A dual - live - wire inverter and its grid - end detection method

Abstract

The present invention discloses a dual - live - wire inverter and a grid - side detection method thereof. The grid - side detection method of the dual - live - wire inverter includes the following steps: S1: Obtain the instantaneous value of the first - phase voltage and the instantaneous value of the second - phase voltage of the inverter; S2: Normalize the instantaneous value of the first - phase voltage and the instantaneous value of the second - phase voltage of the inverter to obtain the per - unit value of the first - phase voltage and the per - unit value of the second - phase voltage respectively; S3: Multiply the per - unit value of the first - phase voltage and the per - unit value of the second - phase voltage to obtain the per - unit value product; S4: Judge whether the phase sequence of the inverter is normal according to the per - unit value product. The present invention can quickly detect the connection of the grid - side of the dual - live - wire inverter without a complex phase - locked loop.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage systems, and particularly to a dual-line inverter and a grid-side detection method thereof. Background Art

[0002] There are various grid standards globally. For example, in some countries / regions, there are two grid specifications: 120V / 240V dual-line grid and 120V / 208V three-phase grid. Among them, the dual-line, also known as split-phase, is a grid specification applied in many countries. Before the dual-line inverter is connected to the grid, it is necessary to detect the output port voltage first to ensure: a. The grid specification is consistent with the inverter output specification; b. The wiring is correct, otherwise grid connection failure will occur.

[0003] As Figure 1a , the output ports of the dual-line inverter 10 are correctly connected to the grid 20, where the L1 terminal of the inverter 10 is connected to the L1 terminal of the grid 20, and the L2 terminal of the inverter 10 is connected to the L2 terminal of the grid 20. At this time, the output voltages VL1N (the voltage between port L1 and port N) and VL2N (the voltage between port L2 and port N) of the inverter 10 are normal in amplitude and have a phase difference of 180°. In addition, since there is no distinction between positive and negative phase sequences for the dual-line inverter, as Figure 1b , if the L1 terminal of the inverter 10 is connected to the L2 terminal of the grid 20, and the L2 terminal of the inverter 10 is connected to the L1 terminal of the grid 20, it is also a correct connection. At this time, the amplitudes of the output voltages VL1N and VL2N of the inverter 10 are also normal and the phase difference is 180°.

[0004] As Figure 2 , the port connection between the dual-line inverter 10 and the grid 20 is incorrect, where both the L1 and L2 ports of the inverter 10 are connected to the L2 port of the grid 20. The port voltages VL1N and VL2N of the inverter 10 are normal in amplitude and equal in phase. At this time, the output port voltage of the dual-line inverter does not meet the aforementioned condition b.

[0005] As Figure 3a , the dual-line inverter is connected to a three-phase grid, and the L1 and L2 ports of the inverter are respectively connected to the L1 and L2 ports of the grid. The port voltages VL1N and VL2N of the inverter are normal in amplitude and have a phase difference of 120°; as Figure 3b , the dual-line inverter is connected to a three-phase grid, and the L1 and L2 ports of the inverter are respectively connected to the L1 and L3 ports of the grid. The port voltages VL1N and VL2N of the inverter are normal in amplitude and have a phase difference of 120°. Figure 3a And Figure 3b The output port voltages of the dual-line inverters in

[0006] Incorrect connection or incorrect grid specification will both cause the inverter grid connection failure. The above are just several examples of common wiring errors. ExceptFigure 1a and Figure 1b Any connection other than the correct connection shown in Figure 1b can be considered a connection error, which will not be listed one by one here.

[0007] For the inverter to be connected to the grid, it is necessary to ensure the synchronization of voltage amplitude, phase, and frequency. Since when the grid voltage amplitude and frequency are normal, it is necessary to detect the grid phase before the inverter is connected to the grid. The conventional method in the prior art is as follows: After the inverter is connected to L1, L2, and N at the grid end one by one, the inverter uses two phase-locked loops to track the phases of its own port voltages VL1N and VL2N respectively, and determines whether the phase difference between VL1N and VL2N is 180°. For common software phase-locked loops, software filtering, coordinate transformation, low-pass filtering, integration, and other links are usually required, but this algorithm is relatively complex.

