Current limiting reactor parameter design method and device, electronic equipment and storage medium

Abstract

The invention discloses a current limiting reactor parameter design method and device, electronic equipment and a storage medium, and aims to solve the problem of how to more systematically and comprehensively design a port current limiting reactor so as to quickly suppress fault current when a power supply line fault occurs in an MACP-CHB-ESS system. Based on a current ripple constraint condition of the power supply line under a steady-state working condition, deducing a first lower limit constraint value of a current-limiting reactor of a port of the power supply line; determining a port current limiting reactor lower limit constraint value based on a port voltage minimum constraint condition of the non-fault power supply line under a transient condition in combination with the first lower limit constraint value; deducing an upper limit constraint value of a port current-limiting reactor based on a port short-circuit current minimum constraint condition of the fault power supply line under a transient condition; and according to the port current-limiting reactor lower limit constraint value and the port current-limiting reactor upper limit constraint value, determining a current-limiting reactor design value of each power supply line in the MACP-CHB-ESS system.

Description

Technical Field

[0001] The present invention relates to the technical field of power distribution, and particularly to a method and device for designing parameters of a current-limiting reactor, an electronic device, and a storage medium. Background Art

[0002] The traditional distribution network architecture is mainly radial, adopting the "closed-loop design and open-loop operation" mode. With the high proportion access and increasing penetration of new types of power sources and loads, the operation and protection design of the power supply lines in the distribution network will face huge challenges. Energy storage technology has the ability to transfer the energy flow in the time dimension, can smooth the system power fluctuation, cut peaks and fill valleys, improve the power quality, and enhance the power grid's ability to absorb new energy. It is an effective solution to cope with the grid connection of new energy.

[0003] The flexible interconnected distribution system of power source, grid, load, and energy storage is an integrated distribution system that combines power sources, grids, loads, and energy storage, and realizes flexible coordination and optimized management among various parts through flexible interconnection technology. The core of this system is to achieve intelligent distribution and dynamic regulation of power resources through advanced control technologies and distribution equipment, so as to improve energy utilization efficiency, enhance the stability and resilience of the power grid, and at the same time promote the efficient utilization of renewable energy. The multi-port cascaded H-bridge battery energy storage system (MACP-CHB-ESS) in the flexible interconnected distribution system of power source, grid, load, and energy storage is an advanced power electronic architecture, aiming to improve the flexibility, efficiency, and reliability of the battery energy storage system. This system connects different types of energy storage units in a cascaded manner through multiple H-bridge inverters and allows these units to interact efficiently with the power grid or other loads.

[0004] Through the MACP-CHB-ESS system, multiple medium-voltage AC ports can be interconnected with the same large-capacity energy storage system. However, due to the power interaction between multiple ports, when a fault occurs in a certain power supply line, it will lead to more complex voltage and current distribution characteristics in its fault state. It is easy to cause risks such as excessive fault current (which may trigger cascading faults in severe cases), damage to energy storage units, voltage sag or fluctuation, and local fault expansion. At the same time, the fault transmission will cause the voltage at non-fault ports to drop, which is not conducive to the operation of the system. Generally speaking, when the shared energy storage flexible interconnection device in the MACP-CHB-ESS system encounters a short-circuit fault, its impact is not limited to the device itself, but also brings profound negative effects on the stability and security of the entire power system, causing large-scale economic losses and potential safety hazards. Therefore, it is crucial to take effective limiting measures. Summary of the Invention

[0005] The present invention provides a method, device, electronic device and storage medium for designing parameters of a current-limiting reactor, which are used to solve or partially solve the technical problem of how to design a port current-limiting reactor more systematically and comprehensively to quickly suppress the fault current when a power supply line fault occurs in the MACP-CHB-ESS system.

[0006] The present invention provides a method for designing parameters of a current-limiting reactor, which is applicable to the MACP-CHB-ESS system in a flexible interconnected distribution system of source-network-load-storage. A current-limiting reactor is configured at the outlet of each power supply line in the MACP-CHB-ESS system. The method includes:

[0007] Based on the current ripple constraint condition of the power supply line under steady-state conditions, derive the first lower limit constraint value of the port current-limiting reactor of the power supply line;

[0008] Based on the minimum port voltage constraint condition of the non-fault power supply line under transient conditions, and in combination with the first lower limit constraint value, determine the lower limit constraint value of the port current-limiting reactor of the power supply line;

[0009] Based on the minimum port short-circuit current constraint condition of the fault power supply line under transient conditions, derive the upper limit constraint value of the port current-limiting reactor of the power supply line;

[0010] According to the lower limit constraint value of the port current-limiting reactor and the upper limit constraint value of the port current-limiting reactor, determine the design value of the current-limiting reactor of each power supply line in the MACP-CHB-ESS system.

[0011] Optionally, the MACP-CHB-ESS system includes a PFCM power flow control module. The step of deriving the first lower limit constraint value of the port current-limiting reactor of the power supply line based on the current ripple constraint condition of the power supply line under steady-state conditions includes:

[0012] Obtain the system switching frequency, the equivalent current-limiting reactor value of the power supply line and the DC bus voltage of the PFCM power flow control module under steady-state conditions;

[0013] According to the system switching frequency, the equivalent current-limiting reactor value and the DC bus voltage, with the constraint target of limiting the current ripple of the power supply line within the maximum current ripple value, construct the current ripple constraint condition of the power supply line;

[0014] According to the current ripple constraint condition, perform reverse derivation to determine the first lower limit constraint value of the port current-limiting reactor of the power supply line.

