Black start method, device and system controller for an off-grid energy storage system

Abstract

The present application provides a black start method, device and system controller for an off-grid energy storage system, relating to the technical field of power systems. The method includes: determining at least one self-starting energy storage unit from at least one energy storage unit; controlling a power conversion system in the self-starting energy storage unit to perform zero-start voltage boosting according to a preset control strategy and a boosting start function. In the embodiment of the present application, the power conversion system in the self-starting energy storage unit is controlled to perform zero-start voltage boosting according to the preset control strategy and the boosting start function, so that the zero-start voltage boosting method can adapt to energy storage application scenarios with multiple voltage levels and multiple application scenarios.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of power systems, and particularly 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 new energy power generation systems have been applied to remote mountainous areas, unpowered areas, islands and other places. The stability of the off-grid energy storage system of the off-grid new energy power generation system is weak, and when a fault occurs in the external power grid or the energy storage system shuts down, it is necessary to perform a black start on the off-grid energy storage system.

[0003] Currently, the black start process of off-grid energy storage systems mostly adopts multi-machine parallel connection or multi-machine master-slave sequential zero-start voltage boost. The zero-start voltage boost strategy usually adopts a stepped slope voltage boost with several voltage target values. After 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 boost method in the prior art cannot adapt to the 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 the energy storage application scenarios with multiple voltage levels and multiple application scenarios.

[0006] In a first aspect, a black start method for an off-grid energy storage system is provided, and the method includes:

[0007] Determine at least one self-starting energy storage unit from at least one energy storage unit;

[0008] According to a pre-set control strategy and a boost start function, control the energy storage converter in the self-starting energy storage unit to perform zero-start voltage boost.

[0009] In a possible implementation manner, the number of the energy storage units is multiple. After controlling the energy storage converter in the self-starting energy storage unit to perform zero-start voltage boost, the method further includes:

[0010] If the bus voltage of the off-grid energy storage system is greater than or equal to the set rated bus voltage, control other energy storage units other than the self-starting energy storage unit in the multiple energy storage units to start.

[0011] In a possible implementation manner, before controlling the energy storage converter in the self-starting energy storage unit to perform zero-start voltage boost according to a pre-set control strategy and a boost start function, the method further includes:

[0012] If the number of energy storage converters of the self-starting energy storage unit is one, determine the control strategy as the virtual synchronous machine control strategy; or

[0013] If the number of energy storage converters of the self-starting energy storage unit is multiple, and a high-speed communication network is set between the system controller and the energy storage converters of multiple self-starting energy storage units, determine the control strategy as the virtual synchronous machine control strategy.

[0014] In a possible implementation manner, before controlling the energy storage converter in the self-starting energy storage unit to boost from zero voltage according to the preset control strategy and boost start function, it further includes:

[0015] If the number of energy storage converters of the self-starting energy storage unit is multiple, the energy storage converters of multiple self-starting energy storage units are dispersedly arranged and a high-speed communication network is not set between the system controller and the energy storage converters of multiple self-starting energy storage units, determine the control strategy as the constant voltage and constant frequency control strategy.

[0016] In a possible implementation manner, before controlling the energy storage converter in the self-starting energy storage unit to boost from zero voltage according to the preset control strategy and boost start function, it further includes:

[0017] If the rated bus voltage is greater than the set level voltage, and the ratio of the total capacity of the energy storage converters of the self-starting energy storage unit to the sum of the no-load loss capacities of all transformers in the off-grid energy storage system is greater than the set ratio, determine the boost start function as the logarithm-ramp function; or,

[0018] If the rated bus voltage is less than or equal to the set level voltage, determine the boost start function as the ramp function; or,

[0019] If the rated bus voltage is greater than the set level voltage, and the ratio of the total capacity of the energy storage converters of the self-starting energy storage unit to the sum of the no-load loss capacities of all transformers in the off-grid energy storage system is less than or equal to the set ratio, determine the boost start function as the ramp function.

[0020] In a possible implementation manner, if the control strategy is the virtual synchronous machine control strategy, controlling the energy storage converter in the self-starting energy storage unit to boost from zero voltage according to the preset control strategy and boost start function includes:

[0021] Send the 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 according to the virtual synchronous voltage reference value.

