Photovoltaic air conditioning system, and leakage current monitoring method and device therefor

Abstract

Disclosed in the present invention are a photovoltaic air conditioning system, and a leakage current monitoring method and device therefor. The monitoring method comprises: acquiring a leakage current value I of a direct current bus on an output side of a boost circuit; when the leakage current value I is not less than a threshold Imax, generating a PWM driving signal at a first duty cycle, and using the PWM driving signal to drive a switching transistor in the boost circuit; and controlling a relay to be turned off, such that a PTC thermistor is connected in series to a photovoltaic cell and the boost circuit, wherein the first duty cycle is not less than a set duty cycle limit. The present invention can simply achieve leakage current monitoring of photovoltaic air conditioning systems at a relatively low cost.

Description

Photovoltaic air conditioning system and its leakage current monitoring method and monitoring device Technical Field

[0001] This invention belongs to the field of energy-saving air conditioning technology, specifically, it relates to the field of photovoltaic air conditioning technology, and more specifically, it relates to photovoltaic air conditioning systems and their leakage current monitoring methods and devices. Background Technology

[0002] As an energy-saving air conditioning system, photovoltaic air conditioning systems have been widely applied in various fields such as production and daily life due to the increasingly urgent need for energy conservation and emission reduction and the continuous maturation of photovoltaic technology.

[0003] When a photovoltaic air conditioning system is operating normally, leakage current exists in the power supply circuit between the solar photovoltaic array and the load. If personnel come into contact with this leakage current, it can cause a safety accident. Therefore, leakage current monitoring and control are necessary to reduce safety hazards.

[0004] In existing photovoltaic air conditioning systems, AC leakage current is typically collected from the inverter output of the power supply circuit, and a dedicated cutoff circuit is set up for the boost circuit. When AC leakage current is detected, the boost circuit is shut down using the cutoff circuit. Because a dedicated boost circuit cutoff circuit device and an AC leakage current detection device are required to form a leakage current monitoring device, the leakage current monitoring device for photovoltaic air conditioning systems is large, costly, complex in structure, and has low stability, making it difficult to promote its application. Technical issues

[0005] One of the objectives of this invention is to provide a method and device for monitoring leakage current in a photovoltaic air conditioning system, so as to achieve leakage current monitoring in a simple manner and at a low cost. Technical solutions

[0006] To achieve the above-mentioned objectives, the leakage current monitoring method for photovoltaic air conditioning systems provided by this invention adopts the following technical solution:

[0007] A method for monitoring leakage current in a photovoltaic air conditioning system, the photovoltaic air conditioning system including a photovoltaic cell, a boost circuit, and a PTC thermistor disposed between the photovoltaic cell and the boost circuit, wherein a relay is connected in parallel with the PTC thermistor, the method comprising:

[0008] Obtain the leakage current value I on the DC bus of the output side of the boost circuit;

[0009] When the leakage current value I is not less than the threshold I maxAt the same time, a PWM drive signal is generated with a first duty cycle, and the PWM drive signal drives the switching transistor in the boost circuit; simultaneously, the relay is controlled to open, so that the PTC thermistor is connected in series with the photovoltaic cell and the boost circuit; the first duty cycle is not less than a set duty cycle limit value.

[0010] In some embodiments of this application, the first duty cycle is determined using the following process:

[0011] When the leakage current value I is not less than the threshold I max At that time, the leakage current value I and the threshold I are obtained. max The difference is used to determine an adjustment coefficient; the adjustment coefficient is positively correlated with the difference.

[0012] The product of the adjustment coefficient and the set duty cycle limit is determined as the first duty cycle;

[0013] The adjustment coefficient is greater than 1 and less than the reciprocal of the set duty cycle limit.

[0014] In some embodiments of this application, the method further includes:

[0015] When the difference is not less than the difference limit and continues for a set duration, the first duty cycle is set to 1.

[0016] In some embodiments of this application, the method further includes:

[0017] When the leakage current value I is less than the threshold I max At the same time, a PWM drive signal is generated with a second duty cycle, and the PWM drive signal drives the switching transistor in the boost circuit; simultaneously, the relay is controlled to close, so that the relay is connected in series with the photovoltaic cell and the boost circuit; the second duty cycle is determined according to the boost target, and the second duty cycle is not greater than the first duty cycle.

