Inverter

Abstract

The utility model provides an inverter, and the inverter comprises an inverter circuit which comprises a DC side and an AC side, the DC side is connected with a DC bus, and the AC side is electrically connected with an anti-surge circuit; the anti-surge circuit comprises a differential mode filtering module and a common mode filtering module, the differential mode filtering module comprises a differential mode inductor, the first end of the differential mode inductor is connected with the alternating current side port of the inverter circuit, and the second end of the differential mode inductor is connected to the common mode filtering module; the common-mode filtering module comprises a common-mode inductor, and the differential-mode inductor is electrically connected to a power grid phase line through the common-mode inductor; wherein the differential mode inductor and the common mode inductor are connected in parallel with a discharge tube. According to the inverter provided by the invention, when differential-mode and common-mode surges occur, the voltage of the differential-mode and common-mode inductors is clamped, and resonance energy is prevented from passing through the differential-mode and common-mode anti-surge modules, so that the reliability of the differential-mode and common-mode anti-surge modules can be improved, and the service life of the differential-mode and common-mode anti-surge modules can be prolonged.

Description

Technical Field

[0001] The utility model belongs to the technical field of power electronics, and particularly relates to an inverter. Background Art

[0002] The grid-connected inverter is connected to the power grid and will be subjected to surges from the power grid during daily operation. In order to avoid irreversible damage to the inverter caused by surges, engineers will add surge protection design at the output part of the inverter. The state and the industry have also issued relevant regulations on the surge protection ability of inverters. The currently commonly used design for protecting inverters against surges is to use one or two surge protection devices at the L / N (live wire / neutral wire) of the output AC port to cope with differential-mode surge interference, such as varistors, gas discharge tubes, semiconductor discharge tubes, etc. For common-mode surge interference, varistors in series with discharge tubes are used for the L and N of the AC port to the PE (live wire, neutral wire to ground wire).

[0003] However, since the AC port requires an EMC circuit composed of a common-mode inductor, a differential-mode inductor, an X capacitor, and a Y capacitor, when subjected to a surge impact, although the surge protection circuit can absorb the surge energy, convert it into heat consumption, and clamp the voltage within the safe range of the device, the inductor and capacitor will resonate. The resonance will cause the voltage across the inductor to become higher, exceeding the clamping voltage of the surge protection circuit. Part of the resonant energy will flow through the surge protection circuit, increasing the heat generation of the surge protection circuit, resulting in weakened reliability and reduced lifespan of the surge protection circuit, and it is prone to damage. Summary of the Utility Model

[0004] The purpose of this application is to provide an inverter to solve the problem in the related technology that when the inverter is subjected to a surge impact, the inductor and capacitor at the AC port of the inverter will resonate, resulting in part of the resonant energy flowing through the surge protection circuit, increasing the heat generation of the surge protection circuit, and weakening the reliability and reducing the lifespan of the surge protection circuit.

[0005] Based on the above purpose, this application provides an inverter, which includes:

[0006] An inverter circuit, which includes a DC side and an AC side. The DC side is connected to the DC bus, and the AC side is electrically connected to the surge protection circuit;

[0007] A surge protection circuit, which includes a differential-mode filtering module and a common-mode filtering module.

[0008] The differential-mode filtering module includes a differential-mode inductor. The first end of the differential-mode inductor is connected to the AC side port of the inverter circuit, and the second end of the differential-mode inductor is connected to the common-mode filtering module;

[0009] The common-mode filtering module includes a common-mode inductor. The differential-mode inductor is electrically connected to the grid phase line through the common-mode inductor.

[0010] Among them, a differential-mode inductor and a common-mode inductor are connected in parallel with a discharge tube.

[0011] Furthermore, the breakdown voltage of the discharge tube is greater than the absolute value of the operating voltage of the inductor in parallel with the discharge tube.

[0012] Furthermore, the breakdown voltage of the discharge tube is greater than the absolute value of the access voltage of the inductor in parallel with the discharge tube.

[0013] Furthermore, the breakdown voltage of the discharge tube is greater than 1.3 times the larger value of the absolute values of the operating voltage and the access voltage of the inductor in parallel with the discharge tube.

[0014] Furthermore, the differential-mode inductor includes a first differential-mode inductor and a second differential-mode inductor.

[0015] Furthermore, the first end of the first differential-mode inductor is connected to the first AC side port of the inverter circuit, and the second end of the first differential-mode inductor is connected to the first input end of the common-mode inductor.

[0016] The first end of the second differential-mode inductor is connected to the second AC side port of the inverter circuit, and the second end of the second differential-mode inductor is connected to the second input end of the common-mode inductor;

[0017] The first input end and the second input end are two ends of different coils in the common-mode inductor.

[0018] Furthermore, the differential-mode filtering module includes two capacitors of the first type. One capacitor of the first type is arranged between the differential-mode inductor and the inverter circuit, and the other capacitor of the first type is arranged between the differential-mode inductor and the common-mode inductor.

