Grid-forming energy storage converter and control method therefor

Abstract

The present application relates to the technical field of power electronics, and provides a grid-forming energy storage converter, a control method, an electronic device, and a storage medium. The grid-forming energy storage converter comprises: a conversion unit, configured to correspondingly convert an alternating current or a direct current on the basis of a conversion instruction; an electrochemical battery, configured to, on the basis of the conversion instruction, convert electric energy into chemical energy for storage or convert stored chemical energy into electric energy for release; and an opening / closing device, which has one end connected to the conversion unit and the other end connected to the electrochemical battery, and is configured to close on the basis of a connection instruction so as to connect the conversion unit and the electrochemical battery, and open on the basis of a disconnection instruction so as to disconnect the conversion unit from the electrochemical battery. By providing the opening / closing device between the conversion unit and the electrochemical battery, the conversion unit can be disconnected from the electrochemical battery in a zero active power state, thereby avoiding frequent charging-discharging switching of the electrochemical battery, reducing the impact on the service life of the battery.

Description

Grid-forming energy storage converter and control method thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of power electronics, for example to a grid-forming energy storage converter and a control method thereof. BACKGROUND

[0002] Electrochemical energy storage is one of the key development areas of future power systems. Lithium-ion batteries, as an important energy storage technology, have been widely adopted due to their high power density and energy density, long cycle life, and low self-discharge rate. Charging and discharging are common operations during the use of batteries, but frequent charging and discharging can have an impact on the battery. Excessive charging and discharging can cause the internal temperature of the battery to rise, thereby shortening the life of the battery and reducing its performance. Therefore, in order to prolong the service life of the battery and maintain its good performance, it is necessary to avoid the impact of frequent charging and discharging on the battery. Grid-forming energy storage is applied to high-proportion new energy systems to undertake peak shaving and rapid grid support. Due to the volatility of new energy generation and the limitation of energy storage capacity, grid-forming energy storage systems will be in a zero active state for a long time every day. At this time, the direct current battery is subject to frequent charging and discharging conversion, which has an impact on the battery life.

[0003] In related technologies, grid-forming energy storage generally solves this problem by means of standby latching converter. However, grid-forming energy storage converters need to respond to grid events instantaneously, and standby mode is not suitable. Therefore, it is currently difficult to solve the contradiction between rapid grid support in zero power state and the impact of frequent charging and discharging on the battery. SUMMARY

[0004] The present application aims to provide a grid-forming energy storage converter, a control method, an electronic device and a storage medium, which can solve the contradiction between rapid grid support in zero power state and the impact of frequent charging and discharging on the battery.

[0005] According to an aspect of the present application, a grid-forming energy storage converter is provided, comprising: a converter unit configured to convert alternating current and direct current according to a conversion instruction; an electrochemical battery configured to convert electrical energy into chemical energy for storage or convert stored chemical energy into electrical energy for release according to the conversion instruction; a switching device connected to the converter unit at one end and connected to the electrochemical battery at the other end, configured to close according to a closing instruction to connect the converter unit and the electrochemical battery, and configured to disconnect according to a disconnecting instruction to disconnect the connection between the converter unit and the electrochemical battery.

[0006] According to some embodiments, when the absolute value of the active instruction of the grid-forming energy storage converter is less than the power threshold value P th , and in the steady state mode, the switching device is in the disconnected state; when the absolute value of the active instruction of the grid-forming energy storage converter is less than the power threshold value Pth , and in the zero power transient state, the on-off device is in the closed state.

[0007] According to some embodiments, in the on-off device is in the open state, a direct current voltage control mode is adopted to maintain the stability of the direct current voltage; and in the on-off device is in the closed state, an active power control mode is adopted to maintain the stability of the direct current voltage.

[0008] According to some embodiments, the on-off device is a semiconductor device; and the semiconductor device includes a bidirectional semiconductor device, which includes a bidirectional thyristor, a bidirectional silicon controlled rectifier, and a bidirectional integrated gate-commutated thyristor.

[0009] According to some embodiments, the grid-forming energy storage converter further includes a current limiting unit connected to one end of the on-off device and the other end of the electrochemical cell, for limiting the current between the conversion unit and the electrochemical cell when the on-off device is in the closed state.

[0010] According to some embodiments, the current limiting unit is an inductor, or a resistor, or an inductor in parallel / series resistor.

[0011] According to some embodiments, the conversion unit includes a direct current capacitor connected to one end of the on-off device in parallel with the electrochemical cell, for storing electric charge and blocking direct current.

[0012] According to some embodiments, the direct current capacitor is a conventional capacitor, or a super capacitor, or a conventional capacitor in parallel with a super capacitor.

[0013] According to some embodiments, the conversion unit is a two-level topology, or a three-level topology, or a sub-module topology of a modular multilevel converter.