[0008] The disclosure of the above background technical content is only used to assist in understanding the concept and technical solution of the present invention, and it does not necessarily belong to the prior art of this patent application. Without clear evidence indicating that the above content was publicly available on the filing date of this patent application, the above background technology should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0009] To solve the above technical problems, the present invention proposes a two-wire inverter and its grid-end detection method, which can quickly detect the connection of the grid end of the two-wire inverter without a complex phase-locked loop.

[0010] To achieve the above object, the present invention adopts the following technical solutions:

[0011] In a first aspect, the present invention discloses a grid-end detection method for a two-wire inverter, including the following steps:

[0012] S1: Obtain the instantaneous value of the first-phase voltage and the instantaneous value of the second-phase voltage of the inverter;

[0013] S2: Normalize the instantaneous value of the first-phase voltage and the instantaneous value of the second-phase voltage of the inverter to obtain the per-unit value of the first-phase voltage and the per-unit value of the second-phase voltage respectively;

[0014] S3: Multiply the per-unit value of the first-phase voltage and the per-unit value of the second-phase voltage to obtain a per-unit value product;

[0015] S4: Judge whether the phase sequence of the inverter is normal according to the per-unit value product.

[0016] Preferably, step S4 specifically includes: judging whether the per-unit value product is greater than a preset threshold. If so, it is determined that the phase sequence of the inverter is abnormal; otherwise, it is determined that the phase sequence of the inverter is normal.

[0017] Preferably, the value range of the preset threshold is [-0.375, -0.5].

[0018] Preferably, step S4 specifically includes: repeating steps S1 to S3 multiple times to calculate k per-unit value products, and calculating a filtered value of the per-unit value products based on k the per-unit value products; judging whether the phase sequence of the inverter is normal according to the filtered value of the per-unit value products, where k is a positive integer greater than 2.

[0019] Preferably, k the number of sampling points is greater than the inverter power frequency period, and the number of sampling points of the inverter power frequency period = sampling frequency / inverter output voltage frequency, where the sampling frequency refers to the frequency of obtaining the first-phase voltage instantaneous value and the second-phase voltage instantaneous value of the inverter in step S1.

[0020] Preferably, calculating a filtered value of the per-unit value products according to k the per-unit value products specifically uses the following formula:

[0021]

[0022] In the formula, VT AVE ( k ) represents the filtered value of the per-unit value products, N represents the number of sampling points of the inverter power frequency period, V 2 ( i ) represents the per-unit value product calculated corresponding to the first-phase voltage instantaneous value and the second-phase voltage instantaneous value of the inverter obtained for the i th time.

[0023] Preferably, the per-unit value product i calculated corresponding to the first-phase voltage instantaneous value and the second-phase voltage instantaneous value of the inverter obtained for the V 2 ( i ) is:

[0024]

[0025] In the formula, represents the first-phase voltage per-unit value calculated based on the first-phase voltage instantaneous value of the inverter obtained for the i th time, and , V L1N ( i ) represents the first-phase voltage instantaneous value of the inverter obtained for the i th time, VL1N_RMS is the effective value of the first-phase voltage of the inverter; represents according to the i per-unit value of the second-phase voltage calculated from the instantaneous value of the second-phase voltage of the inverter obtained for the th time, and V L2N ( i ) represents the instantaneous value of the second-phase voltage of the inverter obtained for the i th time, V L2N_RMS is the effective value of the second-phase voltage of the inverter.

[0026] Preferably, before performing step S1, it further includes: detecting whether the frequency and voltage of the grid side are normal. If normal, start to perform step S1.

[0027] In a second aspect, the present invention discloses a two-wire inverter. The two phases of the inverter are respectively connected to the grid side, and the inverter is used to judge whether the phase sequence of the inverter is normal according to the grid-side detection method of the two-wire inverter described in the first aspect.

