Grounding form detection circuit and photovoltaic system

Abstract

The utility model discloses a grounding form detection circuit and a photovoltaic system. The grounding form detection circuit comprises a control module, at least one DC input end and at least one detection branch. The detection branch comprises a current detection module and a voltage amplification module; the first input end of the voltage amplification module is connected with the first output end of the current detection module, the second input end of the voltage amplification module is connected with the second output end of the current detection module, and the voltage amplification module is used for converting the current signal into a voltage signal, amplifying the voltage signal and outputting the amplified voltage signal to the control module; the control module is used for determining that the grounding form of the transformer is a neutral point grounding system when at least one voltage signal is greater than a first set threshold value, and determining that the grounding form of the transformer is a neutral point non-grounding system when the voltage signals are smaller than the first set threshold value. According to the utility model, the grounding form of the transformer can be automatically identified, so that manual identification is replaced, identification errors are reduced, and the photovoltaic inverter can be prevented from being damaged.

Description

Technical Field

[0001] The utility model relates to the technical field of photovoltaic inversion, in particular to a grounding form detection circuit and a photovoltaic system. Background Art

[0002] With the development of photovoltaic technology, more and more inverters are equipped with the Potential Induced Degradation (PID) function as standard. This function includes daytime suppression and nighttime repair. When photovoltaic inverters are equipped with this function, the degradation of photovoltaic modules can be further reduced, and even "zero" degradation can be achieved, thereby increasing the power generation of the power station.

[0003] There are two common transformer connection methods for photovoltaic systems: ungrounded neutral and grounded neutral. The inverter's PID protection function only applies to ungrounded neutral systems. Enabling the PID protection function in a grounded neutral system can damage the inverter. Therefore, correctly identifying the transformer grounding method in a photovoltaic inverter system is crucial.

[0004] Existing measures restrict the transformer grounding type of PV inverters through specifications or user manuals. Identifying transformer grounding types requires specialized knowledge and is prone to human error. If the PV system transformer grounding type is misidentified, the PV inverter's anti-PID function remains enabled, which can easily damage the inverter and cause significant losses. Utility Model Content

[0005] The utility model provides a grounding form detection circuit and a photovoltaic system, which can automatically identify the grounding form of a transformer, thereby replacing manual identification, reducing identification errors, and thus facilitating the prevention of damage to the photovoltaic inverter.

[0006] In a first aspect, an embodiment of the present invention provides a grounding type detection circuit, which is applied to a photovoltaic system, wherein the photovoltaic system includes a solar panel, a photovoltaic inverter and a transformer, the input end of the photovoltaic inverter is connected to the solar panel, and the output end of the photovoltaic inverter is connected to the transformer; the grounding type detection circuit includes: a control module, at least one DC input end and at least one detection branch, each detection branch corresponding to the DC input end; the DC input end is used to be electrically connected to the photovoltaic inverter; the detection branch includes a current detection module and a voltage amplification module; the input end of the current detection module is connected to the DC input end, and is used to collect the current signal flowing through the DC input end and convert the current signal into a voltage signal; the input end of the voltage amplification module is connected to the output end of the current detection module, and the output end of the voltage amplification module is connected to the input end of the control module, and is used to amplify the voltage signal and output it to the control module; the control module is used to determine that the grounding type of the transformer is a neutral point grounding system when at least one voltage signal is greater than a first set threshold, and to determine that the grounding type of the transformer is a neutral point ungrounded system when all voltage signals are less than the first set threshold.

[0007] Optionally, the current detection module includes a current detection unit and a first capacitor, the current detection unit includes a current transformer or a Hall current sensor; the first end of the current detection unit is connected to the DC input end, the second end of the current detection unit is connected to the first capacitor, and the second end of the first capacitor is grounded; the third end of the current detection unit is connected to the first input end of the voltage amplification module, and the fourth end of the current detection unit is connected to the second input end of the voltage amplification module.

[0008] Optionally, the voltage amplification module includes a first resistor, a second resistor, a third resistor, a fourth resistor, a second capacitor, a third capacitor and a first operational amplifier; the first end of the first resistor serves as the first input end of the voltage amplification module, and the second end of the first resistor is connected to the inverting input end of the first operational amplifier; the first end of the second resistor serves as the second input end of the voltage amplification module, and the second end of the second resistor is connected to the non-inverting input end of the first operational amplifier; the first end of the third resistor is connected to the inverting input end of the first operational amplifier, and the second end of the third resistor is connected to the output end of the first operational amplifier, and the output end of the first operational amplifier serves as the output end of the voltage amplification module; the second capacitor is connected to the third resistor in parallel; the first end of the fourth resistor is connected to the non-inverting input end of the first operational amplifier, the second end of the fourth resistor is grounded, and the third capacitor is connected to the fourth resistor in parallel.

[0009] Optionally, the detection branch also includes a switch module; the control end of the switch module is connected to the output end of the control module, the first end of the switch module is connected to the DC input end, the second end of the switch module is connected to the input end of the current detection module, and the control module is also used to control the conduction state of the switch module.

[0010] Optionally, the switch module includes a first switch unit and a second switch unit; the control end of the first switch unit serves as the control end of the switch module, the first end of the first switch unit is grounded, and the second end of the first switch unit is connected to the first end of the second switch unit; the second end of the second switch unit is connected to the first voltage, the third end of the second switch unit serves as the first end of the switch module, and the fourth end of the second switch unit serves as the second end of the switch module.

[0011] Optionally, the first switch unit includes a transistor, a fifth resistor and a sixth resistor; the first end of the fifth resistor serves as the control end of the first switch unit, the second end of the fifth resistor is connected to the gate of the transistor, the first pole of the transistor serves as the first end of the first switch unit, and the second pole of the transistor serves as the second end of the second switch unit; and / or, the second switch unit includes a relay, the relay includes a coil and a contact; the first end of the coil serves as the first end of the second switch unit, and the second end of the coil serves as the second end of the second switch unit; the first end of the contact serves as the third end of the second switch unit, and the second end of the contact serves as the fourth end of the second switch unit.

