Insulation resistance detection framework and method

Abstract

The invention discloses an insulation resistance detection framework and method, and the framework comprises a switch module which is connected between an inverter zero line of a photovoltaic system and a power grid side zero line, so as to enable the inverter zero line to be connected or disconnected with the power grid side zero line; the insulation resistance detection module is used for detecting the ground insulation state of the photovoltaic string; and the control module comprises a controller, and the controller is suitable for outputting a control signal to control the state of the switch module and control the state of the insulation resistance detection module, so that the switch module is in an open circuit state under the condition that the insulation resistance detection module is in an on state. The switch module and the insulation resistance detection module are controlled through the control module, so that the switch module is in an open circuit state under the condition that the insulation resistance detection module is in an open state, and the influence of a power grid side grounding loop on insulation resistance detection of a photovoltaic side is avoided.

Description

Technical Field

[0001] The present application relates to the field of renewable energy power generation technology, and in particular to an insulation impedance detection architecture and method. Background Art

[0002] Before the inverter is connected to the grid, the insulation performance of the photovoltaic strings is usually tested to ensure system safety. Figure 1 As shown in the insulation impedance detection module, by introducing detection resistors R1 and R2 and measuring the voltage values ​​across the resistors R1 and R2, the insulation impedance R of the photovoltaic string to ground is obtained by solving multiple sets of equations using KCL or KVL. P and R n , the insulation impedance value to ground is compared with the preset threshold value to determine whether there is an insulation fault in the photovoltaic system.

[0003] However, the insulation detection architecture in the related art has the following defects: the insulation impedance detection equivalent circuit of the three-phase four-wire photovoltaic system in the related art is as follows: Figure 2 As shown in the figure, during the insulation impedance detection on the photovoltaic side, due to the resistance R g Due to the ground loop, the voltage of the sense resistors R1 and R2 is clamped to V dc1 and -V dc2 , which in turn interferes with the detection, affects the accuracy of the test results, and even causes misjudgment. Summary of the invention

[0004] One of the objectives of the present invention is to provide an insulation impedance detection framework to improve the accuracy of insulation impedance detection results.

[0005] Another object of the present invention is to provide an insulation impedance detection method, which can utilize the above insulation impedance detection architecture to perform insulation impedance detection.

[0006] In order to achieve at least one of the above purposes, the technical solution adopted by the present invention is: an insulation impedance detection architecture, comprising: a switch module, the switch module is connected between the inverter neutral line of the photovoltaic system and the grid-side neutral line, so as to connect or disconnect the inverter neutral line and the grid-side neutral line; an insulation impedance detection module, the insulation impedance detection module is used to detect the insulation state of the photovoltaic string to the ground; and a control module, the control module includes a controller, the controller is suitable for outputting a control signal to control the state of the switch module, and the state of the insulation impedance detection module, so that when the insulation impedance detection module is in the on state, the switch module is in the open circuit state.

[0007] As a preference, the controller is suitable for outputting a switch control signal relay_ctrl1 and a detection control signal relay_ctrl2, the switch control signal relay_ctrl1 acts on the switch module to control the state of the switch module, the switch control signal relay_ctrl1 and the detection control signal relay_ctrl2 act together on the insulation impedance detection module, so that when the switch module is in an open circuit state, the insulation impedance detection module is suitable for being in an open state.

[0008] As a preferred embodiment, the control module further includes a NOT gate unit and a first AND gate unit, the input end of the NOT gate unit is used to receive the switch control signal relay_ctrl1, one of the input ends of the first AND gate unit is used to receive the output signal of the NOT gate unit, the other input end of the first AND gate unit is used to receive the detection control signal relay_ctrl2, and the first AND gate unit outputs an intermediate signal relay_ctrl2' to act on the insulation impedance detection module, so that when the switch module is in an open circuit state, the insulation impedance detection module is suitable to be in an open state.

[0009] As a preferred embodiment, the control module also includes a delay module. The switch control signal relay_ctrl1 output by the controller passes through the delay module to delay the set time △t, and then acts on the insulation impedance detection module together with the detection control signal relay_ctrl2, so that when the insulation impedance detection module is in the on state, the switch module can be in the open circuit state.

[0010] Preferably, the delay module includes a second AND gate unit, one of the input ends of the second AND gate unit is connected to the controller, and the other input ends of the second AND gate unit are all set high, so that the output signal of the second AND gate unit is suitable for adjustment according to the switch control signal relay_ctrl1, and the output signal of the second AND gate unit and the detection control signal relay_ctrl2 act together on the insulation impedance detection module, so that when the insulation impedance detection module is in the on state, the switch module is in the open circuit state.

[0011] Preferably, the insulation impedance detection architecture further includes a protection unit and a third AND gate unit, the protection unit is suitable for outputting a blocking signal relay_block, one of the input ends of the third AND gate unit is used to receive the output blocking signal relay_block, the other input end of the third AND gate unit is used to receive the switch control signal relay_ctrl1, and the third AND gate unit outputs a switch drive signal relay_drv1 to act on the switch module to control the state of the switch module.