[0028] In a third aspect, the present invention discloses a computer-readable storage medium. A computer program is stored in the computer-readable storage medium. Wherein, the computer program is set to be run by a processor to execute the grid-side detection method of the two-wire inverter described in the first aspect.

[0029] Compared with the prior art, the beneficial effect of the present invention is that: the present invention proposes a two-wire inverter and its grid-side detection method. Based on the instantaneous values of the voltages of each phase of the inverter, per-unit normalization is performed, and the product of the per-unit values is calculated to judge whether the phase sequence of the inverter is normal. Among them, no complex phase-locked loop is required, and problems such as incorrect grid wiring and incorrect grid specifications can be quickly identified. Description of the Drawings

[0030] Figure 1a and Figure 1b are respectively schematic diagrams of the correct connection of the output ports of the two-wire inverter to the grid;

[0031] Figure 2 is a schematic diagram of the incorrect connection of the output ports of the two-wire inverter to the grid;

[0032] Figure 3a and Figure 3b are respectively schematic diagrams of the connection of the two-wire inverter to the three-phase grid;

[0033] Figure 4 is a flowchart of the grid-side detection method of the two-wire inverter according to Embodiment 1 of the present invention;

[0034] Figure 5Flow chart of the grid - end detection method for the dual - live - wire inverter according to a specific embodiment of the present invention;

[0035] Figure 6 Graph showing the relationship between the standard threshold and the phase difference;

[0036] Figure 7 Schematic diagram of the measurement results of the first example of the present invention;

[0037] Figure 8 Schematic diagram of the measurement results of the second example of the present invention;

[0038] Figure 9 Schematic diagram of the measurement results of the third example of the present invention;

[0039] Figure 10 Schematic diagram of the measurement results of the fourth example of the present invention. Detailed implementation manners

[0040] The following provides a detailed description of the implementation manners of the present invention. It should be emphasized that the following description is merely exemplary and not intended to limit the scope of the present invention and its applications.

[0041] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on that other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to that other element. Additionally, the connection can be for a fixing function or for a circuit / signal connection function.

[0042] It should be understood that the orientation or positional relationship indicated by terms such as "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the embodiments of the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0043] Furthermore, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the embodiments of the present invention, "a plurality" means two or more unless otherwise specifically defined.

[0044] As Figure 4 shown, the first embodiment of the present invention discloses a grid - end detection method for a dual - live - wire inverter, including the following steps:

[0045] S1: Obtain the instantaneous values of the first-phase voltage and the second-phase voltage of the inverter;

[0046] S2: Normalize the instantaneous values of the first-phase voltage and the second-phase voltage of the inverter to obtain the per-unit value of the first-phase voltage and the per-unit value of the second-phase voltage respectively;

[0047] S3: Multiply the per-unit value of the first-phase voltage and the per-unit value of the second-phase voltage to obtain the per-unit value product;

[0048] S4: Determine whether the phase sequence of the inverter is normal according to the per-unit value product.

[0049] Among them, step S4 specifically includes: determining whether the per-unit value product is greater than a preset threshold. If so, it is determined that the phase sequence of the inverter is abnormal; otherwise, it is determined that the phase sequence of the inverter is normal. The value range of the preset threshold is [-0.375, -0.5]. In a specific example, the preset threshold is -0.375.

[0050] Further, step S4 specifically includes: repeating steps S1 to S3 multiple times to calculate k per-unit value products, and calculating the filtered value of the per-unit value products according to k per-unit value products; determining whether the phase sequence of the inverter is normal according to the filtered value of the per-unit value products, where k is a positive integer greater than 2. That is, determining whether the filtered value of the per-unit value product is greater than the preset threshold. If so, it is determined that the phase sequence of the inverter is abnormal; otherwise, it is determined that the phase sequence of the inverter is normal.

[0051] Among them, k is greater than the number of sampling points in the inverter power frequency period. The number of sampling points in the inverter power frequency period = sampling frequency / inverter output voltage frequency, where the sampling frequency refers to the frequency of obtaining the instantaneous values of the first-phase voltage and the second-phase voltage of the inverter in step S1.

