Photovoltaic inverter and identification of photovoltaic inverter resonance, control method

Abstract

The application provides a photovoltaic inverter, comprising: an output end of an MPPT circuit is connected with an input end of a group of bus capacitors, an output end of the group of bus capacitors is connected with an input end of an inverter circuit, an output end of the inverter circuit is connected with an input end of a current sensor, an output end of the current sensor is connected with an input end of a filter circuit, and an output end of the filter circuit is connected with an input end of a filter inductor group; a first switch is arranged at at least one position of an output end of the at least one MPPT circuit, the inverter circuit and the filter circuit, and the first switch is used for controlling the output of alternating current; the filter inductor group comprises a differential mode inductor, a temperature sensor is arranged on the differential mode inductor, and the temperature sensor is used for detecting the temperature of the differential mode inductor; and a controller controls the opening or conduction of the first switch according to the temperature of the differential mode inductor. According to the technical scheme, the controller can accurately identify whether the photovoltaic inverter resonates, and the resonance can be inhibited or weakened.

Description

Technical Field

[0001] This application relates to the field of power technology, and more specifically, to the design of a photovoltaic inverter and a method for identifying and controlling the resonance of the photovoltaic inverter. Background Technology

[0002] Currently, the energy crisis is becoming increasingly severe, and clean energy is receiving more and more attention from various countries. Among them, photovoltaic power generation occupies an important position in clean energy. The grid-connected inverter in the photovoltaic power generation system is an extremely important piece of equipment. A grid-connected inverter is a device that converts direct current (DC) into alternating current (AC). A photovoltaic inverter mainly consists of an inverter circuit, an AC filter, an AC switch, and an AC electromagnetic interference (EMI) filter.

[0003] As the photovoltaic industry continues to expand, the number of grid-connected inverters is also increasing, and the scale and structure of grid connections are becoming increasingly complex, making inverter resonance problems more and more apparent. One reason is that most distributed generation systems are located in remote areas, and the transmission lines connecting to the public grid often introduce significant grid impedance, leading to more frequent resonance. Another reason is the increasing number of grid-connected inverters, resulting in harmonic superposition, changes in system impedance, and a higher likelihood of resonance between multiple inverters. This leads to unstable operation of photovoltaic inverters, affecting power generation, and even causing grid-connected inverters to burn out. It also undermines the safe and stable operation of the power grid.

[0004] Therefore, how to accurately identify whether a photovoltaic inverter is resonating, and how to suppress or weaken the resonance when it occurs, is a problem that urgently needs to be solved. Summary of the Invention

[0005] This application provides a photovoltaic inverter and a method for identifying and controlling photovoltaic inverter resonance, which can accurately identify whether a photovoltaic inverter is resonating and suppress or weaken the resonance when the photovoltaic inverter is resonating.

[0006] In one aspect, a photovoltaic inverter is provided, comprising: at least one MPPT circuit, a set of bus capacitors, an inverter circuit, a current sensor, a filter circuit, a filter inductor group, a controller, and a first switch. The at least one MPPT circuit is used to connect multiple photovoltaic modules and adjust the output voltage of the photovoltaic modules to track the maximum power operating point of the multiple photovoltaic modules during normal operation. The output terminal of the at least one MPPT circuit is connected to the input terminal of a group of bus capacitors. The output terminal of the group of bus capacitors is connected to the input terminal of the inverter circuit, which converts DC power to AC power. The output terminal of the inverter circuit is connected to the input terminal of the current sensor, which is connected to the input terminal of the filter circuit. The output terminal of the filter circuit is connected to the input terminal of the filter inductor group. At least one of the output terminals of the at least one MPPT circuit, the inverter circuit, and the filter circuit is provided with a first switch, which is used to control the output of the AC power. The filter inductor group includes a differential mode inductor, and a temperature sensor is provided on the differential mode inductor to detect the temperature of the differential mode inductor. The controller is specifically used to control the opening or closing of the first switch according to the temperature of the differential mode inductor.

[0007] Optionally, the filter inductor group may further include a common-mode inductor, the output port of which is connected to the input port of the differential-mode inductor.

[0008] It should be understood that the aforementioned photovoltaic inverter can use an inverter circuit to convert direct current into alternating current, and use a filter circuit to filter the alternating current obtained by the inverter conversion. The common-mode inductor and differential-mode inductor in the filter inductor group are used to filter the common-mode signal and differential-mode signal in the alternating current obtained by the inverter conversion, respectively, and the filtered alternating current is transmitted to the AC system. After obtaining the alternating current, the AC system can use it to supply power to the grid.

[0009] It should be noted that the first switch can be an insulated gate bipolar transistor (IGBT) located in the MPPT circuit, an IGBT located in the inverter circuit, or a grid-connected relay located at the output of the filter circuit. It should be understood that the embodiments of this application do not impose limitations on this.

[0010] It should also be noted that the controller controlling the first switch to open can be understood as: the controller reduces the frequency of the first switch in the inverter circuit by controlling the opening of the first switch, or it can also be that the controller reduces the output current by controlling the opening of the first switch.

[0011] In the technical solution of this application, a temperature sensor is used to detect the temperature of the differential mode inductor, and the controller controls the opening or closing of the first switch based on the temperature of the differential mode inductor. Based on the above technical solution, the controller can more accurately identify whether the photovoltaic inverter is resonating, and suppress or weaken the resonance when the photovoltaic inverter is resonating.

[0012] In conjunction with the first aspect, in some implementations of the first aspect, the controller is specifically used to: control the first switch to open based on the temperature of the differential mode inductor being greater than a first threshold; or, control the first switch to open based on the temperature of the differential mode inductor being less than or equal to the first threshold. Based on the above technical solution, the controller can more accurately identify whether the photovoltaic inverter is resonating, and suppress or weaken the resonance when the photovoltaic inverter is resonating.

