PV terminal temperature detection device and photovoltaic inverter

Abstract

The utility model is applicable to the technical field of photovoltaic inverters, and provides a PV terminal temperature detection device and a photovoltaic inverter.The PV terminal temperature detection device comprises a thermistor arranged on a wave soldering side of a core pin of a metal core in a PV terminal; and the surface of the thermistor, the wave-soldering side of the core pin and the copper sheet of the core pin are coated with heat-conducting glue. As the thermistor is placed on one side of the wave-soldering pin, the thermistor is closer to the core pin, and the heat transfer effect is better. Meanwhile, the thermistor, the core pin and the copper sheet are coated with heat-conducting glue, and most of heat generated by the metal core and the copper sheet is transferred to the thermistor, so that the master control chip can judge the state of the current PV terminal more quickly and accurately.

Description

Technical Field

[0001] This utility model belongs to the field of photovoltaic inverter technology, and in particular relates to a PV terminal temperature detection device and a photovoltaic inverter. Background Technology

[0002] Currently, photovoltaic inverters primarily use thermistors to detect the temperature of the PV terminals. The main detection method involves transferring heat from the metal core inside the PV terminal to the copper foil on the metal core pins, and then transferring the heat from the copper foil to the thermistor on the back, causing a change in the thermistor's resistance. Based on the principle of voltage division, the divided voltage is output through a diode, and after passing through a conditioning circuit, it is input to the AD port of the main control chip.

[0003] To ensure a certain safety distance, the thermistor is not placed entirely on the PV terminal pins. Instead, its two ends are placed next to the copper foil on the back of the pins, with a certain distance between them and the PV terminal pins. This distance must ensure functional insulation distance, which is greater than 3.1mm. This results in a certain deviation between the actual temperature of the metal core and the temperature of the thermistor. When the inverter's internal fan is running, it carries away the heat from the copper foil on the terminal pins, which also lowers the temperature of the thermistor. As a result, the temperature read is lower than the actual temperature. Utility Model Content

[0004] This invention provides a PV terminal temperature detection device, which aims to solve the problem that the detected temperature of the PV terminal is lower than the actual temperature.

[0005] This utility model is implemented as follows: a PV terminal temperature detection device, comprising:

[0006] A thermistor is disposed on the wave soldering side of the core pin of the metal core inside the PV terminal; the surface of the thermistor, the wave soldering side of the core pin, and the copper foil of the core pin are all coated with thermally conductive adhesive.

[0007] Furthermore, the PV terminals are in multiple sets, each set of PV terminals includes at least one PV terminal, and each PV terminal is provided with a thermistor;

[0008] The PV terminal temperature detection device also includes:

[0009] The maximum value circuit is connected to the output terminals of each thermistor set in a group of PV terminals, and is used to output the voltage signal corresponding to the maximum resistance value of each thermistor.

[0010] The main control chip, connected to the maximum value extraction circuit, is used to generate a signal indicating whether the temperature of the PV terminals is abnormal based on the voltage signal and a preset threshold.

[0011] Furthermore, the PV terminal temperature detection device also includes:

[0012] The signal gating circuit has its input terminal connected to the output terminal of the maximum value taking circuit corresponding to each group of PV terminals, and its output terminal connected to the main control chip. It is used to select the voltage signal corresponding to any group of PV terminals.

[0013] The main control chip is used to generate a signal indicating whether the temperature of any selected group of PV terminals is abnormal, based on the voltage signal and a preset threshold.

[0014] Furthermore, the PV terminal temperature detection device further includes:

[0015] A signal conditioning circuit, connected between the signal gating circuit and the main control chip, is used to filter the selected voltage signal.

[0016] Furthermore, the signal conditioning circuit is also used to step down the selected voltage signal.

[0017] Furthermore, each PV terminal is configured to correspond one-to-one with the MPPT boost circuit.

[0018] Furthermore, the maximum value extraction circuit includes multiple operational amplifiers, each with an input terminal connected to a thermistor, and the output terminals of all operational amplifiers are connected together to the main control chip.

[0019] Furthermore, the maximum value circuit includes multiple operational amplifiers, each with its input terminal connected to a thermistor, and the output terminals of all operational amplifiers are connected together and then connected to the input terminal of the signal gating circuit.

[0020] This utility model also provides a photovoltaic inverter, comprising:

[0021] PV terminals; and

[0022] The PV terminal temperature detection device as described above.

[0023] Furthermore, the photovoltaic inverter includes a string photovoltaic inverter.

