A detection and protection method and detection system for ground leakage current of parallel inverter

Abstract

The present invention relates to a detection and protection method and detection system for ground leakage current of a parallel inverter, wherein the detection and protection method comprises: collecting the ground leakage current value of each inverter, the current value of the high-voltage end of the buck circuit of each inverter, and the total current value of the high-voltage end of the buck circuit of the parallel module, and transmitting them to a data processing module; calculating the current average value of the parallel module and the actual ground leakage current value of each inverter, marking the inverter whose actual ground leakage current value is greater than the set value as an abnormal inverter, judging whether there is an abnormal inverter, and if so, the data processing module alarms and controls the abnormal inverter to stop working. The present invention can eliminate the influence of reactive circulating current on ground leakage current detection through the difference between the current of the high-voltage end of the buck circuit of a single inverter and the average current value of the parallel module, ensure the normal use of the ground leakage current detection function of the parallel module, and improve the stability of the parallel module, the accuracy and reliability of ground leakage current detection.

Description

Technical Field

[0001] The present invention relates to the technical field of current detection, and in particular to a detection and protection method and a detection system for ground leakage current of a parallel inverter. Background Art

[0002] The traditional inverter ground leakage current detection method is as follows: When the traditional inverter detects ground leakage current through the normal operation of the electrical equipment, the currents of the phase line and the neutral line entering the current transformer are equal and opposite in direction. The magnetic fluxes generated by the two currents in the transformer cancel each other out, and there is no induced current signal output on the secondary side of the transformer, and the switch remains in the on state; when the equipment has a relative casing leakage fault, the magnetic flux generated by the phase line current in the transformer is greater than the magnetic flux generated by the neutral line current, and residual magnetic flux appears in the current transformer and induces a current signal, which is amplified and sent to the digital signal processor for processing. When the leakage current reaches the set value, it will drive the switch actuator to trip and cut off the power supply.

[0003] With the development of energy storage inverters, the photovoltaic market has generated diversified demands, and the demand for parallel use of inverters has also increased. According to the parallel topology, parallel wiring is performed on the high-voltage side of the buck circuit when the inverter is in parallel state. The ground leakage current detection is performed on each machine. During the entire parallel operation process, reactive circulating current may be generated between each machine in the parallel system. From the perspective of a single inverter, the generated reactive circulating current will be considered as leakage current. If it continues for a period of time, it will mistakenly trigger the ground leakage current protection function of the single inverter and fail to operate normally.

[0004] Therefore, it is necessary to provide a detection and protection method and detection system for the ground leakage current of a parallel inverter, which can eliminate reactive circulating current, improve the stability of the parallel system, and improve the accuracy and reliability of parallel ground leakage current detection. Summary of the invention

[0005] In order to overcome the deficiencies of the prior art, the present invention provides a detection and protection method and a detection system for ground leakage current of a parallel inverter.

[0006] The technical solution of the present invention is as follows:

[0007] A detection and protection method for ground leakage current of a parallel inverter, the detection and protection method comprising:

[0008] S1: Collect the ground leakage current value I1 of each inverter participating in the parallel operation, the current value I2 of the high-voltage end of the buck circuit of each inverter, and the total current value I3 of the high-voltage end of the buck circuit of the parallel operation module, and transmit them to the data processing module;

[0009] S2: The data processing module calculates the current average value I4 of the high-voltage end of the buck circuit of the parallel module and the actual ground leakage current value I5 of each inverter, sets the set value I6, marks the inverter whose actual ground leakage current value I5 is greater than the set value I6 as an abnormal inverter, and marks the other inverters as normal inverters, and determines whether there is an abnormal inverter. If so, proceed to the next step, if not, proceed to the next sampling moment and return to step S1;

[0010] S3: The data processing module alarms, transmits a stop signal to the abnormal inverter and controls the abnormal inverter to stop working, enters the next sampling moment and returns to step S1.

[0011] As a further improvement of the present invention, step SA is provided before step S1;

[0012] SA: All the inverters are respectively provided with a first timing t1=0;

[0013] Step SB is provided between step S2 and step S3;

[0014] SB: Determine whether each abnormal inverter satisfies t1>T1 respectively, where T1 is the set time. If so, proceed to step S3; if not, proceed to the next sampling moment and the first timing t1 of all the abnormal inverters is t1=t1+n, where n is the sampling interval time, and the first timing t1 of all the normal inverters is 0, and return to step S1.

