N-line missing detection method and inverter system

Abstract

The invention discloses an N-line lacking detection method and an inverter system, and the method comprises the steps: obtaining a first phase voltage of a first phase through a control unit in response to a condition that a first line voltage, a second line voltage, a third line voltage and a line voltage of an N line are located in a preset range, acquiring a first impedance of a filter capacitor electrically connected with the first phase in the filter circuit, and acquiring a second impedance of a load of the AC / DC converter; obtaining a first difference value between the second phase voltage of the second phase and the first phase voltage and / or a second difference value between the third phase voltage of the third phase and the first phase voltage through the control unit based on the first phase voltage, the first impedance and the second impedance; and determining that the inverter system lacks N lines in response to the fact that the first difference value is greater than a preset threshold value and / or the second difference value is greater than the preset threshold value. By means of the mode, a detection circuit does not need to be additionally arranged, the cost is reduced, the size of an inverter system is reduced, and the reliability of N-line-lacking detection is improved.

Description

Technical Field

[0001] This application relates to the field of inverter technology, and in particular to a method for detecting a missing N-line and an inverter system. Background Technology

[0002] As market demands vary, inverters are becoming increasingly functional, including energy storage circuits and inverter circuits.

[0003] Existing inverters are connected to the grid via phases A, B, C, and the neutral (N) line. To detect a missing N line fault between the inverter and the grid, existing inverters require an additional N line detection circuit or other detection circuit. This additional circuit increases cost and size. Summary of the Invention

[0004] In view of the above problems, this application provides a method for detecting missing N-line and an inverter system, which eliminates the need for additional detection circuits, reduces costs and shrinks the size of the inverter system.

[0005] In a first aspect, this application provides a method for detecting a missing neutral (N) line, applied to an inverter system electrically connected to a power grid. The inverter system includes a control unit, an AC / DC converter, and a filter circuit. The filter circuit is electrically connected to the first phase, second phase, third phase, and neutral (N) line of the power grid. The control unit is electrically connected to the AC / DC converter, the first phase, the second phase, the third phase, and the neutral (N) line. The AC / DC converter is electrically connected to the first phase and the neutral (N) line. The detection method includes:

[0006] The first line voltage of the first phase, the second line voltage of the second phase, the third line voltage of the third phase, and the line voltage of the N line are obtained through the control unit.

[0007] In response to the first line voltage, the second line voltage, the third line voltage, and the line voltage of the N line being within a preset range, the first phase voltage of the first phase is obtained through the control unit, the first impedance of the filter capacitor electrically connected to the first phase in the filter circuit is obtained, and the second impedance of the load of the AC / DC converter is obtained.

[0008] The control unit obtains a first difference between the second phase voltage of the second phase and the first phase voltage, and / or a second difference between the third phase voltage of the third phase and the first phase voltage, based on the first phase voltage, the first impedance, and the second impedance.

[0009] If the first difference is greater than a preset threshold, and / or the second difference is greater than the preset threshold, then it is determined that the inverter system is missing the N-line.

[0010] In some embodiments, the filtering circuit includes a first filtering capacitor, a second filtering capacitor, and a third filtering capacitor. One end of the first filtering capacitor is electrically connected to the first phase, one end of the second filtering capacitor is electrically connected to the second phase, and one end of the third filtering capacitor is electrically connected to the third phase. The other ends of the first filtering capacitor, the second filtering capacitor, and the third filtering capacitor are all electrically connected to the neutral (N) line. The parameters of the first filtering capacitor, the second filtering capacitor, and the third filtering capacitor are the same. The step of obtaining a first difference between the second phase voltage of the second phase and the first phase voltage based on the first phase voltage, the first impedance, and the second impedance by the control unit, and / or obtaining a second difference between the third phase voltage of the third phase and the first phase voltage, includes:

[0011] The control unit calculates the ratio of the first impedance to the second impedance;

[0012] The control unit multiplies the ratio by the first phase voltage to obtain the first difference.

[0013] And / or, the control unit multiplies the ratio by the first phase voltage to obtain the second difference.

[0014] In some embodiments, the inverter system further includes a DC / AC converter, a DC / DC converter, and a power supply circuit. The DC / AC converter is electrically connected to the first phase, second phase, third phase, and neutral line of the power grid. The DC / DC converter is electrically connected to the DC / AC converter. The power supply circuit is connected to both the AC / DC converter and the DC / DC converter, and is used to supply power to the control unit. The DC / DC converter is electrically connected to both the battery module and the photovoltaic module. The detection method further includes:

[0015] In response to being in N-line detection mode, the control unit detects the first voltage output by the photovoltaic module and compares the first voltage with a first voltage threshold.

[0016] In response to the first voltage being less than the first voltage threshold, the step of obtaining the first line voltage of the first phase, the second line voltage of the second phase, the third line voltage of the third phase, and the line voltage of the N line through the control unit is performed.

[0017] In some embodiments, the control unit is electrically connected to the battery assembly, and the battery assembly supplies power to the power circuit via the DC / DC converter; the detection method further includes:

[0018] The control unit controls the battery assembly to enter sleep mode.

[0019] The control unit controls the AC / DC converter to supply power to the power circuit.

[0020] In some embodiments, after the step of controlling the battery assembly to enter a sleep mode via the control unit, the detection method further includes:

[0021] The control unit detects the second voltage output by the DC / DC converter at preset time intervals and compares the second voltage with a second voltage threshold.