[0018] To achieve the aforementioned objectives, the leakage current monitoring device for the photovoltaic air conditioning system provided by this invention employs the following technical solution:

[0019] A leakage current monitoring device for a photovoltaic air conditioning system, the photovoltaic air conditioning system including a photovoltaic cell, a boost circuit, and a PTC thermistor disposed between the photovoltaic cell and the boost circuit, wherein a relay is connected in parallel with the PTC thermistor, the device comprising:

[0020] The leakage current detection unit is used to obtain the leakage current value I on the DC bus of the output side of the boost circuit;

[0021] Control unit, which is at least used when the leakage current value I is not less than the threshold I maxAt the same time, a PWM drive signal is generated with a first duty cycle, and the PWM drive signal drives the switching transistor in the boost circuit; at the same time, it also controls the relay to open, so that the PTC thermistor is connected in series with the photovoltaic cell and the boost circuit; the first duty cycle is not less than a set duty cycle limit value.

[0022] In some embodiments of this application, the control unit determines the first duty cycle using the following process:

[0023] When the leakage current value I is not less than the threshold I max At that time, the leakage current value I and the threshold I are obtained. max The difference is used to determine an adjustment coefficient; the adjustment coefficient is positively correlated with the difference.

[0024] The product of the adjustment coefficient and the set duty cycle limit is determined as the first duty cycle;

[0025] The adjustment coefficient is greater than 1 and less than the reciprocal of the set duty cycle limit.

[0026] In some embodiments of this application, the control unit is further configured to set the first duty cycle to 1 when it is determined that the difference is not less than the difference limit and the duration is continuously set.

[0027] In some embodiments of this application, the control unit is further configured to, when the leakage current value I is less than a threshold I max At the same time, a PWM drive signal is generated with a second duty cycle, and the PWM drive signal drives the switching transistor in the boost circuit; simultaneously, the relay is controlled to close, so that the relay is connected in series with the photovoltaic cell and the boost circuit; the second duty cycle is determined according to the boost target, and the second duty cycle is not greater than the first duty cycle.

[0028] Another object of the present invention is to provide a photovoltaic air conditioning system, including a photovoltaic cell, a boost circuit, and a PTC thermistor disposed between the photovoltaic cell and the boost circuit, wherein a relay is connected in parallel with the PTC thermistor, and the system further includes the aforementioned leakage current monitoring device for photovoltaic air conditioning systems.

[0029] Another object of the present invention is to provide a computer storage medium storing a computer program, wherein when the computer program is executed by a processor, the above-mentioned leakage current monitoring method for a photovoltaic air conditioning system is implemented. Beneficial effects

[0030] Compared with the prior art, the advantages and positive effects of the present invention are:

[0031] The photovoltaic air conditioning system and its leakage current monitoring method and device provided by this invention detect the leakage current value on the DC bus of the boost circuit output side. When the leakage current value exceeds a threshold, the switching transistor in the boost circuit is controlled to operate with a larger duty cycle than the set duty cycle limit, and the relay between the photovoltaic cell and the boost circuit in the photovoltaic air conditioning system is disconnected. This causes the PTC thermistor connected in parallel with the relay to be connected in series with the boost circuit. The switching transistor is driven by a larger duty cycle and conducts for a long time. The PTC thermistor continuously heats up and its resistance increases, ultimately achieving the purpose of disconnecting the power output of the photovoltaic cell, realizing leakage current protection for the photovoltaic air conditioning system and reducing safety hazards. In this invention, the leakage current value on the DC bus can be detected by a simple leakage current detection device, and the purpose of disconnecting the power output of the photovoltaic cell and performing leakage current protection is achieved by controlling the relay, PTC thermistor and switching transistor in the existing structure of the photovoltaic air conditioning system. There is no need to set up an additional dedicated disconnection circuit device. Therefore, the leakage current monitoring device has a simple structure, small size, low cost and high stability, and the monitoring method and process are simple and easy to implement, making it suitable for application in photovoltaic air conditioning systems.

[0032] Other features and advantages of the present invention will become clearer after reading the detailed embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 is a schematic diagram of a structure of an embodiment of the photovoltaic air conditioning system proposed in this invention;

[0035] Figure 2 is a flowchart of an embodiment of the leakage current monitoring method for photovoltaic air conditioning systems proposed in this invention;

[0036] Figure 3 is a flowchart of another embodiment of the photovoltaic air conditioning system leakage monitoring method proposed in this invention. Embodiments of the present invention

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Figure 1 shows a schematic diagram of an embodiment of the photovoltaic air conditioning system proposed in this invention.