[0052] According to k per-unit value products to calculate the filtered value of the per-unit value products, specifically using the following formula:

[0053]

[0054] In the formula, VT AVE ( k ) represents the filtered value of the per-unit value product, N represents the number of sampling points in the inverter power frequency period, V 2 ( i ) represents thei The per-unit value product calculated corresponding to the instantaneous value of the first-phase voltage and the instantaneous value of the second-phase voltage of the inverter obtained in the

[0055] According to the i per-unit value product calculated corresponding to the instantaneous value of the first-phase voltage and the instantaneous value of the second-phase voltage of the inverter obtained in the V 2 ( i ) is:

[0056]

[0057] In the formula, represents the per-unit value of the first-phase voltage calculated according to the instantaneous value of the first-phase voltage of the inverter obtained in the i th acquisition, and , V L1N ( i ) represents the instantaneous value of the first-phase voltage of the inverter obtained in the i th acquisition, V L1N_RMS is the effective value of the first-phase voltage of the inverter; represents the per-unit value of the second-phase voltage calculated according to the instantaneous value of the second-phase voltage of the inverter obtained in the i th acquisition, and , V L2N ( i ) represents the instantaneous value of the second-phase voltage of the inverter obtained in the i th acquisition, V L2N_RMS is the effective value of the second-phase voltage of the inverter.

[0058] Wherein, before performing step S1, it further includes: detecting whether the frequency and voltage of the grid side are normal, and if so, starting to execute step S1.

[0059] The following further details the grid-side detection method of the dual-line inverter disclosed in Embodiment 1 of the present invention in conjunction with specific embodiments.

[0060] As Figure 5 shown, the grid-side detection method of the dual-line inverter in the specific embodiment of the present invention includes the following steps:

[0061] A1: After determining that the grid frequency and grid voltage are normal, start grid phase detection.

[0062] A2: The CPU controller samples the instantaneous value of the inverter voltage V L1N ( i ) and V L2N( i ), V L1N ( i ) represents the instantaneous value of the first-phase voltage of the inverter at the i th sampling moment, V L2N ( i ) represents the instantaneous value of the second-phase voltage of the inverter at the i th sampling moment, i represents the i th sampling moment, i = 1, 2, 3, ……;

[0063] Normalize V L1N ( i ) and V L2N ( i ) respectively to obtain the per-unit values and of the two-phase voltages:

[0064] (1)

[0065] (2)

[0066] In the formula, V L1N_RMS is the effective value of the first-phase voltage of the inverter, V L2N_RMS is the effective value of the second-phase voltage of the inverter.

[0067] A3: Multiply the per-unit values of the two-phase voltages to obtain the per-unit value product:

[0068] (3)

[0069] A4: Repeat steps A2 to A3 until the last sampling is the k th time and k is greater than N. Calculate the average value of the per-unit value products obtained from the first N samplings to obtain the filtered value of the per-unit value product:

[0070] (4)

[0071] where N is the number of sampling points in the inverter power frequency period. For example, if the inverter output voltage frequency is 50 Hz and the sampling frequency is 20 KHz, then N = 20 KHz / 50 Hz = 400.

[0072] A5: Judge the filtered value VT AVE ( kIs it greater than the preset threshold? VT TH , if VT AVE ( k ) > VT TH , it is determined that the phase sequence is abnormal, otherwise it is determined that the phase sequence is normal.

[0073] The following is the derivation of the value of the preset threshold VT TH : First, assume that the phase difference is θ , and obtain the theoretical standard threshold at this phase difference VT ( θ );

[0074] Among them, the grid voltage can be approximated as a sine wave, and is equivalent to:

[0075] (5)

[0076] Substitute is equivalent to:

[0077] (6)

[0078] Then VT ( θ )'s theoretical value is:

[0079] (7)

[0080] In the formula, N is the number of sampling points in the inverter power frequency cycle.

