Detection circuit and detection method for ground insulation resistance of photovoltaic panel

Abstract

The invention discloses a detection circuit and a detection method for ground insulation resistance of a photovoltaic panel. The detection circuit for the ground insulation impedance of the photovoltaic panel comprises a first switch, a second switch and a third switch, wherein the first end of the first switch is connected to a connection point of a first insulation impedance and a second insulation impedance; the second end of the first switch is connected to a second grounding point; the first end of the voltage dividing module is connected with the first output end of the photovoltaic panel, the second end of the voltage dividing module is connected with the second output end of the photovoltaic panel, and the third end of the voltage dividing module is connected with the second end of the first switch; the voltage division module at least comprises a resistance voltage division unit which performs voltage division on the first end and the second end of the voltage division module and outputs the voltage through the third end of the voltage division module; the voltage sampling module is used for detecting the output voltage of the photovoltaic panel and detecting the voltage between the second end and the third end of the voltage division module; and judging whether the first grounding point and the second grounding point are in common ground according to the detected voltage change.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photovoltaic technology, and in particular to a detection circuit and method for photovoltaic panel ground insulation impedance. BACKGROUND

[0002] In a photovoltaic inverter system, the photovoltaic panel ground insulation impedance and the circuit connected to the photovoltaic panel are connected to the grounding point. When the photovoltaic inverter is normally running, the common ground of each grounding point needs to be ensured, so as to ensure the equipotential of each grounding point. This not only relates to whether the photovoltaic inverter can normally and stably run, but also relates to the personal safety problem.

[0003] However, when the prior art detects the common ground of the grounding point, abnormal situations such as mis-detection or undetectable may occur due to various influences of the surrounding environment. SUMMARY

[0004] The present application provides a detection circuit and method for photovoltaic panel ground insulation impedance to solve the problem of poor detection effect of the common ground.

[0005] According to an aspect of the present application, a detection circuit for photovoltaic panel ground insulation impedance is provided, the ground insulation impedance includes a first insulation impedance and a second insulation impedance, the first insulation impedance and the second insulation impedance are connected in series between a first output end and a second output end of the photovoltaic panel; a connection point of the first insulation impedance and the second insulation impedance is connected to a first grounding point;

[0006] The detection circuit for photovoltaic panel ground insulation impedance includes:

[0007] a first switch, a first end of the first switch is connected to the connection point of the first insulation impedance and the second insulation impedance; a second end of the first switch is connected to a second grounding point;

[0008] a voltage dividing module, a first end of the voltage dividing module is connected to the first output end of the photovoltaic panel, a second end of the voltage dividing module is connected to the second output end of the photovoltaic panel, a third end of the voltage dividing module is connected to the second end of the first switch; the voltage dividing module at least includes a resistance voltage dividing unit, which divides the voltage at the first end and the second end of the voltage dividing module and outputs through the third end of the voltage dividing module;

[0009] a voltage sampling module, which is used to detect the output voltage of the photovoltaic panel and the voltage between the second end and the third end of the voltage dividing module; according to the detected voltage change, it is judged whether the first grounding point and the second grounding point are common ground.

[0010] Optionally, the resistance voltage dividing unit includes:

[0011] a first resistor and a second resistor, the first resistor and the second resistor are connected in series between a first output end and a second output end of the photovoltaic panel, and a connection point of the first resistor and the second resistor is connected to a second grounding point; the voltage sampling module is configured to detect a voltage of the second resistor.

[0012] Optionally, the voltage dividing module further comprises:

[0013] a switch switching unit, configured to control a resistance connection relationship in the resistance voltage dividing unit; and calculate resistance values of the first insulation impedance and the second insulation impedance according to the voltage value detected by the voltage sampling module.

[0014] Optionally, the switch switching unit comprises a fourth switch, and the resistance voltage dividing unit comprises a third resistor, a fifth resistor and a sixth resistor.

[0015] a first end of the third resistor is connected to the first output end of the photovoltaic panel, a second end of the third resistor is connected to a first end of the fourth switch, a second end of the fourth switch is connected to a first end of the fifth resistor, a third end of the fourth switch is connected to a first end of the sixth resistor, a second end of the fifth resistor is connected to a second end of the sixth resistor, and the second end of the fifth resistor is also connected to the second output end of the photovoltaic panel; the second end of the fourth switch is a normally closed port, and the third end of the fourth switch is a normally open port.

[0016] the switch switching unit is configured to control closing or turning off of the fourth switch to control voltage division of the resistance voltage dividing unit.

[0017] Optionally, the resistance voltage dividing unit further comprises a fourth resistor, and the switch switching unit further comprises a second switch and a third switch.