[0022] In a possible implementation manner, the step of sending a virtual synchronous voltage reference value to the energy storage converters in each of the self-starting energy storage units according to the boost starting function includes:

[0023] Obtaining a zero-start boost voltage reference value corresponding to different moments according to the boost starting function;

[0024] 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;

[0025] Sending the virtual synchronous voltage reference value to the corresponding energy storage converter.

[0026] In a possible implementation manner, if the control strategy is a constant voltage and constant frequency control strategy, the step of controlling the zero-start boost of the energy storage converter in the self-starting energy storage unit according to the preset control strategy and the boost starting function includes:

[0027] Sending a self-starting instruction to the energy storage converter of any one of the self-starting energy storage units, so that the energy storage converter of any one of the self-starting energy storage units responds to the self-starting instruction and boosts according to the constant voltage and constant frequency voltage reference value corresponding to different moments obtained in advance. If the energy storage converters of each of the other self-starting energy storage units determine that the voltage of their output ports is greater than or equal to a predetermined voltage, they boost according to the boost starting function obtained in advance.

[0028] In a second aspect, a black start device for an off-grid energy storage system is provided, including:

[0029] A determination module, configured to determine at least one self-starting energy storage unit from at least one energy storage unit;

[0030] A first control module, configured to control the zero-start boost of the energy storage converters in the self-starting energy storage units according to a preset control strategy and a boost starting function.

[0031] In a third aspect, a system controller is provided, including: one or more processors; a memory; and one or more computer programs, where the one or more computer programs are stored in the memory, and the one or more computer programs include instructions that, when executed by the system controller, cause the system controller to execute the black start method of the off-grid energy storage system in the first aspect or any possible implementation manner of the first aspect.

[0032] In the technical solution provided by 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 boost from zero according to a preset control strategy and a boost starting function. In the embodiment of the present application, the energy storage converter in the self-starting energy storage unit is controlled to boost from zero according to a preset control strategy and a boost starting function, so that the method of boosting from zero can adapt to energy storage application scenarios with multiple voltage levels and multiple application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0034] Figure 1 FIG.

[0035] Figure 2 FIG.

[0036] Figure 3 FIG.

[0037] Figure 4 FIG.

[0038] Figure 5 FIG.

[0039] Figure 6 FIG.

[0040] Figure 7 FIG.

[0041] Figure 8 FIG.

[0042] Figure 9 FIG.

[0043] Figure 10 FIG. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] To better understand the technical solution of the present application, the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0045] It should be clear that the described embodiments are only a 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 those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0046] 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 of "a", "the" and "said" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0047] It should be understood that the term " / and" used herein is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, a and / or b may represent: a exists alone, a and b exist simultaneously, and b exists alone. In addition, the character " / " herein generally represents an "or" relationship between the associated objects before and after.

[0048] Figure 1 The following is a schematic structural diagram of an off-grid energy storage system provided for the embodiments of the present application. As Figure 1 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 alternative 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.

[0049] In the embodiments of the present application, the number of the energy storage unit, the photovoltaic unit, the wind power unit, and the load unit may all be one or more. Figure 1 The case where the number of the energy storage unit, the photovoltaic unit, the wind power unit, and the load unit is multiple is taken as an example for description.

[0050] As Figure 1As shown, each energy storage unit is connected to the bus through a corresponding energy storage transformer. Each energy storage unit may include an energy storage converter and a battery unit. For example, energy storage unit 1 may include energy storage converter 1 and battery unit 1, energy storage unit 2 may include energy storage converter 2 and battery unit 2, and so on. Energy storage unit n may include energy storage converter n and battery unit n. For example, battery unit 1 is connected to energy storage converter 1, and energy storage converter 1 is connected to the bus through the corresponding energy storage transformer 1; battery unit 2 is connected to energy storage converter 2, and energy storage converter 2 is connected to the bus through the corresponding energy storage transformer 2; and so on. Battery unit n is connected to energy storage converter n, and energy storage converter n is connected to the bus through the corresponding energy storage transformer n. As Figure 1 shown, each energy storage unit may include an energy storage converter and a battery unit.

[0051] As Figure 1 shown, as an alternative, the energy storage unit is connected to the energy storage transformer through a first switch, and the energy storage transformer is connected to the bus through a second switch. The energy storage converter 1 of energy storage unit 1 is connected to the energy storage transformer 1 through the first switch M1, the energy storage converter 2 of 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 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 bus through the second switch K1, the energy storage transformer 2 is connected to the bus through the second switch K2, and so on. The energy storage transformer n is connected to the bus through the second switch Kn.

