A transformer system, system insulation impedance detection method, device and medium

Abstract

The application provides a transformer system, a system insulation impedance detection method, a device and a medium, so as to improve the system insulation impedance detection precision and without increasing the system cost. The system comprises a plurality of transformers, a sampling circuit and a control circuit; the plurality of transformers are connected in parallel, each transformer comprises a detection circuit; the detection circuit comprises a first switch and at least two resistors, the first switch is connected in parallel with one of the at least two resistors; the control circuit is used for controlling the sampling circuit to collect a first voltage and a second voltage, the first voltage is the voltage between a second bus and a ground wire collected by the sampling circuit when the first switch in a first number of detection circuits is in a conduction state; the second voltage is the voltage between the second bus and the ground wire collected by the sampling circuit when the first switch in a second number of detection circuits is in the conduction state; wherein the second number is different from the first number; and the ground insulation impedance of the transformer system is determined according to the first voltage and the second voltage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electronics, and in particular to a converter system, a system insulation impedance detection method, device and medium. BACKGROUND

[0002] In a converter application scenario, the insulation impedance of the direct current side of the converter to the ground can represent the insulation performance of the direct current system. If the insulation impedance of the direct current side of the converter to the ground is too low, current leakage of the converter may occur, which poses a threat to personnel. Therefore, it has become a basic requirement of safety standards for converters to have insulation impedance detection capability. Generally, an insulation detection circuit is provided in the converter to detect the insulation impedance to the ground when the converter is independently connected between the positive bus and the negative bus.

[0003] In a system in which multiple converters are connected in parallel, the insulation impedance of the system to the ground is small because the multiple converters are in a parallel state. Moreover, the more the number of converters connected in parallel, the smaller the insulation impedance of the system to the ground, and the more difficult it is for the insulation detection circuit provided in a single converter to meet the high-precision detection requirement of the insulation impedance of the system to the ground. SUMMARY

[0004] The present application provides a converter system, a system insulation impedance detection method, device and medium to improve the detection precision of the insulation impedance of the system and without increasing the cost of the system.

[0005] In a first aspect, an embodiment of the present application provides a converter system, comprising a plurality of converters, a sampling circuit and a control circuit; the plurality of converters are connected in parallel between a first bus and a second bus; the sampling circuit is connected between the second bus and a ground wire, the control circuit is connected with each converter, and the control circuit is also connected with the sampling circuit; each converter comprises a detection circuit; the detection circuit comprises a first switch and at least two resistors connected in series between the second bus and the ground wire, the first switch is connected in parallel with one of the at least two resistors, and the first switch is controlled by the control circuit; the sampling circuit is configured to collect a voltage between the second bus and the ground wire; the control circuit is configured to control the sampling circuit to collect a first voltage and a second voltage, the first voltage is a voltage between the second bus and the ground wire collected by the sampling circuit when the first switch in a first number of detection circuits is in a conductive state, the second voltage is a voltage between the second bus and the ground wire collected by the sampling circuit when the first switch in a second number of detection circuits is in a conductive state, the second number is different from the first number, and the insulation impedance of the converter system to the ground is determined according to the first voltage and the second voltage.

[0006] With the above system structure, the control circuit determines the ground insulation impedance of the transformer system by using the voltage between the second bus and the ground wire when the switches in different numbers of detection circuits are in the on state, without the need for additional elements. Since the detection circuits are connected in parallel, the equivalent detection resistance between the second bus and the ground wire in the transformer system when the switches in different numbers of detection circuits are in the on state is smaller than the detection resistance in the detection circuit of a single transformer, which can reduce the maximum sampling deviation when the sampling circuit obtains the voltage, thereby improving the detection accuracy of the ground impedance of the system.

[0007] In a possible design, the detection circuit specifically includes two resistors connected in series between the second bus and the ground wire, and the first switch is connected in parallel with a first resistor of the two resistors. The control circuit determines the ground insulation impedance of the transformer system according to the first voltage and the second voltage, and the ground insulation impedance of the transformer system conforms to the following formula:

[0008]

[0009] Riso is the ground insulation impedance of the transformer, Rz2 is the insulation impedance between the second bus and the ground wire, and Rz1 is the insulation impedance between the first bus and the ground wire. Wherein, , ; Rd1 is the equivalent detection resistance between the second bus and the ground wire when the first switch in the first number of detection circuits is in the on state; Rd2 is the equivalent detection resistance between the second bus and the ground wire when the first switch in the second number of detection circuits is in the on state; Rd1= , Rd2= , i is the first number, , j is the second number, , and , RB is the resistance value of the first resistor, RA is the resistance value of the second resistor other than the first resistor of the two resistors, and n is the number of the plurality of transformers; VB is the voltage between the first bus and the second bus, V1 is the first voltage, and V2 is the second voltage.

[0010] With the above system structure, each detection circuit includes a first resistor and a second resistor connected in series between the second bus and the ground wire. The control circuit can determine the ground insulation impedance of the transformer system according to the first resistor, the second resistor, the first voltage, the second voltage, the number of the plurality of transformers, and the relationship between the first number and the second number.

[0011] In a possible design, the detection circuit further includes at least one resistor connected between the first bus and the ground wire.

[0012] With the above system structure, since the detection circuits are connected in parallel, when the switches in different numbers of detection circuits are in the on state, the equivalent detection resistance between the first bus and the ground in the converter system is smaller than the detection resistance in the detection circuit of a single converter, which can reduce the maximum sampling deviation when the sampling circuit obtains the voltage, thereby improving the detection accuracy of the system ground impedance.

[0013] In a possible design, the detection circuit further includes a third resistor connected between the first bus and the ground.

[0014] The control circuit determines the ground insulation impedance of the converter system according to the first voltage and the second voltage, and the determination conforms to the following formula:

[0015]

[0016] Riso is the ground insulation impedance of the converter, Rz2 is the insulation impedance between the second bus and the ground, and Rz1 is the insulation impedance between the first bus and the ground; wherein, , ; Rd1 is the equivalent detection resistance between the second bus and the ground when the first switch in the first number of detection circuits is in the on state, and Rd2 is the equivalent detection resistance between the second bus and the ground when the first switch in the second number of detection circuits is in the on state; Rd1= , Rd2= , i is the first number, , j is the second number, , and , RB is the resistance value of the first resistor, RA is the resistance value of the second resistor excluding the first resistor, n is the number of the plurality of transformers, RC is the resistance value of the third resistor, VB is the voltage between the first bus and the second bus, V1 is the first voltage, and V2 is the second voltage.

[0017] With the above system structure, each detection circuit includes a first resistor and a second resistor connected in series between the second bus and the ground, and a third resistor connected between the first bus and the ground. The control circuit can determine the ground insulation impedance of the converter system according to the relationship between the first resistor, the second resistor, the third resistor, the first voltage, the second voltage, the number of the plurality of transformers, the first number, and the second number.

[0018] In a possible design, the detection circuit further includes a second switch and at least two resistors connected in series between the first bus and the ground, and the second switch is connected in parallel with one of the at least two resistors connected in series between the first bus and the ground, and the second switch is controlled by the control circuit.

[0019] In a possible design, the detection circuit specifically includes two resistors connected in series between the second bus and the ground, and the first switch is connected in parallel with a first resistor of the two resistors; the detection circuit further includes two resistors connected in series between the first bus and the ground and a second switch, and the second switch is connected in parallel with a fourth resistor of the two resistors connected in series between the first bus and the ground; if the first switch in each detection circuit is in a conducting state, the second switch in each detection circuit is in a non-conducting state; if the first switch in each detection circuit is in a non-conducting state, the second switch in each detection circuit is in a conducting state.

[0020] In a possible design, the first quantity is zero, and the second quantity is the number of the plurality of transformers; the fourth resistor has the same resistance as the second resistor, and a fifth resistor of the two resistors connected in series between the first bus and the ground, except the fourth resistor, has the same resistance as the first resistor; the control circuit determines the ground insulation impedance of the transformer system according to the first voltage and the second voltage, and the ground insulation impedance of the transformer system satisfies the following formula:

[0021]

[0022] Riso is the ground insulation impedance of the transformer, RB is the resistance of the first resistor, RA is the resistance of a second resistor of the two resistors connected in series between the second bus and the ground, except the first resistor, n is the number of the plurality of transformers, VB is the voltage between the first bus and the second bus, V1 is the first voltage, and V2 is the second voltage.

[0023] In a possible design, the control circuit includes a plurality of controllers; the plurality of controllers correspond to the plurality of transformers one by one; each controller is connected to a corresponding transformer, and is configured to control a switch in a detection circuit of the corresponding transformer; the plurality of controllers include one or more master controllers, and the master controller is configured to send an instruction to other controllers of the plurality of controllers, except the master controller, and the instruction is used to instruct the other controllers to control the switches in the detection circuits of the corresponding transformers.

[0024] In a possible design, the control circuit includes a plurality of controllers; the plurality of controllers include a master controller and a plurality of slave controllers; the plurality of slave controllers correspond to the plurality of converters one by one; each slave controller is connected to a corresponding converter, and is configured to control a switch in a detection circuit of the corresponding converter; and the master controller is configured to send an instruction to each slave controller, where the instruction is used to instruct the slave controller to control the switch in the detection circuit of the corresponding converter.

[0025] In a second aspect, an embodiment of the present application provides a system insulation impedance detection method, applied to a converter system, where the converter system includes a plurality of converters and a sampling circuit; the plurality of converters are connected in parallel between a first bus and a second bus; the sampling circuit is connected between the second bus and a ground wire; each of the converters includes a detection circuit; the detection circuit includes a first switch and at least two resistors connected in series between the second bus and the ground wire, and the first switch is connected in parallel with one of the at least two resistors; the method includes: controlling the sampling circuit to collect a first voltage, where the first voltage is a voltage between the second bus and the ground wire when a first number of the detection circuits are in a conductive state; controlling the sampling circuit to collect a second voltage, where the second voltage is a voltage between the second bus and the ground wire when a second number of the detection circuits are in the conductive state; the second number is different from the first number; and determining an insulation impedance of the converter system to the ground according to the first voltage and the second voltage.

[0026] In a possible design, the detection circuit specifically includes two resistors connected in series between the second bus and the ground wire, and the first switch is connected in parallel with a first resistor of the two resistors; and the insulation impedance of the converter system to the ground is determined according to the first voltage and the second voltage, and conforms to the following formula:

[0027]

[0028] Riso is the insulation impedance of the converter to the ground, Rz2 is the insulation impedance between the second bus and the ground wire, and Rz1 is the insulation impedance between the first bus and the ground wire; where, , ; Rd1 is an equivalent detection resistance between the second bus and the ground wire when the first switch in the first number of detection circuits is in the conductive state; Rd2 is an equivalent detection resistance between the second bus and the ground wire when the first switch in the second number of detection circuits is in the conductive state, and Rd1= , Rd2= ; i is the first number, , and j is the second number, , RB is the resistance value of the first resistor, RA is the resistance value of the second resistor of the two resistors except the first resistor, n is the number of the plurality of transformers; VB is the voltage between the first bus and the second bus, V1 is the first voltage, and V2 is the second voltage.

[0029] In a possible design, the detection circuit further includes at least one resistor connected between the first bus and the ground wire.

[0030] In a possible design, the detection circuit further includes a third resistor connected between the first bus and the ground wire; and the ground insulation impedance of the transformer system is determined according to the first voltage and the second voltage, and the ground insulation impedance of the transformer system conforms to the following formula:

[0031]

[0032] Riso is the ground insulation impedance of the transformer, Rz2 is the insulation impedance between the second bus and the ground wire, and Rz1 is the insulation impedance between the first bus and the ground wire; wherein, , ; Rd1 is the equivalent detection resistance between the second bus and the ground wire when the first switch in the first number of detection circuits is in the conductive state, Rd2 is the equivalent detection resistance between the second bus and the ground wire when the first switch in the second number of detection circuits is in the conductive state; Rd1= , Rd2= , i is the first number, , j is the second number, , RB is the resistance value of the first resistor, RA is the resistance value of the second resistor of the two resistors except the first resistor, n is the number of the plurality of transformers; RC is the resistance value of the third resistor, VB is the voltage between the first bus and the second bus, V1 is the first voltage, and V2 is the second voltage.

