Insulation resistance detection device, method and system

Abstract

The invention discloses an insulation resistance detection device, method and system, and relates to the field of insulation detection.According to the scheme, a controller controls on or off of a first switch and a second switch so as to control whether a first resistor module is connected between a direct current positive electrode of an optical storage system and the ground or not; controlling whether the second resistor module is connected between the direct-current negative electrode of the optical storage system and the ground or not; the controller can calculate the insulation resistance from the direct-current positive electrode to the ground and the insulation resistance from the direct-current negative electrode to the ground of the optical storage system through the voltage from the direct-current negative electrode of the optical storage system to the ground and the voltage from the direct-current positive electrode to the direct-current negative electrode of the optical storage system, which are acquired by the first sampling circuit and the second sampling circuit. And whether the insulation impedance of the optical storage system has a fault is accurately and timely detected according to the calculated insulation impedance.

Description

Technical Field

[0001] The present invention relates to the field of insulation detection, and in particular to an insulation impedance detection device, method and system. Background Art

[0002] Photovoltaic power generation equipment and electrochemical energy storage power generation equipment are both installed in outdoor environments, and their DC side cables are mostly laid underground or in cable trenches, which are easily soaked by rainwater. In addition, after long-term operation, their insulation layers may be damaged and the cables may age, thus gradually destroying the insulation strength of the cables, thereby affecting the DC side insulation impedance of the photovoltaic power generation equipment and the electrochemical energy storage power generation equipment.

[0003] Furthermore, at present, photovoltaic power generation equipment and electrochemical energy storage power generation equipment are developing towards larger capacity, and DC high voltage has become the mainstream technical solution. The increase in voltage levels has also triggered considerations on the safe operation of power generation equipment and the safe operation of personnel. In particular, photovoltaic power generation systems, because the photovoltaic panels in photovoltaic power generation systems are installed in the open air, are extremely susceptible to environmental factors such as dust, rain and snow, which causes changes in their insulation impedance to the ground, thereby affecting the normal operation of equipment in the photovoltaic power generation system, and in severe cases, causing casualties. For example: when the insulation impedance of the photovoltaic panel to the ground is too low, if the photovoltaic inverter in the photovoltaic power generation system is connected to the grid for power generation, the leakage current generated during the grid-connected power generation process will more easily cause electric shock to personnel. Similarly, the above problems also exist in electrochemical energy storage power generation systems. However, there is no way in the prior art to accurately complete the detection of the insulation impedance of photovoltaic power generation systems and electrochemical energy storage systems to the ground. Summary of the invention

[0004] The object of the present invention is to provide an insulation impedance detection device, method and system. In this scheme, a controller is used to control the opening or closing of a first switch and a second switch to control whether the first resistance module is connected between the DC positive pole and the ground of the photovoltaic storage system, and whether the second resistance module is connected between the DC negative pole and the ground of the photovoltaic storage system. The insulation impedance from the DC positive pole to the ground and the insulation impedance from the DC negative pole to the ground of the photovoltaic storage system are calculated by collecting the voltage between the DC negative pole to the ground of the photovoltaic storage system and the voltage between the DC positive pole to the DC negative pole of the photovoltaic storage system, so as to accurately and timely detect whether the insulation impedance of the photovoltaic storage system is faulty.

[0005] In order to solve the above technical problems, the present invention provides an insulation impedance detection device, comprising: a first resistance module, a second resistance module, a first switch, a second switch, a first sampling circuit, a second sampling circuit, and a controller;

[0006] The control end of the controller is respectively connected to the control end of the first switch and the control end of the second switch, and the input end is respectively connected to the output end of the first sampling circuit and the output end of the second sampling circuit, for controlling the opening or closing of the first switch and the second switch;

[0007] A first end of the first switch is connected to the DC positive electrode of the photovoltaic storage system, and a second end is connected to the first end of the first resistance module;

[0008] The second end of the first resistance module is connected to the ground;

[0009] A first end of the second switch is connected to the ground, and a second end of the second switch is connected to the first end of the second resistance module;

[0010] The second end of the second resistance module is connected to the DC negative electrode of the photovoltaic storage system;

[0011] The first input end of the first sampling circuit is connected to the DC negative pole of the photovoltaic storage system, and the second end is connected to the ground, and is used to collect the voltage between the DC negative pole of the photovoltaic storage system and the ground;

[0012] The first input end of the second sampling circuit is connected to the DC positive pole of the photovoltaic storage system, and the second end is connected to the DC negative pole of the photovoltaic storage system, and is used to collect the voltage between the DC positive pole and the DC negative pole of the photovoltaic storage system.

[0013] Optionally, the first resistor module includes: a first resistor, a second resistor, and a third switch;

[0014] The first end of the first resistor is connected to the DC positive electrode of the photovoltaic storage system, and the second end is respectively connected to the first end of the second resistor and the first end of the third switch;

[0015] The second end of the second resistor is connected to the ground;

[0016] The second end of the third switch is connected to the ground, and the control end is connected to the controller.

[0017] Optionally, the second resistor module includes: a third resistor, a fourth resistor, and a fourth switch;

[0018] The first end of the third resistor is connected to the ground, and the second end is connected to the first end of the fourth resistor and the first end of the fourth switch respectively;

[0019] The second end of the fourth resistor is connected to the DC negative electrode of the photovoltaic storage system;

[0020] The second end of the fourth switch is connected to the DC negative pole of the photovoltaic storage system.