[0015] As a further improvement of the present invention, the set value I6 is 30mA or 60mA or 150mA; when I6=30mA, T1=300ms; when I6=60mA, T1=150ms; when I6=150mA, T1=40ms.

[0016] As a further improvement of the present invention, a step TA is provided before step S1;

[0017] TA: All the inverters are respectively provided with three timings, wherein the second timing t2=0, the third timing t3=0, and the fourth timing t4=0;

[0018] Steps TB, TC, TD and TE are provided between step S2 and step S3;

[0019] TB: Set the set values ​​I7 and I8, I6<I7<I8, and respectively judge the relationship between the actual ground leakage current value I5 of each abnormal inverter and the set values ​​I7 and I8. If I6<I5≤I7, the third timing and the fourth timing of the abnormal inverter are t3=t4=0, and enter step TC; if I7<I5≤I8, the fourth timing t4 of the abnormal inverter is 0, and enter step TD; if I5>I8, enter step TE;

[0020] TC: Determine whether each abnormal inverter satisfies t2>T2, T2 is the set time, if yes, go to step S3; if not, go to the next sampling moment and the second timing t2=t2+n of the abnormal inverter, n is the sampling interval time, the second timing, third timing, and fourth timing of all the normal inverters are t2=t3=t4=0, and return to step S1;

[0021] TD: Determine whether each abnormal inverter satisfies t2>T2 or t3>T3, T3 is the set time, if yes, go to step S3; if not, go to the next sampling moment and the third timing t3=t3+n of the abnormal inverter, the second timing t2=t2+n, n is the sampling interval time, the second timing, third timing, and fourth timing of all the normal inverters are t2=t3=t4=0, and return to step S1;

[0022] TE: Determine whether each abnormal inverter satisfies t2>T2 or t3>T3 or t4>T4, where T4 is the set time. If so, enter step S3; if not, enter the next sampling moment and the fourth timing t4=t4+n, the third timing t3=t3+n, and the second timing t2=t2+n of the abnormal inverter, where n is the sampling interval time. The second timing, third timing, and fourth timing of all the normal inverters are t2=t3=t4=0, and return to step S1.

[0023] As a further improvement of the present invention, the set values ​​I6=30mA, I7=60mA, I8=150mA, and the set time T2=300ms, T3=150ms, T4=40ms.

[0024] As a further improvement of the present invention, the sampling interval time n=1 ms.

[0025] As a further improvement of the present invention, the calculation formulas of the current average value I4 at the high voltage end of the step-down circuit of the parallel module and the actual ground leakage current value I5 are respectively:

[0026] I4=I3 / N,

[0027] I5=I1-(I2-I4),

[0028] Wherein, N is the number of inverters participating in the parallel connection.

[0029] A detection system includes a parallel module composed of a plurality of inverters connected in parallel, a hardware sampling module and a data processing module, wherein the hardware sampling module collects current signals of the parallel module and transmits the current signals to the data processing module, and the data processing module analyzes the current signals and sends control signals to the parallel module.

[0030] As a further improvement of the present invention, the hardware sampling module includes a saturated inductor leakage current coupling circuit, an oscillation circuit, a current sampling circuit, a filter proportional amplifier circuit, a current source circuit, a differential sampling circuit and a protection circuit; the saturated inductor leakage current coupling circuit, the oscillation circuit, the current sampling circuit and the filter proportional amplifier circuit are electrically connected in sequence and connected to the first input end of the differential sampling circuit; the current source circuit is electrically connected to the second input end of the differential sampling circuit; the protection circuit is electrically connected to the oscillation circuit, the current sampling circuit and the filter proportional amplifier circuit respectively.

[0031] As a further improvement of the present invention, the data processing module includes a master digital signal processor and several slave digital signal processors, and the slave digital signal processors correspond to the inverters one by one; the master digital signal processor obtains the total current value I3, calculates the current average value I4 and sends the current average value I4 to the slave digital signal processors; the slave digital signal processors calculate and judge the actual ground leakage current value I5 of the corresponding inverter, and send control signals to the corresponding inverters.

