Temperature detection method and circuit of inversion inductor and photovoltaic inverter

Abstract

The invention is suitable for the field of photovoltaic technology, and provides a temperature detection method and circuit of an inversion inductor and a photovoltaic inverter, and the temperature detection method of the inversion inductor comprises the following steps: detecting the inductance voltage at the two ends of the inversion inductor in an inversion topology circuit, and carrying out the filtering processing of the inductance voltage through a voltage filter; obtaining an inductive current of the inversion inductor; calculating the active power of the inversion inductor according to the inductance current and the inductance voltage after filtering processing; calculating a direct current resistance value of the inversion inductor according to the active power of the inversion inductor; and determining the temperature of the inversion inductor based on the direct current resistance value of the inversion inductor. According to the technical scheme, the temperature of the inversion inductor can be rapidly and accurately detected, and normal operation of the photovoltaic inverter is prevented from being affected by too high temperature.

Description

Technical Field

[0001] The invention belongs to the field of photovoltaic technology, and in particular relates to a temperature detection method and circuit of an inverter inductor and a photovoltaic inverter. Background Art

[0002] The working circuit of the photovoltaic inverter is equipped with multiple inductors. The inductor is one of the most critical components of the photovoltaic inverter, and its main functions include energy storage, voltage boost, filtering, and EMI elimination.

[0003] However, for current photovoltaic inverters, due to factors such as product cost and system complexity, the temperature of the inverter inductor is generally not measured. During the research and development process, the temperature of the inverter inductor under normal working conditions is only tested, as long as the temperature of the inverter inductor meets the requirements. However, if the temperature of the inverter inductor is unknown, once the temperature of the inverter inductor is too high, the internal potting glue, casing and other materials of the inverter inductor will age and fail, causing damage to the photovoltaic inverter.

[0004] If the temperature of the inverter inductor is measured, it is necessary to embed thermocouples, thermistors and other devices to measure the temperature of the inverter inductor. However, embedding thermocouples, thermistors and other devices will increase system complexity and product cost. Summary of the invention

[0005] The embodiment of the present invention provides a temperature detection method for an inverter inductor, aiming to quickly and accurately measure the temperature of the inverter inductor and reduce the temperature measurement cost of the inverter inductor.

[0006] The embodiment of the present invention is implemented as follows: a temperature detection method of an inverter inductor is applied to a temperature detection circuit of an inverter inductor, and the temperature detection method of the inverter inductor comprises the following steps:

[0007] Detecting the inductor voltage at both ends of the inverter inductor in the inverter topology circuit and filtering the inductor voltage through a voltage filter;

[0008] Obtaining the inductor current of the inverter inductor;

[0009] Calculating the active power of the inverter inductor according to the inductor current and the filtered inductor voltage;

[0010] Calculating the DC resistance value of the inverter inductor according to the active power of the inverter inductor;

[0011] The temperature of the inverter inductor is determined based on the direct current resistance value of the inverter inductor.

[0012] Furthermore, the step of calculating the active power of the inverter inductor according to the inductor current and the filtered inductor voltage includes:

[0013] Calculating the effective value of the inductor voltage and determining the voltage phase of the inductor voltage by phase locking;

[0014] Obtaining the effective current value and current phase of the inductor current;

[0015] The active power of the inverter inductor is calculated according to the voltage effective value, the voltage phase, the current effective value, and the current phase.

[0016] Furthermore, the step of calculating the active power of the inverter inductor of the inductor according to the voltage effective value, the voltage phase, the current effective value and the current phase includes:

[0017] Acquiring filtering parameters of the voltage filter;

[0018] Calculating the voltage effective value and voltage phase of the inductor voltage before filtering by the voltage filter according to the filtering parameter, the voltage effective value and the voltage phase;

[0019] Based on the active power calculation formula Calculate the active power of the inverter inductor of the inductor; the UL is the effective value of the voltage before filtering, the IL is the effective value of the current, and the is the voltage phase before filtering, is the current phase;

[0020] The DC resistance value of the inverter inductor is calculated according to the active power of the inverter inductor.