[0014] According to an aspect of the present application, a control method of a grid-forming energy storage converter is provided, which is applied to the grid-forming energy storage converter described above, and includes: controlling the conversion unit to perform corresponding conversion between alternating current and direct current according to a conversion instruction; controlling the electrochemical cell to store chemical energy by converting electrical energy into chemical energy, or release electrical energy by converting stored chemical energy into electrical energy according to the conversion instruction; controlling the on-off device to be closed to connect the conversion unit and the electrochemical cell according to a connection instruction; and controlling the on-off device to be opened to disconnect the conversion unit and the electrochemical cell according to a disconnection instruction; wherein one end of the on-off device is connected to the conversion unit, and the other end is connected to the electrochemical cell.

[0015] According to some embodiments, the control method of the grid-forming energy storage converter further includes: step 1: judging the relationship between the absolute value of the active power instruction and the power threshold value P th ; in the case that the absolute value of the active power instruction is greater than the power threshold value P thIf the first state is not the first state, go to step 6; step 2: determine whether the on-off device is in a closed state, if the on-off device is in the closed state, go to step 4, if the on-off device is in an open state, go to step 3; step 3: control the on-off device to be closed, and go to step 4; step 4: determine whether the control mode is an active power control mode, if the control mode is the active power control mode, go to step 1, if the control mode is not the active power control mode, go to step 5; step 5: switch the control mode to the active power control mode, and go to step 1; step 6: determine whether it is a transient mode, if it is the transient mode, go to step 2, if it is not the transient mode, go to step 7; step 7: determine whether the on-off device is in the open state, if the on-off device is in the open state, go to step 9, if the on-off device is not in the open state, go to step 8; step 8: control the on-off device to be open, and go to step 9; step 9: determine whether the control mode is a direct current voltage control mode, if the control mode is the direct current voltage control mode, go to step 1, if the control mode is not the direct current voltage control mode, go to step 10; step 10: switch the control mode to the direct current voltage control mode, and go to step 1.

[0016] According to some embodiments, determining whether it is a transient mode comprises: obtaining a voltage of the direct current capacitor and a port voltage of the electrochemical cell, and calculating a voltage difference value; when an absolute value of the voltage difference value is greater than a voltage threshold value U th , and a duration t 11 is greater than a threshold value, determining that it is the transient mode; or, obtaining an alternating current active power of the grid-forming energy storage converter, a transient power threshold value P th1 ; when an absolute value of the alternating current active power is greater than P th1 , and a duration t 12 is greater than a threshold value, determining that it is the transient mode.

[0017] According to an aspect of the present application, an electronic device is provided, comprising: a processor; a memory storing a computer program, when the computer program is executed by the processor, the computer program causes the processor to execute the control method of the grid-forming energy storage converter as described above.

[0018] According to an aspect of the present application, a non-transitory computer readable medium is provided, and the non-transitory computer readable medium stores readable instructions, when the instructions are executed by a processor, the instructions cause the processor to execute the control method of the grid-forming energy storage converter as described above.

[0019] It should be understood that the above general description and the following detailed description are only exemplary and cannot limit the present application. Advantages:

[0020] Through the above embodiments provided in the present application, the on-off device is arranged between the current conversion unit and the electrochemical cell, and through the on command, the on-off device can be quickly closed to connect the current conversion unit and the electrochemical cell, to ensure the continuity of energy conversion and storage, and to realize the fast grid support in the zero power state. At the same time, through the off command, the on-off device can be quickly disconnected to disconnect the connection between the current conversion unit and the electrochemical cell, so that the frequent charge-discharge conversion of the electrochemical cell can be avoided when the grid-connected energy storage system operates in the zero active state, and the influence on the battery life is reduced. Through the introduction of the current limiting unit, the overcurrent caused by the voltage difference between the DC capacitor and the electrochemical cell port can be avoided. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art according to these drawings without departing from the scope of the present application.

[0022] FIG. 1 shows a structural schematic diagram of a grid-connected energy storage converter according to an exemplary embodiment;

[0023] FIG. 2 shows a structural schematic diagram of another grid-connected energy storage converter according to an exemplary embodiment;

[0024] FIG. 3 shows a structural schematic diagram of a two-level grid-connected energy storage converter according to an exemplary embodiment;

[0025] FIG. 4 shows a structural schematic diagram of a three-level grid-connected energy storage converter according to an exemplary embodiment;

[0026] FIG. 5 shows a structural schematic diagram of a modular multi-level grid-connected energy storage converter according to an exemplary embodiment;

[0027] FIG. 6 shows a flow chart of a control method of a grid-connected energy storage converter according to an exemplary embodiment;

[0028] FIG. 7 shows a flow chart of another control method of a grid-connected energy storage converter according to an exemplary embodiment;

[0029] FIG. 8 shows a basic logic block diagram of the control method of another grid-connected energy storage converter according to an exemplary embodiment;

[0030] FIG. 9 shows a control block diagram of a grid-connected energy storage converter in a zero power state according to an exemplary embodiment;

[0031] FIG. 10 shows a structural schematic diagram of an electronic device according to an exemplary embodiment.