[0015] Optionally, the step of determining the lower limit constraint value of the port current-limiting reactor of the power supply line based on the minimum port voltage constraint condition of the non-fault power supply line under transient conditions and in combination with the first lower limit constraint value includes:

[0016] Obtain the equivalent electromotive force, equivalent impedance, and equivalent current of the non-faulty power supply line under transient conditions;

[0017] According to the equivalent electromotive force, the equivalent impedance, and the equivalent current, with suppressing the minimum value of the short-circuit current amplitude as the constraint objective, construct the minimum port voltage constraint condition;

[0018] Derive backward according to the minimum port voltage constraint condition to obtain the second lower limit constraint value of the current-limiting reactor at the port of the power supply line;

[0019] Determine the lower limit constraint value of the current-limiting reactor at the port of the power supply line according to the first lower limit constraint value and the second lower limit constraint value.

[0020] Optionally, the lower limit constraint value of the current-limiting reactor at the port of the power supply line is shown in the following formula:

[0021]

[0022] Wherein, is the value of the current-limiting reactor at the port; max represents taking the maximum value; , are respectively the first lower limit constraint value and the second lower limit constraint value of the current-limiting reactor at the port of the power supply line; is the DC bus voltage of the PFCM power flow control module; is the system switching frequency; is the preset maximum current ripple; is the equivalent current-limiting reactor value of the power supply line; , are respectively the equivalent electromotive force and equivalent impedance of the non-faulty power supply line under transient conditions; is the preset minimum port voltage; is the imaginary unit; is the angular frequency.

[0023] Optionally, deriving the upper limit constraint value of the current-limiting reactor at the port of the power supply line based on the minimum port short-circuit current constraint condition of the faulty power supply line under transient conditions includes:

[0024] Obtain the equivalent electromotive force and equivalent impedance of the non-faulty power supply line under transient conditions;

[0025] Calculate the short-circuit current flowing through the fault port of the faulty power supply line according to the equivalent electromotive force and the equivalent impedance;

[0026] Based on the short-circuit current flowing through the fault port of the faulty power supply line, with suppressing the maximum value of the short-circuit current amplitude as the constraint objective, construct the minimum port short-circuit current constraint condition;

[0027] Derive backward according to the minimum port short - circuit current constraint condition to obtain the upper - limit constraint value of the port current - limiting reactor of the power supply line.

[0028] Optionally, the upper - limit constraint value of the port current - limiting reactor of the power supply line is shown as the following formula:

[0029]

[0030] Wherein, is the value of the port current - limiting reactor; is the upper - limit constraint value of the port current - limiting reactor of the power supply line; and are respectively the equivalent electromotive force and equivalent impedance of the non - fault power supply line under transient conditions; is the preset protection action current value; is the imaginary unit; is the angular frequency.

[0031] Optionally, the designed value of the current - limiting reactor of each power supply line in the MACP - CHB - ESS system is shown as the following formula:

[0032]

[0033] Wherein, is the value of the port current - limiting reactor; max means taking the maximum value; and and are respectively the first lower - limit constraint value, the second lower - limit constraint value, and the upper - limit constraint value of the port current - limiting reactor of the power supply line; is the DC bus voltage of the PFCM power - flow control module; is the system switching frequency; is the preset maximum current ripple; is the equivalent current - limiting reactor value of the power supply line; and are respectively the equivalent electromotive force and equivalent impedance of the non - fault power supply line under transient conditions; is the preset minimum port voltage; is the preset protection action current value; is the imaginary unit; is the angular frequency.

[0034] The present invention also provides a device for designing parameters of a current - limiting reactor, which is applicable to the MACP - CHB - ESS system in a flexible interconnected distribution system of source - network - load - storage. Each power supply line in the MACP - CHB - ESS system is configured with a current - limiting reactor at its outlet; the device includes:

[0035] The first lower limit constraint value derivation unit is configured to derive the first lower limit constraint value of the current-limiting reactor at the power supply line port based on the current ripple constraint condition of the power supply line under steady-state operating conditions;

[0036] The lower limit constraint value derivation unit of the port current-limiting reactor is configured to determine the lower limit constraint value of the port current-limiting reactor of the power supply line based on the minimum port voltage constraint condition of the non-faulty power supply line under transient operating conditions and in combination with the first lower limit constraint value;

[0037] The upper limit constraint value derivation unit of the port current-limiting reactor is configured to derive the upper limit constraint value of the port current-limiting reactor of the power supply line based on the minimum port short-circuit current constraint condition of the faulty power supply line under transient operating conditions;

[0038] The current-limiting reactor design value determination unit is configured to determine the design value of the current-limiting reactor for each power supply line in the MACP-CHB-ESS system according to the lower limit constraint value and the upper limit constraint value of the port current-limiting reactor.

[0039] The present invention also provides an electronic device, which includes a processor and a memory:

[0040] The memory is configured to store program code and transmit the program code to the processor;

[0041] The processor is configured to execute the current-limiting reactor parameter design method according to the instructions in the program code as described in any one of the above.

[0042] The present invention also provides a computer-readable storage medium, which is configured to store program code, and the program code is used to execute the current-limiting reactor parameter design method as described in any one of the above.

[0043] It can be seen from the above technical solutions that the present invention has the following advantages:

[0044] A parameter design method for current-limiting reactors applicable to the MACP-CHB-ESS system is proposed. First, based on the current ripple constraint condition of the power supply line under steady-state conditions, the first lower limit constraint value of the current-limiting reactor at the power supply line port is derived; then, based on the minimum port voltage constraint condition of the non-faulty power supply line under transient conditions, combined with the first lower limit constraint value, the lower limit constraint value of the port current-limiting reactor is determined; then, based on the minimum port short-circuit current constraint condition of the faulty power supply line under transient conditions, the upper limit constraint value of the port current-limiting reactor is derived; finally, according to the lower limit constraint value and the upper limit constraint value of the port current-limiting reactor, the design values of the current-limiting reactors for each power supply line in the MACP-CHB-ESS system are determined. Thus, by deeply analyzing the current characteristics of the power supply line under different operating modes, the parameters of the port current-limiting reactor are accurately designed to realize the optimized regulation of the power supply line current, so that the output characteristics of the energy storage system meet the design requirements. When a short-circuit fault occurs in the AC power supply line, due to the power interconnection between multiple power supply lines in the shared energy storage system, the short-circuit current will be limited by the reactors at each port. Thus, the reactors in the power supply line can not only effectively suppress the short-circuit current but also improve the voltage stability of the non-faulty power supply line under transient conditions. Brief Description of the Drawings