[0013] In conjunction with the first aspect, in some implementations of the first aspect, the temperature sensor is used to detect the temperature of the differential-mode inductor at a first moment and generate a first signal based on the temperature of the differential-mode inductor; and to detect the temperature of the differential-mode inductor at a second moment and generate a second signal based on the temperature of the differential-mode inductor. Specifically, the controller is used to control the opening or closing of the first switch according to the first signal and the second signal, wherein the first moment precedes the second moment. Based on the above technical solution, the controller can more accurately identify whether the photovoltaic inverter is resonating, and suppress or weaken the resonance when the photovoltaic inverter is resonating.

[0014] In conjunction with the first aspect, in some implementations of the first aspect, the controller is specifically used to: determine the first temperature value based on the first signal; determine the second temperature value based on the second signal; and control the opening or closing of the first switch based on the first temperature value and the second temperature value. Based on the above technical solution, the controller can more accurately identify whether the photovoltaic inverter is resonating, and suppress or weaken the resonance when the photovoltaic inverter is resonating.

[0015] In conjunction with the first aspect, in some implementations of the first aspect, the controller is specifically used to: control the first switch to open based on the difference between the first temperature value and the second temperature value being greater than a second threshold; or, control the first switch to open based on the difference between the first temperature value and the second temperature value being less than or equal to the second threshold. Based on the above technical solution, the controller can more accurately identify whether the photovoltaic inverter is resonating, and suppress or weaken the resonance when the photovoltaic inverter is resonating.

[0016] In conjunction with the first aspect, in some implementations of the first aspect, the controller is specifically used to: control the first switch to open based on the rate of change of the first temperature value and the second temperature value being greater than a third threshold; or, control the first switch to open based on the rate of change of the first temperature value and the second temperature value being less than or equal to the third threshold. Based on the above technical solution, the controller can more accurately identify whether the photovoltaic inverter is resonating, and suppress resonance when the photovoltaic inverter is resonating.

[0017] In conjunction with the first aspect, in certain implementations of the first aspect, the temperature sensor includes at least one of the following: Negative temperature coefficient (NTC) sensors, integrated circuit (IC) temperature sensors, and resistive-capacitive sensors are used. Based on these technical solutions, the controller can accurately identify whether the photovoltaic inverter is resonating and suppress or weaken the resonance when it occurs.

[0018] In conjunction with the first aspect, in some implementations of the first aspect, the temperature sensor is disposed on the differential-mode inductor or on the printed circuit board (PCB) where the differential-mode inductor is located. Based on the above technical solution, the controller can more accurately identify whether the photovoltaic inverter is resonating, and suppress or weaken the resonance when the photovoltaic inverter is resonating.

[0019] In conjunction with the first aspect, in some implementations of the first aspect, the temperature sensor is fixed to the differential mode inductor or the PCB on which the differential mode inductor is located by means of adhesive and / or mechanical structure. Based on the above technical solution, the controller can more accurately identify whether the photovoltaic inverter is resonating, and suppress or weaken the resonance when the photovoltaic inverter is resonating.

[0020] In a second aspect, a photovoltaic power generation system is provided, comprising a photovoltaic module and a photovoltaic inverter as described in the first aspect and some implementations thereof, wherein the output port of the photovoltaic module is connected to the input port of the photovoltaic inverter, the output port of the photovoltaic inverter is used to connect to the input of an AC system, the photovoltaic module is used to generate direct current, the photovoltaic inverter is used to invert the direct current, and input the inverted AC power into the power grid system.

[0021] A photovoltaic power generation system is typically constructed using a photovoltaic inverter in any of the implementation methods of the first aspect described above. The controller receives a first signal sent by a temperature sensor and then controls a first switch based on the first signal. This allows for relatively accurate identification of whether the photovoltaic inverter is resonating and suppression or reduction of resonance when the photovoltaic inverter is resonating.

[0022] The aforementioned photovoltaic modules can also be called photovoltaic arrays or solar panels. A photovoltaic module is a device that directly converts solar energy into electrical energy using the photovoltaic effect that occurs in semiconductor materials under illumination.

[0023] Optionally, the photovoltaic power generation system further includes a rectifier connected between the output port of the photovoltaic module and the input port of the inverter. The rectifier is used to rectify the DC power generated by the photovoltaic module and input the rectified DC power to the inverter.

[0024] Thirdly, a method for identifying and controlling resonance in a photovoltaic inverter is provided. This method is applied to a photovoltaic inverter, which includes: at least one MPPT circuit, a set of bus capacitors, an inverter circuit, a current sensor, a filter circuit, a filter inductor group, a controller, and a first switch. The at least one MPPT circuit is used to connect multiple photovoltaic modules and adjust the output voltage of the photovoltaic modules to track the maximum power operating point of the multiple photovoltaic modules during normal operation. The output terminal of the at least one MPPT circuit is connected to the input terminal of the set of bus capacitors, and the output terminal of the set of bus capacitors is connected to the input terminal of the inverter circuit. The inverter circuit is used to convert DC power... The inverter circuit converts the current to alternating current. Its output is connected to the input of a current sensor, which in turn is connected to the input of a filter circuit. The filter circuit's output is connected to the input of a filter inductor group. At least one of the outputs of the at least one MPPT circuit, the inverter circuit, and the filter circuit is equipped with a first switch, which controls the output of the alternating current. The filter inductor group includes a differential-mode inductor, and a temperature sensor is mounted on the differential-mode inductor. The method includes: the temperature sensor detecting the temperature of the differential-mode inductor; and the controller controlling the opening or closing of the first switch based on the temperature of the differential-mode inductor.

[0025] In the technical solution of this application, a temperature sensor detects the temperature of the differential mode inductor, and the controller controls the opening or closing of the first switch based on the temperature of the differential mode inductor. Based on the above technical solution, the controller can accurately identify whether the photovoltaic inverter is resonating, and suppress or weaken the resonance when it occurs.

[0026] In conjunction with the third aspect, in some implementations of the third aspect, the controller controls the opening or closing of the first switch based on the temperature of the differential mode inductor, including: the controller controls the first switch to open when the temperature of the differential mode inductor is greater than a first threshold; or, the controller controls the first switch to close when the temperature of the differential mode inductor is less than or equal to the first threshold. Based on the above technical solution, the controller can more accurately identify whether the photovoltaic inverter is resonating, and suppress or weaken the resonance when the photovoltaic inverter is resonating.