[0032] Legend: AC, alternating current; DC, direct current; C, first direct current capacitor; C1, second direct current capacitor; C2, third direct current capacitor; 1, grid-connected energy storage converter; 11, grid-connected energy storage converter's conversion unit; 12, switching device; 13, electrochemical cell; 14, current limiting device; 2, two-level grid-connected energy storage converter; 21, two-level grid-connected energy storage converter's conversion unit; 22, two-level grid-connected energy storage converter's switching unit; 23, two-level grid-connected energy storage converter's current limiting unit; 3, three-level grid-connected energy storage converter; 31, three-level grid-connected energy storage converter's conversion unit; 32, three-level grid-connected energy storage converter's switching unit; 33, three-level grid-connected energy storage converter's current limiting unit; L, inductor; R, resistor; 40, modular multilevel grid-connected energy storage converter's sub-module; 41, modular multilevel grid-connected energy storage converter's conversion unit; 42, modular multilevel grid-connected energy storage converter's switching unit; 43, modular multilevel grid-connected energy storage converter's current limiting unit; SM1, modular multilevel grid-connected energy storage converter's first sub-module; SM2, modular multilevel grid-connected energy storage converter's second sub-module; SMn, modular multilevel grid-connected energy storage converter's nth sub-module; 1000, electronic device; 1001, memory; 1002, processor. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0034] The specific implementation can refer to the following embodiments.

[0035] FIG. 1 shows a structure schematic diagram of a grid-connected energy storage converter according to an exemplary embodiment. As shown in FIG. 1, the grid-connected energy storage converter 1 includes the grid-connected energy storage converter's conversion unit 11, the switching device 12, and the electrochemical cell 13.

[0036] The grid-connected energy storage converter's conversion unit 11 is configured to convert the alternating current and the direct current according to the conversion instruction.

[0037] The electrochemical cell 13 is configured to convert the electrical energy into chemical energy for storage or convert the stored chemical energy into electrical energy for release according to the conversion instruction.

[0038] The on-off device 12 is connected with the conversion unit 11 of the grid-connected energy storage converter at one end and connected with the electrochemical cell 13 at the other end, and is used to close according to the on command to connect the conversion unit 11 of the grid-connected energy storage converter and the electrochemical cell 13, and is used to disconnect according to the off command to disconnect the conversion unit 11 of the grid-connected energy storage converter and the electrochemical cell 13.

[0039] In FIG. 1, AC is used to represent alternating current, DC is used to represent direct current, the conversion unit 11 of the grid-connected energy storage converter can include a current mode switching component and a first direct current capacitor C. The arrow direction can be used to represent the direction of current, U C may be used to represent the voltage of the first direct current capacitor C, U E may be used to represent the voltage of the electrochemical cell 13.

[0040] The conversion command can be used to represent the command of the switching mode of direct current and alternating current. In some implementations, when the energy in the power grid is excessive or the electricity price is low, the conversion unit 11 of the grid-connected energy storage converter in the grid-connected energy storage converter 1 converts the alternating current in the power grid into direct current, and stores the energy into the electrochemical cell 13, so as to correspond to the storage operation of the electrochemical cell 13. When the power grid needs additional energy or the electricity price is high, the operation of the energy release of the electrochemical cell 13 can be corresponded. At this time, the conversion unit 11 of the grid-connected energy storage converter in the grid-connected energy storage converter 1 converts the direct current in the electrochemical cell 13 into alternating current, and delivers the energy to the power grid.

[0041] The on-off device 12 can have two states of closing and opening. When the on-off device 12 is closed, the conversion unit 11 of the grid-connected energy storage converter and the electrochemical cell 13 are connected. When the on-off device 12 is opened, the connection between the conversion unit 11 of the grid-connected energy storage converter and the electrochemical cell 13 is disconnected.

[0042] The on-off device 12 can have two states of closing and opening. When the on-off device 12 is closed, the conversion unit 11 of the grid-connected energy storage converter and the electrochemical cell 13 are connected. When the on-off device 12 is opened, the connection between the conversion unit 11 of the grid-connected energy storage converter and the electrochemical cell 13 is disconnected.

[0043] According to some embodiments, when the absolute value of the active command of the grid-connected energy storage converter is less than the power threshold value P th , and in the steady state mode, the on-off device is in the open state; when the absolute value of the active command of the grid-connected energy storage converter is less than the power threshold value P th, and in the zero-power transient state, the switching device is in a closed state.

[0044] In some implementations, a maintenance personnel of the power system can send an active power instruction to the grid-forming energy storage converter according to the actual operation of the power grid, which can be used to indicate how much power the grid-forming energy storage converter needs to output. The power threshold value P th , and in the zero-power transient state, the switching device is in a closed state. th , and in the steady-state mode, it can be indicated that the power system has not been disturbed and is in a zero-active state. At this time, the switching device is opened, so that the electrochemical battery does not have to be frequently charged and discharged. The disturbance can be caused by changes in system operation time, environmental conditions, etc.

[0045] , and in the zero-power transient state, the switching device is in a closed state. th , and in the zero-power transient state, the switching device is in a closed state.