[0019] Furthermore, the surge protection circuit includes a differential-mode surge protection module.

[0020] The differential-mode surge protection module is arranged between the differential-mode inductor and the inverter circuit;

[0021] Or, the differential-mode surge protection module is arranged between the common-mode inductor and the power grid;

[0022] Or, the surge protection circuit includes two differential-mode surge protection modules. One differential-mode surge protection module is arranged between the differential-mode inductor and the inverter circuit, and the other differential-mode surge protection module is arranged between the common-mode inductor and the power grid.

[0023] Furthermore, the inverter is a single-phase inverter or a three-phase inverter.

[0024] Furthermore, the discharge tube is a gas discharge tube or a semiconductor discharge tube.

[0025] According to the above description, in the inverter provided by the present application, discharge tubes are connected in parallel with the differential-mode inductor and the common-mode inductor. When a differential-mode surge occurs, the discharge tubes connected in parallel across the differential-mode inductor conduct to clamp the voltage across the differential-mode inductor, preventing resonant energy from passing through the differential-mode surge protection module. When a common-mode surge occurs, the discharge tubes connected in parallel with the common-mode inductor conduct to clamp the voltage across the common-mode inductor, preventing resonant energy from passing through the common-mode surge protection module. Through the above settings, the reliability and lifespan of the differential-mode surge protection module and the common-mode surge protection module can be improved. Description of the Drawings

[0026] Figure 1 Schematic diagram of a single-phase inverter provided by the first embodiment of the present application;

[0027] Figure 2 Voltage waveform across the first differential-mode inductor without discharge tubes connected in parallel under a 6 kV differential-mode surge with an internal resistance of 2 Ω;

[0028] Figure 3 Voltage waveform across the first differential-mode inductor with discharge tubes connected in parallel under a 6 kV differential-mode surge with an internal resistance of 2 Ω;

[0029] Figure 4 Schematic diagram of a single-phase inverter provided by the second embodiment of the present application;

[0030] Figure 5 Voltage waveform across the common-mode inductor without discharge tubes connected in parallel under a 6 kV common-mode surge with an internal resistance of 2 Ω;

[0031] Figure 6 Voltage waveform across the common-mode inductor with discharge tubes connected in parallel under a 6 kV common-mode surge with an internal resistance of 2 Ω;

[0032] Figure 7 Schematic diagram of a single-phase inverter provided by the third embodiment of the present application;

[0033] Figure 8 Schematic diagram of a single-phase inverter provided by the fourth embodiment of the present application;

[0034] Figure 9 Schematic diagram of a single-phase inverter provided by the fifth embodiment of the present application;

[0035] Figure 10 Schematic diagram of a three-phase inverter provided by an embodiment of the present application. Detailed Embodiments

[0036] The present invention will be described in detail below in conjunction with the specific embodiments shown in the drawings. However, these embodiments do not limit the present invention, and any structural, method, or functional transformation made by those of ordinary skill in the art based on these embodiments is included within the protection scope of the present invention.

[0037] The purpose of the present application is to provide an inverter, which solves the problem that in the related art, when the inverter is subjected to a surge impact, the inductance and capacitance at the AC port of the inverter will resonate, resulting in part of the resonant energy flowing through the surge protection circuit, increasing the heat generation of the surge protection circuit, reducing the reliability of the surge protection circuit, and shortening its service life.

[0038] Based on the above purpose, the present application provides an inverter, which includes an inverter circuit and a surge protection circuit. Among them, the inverter circuit includes a DC side and an AC side. The DC side is connected to the DC bus, the AC side is electrically connected to the surge protection circuit, and the inverter circuit is connected to the power grid through the surge protection circuit.

[0039] The surge protection circuit includes a differential-mode filtering module and a common-mode filtering module. The differential-mode filtering module includes a differential-mode inductor. The first end of the differential-mode inductor is connected to the AC side port of the inverter circuit, and the second end of the differential-mode inductor is connected to the common-mode filtering module. The common-mode filtering module includes a common-mode inductor, and the differential-mode inductor is electrically connected to the power grid phase line through the common-mode inductor.

[0040] Among them, a discharge tube is connected in parallel with the differential-mode inductor and / or the common-mode inductor.

[0041] Specifically, as Figure 1 shown. In one embodiment, the inverter is a single-phase inverter.

[0042] The differential-mode filtering module 121 includes a first type of capacitor and a differential-mode inductor.

[0043] Among them, the first type of capacitor includes a first type of capacitor C4 and a first type of capacitor C5, and the differential-mode inductor includes a first differential-mode inductor L1 and a second differential-mode inductor L2. It should be noted that the differential-mode inductor described in the embodiments of the present application can be composed of a single coil wound around an iron core.