[0032] According to the present invention of the above scheme, the beneficial effects of the present invention are:

[0033] The present invention provides a detection and protection method and a detection system for the ground leakage current of a parallel inverter, which can eliminate the influence of reactive circulating current on the ground leakage current detection through the difference between the current at the high-voltage end of a single inverter step-down circuit and the average current value of a parallel module, ensure the normal use of the ground leakage current detection function of the parallel module, improve the stability of the parallel module, and improve the accuracy and reliability of the parallel ground leakage current detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a flow chart of a first embodiment of the present invention;

[0035] Figure 2 is a flow chart of a second embodiment of the present invention;

[0036] Figure 3 is a flow chart of the third embodiment of the present invention. DETAILED DESCRIPTION

[0037] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0039] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0040] See also Figure 1 The present invention provides a first embodiment of a detection and protection method for ground leakage current of a parallel inverter, which can eliminate the influence of reactive circulating current on ground leakage current detection by the difference between the current at the high-voltage end of a single inverter step-down circuit and the average current value of a parallel module, thereby ensuring the normal use of the ground leakage current detection function of the parallel module, improving the stability of the parallel module, and improving the accuracy and reliability of parallel ground leakage current detection, wherein the detection and protection method includes:

[0041] S1: The hardware sampling module collects the ground leakage current value I1 of each inverter participating in the parallel operation, the current value I2 of the high-voltage end of the buck circuit of each inverter, and the total current value I3 of the high-voltage end of the buck circuit of the parallel operation module, and transmits them to the data processing module;

[0042] S2: The data processing module calculates the average current value I4 at the high-voltage end of the buck circuit of the parallel module and the actual ground leakage current value I5 of each inverter. The calculation formulas of the average current value I4 at the high-voltage end of the buck circuit of the parallel module and the actual ground leakage current value I5 are:

[0043] I4=I3 / N,

[0044] I5=I1-(I2-I4),

[0045] Where N is the number of inverters participating in parallel operation;

[0046] Set a set value I6, mark the inverter whose actual ground leakage current value I5 is greater than the set value I6 as an abnormal inverter, and mark the other inverters as normal inverters, and determine whether there is an abnormal inverter. If so, proceed to the next step, if not, proceed to the next sampling moment and return to step S1;

[0047] S3: The data processing module alarms, transmits a stop signal to the abnormal inverter and controls the abnormal inverter to stop working, enters the next sampling moment and returns to step S1. After the abnormal inverter stops working, it immediately leaves the parallel mode and disconnects from other inverters. The remaining unmarked inverters continue to work in parallel normally. The hardware sampling module continues to collect data for the normally working inverters to ensure the stable operation of the parallel module.

[0048] See also Figure 2 The present invention provides a second embodiment of a detection and protection method for ground leakage current of a parallel inverter, the detection and protection method comprising:

[0049] SA: All inverters are respectively provided with a first timer, and the first timer is assigned a value of 0, that is, t1 = 0;

[0050] S1: Collect the ground leakage current value I1 of each inverter participating in the parallel operation, the current value I2 of the high-voltage end of the buck circuit of each inverter, and the total current value I3 of the high-voltage end of the buck circuit of the parallel operation module, and transmit them to the data processing module;

[0051] S2: The data processing module calculates the current average value I4 of the high-voltage end of the buck circuit of the parallel module and the actual ground leakage current value I5 of each inverter, sets the set value I6, marks the inverter whose actual ground leakage current value I5 is greater than the set value I6 as an abnormal inverter, and marks the other inverters as normal inverters, and determines whether there is an abnormal inverter. If so, proceed to the next step, if not, proceed to the next sampling moment and return to step S1;

[0052] SB: Determine whether each abnormal inverter satisfies t1>T1, T1 is the set time, if yes, go to step S3; if not, go to the next sampling moment and all abnormal inverters re-assign the current time of the first timing t1 plus the sampling interval time to the first timing t1, that is, the re-assigned first timing t1=t1+n, n is the sampling interval time; assign 0 to the first timing of all normal inverters, that is, t1=0, and return to step S1;

[0053] S3: The data processing module alarms, transmits a stop signal to the abnormal inverter and controls the abnormal inverter to stop working, enters the next sampling moment and returns to step S1.