[0021] In order to solve the above technical problems, the present invention further provides an insulation impedance detection method, which is applied to the controller in the insulation impedance detection device as described above, and the method comprises:

[0022] Controlling the first switch and the second switch to close, controlling the third switch to close and the fourth switch to open, and determining a first voltage between the DC positive electrode of the photovoltaic storage system and the DC negative electrode and a second voltage between the ground and the DC negative electrode of the photovoltaic storage system;

[0023] Controlling the third switch to be opened and the fourth switch to be closed, and determining a third voltage between the DC positive electrode and the DC negative electrode of the photovoltaic storage system and a fourth voltage between the ground and the DC negative electrode of the photovoltaic storage system;

[0024] A first insulation impedance of the DC positive pole of the photovoltaic storage system to ground and a second insulation impedance of the DC negative pole of the photovoltaic storage system to ground are determined according to the first voltage, the second voltage, the third voltage and the fourth voltage.

[0025] Optionally, before controlling the first switch and the second switch to be closed, controlling the third switch to be closed and the fourth switch to be opened, and determining a first voltage between the DC positive electrode of the photovoltaic storage system and the DC negative electrode and a second voltage between the ground and the DC negative electrode of the photovoltaic storage system, the method further includes:

[0026] Determining whether the photovoltaic storage system currently meets the grid-connected operation conditions;

[0027] If the photovoltaic storage system currently meets the grid-connected operation conditions, the steps of triggering and controlling the first switch and the second switch to close, controlling the third switch to close and the fourth switch to open, and determining a first voltage between the DC positive pole of the photovoltaic storage system and the DC negative pole, and a second voltage between the ground and the DC negative pole of the photovoltaic storage system.

[0028] Optionally, the determining whether the photovoltaic storage system currently meets the grid-connected operation conditions includes:

[0029] Determine whether the current voltage effective value of the AC electric energy output by the photovoltaic inverter in the photovoltaic storage system is equal to the voltage effective value of the power grid, whether the current frequency is equal to the frequency of the power grid, whether the current phase is equal to the phase of the power grid, and whether the current phase sequence is equal to the phase sequence of the power grid;

[0030] Accordingly, if the photovoltaic storage system currently meets the grid-connected operation conditions, it includes:

[0031] If the current effective value of the voltage of the AC power output by the photovoltaic inverter is equal to the effective value of the voltage of the power grid, the current frequency is equal to the frequency of the power grid, the current phase is equal to the phase of the power grid, and the current phase sequence is equal to the phase sequence of the power grid, then it is determined that the photovoltaic storage system currently meets the grid-connected operation conditions.

[0032] Optionally, determining a first voltage between a DC positive electrode and a DC negative electrode of the photovoltaic storage system and a second voltage between ground and a DC negative electrode of the photovoltaic storage system includes:

[0033] Obtaining a first resistance value of the first resistor, a second resistance value of the second resistor, a third resistance value of the third resistor, and a fourth resistance value of the fourth resistor;

[0034] Determine the first voltage according to the first resistance value, the third resistance value, the fourth resistance value and a first voltage determination formula;

[0035] Determine the second voltage according to the first resistance value, the third resistance value, the fourth resistance value and a second voltage determination formula;

[0036] Correspondingly, determining a third voltage between the DC positive electrode and the DC negative electrode of the photovoltaic storage system and a fourth voltage between the ground and the DC negative electrode of the photovoltaic storage system includes:

[0037] Determine the third voltage according to the first resistance value, the second resistance value, the third resistance value and a third voltage determination formula;

[0038] Determine the fourth voltage according to the first resistance value, the second resistance value, the third resistance value and a fourth voltage determination formula;

[0039] Wherein, the first voltage determination formula is: ; is the first resistance value, is the third resistance value, is the fourth resistance value, is the first insulation resistance, is the second insulation resistance, is the first voltage, is the second voltage;

[0040] The second voltage determination formula is: ;

[0041] The third voltage determination formula is: ; is the second resistance value, is the third voltage, is the fourth voltage;

[0042] The fourth voltage determination formula is: .

[0043] Optionally, determining a first voltage between a DC positive electrode and a DC negative electrode of the photovoltaic storage system and a second voltage between ground and a DC negative electrode of the photovoltaic storage system includes:

[0044] Determining a first voltage between the DC positive electrode of the photovoltaic storage system and the DC negative electrode and a second voltage between the ground and the DC negative electrode of the photovoltaic storage system after a first preset delay time;

[0045] Correspondingly, determining a third voltage between the DC positive electrode and the DC negative electrode of the photovoltaic storage system and a fourth voltage between the ground and the DC negative electrode of the photovoltaic storage system includes:

[0046] After a delay of a second preset time, a third voltage between the DC positive electrode and the DC negative electrode of the photovoltaic storage system and a fourth voltage between the ground and the DC negative electrode of the photovoltaic storage system are determined.

[0047] Optionally, after determining a first insulation impedance of a DC positive pole of the photovoltaic storage system to ground and a second insulation impedance of a DC negative pole of the photovoltaic storage system to ground according to the first voltage, the second voltage, the third voltage and the fourth voltage, the method further includes:

[0048] Determining whether the first insulation impedance is less than a first impedance alarm value and whether the second insulation impedance is less than a second impedance alarm value;

[0049] If the first insulation impedance is less than the first impedance alarm value and the second insulation impedance is less than the second impedance alarm value, it is determined that an insulation impedance fault occurs in the photovoltaic storage system, and after a delay of a third preset time, the first switch and the second switch are triggered to close, the third switch is controlled to close and the fourth switch is disconnected, and a first voltage between the DC positive electrode of the photovoltaic storage system and the DC negative electrode and a second voltage between the ground and the DC negative electrode of the photovoltaic storage system are determined;

[0050] If the first insulation impedance is not less than a first impedance alarm value and the second insulation impedance is not less than a second impedance alarm value, it is determined that the insulation impedance fault does not occur in the photovoltaic storage system.