[0012] As a preferred embodiment, the insulation impedance detection architecture also includes a protection unit and a fourth AND gate unit, the protection unit is suitable for outputting a blocking signal relay_block, one of the input ends of the fourth AND gate unit is used to receive the output blocking signal relay_block, and the other input end of the fourth AND gate unit is connected to the controller, so that the output signal of the fourth AND gate unit is suitable for adjustment according to the blocking signal relay_block, the switch control signal relay_ctrl1 and the detection control signal relay_ctrl2, and the fourth AND gate unit outputs a detection drive signal relay_drv2 to act on the insulation impedance detection module to control the state of the insulation impedance detection module.

[0013] In order to achieve at least one of the above purposes, the technical solution adopted by the present invention is: an insulation impedance detection method using any of the above insulation impedance detection architectures, comprising the following steps: The controller output switch control signal relay_ctrl1 of the control module is set to a low level, so that the switch module is in an open circuit state; The controller output detection control signal relay_ctrl2 is set to a high level, so that the insulation impedance detection module is in an on state to detect the insulation impedance value of the photovoltaic string; Determining whether the insulation resistance value is greater than a threshold; Under the condition that the insulation impedance value is greater than the threshold value, the switch control signal relay_ctrl1 is set to a high level, so that the switch module is in a closed state, and the photovoltaic string can be connected to the grid.

[0014] Preferably, the insulation impedance detection method further comprises the step of setting the output intermediate signal relay_ctrl2' of the first AND gate unit of the control module to a low level under the condition that the insulation impedance value is greater than a threshold value, so that the insulation impedance detection module is in a closed state.

[0015] As a preferred embodiment, the insulation impedance detection method also includes the steps of: under the condition that the photovoltaic string group is connected to the grid, the controller outputs the switch control signal relay_ctrl1 and sets it to a high level, so that the photovoltaic system operates in a three-phase four-wire system; or under the condition that the photovoltaic string group is connected to the grid, the controller outputs the switch control signal relay_ctrl1 and sets it to a low level, so that the photovoltaic system operates in a three-phase three-wire system.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The control module controls the switch module and the insulation impedance detection module, so that when the insulation impedance detection module is in the on state, the switch module is in the open circuit state, that is, the inverter neutral line of the photovoltaic system is disconnected from the grid side neutral line, and then in the three-phase four-wire mode, it is helpful to avoid the influence of the grid side grounding loop on the insulation impedance detection of the photovoltaic side, so as to improve the accuracy of the insulation impedance detection of the photovoltaic side. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The three-phase four-wire architecture diagram of a photovoltaic system in the related art.

[0018] Figure 2 The equivalent circuit diagram of the photovoltaic side insulation impedance detection of the photovoltaic system in the related art.

[0019] Figure 3 This is a diagram of the photovoltaic system and insulation impedance detection architecture of this application.

[0020] Figure 4 This is an equivalent circuit diagram of the photovoltaic side insulation impedance detection of the photovoltaic system of the present application.

[0021] Figure 5 This is a control strategy diagram of the control module of this application.

[0022] Figure 6 This is a flow chart of the insulation impedance detection method of the present application.

[0023] Figure 7 Control timing diagram of the insulation impedance detection method of the present application.

[0024] Figure 8 This is a schematic diagram of the photovoltaic system and insulation impedance detection architecture of the present application in the initialization stage.

[0025] Fig. 9 It is a schematic diagram of the photovoltaic system and the insulation impedance detection architecture of the present application in the insulation impedance detection stage.

[0026] Fig.10 This is a schematic diagram of the photovoltaic system and insulation impedance detection architecture of the present application during the grid-connected working stage.

[0027] Fig.11 This is a control timing diagram of the photovoltaic system and insulation impedance detection architecture of the present application when grid-connected operation is prohibited.

[0028] Fig.12 A schematic diagram of the photovoltaic system and the insulation impedance detection architecture of the present application when grid-connected operation is prohibited.

[0029] Fig.13 This is a control timing diagram of the photovoltaic system of the present application switching from a three-phase four-wire system to a three-phase three-wire system.

[0030] In the figure: 101, insulation impedance detection module; 102, switch module; 103, control module; 1031, reset pull-down device; 1032, delay module; 1033, protection unit; 401, NOT gate unit; 402, first AND gate unit; 403, second AND gate unit; 404, third AND gate unit; 405, fourth AND gate unit; 406, controller. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form a new embodiment.

[0032] It should be noted that the terms "first", "second", etc. in the description and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0033] The terms "including" and "having" and any variations thereof in the specification and claims of this application are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or apparatuses.

[0034] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, a contact connection, or an indirect connection through an intermediate medium, and it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] In order to facilitate the understanding of the following solutions, this application will be described through a photovoltaic system. Figure 1 As shown in the figure, a three-phase four-wire photovoltaic system in the related art mainly includes a PV unit, a DC / DC unit, a DC / AC unit and a relay group. Specifically, the PV unit is connected to the DC bus through the DC / DC unit, and the DC bus is connected to the power grid and the load through the bus capacitor, the DC / AC unit and the relay group. Furthermore, the positive and negative poles of the photovoltaic side are respectively connected to the ground through the insulation impedance R P and R n Grounding, the neutral line on the grid side passes through the resistor R g Grounding. Further, Figure 2 As shown, in the insulation resistance detection module 101, by introducing detection resistors R1 and R2 and measuring the voltage values ​​across the resistors R1 and R2, multiple sets of equations are solved by using KCL (Kirchhoff's Current Law) or KVL (Kirchhoff's Voltage Law) to obtain the insulation resistance R of the photovoltaic string to ground. P and R n , the insulation impedance value to ground is compared with the preset threshold value to determine whether there is an insulation fault in the photovoltaic system.

