Black start method and device of off-network energy storage system and system controller

Abstract

The invention provides a black-start method and device for an off-grid energy storage system and a system controller, and relates to the technical field of power systems. The method comprises the following steps: determining at least one self-starting energy storage unit from at least one energy storage unit; and controlling an energy storage converter in the self-starting energy storage unit to boost from zero according to a preset control strategy and a boost starting function. According to the embodiment of the invention, the energy storage converter in the self-starting energy storage unit is controlled to boost from zero according to the preset control strategy and the boost starting function, so that the method for boosting from zero can adapt to energy storage application scenes of multiple voltage levels and multiple application scenes.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of power systems, and in particular to a black start method, device, and system controller for an off-grid energy storage system. Background Art

[0002] In recent years, more and more off-grid renewable energy power generation systems have been applied in remote mountainous areas, areas without electricity, islands, etc. The off-grid energy storage system of the off-grid renewable energy power generation system has weak stability. When the external power grid fails or the energy storage system shuts down, the off-grid energy storage system needs to be black-started.

[0003] At present, the black start process of off-grid energy storage systems mostly adopts multi-machine parallel operation or multi-machine master-slave sequence zero-start voltage boost. The zero-start voltage boost strategy usually adopts a step-by-step slope boost of several voltage target values. When the voltage at the energy storage system port is boosted to the rated voltage, other power sources and loads can be started.

[0004] However, the zero-start voltage boosting method in the prior art cannot adapt to energy storage application scenarios with multiple voltage levels and multiple application scenarios. Summary of the invention

[0005] In view of this, the embodiments of the present application provide a black start method, device and system controller for an off-grid energy storage system, which are used to adapt to energy storage application scenarios with multiple voltage levels and multiple application scenarios.

[0006] A first aspect provides a black start method for an off-grid energy storage system, the method comprising: Determining at least one self-starting energy storage unit from at least one energy storage unit; According to the preset control strategy and boost start function, the energy storage converter in the self-starting energy storage unit is controlled to boost voltage from zero.

[0007] In a possible implementation, there are multiple energy storage units, and after controlling the energy storage converter in the self-starting energy storage unit to start voltage boost from zero, the method further includes: If the bus voltage of the off-grid energy storage system is greater than or equal to the set rated bus voltage, other energy storage units except the self-starting energy storage unit among the multiple energy storage units are controlled to start.

[0008] In a possible implementation, before controlling the energy storage converter in the self-starting energy storage unit to boost voltage from zero according to the preset control strategy and boost startup function, the method further includes: If the number of the energy storage converter of the self-starting energy storage unit is one, the control strategy is determined to be a virtual synchronous machine control strategy; or If there are multiple energy storage converters in the self-starting energy storage unit, and a high-speed communication network is set between the system controller and the multiple energy storage converters in the self-starting energy storage unit, the control strategy is determined to be a virtual synchronous machine control strategy.

[0009] In a possible implementation, before controlling the energy storage converter in the self-starting energy storage unit to boost voltage from zero according to the preset control strategy and boost startup function, the method further includes: If there are multiple energy storage inverters in the self-starting energy storage unit, the multiple energy storage inverters of the self-starting energy storage units are arranged in a dispersed manner and no high-speed communication network is set between the system controller and the multiple energy storage inverters of the self-starting energy storage units, the control strategy is determined as a constant voltage and constant frequency control strategy.

[0010] In a possible implementation, before controlling the energy storage converter in the self-starting energy storage unit to boost voltage from zero according to the preset control strategy and boost startup function, the method further includes: If the rated bus voltage is greater than the set level voltage, and the ratio of the total capacity of the energy storage converter of the self-starting energy storage unit to the sum of the no-load loss capacity of all transformers in the off-grid energy storage system is greater than the set ratio, the boost start function is determined as a logarithmic-ramp function; or, If the rated bus voltage is less than or equal to the set level voltage, the boost start function is determined as a ramp function; or, If the rated bus voltage is greater than the set level voltage, and the ratio of the total capacity of the energy storage inverter of the self-starting energy storage unit to the sum of the no-load loss capacity of all transformers in the off-grid energy storage system is less than or equal to the set ratio, the boost starting function is determined as a ramp function.

[0011] In a possible implementation, if the control strategy is a virtual synchronous machine control strategy, controlling the energy storage converter in the self-starting energy storage unit to start voltage boosting from zero according to the preset control strategy and boosting start function includes: A virtual synchronous voltage reference value is issued to the energy storage converter in each of the self-starting energy storage units according to the boost start function, so that the energy storage converter boosts voltage according to the virtual synchronous voltage reference value.

[0012] In a possible implementation, the sending of a virtual synchronous voltage reference value to the energy storage converter in each of the self-starting energy storage units according to the boost startup function includes: Acquire zero-start boost voltage reference values ​​corresponding to different moments according to the boost start function; Calculating the virtual synchronous voltage reference value corresponding to the energy storage converter according to the zero-start boost voltage reference value and the reactive power of the energy storage converter; The virtual synchronous voltage reference value is sent to the corresponding energy storage converter.