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0046] Figure 1 It is a schematic diagram of the topological structure of a MACP-CHB-ESS system;

[0047] Figure 2 It is a flowchart of the steps of a parameter design method for current-limiting reactors;

[0048] Figure 3 It is a schematic diagram of the working principle of the post-fault blocking protection of a MACP-CHB-ESS;

[0049] Figure 4 It is a schematic diagram of the current path when a fault occurs in power supply line 2;

[0050] Figure 5 It is a schematic diagram of a three-phase short-circuit fault in power supply line 2;

[0051] Figure 6 It is a schematic diagram of the equivalent circuit when a three-phase short-circuit fault occurs in power supply line 2;

[0052] Figure 7 Schematic diagram of the simulation waveform of the current harmonics analysis of three power supply lines in a specific example;

[0053] Figure 8 Schematic diagram of the simulation waveform of the short - circuit current at port 1 in a specific example;

[0054] Figure 9 Schematic diagram of the simulation waveform of the short - circuit current at port 2 in a specific example;

[0055] Figure 10 Schematic diagram of the simulation waveform of the short - circuit current at port 3 in a specific example;

[0056] Figure 11 Schematic diagram of the simulation waveform of the voltage at port 1 in a specific example;

[0057] Figure 12 Schematic diagram of the simulation waveform of the voltage at port 3 in a specific example;

[0058] Figure 13 Structural block diagram of a device for designing the parameters of a current - limiting reactor. Detailed implementation manners

[0059] The embodiments of the present invention provide a method, a device, an electronic device and a storage medium for designing the parameters of a current - limiting reactor, which are used to solve or partially solve the technical problem of how to design the port current - limiting reactor more systematically and comprehensively to quickly suppress the fault current when a power supply line fault occurs in the MACP - CHB - ESS system.

[0060] To make the objectives, features and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments described below are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0061] As an example, multiple medium-voltage AC ports can be interconnected with the same large-capacity energy storage system through the MACP-CHB-ESS system. However, due to the power interaction between multiple ports, when a power supply line fails, the voltage and current distribution characteristics in its fault state become more complex. This can easily lead to risks such as excessive fault current (which may trigger cascading failures in severe cases), damage to energy storage units, voltage dips or fluctuations, and local fault expansion. At the same time, fault propagation will cause the voltage at non-fault ports to drop, which is not conducive to the operation of the system. Generally speaking, when the shared energy storage flexible interconnection device in the MACP-CHB-ESS system encounters a short-circuit fault, its impact is not limited to the device itself, but also has a profound negative effect on the stability and security of the entire power system, leading to large-scale economic losses and potential safety hazards. Therefore, it is crucial to take effective limiting measures.

[0062] Therefore, one of the core inventive points of the embodiments of the present invention lies in: According to the waveform characteristics of the device during normal operation and the demand for suppressing short-circuit current under transient conditions, a reasonable parameter design method for the current-limiting reactor at the MACP-CHB-ESS port is proposed. By deeply analyzing the current characteristics of the power supply line in different operating modes, the reactor parameters at the energy storage device port are accurately designed to achieve optimized regulation of the power supply line current, so that the output characteristics of the energy storage system meet the design requirements. When a short-circuit fault occurs in the AC power supply line, due to the power interconnection between multiple power supply lines in the shared energy storage system, the short-circuit current will be limited by the reactors at each port. Thus, the reactors in the power supply line can not only effectively suppress the short-circuit current, but also improve the voltage stability of the non-fault power supply line under transient conditions. By adopting the technical solution of the present invention, not only can the electrical indicators that meet the requirements be output under various operating states, but also the current-limiting potential of the MACP-CHB-ESS device can be fully exploited. When a short-circuit fault occurs, the current-limiting reactor limits the growth rate of the current through its inductive impedance, thereby effectively suppressing the short-circuit current during the transient period. On the one hand, it can reduce the voltage fluctuation of the non-fault power supply line, which helps to improve the fault ride-through ability of the system and the regulation and recovery function of the power flow after the fault. On the other hand, it can reduce the breaking current requirement of the circuit breaker, enabling the use of circuit breakers with smaller capacity and lower cost, saving the cost of the energy storage system. In addition, the technical solution proposed by the present invention can also provide data and theoretical support for the selection of current-limiting reactors in the future engineering application of MACP-CHB-ESS, effectively reducing the current ripple of the power supply line and improving the power supply quality of the system.

[0063] Refer to Figure 1 , which shows a schematic diagram of the topological structure of the MACP-CHB-ESS system in a source-network-load-storage flexible interconnection distribution system provided by the embodiments of the present invention.

[0064] At the outlet of each power supply line in the MACP-CHB-ESS system, a current-limiting reactor is configured. Taking phase A and three power supply terminals as an example. Between the ports of each power supply line, a mechanical circuit breaker is installed between the reactor and the Point of Common Coupling (PCC). Among them, the reactor is marked with identification.

[0065] In the MACP-CHB-ESS system, a current-limiting reactor is configured at the outlet of each power supply line to suppress fault current. When a short-circuit fault occurs, the current-limiting reactor limits the rapid rise of the current through its inductive impedance and reduces the peak value of the short-circuit current. Thus, the thermal shock and electrodynamic shock on power equipment are reduced.

[0066] Under grid-connected conditions, the current-limiting reactor can make the harmonics of the grid-connected current meet the system operation requirements. However, short-circuit currents below a certain threshold may reduce the sensitivity of relay protection equipment. Therefore, the embodiments of the present invention comprehensively consider the filtering requirements under steady-state conditions and the current-limiting requirements under transient conditions, and propose a reasonable parameter design method for the MACP-CHB-ESS current-limiting reactor to meet the performance requirements of the equipment under various operating conditions.

