Method and device for controlling virtual impedance of energy storage converter, and energy storage converter

Abstract

The application provides a control method and device of virtual impedance of an energy storage converter and the energy storage converter, and relates to the technical field of energy storage. The method comprises the following steps: obtaining a first drop depth of a grid voltage; judging whether the first drop depth is less than a set value; if it is judged that the first drop depth is less than the set value, generating an angle estimation value according to an obtained active power and a power angle; according to a corresponding relationship between the active power, the power angle estimation value and the virtual impedance, querying out a virtual impedance corresponding to the active power and the power angle estimation value; and if it is judged that the virtual impedance meets a set impedance range, adding the virtual impedance to a VSG control module. The application realizes the self-adaptation of the virtual impedance, thereby realizing the self-adaptation of the grid voltage and frequency, and further realizing that the energy storage converter does not need to be switched to a grid-connected type converter control strategy during low-voltage ride-through.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to a method, apparatus and energy storage converter for controlling the virtual impedance of an energy storage converter. Background Technology

[0002] Currently, the installed capacity of wind power, solar power, and biomass power generation is continuously expanding, and new energy sources are accounting for an increasingly larger proportion of traditional thermal power generation. When connecting new energy sources to the grid, they often adopt phase-locked loop (PLL) voltage control to regulate output current. Grid-connected converters represent a new trend in converter technology development. Adopting grid-connected converters requires improvements to the control strategies of existing converters to adapt to the transient and stability requirements of the system. In the face of grid voltage fluctuations, low-voltage ride-through is a key technical indicator, making the control strategies employed for low-voltage ride-through particularly important.

[0003] In the prior art, during low-voltage ride-through, the power conversion system (PCS) typically needs to switch to the control strategy of the grid-connected converter. Summary of the Invention

[0004] In view of this, embodiments of this application provide a method, apparatus and energy storage converter for controlling the virtual impedance of an energy storage converter, which is used to achieve the self-adaptation of virtual impedance, thereby achieving the self-adaptation of grid voltage and frequency, and thus realizing the control strategy of the energy storage converter not needing to switch to a grid-connected converter during low-voltage ride-through.

[0005] The first aspect provides a method for controlling the virtual impedance of an energy storage converter, including:

[0006] Obtain the first voltage drop depth of the grid;

[0007] Determine whether the first drop depth is less than a set value;

[0008] If it is determined that the first drop depth is less than the set value, the estimated value of the power angle is generated based on the obtained active power and power angle.

[0009] Based on the established correspondence between active power, estimated power angle, and virtual impedance, the virtual impedance corresponding to the active power and estimated power angle is retrieved.

[0010] If it is determined that the virtual impedance meets the set impedance range, the virtual impedance is added to the VSG control module.

[0011] In one possible implementation, the method for controlling the virtual impedance of the energy storage converter when it is determined that the first drop depth is less than the set value further includes:

[0012] generate a reactive current value according to the first dip depth;

[0013] output the reactive current value to a power grid, so that the power grid adjusts the grid voltage through the reactive current value.

[0014] In a possible implementation, after the virtual impedance is added to the VSG control module, the method further includes:

[0015] obtaining a second dip depth of the grid voltage;

[0016] determining whether the second dip depth is greater than or equal to the set value;

[0017] if it is determined that the second dip depth is greater than or equal to the set value, controlling the virtual impedance to exit from the VSG control module.

[0018] In a possible implementation, the method for controlling the virtual impedance of the energy storage converter further includes:

[0019] if it is determined that the second dip depth is less than the set value, continuing to perform the step of obtaining the first dip depth of the grid voltage.

[0020] In a possible implementation, the method for controlling the virtual impedance of the energy storage converter further includes:

[0021] if it is determined that the first dip depth is greater than or equal to the set value, controlling the virtual impedance to exit from the VSG control module.

[0022] In a possible implementation, the generating an angle estimation value according to the obtained active power and power angle includes:

[0023] generating the active power according to the obtained impedance angle, power angle, grid voltage, line reactance and synchronous generator terminal voltage;

[0024] generating a power angle fluctuation estimation proportionality coefficient according to the active power and the power angle;

[0025] generating the power angle estimation value according to the power angle fluctuation estimation proportionality coefficient, the active power and steady-state operating point output power.

[0026] In a possible implementation, the generating the power angle estimation value according to the power angle fluctuation estimation proportionality coefficient, the active power and steady-state operating point output power includes:

[0027] multiplying a difference between the active power and the steady-state operating point output power by the power angle fluctuation estimation proportionality coefficient to generate the power angle estimation value.