[0012] Optionally, the detection branch also includes a voltage follower; the voltage amplification module is connected to the input end of the control module through the voltage follower; the voltage follower includes a second operational amplifier, a seventh resistor and an eighth resistor; the first end of the seventh resistor is connected to the output end of the voltage amplification module, and the second end of the seventh resistor is connected to the in-phase input end of the second operational amplifier; the first end of the eighth resistor is connected to the second voltage, and the second end of the eighth resistor is connected to the second end of the seventh resistor; the inverting input of the second operational amplifier is single-endedly connected to the output end of the second operational amplifier, the output end of the second operational amplifier is connected to the input end of the control module, the first power supply end of the second operational amplifier is connected to the third voltage, and the second power supply end of the second operational amplifier is grounded.

[0013] Optionally, the grounding form detection circuit also includes a DC power supply; the input end of the DC power supply is connected to the DC input end or the output end of the photovoltaic inverter, and the output end of the DC power supply is connected to the power input end of the current detection module and the power input end of the control module, and is used to power the current detection module and the control module when the open circuit voltage of the solar panel is greater than the second set threshold.

[0014] Optionally, the grounding form detection circuit also includes a communication module, and the control module is connected to the photovoltaic inverter through the communication module. The control module is used to send a first control signal when it is determined that the grounding form of the transformer is a neutral point grounding system, and send a second control signal when it is determined that the grounding form of the transformer is a neutral point ungrounded system.

[0015] The grounding type detection circuit provided by the present invention includes a control module, at least one DC input terminal, and at least one detection branch. The current detection module collects the current signal flowing through the DC input terminal and converts the current signal into a voltage signal. The voltage amplification module amplifies the voltage signal and outputs it to the control module. The control module determines that the transformer grounding type is a neutral-grounded system when at least one voltage signal is greater than a first set threshold and outputs a first control signal. Upon receiving the first control signal, the photovoltaic inverter disables the anti-PID function, thereby preventing damage to the photovoltaic inverter and providing protection. When all voltage signals are less than the first set threshold, the control module determines that the transformer grounding type is an ungrounded neutral system and outputs a second control signal. Upon receiving the second control signal, the photovoltaic inverter enables the anti-PID function. In other words, the grounding type detection circuit provided by the present invention can automatically identify the transformer grounding type, replacing manual identification and reducing identification errors, thereby preventing damage to the photovoltaic inverter.

[0016] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present invention, nor is it intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 This is a schematic structural diagram of a photovoltaic system provided by an embodiment of the present utility model;

[0019] Figure 2 This is a structural diagram of a grounding detection circuit provided by an embodiment of the present utility model;

[0020] Figures 3 to 7 This is a schematic diagram of a transformer connection method in a photovoltaic system provided by an embodiment of the utility model.

[0021] Figure 8 This is a leakage current sampling waveform diagram provided by an embodiment of the present utility model;

[0022] Figure 9 This is another leakage current sampling waveform diagram provided by an embodiment of the present utility model;

[0023] Figure 10This is a structural diagram of another grounding detection circuit provided by an embodiment of the present utility model;

[0024] Figure 11 This is a structural diagram of another grounding detection circuit provided by an embodiment of the present utility model;

[0025] Figure 12 This is a structural diagram of another grounding detection circuit provided by an embodiment of the present utility model;

[0026] Figure 13 This is a structural diagram of another grounding detection circuit provided by an embodiment of the present utility model;

[0027] Figure 14 This is a structural diagram of another grounding detection circuit provided by an embodiment of the present utility model;

[0028] Figure 15 This is a structural diagram of another grounding detection circuit provided by an embodiment of the present utility model;

[0029] Figure 16 This is a structural diagram of another grounding detection circuit provided by an embodiment of the present utility model. DETAILED DESCRIPTION

[0030] In order to help those skilled in the art better understand the present invention, the following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0031] It should be noted that the terms "first," "second," and the like in the specification and claims of the present invention and the accompanying drawings are used to distinguish similar items and are not necessarily used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, such that the embodiments of the present invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "including," "having," and any variations thereof are intended to cover non-exclusive inclusions.

[0032] Figure 1 It is a structural schematic diagram of a photovoltaic system provided by an embodiment of the present utility model. Figure 2 This is a schematic diagram of a grounding detection circuit provided by an embodiment of the present utility model. Figure 1 and Figure 2The grounding form detection circuit 1 is applied to a photovoltaic system, which includes a solar panel 2, a photovoltaic inverter 3 and a transformer 4. The input end of the photovoltaic inverter 3 is connected to the solar panel 2, and the output end of the photovoltaic inverter 3 is connected to the transformer 4.

[0033] The grounding type detection circuit 1 includes: a control module 11, at least one DC input terminal 12 and at least one detection branch 13, each detection branch 13 is connected to a corresponding DC input terminal 12; the DC input terminal 12 is used to be electrically connected to the photovoltaic inverter 3. Figure 2 The schematic diagram shows that the grounding type detection circuit 1 includes two DC input terminals 12 and two detection branches 13 .

[0034] The detection branch 13 includes a current detection module 131 and a voltage amplification module 132. The input end of the current detection module 131 is connected to the DC input end 12, and is used to collect the current signal flowing through the DC input end 12.

[0035] The input end of the voltage amplifying module 132 is connected to the output end of the current detecting module 131 , and the output end of the voltage amplifying module 132 is connected to the input end of the control module 11 , for converting the current signal into a voltage signal and amplifying the voltage signal and outputting it to the control module 11 .

[0036] Control module 11 is configured to determine that transformer 4 is grounded in a neutral-point grounded system when at least one voltage signal is greater than a first set threshold, and to determine that transformer 4 is grounded in an ungrounded neutral-point system when all voltage signals are less than the first set threshold. Communication port P1 of control module 11 is connected to photovoltaic inverter 3.

