A method for ac capacitor fault protection of grid-connected equipment

Abstract

The application discloses a kind of grid-connected equipment AC capacitor fault protection methods, grid-connected equipment includes three-phase AC port, circuit breaker, filter inductance, AC-DC converter, controller;Controller is according to the current signal output of first current sensor, second current sensor and third current sensor and is obtained by regulating calculation current sensor primary side current real-time value;The controller is according to the current real-time value obtained by the connection relationship and detection combination strategy of first current sensor, second current sensor and third current sensor and capacitor component calculates the sum of three-phase equivalent current real-time value and current real-time value of single capacitor group;This grid-connected equipment AC capacitor fault protection method only needs to use current sensor to meet the current range of single capacitor to achieve the real-time detection and protection of each group of AC capacitor operating state of grid-connected equipment, low in cost, protection is more comprehensive and accurate.

Description

Technical Field

[0001] This invention relates to the field of power generation and distribution, and in particular to a method for AC capacitor fault protection of grid-connected equipment. Background Technology

[0002] Power electronic equipment generates abundant high-frequency harmonics during operation due to the high-frequency operation of semiconductor switching devices. To reduce the harmonics injected into the power grid, LC or LCL filters are typically added at the grid connection port. AC capacitors, as the main filtering components, are highly sensitive to frequency and frequently experience overload, open circuit, and short circuit faults during use, leading to serious accidents such as power grid tripping, equipment damage, and even fires.

[0003] To promptly detect capacitor abnormalities and implement protection and troubleshooting measures, the total capacitor current is typically measured. For example... Figure 1 As shown, Figure 1 The system uses a current sensor to collect the total current of all filter capacitors. By analyzing the collected current, it determines whether the capacitors are overloaded, short-circuited, or open-circuited.

[0004] However, this method has drawbacks such as high cost and limited protection effectiveness, mainly reflected in:

[0005] The range of the current sensor needs to be selected based on the total current. When there are many capacitors, the range of the current sensor needs to be very large, which will increase the cost.

[0006] To ensure the normal operation of the power grid and system, the protection threshold needs to be set with sufficient margin relative to the normal current. In this way, when one capacitor is short-circuited or open-circuited, the total current changes only slightly and is unlikely to trigger the protection threshold. However, the other two phase capacitors of the faulty capacitor bank are already significantly overloaded and overvoltaged. Long-term operation will cause the capacitors to break down and short-circuit, thus amplifying the fault. Summary of the Invention

[0007] The technical problem to be solved by this invention is to propose a method for AC capacitor fault protection of grid-connected equipment. This method only requires the use of a current sensor that meets the current range of a single capacitor to achieve real-time detection and protection of the operating status of each group of AC capacitors in the grid-connected equipment. It is low in cost, provides more comprehensive and accurate protection, and ensures the safe and reliable operation of AC capacitors and the system.

[0008] To address the aforementioned technical problems, this invention provides a method for AC capacitor fault protection in grid-connected equipment. The grid-connected equipment includes a three-phase AC port, a circuit breaker, a filter inductor, an AC / DC converter, and a controller. The filter inductor is connected to the AC output ports A2, B2, and C2 of the AC / DC converter. A first current sensor, a second current sensor, and a third current sensor are present. The circuit breaker is connected in series between the three-phase AC port and the filter inductor. The grid-connected equipment also includes a capacitor assembly comprising at least three capacitor groups: a first capacitor group, a second capacitor group, ..., an Nth capacitor group. The first capacitor group, the second capacitor group, ..., the Nth capacitor group are connected in parallel to ports A1, B1, and C1 of the connection line between the circuit breaker and the filter inductor. The controller is connected to the circuit breaker and the AC / DC converter. The first current sensor, the second current sensor, and the third current sensor are connected in series on the connection line between the electrical port of the capacitor assembly and ports A1, B1, and C1.

[0009] The first current sensor, the second current sensor, and the third current sensor respectively detect one phase current of each capacitor bank in the capacitor assembly according to a detection combination strategy; one current sensor corresponds to one phase current of one capacitor bank, or one current sensor corresponds to one phase current of each of two capacitor banks.