[0033] In a possible design, the detection circuit further includes a second switch and at least two resistors connected in series between the first bus and the ground wire, and the second switch is connected in parallel with one of the at least two resistors connected in series between the first bus and the ground wire.

[0034] In a possible design, the detection circuit specifically includes two resistors connected in series between the second bus and the ground wire, the first switch is connected in parallel with a first resistor among the two resistors; the detection circuit further includes two resistors connected in series between the first bus and the ground wire and a second switch, the second switch is connected in parallel with a fourth resistor among the two resistors connected in series between the first bus and the ground wire; if the first switch in each detection circuit is in a conducting state, the second switch in each detection circuit is in a non-conducting state; if the first switch in each detection circuit is in a non-conducting state, the second switch in each detection circuit is in a conducting state.

[0035] In a possible design, the first quantity is zero, the second quantity is the number of the plurality of transformers, and the fourth resistor has the same resistance as the second resistor; a fifth resistor among the two resistors connected in series between the first bus and the ground wire and other than the fourth resistor has the same resistance as the first resistor; the ground insulation impedance of the transformer system is determined according to the first voltage and the second voltage, and the ground insulation impedance of the transformer system conforms to the following formula:

[0036] The ground insulation impedance of the transformer system is determined by using the following formula:

[0037]

[0038] Riso is the ground insulation impedance of the transformer, RB is the resistance of the first resistor, and RA is the resistance of a second resistor among the two resistors connected in series between the second bus and the ground wire and other than the first resistor;

[0039] n is the number of the plurality of transformers;

[0040] VB is the voltage between the first bus and the second bus;

[0041] V1 is the first voltage, and V2 is the second voltage.

[0042] In a third aspect, the embodiments of the present application provide a system insulation impedance detection method, applied to a converter system, the converter system comprising a plurality of converters, a sampling circuit and a control circuit; the plurality of converters are connected in parallel between a first bus and a second bus; the sampling circuit is connected between the second bus and a ground wire, the control circuit is connected with each converter, and the control circuit is connected with the sampling circuit; each converter comprises a detection circuit; the detection circuit comprises a first switch and at least two resistors connected in series between the second bus and the ground wire, and the first switch is connected in parallel with one of the at least two resistors; the control circuit comprises a plurality of controllers, the plurality of controllers comprising a master controller and a plurality of slave controllers, one slave controller corresponding to one converter; the method comprises: the master controller controls the sampling circuit to collect a first voltage between the second bus and the ground wire, the first voltage being a voltage between the second bus and the ground wire when the first switch in a first number of the detection circuits is in a conducting state; the master controller controls the sampling circuit to collect a second voltage between the second bus and the ground wire, the second voltage being a voltage between the second bus and the ground wire when the first switch in a second number of the detection circuits is in a conducting state; wherein the second number is different from the first number; and the master controller determines the ground insulation impedance of the converter system according to a preset relationship among the resistors in the detection circuit, the number of the plurality of converters, the first number, the second number, the first voltage and the second voltage.

[0043] In a possible design, if the first number is not zero, before the master controller controls the sampling circuit to collect the first voltage between the second bus and the ground wire, the method further comprises: the master controller sends a first switching instruction to the first number of slave controllers, the first switching instruction being used to instruct the slave controller to control the first switch in the detection circuit to be in a conducting state; and the master controller controls the sampling circuit to collect the first voltage between the second bus and the ground wire, comprising: after the master controller sends the first switching instruction to the first number of slave controllers for a first time length, the master controller controls the sampling circuit to collect the first voltage between the second bus and the ground wire.

[0044] In a possible design, if the second quantity is not zero, before the main controller controls the sampling circuit to collect the second voltage between the second bus and the ground, the method further includes: the main controller sending a second switching instruction to the second quantity of slave controllers, where the second switching instruction is used to instruct the slave controllers to control a first switch in the detection circuit to be in a conducting state; and the main controller controls the sampling circuit to collect the second voltage between the second bus and the ground, including: after the main controller sends the second switching instruction to the second quantity of slave controllers for a second time length, the main controller controls the sampling circuit to collect the first voltage between the second bus and the ground.

[0045] In a possible design, the detection circuit further includes a second switch and at least two resistors connected in series between the first bus and the ground, and the second switch is connected in parallel with one of the at least two resistors connected in series between the first bus and the ground.

[0046] In a possible design, if the first quantity is zero, before the main controller controls the sampling circuit to collect the first voltage between the second bus and the ground, the method further includes: the main controller sending a third switching instruction to the first quantity of slave controllers, where the third switching instruction is used to instruct the slave controllers to control a second switch in the detection circuit to be in a conducting state; and the main controller controls the sampling circuit to collect the first voltage between the second bus and the ground, including: after the main controller sends the third switching instruction to the first quantity of slave controllers for a third time length, the main controller controls the sampling circuit to collect the first voltage between the second bus and the ground.

[0047] In a possible design, if the second quantity is zero, before the main controller controls the sampling circuit to collect the second voltage between the second bus and the ground, the method further includes: the main controller sending a fourth switching instruction to the second quantity of slave controllers, where the fourth switching instruction is used to instruct the slave controllers to control a second switch in the detection circuit to be in a conducting state; and the main controller controls the sampling circuit to collect the second voltage between the second bus and the ground, including: after the main controller sends the fourth switching instruction to the second quantity of slave controllers for a fourth time length, the main controller controls the sampling circuit to collect the second voltage between the second bus and the ground.

[0048] In a possible design, the plurality of slave controllers correspond to the plurality of transformers in a one-to-one manner.

[0049] In a possible design, the main controller corresponds to one transformer; and the method further includes: before the main controller controls the sampling circuit to collect the first voltage between the second bus and the ground, the main controller controls the first switch in the detection circuit of the transformer corresponding to the main controller to be in a conducting state; and the main controller determines the ground insulation impedance of the transformer system according to a preset relationship among the resistance in the detection circuit, the number of the plurality of transformers, the first number, the second number, the first voltage and the second voltage, including: the main controller determines the ground insulation impedance of the transformer system according to a preset relationship among the resistance in the detection circuit, the number of the plurality of transformers, the third number, the second number, the first voltage and the second voltage, where the third number is a sum of the first number and 1. Alternatively, before the main controller controls the sampling circuit to collect the second voltage between the second bus and the ground, the main controller controls the first switch in the detection circuit of the transformer corresponding to the main controller to be in a conducting state; and the main controller determines the ground insulation impedance of the transformer system according to a preset relationship among the resistance in the detection circuit, the number of the plurality of transformers, the first number, the second number, the first voltage and the second voltage, including: the main controller determines the ground insulation impedance of the transformer system according to a preset relationship among the resistance in the detection circuit, the number of the plurality of transformers, the first number, the fourth number, the first voltage and the second voltage, where the fourth number is a sum of the second number and 1.

[0050] In a possible design, the first number is less than or equal to the number of the plurality of transformers, and the second number is less than or equal to the number of the plurality of transformers; or the first number is equal to the number of the plurality of transformers, and the second number is zero; or the second number is equal to the number of the plurality of transformers, and the first number is zero.

[0051] In a fourth aspect, an embodiment of the present application provides a system insulation impedance detection method, applied to a converter system, the converter system comprising a plurality of converters, a sampling circuit and a control circuit; the plurality of converters are connected in parallel between a first bus and a second bus; the sampling circuit is connected between the second bus and a ground wire, the control circuit is connected with each converter, and the control circuit is connected with the sampling circuit; each converter comprises a detection circuit; the detection circuit comprises a first switch and at least two resistors connected in series between the second bus and the ground wire, and the first switch is connected in parallel with one of the at least two resistors; the control circuit comprises a plurality of controllers, the plurality of controllers comprising a master controller and a plurality of slave controllers, one slave controller corresponding to one converter; the method comprises: receiving, by a slave controller, a switching instruction sent by the master controller; if the switching instruction is a first switching instruction, controlling the first switch in the detection circuit of the converter corresponding to the slave controller to be in a conduction state, and the first switching instruction is used to instruct the slave controller to control the first switch to be in the conduction state.

[0052] In a possible design, the detection circuit further comprises a second switch and at least two resistors connected in series between the first bus and the ground wire, and the second switch is connected in parallel with one of the at least two resistors connected in series between the first bus and the ground wire; the method further comprises: if the switching instruction is a second switching instruction, controlling the second switch in the detection circuit of the converter corresponding to the slave controller to be in a conduction state, and the second switching instruction is used to instruct the slave controller to control the second switch to be in the conduction state.

[0053] In a fifth aspect, an embodiment of the present application provides a system insulation impedance detection device, applied to a converter system, the converter system comprising a plurality of converters, the plurality of converters being connected in parallel between a first bus and a second bus, and each converter comprising a detection circuit; the detection circuit comprising a first switch and at least two resistors connected in series between the second bus and a ground wire, and the first switch being connected in parallel with one of the at least two resistors connected in series between the second bus and the ground wire; the device comprising: an acquisition unit, configured to acquire a first voltage and a second voltage, the first voltage being a voltage between the second bus and the ground wire when the first switch in a first number of the detection circuits is in a conduction state, and the second voltage being a voltage between the second bus and the ground wire when the first switch in a second number of the detection circuits is in the conduction state; wherein the second number is different from the first number; a memory, configured to store programs, instructions or codes; and a processor, configured to execute the programs, instructions or codes in the memory to complete the method in the first aspect and any possible design thereof, the second aspect and any possible design thereof, or the third aspect and any possible design thereof.

[0054] In a sixth aspect, the embodiments of the present application provide a non-volatile computer readable storage medium for storing a computer program, which is loaded by a processor to execute the method in the first aspect and any possible design thereof, the second aspect and any possible design thereof, or the third aspect and any possible design thereof.

[0055] The technical effects achieved by the second aspect and the sixth aspect can refer to the technical effects achieved by the corresponding design of the first aspect, which will not be repeated here. BRIEF DESCRIPTION OF DRAWINGS

[0056] Figure 1 Structure diagram of an insulation detection circuit in a single transformer;

[0057] Figure 2 Structure diagram of a transformer system;

[0058] Figure 3 Structure diagram of another transformer system;

[0059] Figure 4 Structure diagram of a detection circuit in a transformer system;

[0060] Figure 5 Structure diagram of another transformer system;

[0061] Figure 6 Structure diagram of a detection circuit in another transformer system;

[0062] Figure 7 Structure diagram of a detection circuit in another transformer system;

[0063] Figure 8 Structure diagram of a control circuit in a transformer system;

[0064] Figure 9 Structure diagram of a control circuit in another transformer system;

[0065] Figure 10 Schematic flow chart of a system insulation impedance detection method;

[0066] Figure 11 Schematic flow chart of another system insulation impedance detection method;

[0067] Figure 12 Schematic flow chart of another system insulation impedance detection method;

[0068] Figure 13 Schematic flow chart of another system insulation impedance detection method;

[0069] Figure 14 is a schematic flow chart of another system insulation impedance detection method;

[0070] Figure 15 is a schematic structural diagram of a system insulation impedance detection device. DETAILED DESCRIPTION

[0071] First, the process of detecting the insulation impedance of a single transformer to ground by using an insulation detection circuit is introduced. As shown in FIG. 1, a transformer 11 is connected between a positive bus and a negative bus, and the transformer 11 includes an insulation detection circuit 110. The insulation impedance of the transformer 11 to ground can be represented by an equivalent resistance RZ1 and an equivalent resistance RZ2. The equivalent resistance RZ1 can be regarded as the insulation impedance of the ground terminal PE of the transformer 11 to the positive bus, and the equivalent resistance RZ2 can be regarded as the insulation impedance of the ground terminal PE of the transformer 11 to the negative bus. The resistance of the parallel connection of the equivalent resistance RZ1 and the equivalent resistance RZ2 is the insulation impedance Riso of the transformer 11 to ground. Figure 1

[0072] The insulation detection circuit 110 can include a first resistance, a second resistance, a third resistance, and a fourth resistance connected in series. The resistance values of the four resistances are denoted as R1, R2, R1, and R2, respectively. The insulation detection circuit 110 further includes a first switch K11 and a second switch K12. The first switch K11 is connected in parallel with the second resistance, and the second switch K12 is connected in parallel with the fourth resistance. The connection point between the second resistance and the third resistance is connected to the ground terminal PE of the transformer 11.