[0027] In conjunction with the third aspect, in some implementations of the third aspect, the method further includes: the temperature sensor detecting the temperature of the differential mode inductor at a first moment and generating a first signal based on the temperature of the differential mode inductor; the temperature sensor detecting the temperature of the differential mode inductor at a second moment and generating a second signal based on the temperature of the differential mode inductor; and the controller controlling the opening or closing of the first switch according to the first signal and the second signal, wherein the first moment precedes the second moment. Based on the above technical solution, the controller can more accurately identify whether the photovoltaic inverter is resonating, and suppress or weaken the resonance when the photovoltaic inverter is resonating.

[0028] In conjunction with the third aspect, in some implementations of the third aspect, the controller controls the opening or closing of the first switch based on the first signal and the second signal, including: the controller determining the first temperature value based on the first signal; the controller determining the second temperature value based on the second signal; and the controller controlling the opening or closing of the first switch based on the first temperature value and the second temperature value. Based on the above technical solution, the controller can more accurately identify whether the photovoltaic inverter is resonating, and suppress or weaken the resonance when the photovoltaic inverter is resonating.

[0029] In conjunction with the third aspect, in some implementations of the third aspect, the controller controls the opening or closing of the first switch based on the first temperature value and the second temperature value, including: the controller controls the first switch to open based on the difference between the first temperature value and the second temperature value being greater than a second threshold; or, the controller controls the first switch to close based on the difference between the first temperature value and the second temperature value being less than or equal to the second threshold. Based on the above technical solution, the controller can more accurately identify whether the photovoltaic inverter is resonating, and suppress or weaken the resonance when the photovoltaic inverter is resonating.

[0030] In conjunction with the third aspect, in some implementations of the third aspect, the controller controls the opening or closing of the first switch based on the first temperature value and the second temperature value, including: the controller controls the first switch to open based on the rate of change of the first temperature value and the second temperature value being greater than a third threshold; or, the controller controls the first switch to close based on the rate of change of the first temperature value and the second temperature value being less than or equal to the third threshold. Based on the above technical solution, the controller can more accurately identify whether the photovoltaic inverter is resonating, and suppress or weaken the resonance when the photovoltaic inverter is resonating.

[0031] In conjunction with the third aspect, in some implementations of the third aspect, the temperature sensor includes at least one of the following: Negative temperature coefficient (NTC) sensors, integrated circuit (IC) temperature sensors, and resistive-capacitive sensors are used. Based on these technical solutions, the controller can accurately identify whether the photovoltaic inverter is resonating and suppress or weaken the resonance when it occurs.

[0032] In conjunction with the third aspect, in some implementations of the third aspect, the temperature sensor is located on the differential-mode inductor or on the printed circuit board (PCB) where the differential-mode inductor is located. Based on the above technical solution, the controller can more accurately identify whether the photovoltaic inverter is resonating, and suppress or weaken the resonance when the photovoltaic inverter is resonating.

[0033] In conjunction with the third aspect, in some implementations of the third aspect, the temperature sensor is fixed to the differential mode inductor or the PCB on which the differential mode inductor is located by means of adhesive and / or mechanical structure. Based on the above technical solution, the controller can more accurately identify whether the photovoltaic inverter is resonating, and suppress or weaken the resonance when the photovoltaic inverter is resonating. Attached Figure Description

[0034] Figure 1 This is a schematic block diagram of a photovoltaic inverter according to an embodiment of this application.

[0035] Figure 2 This is a schematic block diagram of a photovoltaic inverter provided in another embodiment of this application.

[0036] Figure 3 This is a schematic block diagram of a photovoltaic power generation system provided in the embodiments of this application.

[0037] Figure 4 This is a schematic flowchart of a photovoltaic inverter resonance control method provided in an embodiment of this application.

[0038] Figure 5 This is a schematic diagram of the controller device according to an embodiment of this application.

[0039] Figure label: 100 - Photovoltaic inverter; 111 - A set of bus capacitors; 112 - Inverter circuit; 113 - Current sensor; 114 - Filter circuit; 1141 - Inverter inductor; 1142 - Filter capacitor; 115 - First switch; 116 - Filter inductor group; 1161 - Differential mode inductor; 1162 - Common mode inductor; 117 - MPPT circuit; 118 - DC switch; 119 - DC EMI filter circuit; 120 - Controller; 130 - Temperature sensor. Detailed Implementation

[0040] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0041] The following is combined Figures 1 to 4 The photovoltaic inverter of the present application embodiment will be described in detail.

[0042] Figure 1 This is a schematic block diagram of a photovoltaic inverter according to an embodiment of this application. Figure 1 The photovoltaic inverter 100 shown includes: at least one maximum power point tracking (MPPT) circuit 117, a set of bus capacitors 111, an inverter circuit 112, a current sensor 113, a filter circuit 114, a first switch 115, and a filter inductor group 116 (differential mode inductor 1161).

[0043] At least one MPPT circuit 117 is used to connect multiple photovoltaic modules (not shown in the figure) and to adjust the output voltage of the photovoltaic modules to track the maximum power operating point of multiple photovoltaic modules during normal operation. Specifically, the output of at least one MPPT circuit is connected to the input port of a set of bus capacitors 111, the output port of the set of bus capacitors 111 is connected to the input port of inverter circuit 112, which converts DC power to AC power. The input port of current sensor 113 is connected to the output port of inverter circuit 112, the output port of current sensor 113 is connected to the input port of filter circuit 114, and the output port of filter circuit 114 is connected to the input port of filter inductor group 116. The filter circuit 114 also includes inverter inductor 1141 and filter capacitor 1142.

[0044] It should be understood that the aforementioned photovoltaic module refers to a device that directly converts solar energy into electrical energy using the photovoltaic effect that occurs in semiconductor materials under illumination. The aforementioned photovoltaic module can also be called a photovoltaic array or a solar panel. This application does not limit this.

