Insulation resistance detection circuit, detection method and inverter

Abstract

The invention discloses an insulation resistance detection circuit, a detection method and an inverter, and belongs to the technical field of electric power. The insulation impedance detection circuit is applied to an inverter and comprises a switch switching unit which is electrically connected with a first end of an impedance unit connected with a night repair power supply circuit and is configured to control connection and disconnection between the first end of the impedance unit and a positive bus and / or control connection and disconnection between the first end of the impedance unit and a negative bus; and the detection unit is electrically connected with the positive bus and the negative bus, and is configured to detect bus voltages of the positive bus and the negative bus when the switch switching unit is in different conduction states, and determine ground insulation resistance according to the bus voltages. By additionally arranging the switch switching unit and multiplexing the impedance unit of the original night repair power supply circuit in the inverter to detect the voltage to ground of the positive bus and the negative bus, high-accuracy ground insulation impedance detection is realized, the number of added devices is small, and the cost of the added system is low.

Description

Technical Field

[0001] The present application belongs to the field of electric power technology, and in particular relates to an insulation impedance detection circuit, a detection method and an inverter. Background Art

[0002] The photovoltaic inverter system can feed the energy in the photovoltaic array to the power grid and users through power conversion links such as rectification (DC / DC) and inversion (DC / AC). In some abnormal situations of the system, the DC side insulation impedance to ground is reduced and the leakage current may cause harm to personnel and equipment. Therefore, the system usually needs to set up ground insulation impedance detection to actually respond to abnormal ground insulation impedance.

[0003] At present, the ground insulation impedance detection scheme usually adds a dedicated detection circuit to realize signal detection and calculation, which undoubtedly greatly increases the cost of the system. Summary of the invention

[0004] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application proposes an insulation impedance detection circuit, a detection method and an inverter, and adds a nighttime repair power supply circuit in the multiplexing inverter to achieve high-accuracy insulation impedance detection to the ground, with low additional system cost.

[0005] In a first aspect, the present application provides an insulation impedance detection circuit, which is applied to an inverter, wherein the inverter includes a positive bus, a negative bus, a ground node, a nighttime repair power supply circuit, a first switch, and an impedance unit, wherein a first output end of the nighttime repair power supply circuit is electrically connected to a first end of the first switch, a second output end of the nighttime repair power supply circuit is electrically connected to a first end of the impedance unit, one of a second end of the first switch and a second end of the impedance unit is electrically connected to the ground node, and the other is electrically connected to the positive bus or the negative bus;

[0006] The insulation impedance detection circuit includes:

[0007] A switch unit is electrically connected to the first end of the impedance unit and is configured to control the on-off between the first end of the impedance unit and the positive bus, and / or control the on-off between the first end of the impedance unit and the negative bus;

[0008] The detection unit is electrically connected to the positive bus and the negative bus, and is configured to detect the bus voltages of the positive bus and the negative bus when the switch switching unit is in different conduction states, and determine the insulation impedance to ground according to the bus voltages.

[0009] According to one embodiment of the present application, the switch switching unit includes:

[0010] A switchable switch comprises a first contact, a second contact and a switching part, wherein the first contact is electrically connected to the positive bus, the second contact is electrically connected to the negative bus, the first end of the switching part is electrically connected to the first end of the impedance unit, and the second end of the switching part switches between three states: connected to the first contact, connected to the second contact, or left empty.

[0011] According to one embodiment of the present application, the detection unit is configured to obtain a first positive bus voltage and a first negative bus voltage of the switch switching unit in a first state, and obtain a second positive bus voltage and a second negative bus voltage of the switch switching unit in a second state;

[0012] In the first state, the first switch is turned off, and the second end of the switching part is connected to the first contact; in the second state, the first switch is turned off, and the second end of the switching part is connected to the second contact.

[0013] According to one embodiment of the present application, the switch switching unit includes:

[0014] a second switch, wherein a first end of the second switch is electrically connected to a first end of the impedance unit, and a second end of the second switch is electrically connected to the negative bus; and / or,

[0015] A third switch, wherein a first end of the third switch is electrically connected to the first end of the impedance unit, and a second end of the third switch is electrically connected to the positive bus.