[0028] In a possible implementation, the virtual impedance comprises a virtual resistance and a virtual reactance; and before the querying the virtual impedance corresponding to the active power and the power angle estimation value according to the correspondence between the active power, the power angle estimation value and the virtual impedance, the method further comprises:

[0029] obtaining a plurality of historical active powers and historical power angle estimation values corresponding to each of the historical active powers;

[0030] generating a virtual resistance corresponding to each of the historical power angle estimation values according to each of the historical power angle estimation values and a reference reactance;

[0031] generating a virtual reactance corresponding to each of the historical power angle estimation values according to each of the historical power angle estimation values and a reference resistance;

[0032] establishing a correspondence between the active power, the power angle estimation value and the virtual impedance according to the plurality of historical active powers, the historical power angle estimation values corresponding to each of the historical active powers and the virtual impedance corresponding to each of the historical power angle estimation values.

[0033] The second aspect provides a virtual impedance control device of an energy storage converter, comprising:

[0034] an obtaining module configured to obtain a first drop depth of a grid voltage;

[0035] a first judging module configured to judge whether the first drop depth is less than a set value;

[0036] a first generating module configured to generate a power angle estimation value according to the obtained active power and power angle, if the first judging module judges that the first drop depth is less than the set value;

[0037] a querying module configured to query a virtual impedance corresponding to the active power and the power angle estimation value according to a correspondence between the active power, the power angle estimation value and the virtual impedance;

[0038] a second judging module configured to judge whether the virtual impedance meets a set impedance range;

[0039] a control module configured to add the virtual impedance to a VSG control module, if the second judging module judges that the virtual impedance meets the set impedance range.

[0040] In a possible implementation, the virtual impedance control device of the energy storage converter further comprises a third judging module;

[0041] the obtaining module is further configured to obtain a second drop depth of the grid voltage;

[0042] the third judging module is configured to judge whether the second drop depth is greater than or equal to the set value.

[0043] The control module is further configured to control the virtual impedance to exit from the VSG control module if the third judging module judges that the second dip depth is greater than or equal to the set value.

[0044] In a possible implementation, the third judging module is further configured to trigger the acquisition module to continue to acquire the first dip depth of the grid voltage if it is judged that the second dip depth is less than the set value.

[0045] In a possible implementation, the control module is further configured to control the virtual impedance to exit from the VSG control module if the first judging module judges that the first dip depth is greater than or equal to the set value.

[0046] In a possible implementation, the first generating module is specifically configured to generate the active power according to the acquired impedance angle, power angle, grid voltage, line reactance and synchronous generator terminal voltage; generate the power angle estimation value according to the active power and the power angle estimation value, and the active power and the steady-state operating point output power.

[0047] The third aspect provides a control device of a virtual impedance of a storage converter.

[0048] The fourth aspect provides a storage system, which comprises the storage converter in the third aspect.

[0049] The application has the following beneficial effects:

[0050] In the technical scheme provided by the application, if it is judged that the first dip depth of the grid voltage is less than the set value, the power angle estimation value is generated according to the acquired active power and power angle, and the virtual impedance corresponding to the active power and power angle estimation value is queried according to the corresponding relationship between the active power, power angle estimation value and virtual impedance, and if it is judged that the virtual impedance meets the set impedance range, the virtual impedance is added to the VSG control module. The virtual impedance is determined by the corresponding relationship between the active power, power angle estimation value and virtual impedance, the adaptive virtual impedance is realized, the adaptive grid voltage and frequency are realized, and the storage converter does not need to switch to the control strategy of the grid-connected type converter during the low-voltage ride-through period. BRIEF DESCRIPTION OF DRAWINGS

[0051] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can be obtained based on these drawings without creative labor.

[0052] Figure 1 A flow chart of a method for controlling virtual impedance of an energy storage converter provided in an embodiment of the present application;

[0053] Figure 2 A flow chart of a method for generating power angle estimation provided in an embodiment of the present application;

[0054] Figure 3 A flow chart of a method for establishing a corresponding relationship between active power, power angle estimation and virtual impedance provided in an embodiment of the present application;

[0055] Figure 4 A structural schematic diagram of a virtual impedance control device of an energy storage converter provided in an embodiment of the present application;

[0056] Figure 5 A structural schematic diagram of a main controller provided in an embodiment of the present application. DETAILED DESCRIPTION

[0057] In order to better understand the technical solutions of the present application, the embodiments of the present application will be described in detail below with reference to the drawings.

[0058] It should be clear that the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0059] The terms used in the embodiments of the present application are only for the purpose of describing the specific embodiments, and are not intended to limit the present application. The singular forms "a", "an" and "the" 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.

[0060] It should be understood that the term "and / or" used herein is only to describe the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects are a "or" relationship.

[0061] In the embodiment of the present application, the energy storage converter can adopt a grid-forming converter, the grid-forming converter can output voltage and frequency inside, and can realize grid-connected and off-grid switching. The grid-forming converter can adopt the principle of simulating a synchronous generator, adopt a virtual synchronous generator (VSG) control strategy, and the VSG control strategy can solve the low inertia problem caused by the access of large-scale distributed power generation equipment to the power grid. The VSG can simulate the frequency and voltage regulation capability of the synchronous generator, and can also simulate the inertia and damping of the synchronous generator, so that the anti-interference capability of the grid-forming converter is greatly enhanced, and the stability of the power grid operation is improved. In the embodiment of the present application, when the power grid is in a low-voltage ride-through state, the VSG control strategy is used to synchronize the power grid.