[0037] Specifically, Figures 3 to 7 This is a schematic diagram of transformer connection in a photovoltaic system provided by an embodiment of the utility model. Figure 3 The winding of the transformer 4 connected to the output side of the photovoltaic inverter is connected in a star configuration, with the neutral point N line grounded, and the grid side is connected in a delta configuration; Figure 4 The figure shows that the winding of transformer 4 connected to the output side of the photovoltaic inverter is connected in star connection, the neutral point N line is not grounded, and the grid side is connected in delta connection; Figure 5 As shown, the winding of the transformer 4 connected to the output side of the photovoltaic inverter is in star connection, and the neutral point N line is grounded, and the grid side is in star connection; Figure 6 The figure shows that the winding of transformer 4 on the output side of the photovoltaic inverter is connected in star connection, the neutral point N line is not grounded, and the grid side is connected in star connection; Figure 7 As shown, the winding of the transformer 4 connected on the output side of the photovoltaic inverter is connected in a delta connection, and the grid side is connected in a star connection.

[0038] The control module 11 may include a microcontroller. Optionally, the control module 11 may include a single chip microcomputer, a digital signal processor (DSP) or an ARM (Advanced RISC Machines) processor.

[0039] The DC input terminal 12 can be directly connected to the input terminal of the photovoltaic inverter 3, or indirectly connected to the output terminal of the photovoltaic inverter 3. For example, the DC input terminal 12 can be indirectly connected to the output terminal of the photovoltaic inverter 3 through a rectifier module. The rectifier module is used to convert the AC power output by the photovoltaic inverter 3 into DC power and output it to the DC input terminal 12 of the grounding form detection circuit 1. Figure 1 The schematic diagram shows a case where the DC input terminal 12 is directly connected to the input terminal of the photovoltaic inverter 3 .

[0040] The current detection module 131 can be various electronic devices or circuit components. The current detection module 131 can be a resistor, a Hall current sensor, or a current transformer. For example, a Hall current sensor uses the Hall effect to detect current. When current passes through a conductor, a magnetic field is generated around the conductor. When the Hall current sensor is placed in this magnetic field, a Hall voltage is generated that is proportional to the magnetic field strength (i.e., the current magnitude).

[0041] The voltage amplification module 132 may include one or more amplifiers, which may be transistor amplifiers, operational amplifiers, or other types of amplifiers. The function of the amplifier is to amplify the input signal and increase the power of the signal, so that the amplitude of the output signal is greater than the amplitude of the input signal.

[0042] In some embodiments, the grounding form detection circuit 1 includes a DC input terminal 12 and a detection branch 13. The DC input terminal 12 can be indirectly connected to the output terminal of the photovoltaic inverter 3, or directly connected to the positive voltage input terminal or the negative voltage input terminal of the photovoltaic inverter 3.

[0043] In some embodiments, the grounding type detection circuit 1 includes two DC input terminals 12 and two detection branches 13. The two DC input terminals include a first DC input terminal and a second DC input terminal. The two detection branches 13 include a first detection branch and a second detection branch. The first detection branch is connected to the first DC input terminal, and the second detection branch is connected to the second DC input terminal. The first DC input terminal is connected to the positive voltage input terminal of the photovoltaic inverter 3, and the second DC input terminal is connected to the negative voltage input terminal of the photovoltaic inverter 3. This configuration can improve detection accuracy.

[0044] In some embodiments, the grounding type detection circuit 1 includes at least three DC input terminals 12 and at least three detection branches 13. At least one DC input terminal 12 is connected to the positive voltage input terminal of the photovoltaic inverter 3, and at least one DC input terminal 12 is connected to the negative voltage input terminal of the photovoltaic inverter 3. Exemplarily, the at least three DC input terminals 12 include a first DC input terminal, a second DC input terminal, and a third DC input terminal. The first DC input terminal and the second DC input terminal are connected to the positive voltage input terminal of the photovoltaic inverter 3, and the third DC input terminal is connected to the negative voltage input terminal of the photovoltaic inverter 3.

[0045] Continue to see Figure 1 and Figure 2 The working principle of the grounding form detection circuit 1 provided in the embodiment of the present utility model is as follows:

[0046] When the photovoltaic inverter 3 is connected to the grid and operates, if the grounding form of the transformer is a neutral point grounding system, the leakage current of the photovoltaic system will flow from the input end of the current detection module 131 to the chassis ground of the grounding form detection circuit 1, thereby forming a loop with the ground of the transformer 4. At this time, the output end of the current detection module 131 will output a voltage signal, which is amplified by the voltage amplifier module 132 and input into the analog-to-digital converter (ADC) channel of the control module 11. The control module 11 compares the internal data with the first set threshold value. When at least one voltage signal is greater than the first set threshold value, the control module 11 determines that the grounding form of the transformer 4 is a neutral point grounding system, outputs a first control signal, and transmits the first control signal to the photovoltaic inverter 3. After receiving the first control signal, the photovoltaic inverter 3 prohibits the anti-PID function from being enabled, which is beneficial to avoid damage to the photovoltaic inverter 3 and plays a protective role. The leakage current sampling waveform is shown in the figure below. Figure 8 shown.

[0047] When the photovoltaic inverter 3 is connected to the grid, if no leakage current is collected in the ground loop from the input end of the current detection module 131 to the chassis, it can be confirmed that the grounding form of the transformer 4 is a neutral point ungrounded system, and the second control signal is output and transmitted to the photovoltaic inverter 3. After receiving the second control signal, the photovoltaic inverter 3 can normally enable the anti-PID function and the photovoltaic inverter will not be damaged. The leakage current sampling waveform is shown in FIG. Figure 9 As shown. Among them, Figure 8 and Figure 9 The horizontal axis is time t, and the vertical axis is current I.