[0013] In a possible implementation, if the control strategy is a constant voltage and constant frequency control strategy, controlling the energy storage converter in the self-starting energy storage unit to start voltage boosting from zero according to a preset control strategy and a boost start function includes: A self-starting instruction is sent to the energy storage inverter of any self-starting energy storage unit, so that the energy storage inverter of any self-starting energy storage unit responds to the self-starting instruction and boosts the voltage according to the pre-acquired constant voltage and constant frequency voltage reference value corresponding to different time periods. If the energy storage inverter of each other self-starting energy storage unit determines that the voltage of its own output port is greater than or equal to the predetermined voltage, it boosts the voltage according to the pre-acquired boost starting function.

[0014] A second aspect provides a black start device for an off-grid energy storage system, comprising: A determination module, used to determine at least one self-starting energy storage unit from at least one energy storage unit; The first control module is used to control the energy storage converter in the self-starting energy storage unit to boost voltage from zero according to a preset control strategy and boost start function.

[0015] The third aspect provides a system controller, comprising: one or more processors; a memory; and one or more computer programs, wherein the one or more computer programs are stored in the memory, and the one or more computer programs include instructions, which, when executed by the system controller, enable the system controller to execute the black start method of the off-grid energy storage system in the above-mentioned first aspect or any possible implementation of the first aspect.

[0016] In the technical solution provided in the embodiment of the present application, at least one self-starting energy storage unit is determined from at least one energy storage unit, and the energy storage converter in the self-starting energy storage unit is controlled to start boosting from zero according to a preset control strategy and a boost start function. The embodiment of the present application controls the energy storage converter in the self-starting energy storage unit to start boosting from zero according to a preset control strategy and a boost start function, so that the method of starting boosting from zero can adapt to energy storage application scenarios with multiple voltage levels and multiple application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0018] Figure 1 A schematic diagram of the structure of an off-grid energy storage system provided in an embodiment of the present application; Figure 2 A flow chart of a black start method for an off-grid energy storage system provided in an embodiment of the present application; Figure 3 A flow chart of a method for determining a self-starting energy storage unit provided in an embodiment of the present application; Figure 4 A flowchart of a method for determining a boost start function provided in an embodiment of the present application; Figure 5 A schematic diagram of a ramp function provided in an embodiment of the present application; Figure 6 A schematic diagram of a logarithmic ramp function provided in an embodiment of the present application; Figure 7 A flowchart of a method for issuing a virtual synchronous voltage reference value provided in an embodiment of the present application; Figure 8 A flowchart of a method for zero-start voltage boosting provided in an embodiment of the present application; Fig. 9 A schematic diagram of the structure of a black start device for an off-grid energy storage system provided in an embodiment of the present application; Fig.10 A schematic diagram of the structure of a system controller provided in an embodiment of the present application. DETAILED DESCRIPTION

[0019] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0020] It should be clear that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0021] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0022] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0023] Figure 1 A schematic diagram of the structure of an off-grid energy storage system provided in an embodiment of the present application is shown in FIG. Figure 1 As shown, the off-grid energy storage system may include: a system controller, n energy storage units, a new energy unit and k load units. As an optional solution, the new energy unit may include m photovoltaic units and i wind power units. For example, n, k, m and i are all positive integers, and n≥1, k≥1, m≥1, i≥1. The system controller may be connected to the energy storage unit, the new energy unit and the load unit.

[0024] In the embodiments of the present application, the number of energy storage units, photovoltaic units, wind power units and load units can be one or more. Figure 1 In the description, the number of energy storage units, photovoltaic units, wind power units and load units is multiple as an example.

[0025] like Figure 1 As shown, each energy storage unit is connected to the busbar through a corresponding energy storage transformer. Each energy storage unit may include an energy storage inverter and a battery unit. For example, energy storage unit 1 may include energy storage inverter 1 and battery unit 1, energy storage unit 2 may include energy storage inverter 2 and battery unit 2, and so on. Energy storage unit n may include energy storage inverter n and battery unit n. For example, battery unit 1 is connected to energy storage inverter 1, and energy storage inverter 1 is connected to the busbar through the corresponding energy storage transformer 1; battery unit 2 is connected to energy storage inverter 2, and energy storage inverter 2 is connected to the busbar through the corresponding energy storage transformer 2; and so on. Battery unit n is connected to energy storage inverter n, and energy storage inverter n is connected to the busbar through the corresponding energy storage transformer n. As Figure 1 As shown, each energy storage unit may include an energy storage converter and a battery unit.

[0026] like Figure 1As shown, as an optional solution, the energy storage unit is connected to the energy storage transformer through the first switch, and the energy storage transformer is connected to the busbar through the second switch. The energy storage converter 1 of the energy storage unit 1 is connected to the energy storage transformer 1 through the first switch M1, the energy storage converter 2 of the energy storage unit 2 is connected to the energy storage transformer 2 through the first switch M2, and so on, the energy storage converter n of the energy storage unit n is connected to the energy storage transformer n through the first switch Mn. The energy storage transformer 1 is connected to the busbar through the second switch K1, the energy storage transformer 2 is connected to the busbar through the second switch K2, and so on, the energy storage transformer n is connected to the busbar through the second switch Kn.

[0027] like Figure 1 As shown, the embodiment of the present application is described by taking one energy storage transformer corresponding to one energy storage unit as an example. In practical applications, as another optional solution, one energy storage transformer can correspond to and be connected to multiple energy storage units, that is, multiple energy storage units are connected to the busbar through one energy storage transformer, which is not specifically drawn.

