Method for operating a photovoltaic inverter

Abstract

Method for operating a photovoltaic inverter (1) for converting a direct current voltage (U DC ) into an alternating voltage (U AC ) is provided, wherein the photovoltaic inverter (1) has components (8-i) which are cooled by at least one heat sink (3A) of a cooling device (3) attached to a housing (2) of the photovoltaic inverter (1), wherein the heat sink (3A) has cooling fins along which an airflow flows, which is generated by an external fan (3B) of the cooling device (3) attached to the outside of the housing (2), wherein the external fan (3B) is controlled by a control unit (4) of the photovoltaic inverter (1) provided within the photovoltaic inverter (1), wherein in at least one heating routine the cooling of the components of the photovoltaic inverter (1) by the cooling device (3) during the operation of the photovoltaic inverter (1) is used to increase an internal temperature, T innen , the air located inside the housing (2) of the photovoltaic inverter (1) is partially reduced, wherein the relative humidity in the housing (2) of the photovoltaic inverter (1) is reduced and the components of the photovoltaic inverter (1) are dried, wherein the internal temperature T within the housing (2) of the photovoltaic inverter (1) is increased due to the heating routine innen, expanding air is released at least partially through a water vapor permeable compensating membrane (5A) of a venting device (5) provided on the housing (2) of the photovoltaic inverter (1) into the environment of the photovoltaic inverter (1).

Description

[0001] The invention provides a method for operating a photovoltaic inverter, whereby moisture within a housing of the photovoltaic inverter as well as moisture stored in components or parts of the photovoltaic inverter is reduced.

[0002] Electronic devices contain electronic components that are sensitive to moisture. These electronic components can be mounted on component carriers, particularly circuit boards or printed circuit boards, which connect the electronic components via conductive traces to implement an electronic circuit. The electronic components and the circuit boards are located within the housing of the electronic device.

[0003] High humidity inside the housing can affect the properties of the electronic components and the electrical wiring connecting them. For example, the electrical device in question might be a photovoltaic inverter, which contains electronic components for converting direct current (DC) to alternating current (AC). If such devices are located in damp rooms and / or are primarily operated at partial load, the humidity inside the device or within the housing increases. This moisture can penetrate or diffuse into the interior of electronic components. For instance, photovoltaic inverters contain filter circuits and / or an intermediate circuit, which include capacitors, often film capacitors.As humidity increases inside the photovoltaic inverter's housing, this moisture can penetrate the film capacitors and damage them. A similar situation exists with transistor modules and other moisture-sensitive components within the inverter. Overall, the reliability and lifespan of the electrical device, particularly the photovoltaic inverter, are reduced due to the presence of moisture inside the unit.

[0004] Conventional devices reduce humidity by using a hermetically sealed housing that prevents air exchange with the outside or surrounding environment. However, for many devices, it is not possible to achieve a completely hermetically sealed housing. Furthermore, the technical effort required to create a completely hermetically sealed housing is relatively high. Therefore, conventional devices use internal heating elements with heating resistors or, if necessary, hygrostatic devices to reduce humidity. A disadvantage of this conventional approach is that the internal humidity must be monitored by a humidity sensor. Additionally, internal heating for humidity reduction requires a relatively large amount of energy and incurs additional component costs.

[0005] US 2014 / 0216681A1 describes a cooling arrangement with a heat exchanger for removing heat from a device chamber containing an electrical device. A controller regulates the cooling capacity of the heat exchanger. Reducing the cooling capacity of the heat exchanger increases the temperature inside the device chamber and thereby decreases the relative humidity.

[0006] CN 1 12 492 842 A describes the control of a compressor of a cooling device as a function of a sensor-detected temperature and humidity within a power enclosure, in order to reduce humidity and prevent condensation within the power enclosure.

[0007] It is therefore an object of the present invention to provide a method that reliably reduces the humidity inside a housing of an electronic device, in particular the humidity inside a housing of a photovoltaic inverter, with minimal technical effort.

[0008] This problem is solved according to the invention by a method with the features specified in claim 1 and by a photovoltaic inverter with the features specified in claim 10.