[0054] When an inverter is marked as an abnormal inverter, the data processing module continuously monitors the inverter. A set time T1 is set inside the data processing module. If the actual ground leakage current value I5 of the inverter in the T1 time period is greater than the set value I6, it is determined that the inverter is indeed abnormal, and the data processing module controls it to stop working; if the actual ground leakage current value I5 of the inverter in the T1 time period is unstable and fluctuates, that is, sometimes greater than the set value I6 and sometimes less than the set value I6, it is determined that the inverter has ground leakage current fluctuations and there is no accurate abnormality. Therefore, when the actual ground leakage current value I5 is less than or equal to the set value I6 in the T1 time period, the data processing module cancels the abnormal mark of the inverter and restores it to a normal inverter for data collection and monitoring, which can effectively avoid the data processing module from misjudging the inverter due to short-term ground leakage current fluctuations, and miscontrolling it to stop working, causing unnecessary impact on the work of the parallel module, and can effectively improve the accuracy and reliability of ground leakage current monitoring.

[0055] Preferably, in actual use, multiple groups of data can be set and coordinated for the set value I6 and the set time T1 according to specific usage requirements to improve the overall practicality and usage compatibility. For example, the set value I6 is 30mA or 60mA or 150mA; when I6=30mA, T1=300ms; when I6=60mA, T1=150ms; when I6=150mA, T1=40ms; similarly, the sampling interval n can also be set according to usage requirements. Shortening the sampling interval can improve the accuracy of the data, while increasing the sampling interval can appropriately reduce the cost. Preferably, the sampling interval n=1ms.

[0056] See also Figure 3 The present invention provides a third embodiment of a detection and protection method for ground leakage current of a parallel inverter, the detection and protection method comprising:

[0057] TA: All inverters are respectively provided with three timings, and the second timing, third timing and fourth timing of each are assigned a value of 0, that is, the second timing t2 = 0, the third timing t3 = 0, and the fourth timing t4 = 0;

[0058] S1: Collect the ground leakage current value I1 of each inverter participating in the parallel operation, the current value I2 of the high-voltage end of the buck circuit of each inverter, and the total current value I3 of the high-voltage end of the buck circuit of the parallel operation module, and transmit them to the data processing module;

[0059] S2: The data processing module calculates the current average value I4 of the high-voltage end of the buck circuit of the parallel module and the actual ground leakage current value I5 of each inverter, sets the set value I6, marks the inverter whose actual ground leakage current value I5 is greater than the set value I6 as an abnormal inverter, and marks the other inverters as normal inverters, and determines whether there is an abnormal inverter. If so, proceed to the next step, if not, proceed to the next sampling moment and return to step S1;

[0060] TB: Set the set values ​​I7 and I8, I6<I7<I8, and judge the relationship between the actual ground leakage current value I5 of each abnormal inverter and the set values ​​I7 and I8 respectively. If I6<I5≤I7, the third timing and the fourth timing of the abnormal inverter are both assigned 0, that is, t3=t4=0, and enter step TC; if I7<I5≤I8, the fourth timing of the abnormal inverter is assigned 0, that is, t4=0, and enter step TD; if I5>I8, enter step TE;

[0061] TC: Determine whether each abnormal inverter satisfies t2>T2, T2 is the set time, if yes, go to step S3; if not, go to the next sampling moment and reassign the current time of the second timing t2 of the abnormal inverter plus the sampling interval time to the second timing t2, that is, the reassigned second timing t2=t2+n, n is the sampling interval time; the second timing, third timing, and fourth timing of all normal inverters are assigned 0, that is, t2=t3=t4=0, and return to step S1;

[0062] TD: Determine whether each abnormal inverter satisfies t2>T2 or t3>T3, T3 is the set time, if yes, go to step S3; if not, go to the next sampling moment and reassign the current time of the third timing t3 of the abnormal inverter plus the sampling interval to the third timing t3, and reassign the current time of the second timing t2 plus the sampling interval to the second timing t2, that is, the reassigned third timing t3=t3+n, the reassigned second timing t2=t2+n, n is the sampling interval; the second timing, third timing, and fourth timing of all normal inverters are assigned 0, that is, t2=t3=t4=0, and return to step S1;