[0073] In the process of detecting the insulation of the transformer, two control processes can be divided. The first control process is to control the first switch K11 to be in a closed state, the second switch K12 to be in an open state, and to detect the voltage U1 between the ground terminal PE and the negative bus. The second control process is to control the first switch K11 to be in an open state, the second switch K12 to be in a closed state, and to detect the voltage U2 between the ground terminal PE and the negative bus again.

[0074] In the first control process, the first resistance in the insulation detection circuit 110 is connected in parallel with the equivalent resistance RZ1, and the third resistance and the fourth resistance are connected in series and then connected in parallel with the equivalent resistance RZ2. The voltage across the equivalent resistance RZ1 is UBUS-U1, and the voltage across the equivalent resistance RZ2 is U1. According to the property that the currents in series circuits are equal, the following relationship can be determined:

[0075] ​​​Similarly, in the second control process, the first resistor and the second resistor are connected in series and are connected in parallel with the equivalent resistor RZ1 in the insulation detection circuit 110. The third resistor and the equivalent resistor RZ1 are connected in parallel. The voltage across the equivalent resistor R1+ is UBUS-U2, and the voltage across the equivalent resistor R1- is U2. According to the property that the currents in the series circuit are equal, the relationship can be determined as .

[0076] The relationship obtained in the two control processes can be determined as According to the expression of the ground insulation impedance Riso of the converter 11, it can be seen that the accuracy of Riso depends on the difference between the voltages between the ground terminal PE and the negative bus of the converter 11 in the two control processes, or the difference between the two disturbance voltages Ud=U1-U2.

[0077] Therefore, improving the accuracy of determining the difference between the two disturbance voltages Ud can improve the accuracy of detecting Riso.

[0078] In the detection condition of the insulation detection circuit structure described above, it is assumed that the voltage UBUS between the positive and negative buses is 1200V, R1 is 1800kΩ, and R2 is 1200kΩ. If Riso is 50kΩ, then the difference between the two detected voltages Ud is 12.6V.

[0079] Taking the ground insulation impedance of each converter as 50kΩ as an example. Figure 2 The structure of a multi-converter parallel system is shown in FIG. 1. Multiple converters are connected in parallel before the positive and negative buses, and each converter includes a conversion circuit and an insulation impedance detection circuit. The converters can be controlled by signals received at the input. If the multi-converter parallel system includes 10 parallel converters, the ground insulation impedance of the system is 5kΩ, and the difference between the two detected voltages Ud is 1.33V.

[0080] Since the difference between the two disturbance voltages Ud is determined based on U1 and U2, and U1 and U2 are obtained by AD sampling, the accuracy of Ud is related to the AD sampling capability. Taking 12-bit AD sampling as an example, considering the upper limit of U1 and U2, the sampling circuit at least satisfies a sampling capability of 1500V. Then the maximum sampling error is V. When Ud is 12.6V, the maximum sampling deviation is 5.8%. When Ud is 1.33V, the maximum sampling deviation is 55.1%.

[0081] When directly using the insulation detection circuit in the converter to detect the ground insulation impedance of a multi-converter parallel system, the voltage sampling deviation is large, which causes the detection accuracy of the ground insulation impedance to decrease, making it difficult to accurately detect the ground insulation impedance of the system, and the detection accuracy is low.

[0082] ​When Ud is large, the maximum sampling deviation is small. One way is to increase Ud by reducing the resistance value in the insulation detection circuit, so as to reduce the maximum sampling deviation and improve the system ground impedance detection accuracy. Assuming that the resistance value of each resistor in the insulation detection circuit is adjusted, R1 is 900 kΩ, and R2 is 600 kΩ. Taking the ground insulation impedance of each converter as 50 kΩ as an example. If the system including 10 parallel converters has 10 parallel converters, the ground insulation impedance of the system is 5 kΩ. At this time, the difference between the two detection voltages Ud is 2.64 V, and the maximum deviation is 27.7%.

[0083] In this way, although the system impedance detection accuracy can be improved, the resistance power in the insulation detection circuit increases after the resistance value is reduced. For example, when the relay in the converter is attracted, the maximum power of the first resistor increases from 1.25 W to 2.5 W, and the voltage UBUS is 1500 V. The increase of the resistance power in the insulation detection circuit causes the heating problem, and a corresponding heat dissipation device needs to be introduced. Therefore, when the insulation detection circuit is reduced to improve the system insulation impedance detection accuracy, the power level of each resistor in the insulation detection circuit is the bottleneck of improving the system insulation impedance detection accuracy.

[0084] Another way is to improve the AD sampling capacity. For example, the voltage UBUS of the positive and negative bus is 1200 V, R1 is 1800 kΩ, and R2 is 1200 kΩ. In a system including 10 parallel converters, the ground insulation impedance of the system is 5 kΩ. After the 12-bit AD sampling is improved to 14-bit AD sampling, the maximum sampling error is V, and the maximum sampling deviation is 13.8%.

[0085] The way of improving the AD sampling capacity to improve the system impedance detection accuracy needs to use a master control chip or an expansion chip with a higher AD conversion bit number, which increases the system cost of the multi-parallel converter system.

[0086] Therefore, the application provides a system insulation impedance detection method and a converter system to improve the system insulation impedance detection accuracy without increasing the system cost.

[0087] The system insulation impedance detection method provided by the application can be applied to a converter system. The converter system provided by the application is introduced as follows. Figure 3As shown, the converter system includes a plurality of converters, a sampling circuit and a control circuit. The control circuit can be connected with each converter, and the control circuit can control each converter. The converter in the embodiment of the application can be used in an energy storage system to charge and discharge a battery. For example, a direct current / direct current converter. The converter in the embodiment of the application can also be a direct current / alternating current converter, which is used in a photovoltaic system and has a photovoltaic power generation function.

[0088] The converter can include a conversion circuit and a detection circuit. The conversion circuit is used to implement the function of the converter, such as direct current / direct current conversion, direct current / alternating current conversion, etc. The detection circuit is used to detect the ground insulation impedance of the converter. One end of each converter is connected to the first bus, and the other end is connected to the second bus. The converter system can also include a control circuit for controlling each converter, such as controlling the conversion circuit to work and controlling the detection circuit to detect the ground insulation impedance. The converter system also includes a sampling circuit connected between the second bus and the ground wire, which is used to collect the voltage between the second bus and the ground wire when the detection system detects the ground insulation impedance. The control circuit can also connect the sampling circuit to control the sampling circuit to collect the voltage between the second bus and the ground wire.

[0089] In the embodiment of the application, the first bus is the positive bus, and the second bus is the negative bus. Alternatively, the first bus is the negative bus, and the second bus is the positive bus. In the following embodiments, the first bus is the positive bus BUS+, and the second bus is the negative bus BUS- as an example.

[0090] The detection circuit in each converter can include a plurality of resistors and at least one switch.

[0091] In one possible implementation, the plurality of resistors in each detection circuit are connected in series between the second bus and the ground wire. For example, Figure 3 As shown, the converter system includes n converters, and each converter is connected in parallel between the positive and negative buses. For example, the first end of the converter 1 is connected to the positive bus BUS+, the second end of the converter is connected to the negative bus BUS-, and the ground end of the converter 1 is connected to the ground wire. The connection mode of the other converters to the positive bus BUS+, the negative bus BUS- and the ground wire is the same as that of the converter 1. Here, it is not described again.

[0092] Among them, the detection circuit in each converter is connected between the negative bus BUS- and the ground wire. For example, Figure 3 As shown, the detection circuit 1 in the converter 1 is connected between the negative bus BUS- and the ground wire. The detection circuit n in the converter n is connected between the negative bus BUS- and the ground wire.

[0093] The transformer system can further comprise a control circuit for controlling the transformers, such as controlling the operation of the transforming circuit and controlling the detection circuit to detect the ground insulation impedance. The transformer system can further comprise a sampling circuit connected between the negative bus BUS- and the ground wire for sampling the voltage between the negative bus BUS- and the ground wire when the detection system detects the ground insulation impedance. The control circuit can also be connected to the sampling circuit for controlling the sampling circuit to sample the voltage between the negative bus BUS- and the ground wire.

[0094] In one example, the detection circuit can comprise at least two resistors and at least one switch. The at least two resistors can be connected in series between the negative bus BUS- and the ground wire, and the at least one switch can be connected to any one of the at least two resistors. The control circuit can switch the resistors connected between the positive bus BUS+ and the negative bus BUS- by switching the on-off state of the switch in the detection circuit. It should be understood that the resistor not connected in parallel with the switch can also be replaced by a plurality of series-connected resistors.

[0095] As shown in FIG. 1, the detection circuit n can comprise two series-connected detection resistors and one switching switch Qn, such as a first detection resistor RA n and a second detection resistor RB n. Similarly, the first detection resistor in the detection circuit 1 is denoted as RA 1, the second detection resistor is denoted as RB 1, and the switching switch is denoted as Q1. In the plurality of detection circuits shown in FIG. 1, the switching switch Qn is connected in parallel with the second detection resistor RB n as an example. The first detection resistor in each detection circuit has the same resistance value, and the second detection resistor in each detection circuit also has the same resistance value. Figure 4 Figure 4 As shown in FIG. 1, the detection circuit n can comprise two series-connected detection resistors and one switching switch Qn, such as a first detection resistor RA n and a second detection resistor RB n. Similarly, the first detection resistor in the detection circuit 1 is denoted as RA 1, the second detection resistor is denoted as RB 1, and the switching switch is denoted as Q1. In the plurality of detection circuits shown in FIG. 1, the switching switch Qn is connected in parallel with the second detection resistor RB n as an example. The first detection resistor in each detection circuit has the same resistance value, and the second detection resistor in each detection circuit also has the same resistance value.

[0096] The ground insulation impedance Riso of the transformer system can be equivalent to the impedance in parallel between the ground insulation impedance Rz1 between the positive bus BUS+ and the ground wire and the ground insulation impedance Rz2 between the negative bus BUS- and the ground wire, that is, Riso = Rz1 / / Rz2, where A / / B represents the resistance value of the resistor A connected in parallel with the resistor B.

[0097] The system insulation impedance detection method provided in the embodiments of the present application can be executed by a control circuit. The control circuit can control at least one detection circuit to switch the resistor connected between the negative bus BUS- and the ground wire. Generally, the initial state of the switching switch in each detection circuit is the off state, and thus the resistor connected between the negative bus BUS- and the ground wire in each detection circuit is the first detection resistor and the second detection resistor connected in series.

[0098] ​The control circuit can control the sampling circuit to collect the voltage Uc1 between the negative bus BUS- and the ground wire before the system insulation impedance detection. Since the n detection circuits are in parallel connection, when the switching switch in each detection circuit is in open state, the equivalent detection resistance between the negative bus BUS- and the ground wire is , the voltage across the equivalent ground insulation impedance Rz1 between the positive bus BUS+ and the ground wire is UBUS-Uc1, and the voltage across the equivalent ground insulation impedance Rz2 between the negative bus BUS- and the ground wire is Uc1. Therefore, the relationship between the equivalent ground insulation impedance Rz1 between the positive bus BUS+ and the ground wire and the equivalent ground insulation impedance Rz2 between the negative bus BUS- and the ground wire is, .