[0036] However, if Figure 2 As shown in the figure, during the insulation impedance detection on the photovoltaic side, due to the resistance R g Due to the ground loop, the voltage of the sense resistors R1 and R2 is clamped to V dc1 and -V dc2 , which in turn interferes with the detection, affects the accuracy of the test results, and even causes misjudgment.

[0037] Based on the above content, in order to improve the accuracy of the insulation impedance detection on the photovoltaic side, one aspect of the present application provides an insulation impedance detection architecture, such as Figure 3-Figure 5 As shown, it includes: a switch module 102, an insulation impedance detection module 101 and a control module 103. The switch module 102 is connected between the inverter neutral line of the photovoltaic system and the grid neutral line, so that the inverter neutral line is connected or disconnected with the grid neutral line. The insulation impedance detection module 101 is used to detect the insulation state of the photovoltaic string to the ground. The control module 103 includes a controller 406, and the controller 406 is suitable for outputting a control signal to control the state of the switch module 102 and the state of the insulation impedance detection module 101, so that when the insulation impedance detection module 101 is in the on state, the switch module 102 is in the open circuit state.

[0038] Specifically, when the insulation impedance detection of the photovoltaic side is required, the controller 406 of the control module 103 is suitable for outputting a control signal to put the switch module 102 in an open circuit state, thereby disconnecting the neutral line of the inverter from the neutral line of the grid side; further, under the condition that the switch module 102 is in an open circuit state, the controller 406 is suitable for outputting a control signal to turn on the insulation impedance detection module 101, thereby facilitating the resistance R g Interference with the insulation impedance detection on the photovoltaic side; Wait for the insulation impedance detection module 101 to complete the insulation impedance R to ground P and R n After the detection and the insulation impedance value to ground meets the requirement, the controller 406 is adapted to output a control signal to close the switch module 102, thereby connecting the neutral line of the inverter to the neutral line of the grid side, and restoring the photovoltaic system to the three-phase four-wire mode. The relay group is closed to achieve grid connection.

[0039] It should be understood that the control signal output by the controller 406 of the control module 103 controls the switch module 102 and the insulation impedance detection module 101, so that when the insulation impedance detection module 101 is in the on state, the switch module 102 is in the open circuit state, that is, the inverter neutral line of the photovoltaic system is disconnected from the grid side neutral line, and then in the three-phase four-wire mode, it is helpful to avoid the influence of the grid side grounding loop on the insulation impedance detection of the photovoltaic side, so as to improve the accuracy of the insulation impedance detection of the photovoltaic side.

[0040] In some embodiments, Figure 5 As shown, the controller 406 is suitable for outputting a switch control signal relay_ctrl1 and a detection control signal relay_ctrl2. The switch control signal relay_ctrl1 acts on the switch module 102 to control the state of the switch module 102. The switch control signal relay_ctrl1 and the detection control signal relay_ctrl2 act together on the insulation impedance detection module 101, so that when the switch module 102 is in an open circuit state, the insulation impedance detection module 101 is suitable for being in an open state.

[0041] It should be understood that the switch control signal relay_ctrl1 acts on the switch module 102 alone, which is conducive to preventing the state of the switch module 102 from being interfered by the detection control signal relay_ctrl2, making the control of the switch module 102 simpler. Further, the switch control signal relay_ctrl1 and the detection control signal relay_ctrl2 act on the insulation impedance detection module 101 together, so that the state of the insulation impedance detection module 101 is affected by the switch control signal relay_ctrl1, so that the insulation impedance detection module 101 can be in the open state only when the switch module 102 is in the open circuit state, which is conducive to avoiding the resistor R g Interference with insulation impedance detection on the PV side.

[0042] It is worth mentioning that when the switch module 102 is in an open circuit state, the insulation impedance detection module 101 is suitable for being in an open state, which means that when the switch control signal relay_ctrl1 makes the switch module 102 in an open circuit state, the insulation impedance detection module 101 is affected by the detection control signal relay_ctrl2 and can be in an open state or a closed state. When the switch control signal relay_ctrl1 makes the switch module 102 in a closed state, the insulation impedance detection module 101 will not be affected by the detection control signal relay_ctrl2 and remain in a closed state. In other words, the insulation impedance detection module 101 can only be in an open state when the switch module 102 is in an open circuit state; this is conducive to avoiding the insulation impedance detection module 101 from being mistakenly started when the switch module 102 is in a closed state.

[0043] It should be known that the controller 406 is a commonly used MCU controller in the art, and the specific structure and working principle are well-known technologies to those skilled in the art, so they will not be elaborated in detail here; common MCU controllers include DSP, etc., and this application does not make specific restrictions on this.