[0024] The PV terminal temperature detection device and photovoltaic inverter provided by this utility model have a better heat transfer effect because the thermistor is placed on the side of the wave soldering pins, which is closer to the core pins. At the same time, thermally conductive adhesive is applied to the thermistor, the core pins, and the copper foil, which transfers most of the heat generated by the metal core and copper foil to the thermistor, thereby enabling the main control chip to determine the current status of the PV terminal more quickly and accurately. Attached Figure Description

[0025] Figure 1This is a schematic diagram of a PV terminal temperature detection device provided by this utility model;

[0026] Figure 2 This is a schematic diagram of another PV terminal temperature detection device provided by this utility model. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.

[0028] Currently, photovoltaic inverters primarily use thermistors to detect the temperature of the photovoltaic string terminals. The main detection method involves transferring heat from the metal core inside the photovoltaic string terminals to the copper foil on the metal core pins, and then transferring the heat from the copper foil to the thermistor on the back, causing a change in the thermistor's resistance. Based on the principle of voltage division, the divided voltage is output through a diode, and after passing through a conditioning circuit, it is input to the AD port of the main control chip.

[0029] To ensure a certain safety distance, the thermistor is not placed entirely on the terminal pins. Instead, its two ends are placed next to the copper foil on the back of the pins, with a certain distance between them. This distance must ensure functional insulation distance, i.e., greater than 3.1mm. This results in a certain deviation between the actual temperature of the metal core and the temperature of the thermistor. When the internal fan of the inverter is running, it carries away the heat from the copper foil of the terminal pins, which also lowers the temperature of the thermistor. As a result, the temperature read is lower than the actual temperature.

[0030] In addition, the voltage value output by the diode in the sampling circuit has low accuracy and large error, and when there are many PV terminals, it requires a lot of port resources of the main control chip.

[0031] Therefore, existing methods for PV terminal temperature detection have certain limitations.

[0032] In related technologies, the thermistor and PV terminal are placed on the same side (i.e., the other side of the wave soldering pins), and there is no thermally conductive adhesive on the surface of the thermistor, nor is the thermistor and copper foil connected together by thermally conductive adhesive. In this invention, the thermistor is placed on the side of the wave soldering pins, closer to the core pins, resulting in better heat transfer. Simultaneously, applying thermally conductive adhesive to the thermistor, core pins, and copper foil transfers most of the heat generated by the metal core and copper foil to the thermistor, further improving heat transfer and enabling the main control chip to determine the current state of the PV terminal more quickly and accurately.

[0033] Furthermore, the temperature sampling circuits in related technologies use resistor voltage division to output sampled values ​​via diodes before sending them to the main control chip, which consumes a significant amount of the main control chip's port resources. In contrast, this invention converts the NTC signals corresponding to multiple PV terminals into voltage signals, takes the maximum value, and then sends the maximum value to the main control chip's I / O port. This conversion yields the current temperature of the PV terminals, significantly saving port resources.

[0034] Example 1

[0035] This embodiment provides a PV terminal temperature detection device, such as... Figure 1 As shown, it includes:

[0036] The thermistor 101 is disposed on the wave soldering side of the core pin 102 of the metal core inside the PV terminal; the surface of the thermistor 101, the wave soldering side of the core pin 102, and the copper skin 103 of the core pin are all coated with thermally conductive adhesive 104.

[0037] In the specific implementation, the wave soldering side of the thermistor 101 and the core lead 102 are placed on the same side, and sufficient safety clearance is reserved between the thermistor 101 and the core lead 102, for example, a safety clearance greater than 3.1mm. Commercially available thermal conductive adhesives can be used, and the specific model is not limited. For example, Guangdong Deju-CollTech N-Sil 8580 can be used.

[0038] In this embodiment, by uniformly applying thermally conductive adhesive 104 to the thermistor 101 and the core pin 102, and simultaneously applying a suitable amount of thermally conductive adhesive to the copper foil 103 of the core pin 102, the heat of the metal core inside the PV terminal is quickly transferred to the copper foil contacted by the wave soldering side of the core pin 102, and then the heat of the copper foil is transferred to the thermistor 101 located on the same side. The temperature of the metal core is then obtained by the temperature detection circuit. This heat transfer process ensures that the temperature of the copper foil 103 and the metal core itself is effectively transferred to the thermistor 101. Compared to placing the thermistor on the back of the core pin (the non-wave soldering side), even with a fan inside the photovoltaic inverter, the thermally conductive adhesive covering the metal core and the thermistor 101, and the thermistor 101 being located on the wave soldering side, minimizes heat loss, resulting in more accurate and faster temperature detection.