[0044] The first end of the first differential-mode inductor L1 is connected to the first AC side port of the inverter circuit 11, the second end of the first differential-mode inductor L1 is connected to the first input end of the common-mode inductor L3, the first end of the second differential-mode inductor L2 is connected to the second AC side port of the inverter circuit 11, and the second end of the second differential-mode inductor L2 is connected to the second input end of the common-mode inductor L3. Among them, the first input end and the second input end of the common-mode inductor L3 are two ends of different coils in the common-mode inductor L3.

[0045] The first type of capacitor C4 is arranged between the inverter circuit 11 and the differential-mode inductor. The first end of the first type of capacitor C4 is connected to the first AC side port of the inverter circuit 11, and the second end of the first type of capacitor C4 is connected to the second AC side port of the inverter circuit 11.

[0046] The first type of capacitor C5 is disposed between the differential-mode inductor and the common-mode inductor L3. The first end of the first type of capacitor C5 is connected to the first input terminal of the common-mode inductor L3, and the second end of the first type of capacitor C5 is connected to the second input terminal of the common-mode inductor L3. Both the first type of capacitor C4 and the first type of capacitor C5 are X capacitors, and the X capacitor is a type of safety capacitor to suppress differential-mode interference.

[0047] The common-mode filtering module 122 includes a second type of capacitor and the common-mode inductor L3. It should be noted that in a single-phase inverter, the common-mode inductor is usually formed by symmetrically winding two coils with the same size and the same number of turns on the same ferrite toroidal core to form a four-terminal device.

[0048] The first output terminal of the common-mode inductor L3 is connected to one phase wire of the power grid, and the second output terminal of the common-mode inductor L3 is electrically connected to the other phase wire of the power grid. Among them, the first input terminal and the first output terminal of the common-mode inductor L3 are two ends of the same coil in the common-mode inductor L3, and the second input terminal and the second output terminal of the common-mode inductor L3 are two ends of the same coil in the common-mode inductor L3.

[0049] In a single-phase inverter, the common-mode filtering module 122 includes two second types of capacitors. Among them, the first end of the second type of capacitor C7 is connected to the first output terminal of the common-mode inductor L3, and the second end of the second type of capacitor C7 is grounded. The first end of the second type of capacitor C6 is connected to the second output terminal of the common-mode inductor L3, and the second end of the second type of capacitor C6 is grounded. Both the second type of capacitor C7 and the second type of capacitor C6 are Y capacitors, and the Y capacitor is a type of safety capacitor to suppress common-mode interference.

[0050] Continue to refer to Figure 1 , the surge protection circuit 12 further includes a differential-mode surge protection module for performing differential-mode suppression on the signal passing through the differential-mode filtering module 121. As Figure 1 shown, the surge protection circuit 12 includes a first differential-mode surge protection module 123 and a second differential-mode surge protection module 124 to constitute two-stage differential-mode surge protection. Exemplarily, in a single-phase inverter, the differential-mode surge protection module includes a differential-mode surge protection device.

[0051] The first differential-mode surge protection module 123 is disposed between the common-mode inductor L3 and the power grid as the first-stage differential-mode surge protection. Exemplarily, the differential-mode surge protection device includes a varistor and a discharge tube. The first output terminal of the common-mode inductor L3 is connected to the first end of the discharge tube GDT3 through the varistor MOV4, and the second end of the discharge tube GDT3 is connected to the second output terminal of the common-mode inductor L3.

[0052] The second differential-mode surge protection module 124 is disposed between the differential-mode inductor and the inverter circuit 11 as the second-stage differential-mode surge protection. Specifically, the first AC-side port of the inverter circuit 11 is connected to the first end of the discharge tube GDT1 through the varistor MOV1, and the second end of the discharge tube GDT1 is connected to the second AC-side port of the inverter circuit 11.

[0053] Continue to refer to Figure 1 , the surge protection circuit 12 further includes a common-mode surge protection module 125 for performing common-mode suppression on the signal passing through the common-mode filtering module 122. Exemplarily, the common-mode surge protection module 125 includes a varistor and a discharge tube. The first output end of the common-mode inductor L3 is connected to the first end of the discharge tube GDT2 through the varistor MOV2, and the second output end of the common-mode inductor L3 is connected to the first end of the discharge tube GDT2 through the varistor MOV3. Moreover, the second end of the discharge tube GDT2 is grounded, thereby forming the common-mode surge protection module 125 for performing common-mode suppression on the signal passing through the common-mode filtering module 122.

[0054] Continue to refer to Figure 1 , the inverter provided by the embodiment of the present application also has discharge tubes connected in parallel at both ends of the differential-mode inductor (that is, the discharge tube GDT4 is connected in parallel at both ends of the first differential-mode inductor L1, and the discharge tube GDT5 is connected in parallel at both ends of the second differential-mode inductor L2).