[0048] It should be noted that the embodiment of the present invention does not specifically limit the specific value of the first set threshold value, and can be set according to actual conditions. For example, the first set threshold value can be 1.5V.

[0049] The PV inverter's PID prevention function is designed to prevent performance degradation of the solar panels 2 due to potential differences during long-term operation. In a PV system, the potential difference between the solar panels 2 and the ground can generate leakage current within the panels 2 when it reaches a certain level. This PID phenomenon can cause the panels' output power to drop, reducing the overall efficiency of the PV system. The PID prevention function can mitigate this performance degradation and improve the PV system's power generation efficiency.

[0050] The grounding type detection circuit provided by the present invention includes a control module, at least one DC input terminal, and at least one detection branch. The current detection module collects the current signal flowing through the DC input terminal and converts the current signal into a voltage signal. The voltage amplification module amplifies the voltage signal and outputs it to the control module. The control module determines that the transformer grounding type is a neutral-grounded system when at least one voltage signal is greater than a first set threshold and outputs a first control signal. Upon receiving the first control signal, the photovoltaic inverter disables the anti-PID function, thereby preventing damage to the photovoltaic inverter and providing protection. When all voltage signals are less than the first set threshold, the control module determines that the transformer grounding type is an ungrounded neutral system and outputs a second control signal. Upon receiving the second control signal, the photovoltaic inverter enables the anti-PID function. In other words, the grounding type detection circuit provided by the present invention can automatically identify the transformer grounding type, replacing manual identification and reducing identification errors, thereby preventing damage to the photovoltaic inverter.

[0051] Figure 10 This is a schematic diagram of another grounding detection circuit provided by the embodiment of the present utility model. Figure 10 As shown, the current detection module 131 includes a current detection unit CT1 and a first capacitor C1. The current detection unit CT1 includes a current transformer or a Hall current sensor.

[0052] A first end of the current detection unit CT1 is connected to the DC input terminal 12 , a second end of the current detection unit CT1 is connected to the first capacitor C1 , and a second end of the first capacitor C1 is grounded.

[0053] The third terminal of the current detection unit CT1 is connected to the first input terminal of the voltage amplification module 132 , and the fourth terminal of the current detection unit CT1 is connected to the second input terminal of the voltage amplification module 132 .

[0054] Specifically, the first capacitor C1 is used to provide a current discharge path to the chassis ground for the leakage current on the primary coil of the current detection unit CT1. The present embodiment does not specifically limit the capacitance value of the first capacitor C1 and can be set according to actual needs.

[0055] Figure 11 This is a schematic diagram of another grounding detection circuit provided by the embodiment of the present utility model. Figure 11 As shown, the voltage amplification module 132 includes a first resistor R1 , a second resistor R2 , a third resistor R3 , a fourth resistor R4 , a second capacitor C2 , a third capacitor C3 and a first operational amplifier U1 .

[0056] The first end of the first resistor R1 serves as the first input of the voltage amplification module 132, and the second end of the first resistor R1 is connected to the inverting input of the first operational amplifier U1. The first end of the second resistor R2 serves as the second input of the voltage amplification module 132, and the second end of the second resistor R2 is connected to the non-inverting input of the first operational amplifier U1. The first end of the third resistor R3 is connected to the inverting input of the first operational amplifier U1, and the second end of the third resistor R3 is connected to the output of the first operational amplifier U1, and the output of the first operational amplifier U1 serves as the output of the voltage amplification module 132. The second capacitor C2 is connected in parallel with the third resistor R3. The first end of the fourth resistor R4 is connected to the non-inverting input of the first operational amplifier U1, the second end of the fourth resistor R4 is grounded, and the third capacitor C3 is connected in parallel with the fourth resistor R4.

[0057] Specifically, the first resistor R1 and the second resistor R2 play the role of current limiting and voltage dividing in the input loop of the first operational amplifier U1 , and participate in determining the input signal size of the first operational amplifier U1 .

[0058] The first end of the third resistor R3 is connected to the inverting input of the first operational amplifier U1, and the second end is connected to the output of the first operational amplifier U1, forming a feedback loop. This feedback loop determines the amplification factor of the first operational amplifier U1. The second capacitor C2, connected in parallel with the third resistor R3, acts as a filter, reducing noise and interference in the circuit and making the output signal more stable.

[0059] The first end of the fourth resistor R4 is connected to the non-inverting input of the first operational amplifier U1, and the second end is grounded. The fourth resistor R4 provides a ground reference for the non-inverting input of the first operational amplifier U1 and, together with the second resistor R2, determines the magnitude of the input signal at the non-inverting input of the first operational amplifier U1.

[0060] The third capacitor C3 is connected in parallel with the fourth resistor R4 to play a filtering role, further reducing noise and interference in the input signal.

[0061] The first operational amplifier (U1) is the core component of the voltage amplifier module, amplifying the input signal. Its inverting and non-inverting inputs receive the input signal from the resistor network. Based on the feedback loop (composed of the third resistor R3 and the second capacitor C2) and the internal characteristics of the first operational amplifier, it amplifies the input signal and outputs the amplified voltage signal from its output.

[0062] Figure 12 This is a schematic diagram of another grounding detection circuit provided by the embodiment of the present utility model. Figure 12 As shown, the detection branch 13 also includes a switch module 133, the control end ctr1 of the switch module 133 is connected to the output end of the control module 11, the first end of the switch module 133 is connected to the DC input end 12, and the second end of the switch module 133 is connected to the input end of the current detection module 131. The control module 11 is also used to control the conduction state of the switch module 133.

[0063] The switch module 133 includes a switch that implements on-off control via an electrical signal, or a switch that implements on-off control based on the characteristics of the component itself. The switch module 133 can be either a unidirectional switch, such as a unidirectional switch consisting of a bidirectional switch connected in series with a diode, or a bidirectional switch, such as a metal oxide semiconductor field effect transistor (MOSFET) or an insulated gate bipolar transistor (IGBT) with an anti-parallel freewheeling diode.