[0039] Example 2

[0040] Based on Embodiment 1, there are multiple sets of PV terminals, each set including at least one PV terminal, and each PV terminal is equipped with a thermistor. The PV terminal temperature detection device provided in this embodiment, such as... Figure 2 As shown, it also includes:

[0041] The maximum value circuit 201 is connected to the output terminals of each thermistor set by a group of PV terminals, and is used to output the voltage signal corresponding to the maximum resistance value of each thermistor.

[0042] The main control chip 202 is connected to the maximum value extraction circuit 201 and is used to generate a signal indicating whether the temperature of the PV terminals is abnormal based on the voltage signal and a preset threshold.

[0043] In practical applications, each MPPT boost circuit of a photovoltaic inverter is connected to at least one PV terminal. Terminals with the same DC input are grouped together as the input of one MPPT boost circuit. That is, each group of PV terminals is set up in a one-to-one correspondence with an MPPT boost circuit.

[0044] In some specific implementations, the maximum value circuit 201 includes multiple operational amplifiers, each operational amplifier's input terminal is connected to a thermistor 101, and the output terminals of each operational amplifier are connected together and then connected to the main control chip 202.

[0045] In this embodiment, the thermistors (NTCm1, NTCm2, ... NTCmm) on the wave soldering side of the core pins 102 of each PV terminal group are connected to the corresponding maximum value extraction circuit 201 to output the maximum value among the thermistor resistance values ​​set for that PV terminal group. This reduces the I / O port pressure on the main control chip 202. When the temperature of a PV terminal changes, the resistance value of its corresponding thermistor changes accordingly, and the output voltage of this path is greater than the output voltages of other paths. This output voltage is the maximum voltage corresponding to that PV terminal group. After the maximum voltage corresponding to each PV terminal group is sent to the main control chip, it is compared with a preset threshold. When the maximum voltage exceeds the preset threshold, a signal indicating an abnormal temperature for that PV terminal group is generated. Conversely, a signal indicating that the temperature of that PV terminal group is normal is generated. Thus, it is possible to determine which PV terminal group the fault is located in.

[0046] To further reduce the pressure on the I / O ports of the main control chip, this embodiment employs a signal gating circuit. Utilizing the characteristic of this circuit to select only one signal at a time, temperature acquisition can be achieved using only one I / O port provided by the main control chip, thus obtaining the temperature detection result without affecting the normal use of other I / O ports on the main control chip. Specifically, the PV terminal temperature detection device also includes:

[0047] The signal selection circuit 203 has its input terminal connected to the output terminal of the maximum value extraction circuit 201 corresponding to each group of PV terminals, and its output terminal connected to the main control chip 202. It is used to select the voltage signal corresponding to any group of PV terminals.

[0048] Accordingly, the main control chip 202 is used to generate a signal indicating whether the temperature of any selected set of PV terminals is abnormal based on the voltage signal and a preset threshold.

[0049] In some specific implementations, the maximum value circuit 201 includes multiple operational amplifiers, the input of each operational amplifier is connected to a thermistor 101, and the outputs of each operational amplifier are connected to the input of the signal gating circuit 203.

[0050] In this embodiment, the voltage signals corresponding to each group of PV terminals (corresponding to the maximum resistance value) are sent to the signal selection circuit 203. Each time, the signal selection circuit 203 selects one voltage signal and sends it to the main control chip 202 for comparison with a preset threshold, thereby generating a signal indicating whether the temperature of that group of PV terminals is abnormal. This effectively solves the problems of low accuracy and large error of the voltage value output by the diode, and the need to occupy a lot of port resources of the main control chip when there are many photovoltaic inverter strings.

[0051] In some specific implementations, the PV terminal temperature detection device of this embodiment further includes:

[0052] The signal conditioning circuit 204 is connected between the signal gating circuit 203 and the main control chip 202, and is used to filter the selected voltage signal.

[0053] In some cases, the signal conditioning circuit 204 is also used to step down the selected voltage signal.

[0054] In this embodiment, before the selected voltage signal is sent to the IO port of the main control chip 202, it is filtered by the signal conditioning circuit 204 to remove signal interference. In addition, if the voltage at the IO port of the main control chip 202 is inconsistent with the output voltage of the signal selection circuit 203, the selected voltage signal is stepped down before being sent to the main control chip 202 to realize the temperature detection of the PV terminal.