[0055] According to Figure 1 the inverter shown, when a differential-mode surge occurs between the power grid power lines (between the L line and the N line), the first differential-mode surge protection module 123 starts to work first, clamps the voltage between the L line and the N line at a voltage higher than the normal operating voltage of the inverter, and releases the energy by generating heat and light. When the first differential-mode surge protection module 123 cannot dissipate the energy in time, the excess energy will be dissipated through the second differential-mode surge protection module 124 at this time.

[0056] In addition, when a differential-mode surge occurs, the differential-mode inductors (inductor L1 and L2) will resonate with the first-type capacitors (capacitors C4 and C5), and the resonance will cause the voltage at both ends of the differential-mode inductor to rise, exceeding the clamping voltage of the differential-mode surge protection module. Part of the resonant energy will flow through the differential-mode surge protection module, increasing the heat that the differential-mode surge protection module needs to dissipate. The inverter provided by the present application respectively has discharge tubes connected in parallel at both ends of the first differential-mode inductor L1 and the second differential-mode inductor L2. When the differential-mode inductor resonates with the first-type capacitor, the voltage at both ends of the differential-mode inductor rises, causing the discharge tube connected in parallel at both ends of the differential-mode inductor to conduct, so as to clamp the voltage at both ends of the differential-mode inductor, avoiding the resonant energy passing through the two-stage differential-mode surge protection module due to the resonance between the differential-mode inductor and the first-type capacitor, thereby improving the reliability and service life of the differential-mode surge protection module.

[0057] AsFigure 2 and Figure 3 as shown Figure 2 is the voltage waveform across the first differential-mode inductor L1 without a discharge tube in parallel at both ends under a 6 kV differential-mode surge with an internal resistance of 2 Ω; Figure 3 is the voltage waveform across the first differential-mode inductor L1 with a discharge tube in parallel at both ends under a 6 kV differential-mode surge with an internal resistance of 2 Ω. According to Figure 2 and Figure 3 it can be seen that through the solution of this patent, the maximum voltage across the differential-mode inductor can be clamped from 848 V to 320 V, effectively avoiding the resonant energy passing through the two-stage differential-mode surge protection module, thereby improving the reliability and lifespan of the differential-mode surge protection module.

[0058] As Figure 4 shown, in one embodiment, a discharge tube is connected in parallel to the common-mode inductor L3. Specifically, the first end of the discharge tube GDT6 is connected to the first input terminal of the common-mode inductor L3, and the second end of the discharge tube GDT6 is connected to the first output terminal of the common-mode inductor L3. The first end of the discharge tube GDT7 is connected to the second input terminal of the common-mode inductor L3, and the second end of the discharge tube GDT7 is connected to the second output terminal of the common-mode inductor L3. The rest of the inverter is similar to the inverter Figure 1 shown, and will not be elaborated here.

[0059] According to Figure 4 the inverter shown, when a common-mode surge occurs, the common-mode surge protection module 125 starts to work first, clamping the voltage between the L line and the PE line of the power grid, and the voltage between the N line and the PE line of the power grid, and releasing the energy in the form of heat and light.

[0060] In addition, when a common-mode surge occurs, the common-mode inductor L3 will resonate with the Y capacitors (i.e., the second-type capacitors C7 and C6), and the resonance will cause the voltage across the Y capacitors to increase, exceeding the clamping voltage of the common-mode surge protection module 125. Part of the resonant energy will flow through the common-mode surge protection module 125, increasing the heat that needs to be dissipated by the common-mode surge. In this application, by connecting discharge tubes (discharge tube GDT6 and discharge tube GDT7) in parallel to the common-mode inductor L3, when the common-mode inductor L3 resonates with the Y capacitors, the voltage across the common-mode inductor L3 increases, causing the discharge tubes GDT6 and GDT7 to conduct, so as to clamp the voltage across the common-mode inductor L3, avoiding the resonant energy passing through the common-mode surge protection module 125 due to the resonance between the common-mode inductor L3 and the second-type capacitors, thereby improving the reliability and lifespan of the common-mode surge protection module 125.

[0061] As Figure 5 and Figure 6 shown Figure 5 is the voltage waveform across the common-mode inductor L3 without a discharge tube in parallel at both ends under a 6 kV common-mode surge with an internal resistance of 2 Ω;Figure 6 The voltage waveform when a discharge tube is connected in parallel across both ends of the common-mode inductor L3 under the condition of a 6 kV common-mode surge with an internal resistance of 2 Ω. According to Figure 5 and Figure 6 it can be seen that the maximum voltage across both ends of the common-mode inductor L3 can be clamped from 1824 V to 400 V, effectively avoiding the resonant energy from passing through the common-mode surge protection module 125, thereby improving the reliability and lifespan of the common-mode surge protection module 125.