[0010] The controller performs conditioning and calculation based on the output current signals of the first current sensor, the second current sensor and the third current sensor to obtain the real-time values ​​of the primary current of the current sensor i1, i2 and i3;

[0011] The controller calculates the real-time three-phase equivalent current value i of a single capacitor bank based on the real-time current values ​​i1, i2, and i3 obtained from the connection relationships and detection combination strategies of the first, second, and third current sensors and the capacitor assembly. A i B i C The sum of real-time current values ​​i all and i A i B i C and i all Effective value I A and I B and I C and I all ;

[0012] The controller is based on I A and I B and I C The capacitor bank is compared with a preset threshold to determine whether it is overloaded. If I A and I B and I CWhen the load exceeds a preset threshold, the controller determines that the capacitor is overloaded, sends a shutdown command to the AC / DC converter to stop the AC / DC converter from working, and simultaneously sends a disconnect signal to the circuit breaker.

[0013] The controller is based on I all Compare with a preset threshold to determine if the capacitor is short-circuited or open-circuited; if I all When the value exceeds a preset threshold, it is determined that the capacitor has a short circuit or open circuit fault. The controller sends a shutdown command to the AC / DC converter to stop the AC / DC converter from working, and at the same time sends a disconnect signal to the circuit breaker.

[0014] Where N≥3.

[0015] Preferably, the capacitor assembly includes three capacitor banks: a first capacitor bank, a second capacitor bank, and a third capacitor bank; the detection combination strategy is as follows: the first current sensor detects the A-phase current of the first capacitor bank to obtain the real-time value i1 of the primary current of the current sensor; the second current sensor detects the B-phase current of the second capacitor bank to obtain the real-time value i2 of the primary current of the current sensor; and the third current sensor detects the C-phase current of the third capacitor bank to obtain the real-time value i3 of the primary current of the current sensor.

[0016] i A =i1

[0017] i B =i2

[0018] i C =i3

[0019] i all =i1+i2+i3

[0020] I A =RMSi A

[0021] I B =RMSi B

[0022] I C =RMSi C

[0023] I all =RMSi all

[0024] Among them, i A i B i C i represents the real-time value of the three-phase equivalent current of a single capacitor bank. all I is the sum of the real-time current values. A and IB and I C and I all For i A i B i C i all Valid value.

[0025] Preferably, the capacitor assembly includes four capacitor banks: a first capacitor bank, a second capacitor bank, a third capacitor bank, and a fourth capacitor bank; the detection combination strategy is as follows: a first current sensor detects the A-phase current of the first capacitor bank to obtain the real-time value i1 of the primary current of the current sensor; a second current sensor detects the B-phase current of the second capacitor bank to obtain the real-time value i2 of the primary current of the current sensor; and a third current sensor detects the B-phase current of the third capacitor bank and the A-phase current of the fourth capacitor bank to obtain the real-time value i3 of the primary current of the current sensor.

[0026] i A =i1

[0027] i B =i2

[0028] i C =-i3

[0029] i all =i1+i2-i3

[0030] I A =RMSi A

[0031] I B =RMSi B

[0032] I C =RMSi C

[0033] I all =RMSi all

[0034] Among them, i A i B i C i represents the real-time value of the three-phase equivalent current of a single capacitor bank. all I is the sum of the real-time current values. A and I B and I C For i A i B i C Valid value.

[0035] Preferably, the capacitor assembly includes five capacitor groups: a first capacitor group, a second capacitor group, a third capacitor group, a fourth capacitor group, and a fifth capacitor group; the detection combination strategy is as follows: the first current sensor detects the A-phase current of the first capacitor group to obtain the real-time value i1 of the primary current of the current sensor; the second current sensor detects the A-phase current of the second capacitor group and the C-phase current of the third capacitor group to obtain the real-time value i2 of the primary current of the current sensor; and the third current sensor detects the B-phase current of the fourth capacitor group and the A-phase current of the fifth capacitor group to obtain the real-time value i3 of the primary current of the current sensor.