[0022] In response to the second voltage being less than the second voltage threshold, the step of obtaining a first difference between the second phase voltage of the second phase and the first phase voltage, and / or a second difference between the third phase voltage of the third phase and the first phase voltage, by the control unit based on the first phase voltage, the first impedance and the second impedance.

[0023] In some embodiments, the inverter system further includes a first voltage sampling circuit, which is electrically connected to the control unit and connected between the DC / AC converter and the DC / DC converter. The step of controlling the AC / DC converter to supply power to the power supply circuit via the control unit includes:

[0024] The control unit obtains the sampling voltage of the first voltage sampling circuit;

[0025] In response to the gradual decrease of the sampling voltage, the control unit sends an enable signal to the AC / DC converter to control the AC / DC converter to supply power to the power circuit.

[0026] In some embodiments, the inverter system further includes a second voltage sampling circuit, which is electrically connected to the control unit and the photovoltaic module, respectively. The step of detecting the first voltage output by the photovoltaic module through the control unit includes:

[0027] The first voltage is obtained from the second voltage sampling circuit through the control unit.

[0028] In some embodiments, the inverter system further includes a third voltage sampling circuit, which is electrically connected to the control unit, the first phase, the second phase, the third phase, and the neutral line of the power grid, respectively. The step of obtaining the first line voltage of the first phase, the second line voltage of the second phase, the third line voltage of the third phase, and the line voltage of the neutral line through the control unit includes:

[0029] The control unit obtains the first line voltage, the second line voltage, the third line voltage, and the line voltage of the N line from the third voltage sampling circuit.

[0030] Secondly, this application provides an inverter system electrically connected to a power grid. The inverter system includes a control unit, an AC / DC converter, and a filter circuit. The filter circuit is electrically connected to a first phase, a second phase, a third phase, and the neutral (N) line of the power grid. The control unit is electrically connected to the AC / DC converter, the first phase, the second phase, the third phase, and the N line. The AC / DC converter is electrically connected to the first phase and the N line. The control unit is configured to: acquire the first line voltage of the first phase, the second line voltage of the second phase, the third line voltage of the third phase, and the line voltage of the N line; and respond to the first line voltage... If the voltage of the first phase, the second line voltage, the third line voltage, and the line voltage of the N line are within a preset range, the first phase voltage of the first phase is obtained, the first impedance of the filter capacitor electrically connected to the first phase in the filter circuit is obtained, and the second impedance of the load of the AC / DC converter is obtained; based on the first phase voltage, the first impedance, and the second impedance, a first difference between the second phase voltage of the second phase and the first phase voltage, and / or a second difference between the third phase voltage of the third phase and the first phase voltage is obtained; in response to the first difference being greater than a preset threshold, and / or the second difference being greater than the preset threshold, it is determined that the inverter system is missing the N line.

[0031] In some embodiments, the inverter system further includes a DC / AC converter, a DC / DC converter, and a power supply circuit. The DC / AC converter is electrically connected to the first phase, the second phase, the third phase, and the neutral line of the power grid. The DC / DC converter is electrically connected to the DC / AC converter. The power supply circuit is connected to both the AC / DC converter and the DC / DC converter, and is used to supply power to the control unit. The DC / DC converter is electrically connected to both the battery module and the photovoltaic module.

[0032] When the inverter system is not in N-line detection mode, the battery module or the photovoltaic module supplies power to the power circuit through the DC / DC converter;

[0033] When the inverter system is in neutral (N) detection mode, the control unit controls the AC / DC converter to supply power to the power supply circuit.

[0034] Unlike existing technologies, this application, in response to the first line voltage, second line voltage, third line voltage, and neutral line voltage falling within a preset range, obtains the first phase voltage of the first phase, the first impedance of the filter capacitor electrically connected to the first phase in the filter circuit, and the second impedance of the load of the AC / DC converter through a control unit. Based on the first phase voltage, the first impedance, and the second impedance, the control unit obtains a first difference between the second phase voltage and the first phase voltage of the second phase, and / or a second difference between the third phase voltage and the first phase voltage of the third phase. If the first difference is greater than a preset threshold, and / or the second difference is greater than a preset threshold, it is determined that the inverter system is missing a neutral line. By using the first difference between the second phase voltage and the first phase voltage, and / or the second difference between the third phase voltage and the first phase voltage, it is possible to determine whether the inverter system is missing a neutral line, without the need for additional detection circuitry, reducing costs and the size of the inverter system, and improving the reliability of detecting a missing neutral line. Attached Figure Description

[0035] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0036] Figure 1 This is a circuit diagram of the first embodiment of the inverter system of this application;

[0037] Figure 2 yes Figure 1 A flowchart illustrating the first embodiment of the method for detecting a missing neutral (N) line in a medium-voltage inverter system;

[0038] Figure 3 yes Figure 2 A flowchart illustrating the first embodiment of step S103;

[0039] Figure 4 yes Figure 1 A schematic diagram of the equivalent circuit of an inverter system lacking the neutral (N) line.