[0051] In order to solve the above technical problems, the present invention further provides an insulation impedance detection system, which is applied to the controller in the insulation impedance detection device as described above, and the system comprises:

[0052] A first control unit is used to control the first switch and the second switch to be closed, control the third switch to be closed and the fourth switch to be opened, and determine a first voltage between the DC positive electrode of the photovoltaic storage system and the DC negative electrode and a second voltage between the ground and the DC negative electrode of the photovoltaic storage system;

[0053] A second control unit, used for controlling the third switch to be opened and the fourth switch to be closed, and determining a third voltage between the DC positive electrode of the photovoltaic storage system and the DC negative electrode and a fourth voltage between the ground and the DC negative electrode of the photovoltaic storage system;

[0054] A determination unit is used to determine a first insulation impedance of the DC positive pole of the photovoltaic storage system to the ground and a second insulation impedance of the DC negative pole of the photovoltaic storage system to the ground according to the first voltage, the second voltage, the third voltage and the fourth voltage.

[0055] The object of the present invention is to provide an insulation impedance detection device, method and system. In this scheme, a controller is used to control the opening or closing of a first switch and a second switch to control whether the first resistance module is connected between the DC positive pole and the ground of the photovoltaic storage system, and whether the second resistance module is connected between the DC negative pole and the ground of the photovoltaic storage system. The controller can calculate the insulation impedance from the DC positive pole to the ground and the insulation impedance from the DC negative pole to the ground of the photovoltaic storage system through the voltage between the DC negative pole and the ground of the photovoltaic storage system and the voltage between the DC positive pole and the DC negative pole of the photovoltaic storage system collected by the first sampling circuit and the second sampling circuit, and make accurate and timely detection of whether the insulation impedance of the photovoltaic storage system is faulty based on the calculated insulation impedance. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0057] Figure 1 A schematic structural diagram of an insulation impedance detection device provided by the present invention;

[0058] Figure 2 A schematic structural diagram of another insulation impedance detection device provided by the present invention;

[0059] Figure 3 A schematic structural diagram of another insulation impedance detection device provided by the present invention;

[0060] Figure 4 A process flow chart of an insulation impedance detection method provided by the present invention;

[0061] Figure 5 A structural schematic diagram of an insulation impedance detection system provided by the present invention. DETAILED DESCRIPTION

[0062] The core of the present invention is to provide an insulation impedance detection device, method and system. This scheme controls the opening or closing of the first switch and the second switch through a controller to control whether the first resistance module is connected between the DC positive pole and the ground of the photovoltaic storage system, and controls whether the second resistance module is connected between the DC negative pole and the ground of the photovoltaic storage system. The insulation impedance from the DC positive pole to the ground and the insulation impedance from the DC negative pole to the ground of the photovoltaic storage system are calculated by collecting the voltage between the DC negative pole to the ground of the photovoltaic storage system and the voltage between the DC positive pole to the DC negative pole of the photovoltaic storage system, and thereby accurately and timely detect whether the insulation impedance of the photovoltaic storage system is faulty.

[0063] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0064] Please refer to Figure 1 , Figure 1 The present invention provides a schematic diagram of the structure of an insulation impedance detection device. The insulation impedance detection device includes: a first resistance module 1, a second resistance module 2, a first switch 3, a second switch 4, a first sampling circuit 5, a second sampling circuit 6, and a controller 7;

[0065] The control end of the controller 7 is connected to the control end of the first switch 3 and the control end of the second switch 4 respectively, and the input end is connected to the output end of the first sampling circuit 5 and the output end of the second sampling circuit 6 respectively, for controlling the opening or closing of the first switch 3 and the second switch 4;

[0066] A first end of the first switch 3 is connected to the DC positive electrode of the photovoltaic storage system, and a second end is connected to the first end of the first resistor module 1;

[0067] The second end of the first resistance module 1 is connected to the ground;

[0068] A first end of the second switch 4 is connected to the ground, and a second end is connected to the first end of the second resistance module 2;

[0069] The second end of the second resistor module 2 is connected to the DC negative electrode of the photovoltaic storage system;

[0070] The first input terminal of the first sampling circuit 5 is connected to the DC negative electrode of the photovoltaic storage system, and the second terminal is connected to the ground, so as to collect the voltage between the DC negative electrode of the photovoltaic storage system and the ground;

[0071] The first input end of the second sampling circuit 6 is connected to the DC positive electrode of the photovoltaic storage system, and the second end is connected to the DC negative electrode of the photovoltaic storage system, and is used to collect the voltage between the DC positive electrode and the DC negative electrode of the photovoltaic storage system.

[0072] In the present invention, considering that the insulation impedance of the DC side of the photovoltaic storage system is related to the voltage from the DC negative terminal to the ground and the voltage from the DC positive terminal to the DC negative terminal of the photovoltaic storage system, the present solution sets a first resistor module 1, a second resistor module 2, a first switch 3, a second switch 4, a first sampling circuit 5, a second sampling circuit 6, and a controller 7, wherein the controller 7 not only controls the insulation impedance detection process by controlling the opening or closing of the first switch 3 and the second switch 4, but also can accurately and timely detect whether the insulation impedance of the DC side of the photovoltaic storage system is faulty through the voltage from the ground to the DC negative terminal of the photovoltaic storage system sampled by the first sampling circuit 5 and the voltage from the DC positive terminal to the DC negative terminal of the photovoltaic storage system sampled by the second sampling circuit 6, thereby improving the safety of the photovoltaic storage system in practical applications.