[0099] Then, the control circuit controls at least one detection circuit in the converter system to switch the resistance connected between the negative bus BUS- and the ground wire. For example, the control circuit can control the switching switch in at least one detection circuit to be in closed state, so as to realize switching the resistance connected between the negative bus BUS- and the ground wire in the detection circuit.

[0100] In one example, the control circuit controls one detection circuit to switch the resistance connected between the negative bus BUS- and the ground wire. That is, the control circuit controls the switching switch in one switching circuit to be in closed state. For example, the control circuit can control the switching switch Q1 in the detection circuit 1 to be in conducting state. Since the switching switch Q1 is in conducting state, the second detection resistance RB2 in the detection circuit 1 is short-circuited. Thus, in the detection circuit 1, the resistance connected between the negative bus BUS- and the ground wire is changed from RA1+RA2 to RA1.

[0101] In the converter system, the resistance connected between the negative bus BUS- and the ground wire in the n-1 detection circuits other than the detection circuit 1 does not change. In this case, the equivalent detection resistance between the negative bus BUS- and the ground wire in the converter system is , that is, .

[0102] The control circuit controls the sampling circuit to collect the voltage Uc2 between the negative bus BUS- and the ground wire. After the switching switch in the detection circuit 1 is in conducting state, the equivalent detection resistance between the negative bus BUS- and the ground wire is , the voltage across the equivalent ground insulation impedance Rz1 between the positive bus BUS+ and the ground wire is UBUS-Uc3, and the voltage across the equivalent ground insulation impedance Rz2 between the negative bus BUS- and the ground wire is Uc2. Therefore, the relationship between the equivalent ground insulation impedance Rz1 between the positive bus BUS+ and the ground wire and the equivalent ground insulation impedance Rz2 between the negative bus BUS- and the ground wire is, .

[0103] The control circuit can determine the equivalent ground insulation impedance Rz2 between the negative bus BUS- and the ground and the equivalent ground insulation impedance Rz1 between the positive bus BUS+ and the ground according to the relationship between the equivalent ground insulation impedance Rz1 between the positive bus BUS+ and the ground and the equivalent ground insulation impedance Rz2 between the negative bus BUS- and the ground before the switching switch in the switching detection circuit 1 is in the conducting state , and the relationship between the equivalent ground insulation impedance Rz1 between the positive bus BUS+ and the ground and the equivalent ground insulation impedance Rz2 between the negative bus BUS- and the ground after the switching switch in the switching detection circuit 1 is in the conducting state . The ground insulation impedance of the converter system is Rz1 / / Rz2.

[0104] In actual application scenarios, Rz1 and Rz2 can be solved by simultaneously solving the equations and the equation . By simultaneously solving the two equations, the relationship between Rz1 and UBUS, Uc1, Uc2, RA1, RB1 and n, and the relationship between Rz2 and UBUS, Uc1, Uc2, RA1, RB1 and n can be solved.

[0105] The control circuit can obtain Rz1 and Rz2 based on the predetermined relationship between Rz1 and UBUS, Uc1, Uc2, RA1, RB1 and n, the relationship between Rz2 and UBUS, Uc1, Uc2, RA1, RB1 and n, and the two acquisition results of the sampling circuit before and after the switching switch in the control circuit switching detection circuit 1 is in the conducting state. Then, the ground insulation impedance of the converter system is obtained by solving the parallel results of Rz1 and Rz2. In addition, the control circuit can also directly obtain the ground insulation impedance of the converter system based on the predetermined relationship between Rz1 and UBUS, Uc1, Uc2, RA1, RB1 and n, the relationship between Rz2 and UBUS, Uc1, Uc2, RA1, RB1 and n, the two acquisition results of the sampling circuit before and after the switching switch in the control circuit switching detection circuit 1 is in the conducting state, and the parallel relationship between Rz1 and Rz2.

[0106] In the embodiment of the application, before the control circuit controls the switch Q1 in the detection circuit 1 to be in the conducting state, the control circuit also controls the sampling circuit to acquire the voltage between the negative bus BUS- and the ground. In this case, the equivalent detection resistance in the converter system is , which is much smaller than the detection resistance in the corresponding case when the ground insulation impedance of a single converter detection system is detected The control circuit controls the switch Q1 in the detection circuit 1 to be in the on state, and controls the sampling circuit to collect the voltage between the negative bus BUS- and the ground wire. In this case, the equivalent detection resistance in the converter system is , which is also much smaller than the detection resistance RA1 in the case of detecting the ground insulation impedance using a single converter detection system.

[0107] Compared with the detection of the ground insulation impedance using a single converter detection system, since the control circuit uses multiple detection circuits to participate in the detection process of the ground insulation impedance in the system, and reduces the equivalent detection resistance in the system by controlling the switches in the multiple detection circuits, the Uc1-Uc2 can be increased to reduce the maximum sampling deviation, thereby improving the detection accuracy of the ground impedance in the system. Moreover, it is not necessary to replace the detection resistors in the detection circuits due to the parallel connection of multiple converters.

[0108] In another example, during the detection process of the ground insulation impedance in the system, the control circuit can control i detection circuits ( ) to switch the resistors connected between the negative bus BUS- and the ground wire. That is, the control circuit controls the switching switches in the i switching circuits to be in the closed state. For example, the control circuit can control the switching switches in the detection circuit 1 to the detection circuit i to be in the on state, so that the resistor connected between the positive bus BUS+ and the negative bus BUS- in each of the detection circuit 1 to the detection circuit i changes from RA1+RB1 to RA1.

[0109] In the converter system, the resistors connected between the negative bus BUS- and the ground wire in the n-i detection circuits other than the detection circuit 1 to the detection circuit i do not change. In this case, the equivalent detection resistance between the negative bus BUS- and the ground wire in the converter system is , that is, .

[0110] The control circuit controls the sampling circuit to collect the voltage between the negative bus BUS- and the ground wire. After the switching switches in the detection circuit 1 to the detection circuit i are in the on state, the equivalent detection resistance between the negative bus BUS- and the ground wire is , the equivalent ground insulation impedance Rz1 between the positive bus BUS+ and the ground wire is UBUS-Uc2, and the equivalent ground insulation impedance Rz2 between the negative bus BUS- and the ground wire is Uc3. The relationship between the equivalent ground insulation impedance Rz1 between the positive bus BUS+ and the ground wire and the equivalent ground insulation impedance Rz2 between the negative bus BUS- and the ground wire in the system is, .

[0111] The control circuit can determine the equivalent ground insulation impedance Rz2 between the negative bus BUS- and the ground and the equivalent ground insulation impedance Rz1 between the positive bus BUS+ and the ground according to the relationship between the equivalent ground insulation impedance Rz1 between the positive bus BUS+ and the ground and the equivalent ground insulation impedance Rz2 between the negative bus BUS- and the ground before the switching switch in the switching detection circuit 1 to the switching detection circuit i is in the conducting state and the relationship between the equivalent ground insulation impedance Rz1 between the positive bus BUS+ and the ground and the equivalent ground insulation impedance Rz2 between the negative bus BUS- and the ground after the switching switch in the switching detection circuit 1 to the switching detection circuit i is in the conducting state. , the equivalent ground insulation impedance Rz2 between the negative bus BUS- and the ground and the equivalent ground insulation impedance Rz1 between the positive bus BUS+ and the ground. , the equivalent ground insulation impedance Rz2 between the negative bus BUS- and the ground and the equivalent ground insulation impedance Rz1 between the positive bus BUS+ and the ground.

[0112] Similarly, by solving the equation and the equation , Rz1 and Rz2 can be solved. By solving the two equations, the relationship between Rz1 and UBUS, Uc1, Uc3, RA1, RB1, n, i and the relationship between Rz2 and UBUS, Uc1, Uc3, RA1, RB1, n, i can be solved.

[0113] The control circuit can obtain Rz1 and Rz2 based on the predetermined relationship between Rz1 and UBUS, Uc3, Uc2, RA1, RB1, n, i, the relationship between Rz2 and UBUS, Uc1, Uc3, RA1, RB1, n, i, and the two acquisition results of the sampling circuit before and after the switching switch in the switching detection circuit 1 to the switching detection circuit i is in the conducting state. Then, by solving the parallel results of Rz1 and Rz2, the ground insulation impedance Rz of the converter system .

[0114] In addition, the control circuit can also obtain the ground insulation impedance Rz of the converter system directly based on the predetermined relationship between Rz1 and UBUS, Uc3, Uc2, RA1, RB1, n, i, the relationship between Rz2 and UBUS, Uc1, Uc3, RA1, RB1, n, i, the two acquisition results of the sampling circuit before and after the switching switch in the switching detection circuit 1 to the switching detection circuit i is in the conducting state, and the parallel relationship between Rz1 and Rz2. .

[0115] In the embodiment of the application, the control circuit controls i (i is an integer greater than or equal to 1) switching detection circuits 1 to i, and the switching detection circuit 1 to the switching detection circuit i is connected in parallel between the positive bus BUS+ and the negative bus BUS- of the converter system. The control circuit can control any i detection circuits in the n detection circuits to switch when the detection circuit switches the resistance connected between the negative bus BUS- and the ground wire. The control circuit can also select i detection circuits from the n detection circuits according to a preset mode, for example, determine the i detection circuits according to the order of the transformer identification, or determine the i detection circuits according to the priority of the transformer.

[0116] In the embodiment of the application, when the control circuit controls the switches in the i detection circuits to be in the conducting state and then controls the sampling circuit to collect the voltage between the negative bus BUS- and the ground wire again, the equivalent detection resistance in the transformer system is If i is greater than 1, is less than . And i increases, decreases. It can be seen that the control circuit controls more switches in the detection circuits to be in the conducting state, that is, controls more detection circuits to reduce the resistance connected between the negative bus BUS- and the ground wire, which can further reduce the size of the equivalent detection resistance in the system. Thus, Uc1-Uc2 is larger, the maximum sampling deviation is reduced, and the detection precision of the system to ground impedance is improved.

[0117] In the embodiment of the application, when the control circuit obtains Uc1, the switching switches in the detection circuits are in the open state, that is, there are j=0 detection circuits in which the switching switches are in the conducting state. When Uc3 is obtained, the switching switches in the i detection circuits are in the conducting state.

[0118] Alternatively, the control circuit can also control the switching switches of j (0 ) detection circuits to be in the open state, and obtain the first voltage between the negative bus BUS- and the ground wire, and then control the switching switches of i (0 ) detection circuits to be in the open state, and obtain the second voltage between the negative bus BUS- and the ground wire, wherein i and j are not equal. The control circuit can determine the ground insulation impedance of the transformer system by using the following formula:

[0119]

[0120] Riso is the ground insulation impedance of the transformer, Rz2 is the insulation impedance between the second bus and the ground wire, Rz1 is the insulation impedance between the first bus and the ground wire, , ;

[0121] Rd1 is the equivalent detection resistance between the second bus and the ground when the switch in the i detection circuit is in the on state, and Rd2 is the equivalent detection resistance between the second bus and the ground when the switch in the j detection circuit is in the on state. Rd1= , Rd2= , i is the first number, , j is the second number, ,and , RB is RB1, RA is RA1, n is the number of transformers in the system, VB is UBUS, V1 is the first voltage, and V2 is the second voltage.

[0122] In another possible implementation, multiple resistors in each detection circuit are connected in series between the first bus and the second bus. That is, the first end of the detection circuit in each converter is connected to the first bus, the second end is connected to the second bus, and the third end is connected to the ground.

[0123] like Figure 5 As shown, the first terminal a1 of detection circuit 1 in converter 1 is connected to the positive bus BUS+, the second terminal b1 of detection circuit 1 is connected to the negative bus BUS-, and the third terminal c1 of detection circuit 1 is connected to ground. The first terminal an of detection circuit n in converter n is connected to the positive bus BUS+, the second terminal bn of detection circuit n is connected to the negative bus BUS-, and the third terminal cn of detection circuit n is connected to ground. Detection circuit n in converter n is connected between the negative bus BUS- and ground.