[0036] i A =i1

[0037] i B =-i2

[0038] i C =-i3

[0039] i all =i1-i2-i3

[0040] I A =RMSi A

[0041] I B =RMSi B

[0042] I C =RMSi C

[0043] I all =RMSi all

[0044] Among them, i A i B i C i represents the real-time value of the three-phase equivalent current of a single capacitor bank. al

[0045] I is the sum of the real-time current values. A and I B and I C For i A i B i C Valid value.

[0046] Preferably, the capacitor assembly includes six capacitor banks: a first capacitor bank, a second capacitor bank, a third capacitor bank, a fourth capacitor bank, a fifth capacitor bank, and a sixth capacitor bank. The detection combination strategy is as follows: a first current sensor detects the A-phase current of the first capacitor bank and the B-phase current of the second capacitor bank to obtain the real-time value i1 of the primary current of the current sensor; a second current sensor detects the C-phase current of the third capacitor bank and the A-phase current of the fourth capacitor bank to obtain the real-time value i2 of the primary current of the current sensor; and a third current sensor detects the B-phase current of the fifth capacitor bank and the C-phase current of the sixth capacitor bank to obtain the real-time value i3 of the primary current of the current sensor.

[0047] i A =-i3

[0048] i B =-i2

[0049] i C =-i1

[0050] i all = -i1-i2-i3

[0051] I A =RMSi A

[0052] I B =RMSi B

[0053] I C =RMSi C

[0054] I all =RMSi all

[0055] Among them, i A i B i C i represents the real-time value of the three-phase equivalent current of a single capacitor bank. al

[0056] I is the sum of the real-time current values. A and I B and I C For i A i B i C Valid value.

[0057] Preferably, the grid-connected equipment is a converter, a frequency converter, or an inverter.

[0058] Preferably, the filter inductor, in conjunction with the capacitor assembly, is used to suppress and filter out high-frequency AC harmonics output by the AC-DC converter.

[0059] Preferably, the capacitor bank consists of three single-phase capacitors or one three-phase capacitor; the three-phase capacitor can be connected in a star or delta configuration.

[0060] After adopting the above method, the grid-connected equipment includes a three-phase AC port, a circuit breaker, a filter inductor, an AC-DC converter, and a controller; the filter inductor is connected to the AC output ports A2, B2, and C2 of the AC-DC converter; a first current sensor, a second current sensor, and a third current sensor are included; the circuit breaker is connected in series between the three-phase AC port and the filter inductor; the grid-connected equipment also includes a capacitor assembly, which includes at least three capacitor groups: a first capacitor group, a second capacitor group...a ​​Nth capacitor group; the first capacitor group, the second capacitor group...a ​​Nth capacitor group are connected in parallel to ports A1, B1, and C1 of the connection line between the circuit breaker and the filter inductor; the controller is connected to... The circuit breaker and AC / DC converter; the first current sensor, the second current sensor, and the third current sensor are connected in series on the connection lines between the electrical ports of the capacitor assembly and ports A1, B1, and C1; the first current sensor, the second current sensor, and the third current sensor respectively detect one phase current of each capacitor bank in the capacitor assembly according to a detection combination strategy; one current sensor corresponds to one phase current of one capacitor bank, or one current sensor corresponds to one phase current of each of two capacitor banks; the controller performs conditioning calculations based on the output current signals of the first current sensor, the second current sensor, and the third current sensor to obtain the real-time values ​​i1, i2, and i3 of the primary current of the current sensor;

[0061] The controller calculates the real-time three-phase equivalent current value i of a single capacitor bank based on the real-time current values ​​i1, i2, and i3 obtained from the connection relationships and detection combination strategies of the first, second, and third current sensors with the capacitor assembly. A i B i C The sum of the real-time current values ​​i all , and i A i B i C and i all Effective value I A and I B and I C and I all The controller is based on I A and I B and I C The capacitor bank is compared with a preset threshold to determine whether it is overloaded. If I A and I and I CWhen the load exceeds a preset threshold, an overload is detected in the capacitor. The controller then issues a shutdown command to the AC / DC converter, causing it to stop operating, and simultaneously sends a disconnect signal to the circuit breaker. The controller then determines the overload based on I... all Compare with a preset threshold to determine if the capacitor is short-circuited or open-circuited; if I all When the current exceeds a preset threshold, a short circuit or open circuit fault is determined in the capacitor. The controller sends a shutdown command to the AC / DC converter to stop its operation and simultaneously sends a disconnect signal to the circuit breaker. This AC capacitor fault protection method for grid-connected equipment only requires a current sensor that meets the current range of a single capacitor to achieve real-time detection and protection of the operating status of each group of AC capacitors in the grid-connected equipment. It is low-cost, provides more comprehensive and accurate protection, and ensures the safe and reliable operation of AC capacitors and the system. Attached Figure Description

