A method for detecting the midpoint of an alternating current side power grid voltage and related components

Abstract

The application discloses a kind of detection methods of alternating side power grid voltage midpoint and related components, it is related to electrical detection field, between the first fire line of inverter and N line, unidirectional conduction first discharge module is set, when the connection of N line and electric load is disconnected, first discharge module positive conduction, since the phase voltage between first fire line and N line is alternating current, only half cycle phase voltage can pass through unidirectional conduction first discharge module, so that the arithmetic mean of first phase voltage between first fire line and N line in preset number of voltage periods will change.Therefore, when detecting that the arithmetic mean of first phase voltage in preset number of voltage periods exceeds preset rated threshold, it can be determined that voltage midpoint is not reliably connected, without higher measurement accuracy, more easily detect the change of phase voltage, can more accurately determine whether voltage midpoint is reliably connected, simple to implement, higher reliability.

Description

Technical Field

[0001] This invention relates to the field of electrical testing, and in particular to a method and related components for detecting the midpoint of AC power grid voltage. Background Technology

[0002] Currently, new energy power generation technologies such as solar and wind power are developing rapidly and their applications are becoming increasingly widespread. Inverters can convert direct current (DC) generated by new energy power generation into alternating current (AC). When the AC output of the inverter is the same as the AC output of the grid (i.e., the waveform, frequency, amplitude, phase, and phase sequence are all the same), grid-connected operation can be achieved. This involves connecting one end of the inverter to the grid and the other end to the input terminal of the electrical load connected to the grid. This allows the AC output of the inverter to either power the electrical load independently or, together with the grid, power the electrical load, thus enabling the use of electricity generated by new energy power generation to supply power to the electrical load.

[0003] To ensure the safety and stability of the grid connection process, safety testing of the inverter is required. When the grid connected to the inverter is an AC grid with a voltage neutral point, the conventional safety testing method is to check whether the voltage neutral point is reliably connected, that is, to check whether the input terminal of the electrical load is connected to the neutral line (N line). In existing technology, the reliable connection of the voltage neutral point is generally checked by directly measuring the phase voltage between the first live wire and the neutral line and / or the phase voltage between the second live wire and the neutral line. If the measurement result is not within the rated threshold range, it is determined that the voltage neutral point is not reliably connected. However, the voltage difference between the phase voltage when the voltage neutral point is reliably connected and the phase voltage when the voltage neutral point is not reliably connected is small, which can easily lead to misjudgment and low reliability. To reduce misjudgment, higher measurement accuracy is required, which is difficult to implement. Summary of the Invention

[0004] The purpose of this invention is to provide a method and related components for detecting the voltage midpoint of an AC power grid. This method does not require high measurement accuracy, makes it easier to detect changes in phase voltage, and can more accurately determine whether the voltage midpoint is reliably connected. It is simple to implement and has higher reliability.

[0005] To solve the above technical problems, the present invention provides a method for detecting the midpoint of AC grid voltage, applied to an inverter. The inverter includes a first discharge module with unidirectional conduction. A first terminal of the first discharge module is connected to the first live wire of the inverter, and a second terminal of the first discharge module is connected to the neutral (N) line of the inverter. The first discharge module is used to discharge the first phase voltage between the first live wire and the neutral (N) line when the connection between the neutral (N) line and the electrical load is disconnected and the inverter is forward-conducting. The detection method includes:

[0006] Obtain the first average value of the first phase voltage between the first live wire and the N wire, wherein the first average value is the arithmetic average value of the first phase voltage over a preset number of voltage cycles;

[0007] Determine whether the first average value is within a preset nominal threshold range;

[0008] If the first average value is not within the rated threshold range, it is determined that the voltage midpoint is not reliably connected.

[0009] Preferably, the preset number is 1.