[0055] Using the method in this embodiment, when the temperature of a certain PV terminal of the photovoltaic inverter is high, the fault point can be quickly determined in which set of DC inputs. At the same time, the use of the signal gating chip can effectively save the IO resources of the main control chip.

[0056] Example 3

[0057] This utility model also provides a photovoltaic inverter, comprising:

[0058] PV terminals; and

[0059] The PV terminal temperature detection device of the aforementioned embodiment.

[0060] In some specific implementations, photovoltaic inverters include string photovoltaic inverters.

[0061] In practical applications, when poor connection between the two PV terminals leads to poor contact of the internal metal core, the metal core heats up, causing the copper foil on the pins to heat up as well. This heat is transferred to the thermistor via thermally conductive adhesive, and the temperature detection circuit then obtains the current temperature of the metal core (PV terminal), thus determining the current state of the photovoltaic string. Even if the photovoltaic inverter has an internal fan, the thermally conductive adhesive covering the core and the thermistor minimizes heat loss, resulting in more accurate and faster temperature detection. During grid-connected operation, the photovoltaic inverter can detect any abnormal temperatures at the PV terminals in real time, quickly, and effectively.

[0062] The PV terminal temperature detection device and photovoltaic inverter provided in this embodiment of the invention feature improved heat transfer because the thermistor is placed on the wave soldering pin side, closer to the core pins. Simultaneously, thermally conductive adhesive is applied to the thermistor, core pins, and copper foil, transferring most of the heat generated by the metal core and copper foil to the thermistor, enabling the main control chip to determine the current PV terminal status more quickly and accurately. Furthermore, the NTC signals corresponding to multiple PV terminals are converted into voltage signals, the maximum value is taken, and then the maximum value is sent to the I / O port of the main control chip to obtain the current PV terminal temperature, significantly saving port resources.

[0063] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A PV terminal temperature detection device, characterized in that, include: A thermistor is disposed on the wave soldering side of the core pin of the metal core inside the PV terminal; the surface of the thermistor, the wave soldering side of the core pin, and the copper foil of the core pin are all coated with thermally conductive adhesive.

2. The PV terminal temperature detection device according to claim 1, characterized in that, The PV terminals are in multiple groups, each group of PV terminals includes at least one PV terminal, and each PV terminal is equipped with a thermistor. The PV terminal temperature detection device also includes: The maximum value circuit is connected to the output terminals of each thermistor set in a group of PV terminals, and is used to output the voltage signal corresponding to the maximum resistance value of each thermistor. The main control chip, connected to the maximum value extraction circuit, is used to generate a signal indicating whether the temperature of the PV terminals is abnormal based on the voltage signal and a preset threshold.

3. The PV terminal temperature detection device according to claim 2, characterized in that, The PV terminal temperature detection device also includes: The signal gating circuit has its input terminal connected to the output terminal of the maximum value taking circuit corresponding to each group of PV terminals, and its output terminal connected to the main control chip. It is used to select the voltage signal corresponding to any group of PV terminals. The main control chip is used to generate a signal indicating whether the temperature of any selected group of PV terminals is abnormal, based on the voltage signal and a preset threshold.

4. The PV terminal temperature detection device according to claim 3, characterized in that, Also includes: A signal conditioning circuit, connected between the signal gating circuit and the main control chip, is used to filter the selected voltage signal.

5. The PV terminal temperature detection device according to claim 4, characterized in that, The signal conditioning circuit is also used to step down the selected voltage signal.

6. The PV terminal temperature detection device according to claim 2, characterized in that, Each PV terminal group is configured to correspond one-to-one with the MPPT boost circuit.

7. The PV terminal temperature detection device according to claim 2, characterized in that, The maximum value circuit includes multiple operational amplifiers, each with an input terminal connected to a thermistor, and the output terminals of all operational amplifiers are connected together and then connected to the main control chip.

8. The PV terminal temperature detection device according to claim 2, characterized in that, The maximum value circuit includes multiple operational amplifiers, each with an input terminal connected to a thermistor. The output terminals of all operational amplifiers are connected together and then connected to the input terminal of a signal gating circuit.

9. A photovoltaic inverter, characterized in that, include: PV terminal; as well as The PV terminal temperature detection device as described in any one of claims 1 to 8.

10. The photovoltaic inverter according to claim 9, characterized in that, The photovoltaic inverter includes a string photovoltaic inverter.

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