[0040] Figure 5 This is a circuit diagram of the second embodiment of the inverter system of this application;

[0041] Figure 6 yes Figure 5 A flowchart illustrating the second embodiment of the method for detecting a missing neutral (N) line in a medium-voltage inverter system;

[0042] Figure 7 yes Figure 5 A flowchart illustrating the third embodiment of the method for detecting the missing neutral (N) line in a medium-voltage inverter system. Detailed Implementation

[0043] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0045] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0046] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0047] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0048] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0049] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0050] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a connection between two components or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0051] Existing inverter technologies require the addition of a neutral (N) line detection circuit or other detection circuits between the inverter and the power grid. This additional requirement increases both cost and size.

[0052] To reduce costs and size, this application also provides a method for detecting missing N-lines. Please see [link to application]. Figure 1-2 As shown, Figure 1 This is a circuit diagram of the first embodiment of the inverter system of this application; Figure 2 yes Figure 1 A flowchart illustrating the first embodiment of the method for detecting a missing neutral (N) line in an inverter system. In this embodiment, the inverter system 10 is electrically connected to the power grid 20, which has a first phase A, a second phase B, a third phase C, and a neutral (N) line. That is, the inverter system 10 is electrically connected to the first phase A, the second phase B, the third phase C, and the neutral (N) line, respectively. The power grid 20 provides mains power, which refers to industrial frequency alternating current (AC).

[0053] The inverter system 10 of this embodiment includes a control unit 11, an AC / DC converter 12, and a filter circuit 13. The filter circuit 13 is electrically connected to the first phase A, the second phase B, the third phase C, and the neutral line of the power grid 20, respectively. The control unit 11 is electrically connected to the AC / DC converter 12 and the first phase A, the second phase B, the third phase C, and the neutral line of the power grid 20, respectively.

[0054] The AC / DC converter 12 is electrically connected to the first phase A and N lines respectively, that is, the input terminals of the AC / DC converter 12 are electrically connected to the first phase A and N lines respectively, and the output terminal of the AC / DC converter 12 is electrically connected to the load (i.e., the power supply circuit in other embodiments). The AC / DC converter 12 is used to convert the alternating current of the power grid 20 into direct current to supply power to the load. The control unit 11 is electrically connected to the AC / DC converter 12 so that the control unit 11 can control the AC / DC converter 12 to supply power to the load.

[0055] The method for detecting a missing N-line in this embodiment includes the following steps:

[0056] S101: The first line voltage of the first phase A, the second line voltage of the second phase B, the third line voltage of the third phase C, and the line voltage of the N line are obtained through the control unit 11.

[0057] The control unit 11 acquires the first line voltage of phase A, the second line voltage of phase B, the third line voltage of phase C, and the line voltage of the neutral line. The control unit 11 is electrically connected to the first phase A, second phase B, third phase C, and neutral line of the power grid 20, respectively, and thus detects and obtains the first line voltage of phase A, the second line voltage of phase B, the third line voltage of phase C, and the line voltage of the neutral line.

[0058] The control unit 11 compares the first line voltage of the first phase A, the second line voltage of the second phase B, the third line voltage of the third phase C, and the line voltage of the N line with preset ranges respectively; in response to the first line voltage, the second line voltage, the third line voltage, and the line voltage of the N line being within the preset range, the process proceeds to step S102.

[0059] S102: In response to the first line voltage, the second line voltage, the third line voltage and the line voltage of the N line being within a preset range, the first phase voltage Van of the first phase A is obtained through the control unit 11, the first impedance Rc1 of the filter capacitor electrically connected to the first phase A in the filter circuit 13 is obtained, and the second impedance RL of the load of the AC / DC converter 12 is obtained.

[0060] When the first line voltage, the second line voltage, the third line voltage, and the line voltage of the N line are all within a preset range, the first phase voltage Van of the first phase A is obtained by the control unit 11, the first impedance Rc1 of the filter capacitor electrically connected to the first phase A in the filter circuit 13 is obtained by the control unit 11, and the second impedance RL of the load of the AC / DC converter 12 is obtained.

[0061] S103: The control unit 11 obtains the first difference d1 between the second phase voltage Vbn of the second phase B and the first phase voltage Van, and / or the second difference d2 between the third phase voltage Vcn of the third phase C and the first phase voltage Van, based on the first phase voltage Van, the first impedance Rc1 and the second impedance RL.

[0062] When the neutral (N) line of inverter system 10 is not missing, the voltages of the first phase (Van), the second phase (Vbn), and the third phase (Vcn) are equal. When the neutral (N) line of inverter system 10 is missing, the voltages of the second phase (Vbn) and the third phase (Vcn) are equal.

[0063] The control unit 11 obtains a first difference d1 between the second phase voltage Vbn of the second phase B and the first phase voltage Van, and / or a second difference d2 between the third phase voltage Vcn of the third phase C and the first phase voltage Van, based on the first phase voltage Van, the first impedance Rc1 and the second impedance RL.

[0064] Specifically, the control unit 11 obtains a first difference d1 based on the first phase voltage Van, the first impedance Rc1, and the second impedance RL; or, the control unit 11 obtains a second difference d2 based on the first phase voltage Van, the first impedance Rc1, and the second impedance RL; or, the control unit 11 obtains a first difference d1 and a second difference d2 based on the first phase voltage Van, the first impedance Rc1, and the second impedance RL.

[0065] The control unit 11 compares the first difference d1 and / or the second difference d2 with a preset threshold respectively; in response to the first difference d1 being greater than the preset threshold and / or the second difference d2 being greater than the preset threshold, the process proceeds to step S104.