[0124] The converter system may also include a control circuit for controlling each converter, such as controlling the operation of the conversion circuit and controlling the detection circuit to perform ground insulation impedance testing. The converter system may also include a sampling circuit connected between the negative busbar BUS- and ground to collect the voltage between the negative busbar BUS- and ground when testing the system's ground insulation impedance. The control circuit may also be connected to the sampling circuit to control the sampling circuit to collect the voltage between the negative busbar BUS- and ground.

[0125] In the embodiments of the present application, among the multiple resistors included in each detection circuit, at least one resistor is connected between the first busbar and the ground line, and at least two resistors are connected between the second busbar and the ground line, or at least one resistor is connected between the second busbar and the ground line, and at least one resistor is connected between the first busbar and the ground line. In the following embodiments, at least one resistor is connected between the first busbar and the ground line, and at least two resistors are connected between the second busbar and the ground line as an example for description.

[0126] In one example, the detection circuit includes multiple resistors and a switch, one resistor is connected between a first bus and a ground line, two resistors are connected between a second bus and a ground line, and the switch is connected in parallel with one of the two resistors.

[0127] like Figure 6 As shown, the detection circuit n may include three detection resistors connected in series and a switch Qn, such as a first detection resistor RAn, a second detection resistor RBn, and a third detection resistor RCn. At least one detection resistor is included between the ground terminal of the detection circuit n and the positive bus BUS+, and at least one detection resistor is included between the ground terminal of the detection circuit n and the negative bus BUS-. Figure 6 , the third detection resistor RCn is connected between the positive bus BUS+ and the ground line. Similarly, the first detection resistor in detection circuit 1 is denoted as RA1, the second detection resistor is denoted as RB1, the third detection resistor is denoted as RC1, and the switch is denoted as Q1. Typically, the resistance of RC1 is greater than that of RA1 and RB1. For example, the resistance of RC1 is the sum of RA1 and RB1. The first detection resistor in each detection circuit has the same resistance, the second detection resistor in each detection circuit has the same resistance, and the third detection resistor in each detection circuit has the same resistance.

[0128] When the switches in each detection circuit are in the off state, the equivalent detection resistance Rd1 between the positive bus BUS+ and the ground is The equivalent detection resistance Rd2 between the negative busbar BUS- and the ground is The control circuit can control the sampling circuit to collect the voltage Uc4 between the negative busbar BUS- and the ground. In this case, the relationship between the equivalent insulation resistance Rz1 between the system positive busbar BUS+ and the ground and the equivalent insulation resistance Rz2 between the negative busbar BUS- and the ground is: .

[0129] Then, the control circuit can control i ( ) The detection circuit switches the resistor connected between the positive bus BUS+ and the negative bus BUS-. Specifically, the control circuit controls the switches in each of the i switching circuits to be closed. For example, the control circuit may control the switches in detection circuits 1 through i to be on, so that the resistor connected between the positive bus BUS+ and the negative bus BUS- in each of detection circuits 1 through i changes from RA1+RB1+RC1 to RA1+RC1.

[0130] After the control circuit controls i detection circuits to switch the resistors connected between the positive bus BUS+ and the negative bus BUS-, it controls the sampling circuit to collect the voltage Uc5 between the negative bus BUS- and the ground. When the switches in the i detection circuits are in the on state, the equivalent detection resistance Rd1 between the positive bus BUS+ and the ground is , the equivalent detection resistance Rd2 between the negative busbar BUS- and the ground is The control circuit can be i ( After the detection circuit switches the resistor connected between the positive bus BUS+ and the negative bus BUS-, it can control the sampling circuit to collect the voltage Uc5 between the negative bus BUS- and the ground. In this case, the relationship between the equivalent insulation resistance Rz1 between the system's positive bus BUS+ and ground and the equivalent insulation resistance Rz2 between the negative bus BUS- and ground is: .

[0131] Through the simultaneous equations and equation , we can solve for Rz1 and Rz2. By combining these two equations, we can solve the relationship between Rz1 and UBUS, Uc1, Uc3, RA1, RB1, RC1, n, and i, and the relationship between Rz2 and UBUS, Uc1, Uc3, RA1, RB1RC1, n, and i.

[0132] The control circuit can obtain Rz1 and Rz2 based on the predetermined relationship between Rz1 and UBUS, Uc1, Uc3, RA1, RB1, RC1, n, i, the relationship between Rz2 and UBUS, Uc1, Uc3, RA1, RB1RC1, n, i, and the sampling circuit's two acquisition results before and after the control circuit switches the switch from detection circuit 1 to detection circuit i to the on state. Then, by solving the parallel result of Rz1 and Rz2, the insulation impedance of the converter system to ground is obtained. .

[0133] It should be understood that in the embodiments of the present application, the control circuit can control the sampling circuit to collect the voltage between the negative bus BUS- and the ground line when the switches in each detection circuit are in the off state. The control circuit then controls the switch in at least one of the multiple detection circuits to be in the on state, thereby changing the equivalent detection resistance in the converter system. The sampling circuit is then controlled to collect the voltage between the negative bus BUS- and the ground line. The system insulation resistance to ground can be determined based on the voltages collected by the two sampling circuits, the bus voltage, the detection resistors in the detection circuits, the number of detection circuits, and the number of detection circuits whose resistances are controlled to be switched between the positive and negative bus lines.

[0134] In the embodiment, before the control circuit controls the switches in the i detection circuits to be in the conducting state, the equivalent detection resistance Rd1 between the positive bus BUS+ and the ground is , and after the control circuit controls the switches in the i detection circuits to be in the conducting state, the equivalent detection resistance Rd1 between the positive bus BUS+ and the ground is also . Compared with the detection resistance RC1 in the detection circuit of a single converter, the equivalent detection resistance Rd1 between the positive bus BUS+ and the ground is much smaller than RC1.

[0135] In addition, before the control circuit controls the switches in the i detection circuits to be in the conducting state, the equivalent detection resistance Rd2 between the negative bus BUS- and the ground is , which is smaller than the detection resistance in the corresponding case of the detection circuit of a single converter . After the control circuit controls the switches in the i detection circuits to be in the conducting state, the equivalent detection resistance Rd2 between the negative bus BUS- and the ground is , which is also smaller than the detection resistance in the corresponding case of the detection circuit of a single converter .

[0136] The greater the number i of the controlled detection circuits controlled by the control circuit in the i detection circuits, the smaller the equivalent detection resistance Rd2 between the negative bus BUS- and the ground. Thus, in the process of detecting the ground insulation impedance of the converter system, the control circuit can control more switches in the detection circuits to be in the conducting state, that is, control more detection circuits to reduce the resistance connected between the negative bus BUS- and the ground, so as to further reduce the size of the equivalent detection resistance in the system. Thus, Uc1-Uc2 is greater, the maximum sampling deviation is reduced, and the detection precision of the ground impedance of the system is improved.

[0137] In a possible implementation, the control circuit can also control the switching switches of j (0 ) detection circuits to be in the open state, and obtain a first voltage between the negative bus BUS- and the ground, and then control the switching switches of i (0 ) detection circuits to be in the open state, and obtain a second voltage between the negative bus BUS- and the ground, where i and j are not equal.

[0138] The control circuit can determine the ground insulation impedance of the converter system by using the following formula:

[0139]

[0140] Riso is the ground insulation impedance of the converter, Rz2 is the insulation impedance between the second bus and the ground, and Rz1 is the insulation impedance between the first bus and the ground. , ;

[0141] Rd1 is the equivalent detection resistance between the second bus and the ground when the switches in the first number of detection circuits are in the on state, and Rd2 is the equivalent detection resistance between the second bus and the ground when the first switches in the second number of detection circuits are in the on state. Rd1= , Rd2= , i is the first number, , j is the second number, ,and , RB is RB1, RA is RA1, RC is RC1, n is the number of the multiple transformers, VB is UBUS, V1 is the first voltage, and V2 is the second voltage.

[0142] In another example, the detection circuit includes multiple resistors and two switches. At least two resistors are connected between a first busbar and a ground line, and one of the resistors is connected in parallel with one of the switches. At least two resistors are connected between a second busbar and a ground line, and one of the resistors is connected in parallel with another of the switches.

[0143] like Figure 7 As shown, the detection circuit n may include four detection resistors and two switches, namely, a first detection resistor RAn, a second detection resistor RBn, a third detection resistor RCn, and a fourth detection resistor RDn, and a first switch Kn and a second switch Tn. The first detection resistor RAn and the second detection resistor RBn are connected between the negative busbar BUS- and the ground line. The third detection resistor RCn and the fourth detection resistor RDn are connected between the positive busbar BUS+ and the ground line. The first switch Kn can be connected in parallel with either the first detection resistor RAn or the second detection resistor RBn. For example, the first switch Kn is connected in parallel with the second detection resistor RBn. The second switch Tn can be connected in parallel with either the third detection resistor RCn or the fourth detection resistor RDn. For example, the second switch Tn is connected in parallel with the fourth detection resistor RDn.

[0144] The control circuit can switch the resistors connected between the positive and negative busbars in the detection circuit by controlling the on / off states of the first and second switches. For example, in detection circuit n, if the first and second switches Kn and Tn are both in the off state, the resistors connected between the positive and negative busbars are RAn + RBn + RCn + RDn. If the first switch Kn is in the off state, the second switch Tn is in the on state, and the fourth detection resistor is short-circuited RDn, the resistors connected between the positive and negative busbars are RAn + RBn + RCn. If the first switch Kn is in the on state, the second switch Tn is in the off state, and the second detection resistor is short-circuited, the resistors connected between the positive and negative busbars are RAn + RCn + RDn. If the first switch Kn is in the on state, the second switch Tn is in the on state, and the second detection resistor RBn and the fourth detection resistor RDn are short-circuited, the resistors connected between the positive and negative busbars are RAn + RCn + RDn.

[0145] The control circuit can flexibly control the first and second switches in the multiple detection circuits to switch at least one of the multiple detection circuits to the resistor between the positive and negative busbars. The control circuit can control the sampling circuit to collect the voltage between the negative busbar and the ground before switching at least one of the multiple detection circuits to the resistor between the positive and negative busbars. And after switching at least one of the multiple detection circuits to the resistor between the positive and negative busbars, the control circuit can control the sampling circuit to collect the voltage between the negative busbar and the ground again.

[0146] The control circuit can determine the system's insulation resistance Riso to ground by using the equivalent detection resistor Rd1 and the equivalent detection resistor Rd2 connected between the positive bus and the ground before at least one detection circuit in the multiple detection circuits in the switching converter system is connected to the resistor between the positive and negative bus bars, the equivalent detection resistor Rd3 and the equivalent detection resistor Rd4 connected between the positive bus and the ground after at least one detection circuit in the multiple detection circuits in the switching converter system is connected to the resistor between the positive and negative bus bars, and the voltages collected twice by the sampling circuit.

[0147] In one possible implementation, the control circuit may control i ( ) The first switch in the detection circuit is in the closed state. In this case, the equivalent detection resistance between the positive bus BUS+ and the ground in the converter system is , the equivalent detection resistance between the negative bus BUS- and the ground in the converter system is Then, the control circuit controls the sampling circuit to collect the voltage between the negative bus BUS- and the ground, which is recorded as Uc7. The equivalent impedance between the positive bus BUS+ and the ground in the converter system is The equivalent impedance between the negative busbar BUS- and the ground The relationship is, .

[0148] The control circuit can control j ( ) The second switch in the detection circuit is in the closed state. In this case, the equivalent detection resistance between the positive bus BUS+ and the ground in the converter system is , the equivalent detection resistance between the negative bus BUS- and the ground in the converter system is Then, the control circuit controls the sampling circuit to collect the voltage between the negative bus BUS- and the ground, which is recorded as Uc8. The equivalent impedance between the positive bus BUS+ and the ground in the converter system is The equivalent impedance between the negative busbar BUS- and the ground The relationship is, .