[0044] It is worth mentioning that the ground line GND_MCU of the controller 406 is implemented as a weak ground, that is, the ground line GND_MCU is not electrically connected to the ground lines of other modules in the photovoltaic system, which is beneficial to improve the reliability of the controller 406.

[0045] In some embodiments, Figure 5As shown, the control module 103 also includes a NOT gate unit 401 and a first AND gate unit 402, the input end of the NOT gate unit 401 is used to receive the switch control signal relay_ctrl1, one of the input ends of the first AND gate unit 402 is used to receive the output signal of the NOT gate unit 401, and the other input end of the first AND gate unit 402 is used to receive the detection control signal relay_ctrl2, and the first AND gate unit 402 outputs an intermediate signal relay_ctrl2' to act on the insulation impedance detection module 101, so that when the switch module 102 is in an open circuit state, the insulation impedance detection module 101 is suitable for being in an open state.

[0046] Specifically, when the insulation impedance detection of the photovoltaic side is required, the switch control signal relay_ctrl1 output by the control module 103 is low level, so that the switch module 102 is in an open circuit state, thereby disconnecting the neutral line of the inverter from the neutral line of the grid side. Further, the detection control signal relay_ctrl2 output by the control module 103 is high level. It should be understood that the low-level switch control signal relay_ctrl1 is input to the NOT gate unit 401, and then the output signal of the NOT gate unit 401 is high level. In other words, the two input signals of the first AND gate unit 402 are both high level, and then the first AND gate unit 402 outputs the intermediate signal relay_ctrl2' as a high level, so that the insulation impedance detection module 101 can be turned on.

[0047] When the insulation impedance detection module 101 completes the insulation impedance to ground R P and R n After the detection and the insulation impedance value to ground meets the requirement, the switch control signal relay_ctrl1 output by the control module 103 is switched to a high level, so that the switch module 102 is in a closed state, thereby connecting the neutral line of the inverter to the neutral line of the grid side, and the photovoltaic system is restored to the three-phase four-wire mode, and the relay group is closed to achieve grid connection. It should be understood that the high-level switch control signal relay_ctrl1 is input to the NOT gate unit 401, and then the output signal of the NOT gate unit 401 is a low level. In other words, at least one input signal of the first AND gate unit 402 is a low level, and then the first AND gate unit 402 outputs the intermediate signal relay_ctrl2' as a low level, so that the insulation impedance detection module 101 can be turned off, and it is helpful to avoid the insulation impedance detection module 101 from being mistakenly started when the switch module 102 is in a closed state.

[0048] It should be known that the specific structure and working principle of the NOT gate unit 401 are well-known technologies for those skilled in the art, so they will not be elaborated in detail here; the working logic of the NOT gate unit 401 is that when the input terminal is at a high level, the output is a low level, and when the input terminal is at a low level, the output is a high level. The specific structure and working principle of the AND gate unit are well-known technologies for those skilled in the art, so they will not be elaborated in detail here; the working logic of the AND gate unit is that when both input terminals are at a high level, the output is a high level.

[0049] In some embodiments, Figure 5 As shown, the control module 103 also includes a delay module 1032. After the switch control signal relay_ctrl1 output by the controller 406 passes through the delay module 1032 and is delayed for a set time △t, it acts together with the detection control signal relay_ctrl2 on the insulation impedance detection module 101, so that when the insulation impedance detection module 101 is in the on state, the switch module 102 is in the open circuit state.

[0050] It should be understood that the switch control signal relay_ctrl1 acts on the insulation impedance detection module 101 after being delayed by the setting time △t through the delay module 1032, which is conducive to making the time when the detection control signal relay_ctrl2 acts on the insulation impedance detection module 101 later than the time when the switch control signal relay_ctrl1 acts on the switch module 102, thereby ensuring that the insulation impedance detection module 101 is started only after the switch module 102 is completely in an open circuit state, further improving the insulation impedance R to ground. P and R n Accuracy of measurement.

[0051] In some embodiments, Figure 5 As shown, the delay module 1032 includes a second AND gate unit 403, one of the input ends of the second AND gate unit 403 is connected to the controller 406, and the other input ends of the second AND gate unit 403 are all set high, so that the output signal of the second AND gate unit 403 is suitable for adjustment according to the switch control signal relay_ctrl1, and the output signal of the second AND gate unit 403 and the detection control signal relay_ctrl2 act together on the insulation impedance detection module 101, so that when the insulation impedance detection module 101 is in the on state, the switch module 102 is in the open circuit state.

[0052] In at least one embodiment, the delay module 1032 further includes a resistor and a capacitor, the resistor and the second AND gate unit 403 are sequentially connected between the NOT gate unit 401 and the first AND gate unit 402, and the grounded capacitor is connected between the resistor and the second AND gate unit 403, thereby playing the role of delaying the setting time △t through the charging and discharging of the resistor and the capacitor. That is, the switch control signal relay_ctrl1 output by the control unit is inverted by the NOT gate unit 401, and then delayed by the setting time △t through the delay effect of the resistor and the capacitor, and then input into the second AND gate unit 403.