[0016] According to one embodiment of the present application, the detection unit is configured to obtain a third positive bus voltage and a third negative bus voltage of the switch switching unit in a third state, and obtain a fourth positive bus voltage and a fourth negative bus voltage of the switch switching unit in a fourth state;

[0017] In the third state, the first switch and the third switch are both turned off, and the second switch is turned on; in the fourth state, the first switch and the second switch are both turned off, and the third switch is turned on.

[0018] According to one embodiment of the present application, the switch switching unit does not include a second switch, and the detection unit is configured to obtain a fifth positive bus voltage and a fifth negative bus voltage of the switch switching unit in a fifth state, and obtain a sixth positive bus voltage and a sixth negative bus voltage of the switch switching unit in a sixth state;

[0019] In the fifth state, the first switch is turned off and the third switch is turned on; in the sixth state, both the first switch and the third switch are turned off.

[0020] According to one embodiment of the present application, the switch switching unit does not include a third switch, and the detection unit is configured to obtain a seventh positive bus voltage and a seventh negative bus voltage of the switch switching unit in a seventh state, and obtain an eighth positive bus voltage and an eighth negative bus voltage of the switch switching unit in an eighth state;

[0021] In the seventh state, the first switch is turned off and the second switch is turned on; in the eighth state, both the first switch and the second switch are turned off.

[0022] In a second aspect, the present application provides an insulation impedance detection method, which is applied to the insulation impedance detection circuit according to the above, and the insulation impedance detection method includes:

[0023] Controlling the first switch to turn off;

[0024] Controlling the switch switching unit to switch between different conduction states, the conduction state including the on-off between the first end of the impedance unit and the positive bus or the negative bus;

[0025] Obtain bus voltages of a positive bus and a negative bus in at least two different conduction states;

[0026] Determine the insulation resistance to ground based on the bus voltage.

[0027] According to one embodiment of the present application, before controlling the first switch to be turned off, the method further includes:

[0028] Determine whether the nighttime repair power circuit meets the cut-out conditions according to the operating status of the inverter;

[0029] If yes, the step of controlling the first switch to turn off is executed.

[0030] In a third aspect, the present application provides an inverter, comprising the aforementioned insulation impedance detection circuit.

[0031] According to the insulation impedance detection circuit, detection method and inverter of the present application, by adding a switch switching unit and reusing the impedance unit of the original night repair power supply circuit in the inverter to detect the ground voltage of the positive bus and the negative bus, and then calculate the insulation impedance to the ground, high-accuracy ground insulation impedance detection is achieved, and fewer devices are added, and the increased system cost is low.

[0032] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0034] Figure 1 is a circuit block diagram of an insulation impedance detection circuit provided in an embodiment of the present application;

[0035] Figure 2It is one of the circuit principle diagrams of the insulation impedance detection circuit provided in the embodiment of the present application;

[0036] Figure 3 This is the second circuit schematic diagram of the insulation impedance detection circuit provided in the embodiment of the present application;

[0037] Figure 4 This is the third circuit schematic diagram of the insulation impedance detection circuit provided in the embodiment of the present application;

[0038] Figure 5 This is the fourth circuit schematic diagram of the insulation impedance detection circuit provided in the embodiment of the present application;

[0039] Figure 6 This is the fifth circuit schematic diagram of the insulation impedance detection circuit provided in the embodiment of the present application;

[0040] Figure 7 This is one of the flow charts of the insulation impedance detection method provided in the embodiment of the present application;

[0041] Figure 8 This is the second flow chart of the insulation impedance detection circuit provided in the embodiment of the present application.

[0042] Reference numerals:

[0043] Insulation impedance detection circuit 100, switch switching unit 110, detection unit 120, nighttime repair power supply circuit 200, first to third switches S1-S3, impedance unit R0, switchable switch S. DETAILED DESCRIPTION

[0044] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0045] In the following description, "circuit" refers to a conductive loop composed of at least one element or subcircuit through electrical connection or electromagnetic connection. When an element or circuit is said to be "coupled to" or "connected to" another element or an element / circuit is said to be "coupled to" or "connected to" two nodes, it can be directly coupled or connected to another element or there can be an intermediate element, and the connection between the elements can be physical, logical, or a combination thereof. On the contrary, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there is no intermediate element between the two.