[0062] In the embodiment of the present application, the DC side of the energy storage converter is connected to a DC power supply, and the AC side of the energy storage converter is connected to the power grid. The energy storage converter can include a main controller, and the main controller can include a VSG control module. The control method of the virtual impedance of the energy storage converter provided in the embodiment of the present application can be executed by the main controller.

[0063] Figure 1 A flowchart of a control method of a virtual impedance of an energy storage converter provided in the embodiment of the present application is shown in Figure 1 The method comprises the following steps.

[0064] Step 102: Obtain a first drop depth of a power grid voltage.

[0065] When the energy storage converter is in a normal operation mode, the main controller obtains the first drop depth of the power grid voltage in response to the energy storage converter being in the normal operation mode.

[0066] Step 102 can specifically include that the main controller detects the current first power grid voltage, and takes the ratio of the first power grid voltage to the rated voltage of the energy storage converter as the first drop depth. That is, the first drop depth = the first power grid voltage / the rated voltage.

[0067] Step 104: Determine whether the first drop depth is less than a set value, if yes, execute step 106; if no, execute step 120.

[0068] In the embodiment of the present application, if it is determined that the first drop depth is less than the set value, it indicates that the power grid is in a low-voltage ride-through state, and step 106 can be continuously executed; if it is determined that the first drop depth is equal to the set value, it indicates that the power grid is in a normal operation state, and step 120 can be continuously executed.

[0069] In the embodiment of the present application, the setting of the set value can be set as needed, for example, the set value can be 0.9. In actual application, the set value can also be set to other values, which is not limited in the embodiment of the present application.

[0070] Step 106, generating a reactive current value according to the first drop depth, and outputting the reactive current value to the power grid to make the power grid adjust the power grid voltage through the reactive current value.

[0071] Specifically, the power grid can multiply the reactive current value by the rated power grid phase voltage to obtain a multiplication result, and then multiply the multiplication result by to obtain the reactive power, and adjust the power grid voltage according to the reactive power.

[0072] The VSG control module simulates the primary frequency modulation characteristic of a traditional synchronous generator, and the reactive current value and the power grid voltage are controlled through droop control. During low-voltage ride-through, the given reactive power is replaced with the droop control, so as to quickly reach the power grid balance state.

[0073] In the embodiment of the application, the reactive current value is generated according to the first drop depth, so that the power grid adjusts the power grid voltage through the reactive current value, realizes reactive current compensation, can adjust the reactive power when the power grid voltage drops or rises, reduces the power grid voltage fluctuation, thereby being conducive to the stability of the power grid system, protecting the normal operation of the key equipment and ensuring that the key equipment does not be off-grid; at the same time, the line reactive power loss can be reduced, the overall power transmission efficiency is improved, and the quality of the power grid is improved.

[0074] As an optional solution, the main controller can calculate the reactive current value through the following formula:

[0075]

[0076] wherein, the reactive current value is Iq, the first drop depth is ΔV, and the rated current of the energy storage converter is Icr.

[0077] The reactive current value calculated by the above formula can achieve the effect of reactive current compensation, thereby stabilizing the power grid voltage.

[0078] Step 108, generating an angle estimation value according to the obtained active power and power angle.

[0079] As an optional solution, Figure 2 a flowchart of a method for generating an angle estimation value provided in the embodiment of the application is shown in FIG. 8, and step 108 specifically can include: Figure 2

[0080] Step 1082, generating the active power according to the obtained impedance angle, power angle, power grid voltage, line reactance and synchronous generator terminal voltage.

[0081] The main controller can calculate the active power through the formula: ​, the active power is calculated. Wherein, is the active power, is the grid voltage, is the synchronous generator terminal voltage, is the line reactance, is the impedance angle, is the power angle.

[0082] The main controller calculates the active power through the above formula, which reflects the influence of the change of the power angle on the active power.

[0083] Step 1084, generating the power angle fluctuation estimation proportionality coefficient according to the active power and the power angle.

[0084] When the grid is in the low-voltage ride-through state, the virtual impedance is greatly affected by the power angle fluctuation, and needs to be adjusted in real time according to the change of the power angle. In order to realize the adjustment of the virtual impedance, the power angle fluctuation estimation proportionality coefficient needs to be calculated first.

[0085] As an optional solution, step 1084 can specifically include:

[0086] Step S11, calculating the partial derivative linearization approximation processing number of the active power and the power angle according to the impedance angle, the power angle, the grid voltage and the line reactance.

[0087] The main controller can calculate the partial derivative linearization approximation processing number of the active power and the power angle through the formula: D( ) ) is the partial derivative linearization approximation processing number of the active power and the power angle, is the grid voltage, is the line reactance, is the impedance angle, is the power angle.