[0053] It is worth mentioning that by setting the second AND gate unit 403 between the NOT gate unit 401 and the first AND gate unit 402, the reliability of the delay module 1032 is improved, which is beneficial to further avoid the insulation impedance detection module 101 being mistakenly started when the switch module 102 is in the closed state.

[0054] In some embodiments, Figure 5 As shown, the insulation impedance detection architecture also includes a protection unit 1033 and a third AND gate unit 404. The protection unit 1033 is suitable for outputting a blocking signal relay_block. One of the input ends of the third AND gate unit 404 is used to receive the output blocking signal relay_block. The other input end of the third AND gate unit 404 is used to receive the switch control signal relay_ctrl1. The third AND gate unit 404 outputs a switch drive signal relay_drv1 to act on the switch module 102 to control the state of the switch module 102.

[0055] In some embodiments, Figure 5 As shown, the insulation impedance detection architecture also includes a protection unit 1033 and a fourth AND gate unit 405. The protection unit 1033 is suitable for outputting a blocking signal relay_block. One of the input ends of the fourth AND gate unit 405 is used to receive the output blocking signal relay_block. The other input end of the fourth AND gate unit 405 is connected to the controller 406, so that the output signal of the fourth AND gate unit 405 is suitable for adjustment according to the blocking signal relay_block, the switch control signal relay_ctrl1 and the detection control signal relay_ctrl2. The fourth AND gate unit 405 outputs a detection drive signal relay_drv2 to act on the insulation impedance detection module 101 to control the state of the insulation impedance detection module 101.

[0056] It should be understood that during the normal operation of the photovoltaic system, the blocking signal relay_block output by the protection unit 1033 always maintains a high level, so that the switch module 102 and the insulation impedance detection module 101 can work normally under the control of the control module 103. Under the condition that the photovoltaic system is abnormal, the blocking signal relay_block output by the protection unit 1033 can be switched to a low level, so that the switch drive signal relay_drv1 and the detection drive signal relay_drv2 are both maintained at a low level, that is, the switch module 102 is not affected by the control module 103 to maintain an open circuit state; and the insulation impedance detection module 101 is not affected by the control module 103 to maintain a closed state. It is thus beneficial to prevent further damage to various modules or devices of the photovoltaic system, and to prevent the spread of abnormalities and faults.

[0057] It should be known that the specific structure and working principle of the protection unit 1033 are well-known technologies to those skilled in the art, and therefore will not be elaborated in detail here.

[0058] In some embodiments, Figure 4 As shown, the insulation impedance detection module 101 includes resistors R1 and R2, and switches S11 and S12. Specifically, the switch S11 and the resistor R1 are connected in series between the positive DC bus and the ground, and the insulation impedance R P In parallel, switch S12 and resistor R2 are connected in series between the negative DC bus and the ground, and are isolated from the ground by the insulation impedance R n It should be understood that when the switches S11 and S12 are closed under the control of the control module 103, the insulation impedance detection module 101 is in an open state, and when the switches S11 and S12 are disconnected under the control of the control module 103, the insulation impedance detection module 101 is in a closed state.

[0059] Furthermore, by detection, the voltages of resistors R1 and R2 are V R1 and V R2 According to the voltage division principle, we can get: (1) (2) Furthermore, by combining equations (1) and (2), the insulation resistance to ground R can be obtained: P and R n It is worth mentioning that the above solution is only an example, and the present application does not impose any specific restrictions on the implementation of the insulation impedance detection circuit.

[0060] It is worth mentioning that Figure 3As shown, two ends of the insulation impedance detection module 101 are respectively connected to the positive DC bus and the negative DC bus, and the other third section is safely grounded to improve the safety of the photovoltaic system.

[0061] In some embodiments, the switch module 102 is implemented as a bidirectional power switch device, including but not limited to a relay, a bidirectional thyristor, and an insulated gate bipolar transistor (bidirectional IGBT), which is not specifically limited in the present application.

[0062] In some embodiments, Figure 5 As shown, the insulation impedance detection architecture also includes a reset pull-down device 1031. When the photovoltaic system enters the insulation impedance detection on the photovoltaic side, the switch control signal relay_ctrl1 output by the controller 406 is low level, and the detection control signal relay_ctrl2 output by the controller 406 is high level, so that when the insulation impedance detection module 101 is in the open state, the switch module 102 can be in the open circuit state. After the insulation impedance value to ground meets the requirements, the switch control signal relay_ctrl1 can be switched to a high level by resetting the pull-down device 1031, and then the switch module 102 can be switched to a closed state, so that the neutral line of the inverter is connected to the neutral line on the grid side, and the photovoltaic system can be restored to the three-phase four-wire mode, and the relay group is closed to achieve grid connection.

[0063] It should be known that the specific structure and working principle of the reset pull-down device 1031 are well known to those skilled in the art, and thus will not be elaborated in detail herein.