[0062] Figure 1 This is a circuit diagram for capacitor fault detection and protection in existing technology;

[0063] Figure 2 This is a fault protection circuit diagram of three sets of AC capacitors in a grid-connected equipment AC capacitor fault protection method according to the present invention;

[0064] Figure 3 This is a fault protection circuit diagram for four groups of AC capacitors in a grid-connected equipment AC capacitor fault protection method according to the present invention.

[0065] Figure 4 This is a fault protection circuit diagram for five groups of AC capacitors in a grid-connected equipment AC capacitor fault protection method according to the present invention.

[0066] Figure 5 This is a circuit diagram showing the fault protection of six AC capacitors in a grid-connected equipment AC capacitor fault protection method according to the present invention. Detailed Implementation

[0067] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0068] Example 1

[0069] This embodiment discloses a method for AC capacitor fault protection of grid-connected equipment. The grid-connected equipment includes a three-phase AC port 1, a circuit breaker 2, a filter inductor 3, an AC / DC converter 4, and a controller 5. The filter inductor 3 is connected to the AC output ports A2, B2, and C2 of the AC / DC converter 4. A first current sensor 8, a second current sensor 9, and a third current sensor 10 are included. The circuit breaker 2 is connected in series between the three-phase AC port 1 and the filter inductor 3. The grid-connected equipment also includes a capacitor assembly, which includes at least three capacitor groups: a first capacitor group, a second capacitor group, ..., an Nth capacitor group. The first capacitor group, the second capacitor group, ..., the Nth capacitor group are connected in parallel to ports A1, B1, and C1 of the connection line between the circuit breaker 2 and the filter inductor 3. The controller 5 is connected to the circuit breaker 2 and the AC / DC converter 4. The first current sensor 8, the second current sensor 9, and the third current sensor 10 are connected in series on the connection lines between the electrical ports of the capacitor assembly and ports A1, B1, and C1.

[0070] The first current sensor 8, the second current sensor 9, and the third current sensor 10 respectively detect one phase current of each capacitor bank in the capacitor assembly according to the detection combination strategy; one current sensor corresponds to one phase current of one capacitor bank, or one current sensor corresponds to one phase current of each of two capacitor banks.

[0071] The controller 5 performs conditioning and calculation based on the output current signals of the first current sensor 8, the second current sensor 9 and the third current sensor 10 to obtain the real-time values ​​of the primary current of the current sensor i1, i2 and i3.

[0072] Based on the connection relationships between the first current sensor 8, the second current sensor 9, and the third current sensor 10 and the capacitor assembly, and the detection combination strategy, the controller 5 calculates the real-time three-phase equivalent current value i of a single capacitor bank. A i B i C The sum of real-time current values ​​i all , and i A i B i C and i all Effective value I A and I B and I C and I all ;

[0073] Controller 5 according to I A and I B and I C The capacitor bank is compared with a preset threshold to determine whether it is overloaded. If I A and I B and IC When the load exceeds the preset threshold, the controller determines that the capacitor is overloaded, sends a shutdown command to the AC / DC converter 4 to stop the AC / DC converter 4 from working, and sends a disconnect signal to the circuit breaker 2 at the same time.

[0074] Controller 5 according to I all Compare with a preset threshold to determine if the capacitor is short-circuited or open-circuited; if I all When the value exceeds the preset threshold, it is determined that the capacitor has a short circuit or open circuit fault. The controller 5 sends a shutdown command to the AC-DC converter 4 to stop the AC-DC converter 4 from working, and at the same time sends a disconnect signal to the circuit breaker 2.

[0075] Where N≥3.