[0045] Optionally, in some embodiments, the filter inductor group 116 includes a differential mode inductor 1161, that is, the output port of the filter inductor 114 is connected to the input port of the differential mode inductor 1161, and the differential mode inductor 1161 is used to filter differential mode signals in the AC power.

[0046] Optionally, in some embodiments, the filter inductor group 116 may further include a differential-mode inductor 1161 and a common-mode inductor 1162. That is, the output port of the filter inductor 114 is connected to the input port of the differential-mode inductor 1161, and the output port of the differential-mode inductor 1161 is connected to the input port of the common-mode inductor 1162. The common-mode inductor 1162 is used to filter common-mode signals in the AC power.

[0047] like Figure 1As shown, an AC system (not shown in the figure) can also be connected between the output port of the photovoltaic inverter 100 and the power grid. The photovoltaic inverter 100 can use the inverter circuit 112 to convert DC power into AC power, and use the filter circuit 114 to filter the AC power obtained by the inverter conversion. The common-mode inductor 1162 and the differential-mode inductor 1161 are used to filter the common-mode signal and differential-mode signal in the AC power obtained by the inverter conversion, respectively, and the filtered AC power is transmitted to the AC system, which can be used to supply power to the power grid after obtaining the AC power.

[0048] Currently, the industry typically uses inverter current detection to identify whether a photovoltaic inverter is resonating. Specifically, the inverter current of the grid-connected photovoltaic inverter 100 is collected in real time by current sensor 113, and the current signal is converted into a voltage signal. After conditioning circuit, the voltage signal is transmitted to controller 120. Controller 120 obtains the spectrum and fundamental frequency of the inverter current signal through Fourier transform, compares it with the characteristics of the current signal that has not resonated, identifies whether the photovoltaic inverter is resonating, and suppresses the resonance through a relatively complex control algorithm.

[0049] However, the above-mentioned inverter current detection method mainly relies on the quality of the sampled current signal of the current sensor and complex software algorithms. Since the quality of the sampled current signal of the current sensor is greatly affected by the hardware circuit and the internal temperature of the whole machine, it often leads to problems of missed identification or false identification of resonance, thereby affecting the stability of photovoltaic inverters and the safe operation of the power grid.

[0050] Based on this, this application provides a photovoltaic inverter 100. By introducing a temperature sensor 130 into the photovoltaic inverter 100, it is possible to more accurately identify whether the photovoltaic inverter is resonating, and suppress or weaken the resonance when the photovoltaic inverter is resonating.

[0051] Furthermore, such as Figure 1 As shown, the photovoltaic inverter 100 also includes a controller 120 and a temperature sensor 130. The temperature sensor 130 can be disposed on the differential mode inductor 1161 and is used to detect the temperature of the differential mode inductor 1161. The controller 120 controls the opening or closing of the first switch 115 based on the temperature of the differential mode inductor 1161.

[0052] Specifically, after the temperature sensor 130 detects the temperature of the differential mode inductor 1161, it converts the temperature into a corresponding voltage value and sends the voltage value to the analog-to-digital converter (ADC) interface of the controller 120. After receiving the voltage value, the controller 120 further obtains the temperature value of the differential mode inductor 1161 by calculating or looking up a table.

[0053] Optionally, in one possible implementation, the controller 120 controls the first switch 115 to open based on the temperature of the differential mode inductor 1161 being greater than a first threshold; or, the controller 120 controls the first switch to open based on the temperature of the differential mode inductor 1161 being less than or equal to the first threshold.

[0054] Among them, such as Figure 1 A first switch 115 is provided at at least one of the output terminals of at least one MPPT circuit 117, inverter circuit 112, and filter circuit 114 shown. The first switch 115 is used to control the output of AC power.

[0055] It should be noted that a first switch is provided at at least one of the output terminals of at least one MPPT circuit 117, inverter circuit 112, and filter circuit 114, and the following examples are possible.

[0056] For example, the first switch can be set in at least one MPPT circuit 117, the first switch (IGBT) can be set in the inverter circuit 112, or the first switch (grid relay) can be set at the output of the filter circuit 114.

[0057] For example, a first switch (IGBT) can be set in at least one MPPT circuit 117 and an inverter circuit 112 respectively, or a first switch (IGBT) can be set in at least one MPPT circuit 117 and a first switch (grid-connected relay) can be set at the output terminal of the filter circuit 114, or a first switch (IGBT) can be set in the inverter circuit 112 and a first switch (grid-connected relay) can be set at the output terminal of the filter circuit 114.

[0058] It should be understood that the setting position of the first switch mentioned above is only for illustrative purposes, and the embodiments of this application do not limit it.

[0059] It should be understood that the first threshold is a pre-set temperature threshold.

[0060] It should be noted that the controller controlling the first switch to open can be understood as: the controller reduces the frequency of the first switch in the inverter circuit by controlling the opening of the first switch, or it can also be understood as the controller reduces the output current by controlling the opening of the first switch.

[0061] Optionally, in one possible implementation, the temperature sensor 130 detects the temperature of the magnetic core of the differential mode inductor 1161 to obtain the corresponding temperature value, converts the temperature value into a voltage value, and then compares the voltage value with a threshold value through hardware circuitry to generate a first signal, which is then sent to the controller 120. The controller 120 controls the opening or closing of the first switch 115 based on the first signal.

[0062] For example, when the temperature sensor 130 determines through comparison that the voltage value is greater than a set threshold, it generates a first signal "1". After receiving the first signal "1", the controller 120 determines that the photovoltaic inverter 100 has resonated based on the first signal "1", and then the controller 120 controls the first switch 115 to open. Alternatively, for example, when the temperature sensor 130 determines through comparison that the voltage value is less than or equal to a set threshold, it generates a first signal "0". After receiving the first signal "0", the controller 120 determines that the inverter 100 has not resonated based on the first signal "0", and then the controller 120 controls the first switch 115 to turn on.