[0149] Through the simultaneous equations and equation , Rz1 and Rz2 can be solved. Alternatively, the relationship between Rz1 and UBUS, Uc7, Uc8, RA1, RB1, RC1, RD1, n, j, and i can be solved, as well as the relationship between Rz2 and UBUS, Uc7, Uc8, RA1, RB1, RC1, RD1, n, j, and i. Combining the relationship between the converter system's insulation resistance to ground, Riso, and Rz1 and Rz2, the relationship between the converter system's insulation resistance to ground, Riso, and UBUS, Uc7, Uc8, RA1, RB1, RC1, RD1, n, j, and i can be determined.

[0150] The control circuit can determine the insulation impedance of the converter system to ground based on the relationship between the insulation impedance Riso of the converter system and UBUS, Uc7, Uc8, RA1, RB1, RC1, RD1, n, j and i, as well as the voltages collected twice by the sampling circuit, thereby realizing the detection of the insulation impedance of the converter system to ground in a multi-converter parallel system.

[0151] In one example, RC1 can be equal to RB1, and RA1 can be equal to RD1. The control circuit can control the first switch in the n detection circuit to be in a closed state, and the equivalent detection resistance between the positive bus BUS+ and the ground in the converter system is , the equivalent detection resistance between the negative bus BUS- and the ground in the converter system is The sampling circuit collects the voltage between the negative bus BUS- and the ground, denoted as Uc9. The equivalent impedance between the positive bus BUS+ and the ground in the converter system and the equivalent impedance between the negative bus BUS- and the ground are related as, .

[0152] The control circuit can control the second switch in the n detection circuits to be in the closed state. In this case, the equivalent detection resistance between the positive bus BUS+ and the ground in the converter system is , and the equivalent detection resistance between the negative bus BUS- and the ground in the converter system is . Then, the control circuit controls the sampling circuit to collect the voltage between the negative bus BUS- and the ground, denoted as Uc10. The equivalent impedance between the positive bus BUS+ and the ground in the converter system and the equivalent impedance between the negative bus BUS- and the ground are related as, .

[0153] By solving the equations and , the relationship between the ground insulation impedance Riso of the converter system and UBUS, Uc9, Uc10, RA1, RB1, RC1, RD1, n, j and i can be solved. Among them, RC1=RB1, RA1=RD1, i=n, j=n. The ground insulation impedance of the converter system is

[0154] Compared with detecting the ground insulation impedance by using a single converter, before the control circuit controls the first switch in the i detection circuits to be in the conducting state and after the control circuit controls the first switch in the i detection circuits to be in the conducting state, the equivalent detection resistance Rd1 between the positive bus BUS+ and the ground in the converter system is smaller than the detection resistance of the detection circuit of the single converter in the corresponding case. And the larger the number i of the detection circuits whose first switches are controlled to change the state by the control circuit, the smaller the equivalent detection resistance Rd1 between the positive bus BUS+ and the ground.

[0155] And, before the control circuit controls the second switch in the j detection circuits to be in the conducting state and after the control circuit controls the second switch in the j detection circuits to be in the conducting state, the equivalent detection resistance Rd2 between the negative bus BUS- and the ground in the converter is also smaller than the detection resistance of the detection circuit of the single converter in the corresponding case. The larger the number j of the detection circuits whose second switches are controlled by the control circuit, the smaller the equivalent detection resistance Rd2 between the negative bus BUS- and the ground.

[0156] Therefore, in the process of detecting the insulation impedance to ground of the converter system, the control circuit can control more of the second switching switches in the detection circuits to be in the on state, i.e., control more of the detection circuits to reduce the resistance connected between the negative bus BUS- and the ground wire, so as to further reduce the size of the equivalent detection resistance Rd2 in the system. The control circuit can also control more of the first switching switches in the detection circuits to be in the on state, i.e., control more of the detection circuits to reduce the resistance connected between the positive bus BUS+ and the ground wire, so as to further reduce the size of the equivalent detection resistance Rd1 in the system. Both of these methods can make Uc1-Uc2 larger, reduce the maximum sampling deviation, and thus improve the detection accuracy of the insulation impedance to ground of the system.

[0157] According to the foregoing description, the detection accuracy of the insulation impedance to ground of a single converter is related to the difference between the two disturbance voltages. Assuming that n = 10, RC1 = RB1 = 1800kΩ, RA1 = RD1 = 1200kΩ, and UBUS = 1200V. If the method for detecting the insulation impedance to ground of the converter system in the embodiment of the application is used, the voltage Uc9 is collected after the control circuit controls the first switching switches in the n detection circuits to be in the on state. The voltage Uc10 is collected after the control circuit controls the second switching switches in the n detection circuits to be in the on state. The difference between the two disturbance voltages is Uc9-Uc10. In actual detection conditions, the difference between the two disturbance voltages Uc9-Uc10 is also 12.6V. The converter system can use a sampling circuit with a 12-bit sampling function, which can guarantee that the maximum detection error is 5.8%. As can be seen, the insulation impedance to ground of the converter system is much smaller than the insulation impedance to ground of a single converter, and the detection control method provided in the embodiment of the application can achieve the detection accuracy of the insulation impedance to ground of the converter system. Compared with the detection accuracy of the insulation impedance to ground of the system detected by the detection circuit in a single converter, the detection control method provided in the embodiment of the application improves the detection accuracy of the insulation impedance to ground of the system, and the detection accuracy of the insulation impedance to ground of the system can be the same as or consistent with the detection accuracy of the insulation impedance to ground of a single converter detected by the detection circuit in the single converter.

[0158] It should be understood that the structure or form of the detection circuit provided in the foregoing embodiment is used to illustrate the control operation of the detection circuit in the process of detecting the insulation impedance of the system by the control circuit, and does not serve as the structure or form of the specific detection circuit in each converter. The structure or form of each detection circuit can also have more implementation manners. For example, there is one resistance in each detection circuit, i.e., among the multiple resistances between the positive bus and the ground wire, and among the multiple resistances between the negative bus and the ground wire.

[0159] In a possible design, the control circuit can include multiple controllers. The number of controllers can be no less than the number of converters in the converter system.

[0160] In one example, the number of controllers can be equal to the number of transformers. There is a one-to-one correspondence between the controllers and the transformers. For example, as shown in FIG. 8, the nth controller can control the nth transformer. For example, the nth controller can control the switching circuit in the nth transformer, and the nth controller can also control the switching switch in the detection circuit in the nth transformer. Any one of the plurality of controllers can serve as a master controller, and the other n-1 controllers serve as slave controllers. Figure 8 In another example, the number of controllers can be greater than the number of transformers. As shown in FIG. 9, the plurality of controllers can include one master controller and n slave controllers. There is a one-to-one correspondence between the n slave controllers and the n transformers.

[0161] Figure 9 The master controller can communicate with each slave controller through a power line carrier communication mode. When performing system insulation impedance detection on the transformer system, the master controller can start the detection process.

[0162] In the embodiments of the present application, the master controller can directly control the sampling circuit in the transformer system to collect the voltage between the negative bus BUS- and the ground. The master controller can send switching instructions to each slave controller. After each slave controller receives the switching instruction, it switches the resistance between the positive and negative buses in the detection circuit of the transformer where it is located. For example, the kth slave controller corresponds to the kth transformer. After the kth slave controller receives the switching instruction, it controls the switching switch in the detection circuit of the kth transformer to be in the on state.

[0163] In the scenario where the detection circuit of each transformer in the transformer system includes a plurality of switches, for example, including a first switching switch and a second switching switch. The master controller can send a first switching instruction to the slave controller. After each slave controller receives the first switching instruction, it controls the first switching switch in the detection circuit of the transformer where it is located to be in the on state. The master controller can also send a second switching instruction to the slave controller. After each slave controller receives the second switching instruction, it controls the second switching switch in the detection circuit of the transformer where it is located to be in the on state.

[0164] In the scenario where the detection circuit of each transformer in the transformer system includes a plurality of switches, for example, including a first switching switch and a second switching switch. The master controller can send a first switching instruction to the slave controller. After each slave controller receives the first switching instruction, it controls the first switching switch in the detection circuit of the transformer where it is located to be in the on state. The master controller can also send a second switching instruction to the slave controller. After each slave controller receives the second switching instruction, it controls the second switching switch in the detection circuit of the transformer where it is located to be in the on state.

[0165] ​The embodiment of the present application further provides a system insulation impedance detection method, which can be applied to a converter system. The converter system comprises a plurality of converters, a sampling circuit and a control circuit. Each converter comprises a conversion circuit and a detection circuit. Each converter is connected between a first bus and a second bus. The sampling circuit is connected between the second bus and a ground. Each detection circuit comprises at least two detection resistors connected in series between the second bus and the ground and at least one switch. The at least one switch is connected in parallel with a first detection resistor in the at least two detection resistors connected in series between the second bus and the ground. As shown in Figure 10 , the method can comprise the following steps, which can be implemented by the control circuit.

[0166] S1101, the control circuit controls the sampling circuit to collect a first voltage, the first voltage being a voltage between the second bus and the ground when a first switch in a first number of the detection circuits is in a conductive state.

[0167] S1102, the control circuit controls the sampling circuit to collect a second voltage, the second voltage being a voltage between the second bus and the ground when a first switch in a second number of the detection circuits is in a conductive state; wherein the second number is different from the first number.

[0168] S1103, the control circuit determines the ground insulation impedance of the converter system according to the first voltage and the second voltage.

[0169] In the embodiment of the present application, the control circuit can control the switch in the detection circuit to be in a conductive state or a disconnected state. The control circuit can control the sampling circuit to collect the first voltage after controlling the first switch in the first number of the detection circuits to be in the conductive state. The control circuit can also control the sampling circuit to collect the second voltage after controlling the first switch in the second number of the detection circuits to be in the conductive state.

[0170] In a possible implementation, the detection circuit comprises two resistors connected in series between the second bus and the ground, and the first switch is connected in parallel with a first resistor; the control circuit can determine the ground insulation impedance of the converter system by using the following formula:

[0171]

[0172] Riso is the ground insulation impedance of the converter, Rz2 is the insulation impedance between the second bus and the ground, Rz1 is the insulation impedance between the first bus and the ground, , ;

[0173] Rd1 is the equivalent detection resistance between the second bus and ground when the first switch in the first number of detection circuits is in the on state, Rd2 is the equivalent detection resistance between the second bus and ground when the first switch in the second number of detection circuits is in the on state, Rd1= , Rd2= , i is the first number, , j is the second number, , RB is the first resistance, RA is the second resistance of the two resistances excluding the first resistance, n is the number of the plurality of transformers, VB is the voltage between the first bus and the second bus, V1 is the first voltage, and V2 is the second voltage.

[0174] In a possible implementation, the detection circuit further includes at least one resistance connected between the first bus and ground.

[0175] In a possible implementation, the detection circuit further includes a third resistance connected between the first bus and ground; the control circuit determines the ground insulation impedance of the transformer system using the following formula:

[0176]

[0177] Riso is the ground insulation impedance of the transformer, Rz2 is the insulation impedance between the second bus and ground, Rz1 is the insulation impedance between the first bus and ground, , ;

[0178] Rd1 is the equivalent detection resistance between the second bus and ground when the first switch in the first number of detection circuits is in the on state, Rd2 is the equivalent detection resistance between the second bus and ground when the first switch in the second number of detection circuits is in the on state, Rd1= , Rd2= , i is the first number, , j is the second number, , RB is the first resistance, RA is the second resistance of the two resistances excluding the first resistance, RC is the third resistance, n is the number of the plurality of transformers, VB is the voltage between the first bus and the second bus, V1 is the first voltage, and V2 is the second voltage.

[0179] In a possible implementation, the detection circuit further includes a second switch and at least two resistors connected in series between the first bus and the ground, and the second switch is connected in parallel with one of the at least two resistors connected in series between the first bus and the ground. The second switch can be controlled by the control circuit.