[0073] The present embodiment provides an insulation impedance detection device. The present scheme controls the opening or closing of the first switch 3 and the second switch 4 through the controller 7 to control whether the first resistance module 1 is connected between the DC positive pole and the ground of the photovoltaic storage system, and controls whether the second resistance module 2 is connected between the DC negative pole and the ground of the photovoltaic storage system. The controller 7 can calculate the insulation impedance from the DC positive pole to the ground and the insulation impedance from the DC negative pole to the ground of the photovoltaic storage system through the voltage from the DC negative pole to the ground of the photovoltaic storage system and the voltage from the DC positive pole to the DC negative pole of the photovoltaic storage system collected by the first sampling circuit 5 and the second sampling circuit 6, and make accurate and timely detection of whether the insulation impedance of the photovoltaic storage system is faulty based on the calculated insulation impedance.

[0074] Based on the above embodiments:

[0075] As an optional embodiment, the first resistor module 1 includes: a first resistor, a second resistor, and a third switch K3;

[0076] The first end of the first resistor is connected to the DC positive electrode of the photovoltaic storage system, and the second end is connected to the first end of the second resistor and the first end of the third switch K3 respectively;

[0077] The second end of the second resistor is connected to the ground;

[0078] A second end of the third switch K3 is connected to the ground, and a control end thereof is connected to the controller 7 .

[0079] In the present invention, Figure 2As shown, considering that the insulation impedance from the DC positive terminal of the photovoltaic storage system to the ground may be relatively small, in order to ensure the accuracy of the insulation impedance detection, it is necessary to make the actual resistance value of the first resistor module 1 variable. Therefore, the present solution sets a first resistor, a second resistor, and a third switch K3 in the first resistor module 1, wherein the opening or closing of the third switch K3 is controlled by the controller 7, so that the resistance value of the equivalent resistor in parallel with the insulation impedance from the DC positive terminal of the photovoltaic storage system to the ground can be changed, thereby avoiding the situation where the insulation impedance detection fails due to the resistance value of the equivalent resistor, thereby improving the accuracy of the solution.

[0080] As an optional embodiment, the second resistor module 2 includes: a third resistor, a fourth resistor, and a fourth switch K4;

[0081] A first end of the third resistor is connected to the ground, and a second end thereof is connected to a first end of the fourth resistor and a first end of the fourth switch K4 respectively;

[0082] The second end of the fourth resistor is connected to the DC negative electrode of the photovoltaic storage system;

[0083] The second end of the fourth switch K4 is connected to the DC negative pole of the photovoltaic storage system.

[0084] In the present invention, Figure 2 As shown, considering that the insulation impedance of the negative DC terminal of the photovoltaic storage system to the ground may be relatively small, in order to ensure the accuracy of the insulation impedance detection, it is necessary to make the actual resistance value of the second resistor module 2 variable. Therefore, the present scheme sets a third resistor, a fourth resistor, and a fourth switch K4 in the second resistor module 2, wherein the opening or closing of the fourth switch K4 is controlled by the controller 7, so that the resistance value of the equivalent resistor in parallel with the insulation impedance from the negative DC terminal of the photovoltaic storage system to the ground can be changed, thereby avoiding the situation where the insulation impedance detection fails due to the resistance value of the equivalent resistor, thereby improving the accuracy of the scheme.

[0085] It should be noted that in actual applications, multiple resistors and multiple switches can be set in the first resistor module 1 and the second resistor module 2, and the connection mode of the multiple resistors can be controlled by the switches. For example, multiple resistors can be connected in parallel, or multiple resistors can be connected in series, or another certain number of resistors can be connected in parallel and then connected in series with other resistors to meet the actual insulation impedance detection requirements. However, if only one resistor is set in a resistor module, for example, the second resistor module 2 only contains one resistor, if the insulation impedance from the DC negative end of the photovoltaic storage system to the ground is small, and is less than or close to the resistance value of this resistor, then the equivalent resistance of the DC negative end of the photovoltaic storage system to the ground will not be greatly changed before and after the second switch 4 is switched on, that is, the voltage change from the DC negative end of the photovoltaic storage system to the ground is not large. If the error of the sampling circuit in the processing process is added, the insulation impedance of the DC negative end of the photovoltaic storage system to the ground obtained in the end will be less than the actual value, and sometimes even a negative number will be solved, resulting in a false alarm of the insulation impedance fault of the photovoltaic storage system.

[0086] It should also be noted that, in actual applications, considering that the sampling circuit needs to transmit the corresponding signal to the controller 7 after collecting the voltage, but the signal is easily affected by environmental factors during the transmission process, the present solution can also be based on the current insulation impedance detection device. An additional signal amplification module and a filtering module are additionally set up to amplify and filter the voltage signal collected by the sampling circuit in turn to improve the accuracy of the insulation impedance detection process.

[0087] It should also be noted that if Figure 3 As shown, the present solution can also remove the third switch K3, thereby simplifying the circuit and control logic, and by controlling the opening and closing of the fourth switch K4, and collecting the voltage between the DC negative pole of the photovoltaic storage system and the ground and the voltage between the DC positive pole and the DC negative pole of the photovoltaic storage system according to the sampling circuit (integrating the first sampling circuit 5 and the second sampling circuit 6), the first insulation impedance and the second insulation impedance are obtained.

[0088] Please refer to Figure 4 , Figure 4 The present invention provides a process flow chart of an insulation impedance detection method. The insulation impedance detection method is applied to the controller 7 in the insulation impedance detection device as described above, and the method comprises:

[0089] S11: Control the first switch 3 and the second switch 4 to be closed, control the third switch K3 to be closed and the fourth switch K4 to be opened, and determine a first voltage between the DC positive electrode of the photovoltaic storage system and the DC negative electrode and a second voltage between the ground and the DC negative electrode of the photovoltaic storage system;

[0090] S12: Control the third switch K3 to be opened and the fourth switch K4 to be closed, and determine a third voltage between the DC positive electrode of the photovoltaic storage system and the DC negative electrode and a fourth voltage between the ground and the DC negative electrode of the photovoltaic storage system;

[0091] S13: Determine a first insulation impedance of the DC positive pole of the photovoltaic storage system to the ground and a second insulation impedance of the DC negative pole of the photovoltaic storage system to the ground according to the first voltage, the second voltage, the third voltage and the fourth voltage.

