CN115032455A - DC insulation impedance detection method - Google Patents
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- CN115032455A CN115032455A CN202210641436.3A CN202210641436A CN115032455A CN 115032455 A CN115032455 A CN 115032455A CN 202210641436 A CN202210641436 A CN 202210641436A CN 115032455 A CN115032455 A CN 115032455A
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Abstract
The invention is suitable for the technical field of power electronics, and provides a direct-current insulation impedance detection method, which comprises the following steps: acquiring a first positive direct current bus voltage and a first negative direct current bus voltage when the midpoint of the first unbalanced bridge is connected with a grounding wire and the midpoint of the second unbalanced bridge is suspended; acquiring a second positive direct current bus voltage and a second negative direct current bus voltage when the midpoint of the first unbalanced bridge is suspended and the midpoint of the second unbalanced bridge is connected with a grounding wire; and determining the insulation impedance of the positive direct current bus and the insulation impedance of the negative direct current bus according to the first positive direct current bus voltage, the first negative direct current bus voltage, the second positive direct current bus voltage and the second negative direct current bus voltage. According to the invention, the balance bridge and the unbalance bridge are connected between the positive bus and the negative bus, and detection is carried out only after the middle point of the bridge arm is connected with the grounding wire during detection, so that the fluctuation of the direct current bus voltage is reduced, and the detection result is more accurate.
Description
Technical Field
The invention belongs to the technical field of power electronics, and particularly relates to a direct-current insulation impedance detection method.
Background
The dc system is used to provide dc power to the load, and is usually not grounded to ensure the continuity and reliability of the power supply. When the direct current system is abnormally grounded, potential safety hazards exist. Therefore, it is necessary to detect the insulation resistance of the dc system and find the ground fault in time.
In the prior art, a switch is usually connected into an unbalanced bridge and a balanced bridge to detect the insulation impedance, but the connection of the balanced bridge and the unbalanced bridge changes the ground state of a direct current system, so that the voltage of a direct current bus fluctuates, and the detected insulation impedance is not accurate enough.
Disclosure of Invention
In view of this, an embodiment of the present invention provides a method for detecting dc insulation impedance, so as to solve a problem in the prior art that access to a balanced bridge and an unbalanced bridge changes a ground state of a dc system, which results in an inaccurate dc insulation impedance detection result.
The first aspect of the embodiments of the present invention provides a dc insulation impedance detection method, which is applied to a dc insulation impedance detection device; the DC insulation resistance detection device comprises: a first unbalanced bridge, a second unbalanced bridge and a balanced bridge; the first unbalanced bridge, the second unbalanced bridge and the balance bridge are connected between the positive direct current bus and the negative direct current bus, and the middle point of the balance bridge is connected with the grounding wire; the method comprises the following steps:
acquiring a first positive direct current bus voltage and a first negative direct current bus voltage when the midpoint of the first unbalanced bridge is connected with a grounding wire and the midpoint of the second unbalanced bridge is suspended;
acquiring a second positive direct current bus voltage and a second negative direct current bus voltage when the midpoint of the first unbalanced bridge is suspended and the midpoint of the second unbalanced bridge is connected with the grounding wire;
and determining the insulation impedance of the positive direct current bus and the insulation impedance of the negative direct current bus according to the first positive direct current bus voltage, the first negative direct current bus voltage, the second positive direct current bus voltage and the second negative direct current bus voltage.
The embodiment of the invention provides a direct current insulation impedance detection method, which is applied to a direct current insulation impedance detection device; the DC insulation resistance detection device comprises: a first unbalanced bridge, a second unbalanced bridge and a balanced bridge; the first unbalanced bridge, the second unbalanced bridge and the balance bridge are connected between the positive direct current bus and the negative direct current bus, and the middle point of the balance bridge is connected with the grounding wire; the method comprises the following steps: acquiring a first positive direct current bus voltage and a first negative direct current bus voltage when the midpoint of the first unbalanced bridge is connected with a grounding wire and the midpoint of the second unbalanced bridge is suspended; acquiring a second positive direct current bus voltage and a second negative direct current bus voltage when the midpoint of the first unbalanced bridge is suspended and the midpoint of the second unbalanced bridge is connected with the grounding wire; and determining the insulation impedance of the positive direct current bus and the insulation impedance of the negative direct current bus according to the first positive direct current bus voltage, the first negative direct current bus voltage, the second positive direct current bus voltage and the second negative direct current bus voltage. In the embodiment of the invention, the balance bridge and the unbalanced bridge are always connected between the positive bus and the negative bus, and the midpoint of the unbalanced bridge is connected with the grounding wire only during measurement, so that the voltage fluctuation of the direct current bus can be greatly reduced, and the detection precision of the insulation impedance is effectively improved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.
Fig. 1 is a schematic circuit diagram of a dc insulation resistance detection apparatus according to an embodiment of the present invention;
fig. 2 is a schematic diagram of an implementation flow of a dc isolation impedance detection method according to an embodiment of the present invention;
FIG. 3 is an equivalent circuit diagram of a first unbalanced bridge according to an embodiment of the present invention;
FIG. 4 is an equivalent circuit diagram of a second unbalanced bridge according to an embodiment of the present invention;
fig. 5 is a schematic circuit diagram of a differential sampling circuit according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of a DC insulation resistance detection system according to an embodiment of the present invention;
fig. 7 is a schematic diagram of a detection terminal according to an embodiment of the present invention.