[0067] Referring to Figure 2 , a step flowchart of a parameter design method for a current-limiting reactor applicable to the Figure 1 shown system is shown, which may specifically include the following steps:

[0068] Step 201, based on the current ripple constraint condition of the power supply line under steady-state conditions, derive the first lower limit constraint value of the current-limiting reactor at the power supply line port;

[0069] As can be seen from the above Figure 1 , the MACP-CHB-ESS system includes a PFCM (Power Factor Control Management) power flow control module. The power management of the PFCM plays a key role in the reactor design at the outlet of the power supply line. Specifically, the reactor design at the outlet of the power supply line is closely related to the DC bus voltage of the PFCM and the switching frequency of the power switch. Therefore, when selecting the reactor parameters at the outgoing line end, the filtering effect of the system switching frequency on current harmonics needs to be considered first.

[0070] Thus, in a specific implementation, the implementation process of deriving the first lower limit constraint value of the current-limiting reactor at the power supply line port based on the current ripple constraint condition of the power supply line under steady-state conditions mainly may include the following sub-steps S01 to S03:

[0071] Step S01: Obtain the system switching frequency, the value of the equivalent current-limiting reactor of the power supply line, and the DC bus voltage of the PFCM power flow control module under steady-state operating conditions;

[0072] Step S02: Based on the system switching frequency, the value of the equivalent current-limiting reactor, and the DC bus voltage, with the constraint objective of limiting the current ripple of the power supply line within the maximum current ripple value, construct the current ripple constraint condition of the power supply line;

[0073] If the current ripple of the power supply line is limited to the following, then the corresponding current ripple constraint condition can be derived as shown in Equation (1) below:

[0074] (1)

[0075] Where, is the value of the port current-limiting reactor; is the DC bus voltage of the PFCM power flow control module; is the system switching frequency; is the preset maximum current ripple value; is the value of the equivalent current-limiting reactor of the power supply line.

[0076] Step S03: Based on the current ripple constraint condition, perform reverse derivation to determine the first lower limit constraint value of the port current-limiting reactor of the power supply line.

[0077] According to Equation (1), it can be obtained that under the requirement that the current ripple of the power supply line does not exceed , the filtering current-limiting reactor at the PFCM port (i.e., the port current-limiting reactor of the power supply line) can be designed in the form of the first lower limit constraint value as shown in Equation (2) below:

[0078] (2)

[0079] Therefore, based on Steps S01 to S03, the present invention proposes a reactor design process for the power supply line of a shared energy storage system to meet the smooth waveform requirement. According to the reactor parameters calculated by Equation (2), the harmonic management requirements of the MACP-CHB-ESS system for the output current can be satisfied.

[0080] Step 202, based on the minimum port voltage constraint condition of the non-faulty power supply line under transient operating conditions, combined with the first lower limit constraint value, determine the lower limit constraint value of the port current-limiting reactor of the power supply line;

[0081] For the port current-limiting reactor under fault conditions (transient conditions), the design focus can be placed on the impact of the voltage drop at the non-fault port and the response sensitivity of the protection device. The reason is that compared with the main equipment in traditional power systems (such as transformers and sectional switches), power electronic components are more sensitive to the voltage and current caused by faults and have lower tolerance capabilities.

[0082] Therefore, when a fault occurs, to prevent current from flowing through the power module, it is necessary to quickly turn off the parallel CHB-ESS and PFCM power flow regulation modules and bypass the PFCM power flow regulation module. Based on this, the schematic diagram of the locking protection working principle after the MACP-CHB-ESS fault is given as Figure 3 shown. The reactor design parameter scheme proposed in the embodiments of the present invention is also based on this protection strategy.

[0083] The lower limit design of the port current-limiting reactor for the power supply line is actually the design for suppressing the minimum value of the short-circuit current amplitude. In a specific implementation, based on the minimum value constraint condition of the port voltage of the non-fault power supply line under transient conditions and combined with the first lower limit constraint value, the implementation process of determining the lower limit constraint value of the port current-limiting reactor for the power supply line may include the following sub-steps S11 to S14:

[0084] Step S11: Obtain the equivalent electromotive force, equivalent impedance, and equivalent current of the non-fault power supply line under transient conditions;

[0085] Step S12: According to the equivalent electromotive force, equivalent impedance, and equivalent current, construct a minimum port voltage constraint condition with suppressing the minimum value of the short-circuit current amplitude as the constraint target;

[0086] Taking the short-circuit event of power supply line 2 as an example. When a fault occurs in power supply line 2 and the protection device has not been activated, the fault current path of the MACP-CHB-ESS flexible connection system of the three power supply lines is as Figure 4 shown. It can be seen that due to the power exchange between multiple ports, the fault current may conduct to other ports, causing all three power supply lines to be affected by the short-circuit current. By setting current-limiting reactors, this fault current can be effectively suppressed, thereby reducing the impact on non-fault power supply lines.

[0087] Considering the most severe short-circuit situation, when a three-phase short-circuit fault occurs at the power supply line port of the MACP-CHB-ESS system, the short-circuit current reaches the highest peak value, and at the same time, the voltage drop also increases. Among them, the schematic diagram of power supply line 2 having a three-phase short-circuit fault is as Figure 5 shown, and the schematic diagram of the equivalent circuit when a three-phase short-circuit fault occurs is as Figure 6 shown.

[0088] At this time, the current in the non-fault power supply line 1 and power supply line 3 , can be respectively expressed as:

[0089] (3)

[0090] wherein, , respectively represent the grid-side voltages of power supply line 1 and power supply line 3; , respectively represent the equivalent impedances of power supply line 1 and power supply line 3; is the imaginary unit; is the angular frequency.