[0009] The invention thus provides a method for operating a photovoltaic inverter designed to convert a direct current voltage into an alternating current voltage, wherein the photovoltaic inverter has components that are cooled by at least one heat sink of a cooling device attached to a housing of the photovoltaic inverter, wherein the heat sink has cooling fins along which an airflow flows, which is generated by an external fan of the cooling device attached to the outside of the housing, wherein the external fan is controlled by a control unit of the photovoltaic inverter provided within the photovoltaic inverter, wherein in at least one heating routine the cooling of the components of the photovoltaic inverter by the cooling device during operation of the photovoltaic inverter is used to increase an internal temperature, T innen, the air inside the photovoltaic inverter housing is partially reduced, thereby decreasing the relative humidity inside the photovoltaic inverter housing and drying the components of the photovoltaic inverter, whereby the internal temperature T inside the photovoltaic inverter housing is increased due to the heating routine. innen , expanding air is at least partially released into the environment of the photovoltaic inverter through a water vapor permeable (pressure) equalization membrane of a venting device provided on the housing of the photovoltaic inverter.

[0010] In one possible embodiment of the method according to the invention, a circulating airflow is generated inside the housing of the photovoltaic inverter.

[0011] In one possible embodiment of the method according to the invention, the external fan of the cooling device, which is attached to the outside of the housing of the photovoltaic inverter, is automatically deactivated by the control of the photovoltaic inverter at regular intervals or during adjustable periods in order to reduce cooling.

[0012] In one possible embodiment of the method according to the invention, the control of the photovoltaic inverter initiates the heating routine for heating components of the photovoltaic inverter in one or more heating cycles upon detection of a predetermined event or a predetermined state of the photovoltaic inverter, wherein in each heating cycle of the heating routine an expansion of the internal air in the housing takes place, whereby moist internal air is transported outwards into the environment of the photovoltaic inverter.

[0013] In one possible embodiment of the method according to the invention, at least one internal fan arranged in the housing is controlled by the control system of the photovoltaic inverter in such a way that a circulating airflow is generated inside the housing of the photovoltaic inverter.

[0014] In one possible embodiment of the method according to the invention, the control of the photovoltaic inverter at least partially deactivates an external fan during the operation of the photovoltaic inverter to reduce the humidity present inside the housing of the photovoltaic inverter, the external fan of the cooling device and / or to increase the internal temperature of the air located inside the housing, and / or activates an internal fan to generate an airflow circulating inside the housing.

[0015] In one possible embodiment of the method according to the invention, the external fan of the cooling device is automatically deactivated by the control of the photovoltaic inverter at regular intervals and / or during adjustable periods.

[0016] In one possible embodiment of the method according to the invention, power electronic components are additionally operated in suitable operating modes during the heating routine.

[0017] In one possible embodiment of the method according to the invention, an additional intermediate circuit discharge resistor of an intermediate circuit of the photovoltaic inverter is connected during the heating routine.

[0018] The invention further provides a photovoltaic inverter for converting a direct current voltage into an alternating current voltage, wherein the photovoltaic inverter comprises components which are cooled by at least one heat sink of a cooling device attached to a housing of the photovoltaic inverter, wherein the heat sink has cooling fins along which an airflow flows which is generated by an external fan of the cooling device attached to the outside of the housing, wherein the external fan is controlled by a control unit of the photovoltaic inverter provided within the photovoltaic inverter, wherein in at least one heating routine the cooling of the components of the photovoltaic inverter by the cooling device during operation of the photovoltaic inverter is used to increase an internal temperature, T innen, the air inside the photovoltaic inverter housing is partially reduced, thereby decreasing the relative humidity inside the photovoltaic inverter housing and drying the components of the photovoltaic inverter, whereby the internal temperature T inside the photovoltaic inverter housing is increased due to the heating routine. innen , expanding air is at least partially released into the environment of the photovoltaic inverter through a water vapor permeable compensating membrane of a venting device provided on the housing of the photovoltaic inverter.

[0019] The photovoltaic inverter serves to convert a direct current voltage into an alternating current voltage, wherein the photovoltaic inverter has components that can be cooled by at least one cooling device attached to a housing of the photovoltaic inverter, which is controlled by a control unit of the photovoltaic inverter, which partially and temporarily reduces the cooling of the power electronic components carried out by the cooling device during the operation of the photovoltaic inverter in order to increase the internal temperature of the air located inside the housing of the photovoltaic inverter, so that the air located inside the housing, together with the components located in the housing, heats up and the moisture stored in and attached to the components passes into the internal air.The heated indoor air expands and partially escapes to the outside environment via a ventilation device provided on the housing of the photovoltaic inverter to reduce the humidity inside the housing.