[0039] As shown in Figure 1, the photovoltaic air conditioning system of this embodiment includes a photovoltaic cell 11, a boost circuit 12, and a PTC thermistor disposed between the photovoltaic cell 11 and the boost circuit 12. The PTC thermistor is also connected in parallel with a relay K. The PTC thermistor and relay K form the pre-charging circuit of the system. The boost circuit 12 includes an inductor L, a diode D, a capacitor C, and an IGBT switching transistor. The output of the boost circuit 12 is connected to the load and other subsequent circuit structures. In some other embodiments, the switching transistor may be of other types, such as a MOSFET.

[0040] In this embodiment, the photovoltaic air conditioning system also includes a leakage current monitoring device 13. Specifically, the leakage current monitoring device 13 includes a leakage current detection unit and a control unit. The leakage current detection unit is used to detect the leakage current value I on the DC bus of the boost circuit output side. The specific structure of the leakage current detection unit is implemented using a DC bus leakage current detection circuit in the prior art, and this embodiment does not limit or elaborate on it.

[0041] The control unit is connected to the leakage current detection unit, the relay K in the pre-charge circuit, and the IGBT switch in the boost circuit 12. The control unit acquires the leakage current value I on the DC bus detected by the leakage current detection unit and compares this leakage current value I with a threshold value I. max A comparison is made. Where the threshold I... max The value is known. The leakage current I is not less than the threshold I. max At this time, the control unit generates a PWM drive signal with a first duty cycle and drives the IGBT switching transistor with the PWM drive signal. Simultaneously, the control unit also controls the relay K to open, causing the PTC thermistor to be connected in series with the photovoltaic cell 12 and the boost circuit 13. The first duty cycle is not less than a set duty cycle limit. Since the set duty cycle limit is a relatively large duty cycle, the first duty cycle is a relatively large duty cycle greater than the set duty cycle limit.

[0042] When the leakage current value I is not less than the threshold I max At this time, the control unit controls the IGBT switch to be turned on for a long time under the drive of a large first duty cycle, so that the PTC thermistor continues to heat up and its resistance increases continuously. This can quickly disconnect the power output of the photovoltaic cell 11 to the boost circuit 12. After disconnecting the output of the photovoltaic cell 11, no leakage current is generated on the DC side of the output side of the boost circuit 12, thereby realizing leakage protection for the photovoltaic air conditioning system and reducing safety hazards.

[0043] The photovoltaic air conditioning system of the above embodiment, by using a leakage current monitoring device 13 composed of a leakage current detection unit and a control unit, can detect the leakage current value on the DC bus through a simple leakage current detection device, and achieve the purpose of disconnecting the photovoltaic cell power output and performing leakage protection by controlling the relays, PTC thermistors and switching tubes in the existing structure of the photovoltaic air conditioning system, without the need to set up an additional dedicated cut-off circuit device. Therefore, the leakage current monitoring device has a simple structure, small size, low cost, high stability, and the monitoring process is simple and easy to implement, making it suitable for leakage current monitoring in photovoltaic air conditioning systems.

[0044] In some other embodiments, the control unit compares the leakage current value I detected by the leakage current detection unit with a threshold I. max After comparison, if the leakage current value I is less than the threshold I max The control unit generates a PWM drive signal with a second duty cycle and drives the IGBT switching transistor with this PWM drive signal. Simultaneously, the control unit also controls the relay K to close, connecting the relay K in series with the photovoltaic cell 12 and the boost circuit 13. The second duty cycle is determined according to the boost target. In this state, the photovoltaic cell 11 outputs electrical energy normally, and the boost circuit 12 operates normally according to the boost target, providing the required DC power to subsequent circuits. Furthermore, the second duty cycle is no greater than the first duty cycle to maintain the stability of the boost circuit and the safety of the photovoltaic air conditioning system.

[0045] In some embodiments, the control unit determines the first duty cycle using the following process:

[0046] The control unit determines that the leakage current value I detected by the leakage current detection unit is not less than the threshold I. max At that time, obtain the leakage current value I and the threshold I. max The difference between the leakage current value I and the threshold value I is then used to determine the adjustment coefficient. The adjustment coefficient is positively correlated with the difference, i.e., the leakage current value I and the threshold value I are related. max The larger the difference, the larger the adjustment coefficient; conversely, the smaller the difference, the smaller the adjustment coefficient. Furthermore, the adjustment coefficient must be greater than 1 and less than the reciprocal of the set duty cycle limit. If the set duty cycle limit is a positive number less than 1, then its reciprocal is a positive number greater than 1.