[0046] In some embodiments, when the absolute value of the active power instruction is less than the power threshold value P th , and in the steady-state mode, the switching device remains in an open state, which can reduce energy loss caused by unnecessary current flow, thereby improving the energy efficiency of the entire grid-forming energy storage converter. By opening the switching device in the steady-state mode, power supply can be quickly restored when needed, ensuring stable operation of the power system.

[0047] According to some embodiments, when the switching device is in an open state, a DC voltage control method is used to maintain the stability of the DC voltage; when the switching device is in a closed state, an active power control method is used to maintain the stability of the DC voltage.

[0048] The conversion unit can convert AC power in the power grid into DC power, and a DC voltage control method is used to maintain the stability of the DC voltage of the grid-forming energy storage converter. The active power control method can include generator control methods, load control methods, and power grid structure optimization methods to maintain the stability of the DC voltage of the grid-forming energy storage converter.

[0049] In some embodiments, when the switching device is open, a DC voltage control method is used to directly and accurately control the DC side of the grid-forming energy storage converter, ensuring the stability of the DC voltage. This is crucial for protecting energy storage equipment and maintaining the stability of the power system. When the switching device is closed, an active power control method can be used to adjust the output power of the grid-forming energy storage converter according to the actual situation of the power grid, further maintaining the stability of the DC voltage, and also enhancing the interaction with the power grid.

[0050] According to some embodiments, the on-off device is a semiconductor device; wherein the semiconductor device comprises a bidirectional semiconductor device, and the bidirectional semiconductor device comprises a bidirectional thyristor, a bidirectional silicon controlled rectifier, or a bidirectional integrated gate-commutated thyristor.

[0051] In some implementations, a reverse series IGBT (Insulated Gate Bipolar Transistor, a composite full-controlled voltage-driven power semiconductor device) can also be included.

[0052] The present embodiment uses a bidirectional semiconductor device as the on-off device, which can work efficiently at high frequency and has relatively low power consumption due to its special physical characteristics, thus helping to reduce the energy consumption of the overall system.

[0053] FIG. 2 shows a structural schematic diagram of another grid-forming energy storage converter according to an exemplary embodiment. As shown in FIG. 2, the grid-forming energy storage converter 1 further comprises a current-limiting device 14 connected to the on-off device 12 at one end and to the electrochemical cell 13 at the other end, for limiting the current between the current conversion unit 11 of the grid-forming energy storage converter and the electrochemical cell 13 when the on-off device 12 is in a closed state.

[0054] According to some embodiments, the current-limiting device 14 can be an inductor, or a resistor, or an inductor in parallel with a resistor, or an inductor in series with a resistor.

[0055] When the inductor is used as the current-limiting device, its inductance characteristic is used to limit the rate of change of current. When the on-off device 12 is closed, the inductor will generate a self-induced electromotive force opposite to the power source electromotive force, thereby limiting the increase of current. The selection of the inductor needs to consider its inductance value and rated current to ensure that it can effectively limit the current within the normal working range. When the resistor is used as the current-limiting device, its resistance value is used to limit the size of the current. In the circuit, a resistor with an appropriate resistance value is connected in series, and when the current passes through, the resistor will generate a voltage drop, thereby limiting the size of the current. The selection of the resistor needs to consider its resistance value and power bearing capacity to ensure that it will not be damaged due to overheating within the normal working range.

[0056] The inductor in parallel with the resistor combines the current-limiting characteristics of the inductor and the resistor. The inductor is mainly used to limit the rate of change of current, while the resistor is used to limit the size of the current. This way can more quickly limit the current when the on-off device is closed, and further limit the size of the current through the resistor after stabilization. The inductor in series with the resistor also combines the current-limiting characteristics of the inductor and the resistor. Unlike the inductor in parallel with the resistor, the inductor in series with the resistor limits the rate of change of current while directly limiting the size of the current. This way can be more suitable in scenarios where more stringent current limiting is required.

[0057] The embodiment can be flexibly configured according to specific application scenarios and requirements by selecting appropriate current limiting device implementation modes (inductor, resistor, inductor in parallel with resistor, inductor in series with resistor). This helps to meet the needs of different power systems for current limiting functions. By introducing the current limiting device, overcurrent caused by the voltage difference between the DC capacitor and the electrochemical cell port can be avoided.

[0058] According to some embodiments, the conversion unit 11 of the grid-forming energy storage converter includes a first DC capacitor C connected in parallel with the electrochemical cell 13 and connected to one end of the switching device 12, for storing electric charge and blocking direct current.

[0059] According to example embodiments, the first DC capacitor C can be a conventional capacitor, or a super capacitor, or a conventional capacitor in parallel with a super capacitor.

[0060] A conventional capacitor is a widely used type of capacitor with relatively stable performance. In the conversion unit 11 of the grid-forming energy storage converter, a conventional capacitor can be used as the first DC capacitor C for storing electric charge and blocking direct current. By selecting appropriate capacitance values and voltage ratings, the conventional capacitor can meet the basic requirements of the first DC capacitor C of the conversion unit 11 of the grid-forming energy storage converter. A super capacitor is a type of capacitor with high energy density, high power density, and long cycle life. In the conversion unit 11 of the grid-forming energy storage converter, a super capacitor can be used as the first DC capacitor C to provide faster charging and discharging speed and higher energy density, which helps to improve the response speed and energy conversion efficiency of the conversion unit 11 of the grid-forming energy storage converter.