[0064] Continue to refer Figure 1 and Figure 12 The working principle of the grounding form detection circuit 1 provided in the embodiment of the present utility model is as follows:

[0065] When solar panel 2 is exposed to sunlight, its open-circuit voltage continues to rise. When the open-circuit voltage of solar panel 2 exceeds a second predetermined threshold, the DC power supply within grounding type detection circuit 1 begins operating, supplying power to current detection module 131, voltage amplification module 132, and control module 11. Control module 11 then begins operating, turning switch module 133 on. The present embodiment does not impose any specific limitations on the value of the second predetermined threshold; it may be set based on practical circumstances. For example, the second predetermined threshold may be 500V.

[0066] When photovoltaic inverter 3 is grid-connected and operating, if the transformer grounding type is a neutral-grounded system, leakage current from the photovoltaic system will flow from the input of current detection module 131 to the chassis ground of grounding type detection circuit 1, thereby forming a loop with the ground of transformer 4. At this point, the output of current detection module 131 will output a voltage signal. This voltage signal is amplified by voltage amplifier module 132 and input into the analog-to-digital converter (ADC) channel of control module 11. Control module 11 performs internal data conversion and compares it with a first set threshold. When at least one voltage signal is greater than the first set threshold, control module 11 determines that transformer 4 is grounded as a neutral-grounded system, outputs a first control signal, and transmits the first control signal to photovoltaic inverter 3. Upon receiving the first control signal, photovoltaic inverter 3 disables the anti-PID function, thereby preventing damage to photovoltaic inverter 3 and providing protection.

[0067] When photovoltaic inverter 3 is grid-connected, if no leakage current is detected in the circuit from the input of current detection module 131 to the chassis ground, it can be confirmed that transformer 4 is grounded with an ungrounded neutral point. A second control signal is then output and transmitted to photovoltaic inverter 3. After receiving the second control signal, photovoltaic inverter 3 can normally enable the anti-PID function, and the photovoltaic inverter will not be damaged.

[0068] Figure 13 This is a schematic diagram of another grounding detection circuit provided by the embodiment of the present utility model. Figure 13 As shown, the switch module 133 includes a first switch unit 1331 and a second switch unit 1332; the control end of the first switch unit 1331 serves as the control end ctr1 of the switch module 133, the first end of the first switch unit 131 is grounded, and the second end of the first switch unit 1331 is connected to the first end of the second switch unit 1332; the second end of the second switch unit 1332 is connected to the first voltage VCC1, the third end of the second switch unit 1332 serves as the first end of the switch module 133, and the fourth end of the second switch unit 1332 serves as the second end of the switch module 133. As a preferred embodiment provided by the present invention, Figure 14 This is a schematic diagram of another grounding detection circuit provided by the embodiment of the present utility model. Figure 14 As shown, the first switch unit 1331 includes a transistor T1, a fifth resistor R5 and a sixth resistor R6.

[0069] The first end of the fifth resistor R5 serves as the control end of the first switch unit 1331, the second end of the fifth resistor R5 is connected to the gate of the transistor T1, the first electrode of the transistor T1 serves as the first end of the first switch unit 1331, and the second electrode of the transistor T1 serves as the second end of the second switch unit 1332.

[0070] And / or, the second switch unit 1332 includes a relay K1, which includes a coil S1 and a contact ab; the first end of the coil S1 serves as the first end of the second switch unit 1332, and the second end of the coil S1 serves as the second end of the second switch unit 1332. The first end of the contact K1 serves as the third end of the second switch unit 1332, and the second end of the contact K1 serves as the fourth end of the second switch unit 1332.

[0071] Specifically, the present embodiment of the present invention does not specifically limit the type of relay K1. For example, relay K1 may be a solid-state relay or a reed relay. Alternatively, it may be replaced with a switching device such as an IGBT or MOS transistor. The present embodiment of the present invention does not specifically limit the type of transistor T1. For example, transistor T1 may be a triode, an IGBT, or a MOS transistor.

[0072] Continue to refer Figure 1 and Figure 14 The working principle of the grounding form detection circuit 1 provided in the embodiment of the present utility model is as follows:

[0073] When solar panel 2 is exposed to sunlight, its open-circuit voltage continues to rise. When the open-circuit voltage of solar panel 2 exceeds a second set threshold, the DC power supply within grounding type detection circuit 1 begins operating, supplying power to current detection module 131, voltage amplification module 132, and control module 11. Control module 11 begins operating by outputting a high level via its input / output pins to the voltage divider circuit formed by the fifth resistor R5 and the sixth resistor R6, which drives transistor T1 to conduct, thereby energizing coil S1 of relay K1 and closing contacts ab of relay K1.

[0074] When photovoltaic inverter 3 is grid-connected and operating, if the transformer grounding type is a neutral-grounded system, leakage current from the photovoltaic system will flow through relay K1 and the input of current detection module 131 within grounding type detection circuit 1, all the way to the chassis ground of grounding type detection circuit 1, thereby forming a loop with the ground of transformer 4. At this point, the output of current detection module 131 will output a voltage signal. This voltage signal is amplified by voltage amplifier module 132 and input into the ADC channel of control module 11. Control module 11 performs internal data conversion and compares it with a first set threshold. If at least one voltage signal is greater than the first set threshold, control module 11 determines that transformer 4 is grounded as a neutral-grounded system, outputs a first control signal, and transmits the first control signal to photovoltaic inverter 3. Upon receiving the first control signal, photovoltaic inverter 3 disables the anti-PID function, thereby preventing damage to photovoltaic inverter 3 and providing protection.