[0062] As Figure 7 shown, in one embodiment, discharge tubes (discharge tubes GDT4 and GDT5) are connected in parallel across the differential-mode inductor, and discharge tubes (discharge tubes GDT6 and GDT7) are connected in parallel across the common-mode inductor L3. Through this design, when a differential-mode surge occurs and the differential-mode inductor resonates with the first type of capacitor, the discharge tubes connected in parallel across the differential-mode inductor can conduct to clamp the voltage across both ends of the differential-mode inductor, avoiding the resonant energy from passing through the differential-mode surge protection module due to the resonance between the differential-mode inductor and the first type of capacitor, thereby improving the reliability and lifespan of the differential-mode surge protection module. When a common-mode surge occurs and the common-mode inductor L3 resonates with the second type of capacitor, the discharge tubes connected in parallel across the common-mode inductor L3 can conduct to clamp the voltage across both ends of the common-mode inductor L3, avoiding the resonant energy from passing through the common-mode surge protection module 125 due to the resonance between the common-mode inductor L3 and the second type of capacitor, thereby improving the reliability and lifespan of the common-mode surge protection module 125.

[0063] It should be noted that, as Figure 7 shown, the inverter is designed with two-stage differential-mode surge protection modules to enhance the protection ability of the circuit. In another embodiment, the inverter can be designed with only one differential-mode surge protection module. For example, as Figure 8 shown, the inverter is designed with only one differential-mode surge protection module, and this differential-mode surge protection module 123 is arranged between the common-mode inductor L3 and the power grid. Or, as Figure 9 shown, the inverter is designed with only one differential-mode surge protection module, and this differential-mode surge protection module 124 is arranged between the differential-mode inductor and the inverter circuit 11.

[0064] In one embodiment, the breakdown voltage of the discharge tube configured to be connected in parallel across the differential-mode inductor (or, the common-mode inductor L3) is greater than the absolute value of the operating voltage of the inductor across which the discharge tube is connected in parallel. By selecting the parameters of the discharge tube as described above, it is possible to avoid the discharge tube from affecting the normal operation of the inverter.

[0065] Taking the differential-mode inductor as an example, the breakdown voltage VDC of the discharge tube connected in parallel across both ends of the differential-mode inductor is greater than the absolute value of the operating voltage △V(t) of the differential-mode inductor. The voltage △V(t) across both ends of the differential-mode inductor satisfies the following relationship:

[0066]

[0067] Specifically, the calculation and derivation of the normal voltage across the differential-mode inductor are as follows:

[0068] The current of the inverter is a sinusoidal current. The current Iout flowing through the inductor as a function of time can be expressed by Equation (1) as follows:

[0069]

[0070] In the formula, A represents the effective value of the output alternating current, f represents the frequency of the local power grid, and t represents time.

[0071] Taking the derivative of both sides of Equation 1 gives the following Equation (2):

[0072]

[0073] When the differential-mode inductors L1 and L2 are operating normally, the current is an alternating waveform. According to the volt-second balance principle,

[0074]

[0075] △V represents the voltage across the differential-mode inductor (inductor L1 or L2), △I represents the change in the differential-mode inductor current, and L represents the inductance of the differential-mode inductor.

[0076] From Equation (2) and Equation (3), it can be seen that the normal voltage across the differential-mode inductor can be expressed by Equation 4:

[0077]

[0078] The calculation method of the voltage across the common-mode inductor L3 is the same as that of the voltage across the differential-mode inductor, and will not be elaborated here.

[0079] In another embodiment, the breakdown voltage of the discharge tube configured to be connected in parallel with the differential-mode inductor (or, the common-mode inductor L3) is greater than the absolute value of the access voltage of the discharge tube. In this way, when the inverter is just connected to the power grid, the power grid charging the first type of capacitor can be avoided, resulting in the breakdown of the discharge tube, and the safety of the inverter can be increased.

[0080] The calculation of the access voltage across the inductor is as follows:

[0081]

[0082] In the formula, Vac represents the effective value of the local power grid voltage, and f represents the frequency of the local power grid.

[0083] In another embodiment, the breakdown voltage of the discharge tube configured to be in parallel with the differential-mode inductor (or, common-mode inductor L3) is greater than 1.3 times the larger value of the operating voltage and the absolute value of the access voltage of the differential-mode inductor (or, common-mode inductor L3). In this way, a certain safety margin can be reserved when selecting the discharge tube, increasing the safety of the inverter.

[0084] As Figure 10 shown, in one embodiment, the inverter can be a three-phase inverter. In this embodiment, the inverter includes an inverter circuit 11, a differential-mode filtering module 121, and a common-mode filtering module 122. Among them, the inverter circuit 11 is a three-phase inverter circuit 11. For the convenience of description, the three-phase output terminals of the three-phase inverter circuit 11 are respectively defined as the first bridge arm output terminal, the second bridge arm output terminal, and the third bridge arm output terminal.