[0061] In some application scenarios, both cost and performance requirements may need to be considered. At this time, a conventional capacitor in parallel with a super capacitor implementation mode can be used. By connecting a conventional capacitor and a super capacitor in parallel, the performance of the first DC capacitor C can be improved while keeping the cost relatively low. This implementation mode can adjust the capacity ratio of the conventional capacitor and the super capacitor according to specific requirements to achieve the best performance.

[0062] The embodiment can significantly improve the performance and reliability of the power system by selecting appropriate capacitor implementation modes (conventional capacitor, super capacitor, conventional capacitor in parallel with super capacitor).

[0063] According to some embodiments, the conversion unit 11 of the grid-forming energy storage converter can be a two-level topology, or a three-level topology, or a submodule topology of a modular multilevel converter. FIG. 3 shows a structural schematic diagram of a two-level grid-forming energy storage converter according to an exemplary embodiment. As shown in FIG. 3, the two-level grid-forming energy storage converter 2 includes a conversion unit 21 of the two-level grid-forming energy storage converter, a switching unit 22 of the two-level grid-forming energy storage converter, and a current limiting unit 23 of the two-level grid-forming energy storage converter. Wherein, C can be used to represent a first DC capacitor, U C may be used to represent the voltage of the first DC capacitor C, E may be used to represent the voltage of the electrochemical cell 13.

[0064] The conversion unit 21 of the two-level grid-forming energy storage converter adopts a three-phase half-bridge two-level topology and includes a first DC capacitor C. The switching unit 22 of the two-level grid-forming energy storage converter adopts a bidirectional GTO (Gate-Turn-Off Thyristor), and the current limiting unit 23 of the two-level grid-forming energy storage converter adopts an inductor. The switching unit 22 of the two-level grid-forming energy storage converter and the current limiting unit 23 of the two-level grid-forming energy storage converter are connected in series, one end of which is connected to one end of the first DC capacitor C, and the other end is connected to one end of the electrochemical cell 13. The connection to one end of the electrochemical cell 13 can be direct connection or indirect connection through other devices.

[0065] FIG. 4 shows a structural schematic diagram of a three-level grid-forming energy storage converter according to an exemplary embodiment. As shown in FIG. 4, the three-level grid-forming energy storage converter 3 includes a conversion unit 31 of the three-level grid-forming energy storage converter, a switching unit 32 of the three-level grid-forming energy storage converter, and a current limiting unit 33 of the three-level grid-forming energy storage converter.

[0066] The conversion unit 31 of the three-level grid-forming energy storage converter adopts a neutral-point-clamped three-level topology and includes a second DC capacitor C1 and a third DC capacitor C2 connected in series. The switching unit 32 of the three-level grid-forming energy storage converter adopts a bidirectional thyristor, and the current limiting unit 33 of the three-level grid-forming energy storage converter adopts an inductor L and a resistor R connected in parallel. The switching unit 32 of the three-level grid-forming energy storage converter and the current limiting unit 33 of the three-level grid-forming energy storage converter are connected in series, one end of which is connected to one end of the second DC capacitor C1, and the other end is connected to one end of the electrochemical cell 13. The connection to one end of the electrochemical cell 13 can be direct connection or indirect connection through other devices.

[0067] Figure 5 shows a structural schematic diagram of a modular multilevel grid-forming energy storage converter according to an example embodiment. As shown in Figure 5, the modular multilevel grid-forming energy storage converter includes a plurality of modular multilevel grid-forming energy storage converter sub-modules 40, each of which includes a modular multilevel grid-forming energy storage converter conversion unit 41, a modular multilevel grid-forming energy storage converter switching unit 42, and a modular multilevel grid-forming energy storage converter current limiting unit 43. The modular multilevel grid-forming energy storage converter conversion unit 41 adopts a single-phase half-bridge and includes a first direct-current capacitor C. The modular multilevel grid-forming energy storage converter switching unit 42 adopts reverse series IGBT, and the modular multilevel grid-forming energy storage converter current limiting unit 43 adopts an inductor. The modular multilevel grid-forming energy storage converter switching unit 42 and the modular multilevel grid-forming energy storage converter current limiting unit 43 are connected in series, with one end connected to one end of the first direct-current capacitor C and the other end connected to one end of the electrochemical cell 13. The connection to the electrochemical cell 13 can be direct or indirect through other devices. Wherein SM1, SM2, …, and SMn can each be a specific modular multilevel grid-forming energy storage converter sub-module 40. SM1 is the first modular multilevel grid-forming energy storage converter sub-module, SM2 is the second modular multilevel grid-forming energy storage converter sub-module, and SMn is the nth modular multilevel grid-forming energy storage converter sub-module.

[0068] The present embodiment can adapt to different application scenarios to achieve the best technical effect by selecting the appropriate topology according to specific needs.