[0076] Example 2

[0077] Please see Figure 2 , Figure 2 This is a fault protection circuit diagram of three sets of AC capacitors in a grid-connected equipment AC capacitor fault protection method according to the present invention;

[0078] This embodiment is based on Embodiment 1. In this embodiment, the capacitor assembly includes three capacitor groups: a first capacitor group 11, a second capacitor group 13, and a third capacitor group 16. The detection combination strategy is as follows: the first current sensor 8 detects the A-phase current of the first capacitor group 11 to obtain the real-time value i1 of the primary current of the current sensor; the second current sensor 9 detects the B-phase current of the second capacitor group 13 to obtain the real-time value i2 of the primary current of the current sensor; and the third current sensor 10 detects the C-phase current of the third capacitor group 16 to obtain the real-time value i3 of the primary current of the current sensor.

[0079] i A =i1

[0080] i B =i2

[0081] i C =i3

[0082] i all =i1+i2+i3

[0083] I A =RMSi A

[0084] I B =RMSi B

[0085] I C =RMSi C

[0086] I all =RMSiall

[0087] Among them, i A i B i C i represents the real-time value of the three-phase equivalent current of a single capacitor bank. all I is the sum of the real-time current values. A and I B and I C and I all For i A i B i C i all Valid value.

[0088] Example 3

[0089] Please see Figure 3 , Figure 3 This is a fault protection circuit diagram for four groups of AC capacitors in a grid-connected equipment AC capacitor fault protection method according to the present invention.

[0090] This embodiment is based on Embodiment 1. In this embodiment, the capacitor assembly includes four capacitor groups: a first capacitor group 11, a second capacitor group 13, a third capacitor group 15, and a fourth capacitor group 16. The detection combination strategy is as follows: the first current sensor 8 detects the A-phase current of the first capacitor group 11 to obtain the real-time value i1 of the primary current of the current sensor; the second current sensor 9 detects the B-phase current of the second capacitor group 13 to obtain the real-time value i2 of the primary current of the current sensor; and the third current sensor 10 detects the B-phase current of the third capacitor group 15 and the A-phase current of the fourth capacitor group 16 to obtain the real-time value i3 of the primary current of the current sensor.

[0091] i A =i1

[0092] i B =i2

[0093] i C =-i3

[0094] i all =i1+i2-i3

[0095] I A =RMSi A

[0096] I B =RMSi B

[0097] I C =RMSi C

[0098] Iall =RMSi all

[0099] Among them, i A i B i C i represents the real-time value of the three-phase equivalent current of a single capacitor bank. all I is the sum of the real-time current values. A and I B and I C For i A i B i C Valid value.

[0100] Example 4

[0101] Please see Figure 4 , Figure 4 This is a fault protection circuit diagram for five groups of AC capacitors in a grid-connected equipment AC capacitor fault protection method according to the present invention.

[0102] This embodiment is based on Embodiment 1. In this embodiment, the capacitor assembly includes five capacitor groups: a first capacitor group 11, a second capacitor group 13, a third capacitor group 14, a fourth capacitor group 15, and a fifth capacitor group 16. The detection combination strategy is as follows: the first current sensor 8 detects the A-phase current of the first capacitor group 11 to obtain the real-time value i1 of the primary current of the current sensor; the second current sensor 9 detects the A-phase current of the second capacitor group 13 and the C-phase current of the third capacitor group 14 to obtain the real-time value i2 of the primary current of the current sensor; and the third current sensor 10 detects the B-phase current of the fourth capacitor group 15 and the A-phase current of the fifth capacitor group 16 to obtain the real-time value i3 of the primary current of the current sensor.

[0103] i A =i1

[0104] i B =-i2

[0105] i C =-i3

[0106] i all =i1-i2-i3

[0107] I A =RMSi A

[0108] I B =RMSi B

[0109] I C =RMSi C

[0110] I all =RMSi all

[0111] Among them, i A i B i C i represents the real-time value of the three-phase equivalent current of a single capacitor bank. all I is the sum of the real-time current values. A and I B and I C For i A i B i C Valid value.