[0046] In the description, the terms "first", "second", etc. are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the numerical descriptors used in this way are interchangeable where appropriate, so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are generally of the same type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0047] In addition, descriptions with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0048] Reference Figure 1 , Figure 1 The structure of an insulation impedance detection circuit is shown. An embodiment of the present application proposes an insulation impedance detection circuit. In this embodiment, the insulation impedance detection circuit 100 is applied to an inverter, and the inverter includes a positive bus V+, a negative bus V-, a ground node PE, a night repair power supply circuit 200, a first switch S1 and an impedance unit R0. The first output end of the night repair power supply circuit 200 is electrically connected to the first end of the first switch S1, and the second output end of the night repair power supply circuit 200 is electrically connected to the first end of the impedance unit R0. One of the second end of the first switch S1 and the second end of the impedance unit R0 is electrically connected to the ground node PE, and the other is electrically connected to the positive bus V+ or the negative bus V-. The insulation impedance detection circuit 100 includes a switch unit 110 and a detection unit 120. The switch unit 110 is electrically connected to the first end of the impedance unit R0 and is configured to control the on / off between the first end of the impedance unit R0 and the positive bus V+, and / or control the on / off between the first end of the impedance unit R0 and the negative bus V-; the detection unit 120 is electrically connected to the positive bus V+ and the negative bus V-, and is configured to detect the bus voltages of the positive bus V+ and the negative bus V- when the switch unit 110 is in different conduction states, and determine the insulation impedance to ground according to the bus voltages.

[0049] It can be understood that the night repair power supply circuit 200 is used to repair the photovoltaic components at night, especially to compensate for the PID (Potential Induced Degradation) effect. At night or when the inverter has no power generation function, the night repair power supply circuit 200 is started, and the positive and negative bus bars of the inverter are short-circuited by controlling the opening and closing of the first switch S1, and a certain forward bias voltage is set between the positive and negative bus bars of the inverter and the ground node PE. This forward bias voltage helps to bias repair the photovoltaic components and reduce the PID effect. During the bias repair process, the forward bias voltage will act on the surface of the photovoltaic component, so that the charge distribution inside the component tends to be uniform, thereby reducing the performance degradation caused by the PID effect. Among them, the specific structure and principle of the night repair power supply circuit 200 have mature technology, and this embodiment will not be repeated here.

[0050] As an example, the first output end of the nighttime repair power supply circuit 200 is electrically connected to the first end of the first switch S1, the second end of the first switch S1 is electrically connected to the negative bus V-, the second output end of the nighttime repair power supply circuit 200 is electrically connected to the first end of the impedance unit R0, and the second end of the impedance unit R0 is electrically connected to the ground node PE. During the day, the nighttime repair power supply circuit 200 does not work, and the first switch S1 is in an open state; at night or when the inverter has no power generation function, the nighttime repair power supply circuit is started, and the first switch S1 is in a closed state. Of course, the connection method of the first switch S1 and the impedance unit R0 can also be other methods, and this embodiment is not limited to this.

[0051] In this embodiment, on the basis of repairing the power supply circuit 200 at night, the insulation impedance detection circuit 100 is provided to reuse the impedance unit R0 to implement the insulation impedance detection, thereby reducing the additional hardware cost. Figure 1 In the figure, Rn is the insulation impedance of the negative bus V- to the ground, and Rm is the insulation impedance of the positive bus V+ to the ground. The switch unit 110 can connect the impedance unit R0 between the negative bus V- and the ground or between the positive bus V+ and the ground, thereby affecting the actual impedance of the negative bus V- to the ground or the positive bus V+ to the ground. Therefore, the insulation impedance can be calculated by establishing a voltage relationship for solution. Among them, the specific calculation method is determined according to the switching condition of the impedance unit R0, which will be described in detail later.

[0052] The detection unit 120 can be integrated into the controller in the inverter, or it can be an independent unit. The detection unit 120 is mainly used to sample the bus voltage and perform calculations. The switch unit 110 can be controlled by the detection unit 120 or by the controller in the inverter.