[0066] S104: In response to the first difference d1 being greater than a preset threshold and / or the second difference d2 being greater than a preset threshold, it is determined that the inverter system 10 is missing a N line.

[0067] If the first difference d1 is greater than a preset threshold, and / or the second difference d2 is greater than a preset threshold, the control unit 11 determines that the inverter system 10 is missing the N line.

[0068] Specifically, if the first difference d1 is greater than a preset threshold, the control unit 11 determines that the inverter system 10 is missing an N-line; or, if the second difference d2 is greater than a preset threshold, the control unit 11 determines that the inverter system 10 is missing an N-line; or, if both the first difference d1 and the second difference d2 are greater than a preset threshold, the control unit 11 determines that the inverter system 10 is missing an N-line.

[0069] In this embodiment, the control unit 11 obtains a first difference d1 between the second phase voltage Vbn of the second phase B and the first phase voltage Van, based on the first phase voltage Van, the first impedance Rc1, and the second impedance RL, and / or obtains a second difference d2 between the third phase voltage Vcn of the third phase C and the first phase voltage Van. In response to the first difference d1 being greater than a preset threshold, and / or the second difference d2 being greater than a preset threshold, it is determined that the inverter system 10 is missing a neutral (N) line. By using the first difference d1 and / or the second difference d2, it is possible to determine whether the inverter system 10 is missing a neutral (N) line, without the need for additional detection circuitry, reducing costs and the size of the inverter system 10, and improving the reliability of detecting a missing neutral (N) line. Furthermore, by obtaining the first difference d1 and / or the second difference d2 based on the first phase voltage Van, the first impedance Rc1, and the second impedance RL through the control unit 11, the accuracy of the first difference d1 and / or the second difference d2 can be improved.

[0070] According to some embodiments of this application, please refer to Figure 1 , Figure 3 and Figure 4 As shown, Figure 3 yes Figure 2 A flowchart illustrating the first embodiment of step S103; Figure 4 yes Figure 1 The equivalent circuit diagram of the inverter system lacking the neutral (N) line is shown in the figure. The filter circuit 13 in this embodiment includes a first filter capacitor C1, a second filter capacitor C2, and a third filter capacitor C3. One end of the first filter capacitor C1 is electrically connected to the first phase A, one end of the second filter capacitor C2 is electrically connected to the second phase B, and one end of the third filter capacitor C3 is electrically connected to the third phase B. The other ends of the first filter capacitor C1, the second filter capacitor C2, and the third filter capacitor C3 are all electrically connected to the neutral (N) line. The parameters of the first filter capacitor C1, the second filter capacitor C2, and the third filter capacitor C3 are the same. For example, the capacitance of the first filter capacitor C1, the second filter capacitor C2, and the third filter capacitor C3 are the same.

[0071] Since the parameters of the first filter capacitor C1, the second filter capacitor C2, and the third filter capacitor C3 are the same, the impedances Rc1 of the first filter capacitor C1, Rc2 of the second filter capacitor C2, and Rc3 of the third filter capacitor C3 are equal.

[0072] In the case where the inverter system 10 lacks the N-line, the other ends of the first filter capacitor C1, the second filter capacitor C2, and the third filter capacitor C3 are all electrically connected to the AC / DC converter 12. The node where the other ends of the first filter capacitor C1, the second filter capacitor C2, and the third filter capacitor C3 are connected to the AC / DC converter 12 is the N-point.

[0073] The first filter capacitor C1 is the filter capacitor that is electrically connected to the first phase A in the filter circuit 13 in the above embodiment; the control unit 11 obtains the impedance of the first filter capacitor C1 as the first impedance Rc1.

[0074] The currents of the first filter capacitor C1, the second filter capacitor C2, and the third filter capacitor C3 all satisfy the following formula:

[0075]

[0076] Where i is the current of the filter capacitor in filter circuit 13, C is the capacitance of the first filter capacitor C1, and the voltage V in formula (1) satisfies the following formula:

[0077] V=Um*sinwt (2)

[0078] Where Um is the first phase voltage Van, the second phase voltage Vbn, or the third phase voltage Vcn.

[0079] In the case of inverter system 10 lacking the N line, control unit 11 obtains the current formula at point N based on Hough's current law, formulas (1) and (2) as follows:

[0080]

[0081] Among them, Hough's current law is the existing Hough's current law in the technology, and will not be elaborated here.

[0082] The control unit 11 simplifies formula (3) to obtain the following formula:

[0083]

[0084] sin(wt+π / 2)+sin(wt+7π / 6)+sin(wt+11π / 6)=0 (5)

[0085] Combining formulas (4) and (5), the control unit 11 can be used to obtain the following formula:

[0086]

[0087] Based on formula (6), control unit 11 can obtain that the second phase voltage Vbn and the third phase voltage Vcn are both greater than the first phase voltage Van. That is, when the inverter system 10 is missing the N line, the first phase voltage Van will be deflected.

[0088] The impedances Rc1 of the first filter capacitor C1, Rc2 of the second filter capacitor C2, and Rc3 of the third filter capacitor C3 are equal. Therefore, the control unit 11 obtains the first impedance Rc1 corresponding to the first filter capacitor C1.