[0180] In a possible implementation, the detection circuit further includes two resistors connected in series between the first bus and the ground and a second switch connected in parallel with a fourth resistor of the two resistors connected in series between the first bus and the ground; if the first switch in each detection circuit is in a conducting state, the second switch in each detection circuit is in a nonconducting state; if the first switch in each detection circuit is in a nonconducting state, the second switch in each detection circuit is in a conducting state.

[0181] In a possible implementation, the first quantity is zero, and the second quantity is the number of the plurality of transformers; the fourth resistor has the same resistance as the second resistor, and a fifth resistor of the two resistors connected in series between the first bus and the ground, except the fourth resistor, has the same resistance as the first resistor. The control circuit can determine the insulation impedance of the transformer system according to the following formula:

[0182]

[0183] Riso is the insulation impedance of the transformer, RB is the first resistor, RA is the second resistor of the two resistors except the first resistor, n is the number of the plurality of transformers, VB is the voltage between the first bus and the second bus, V1 is the first voltage, and V2 is the second voltage.

[0184] Embodiments of the present application further provide a system insulation impedance detection method, which can be applied to a transformer system. The transformer system includes a plurality of transformers, a sampling circuit, and a control circuit. Each transformer includes a transformation circuit and a detection circuit. Each transformer is connected between a first bus and a second bus. The sampling circuit is connected between the second bus and a ground. Each detection circuit includes at least two detection resistors connected in series between the second bus and the ground and at least one switch. The at least one switch is connected in parallel with a first detection resistor of the at least two detection resistors connected in series between the second bus and the ground. The plurality of controllers include a master controller and a plurality of slave controllers, and the slave controllers are configured to control the switching switches of the detection circuits in the corresponding transformers.

[0185] In an example, the plurality of slave controllers can correspond to the plurality of transformers one by one. The master controller sends instructions to part of the slave controllers each time. For example, the master controller sends instructions to the slave controllers in the first transformer and the second transformer each time. Figure 11As shown, the method comprises the following steps:

[0186] S1201, the master controller sends a first switching instruction to a first number of first slave controllers, the first switching instruction being used to instruct the first switch in the detection circuit of the corresponding converter to be in a conductive state.

[0187] S1202, the first slave controller receives the first switching instruction.

[0188] S1203, the first slave controller controls the first switch in the detection circuit of the corresponding converter to be in a conductive state.

[0189] The first slave controller can control the first switch in the detection circuit of the corresponding converter to be in a conductive state in response to the first switching instruction. The second switch in the detection circuit of the corresponding converter of the first slave controller is in a disconnected state. The switches in the second slave controllers other than the first slave controller among the plurality of slave controllers are all in a disconnected state.

[0190] S1204, the master controller acquires a first voltage between the second bus and the ground after a preset time length.

[0191] In the embodiments of the present application, the master controller can send the first switching instruction to the plurality of first slave controllers synchronously, or can send the first switching instruction to the plurality of first slave controllers within a preset time length. Such a design can ensure that when the master controller acquires the first voltage between the second bus and the ground after the preset time length, the first switches in the detection circuits of the first number of converters in the system are in a conductive state.

[0192] The sampling circuit in the converter system can be integrated in the master controller, or in other words, the master controller can comprise the sampling circuit, which is used to acquire the voltage between the second bus and the ground.

[0193] S1205, the master controller sends a second switching instruction to a second number of second slave controllers, the second switching instruction being used to instruct the second switch in the detection circuit of the corresponding converter to be in a conductive state.

[0194] S1206, the second slave controller receives the second switching instruction.

[0195] S1207, the second slave controller controls the second switch in the detection circuit of the corresponding converter to be in a conductive state.

[0196] The first slave controller can control the second switch in the detection circuit of the corresponding converter to be in a conductive state in response to the second switching instruction. The first switch in the detection circuit of the corresponding converter of the second slave controller is in a disconnected state. The switches in the first slave controllers other than the second slave controller among the plurality of slave controllers are all in a disconnected state.

[0197] S1208, the main controller acquires a second voltage between the second bus and the ground wire after the preset time length.

[0198] In the embodiments of the present application, the main controller can synchronously send the second switching instruction to the plurality of second slave controllers, or send the second switching instruction to the plurality of second slave controllers within the preset time length. Such a design can ensure that when the main controller acquires the second voltage between the second bus and the ground wire after the preset time length, the second switch in the detection circuit of the second number of transformers in the system is in the conducting state.

[0199] S1209, the main controller determines the ground insulation impedance of the transformer system based on the at least two detection resistors, the number of the plurality of transformers, the first number, the second number, the first voltage and the second voltage.

[0200] In a possible implementation, after determining the ground insulation impedance of the transformer system, the main controller sends a detection end instruction to each slave controller to make each slave controller know that the detection is over.

[0201] In another example, the main controller corresponds to a first transformer, and the plurality of slave controllers correspond to a plurality of second transformers other than the first transformer in the plurality of transformers one by one. As shown in the figure, the interaction process between the main controller and the slave controller is as follows: Figure 12

[0202] S1301, the main controller sends a first switching instruction to a first number of first slave controllers, and the first switching instruction is used to instruct to control the first switch to be in the conducting state.

[0203] S1302, the main controller controls the first switch in the detection circuit of the first transformer to be in the conducting state.

[0204] S1303, the first slave controller receives the first switching instruction.

[0205] Steps S1302 and S1303 can occur synchronously or asynchronously, and the sequence of the two steps is not specifically limited.

[0206] S1304, the first slave controller controls the first switch in the detection circuit of the corresponding transformer to be in the conducting state.

[0207] S1305, the main controller acquires a first voltage between the second bus and the ground wire after a preset time length.

[0208] S1306, the main controller sends a second switching instruction to a second number of second slave controllers, and the second switching instruction is used to instruct to control the second switch to be in the conducting state.

[0209] ​S1307, the master controller controls the second switch in the detection circuit of the first transformer to be in a conductive state.

[0210] S1308, the second slave controller receives the second switching instruction.

[0211] S1309, the second slave controller controls the second switch in the detection circuit of the corresponding transformer to be in a conductive state.

[0212] S1310, the master controller acquires a second voltage between the second bus and the ground after a preset time length.

[0213] S1311, the master controller determines the ground insulation impedance of the transformer system based on the at least two detection resistors, the number of the plurality of transformers, the third number, the fourth number, the first voltage, and the second voltage, the third number being a sum of the first number and 1, and the fourth number being a sum of the second number and 1.

[0214] In another example, the master controller corresponds to a first transformer, and the plurality of slave controllers correspond to a plurality of second transformers other than the first transformer one by one. The master controller can send an instruction to all slave controllers. As shown in the following table, the interaction process between the master controller and the slave controllers is as follows: Figure 13

[0215] S1401, the master controller sends a first switching instruction to all slave controllers, the first switching instruction being used to instruct to control the first switch to be in a conductive state.

[0216] S1402, the master controller controls the first switch in the detection circuit of the first transformer to be in a conductive state.

[0217] S1403, the slave controller receives the first switching instruction.

[0218] Steps S1402 and S1403 can occur synchronously or asynchronously, and the sequence of the two steps is not specifically limited.

[0219] S1404, the slave controller controls the first switch in the detection circuit of the corresponding transformer to be in a conductive state.

[0220] S1405, the master controller acquires a first voltage between the second bus and the ground after a preset time length.

[0221] S1406, the master controller sends a second switching instruction to all slave controllers, the second switching instruction being used to instruct to control the second switch to be in a conductive state.

[0222] S1407, the master controller controls the second switch in the detection circuit of the first transformer to be in a conductive state.​

[0223] S1408, receiving a second switching instruction from the controller.

[0224] S1409, controlling the second switch in the detection circuit of the corresponding transformer to be in an on state from the controller.

[0225] S1410, acquiring a second voltage between the second bus and the ground wire after the preset time length by the main controller.

[0226] S1411, determining the ground insulation impedance of the transformer system based on the at least two detection resistors, the number of the plurality of transformers, the first voltage, and the second voltage by the main controller.

[0227] In a possible implementation, the main controller can also start the system insulation impedance detection in response to a system insulation impedance detection instruction. For example, the main controller can execute step S1412 before step S1401 to determine whether the system insulation impedance detection instruction is received. If yes, the next step is to execute step S1401 to start the detection. If no, the main controller continues to wait for the system insulation impedance detection instruction and determines whether the system insulation impedance detection instruction is received.

[0228] Similarly, before step S1403, the slave controller can also wait for the instruction sent by the main controller, or execute step S1413 to determine whether the first switching instruction is received. If yes, step S1404 can be directly executed. If no, the slave controller continues to wait for the first switching instruction and determines whether the first switching instruction is received.

[0229] The slave controller can also execute step S1414 to determine whether the second switching instruction is received after executing step S1404 and before executing step S1409. If yes, step S1409 can be directly executed. If no, the slave controller continues to wait for the second switching instruction and determines whether the second switching instruction is received.

[0230] In another possible implementation, the main controller can send an insulation impedance detection end instruction to each slave controller after executing step S1411, for example, step S1415. Then, the main controller executes step S1416 to end the detection, that is, to end the detection process.

[0231] The slave controller can wait for the insulation impedance detection end instruction sent by the main controller after executing step S1409. The slave controller can also execute step S1417 to determine whether the insulation impedance detection end instruction is received. If yes, the detection can be ended, for example, step S1418 is executed. If no, the slave controller continues to wait for the insulation impedance detection end instruction and determines whether the insulation impedance detection end instruction is received.

[0232] In yet another example, the plurality of slave controllers can correspond to the plurality of transformers one-to-one. The master controller sends instructions to all slave controllers each time. As shown, the interaction process between the master controller and the slave controllers is as follows: Figure 14

[0233] S1501, the master controller sends a first switching instruction to all slave controllers, the first switching instruction being used to instruct the first switch in the detection circuit of the corresponding transformer to be in the on state.

[0234] S1502, the slave controller receives the first switching instruction.

[0235] S1503, the slave controller controls the first switch in the detection circuit of the corresponding transformer to be in the on state.

[0236] The slave controller can control the first switch in the detection circuit of the corresponding transformer to be in the on state in response to the first switching instruction. The second switch in the detection circuit of the corresponding transformer of the slave controller is in the off state.

[0237] S1504, the master controller acquires a first voltage between the second bus and the ground after a preset time length.

[0238] S1505, the master controller sends a second switching instruction to the slave controller, the second switching instruction being used to instruct the second switch to be in the on state.

[0239] S1506, the slave controller receives the second switching instruction.

[0240] S1507, the slave controller controls the second switch in the detection circuit of the corresponding transformer to be in the on state.

[0241] The slave controller can control the second switch in the detection circuit of the corresponding transformer to be in the on state in response to the second switching instruction. The first switch in the detection circuit of the corresponding transformer of the slave controller is in the off state.

[0242] S1508, the master controller acquires a second voltage between the second bus and the ground after the preset time length.

[0243] S1509, the master controller determines the ground insulation impedance of the transformer system based on the at least two detection resistors, the number of the plurality of transformers, the first voltage and the second voltage.

[0244] In a possible implementation, after determining the ground insulation impedance of the transformer system, the master controller sends a detection end instruction to all slave controllers, so that each slave controller knows that the detection is over.

[0245] ​The embodiment of the present application also provides a system insulation impedance detection device, which is applied to a converter system, such as the converter system provided by the embodiment of the present application. The converter system comprises a plurality of converters connected in parallel between a first bus and a second bus, and each of the converters comprises a detection circuit. The detection circuit comprises a first switch and at least two resistors connected in series between the second bus and a ground wire, and the first switch is connected in parallel with one of the at least two resistors connected in series between the second bus and the ground wire. Figure 15 As shown in the figure, the device comprises:

[0246] a sampling circuit 1601 configured to acquire a voltage between the second bus and the ground wire;

[0247] a memory 1602 configured to store programs, instructions or codes;

[0248] a processor 1603 configured to execute the programs, instructions or codes in the memory, complete any one of the system insulation impedance detection processes provided by the embodiment of the present application, or execute any one of the system insulation impedance detection methods provided by the embodiment of the present application.