[0063] TE: Determine whether each abnormal inverter satisfies t2>T2 or t3>T3 or t4>T4, T4 is the set time. If yes, enter step S3; if not, enter the next sampling moment and reassign the current time of the fourth timing t4 of the abnormal inverter plus the sampling interval to the fourth timing t4, reassign the current time of the third timing t3 plus the sampling interval to the third timing t3, and reassign the current time of the second timing t2 plus the sampling interval to the second timing t2, that is, the reassigned fourth timing t4=t4+n, the reassigned third timing t3=t3+n, and the reassigned second timing t2=t2+n, where n is the sampling interval; the second timing, third timing, and fourth timing of all normal inverters are assigned 0, that is, t2=t3=t4=0, and return to step S1;

[0064] S3: The data processing module alarms, transmits a stop signal to the abnormal inverter and controls the abnormal inverter to stop working, enters the next sampling moment and returns to step S1.

[0065] When an inverter is marked as an abnormal inverter, the data processing module continuously monitors the inverter. Since there are large differences in the actual ground leakage current values ​​I5 of the inverters, the degree of danger also varies greatly. The larger the actual ground leakage current value I5, the higher the degree of danger and the shorter the abnormal judgment time. As a result, the mode with only one set of set values ​​and set times has certain limitations. Therefore, the monitoring accuracy is improved by setting multiple sets of set values ​​and set times to analyze and judge the ground leakage current value I5. For example, three set values ​​are set, namely I6, I7 and I8, I6<I7<I8, and the corresponding three set times are set, namely T2, T3 and T4, T2>T3>T4. When the actual ground leakage current value I5 falls into a specific interval, the specific set time is used for abnormal judgment. The high current interval and the low current interval are not a selection exclusion relationship, but an inclusive relationship. When the actual ground leakage current value I5 falls into the high current setting interval, it must satisfy its The requirement of falling into the low current setting interval is that if the actual ground leakage current value I5 falls into the interval I7<I5≤I8, the third timing t3 works and determines whether t3>T3, then the actual ground leakage current value I5 must be greater than the set value I6, so the second timing t2 also works and determines whether t2>T2, and the two sets of time judgments are performed simultaneously. Only one judgment needs to be met, that is, t3>T3 or t2>T2, to determine that the inverter is indeed abnormal, and the data processing module controls it to stop working; similarly, if the actual ground leakage current value I5 jumps between the time intervals I7<I5≤I8 and I6<I5≤I7, although it cannot meet the judgment standard of the set time T3 of the high current interval I7<I5≤I8, but if the total time in the two intervals reaches the set time T2, then the judgment standard of the set time T2 of the low current interval I6<I5≤I7 is met, then it is determined that the inverter is indeed abnormal, and the data processing module controls it to stop working.

[0066] Preferably, the setting values ​​are I6=30mA, I7=60mA, I8=150mA, the setting time is T2=300ms, T3=150ms, T4=40ms, and the sampling interval time n=1ms.

[0067] The present invention provides a detection system, comprising a parallel module composed of a plurality of inverters connected in parallel, a hardware sampling module and a data processing module, wherein the hardware sampling module collects current signals of the parallel module and transmits the current signals to the data processing module, the data processing module analyzes the current signals and sends control signals to the parallel module, preferably, the current signals include ground leakage current values ​​I1 of each inverter involved in the parallel operation, current values ​​I2 of the high-voltage end of the buck circuit of each inverter, and a total current value I3 of the high-voltage end of the buck circuit of the parallel module.

[0068] As an embodiment of the present invention, the hardware sampling module includes a saturated inductor leakage current coupling circuit, an oscillation circuit, a current sampling circuit, a filter proportional amplifier circuit, a current source circuit, a differential sampling circuit and a protection circuit; the saturated inductor leakage current coupling circuit inputs the ground leakage current to the hardware sampling module; the oscillation circuit quickly identifies and responds to the electronic control part of potential electrical safety hazards, and adopts an asymmetric circuit so that the circuit can start oscillation smoothly regardless of the state; the current sampling circuit collects the current passing through the oscillation circuit; the filter proportional amplifier circuit attenuates the oscillation signal and proportionally amplifies the coupled leakage current signal; the current source circuit simulates a 50mA current entering the module during the ground leakage current self-test to detect whether the module is normal; the differential sampling circuit performs differential operation on the two current signals; the saturated inductor leakage current coupling circuit, the oscillation circuit , the current sampling circuit and the filter proportional amplifier circuit are electrically connected in sequence and connected to the first input end of the differential sampling circuit. The ground leakage current is input through the saturated inductor leakage current coupling circuit, and is converted into a first input signal through the oscillation circuit, the current sampling circuit and the filter proportional amplifier circuit to reach the differential sampling circuit; the current source circuit is electrically connected to the second input end of the differential sampling circuit, and the ground leakage current self-test signal reaches the differential sampling circuit as the second input signal; the differential sampling circuit performs a differential operation on the two input signals, and then transmits the output signal to the data processing module; the protection circuit is electrically connected to the oscillation circuit, the current sampling circuit and the filter proportional amplifier circuit respectively, and the protection circuit mainly consists of two parts, a voltage clamping circuit and an overcurrent protection circuit, both of which are arranged in the oscillation circuit, and certain protection measures are also added in the filter proportional amplifier circuit and the current sampling circuit.