Detailed Description
In the following description, for purposes of explanation and not limitation, specific details are set forth such as particular system structures, techniques, etc. in order to provide a thorough understanding of the embodiments of the invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.
In order to explain the technical means of the present invention, the following description will be given by way of specific examples.
Referring to fig. 1 and fig. 2, an embodiment of the present invention provides a dc insulation resistance detection method, which is applied to a dc insulation resistance detection apparatus; the DC insulation resistance detection device comprises: a first unbalanced bridge, a second unbalanced bridge and a balanced bridge; the first unbalanced bridge, the second unbalanced bridge and the balance bridge are connected between the positive direct current BUS and the negative direct current BUS, and the middle point of the balance bridge is connected with the grounding wire; the method comprises the following steps:
s101: acquiring a first positive direct current bus voltage and a first negative direct current bus voltage when the midpoint of the first unbalanced bridge is connected with a grounding wire and the midpoint of the second unbalanced bridge is suspended;
s102: acquiring a second positive direct current bus voltage and a second negative direct current bus voltage when the midpoint of the first unbalanced bridge is suspended and the midpoint of the second unbalanced bridge is connected with the grounding wire;
s103: and determining the insulation resistance of the positive direct current BUS BUS + and the insulation resistance of the negative direct current BUS BUS-according to the first positive direct current BUS voltage, the first negative direct current BUS voltage, the second positive direct current BUS voltage and the second negative direct current BUS voltage.
Referring to fig. 1, in the embodiment of the present invention, the first unbalanced bridge, the second unbalanced bridge, and the balanced bridge are always connected between the positive dc BUS + and the negative dc BUS-, and the midpoint of the balanced bridge is connected to the ground line. And in the insulation detection process, connecting the middle points of the first unbalanced bridge and the second unbalanced bridge with the grounding wire respectively. Because the first unbalanced bridge and the second unbalanced bridge are both in a bridge circuit structure and are originally connected between the positive direct current BUS BUS + and the negative direct current BUS BUS-, the influence of the connecting ground wire on a direct current system is small, the influence on the voltage of the positive and negative buses is also small, the obtained voltage of the positive and negative buses is more accurate, and therefore the detected insulation impedance is more accurate.
In some embodiments, referring to fig. 1, the first unbalanced bridge may include: a fifth resistor R5, a sixth resistor R6 and a first optocoupler U1;
a first input end and a second input end of the first optical coupler U1 are used for receiving control signals, a first output end of the first optical coupler U1 is connected with a ground wire, and a second output end of the first optical coupler U1 is connected with a first end of the fifth resistor R5 and a first end of the sixth resistor R6 respectively;
the second end of the fifth resistor R5 is connected with the positive direct current BUS BUS +;
a second terminal of the sixth resistor R6 is connected to the negative dc BUS-.
In the embodiment of the invention, when the first optocoupler U1 is switched on, the midpoint of the first unbalanced bridge is connected with the ground wire; conversely, when the first optocoupler U1 is not conducting, the midpoint of the first unbalanced bridge is floating. The suspension and grounding of the middle point of the first unbalanced bridge are realized through the first optical coupler U1, the control is simple, and the realization is facilitated.
As above, the second unbalanced bridge may include: seventh resistance R7, eighth resistance R8 and second opto-coupler U2. The specific circuit structure is shown in fig. 1, and is not described herein again.
Specifically, the fifth resistor R5, the sixth resistor R6, the seventh resistor R7 and the eighth resistor R8 may be a single resistor, or may be formed by connecting a plurality of resistors in parallel or in series, which is not limited herein.
In some embodiments, S103 may include:
s1031: acquiring an upper bridge arm resistance of a balanced bridge, an upper bridge arm resistance of a first unbalanced bridge, a lower bridge arm resistance of the first unbalanced bridge, an upper bridge arm resistance of a second unbalanced bridge and a lower bridge arm resistance of the second unbalanced bridge;
s1032: and determining the insulation impedance of the positive direct current BUS BUS + and the insulation impedance of the negative direct current BUS BUS-according to the upper bridge arm resistance of the balanced bridge, the upper bridge arm resistance of the first unbalanced bridge, the lower bridge arm resistance of the first unbalanced bridge, the upper bridge arm resistance of the second unbalanced bridge, the lower bridge arm resistance of the second unbalanced bridge, the first positive direct current BUS voltage, the first negative direct current BUS voltage, the second positive direct current BUS voltage and the second negative direct current BUS voltage.
In some embodiments, the insulation resistance of the positive DC BUS BUS + and the insulation resistance of the negative DC BUS BUS-may be calculated as:
wherein, U 1+ Is the first positive DC bus voltage, U 1- Is the first negative DC bus voltage, U 2+ Is the second positive DC bus voltage, U 2- Is the second negative dc bus voltage; r 0 Is the upper arm resistance (sum of the first resistor R1 and the second resistor R2) of the balance bridge x1 Is the insulation resistance of the positive DC BUS BUS + x2 Insulation resistance, R, for negative DC BUS BUS- 11 Is the upper arm resistance (resistance of a fifth resistor R5) of the first unbalanced bridge 12 The lower arm resistance of the first unbalanced bridge (the resistance of a sixth resistor R6), R 21 Is the upper arm resistance (the resistance of a seventh resistor R7), R of the second unbalanced bridge 22 The lower arm resistance of the second unbalanced bridge (the resistance of the eighth resistor R8).