[0047] Then, the control unit determines the first duty cycle by multiplying the adjustment coefficient by the set duty cycle limit.

[0048] Since the adjustment factor is a positive number greater than 1, the determined first duty cycle is greater than the set duty cycle limit.

[0049] The first duty cycle is determined using the above method. The larger the leakage current value I is, the more closely it relates to the threshold I. maxThe larger the difference, the larger the adjustment coefficient, and the larger the first duty cycle determined by the adjustment coefficient. The larger the first duty cycle, the faster the PTC thermistor can disconnect the power output of the photovoltaic cell 11, thus achieving rapid leakage protection action when the leakage current value is large and the danger level is high. Conversely, when the leakage current value is small, the first duty cycle determined by the above method is also small, thus allowing for smooth adjustment of leakage protection action when the leakage current value is small and the danger level is low, avoiding impact on the stability of the system.

[0050] In some other embodiments, if the control unit determines that the leakage current value I is equal to the threshold I... max If the difference is not less than the difference limit and continues for a set duration, it indicates that the large leakage current lasts for a long time and the danger level is very high. Therefore, the first duty cycle is set to 1, which is the maximum duty cycle. The maximum duty cycle is used to control the IGBT switch to continue conducting, thereby accelerating the disconnection of the output of the photovoltaic cell 11.

[0051] Figure 2 shows a flowchart of an embodiment of the leakage current monitoring method for a photovoltaic air conditioning system proposed in this invention. Referring to the structural schematic diagram of an embodiment of the photovoltaic air conditioning system shown in Figure 1, in this method embodiment, the photovoltaic air conditioning system includes a photovoltaic cell 11, a boost circuit 12, and a PTC thermistor disposed between the photovoltaic cell 11 and the boost circuit 12. The PTC thermistor is also connected in parallel with a relay K, and the PTC thermistor and the relay K form a pre-charging circuit for the system. The boost circuit 12 includes an inductor L, a diode D, a capacitor C, and an IGBT switching transistor. The output of the boost circuit 12 is connected to the load and other subsequent circuit structures. In some other embodiments, the switching transistor may also be of other types, such as a MOSFET.

[0052] As shown in Figure 2, the photovoltaic air conditioning system in this embodiment uses the following process for leakage current monitoring.

[0053] S21: Obtain the leakage current value I on the DC bus of the boost circuit output side.

[0054] A leakage current detection unit can be used to detect the leakage current value I on the DC bus output side of the boost circuit 12. The specific structure of the leakage current detection unit is implemented using the DC bus leakage current detection circuit in the prior art, and this embodiment does not limit or elaborate on it.

[0055] S22: When the leakage current value I is not less than the threshold Imax, a PWM drive signal is generated with the first duty cycle to drive the switching transistor in the boost circuit; at the same time, the control relay is disconnected, so that the PTC thermistor is connected in series with the photovoltaic cell and the boost circuit.

[0056] Threshold I maxGiven a known value, if the leakage current I is not less than the threshold Imax, it indicates a large leakage current and a potential safety hazard. A PWM drive signal is then generated with the first duty cycle to drive the IGBT switch in the boost circuit 12; simultaneously, the relay K is disconnected, connecting the PTC thermistor in series with the photovoltaic cell 11 and the boost circuit 12. The first duty cycle is not less than a set duty cycle limit. Since the set duty cycle limit is a relatively large duty cycle, the first duty cycle is a relatively large duty cycle greater than the set duty cycle limit.

[0057] Using the method of this embodiment, when the leakage current value I is not less than the threshold I max During this process, the switching transistor will be on for an extended period under a relatively large first duty cycle, causing the PTC thermistor to continuously heat up and its resistance to increase. This allows for a rapid disconnection of the photovoltaic cell's power output to the boost circuit. After disconnecting the photovoltaic cell's output, no leakage current is generated on the DC side of the boost circuit's output, thus achieving leakage protection for the photovoltaic air conditioning system and reducing safety hazards. Furthermore, this embodiment can detect the leakage current value on the DC bus using a simple leakage detection device. By controlling the relays, PTC thermistors, and switching transistors in the existing structure of the photovoltaic air conditioning system, it achieves the purpose of disconnecting the photovoltaic cell's power output and providing leakage protection, eliminating the need for an additional dedicated disconnection circuit. Therefore, the leakage monitoring device is simple in structure, small in size, low in cost, and highly stable. The monitoring method and process are also simple and easy to implement, making it suitable for application in photovoltaic air conditioning systems.