[0020] The reduced humidity inside the housing increases both the reliability of the photovoltaic inverter and its service life.

[0021] The humidity inside the photovoltaic inverter housing is reduced without the need for a sensor, especially a humidity sensor. This allows for reliable reduction of moisture levels in components and the air inside the photovoltaic inverter housing without any additional hardware.

[0022] In one possible embodiment of the photovoltaic inverter according to the invention, the venting device provided on the housing of the photovoltaic inverter has a water vapor permeable equalization membrane, in particular a pressure equalization membrane.

[0023] In an alternative embodiment of the photovoltaic inverter according to the invention, the venting device provided on the housing of the photovoltaic inverter has a controllable balancing valve.

[0024] In another possible embodiment of the photovoltaic inverter according to the invention, the cooling device attached to the housing of the photovoltaic inverter has a heat sink with cooling fins and an external fan to generate an airflow, wherein the airflow flows along the cooling fins of the heat sink.

[0025] In another possible embodiment of the photovoltaic inverter according to the invention, the control unit of the photovoltaic inverter provided inside the housing of the photovoltaic inverter is connected to the external fan attached to the outside of the housing via a control interface.

[0026] This component carrier is, for example, a printed circuit board.

[0027] In another possible embodiment of the photovoltaic inverter according to the invention, at least one internal fan is provided, which generates a circulating airflow inside the housing of the photovoltaic inverter on the component carrier.

[0028] In another possible embodiment of the photovoltaic inverter according to the invention, the inverter's control system deactivates the external fan during operation to reduce the humidity inside the inverter's housing, at least temporarily and partially, without exceeding a critical component temperature. This is done to increase the internal temperature of the air inside the housing. An existing internal temperature sensor can be used to assess whether a temperature exceedance has occurred. Simultaneously, the control system can activate the internal fan to increase the airflow circulating within the housing.

[0029] In one possible embodiment of the photovoltaic inverter according to the invention, the control unit automatically initiates a heating routine to warm the components and the interior of the photovoltaic inverter upon detection of a specific event or a predetermined condition, e.g., if a defined internal housing temperature is not reached for a certain period of time. This heating routine can comprise one or more heating cycles.

[0030] In another possible embodiment of the photovoltaic inverter according to the invention, the external fan is automatically deactivated by the control of the photovoltaic inverter at regular intervals and / or during adjustable periods.

[0031] In another possible embodiment of the photovoltaic inverter according to the invention, moisture accumulation in components of the photovoltaic inverter, in particular film capacitors, is reduced or at least partially reversed due to a reduced indoor humidity within the housing of the photovoltaic inverter during the heating routine.

[0032] In another possible embodiment of the photovoltaic inverter according to the invention, the water vapor permeable compensating membrane of the venting device is designed to be impermeable to particles in the air.

[0033] The method according to the invention serves to reduce moisture within the housing of an electronic device, in particular a photovoltaic inverter, wherein cooling, which is carried out by a cooling device attached to the outside of the device housing, is temporarily reduced to increase the internal temperature of the air located inside the device housing, so that the air located inside the device housing heats up and expands and escapes at least partially to the outside into the environment through a ventilation device provided on the device housing of the electronic device in order to reduce the humidity existing inside the device housing, thereby reducing moisture accumulation in components and / or moisture accumulation on components of the photovoltaic inverter that are located inside the housing of the photovoltaic inverter.In one embodiment, moisture that has accumulated in or on components is transferred into the interior air by means of a temporarily increased component temperature due to reduced cooling and is then removed from the inside of the housing by means of a ventilation device.

[0034] Possible embodiments of the inventive method and the corresponding inventive photovoltaic inverter are described in detail below with reference to the attached figures. Fig. Figure 1 shows a sectional view through a housing of an embodiment of a photovoltaic inverter according to the invention, which is operated according to the method according to the invention; Fig. Figure 2 schematically shows a possible circuit of the photovoltaic inverter.