In the embodiment of the invention, the impedances of the bridge arms of the balance bridge, the first unbalanced bridge and the second unbalanced bridge are known, and the insulation impedance R of the direct current BUS BUS + can be calculated according to ohm's law x1 Insulation resistance R of negative DC BUS BUS- x2 。
For example, FIG. 3 shows an equivalent circuit diagram for a first balun when it is switched in, the first beingThe upper bridge arm of the balance bridge is connected with the upper bridge arm of the balance bridge and the insulation resistance of the positive direct current BUS BUS + in parallel; the lower bridge arm of the first unbalanced bridge is connected with the lower bridge arm of the balanced bridge and the insulation resistance of the negative direct current BUS in parallel. Thereby obtaining the result that,
similarly, fig. 4 shows an equivalent circuit diagram of the second unbalanced bridge, which can be obtained,
wherein R is x1 And R x2 The unknown quantity and the other known quantities are solved to obtain R x1 And R x2 The solution of (1).
The impedance of the first unbalanced bridge is different from the impedance of the second unbalanced bridge, so that the voltage of the first positive direct current bus is different from that of the second positive direct current bus, and/or the voltage of the first negative direct current bus is different from that of the second negative direct current bus, and the values of the two insulation impedances can be calculated according to the binary equation.
In some embodiments, before S103, the method may further include:
s104: acquiring a first positive bus ripple voltage and a first negative bus ripple voltage when the midpoint of the first unbalanced bridge is connected with the ground wire and the midpoint of the second unbalanced bridge is suspended;
s105: acquiring a second positive bus ripple voltage and a second negative bus ripple voltage when the midpoint of the first unbalanced bridge is suspended and the midpoint of the second unbalanced bridge is connected with the ground wire;
s106: correcting the first positive direct current bus voltage according to the first positive bus ripple voltage to obtain a corrected first positive direct current bus voltage; correcting the first negative direct current bus voltage according to the first negative bus ripple voltage to obtain a corrected first negative direct current bus voltage;
s107: correcting the second positive direct-current bus voltage according to the second positive bus ripple voltage to obtain a corrected second positive direct-current bus voltage; correcting the second negative direct current bus voltage according to the second negative bus ripple voltage to obtain a corrected second negative direct current bus voltage;
s103 may specifically include: and determining the insulation resistance of the positive direct current BUS BUS + and the insulation resistance of the negative direct current BUS BUS-according to the corrected first positive direct current BUS voltage, the corrected first negative direct current BUS voltage, the corrected second positive direct current BUS voltage and the corrected second negative direct current BUS voltage.
In the embodiment of the invention, due to the existence of the bus ripple voltage, the obtained direct current bus voltage (the first positive direct current bus voltage, the second positive direct current bus voltage, the first negative direct current bus voltage and the second negative direct current bus voltage) is inaccurate, so that the insulation impedance obtained through the ohm's law calculation has deviation and is not accurate enough. Based on the above, in the embodiment of the present invention, the bus ripple voltage (the first positive bus ripple voltage, the first negative bus ripple voltage, the second positive bus ripple voltage, and the second negative bus ripple voltage) is obtained, the dc bus voltage is corrected to obtain a more accurate dc bus voltage, and then the insulation impedance is calculated according to the corrected dc bus voltage, so that the calculation result is more accurate.
In some embodiments, S106 may include:
1. determining an effective value of the first positive bus ripple voltage;
2. subtracting the effective value of the ripple voltage of the first positive bus from the voltage of the first positive direct current bus to obtain the corrected voltage of the first positive direct current bus;
3. determining an effective value of the first negative bus ripple voltage;
4. subtracting the effective value of the ripple voltage of the first negative bus from the voltage of the first negative direct current bus to obtain a corrected voltage of the first negative direct current bus; and the voltage of the first negative direct current bus is a negative value.
In the embodiment of the invention, the effective value of the bus ripple voltage is subtracted from the direct current bus voltage, so that the influence of the bus ripple voltage is filtered, and the more accurate direct current bus voltage is obtained.
Further, S107 may be modified by the same method, which is not described in detail.
In some embodiments, referring to fig. 1, the balance bridge may include: a first resistor R1, a second resistor R2, a third resistor R3 and a fourth resistor R4; the first end of the first resistor R1 is connected with the positive direct current BUS BUS +, and the second end of the first resistor R1 is connected with the ground wire through the second resistor R2; the first end of the third resistor R3 is connected with the grounding wire, and the second end of the third resistor R3 is connected with the negative direct current BUS BUS-through the fourth resistor R4;
s101 may include:
s1011: acquiring the voltage of a third resistor R3 when the midpoint of the first unbalanced bridge is connected with the ground wire and the midpoint of the second unbalanced bridge is suspended;
s1012: determining a first negative direct current bus voltage according to the voltage of the third resistor R3;
s1013: a first positive DC bus voltage is determined based on the first negative DC bus voltage.
In some embodiments, S1013 may specifically include: and obtaining a first pressure difference between the positive direct current BUS BUS + and the negative direct current BUS BUS-, and subtracting the absolute value of the first negative direct current BUS voltage from the first pressure difference to obtain the first positive direct current BUS voltage.