[0249] The embodiment of the present application provides a system insulation impedance detection device, which can comprise a processor and a memory. The memory is configured to store programs, instructions or codes, and the processor is configured to execute the programs, instructions or codes in the memory, complete any one of the system insulation impedance detection processes provided by the embodiment of the present application, or execute any one of the system insulation impedance detection methods provided by the embodiment of the present application.

[0250] The embodiment of the present application provides a non-volatile computer readable storage medium for storing a computer program. The computer program is loaded by a processor to execute any one of the system insulation impedance detection methods provided by the embodiment of the present application.

[0251] Obviously, those skilled in the art can make various modifications and variations to the embodiment of the present application without departing from the spirit and scope of the embodiment of the present application. Thus, if these modifications and variations of the embodiment of the present application belong to the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these modifications and variations.

Claims

1. A converter system, characterized by The application relates to a transformer system comprising: a plurality of transformers, a sampling circuit and a control circuit; the plurality of transformers are connected in parallel between a first bus and a second bus; the sampling circuit is connected between the second bus and a ground wire, and the control circuit is connected with each transformer, and the control circuit is also connected with the sampling circuit; each transformer comprises a detection circuit; the detection circuit comprises a first switch and at least two resistors connected in series between the second bus and the ground wire, and the first switch is connected in parallel with one of the at least two resistors, and the first switch is controlled by the control circuit; the sampling circuit is used for collecting a voltage between the second bus and the ground wire; the control circuit is used for controlling the sampling circuit to collect a first voltage and a second voltage; the first voltage is a voltage between the second bus and the ground wire collected by the sampling circuit when the first switch in a first number of detection circuits is in a conducting state; the second voltage is a voltage between the second bus and the ground wire collected by the sampling circuit when the first switch in a second number of detection circuits is in the conducting state; the second number is different from the first number; and the ground insulation impedance of the transformer system is determined according to the first voltage and the second voltage.

2. The system of claim 1, wherein, The detection circuit specifically comprises two resistors connected in series between the second bus and the ground wire, and the first switch is connected in parallel with a first resistor of the two resistors. The ground insulation impedance of the transformer system determined by the control circuit according to the first voltage and the second voltage conforms to the following formula: Riso is the ground insulation impedance of the transformer, Rz2 is the insulation impedance between the second bus and the ground wire, and Rz1 is the insulation impedance between the first bus and the ground wire. wherein Rd1 is the equivalent detection resistance between the second bus and the ground wire when the first switch in the first number of detection circuits is in the conducting state. Rd2 is the equivalent detection resistance between the second bus and the ground wire when the first switch in the second number of detection circuits is in the conducting state. i is the first number, i ∈ [0, n], j is the second number, j ∈ [0, n], and i ≠ j, RB is the resistance value of the first resistor, RA is the resistance value of the second resistor other than the first resistor of the two resistors, and n is the number of the plurality of transformers. VB is the voltage between the first bus and the second bus, V1 is the first voltage, and V2 is the second voltage.

3. The system of claim 1 or 2, wherein, The detection circuit further comprises at least one resistor connected between the first bus and the ground wire.

4. The system of claim 2, wherein, The detection circuit further comprises a third resistor connected between the first bus and the ground wire. The ground insulation impedance of the transformer system determined by the control circuit according to the first voltage and the second voltage conforms to the following formula: Riso is the ground insulation impedance of the transformer, Rz2 is the insulation impedance between the second bus and the ground wire, and Rz1 is the insulation impedance between the first bus and the ground wire. wherein Rd1 is the equivalent detection resistance between the second bus and the ground wire when the first switch in the first number of detection circuits is in the conducting state, and Rd2 is the equivalent detection resistance between the second bus and the ground wire when the first switch in the second number of detection circuits is in the conducting state. i is the first number, i ∈ [0, n], j is the second number, j ∈ [0, n], and i ≠ j, RB is the resistance value of the first resistor, RA is the resistance value of the second resistor other than the first resistor of the two resistors; n is the number of the plurality of transformers; RC is the resistance of the third resistor, VB is the voltage between the first bus and the second bus, V1 is the first voltage, and V2 is the second voltage.

5. The system of any one of claims 1-3, wherein, The detection circuit further comprises a second switch and at least two resistors connected in series between the first bus and the ground, and the second switch is connected in parallel with one of the at least two resistors connected in series between the first bus and the ground, and the second switch is controlled by the control circuit.

6. The system of claim 1, wherein, The detection circuit specifically comprises two resistors connected in series between the second bus and the ground, and the first switch is connected in parallel with a first resistor of the two resistors; The detection circuit further comprises two resistors connected in series between the first bus and the ground and a second switch, and the second switch is connected in parallel with a fourth resistor of the two resistors connected in series between the first bus and the ground; If the first switch in each detection circuit is in an on state, the second switch in each detection circuit is in an off state; If the first switch in each detection circuit is in an off state, the second switch in each detection circuit is in an on state.

7. The system of claim 6, wherein, The first number is zero, and the second number is the number of the plurality of transformers; the fourth resistor has the same resistance as the second resistor, and a fifth resistor of the two resistors connected in series between the first bus and the ground, except the fourth resistor, has the same resistance as the first resistor; The control circuit determines the ground insulation impedance of the transformer system according to the first voltage and the second voltage, and the ground insulation impedance of the transformer system conforms to the following formula: Riso is the ground insulation impedance of the transformer, and RB is the resistance of the first resistor; RA is the resistance of a second resistor of the two resistors connected in series between the second bus and the ground, except the first resistor; n is the number of the plurality of transformers; VB is the voltage between the first bus and the second bus; V1 is the first voltage, and V2 is the second voltage.

8. The system of claim 1, wherein, The control circuit comprises a plurality of controllers; the plurality of controllers correspond one-to-one to the plurality of transformers; Each controller is connected to a corresponding transformer and is configured to control a switch in a detection circuit of the corresponding transformer; The plurality of controllers comprises one or more master controllers, and the master controller is configured to send an instruction to other controllers in the plurality of controllers, except the master controller, and the instruction is configured to instruct the other controllers to control a switch in a detection circuit of a corresponding transformer.

9. The system of claim 1, wherein, The control circuit comprises a plurality of controllers; the plurality of controllers comprises a master controller and a plurality of slave controllers; the plurality of slave controllers correspond one-to-one to the plurality of transformers; Each slave controller is connected to a corresponding transformer and is configured to control the corresponding transformer; The master controller is configured to send an instruction to each slave controller, and the instruction is configured to instruct the slave controller to control a switch in a detection circuit of a corresponding transformer.

10. A system insulation impedance detection method, characterized by, The application is applied to a converter system, the converter system comprises a plurality of converters and a sampling circuit; the plurality of converters are connected in parallel between a first bus and a second bus; the sampling circuit is connected between the second bus and a ground wire; each of the converters comprises a detection circuit; the detection circuit comprises a first switch and at least two resistors connected in series between the second bus and the ground wire, and the first switch is connected in parallel with one of the at least two resistors; The method comprises: controlling the sampling circuit to collect a first voltage, the first voltage being a voltage between the second bus and the ground wire when the first switch in a first number of the detection circuits is in a conducting state; controlling the sampling circuit to collect a second voltage, the second voltage being a voltage between the second bus and the ground wire when the first switch in a second number of the detection circuits is in the conducting state; wherein the second number is different from the first number; determining a ground insulation impedance of the converter system according to the first voltage and the second voltage.

11. The method of claim 10, wherein, The detection circuit specifically comprises two resistors connected in series between the second bus and the ground wire, and the first switch is connected in parallel with a first resistor of the two resistors; determining that the ground insulation impedance of the converter system conforms to the following formula according to the first voltage and the second voltage: Riso is the ground insulation impedance of the converter, Rz2 is the insulation impedance between the second bus and the ground wire, and Rz1 is the insulation impedance between the first bus and the ground wire; wherein, Rd1 is an equivalent detection resistance between the second bus and the ground wire when the first switch in the first number of the detection circuits is in the conducting state; Rd2 is an equivalent detection resistance between the second bus and the ground wire when the first switch in the second number of detection circuits is in an on state, i is the first number, i ∈ [0, n], j is the second number, j ∈ [0, n], RB is the resistance value of the first resistor, RA is the resistance value of a second resistor of the two resistors except the first resistor, and n is the number of the plurality of converters; VB is the voltage between the first bus and the second bus, V1 is the first voltage, and V2 is the second voltage.

12. The method of claim 10, wherein, The detection circuit further comprises at least one resistor connected between the first bus and the ground wire.

13. The method of claim 10, wherein, The detection circuit further comprises a third resistor connected between the first bus and the ground wire; determining that the ground insulation impedance of the converter system conforms to the following formula according to the first voltage and the second voltage: Riso is the ground insulation impedance of the converter, Rz2 is the insulation impedance between the second bus and the ground wire, and Rz1 is the insulation impedance between the first bus and the ground wire; wherein, Rd1 is an equivalent detection resistance between the second bus and the ground wire when the first switch in the first number of the detection circuits is in the conducting state, and Rd2 is an equivalent detection resistance between the second bus and the ground wire when the first switch in the second number of the detection circuits is in the conducting state; i is the first number, i ∈ [0, n], j is the second number, j ∈ [0, n], RB is the resistance value of the first resistor, RA is the resistance value of the second resistor of the two resistors other than the first resistor, and n is the number of the plurality of transformers. RC is the resistance value of the third resistor, VB is the voltage between the first bus and the second bus, V1 is the first voltage, and V2 is the second voltage.

14. The method of claim 10, wherein, The detection circuit further comprises a second switch and at least two resistors connected in series between the first bus and the ground, and the second switch is connected in parallel with one of the at least two resistors connected in series between the first bus and the ground.

15. The method of claim 10, wherein, The detection circuit specifically comprises two resistors connected in series between the second bus and the ground, and the first switch is connected in parallel with a first resistor of the two resistors; The detection circuit further comprises two resistors connected in series between the first bus and the ground and a second switch, and the second switch is connected in parallel with a fourth resistor of the two resistors connected in series between the first bus and the ground; If the first switch in each detection circuit is in an on state, the second switch in each detection circuit is in an off state; If the first switch in each detection circuit is in an off state, the second switch in each detection circuit is in an on state.

16. The method of claim 15, wherein, The first number is zero, and the second number is the number of the plurality of transformers; the fourth resistor has the same resistance as the second resistor, and a fifth resistor of the two resistors connected in series between the first bus and the ground, except the fourth resistor, has the same resistance as the first resistor; According to the first voltage and the second voltage, the ground insulation impedance of the transformer system is determined to meet the following formula: Riso is the ground insulation impedance of the transformer, RB is the resistance of the first resistor, and RA is the resistance of a second resistor of the two resistors connected in series between the second bus and the ground, except the first resistor; n is the number of the plurality of transformers; VB is the voltage between the first bus and the second bus; V1 is the first voltage, and V2 is the second voltage.

17. A system insulation impedance detection apparatus, characterized by, The application is applied to a transformer system, the transformer system comprises a plurality of transformers connected in parallel between a first bus and a second bus, each transformer comprising a detection circuit; the detection circuit comprises a first switch and at least two resistors connected in series between the second bus and the ground, and the first switch is connected in parallel with one of the at least two resistors connected in series between the second bus and the ground. The device comprises: a sampling circuit for sampling the voltage between the second bus and the ground; a memory for storing programs, instructions or codes; a processor for executing the programs, instructions or codes in the memory to complete the method of any one of claims 10-16.

18. A non-transitory computer readable storage medium, comprising: A computer program for storing is loaded by a processor to execute the method of any one of claims 10-16. A computer program for storing is loaded by a processor to execute the method of any one of claims 10-16.

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