[0091] Furthermore, the voltages , at the non-faulty power supply line ports (corresponding to power supply line 1 and power supply line 3) can be obtained as follows:

[0092] (4)

[0093] The fact that the non-faulty port voltage is lower than a certain threshold is not conducive to the realization of fault ride-through and post-fault power flow regulation and restoration of the MACP-CHB-ESS system. If it is required that the minimum non-faulty port voltage is , that is, the minimum port voltage constraint condition shown in the following formula (5) is satisfied:

[0094] (5)

[0095] wherein, is the preset minimum port voltage; , , respectively represent the equivalent electromotive force, equivalent impedance, and equivalent current of the non-faulty power supply line under transient conditions.

[0096] Step S13: Perform reverse derivation according to the minimum port voltage constraint condition to obtain the second lower limit constraint value of the current-limiting reactor at the power supply line port;

[0097] From formulas (3) to (5), it can be obtained that the current-limiting reactor at the power supply line port should satisfy the form of the second lower limit constraint value shown in the following formula (6):

[0098] (6)

[0099] Step S14: Determine the lower limit constraint value of the current-limiting reactor at the power supply line port according to the first lower limit constraint value and the second lower limit constraint value.

[0100] Equations (2) and (6) respectively give the expressions for meeting the smoothing requirement of the current-limiting reactor at the power supply line port of the MACP-CHB-ESS system under steady-state conditions and the requirement for limiting the short-circuit current amplitude under transient conditions. In the design, to meet the requirements of both smoothing the waveform and limiting the short-circuit current simultaneously, the minimum value of the current-limiting reactor at the power supply line port should be taken as the lower limit constraint value shown in the following equation (7):

[0101] (7)

[0102] where max represents taking the maximum value.

[0103] Step 203: Based on the minimum short-circuit current constraint condition of the power supply line port under transient conditions, derive the upper limit constraint value of the current-limiting reactor at the power supply line port;

[0104] The upper limit design of the current-limiting reactor at the power supply line port is actually a design for suppressing the maximum value of the short-circuit current amplitude. In the specific implementation, based on the minimum short-circuit current constraint condition of the power supply line port under transient conditions, the implementation process of deriving the upper limit constraint value of the current-limiting reactor at the power supply line port may include the following sub-steps S21 to S24:

[0105] Step S21: Obtain the equivalent electromotive force and equivalent impedance of the non-faulty power supply line under transient conditions;

[0106] Step S22: Calculate the short-circuit current flowing through the fault port of the faulty power supply line according to the equivalent electromotive force and equivalent impedance;

[0107] If the parameter design of the current-limiting reactor is too large, the short-circuit current will be too low, resulting in the protection device at the device port being unable to accurately identify whether a fault has occurred. Furthermore, it is impossible to effectively cut off the connection between the energy storage device and the faulty power supply line. Therefore, there should be an upper limit constraint for the parameters of the current-limiting reactor.

[0108] According to Kirchhoff's Current Law (KCL), the short-circuit current flowing through the fault port corresponding to the faulty power supply line 2 is:

[0109] (8)

[0110] where 、 are the currents flowing through power supply line 1 and power supply line 3 respectively when power supply line 2 fails; 、 are the equivalent power sources and equivalent impedances of power supply line 1 and power supply line 3 respectively. When the parameters of the two power supply lines are matched, can be expressed as:

[0111] (9)

[0112] Step S23: Based on the short-circuit current flowing through the fault port of the faulty power supply line, with suppressing the maximum value of the short-circuit current amplitude as the constraint objective, construct the minimum port short-circuit current constraint condition;

[0113] Suppose that under the lowest sensitivity requirement, the protection operating current is . Then the short-circuit current flowing through the fault port of the faulty power supply line should satisfy the minimum port short-circuit current constraint condition shown in the following formula (10):

[0114] (10)

[0115] Wherein, is the preset protection operating current value.

[0116] Step S24: Perform reverse derivation according to the minimum port short-circuit current constraint condition to obtain the upper limit constraint value of the port current-limiting reactor of the power supply line.

[0117] From formula (9) and formula (10), it can be obtained that the port current-limiting reactor of the power supply line should satisfy the upper limit constraint value form shown in the following formula (11):

[0118] (11)

[0119] Step 204, determine the design value of the current-limiting reactor of each power supply line in the MACP-CHB-ESS system according to the lower limit constraint value of the port current-limiting reactor and the upper limit constraint value of the port current-limiting reactor.

[0120] Therefore, comprehensively considering the requirements of the current-limiting reactor for smoothing the waveform, current limiting, and protection operating sensitivity, the design value of the current-limiting reactor of each power supply line in the MACP-CHB-ESS system should satisfy the form shown in the following formula (12):

[0121] (12)

[0122] Thus, by deeply analyzing the power distribution requirements of the MACP-CHB-ESS system, combining the current regulation requirements during steady-state operation and the short-circuit current limitation requirements under transient conditions, the reactors at the ports of the power supply lines in the MACP-CHB-ESS system are scientifically configured.

[0123] In the embodiments of the present invention, according to the waveform characteristics of the device during normal operation and the requirement for suppressing short-circuit current under transient conditions, a reasonable method for designing the parameters of the port current-limiting reactor of MACP-CHB-ESS is proposed. By deeply analyzing the current characteristics of the power supply line under different operating modes, the parameters of the port current-limiting reactor are accurately designed to realize the optimal regulation of the power supply line current, so that the output characteristics of the energy storage system meet the design requirements. When a short-circuit fault occurs in the AC power supply line, due to the power interconnection between multiple power supply lines in the shared energy storage system, the short-circuit current will be limited by each port reactor. Thus, the reactors in the power supply line can not only effectively suppress the short-circuit current, but also improve the voltage stability of the non-fault power supply line under transient conditions. By adopting the technical solution of the present invention, not only can the electrical indexes meeting the requirements be output under various operating states, but also the current-limiting potential of the MACP-CHB-ESS device can be fully exploited. When a short-circuit fault occurs, the current-limiting reactor limits the growth rate of the current through its inductive impedance, thereby effectively suppressing the short-circuit current during the transient period. On the one hand, it can reduce the voltage fluctuation of the non-fault power supply line, which helps to improve the fault ride-through ability of the system and the regulation and recovery function of the power flow after the fault. On the other hand, it can reduce the opening current requirement of the circuit breaker, so that a circuit breaker with a smaller capacity and lower cost can be used, saving the cost of the energy storage system. In addition, the technical solution proposed by the present invention can also provide data and theoretical support for the selection of the current-limiting reactor in the future engineering application of MACP-CHB-ESS, and can effectively reduce the current ripple of the power supply line and improve the power supply quality of the system.