[0112] Example 5

[0113] Please see Figure 5 , Figure 5 This is a fault protection circuit diagram for six groups of AC capacitors in a grid-connected equipment AC capacitor fault protection method according to the present invention;

[0114] This embodiment is based on Embodiment 1. In this embodiment, the capacitor assembly includes six capacitor groups: a first capacitor group 11, a second capacitor group 12, a third capacitor group 13, a fourth capacitor group 14, a fifth capacitor group 15, and a sixth capacitor group 16. The detection combination strategy is as follows: the first current sensor 8 detects the A-phase current of the first capacitor group 11 and the B-phase current of the second capacitor group 12 to obtain the real-time value i1 of the primary current of the current sensor; the second current sensor 9 detects the C-phase current of the third capacitor group 13 and the A-phase current of the fourth capacitor group 14 to obtain the real-time value i2 of the primary current of the current sensor; and the third current sensor 10 detects the B-phase current of the fifth capacitor group 15 and the C-phase current of the sixth capacitor group 16 to obtain the real-time value i3 of the primary current of the current sensor.

[0115] i A =-i3

[0116] i B =-i2

[0117] i C =-i1

[0118] i all = -i1-i2-i3

[0119] I A =RMSi A

[0120] I B =RMSi B

[0121] I C=RMSi C

[0122] I all =RMSi aIl

[0123] Among them, i A i B i C i represents the real-time value of the three-phase equivalent current of a single capacitor bank. all I is the sum of the real-time current values. A and I B and I C For i A i B i C Valid value.

[0124] Example 6

[0125] This embodiment is based on Embodiment 1. In this embodiment, the grid-connected device is a converter, frequency converter, or inverter.

[0126] The filter inductor, in conjunction with the capacitor assembly, is used to suppress and filter out high-frequency AC harmonics output from the AC-DC converter.

[0127] The capacitor bank consists of three single-phase capacitors or one three-phase capacitor; the three-phase capacitor can be connected in a star or delta configuration.

[0128] This grid-connected equipment AC capacitor fault protection method only requires a current sensor that meets the current range of a single capacitor to achieve real-time detection and protection of the operating status of each group of AC capacitors in the grid-connected equipment. It is low in cost and provides more comprehensive and accurate protection.

[0129] It should be understood that the above are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the patent. Any equivalent structural or procedural transformations made using the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A method for protecting grid-connected equipment from AC capacitor faults, characterized in that, The grid-connected equipment includes a three-phase AC port, a circuit breaker, a filter inductor, an AC / DC converter, and a controller; the filter inductor is connected to the AC output ports A2, B2, and C2 of the AC / DC converter; a first current sensor, a second current sensor, and a third current sensor are present; the circuit breaker is connected in series between the three-phase AC port and the filter inductor; the grid-connected equipment also includes a capacitor assembly, which includes at least three capacitor groups: a first capacitor group, a second capacitor group...a ​​Nth capacitor group; the first capacitor group, the second capacitor group...a ​​Nth capacitor group are connected in parallel to ports A1, B1, and C1 of the connection line between the circuit breaker and the filter inductor; the controller is connected to the circuit breaker and the AC / DC converter; the first current sensor, the second current sensor, and the third current sensor are connected in series on the connection line between the electrical port of the capacitor assembly and ports A1, B1, and C1; The first current sensor, the second current sensor, and the third current sensor respectively detect one phase current of each capacitor bank in the capacitor assembly according to a detection combination strategy; One current sensor corresponds to one phase current of one capacitor bank, or one current sensor corresponds to one phase current of each of two capacitor banks; The controller obtains the real-time current value based on the connection relationship between the first current sensor, the second current sensor, the third current sensor, and the capacitor assembly, and the detection combination strategy. , , Calculate the real-time value of the three-phase equivalent current of a single capacitor bank. , , The sum of real-time current values ,as well as , , and effective value and and and ; The controller according to and and The capacitor bank is compared with a preset threshold to determine whether it is overloaded. and and When the load exceeds a preset threshold, the controller determines that the capacitor is overloaded, sends a shutdown command to the AC / DC converter to stop the AC / DC converter from working, and simultaneously sends a disconnect signal to the circuit breaker. The controller according to The capacitor is compared with a preset threshold to determine whether it is short-circuited or open-circuited; if... When the value exceeds a preset threshold, it is determined that the capacitor has a short circuit or open circuit fault. The controller sends a shutdown command to the AC / DC converter to stop the AC / DC converter from working, and at the same time sends a disconnect signal to the circuit breaker. in, .