[0085] As Figure 10 shown, the differential-mode filtering module 121 includes three differential-mode inductors and six first-type capacitors, the common-mode filtering module 122 includes a common-mode inductor L4, and the differential-mode filtering module 121 is electrically connected to the power grid through the common-mode filtering module 122. It should be noted that in a three-phase inverter, the common-mode inductor is usually formed by symmetrically winding three coils with the same size and the same number of turns on the same ferrite toroidal core to form a six-terminal device.

[0086] Specifically, as Figure 10 shown, the first end of the first differential-mode inductor L1 is connected to the first bridge arm output terminal, the second end of the first differential-mode inductor L1 is connected to the first input terminal of the common-mode inductor L4, the first output terminal of the common-mode inductor L4 is connected to the first phase line of the power grid, and the first input terminal and the first output terminal of the common-mode inductor L4 are two ends of the same coil in the common-mode inductor L4.

[0087] The first end of the second differential-mode inductor L2 is connected to the second bridge arm output terminal, the second end of the second differential-mode inductor L2 is connected to the second input terminal of the common-mode inductor L4, the second output terminal of the common-mode inductor L4 is connected to the second phase line of the power grid, and the second input terminal and the second output terminal of the common-mode inductor L4 are two ends of the same coil in the common-mode inductor L4.

[0088] The first end of the third differential-mode inductor L3 is connected to the third bridge arm output terminal, the second end of the third differential-mode inductor L3 is connected to the third input terminal of the common-mode inductor L4, the third output terminal of the common-mode inductor L4 is connected to the third phase line of the power grid, and the third input terminal and the third output terminal of the common-mode inductor L4 are two ends of the same coil in the common-mode inductor L4.

[0089] As Figure 10As shown, in the differential-mode filtering module 121, the first-type capacitors C4, C5, and C6 are arranged between the three-phase inverter circuit 11 and the differential-mode inductor. Among them, the first end of the first-type capacitor C4 is connected to the first end of the first differential-mode inductor L1, the first end of the first-type capacitor C5 is connected to the first end of the second differential-mode inductor L2, and the first end of the first-type capacitor C6 is connected to the first end of the third differential-mode inductor L3. Moreover, the second ends of the first-type capacitor C4, the first-type capacitor C5, and the first-type capacitor C6 are connected to each other.

[0090] The first-type capacitors C7, C8, and C9 are arranged between the differential-mode inductor and the common-mode inductor L4. Among them, the first end of the first-type capacitor C7 is connected to the second end of the first differential-mode inductor L1, the first end of the first-type capacitor C8 is connected to the second end of the second differential-mode inductor L2, and the first end of the first-type capacitor C9 is connected to the second end of the third differential-mode inductor L3. Moreover, the second ends of the first-type capacitor C7, the first-type capacitor C8, and the first-type capacitor C9 are connected to each other.

[0091] As Figure 10 shown, the differential-mode filtering module 121 further includes a first differential-mode surge protection module 123 and a second differential-mode surge protection module 124 for performing differential-mode suppression on the signal passing through the differential-mode filtering module 121. The first differential-mode surge protection module 123 is arranged between the common-mode inductor L4 and the power grid, serving as the first-stage differential-mode surge protection. The second differential-mode surge protection module 124 is arranged between the differential-mode inductor and the inverter circuit 11, serving as the second-stage differential-mode surge protection.

[0092] The first differential-mode surge protection module 123 includes three differential-mode surge protection devices, and these three differential-mode surge protection devices have the same structure. Exemplarily, the differential-mode surge protection device includes a varistor and a discharge tube. The first end of the varistor is connected to a power grid phase line as the first end of the differential-mode surge protection device, the second end of the varistor is connected to the first end of the discharge tube, and the second end of the discharge tube is connected to another power grid phase line as the second end of the differential-mode surge protection device. Specifically, the first end of the first differential-mode surge protection device is connected to the first power grid phase line, and the second end is connected to the second power grid phase line; the first end of the second differential-mode surge protection device is connected to the second power grid phase line, and the second end is connected to the third power grid phase line; the first end of the third differential-mode surge protection device is connected to the first power grid phase line, and the second end is connected to the third power grid phase line.

[0093] The second differential-mode surge protection module 124 includes three differential-mode surge protection devices. Among them, the first end of the fourth differential-mode surge protection device is connected to the first end of the first differential-mode inductor L1, and the second end of the fourth differential-mode surge protection device is connected to the first end of the second differential-mode inductor L2; the first end of the fifth differential-mode surge protection device is connected to the first end of the second differential-mode inductor L2, and the second end of the fifth differential-mode surge protection device is connected to the first end of the third differential-mode inductor L3; the first end of the sixth differential-mode surge protection device is connected to the first end of the first differential-mode inductor L1, and the second end of the sixth differential-mode surge protection device is connected to the first end of the third differential-mode inductor L3.