[0063] Optionally, in one possible implementation, temperature sensor 130 detects the temperature of the core of differential mode inductor 1161 at a first moment and generates a first signal based on the detected temperature of differential mode inductor 1161 at the first moment. Temperature sensor 130 then detects the temperature of the core of differential mode inductor 1161 at a second moment and generates a second signal based on the detected temperature of differential mode inductor 1161 at the second moment. Controller 120 receives the first and second signals sent by temperature sensor 130 and controls the opening or closing of first switch 115 according to the first and second signals, wherein the first moment precedes the second moment.

[0064] Specifically, the first and second signals can be voltage signal values. After detecting the first and second temperature values ​​of the differential mode inductor 1161, the temperature sensor 130 converts the first temperature value into a first voltage value and the second temperature value into a second voltage value. The first and second voltage values ​​are then sent to the analog-to-digital converter (ADC) interface of the controller 120.

[0065] Upon receiving the first signal and the second signal, the controller 120 determines a first temperature value based on the first signal (first voltage value) and a second temperature value based on the second signal (second voltage value). The first temperature value is the temperature of the differential-mode inductor 1161 detected by the temperature sensor 130 at a first moment, and the second temperature value is the temperature of the differential-mode inductor 1161 detected by the temperature sensor 130 at a second moment. The controller 120 controls the opening or closing of the first switch 115 based on the first and second temperature values.

[0066] Optionally, the controller 120 controls the first switch 115 to open based on the difference between the first temperature value and the second temperature value being greater than the second threshold, or the controller 120 controls the first switch 115 to open based on the difference between the first temperature value and the second temperature value being less than or equal to the second threshold.

[0067] Optionally, the controller 120 controls the first switch 115 to open based on the rate of change of the first temperature value and the second temperature value being greater than the third threshold; or, the controller 120 controls the first switch 115 to open based on the rate of change of the first temperature value and the second temperature value being less than or equal to the third threshold.

[0068] It should be understood that the second and third thresholds are both pre-set thresholds.

[0069] It should be noted that the controller controls the first switch 115 to open, which can be understood as: the controller reduces the frequency of the first switch in the inverter circuit by controlling the opening of the first switch 115, or the controller reduces the output current by controlling the opening of the first switch.

[0070] It should also be noted that after receiving the first signal (first voltage value) and the second signal (second voltage value), the controller 120 may calculate the first temperature value and the second temperature value based on the first voltage value and the second voltage value respectively, or the controller 120 may obtain the first temperature value corresponding to the first voltage value and the second temperature value corresponding to the second voltage value by looking up a table. It should be understood that the embodiments of this application do not limit how the controller 120 obtains the corresponding temperature value from the voltage value.

[0071] Optionally, in one possible implementation, after receiving the first signal (first voltage value) and the second signal (second voltage value) sent by the temperature sensor 130, the controller 120 can directly determine that the photovoltaic inverter 100 has resonated based on the difference between the first voltage value and the second voltage value being greater than a fourth threshold, and then control the first switch 115 to open. Alternatively, the controller 120 can determine that the photovoltaic inverter 100 has not resonated based on the difference between the first voltage value and the second voltage value being less than or equal to the fourth threshold, and then control the first switch 115 to turn on.

[0072] Optionally, in one possible implementation, after receiving the first signal (first voltage value) and the second signal (second voltage value) sent by the temperature sensor 130, the controller 120 can directly determine that the photovoltaic inverter 100 has resonated based on the rate of change of the first voltage value and the second voltage value being greater than a fifth threshold, and then control the first switch 115 to open. Alternatively, the controller 120 can determine that the photovoltaic inverter 100 has not resonated based on the rate of change of the first voltage value and the second voltage value being less than or equal to the fifth threshold, and then control the first switch 115 to turn on.

[0073] It should be understood that the fourth and fifth thresholds are both pre-set thresholds.

[0074] According to the technical solution provided in this application, the temperature of the differential mode inductor can be detected in real time by a temperature sensor without relying on the sampling quality of the current sensor or complex software control algorithms. The controller further controls the opening or closing of the first switch based on the temperature of the differential mode inductor. This can more accurately identify whether the photovoltaic inverter is resonating, and when it is determined that the photovoltaic inverter is resonating, the controller controls the first switch to open or close, thereby suppressing or weakening the resonance.

[0075] Figure 2 This is a schematic diagram of the structure of another photovoltaic inverter 100 provided in the embodiments of this application, as shown below. Figure 2 As shown, the photovoltaic inverter 100 may also include a DC switch 118 and a DC electromagnetic interference (EMI) filter circuit 119.

[0076] Specifically, DC switch 118 is connected to the input port of photovoltaic module (not shown in the figure) and DC EMI filter circuit 119, the output port of DC EMI filter circuit 119 is connected to the input port of MPPT circuit 117, and the output port of MPPT circuit 117 is connected to the input port of bus capacitor 111. Figure 2 For a detailed structural diagram of the photovoltaic inverter 100 shown, please refer to... Figure 1 The details described herein will not be repeated here.

[0077] Optionally, in one possible implementation, the temperature sensor 130 may be a negative temperature coefficient NTC sensor, an integrated circuit IC type temperature sensor, or a resistive-capacitive sensor, etc. It should be understood that the embodiments of this application do not limit this.

[0078] Optionally, in one possible implementation, the temperature sensor 130 can be disposed on the differential mode inductor 1161, or it can be disposed on the printed circuit board (PCB) where the differential mode inductor 1161 is located. It should be understood that the embodiments of this application do not limit this.

[0079] Optionally, the temperature sensor 130 can be mounted on the differential mode inductor 1161 or the PCB board on which the differential mode inductor 1161 is located by an adhesive, or it can be fixed to the differential mode inductor 1161 or the PCB board on which the differential mode inductor 1161 is located by a mechanical structure.

[0080] For example, the adhesive may be epoxy resin, polyethylene adhesive, acrylic polyurethane, ultraviolet rays (UV) adhesive, and other high-temperature resistant adhesives, or the adhesive may be a mixture of at least one of the above-mentioned epoxy resin, polyethylene adhesive, acrylic polyurethane, and UV adhesive. It should be understood that the embodiments of this application are not limited in this respect.