[0089] Step S103 in this embodiment includes the following steps:

[0090] S201: The ratio of the first impedance Rc1 and the second impedance RL is calculated by the control unit 11.

[0091] The control unit 11 divides the first impedance Rc1 by the second impedance RL to obtain the ratio of the first impedance Rc1 to the second impedance RL, which is Rc1 / RL.

[0092] S202: The ratio is multiplied by the first phase voltage Van by the control unit 11 to obtain the first difference d1, and / or the ratio is multiplied by the first phase voltage Van by the control unit 11 to obtain the second difference d2.

[0093] The first difference d1 is obtained by multiplying the ratio by the first phase voltage Van through the control unit 11, that is, the first difference d1 is equal to Van*Rc1 / RL; and / or, the second difference d2 is obtained by multiplying the ratio by the first phase voltage Van through the control unit 11, that is, the second difference d2 is equal to Van*Rc1 / RL.

[0094] In this embodiment, the control unit 11 calculates the ratio of the first impedance Rc1 and the second impedance RL. The control unit 11 obtains the first difference d1, which is equal to the ratio multiplied by the first phase voltage Van. The control unit 11 also obtains the second difference d2, which is equal to the ratio multiplied by the first phase voltage Van. The calculation of the first difference d1 and / or the second difference d2 is easy to implement, improves the accuracy of the first difference d1 and / or the second difference d2, and thus improves the reliability of detecting missing N wires.

[0095] According to some embodiments of this application, please refer to Figure 5 and Figure 6 As shown, Figure 5 This is a circuit diagram of the second embodiment of the inverter system of this application; Figure 6 yes Figure 5 A flowchart illustrating a second embodiment of the method for detecting a missing neutral (N) line in an inverter system. The inverter system 10 in this embodiment further includes a DC / AC converter 14, a DC / DC converter 15, and a power supply circuit 16. The power supply circuit 16 is the load described in the previous embodiment.

[0096] DC / AC converter 14 is electrically connected to the first phase A, second phase B, third phase C and neutral line of the power grid 20. DC / DC converter 15 is electrically connected to DC / AC converter 14. Power supply circuit 16 is connected to AC / DC converter 12 and DC / DC converter 15 respectively. Power supply circuit 16 is used to supply power to control unit 11. DC / DC converter 15 is electrically connected to battery module 30 and photovoltaic module 40 respectively.

[0097] The power supply circuit 16 can be a conventional power supply circuit, used to convert the voltage provided by the AC / DC converter 12 or DC / DC converter 15 into the operating voltage of the control unit 11. The battery assembly 30 is used for energy storage, or to supply power to the power supply circuit 16 via the DC / DC converter 15; the photovoltaic module 40 charges the battery assembly 30 via the DC / DC converter 15, or the photovoltaic module 40 supplies power to the grid 20 via the DC / DC converter 15 and the DC / AC converter 14.

[0098] The detection method in this embodiment includes the following steps:

[0099] S301: In response to being in N-line detection mode, the control unit 11 detects the first voltage output by the photovoltaic module 40 and compares the first voltage with a first voltage threshold.

[0100] The inverter system 10 is equipped with an N-line detection mode. When the inverter system 10 is in the N-line detection mode, the control unit 11 detects the first voltage output by the photovoltaic module 40 and compares the first voltage with a first voltage threshold. If the first voltage is less than the first voltage threshold, the process proceeds to step S302; if the first voltage is greater than or equal to the first voltage threshold, the process returns to step S301.

[0101] Optionally, the control unit 11 is pre-set with an N-line detection time period. When the control unit 11 detects that the current time has reached the N-line detection time period, the inverter system 10 is in N-line detection mode.

[0102] S302: In response to the first voltage being less than the first voltage threshold, the first line voltage of the first phase A, the second line voltage of the second phase B, the third line voltage of the third phase C, and the line voltage of the N line are obtained by the control unit 11.

[0103] Step S302 is the same as step S101 described above, and will not be repeated here.

[0104] In this embodiment, the control unit 11 detects the first voltage output by the photovoltaic module 40 and compares the first voltage with a first voltage threshold. This ensures that the photovoltaic module 40 stops working and prevents the photovoltaic module 40 from supplying power to the power circuit 16 through the DC / DC converter 15, thereby improving the reliability of detecting the missing N line.

[0105] According to some embodiments of this application, please refer to Figure 5 and Figure 7 As shown, Figure 7 yes Figure 5 A flowchart illustrating the third embodiment of the method for detecting a missing neutral (N) line in a medium-voltage inverter system. In this embodiment, the control unit 11 is electrically connected to the battery assembly 30, which supplies power to the power circuit 16 via a DC / DC converter 15; the control unit 11 is also electrically connected to the DC / DC converter 15 and the DC / AC converter 14.

[0106] When the battery assembly 30 supplies power to the power circuit 16 via the DC / DC converter 15, the control unit 11 controls the AC / DC converter 12 to not supply power to the power circuit 16.

[0107] The detection method in this embodiment includes the following steps:

[0108] S401: In response to being in N-line detection mode, the control unit 11 detects the first voltage output by the photovoltaic module 40 and compares the first voltage with a first voltage threshold.

[0109] S402: In response to the first voltage being less than the first voltage threshold, the first line voltage of the first phase A, the second line voltage of the second phase B, the third line voltage of the third phase C, and the line voltage of the N line are obtained by the control unit 11.