[0069] Figure 6 shows a flowchart of a control method of a grid-forming energy storage converter according to an example embodiment. The control method of the grid-forming energy storage converter is applied to the grid-forming energy storage converter in the above embodiments and includes the following steps:

[0070] S601, according to the conversion instruction, controlling the conversion unit to perform corresponding conversion between alternating current and direct current.

[0071] S602, according to the conversion instruction, controlling the electrochemical cell to convert electrical energy into chemical energy for storage or to convert stored chemical energy into electrical energy for release.

[0072] S603, according to the on instruction, controlling the switching device to close to connect the conversion unit and the electrochemical cell; and according to the off instruction, controlling the switching device to open to disconnect the conversion unit and the electrochemical cell; wherein one end of the switching device is connected to the conversion unit and the other end is connected to the electrochemical cell.

[0073] According to an example embodiment, the converter instruction, the on instruction and the off instruction can be sent by the controller. In some implementations, the controller can monitor the real-time operation of the power grid and send the instructions accordingly. In other implementations, the maintenance personnel of the power system can input the instructions through the controller to control the operation of the converter unit, the electrochemical cell and the switching device.

[0074] FIG. 7 shows a flow chart of a control method of another grid-forming energy storage converter according to an example embodiment, the control method comprising:

[0075] Step 1: determining the relationship between the absolute value of the active power instruction and the power threshold value P th , and in the first state where the absolute value of the active power instruction is greater than the power threshold value P th , executing Step 2, and in the non-first state, executing Step 6;

[0076] Step 2: determining whether the switching device is in the closed state, and if so, executing Step 4, and if not, executing Step 3;

[0077] Step 3: controlling the switching device to be closed, and executing Step 4;

[0078] Step 4: determining whether the control mode is the active power control mode, and if so, executing Step 1, and if not, executing Step 5;

[0079] Step 5: switching the control mode to the active power control mode, and executing Step 1;

[0080] Step 6: determining whether it is in the transient mode, and if so, executing Step 2, and if not, executing Step 7;

[0081] Step 7: determining whether the switching device is in the open state, and if so, executing Step 9, and if not, executing Step 8;

[0082] Step 8: controlling the switching device to be opened, and executing Step 9;

[0083] Step 9: determining whether the control mode is the DC voltage control mode, and if so, executing Step 1, and if not, executing Step 10;

[0084] Step 10: switching the control mode to the DC voltage control mode, and executing Step 1.

[0085] According to an example embodiment, the power threshold value P th has a value range of 0.001 to 0.1 times the rated power, and in some implementations, Pth The value can be 0.01 times of the rated power.

[0086] FIG. 8 shows a basic logic block diagram of a control method of another grid-forming energy storage converter according to an exemplary embodiment, which can represent the logic process when the corresponding control method in FIG. 7 is executed.

[0087] The method performs similar functions as the grid-forming energy storage converter provided above, and other functions can be referred to the previous description, which will not be described here.

[0088] According to some embodiments, the judgment method of the transient mode is as follows: when not in the transient mode, one of the following two conditions is met to enter the transient mode: the voltage of the DC capacitor and the port voltage of the electrochemical cell are obtained, and the voltage difference is calculated; when the absolute value of the voltage difference is greater than the voltage threshold value U th , and the duration t 11 , it is judged to be in the transient mode; or, the AC active power of the grid-forming energy storage converter, the transient power threshold value P th1 is obtained; when the absolute value of the AC active power is greater than P th1 , and the duration t 12 , it is judged to be in the transient mode.

[0089] In some implementations, when in the transient mode, the absolute value of the active power is less than the power threshold value P th , and after the duration t2, the transient mode is exited. When the absolute value of the voltage difference is greater than the voltage threshold value U th , and the duration t 11 , it is judged to be in the transient mode, so t 11 is the duration of the case that the absolute value of the difference between U C and U E is greater than the voltage threshold value.

[0090] When the absolute value of the AC active power is greater than P th1 , and the duration t 12 , it is judged to be in the transient mode. Wherein, P th1 is the transient power threshold value, so t 12 is the duration of the case that the absolute value of the AC active power is greater than the transient power threshold value. Wherein, the voltage threshold value U th is in the range of 0.01 to 1 times of the rated DC voltage, the transient power threshold value P th1 is greater than or equal to the power threshold value P th , and less than or equal to the maximum active power of the grid-forming energy storage converter. t 11 , t 12 can be set in combination with the actual operation process of the grid-forming energy storage converter.

[0091] The embodiment can accurately determine when to enter the transient mode by monitoring the difference between the voltage of the DC capacitor and the port voltage of the electrochemical cell in real time and setting a voltage threshold value U th and the duration t 11 . Similarly, by monitoring the AC active power of the grid-connected energy storage converter and comparing it with the transient power threshold value P th1 , combined with the duration t 12 , the transient state can also be accurately identified. Further, the transient mode can be identified within a short time, so that the response speed is improved.