[0064] Another aspect of the present application provides an insulation impedance detection method using the above insulation impedance detection architecture, such as Figure 6 As shown, the following steps are included: the controller 406 outputs a switch control signal relay_ctrl1 set to a low level, so that the switch module 102 is in an open state; the controller 406 outputs a detection control signal relay_ctrl2 set to a high level, so that the insulation impedance detection module 101 is in an open state to detect the insulation impedance value of the photovoltaic string; it is determined whether the insulation impedance value is greater than a threshold value; under the condition that the insulation impedance value is greater than the threshold value, the switch control signal relay_ctrl1 is set to a high level, so that the switch module 102 is in a closed state, and the photovoltaic string can be connected to the grid.

[0065] Specifically, Figure 6-Figure 10 As shown, the insulation impedance detection method includes an initialization phase, an insulation impedance detection phase and a grid-connected working phase. For ease of understanding, each phase of the insulation impedance detection method will be described in detail below.

[0066] S1. Initialization phase.

[0067] like Figure 7 and Figure 8 As shown, in the initialization stage, the photovoltaic string has not yet been connected to the grid, and the photovoltaic system performs initialization operations, including but not limited to auxiliary power supply power-on, hardware connection check, sensor calibration, system parameter configuration, etc., and this application does not impose specific restrictions on this. After the photovoltaic system completes the initialization operation, it enters the insulation impedance detection stage.

[0068] Specifically, in the initialization stage, the switch control signal relay_ctrl1 is high, and then the switch drive signal relay_drv1 is high, so that the switch module 102 is in a closed state; the detection control signal relay_ctrl1 is low, and then the detection drive signal relay_drv2 is low, so that the insulation impedance detection module 101 is in a closed state. The photovoltaic system performs initialization operation and self-test, and after determining that the photovoltaic system is normal, it enters the insulation group resistance detection stage.

[0069] S2: Insulation impedance detection stage.

[0070] like Figure 7 and Fig. 9 As shown, in the insulation impedance detection stage, the switch module 102 is in an open circuit state, that is, the inverter neutral line of the photovoltaic system is disconnected from the grid neutral line, and then in the three-phase four-wire mode, it is helpful to avoid the influence of the grid-side grounding loop on the insulation impedance detection of the photovoltaic side. Further, the insulation impedance detection module 101 is in an open state, so as to detect the insulation impedance R P and R n The insulation impedance value of the photovoltaic system is measured and judged whether the insulation impedance value is greater than the threshold value. When the insulation impedance value is greater than the threshold value, that is, the insulation performance of the photovoltaic system has reached the safety standard, the grid-connected working stage is entered.

[0071] Specifically, in the insulation impedance detection stage, the switch control signal relay_ctrl1 is switched to a low level, and then the switch drive signal relay_drv1 is a low level, so that the switch module 102 is in an open circuit state, that is, the electrical connection between the grid side and the neutral line is disconnected, which is beneficial to avoid the influence of the grid side grounding loop on the photovoltaic side insulation impedance detection, and is beneficial to improve the accuracy of insulation impedance detection.

[0072] Further, the detection control signal relay_ctrl2 is switched to a high level, and it can be known from the above content that the low-level switch control signal relay_ctrl1 is inverted by the NOT gate unit 401 and the delay module 1032 delays the setting time △t to obtain a high-level signal, and then the first AND gate unit 402 outputs the intermediate signal relay_ctrl2' as a high level, and the detection drive signal relay_drv2 is a high level, so that the insulation impedance detection module 101 is in the on state, and the insulation impedance to ground R is detected. P and R n The insulation resistance value.

[0073] It is worth mentioning that the delay module 1032 is conducive to making the time when the detection control signal relay_ctrl2 acts on the insulation impedance detection module 101 later than the time when the switch control signal relay_ctrl1 acts on the switch module 102, thereby ensuring that the insulation impedance detection module 101 is started and turned on only after the switch module 102 is completely in the open circuit state, so as to further improve the insulation impedance R to ground. P and R n Accuracy of measurement.

[0074] It should be understood that when the insulation impedance value is greater than the threshold value, that is, the insulation performance of the photovoltaic system has reached the safety standard, the grid-connected operation stage is entered. If the insulation impedance value measured in the insulation impedance detection stage is less than the threshold value, the grid-connected operation is prohibited.

[0075] S3, grid-connected working stage.

[0076] like Figure 7 and Fig.10 As shown, in the grid-connected working stage, the switch control signal relay_ctrl1 is switched to a high level, and then the switch drive signal relay_drv1 is a high level, so that the switch module 102 is in a closed state, and then the neutral line of the inverter is connected to the neutral line of the grid side, and the photovoltaic system is restored to the three-phase four-wire mode, and the relay group is closed to achieve grid-connected work.

[0077] Furthermore, as described above, under the condition that the switch control signal relay_ctrl1 makes the switch module 102 in a closed state, that is, under the condition that the switch control signal relay_ctrl1 is at a high level, the insulation impedance detection module 101 will not be affected by the detection control signal relay_ctrl2 through the NOT gate unit 401 and the first AND gate unit 402, and will remain in a closed state, which is beneficial to reduce the energy loss of the photovoltaic system.

[0078] It should be understood that after determining that the insulation impedance value is greater than the threshold in the insulation impedance detection stage, or in the grid-connected working stage, the detection control signal relay_ctrl2 can be switched to a low level to further ensure that the insulation impedance detection module 101 is in a closed state, which is beneficial to improving the reliability of the photovoltaic system.