[0053] In addition, the detection unit can also generate an early warning signal when the calculated insulation impedance exceeds the safety range, thereby shutting down the inverter to protect the safety of personnel and equipment. If the calculated insulation impedance is within the safety range, a safety signal is generated, or no feedback signal is given.

[0054] According to the insulation impedance detection circuit 100 of the present application, by adding a switch switching unit 110 and reusing the impedance unit R0 of the original night repair power supply circuit 200 in the inverter, the ground voltage of the positive bus V+ and the negative bus V- is detected, and then the insulation impedance to the ground is calculated, thereby achieving high-accuracy ground insulation impedance detection, with fewer added devices and lower added system cost.

[0055] Reference Figure 2 , Figure 2 A circuit schematic diagram of an insulation impedance detection circuit is shown. In some embodiments, the switch switching unit 110 includes a switchable switch S, which has a first contact, a second contact, and a switch portion, the first contact is electrically connected to the positive bus V+, the second contact is electrically connected to the negative bus V-, the first end of the switch portion is electrically connected to the first end of the impedance unit R0, and the second end of the switch portion switches between three states of being connected to the first contact, connected to the second contact, or being left empty.

[0056] The switchable switch S may be a single-pole double-throw switch, a relay or a semiconductor switch device, etc., which may be controlled by the detection unit 120 or a controller in the inverter. The switchable switch S provides three voltage states between the bus and the ground by controlling whether the impedance unit R0 is connected to the bus, and whether it is connected to the positive bus V+ or the negative bus V-, thereby calculating the insulation resistance to the ground according to the voltage relationship under different voltage states.

[0057] As an example, the detection unit 120 is configured to obtain a first positive bus voltage and a first negative bus voltage of the switch switching unit 110 in a first state, and to obtain a second positive bus voltage and a second negative bus voltage of the switch switching unit 110 in a second state; wherein, in the first state, the first switch S1 is turned off, and the second end of the switching unit is connected to the first contact; and in the second state, the first switch S1 is turned off, and the second end of the switching unit is connected to the second contact.

[0058] In this example, when the inverter performs insulation resistance detection to the ground, the nighttime repair power supply circuit 200 does not work, that is, the first switch S1 is turned off, and the impedance unit R0 is connected to the positive bus V+ or the negative bus V-, respectively, to establish two voltage relationships, and then the insulation impedance is calculated. In addition, when the nighttime repair power supply circuit 200 works, the first switch S1 is turned on, and the second end of the switching part of the switchable switch S is empty.

[0059] In the first state, the impedance unit R0 is connected to the positive bus V+, then Vm1*(Rm+R0) / (Rm*R0)=-Vn1 / Rn; wherein Vm1 represents the insulation impedance of the positive bus V+ to the ground detected in this state, and Vn1 represents the insulation impedance of the negative bus V- to the ground detected in this state.

[0060] In the second state, the impedance unit R0 is connected to the negative bus V-, then Vm2 / Rm=-Vn2*(Rn+R0) / (Rn*R0); wherein Vm2 represents the insulation impedance of the positive bus V+ to the ground detected in this state, and Vn2 represents the insulation impedance of the negative bus V- to the ground detected in this state.

[0061] Combining the above two equations, we can get: Rm = (R0*Vm2*Vn1-R0*Vm1*Vn2) / (Vm1*Vn2-Vn2*Vn1), and Rn = (R0*Vm1*Vn2-R0*Vm2*Vn1) / (Vm2*Vm1-Vm1*Vn2). Among them, Rm is the actual insulation impedance of the positive bus V+ to the ground, and Rn is the actual insulation impedance of the positive bus V+ to the ground.

[0062] Reference Figure 3 , Figure 3 The schematic diagram of an insulation impedance detection circuit is shown in FIG. Figure 2 Compared with the embodiment, the difference lies in the connection position of the first switch S1 and the impedance unit R0. In this example, the second end of the first switch S1 is electrically connected to the ground node PE, and the second end of the impedance unit R0 is electrically connected to the negative bus V-. The process of detecting the insulation impedance to ground by the detection unit 120 can be the same as the above embodiment, which is not repeated here.