[0028] like Figure 1 As shown, load units 1 to load units n are connected to the busbar through load transformers; photovoltaic units 1 to photovoltaic units m are connected to the busbar through photovoltaic transformers; wind power units 1 to wind power units i are connected to the busbar through wind power transformers. As an optional solution, each load unit corresponds to a load transformer, and each load unit is connected to the busbar through a load transformer; as another optional solution, multiple load units correspond to one load transformer, and multiple load units are connected to the busbar through one load transformer. As an optional solution, each photovoltaic unit corresponds to a photovoltaic transformer, and each photovoltaic unit is connected to the busbar through a photovoltaic transformer; as another optional solution, multiple photovoltaic units correspond to one photovoltaic transformer, and multiple photovoltaic units are connected to the busbar through one photovoltaic transformer. As an optional solution, each wind power unit corresponds to a wind power transformer, and each wind power unit is connected to the busbar through a wind power transformer; as another optional solution, multiple wind power units correspond to one wind power transformer, and multiple wind power units are connected to the busbar through one wind power transformer. As shown Figure 1 As shown, the load transformer, photovoltaic transformer and wind power transformer are each taken as one as an example. In actual applications, the number of load transformers, the number of photovoltaic transformers and the number of wind power transformers can all be multiple, and this situation is no longer specifically drawn.

[0029] like Figure 1 As shown, the system controller can be connected to the energy storage inverter, the battery unit, the photovoltaic unit, the wind power unit, the load unit and the bus.

[0030] like Figure 1As shown, as an optional solution, the wind power transformer is connected to the busbar through the third switch C1, the photovoltaic transformer is connected to the busbar through the fourth switch C2, and the load transformer is connected to the busbar through the fifth switch C3.

[0031] like Figure 1 As shown, the off-grid energy storage system is connected to the external public power grid through an incoming switch K and a step-up transformer.

[0032] In the embodiment of the present application, as an optional solution, the incoming switch K, the first switch, the second switch, the third switch, the fourth switch and the fifth switch can all be circuit breakers or contactors.

[0033] based on Figure 1 The off-grid energy storage system shown, an embodiment of the present application provides a black start method for an off-grid energy storage system. Figure 2 A flowchart of a black start method for an off-grid energy storage system provided in an embodiment of the present application is shown in FIG. Figure 2 As shown, the method includes: Step 102: The system controller determines at least one self-starting energy storage unit from at least one energy storage unit.

[0034] As an optional solution, when the number of the energy storage unit is one, the system controller determines the energy storage unit as a self-starting energy storage unit. In this case, the number of the self-starting energy storage unit is one.

[0035] As another optional solution, when there are multiple energy storage units, the system controller determines at least one self-starting energy storage unit from the multiple energy storage units. Figure 3 A flowchart of a method for determining a self-starting energy storage unit provided in an embodiment of the present application, such as Figure 3 As shown, step 102 may specifically include: Step 1022: The system controller detects the state of charge (SOC) of the battery cells in all energy storage units.

[0036] Step 1024: The system controller sorts the energy storage units from high to low according to the state of charge, selects a set number of energy storage units with the highest SOC, and uses the selected set number of energy storage units as self-starting energy storage units.

[0037] In the embodiment of the present application, the set number can be one or more. Figure 1 As shown, the number is set to 1, then among the energy storage units 1 to n, the system controller determines that the energy storage unit 1 with the highest SOC is used as the self-starting energy storage unit. Figure 1As shown, the set number is 3, then among energy storage units 1 to n, the system controller determines the three energy storage units with the highest SOC as self-starting energy storage units. For example, the three self-starting energy storage units may include energy storage unit 1, energy storage unit 3, and energy storage unit n.

[0038] In the embodiment of the present application, the system controller selects a battery cell with a high SOC, thereby improving the black start success rate of the off-grid energy storage system.

[0039] Step 104: The system controller controls the energy storage converter in the self-starting energy storage unit to boost the voltage from zero according to the preset control strategy and boost start function.

[0040] As an optional solution, before step 104, the following steps may also be included: Step S11: The system controller controls the battery unit in the self-starting energy storage unit to start.

[0041] Step S12, the system controller determines whether the output voltage of the battery unit in the self-starting energy storage unit within the first set time period is greater than or equal to the set stable voltage value, if so, execute step 104; if not, the process ends.

[0042] Specifically, after the battery cell in the self-starting energy storage unit is started, the system controller can detect the output voltage of the battery cell in the self-starting energy storage unit. If the system controller determines that the output voltage is greater than or equal to the set stable voltage value within the first set time period, it indicates that the output voltage of the battery cell has reached a stable state, and step 104 can be executed; if the system controller determines that the output voltage is less than the set stable voltage value within the first set time period, it indicates that the output voltage of the battery cell has not reached a stable state within the first set time period, then the black start process ends, and subsequent manual troubleshooting can be performed. Among them, the output voltage of the battery cell is the voltage of the output port where the battery cell is connected to the energy storage inverter. The first set time period can be set according to actual needs. For example, the first set time period can be 5s.

[0043] As an optional solution, when there are multiple energy storage units, after step 104, the following steps may also be included: Step 106: If the system controller determines that the bus voltage of the off-grid energy storage system is greater than or equal to the set rated bus voltage, the system controller controls other energy storage units except the self-starting energy storage unit among the multiple energy storage units to start.