[0075] When photovoltaic inverter 3 is grid-connected, if no leakage current is detected in the circuit from the input of current detection module 131 to the chassis ground, it can be confirmed that transformer 4 is grounded with an ungrounded neutral point. A second control signal is then output and transmitted to photovoltaic inverter 3. After receiving the second control signal, photovoltaic inverter 3 can normally enable the anti-PID function, and the photovoltaic inverter will not be damaged.

[0076] Figure 15 This is a schematic diagram of another grounding detection circuit provided by the embodiment of the present utility model. Figure 15 As shown, the detection branch 13 further includes a voltage follower 134. The voltage amplification module 132 is connected to the input end of the control module 11 via the voltage follower 134. The voltage follower 134 includes a second operational amplifier U2, a seventh resistor R7, and an eighth resistor R8.

[0077] A first end of a seventh resistor R7 is connected to the output of the voltage amplifier module 132, and a second end of the seventh resistor R7 is connected to the non-inverting input of the second operational amplifier U2. A first end of an eighth resistor R8 is connected to the second voltage VCC2, and a second end of the eighth resistor R8 is connected to the second end of the seventh resistor R7. The inverting input of the second operational amplifier U2 is connected to the output of the second operational amplifier U2, and the output of the second operational amplifier U2 is connected to the input of the control module 11. A first power supply terminal of the second operational amplifier U2 is connected to the third voltage VCC3, and a second power supply terminal of the second operational amplifier U2 is grounded.

[0078] Specifically, the inverting input of the second operational amplifier U2 is connected to its output, ideally ensuring that its amplification factor is 1. This ensures that the output closely follows the input signal, resulting in high input impedance and low output impedance. The addition of a voltage follower 134 to the detection branch 13 provides isolation, buffering, and enhanced signal driving capability, ensuring that the amplified signal is stably and accurately transmitted to the control module 11.

[0079] Optionally, continue to refer to Figure 15 The grounding form detection circuit 1 also includes a DC power supply 14, an input end of the DC power supply 14 is connected to the DC input end 12 or the output end of the photovoltaic inverter 3, and an output end of the DC power supply 14 is connected to the power input end of the current detection module 131 and the power input end of the control module 11, and is used to power the current detection module 131 and the control module 11 when the open-circuit voltage of the solar panel 2 is greater than the second set threshold.

[0080] Specifically, the DC power supply 14 is an electronic device capable of providing a stable DC voltage output. The DC power supply 14 may include at least two DC power conversion modules and at least two AC power conversion modules. The DC power conversion modules are configured to convert an open-circuit voltage into a first voltage VCC1, a second voltage VCC2, and a third voltage VCC3. The AC power conversion modules are configured to convert the AC power output by the photovoltaic inverter 3 into a first voltage VCC1, a second voltage VCC2, and a third voltage VCC3. The first voltage VCC1, the second voltage VCC2, and the third voltage VCC3 may have different magnitudes. For example, the first voltage VCC1 may be 12V, the second voltage VCC2 may be 3V, and the third voltage VCC3 may be 5V.

[0081] Open-circuit voltage refers to the voltage across the solar panel 2 when no load is connected. If the open-circuit voltage exceeds a preset second threshold, it indicates that the output voltage of the solar panel 2 is high, possibly indicating a specific operating state. In this case, the DC power supply 14 is activated to power the current detection module 131 and the control module 11, thereby detecting and monitoring the grounding condition of the transformer 4.

[0082] Optionally, continue to refer to Figure 15 The grounding form detection circuit 1 also includes a communication module 15, and the control module 11 is connected to the photovoltaic inverter 3 through the communication module 15. The control module 11 is used to send a first control signal when it is determined that the grounding form of the transformer 4 is a neutral point grounding system, and send a second control signal when it is determined that the grounding form of the transformer 4 is a neutral point ungrounded system.

[0083] The communication module 15 may include hardware and software. The hardware part includes a communication interface (such as a serial port, an Ethernet port, a wireless communication module, etc.), a signal processor, etc., which is responsible for data transmission at the physical level. The software part includes a communication protocol stack, a driver, etc., which ensures the correct encoding, decoding and transmission of data. The communication module 15 performs data transmission according to a specific communication protocol. Exemplary communication protocols include Modbus, CAN bus and Ethernet communication protocols. The communication module 15 can be a serial communication module, such as an RS-232 or RS-485 communication module. The communication module 15 can also be an Ethernet communication module, such as an Ethernet controller chip or a microcontroller with an integrated Ethernet interface. The communication module 15 can also be a wireless communication module, such as a Wi-Fi module, a Bluetooth module, a ZigBee module, etc. The communication module 15 can also be an industrial bus communication module, such as a CAN bus module, a Profibus module, etc. Information interaction between the control module 11 and the photovoltaic inverter 3 can be achieved through the communication module 15. The control module 11 transmits the transformer grounding type and other test results determined by the control module 11 to the photovoltaic inverter 3. It also receives information such as the operating status of the photovoltaic inverter 3, ensuring the coordinated operation of the entire photovoltaic system. Furthermore, the communication module 15 transmits the operating data of the grounding type detection circuit 1 to a remote monitoring center, allowing operators to understand the operating status of the grounding type detection circuit 1 in real time and make remote control adjustments when necessary.

[0084] Continue to refer Figure 1 and Figure 15 The working principle of the grounding form detection circuit 1 provided in the embodiment of the present utility model is as follows:

[0085] When the solar panel 2 is exposed to sunlight, the open-circuit voltage of the solar panel 2 continues to rise. When the open-circuit voltage of the solar panel 2 exceeds the second set threshold, the DC power supply 14 within the grounding type detection circuit 1 starts to operate, supplying power to the current detection module 131, the voltage amplification module 132, and the control module 11. The control module 11 starts to operate.