In the embodiment of the invention, if the direct current system has an insulation impedance fault, the midpoint of the direct current bus is unbalanced, and the voltage difference exists between the midpoint of the direct current bus and the grounding wire, so that the directly obtained positive direct current bus voltage and negative direct current bus voltage are inaccurate. In the embodiment of the invention, the midpoint of the balance bridge is connected with the grounding wire, the voltage value of two ends of a certain resistor (for example, a third resistor R3) in the balance bridge can be accurately detected as absolute 0 level, and then the voltage of the first negative direct current bus is calculated according to ohm's law.
The differential pressure between the positive direct current BUS BUS + and the negative direct current BUS BUS-is not influenced by the level 0 and the midpoint voltage of the BUS, and the accuracy is higher, so that the absolute value of the first negative direct current BUS voltage can be subtracted from the first differential pressure to obtain the first positive direct current BUS voltage. The bus voltage calculated by the method is not influenced by the midpoint voltage of the bus, and is more accurate, so that the calculated insulation resistance is more accurate. The positive dc bus voltage and the negative dc bus voltage can be calculated from the voltage of any resistor in the balance bridge, and is not limited to the third resistor R3.
Furthermore, a differential voltage sampling circuit can be adopted to obtain the first differential pressure, and the obtained first differential pressure is more accurate.
In some embodiments, S1011 may include: and a differential voltage sampling circuit is adopted to obtain the voltage of the third resistor R3 when the midpoint of the first unbalanced bridge is connected with the ground wire and the midpoint of the second unbalanced bridge is suspended.
In the embodiment of the invention, the voltage of the third resistor R3 can be detected by adopting a differential voltage sampling circuit, and the detection result is accurate.
In some embodiments, referring to fig. 5, the differential voltage sampling circuit may include: the device comprises a first amplification module 11, a second amplification module 12, an isolation module 13, a differential amplification module 14 and a main control module 15;
the input end of the first amplification module 11 is connected with the first end of the third resistor R3, and the output end of the first amplification module 11 is connected with the first input end of the isolation module 13;
the input end of the second amplifying module 12 is connected to the second end of the third resistor R3, and the output end of the second amplifying module 12 is connected to the second input end of the isolating module 13;
a first output end of the isolation module 13 is connected with a first input end of the differential amplification module 14, and a second output end of the isolation module 13 is connected with a second input end of the differential amplification module 14;
the output of the differential amplification block 14 outputs the sampled signal.
In some embodiments, before S101, the method may further include:
s108: acquiring the pressure difference between the midpoint of the bus and the grounding wire;
s109: if the voltage difference is larger than the preset voltage value, determining that an insulation resistance fault exists, and executing the step of obtaining a first positive direct current BUS voltage and a first negative direct current BUS voltage when the midpoint of the first unbalanced bridge is connected with the grounding wire and the midpoint of the second unbalanced bridge is suspended until determining the insulation resistance of the positive direct current BUS BUS + and the insulation resistance of the negative direct current BUS BUS-according to the first positive direct current BUS voltage, the first negative direct current BUS voltage, the second positive direct current BUS voltage and the second negative direct current BUS voltage;
s1010: and if the differential pressure is not greater than the preset difference value, determining that no insulation resistance fault exists.
When the direct current system has no ground fault, the pressure difference between the midpoint of the bus and the ground wire is very small; when a ground fault occurs, the voltage of the positive and negative buses is unbalanced firstly due to the unbalance of the insulation resistance of the positive direct current BUS BUS + and the insulation resistance of the negative direct current BUS BUS-, and the voltage difference between the midpoint of the buses and the ground wire is rapidly increased. Therefore, the insulation impedance fault can be quickly identified through the pressure difference between the midpoint of the bus and the grounding wire, and the countermeasures can be taken in time. And then the insulation resistance is calculated by adopting the methods from S101 to S103, and the position of the insulation fault is accurately identified.
It should be understood that, the sequence numbers of the steps in the foregoing embodiments do not imply an execution sequence, and the execution sequence of each process should be determined by functions and internal logic of the process, and should not limit the implementation process of the embodiments of the present invention in any way.
Corresponding to the above embodiment, referring to fig. 6, an embodiment of the present invention further provides a dc insulation resistance detection system, which is applied to a dc insulation resistance detection device; the DC insulation resistance detection device comprises: a first unbalanced bridge, a second unbalanced bridge and a balanced bridge; the first unbalanced bridge, the second unbalanced bridge and the balance bridge are connected between the positive direct current BUS and the negative direct current BUS, and the middle point of the balance bridge is connected with the grounding wire; the above-mentioned system includes:
a first voltage obtaining unit 21, configured to obtain a first positive dc bus voltage and a first negative dc bus voltage when a midpoint of the first unbalanced bridge is connected to the ground line and a midpoint of the second unbalanced bridge is suspended;
a second voltage obtaining unit 22, configured to obtain a second positive dc bus voltage and a second negative dc bus voltage when the midpoint of the first unbalanced bridge is suspended and the midpoint of the second unbalanced bridge is connected to the ground line;
and an insulation resistance calculation unit 23, configured to determine an insulation resistance of the positive dc BUS + and an insulation resistance of the negative dc BUS-, according to the first positive dc BUS voltage, the first negative dc BUS voltage, the second positive dc BUS voltage, and the second negative dc BUS voltage.