[0018] a first end of the second switch is connected to the first output end of the photovoltaic panel, a second end of the second switch is connected to a third end of the third switch through a second line, a third end of the second switch is connected to a second end of the third switch through a first line, a first end of the third resistor is connected to the second line, and a first end of the fourth resistor is connected to the first line; a second end of the third resistor is connected to a second end of the fourth resistor; the second end of the second switch is a normally closed port, and the third end of the second switch is a normally open port.

[0019] a first end of the third switch is connected to a first end of a voltage boosting module, the second end of the third switch is a normally closed port, and the third end of the third switch is a normally open port.

[0020] The switch switching unit is configured to control the closing or turning off of the second switch, the third switch and the fourth switch, so as to control the voltage division of the resistance voltage division unit.

[0021] Optionally, the detection circuit of the ground insulation impedance of the photovoltaic panel further comprises an impedance limiting unit.

[0022] The impedance limiting unit is connected in parallel with the ground insulation impedance, and the impedance limiting unit is further connected to the second grounding point; the impedance limiting unit is configured to limit the impedance value of the ground insulation impedance, so as to improve the voltage value detected by the voltage sampling module.

[0023] Optionally, the impedance limiting unit comprises a seventh resistor and an eighth resistor.

[0024] The impedance values of the first insulation impedance and the second insulation impedance are of a first order of magnitude, and the impedance values of the seventh resistor and the eighth resistor are of a second order of magnitude; the first order of magnitude and the second order of magnitude are the same order of magnitude; a first end of the seventh resistor is connected to a first end of the first insulation impedance, a second end of the seventh resistor is connected to a first end of the eighth resistor, a second end of the eighth resistor is connected to a second end of the second insulation impedance, and the second end of the seventh resistor is further connected to the second grounding point.

[0025] According to another aspect of the present application, a detection method of a ground insulation impedance of a photovoltaic panel is provided, which is applied to the detection circuit of the ground insulation impedance of the photovoltaic panel according to any of the embodiments of the present application; the detection method of the ground insulation impedance of the photovoltaic panel comprises the following steps:

[0026] controlling the first switch to be turned off, and the voltage sampling module detecting the voltage between the second end and the third end of the voltage division module and generating a first voltage;

[0027] controlling the first switch to be closed, and the voltage sampling module detecting the voltage between the second end and the third end of the voltage division module again and generating a second voltage;

[0028] when the first voltage and the second voltage are different, determining that the first grounding point and the second grounding point are not grounded.

[0029] Optionally, the detection method of the ground insulation impedance of the photovoltaic panel further comprises the following steps:

[0030] controlling the first switch to be kept in a closed state;

[0031] the switch switching unit switches the connection relationship of the resistors in the resistance voltage division unit, and the voltage sampling module detects the voltage between the second end and the third end of the voltage division module;

[0032] According to the multiple voltage values detected by the voltage sampling module, the resistance values of the first insulation impedance and the second insulation impedance are calculated.

[0033] Optionally, the method for detecting the insulation impedance of the photovoltaic panel to ground further comprises:

[0034] The second switch and the third switch are controlled to be in an off state.

[0035] The photovoltaic panel is connected to the detection circuit of the insulation impedance to ground.

[0036] The voltage sampling module detects the output voltage of the photovoltaic panel, and determines the connection state of the photovoltaic panel according to the output voltage of the photovoltaic panel.

[0037] The technical solution provided by the embodiment of the application comprises the following steps: a first switch and a voltage dividing module are arranged, and the voltage change between the second end and the third end of the voltage dividing module is detected by a voltage sampling module in different states of the closure or the off of the first switch, so that the detection of whether the first grounding point and the second grounding point share the same ground is realized, and the judgment of whether the insulation impedance to ground is reliably grounded is realized. The application judges whether the first grounding point and the second grounding point share the same ground by voltage, is not affected by the external environment, has high accuracy, and effectively avoids the safety hazards caused by the non-connection or poor contact of the ground wire.

[0038] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the application, nor is it used to limit the scope of the application. Other features of the application will become apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the application, the drawings needed in the embodiment description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0040] Figure 1 is a structural schematic diagram of a detection circuit of an insulation impedance of a photovoltaic panel to ground according to an embodiment of the application;

[0041] Figure 2 is a structural schematic diagram of another detection circuit of an insulation impedance of a photovoltaic panel to ground according to an embodiment of the application;

[0042] Figure 3 is a structural schematic diagram of still another detection circuit of an insulation impedance of a photovoltaic panel to ground according to an embodiment of the application;

[0043] Figure 4is a structural schematic view of still another photovoltaic panel ground insulation impedance detection circuit according to an embodiment of the present application;

[0044] Figure 5 is a structural schematic view of still another photovoltaic panel ground insulation impedance detection circuit according to an embodiment of the present application;

[0045] Figure 6 is a structural schematic view of still another photovoltaic panel ground insulation impedance detection circuit according to an embodiment of the present application;

[0046] Figure 7 is a flow chart of a photovoltaic panel ground insulation impedance detection method according to an embodiment of the present application;

[0047] Figure 8 is a flow chart of another photovoltaic panel ground insulation impedance detection method according to an embodiment of the present application;

[0048] Figure 9 is a flow chart of still another photovoltaic panel ground insulation impedance detection method according to an embodiment of the present application;

[0049] Figure 10 is a flow chart of still another photovoltaic panel ground insulation impedance detection method according to an embodiment of the present application. DETAILED DESCRIPTION

[0050] In order to make the personnel in the art better understand the present application scheme, the technical scheme in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the person of ordinary skill in the art without making creative labor should belong to the protection scope of the present application.