[0044] In the embodiment of the present application, after the system controller controls the energy storage converter in the self-starting energy storage unit to start voltage boosting from zero, the bus voltage will increase. As an optional solution, before step 106, it also includes: Step S21, the system controller determines whether the bus voltage of the off-grid energy storage system is greater than or equal to the set rated bus voltage within the second set time period. If so, step 106 is executed; if not, the process ends.

[0045] In the embodiment of the present application, the system controller detects the bus voltage of the off-grid energy storage system. If the system controller determines that the bus voltage of the off-grid energy storage system is greater than or equal to the rated bus voltage within the second set time period, indicating that the zero-start voltage boost is completed and the off-grid energy storage system has reached the conditions for starting other energy storage units, then step 106 is continued to be executed; if the system controller determines that the bus voltage of the off-grid energy storage system is less than the rated bus voltage within the second set time period, indicating that the conditions for starting other energy storage units are not reached, then the black start process ends, and manual troubleshooting can be performed later.

[0046] In the embodiment of the present application, if the bus voltage is greater than or equal to the rated bus voltage, the system controller may control other energy storage units to start in sequence. Figure 1 As shown, if the number of self-starting energy storage units is 3, the number of other energy storage units is n-3, and the system controller controls the n-3 energy storage units to start in sequence.

[0047] As an optional solution, after step 104 or step 106, the method further includes: Step 108: The system controller controls the load unit, the photovoltaic unit, and the wind power unit to start.

[0048] After all energy storage units are started, step 108 may be performed to complete the start-up of the load unit and the new energy unit. The start-up sequence of the load unit, the photovoltaic unit and the wind power unit may be set by the system controller.

[0049] As an optional solution, before step 102, the method further includes: Step 100: The system controller controls the energy storage unit, the load unit, the new energy unit and the switch devices in the off-grid energy storage system to be set to a black start mode.

[0050] As an optional solution, the new energy unit may include a photovoltaic unit and a wind power unit, and the switch device may include a first switch, a second switch, a third switch, a fourth switch, and a fifth switch. Specifically, the system controller may control the energy storage unit, the load unit, the photovoltaic unit, the wind power unit, the first switch, the second switch, the third switch, the fourth switch, and the fifth switch to switch to the black start mode.

[0051] In the embodiment of the present application, the energy storage unit, the load unit, the new energy unit and the switch device are set to a black start mode, which effectively prevents failures during the black start process, thereby protecting the power grid equipment.

[0052] As an optional solution, after step 108, the method further includes: Step 110: The system controller controls the energy storage unit, the load unit, the new energy unit and the switch devices in the off-grid energy storage system to be set to an off-grid operation mode.

[0053] Specifically, the system controller can control the energy storage unit, the load unit, the photovoltaic unit, the wind power unit, the first switch, the second switch, the third switch, the fourth switch and the fifth switch to be set to an off-grid operation mode.

[0054] In the embodiment of the present application, the energy storage unit, the load unit, the new energy unit and the switch device are set to an off-grid operation mode, thereby ensuring the normal operation of the off-grid energy storage system.

[0055] As an optional solution, after receiving the black start instruction, the system controller first determines whether the off-grid energy storage system meets the set black start conditions before starting to execute the control process of the black start method. The method also includes: Step S31: The system controller determines whether the off-grid energy storage system meets the black start condition according to the received black start instruction. If yes, continue to execute step 100 or step 102; if no, the process ends.

[0056] As an optional solution, if the black start method includes step 100, if it is determined in step S31 that the off-grid energy storage system meets the black start condition, step 100 may be continued. As another optional solution, if the black start method does not include step 100, if it is determined in step S31 that the off-grid energy storage system meets the black start condition, step 102 may be continued.

[0057] As an optional solution, a black start instruction may be manually input to the system controller. After receiving the manually input black start instruction, the system controller responds to the black start instruction and determines whether the off-grid energy storage system meets the black start condition.

[0058] As an optional solution, the black start conditions include: the current capacity of the battery unit in each self-starting energy storage unit is greater than the black start power, the incoming switch between the off-grid energy storage system and the public power grid is in the open state, the switch devices in the off-grid energy storage system are in the closed state, and the new energy unit and load unit in the off-grid energy storage system are in the off-state or shutdown state.

[0059] In the embodiment of the present application, a black start condition is set in which the current capacity of the battery cell in each self-starting energy storage unit is greater than the black start power, which can improve the success rate of the black start; a black start condition is set in which the incoming switch is in an open state, thereby ensuring that the system is in an off-grid state; a black start condition is set in which all switch devices in the off-grid energy storage system are in a closed state, thereby ensuring the stability of the system after the black start and preventing the system from shutting down again.

[0060] In the embodiment of the present application, when the construction of the off-grid energy storage system is completed, the system controller can pre-set the control strategy and boost start function according to the off-grid energy storage system.

[0061] As an optional solution, the control strategy may include a virtual synchronous machine control strategy or a constant voltage and constant frequency control strategy. Before step 104, the method further includes: If the system controller determines that the number of energy storage converters from the startup energy storage unit is one, the control strategy is determined as a virtual synchronous machine control strategy.

[0062] Alternatively, if the system controller determines that there are multiple energy storage converters in the self-starting energy storage system, and a high-speed communication network is set between the system controller and the multiple energy storage converters of the self-starting energy storage system, the control strategy is determined as a virtual synchronous machine control strategy.