[0088] Wherein, the partial derivative of the formula in step 1082 is obtained to obtain D( ).

[0089] Step S12, taking the reciprocal of the sum of the partial derivative linearization approximation processing number and the correction parameter as the power angle fluctuation estimation proportionality coefficient.

[0090] Wherein, the correction parameter can be k , k is the correction coefficient, is the impedance angle deviation value.

[0091] In the embodiment of the present application, the partial derivative linearization approximation number of the active power and the power angle is calculated according to the impedance angle, the power angle, the grid voltage and the line reactance, and the reciprocal of the sum of the partial derivative linearization approximation number and the correction parameter is taken as the power angle fluctuation estimation proportion coefficient, so that the power angle fluctuation estimation proportion coefficient is calculated in real time, and the virtual impedance is updated and optimized in real time.

[0092] In step 1086, the power angle estimation value is generated according to the power angle fluctuation estimation proportion coefficient, the active power and the steady-state operating point output power.

[0093] As an optional solution, the main controller multiplies the difference between the active power and the steady-state operating point output power by the power angle fluctuation estimation proportion coefficient to generate the power angle estimation value. That is, the main controller can calculate the power angle estimation value through the formula: K( ), wherein the power angle estimation value is K, the power angle fluctuation estimation proportion coefficient is K, the active power is P, and the steady-state operating point output power is P0.

[0094] In the embodiment of the present application, the power angle estimation value is generated by multiplying the difference between the active power and the steady-state operating point output power by the power angle fluctuation estimation proportion coefficient, the power angle estimation value can be calculated in real time, the real-time tracking of the power angle estimation value is realized, the power angle estimation value can be accurately calculated, and the virtual impedance is updated and optimized in real time.

[0095] As can be known from the power and frequency response model of the VSG, the active power is greatly increased or the grid frequency is significantly reduced, which will form the increase of the power angle and the significant deviation of the reactive power. In the embodiment of the present application, when the power angle changes, the power angle estimation value can be calculated through steps 1082 to 1086, the simplified estimation method is adopted, the local linearization processing is adopted near the steady-state operating point, and the optimal power angle estimation value is obtained through the correction parameter, so that the calculated power angle estimation value is more accurate, the VSG control strategy is more perfect, the adaptive virtual impedance design can be better realized, the influence of the active power on the reactive power is solved, the perfect VSG control strategy is used in the special working condition of the low-voltage ride-through, the working stability of the energy storage converter is significantly enhanced, and thus the grid quality is improved.

[0096] In step 110, the virtual impedance corresponding to the active power and the power angle estimation value is queried according to the corresponding relationship between the set active power, the power angle estimation value and the virtual impedance.

[0097] ​​​As an alternative, the main controller can set up a table which can be used to store the correspondence between the active power, the power angle estimation value and the virtual impedance. Then, when performing step 110, the main controller can query the table to obtain the virtual impedance corresponding to the active power and the power angle estimation value.

[0098] In the embodiments of the present application, the virtual impedance is obtained through the correspondence between the active power, the power angle estimation value and the virtual impedance, so that the virtual impedance is quickly obtained.

[0099] As an alternative, the virtual impedance can include a virtual resistance Rv and a virtual inductive Lv.

[0100] In the embodiments of the present application, before step 110, the method further includes the step of establishing the correspondence between the active power, the power angle estimation value and the virtual impedance.

[0101] Figure 3 A flow chart of a method for establishing the correspondence between the active power, the power angle estimation value and the virtual impedance provided by the embodiments of the present application is shown in FIG. 11, which can specifically include the following steps. Figure 3

[0102] Step 1102, obtaining a plurality of historical active powers and historical power angle estimation values corresponding to each historical active power.

[0103] In the embodiments of the present application, during the process of controlling the virtual impedance multiple times before the present time of controlling the virtual impedance, the active power and the power angle estimation value are generated, which can be generated by using the calculation method in step 108. Here, the active power generated during the process of controlling the virtual impedance multiple times before can be referred to as the historical active power, and the power angle estimation value generated during the process of controlling the virtual impedance multiple times before can be referred to as the historical power angle estimation value.

[0104] Step 1104, generating the virtual resistance corresponding to each historical power angle estimation value according to each historical power angle estimation value and the reference inductive.

[0105] As an alternative, the virtual resistance can be calculated by the formula: Rv = K1* Lv, where K1 is a constant coefficient. Rv is the virtual resistance, Lv is the reference inductive, is the historical power angle estimation value, and K1 is the constant coefficient.

[0106] Step 1106, generating the virtual inductive corresponding to each historical power angle estimation value according to each historical power angle estimation value and the reference resistance.

[0107] As an alternative, the virtual inductive can be calculated by the formula: Lv = K2* Rv, where K2 is a constant coefficient. ​​​a virtual resistance, a reference resistance, a historical power angle estimation value, a constant coefficient.