[0110] Steps S401-S402 and S301-S302 will not be described again here.

[0111] S403: In response to the first line voltage, the second line voltage, the third line voltage, and the line voltage of the N line being within a preset range, the control unit 11 controls the battery assembly 30 to enter a sleep mode.

[0112] In response to the first line voltage, the second line voltage, the third line voltage, and the line voltage of the N line being within a preset range, the control unit 11 controls the battery assembly 30 to enter a sleep mode. For example, the control unit 11 sends a command to the battery assembly 30 to enter a sleep mode, thereby controlling the battery assembly 30 to enter a sleep mode.

[0113] S404: The control unit 11 detects the second voltage output by the DC / DC converter 15 at preset intervals and compares the second voltage with a second voltage threshold.

[0114] After the control unit 11 sends a command to the battery assembly 30 to enter sleep mode, after a preset time interval, the control unit 11 detects the second voltage output by the DC / DC converter 15 and compares the second voltage with a second voltage threshold. If the second voltage is less than the second voltage threshold, the battery assembly 30 stops outputting power, and the control unit 11 controls the AC / DC converter 12 to supply power to the power circuit 16, proceeding to step S405. If the second voltage is greater than or equal to the second voltage threshold, the process returns to step S401.

[0115] S405: The first phase voltage Van of the first phase A is obtained through the control unit 11, the first impedance Rc1 of the filter capacitor electrically connected to the first phase A in the filter circuit 13 is obtained, and the second impedance RL of the load of the AC / DC converter 12 is obtained.

[0116] S406: The control unit 11 obtains a first difference d1 between the second phase voltage Vbn of the second phase B and the first phase voltage Van, and / or a second difference d2 between the third phase voltage Vcn of the third phase C and the first phase voltage Van, based on the first phase voltage Van, the first impedance Rc1 and the second impedance RL.

[0117] The control unit 11 compares the first difference d1 and / or the second difference d2 with a preset threshold; in response to the first difference d1 being greater than the preset threshold and / or the second difference d2 being greater than the preset threshold, it proceeds to step S407. In response to the first difference d1 being less than or equal to the preset threshold and the second difference d2 being less than or equal to the preset threshold, it returns to step S401.

[0118] S407: In response to the first difference d1 being greater than a preset threshold and / or the second difference d2 being greater than a preset threshold, it is determined that inverter system 10 is missing a neutral line.

[0119] Steps S405-S407 are the same as steps S102-S104, and will not be repeated here.

[0120] In this embodiment, the control unit 11 controls the battery assembly 30 to enter a sleep mode, detects the second voltage output by the DC / DC converter 15 at preset intervals, and compares the second voltage with a second voltage threshold. In response to the second voltage being less than the second voltage threshold, the control unit 11 controls the AC / DC converter 12 to supply power to the power circuit 16. This ensures that the battery assembly 30 stops working, prevents the battery assembly 30 from supplying power to the power circuit 16 through the DC / DC converter 15, and improves the reliability of detecting a missing neutral wire.

[0121] According to some embodiments of this application, please refer to Figure 5As shown, the inverter system 10 of this embodiment further includes a first voltage sampling circuit 19, a second voltage sampling circuit 17, and a third voltage sampling circuit 18. The first voltage sampling circuit 19, the second voltage sampling circuit 17, and the third voltage sampling circuit 18 of this embodiment can all be voltage sampling circuits in the prior art, and will not be described in detail here.

[0122] The first voltage sampling circuit 19 is electrically connected to the control unit 11, and is connected between the DC / AC converter 14 and the DC / DC converter 15. The control unit 11 acquires the second voltage output of the DC / DC converter 15 through the first voltage sampling circuit 19 to obtain the sampled voltage; that is, the sampled voltage is equal to the second voltage.

[0123] In this embodiment, the steps of controlling the AC / DC converter 12 to supply power to the power circuit 16 by the control unit 11 include: obtaining the sampling voltage of the first voltage sampling circuit 19 by the control unit 11; and in response to the gradual decrease of the sampling voltage, sending an enable signal to the AC / DC converter 12 by the control unit 11 to control the AC / DC converter 12 to supply power to the power circuit 16.

[0124] The second voltage sampling circuit 17 is electrically connected to the control unit 11 and the photovoltaic module 40 respectively. The control unit 11 collects the first voltage output by the photovoltaic module 40 through the second voltage sampling circuit 17.

[0125] Step S401 includes: obtaining a first voltage from the second voltage sampling circuit 17 through the control unit 11.

[0126] The third voltage sampling circuit 18 is electrically connected to the control unit 11 and the first phase A, second phase B, third phase C and N line of the power grid 20 respectively; the control unit 11 collects the first line voltage, second line voltage, third line voltage and N line line voltage through the third voltage sampling circuit 18 respectively.

[0127] Step S101 includes: acquiring the first line voltage, the second line voltage, the third line voltage, and the line voltage of the N line from the third voltage sampling circuit 18 through the control unit 11.