[0092] FIG. 9 shows a control block diagram of a grid-connected energy storage converter in a zero-power state according to an exemplary embodiment. As shown in FIG. 9, the RS flip-flop is used to determine the transient mode. When not in the transient mode, the absolute value of the difference between the voltage U C of the first DC capacitor and the voltage U E of the electrochemical cell is greater than the voltage threshold value U th , and the duration t 11 , or the absolute value of the AC active power P vsc of the grid-connected energy storage converter is greater than the transient power threshold value P th1 , and the duration t 12 , preferably the duration t 11 and t 12 can be selected as one execution period of the control program; when in the transient mode, the absolute value of the AC active power P vsc of the grid-connected energy storage converter is less than the power threshold value P th , and after the duration t2, the transient mode is exited. Therefore, t2 can correspond to the duration of the case where the absolute value of P vsc is less than P th . As described above in step 6, when in the transient mode, the active power control is switched to the active power control, and at this time the power change value ΔP add is 0; when in the transient mode, the DC voltage control is switched to the DC voltage control, and at this time the additional power command ΔP C is obtained according to the deviation between the DC capacitor voltage U C and the DC voltage command value U Cref after the PI controller, and is added to the active power set value P set as the additional power command, wherein the active power direction is positive for power generation.

[0093] FIG. 10 shows a structural schematic diagram of an electronic device according to an exemplary embodiment. As shown in FIG. 10, the electronic device 1000 of the embodiment can include a memory 1001 and a processor 1002.

[0094] The memory 1001 stores a computer program, which, when executed by the processor 1002, causes the aforementioned processor 1002 to perform the method in the above embodiment.

[0095] The processor 1002 and the memory 1001 are connected, for example, through a bus.

[0096] Optionally, the electronic device 1000 can further include a transceiver. It should be noted that the transceiver in actual application is not limited to one, and the structure of the electronic device 1000 does not constitute a limitation on the embodiments of the present application.

[0097] The processor 1002 can be a CPU (Central Processing Unit, central processor), a general-purpose processor, a DSP (Digital Signal Processor, digital signal processor), an ASIC (Application Specific Integrated Circuit, application specific integrated circuit), an FPGA (Field Programmable Gate Array, field programmable gate array) or other programmable logic devices, transistor logic devices, hardware components or any combination thereof. It can implement or execute various exemplary logical blocks, modules and circuits described in combination with the disclosure of the present application. The processor 1002 can also be a combination of computing functions, such as one or more microprocessor combinations, combinations of DSP and microprocessor, etc.

[0098] The bus can include a path for transmitting information between the above-mentioned components. The bus can be a PCI (Peripheral Component Interconnect, peripheral component interconnect) bus or an EISA (Extended Industry Standard Architecture, extended industry standard architecture) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, only one thick line is shown in the figure, but it does not mean that there is only one bus or only one type of bus.

[0099] The memory 1001 can be a ROM (Read Only Memory) or other type of static storage device that can store static information and instructions, a RAM (Random ACCess Memory) or other type of dynamic storage device that can store information and instructions, an EEPROM (EleCtriCally Erasable Programmable Read Only Memory), a CD-ROM (CompaCt DisC Read Only Memory) or other optical disk storage, a magnetic disk storage or other magnetic storage devices, or any other medium capable of storing desired program code in the form of instructions or data structures and that can be accessed by a computer, but is not limited thereto.

[0100] The memory 1001 is used to store application program codes for implementing the solutions of the present application, and is controlled by the processor 1002 to perform. The processor 1002 is used to execute the application program codes stored in the memory 1001 to realize the content shown in the foregoing method embodiments.

[0101] The electronic device includes, but is not limited to, a mobile terminal such as a mobile phone, a notebook computer, a digital broadcast receiver, a PDA (Personal Digital Assistant), a PAD (Tablet Personal Computer), a PMP (Portable Multimedia Player), a vehicle terminal (such as a vehicle navigation terminal), and the like, and a fixed terminal such as a digital TV, a desktop computer, and the like. It can also be a server or the like. The electronic device shown in FIG. 10 is only an example, and should not bring any limitation to the functions and use range of the embodiments of the present application.

[0102] The electronic device of the present embodiment can be used to execute the method of any of the foregoing embodiments, and has similar implementation principles and technical effects, which will not be described herein.

[0103] The present application also provides a non-transitory computer-readable storage medium having computer-readable instructions stored thereon, and the processor executes the method in the above embodiments when the instructions are executed.

[0104] Those skilled in the art can understand that all or part of the steps of the foregoing method embodiments can be completed by program instruction related hardware. The foregoing program can be stored in a non-transitory computer-readable storage medium. The program, when executed, performs steps including the foregoing method embodiments; and the foregoing storage medium includes a ROM, a RAM, a magnetic disk or an optical disk, and various other program code storage media.

[0105] The above has introduced the embodiments of the present application in detail, and the principles and implementation manners of the present application are described by applying specific examples. The above embodiment descriptions are only used to help understand the method of the present application and its core idea. Meanwhile, the changes or deformations made by the person skilled in the art according to the idea of the present application, based on the specific implementation manners and application scope of the present application, all belong to the protection scope of the present application. In summary, the content of the present specification should not be understood as the limitation of the present application.