[0063] Alternatively, if the system controller determines that there are multiple energy storage converters of the self-starting energy storage unit, the energy storage converters of the multiple self-starting energy storage units are dispersedly arranged, and no high-speed communication network is set between the system controller and the energy storage converters of the multiple self-starting energy storage units, the control strategy is determined to be a constant voltage and constant frequency control strategy. Specifically, the dispersed arrangement between the multiple energy storage converters may include: the communication distance between the energy storage converters is greater than the set distance, for example, if the communication mode is network cable communication, the set distance may be 200m; if the communication mode is optical fiber communication, the set distance may be 1000m.

[0064] In an embodiment of the present application, as an optional scheme, since each energy storage unit may include an energy storage inverter, each self-starting energy storage unit may include an energy storage inverter. Therefore, if a self-starting energy storage unit is determined, the energy storage inverter of the self-starting energy storage unit is determined, that is, the number of energy storage inverters of the self-starting energy storage unit is determined to be one; if multiple self-starting energy storage units are determined, the energy storage inverters of multiple self-starting energy storage units are determined, that is, the number of energy storage inverters of the self-starting energy storage unit is determined to be multiple.

[0065] As an alternative, the boost start function may include a logarithmic ramp function or a ramp function. Figure 4 A flowchart of a method for determining a boost start function provided in an embodiment of the present application is shown in FIG. Figure 4 As shown, before step 104, the method further includes: Step S41, the system controller determines whether the rated bus voltage is greater than the set level voltage, if so, execute step S42; if not, execute step S43.

[0066] Specifically, if the system controller determines that the rated bus voltage is greater than the set level voltage, it can indicate that the off-grid energy storage system is a medium-high voltage system, and step S42 is executed; if it determines that the rated bus voltage is less than or equal to the set level voltage, it can indicate that the off-grid energy storage system is a low voltage system, and step S43 is executed.

[0067] The set level voltage can be set according to actual needs. For example, the set level voltage can be 400V.

[0068] Step S42, the system controller determines whether the ratio of the total capacity of the energy storage converter of the self-starting energy storage unit to the sum of the no-load loss capacity of all transformers in the off-grid energy storage system is greater than the set ratio, if not, execute step S43; if yes, execute step S44.

[0069] Specifically, if the system controller determines that the ratio of the capacity of the energy storage inverter to the sum of the no-load loss capacity of all transformers in the off-grid energy storage system is less than or equal to the set ratio, step S43 is executed; if it determines that the ratio of the capacity of the energy storage inverter to the sum of the no-load loss capacity of all transformers in the off-grid energy storage system is greater than the set ratio, step S44 is executed.

[0070] The total capacity of the energy storage converter of the self-starting energy storage unit is the sum of the capacities of the energy storage converters of all the self-starting energy storage units. As an optional solution, when the capacities of all the energy storage converters are equal by default, the total capacity of the energy storage converters of the self-starting energy storage unit can be equal to the set number of self-starting energy storage units*the capacity of the energy storage converter.

[0071] For example, all transformers in an off-grid energy storage system may include all load transformers, all photovoltaic transformers, all wind power transformers, and all energy storage transformers.

[0072] The setting ratio may be set according to actual needs, for example, the setting ratio may be 30%.

[0073] Step S43: the system controller determines the boost start function as a ramp function, and the process ends.

[0074] Figure 5 A schematic diagram of a ramp function provided in an embodiment of the present application is shown in FIG. Figure 5 As shown, the ramp function is the time With zero starting voltage reference value A linear function, with the horizontal axis being the time , the vertical axis is the reference value of the zero-starting boost voltage , and The relationship between them is shown in the following formula:

[0075] in, is the rated voltage of the energy storage converter, is the slope.

[0076] Step S44: the system controller determines the boost start function as a logarithmic ramp function, and the process ends.

[0077] Figure 6 A schematic diagram of a logarithmic ramp function provided in an embodiment of the present application is shown in FIG. Figure 6 As shown, the logarithmic-ramp function is a function combining the logarithmic function and the ramp function. The logarithmic-ramp function is the time With zero starting voltage reference value A linear function, with the horizontal axis being the time , the vertical axis is the reference value of the zero-starting boost voltage , and The relationship between them is shown in the following formula:

[0078] in, is the rated voltage of the energy storage converter, is the slope, is a fixed constant.

[0079] As an optional scheme, if the control strategy is a virtual synchronous machine control strategy, step 104 may include: step S51, the system controller sends a virtual synchronous voltage reference value to the energy storage converter in each self-starting energy storage unit according to the boost start function, so that the energy storage converter boosts the voltage according to the virtual synchronous voltage reference value.

[0080] Figure 7 A flowchart of a method for issuing a virtual synchronous voltage reference value provided in an embodiment of the present application is shown in FIG. Figure 7 As shown, step S51 may specifically include: Step S511: The system controller obtains zero-start boost voltage reference values ​​corresponding to different moments according to the boost start function.

[0081] like Figure 5 or Figure 6 As shown, the system controller obtains the zero-start boost voltage reference value corresponding to different time t according to the boost start function at the set time interval. The set time interval can be a ms level time interval.

[0082] Step S512: The system controller calculates a virtual synchronous voltage reference value corresponding to the energy storage converter according to the zero-start boost voltage reference value and the reactive power of the energy storage converter.

[0083] The system controller uses the formula , the zero-start boost voltage reference value and the reactive power of the energy storage converter are calculated to generate a virtual synchronous voltage reference value. is the virtual synchronous voltage reference value, is the zero-start boost voltage reference value, is the voltage regulation coefficient, is the reactive power of the energy storage converter.