[0051] It should be noted that the terms "first", "second", and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0052] The embodiment of the present application provides a photovoltaic panel ground insulation impedance detection circuit. Figure 1 The embodiment of the present application provides a photovoltaic panel ground insulation impedance detection circuit. Figure 1 The ground insulation impedance comprises a first insulation impedance Rx and a second insulation impedance Ry, and the first insulation impedance Rx and the second insulation impedance Ry are connected in series between the first output end and the second output end of the photovoltaic panel; the connection point of the first insulation impedance Rx and the second insulation impedance Ry is connected to a first grounding point PE1. The photovoltaic panel ground insulation impedance detection circuit comprises a first switch K1, a voltage division module 1 and a voltage sampling module 4. The first end of the first switch K1 is connected to the connection point of the first insulation impedance Rx and the second insulation impedance Ry; the second end of the first switch K1 is connected to a second grounding point PE2. The first end of the voltage division module 1 is connected to the first output end of the photovoltaic panel, the second end of the voltage division module 1 is connected to the second output end of the photovoltaic panel, and the third end of the voltage division module 1 is connected to the second end of the first switch K1; the voltage division module 1 at least comprises a resistance voltage division unit, which divides the voltage of the first end and the second end of the voltage division module and outputs through the third end of the voltage division module 1. The voltage sampling module 4 is used for detecting the output voltage of the photovoltaic panel and detecting the voltage between the second end and the third end of the voltage division module; according to the detected voltage change, whether the first grounding point PE1 and the second grounding point PE2 are common ground is judged.

[0053] When the first output end and the second output end of the photovoltaic panel are connected to the photovoltaic panel ground insulation impedance detection circuit, the electric energy output by the photovoltaic panel can be transmitted to the ground insulation impedance (including the first insulation impedance Rx and the second insulation impedance Ry) and the voltage division module 1, and then the voltage is generated on the ground insulation impedance and the resistance voltage division unit of the voltage division module 1. By controlling the closing or turning off of the first switch K1, the voltage change between the second end and the third end of the voltage division module 1 is detected, and the grounding effect of the ground insulation impedance can be judged.

[0054] Specifically, when the first grounding point PE1 and the second grounding point PE2 are not common ground, it is equivalent to that the voltages of the grounding ends connected by the first grounding point PE1 and the second grounding point PE2 are different. When the first switch K1 is closed, the first end and the third end of the voltage division module 1 are connected in parallel with the first insulation impedance Rx, and the second end and the third end of the voltage division module 1 are connected in parallel with the second insulation impedance Ry. At this time, the voltage sampling module 4 can detect the voltage between the second end and the third end of the voltage division module 1, and the voltage is determined by the first insulation impedance Rx, the second insulation impedance Ry and the resistance value of the resistance voltage division unit in the voltage division module.

[0055] Exemplarily, the voltage sampling module 4 can comprise a first voltage sampling unit and a second voltage sampling unit, the first voltage sampling unit is connected between the first output end and the second output end of the photovoltaic panel, and is used for detecting the output voltage of the photovoltaic panel, and the second voltage sampling unit is connected between the second end and the third end of the voltage dividing module, and is used for detecting the voltage between the second end and the third end of the voltage dividing module.

[0056] When the first switch K1 is off, the parallel relationship between the voltage dividing module 1 and the first insulation impedance Rx and the second insulation impedance Ry is disconnected, and the voltage between the second end and the third end of the voltage dividing module 1 is not associated with the first insulation impedance Rx and the second insulation impedance Ry. At this time, the voltage sampling module 4 can detect the voltage between the second end and the third end of the voltage dividing module 1, which is only determined by the resistance value of the resistance voltage dividing unit in the voltage dividing module. Obviously, the detected voltage between the second end and the third end of the voltage dividing module 1 is different in the closed and off states of the first switch K1.

[0057] When the first grounding point PE1 and the second grounding point PE2 are common ground, that is, the first grounding point PE1 and the second grounding point PE2 have the same voltage reference point, when the first switch K1 is closed, the first end and the third end of the voltage dividing module 1 are in parallel with the first insulation impedance Rx, and the second end and the third end of the voltage dividing module 1 are in parallel with the second insulation impedance Ry. When the first switch K1 is off, because the first grounding point PE1 and the second grounding point PE2 are common ground, the first grounding point PE1 and the second grounding point PE2 are connected through an external ground line, the first end and the third end of the voltage dividing module 1 are in parallel with the first insulation impedance Rx, and the second end and the third end of the voltage dividing module 1 are in parallel with the second insulation impedance Ry. At this time, after the first switch K1 is controlled to be closed or off, the voltage between the second end and the third end of the voltage dividing module 1 remains unchanged.