2. The method for AC capacitor fault protection of grid-connected equipment according to claim 1, characterized in that, The capacitor assembly includes three capacitor banks: a first capacitor bank, a second capacitor bank, and a third capacitor bank. The detection combination strategy is as follows: the first current sensor detects the A-phase current of the first capacitor bank to obtain the real-time value of the primary current of the current sensor. The second current sensor detects the B-phase current of the second capacitor bank to obtain the real-time value of the primary current of the current sensor. The third current sensor detects the C-phase current of the third capacitor bank to obtain the real-time value of the primary current of the current sensor. ; ， ， ， ， ， ， ， ， in, , , This represents the real-time value of the three-phase equivalent current of a single capacitor bank. This is the sum of the real-time current values. and and and for , , , Valid value.

3. The method for AC capacitor fault protection of grid-connected equipment according to claim 1, characterized in that, The capacitor assembly includes four capacitor banks: a first capacitor bank, a second capacitor bank, a third capacitor bank, and a fourth capacitor bank. The detection combination strategy is as follows: a first current sensor detects the A-phase current of the first capacitor bank to obtain the real-time value of the primary current of the current sensor. The second current sensor detects the B-phase current of the second capacitor bank to obtain the real-time value of the primary current of the current sensor. The third current sensor detects the B-phase current of the third capacitor bank and the A-phase current of the fourth capacitor bank to obtain the real-time value of the primary current of the current sensor. ; ， ， ， ， ， ， ， ， in, , , This represents the real-time value of the three-phase equivalent current of a single capacitor bank. This is the sum of the real-time current values. and and for , , Valid value.

4. The method for AC capacitor fault protection of grid-connected equipment according to claim 1, characterized in that, The capacitor assembly includes five capacitor groups: a first capacitor group, a second capacitor group, a third capacitor group, a fourth capacitor group, and a fifth capacitor group. The detection combination strategy is as follows: the first current sensor detects the A-phase current of the first capacitor group to obtain the real-time value of the primary current of the current sensor. The second current sensor detects the A-phase current of the second capacitor bank and the C-phase current of the third capacitor bank to obtain the real-time value of the primary current of the current sensor. The third current sensor detects the B-phase current of the fourth capacitor bank and the A-phase current of the fifth capacitor bank to obtain the real-time value of the primary current of the current sensor. ; ， ， ， ， ， ， ， ， in, , , This represents the real-time value of the three-phase equivalent current of a single capacitor bank. This is the sum of the real-time current values. and and for , , Valid value.

5. The method for AC capacitor fault protection of grid-connected equipment according to claim 1, characterized in that, The capacitor assembly includes six capacitor groups: a first capacitor group, a second capacitor group, a third capacitor group, a fourth capacitor group, a fifth capacitor group, and a sixth capacitor group. The detection combination strategy is as follows: a first current sensor detects the A-phase current of the first capacitor group and the B-phase current of the second capacitor group to obtain the real-time value of the primary current of the current sensor. The second current sensor detects the C-phase current of the third capacitor bank and the A-phase current of the fourth capacitor bank to obtain the real-time value of the primary current of the current sensor. The third current sensor detects the B-phase current of the fifth capacitor bank and the C-phase current of the sixth capacitor bank to obtain the real-time value of the primary current of the current sensor. ; ， ， ， ， ， ， ， ， in, , , This represents the real-time value of the three-phase equivalent current of a single capacitor bank. This is the sum of the real-time current values. and and for , , Valid value.

6. The method for AC capacitor fault protection of grid-connected equipment according to claim 1, characterized in that, The filter inductor, in conjunction with the capacitor assembly, is used to suppress and filter out high-frequency AC harmonics output from the AC-DC converter.

7. The method for AC capacitor fault protection of grid-connected equipment according to claim 1, characterized in that, The capacitor bank consists of three single-phase capacitors or one three-phase capacitor; the three-phase capacitor can be connected in a star or delta configuration.

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