[0084] Due to the reactive power of different energy storage converters may be different, so it is necessary to calculate the reactive power of each energy storage converter Calculate the virtual synchronous voltage reference value corresponding to each energy storage converter .

[0085] Step S513: The system controller sends the virtual synchronous voltage reference value to the corresponding energy storage converter.

[0086] As another option, Figure 8 A flowchart of a method for zero-start boosting provided in an embodiment of the present application is shown in FIG. Figure 8 As shown, if the control strategy is a constant voltage and constant frequency control strategy, step 104 may include: Step S61: The system controller sends an automatic start instruction to the energy storage converter of any self-starting energy storage unit.

[0087] Step S62: the energy storage converter of any self-starting energy storage unit responds to the automatic start instruction and boosts the voltage according to the pre-acquired constant voltage and constant frequency voltage reference values ​​corresponding to different times.

[0088] In the embodiment of the present application, the energy storage converter of any self-starting energy storage unit can obtain in advance the constant voltage and constant frequency voltage reference values ​​corresponding to different times t.

[0089] As an alternative, Figure 5 or Figure 6 As shown, the system controller obtains the zero-start boost voltage reference value corresponding to different times t according to the set time interval according to the boost start function. The set time interval can be a ms-level time interval. The system controller determines the zero-start boost voltage reference value as a constant voltage and constant frequency voltage reference value, wherein the constant voltage and constant frequency voltage reference value is equal to the zero-start boost voltage reference value, that is, , is the constant voltage and constant frequency voltage reference value, The system controller sends the constant voltage and frequency voltage reference value to the energy storage converter of any self-starting energy storage unit, so that the energy storage converter can obtain the constant voltage and frequency voltage reference value corresponding to different times in advance.

[0090] Step S63, the energy storage converter of each other self-starting energy storage unit determines whether the voltage of its own output port is greater than or equal to the predetermined voltage, if so, execute step S64; if not, execute step S63.

[0091] Among them, the output port of the energy storage converter is the port through which the energy storage converter is connected to the energy storage transformer.

[0092] In the embodiment of the present application, the voltage boost of the energy storage converter of any self-starting energy storage unit will drive the voltage of the output port of the energy storage converter of other self-starting energy storage units to rise. If the energy storage converter of other self-starting energy storage units determines that the voltage of their own output port is greater than or equal to the predetermined voltage, step S64 is continued to be executed; if it is determined that the voltage of their own output port is less than the predetermined voltage, step S63 is executed to continue to wait for the voltage of the output port of the energy storage converter of other self-starting energy storage units to be greater than the predetermined voltage.

[0093] Step S64: the energy storage converters of other self-starting energy storage units boost voltage according to the pre-acquired boost start function.

[0094] As an optional solution, when the voltage of the output port of the energy storage converter of a self-starting energy storage unit is greater than or equal to a predetermined voltage, the energy storage converter of the self-starting energy storage unit may execute step S64.

[0095] As an optional solution, the system controller may send the boost startup function to the energy storage converter of each self-starting energy storage unit in advance, so that the energy storage converter of each self-starting energy storage unit obtains the boost startup function in advance.

[0096] Specifically, since the voltage of the output port of the energy storage converter of the self-starting energy storage unit is greater than or equal to the predetermined voltage, the energy storage converter can start boosting from the current voltage of its own output port according to the boost startup function.

[0097] In the technical solution provided in the embodiment of the present application, at least one self-starting energy storage unit is determined from at least one energy storage unit, and the energy storage converter in the self-starting energy storage unit is controlled to start boosting from zero according to a preset control strategy and a boost starting function. The embodiment of the present application controls the energy storage converter in the self-starting energy storage unit to start boosting from zero according to a preset control strategy and a boost starting function, so that the method of starting boosting from zero can adapt to energy storage application scenarios with multiple voltage levels and multiple application scenarios, and has the practicability of guiding actual applications.

[0098] In the technical solution of the embodiment of the present application, the control strategy adopts a virtual synchronous machine control strategy, and the boost start function adopts a logarithmic-ramp function, thereby improving the black start success rate of the off-grid energy storage system and reducing the black start time.

[0099] Fig. 9 A schematic diagram of the structure of a black start device for an off-grid energy storage system provided in an embodiment of the present application is shown in FIG. Fig. 9 The device comprises: a first determining module 11 and a first controlling module 12 .

[0100] The first determination module 11 is used to determine at least one self-starting energy storage unit from at least one energy storage unit; the first control module 12 is used to control the energy storage converter in the self-starting energy storage unit to start voltage boost from zero according to a preset control strategy and voltage boost start function.

[0101] In a possible implementation, when there are multiple energy storage units, the device further includes a second control module 13 and a first judgment module 14 .

[0102] The second control module 13 is used to control the start-up of other energy storage units in the self-starting energy storage units among the multiple energy storage units if the first judgment module 14 judges that the bus voltage of the off-grid energy storage system is greater than or equal to the set rated bus voltage.

[0103] In a possible implementation manner, the device further includes: a second determining module 15.