[0052] As Figure 1 shown, in the embodiment of the present application, an example is described in which one energy storage transformer corresponds to one energy storage unit. In practical applications, as another alternative, one energy storage transformer may correspond to and be connected to multiple energy storage units, that is, multiple energy storage units are connected to the bus through one energy storage transformer, and this situation is not specifically drawn.

[0053] As Figure 1As shown in the figure, load unit 1 to load unit n are connected to the bus through load transformers; photovoltaic unit 1 to photovoltaic unit m are connected to the bus through photovoltaic transformers; and wind power unit 1 to wind power unit i are connected to the bus through wind power transformers. As an alternative, each load unit corresponds to one load transformer, and each load unit is connected to the bus through one load transformer; as another alternative, multiple load units correspond to one load transformer, and multiple load units are connected to the bus through one load transformer. As an alternative, each photovoltaic unit corresponds to one photovoltaic transformer, and each photovoltaic unit is connected to the bus through one photovoltaic transformer; as another alternative, multiple photovoltaic units correspond to one photovoltaic transformer, and multiple photovoltaic units are connected to the bus through one photovoltaic transformer. As an alternative, each wind power unit corresponds to one wind power transformer, and each wind power unit is connected to the bus through one wind power transformer; as another alternative, multiple wind power units correspond to one wind power transformer, and multiple wind power units are connected to the bus through one wind power transformer. As Figure 1 shown, one load transformer, one photovoltaic transformer, and one wind power transformer are taken as examples. 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 not specifically drawn here.

[0054] As Figure 1 shown, the system controller can be connected to the energy storage converter, battery unit, photovoltaic unit, wind power unit, load unit, and bus.

[0055] As Figure 1 shown, as an alternative, the wind power transformer is connected to the bus through the third switch C1, the photovoltaic transformer is connected to the bus through the fourth switch C2, and the load transformer is connected to the bus through the fifth switch C3.

[0056] As Figure 1 shown, the off-grid energy storage system is connected to the external public grid through the incoming line switch K and the step-up transformer.

[0057] In the embodiments of the present application, as an alternative, the incoming line 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.

[0058] Based on Figure 1 the off-grid energy storage system shown, the embodiments of the present application provide a black start method for the off-grid energy storage system. Figure 2 This is a flowchart of a black start method for the off-grid energy storage system provided by the embodiments of the present application. As Figure 2 shown, the method includes:

[0059] Step 102: The system controller determines at least one self-starting energy storage unit from at least one energy storage unit.

[0060] As an alternative, when the number of energy storage units is one, the system controller determines this energy storage unit as the self-starting energy storage unit. At this time, the number of self-starting energy storage units is one.

[0061] As another alternative, when the number of energy storage units is multiple, the system controller determines at least one self-starting energy storage unit from the multiple energy storage units. Figure 3 The flowchart of a method for determining a self-starting energy storage unit provided by an embodiment of the present application is as Figure 3 shown. Specifically, step 102 may include:

[0062] Step 1022: The system controller detects the state of charge (SOC) of the battery units in all energy storage units.

[0063] Step 1024: The system controller sorts according to the state of charge from high to low, selects a set number of energy storage units with the highest SOC, and uses the selected set number of energy storage units as the self-starting energy storage units.

[0064] In the embodiment of the present application, the set number can be one or more. For example, as Figure 1 shown, when the set number is 1, among energy storage unit 1 to energy storage unit n, the system controller determines the energy storage unit 1 with the highest SOC as the self-starting energy storage unit. Another example, as Figure 1 shown, when the set number is 3, among energy storage unit 1 to energy storage unit n, the system controller determines 3 energy storage units with the highest SOC as the self-starting energy storage units. For example, the 3 self-starting energy storage units may include energy storage unit 1, energy storage unit 3, and energy storage unit n.

[0065] In the embodiment of the present application, the system controller selects battery units with high SOC, thereby improving the black start success rate of the off-grid energy storage system.

[0066] 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 a pre-set control strategy and a boost start function.

[0067] As an alternative, before step 104, it may further include:

[0068] Step S11: The system controller controls the battery unit in the self-starting energy storage unit to start.