In some embodiments, the insulation resistance calculation unit 23 may include:
the resistance obtaining subunit 231 is configured to obtain an upper arm resistance of the balanced bridge, an upper arm resistance of the first unbalanced bridge, a lower arm resistance of the first unbalanced bridge, an upper arm resistance of the second unbalanced bridge, and a lower arm resistance of the second unbalanced bridge;
and a result output subunit 232, configured to determine an insulation impedance of the positive dc BUS + and an insulation impedance of the negative dc BUS-according to an upper arm resistance of the balanced bridge, an upper arm resistance of the first unbalanced bridge, a lower arm resistance of the first unbalanced bridge, an upper arm resistance of the second unbalanced bridge, a lower arm resistance of the second unbalanced bridge, a first positive dc BUS voltage, a first negative dc BUS voltage, a second positive dc BUS voltage, and a second negative dc BUS voltage.
In some embodiments, the insulation resistance of the positive DC BUS BUS + and the insulation resistance of the negative DC BUS BUS-may be calculated as:
wherein, U 1+ Is the first positive DC bus voltage, U 1- Is the first negative DC bus voltage, U 2+ Is the second positive DC bus voltage, U 2- Is the second negative DC bus voltage; r 0 Is the upper arm resistance of a balance bridge, R x1 Is the insulation resistance of the positive DC BUS BUS +, R x2 Is negativeInsulation resistance, R, of DC BUS BUS- 11 Is the upper leg resistance, R, of the first unbalanced bridge 12 Is the lower leg resistance, R, of the first unbalanced bridge 21 Is the upper arm resistance, R, of the second unbalanced bridge 22 The lower arm resistance of the second unbalanced bridge.
In some embodiments, the system may further include:
a first ripple obtaining unit 24, configured to obtain a first positive bus ripple voltage and a first negative bus ripple voltage when a midpoint of the first unbalanced bridge is connected to the ground line and a midpoint of the second unbalanced bridge is suspended;
a second ripple acquiring unit 25, configured to acquire a second positive bus ripple voltage and a second negative bus ripple voltage when the midpoint of the first unbalanced bridge is suspended and the midpoint of the second unbalanced bridge is connected to the ground line;
the first correction unit 26 is configured to correct the first positive dc bus voltage according to the first positive bus ripple voltage, so as to obtain a corrected first positive dc bus voltage; correcting the first negative direct current bus voltage according to the first negative bus ripple voltage to obtain a corrected first negative direct current bus voltage;
the second correcting unit 27 is configured to correct the second positive dc bus voltage according to the second positive bus ripple voltage, so as to obtain a corrected second positive dc bus voltage; correcting the second negative direct current bus voltage according to the second negative bus ripple voltage to obtain a corrected second negative direct current bus voltage;
the insulation resistance calculation unit 23 may be specifically configured to: and determining the insulation resistance of the positive direct current BUS BUS + and the insulation resistance of the negative direct current BUS BUS-according to the corrected first positive direct current BUS voltage, the corrected first negative direct current BUS voltage, the corrected second positive direct current BUS voltage and the corrected second negative direct current BUS voltage.
In some embodiments, the first modification unit 26 may be specifically configured to:
1. determining an effective value of the first positive bus ripple voltage;
2. subtracting the effective value of the ripple voltage of the first positive bus from the voltage of the first positive direct current bus to obtain the corrected voltage of the first positive direct current bus;
3. determining an effective value of the first negative bus ripple voltage;
4. subtracting the effective value of the ripple voltage of the first negative bus from the voltage of the first negative direct current bus to obtain a corrected voltage of the first negative direct current bus; the first negative direct current bus voltage is a negative value.
In some embodiments, the balance bridge comprises: a first resistor R1, a second resistor R2, a third resistor R3 and a fourth resistor R4; the first end of the first resistor R1 is connected with the positive direct current BUS BUS +, and the second end of the first resistor R1 is connected with the ground wire through the second resistor R2; the first end of the third resistor R3 is connected with the grounding wire, and the second end of the third resistor R3 is connected with the negative direct current BUS BUS-through the fourth resistor R4;
the first voltage obtaining unit 21 may include:
the resistance voltage acquiring subunit 211 is configured to acquire a voltage of the third resistor R3 when the midpoint of the first unbalanced bridge is connected to the ground line and the midpoint of the second unbalanced bridge is suspended;
a first dc bus voltage determining subunit 212 configured to determine a first negative dc bus voltage from the voltage of the third resistor R3;
the second dc bus voltage determining subunit 213 is configured to determine the first positive dc bus voltage from the first negative dc bus voltage.
In some embodiments, the resistance voltage obtaining subunit 211 may be specifically configured to: and a differential voltage sampling circuit is adopted to obtain the voltage of the third resistor R3 when the midpoint of the first unbalanced bridge is connected with the ground wire and the midpoint of the second unbalanced bridge is suspended.
In some embodiments, the differential voltage sampling circuit may include: the device comprises a first amplification module 11, a second amplification module 12, an isolation module 13, a differential amplification module 14 and a main control module 15;
the input end of the first amplification module 11 is connected with the first end of the third resistor R3, and the output end of the first amplification module 11 is connected with the first input end of the isolation module 13;
the input end of the second amplifying module 12 is connected to the second end of the third resistor R3, and the output end of the second amplifying module 12 is connected to the second input end of the isolating module 13;
a first output end of the isolation module 13 is connected with a first input end of the differential amplification module 14, and a second output end of the isolation module 13 is connected with a second input end of the differential amplification module 14;
the output of the differential amplification block 14 outputs the sampled signal.