[0094] Continue to refer to Figure 10 , in the three-phase inverter provided in the embodiment of the present application, the common-mode filtering module 122 includes four capacitors of the second type. Among them, the first end of the capacitor C11 of the second type is connected to the first phase line of the power grid, the first end of the capacitor C12 of the second type is connected to the second phase line of the power grid, the first end of the capacitor C13 of the second type is connected to the third phase line of the power grid, the first end of the capacitor C10 of the second type is connected to the neutral line of the power grid, and the second ends of the capacitor C11, the capacitor C12, the capacitor C13, and the capacitor C10 of the second type are commonly grounded.

[0095] The common-mode filtering module 122 further includes a common-mode surge protection module 125 for performing common-mode suppression on the signal passing through the common-mode filtering module 122. As Figure 10 shown, the common-mode surge protection module 125 includes four varistors and a discharge tube. The first end of the varistor MOV7 is connected to the first phase line of the power grid, the first end of the varistor MOV8 is connected to the second phase line of the power grid, the first end of the varistor MOV9 is connected to the third phase line of the power grid, the first end of the varistor MOV10 is connected to the neutral line of the power grid, and the second ends of the varistor MOV7, the varistor MOV8, the varistor MOV9, and the varistor MOV10 are commonly connected to the first end of the discharge tube GDT7, and the second end of the discharge tube GDT7 is grounded.

[0096] Continue to refer to Figure 10 , the inverter provided in the present application is further provided with a discharge tube connected in parallel with the differential-mode inductor. Specifically, the first end of the discharge tube GDT8 is connected to the first end of the first differential-mode inductor L1, and the second end of the discharge tube GDT8 is connected to the second end of the first differential-mode inductor L1; the first end of the discharge tube GDT9 is connected to the first end of the second differential-mode inductor L2, and the second end of the discharge tube GDT9 is connected to the second end of the second differential-mode inductor L2; the first end of the discharge tube GDT10 is connected to the first end of the third differential-mode inductor L3, and the second end of the discharge tube GDT10 is connected to the second end of the third differential-mode inductor L3.

[0097] Figure 10The surge protection operating principle of the three-phase inverter shown is similar to that of Figure 7 a single-phase inverter. When a differential-mode surge occurs, the differential-mode inductor resonates with the first type of capacitor, causing the voltage across the differential-mode inductor to increase, enabling the discharge tube connected in parallel across the differential-mode inductor to conduct, clamping the voltage across the differential-mode inductor, and preventing the resonant energy from passing through the differential-mode surge protection module due to the resonance between the differential-mode inductor and the first type of capacitor, thereby improving the reliability and lifespan of the differential-mode surge protection module.

[0098] Continuing to refer to Figure 10 , the inverter provided in this application is also provided with a discharge tube connected in parallel with the common-mode inductor L4. Specifically, the first end of the discharge tube GDT11 is connected to the first input terminal of the common-mode inductor L4, and the second end of the discharge tube GDT11 is connected to the first output terminal of the common-mode inductor L4; the first end of the discharge tube GDT12 is connected to the second input terminal of the common-mode inductor L4, and the second end of the discharge tube GDT12 is connected to the first output terminal of the common-mode inductor L4; the first end of the discharge tube GDT13 is connected to the third input terminal of the common-mode inductor L4, and the second end of the discharge tube GDT11 is connected to the third output terminal of the common-mode inductor L4.

[0099] Similar to a single-phase inverter, when a common-mode surge occurs, the common-mode inductor L4 resonates with the second type of capacitor, causing the voltage across the common-mode inductor L4 to increase, enabling the discharge tube connected in parallel with the common-mode inductor L4 to conduct, clamping the voltage across the common-mode inductor L4, and preventing the resonant energy from passing through the common-mode surge protection module 125 due to the resonance between the common-mode inductor L4 and the second type of capacitor, thereby improving the reliability and lifespan of the common-mode surge protection module 125.

[0100] Based on Figure 10 the inverter shown, in one embodiment, the breakdown voltage of the discharge tube configured to be connected in parallel with the differential-mode inductor (or, the common-mode inductor L4) is greater than the absolute value of the operating voltage of the inductor to which the discharge tube is connected. By selecting the parameters of the discharge tube as described above, it is possible to prevent the discharge tube from affecting the normal operation of the inverter.

[0101] Taking the differential-mode inductor as an example, the breakdown voltage VDC of the discharge tube connected in parallel across the differential-mode inductor is greater than the absolute value of the operating voltage △V(t) of the differential-mode inductor. The voltage △V(t) across the differential-mode inductor satisfies the following relationship:

[0102]

[0103] Specifically, the calculation and derivation of the normal voltage across the differential-mode inductor are as follows:

[0104] When the three-phase inverter is operating normally, the phase current formula between LA and LB is as follows:

[0105]

[0106] Wherein, A represents the effective value of the output single-phase alternating current, f represents the frequency of the local power grid, and t represents time.