[0021] Furthermore, after the step of calculating the voltage effective value and the voltage phase of the inductor voltage before filtering by the voltage filter according to the filtering parameter, the voltage effective value and the voltage phase, it also includes:

[0022] Based on reactive power calculation formula Calculating the reactive power of the inverter inductor; calculating the inductance value of the inverter inductor according to the reactive power of the inverter inductor;

[0023] Determining whether the inductance value of the inverter inductor is greater than a first inductance threshold;

[0024] When the inductance value of the inverter inductor is greater than the first inductance threshold, a first alarm prompt is issued.

[0025] Furthermore, after the step of calculating the inductance value of the inverter inductor according to the reactive power of the inverter inductor, the method further includes:

[0026] Determining whether the inductance value of the inverter inductor is less than a second inductance threshold;

[0027] When the inductance value of the inverter inductor is less than the second inductance threshold, a second alarm prompt is issued.

[0028] Furthermore, the step of determining the temperature of the inverter inductor based on the DC resistance value of the inverter inductor includes:

[0029] Obtaining a mapping relationship between a DC resistance value of the inverter inductor and temperature;

[0030] Determining a temperature corresponding to a DC resistance value of the inverter inductor based on the mapping relationship;

[0031] The determined temperature is used as the temperature of the inverter inductor.

[0032] Furthermore, after the step of determining the temperature of the inverter inductor based on the DC resistance value of the inverter inductor, the method further includes:

[0033] Determining whether the temperature of the inverter inductor is greater than a preset temperature threshold;

[0034] When the temperature of the inverter inductor is greater than the preset temperature threshold, the inductor protection mechanism is started.

[0035] The present invention also provides a temperature detection circuit for an inverter inductor, the temperature detection circuit for the inverter inductor comprising a voltage detection filter circuit and a temperature calculation device; the detection end of the voltage detection filter circuit is connected to the inverter inductor in the inverter topology circuit, the output end of the voltage detection filter circuit is connected to the first input end of the temperature calculation device, and the second input end of the temperature calculation device receives the inductor current of the inverter inductor in the inverter topology circuit;

[0036] The voltage detection filter circuit is used to detect the inductor voltage at both ends of the inverter inductor in the inverter topology circuit and filter the inductor voltage through a voltage filter;

[0037] The temperature calculation device is used to calculate the active power of the inverter inductor according to the inductor current and the filtered inductor voltage; calculate the DC resistance value of the inverter inductor according to the active power of the inverter inductor; and determine the temperature of the inverter inductor based on the DC resistance value of the inverter inductor.

[0038] Furthermore, the voltage detection filter circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a first capacitor, a second capacitor and an operational amplifier;

[0039] One end of the first resistor is connected to one end of the inverter inductor, the other end of the first resistor is connected to one end of the second resistor and one end of the second capacitor, and the other end of the second resistor is connected to one end of the first capacitor and the first input end of the operational amplifier;

[0040] The other end of the first capacitor is connected to one end of the third resistor and the other end of the inverter inductor, and the other end of the third resistor is connected to one end of the fourth resistor and the second input end of the operational amplifier;

[0041] The other end of the second capacitor and the other end of the fourth resistor are connected to the output end of the operational amplifier, and the output end of the operational amplifier is connected to the first input end of the temperature calculation device.

[0042] The present invention further provides a photovoltaic inverter, comprising the temperature detection circuit of the inverter inductor as described in any one of the above items.

[0043] The technical solution of the present invention obtains the inductor current of the inverter inductor and detects the inductor voltage at both ends of the inverter inductor, and outputs the detected inductor voltage after filtering, and then calculates the active power of the inverter inductor based on the inductor current and the filtered inductor voltage, calculates the DC resistance value of the inverter inductor using the active power of the inverter inductor, and finally quickly and accurately obtains the temperature of the inverter inductor through the DC resistance value of the inverter inductor. Since the temperature measurement of the inverter inductor does not require the embedding of devices such as thermocouples and thermistors, it can not only detect the temperature of the inverter inductor in real time, improve the reliability of the photovoltaic inverter, but also effectively reduce the cost of the temperature measurement of the inverter inductor. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a flow chart of an embodiment of a temperature detection method of an inverter inductor according to the present invention;

[0045] Figure 2 is a circuit structure block diagram of an embodiment of a temperature detection circuit of an inverter inductor;

[0046] Figure 3 is a phase diagram of an embodiment of an inductive reactance voltage and an inductive impedance voltage;