[0124] To enable those skilled in the art to better understand the technical solution of the present invention, the embodiments of the present invention are described below through a specific example.

[0125]

[0126] Table 1: Simulation model parameter table

[0127] Taking the parameters of the multi-power-supply-line energy storage system shown in Table 1 as an example, the parameters of the three-port MACP-CHB-ESS current-limiting reactor are designed.

[0128] Set the maximum current ripple of the power supply line not exceeding 10% of the rated current amplitude of the power supply line. Under transient conditions, the voltage of the non-fault port (i.e., the minimum value of the port voltage of the non-fault power supply line) is not lower than 80% of the rated voltage of the energy storage system. Set the minimum short-circuit current for the protection at the power supply line of the energy storage device to be 6 times the maximum load current. According to the formula (12) introduced in the foregoing embodiment and substituting the parameters in Table 1, the value range of the current-limiting reactor at each power supply line in the MACP-CHB-ESS system can be obtained as shown in the following formula (13):

[0129] (13)

[0130] The technical solutions introduced in the previous embodiments are further described below in combination with a specific simulation example. Combining the above example, simulation verification is carried out for the steady-state condition and transient condition of the system respectively. Specifically, the simulation conditions are designed as follows: the MACP-CHB-ESS system operates in a steady state before 0.5 s, and a three-phase short-circuit fault occurs at the outlet of port 2 at 0.5 s. Among them, in order to more obviously reflect the effect of the current-limiting reactor in the power supply line on suppressing the short-circuit current, during the simulation process, at the moment of the fault occurrence, the current-limiting reactor is first bypassed and then put into operation 0.5 s after the fault occurs. The specific simulation parameters are shown in Table 1 above, and the relevant simulation waveforms of the experiment are as Figures 7 to 12 shown. Among them, Figure 7 is a schematic diagram of the simulation waveform of the harmonic analysis of the power supply line current; Figure 8 is a schematic diagram of the simulation waveform of the short-circuit current at port 1; Figure 9 is a schematic diagram of the simulation waveform of the short-circuit current at port 2; Figure 10 is a schematic diagram of the simulation waveform of the short-circuit current at port 3; Figure 11 is a schematic diagram of the simulation waveform of the voltage at port 1; Figure 12 is a schematic diagram of the simulation waveform of the voltage at port 3.

[0131] The simulation results show that under normal conditions, the harmonic of the power supply line current of the MACP-CHB-ESS system can meet the requirements. Even if the most serious three-phase short-circuit fault occurs at a certain AC port, the short-circuit current and the voltage dip at the non-fault outlet can be effectively suppressed. Thus, it is beneficial to the fault ride-through of the device and the restoration of the power flow regulation function after the fault.

[0132] Referring to Figure 13 , a structural block diagram of a device for designing the parameters of a current-limiting reactor provided by an embodiment of the present invention is shown, which is applicable to the MACP-CHB-ESS system in the flexible interconnected distribution system of the source-network-load-storage. A current-limiting reactor is configured at the outlet of each power supply line in the MACP-CHB-ESS system; the device may specifically include:

[0133] The first lower limit constraint value derivation unit 1301 is used to derive the first lower limit constraint value of the current-limiting reactor at the power supply line port based on the current ripple constraint condition of the power supply line under the steady-state condition;

[0134] The port current-limiting reactor lower limit constraint value derivation unit 1302 is used to determine the lower limit constraint value of the current-limiting reactor at the power supply line port based on the minimum port voltage constraint condition of the non-fault power supply line under the transient condition and in combination with the first lower limit constraint value;

[0135] The upper limit constraint value derivation unit 1303 of the port current-limiting reactor is used to derive the upper limit constraint value of the port current-limiting reactor of the power supply line based on the minimum value constraint condition of the port short-circuit current of the faulty power supply line under transient conditions;

[0136] The current-limiting reactor design value determination unit 1304 is used to determine the design value of the current-limiting reactor for each power supply line in the MACP-CHB-ESS system according to the lower limit constraint value of the port current-limiting reactor and the upper limit constraint value of the port current-limiting reactor.

[0137] In some alternative embodiments, the MACP-CHB-ESS system includes a PFCM power flow control module; the first lower limit constraint value derivation unit 1301 includes:

[0138] The steady-state condition data acquisition unit is used to acquire the system switching frequency, the equivalent current-limiting reactor value of the power supply line, and the DC bus voltage of the PFCM power flow control module under steady-state conditions;

[0139] The current ripple constraint condition construction unit of the power supply line is used to construct the current ripple constraint condition of the power supply line with the goal of restricting the current ripple of the power supply line within the maximum current ripple value according to the system switching frequency, the equivalent current-limiting reactor value, and the DC bus voltage;

[0140] The first lower limit constraint value determination unit is used to perform reverse derivation according to the current ripple constraint condition to determine the first lower limit constraint value of the port current-limiting reactor of the power supply line.