[0079] In some embodiments, Fig.11 and Fig.12 As shown, the specific prohibition of grid connection is as follows: the switch control signal relay_ctrl1 and the detection control signal relay_ctrl2 are switched to a low level, so that the intermediate signal relay_ctrl2', the switch drive signal relay_drv1 and the detection drive signal relay_drv2 are all maintained at a low level, thereby making the switch module 102 in an open circuit state, and making the insulation impedance detection module 101 in a closed state, which is conducive to preventing the various modules or devices of the photovoltaic system from being further damaged. Further, the photovoltaic system is suitable for sending an alarm signal, such as an alarm signal sent by the control module 103 or the insulation impedance detection module 101, to prompt the operator to perform detection and maintenance, thereby protecting the various devices of the photovoltaic system and reducing potential safety risks.

[0080] In some embodiments, the insulation impedance detection method further includes the step of setting the intermediate signal relay_ctrl2 ′ to a low level under the condition that the insulation impedance value is greater than a threshold value, so that the insulation impedance detection module 101 is in a closed state.

[0081] It should be understood that, as described above, in the grid-connected working stage, the switch control signal relay_ctrl1 is switched to a high level. If the detection control signal relay_ctr2 is still kept at a high level at this time, due to the effect of the delay module 1032, the intermediate signal relay_ctrl2' will delay the setting time △t before switching from a high level to a low level. That is to say, under the condition that the switch control signal relay_ctrl1 makes the switch module 102 already in a closed state, due to the effect of the delay module 1032, the insulation impedance detection module 101 may still be in an open state or not completely closed, thereby causing partial energy loss of the photovoltaic system.

[0082] In this embodiment, when it is determined that the insulation impedance value is greater than the threshold value, the intermediate signal relay_ctrl2' is immediately set to a low level; or when the switch control signal relay_ctrl1 is switched to a high level, the intermediate signal relay_ctrl2' is switched to a low level, so that before the switch module 102 is in a closed state, or when the switch module 102 is in a closed state, the insulation impedance detection module 101 is in a closed state, so as to save energy of the photovoltaic system.

[0083] In at least one embodiment, when it is determined that the insulation impedance value is greater than a threshold value, or when the switch control signal relay_ctrl1 is switched to a high level, the detection control signal relay_ctr2 is switched to a low level, so that the insulation impedance detection module 101 is in a closed state before the switch module 102 is in a closed state, or when the switch module 102 is in a closed state.

[0084] In some embodiments, the insulation impedance detection method further includes the step of: under the condition that the photovoltaic string is connected to the grid, the controller 406 outputs the switch control signal relay_ctrl1 and sets it to a high level, so that the photovoltaic system works in a three-phase four-wire system; or under the condition that the photovoltaic string is connected to the grid, the controller 406 outputs the switch control signal relay_ctrl1 and sets it to a low level, so that the photovoltaic system works in a three-phase three-wire system. In other words, by switching the switch control signal relay_ctrl1 output by the controller 406 between a high level and a low level, the photovoltaic system can be operated in a three-phase four-wire system or a three-phase three-wire system. It is worth mentioning that under the condition that the photovoltaic system works in a three-phase three-wire system, the practical use of the neutral line can be reduced, which is conducive to simplifying the structure of the photovoltaic system.

[0085] like Fig.13 As shown, taking the photovoltaic system switching from working in a three-phase four-wire system to working in a three-phase three-wire system as an example, as described above, under the condition that the switch control signal relay_ctrl1 makes the switch module 102 in a closed state, the photovoltaic system works in a three-phase four-wire system, and the insulation impedance detection module 101 will not be affected by the detection control signal relay_ctrl2 and remain in a closed state. Further, under the condition that the switch control signal relay_ctrl1 makes the switch module 102 in an open circuit state, the inverter neutral line of the photovoltaic system is disconnected from the grid side neutral line, so that the photovoltaic system works in a three-phase three-wire system.

[0086] It should be understood that, as described above, when the photovoltaic system operates in a three-phase three-wire system, the insulation impedance detection module 101 is affected by the detection control signal relay_ctrl2 and is turned on or off according to whether the inverter is started.

[0087] In at least one embodiment, Fig.13As shown, after the photovoltaic system switches from working in a three-phase four-wire system to working in a three-phase three-wire system, the controller 406 outputs a detection control signal relay_ctrl2 of a high level, so that the insulation impedance detection module 101 is in an on state, so that the insulation impedance detection on the photovoltaic side can be performed. After it is detected that the insulation impedance value to the ground meets the requirements, the detection control signal relay_ctrl2 is switched to a low level, so that the insulation impedance detection module 101 is in a off state, which is beneficial to improve the reliability and safety of the photovoltaic system.

[0088] In some embodiments, the photovoltaic system further includes insulation impedance detection on the grid side, that is, an insulation impedance detection module 101 is respectively provided on the photovoltaic side and the grid side of the photovoltaic system to further improve the reliability and safety of the photovoltaic system. It should be known that before the inverter is started, the grid side is not affected by the photovoltaic side, and the specific structure and working principle of the insulation impedance detection on the grid side are well-known technologies to those skilled in the art, so they will not be elaborated in detail here.