[0081] Combined with the above formula (7), the standard threshold VT ( θ ) and θ 's relationship is as Figure 6 shown. In this way, the correctness of the phase can be judged by comparing the relationship between the actual value and the theoretical value. When the grid is correctly connected, the phase difference between the voltages V L1 and V L2 is 180°. Correspondingly, VT (180°) = -0.5; among them, the error range is usually ±30°. Therefore, it is considered that the phase difference between V L1 and V L2 is normal when it is between 150° and 210°, while VT (150°)= VT (210°) = -0.375.

[0082] Therefore, in this specific embodiment, the preset threshold VT THSet to equal -0.375, when VT AVE ( k ) > VT TH it is determined that the phase sequence is abnormal, otherwise it is determined that the phase is normal.

[0083] Specific examples are as follows:

[0084] Example 1:

[0085] As Figure 1a shown in the connection method, L1N and L2N are connected to a dual-phase power grid, and V L1N leads by 180°, and the measurement results are as Figure 7 , where the abscissa represents time, the ordinate in the upper figure represents the actual voltage values of each phase of the inverter collected, and the ordinate in the lower figure represents the measured values VT AVE ( k ); after measuring for 60 ms VT AVE it stabilizes at about -0.5. Since VT AVE ( k ) < VT TH , it is determined that the power grid connection is normal.

[0086] Example 2:

[0087] As Figure 2 shown in the connection method, L1N and L2N are connected to a dual-phase power grid, and V L1N is in the same phase as V L2N , and the measurement results are as Figure 8 , where the abscissa represents time, the ordinate in the upper figure represents the actual voltage values of each phase of the inverter collected, and the ordinate in the lower figure represents the measured values VT AVE ( k ); after measuring for 60 ms VT AVE it stabilizes at about 0.5. Since VT AVE > VT TH , it is determined that the power grid connection is abnormal.

[0088] Example 3:

[0089] As Figure 3a shown in the connection method, L1N and L2N are connected to a three-phase power grid, and V L1N leads by 120°, and the measurement results are as Figure 9 , where the abscissa represents time, the ordinate in the upper figure represents the actual voltage values of each phase of the inverter collected, and the ordinate in the lower figure represents the measured values VTAVE ( k );After measuring for 60 ms VT AVE It stabilizes at around -0.25. Since VT AVE > VT TH , it is determined that the grid connection is abnormal.

[0090] Example 4:

[0091] As shown in the connection method Figure 3b shown, L1N and L2N are connected to the three-phase grid, and V L1N lags by 120°. The measurement results are as Figure 10 shown, where the abscissa represents time, the ordinate in the upper figure represents the actual voltage values of each phase of the inverter collected, and the ordinate in the lower figure represents the measured values VT AVE ( k );After measuring for 60 ms VT AVE It stabilizes at around -0.25. Since VT AVE > VT TH , it is determined that the grid connection is abnormal.

[0092] From the test results of the above Examples 1 to 4, it can be seen that the method of the present invention can accurately detect the grid-side connection error of the dual-fire inverter.

[0093] As in the above various examples, the grid-side detection method of the dual-fire inverter proposed by the present invention can quickly identify the grid wiring error and the grid specification error without a complex phase-locked loop.

[0094] Embodiment 2 of the present invention discloses a dual-fire inverter. Two phases of the inverter are respectively connected to the grid side, and the inverter is used to judge whether the phase sequence of the inverter is normal according to the grid-side detection method of the dual-fire inverter in Embodiment 1.

[0095] Embodiment 3 of the present invention discloses a computer-readable storage medium. A computer program is stored in the computer-readable storage medium, wherein the computer program is set to be run by a processor to execute the steps of the grid-side detection method of the dual-fire inverter in the above Embodiment 1.

[0096] Optionally, the above computer-readable storage medium may include, but is not limited to: various media such as USB flash drives, read-only memories (ROM for short), random access memories (RAM for short), mobile hard disks, magnetic disks, or optical discs that can store computer programs.

[0097] The background section of the present invention may include background information about the problems or circumstances of the present invention, rather than the prior art described by others. Therefore, the content included in the background art section is not an admission of the prior art by the applicant.