[0069] Step S12: The system controller determines whether the output voltage of the battery unit in the self-starting energy storage unit is greater than or equal to the set stable voltage value within the first set time period. If so, step 104 is executed; if not, the process ends.

[0070] Specifically, after the battery unit in the self-starting energy storage unit starts, the system controller can detect the output voltage of the battery unit 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 unit 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 unit has not reached a stable state within the first set time period, and the black start process ends. Subsequently, manual troubleshooting can be performed. Among them, the output voltage of the battery unit is the voltage at the output port where the battery unit is connected to the energy storage converter. The first set time period can be set according to actual needs. For example, the first set time period can be 5s.

[0071] As an alternative solution, when the number of energy storage units is multiple, after step 104, it may further include:

[0072] 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, it controls the start of other energy storage units other than the self-starting energy storage unit among the multiple energy storage units.

[0073] In the embodiment of the present application, after the system controller controls the zero-start boost of the energy storage converter in the self-starting energy storage unit, the bus voltage will increase. Then, as an alternative solution, before step 106, it further includes:

[0074] 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.

[0075] 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, it indicates that the zero-start boost ends and the off-grid energy storage system has reached the condition for starting other energy storage units, and step 106 is continued to be executed; if it is determined that the bus voltage of the off-grid energy storage system is less than the rated bus voltage within the second set time period, it indicates that the condition for starting other energy storage units has not been reached, and the black start process ends. Subsequently, manual troubleshooting can be performed.

[0076] In the embodiment of the present application, if the bus voltage is greater than or equal to the rated bus voltage, the system controller can sequentially control the start of other energy storage units. For example,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 start of the n - 3 energy storage units in sequence.

[0077] As an alternative, after step 104 or step 106, the method further includes:

[0078] Step 108, the system controller controls the start of the load unit, the photovoltaic unit, and the wind power unit.

[0079] After all the energy storage units are started, step 108 can be executed to complete the start of the load unit and the new energy units. The start sequence of the load unit, the photovoltaic unit, and the wind power unit can be set by the system controller itself.

[0080] As an alternative, before step 102, the method further includes:

[0081] Step 100, the system controller controls the switch devices in the energy storage unit, the load unit, the new energy unit, and the off-grid energy storage system to be set to the black start mode.

[0082] As an alternative, the new energy unit may include a photovoltaic unit and a wind power unit, and the switch devices may include a first switch, a second switch, a third switch, a fourth switch, and a fifth switch. 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 switch to the black start mode.

[0083] In the embodiments of the present application, setting the energy storage unit, the load unit, the new energy unit, and the switch devices to the black start mode effectively prevents failures during the black start process, thereby realizing the protection of grid equipment.

[0084] As an alternative, after step 108, the method further includes:

[0085] Step 110, the system controller controls the switch devices in the energy storage unit, the load unit, the new energy unit, and the off-grid energy storage system to be set to the off-grid operation mode.

[0086] 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 the off-grid operation mode.

[0087] In the embodiments of the present application, setting the energy storage unit, the load unit, the new energy unit, and the switch devices to the off-grid operation mode ensures the normal operation of the off-grid energy storage system.

[0088] As an alternative, after receiving the black start instruction, the system controller can start executing the control process of the black start method only after determining that the off-grid energy storage system meets the set black start conditions. Then the method further includes:

[0089] Step S31: The system controller determines whether the off-grid energy storage system meets the black start conditions according to the received black start instruction. If so, continue to execute step 100 or step 102; if not, the process ends.

[0090] As an alternative, when 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 conditions, step 100 can be continued. As another alternative, when 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 conditions, step 102 can be continued.

[0091] As an alternative, the black start instruction can be input to the system controller manually. After the system controller receives the manually input black start instruction, it determines whether the off-grid energy storage system meets the black start conditions in response to the black start instruction.

[0092] As an alternative, 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 line switch between the off-grid energy storage system and the public power grid is in the off state, all the switching devices in the off-grid energy storage system are in the on state, and the new energy unit and the load unit in the off-grid energy storage system are in the off or shutdown state.

[0093] In the embodiments of the present application, setting the black start condition that the current capacity of the battery unit in each self-starting energy storage unit is greater than the black start power can improve the black start success rate; setting the black start condition that the incoming line switch is in the off state ensures that the system is in the off-grid state; setting the black start condition that all the switching devices in the off-grid energy storage system are in the on state ensures the stability of the system after black start and prevents the system from shutting down again.