[0081] For example, the mechanical structure can be a screw structure, such as the temperature sensor 130 being fixed to the differential mode inductor 1161 or the PCB board on which the differential mode inductor 1161 is located by screws. It should be understood that the embodiments of this application are not limited herein.

[0082] This application also provides a photovoltaic power generation system, such as... Figure 3 As shown, the photovoltaic power generation system includes: photovoltaic modules, an AC power grid, and a photovoltaic inverter according to an embodiment of this application.

[0083] The photovoltaic module's output port is connected to the photovoltaic inverter's input port. The photovoltaic inverter's output port is used to connect to the grid's input port. The photovoltaic module generates direct current (DC), and the photovoltaic inverter inverts the DC and inputs the resulting alternating current (AC) into the grid, which then provides the AC power.

[0084] Furthermore, a photovoltaic module refers to a device that directly converts solar energy into electrical energy using the photovoltaic effect that occurs in semiconductor materials under illumination. The aforementioned photovoltaic modules can also be called photovoltaic arrays or solar panels.

[0085] To rectify the direct current generated by the photovoltaic modules, a rectifier can be installed in the photovoltaic power generation system. This rectifier is connected between the output port of the photovoltaic modules and the input port of the photovoltaic inverter. The rectifier is used to rectify the direct current generated by the photovoltaic modules and input the rectified direct current into the photovoltaic inverter.

[0086] It should be understood that, in addition to the photovoltaic power generation system provided in this application, the inverter structure provided in this application can also be applied to other power generation or frequency converters and other power equipment with differential mode inductance in the power circuit.

[0087] Figure 4 This is a schematic flowchart illustrating a control method for photovoltaic inverter resonance provided in an embodiment of this application, as shown below. Figure 4 As shown, the process includes steps S410 and S420, which will be described in detail below.

[0088] S410, the controller obtains the temperature of the differential mode inductor.

[0089] S420, the controller controls the opening or closing of the first switch based on the temperature of the differential mode inductor.

[0090] Specifically, the temperature sensor detects the temperature of the core of the differential mode inductor and converts the detected temperature value into a voltage value, which is then transmitted to the ADC port of the controller. After receiving the voltage value, the controller further obtains the temperature of the differential mode inductor by performing calculations or looking up a table, and controls the opening or closing of the first switch based on the temperature of the differential mode inductor.

[0091] Optionally, in one possible implementation, the controller controls the first switch to open based on the temperature of the differential mode inductor being greater than a first threshold; or, the controller controls the first switch to open based on the temperature of the differential mode inductor being less than or equal to the first threshold.

[0092] It should be understood that the first threshold is a pre-set temperature threshold.

[0093] It should be noted that the controller controlling the first switch to open can be understood as: the controller reduces the frequency of the first switch in the inverter circuit by controlling the opening of the first switch, or it can also be understood as the controller reduces the output current by controlling the opening of the first switch.

[0094] Optionally, in one possible implementation, the temperature sensor detects the temperature of the magnetic core of the differential-mode inductor to obtain a corresponding temperature value, converts this temperature value into a corresponding voltage value, and then generates a first signal by comparing the voltage value with a threshold value. This first signal is then sent to the controller. The controller controls the opening or closing of the first switch based on this first signal.

[0095] For example, when the temperature sensor determines that the voltage value is greater than a set threshold by comparison, it generates a first signal "1". After receiving the first signal "1", the controller determines that the photovoltaic inverter has resonated, and then controls the first switch to open. Alternatively, for example, when the temperature sensor determines that the voltage value is less than or equal to a set threshold by comparison, it generates a first signal "0". After receiving the first signal "0", the controller determines that the photovoltaic inverter has not resonated, and then controls the first switch to open.

[0096] Alternatively, in one possible implementation, the method may further include steps S430 and S440.

[0097] S430, the temperature sensor detects the temperature of the differential mode inductor at a first moment and generates a first signal based on the temperature of the differential mode inductor, and detects the temperature of the differential mode inductor at a second moment and generates a second signal based on the temperature of the differential mode inductor.

[0098] S440, the controller controls the opening or closing of the first switch based on the first signal and the second signal.

[0099] Specifically, the temperature sensor detects the temperature of the differential-mode inductor's core at a first moment and generates a first signal based on the detected temperature. The temperature sensor then detects the temperature of the differential-mode inductor's core at a second moment and generates a second signal based on the detected temperature. The controller receives the first and second signals from the temperature sensor and controls the opening or closing of the first switch according to the first and second signals, wherein the first moment precedes the second moment.

[0100] The first and second signals can be voltage signal values. After detecting the first and second temperature values ​​of the differential mode inductor, the temperature sensor converts the first temperature value into a first voltage value and the second temperature value into a second voltage value. The first and second voltage values ​​are then sent to the analog-to-digital converter (ADC) interface of the controller.

[0101] Specifically, after receiving the first signal and the second signal, the controller determines a first temperature value based on the first signal (first voltage value) and a second temperature value based on the second signal (second voltage value). The first temperature value is the temperature of the differential-mode inductor detected by the temperature sensor at a first moment, and the second temperature value is the temperature of the differential-mode inductor detected by the temperature sensor at a second moment. The controller controls the opening or closing of the first switch based on the first and second temperature values.

[0102] Optionally, the controller controls the first switch to open if the difference between the first temperature value and the second temperature value is greater than the second threshold, or the controller controls the first switch to open if the difference between the first temperature value and the second temperature value is less than or equal to the second threshold.

[0103] Optionally, the controller controls the first switch to open based on the rate of change of the first temperature value and the second temperature value being greater than the third threshold; or, the controller controls the first switch to open based on the rate of change of the first temperature value and the second temperature value being less than or equal to the third threshold.

[0104] It should be understood that the second and third thresholds are both pre-set thresholds.

[0105] It should be noted that the controller controlling the first switch to open can be understood as: the controller reduces the frequency of the first switch in the inverter circuit by controlling the opening of the first switch, or it can also be understood as the controller reduces the output current by controlling the opening of the first switch.