[0104] The second determination module 15 is used to determine the control strategy as a virtual synchronous machine control strategy if the number of energy storage inverters in the self-starting energy storage unit is one. Alternatively, the second determination module 15 is used to determine the control strategy as a virtual synchronous machine control strategy if the number of energy storage inverters in the self-starting energy storage unit is multiple, and a high-speed communication network is set between the system controller and the multiple energy storage inverters of the self-starting energy storage units. Alternatively, the second determination module 15 is used to determine the control strategy as a constant voltage and constant frequency control strategy if the number of energy storage inverters in the self-starting energy storage unit is multiple, the energy storage inverters of the multiple self-starting energy storage units are dispersedly arranged, and no high-speed communication network is set between the system controller and the multiple energy storage inverters of the self-starting energy storage units.

[0105] In a possible implementation manner, the device further includes: a third determining module 16.

[0106] The third determination module 16 is used to determine the boost start function as a logarithmic-ramp function if the rated bus voltage is greater than the set level voltage, and the ratio of the total capacity of the energy storage inverter of the self-starting energy storage unit to the sum of the no-load loss capacity of all transformers in the off-grid energy storage system is greater than the set ratio. Alternatively, the third determination module 16 is used to determine the boost start function as a ramp function if the rated bus voltage is less than or equal to the set level voltage. Alternatively, the third determination module 16 is used to determine the boost start function as a ramp function if the rated bus voltage is greater than the set level voltage, and the ratio of the total capacity of the energy storage inverter of the self-starting energy storage unit to the sum of the no-load loss capacity of all transformers in the off-grid energy storage system is less than or equal to the set ratio.

[0107] In one possible implementation, if the control strategy is a virtual synchronous machine control strategy, the first control module 12 is specifically used to send a virtual synchronous voltage reference value to the energy storage converter in each of the self-starting energy storage units according to the boost start function, so that the energy storage converter boosts the voltage according to the virtual synchronous voltage reference value.

[0108] In a possible implementation, the first control module 12 is specifically used to obtain a zero-start boost voltage reference value corresponding to different times according to the boost start function; calculate the virtual synchronous voltage reference value corresponding to the energy storage inverter according to the zero-start boost voltage reference value and the reactive power of the energy storage inverter; and send the virtual synchronous voltage reference value to the corresponding energy storage inverter.

[0109] In one possible implementation, if the control strategy is a constant voltage and constant frequency control strategy, the first control module 12 is specifically used to send a self-starting instruction to the energy storage inverter of any self-starting energy storage unit, so that the energy storage inverter of any self-starting energy storage unit responds to the self-starting instruction and boosts the voltage according to the pre-acquired constant voltage and constant frequency voltage reference value corresponding to different times. If the energy storage inverter of each other self-starting energy storage unit determines that the voltage of its own output port is greater than or equal to the predetermined voltage, it boosts the voltage according to the pre-acquired boost start function.

[0110] In a possible implementation manner, the device further includes: a second determination module 17.

[0111] The second judgment module 17 is used to judge whether the off-grid energy storage system meets the black start condition according to the received black start instruction; if it is judged that the off-grid energy storage system meets the black start condition, the first determination module 11 is triggered to execute the step of determining at least one self-starting energy storage unit from multiple energy storage units; wherein the black start condition includes: the current capacity of the battery unit in each of the self-starting energy storage units is greater than the black start power, the incoming switch between the off-grid energy storage system and the public power grid is in the open state, the switch devices in the off-grid energy storage system are all in the closed state, and the new energy unit and the load unit in the off-grid energy storage system are in the off-state or shutdown state.

[0112] In the technical solution provided in the embodiment of the present application, at least one self-starting energy storage unit is determined from at least one energy storage unit, and the energy storage converter in the self-starting energy storage unit is controlled to start boosting from zero according to a preset control strategy and a boost starting function. The embodiment of the present application controls the energy storage converter in the self-starting energy storage unit to start boosting from zero according to a preset control strategy and a boost starting function, so that the method of starting boosting from zero can adapt to energy storage application scenarios with multiple voltage levels and multiple application scenarios, and has the practicability of guiding actual applications.

[0113] An embodiment of the present application provides a computer-readable storage medium, which includes a stored program, wherein when the program is executed, a system controller where the storage medium is located is controlled to execute an embodiment of the black start method for the off-grid energy storage system.

[0114] An embodiment of the present application provides a system controller, comprising: one or more processors; a memory; and one or more computer programs, wherein the one or more computer programs are stored in the memory, and the one or more computer programs include instructions, and when the instructions are executed by the system controller, the system controller executes the black start method of the above-mentioned off-grid energy storage system.

[0115] Fig.10 A schematic diagram of the structure of a system controller provided in an embodiment of the present application is shown in FIG. Fig.10 As shown, the system controller 20 includes: a processor 21, a memory 22, and a computer program 23 stored in the memory 22 and executable on the processor 21. When the computer program 23 is executed by the processor 21, the black start method of the off-grid energy storage system in the embodiment is implemented. To avoid repetition, it is not described one by one here. Alternatively, when the computer program is executed by the processor 21, the functions of each model / unit in the black start device applied to the off-grid energy storage system in the embodiment are realized. To avoid repetition, it is not described one by one here.

[0116] The system controller 20 includes, but is not limited to, a processor 21 and a memory 22. Those skilled in the art will appreciate that Fig.10 It is only an example of the system controller 20 and does not constitute a limitation of the system controller 20. It may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the system controller 20 may also include input and output devices, network access devices, buses, etc.