[0063] Reference Figure 4 , Figure 4 A circuit schematic diagram of an insulation impedance detection circuit is shown. In some embodiments, the switch switching unit 110 includes a second switch S2 and a third switch S3, wherein a first end of the second switch S2 is electrically connected to a first end of the impedance unit R0, and a second end of the second switch S2 is electrically connected to a negative bus V-; a first end of the third switch S3 is electrically connected to a first end of the impedance unit R0, and a second end of the third switch S3 is electrically connected to a positive bus V+.

[0064] The second switch S2 and the third switch S3 may also be relays or semiconductor switch devices, etc. They may be controlled by the detection unit 120 or the controller in the inverter. The second switch S2 controls whether the impedance unit R0 is connected to the negative bus V-, and the third switch S3 controls whether the impedance unit R0 is connected to the positive bus V+. Since the second switch S2 and the third switch S3 are usually not closed at the same time, three voltage states are provided between the bus and the ground, and the insulation resistance to the ground can be calculated according to the voltage relationship under different voltage states.

[0065] As an example, the detection unit 120 is configured to obtain a third positive bus voltage and a third negative bus voltage of the switch switching unit 110 in a third state, and to obtain a fourth positive bus voltage and a fourth negative bus voltage of the switch switching unit 110 in a fourth state; wherein, in the third state, the first switch S1 and the third switch S3 are both turned off, and the second switch S2 is turned on; in the fourth state, the first switch S1 and the second switch S2 are both turned off, and the third switch S3 is turned on.

[0066] In this example, when the inverter performs insulation resistance detection to the ground, the nighttime repair power supply circuit 200 does not work, that is, the first switch S1 is turned off, and the impedance unit R0 is connected to the positive bus V+ or the negative bus V-, respectively, to establish two voltage relationships, and then calculate the insulation impedance. In addition, when the nighttime repair power supply circuit 200 works, the first switch S1 is turned on, and the second switch S2 and the third switch S3 are both turned off.

[0067] In the third state, the impedance unit R0 is connected to the negative bus V-, then Vm3 / Rm=-Vn3*(Rn+R0) / (Rn*R0); wherein Vm3 represents the insulation impedance of the positive bus V+ to the ground detected in this state, and Vn3 represents the insulation impedance of the negative bus V- to the ground detected in this state.

[0068] In the fourth state, the impedance unit R0 is connected to the positive bus V+, then Vm4*(Rm+R0) / (Rm*R0)=-Vn4 / Rn; wherein Vm4 represents the insulation impedance of the positive bus V+ to the ground detected in this state, and Vn4 represents the insulation impedance of the negative bus V- to the ground detected in this state.

[0069] Combining the above two equations, we can get: Rm = (R0*Vm3*Vn4-R0*Vm4*Vn3) / (Vm4*Vn3-Vn3*Vn4), and Rn = (R0*Vm4*Vn3-R0*Vm3*Vn4) / (Vm3*Vm4-Vm4*Vn3). Among them, Rm is the actual insulation impedance of the positive bus V+ to the ground, and Rn is the actual insulation impedance of the positive bus V+ to the ground.

[0070] Reference Figure 5 , Figure 5 1 shows a circuit schematic diagram of an insulation impedance detection circuit. In some embodiments, Figure 4In comparison, the switch switching unit 110 does not include the second switch S2, and the detection unit 120 is configured to obtain the fifth positive bus voltage and the fifth negative bus voltage of the switch switching unit 110 in the fifth state, and to obtain the sixth positive bus voltage and the sixth negative bus voltage of the switch switching unit 110 in the sixth state; wherein, in the fifth state, the first switch S1 is turned off, and the third switch S3 is turned on; in the sixth state, both the first switch S1 and the third switch S3 are turned off.

[0071] In this embodiment, the switch switching unit 110 includes a third switch S3 to control whether the impedance unit R0 is connected to the positive bus V+. This provides two voltage states between the bus and the ground, and the insulation resistance to the ground can be calculated according to the voltage relationship under different voltage states.