[0141] In some alternative embodiments, the port current-limiting reactor lower limit constraint value derivation unit 1302 includes:

[0142] The first transient condition data acquisition unit is used to acquire the equivalent electromotive force, equivalent impedance, and equivalent current of the non-faulty power supply line under transient conditions;

[0143] The port voltage minimum value constraint condition construction unit is used to construct the port voltage minimum value constraint condition with the goal of suppressing the minimum value of the short-circuit current amplitude according to the equivalent electromotive force, the equivalent impedance, and the equivalent current;

[0144] The second lower limit constraint value determination unit is used to perform reverse derivation according to the port voltage minimum value constraint condition to obtain the second lower limit constraint value of the port current-limiting reactor of the power supply line;

[0145] The port current-limiting reactor lower limit constraint value determination unit is used to determine the lower limit constraint value of the port current-limiting reactor of the power supply line according to the first lower limit constraint value and the second lower limit constraint value.

[0146] In some alternative embodiments, the lower limit constraint value of the port current-limiting reactor of the power supply line is shown by the following formula:

[0147]

[0148] Wherein, is the value of the port current-limiting reactor; max represents taking the maximum value; and are respectively the first lower limit constraint value and the second lower limit constraint value of the port current-limiting reactor of the power supply line; is the DC bus voltage of the PFCM power flow control module; is the system switching frequency; is the preset maximum value of current ripple; is the equivalent current-limiting reactor value of the power supply line; and are respectively the equivalent electromotive force and equivalent impedance of the non-faulty power supply line under transient conditions; is the preset minimum value of port voltage; is the imaginary unit; is the angular frequency.

[0149] In some alternative embodiments, the port current-limiting reactor upper limit constraint value derivation unit 1303 includes:

[0150] A second transient condition data acquisition unit, configured to acquire the equivalent electromotive force and equivalent impedance of the non-faulty power supply line under transient conditions;

[0151] A fault port short-circuit current calculation unit, configured to calculate the short-circuit current flowing through the fault port of the faulty power supply line according to the equivalent electromotive force and equivalent impedance;

[0152] A port short-circuit current minimum value constraint condition construction unit, configured to construct a port short-circuit current minimum value constraint condition based on the short-circuit current flowing through the fault port of the faulty power supply line, with suppressing the maximum value of the short-circuit current amplitude as the constraint target;

[0153] A port current-limiting reactor upper limit constraint value determination unit, configured to perform reverse derivation according to the port short-circuit current minimum value constraint condition to obtain the port current-limiting reactor upper limit constraint value of the power supply line.

[0154] In some alternative embodiments, the upper limit constraint value of the port current-limiting reactor of the power supply line is shown by the following formula:

[0155]

[0156] Wherein, is the value of the port current-limiting reactor; is the upper limit constraint value of the port current-limiting reactor of the power supply line; , are respectively the equivalent electromotive force and equivalent impedance of the non-faulty power supply line under transient conditions; is the preset protection operating current value; is the imaginary unit; is the angular frequency.

[0157] In some alternative embodiments, the design value of the current-limiting reactor for each power supply line in the MACP-CHB-ESS system is shown by the following formula:

[0158]

[0159] where, is the value of the port current-limiting reactor; max means taking the maximum value; , , are respectively the first lower limit constraint value, the second lower limit constraint value, and the upper limit constraint value of the port current-limiting reactor of the power supply line; is the DC bus voltage of the PFCM power flow control module; is the system switching frequency; is the preset maximum value of current ripple; is the equivalent current-limiting reactor value of the power supply line; , are respectively the equivalent electromotive force and equivalent impedance of the non-faulty power supply line under transient conditions; is the preset minimum port voltage; is the preset protection operating current value; is the imaginary unit; is the angular frequency.

[0160] For the device embodiments, since they are basically similar to the method embodiments, the description is relatively simple. For the relevant parts, please refer to the partial description of the foregoing method embodiments.

[0161] It should be noted that, in order to enable those skilled in the art to better distinguish data of the same type but with different actual pointing meanings, in the embodiments of the present invention, some technical features are distinguished and described using the first and the second. The first and the second are only used for data distinction and have no other special meanings. It can be understood that the present invention does not limit this.

[0162] The embodiments of the present invention also provide an electronic device, which includes a processor and a memory:

[0163] The memory is used to store program codes and transmit the program codes to the processor;

[0164] The processor is used to execute the parameter design method of the current-limiting reactor according to any embodiment of the present invention in the program code.

[0165] An embodiment of the present invention also provides a computer-readable storage medium, which is used to store program code, and the program code is used to execute the parameter design method of the current-limiting reactor according to any embodiment of the present invention.

[0166] Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working processes of the above-described systems, devices, and units can refer to the corresponding processes in the foregoing method embodiments, and will not be described herein again.

[0167] In several embodiments provided by the present invention, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the units is only a logical function division, and there may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections to each other can be through some interfaces, and the indirect couplings or communication connections of the devices or units can be in electrical, mechanical, or other forms.

[0168] The units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they can be located in one place, or they can be distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0169] In addition, in each embodiment of the present invention, the functional units can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above-mentioned integrated units can be implemented in the form of hardware or in the form of software functional units.

[0170] When the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as USB flash drives, mobile hard disks, read-only memories (ROMs), random access memories (RAMs), magnetic disks, or optical discs.

[0171] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for designing parameters of a current limiting reactor, characterized in that: Applicable to the MACP-CHB-ESS system in the source-grid-load-storage flexible interconnected distribution system, the outlet of each power supply line in the MACP-CHB-ESS system is equipped with a current-limiting reactor; the method comprises: Based on the current ripple constraint condition of the power supply line under steady-state conditions, the first lower limit constraint value of the current limiting reactor at the power supply line port is derived; Based on the minimum value constraint of the port voltage of the non-fault power supply line under transient conditions, combined with the first lower limit constraint value, determine the lower limit constraint value of the port current limiting reactor of the power supply line; Based on the minimum short-circuit current constraint condition of the fault power supply line under transient conditions, the upper limit constraint value of the port current limiting reactor of the power supply line is derived; According to the lower limit constraint value of the port current limiting reactor and the upper limit constraint value of the port current limiting reactor, the design value of the current limiting reactor of each power supply line in the MACP-CHB-ESS system is determined.