[0069] As an embodiment of the present invention, the data processing module includes a master digital signal processor and several slave digital signal processors, and the slave digital signal processors correspond to the inverters one by one; the master digital signal processor obtains the total current value I3, calculates the current average value I4 and sends the current average value I4 to the slave digital signal processors; the slave digital signal processors calculate and judge the actual ground leakage current value I5 of the corresponding inverter, and send a control signal to the corresponding inverter. If the slave digital signal processor determines that the corresponding inverter is an abnormal inverter, it sends a stop signal to the abnormal inverter and stops its operation.

[0070] In summary, the present invention can eliminate the influence of reactive circulating current on ground leakage current detection through the difference between the current at the high-voltage end of a single inverter step-down circuit and the average current value of the parallel module, ensure the normal use of the ground leakage current detection function of the parallel module, improve the stability of the parallel module, and improve the accuracy and reliability of parallel ground leakage current detection; the abnormal inverter immediately leaves the parallel mode after stopping working, disconnects from other inverters, and the remaining unmarked inverters continue to work normally in parallel, and the hardware sampling module continues to collect data for the normally working inverter to ensure the stable operation of the parallel module; when an inverter is marked as an abnormal inverter, the data processing module continuously monitors the inverter, which can effectively avoid the data processing module from misjudging the inverter due to short-term ground leakage current fluctuations, and miscontrolling it to stop working, causing unnecessary impact on the operation of the parallel module, and can effectively improve the accuracy and reliability of ground leakage current monitoring; setting multiple groups of set values ​​and set times to analyze and judge the ground leakage current value I5 can improve the accuracy of inverter abnormal monitoring.

[0071] It should be emphasized that the above are only preferred embodiments of the present invention and do not limit the present invention in any form. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A detection and protection method for ground leakage current of a parallel inverter, characterized in that: The detection and protection method comprises: S1: Collect the ground leakage current value I1 of each inverter participating in the parallel operation, the current value I2 of the high-voltage end of the buck circuit of each inverter, and the total current value I3 of the high-voltage end of the buck circuit of the parallel operation module, and transmit them to the data processing module; S2: The data processing module calculates the current average value I4 of the high-voltage end of the buck circuit of the parallel module and the actual ground leakage current value I5 of each inverter, sets the set value I6, marks the inverter whose actual ground leakage current value I5 is greater than the set value I6 as an abnormal inverter, and marks the other inverters as normal inverters, and determines whether there is an abnormal inverter. If so, proceed to the next step, if not, proceed to the next sampling moment and return to step S1; S3: The data processing module alarms, transmits a stop signal to the abnormal inverter and controls the abnormal inverter to stop working, enters the next sampling moment and returns to step S1.

2. The method for detecting and protecting the ground leakage current of a parallel inverter according to claim 1, characterized in that: Before step S1, step SA is provided; SA: All the inverters are respectively provided with a first timing t1=0; Step SB is provided between step S2 and step S3; SB: Determine whether each abnormal inverter satisfies t1>T1 respectively, where T1 is the set time. If so, proceed to step S3; if not, proceed to the next sampling moment and the first timing t1 of all the abnormal inverters is t1=t1+n, where n is the sampling interval time, and the first timing t1 of all the normal inverters is 0, and return to step S1.