[0035] How to see from the section view according to Fig. As can be seen in Figure 1, the photovoltaic inverter 1 shown there has a housing 2. Inside the housing 2, i.e., in the interior of the device, are various components and electronic parts. The one in Fig. The photovoltaic inverter shown in Figure 1 serves to convert a direct current (DC) voltage into an alternating current (AC) voltage. Generally, inverters are used to convert a DC voltage generated by an energy source, such as photovoltaic modules, into a sinusoidal AC voltage, which can be fed into a power grid or used directly to supply consumers. For this purpose, the inverter shown in Figure 1... Fig. The photovoltaic inverter 1 shown in Figure 1 contains components, in particular power electronic components, which also generate losses in the form of heat during operation of the photovoltaic inverter 1. In the illustrated embodiment, the components of the photovoltaic inverter 1 are cooled by at least one cooling device 3 attached to the housing 2 of the photovoltaic inverter 1. This cooling device 3 is preferably controlled by a controller 4 provided inside the photovoltaic inverter 1. In the photovoltaic inverter 1 according to the invention, the cooling of the power electronic components of the photovoltaic inverter 1 by the cooling device 3 is at least partially and temporarily reduced during operation of the photovoltaic inverter 1 in a heating routine in order to increase the internal temperature of the air inside the housing 2 of the photovoltaic inverter 1.

[0036] Upon detection of an event or upon detection of a predetermined state (triggering), the heating routine can also be initiated or started by the control unit 4 to heat components of the photovoltaic inverter 1.

[0037] Due to the increased internal temperature, the air inside the housing 2 heats up and expands. The expanding air escapes from the housing 2 of the photovoltaic inverter 1 through a vent 5 provided on the housing 2, thereby partially carrying away the humidity present inside the housing.

[0038] The heating routine primarily serves to prevent moisture from accumulating in or on components, or to reduce existing moisture within them. Reducing the relative humidity inside the housing is intended to prevent or at least partially reverse this moisture accumulation. The heating routine increases the internal temperature of the device by reducing or shutting down (corresponding to a reduction to zero) the cooling. This also increases the temperature of the components. The heating routine reduces the relative humidity of the air inside the photovoltaic inverter 1 due to the increased internal temperature. Moisture from the components can thus be transferred into the air inside the housing. The heating routine promotes the drying of damp surfaces (e.g., on circuit boards, components). Moisture diffuses (passively) out of the components.The drying of the surfaces is a faster process than the diffusion of moisture from the components. The released moisture is passively and automatically transferred into the air inside the device. Finally, the moist air is expelled from the housing 2 via the membrane of the ventilation device 5 (secondary). This occurs passively and automatically.

[0039] The increase in the internal temperature through the heating routine therefore occurs either temporarily, as needed, or through triggering, and not beyond a certain level or upper temperature threshold, as otherwise components inside the housing could be damaged or their operating behavior could move outside a specified range.

[0040] At the in Fig. In the embodiment shown in Figure 1, the cooling device 3 attached to the housing 2 of the photovoltaic inverter 1 comprises a heat sink 3A with cooling fins and an external fan 3B for generating an airflow, the airflow generated by the external fan 3B flowing along the cooling fins of the heat sink 3A. The heat sink 3A of the cooling device 3 is preferably thermally connected to power electronic components of the photovoltaic inverter 1 located inside the housing 2 for heat dissipation. In the embodiment shown in Figure 1, the heat sink 3A is connected to the power electronic components of the photovoltaic inverter 1 located inside the housing 2 for heat dissipation. Fig. In the embodiment shown in Figure 1, the heat sink 3A with its cooling fins is located directly above the external fan 3B, so that the airflow generated by the external fan 3B flows upwards along the cooling fins of the heat sink 3A. The control unit 4, located inside the housing 2 of the photovoltaic inverter 1, is preferably connected to the external fan 3B, which is attached to the outside of the housing 2, via a control interface. The control unit 4 can control the operation of the external fan 3B, in particular by activating or deactivating it. In one possible embodiment, the control unit 4 can also control or adjust the speed of the external fan 3B.