[0094] In the embodiments of the present application, when the off-grid energy storage system is completed, the system controller can preset the control strategy and the boost start function according to the off-grid energy storage system.

[0095] As an alternative, the control strategy can include a virtual synchronous machine control strategy or a constant voltage and constant frequency control strategy. Before step 104, the method further includes:

[0096] If the system controller determines that the number of energy storage inverters of the self-starting energy storage unit is one, the control strategy is determined as the virtual synchronous machine control strategy.

[0097] Alternatively, if the system controller determines that the number of energy storage converters of the self-starting energy storage unit is multiple, and a high-speed communication network is provided between the system controller and the energy storage converters of multiple self-starting energy storage systems, the control strategy will be determined as the virtual synchronous machine control strategy.

[0098] Alternatively, if the system controller determines that the number of energy storage converters of the self-starting energy storage unit is multiple, and the energy storage converters of multiple self-starting energy storage units are dispersedly arranged and no high-speed communication network is provided between the system controller and the energy storage converters of multiple self-starting energy storage units, the control strategy will be determined as the constant voltage and constant frequency control strategy. Among them, the dispersed arrangement of multiple energy storage converters may specifically include: the communication distance between the energy storage converters is greater than the set distance. For example, if the communication method is network cable communication, the set distance can be 200m; if the communication method is optical fiber communication, the set distance can be 1000m.

[0099] In the embodiment of the present application, as an optional solution, since each energy storage unit may include one energy storage converter, each self-starting energy storage unit may include one energy storage converter. Therefore, if one self-starting energy storage unit is determined, the energy storage converter of the self-starting energy storage unit is determined, that is, the number of energy storage converters of the self-starting energy storage unit is determined to be one; if multiple self-starting energy storage units are determined, the energy storage converters of multiple self-starting energy storage units are determined, that is, the number of energy storage converters of the self-starting energy storage unit is determined to be multiple.

[0100] As an optional solution, the boost start function may include a logarithm-ramp function or a ramp function. Figure 4 It is a flowchart of a method for determining a boost start function provided by an embodiment of the present application. As Figure 4 shown, before step 104, the method further includes:

[0101] Step S41: The system controller determines whether the rated bus voltage is greater than the set level voltage. If so, step S42 is executed; if not, step S43 is executed.

[0102] 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 the system controller 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.

[0103] Among them, the set level voltage can be set according to actual needs. For example, the set level voltage can be 400V.

[0104] Step S42: The system controller determines whether the ratio of the total capacity of the energy storage converters of the self-starting energy storage unit to the sum of the no-load loss capacities of all transformers in the off-grid energy storage system is greater than the set ratio. If not, step S43 is executed; if so, step S44 is executed.

[0105] Specifically, if the system controller determines that the ratio of the capacity of the energy storage converter to the sum of the no-load loss capacities 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 converter to the sum of the no-load loss capacities of all transformers in the off-grid energy storage system is greater than the set ratio, step S44 is executed.

[0106] Among them, the total capacity of the energy storage converters of the self-starting energy storage unit is the sum of the capacities of the energy storage converters of all self-starting energy storage units. As an optional solution, when it is defaulted that the capacities of all energy storage converters are equal, 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.

[0107] For example, all transformers in the off-grid energy storage system may include all load transformers, all photovoltaic transformers, all wind power transformers, and all energy storage transformers.

[0108] Among them, the set ratio can be set according to actual needs. For example, the set ratio can be 30%.

[0109] Step S43: The system controller determines the boost start function as a ramp function, and the process ends.

[0110] Figure 5 A schematic diagram of a ramp function provided by an embodiment of the present application is as Figure 5 shown. The ramp function is a linear function of time and the zero-start boost voltage reference value . The abscissa is time , and the ordinate is the zero-start boost voltage reference value . The relationship between and is shown by the following formula:

[0111]

[0112] Among them, is the rated voltage of the energy storage converter, and is the slope.

[0113] Step S44: The system controller determines the boost start function as a logarithm-ramp function, and the process ends.

[0114] Figure 6Schematic diagram of a logarithm-ramp function provided by an embodiment of the present application, as Figure 6 shown, the logarithm-ramp function is a function combined by a logarithmic function and a ramp function. The logarithm-ramp function is a linear function of time and the zero-start boost voltage reference value . The abscissa is time , and the ordinate is the zero-start boost voltage reference value . The relationship between is shown by the following formula:

[0115]

[0116] Wherein, is the rated voltage of the energy storage converter, is the slope, is a fixed constant.