[0047] Figure 4 The figure is a schematic diagram of the circuit structure of an embodiment of a temperature detection circuit for an inverter inductor. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0049] The technical solution of the present invention obtains the inductor current of the inverter inductor and detects the inductor voltage at both ends of the inverter inductor, and outputs the detected inductor voltage after filtering, and then calculates the active power of the inverter inductor based on the inductor current and the filtered inductor voltage, calculates the DC resistance value of the inverter inductor using the active power of the inverter inductor, and finally quickly and accurately obtains the temperature of the inverter inductor through the DC resistance value of the inverter inductor. Since the temperature measurement of the inverter inductor does not require the embedding of devices such as thermocouples and thermistors, it can not only detect the temperature of the inverter inductor in real time, improve the reliability of the photovoltaic inverter, but also reduce the cost of the temperature measurement of the inverter inductor.

[0050] Embodiment 1

[0051] Reference Figure 1 The temperature detection method of the inverter inductor is applied to the temperature detection circuit of the inverter inductor. In one embodiment, the structure of the temperature detection circuit of the inverter inductor is as follows: Figure 2 As shown, the temperature detection circuit of the inverter inductor includes a voltage detection filter circuit and a temperature calculation device, and the voltage detection filter circuit includes a voltage filter. The detection end of the voltage detection filter circuit is connected to the inverter inductor in the inverter topology circuit, and is used to detect the inductor voltage at both ends of the inverter inductor and filter out the high-frequency AC voltage; and the output end of the voltage detection filter circuit is connected to the first input end of the temperature calculation device, and the second input end of the temperature calculation device receives the inductor current of the inverter inductor in the inverter topology circuit.

[0052] The voltage detection filter circuit may include a voltage filter. The voltage detection filter circuit is used to detect the inductor voltage at both ends of the inverter inductor and filter out the high-frequency AC voltage.

[0053] The temperature calculation device may include one or more hardware circuit modules such as analog circuits, digital logic circuits or processors, and the processor may run the temperature detection program of the inverter inductor and perform corresponding operations. The processor includes but is not limited to a single-chip microcomputer, a DSP, an ARM, etc.

[0054] The temperature detection method of the inverter inductor comprises the following steps:

[0055] Step S1, detecting the inductor voltage across the inverter inductor in the inverter topology circuit and filtering the inductor voltage through a voltage filter;

[0056] In this embodiment, the inverter topology circuit includes but is not limited to an ANPC inverter topology circuit, an NPC-1 inverter topology circuit, an NPC-T inverter topology circuit, a two-level inverter topology circuit, and a flying three-level inverter topology circuit. The inverter inductor in the inverter topology circuit, that is, the inverter inductor to be detected, can be equivalent to an inductor and a resistor in series, such as Figure 2 The inductor L and the resistor R shown in FIG. 1 are connected in series, and the inverter inductor to be detected is connected to the PCB board through terminals.

[0057] When the photovoltaic inverter is working stably, based on the volt-second balance principle, in the stable working state of the switching power supply, the voltage across the inductor multiplied by the conduction time when the switch tube is turned on is equal to the voltage across the inductor multiplied by the off time when the switch is turned off, that is, the positive volt-second value across the inductor is equal to the negative volt-second value; at the same time, the current of the inverter inductor in the inverter topology circuit is the industrial frequency AC current. It can be seen that the integral of the voltage across the inductor over time in an integer industrial frequency cycle is equal to zero. The voltage across the inductor is equal to the sum of the square wave voltage of the switching frequency output by the inverter bridge arm, the voltage of the power frequency current on the inductive reactance of the inductor, and the voltage of the power frequency current on the resistor impedance. Since the switching frequency is much greater than the power frequency, when the photovoltaic inverter is stably connected to the grid, the square wave voltage of the switching frequency can be filtered out through a voltage detection filter circuit, such as a voltage filter, to extract the voltage of the power frequency current on the inductive reactance and the voltage on the resistor impedance. The voltage detection filter circuit can be a multi-order low-pass filter circuit, which is used to filter the square wave voltage of the switching frequency, extract the voltage of the power frequency current on the inductive reactance and the voltage on the resistor impedance and output them to the temperature calculation module.

[0058] Step S2, obtaining the inductor current of the inverter inductor;

[0059] In practical applications, photovoltaic inverters control grid connection by detecting the inductor current. Therefore, the inductor current of the inverter inductor can be obtained through the photovoltaic inverter, and the current phase, current effective value and other parameters of the inductor current can be calculated without the need to set up additional hardware circuits, so as to achieve the effect of reducing costs and improving efficiency.