[0117] The processor 21 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0118] The memory 22 may be an internal storage unit of the system controller 20, such as a hard disk or memory of the system controller 20. The memory 22 may also be an external storage device of the system controller 20, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the system controller 20. Further, the memory 22 may also include both an internal storage unit of the system controller 20 and an external storage device. The memory 22 is used to store computer programs and other programs and data required by the system controller 20. The memory 22 may also be used to temporarily store data that has been output or is to be output.

[0119] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0120] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0121] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0122] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of hardware plus software functional units.

[0123] The above-mentioned integrated unit implemented in the form of a software functional unit can be stored in a computer-readable storage medium. The above-mentioned software functional unit is stored in a storage medium, including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) or a processor to perform some steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM), random access memory (RAM), disk or optical disk and other media that can store program code.

[0124] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A black start method for an off-grid energy storage system, characterized in that: The method comprises: Determining at least one self-starting energy storage unit from at least one energy storage unit; According to the preset control strategy and boost start function, the energy storage converter in the self-starting energy storage unit is controlled to boost voltage from zero.

2. The method according to claim 1, characterized in that The number of the energy storage units is multiple, and after the control of the energy storage converter in the self-starting energy storage unit to boost voltage from zero, the method further includes: If the bus voltage of the off-grid energy storage system is greater than or equal to the set rated bus voltage, other energy storage units except the self-starting energy storage unit among the multiple energy storage units are controlled to start.

3. The method according to claim 1, characterized in that Before controlling the energy storage converter in the self-starting energy storage unit to boost voltage from zero according to the preset control strategy and boost start function, the method further includes: If the number of the energy storage converter of the self-starting energy storage unit is one, the control strategy is determined to be a virtual synchronous machine control strategy; or If there are multiple energy storage converters in the self-starting energy storage unit, and a high-speed communication network is set between the system controller and the multiple energy storage converters in the self-starting energy storage unit, the control strategy is determined as a virtual synchronous machine control strategy.

4. The method according to claim 1, characterized in that: Before controlling the energy storage converter in the self-starting energy storage unit to boost voltage from zero according to the preset control strategy and boost start function, the method further includes: If there are multiple energy storage inverters in the self-starting energy storage unit, the energy storage inverters of the multiple self-starting energy storage units are arranged in a dispersed manner and no high-speed communication network is set between the system controller and the energy storage inverters of the multiple self-starting energy storage units, the control strategy is determined as a constant voltage and constant frequency control strategy.

5. The method according to claim 1, characterized in that Before controlling the energy storage converter in the self-starting energy storage unit to boost voltage from zero according to the preset control strategy and boost start function, the method further includes: If the rated bus voltage is greater than the set level voltage, and the ratio of the total capacity of the energy storage converter of the self-starting energy storage unit to the sum of the no-load loss capacity of all transformers in the off-grid energy storage system is greater than the set ratio, the boost start function is determined as a logarithmic-ramp function; or, If the rated bus voltage is less than or equal to the set level voltage, the boost start function is determined as a ramp function; or, If the rated bus voltage is greater than the set level voltage, and the ratio of the total capacity of the energy storage converter of the self-starting energy storage unit to the sum of the no-load loss capacity of all transformers in the off-grid energy storage system is less than or equal to the set ratio, the boost starting function is determined as a ramp function.

6. The method according to any one of claims 1 to 3, characterized in that: If the control strategy is a virtual synchronous machine control strategy, controlling the energy storage converter in the self-starting energy storage unit to boost voltage from zero according to the preset control strategy and boost startup function includes: A virtual synchronous voltage reference value is issued to the energy storage converter in each of the self-starting energy storage units according to the boost start function, so that the energy storage converter boosts voltage according to the virtual synchronous voltage reference value.

7. The method according to claim 6, characterized in that The sending of a virtual synchronous voltage reference value to the energy storage converter in each of the self-starting energy storage units according to the boost start function includes: Acquire zero-start boost voltage reference values ​​corresponding to different moments according to the boost start function; Calculating the virtual synchronous voltage reference value corresponding to the energy storage converter according to the zero-start boost voltage reference value and the reactive power of the energy storage converter; The virtual synchronous voltage reference value is sent to the corresponding energy storage converter.

8. The method according to claim 1, 2 or 4, characterized in that: If the control strategy is a constant voltage and constant frequency control strategy, controlling the energy storage converter in the self-starting energy storage unit to boost voltage from zero according to the preset control strategy and boost start function includes: A self-starting instruction is sent to the energy storage inverter of any self-starting energy storage unit, so that the energy storage inverter of any self-starting energy storage unit responds to the self-starting instruction and boosts the voltage according to the pre-acquired constant voltage and constant frequency voltage reference value corresponding to different time periods. If the energy storage inverter of each other self-starting energy storage unit determines that the voltage of its own output port is greater than or equal to the predetermined voltage, it boosts the voltage according to the pre-acquired boost starting function.

9. A black start device for an off-grid energy storage system, characterized in that: include: A determination module, used to determine at least one self-starting energy storage unit from at least one energy storage unit; The first control module is used to control the energy storage converter in the self-starting energy storage unit to boost voltage from zero according to a preset control strategy and boost start function.

10. A system controller, characterized in that: include: one or more processors; Memory; And one or more computer programs, wherein the one or more computer programs are stored in the memory, and the one or more computer programs include instructions, which, when executed by the system controller, enable the system controller to execute the black start method of the off-grid energy storage system according to any one of claims 1 to 8.

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