[0058] In some other embodiments, the first duty cycle is determined using the following process:

[0059] When the leakage current value I is not less than the threshold I max At that time, obtain the leakage current value I and the threshold I. max The difference between the leakage current value I and the threshold value I is then used to determine the adjustment coefficient. The adjustment coefficient is positively correlated with the difference, i.e., the leakage current value I and the threshold value I are related. max The larger the difference, the larger the adjustment coefficient; conversely, the smaller the difference, the smaller the adjustment coefficient. Furthermore, the adjustment coefficient must be greater than 1 and less than the reciprocal of the set duty cycle limit. If the set duty cycle limit is a positive number less than 1, then its reciprocal is a positive number greater than 1.

[0060] Then, the product of the adjustment factor and the set duty cycle limit is determined as the first duty cycle.

[0061] Since the adjustment factor is a positive number greater than 1, the determined first duty cycle is greater than the set duty cycle limit.

[0062] Using the above method to determine the first duty cycle can achieve a rapid leakage protection action when the leakage current value is large and the danger level is high, and smoothly adjust the leakage protection action when the leakage current value is small and the danger level is low, avoiding impacting the stability of the system.

[0063] In some other embodiments, if the difference between the leakage current value I and the threshold value I max is not less than the difference limit value and lasts for a set duration, it indicates that a large leakage current lasts for a long time and the danger level is very high. Then, set the first duty cycle to 1, which is the maximum duty cycle, and control the switch IGBT to conduct continuously at the maximum duty cycle to accelerate the speed of disconnecting the output of the photovoltaic cell 11.

[0064] FIG. 3 shows a flowchart of another embodiment of the leakage monitoring method for a photovoltaic air-conditioning system proposed by the present invention. Referring to the structural schematic diagram of an embodiment of the photovoltaic air-conditioning system shown in FIG. 1, in this method embodiment, the photovoltaic air-conditioning system includes a photovoltaic cell 11, a boost circuit 12, and a PTC thermistor disposed between the photovoltaic cell 11 and the boost circuit 12. A relay K is also connected in parallel with the PTC thermistor, and the PTC thermistor and the relay K form a pre-charge circuit of the system.

[0065] As shown in FIG. 3, the leakage monitoring of the photovoltaic air-conditioning system in this embodiment is carried out by the following process.

[0066] S31: Obtain the leakage current value I on the DC bus on the output side of the boost circuit.

[0067] For the specific implementation process of this step, refer to step S21 of the embodiment in FIG. 2.

[0068] S32: Determine whether I < Imax is satisfied.

[0069] Compare the leakage current value I with the known threshold value I max to judge their magnitudes, and select to execute step S33 or S34 below according to the judgment result.

[0070] S33: When I < Imax, generate a PWM drive signal with a second duty cycle to drive the switch in the boost circuit; meanwhile, control the relay to close so that the relay is connected in series with the photovoltaic cell and the boost circuit.

[0071] If the leakage current value I is less than the threshold value I maxA PWM drive signal is generated with a second duty cycle, and this PWM drive signal drives the IGBT switching transistor. Simultaneously, relay K is controlled to close, connecting relay K in series with photovoltaic cell 12 and boost circuit 13. The second duty cycle is determined according to the boost target. In this state, photovoltaic cell 11 outputs electrical energy normally, and boost circuit 12 operates normally according to the boost target, providing the required DC power to subsequent circuits. Furthermore, the second duty cycle is no greater than the first duty cycle to maintain the stability of the boost circuit and the safety of the photovoltaic air conditioning system.

[0072] S34: When I≥Imax, a PWM drive signal is generated with the first duty cycle to drive the switching transistor in the boost circuit; at the same time, the control relay is disconnected, so that the PTC thermistor is connected in series with the photovoltaic cell and the boost circuit.

[0073] For the specific implementation process of this step, please refer to step S22 of the embodiment shown in Figure 2.

[0074] Other embodiments of the present invention also provide a computer storage medium storing a computer program. When the computer program is executed by a processor, it implements the leakage current monitoring method of the photovoltaic air conditioning system in the embodiments of FIG2 and FIG3 and other embodiments, and achieves the technical effects of the corresponding embodiments.