[0092] In the present invention, the controller 7 controls the third switch K3 to close and the fourth switch K4 to open, so that the two sampling circuits can respectively collect the first voltage between the DC positive pole and the DC negative pole of the photovoltaic storage system and the second voltage between the ground and the DC negative pole. In addition, the controller 7 controls the third switch K3 to open and the fourth switch K4 to close, so that the two sampling circuits can respectively collect the third voltage between the DC positive pole and the DC negative pole of the photovoltaic storage system and the fourth voltage between the ground and the DC negative pole. Finally, the first insulation impedance between the DC positive pole of the photovoltaic storage system and the ground and the second insulation impedance between the DC negative pole of the photovoltaic storage system and the ground can be accurately determined according to the first voltage, the second voltage, the third voltage and the fourth voltage, thereby ensuring the integrity of the solution.

[0093] It should be noted that the entire insulation impedance detection process of this solution is roughly as follows:

[0094] 1. First, the photovoltaic inverter control system will determine whether the current grid-connected operation conditions are met. If they are met, it will start insulation impedance detection;

[0095] 2. Close the first switch 3 and the second switch 4, close the third switch K3, and after a preset delay, detect the voltage between the photovoltaic panel PV- (the DC negative pole of the photovoltaic storage system) and the ground, and the voltage between the photovoltaic panel PV+ (the DC positive pole of the photovoltaic storage system) and PV-. Because there is parasitic capacitance between the photovoltaic panel (the DC side of the photovoltaic storage system) and the ground, in order to ensure that the resistance voltage has reached a stable state during detection, a preset delay time is required. Considering the differences in parasitic capacitance between different photovoltaic systems and the ground, it is generally chosen to extend the preset time to improve detection accuracy. After the preset delay time, disconnect the third switch K3 of the relay, also considering the time required for the voltage to return to a steady state.

[0096] 3. Close the fourth switch K4 of the relay, and after a preset delay, detect the voltage between the photovoltaic panel PV- and the ground, and the voltage between the photovoltaic panel PV+ and PV-. After a preset delay, open the fourth switch K4.

[0097] 4. Substituting the first voltage, the second voltage, the third voltage and the fourth voltage detected above into the insulation impedance determination formula, the values ​​of the first insulation impedance and the second insulation impedance can be calculated.

[0098] 5. Determine whether the first insulation impedance and the second insulation impedance calculated above are both higher than the preset alarm value of the photovoltaic inverter. If higher, stop the insulation impedance detection and execute the grid-connected operation process; if lower, display the insulation impedance too small fault, delay the preset time, and enter the insulation impedance detection logic again. In actual engineering applications, photovoltaic power stations will assess the number of inverter failures, and frequent relay operation will also reduce the life of the relay. Therefore, it is necessary to preset the delay preset time to prevent continuous entry into the insulation impedance detection logic. It can be set to a constant time interval, or the time interval can be accumulated according to the number of detections.

[0099] It should also be noted that the photovoltaic storage system insulation impedance detection method and application device provided by this solution is for a photovoltaic storage system with one DC input, but in actual applications, photovoltaic inverters with multiple MPPT (Maximum Power Point Tracking) independent inputs and energy storage converters with multiple battery cluster inputs are generally used. Due to the characteristics of photovoltaic panels and electrochemical energy storage batteries, it is impossible to keep the voltage of each input equal in engineering design. Therefore, in order to ensure the accuracy of detection and the independence of DC input, for photovoltaic storage systems with multiple inputs, multiple sets of the device of the present invention are generally directly configured, which is not only simple and convenient in application implementation, but also can simplify the control circuit design and control logic.

[0100] It should also be noted that this solution improves the precision and accuracy of insulation impedance detection, ensuring that the photovoltaic storage equipment can be put into operation in a timely manner and reducing the downtime caused by incorrect insulation impedance detection results. In addition, this solution can adapt to photovoltaic storage systems with different DC voltage levels (1500V, 2000V or even higher) through the reasonable design of the resistance value, and has strong applicability.

[0101] As an optional embodiment, before controlling the first switch 3 and the second switch 4 to be closed, controlling the third switch K3 to be closed and the fourth switch K4 to be opened, and determining a first voltage between the DC positive electrode of the photovoltaic storage system and the DC negative electrode and a second voltage between the ground and the DC negative electrode of the photovoltaic storage system, the method further includes:

[0102] Determine whether the photovoltaic storage system currently meets the grid-connected operation conditions;

[0103] If the photovoltaic storage system currently meets the grid-connected operation conditions, the trigger controls the first switch 3 and the second switch 4 to close, controls the third switch K3 to close and the fourth switch K4 to open, and determines the first voltage of the DC positive pole to the DC negative pole of the photovoltaic storage system and the second voltage of the ground to the DC negative pole of the photovoltaic storage system.

[0104] In the present invention, it is considered that if the photovoltaic storage system does not meet the grid-connected operation conditions, then there must be a fault in it. At this time, the measurement of whether the insulation impedance has a fault will be inaccurate. Therefore, this scheme first determines whether the photovoltaic storage system currently meets the grid-connected operation conditions. If the photovoltaic storage system currently meets the grid-connected operation conditions, this scheme will perform the above-mentioned insulation impedance determination process. By judging the status of the photovoltaic storage system, it can be accurately determined whether the insulation impedance detection process can be performed, thereby avoiding waste of resources.