[0086] When photovoltaic inverter 3 is grid-connected and operating, if the transformer grounding type is a neutral-grounded system, leakage current from the photovoltaic system will flow through relay K1 and the input of current detection module 131 within grounding type detection circuit 1, all the way to the chassis ground of grounding type detection circuit 1, thereby forming a loop with the ground of transformer 4. At this point, the output of current detection module 131 will output a voltage signal, which is amplified by voltage amplifier module 132 and input into the ADC channel of control module 11. Control module 11 performs internal data conversion and compares the signal with a first set threshold. If at least one voltage signal exceeds the first set threshold, control module 11 determines that transformer 4 is grounded as a neutral-grounded system and outputs a first control signal, which is then transmitted to photovoltaic inverter 3 via communication module 15. Upon receiving the first control signal, photovoltaic inverter 3 disables the anti-PID function, thereby preventing damage to photovoltaic inverter 3 and providing protection.

[0087] When photovoltaic inverter 3 is grid-connected, if no leakage current is detected in the circuit from the input of current detection module 131 to the chassis ground, it can be confirmed that transformer 4 is grounded with an ungrounded neutral point. A second control signal is then output and transmitted to photovoltaic inverter 3 via communication module 15. After receiving the second control signal, photovoltaic inverter 3 can normally enable the anti-PID function, and the photovoltaic inverter will not be damaged.

[0088] Figure 16 This is a schematic diagram of another grounding detection circuit provided by the embodiment of the present utility model. Figure 16 As shown, the grounding type detection circuit 1 includes: a control module 11 , at least one DC input terminal 12 and at least one detection branch 13 , and the detection branch 13 includes a current detection module 131 and a voltage amplification module 132 .

[0089] Optionally, the current detection module 131 includes a current detection unit CT1 and a first capacitor C1 , and the current detection unit CT1 includes a current transformer or a Hall current sensor.

[0090] Optionally, the voltage amplification module 132 includes a first resistor R1 , a second resistor R2 , a third resistor R3 , a fourth resistor R4 , a second capacitor C2 , a third capacitor C3 , and a first operational amplifier U1 .

[0091] Optionally, the detection branch 13 further includes a switch module 133, which includes a first switch unit 1331 and a second switch unit 1332. The first switch unit 1331 includes a transistor T1, a fifth resistor R5, and a sixth resistor R6. The second switch unit 1332 includes a relay K1, which includes a coil S1 and a contact ab.

[0092] Optionally, the detection branch 13 further includes a voltage follower 134. The voltage follower 134 includes a second operational amplifier U2, a seventh resistor R7, and an eighth resistor R8. Optionally, the grounding type detection circuit 1 further includes a DC power supply 14 and a communication module 15.

[0093] Continue to refer Figure 1 and Figure 16 The working principle of the grounding form detection circuit 1 provided in the embodiment of the present utility model is as follows:

[0094] When solar panel 2 is exposed to sunlight, its open-circuit voltage continues to rise. When the open-circuit voltage of solar panel 2 exceeds a second set threshold, DC power supply 14 within grounding type detection circuit 1 begins operating, supplying power to current detection unit CT1, first operational amplifier U1, second operational amplifier U2, control module 11, communication module 15, transistor T1, and relay K1. Upon receiving power, control module 11 begins operating, outputting a high level via its input / output pins to the voltage divider circuit formed by fifth resistor R5 and sixth resistor R6, which drives transistor T1 to conduct. This in turn engages coil S1 of relay K1, closing contacts ab of relay K1 and enabling grid-connected operation of photovoltaic inverter 3.

[0095] When photovoltaic inverter 3 is grid-connected and operating, if the transformer grounding type is a neutral-grounded system, leakage current from the photovoltaic system will flow through relay K1, the primary coil of current detection unit CT1, and first capacitor C1 within grounding type detection circuit 1, all the way to the chassis ground of grounding type detection circuit 1, thereby forming a loop with the ground of transformer 4. At this point, the secondary coil of current detection unit CT1 will induce a voltage signal. This voltage signal is amplified by voltage amplifier module 132, consisting of first resistor R1, second resistor R2, third resistor R3, fourth resistor R4, second capacitor C2, third capacitor C3, and first operational amplifier U1, and then output to the analog-to-digital converter (ADC) channel of control module 11. Control module 11 then performs internal data conversion and compares the signal with a first set threshold. If at least one voltage signal exceeds the first set threshold, control module 11 determines that transformer 4 is grounded as a neutral-grounded system and outputs a first control signal, which is then transmitted to photovoltaic inverter 3 via communication module 15. The photovoltaic inverter 3 disables the anti-PID function after receiving the first control signal, which helps to avoid damage to the photovoltaic inverter 3 and plays a protective role.

[0096] When photovoltaic inverter 3 is grid-connected, if no leakage current is detected in the primary coil of current detection unit CT1 and the circuit from first capacitor C1 to the chassis ground, it can be confirmed that transformer 4 is grounded with an ungrounded neutral point. A second control signal is output and transmitted to photovoltaic inverter 3 via communication module 15. After receiving the second control signal, photovoltaic inverter 3 can normally enable the anti-PID function, and the photovoltaic inverter will not be damaged.

[0097] In summary, the grounding detection circuit 1 provided in this embodiment of the present invention can determine whether the transformer's neutral point (N) is grounded when the photovoltaic inverter 3 is grid-connected. This circuit can then inform the photovoltaic inverter 3 whether to enable the anti-PID function, thereby preventing damage and providing protection. This circuit can be used on all photovoltaic inverters 3 equipped with an anti-PID function. Furthermore, it utilizes a minimal number of circuit components, has simple control logic, and is easy to implement.

[0098] Based on the same utility model concept, embodiments of the present utility model further provide a photovoltaic system, comprising a grounding type detection circuit according to any of the above-described embodiments, and having corresponding functional modules and beneficial effects. Similarities can be found in the explanation of the grounding type detection circuit and are not further described here. The photovoltaic inverter is configured to disable the anti-potential induced degradation function in response to a first control signal and enable the anti-potential induced degradation function in response to a second control signal.