[0106] It should also be noted that after receiving the first signal (first voltage value) and the second signal (second voltage value), the controller may calculate the first temperature value and the second temperature value based on the first voltage value and the second voltage value respectively, or the controller may obtain the first temperature value corresponding to the first voltage value and the second temperature value corresponding to the second voltage value by looking up a table. It should be understood that the embodiments of this application do not limit how the controller obtains the corresponding temperature value from the voltage value.

[0107] Optionally, in one possible implementation, after receiving the first signal (first voltage value) and the second signal (second voltage value) from the temperature sensor, the controller can directly determine that the photovoltaic inverter has resonated based on the difference between the first voltage value and the second voltage value being greater than a fourth threshold, and then control the first switch to open. Alternatively, the controller can determine that the photovoltaic inverter has not resonated based on the difference between the first voltage value and the second voltage value being less than or equal to the fourth threshold, and then control the first switch to turn on.

[0108] Optionally, in one possible implementation, after receiving the first signal (first voltage value) and the second signal (second voltage value) from the temperature sensor, the controller can directly determine that the photovoltaic inverter has resonated based on the rate of change of the first voltage value and the second voltage value being greater than a fifth threshold, and then control the first switch to open. Alternatively, the controller can determine that the photovoltaic inverter has not resonated based on the rate of change of the first voltage value and the second voltage value being less than or equal to the fifth threshold, and then control the first switch to turn on.

[0109] It should be understood that the fourth and fifth thresholds are both pre-set thresholds.

[0110] Optionally, in one possible implementation, the temperature sensor can be a negative temperature coefficient NTC sensor, an integrated circuit (IC) type temperature sensor, or a resistive-capacitive sensor, etc. It should be understood that the embodiments of this application do not limit this.

[0111] Optionally, in one possible implementation, the temperature sensor can be located on the differential mode inductor, or it can be located on the printed circuit board (PCB) where the differential mode inductor is located. It should be understood that the embodiments of this application do not limit this.

[0112] Optionally, the temperature sensor can be mounted on the differential mode inductor or the PCB board on which the differential mode inductor is located using an adhesive, or it can be fixed to the differential mode inductor or the PCB board on which the differential mode inductor is located using a mechanical structure.

[0113] For example, the adhesive may be epoxy resin, polyethylene adhesive, acrylic polyurethane, ultraviolet rays (UV) adhesive, and other high-temperature resistant adhesives, or the adhesive may be a mixture of at least one of the above-mentioned epoxy resin, polyethylene adhesive, acrylic polyurethane, and UV adhesive. It should be understood that the embodiments of this application are not limited in this respect.

[0114] For example, the mechanical structure can be a screw structure, for instance, the temperature sensor can be fixed to the differential mode inductor or the PCB board on which the differential mode inductor is located by screws. It should be understood that the embodiments of this application are not limited herein.

[0115] Based on the above technical solution, the controller can accurately identify whether the photovoltaic inverter is resonating. When it is determined that the photovoltaic inverter is resonating, the controller controls the opening or closing of the first switch to suppress or weaken the resonance.

[0116] Figure 5 This is a schematic diagram of the controller device according to an embodiment of this application. Figure 5 As shown, the control device includes a processor 510 and a communication interface 520. Optionally, the control device may further include a memory 530. Optionally, the memory 530 may be included in the processor 510. The processor 510, communication interface 520, and memory 530 communicate with each other through internal connection paths. The memory 530 is used to store instructions, and the processor 510 is used to execute the instructions stored in the memory 530 to implement the photovoltaic inverter resonance identification and control method provided in this embodiment.

[0117] Optionally, the control device can be used to perform the functions of the controller 120 described above.

[0118] As used in this specification, the terms "component," "module," "system," etc., are used to refer to computer-related entities, hardware, firmware, combinations of hardware and software, software, or software in execution. For example, a component can be, but is not limited to, a process running on a processor, a processor, an object, an executable file, an execution thread, a program, and / or a computer. As illustrated, applications running on computing devices and computing devices can both be components. One or more components may reside in a process and / or an execution thread, and components may be located on a single computer and / or distributed among two or more computers. Furthermore, these components can be executed from various computer-readable media on which various data structures are stored. Components can communicate, for example, via local and / or remote processes based on signals having one or more data packets (e.g., data from two components interacting with another component between a local system, a distributed system, and / or a network, such as the Internet interacting with other systems via signals).

[0119] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0120] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0121] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0122] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0123] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0124] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0125] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A photovoltaic inverter, characterized in that, include: It includes at least one MPPT circuit, a set of bus capacitors, an inverter circuit, a current sensor, a filter circuit, a filter inductor group, a controller, and a first switch. The at least one MPPT circuit is used to connect multiple photovoltaic modules and to adjust the output voltage of the photovoltaic modules to track the maximum power operating point of the multiple photovoltaic modules during normal operation. The output terminal of the at least one MPPT circuit is connected to the input terminal of the group of bus capacitors. The output terminal of the group of bus capacitors is connected to the input terminal of the inverter circuit. The inverter circuit is used to convert DC power to AC power. The output terminal of the inverter circuit is connected to the input terminal of the current sensor. The output terminal of the current sensor is connected to the input terminal of the filter circuit. The output terminal of the filter circuit is connected to the input terminal of the filter inductor group. The first switch is provided at at least one of the output terminals of the at least one MPPT circuit, the inverter circuit, and the filter circuit, and the first switch is used to control the output of the AC power. The filter inductor group includes a differential mode inductor, and a temperature sensor is disposed on the differential mode inductor for detecting the temperature of the differential mode inductor. The controller is specifically used for: The opening or closing of the first switch is controlled by the temperature of the differential mode inductor.

2. The photovoltaic inverter according to claim 1, characterized in that, The controller is specifically used for: If the temperature of the differential mode inductor exceeds a first threshold, the first switch is controlled to open; or... The first switch is controlled to turn on when the temperature of the differential mode inductor is less than or equal to the first threshold.