[0041] At the in Fig. In the embodiment shown in Figure 1, the photovoltaic inverter 1 additionally has an internal fan 6 which can generate a circulating airflow within the housing 2 of the photovoltaic inverter 1 on a component carrier 7. In the embodiment shown in Figure 1, the photovoltaic inverter 1 is equipped with an internal fan 6 which can generate a circulating airflow within the housing 2 of the photovoltaic inverter 1. Fig. In the embodiment shown in Figure 1, the component carrier is a circuit board or printed circuit board. The component carrier 7 has a front surface 7A and a back surface 7B. Various electronic components 8-i, in particular power electronic components, can be located on the front surface of the component carrier 7, which have different technical functions depending on the circuit. The method according to the invention is suitable for any moisture-sensitive components, in particular passive or active electronic components. The number and type of the different components 8-i can vary depending on the circuit. The various components 8-i are connected to each other via conductor tracks on the component carrier 7, which is designed as a printed circuit board, to implement the respective circuit. In the embodiment shown in Figure 1, the components 8-i are connected to each other via conductor tracks on the component carrier 7, which is designed as a printed circuit board. Fig. In the embodiment shown in Figure 1, a power transistor module 9 with power transistors is located on the back side 7B of the component carrier 7, which is designed as a printed circuit board. These power transistors generate a significant amount of heat during operation of the photovoltaic inverter 1. The heat sink 3A of the cooling device 3 is thermally connected to the power transistor module 9 for heat dissipation. The heat generated by the power transistors of the power transistor module 9 is dissipated to the heat sink 3A, over whose cooling fins the airflow generated by the external fan 3B flows. The component carrier 7, in particular the components shown in Figure 1, is designed to withstand the heat generated by the power transistor module 9. Fig. The printed circuit board (PCB) shown in Figure 1 is preferably arranged vertically within the housing 2. The PCB can also be arranged horizontally. The heating routine interrupts and at least partially reverses moisture absorption into components and moisture absorption onto components attached to the PCB. The venting device 5 provided on the housing 2 is located, for example, in the upper area of ​​the housing 2. The internal fan 6 can generate a circulating airflow within the housing 2. The air flowing upwards at the front 7A of the component carrier 7 is deflected by the internal fan 6 on the inside of the housing 2 and flows downwards along the inside of the housing 2, as shown in Figure 1. Fig. Figure 1 is shown graphically. This achieves a homogenization of the internal air temperature by counteracting natural stratification. To reduce the humidity inside the housing 2 of the photovoltaic inverter 1, the controller 4 can at least partially deactivate the external fan 3B during operation of the photovoltaic inverter 1, thereby increasing the internal temperature of the air inside the housing 2 and reducing heat dissipation. Simultaneously, the controller 4 of the photovoltaic inverter 1 can activate the internal fan 6 to generate the airflow circulating within the housing 2. In one possible embodiment, the external fan 3B is completely deactivated by the controller 4 during operation of the photovoltaic inverter 1, i.e., during the conversion of the DC voltage to the AC voltage.Alternatively, the controller 4 can reduce the speed of the external fan 3B, thus partially deactivating it. In either case, the airflow along the cooling fins of the heat sink 3A is reduced, so less heat is dissipated from the power transistor module 9. This corresponds to the heating routine and causes the air inside the housing 2 to warm up. Since no absolute humidity from the outside air enters during the heating routine due to the housing, the absolute amount of humidity inside the housing remains constant. The relative humidity of the inside air is reduced due to its warming. This dries the components.

[0042] Due to the thermal expansion of the interior air, some of the interior air is released to the outside environment via the ventilation device 5 provided on the housing 2, thereby carrying away some of the interior air's humidity. This results in an overall decrease in the absolute humidity of the air inside the housing 2.

[0043] In one possible embodiment, the automatic deactivation of the external fan 3B by the control unit 4 of the photovoltaic inverter 1 occurs at regular intervals. Furthermore, the deactivation of the external fan 3B can occur during adjustable periods. The control unit 4 has a processor that executes a control program to control the external fan 3B and / or the internal fan 6. For example, the processor of the control unit 4 executes a drying or heating routine that temporarily reduces the speed of the external fan 3B of the cooling device 3 on a regular basis, so that even during partial load operation of the photovoltaic inverter 1, the internal temperature is raised, allowing accumulated moisture to escape from the device and its components and, due to thermal expansion, be carried out of the housing 2 via the ventilation device 5 into the environment.