[0060] Step S3, calculating the active power of the inverter inductor according to the inductor current and the filtered inductor voltage;

[0061] The active power of the inverter inductor can be calculated by the inductor current of the inverter inductor and the filtered inductor voltage, and the DC resistance value of the inverter inductor can be calculated by the active power of the inverter inductor. Finally, the temperature of the inverter inductor can be determined based on the DC resistance value of the inverter inductor.

[0062] In one embodiment, step S3 includes:

[0063] Step S31, calculating the effective value of the inductor voltage and determining the voltage phase of the inductor voltage by phase locking;

[0064] Step S32, obtaining the effective current value and current phase of the inductor current;

[0065] Step S33, calculating the active power of the inverter inductor according to the voltage effective value, the voltage phase, the current effective value and the current phase.

[0066] In this embodiment, the voltage phase of the inductor voltage relative to the grid after phase locking is obtained, and the voltage effective value of the inductor voltage is calculated. In addition, the current phase and current effective value of the inductor current relative to the grid are obtained through the photovoltaic inverter. The active power of the inverter inductor is then calculated based on the determined voltage effective value, voltage phase, current effective value, and current phase.

[0067] Specifically, step S33 includes:

[0068] Step S331, obtaining filtering parameters of the voltage filter;

[0069] Step S332, calculating the voltage effective value and voltage phase of the inductor voltage before being filtered by the voltage filter according to the filtering parameter, the voltage effective value and the voltage phase;

[0070] Step S333, based on the active power calculation formula Calculate the active power of the inverter inductor; the UL is the effective value of the voltage before filtering, the IL is the effective value of the current, is the voltage phase before filtering, is the current phase.

[0071] Step S334: calculating the DC resistance value of the inverter inductor according to the active power of the inverter inductor.

[0072] The filtering parameters of the voltage filter are known. Therefore, the voltage effective value and voltage phase of the inductor voltage before filtering by the voltage filter can be calculated by the filtering parameters of the voltage filter, and then the calculation formula of the active power of the inverter inductor can be used. Calculate the active power of the inverter inductor; in the formula, UL is the effective value of the voltage before being filtered by the voltage filter, IL is the effective value of the current, is the voltage phase before being filtered by the voltage filter, is the current phase. After determining the active power of the inverter inductor, the DC resistance value of the inverter inductor is calculated according to the active power.

[0073] Further, based on the above embodiment, after step S332, the following further steps are included:

[0074] Step S335, based on the reactive power calculation formula Calculating the reactive power of the inverter inductor;

[0075] Step S336, calculating the inductance value of the inverter inductor according to the reactive power of the inverter inductor;

[0076] Step S337, determining whether the inductance value of the inverter inductor is greater than a first inductance threshold;

[0077] Step S338: When the inductance value of the inverter inductor is greater than the first inductance threshold, a first alarm is issued.

[0078] In this embodiment, the reactive power calculation formula of the inverter inductor can be used Calculate the reactive power of the inverter inductor. Combined with the inductor voltage calculation method The inductance value of the inverter inductor can be calculated by XL = 2*π*f*L. Wherein, XL is the inductance reactance value, f is the power frequency, L is the inductance value, and IL is the effective value of the inductance current. If the calculated inductance value of the inverter inductor is greater than the preset first inductance threshold value, it means that the inductor coil and the magnetic core may be abnormal, and a first alarm prompt may be issued through a human-machine display device, such as an LED display screen, an LCD display screen, etc., or through an LED indicator light, for example, a red light indicates that the inductor coil and the magnetic core are abnormal, and a green light indicates that the inductor coil and the magnetic core are operating normally. Of course, a buzzer and other devices can also be set to issue a first alarm prompt.

[0079] Further, based on the above embodiment, after step S336, the following further steps are included:

[0080] Step S339, determining whether the inductance value of the inverter inductor is less than a second inductance threshold;

[0081] Step S3310: When the inductance value of the inverter inductor is less than the second inductance threshold, a second alarm prompt is issued.