[0058] Therefore, by controlling the closing or off of the first switch K1 and detecting the voltage between the second end and the third end of the voltage dividing module, if the voltages before and after are different, it can be judged that the first grounding point PE1 and the second grounding point PE2 are not common ground.

[0059] The technical scheme provided by the embodiment of the application can realize the detection of whether the first grounding point and the second grounding point are common ground by setting the first switch and the voltage dividing module, and detecting the voltage change between the second end and the third end of the voltage dividing module in the closed and off states of the first switch, and further realize the judgment of whether the ground insulation impedance is reliably grounded. The application judges whether the first grounding point and the second grounding point are common ground by voltage, is not affected by the external environment, has high accuracy, and effectively avoids the safety hazards caused by the non-connection or poor contact of the ground wire.

[0060] Figure 2 Another structure diagram of a detection circuit of an insulation impedance of a photovoltaic panel to ground is provided in the embodiments of the present application. Referring to Figure 2 Optionally, on the basis of the above embodiments, the resistance voltage dividing unit comprises: a first resistor R1 and a second resistor R2, the first resistor R1 and the second resistor R2 are connected in series between the first output end and the second output end of the photovoltaic panel, and a connection point of the first resistor R1 and the second resistor R2 is connected to the second grounding point; and the voltage sampling module is configured to detect a voltage of the second resistor R2.

[0061] In the above embodiments, the voltage sampling module is not shown in the subsequent drawings for the purpose of making the drawings clearer and simpler. Figure 2

[0062] When the first grounding point PE1 and the second grounding point PE2 are not grounded in common, the voltage between the second end and the third end of the voltage dividing module 1 is:

[0063] ;

[0064] In the above embodiments, the voltage sampling module is not shown in the subsequent drawings for the purpose of making the drawings clearer and simpler.

[0065] When the first switch K1 is closed, the voltage between the second end and the third end of the voltage dividing module 1 is:

[0066] ;

[0067] In the above embodiments, the voltage sampling module is not shown in the subsequent drawings for the purpose of making the drawings clearer and simpler.

[0068] When the first grounding point PE1 and the second grounding point PE2 are not grounded in common, the voltage between the second end and the third end of the voltage dividing module 1 is:

[0069] ;

[0070] When the first switch K1 is closed, the voltage between the second end and the third end of the voltage dividing module 1 is:

[0071] ;

[0072] Therefore, the embodiments of the present application can realize the detection of whether the first grounding point and the second grounding point are grounded in common by controlling the closing or turning off of the first switch and detecting the voltage between the second end and the third end of the voltage dividing module, and the detection process is simple and the detection precision is high.

[0073] ​On the basis of each of the above embodiments, optionally, the voltage dividing module further comprises: a switch switching unit, the switch switching unit being configured to control a resistance connection relationship in the resistance voltage dividing unit; and the resistance values of the first insulation impedance and the second insulation impedance are calculated according to the voltage value detected by the voltage sampling module.

[0074] Figure 3 Another structure schematic diagram of the detection circuit for the insulation impedance of the photovoltaic panel to the ground is provided in the embodiments of the present application. Refer to Figure 3 On the basis of each of the above embodiments, optionally, the switch switching unit comprises: a fourth switch K4, and the resistance voltage dividing unit comprises: a third resistance R3, a fifth resistance R5 and a sixth resistance R6. The first end of the third resistance R3 is connected with the first output end of the photovoltaic panel, the second end of the third resistance R3 is connected with the first end of the fourth switch K4, the second end of the fourth switch K4 is connected with the first end of the fifth resistance R5, the third end of the fourth switch K4 is connected with the first end of the sixth resistance R6; the second end of the fifth resistance R5 is connected with the second end of the sixth resistance R6, and the second end of the fifth resistance R5 is also connected with the second output end of the photovoltaic panel; the second end of the fourth switch K4 is a normally closed port, and the third end of the fourth switch is a normally open port. The switch switching unit is configured to control the closing or turning off of the fourth switch, so as to control the voltage division of the resistance voltage dividing unit.

[0075] Wherein, the fourth switch K4 is in the off state when not controlled by the switch switching unit, and the first end and the second end of the fourth switch K4 are connected. When the switch switching unit controls the fourth switch K4 to be closed, the first end and the third end of the fourth switch K4 are connected.