2. The current limiting reactor parameter design method according to claim 1, characterized in that: The MACP-CHB-ESS system includes a PFCM power flow control module; the first lower limit constraint value of the current limiting reactor at the power supply line port is derived based on the current ripple constraint condition of the power supply line under steady-state conditions, including: Obtaining the system switching frequency, the equivalent current limiting reactor value of the power supply line and the DC bus voltage of the PFCM power flow control module under steady-state conditions; According to the system switching frequency, the equivalent current limiting reactor value and the DC bus voltage, a current ripple constraint condition of the power supply line is constructed with the current ripple of the power supply line limited to within the current ripple maximum value as a constraint target; Reverse deduction is performed according to the current ripple constraint condition to determine a first lower limit constraint value of the current limiting reactor at the power supply line port.

3. The current limiting reactor parameter design method according to claim 2, characterized in that: The minimum value constraint condition of the port voltage of the non-fault power supply line under transient conditions, combined with the first lower limit constraint value, determines the lower limit constraint value of the port current limiting reactor of the power supply line, including: Obtain the equivalent electromotive force, equivalent impedance and equivalent current of the non-fault power supply line under transient conditions; According to the equivalent electromotive force, the equivalent impedance and the equivalent current, a minimum port voltage constraint condition is constructed with the minimum short-circuit current amplitude suppressed as a constraint target; Reverse deduction is performed according to the port voltage minimum constraint condition to obtain a second lower limit constraint value of the power supply line port current limiting reactor; According to the first lower limit constraint value and the second lower limit constraint value, a lower limit constraint value of the port current limiting reactor of the power supply line is determined.

4. The current limiting reactor parameter design method according to claim 3, characterized in that: The lower limit constraint value of the port current limiting reactor of the power supply line is as follows: in, It is the value of the port current limiting reactor; max means taking the maximum value; , They are respectively the first lower limit constraint value and the second lower limit constraint value of the current limiting reactor at the power supply line port; is the DC bus voltage of the PFCM power flow control module; is the system switching frequency; is the preset maximum current ripple value; is the equivalent current limiting reactor value of the power supply line; , are the equivalent electromotive force and equivalent impedance of the non-fault power supply line under transient conditions respectively; is the preset minimum port voltage; is an imaginary unit; is the angular frequency.

5. The method for designing parameters of a current limiting reactor according to claim 2, characterized in that: The method of deducing the upper limit constraint value of the port current limiting reactor of the power supply line based on the minimum constraint condition of the port short-circuit current of the faulty power supply line under transient conditions includes: Obtain the equivalent electromotive force and equivalent impedance of the non-fault power supply line under transient conditions; Calculating the short-circuit current flowing through the fault port of the faulty power supply line according to the equivalent electromotive force and the equivalent impedance; Based on the short-circuit current flowing through the faulty port of the faulty power supply line, a port short-circuit current minimum value constraint condition is constructed by suppressing the maximum value of the short-circuit current amplitude as a constraint target; Reverse deduction is performed based on the minimum constraint condition of the port short-circuit current to obtain the upper limit constraint value of the port current limiting reactor of the power supply line.

6. The method for designing parameters of a current limiting reactor according to claim 5, characterized in that: The upper limit constraint value of the port current limiting reactor of the power supply line is as follows: in, Set the value for the port current limiting reactor; The upper limit constraint value of the port current limiting reactor of the power supply line; , are the equivalent electromotive force and equivalent impedance of the non-fault power supply line under transient conditions respectively; It is the preset protection action current value; is an imaginary unit; is the angular frequency.

7. The method for designing parameters of a current limiting reactor according to any one of claims 2 to 6, characterized in that: The design value of the current limiting reactor for each power supply line in the MACP-CHB-ESS system is as follows: in, It is the value of the port current limiting reactor; max means taking the maximum value; , , They are respectively a first lower limit constraint value, a second lower limit constraint value, and an upper limit constraint value of the current limiting reactor at the power supply line port; is the DC bus voltage of the PFCM power flow control module; is the system switching frequency; is the preset maximum current ripple value; is the equivalent current limiting reactor value of the power supply line; , are the equivalent electromotive force and equivalent impedance of the non-fault power supply line under transient conditions respectively; is the preset minimum port voltage; It is the preset protection action current value; is an imaginary unit; is the angular frequency.

8. A current limiting reactor parameter design device, characterized in that: Applicable to the MACP-CHB-ESS system in the source-grid-load-storage flexible interconnected distribution system, the outlet of each power supply line in the MACP-CHB-ESS system is equipped with a current-limiting reactor; the device includes: A first lower limit constraint value derivation unit, used to derive a first lower limit constraint value of a current limiting reactor at a power supply line port based on a current ripple constraint condition of the power supply line under steady-state conditions; A port current limiting reactor lower limit constraint value derivation unit, used to determine the port current limiting reactor lower limit constraint value of the power supply line based on the port voltage minimum constraint condition of the non-fault power supply line under transient conditions and in combination with the first lower limit constraint value; A port current limiting reactor upper limit constraint value derivation unit is used to derive an upper limit constraint value of a port current limiting reactor of a power supply line based on a minimum constraint condition of a port short-circuit current of a faulty power supply line under transient conditions; The current limiting reactor design value determination unit is used to determine the current limiting reactor design value of each power supply line in the MACP-CHB-ESS system according to the lower limit constraint value of the port current limiting reactor and the upper limit constraint value of the port current limiting reactor.

9. An electronic device, characterized in that: The device comprises a processor and a memory: The memory is used to store program code and transmit the program code to the processor; The processor is used to execute the current limiting reactor parameter design method according to any one of claims 1 to 7 according to the instructions in the program code.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium is used to store program codes, and the program codes are used to execute the current-limiting reactor parameter design method according to any one of claims 1 to 7.

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