[0128] This application also provides an inverter system 10, such as Figure 1As shown, the inverter system 10 includes a control unit 11, an AC / DC converter 12, and a filter circuit 13. The filter circuit 13 is electrically connected to the first phase A, the second phase B, the third phase C, and the neutral line of the power grid 20. The control unit 11 is electrically connected to the AC / DC converter 12 and the first phase A, the second phase B, the third phase C, and the neutral line of the power grid 20. The AC / DC converter 12 is electrically connected to the first phase A and the neutral line, meaning its input terminals are electrically connected to the first phase A and the neutral line, and its output terminal is electrically connected to the load (i.e., the power supply circuit in other embodiments).

[0129] The control unit 11 is configured to: acquire the first line voltage of the first phase A, the second line voltage of the second phase B, the third line voltage of the third phase C, and the line voltage of the neutral line; in response to the first line voltage, the second line voltage, the third line voltage, and the line voltage of the neutral line being within a preset range, acquire the first phase voltage Van of the first phase A, acquire the first impedance Rc1 of the filter capacitor electrically connected to the first phase A in the filter circuit 13, and acquire the second impedance RL of the load of the AC / DC converter 12; based on the first phase voltage Van, the first impedance Rc1, and the second impedance RL, obtain the first difference d1 between the second phase voltage Vbn of the second phase B and the first phase voltage Van, and / or the second difference d2 between the third phase voltage Vcn of the third phase C and the first phase voltage Van; in response to the first difference d1 being greater than a preset threshold, and / or the second difference d2 being greater than a preset threshold, determine that the inverter system 10 is missing the neutral line.

[0130] In this configuration, one end of the first filter capacitor C1 is electrically connected to the first phase A, one end of the second filter capacitor C2 is electrically connected to the second phase B, and one end of the third filter capacitor C3 is electrically connected to the third phase B. The other ends of the first filter capacitor C1, the second filter capacitor C2, and the third filter capacitor C3 are all electrically connected to the neutral (N) line. The parameters of the first filter capacitor C1, the second filter capacitor C2, and the third filter capacitor C3 are the same.

[0131] According to some embodiments of this application, please refer to Figure 5 As shown, the inverter system 10 of this embodiment also includes a DC / AC converter 14, a DC / DC converter 15, and a power supply circuit 16.

[0132] DC / AC converter 14 is electrically connected to the first phase A, second phase B, third phase C and neutral line of the power grid 20. DC / DC converter 15 is electrically connected to DC / AC converter 14. Power supply circuit 16 is connected to AC / DC converter 12 and DC / DC converter 15 respectively. Power supply circuit 16 is used to supply power to control unit 11. DC / DC converter 15 is electrically connected to battery module 30 and photovoltaic module 40 respectively.

[0133] When the inverter system 10 is not in the neutral (N) detection mode, the battery module 30 or photovoltaic module 40 supplies power to the power circuit 16 through the DC / DC converter 15; when the inverter system 10 is in the neutral (N) detection mode, the control unit 11 controls the AC / DC converter 12 to supply power to the power circuit 16.

[0134] In summary, this application uses control unit 11 to obtain a first difference d1 between the second phase voltage Vbn of the second phase B and the first phase voltage Van, and / or a second difference d2 between the third phase voltage Vcn of the third phase C and the first phase voltage Van, based on the first phase voltage Van, the first impedance Rc1, and the second impedance RL. In response to the first difference d1 being greater than a preset threshold, and / or the second difference d2 being greater than a preset threshold, it is determined that the inverter system 10 is missing a neutral (N) line. By using the first difference d1 and / or the second difference d2, it is possible to determine whether the inverter system 10 is missing a neutral (N) line, without the need for additional detection circuitry, reducing costs and the size of the inverter system 10, and improving the reliability of detecting a missing neutral (N) line.

[0135] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for detecting missing N-line, characterized in that, An inverter system, electrically connected to a power grid, is used in an inverter system. The inverter system includes a control unit, an AC / DC converter, and a filter circuit. The filter circuit is electrically connected to the first phase, second phase, third phase, and neutral (N) line of the power grid. The control unit is electrically connected to the AC / DC converter, the first phase, the second phase, the third phase, and the neutral (N) line. The AC / DC converter is electrically connected to the first phase and the neutral (N) line. The detection method includes: The first line voltage of the first phase, the second line voltage of the second phase, the third line voltage of the third phase, and the line voltage of the N line are obtained through the control unit. In response to the first line voltage, the second line voltage, the third line voltage, and the line voltage of the N line being within a preset range, the first phase voltage of the first phase is obtained through the control unit, the first impedance of the filter capacitor electrically connected to the first phase in the filter circuit is obtained, and the second impedance of the load of the AC / DC converter is obtained. The control unit obtains a first difference between the second phase voltage of the second phase and the first phase voltage, and / or a second difference between the third phase voltage of the third phase and the first phase voltage, based on the first phase voltage, the first impedance, and the second impedance. If the first difference is greater than a preset threshold, and / or the second difference is greater than the preset threshold, then it is determined that the inverter system is missing the N-line.

2. The detection method according to claim 1, characterized in that, The filtering circuit includes a first filtering capacitor, a second filtering capacitor, and a third filtering capacitor. One end of the first filtering capacitor is electrically connected to the first phase, one end of the second filtering capacitor is electrically connected to the second phase, and one end of the third filtering capacitor is electrically connected to the third phase. The other ends of the first, second, and third filtering capacitors are all electrically connected to the neutral (N) line. The parameters of the first, second, and third filtering capacitors are the same. The step of obtaining a first difference between the second phase voltage of the second phase and the first phase voltage based on the first phase voltage, the first impedance, and the second impedance by the control unit, and / or obtaining a second difference between the third phase voltage of the third phase and the first phase voltage, includes: The control unit calculates the ratio of the first impedance to the second impedance; The control unit multiplies the ratio by the first phase voltage to obtain the first difference. And / or, the control unit multiplies the ratio by the first phase voltage to obtain the second difference.