[0072] In this example, when the inverter performs insulation resistance detection to the ground, the nighttime repair power supply circuit 200 does not work, that is, the first switch S1 is turned off, and the impedance unit R0 is connected to or cast out of the positive bus V+ to establish two voltage relationships, thereby calculating the insulation impedance. In addition, when the nighttime repair power supply circuit 200 works, the first switch S1 is turned on and the third switch S3 is turned off.

[0073] In the fifth state, the impedance unit R0 is connected to the positive bus V+, then Vm5*(Rm+R0) / (Rm*R0)=-Vn5 / Rn; wherein Vm5 represents the insulation impedance of the positive bus V+ to the ground detected in this state, and Vn5 represents the insulation impedance of the negative bus V- to the ground detected in this state.

[0074] In the sixth state, the impedance unit R0 is not connected to the positive bus V+, then Vm6 / Rm=-Vn6 / Rn; wherein Vm6 represents the insulation impedance of the positive bus V+ to the ground detected in this state, and Vn6 represents the insulation impedance of the negative bus V- to the ground detected in this state.

[0075] Combining the above two equations, we can get: Rm = (R0*Vm6*Vn5-R0*Vm5*Vn6) / (Vn6*Vn5), Rm is the actual insulation impedance of the positive bus V+ to the ground; and Rn = (R0*Vm5*Vn6-R0*Vm6*Vn5) / (Vm6*Vn5), Rn is the actual insulation impedance of the positive bus V+ to the ground.

[0076] Reference Figure 6 , Figure 6 1 shows a circuit schematic diagram of an insulation impedance detection circuit. In some embodiments, Figure 4In comparison, the switch switching unit 110 does not include the third switch S3, and the detection unit 120 is configured to obtain the seventh positive bus voltage and the seventh negative bus voltage of the switch switching unit 110 in the seventh state, and to obtain the eighth positive bus voltage and the eighth negative bus voltage of the switch switching unit 110 in the eighth state; wherein, in the seventh state, the first switch S1 is turned off, and the second switch S2 is turned on; in the eighth state, both the first switch S1 and the second switch S2 are turned off.

[0077] In this embodiment, the switch switching unit 110 includes a second switch S2 to control whether the impedance unit R0 is connected to the negative bus V-. This provides two voltage states between the bus and the ground, and the insulation resistance to the ground can be calculated according to the voltage relationship under different voltage states.

[0078] In this example, when the inverter performs insulation resistance detection to the ground, the nighttime repair power supply circuit 200 does not work, that is, the first switch S1 is turned off, and the impedance unit R0 is connected to or cast out of the negative bus V- to establish two voltage relationships, thereby calculating the insulation impedance. In addition, when the nighttime repair power supply circuit 200 works, the first switch S1 is turned on and the second switch S2 is turned off.

[0079] In the seventh state, the impedance unit R0 is connected to the negative bus V-, then Vn7*(Rn+R0) / (Rn*R0)=-Vm7 / Rm; wherein Vm7 represents the insulation impedance of the positive bus V+ to the ground detected in this state, and Vn7 represents the insulation impedance of the negative bus V- to the ground detected in this state.

[0080] In the eighth state, the impedance unit R0 is not connected to the negative bus V-, then Vm8 / Rm=-Vn8 / Rn; wherein Vm8 represents the insulation impedance of the positive bus V+ to the ground detected in this state, and Vn8 represents the insulation impedance of the negative bus V- to the ground detected in this state.

[0081] Combining the above two equations, we can get: Rm = (R0*Vn8*Vm7-R0*Vn7*Vm8) / (Vm8*Vm7), Rm is the actual insulation impedance of the positive bus V+ to the ground; and Rn = (R0*Vn7*Vm8-R0*Vn8*Vm7) / (Vn8*Vm7), Rn is the actual insulation impedance of the positive bus V+ to the ground.

[0082] Reference Figure 7 , Figure 7 The flow chart of an insulation impedance detection method is shown. An embodiment of the present application also proposes an insulation impedance detection method. The insulation impedance detection method is applied to the insulation impedance detection circuit described above and includes steps 10, 20, 30 and 40.