[0082] If the inductance value of the inverter inductor is less than the preset second inductance threshold, it means that the internal coil of the inverter inductor may have problems such as open circuit and core damage. At this time, the second alarm prompt can be issued through the human-machine display device, LED indicator, buzzer and other devices, and the first alarm prompt is different from the second alarm prompt. At the same time, maintenance personnel can be arranged to handle it on site in time to further ensure the normal operation of the photovoltaic inverter, so as to effectively improve the reliability of the photovoltaic inverter.

[0083] Step S4, calculating the DC resistance value of the inverter inductor according to the active power of the inverter inductor;

[0084] It can be understood that in the power frequency voltage generated by the power frequency current added to the inductive reactance and the resistor impedance, the resistor impedance voltage is in phase with the inductive current, while the inductive reactance voltage leads the inductive current by 90°, such as Figure 3 As shown, UL1 is the power frequency voltage generated by the power frequency sinusoidal current added to the inductive reactance, UL is the power frequency voltage generated by the power frequency sinusoidal current added to the inductive reactance and the resistive impedance, and XL=2*π*f*L, where XL is the inductive reactance value, f is the power frequency, L is the inductive reactance value, and IL is the effective value of the inductive current.

[0085] Based on this, after calculating the active power of the inverter inductor, the DC resistance value of the inverter inductor can be calculated based on the above content, that is,

[0086] Step S5: determining the temperature of the inverter inductor based on the DC resistance value of the inverter inductor.

[0087] The inverter inductor coil is a metal coil wound around the magnetic core, usually made of copper, aluminum and other materials, and potted with silicone; the losses of the inverter inductor mainly include copper loss, iron loss, eddy current loss, hysteresis loss, etc. These losses will increase the inductor temperature, and the heat is concentrated in the magnetic core and coil. Therefore, the temperature of the coil is very close to the internal temperature of the inductor, and the internal temperature of the inductor can be determined by detecting the coil temperature; the metal resistance temperature sensor, also known as the thermal resistor sensor, is a sensor used to measure temperature. Its working principle is that the resistance value will change with the change of temperature. Once the temperature of the wire changes, the resistance value of the wire will also change accordingly. Therefore, the temperature of the inverter inductor can be calculated by measuring the change of the resistance value of the inverter inductor. The DC resistance of the inductor metal coil is linearly related to the temperature, and the change of the resistance value of the inverter inductor can accurately reflect the change of the inductor temperature. Therefore, after calculating the DC resistance value of the inverter inductor, the current temperature of the inverter inductor can be quickly determined by the relationship between the DC resistance value of the inverter inductor and the temperature.

[0088] In order to better illustrate the relationship between the resistance and temperature of the inverter inductor, the coil material of the inverter inductor is copper. The resistivity of copper at 20°C is ρ = 1.7*10 -8 , the resistivity of the metal coil conductor is expressed as Among them, ρ is resistivity, S is cross-sectional area, R is resistance value, and L is conductor length. It can be seen that the relationship between the resistance value and temperature of the conductor is: R(t)=R0*(1+At+B*t 2 +C*t 3+……), where t is temperature, R0 is resistance at 0℃, R(t) is resistance at t℃, A, B, C…… are temperature coefficients, i.e. constants, and B, C…… are often very small, close to zero, and can be ignored.

[0089] Specifically, in one embodiment, step S5 includes:

[0090] Step S51, obtaining a mapping relationship between the DC resistance value of the inverter inductor and the temperature;

[0091] Step S52, determining a temperature corresponding to the DC resistance value of the inverter inductor based on the mapping relationship;

[0092] Step S53: taking the determined temperature as the temperature of the inverter inductor.

[0093] The technical solution of this embodiment detects the inductor voltage and inductor current at both ends of the inverter inductor, and outputs the detected inductor voltage after filtering, and then calculates the active power of the inverter inductor based on the inductor current and the filtered inductor voltage, and uses the active power to calculate the DC resistance value of the inverter inductor. Finally, the temperature of the inverter inductor is quickly and accurately obtained through the DC resistance value of the inverter inductor. With this arrangement, the real-time temperature of the inverter inductor can be quickly obtained when the photovoltaic inverter is stably connected to the grid, ensuring that the photovoltaic inverter can work safely and reliably, and there is no need to embed devices such as thermocouples and thermistors to detect the temperature of the inverter inductor. While obtaining the real-time temperature of the inverter inductor, the temperature measurement cost of the inverter inductor is effectively saved.