[0117] As an alternative solution, if the control strategy is a virtual synchronous machine control strategy, step 104 may include: step S51, the system controller issues 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 according to the virtual synchronous voltage reference value.

[0118] Figure 7 Flowchart of a method for issuing a virtual synchronous voltage reference value provided by an embodiment of the present application, as Figure 7 shown, step S51 may specifically include:

[0119] Step S511, the system controller obtains the zero-start boost voltage reference value corresponding to different times according to the boost start function.

[0120] As Figure 5 or Figure 6 shown, the system controller obtains the zero-start boost voltage reference value corresponding to different times t according to the boost start function at a set time interval. The set time interval can be a time interval at the millisecond level.

[0121] Step S512, the system controller calculates 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.

[0122] The system controller calculates and generates a virtual synchronous voltage reference value for the zero-start boost voltage reference value and the reactive power of the energy storage converter through the formula . Wherein, 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.

[0123] Since the reactive power of different energy storage converters may be different, it is necessary to calculate the virtual synchronous voltage reference value corresponding to each energy storage converter according to the reactive power of each energy storage converter to calculate the virtual synchronous voltage reference value corresponding to each energy storage converter .

[0124] Step S513: The system controller sends the virtual synchronous voltage reference value to the corresponding energy storage converter.

[0125] As another alternative, Figure 8 is a flowchart of a zero-start boost method provided by an embodiment of the present application. As shown in Figure 8 , if the control strategy is a constant voltage and constant frequency control strategy, step 104 may include:

[0126] Step S61: The system controller sends an automatic start command to the energy storage converter of any self-starting energy storage unit.

[0127] Step S62: The energy storage converter of any self-starting energy storage unit responds to the automatic start command and boosts the voltage according to the constant voltage and constant frequency voltage reference values corresponding to different moments obtained in advance.

[0128] 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 moments t.

[0129] As an alternative, as shown in Figure 5 or Figure 6 , the system controller obtains the zero-start boost voltage reference values corresponding to different moments t at set time intervals according to the boost start function. The set time interval can be a time interval at the millisecond level. The system controller determines the zero-start boost voltage reference values as the constant voltage and constant frequency voltage reference values, where the constant voltage and constant frequency voltage reference values are equal to the zero-start boost voltage reference values, that is , is the constant voltage and constant frequency voltage reference value, is the zero-start boost voltage reference value. The system controller sends the constant voltage and constant frequency voltage reference values to the energy storage converter of any self-starting energy storage unit so that the energy storage converter boosts the voltage according to the constant voltage and constant frequency voltage reference values corresponding to different moments obtained in advance.

[0130] Step S63: The energy storage converter of each of the other self-starting energy storage units determines whether the voltage of its output port is greater than or equal to a predetermined voltage. If so, step S64 is executed; if not, step S63 is executed.

[0131] Among them, the output port of the energy storage converter is the port where the energy storage converter is connected to the energy storage transformer.

[0132] In the embodiment of the present application, when the energy storage converter of any self-starting energy storage unit boosts the voltage, it will drive the voltage at the output port of the energy storage converters 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 at its own output port is greater than or equal to the predetermined voltage, it continues to execute step S64; if it determines that the voltage at its own output port is less than the predetermined voltage, it executes step S63 to continue waiting for the voltage at the output port of the energy storage converter of other self-starting energy storage units to be greater than the predetermined voltage.

[0133] Step S64: The energy storage converters of other self-starting energy storage units boost the voltage according to the pre-obtained boost start function.

[0134] As an alternative solution, when the voltage at the output port of the energy storage converter of a certain self-starting energy storage unit is greater than or equal to the predetermined voltage, the energy storage converter of this self-starting energy storage unit can execute step S64.

[0135] As an alternative solution, the system controller can pre-distribute the boost start function to the energy storage converters of each self-starting energy storage unit so that the energy storage converters of each self-starting energy storage unit can pre-obtain the boost start function.

[0136] Specifically, since the voltage at 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 at its own output port according to the boost start function.