[0075] The aforementioned computer storage media can be implemented using any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk. The computer storage media can be any available storage medium accessible to general-purpose or special-purpose computers.

[0076] In some embodiments, a computer storage medium is coupled to a processor, enabling the processor to read information from and write information to the storage medium. Alternatively, the storage medium can be an integral part of the processor. Both the processor and the storage medium can reside in application-specific integrated circuits (ASICs). Of course, the processor and storage medium can also exist as discrete components in the device.

[0077] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions claimed by the present invention.

Claims

1. A leakage monitoring method of a photovoltaic air conditioning system, the photovoltaic air conditioning system comprising a photovoltaic cell, a boost circuit, and a PTC thermistor provided between the photovoltaic cell and the boost circuit, the PTC thermistor being connected in parallel with a relay, characterized by, The method comprises: obtaining a leakage current value I on the output side DC bus of the boost circuit; When the leakage current value I is not less than a threshold value I max When the leakage current value I is not less than a threshold value I max a first duty cycle, and the first duty cycle is not less than a set duty cycle limit value.

2. The method for monitoring the leakage current of the photovoltaic air conditioning system according to claim 1, wherein, the first duty cycle is determined by the following process: When the leakage current value I is not less than a threshold value I max , a difference between the leakage current value I and the threshold value I max is obtained, and an adjustment coefficient is determined according to the difference. the adjustment coefficient is in positive correlation with the difference value; the product of the adjustment coefficient and the set duty cycle limit value is determined as the first duty cycle; the adjustment coefficient is greater than 1 and less than the reciprocal of the set duty cycle limit value.

3. The method for monitoring the leakage current of the photovoltaic air conditioning system according to claim 2, wherein, The method further comprises: when the difference value is not less than the difference value limit value and lasts for a set duration, the first duty cycle is 1.

4. The method for leakage monitoring of a photovoltaic air conditioning system according to any one of claims 1 to 3, characterized in that, The method further comprises: When the leakage current value I is less than a threshold value I max When the leakage current value I is less than a threshold value I When the leakage current value I is less than a threshold value I 5. A leakage monitoring device for a photovoltaic air conditioning system, the photovoltaic air conditioning system comprising a photovoltaic cell, a boost circuit, and a PTC thermistor provided between the photovoltaic cell and the boost circuit, the PTC thermistor being connected in parallel with a relay, characterized in that, The device comprises: a leakage current detection unit for obtaining a leakage current value I on the output side DC bus of the boost circuit; a control unit for generating a PWM drive signal with a first duty cycle when the leakage current value I is not less than a threshold value I max a control unit for generating a PWM drive signal with a first duty cycle when the leakage current value I is not less than a threshold value I 6. The leakage monitoring device of the photovoltaic air conditioning system according to claim 5, wherein, the control unit determines the first duty cycle by the following process: When the leakage current value I is not less than a threshold value I max , a difference between the leakage current value I and the threshold value I max is obtained, and an adjustment coefficient is determined according to the difference. the adjustment coefficient is in positive correlation with the difference value; the product of the adjustment coefficient and the set duty cycle limit value is determined as the first duty cycle; the adjustment coefficient is greater than 1 and less than the reciprocal of the set duty cycle limit value.

7. The leakage monitoring device of the photovoltaic air conditioning system as claimed in claim 6, wherein, The control unit is further configured to determine the first duty cycle as 1 when it is determined that the difference value is not less than the difference value limit value and lasts for a set duration.

8. The leakage monitoring device of the photovoltaic air conditioning system according to any one of claims 5 to 7, characterized in that, The control unit is further configured to generate a PWM driving signal with a second duty cycle to drive a switch tube in the boost circuit when the leakage current value I is less than a threshold value I max Meanwhile, the control unit controls the relay to be closed so that the relay is connected in series with the photovoltaic cell and the boost circuit. The second duty cycle is determined according to the boost target, and the second duty cycle is not greater than the first duty cycle.

9. A photovoltaic air conditioning system comprising a photovoltaic cell, a boost circuit, and a PTC thermistor provided between the photovoltaic cell and the boost circuit, the PTC thermistor being connected in parallel with a relay, characterized in that, The system further comprises the leakage monitoring device of the photovoltaic air conditioner system according to any one of claims 5 to 8.

10. A computer storage medium having stored thereon a computer program, characterized in that The computer program, when executed by a processor, implements the leakage monitoring method of the photovoltaic air conditioner system according to any one of claims 1 to 4.

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