[0094] The present invention also provides a temperature detection circuit of an inverter inductor, such as Figure 2 As shown, the temperature detection circuit of the inverter inductor includes a voltage detection filter circuit and a temperature calculation device; the detection end of the voltage detection filter circuit is connected to the inverter inductor in the inverter topology circuit, the output end of the voltage detection filter circuit is connected to the first input end of the temperature calculation device, and the second input end of the temperature calculation device receives the inverter inductor current of the inverter inductor in the inverter topology circuit;

[0095] The voltage detection filter circuit is used to detect the inductor voltage at both ends of the inverter inductor in the inverter topology circuit and filter the inductor voltage through a voltage filter.

[0096] The temperature calculation device is used to calculate the active power of the inverter inductor according to the inductor current and the filtered inductor voltage; calculate the DC resistance value of the inverter inductor according to the active power of the inverter inductor; and determine the temperature of the inverter inductor based on the DC resistance value of the inverter inductor.

[0097] The technical solution of this embodiment detects the inductor voltage and inductor current at both ends of the inverter inductor through a voltage detection filter circuit, and outputs the detected inductor voltage after filtering. The temperature calculation device calculates the active power of the inverter inductor based on the inductor current and the filtered inductor voltage, calculates the DC resistance value of the inverter inductor using the active power, and finally quickly and accurately obtains the temperature of the inverter inductor through the DC resistance value of the inverter inductor. With this arrangement, the real-time temperature of the inverter inductor can be quickly obtained when the photovoltaic inverter is stably connected to the grid, ensuring that the photovoltaic inverter can work safely and reliably, and there is no need to embed devices such as thermocouples and thermistors to detect the temperature of the inverter inductor. While obtaining the real-time temperature of the inverter inductor, the temperature detection cost of the inverter inductor is effectively reduced.

[0098] In one embodiment, referring to Figure 4 The voltage detection filter circuit includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a first capacitor C1, a second capacitor C2 and an operational amplifier U1; wherein,

[0099] One end of the first resistor R1 is connected to one end of the inverter inductor, and the inverter inductor to be detected can be equivalent to an inductor L and a resistor R connected in series. The other end of the first resistor R1 is connected to one end of the second resistor R2 and one end of the second capacitor C2, and the other end of the second resistor R2 is connected to one end of the first capacitor C1 and the first input end of the operational amplifier U1; the other end of the first capacitor C1 is connected to one end of the third resistor R3 and the other end of the inverter inductor, and the other end of the third resistor R3 is connected to one end of the fourth resistor R4 and the second input end of the operational amplifier U1; the other end of the second capacitor C2 and the other end of the fourth resistor R4 are connected to the output end of the operational amplifier U1, and the output end of the operational amplifier U1 is connected to the first input end of the temperature calculation device.

[0100] The present invention also provides a photovoltaic inverter, which includes a temperature detection circuit of an inverter inductor as described in any one of the above items. Since the photovoltaic inverter adopts all the technical solutions of all the above embodiments, it at least has all the beneficial effects brought by all the technical solutions of all the above embodiments, which will not be described one by one here. It can be understood that those skilled in the art can combine various implementation methods in the above embodiments under the guidance of the above embodiments to obtain technical solutions of multiple implementation methods.

[0101] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for detecting the temperature of an inverter inductor, applied to a temperature detection circuit of an inverter inductor, characterized in that: The temperature detection method of the inverter inductor comprises the following steps: Detecting the inductor voltage at both ends of the inverter inductor in the inverter topology circuit and filtering the inductor voltage through a voltage filter; Obtaining the inductor current of the inverter inductor; Calculating the active power of the inverter inductor according to the inductor current and the filtered inductor voltage; Calculating the DC resistance value of the inverter inductor according to the active power of the inverter inductor; The temperature of the inverter inductor is determined based on the direct current resistance value of the inverter inductor.

2. The method for detecting the temperature of an inverter inductor according to claim 1, wherein: The step of calculating the active power of the inverter inductor according to the inductor current and the filtered inductor voltage comprises: Calculating the effective value of the inductor voltage and determining the voltage phase of the inductor voltage by phase locking; Obtaining the effective current value and current phase of the inductor current; The active power of the inverter inductor is calculated according to the voltage effective value, the voltage phase, the current effective value, and the current phase.