[0105] As an optional embodiment, determining whether the photovoltaic storage system currently meets the grid-connected operation conditions includes:

[0106] Determine whether the current voltage effective value of the AC power output by the photovoltaic inverter in the photovoltaic storage system is equal to the voltage effective value of the power grid, whether the current frequency is equal to the frequency of the power grid, whether the current phase is equal to the phase of the power grid, and whether the current phase sequence is equal to the phase sequence of the power grid;

[0107] Accordingly, if the PV storage system currently meets the grid-connected operation conditions, including:

[0108] If the current effective value of the voltage of the AC power output by the photovoltaic inverter is equal to the effective value of the voltage of the power grid, the current frequency is equal to the frequency of the power grid, the current phase is equal to the phase of the power grid, and the current phase sequence is equal to the phase sequence of the power grid, then it is determined that the photovoltaic storage system currently meets the grid-connected operation conditions.

[0109] In the present invention, the grid-connected operation conditions of the photovoltaic storage system mainly include: whether the current voltage effective value of the AC power output by the photovoltaic inverter is equal to the voltage effective value of the power grid, whether the current frequency is equal to the frequency of the power grid, whether the current phase is equal to the phase of the power grid, and whether the current phase sequence is equal to the phase sequence of the power grid. If the current voltage effective value of the AC power output by the photovoltaic inverter is equal to the voltage effective value of the power grid, the current frequency is equal to the frequency of the power grid, the current phase is equal to the phase of the power grid, and the current phase sequence is equal to the phase sequence of the power grid, it proves that the current photovoltaic storage system meets the grid-connected operation conditions; conversely, if one of the above multiple conditions is not met, it proves that the current photovoltaic storage system does not meet the grid-connected operation conditions, thereby ensuring the integrity of the grid-connected operation condition judgment process.

[0110] As an optional embodiment, determining a first voltage between a DC positive electrode of the photovoltaic storage system and a DC negative electrode and a second voltage between the ground and the DC negative electrode of the photovoltaic storage system includes:

[0111] Obtaining a first resistance value of the first resistor, a second resistance value of the second resistor, a third resistance value of the third resistor, and a fourth resistance value of the fourth resistor;

[0112] Determine the first voltage according to the first resistance value, the third resistance value, the fourth resistance value and the first voltage determination formula;

[0113] Determine the second voltage according to the first resistance value, the third resistance value, the fourth resistance value and the second voltage determination formula;

[0114] Accordingly, determining a third voltage between the DC positive electrode of the photovoltaic storage system and the DC negative electrode and a fourth voltage between the ground and the DC negative electrode of the photovoltaic storage system includes:

[0115] Determine a third voltage according to the first resistance value, the second resistance value, the third resistance value and a third voltage determination formula;

[0116] Determine a fourth voltage according to the first resistance value, the second resistance value, the third resistance value and a fourth voltage determination formula;

[0117] The first voltage determination formula is: ; is the first resistance value, is the third resistance value, is the fourth resistance value, is the first insulation resistance, is the second insulation resistance, is the first voltage, is a second voltage;

[0118] The second voltage determination formula is: ;

[0119] The third voltage determination formula is: ; is the second resistance value, is the third voltage, is a fourth voltage;

[0120] The fourth voltage determination formula is: .

[0121] In the present invention, the first voltage between the DC positive pole and the DC negative pole of the photovoltaic storage system, the second voltage between the ground and the DC negative pole, the third voltage between the DC positive pole and the DC negative pole of the photovoltaic storage system, and the fourth voltage between the ground and the DC negative pole can all be substituted into the corresponding voltage determination formula by the first resistance value, the second resistance value, the third resistance value, and the fourth resistance value to determine the corresponding voltages respectively, thereby ensuring the integrity of the solution.

[0122] It should be noted that the process of determining the first insulation impedance and the second insulation impedance is specifically as follows: substituting the first resistance, the second resistance, the third resistance, the fourth resistance, the first voltage, the second voltage, the third voltage and the fourth voltage into the first insulation impedance determination formula and the second insulation impedance determination formula respectively, wherein the first insulation impedance determination formula is: ; The second insulation resistance determination formula is: ;in, is the first insulation resistance, is the second insulation resistance.

[0123] As an optional embodiment, determining a first voltage between a DC positive electrode of the photovoltaic storage system and a DC negative electrode and a second voltage between the ground and the DC negative electrode of the photovoltaic storage system includes:

[0124] After a first preset delay time, determining a first voltage between the DC positive electrode of the photovoltaic storage system and the DC negative electrode and a second voltage between the ground and the DC negative electrode of the photovoltaic storage system;

[0125] Accordingly, determining a third voltage between the DC positive electrode of the photovoltaic storage system and the DC negative electrode and a fourth voltage between the ground and the DC negative electrode of the photovoltaic storage system includes:

[0126] After a delay of a second preset time, a third voltage between the DC positive electrode of the photovoltaic storage system and the DC negative electrode and a fourth voltage between the ground and the DC negative electrode of the photovoltaic storage system are determined.

[0127] In the present invention, considering the presence of parasitic capacitance between the positive and negative poles of the DC side of the photovoltaic storage system and the ground, in order to ensure that the voltage has reached a stable state during insulation impedance detection, this scheme will delay the first preset time to trigger the step of determining the first voltage between the DC positive pole and the DC negative pole of the photovoltaic storage system and the second voltage between the ground and the DC negative pole after controlling the third switch K3 to close and the fourth switch K4 to open; similarly, this scheme will trigger the step of determining the third voltage between the DC positive pole and the DC negative pole of the photovoltaic storage system and the fourth voltage between the ground and the DC negative pole after delaying the second preset time after controlling the third switch K3 to open and the fourth switch K4 to close, thereby improving the accuracy of voltage sampling and thereby improving the accuracy of the insulation impedance detection process.