[0099] The above specific embodiments do not limit the scope of protection of this utility model. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model shall be included within the scope of protection of this utility model.

Claims

1. A grounding form detection circuit, used in photovoltaic systems, characterized in that: The photovoltaic system includes a solar panel, a photovoltaic inverter and a transformer, wherein the input end of the photovoltaic inverter is connected to the solar panel, and the output end of the photovoltaic inverter is connected to the transformer; The grounding form detection circuit includes: a control module, at least one DC input terminal and at least one detection branch, each detection branch correspondingly connected to one of the DC input terminals; the DC input terminal is used to be electrically connected to the photovoltaic inverter; The detection branch includes a current detection module and a voltage amplification module; The input end of the current detection module is connected to the DC input end, and is used to collect the current signal flowing through the DC input end and convert the current signal into a voltage signal; The input end of the voltage amplifying module is connected to the output end of the current detecting module, and the output end of the voltage amplifying module is connected to the input end of the control module, for amplifying the voltage signal and outputting it to the control module; The control module is used to determine that the grounding form of the transformer is a neutral point grounding system when at least one of the voltage signals is greater than a first set threshold, and to determine that the grounding form of the transformer is a neutral point ungrounded system when all of the voltage signals are less than the first set threshold.

2. The grounding form detection circuit according to claim 1, characterized in that: The current detection module includes a current detection unit and a first capacitor, and the current detection unit includes a current transformer or a Hall current sensor; A first end of the current detection unit is connected to the DC input end, a second end of the current detection unit is connected to the first capacitor, and a second end of the first capacitor is grounded; The third terminal of the current detection unit is connected to the first input terminal of the voltage amplification module, and the fourth terminal of the current detection unit is connected to the second input terminal of the voltage amplification module.

3. The grounding form detection circuit according to claim 1, characterized in that: The voltage amplification module includes a first resistor, a second resistor, a third resistor, a fourth resistor, a second capacitor, a third capacitor and a first operational amplifier; The first end of the first resistor serves as the first input end of the voltage amplification module, and the second end of the first resistor is connected to the inverting input end of the first operational amplifier; The first end of the second resistor serves as the second input end of the voltage amplification module, and the second end of the second resistor is connected to the non-inverting input end of the first operational amplifier; A first end of the third resistor is connected to the inverting input end of the first operational amplifier, and a second end of the third resistor is connected to the output end of the first operational amplifier. The output end of the first operational amplifier serves as the output end of the voltage amplification module. The second capacitor is connected in parallel with the third resistor. A first end of the fourth resistor is connected to the non-inverting input terminal of the first operational amplifier, a second end of the fourth resistor is grounded, and the third capacitor is connected in parallel to the fourth resistor.

4. The grounding form detection circuit according to claim 1, characterized in that: The detection branch further includes a switch module; The control end of the switch module is connected to the output end of the control module, the first end of the switch module is connected to the DC input end, the second end of the switch module is connected to the input end of the current detection module, and the control module is also used to control the conduction state of the switch module.

5. The grounding type detection circuit according to claim 4, characterized in that: The switch module includes a first switch unit and a second switch unit; The control end of the first switch unit serves as the control end of the switch module, the first end of the first switch unit is grounded, and the second end of the first switch unit is connected to the first end of the second switch unit; The second end of the second switch unit is connected to the first voltage, the third end of the second switch unit serves as the first end of the switch module, and the fourth end of the second switch unit serves as the second end of the switch module.

6. The grounding type detection circuit according to claim 5, characterized in that: The first switch unit includes a transistor, a fifth resistor and a sixth resistor; The first end of the fifth resistor serves as the control end of the first switch unit, the second end of the fifth resistor is connected to the gate of the transistor, the first terminal of the transistor serves as the first end of the first switch unit, and the second terminal of the transistor serves as the second end of the second switch unit; And / or, the second switch unit includes a relay, and the relay includes a coil and contacts; The first end of the coil serves as the first end of the second switch unit, and the second end of the coil serves as the second end of the second switch unit; The first end of the contact serves as the third end of the second switch unit, and the second end of the contact serves as the fourth end of the second switch unit.

7. The grounding type detection circuit according to claim 1, characterized in that: The detection branch also includes a voltage follower; The voltage amplification module is connected to the input end of the control module through the voltage follower; The voltage follower includes a second operational amplifier, a seventh resistor and an eighth resistor; A first end of the seventh resistor is connected to the output end of the voltage amplification module, and a second end of the seventh resistor is connected to the non-inverting input end of the second operational amplifier; The first end of the eighth resistor is connected to the second voltage, and the second end of the eighth resistor is connected to the second end of the seventh resistor; The inverting input of the second operational amplifier is single-endedly connected to the output of the second operational amplifier, the output of the second operational amplifier is connected to the input of the control module, the first power supply of the second operational amplifier is connected to the third voltage, and the second power supply of the second operational amplifier is grounded.

8. The grounding type detection circuit according to claim 1, characterized in that: Also includes a DC power supply; The input end of the DC power supply is connected to the DC input end or the output end of the photovoltaic inverter, and the output end of the DC power supply is connected to the power input end of the current detection module and the power input end of the control module, and is used to power the current detection module and the control module when the open-circuit voltage of the solar panel is greater than a second set threshold.

9. The grounding type detection circuit according to claim 1, characterized in that: It also includes a communication module, and the control module is communicated with the photovoltaic inverter through the communication module. The control module is used to send a first control signal when it is determined that the grounding form of the transformer is the neutral point grounding system, and send a second control signal when it is determined that the grounding form of the transformer is the neutral point ungrounded system.

10. A photovoltaic system, characterized in that: The photovoltaic inverter comprises the grounding form detection circuit according to any one of claims 1 to 9, wherein the photovoltaic inverter is configured to disable or enable an anti-potential induced degradation function according to a first control signal, and enable the anti-potential induced degradation function according to a second control signal.

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