[0044] At the in Fig. In the embodiment shown in 1, external devices or systems, for example modules of a photovoltaic system, can be connected via connector plugs 10. These are preferably positioned close to the housing 2. In the embodiment shown in Fig. In the embodiment shown in Figure 1, the venting device 5 has a water vapor-permeable compensating membrane 5A. In a preferred embodiment, this water vapor-permeable compensating membrane 5A is preferably designed to be impermeable to particles present in the ambient air. In one possible embodiment, the compensating membrane 5A consists of a water vapor-permeable material. The compensating membrane 5A allows water vapor to pass through or diffuse through its pores. Both air and moisture can escape from the interior of the housing 2 to the outside through the compensating membrane 5A of the venting device 5. Conversely, particles are retained by the compensating membrane 5A. This provides additional protection for the components located inside the housing 2 against external contamination such as dust or salt.Alternatively, the venting device 5 can also include a controllable balancing valve. In a possible implementation, this controllable balancing valve can be controlled by the controller 4. As shown in . Fig. As shown in Figure 1, the device implemented in the photovoltaic inverter 1 for reducing humidity does not necessarily require a sensor for measuring humidity. Therefore, no additional hardware is required.

[0045] In one possible embodiment, the photovoltaic inverter 1 has an internal temperature sensor, particularly to prevent temperatures within the housing 2 that could damage the components. The internal temperature sensor provides temperature sensor data to the controller 4, which monitors the internal temperature. This sensor data serves as the basis for the heating routine and ensures that the internal area is kept dry. Based on the sensor data, the controller 4 recognizes, for example, that the interior of the housing has not reached a certain internal temperature for a minimum period of time, thus initiating the heating routine. Such an internal temperature sensor is standard for device protection and monitoring even without the method according to the invention. Therefore, no additional hardware is required.

[0046] Fig.Figure 2 schematically shows a possible wiring configuration of a photovoltaic inverter 1 according to the invention with an integrated controller 4, which controls both an external fan 3B provided directly on the outside of the housing 2 and an internal fan 6. The photovoltaic inverter 1 can optionally have an input DC-DC stage 11, which is connected via an intermediate circuit 12 to an inverter stage 13 of the inverter 1. In the illustrated embodiment, photovoltaic modules of a photovoltaic string 14 are connected to the input of the DC-DC stage 11 of the photovoltaic inverter 1. In the illustrated embodiment, the intermediate circuit 12 includes an intermediate circuit capacitor C. ZK as well as a discharge circuit for discharging the intermediate circuit capacitor C ZK The discharge circuit includes an intermediate circuit discharge resistor R. ZK , to which a switch S is connected serially ZKRis switched on. By closing switch S ZKR can the intermediate circuit capacitor C ZK via the intermediate circuit discharge resistor R ZK discharged. At the intermediate circuit capacitor C ZK For example, this could be a film capacitor, which is sensitive to humidity. On the output side, the inverter stage 13 of the photovoltaic inverter 1 can be connected to a power supply network 15. The alternating voltage generated by the inverter 1 can be fed into the power supply network 15. Alternatively, the generated alternating voltage can also be supplied to local consumers.

[0047] The method according to the invention can reduce moisture that has diffused into and accumulated on components 8-i, as well as the humidity within the housing 2 of an electronic device. This protects electronic components of the device that are sensitive to moisture. This applies in particular to film capacitors, optoelectronic components, module potting compounds, and, for example, semiconductor components. Especially in the case of film capacitors, such as those provided in the intermediate circuit 12 of a photovoltaic inverter 1, humidity can diffuse through their potting compound and damage the capacitor's surface. The method according to the invention is particularly suitable for devices that are installed in warm, humid environments, especially outdoors, or in cool, humid environments, for example, in a damp basement.Furthermore, the method according to the invention is also suitable for devices that are operated largely or even permanently under partial load.

[0048] In these cases, medium or high relative humidity prevails inside the device housing 2, which promotes the diffusion of moisture into the components or electronic parts. While a hermetically sealed housing could prevent the ingress of moisture, this is costly due to the technically complex nature of the internal pressure fluctuations caused by heating or cooling of the internal air.