[0128] As an optional embodiment, after determining the first insulation impedance of the DC positive pole of the photovoltaic storage system to the ground and the second insulation impedance of the DC negative pole of the photovoltaic storage system to the ground according to the first voltage, the second voltage, the third voltage and the fourth voltage, the method further includes:

[0129] Determining whether the first insulation impedance is less than a first impedance alarm value and whether the second insulation impedance is less than a second impedance alarm value;

[0130] If the first insulation impedance is less than the first impedance alarm value and the second insulation impedance is less than the second impedance alarm value, it is determined that an insulation impedance fault occurs in the photovoltaic storage system, and after a delay of a third preset time, the first switch 3 and the second switch 4 are triggered to close, the third switch K3 is controlled to close and the fourth switch K4 is controlled to open, and a first voltage between the DC positive electrode of the photovoltaic storage system and the DC negative electrode and a second voltage between the ground and the DC negative electrode of the photovoltaic storage system are determined;

[0131] If the first insulation impedance is not less than the first impedance alarm value and the second insulation impedance is not less than the second impedance alarm value, it is determined that no insulation impedance fault occurs in the photovoltaic storage system.

[0132] Please refer to Figure 5 , Figure 5 The present invention provides a schematic diagram of the structure of an insulation impedance detection system. The insulation impedance detection system is applied to the controller 7 in the insulation impedance detection device as described above, and the system includes:

[0133] The first control unit 11 is used to control the first switch 3 and the second switch 4 to be closed, control the third switch K3 to be closed and the fourth switch K4 to be opened, and determine a first voltage between the DC positive electrode of the photovoltaic storage system and the DC negative electrode and a second voltage between the ground and the DC negative electrode of the photovoltaic storage system;

[0134] The second control unit 12 is used to control the third switch K3 to be opened and the fourth switch K4 to be closed, and to determine a third voltage between the DC positive electrode of the photovoltaic storage system and the DC negative electrode and a fourth voltage between the ground and the DC negative electrode of the photovoltaic storage system;

[0135] The determination unit 13 is used to determine the first insulation impedance of the DC positive pole of the photovoltaic storage system to the ground and the second insulation impedance of the DC negative pole of the photovoltaic storage system to the ground according to the first voltage, the second voltage, the third voltage and the fourth voltage.

[0136] The insulation impedance detection system provided in this embodiment corresponds to the above method, and thus has the same beneficial effects as the above method. Therefore, for the embodiments of the insulation impedance detection system part, please refer to the description of the embodiments of the method part, which will not be repeated here.

[0137] It should be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0138] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An insulation impedance detection device, characterized in that: include: A first resistance module, a second resistance module, a first switch, a second switch, a first sampling circuit, a second sampling circuit, and a controller; The control end of the controller is respectively connected to the control end of the first switch and the control end of the second switch, and the input end is respectively connected to the output end of the first sampling circuit and the output end of the second sampling circuit, for controlling the opening or closing of the first switch and the second switch; A first end of the first switch is connected to the DC positive electrode of the photovoltaic storage system, and a second end is connected to the first end of the first resistance module; The second end of the first resistance module is connected to the ground; A first end of the second switch is connected to the ground, and a second end of the second switch is connected to the first end of the second resistance module; The second end of the second resistance module is connected to the DC negative electrode of the photovoltaic storage system; The first input end of the first sampling circuit is connected to the DC negative pole of the photovoltaic storage system, and the second end is connected to the ground, and is used to collect the voltage between the DC negative pole of the photovoltaic storage system and the ground; The first input end of the second sampling circuit is connected to the DC positive pole of the photovoltaic storage system, and the second end is connected to the DC negative pole of the photovoltaic storage system, and is used to collect the voltage between the DC positive pole and the DC negative pole of the photovoltaic storage system.

2. The insulation impedance detection device according to claim 1, characterized in that: The first resistor module includes: a first resistor, a second resistor, and a third switch; The first end of the first resistor is connected to the DC positive electrode of the photovoltaic storage system, and the second end is respectively connected to the first end of the second resistor and the first end of the third switch; The second end of the second resistor is connected to the ground; The second end of the third switch is connected to the ground, and the control end is connected to the controller.

3. The insulation impedance detection device according to claim 1, characterized in that: The second resistor module includes: a third resistor, a fourth resistor, and a fourth switch; The first end of the third resistor is connected to the ground, and the second end is connected to the first end of the fourth resistor and the first end of the fourth switch respectively; The second end of the fourth resistor is connected to the DC negative electrode of the photovoltaic storage system; The second end of the fourth switch is connected to the DC negative pole of the photovoltaic storage system.

4. A method for detecting insulation impedance, characterized in that: A controller used in the insulation impedance detection device according to any one of claims 1 to 3, the method comprising: Controlling the first switch and the second switch to close, controlling the third switch to close and the fourth switch to open, and determining a first voltage between the DC positive electrode of the photovoltaic storage system and the DC negative electrode and a second voltage between the ground and the DC negative electrode of the photovoltaic storage system; Controlling the third switch to be opened and the fourth switch to be closed, and determining a third voltage between the DC positive electrode and the DC negative electrode of the photovoltaic storage system and a fourth voltage between the ground and the DC negative electrode of the photovoltaic storage system; A first insulation impedance of the DC positive pole of the photovoltaic storage system to ground and a second insulation impedance of the DC negative pole of the photovoltaic storage system to ground are determined according to the first voltage, the second voltage, the third voltage and the fourth voltage.