[0083] Step 10, controlling the first switch S1 to turn off;

[0084] Step 20, controlling the switch switching unit 110 to switch between different conduction states, where the conduction state includes the on-off between the first end of the impedance unit R0 and the positive bus V+ or the negative bus V-;

[0085] Step 30, obtaining bus voltages of the positive bus V+ and the negative bus V- in at least two different conduction states;

[0086] Step 40: Determine the insulation impedance to ground according to the bus voltage.

[0087] It should be noted that the execution subject of the insulation impedance detection method in this embodiment can be the controller in the inverter, or the aforementioned detection unit 120. Of course, it can also be other devices or modules, and this embodiment does not limit this. The following description takes the controller as the execution subject

[0088] The controller can set the time for executing the insulation impedance detection method according to the requirements. For example, the insulation impedance detection method is executed when the inverter is powered on for the first time, or the inverter executes the insulation impedance detection method once every operation period such as (10 hours or 20 hours). The insulation impedance detection method can be executed during the day or at night.

[0089] It is understandable that the first switch S1 is used to control whether the nighttime repair power supply circuit 200 works. When the first switch S1 is turned off, the nighttime repair power supply circuit 200 does not operate, and the impedance unit R0 does not generate additional current due to the operation of the nighttime repair power supply circuit 200, thereby preventing interference to the ground insulation impedance detection.

[0090] In some embodiments, before step 10, the method further includes: judging whether the nighttime repair power supply circuit 200 meets the switch-out condition according to the operating state of the inverter; if so, executing the step of controlling the first switch S1 to be turned off.

[0091] It should be noted that the controller can determine whether the nighttime repair power circuit 200 is working or the nighttime repair power circuit 200 may need to be put into operation according to the operating parameters of the inverter and / or the operating parameters of the photovoltaic module; if the repair power circuit 200 is not working or the nighttime repair power circuit 200 does not need to be put into operation, it is determined that the nighttime repair power circuit 200 meets the cut-out condition. This can avoid performing insulation detection to the ground and affecting the operation of the inverter.

[0092] As an example, the night repair power supply circuit 200 can be turned on during a specific time period set at night. If the controller detects that the time difference between the current time and the specific time period is less than a threshold, it determines that the night repair power supply circuit 200 may need to be put into operation; otherwise, it determines that the night repair power supply circuit 200 does not need to be put into operation.

[0093] The specific structure of the switch unit 110 can be referred to Figure 2 to Figure 6 The conduction states thereof vary with the specific structures, and the corresponding control is also referred to above, and this embodiment will not be described in detail here. Among them, the order of the various conduction states may not be limited.

[0094] Reference Figure 8 , Figure 8 The flow chart of an insulation impedance detection method is shown in FIG. Figure 2 Taking the insulation impedance detection circuit shown as an example, a process of the insulation impedance detection method is described. The controller performs ISO insulation detection, first disconnects the first switch S1; then first pulls S to the negative bus V- to obtain a sampled voltage; then pulls S to the positive bus V+ to obtain a sampled voltage; then calculates the insulation impedance to ground Rm, Rn; then determines whether Rm, Rn are within the safe range; if so, the detection passes and continues to the next step; if not, the inverter is shut down for inspection, and after starting up, performs ISO insulation detection again, and the above steps are repeated.

[0095] An embodiment of the present application further provides an inverter, the inverter comprising the aforementioned insulation impedance detection circuit. The specific structure and principle of the insulation impedance detection circuit can be referred to the aforementioned embodiments, which also have corresponding technical effects. The inverter may also include a controller, which may also implement the aforementioned insulation impedance detection method, and the specific process of the insulation impedance detection method may be referred to the aforementioned embodiments, which also have corresponding technical effects, and this embodiment will not be repeated here.