[0108] The virtual resistance generated by step 1104 and the virtual reactance generated by step 1106 form a virtual impedance, which includes the virtual resistance and the virtual reactance .

[0109] In the embodiments of the present application, the virtual impedance corresponding to each historical power angle estimation value is generated according to each historical power angle estimation value and the reference reactance, and the virtual reactance corresponding to each historical power angle estimation value is generated according to each historical power angle estimation value and the reference resistance, so as to obtain the virtual impedance corresponding to each historical power angle estimation value. The calculation method is simple and easy to implement, thereby facilitating the establishment of the corresponding relationship between the active power, the power angle estimation value and the virtual impedance.

[0110] Step 1108: establishing the corresponding relationship between the active power, the power angle estimation value and the virtual impedance according to the plurality of historical active powers, the historical power angle estimation value corresponding to each historical active power and the virtual impedance corresponding to each historical power angle estimation value.

[0111] In the embodiments of the present application, the corresponding relationship between the active power, the power angle estimation value and the virtual impedance is a nonlinear relationship.

[0112] As an optional solution, the main controller can be provided with a table, which can be used to store the corresponding relationship between the active power, the power angle estimation value and the virtual impedance. In other words, the corresponding relationship between the active power, the power angle estimation value and the virtual impedance can be stored in the main controller in the form of a table.

[0113] In the embodiments of the present application, the corresponding relationship between the active power, the power angle estimation value and the virtual impedance can be established only according to the plurality of historical active powers, the historical power angle estimation value corresponding to each historical active power and the virtual impedance corresponding to each historical power angle estimation value. The establishment method is simple, and the virtual impedance corresponding to the active power and the power angle estimation value can be conveniently queried through the established corresponding relationship, thereby realizing the rapid acquisition of the virtual impedance and the real-time change of the corresponding relationship according to the needs.

[0114] Step 112: judging whether the virtual impedance meets the set impedance range. If yes, step 114 is performed; if no, step 102 is performed.

[0115] As an optional solution, the impedance range can be: wherein, a virtual reactance, a virtual resistance, a reference inductive reactance, a reference resistance, a steady-state angular frequency, a long-term current-carrying coefficient, a peak current-carrying coefficient of the converter.

[0116] In the embodiments of the present application, if the main controller judges that the virtual impedance meets the above impedance range, it indicates that the virtual impedance has the condition to join the VSG control module, and can join the VSG control module; if the main controller judges that the virtual impedance does not meet the above impedance range, it indicates that the virtual impedance does not have the condition to join the VSG control module, and cannot join the VSG control module. The above impedance range can be used to more accurately judge whether the virtual impedance has the condition to join the VSG control module.

[0117] Step 114: the virtual impedance is added to the VSG control module.

[0118] In the embodiments of the present application, the virtual impedance is added to the VSG control module, so that the output voltage of the energy storage converter and the grid voltage are kept in phase and amplitude synchronization.

[0119] Step 116: a second drop depth of the grid voltage is obtained.

[0120] In the embodiments of the present application, step 116 can specifically include: the main controller detects the current second grid voltage, and takes the ratio of the second grid voltage to the rated voltage of the energy storage converter as the second drop depth. That is: the second drop depth = the second grid voltage / the rated voltage.

[0121] Step 118: it is judged whether the second drop depth is greater than or equal to a set value, if yes, step 120 is executed; if no, step 102 is executed.

[0122] In the embodiments of the present application, if it is judged that the second drop depth is greater than or equal to the set value, it indicates that the grid is in a normal operation state, and step 120 can be continuously executed.

[0123] In the embodiments of the present application, if it is judged that the second drop depth is less than the set value, it indicates that the grid is in a low-voltage ride-through state, and step 102 can be continuously executed to continue the control process of the virtual impedance, so as to realize the self-adaptation of the virtual impedance, thereby realizing the self-adaptation of the grid voltage and frequency, and further realizing that the energy storage converter does not need to switch to the control strategy of the grid-connected converter during the low-voltage ride-through.

[0124] Step 120: the virtual impedance is controlled to exit from the VSG control module.

[0125] In the embodiment of the application, during normal operation, the VSG control module has a frequency modulation and inertia characteristic, has voltage and frequency adaptability, and meets the grid connection requirement, so that the main controller can control the virtual impedance to exit from the VSG control module within a specified time, i.e., remove the virtual impedance and restore the conventional adaptive control.

[0126] In the embodiment of the application, after step 120 is performed, step 102 can be continuously performed to continue to control the virtual impedance.

[0127] In the technical scheme provided by the embodiment of the application, if it is judged that the first drop depth of the grid voltage is less than the set value, the virtual impedance is generated according to the acquired active power and power angle estimation value, the corresponding relationship between the active power, the power angle estimation value and the virtual impedance is set, the virtual impedance corresponding to the active power and the power angle estimation value is queried, and if it is judged that the virtual impedance meets the set impedance range, the virtual impedance is added to the VSG control module. In the embodiment of the application, the virtual impedance is determined according to the corresponding relationship between the active power, the power angle estimation value and the virtual impedance, the adaptive virtual impedance is realized, the adaptive grid voltage and frequency are realized, and thus the control strategy of the energy storage converter does not need to be switched to the grid-connected type converter during the low-voltage ride-through period.