[0076] Therefore, the closing state of the first switch K1 is maintained, and when the fourth switch K4 is turned off, the voltage between the second end and the third end of the voltage dividing module 1 is:

[0077] ;

[0078] Therefore, when the fourth switch K4 is closed, the voltage between the second end and the third end of the voltage dividing module 1 is:

[0079] ;

[0080] Wherein, R3 is the resistance value of the third resistance, R5 is the resistance value of the fifth resistance, and R6 is the resistance value of the sixth resistance.

[0081] In the above two formulas, the voltage between the second end and the third end of the voltage dividing module, the output voltage of the photovoltaic panel, the resistance value of the third resistance R3, the resistance value of the fifth resistance R5 and the resistance value of the sixth resistance R6 are all known. Therefore, the resistance values of the first insulation impedance Rx and the second insulation impedance Ry can be calculated by combining the above two formulas.

[0082] Figure 4 Another structure diagram of the detection circuit for the ground insulation impedance of the photovoltaic panel is provided for the embodiments of the present application. Referring to Figure 4 On the basis of the above embodiments, optionally, the resistance voltage dividing unit further comprises a fourth resistor R4, and the switch switching unit further comprises a second switch K2 and a third switch K3. The first end of the second switch K2 is connected with the first output end of the photovoltaic panel, the second end of the second switch K2 is connected with the third end of the third switch K3 through a second line, the third end of the second switch K2 is connected with the second end of the third switch K3 through a first line 11, the first end of the third resistor R3 is connected to the second line 12, and the first end of the fourth resistor R4 is connected to the first line 11; the second end of the third resistor R3 is connected with the second end of the fourth resistor R4; the second end of the second switch K2 is a normally closed port, and the third end of the second switch K3 is a normally open port. The first end of the third switch K3 is connected with the first end of the voltage boosting module 2, the second end of the third switch K3 is a normally closed port, and the third end of the third switch K3 is a normally open port. The switch switching unit is used for controlling the closing or turning off of the second switch K2, the third switch K3 and the fourth switch K4, so as to control the voltage division of the resistance voltage dividing unit.

[0083] When the second switch K2 and the third switch K3 are turned off and the fourth switch K4 is closed, the voltage between the second end and the third end of the voltage dividing module 1 is:

[0084] ;

[0085] When the second switch K2 and the third switch K3 are turned off and the fourth switch K4 is closed, the voltage between the second end and the third end of the voltage dividing module 1 is:

[0086] ;

[0087] When the second switch K2 and the third switch K3 are turned off and the fourth switch K4 is closed, the voltage between the second end and the third end of the voltage dividing module 1 is:

[0088] ;

[0089] When the second switch K2 and the third switch K3 are turned off and the fourth switch K4 is closed, the voltage between the second end and the third end of the voltage dividing module 1 is:

[0090] ;

[0091] Wherein, R4 is the resistance value of the fourth resistor.

[0092] When the second switch K2 and the third switch K3 are turned off and the fourth switch K4 is closed, the voltage between the second end and the third end of the voltage dividing module 1 is:

[0093] ;

[0094] When the second switch K2 and the fourth switch K4 are closed and the third switch K3 is turned off, the voltage between the second end and the third end of the voltage division module 1 is:

[0095] ;

[0096] When the second switch K2 and the fourth switch K4 are turned off and the third switch K3 is closed, the voltage between the second end and the third end of the voltage division module 1 is:

[0097] ;

[0098] When the second switch K2 is turned off and the third switch K3 and the fourth switch K4 are closed, the voltage between the second end and the third end of the voltage division module 1 is:

[0099] ;

[0100] From the above results, it can be seen that the second switch K2, the third switch K3 and the fourth switch K4 can obtain the voltage value between the second end and the third end of the different voltage division modules in 8 different combination states. The values of the first insulation impedance Rx and the second insulation impedance Ry can be calculated by establishing a binary linear equation system in any two groups of states.

[0101] The detection results of the switch states of the second switch K2, the third switch K3 and the fourth switch K4 and the voltage values between the second end and the third end of the voltage division module are shown in the following table:

[0102] Table 1

[0103]

[0104] In order to simplify the calculation process, the third resistor R3 and the sixth resistor R6 can be set to the same resistance value, and the fourth resistor R4 and the fifth resistor R5 can be set to the same resistance value. In theory, there are C(8, 2)=28 combinations, but according to the above formula, in practice, there are four groups of voltage values that are the same, so there are also six groups of sampling data of the voltage sampling module that are the same in the calculation process. The number of combinations is C(4, 2)=6. By arbitrarily selecting one group of data, the resistance values of the first insulation impedance Rx and the second insulation impedance Ry can be calculated.

[0105] In order to ensure the calculation accuracy, a group of data with relatively large voltage value difference is selected for calculation, so that the resistance values of the first insulation impedance Rx and the second insulation impedance Ry can be calculated more accurately.