[0098] The above content is a further detailed description of the present invention in combination with specific / preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited only to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several alternatives or modifications can be made to these described embodiments, and these alternative or modified forms should all be regarded as falling within the protection scope of the present invention. In the description of this specification, the description with reference to terms such as "an embodiment", "some embodiments", "preferred embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and alterations can be made herein without departing from the scope defined by the appended claims.

Claims

1. A grid-side detection method for a dual-line inverter, characterized in that, It includes the following steps: S1: Obtain the instantaneous values of the first-phase voltage and the second-phase voltage of the inverter; S2: Normalize the instantaneous values of the first-phase voltage and the second-phase voltage of the inverter to obtain the per-unit value of the first-phase voltage and the per-unit value of the second-phase voltage respectively; S3: Multiply the per-unit value of the first-phase voltage and the per-unit value of the second-phase voltage to obtain the per-unit value product; S4: Determine whether the phase sequence of the inverter is normal according to the per-unit value product; Step S4 specifically includes: repeating steps S1 to S3 multiple times to calculate k per-unit value products, and calculating a filtered value of the per-unit value products according to k per-unit value products; judging whether the phase sequence of the inverter is normal according to the filtered value of the per-unit value products, where k is a positive integer greater than 2; According to k The filtered value of the per-unit value product is calculated from the product of per-unit values, specifically using the following formula: ； Wherein, VT AVE ( k ) represents the filtered value of the per-unit value product, N represents the number of sampling points in the inverter power frequency period, V 2 ( i ) represents the per-unit value product calculated corresponding to the instantaneous values of the first-phase voltage and the second-phase voltage of the inverter obtained at the i th time; Among them, k the number of sampling points greater than the inverse power frequency period, and the number of sampling points of the inverse power frequency period = sampling frequency / inverter output voltage frequency, where the sampling frequency refers to the frequency of obtaining the instantaneous values of the first-phase voltage and the second-phase voltage of the inverter in step S1.

2. The grid-side detection method of the dual-line inverter according to claim 1, characterized in that Step S4 specifically includes: determining whether the per-unit value product is greater than a preset threshold value. If so, it is determined that the phase sequence of the inverter is abnormal; otherwise, it is determined that the phase sequence of the inverter is normal.

3. The grid-side detection method of the dual-line inverter according to claim 2, characterized in that, The value range of the preset threshold value is [-0.375, -0.5].

4. The grid-side detection method of the dual-line inverter according to claim 1, characterized in that According to the i per-unit value product calculated corresponding to the instantaneous value of the first-phase voltage and the instantaneous value of the second-phase voltage obtained in the V 2 ( i ) is: ； Wherein, represents the per-unit value of the first-phase voltage calculated based on the instantaneous value of the first-phase voltage of the inverter obtained at the i -th time, and , V L1N ( i ) represents the instantaneous value of the first-phase voltage of the inverter obtained at the i -th time, V L1N_RMS being the effective value of the first-phase voltage of the inverter; represents the per-unit value of the second-phase voltage calculated based on the instantaneous value of the second-phase voltage of the inverter obtained at the i -th time, and , V L2N ( i ) represents the instantaneous value of the second-phase voltage of the inverter obtained at the i -th time, V L2N_RMS being the effective value of the second-phase voltage of the inverter.

5. The grid-end detection method of the dual-line inverter according to claim 1, wherein Before performing step S1, it also includes: detecting whether the frequency and voltage of the grid side are normal. If normal, start to perform step S1.

6. A dual - live - wire inverter, characterized in that, Two phases of the inverter are respectively connected to the grid side, and the inverter is used to determine whether the phase sequence of the inverter is normal according to the grid side detection method of the dual-fire wire inverter according to any one of claims 1 to 5.

7. A computer-readable storage medium, characterized in that, A computer program is stored in the computer-readable storage medium, wherein the computer program is set to be run by a processor to execute the grid side detection method of the dual-fire wire inverter according to any one of claims 1 to 5.

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