In some embodiments, the first unbalanced bridge may include: a fifth resistor R5, a sixth resistor R6 and a first optocoupler U1;
a first input end and a second input end of the first optical coupler U1 are used for receiving control signals, a first output end of the first optical coupler U1 is connected with a ground wire, and a second output end of the first optical coupler U1 is connected with a first end of the fifth resistor R5 and a first end of the sixth resistor R6 respectively;
the second end of the fifth resistor R5 is connected with the positive direct current BUS BUS +;
a second terminal of the sixth resistor R6 is connected to the negative dc BUS-.
In some embodiments, the system may further include:
a differential pressure obtaining unit 28, configured to obtain a differential pressure between a midpoint of the bus and the ground line;
a first insulation fault determining unit 29, configured to determine that an insulation impedance fault exists if the voltage difference is greater than the preset voltage value, and execute a step of obtaining a first positive dc BUS voltage and a first negative dc BUS voltage when the midpoint of the first unbalanced bridge is connected to the ground line and the midpoint of the second unbalanced bridge is suspended, to determine an insulation impedance of the positive dc BUS + and an insulation impedance of the negative dc BUS-according to the first positive dc BUS voltage, the first negative dc BUS voltage, the second positive dc BUS voltage, and the second negative dc BUS voltage;
and a second insulation fault determining unit 210, configured to determine that an insulation impedance fault does not exist if the voltage difference is not greater than the preset difference.
It can be clearly understood by those skilled in the art that, for convenience and simplicity of description, the foregoing division of each functional unit and module is merely used for illustration, and in practical applications, the foregoing function distribution may be performed by different functional units and modules as needed, that is, the internal structure of the detection terminal is divided into different functional units or modules to perform all or part of the above-described functions. Each functional unit and module in the embodiments may be integrated in one processing unit, or each unit may exist alone physically, or two or more units are integrated in one unit, and the integrated unit may be implemented in a form of hardware, or in a form of software functional unit. In addition, specific names of the functional units and modules are only for convenience of distinguishing from each other, and are not used for limiting the protection scope of the present application. The specific working processes of the units and modules in the above-mentioned apparatus may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
Fig. 7 is a schematic block diagram of a detection terminal according to an embodiment of the present invention. As shown in fig. 7, the detection terminal 4 of this embodiment includes: one or more processors 40, a memory 41, and a computer program 42 stored in the memory 41 and executable on the processors 40. The processor 40 implements the steps in the above-described embodiments of the dc isolation impedance detection method, such as steps S101 to S103 shown in fig. 2, when executing the computer program 42. Alternatively, the processor 40, when executing the computer program 42, implements the functions of the modules/units in the above-described dc insulation resistance detection system embodiment, such as the functions of the units 21 to 23 shown in fig. 6.
Illustratively, the computer program 42 may be divided into one or more units, which are stored in the memory 41 and executed by the processor 40 to complete the present application. One or more of the elements may be a series of computer program instruction segments capable of performing specific functions, which are used to describe the execution of the computer program 42 in the test terminal 4. For example, the computer program 42 may be divided into the first voltage acquisition unit 21, the second voltage acquisition unit 22, and the insulation resistance calculation unit 23.
A first voltage obtaining unit 21, configured to obtain a first positive dc bus voltage and a first negative dc bus voltage when a midpoint of the first unbalanced bridge is connected to the ground line and a midpoint of the second unbalanced bridge is suspended;
a second voltage obtaining unit 22, configured to obtain a second positive dc bus voltage and a second negative dc bus voltage when the midpoint of the first unbalanced bridge is suspended and the midpoint of the second unbalanced bridge is connected to the ground line;
and an insulation resistance calculation unit 23, configured to determine an insulation resistance of the positive dc BUS + and an insulation resistance of the negative dc BUS-according to the first positive dc BUS voltage, the first negative dc BUS voltage, the second positive dc BUS voltage, and the second negative dc BUS voltage.
Other elements are not described in detail herein.
The detection terminal 4 includes, but is not limited to, a processor 40 and a memory 41. Those skilled in the art will appreciate that fig. 7 is only one example of a detection terminal and does not constitute a limitation of the detection terminal 4, and may include more or less components than those shown, or combine some components, or different components, for example, the detection terminal 4 may further include an input device, an output device, a network access device, a bus, etc.
The Processor 40 may be a Central Processing Unit (CPU), other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other Programmable logic device, discrete Gate or transistor logic device, discrete hardware component, etc. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.
The memory 41 may be an internal storage unit of the test terminal, such as a hard disk or a memory of the test terminal. The memory 41 may also be an external storage device of the detection terminal, such as a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) Card, a Flash memory Card (Flash Card), and the like provided on the detection terminal. Further, the memory 41 may also include both an internal storage unit of the detection terminal and an external storage device. The memory 41 is used for storing computer programs 42 and other programs and data needed for detecting the terminal. The memory 41 may also be used to temporarily store data that has been output or is to be output.
In the above embodiments, the description of each embodiment has its own emphasis, and reference may be made to the related description of other embodiments for parts that are not described or recited in any embodiment.
Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.
In the embodiments provided in the present application, it should be understood that the disclosed detection terminal and method may be implemented in other ways. For example, the above-described embodiments of the detection terminal are merely illustrative, and for example, a module or a unit may be divided into only one logic function, and may be implemented in other ways, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
Units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated modules/units, if implemented in the form of software functional units and sold or used as separate products, may be stored in a computer readable storage medium. Based on such understanding, all or part of the flow in the method of the embodiments described above can be realized by a computer program, which can be stored in a computer readable storage medium and used to instruct related hardware, and when the computer program is executed by a processor, the steps of the method embodiments described above can be realized. Wherein the computer program comprises computer program code, which may be in the form of source code, object code, an executable file or some intermediate form, etc. The computer readable medium may include: any entity or device capable of carrying computer program code, recording medium, U.S. disk, removable hard disk, magnetic diskette, optical disk, computer Memory, Read-Only Memory (ROM), Random Access Memory (RAM), electrical carrier signal, telecommunications signal, software distribution medium, etc. It should be noted that the computer readable medium may include any suitable increase or decrease as required by legislation and patent practice in the jurisdiction, for example, in some jurisdictions, computer readable media may not include electrical carrier signals and telecommunications signals in accordance with legislation and patent practice.
The above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the embodiments of the present application, and they should be construed as being included in the present application.
Claims (10)
1. A DC insulation resistance detection method is characterized in that the method is applied to a DC insulation resistance detection device; the direct-current insulation resistance detection device comprises: a first unbalanced bridge, a second unbalanced bridge and a balanced bridge; the first unbalanced bridge, the second unbalanced bridge and the balance bridge are connected between a positive direct current bus and a negative direct current bus, and the middle point of the balance bridge is connected with a grounding wire; the method comprises the following steps:
acquiring a first positive direct current bus voltage and a first negative direct current bus voltage when the midpoint of the first unbalanced bridge is connected with the grounding wire and the midpoint of the second unbalanced bridge is suspended;
acquiring a second positive direct-current bus voltage and a second negative direct-current bus voltage when the midpoint of the first unbalanced bridge is suspended and the midpoint of the second unbalanced bridge is connected with the grounding wire;
and determining the insulation impedance of the positive direct current bus and the insulation impedance of the negative direct current bus according to the first positive direct current bus voltage, the first negative direct current bus voltage, the second positive direct current bus voltage and the second negative direct current bus voltage.
2. The dc insulation resistance detection method of claim 1, wherein determining the insulation resistance of the positive dc bus and the insulation resistance of the negative dc bus based on the first positive dc bus voltage, the first negative dc bus voltage, the second positive dc bus voltage, and the second negative dc bus voltage comprises:
acquiring an upper bridge arm resistance of the balanced bridge, an upper bridge arm resistance of the first unbalanced bridge, a lower bridge arm resistance of the first unbalanced bridge, an upper bridge arm resistance of the second unbalanced bridge and a lower bridge arm resistance of the second unbalanced bridge;
and determining the insulation impedance of the positive direct current bus and the insulation impedance of the negative direct current bus according to the upper bridge arm resistance of the balanced bridge, the upper bridge arm resistance of the first unbalanced bridge, the lower bridge arm resistance of the first unbalanced bridge, the upper bridge arm resistance of the second unbalanced bridge, the lower bridge arm resistance of the second unbalanced bridge, the first positive direct current bus voltage, the first negative direct current bus voltage, the second positive direct current bus voltage and the second negative direct current bus voltage.
3. The direct-current insulation resistance detection method according to claim 2, wherein the calculation formula of the insulation resistance of the positive direct-current bus and the insulation resistance of the negative direct-current bus is as follows:
wherein, U 1+ Is the first positive DC bus voltage, U 1- Is the first negative DC bus voltage, U 2+ Is the second positive DC bus voltage, U 2- The second negative direct current bus voltage; r 0 Is the upper bridge arm resistance, R, of the balance bridge x1 Is the insulation resistance, R, of the positive DC bus x2 Is the insulation resistance, R, of the negative DC bus 11 Is the upper leg resistance, R, of the first unbalanced bridge 12 Is the lower leg resistance, R, of the first unbalanced bridge 21 Is the upper arm resistance, R, of the second unbalanced bridge 22 And the resistance of the lower bridge arm of the second unbalanced bridge.
4. The direct current insulation impedance detection method according to any one of claims 1 to 3, wherein before determining the insulation impedance of the positive direct current bus and the insulation impedance of the negative direct current bus according to the first positive direct current bus voltage, the first negative direct current bus voltage, the second positive direct current bus voltage, and the second negative direct current bus voltage, the method further comprises:
acquiring a first positive bus ripple voltage and a first negative bus ripple voltage when the midpoint of the first unbalanced bridge is connected with the grounding wire and the midpoint of the second unbalanced bridge is suspended;
acquiring a second positive bus ripple voltage and a second negative bus ripple voltage when the midpoint of the first unbalanced bridge is suspended and the midpoint of the second unbalanced bridge is connected with the ground wire;
correcting the first positive direct current bus voltage according to the first positive bus ripple voltage to obtain a corrected first positive direct current bus voltage; correcting the first negative direct current bus voltage according to the first negative bus ripple voltage to obtain a corrected first negative direct current bus voltage;
correcting the second positive direct-current bus voltage according to the second positive bus ripple voltage to obtain a corrected second positive direct-current bus voltage; correcting the second negative direct current bus voltage according to the second negative bus ripple voltage to obtain a corrected second negative direct current bus voltage;
the determining the insulation impedance of the positive direct current bus and the insulation impedance of the negative direct current bus according to the first positive direct current bus voltage, the first negative direct current bus voltage, the second positive direct current bus voltage and the second negative direct current bus voltage includes:
and determining the insulation impedance of the positive direct current bus and the insulation impedance of the negative direct current bus according to the corrected first positive direct current bus voltage, the corrected first negative direct current bus voltage, the corrected second positive direct current bus voltage and the corrected second negative direct current bus voltage.