[0106] In the actual setting process of the resistance voltage dividing unit, to avoid the voltage value between the second end and the third end of the voltage dividing module being too close, the resistance values of any two resistors can be set to be the same and much greater or much smaller than the resistance values of the other two resistors. For example, the third resistor R3 and the sixth resistor R6 are set to have the same resistance value, and the fourth resistor R4 and the fifth resistor R5 are set to have the same resistance value. Moreover, the resistance value of the third resistor R3 is much greater than the resistance value of the fourth resistor R4.

[0107] In the prior art, when the photovoltaic panel is connected with the detection circuit of the photovoltaic panel-to-ground insulation impedance, if the polarity of the photovoltaic panel is reversed, an excessively large short-circuit current can directly break the boost module, and even cause damage to the photovoltaic panel.

[0108] Since the second end of the second switch K2 is a normally closed port and is connected to the second line 12, and the second end of the third switch K3 is a normally closed port and is connected to the first line 11, even if the photovoltaic panel is reversely connected to the circuit, the second switch K2 and the third switch K3 are in a disconnected state, and the boost module does not form a power supply loop, thereby forming reverse connection protection for the photovoltaic panel and ensuring the safe operation of the detection circuit of the photovoltaic panel-to-ground insulation impedance. At this time, the positive and negative values of the output voltage of the photovoltaic panel can be detected to determine whether the polarity of the photovoltaic panel is reversed.

[0109] When the boost module, the photovoltaic panel or other components fail, the second switch K2 and the third switch K3 can also be controlled to be turned off, thereby realizing power-off protection for the output of the photovoltaic panel and realizing an emergency power-off protection function, which avoids secondary damage to the photovoltaic panel due to the failure to timely disconnect the circuit after an abnormal fault occurs, thereby preventing the photovoltaic panel from being damaged.

[0110] Figure 5 Another structure diagram of the detection circuit of the photovoltaic panel-to-ground insulation impedance provided by the embodiment of the present application is provided. Figure 5 On the basis of the above-mentioned embodiments, optionally, the boost module 2 comprises a first inductor L, a first transistor Q, a first capacitor C and a first diode D. The first end of the first inductor L is connected with the first end of the third switch K3, the second end of the first inductor L is connected with the first end of the first transistor Q, the second end of the first transistor Q is connected with the second output end of the photovoltaic panel, the first end of the first diode D is connected with the second end of the first inductor L, the first end of the first diode D is connected with the first end of the first capacitor C, and the second end of the first capacitor C is connected with the second end of the first transistor Q.

[0111] Figure 6 Another structure diagram of the detection circuit of the photovoltaic panel-to-ground insulation impedance provided by the embodiment of the present application is provided. Figure 6Based on the above embodiments, optionally, the detection circuit for the photovoltaic panel's insulation impedance to ground further includes an impedance limiting unit 3. The impedance limiting unit 3 is connected in parallel with the insulation impedance to ground, and the impedance limiting unit 3 is also connected to the second grounding point; the impedance limiting unit 3 is used to limit the impedance value of the insulation impedance to ground, so as to improve the voltage value detected by the voltage sampling module.

[0112] To avoid detection errors caused by excessively high or low resistance values ​​of the first insulation impedance Rx or the second insulation impedance Ry, an impedance limiting unit 3 can be connected in parallel across the first insulation impedance Rx and the second insulation impedance Ry. The impedance limiting unit 3 has a fixed resistance value, which can be in the megohm range. After being connected in parallel with the first insulation impedance Rx and the second insulation impedance Ry, even if the resistance values ​​of the first insulation impedance Rx and the second insulation impedance Ry are very high, the voltage between the second and third terminals of the voltage divider module 1 will not be too low, or the difference between two voltage values ​​will be too small, thus preventing errors in the calculation of the resistance values ​​of the first insulation impedance Rx and the second insulation impedance Ry.

[0113] Continue to refer to Figure 6 Based on the above embodiments, optionally, the impedance limiting unit 3 includes a seventh resistor R7 and an eighth resistor R8. The resistance values ​​of the first insulation impedance Rx and the second insulation impedance Ry are both on the first order of magnitude, and the resistance values ​​of the seventh resistor R7 and the eighth resistor R8 are both on the second order of magnitude; the first order of magnitude and the second order of magnitude are of the same order of magnitude; the first end of the seventh resistor R7 is connected to the first end of the first insulation impedance Rx, the second end of the seventh resistor R7 is connected to the first end of the eighth resistor R8, the second end of the eighth resistor R8 is connected to the second end of the second insulation impedance Ry, and the second end of the seventh resistor R7 is also connected to the second grounding point.

[0114] For example, both the first and second orders of magnitude can be at the megaohm level, such as one megaohm, two megaohms, three megaohms, four megaohms, ..., ten megaohms.