3. The detection method according to claim 1 or 2, characterized in that, The inverter system further includes a DC / AC converter, a DC / DC converter, and a power supply circuit. The DC / AC converter is electrically connected to the first phase, second phase, third phase, and neutral line of the power grid. The DC / DC converter is electrically connected to the DC / AC converter. The power supply circuit is connected to both the AC / DC converter and the DC / DC converter, and is used to supply power to the control unit. The DC / DC converter is electrically connected to both the battery module and the photovoltaic module. The detection method further includes: In response to being in N-line detection mode, the control unit detects the first voltage output by the photovoltaic module and compares the first voltage with a first voltage threshold. In response to the first voltage being less than the first voltage threshold, the step of obtaining the first line voltage of the first phase, the second line voltage of the second phase, the third line voltage of the third phase, and the line voltage of the N line through the control unit is performed.

4. The detection method according to claim 3, characterized in that, The control unit is electrically connected to the battery assembly, and the battery assembly supplies power to the power circuit through the DC / DC converter; the detection method further includes: The control unit controls the battery assembly to enter sleep mode. The control unit controls the AC / DC converter to supply power to the power circuit.

5. The detection method according to claim 4, characterized in that, After the step of controlling the battery assembly to enter a sleep mode via the control unit, the detection method further includes: The control unit detects the second voltage output by the DC / DC converter at preset time intervals and compares the second voltage with a second voltage threshold. In response to the second voltage being less than the second voltage threshold, the step of obtaining a first difference between the second phase voltage of the second phase and the first phase voltage, and / or a second difference between the third phase voltage of the third phase and the first phase voltage, by the control unit based on the first phase voltage, the first impedance and the second impedance.

6. The detection method according to claim 4, characterized in that, The inverter system further includes a first voltage sampling circuit, which is electrically connected to the control unit and connected between the DC / AC converter and the DC / DC converter. The step of controlling the AC / DC converter to supply power to the power circuit through the control unit includes: The control unit obtains the sampled voltage of the first voltage sampling circuit; In response to the gradual decrease of the sampling voltage, the control unit sends an enable signal to the AC / DC converter to control the AC / DC converter to supply power to the power circuit.

7. The detection method according to claim 3, characterized in that, The inverter system further includes a second voltage sampling circuit, which is electrically connected to the control unit and the photovoltaic module. The step of detecting the first voltage output by the photovoltaic module through the control unit includes: The first voltage is obtained from the second voltage sampling circuit through the control unit.

8. The detection method according to claim 1, characterized in that, The inverter system further includes a third voltage sampling circuit, which is electrically connected to the control unit, the first phase, the second phase, the third phase, and the neutral line of the power grid, respectively. The step of obtaining the first line voltage of the first phase, the second line voltage of the second phase, the third line voltage of the third phase, and the line voltage of the neutral line through the control unit includes: The control unit obtains the first line voltage, the second line voltage, the third line voltage, and the line voltage of the N line from the third voltage sampling circuit.

9. An inverter system, characterized in that, The inverter system is electrically connected to the power grid. The inverter system includes a control unit, an AC / DC converter, and a filter circuit. The filter circuit is electrically connected to the first phase, second phase, third phase, and neutral (N) line of the power grid. The control unit is electrically connected to the AC / DC converter, the first phase, the second phase, the third phase, and the neutral (N) line. The AC / DC converter is electrically connected to the first phase and the neutral (N) line. The control unit is used to: acquire the first line voltage of the first phase, the second line voltage of the second phase, the third line voltage of the third phase, and the line voltage of the neutral (N) line. In response to the first line voltage, the second line voltage, the third line voltage, and the line voltage of the N line being within a preset range, the first phase voltage of the first phase is obtained, the first impedance of the filter capacitor electrically connected to the first phase in the filter circuit is obtained, and the second impedance of the load of the AC / DC converter is obtained. Based on the first phase voltage, the first impedance, and the second impedance, a first difference between the second phase voltage of the second phase and the first phase voltage is obtained, and / or a second difference between the third phase voltage of the third phase and the first phase voltage is obtained; If the first difference is greater than a preset threshold, and / or the second difference is greater than the preset threshold, then it is determined that the inverter system is missing the N-line.

10. The inverter system according to claim 9, characterized in that, The inverter system further includes a DC / AC converter, a DC / DC converter, and a power supply circuit. The DC / AC converter is electrically connected to the first phase, the second phase, the third phase, and the neutral line of the power grid. The DC / DC converter is electrically connected to the DC / AC converter. The power supply circuit is connected to both the AC / DC converter and the DC / DC converter. The power supply circuit is used to supply power to the control unit. The DC / DC converter is electrically connected to both the battery module and the photovoltaic module. When the inverter system is not in N-line detection mode, the battery module or the photovoltaic module supplies power to the power circuit through the DC / DC converter; When the inverter system is in neutral (N) detection mode, the control unit controls the AC / DC converter to supply power to the power supply circuit.

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