[0128] In the embodiment of the application, during the low-voltage ride-through period, the VSG control strategy is used to synchronize the grid, which essentially decouples the influence of the active power on the reactive power. When the power angle is large, the coupling degree is strong. In the embodiment of the application, the virtual impedance is determined according to the corresponding relationship between the active power, the power angle estimation value and the virtual impedance, the real-time updating of the virtual impedance is realized, the coupling influence is eliminated, and the power angle is compensated. The scheme of the embodiment of the application realizes the dynamic adaptive virtual impedance, eliminates the influence of the active power, and thus guarantees the rapid response of the voltage phase and the frequency.

[0129] Figure 4 A structure diagram of a virtual impedance control device of an energy storage converter provided in the embodiment of the application is shown in FIG. 1. Figure 4 As shown in FIG. 1, the device includes an acquisition module 11, a first judgment module 12, a first generation module 13, a query module 14, a second judgment module 15 and a control module 16.

[0130] The acquisition module 11 is configured to acquire a first drop depth of a grid voltage; the first judging module 12 is configured to judge whether the first drop depth is less than a set value; the first generating module 13 is configured to generate an angle estimation value according to an acquired active power and an angle if the first judging module 12 judges that the first drop depth is less than the set value; the querying module 14 is configured to query a virtual impedance corresponding to the active power and the angle estimation value according to a set corresponding relationship between the active power, the angle estimation value and the virtual impedance; the second judging module 15 is configured to judge whether the virtual impedance meets a set impedance range; and the control module 16 is configured to add the virtual impedance to a VSG control module if the second judging module 15 judges that the virtual impedance meets the set impedance range.

[0131] In a possible implementation, the device further comprises a second generating module 17 and an output module 18.

[0132] The second generating module 17 is configured to generate a reactive current value according to the first drop depth; and the output module 18 is configured to output the reactive current value to a grid, so that the grid adjusts the grid voltage through the reactive current value.

[0133] In a possible implementation, the device further comprises a third judging module 19.

[0134] The acquisition module 11 is further configured to acquire a second drop depth of the grid voltage; the third judging module 19 is configured to judge whether the second drop depth is greater than or equal to the set value; and the control module 16 is further configured to control the virtual impedance to exit from the VSG control module if the third judging module 19 judges that the second drop depth is greater than or equal to the set value.

[0135] In a possible implementation, the third judging module 19 is further configured to trigger the acquisition module 11 to continue to perform the step of acquiring the first drop depth of the grid voltage if it is judged that the second drop depth is less than the set value.

[0136] In a possible implementation, the control module 16 is further configured to control the virtual impedance to exit from the VSG control module if the first judging module 12 judges that the first drop depth is greater than or equal to the set value.

[0137] In a possible implementation, the first generating module 13 is specifically configured to generate the active power according to an acquired impedance angle, an angle, a grid voltage, a line reactance and a synchronous generator terminal voltage; generate the angle fluctuation estimation proportional coefficient according to the active power and the angle; and generate the angle estimation value according to the angle fluctuation estimation proportional coefficient, the active power and a steady-state operating point output power.

[0138] In a possible implementation, the virtual impedance includes a virtual resistance and a virtual reactance, and the apparatus further includes an establishing module 20. The establishing module 20 is configured to establish a correspondence between the active power, the power angle estimation value and the virtual impedance.

[0139] Specifically, the establishing module 20 can be configured to obtain a plurality of historical active powers and a historical power angle estimation value corresponding to each of the historical active powers; generate, according to each of the historical power angle estimation values and a reference reactance, a virtual resistance corresponding to each of the historical power angle estimation values; generate, according to each of the historical power angle estimation values and a reference resistance, a virtual reactance corresponding to each of the historical power angle estimation values; and establish, according to the plurality of historical active powers, the historical power angle estimation value corresponding to each of the historical active powers and the virtual impedance corresponding to each of the historical power angle estimation values, the correspondence between the active power, the power angle estimation value and the virtual impedance.

[0140] In a possible implementation, the second judging module 15 is further configured to, if it is judged that the virtual impedance does not satisfy the set impedance range, trigger the obtaining module 11 to continue to perform the step of obtaining the first drop depth of the grid voltage.

[0141] In the technical scheme provided in the embodiments of the present application, if it is judged that the first drop depth of the grid voltage is less than the set value, the power angle estimation value is generated according to the obtained active power and power angle, the virtual impedance corresponding to the active power and the power angle estimation value is queried according to the set correspondence between the active power, the power angle estimation value and the virtual impedance, and if it is judged that the virtual impedance satisfies the set impedance range, the virtual impedance is added to the VSG control module. In the embodiments of the present application, the virtual impedance is determined through the correspondence between the active power, the power angle estimation value and the virtual impedance, the adaptive virtual impedance is realized, the adaptive grid voltage and frequency are realized, and thus the control strategy of the energy storage converter does not need to be switched to the grid-connected type during the low-voltage ride-through period.