[0115] This invention also provides a method for detecting the ground insulation impedance of a photovoltaic panel. This method is applied to the photovoltaic panel ground insulation impedance detection circuit provided in any embodiment of this invention. Figure 7 This is a flowchart illustrating a method for detecting the insulation impedance of a photovoltaic panel to ground, provided as an embodiment of the present invention. (Reference) Figure 7 Methods for testing the insulation impedance of photovoltaic panels to ground include:

[0116] S110, control the first switch to turn off, the voltage sampling module detects the voltage between the second and third terminals of the voltage divider module and generates the first voltage.

[0117] S120, the first switch is controlled to be closed, and the voltage sampling module detects the voltage between the second end and the third end of the voltage dividing module again and generates a second voltage.

[0118] S130, when the first voltage and the second voltage are different, it is determined that the first grounding point and the second grounding point are not common grounds.

[0119] Figure 8 Another flowchart of the method for detecting the ground insulation impedance of the photovoltaic panel is provided for the embodiment of the application. Referring to Figure 8 On the basis of the above-mentioned embodiments, the method for detecting the ground insulation impedance of the photovoltaic panel further comprises:

[0120] S210, the first switch is controlled to be closed.

[0121] S220, the switch switching unit switches the resistance connection relationship in the resistance voltage dividing unit, and the voltage sampling module detects the voltage between the second end and the third end of the voltage dividing module.

[0122] S230, according to the plurality of voltage values detected by the voltage sampling module, the resistance values of the first insulation impedance and the second insulation impedance are calculated.

[0123] Figure 9 Another flowchart of the method for detecting the ground insulation impedance of the photovoltaic panel is provided for the embodiment of the application. Referring to Figure 9 On the basis of the above-mentioned embodiments, the method for detecting the ground insulation impedance of the photovoltaic panel further comprises:

[0124] S310, the second switch and the third switch are controlled to be in the off state.

[0125] S320, the photovoltaic panel is connected to the detection circuit of the ground insulation impedance.

[0126] S330, the voltage sampling module detects the output voltage of the photovoltaic panel, and according to the output voltage of the photovoltaic panel, the connection state of the photovoltaic panel is determined.

[0127] Figure 10 Another flowchart of the method for detecting the ground insulation impedance of the photovoltaic panel is provided for the embodiment of the application. Referring to Figure 10 On the basis of the above-mentioned embodiments, the method for detecting the ground insulation impedance of the photovoltaic panel further comprises:

[0128] S410, the photovoltaic panel is connected to the detection circuit of the ground insulation impedance.

[0129] S420, it is determined whether the output voltage of the photovoltaic panel is normal, if yes, S430 is executed, and if no, S440 is executed.

[0130] S430, judging whether the first grounding point and the second grounding point are common ground. If yes, S450 is executed, if not, S460 is executed.

[0131] S450, judging whether the resistance values of the first insulation impedance and the second insulation impedance are normal. If yes, S470 is executed, if not, S460 is executed.

[0132] S470, the photovoltaic panel and the detection circuit are in normal operation.

[0133] S440, judging the size of the output voltage of the photovoltaic panel. If too large, S441 is executed; if negative, S442 is executed.

[0134] S441, judging overvoltage.

[0135] S442, judging reverse connection of the photovoltaic panel.

[0136] S460, fault alarm

[0137] S480, controlling the second switch and the third switch to be off.

[0138] In the embodiments of the detection circuit for the insulation impedance of the photovoltaic panel to ground, the specific detection methods have been described for the detection circuit for the insulation impedance of the photovoltaic panel to ground, and these detection methods can be considered as the detection method for the insulation impedance of the photovoltaic panel to ground provided by the embodiments of the present application, and the repeated contents will not be described here.

[0139] It should be understood that the various forms of flow shown above can be reordered, added or deleted steps. For example, each step described in the present application can be executed in parallel, sequentially or in different order, as long as the desired results of the technical solutions of the present application can be achieved, which is not limited herein.

[0140] The above specific embodiments do not constitute a limitation on the protection scope of the present application. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent replacement and improvement within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A detection circuit for photovoltaic panel earth insulation impedance, characterized by, The ground insulation impedance comprises a first insulation impedance and a second insulation impedance, the first insulation impedance and the second insulation impedance are connected in series between the first output end and the second output end of the photovoltaic panel; a connection point of the first insulation impedance and the second insulation impedance is connected to a first grounding point; The detection circuit of the ground insulation impedance of the photovoltaic panel comprises: A first switch, a first end of the first switch is connected to the connection point of the first insulation impedance and the second insulation impedance; a second end of the first switch is connected to a second grounding point; A voltage sampling module is configured to detect the output voltage of the photovoltaic panel and the voltage between the second end and the third end of the voltage dividing module; according to the detected voltage change, it is determined whether the first grounding point and the second grounding point are common grounds. The resistance voltage dividing unit comprises:

2. The photovoltaic panel earth insulation impedance detection circuit according to claim 1, characterized in that, A first resistance and a second resistance, the first resistance and the second resistance are connected in series between the first output end and the second output end of the photovoltaic panel, a connection point of the first resistance and the second resistance is connected to the second grounding point; the voltage sampling module is configured to detect the voltage of the second resistance. The voltage dividing module further comprises:

3. The photovoltaic panel ground insulation impedance detection circuit of claim 1, wherein, A switch switching unit is configured to control the resistance connection relationship in the resistance voltage dividing unit; according to the voltage value detected by the voltage sampling module, the resistance values of the first insulation impedance and the second insulation impedance are calculated. The switch switching unit comprises: a fourth switch, the resistance voltage dividing unit comprises: a third resistance, a fifth resistance and a sixth resistance; 4. The photovoltaic panel earth insulation impedance detection circuit according to claim 3, characterized in that, A first end of the third resistance is connected to the first output end of the photovoltaic panel, a second end of the third resistance is connected to a first end of the fourth switch, a second end of the fourth switch is connected to a first end of the fifth resistance, a third end of the fourth switch is connected to a first end of the sixth resistance; a second end of the fifth resistance is connected to a second end of the sixth resistance, the second end of the fifth resistance is also connected to the second output end of the photovoltaic panel; the second end of the fourth switch is a normally closed port, and the third end of the fourth switch is a normally open port; The switch switching unit is configured to control the closing or turning off of the fourth switch to control the voltage division of the resistance voltage dividing unit. The resistance voltage dividing unit further comprises: a fourth resistance; the switch switching unit further comprises: a second switch and a third switch; 5. The photovoltaic panel earth insulation impedance detection circuit according to claim 4, characterized in that, ​ The first end of the second switch is connected with the first output end of the photovoltaic panel, the second end of the second switch is connected with the third end of the third switch through a second circuit, the third end of the second switch is connected with the second end of the third switch through a first circuit, the first end of the third resistor is connected to the second circuit, and the first end of the fourth resistor is connected to the first circuit; the second end of the third resistor is connected with the second end of the fourth resistor; the second end of the second switch is a normally closed port, and the third end of the second switch is a normally open port; The first end of the third switch is connected with the first end of the voltage boosting module, the second end of the third switch is a normally closed port, and the third end of the third switch is a normally open port; The switch switching unit is used for controlling the closing or turning off of the second switch, the third switch and the fourth switch to control the voltage division of the resistance voltage division unit.

6. The photovoltaic panel ground insulation impedance detection circuit of claim 3, wherein, The photovoltaic panel ground insulation impedance detection circuit further comprises an impedance limiting unit; The impedance limiting unit is connected in parallel with the ground insulation impedance, and the impedance limiting unit is further connected to a second grounding point; the impedance limiting unit is used for limiting the impedance value of the ground insulation impedance to improve the voltage value detected by the voltage sampling module.

7. The photovoltaic panel earth insulation impedance detection circuit according to claim 6, characterized in that, The impedance limiting unit comprises a seventh resistor and an eighth resistor. The impedance values of the first insulation impedance and the second insulation impedance are both of a first order of magnitude, and the impedance values of the seventh resistor and the eighth resistor are both of a second order of magnitude; the first order of magnitude and the second order of magnitude are the same order of magnitude; the first end of the seventh resistor is connected with the first end of the first insulation impedance, the second end of the seventh resistor is connected with the first end of the eighth resistor, the second end of the eighth resistor is connected with the second end of the second insulation impedance, and the second end of the seventh resistor is further connected to the second grounding point.

8. A method for detecting the impedance of the ground insulation of a photovoltaic panel, characterized by, The photovoltaic panel ground insulation impedance detection circuit of any one of claims 1-7; the photovoltaic panel ground insulation impedance detection method comprises: controlling the first switch to be turned off, and the voltage sampling module detects the voltage between the second end and the third end of the voltage division module and generates a first voltage; controlling the first switch to be closed, and the voltage sampling module detects the voltage between the second end and the third end of the voltage division module again and generates a second voltage; when the first voltage and the second voltage are different, it is determined that the first grounding point and the second grounding point are not common grounds.

9. The method of detecting the photovoltaic panel earth insulation impedance according to claim 8, characterized in that, The photovoltaic panel ground insulation impedance detection method further comprises: controlling the first switch to remain in a closed state; the switch switching unit switches the resistance connection relationship in the resistance voltage division unit, and the voltage sampling module detects the voltage between the second end and the third end of the voltage division module; according to the plurality of voltage values detected by the voltage sampling module, the impedance values of the first insulation impedance and the second insulation impedance are calculated.

10. The method of claim 8, wherein the method further comprises: The photovoltaic panel ground insulation impedance detection method further comprises: controlling the second switch and the third switch to be in an off state; connecting the photovoltaic panel to the ground insulation impedance detection circuit; The voltage sampling module detects the output voltage of the photovoltaic panel, and determines the connection state of the photovoltaic panel according to the output voltage of the photovoltaic panel.

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