of the energy storage unit and connecting to the low-voltage bus, comprises: Calculate the ratio of the number of energy storage units in the same group whose SOC is less than the first threshold to the total number of energy storage units; determining a relationship between the ratio and a second threshold; When the ratio is less than the second threshold, the normally working energy storage unit in the same group as the renewable energy generator set is charged to restore the function of the energy storage unit and connect to the low-voltage bus.

4. The black start control method according to claim 2, characterized in that: When the SOC of the energy storage unit is less than the first threshold, charging the energy storage unit to restore the function of the energy storage unit and connecting to the low-voltage bus, comprises: Calculate the ratio of the number of energy storage units in the same group whose SOC is less than the first threshold to the total number of energy storage units; determining a relationship between the ratio and a second threshold; When the ratio is greater than the second threshold, the other renewable energy generating sets are ordered to charge the energy storage unit to restore the function of the energy storage unit and connect it to the low-voltage bus.

5. The black start control method according to claim 2, characterized in that: When the SOC of the energy storage unit is less than the first threshold, charging the energy storage unit to restore the function of the energy storage unit and connecting to the low-voltage bus, comprises: When the SOCs of the energy storage units are all less than the first threshold, the diesel generator is enabled to charge the energy storage units to restore the functions of the energy storage units and connect them to the low-voltage bus.

6. The black start control method according to claim 1, characterized in that: The step of connecting the renewable energy generator set to the main bus until all loads are restored includes: Obtaining the maximum power parameter of the renewable energy generator set; The renewable energy generator set is configured to be connected to the main bus under the maximum power parameter state until the load is fully restored.

7. The black start control method according to claim 1, characterized in that: The step of connecting the renewable energy generator set to the main bus until all loads are restored further comprises: Real-time monitoring of the power generation of the renewable energy power generation unit and the load of the load; Determine the relationship between the power generation of the renewable energy power generation set and the load; When the power generation of the renewable energy generator set is greater than the minimum load requirement of the load, the active power output of the energy storage unit is controlled to be zero; when the power generation of the renewable energy generator set is less than the minimum load requirement of the load, the energy storage unit is controlled to output active power.

8. The black start control method according to claim 7, characterized in that: Also includes: When the SOC of the energy storage unit is less than a third threshold, the energy storage unit stops discharging.

9. The black start control method according to any one of claims 1 to 7, characterized in that: Also includes: Real-time monitoring of bus voltage value; When the voltage fluctuation of the bus is greater than a threshold fluctuation range, an auxiliary power supply is connected to supply power to the bus.

10. A black start controller, characterized in that: Used to control the startup and connection of each component to implement the black start control method described in any one of claims 1 to 8.

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