[0089] The above describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention to be protected. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. An insulation impedance detection architecture, characterized in that: include: A switch module, wherein the switch module is connected between the inverter neutral line of the photovoltaic system and the grid neutral line, so as to connect or disconnect the inverter neutral line and the grid neutral line; An insulation impedance detection module, wherein the insulation impedance detection module is used to detect the insulation status of the photovoltaic string to the ground; as well as A control module, wherein the control module includes a controller, wherein the controller is adapted to output a control signal to control the state of the switch module and the state of the insulation impedance detection module, so that when the insulation impedance detection module is in an on state, the switch module is in an open circuit state.

2. The insulation impedance detection architecture according to claim 1, characterized in that: The controller is suitable for outputting a switch control signal relay_ctrl1 and a detection control signal relay_ctrl2, wherein the switch control signal relay_ctrl1 acts on the switch module to control the state of the switch module, and the switch control signal relay_ctrl1 and the detection control signal relay_ctrl2 act together on the insulation impedance detection module, so that when the switch module is in an open circuit state, the insulation impedance detection module is suitable for being in an open state.

3. The insulation impedance detection architecture according to claim 2, characterized in that: The control module also includes a NOT gate unit and a first AND gate unit, the input end of the NOT gate unit is used to receive the switch control signal relay_ctrl1, one of the input ends of the first AND gate unit is used to receive the output signal of the NOT gate unit, the other input end of the first AND gate unit is used to receive the detection control signal relay_ctrl2, and the first AND gate unit outputs an intermediate signal relay_ctrl2' to act on the insulation impedance detection module, so that when the switch module is in an open circuit state, the insulation impedance detection module is suitable to be in an open state.

4. The insulation impedance detection architecture according to claim 2, characterized in that: The control module also includes a delay module. The switch control signal relay_ctrl1 output by the controller passes through the delay module for a set time △t, and then acts on the insulation impedance detection module together with the detection control signal relay_ctrl2, so that when the insulation impedance detection module is in an on state, the switch module is in an open circuit state.

5. The insulation impedance detection architecture according to claim 4, characterized in that: The delay module includes a second AND gate unit, one of the input ends of the second AND gate unit is connected to the controller, and the other input ends of the second AND gate unit are all set high, so that the output signal of the second AND gate unit is suitable for adjustment according to the switch control signal relay_ctrl1, and the output signal of the second AND gate unit and the detection control signal relay_ctrl2 act together on the insulation impedance detection module, so that when the insulation impedance detection module is in the turned-on state, the switch module is in the open circuit state.

6. The insulation impedance detection architecture according to any one of claims 2 to 5, characterized in that: The insulation impedance detection architecture also includes a protection unit and a third AND gate unit, the protection unit is suitable for outputting a blocking signal relay_block, one of the input ends of the third AND gate unit is used to receive the output blocking signal relay_block, the other input end of the third AND gate unit is used to receive the switch control signal relay_ctrl1, and the third AND gate unit outputs a switch drive signal relay_drv1 to act on the switch module to control the state of the switch module.

7. The insulation impedance detection architecture according to any one of claims 2 to 5, characterized in that: The insulation impedance detection architecture also includes a protection unit and a fourth AND gate unit, the protection unit is suitable for outputting a blocking signal relay_block, one of the input ends of the fourth AND gate unit is used to receive the output blocking signal relay_block, and the other input end of the fourth AND gate unit is connected to the controller, so that the output signal of the fourth AND gate unit is suitable for adjustment according to the blocking signal relay_block, the switch control signal relay_ctrl1 and the detection control signal relay_ctrl2, and the fourth AND gate unit outputs a detection drive signal relay_drv2 to act on the insulation impedance detection module to control the state of the insulation impedance detection module.

8. An insulation impedance detection method using the insulation impedance detection architecture described in any one of claims 1 to 7, characterized in that: The steps include: The controller output switch control signal relay_ctrl1 of the control module is set to a low level, so that the switch module is in an open circuit state; The controller output detection control signal relay_ctrl2 is set to a high level, so that the insulation impedance detection module is in an on state to detect the insulation impedance value of the photovoltaic string; Determining whether the insulation resistance value is greater than a threshold; Under the condition that the insulation impedance value is greater than the threshold value, the switch control signal relay_ctrl1 is set to a high level, so that the switch module is in a closed state, and the photovoltaic string can be connected to the grid.

9. The insulation impedance detection method according to claim 8, characterized in that: The method further includes the step of setting the output intermediate signal relay_ctrl2' of the first AND gate unit of the control module to a low level under the condition that the insulation impedance value is greater than a threshold value, so that the insulation impedance detection module is in a closed state.

10. The insulation impedance detection method according to claim 8, characterized in that: The method also includes the following steps: when the photovoltaic string is connected to the grid, the controller outputs the switch control signal relay_ctrl1 and sets it to a high level, so that the photovoltaic system operates in a three-phase four-wire system; or when the photovoltaic string is connected to the grid, the controller outputs the switch control signal relay_ctrl1 and sets it to a low level, so that the photovoltaic system operates in a three-phase three-wire system.

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