3. The method for detecting the temperature of an inverter inductor according to claim 2, wherein: The step of calculating the active power of the inverter inductor of the inductor according to the voltage effective value, the voltage phase, the current effective value and the current phase comprises: Acquiring filtering parameters of the voltage filter; Calculating the voltage effective value and voltage phase of the inductor voltage before filtering by the voltage filter according to the filtering parameter, the voltage effective value and the voltage phase; The active power of the inverter inductor is calculated based on the active power calculation formula P=UL*IL*cos(φ1-φ2); UL is the effective value of the voltage before filtering, IL is the effective value of the current, φ1 is the voltage phase before filtering, and φ2 is the current phase; The DC resistance value of the inverter inductor is calculated according to the active power of the inverter inductor.

4. The method for detecting the temperature of an inverter inductor according to claim 3, wherein: After the step of calculating the effective value of the voltage and the voltage phase of the inductor voltage before being filtered by the voltage filter according to the filtering parameter, the effective value of the voltage and the voltage phase, the method further includes: Calculate the reactive power of the inverter inductor based on the reactive power calculation formula Q=UL*IL*sin(φ1-φ2); Calculating the inductance value of the inverter inductor according to the reactive power of the inverter inductor; Determining whether the inductance value of the inverter inductor is greater than a first inductance threshold; When the inductance value of the inverter inductor is greater than the first inductance threshold, a first alarm prompt is issued.

5. The method for detecting the temperature of an inverter inductor according to claim 4, characterized in that: After the step of calculating the inductance value of the inverter inductor according to the reactive power of the inverter inductor, the method further includes: Determining whether the inductance value of the inverter inductor is less than a second inductance threshold; When the inductance value of the inverter inductor is less than the second inductance threshold, a second alarm prompt is issued.

6. The method for detecting the temperature of an inverter inductor according to claim 1, wherein: The step of determining the temperature of the inverter inductor based on the DC resistance value of the inverter inductor comprises: Obtaining a mapping relationship between a DC resistance value of the inverter inductor and temperature; Determining a temperature corresponding to a DC resistance value of the inverter inductor based on the mapping relationship; The determined temperature is used as the temperature of the inverter inductor.

7. The method for detecting the temperature of an inverter inductor according to any one of claims 1 to 6, characterized in that: After the step of determining the temperature of the inverter inductor based on the DC resistance value of the inverter inductor, the method further includes: Determining whether the temperature of the inverter inductor is greater than a preset temperature threshold; When the temperature of the inverter inductor is greater than the preset temperature threshold, the inductor protection mechanism is started.

8. A temperature detection circuit for an inverter inductor, characterized in that: The temperature detection circuit of the inverter inductor comprises a voltage detection filter circuit and a temperature calculation device; the detection end of the voltage detection filter circuit is connected to the inverter inductor in the inverter topology circuit, the output end of the voltage detection filter circuit is connected to the first input end of the temperature calculation device, and the second input end of the temperature calculation device receives the inductor current of the inverter inductor in the inverter topology circuit; The voltage detection filter circuit is used to detect the inductor voltage at both ends of the inverter inductor in the inverter topology circuit and filter the inductor voltage through a voltage filter; The temperature calculation device is used to calculate the active power of the inverter inductor according to the inductor current and the filtered inductor voltage; calculate the DC resistance value of the inverter inductor according to the active power of the inverter inductor; and determine the temperature of the inverter inductor based on the DC resistance value of the inverter inductor.

9. The temperature detection circuit of the inverter inductor according to claim 8, characterized in that: The voltage detection filter circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a first capacitor, a second capacitor and an operational amplifier; One end of the first resistor is connected to one end of the inverter inductor, the other end of the first resistor is connected to one end of the second resistor and one end of the second capacitor, and the other end of the second resistor is connected to one end of the first capacitor and the first input end of the operational amplifier; The other end of the first capacitor is connected to one end of the third resistor and the other end of the inverter inductor, and the other end of the third resistor is connected to one end of the fourth resistor and the second input end of the operational amplifier; The other end of the second capacitor and the other end of the fourth resistor are connected to the output end of the operational amplifier, and the output end of the operational amplifier is connected to the first input end of the temperature calculation device.

10. A photovoltaic inverter, characterized in that: The photovoltaic inverter comprises a temperature detection circuit of an inverter inductor as described in any one of claims 8 to 9.

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