[0142] The embodiments of the present application provide an energy storage converter, which can include a control device of a virtual impedance of the energy storage converter. The control device of the virtual impedance of the energy storage converter can adopt the control device of the virtual impedance of the energy storage converter in the embodiments shown in the above, and details are not described herein. Figure 4

[0143] In the embodiments of the present application, as an optional solution, the control device of the virtual impedance of the energy storage converter can be applied to a main controller, that is, the main controller includes the control device of the virtual impedance of the energy storage converter.

[0144] The embodiments of the present application provide an energy storage system, which can include the energy storage converter in the above embodiments, and details are not described herein.

[0145] ​The embodiment of the present application provides a computer readable storage medium, the computer readable storage medium comprises a stored program, wherein the program controls the controller where the computer readable storage medium is located to execute the embodiment of the control method of the virtual impedance of the energy storage converter when the program is running.

[0146] The embodiment of the present application provides a main controller, comprising: one or more processors; a memory; and one or more computer programs, wherein the one or more computer programs are stored in the memory, and the one or more computer programs comprise instructions, when the instructions are executed by the main controller, the main controller executes the embodiment of the control method of the virtual impedance of the energy storage converter.

[0147] Figure 5 The main controller provided by the embodiment of the present application is shown in a structural schematic diagram as shown in the figure, Figure 5 The main controller 30 of the embodiment comprises a processor 31, a memory 32, and a computer program 33 stored in the memory 32 and executable on the processor 31, and the computer program 33 is executed by the processor 31 to realize the control method of the virtual impedance applied to the energy storage converter in the embodiment, to avoid repetition, which will not be described one by one.

[0148] The main controller 30 comprises, but is not limited to, the processor 31 and the memory 32. Those skilled in the art can understand that, Figure 5 The main controller 30 is only an example and does not constitute a limitation on the main controller 30, and can comprise more or fewer components than the diagram, or combine certain components, or different components, for example, the main controller 30 can also comprise an input and output device, a network access device, a bus, etc.

[0149] The processor 31 can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor.

[0150] The memory 32 can be an internal storage unit of the host controller 30, such as a hard disk or a memory of the host controller 30. The memory 32 can also be an external storage device of the host controller 30, such as a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) card, a Flash Card, etc. equipped on the host controller 30. Further, the memory 32 can include both an internal storage unit and an external storage device of the host controller 30. The memory 32 is used to store computer programs and other programs and data required by the network device. The memory 32 can also be used to temporarily store data that has been output or will be output.

[0151] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the system, device and unit described above can refer to the corresponding processes in the foregoing method embodiments, which will not be repeated here.

[0152] In several embodiments provided in the present application, it should be understood that the disclosed system, device and method can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division, and actual implementation can have another division manner. For example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some interface, device or unit, and can be electrical, mechanical or other forms.

[0153] The units described as separate components can or can not be physically separate, and the components shown as units can or can not be physical units, i.e. can be located in one place or distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the embodiment.

[0154] In addition, each functional unit in each embodiment of the present application can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or in the form of hardware plus software functional units.

[0155] The integrated unit implemented in the form of software function unit can be stored in a computer readable storage medium. The software function unit stored in the computer readable storage medium includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) or a processor to execute part of steps of the method described in various embodiments of the present application. The computer readable storage medium described above includes a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and various media capable of storing program codes.

[0156] The above merely provides the preferred embodiments of the present application, but is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for controlling the virtual impedance of an energy storage converter, characterized in that, include: Obtain the first voltage drop depth of the grid; Determine whether the first drop depth is less than a set value; If it is determined that the first drop depth is less than the set value, the estimated value of the power angle is generated based on the obtained active power and power angle. Based on the established correspondence between active power, estimated power angle, and virtual impedance, the virtual impedance corresponding to the active power and estimated power angle is retrieved. If it is determined that the virtual impedance meets the set impedance range, the virtual impedance is added to the VSG control module; The virtual impedance includes virtual resistance and virtual inductive reactance; before querying the virtual impedance corresponding to the active power and the estimated power angle based on the set correspondence between active power, estimated power angle, and virtual impedance, the method further includes: Obtain multiple historical active power values ​​and the corresponding historical power angle estimates for each historical active power value; Based on each historical power angle estimate and the reference inductive reactance, a virtual resistance corresponding to each historical power angle estimate is generated; Based on each historical power angle estimate and the reference resistance, a virtual inductive reactance corresponding to each historical power angle estimate is generated; Based on multiple historical active power values, the historical power angle estimates corresponding to each historical active power value, and the virtual impedance corresponding to each historical power angle estimate, a correspondence between active power, power angle estimates, and virtual impedance is established.