3. The method for detecting and protecting the ground leakage current of the parallel inverter according to claim 2, characterized in that: The set value I6 is 30mA, 60mA or 150mA; when I6=30mA, T1=300ms; when I6=60mA, T1=150ms; when I6=150mA, T1=40ms.

4. The method for detecting and protecting the ground leakage current of a parallel inverter according to claim 1, characterized in that: Before step S1, step TA is provided; TA: All the inverters are respectively provided with three timings, wherein the second timing t2=0, the third timing t3=0, and the fourth timing t4=0; Steps TB, TC, TD and TE are provided between step S2 and step S3; TB: Set the set values ​​I7 and I8, I6<I7<I8, and respectively judge the relationship between the actual ground leakage current value I5 of each abnormal inverter and the set values ​​I7 and I8. If I6<I5≤I7, the third timing and the fourth timing of the abnormal inverter are t3=t4=0, and enter step TC; if I7<I5≤I8, the fourth timing t4 of the abnormal inverter is 0, and enter step TD; if I5>I8, enter step TE; TC: Determine whether each abnormal inverter satisfies t2>T2, T2 is the set time, if yes, go to step S3; if not, go to the next sampling moment and the second timing t2=t2+n of the abnormal inverter, n is the sampling interval time, the second timing, third timing, and fourth timing of all the normal inverters are t2=t3=t4=0, and return to step S1; TD: Determine whether each abnormal inverter satisfies t2>T2 or t3>T3, T3 is the set time, if yes, go to step S3; if not, go to the next sampling moment and the third timing t3=t3+n of the abnormal inverter, the second timing t2=t2+n, n is the sampling interval time, the second timing, third timing, and fourth timing of all the normal inverters are t2=t3=t4=0, and return to step S1; TE: Determine whether each abnormal inverter satisfies t2>T2 or t3>T3 or t4>T4, where T4 is the set time. If so, enter step S3; if not, enter the next sampling moment and the fourth timing t4=t4+n, the third timing t3=t3+n, and the second timing t2=t2+n of the abnormal inverter, where n is the sampling interval time. The second timing, third timing, and fourth timing of all the normal inverters are t2=t3=t4=0, and return to step S1.

5. The method for detecting and protecting the ground leakage current of the parallel inverter according to claim 4, characterized in that: The set values ​​I6=30mA, I7=60mA, I8=150mA, and the set times T2=300ms, T3=150ms, T4=40ms.

6. The method for detecting and protecting the ground leakage current of a parallel inverter according to any one of claims 2 to 5, characterized in that: The sampling interval time n=1 ms.

7. The method for detecting and protecting the ground leakage current of a parallel inverter according to claim 1, characterized in that: The calculation formulas of the current average value I4 at the high voltage end of the step-down circuit of the parallel module and the actual ground leakage current value I5 are respectively: I4=I3 / N, I5=I1-(I2-I4), Wherein, N is the number of inverters participating in the parallel connection.

8. A detection system based on the detection and protection method for ground leakage current of a parallel inverter as claimed in claim 1, characterized in that: It includes a parallel module composed of several inverters connected in parallel, a hardware sampling module and a data processing module. The hardware sampling module collects the current signal of the parallel module and transmits the current signal to the data processing module. The data processing module analyzes the current signal and sends a control signal to the parallel module.

9. The detection system according to claim 8, characterized in that: The hardware sampling module includes a saturated inductor leakage current coupling circuit, an oscillation circuit, a current sampling circuit, a filter proportional amplifier circuit, a current source circuit, a differential sampling circuit and a protection circuit; the saturated inductor leakage current coupling circuit, the oscillation circuit, the current sampling circuit and the filter proportional amplifier circuit are electrically connected in sequence and connected to the first input end of the differential sampling circuit; the current source circuit is electrically connected to the second input end of the differential sampling circuit; the protection circuit is electrically connected to the oscillation circuit, the current sampling circuit and the filter proportional amplifier circuit respectively.

10. The detection system according to claim 8, characterized in that: The data processing module includes a master digital signal processor and several slave digital signal processors, and the slave digital signal processors correspond to the inverters one by one; the master digital signal processor obtains the total current value I3, calculates the current average value I4 and sends the current average value I4 to the slave digital signal processors; the slave digital signal processors calculate and judge the actual ground leakage current value I5 of the corresponding inverter, and send control signals to the corresponding inverters.

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