5. The insulation impedance detection method according to claim 4, characterized in that: Before controlling the first switch and the second switch to close, controlling the third switch to close and the fourth switch to open, and determining a first voltage between the DC positive electrode of the photovoltaic storage system and the DC negative electrode and a second voltage between the ground and the DC negative electrode of the photovoltaic storage system, the method further includes: Determining whether the photovoltaic storage system currently meets the grid-connected operation conditions; If the photovoltaic storage system currently meets the grid-connected operation conditions, the steps of triggering and controlling the first switch and the second switch to close, controlling the third switch to close and the fourth switch to open, and determining a first voltage between the DC positive pole of the photovoltaic storage system and the DC negative pole, and a second voltage between the ground and the DC negative pole of the photovoltaic storage system.

6. The insulation impedance detection method according to claim 5, characterized in that: The determining whether the photovoltaic storage system currently meets the grid-connected operation conditions includes: Determine whether the current voltage effective value of the AC electric energy output by the photovoltaic inverter in the photovoltaic storage system is equal to the voltage effective value of the power grid, whether the current frequency is equal to the frequency of the power grid, whether the current phase is equal to the phase of the power grid, and whether the current phase sequence is equal to the phase sequence of the power grid; Accordingly, if the photovoltaic storage system currently meets the grid-connected operation conditions, it includes: If the current effective value of the voltage of the AC power output by the photovoltaic inverter is equal to the effective value of the voltage of the power grid, the current frequency is equal to the frequency of the power grid, the current phase is equal to the phase of the power grid, and the current phase sequence is equal to the phase sequence of the power grid, then it is determined that the photovoltaic storage system currently meets the grid-connected operation conditions.

7. The insulation impedance detection method according to claim 4, characterized in that: Determining a first voltage between a DC positive electrode and a DC negative electrode of a photovoltaic storage system and a second voltage between ground and a DC negative electrode of the photovoltaic storage system includes: Obtaining a first resistance value of the first resistor, a second resistance value of the second resistor, a third resistance value of the third resistor, and a fourth resistance value of the fourth resistor; Determine the first voltage according to the first resistance value, the third resistance value, the fourth resistance value and a first voltage determination formula; Determine the second voltage according to the first resistance value, the third resistance value, the fourth resistance value and a second voltage determination formula; Correspondingly, determining a third voltage between the DC positive electrode and the DC negative electrode of the photovoltaic storage system and a fourth voltage between the ground and the DC negative electrode of the photovoltaic storage system includes: Determine the third voltage according to the first resistance value, the second resistance value, the third resistance value and a third voltage determination formula; Determine the fourth voltage according to the first resistance value, the second resistance value, the third resistance value and a fourth voltage determination formula; Wherein, the first voltage determination formula is: ; is the first resistance value, is the third resistance value, is the fourth resistance value, is the first insulation resistance, is the second insulation resistance, is the first voltage, is the second voltage; The second voltage determination formula is: ; The third voltage determination formula is: ; is the second resistance value, is the third voltage, is the fourth voltage; The fourth voltage determination formula is: .

8. The insulation impedance detection method according to claim 4, characterized in that: Determining a first voltage between a DC positive electrode and a DC negative electrode of a photovoltaic storage system and a second voltage between ground and a DC negative electrode of the photovoltaic storage system includes: Determining a first voltage between the DC positive electrode of the photovoltaic storage system and the DC negative electrode and a second voltage between the ground and the DC negative electrode of the photovoltaic storage system after a first preset delay time; Correspondingly, determining a third voltage between the DC positive electrode and the DC negative electrode of the photovoltaic storage system and a fourth voltage between the ground and the DC negative electrode of the photovoltaic storage system includes: After a delay of a second preset time, a third voltage between the DC positive electrode and the DC negative electrode of the photovoltaic storage system and a fourth voltage between the ground and the DC negative electrode of the photovoltaic storage system are determined.

9. The insulation impedance detection method according to any one of claims 4 to 8, characterized in that: After determining a first insulation impedance of the DC positive pole of the photovoltaic storage system to ground and a second insulation impedance of the DC negative pole of the photovoltaic storage system to ground according to the first voltage, the second voltage, the third voltage and the fourth voltage, the method further includes: Determining whether the first insulation impedance is less than a first impedance alarm value and whether the second insulation impedance is less than a second impedance alarm value; If the first insulation impedance is less than the first impedance alarm value and the second insulation impedance is less than the second impedance alarm value, it is determined that an insulation impedance fault occurs in the photovoltaic storage system, and after a delay of a third preset time, the first switch and the second switch are triggered to close, the third switch is controlled to close and the fourth switch is disconnected, and a first voltage between the DC positive electrode of the photovoltaic storage system and the DC negative electrode and a second voltage between the ground and the DC negative electrode of the photovoltaic storage system are determined; If the first insulation impedance is not less than a first impedance alarm value and the second insulation impedance is not less than a second impedance alarm value, it is determined that the insulation impedance fault does not occur in the photovoltaic storage system.

10. An insulation impedance detection system, characterized in that: A controller used in an insulation impedance detection device according to any one of claims 1 to 3, the system comprising: A first control unit is used to control the first switch and the second switch to be closed, control the third switch to be closed and the fourth switch to be opened, and determine a first voltage between the DC positive electrode of the photovoltaic storage system and the DC negative electrode and a second voltage between the ground and the DC negative electrode of the photovoltaic storage system; A second control unit, used for controlling the third switch to be opened and the fourth switch to be closed, and determining a third voltage between the DC positive electrode of the photovoltaic storage system and the DC negative electrode and a fourth voltage between the ground and the DC negative electrode of the photovoltaic storage system; A determination unit is used to determine a first insulation impedance of the DC positive pole of the photovoltaic storage system to the ground and a second insulation impedance of the DC negative pole of the photovoltaic storage system to the ground according to the first voltage, the second voltage, the third voltage and the fourth voltage.

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