[0137] In the technical solution provided by 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 the pre-set control strategy and boost start function. In the embodiment of the present application, the energy storage converter in the self-starting energy storage unit is controlled to start boosting from zero according to the pre-set control strategy and boost start function, so that the method of starting boosting from zero can adapt to the energy storage application scenarios of multiple voltage levels and multiple application scenarios, and has the practicality of guiding actual applications.

[0138] In the technical solution of the embodiment of the present application, the control strategy adopts the virtual synchronous machine control strategy, and the boost start function adopts the logarithm-ramp function, thereby improving the black start success rate of the off-grid energy storage system and reducing the black start time.

[0139] Figure 9 For the structural schematic diagram of a black start device of an off-grid energy storage system provided by the embodiment of the present application, as Figure 9 shown, the device includes: a first determination module 11 and a first control module 12.

[0140] The first determination module 11 is configured to determine at least one self-starting energy storage unit from at least one energy storage unit; the first control module 12 is configured to control the zero-start boost of the power conversion inverter in the self-starting energy storage unit according to a preset control strategy and a boost start function.

[0141] In a possible implementation, when the number of energy storage units is multiple, the device further includes a second control module 13 and a first determination module 14.

[0142] The second control module 13 is configured to control the start of other energy storage units in the self-starting energy storage units among the multiple energy storage units if the first determination module 14 determines that the bus voltage of the off-grid energy storage system is greater than or equal to the set rated bus voltage.

[0143] In a possible implementation, the device further includes: a second determination module 15.

[0144] The second determination module 15 is configured to determine the control strategy as a virtual synchronous machine control strategy if the number of power conversion inverters of the self-starting energy storage unit is one. Alternatively, the second determination module 15 is configured to determine the control strategy as a virtual synchronous machine control strategy if the number of power conversion inverters of the self-starting energy storage unit is multiple and a high-speed communication network is provided between the system controller and the power conversion inverters of the multiple self-starting energy storage units. Alternatively, the second determination module 15 is configured to determine the control strategy as a constant voltage and constant frequency control strategy if the number of power conversion inverters of the self-starting energy storage unit is multiple, the power conversion inverters of the multiple self-starting energy storage units are dispersedly arranged, and a high-speed communication network is not provided between the system controller and the power conversion inverters of the multiple self-starting energy storage units.

[0145] In a possible implementation, the device further includes: a third determination module 16.

[0146] The third determination module 16 is configured 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 power conversion inverters of the self-starting energy storage unit to the sum of the no-load loss capacities of all transformers in the off-grid energy storage system is greater than the set ratio. Alternatively, the third determination module 16 is configured 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 configured 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 power conversion inverters of the self-starting energy storage unit to the sum of the no-load loss capacities of all transformers in the off-grid energy storage system is less than or equal to the set ratio.

[0147] In a possible implementation, if the control strategy is a virtual synchronous machine control strategy, the first control module 12 is specifically configured to send a virtual synchronous voltage reference value to the energy storage converters in each of the self-starting energy storage units according to the boost starting function, so that the energy storage converters boost the voltage according to the virtual synchronous voltage reference value.

[0148] In a possible implementation, the first control module 12 is specifically configured to obtain a no-load voltage boost reference value corresponding to different moments according to the boost starting function; calculate the virtual synchronous voltage reference value corresponding to the energy storage converter according to the no-load voltage boost reference value and the reactive power of the energy storage converter; and send the virtual synchronous voltage reference value to the corresponding energy storage converter.

[0149] In a possible implementation, if the control strategy is a constant voltage and constant frequency control strategy, the first control module 12 is specifically configured to send a self-starting instruction to the energy storage converter of any one of the self-starting energy storage units, so that the energy storage converter of any one of the self-starting energy storage units boosts the voltage according to the constant voltage and constant frequency voltage reference value corresponding to different moments obtained in advance in response to the self-starting instruction. If the energy storage converters of each of the other self-starting energy storage units determine that the voltage of their output ports is greater than or equal to a predetermined voltage, they boost the voltage according to the boost starting function obtained in advance.

[0150] In a possible implementation, the device further includes: a second judgment module 17.

[0151] The second judgment module 17 is configured 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, trigger the first determination module 11 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 line switch between the off-grid energy storage system and the public power grid is in the off state, all the switching devices in the off-grid energy storage system are in the on state, and the new energy unit and the load unit in the off-grid energy storage system are in the off or shutdown state.