[0049] In a photovoltaic inverter 1, moisture can accumulate in the inverter's components if the inverter 1 is not operated for a certain period of time, or only for a short period, beyond a predetermined power output, because this results in permanently low component operating temperatures. In this case, the inventive method for reducing component and internal humidity can be implemented. In one possible embodiment, the affected device, in particular the photovoltaic inverter 1, is heated once or in several stages by the control unit 4 to a high, but still tolerable, internal temperature. This heating reduces the relative humidity inside the device's housing 2. Simultaneously, the component temperature of the affected components is increased, for example, the temperature of a film capacitor.This is achieved by additionally drying out affected components, such as film capacitors, within the interior of the device. In the method according to the invention, the increase in the device's internal temperature is preferably not achieved by means of additional components, but rather by reducing the cooling. For example, the speed of the external fan 3B can be reduced, thereby reducing heat dissipation. Simultaneously, the internal fan 6 may continue to operate or even have its speed increased. Additionally, the internally circulating air ensures a uniform heat distribution within the device to prevent harmful hotspots. In one possible embodiment of the method according to the invention, several heating cycles can be provided. During each heating cycle, the internal air in the housing 2 expands. Moist internal air is then carried out to the outside environment.In one possible embodiment, as the photovoltaic inverter 1 cools down, humid outside air can be drawn back in. The absolute amount of moisture emitted is thus determined by the degree to which the internal air of the device is heated and the absolute humidity of the outside air in the vicinity of the photovoltaic inverter 1. The amount of moisture emitted can be increased by means of several heating cycles. The heating and drying routine provided by the controller 4's processor is purely software-based and can be retrofitted via software updates if necessary. In another possible embodiment, the power electronics components or other electronic components present in the photovoltaic inverter 1 can also contribute to heating the interior, preferably using suitable operating modes of the photovoltaic inverter 1.For example, the intermediate circuit discharge resistors R provided in the intermediate circuit. ZKto contribute to the heating of the inverter's interior. For example, the photovoltaic inverter 1 can be put into a shutdown mode by the controller 4. The inventive method or drying routine can be triggered by various events. In one possible embodiment, the method is executed periodically at specific intervals. For example, the inventive method is started automatically once a month. Alternatively, the inventive method can be started automatically after a certain operating time has elapsed without exceeding a certain internal temperature level. Furthermore, in one possible embodiment, a humidity model can be incorporated. The moisture susceptibility of relevant components is stored in a simple model for moisture accumulation, which then triggers the inventive drying routine once a certain threshold is reached.An advantage of the method according to the invention is that it does not require any sensor-based measurement of humidity. In a possible embodiment, additional sensors can of course be provided, which, for example, measure the humidity inside the housing 2 and trigger a heating or drying routine when a certain threshold is exceeded. However, this embodiment requires additional hardware. Reference symbol list 1 photovoltaic inverter 2 cases 3 Cooling device 3A Heat sink 3B Outdoor fan 4 Control 5. Venting device 5A Compensating Membrane 6 internal fans 7 Component carriers 7A Front of the developer 7B Rear of the developer 8-i components 9 Power transistor module 10 connector plugs 11 DC-DC stages 12 Intermediate circle 13 Inverter Stage 14 photovoltaic strings 15 Power supply network