5. The method according to claim 4, wherein the first positive DC bus voltage is corrected according to the first positive bus ripple voltage to obtain a corrected first positive DC bus voltage; correcting the first negative direct current bus voltage according to the first negative bus ripple voltage to obtain a corrected first negative direct current bus voltage, including:
determining an effective value of the first positive bus ripple voltage;
subtracting the effective value of the ripple voltage of the first positive bus from the voltage of the first positive direct current bus to obtain the corrected voltage of the first positive direct current bus;
determining an effective value of the first negative bus ripple voltage;
subtracting the effective value of the ripple voltage of the first negative bus from the voltage of the first negative direct current bus to obtain the corrected voltage of the first negative direct current bus; and the voltage of the first negative direct current bus is a negative value.
6. A dc isolation impedance detection method according to any one of claims 1 to 3, wherein said balance bridge comprises: the circuit comprises a first resistor, a second resistor, a third resistor and a fourth resistor; the first end of the first resistor is connected with the positive direct current bus, and the second end of the first resistor is connected with the grounding wire through the second resistor; the first end of the third resistor is connected with the grounding wire, and the second end of the third resistor is connected with the negative direct current bus through the fourth resistor;
the acquiring a first positive direct current bus voltage and a first negative direct current bus voltage when the midpoint of the first unbalanced bridge is connected with the ground line and the midpoint of the second unbalanced bridge is suspended comprises:
acquiring the voltage of the third resistor when the midpoint of the first unbalanced bridge is connected with the grounding wire and the midpoint of the second unbalanced bridge is suspended;
determining the voltage of the first negative direct current bus according to the voltage of the third resistor;
and determining the first positive direct current bus voltage according to the first negative direct current bus voltage.
7. The method according to claim 6, wherein the obtaining the voltage of the third resistor when the midpoint of the first unbalanced bridge is connected to the ground line and the midpoint of the second unbalanced bridge is suspended comprises:
and acquiring the voltage of the third resistor when the midpoint of the first unbalanced bridge is connected with the grounding wire and the midpoint of the second unbalanced bridge is suspended by adopting a differential voltage sampling circuit.
8. The dc isolation impedance detection method of claim 7, wherein the differential voltage sampling circuit comprises: the device comprises a first amplification module, a second amplification module, an isolation module, a differential amplification module and a main control module;
the input end of the first amplification module is connected with the first end of the third resistor, and the output end of the first amplification module is connected with the first input end of the isolation module;
the input end of the second amplification module is connected with the second end of the third resistor, and the output end of the second amplification module is connected with the second input end of the isolation module;
the first output end of the isolation module is connected with the first input end of the differential amplification module, and the second output end of the isolation module is connected with the second input end of the differential amplification module;
and the output end of the differential amplification module outputs a sampling signal.
9. A dc isolation impedance detection method according to any one of claims 1 to 3, wherein said first unbalance bridge comprises: a fifth resistor, a sixth resistor and a first optocoupler;
a first input end and a second input end of the first optocoupler are used for receiving control signals, a first output end of the first optocoupler is connected with the ground wire, and a second output end of the first optocoupler is respectively connected with a first end of the fifth resistor and a first end of the sixth resistor;
the second end of the fifth resistor is connected with the positive direct current bus;
and the second end of the sixth resistor is connected with the negative direct current bus.
10. The dc isolation impedance detection method according to any one of claims 1 to 3, wherein before the obtaining of the first positive dc bus voltage and the first negative dc bus voltage when the midpoint of the first unbalanced bridge is connected to the ground line and the midpoint of the second unbalanced bridge is suspended, the method further comprises:
acquiring the pressure difference between the midpoint of the bus and the grounding wire;
if the voltage difference is larger than a preset voltage value, determining that an insulation impedance fault exists, and executing the step of obtaining a first positive direct-current bus voltage and a first negative direct-current bus voltage when the midpoint of the first unbalanced bridge is connected with the grounding wire and the midpoint of the second unbalanced bridge is suspended until the step of determining the insulation impedance of the positive direct-current bus and the insulation impedance of the negative direct-current bus according to the first positive direct-current bus voltage, the first negative direct-current bus voltage, the second positive direct-current bus voltage and the second negative direct-current bus voltage;
and if the differential pressure is not greater than the preset difference value, determining that no insulation resistance fault exists.
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| CN202210641436.3A CN115032455A (en) | 2022-06-07 | 2022-06-07 | DC insulation impedance detection method |
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| CN202210641436.3A CN115032455A (en) | 2022-06-07 | 2022-06-07 | DC insulation impedance detection method |
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