[0152] In the technical solution provided by the embodiments 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 boost from no load according to the pre-set control strategy and boost starting function. In the embodiments of the present application, the energy storage converter in the self-starting energy storage unit is controlled to boost from no load according to the pre-set control strategy and boost starting function, so that the no-load voltage boost method can adapt to the energy storage application scenarios of multiple voltage levels and multiple application scenarios, and has the practicability of guiding actual applications.

[0153] An embodiment of the present application provides a computer-readable storage medium, which includes a stored program. When the program runs, it controls the system controller where the storage medium is located to execute the embodiment of the black start method of the off-grid energy storage system described above.

[0154] An embodiment of the present application provides a system controller, including: one or more processors; a memory; and one or more computer programs. The one or more computer programs are stored in the memory, and the one or more computer programs include instructions. When the instructions are executed by the system controller, the system controller is caused to execute the black start method of the off-grid energy storage system described above.

[0155] Figure 10 It is a schematic structural diagram of a system controller provided by an embodiment of the present application. As Figure 10 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, it implements the black start method of the off-grid energy storage system in the embodiment. To avoid repetition, it will not be elaborated here one by one. Alternatively, when the computer program is executed by the processor 21, it implements the functions of each model / unit in the black start device applied to the off-grid energy storage system in the embodiment. To avoid repetition, it will not be elaborated here one by one.

[0156] The system controller 20 includes, but is not limited to, a processor 21 and a memory 22. Those skilled in the art can understand that Figure 10 it is only an example of the system controller 20 and does not constitute a limitation on the system controller 20. It may include more or fewer components than shown in the figure, or combine certain components, or different components. For example, the system controller 20 may also include input / output devices, network access devices, buses, etc.

[0157] The so-called processor 21 may be a central processing unit (CPU), or may also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0158] The memory 22 can be an internal storage unit of the system controller 20, such as the hard disk or memory of the system controller 20. The memory 22 can also be an external storage device of the system controller 20, such as a plug-in hard disk equipped on the system controller 20, a Smart Media Card (SMC), a Secure Digital (SD) card, a Flash Card, etc. Further, the memory 22 can also include both the internal storage unit of the system controller 20 and external storage devices. The memory 22 is used to store computer programs and other programs and data required by the system controller 20. The memory 22 can also be used to temporarily store data that has been output or will be output.

[0159] Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working processes of the above-described systems, devices, and units can refer to the corresponding processes in the foregoing method embodiments and will not be elaborated herein.

[0160] In 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 merely illustrative. For example, the division of the units is only a logical function division, and there can 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 displayed or discussed couplings or direct couplings or communication connections to each other can be through some interfaces, and the indirect couplings or communication connections of the devices or units can be in electrical, mechanical, or other forms.

[0161] The units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they can be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0162] In addition, the functional units in each embodiment of the present application can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above-mentioned integrated units can be implemented in the form of hardware or in the form of a combination of hardware and software functional units.

[0163] The integrated unit implemented in the form of software functional units can be stored in a computer-readable storage medium. The above-mentioned software functional units are stored in a storage medium and include several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) or a processor to execute some steps of the methods described in various embodiments of the present application. The aforementioned storage medium includes: various media that can store program codes such as USB flash drives, mobile hard disks, read-only memories (ROM), random access memories (RAM), magnetic disks, or optical discs.

[0164] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included within 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 a preset control strategy and boost start function, control the energy storage converter in the self-starting energy storage unit to boost voltage from zero; 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; 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; 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 start function is determined as a ramp function; The logarithmic ramp function includes: ； The ramp function includes: ； in, is the zero-start boost voltage reference value, For the moment, is the rated voltage of the energy storage converter, is the slope, is a fixed constant.

2. The method according to claim 1, characterized in that The number of the energy storage units is multiple, and after controlling 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 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.

6. The method according to claim 5, 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.

7. 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.

8. 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; A first control module, used for controlling the zero-start voltage boost of the energy storage converter in the self-starting energy storage unit according to a preset control strategy and a voltage boost start function; The third determination module 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 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 the rated bus voltage is less than or equal to the set level voltage, the boost start function is determined 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 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 start function is determined as a ramp function; The logarithmic ramp function includes: ； The ramp function includes: ； in, is the zero-start boost voltage reference value, For the moment, is the rated voltage of the energy storage converter, is the slope, is a fixed constant.

9. 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 7.

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