3. The photovoltaic inverter according to claim 1, characterized in that, The temperature sensor is used to detect the temperature of the differential mode inductor at a first moment and generate a first signal based on the temperature of the differential mode inductor. The temperature of the differential mode inductor is detected at a second time, and a second signal is generated based on the temperature of the differential mode inductor. The controller is specifically used for: The first switch is controlled to open or close according to the first signal and the second signal, wherein the first moment precedes the second moment.

4. The photovoltaic inverter according to claim 3, characterized in that, The controller is specifically used for: A first temperature value is determined based on the first signal; A second temperature value is determined based on the second signal; The first switch is controlled to open or close based on the first temperature value and the second temperature value.

5. The photovoltaic inverter according to claim 4, characterized in that, The controller is specifically used for: If the difference between the first temperature value and the second temperature value is greater than a second threshold, the first switch is controlled to open; or... The first switch is turned on if the difference between the first temperature value and the second temperature value is less than or equal to the second threshold.

6. The photovoltaic inverter according to claim 4, characterized in that, The controller is specifically used for: If the rate of change of the first temperature value and the second temperature value is greater than a third threshold, the first switch is controlled to open; or... The first switch is turned on if the rate of change of the first temperature value and the second temperature value is less than or equal to the third threshold.

7. The photovoltaic inverter according to any one of claims 1 to 6, characterized in that, The temperature sensor includes at least one of the following: Negative temperature coefficient (NTC) sensors, integrated circuit (IC) temperature sensors, and resistive-capacitive sensors.

8. The photovoltaic inverter according to any one of claims 1 to 6, characterized in that, The temperature sensor is located on the differential mode inductor or on the printed circuit board (PCB) where the differential mode inductor is located.

9. The photovoltaic inverter according to claim 8, characterized in that, The temperature sensor is mounted on the differential mode inductor or on the PCB where the differential mode inductor is located by means of adhesive and / or mechanical structure.

10. A photovoltaic power generation system, characterized in that, The system includes a photovoltaic module and a photovoltaic inverter as described in any one of claims 1 to 9, wherein the output port of the photovoltaic module is connected to the input port of the photovoltaic inverter, the output port of the photovoltaic inverter is used to connect to the input terminal of an AC system, the photovoltaic module is used to generate direct current, the photovoltaic inverter is used to invert the direct current and input the AC power obtained by the inversion process into the AC system.

11. A method for controlling the resonance of a photovoltaic inverter, characterized in that, The method is applied to a photovoltaic inverter, which includes: at least one MPPT circuit, a set of bus capacitors, an inverter circuit, a current sensor, a filter circuit, a filter inductor group, a controller, and a first switch. The at least one MPPT circuit is used to connect multiple photovoltaic modules and to adjust the output voltage of the photovoltaic modules to track the maximum power operating point of the multiple photovoltaic modules during normal operation. The output terminal of the at least one MPPT circuit is connected to the input terminal of the group of bus capacitors. The output terminal of the group of bus capacitors is connected to the input terminal of the inverter circuit. The inverter circuit is used to convert DC power to AC power. The output terminal of the inverter circuit is connected to the input terminal of the current sensor. The output terminal of the current sensor is connected to the input terminal of the filter circuit. The output terminal of the filter circuit is connected to the input terminal of the filter inductor group. The first switch is provided at at least one of the output terminals of the at least one MPPT circuit, the inverter circuit, and the filter circuit, and the first switch is used to control the output of the AC power. The filter inductor group includes a differential mode inductor, and a temperature sensor is disposed on the differential mode inductor for detecting the temperature of the differential mode inductor. The method includes: The controller controls the opening or closing of the first switch based on the temperature of the differential mode inductor.

12. The control method according to claim 11, characterized in that, The controller controls the opening or closing of the first switch based on the temperature of the differential mode inductor, including: The controller controls the first switch to open based on the temperature of the differential mode inductor exceeding a first threshold; or... The controller controls the first switch to turn on when the temperature of the differential mode inductor is less than or equal to the first threshold.

13. The control method according to claim 11, characterized in that, The method further includes: The temperature sensor detects the temperature of the differential mode inductor at a first moment and generates a first signal based on the temperature of the differential mode inductor; The temperature sensor detects the temperature of the differential mode inductor at a second moment and generates a second signal based on the temperature of the differential mode inductor. The controller controls the opening or closing of the first switch according to the first signal and the second signal, wherein the first moment precedes the second moment.

14. The control method according to claim 13, characterized in that, The controller controls the opening or closing of the first switch based on the first signal and the second signal, and further includes: The controller determines a first temperature value based on the first signal; The controller determines the second temperature value based on the second signal; The controller controls the opening or closing of the first switch based on the first temperature value and the second temperature value.

15. The control method according to claim 14, characterized in that, The controller controls the opening or closing of the first switch based on the first temperature value and the second temperature value, including: The controller disconnects the first switch if the difference between the first temperature value and the second temperature value is greater than a second threshold; or... The controller controls the first switch to turn on based on the difference between the first temperature value and the second temperature value being less than or equal to the second threshold.

16. The control method according to claim 14, characterized in that, The controller controls the opening or closing of the first switch based on the first temperature value and the second temperature value, including: The controller disconnects the first switch based on the rate of change of the first and second temperature values ​​exceeding a third threshold; or... The controller controls the first switch to turn on based on the fact that the rate of change of the first temperature value and the second temperature value is less than or equal to the third threshold.

17. The control method according to any one of claims 11 to 16, characterized in that, The temperature sensor includes at least one of the following: Negative temperature coefficient (NTC) sensors, integrated circuit (IC) temperature sensors, and resistive-capacitive sensors.

18. The control method according to any one of claims 11 to 16, characterized in that, The temperature sensor is located on the differential mode inductor or on the printed circuit board (PCB) where the differential mode inductor is located.

19. The control method according to claim 18, characterized in that, The temperature sensor is mounted on the differential mode inductor or on the PCB where the differential mode inductor is located by means of adhesive and / or mechanical structure.

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