Claims

1. A grid-forming energy storage converter, characterized by, The application relates to a network-constructing energy storage converter, comprising: a conversion unit for converting AC power into DC power according to a conversion instruction; an electrochemical cell for storing or releasing electric energy according to the conversion instruction; a switching device connected to one end of the conversion unit and the other end of the electrochemical cell, for closing the conversion unit and the electrochemical cell according to a closing instruction, and opening the connection between the conversion unit and the electrochemical cell according to an opening instruction. When the switching device is in the opening state, a DC voltage control mode is adopted to maintain the stability of the DC voltage; 2. The network infrastructure energy storage inverter of claim 1, wherein, When an absolute value of an active instruction of the network-constructed energy storage converter is less than a power threshold value P th , and in a steady state mode, the switching device is in an open state. When the absolute value of the active instruction of the network-constructed energy storage converter is less than the power threshold value P th , and in a zero-power transient state, the opening and closing device is in a closed state.

3. The network infrastructure energy storage converter of claim 2, wherein, When the switching device is in the closing state, an active power control mode is adopted to maintain the stability of the DC voltage. The switching device is a semiconductor device, wherein the semiconductor device comprises a bidirectional semiconductor device, and the bidirectional semiconductor device comprises a bidirectional thyristor, a bidirectional silicon controlled rectifier or a bidirectional integrated gate-commutated thyristor.

4. The grid-forming energy storage converter of any of claims 1-3, wherein, The application further comprises a current limiting unit connected to one end of the switching device and the other end of the electrochemical cell, for limiting the current between the conversion unit and the electrochemical cell when the switching device is in the closing state.

5. The network infrastructure energy storage converter of claim 1, wherein, The current limiting unit is an inductor, a resistor or an inductor in parallel / series resistor.

6. The network infrastructure energy storage converter of claim 5, wherein, The conversion unit comprises a DC capacitor connected to one end of the switching device and the electrochemical cell in parallel, for storing electric charge and blocking DC current.

7. The network infrastructure energy storage converter of claim 1, wherein, The DC capacitor is a conventional capacitor, a super capacitor or a conventional capacitor in parallel with a super capacitor.

8. The network infrastructure energy storage converter of claim 7, wherein, The conversion unit is a two-level topology, a three-level topology or a sub-module topology of a modular multilevel converter.

9. The network infrastructure energy storage converter of claim 1, wherein, The application is applied to the network-constructing energy storage converter of any one of claims 1-9, comprising:

10. A control method of a grid-forming energy storage converter, characterized by, controlling the conversion unit to convert AC power into DC power according to a conversion instruction; controlling the electrochemical cell to store or release electric energy according to the conversion instruction; controlling the switching device to close the conversion unit and the electrochemical cell according to a closing instruction, and opening the connection between the conversion unit and the electrochemical cell according to an opening instruction, wherein one end of the switching device is connected to the conversion unit and the other end is connected to the electrochemical cell. The application further comprises:

11. The control method of the network configuration type energy storage converter according to claim 10, characterized by, Step 2: judging whether the switching device is in the closing state, if yes, executing step 4, if not, executing step 3; Step 1: judging the relationship between the absolute value of active power instruction and power threshold value P th , in the first state that the absolute value of active power instruction is greater than the power threshold value P th , executing Step 2, in the non-first state, entering Step 6; Step 3: controlling the switching device to close, and executing step 4; Step 4: judging whether the control mode is an active power control mode, if yes, executing step 1, if not, executing step 5; Step 5: switching the control mode to the active power control mode, and executing step 1; Step 6: judging whether it is a transient mode, if yes, executing step 2, if not, executing step 7; ​ Step 7: judging whether the combining and separating device is in an open state, if yes, executing step 9, if not, executing step 8; Step 8: controlling the combining and separating device to be open, and executing step 9; Step 9: judging whether the control mode is a direct current voltage control mode, if yes, executing step 1, if not, executing step 10; Step 10: switching the control mode to the direct current voltage control mode, and executing step 1.

12. The control method of the network configuration type energy storage converter according to claim 11, characterized by, The judging whether it is a transient mode comprises: The voltage of the DC capacitor and the port voltage of the electrochemical cell are acquired, and a voltage difference is calculated; when the absolute value of the voltage difference is greater than a voltage threshold value U th and the duration t 11 is greater than a time threshold value t , it is determined that it is in a transient mode; or, Obtaining an AC active power of the network-configuration type energy storage converter, a transient power threshold value P th1 ; when an absolute value of the AC active power is greater than the P th1 , and a duration t 12 , it is determined that it is a transient mode.

13. An electronic device, comprising: Comprising: A processor; A memory, which stores a computer program, when the computer program is executed by the processor, the processor executes the control method of the network-constructed energy storage converter as claimed in any one of claims 10-12.

14. A non-transitory computer-readable storage medium, comprising: A computer readable instruction is stored thereon, when the instruction is executed by a processor, the processor executes the control method of the network-constructed energy storage converter as claimed in any one of claims 10-12.

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