Claims

[1] Method for operating a photovoltaic inverter (1) for converting a direct current voltage (U DC ) into an alternating voltage (U AC ) is provided, wherein the photovoltaic inverter (1) has components (8-i) which are cooled by at least one heat sink (3A) of a cooling device (3) attached to a housing (2) of the photovoltaic inverter (1), wherein the heat sink (3A) has cooling fins along which an airflow flows, which is generated by an external fan (3B) of the cooling device (3) attached to the outside of the housing (2), wherein the external fan (3B) is controlled by a control unit (4) of the photovoltaic inverter (1) provided within the photovoltaic inverter (1), wherein in at least one heating routine the cooling of the components of the photovoltaic inverter (1) by the cooling device (3) during the operation of the photovoltaic inverter (1) is used to increase an internal temperature, T innen , the air located inside the housing (2) of the photovoltaic inverter (1) is partially reduced, wherein the relative humidity in the housing (2) of the photovoltaic inverter (1) is reduced and the components of the photovoltaic inverter (1) are dried, wherein the internal temperature T within the housing (2) of the photovoltaic inverter (1) is increased due to the heating routine innen, expanding air is released at least partially through a water vapor permeable compensating membrane (5A) of a venting device (5) provided on the housing (2) of the photovoltaic inverter (1) into the environment of the photovoltaic inverter (1). [2] Method according to claim 1, wherein a circulating airflow is generated inside the housing (2) of the photovoltaic inverter (1). [3] Method according to one of the preceding claims 1 or 2, wherein the external fan (3B) of the cooling device (3) attached to the outside of the housing (2) of the photovoltaic inverter (1) is automatically deactivated by the control (4) of the photovoltaic inverter (1) at regular intervals or during adjustable periods to reduce cooling. [4] Method according to any one of the preceding claims 1 to 3, wherein the control (4) of the photovoltaic inverter (1) initiates the heating routine for heating components (8-i) of the photovoltaic inverter (1) in one or more heating cycles upon detection of a predetermined event or a predetermined state of the photovoltaic inverter (1), wherein in each heating cycle of the heating routine an expansion of the internal air located in the housing (2) takes place, whereby moist internal air is transported outwards into the environment of the photovoltaic inverter (1). [5] Method according to any one of the preceding claims 1 to 4, wherein at least one internal fan (6) arranged in the housing (2) is controlled by the control (4) of the photovoltaic inverter (1) in such a way that a circulating airflow is generated inside the housing (2) of the photovoltaic inverter (1). [6] Method according to claim 5, wherein the control (4) of the photovoltaic inverter (1) to reduce the humidity existing inside the housing (2) of the photovoltaic inverter (1) at least partially deactivates the external fan (3B) of the cooling device (3) during operation of the photovoltaic inverter (1) to increase the internal temperature of the air located inside the housing (2) and activates the internal fan (6) to generate the airflow circulating inside the housing (2). [7] Method according to claim 6, wherein the external fan (3B) of the cooling device (3) is automatically deactivated by the control (4) of the photovoltaic inverter (1) at regular intervals and / or during adjustable time periods. [8] Method according to any one of the preceding claims 1 to 7, wherein in the heating routine power electronic components are additionally operated in suitable operating modes. [9] Method according to claim 8, wherein an additional intermediate circuit discharge resistor (R) is used for heating in the heating routine. ZK ) of an intermediate circuit (12) of the photovoltaic inverter (1) is switched on. [10] Photovoltaic inverter (1) for converting a direct current voltage (U DC ) into an alternating voltage (U AC), wherein the photovoltaic inverter (1) comprises components (8-i) which are cooled by at least one heat sink (3A) of a cooling device (3) attached to a housing (2) of the photovoltaic inverter (1), wherein the heat sink (3A) has cooling fins along which an airflow flows, which is generated by an external fan (3B) of the cooling device (3) attached to the outside of the housing (2), wherein the external fan (3B) is controlled by a control unit (4) of the photovoltaic inverter (1) provided within the photovoltaic inverter (1), wherein in at least one heating routine the cooling of the components (8-i) of the photovoltaic inverter (1) by the cooling device (3) during operation of the photovoltaic inverter (1) is used to increase an internal temperature, T innen, the air inside the housing (2) of the photovoltaic inverter (1) is partially reduced, thereby reducing the relative humidity inside the housing (2) of the photovoltaic inverter (1) and / or drying the components of the photovoltaic inverter (1), whereby the internal temperature T inside the housing (2) of the photovoltaic inverter (1) is increased by the heating routine. innen , expanding air is released at least partially through a water vapor permeable compensating membrane (5A) of a venting device (5) provided on the housing (2) of the photovoltaic inverter (1) into the environment of the photovoltaic inverter (1). [11] Photovoltaic inverter (1) according to claim 10, wherein moisture-sensitive components (8-i) are attached to a front (7A) of a component carrier (7) on the back (7B) of which a power transistor module (9) is located, which is thermally connected to the heat sink (3A) of the cooling device (3) for heat dissipation. [12] Photovoltaic inverter (1) according to claim 11, wherein the component carrier (7) has a printed circuit board arranged vertically inside the housing (2). [13] Photovoltaic inverter (1) according to claim 11 or 12, wherein the moisture-sensitive components (8-i) are intermediate circuit capacitors (C ZK ) of an intermediate circuit (12) of the photovoltaic inverter (1).

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