2. The method for controlling the virtual impedance of an energy storage converter according to claim 1, characterized in that, The method for controlling the virtual impedance of the energy storage converter when it is determined that the first drop depth is less than the set value further includes: Based on the first drop depth, generate the reactive current value; The reactive current value is output to the power grid so that the power grid can regulate the grid voltage through the reactive current value.

3. The method for controlling the virtual impedance of an energy storage converter according to claim 1, characterized in that, After adding the virtual impedance to the VSG control module, the method further includes: Obtain the second voltage drop depth of the grid voltage; Determine whether the second drop depth is greater than or equal to the set value; If it is determined that the second drop depth is greater than or equal to the set value, the virtual impedance is controlled to exit the VSG control module.

4. The method for controlling the virtual impedance of an energy storage converter according to claim 3, characterized in that, The method for controlling the virtual impedance of the energy storage converter also includes: If it is determined that the second drop depth is less than the set value, the step of obtaining the first drop depth of the grid voltage continues.

5. The method for controlling the virtual impedance of an energy storage converter according to claim 1, characterized in that, The method for controlling the virtual impedance of the energy storage converter also includes: If it is determined that the first drop depth is greater than or equal to the set value, the virtual impedance is controlled to exit the VSG control module.

6. The method for controlling the virtual impedance of an energy storage converter according to any one of claims 1 to 5, characterized in that, The step of generating the power angle estimation value based on the obtained active power and power angle includes: The active power is generated based on the obtained impedance angle, power angle, grid voltage, line reactance, and synchronous generator terminal voltage. Based on the active power and the power angle, a proportionality coefficient for estimating power angle fluctuation is generated; The estimated power angle value is generated based on the power angle fluctuation estimation ratio, the active power, and the steady-state operating point output power.

7. The method for controlling the virtual impedance of an energy storage converter according to claim 6, characterized in that, The step of generating the estimated power angle value based on the power angle fluctuation estimation proportional coefficient, the active power, and the steady-state operating point output power includes: The difference between the active power and the steady-state operating point output power is multiplied by the power angle fluctuation estimation coefficient to generate the power angle estimation value.

8. A control device for the virtual impedance of an energy storage converter, characterized in that, include: The acquisition module is used to acquire the first voltage drop depth of the power grid. The first judgment module is used to determine whether the first drop depth is less than a set value; The first generation module is used to generate an estimated angle value based on the acquired active power and power angle if the first judgment module determines that the first drop depth is less than the set value. The query module is used to query the virtual impedance corresponding to the active power and the estimated power angle based on the set correspondence between active power, estimated power angle and virtual impedance. The second judgment module is used to determine whether the virtual impedance meets the set impedance range. The control module is used to add the virtual impedance to the VSG control module if the second judgment module determines that the virtual impedance meets the set impedance range. A module is established to obtain multiple historical active power values ​​and the corresponding historical power angle estimates for each historical active power value; based on each historical power angle estimate and the reference inductive reactance, a virtual resistance corresponding to each historical power angle estimate is generated; based on each historical power angle estimate and the reference resistance, a virtual inductive reactance corresponding to each historical power angle estimate is generated; based on multiple historical active power values, the corresponding historical power angle estimates for each historical active power value, and the corresponding virtual impedance, a correspondence between active power, power angle estimates, and virtual impedance is established.

9. The control device for the virtual impedance of the energy storage converter according to claim 8, characterized in that, The control device for the virtual impedance of the energy storage converter also includes: a third judgment module; The acquisition module is also used to acquire the second voltage drop depth of the power grid; The third judgment module is used to determine whether the second drop depth is greater than or equal to the set value; The control module is further configured to control the virtual impedance to exit the VSG control module if the third judgment module determines that the second drop depth is greater than or equal to the set value.

10. The control device for the virtual impedance of the energy storage converter according to claim 9, characterized in that, The third judgment module is also used to trigger the acquisition module to continue executing the step of acquiring the first drop depth of the grid voltage if it is determined that the second drop depth is less than the set value.

11. The control device for the virtual impedance of the energy storage converter according to claim 8, characterized in that, The control module is further configured to control the virtual impedance to exit the VSG control module if the first judgment module determines that the first drop depth is greater than or equal to the set value.

12. The control device for the virtual impedance of the energy storage converter according to any one of claims 8 to 11, characterized in that, The first generation module is specifically used to generate the active power based on the acquired impedance angle, power angle, grid voltage, line reactance and synchronous generator terminal voltage; generate the power angle fluctuation estimation ratio coefficient based on the active power and the power angle; and generate the power angle estimation value based on the power angle fluctuation estimation ratio coefficient, the active power and the steady-state operating point output power.

13. An energy storage converter, characterized in that, include: The device for controlling the virtual impedance of the energy storage converter according to any one of claims 8 to 12.

14. An energy storage system, characterized in that, include: The energy storage converter as described in claim 13.

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