[0096] In this article, the term "comprises", "includes" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "including one..." do not exclude the presence of other identical elements in the process, method, article or device including the element. In addition, it should be noted that the scope of the method and device in the embodiment of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in reverse order according to the functions involved, for example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0097] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. An insulation impedance detection circuit, characterized in that: Applied to an inverter, the inverter comprises a positive bus, a negative bus, a grounding node, a nighttime repair power supply circuit, a first switch and an impedance unit, a first output end of the nighttime repair power supply circuit is electrically connected to a first end of the first switch, a second output end of the nighttime repair power supply circuit is electrically connected to a first end of the impedance unit, one of a second end of the first switch and a second end of the impedance unit is electrically connected to the grounding node, and the other is electrically connected to the positive bus or the negative bus; The insulation impedance detection circuit comprises: a switch unit, electrically connected to the first end of the impedance unit, and configured to control the on-off between the first end of the impedance unit and the positive bus, and / or control the on-off between the first end of the impedance unit and the negative bus; A detection unit is electrically connected to the positive bus and the negative bus, and is configured to detect the bus voltages of the positive bus and the negative bus when the switch switching unit is in different conduction states, and determine the insulation impedance to ground according to the bus voltages.

2. The insulation impedance detection circuit according to claim 1, characterized in that: The switch switching unit comprises: A switchable switch comprises a first contact, a second contact and a switching part, wherein the first contact is electrically connected to the positive bus, the second contact is electrically connected to the negative bus, the first end of the switching part is electrically connected to the first end of the impedance unit, and the second end of the switching part switches between three states: connected to the first contact, connected to the second contact, or left empty.

3. The insulation impedance detection circuit according to claim 2, characterized in that: The detection unit is configured to obtain a first positive bus voltage and a first negative bus voltage of the switch switching unit in a first state, and obtain a second positive bus voltage and a second negative bus voltage of the switch switching unit in a second state; Wherein, in the first state, the first switch is turned off, and the second end of the switching part is connected to the first contact; in the second state, the first switch is turned off, and the second end of the switching part is connected to the second contact.

4. The insulation impedance detection circuit according to claim 1, characterized in that: The switch switching unit comprises: a second switch, wherein a first end of the second switch is electrically connected to a first end of the impedance unit, and a second end of the second switch is electrically connected to the negative bus; and / or, A third switch, wherein a first end of the third switch is electrically connected to the first end of the impedance unit, and a second end of the third switch is electrically connected to the positive bus.

5. The insulation impedance detection circuit according to claim 4, characterized in that: The detection unit is configured to obtain a third positive bus voltage and a third negative bus voltage of the switch switching unit in a third state, and to obtain a fourth positive bus voltage and a fourth negative bus voltage of the switch switching unit in a fourth state; Wherein, in the third state, the first switch and the third switch are both turned off, and the second switch is turned on; in the fourth state, the first switch and the second switch are both turned off, and the third switch is turned on.

6. The insulation impedance detection circuit according to claim 4, characterized in that: The switch switching unit does not include the second switch, and the detection unit is configured to obtain a fifth positive bus voltage and a fifth negative bus voltage of the switch switching unit in a fifth state, and obtain a sixth positive bus voltage and a sixth negative bus voltage of the switch switching unit in a sixth state; Wherein, in the fifth state, the first switch is turned off and the third switch is turned on; in the sixth state, both the first switch and the third switch are turned off.

7. The insulation impedance detection circuit according to claim 4, characterized in that: The switch switching unit does not include the third switch, and the detection unit is configured to obtain a seventh positive bus voltage and a seventh negative bus voltage of the switch switching unit in a seventh state, and obtain an eighth positive bus voltage and an eighth negative bus voltage of the switch switching unit in an eighth state; Wherein, in the seventh state, the first switch is turned off and the second switch is turned on; in the eighth state, both the first switch and the second switch are turned off.

8. An insulation impedance detection method, characterized in that: Applied to the insulation impedance detection circuit according to any one of claims 1 to 7, the insulation impedance detection method comprises: Controlling the first switch to turn off; Controlling the switch switching unit to switch between different conduction states, wherein the conduction state includes the on-off between the first end of the impedance unit and the positive bus or the negative bus; Obtaining bus voltages of the positive bus and the negative bus in at least two different conduction states; The insulation resistance to ground is determined according to the bus voltage.

9. The insulation impedance detection method according to claim 8, characterized in that: Before controlling the first switch to turn off, the method further includes: Determine whether the nighttime repair power circuit meets the cut-out conditions according to the operating status of the inverter; If yes, the step of controlling the first switch to turn off is performed.

10. An inverter, characterized in that: The invention comprises an insulation impedance detection circuit according to any one of claims 1 to 7.

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