[0107] Taking the derivative of the current formula gives the following formula:

[0108]

[0109] According to the volt-second balance principle,

[0110] △V represents the voltage across the differential-mode inductor (inductor L1 or L2), △I represents the change in the differential-mode inductor current, and L represents the inductance of the differential-mode inductor.

[0111] From formula (8) and formula (9), it can be known that the normal voltage across the differential-mode inductor can be expressed by formula (6):

[0112]

[0113] The calculation method of the voltage across the common-mode inductor L4 is the same as that of the voltage across the differential-mode inductor, and will not be elaborated here.

[0114] In another embodiment, the breakdown voltage of the discharge tube configured to be connected in parallel with the differential-mode inductor (or, the common-mode inductor L4) is greater than the absolute value of the access voltage of the discharge tube. In this way, when the inverter is just connected to the power grid, the power grid charging the first type of capacitor can be avoided from causing the breakdown of the discharge tube, increasing the safety of the inverter.

[0115] The access voltage across the inductor is calculated as follows:

[0116]

[0117] Wherein, Van represents the effective value of the local phase voltage, f represents the frequency of the local power grid, and t represents time.

[0118] In another embodiment, the breakdown voltage of the discharge tube configured to be connected in parallel with the differential-mode inductor (or, the common-mode inductor L4) is greater than 1.3 times the larger value of the operating voltage △V of the differential-mode inductor (or, the common-mode inductor L4) and the absolute value of the access voltage VAB(t). In this way, a certain safety margin can be reserved when selecting the discharge tube, increasing the safety of the inverter.

[0119] The above-disclosed are only the preferred embodiments of the present utility model, but they are not intended to limit the scope of the rights of the present utility model. Those of ordinary skill in the art can understand that: without departing from the spirit and scope of the present utility model and the appended claims, changes, modifications, substitutions, combinations, and simplifications should all be equivalent replacement methods and still fall within the scope covered by the utility model.

Claims

1. An inverter, characterized in that, The inverter includes: an inverter circuit, the inverter circuit including a DC side and an AC side, the DC side being connected to a DC bus, and the AC side being electrically connected to a surge protection circuit; a surge protection circuit, the surge protection circuit including a differential-mode filtering module and a common-mode filtering module, the differential-mode filtering module including a differential-mode inductor, a first end of the differential-mode inductor being connected to an AC side port of the inverter circuit, and a second end of the differential-mode inductor being connected to the common-mode filtering module; the common-mode filtering module including a common-mode inductor, the differential-mode inductor being electrically connected to a power grid phase line through the common-mode inductor; wherein, a discharge tube is connected in parallel with the differential-mode inductor and the common-mode inductor.

2. The inverter according to claim 1, wherein the breakdown voltage of the discharge tube is greater than the absolute value of the operating voltage of the inductor in parallel with the discharge tube.

3. The inverter according to claim 2, wherein the breakdown voltage of the discharge tube is greater than the absolute value of the access voltage of the inductor in parallel with the discharge tube.

4. The inverter according to claim 3, wherein the breakdown voltage of the discharge tube is greater than 1.3 times the larger value of the absolute values of the operating voltage and the access voltage of the inductor in parallel with the discharge tube.

5. The inverter according to claim 1, wherein the differential-mode inductor includes a first differential-mode inductor and a second differential-mode inductor.

6. The inverter according to claim 5, wherein a first end of the first differential-mode inductor is connected to a first AC side port of the inverter circuit, and a second end of the first differential-mode inductor is connected to a first input end of the common-mode inductor, a first end of the second differential-mode inductor is connected to a second AC side port of the inverter circuit, and a second end of the second differential-mode inductor is connected to a second input end of the common-mode inductor; the first input end and the second input end are two ends of different coils in the common-mode inductor.

7. The inverter according to claim 1, wherein the differential-mode filtering module includes two capacitors of a first type, one of the capacitors of the first type being disposed between the differential-mode inductor and the inverter circuit, and the other capacitor of the first type being disposed between the differential-mode inductor and the common-mode inductor.

8. The inverter according to claim 1, wherein the surge protection circuit includes a differential-mode surge protection module, the differential-mode surge protection module being disposed between the differential-mode inductor and the inverter circuit; alternatively, the differential-mode surge protection module is disposed between the common-mode inductor and the power grid; alternatively, the surge protection circuit includes two differential-mode surge protection modules, one of the differential-mode surge protection modules being disposed between the differential-mode inductor and the inverter circuit, and the other differential-mode surge protection module being disposed between the common-mode inductor and the power grid.

9. The inverter according to claim 1, wherein the inverter is a single-phase inverter or a three-phase inverter.

10. The inverter according to claim 1, wherein the discharge tube is a gas discharge tube or a semiconductor discharge tube.

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