[0010] Preferably, the inverter further includes a unidirectional second discharge module, the first end of which is connected to the second live wire of the inverter, and the second end of which is connected to the neutral (N) wire of the inverter, for discharging the second phase voltage between the second live wire and the N wire when the connection between the N wire and the electrical load is disconnected and the inverter is forward-biased;

[0011] The detection method further includes:

[0012] Obtain the second average value of the second phase voltage between the second live wire and the N wire, wherein the second average value is the arithmetic average value of the second phase voltage over a preset number of voltage cycles;

[0013] Determine whether the first voltage value is within a preset rated threshold range; if the first average value is not within the rated threshold range, determine that the voltage midpoint is not reliably connected, including:

[0014] Determine whether the first voltage value and the second voltage value are within the preset rated threshold range;

[0015] If either the first average voltage value or the second average value is outside the rated threshold range, then the voltage midpoint is determined to be unreliably connected.

[0016] Preferably, before obtaining the first average value of the first phase voltage between the first live wire and the N wire, the method further includes:

[0017] Determine whether the output voltage of the inverter is the same as the grid voltage of the power grid;

[0018] If they are the same, proceed to the step of obtaining the first average value of the first phase voltage between the first live wire and the N wire.

[0019] Preferably, it further includes:

[0020] If the output voltage of the inverter is different from the grid voltage of the power grid, then the inverter is disconnected from the power grid.

[0021] The present invention also provides a device for detecting the midpoint of AC grid voltage, applied to an inverter, comprising:

[0022] A unidirectional first discharge module, with a first end connected to the first live wire of the inverter and a second end connected to the neutral (N) wire of the inverter, is used to discharge the first phase voltage between the first live wire and the neutral (N) wire when the connection between the neutral (N) wire and the electrical load is disconnected and the inverter is forward-biased.

[0023] The control module is used to execute computer programs to implement the steps of the AC side power grid voltage midpoint detection method as described above.

[0024] Preferably, it further includes:

[0025] The second discharge module has a first end connected to the second live wire of the inverter and a second end connected to the neutral (N) wire of the inverter. It is used to discharge the second phase voltage between the second live wire and the neutral (N) wire when the connection between the neutral (N) wire and the electrical load is disconnected and the neutral (N) wire is forward-biased.

[0026] Preferably, it further includes:

[0027] A first sampling module, wherein a first terminal of the first sampling module is connected to a first terminal of the first discharge module and a first live wire of the inverter, a second terminal of the first sampling module is connected to a second terminal of the first discharge module and a neutral (N) wire of the inverter, and an output terminal of the first sampling module is connected to the control module, for obtaining the first phase voltage between the first live wire and the neutral (N) wire;

[0028] The second sampling module has its first terminal connected to the first terminal of the second discharge module and the second live wire of the inverter, its second terminal connected to the second terminal of the second discharge module and the neutral (N) line of the inverter, and its output terminal connected to the control module, for obtaining the second phase voltage between the second live wire and the neutral (N) line.

[0029] Preferably, the first discharge module includes:

[0030] A diode, wherein the first end of the diode is connected to the first live wire of the inverter, and the second end of the diode is connected to the first end of a resistor, for discharging the first phase voltage between the first live wire and the N wire when the connection between the N wire and the electrical load is disconnected and the N wire is forward conducting;

[0031] The resistor, the second end of which is connected to the N line of the inverter.

[0032] The present invention also provides an inverter, including a voltage midpoint detection device as described above.

[0033] This invention provides a method and related components for detecting the voltage midpoint of an AC power grid. A unidirectional discharge module is installed between the live wire and neutral (N) wire of the inverter. When the N wire is disconnected from the load, the first discharge module conducts forward. Since the first phase voltage between the live wire and N wire is AC, only half a cycle of the phase voltage can pass through the unidirectional discharge module. This means the first discharge module discharges the phase voltage between the live wire and N wire, causing a change in the arithmetic mean of the phase voltage over a preset number of voltage cycles. Therefore, when the arithmetic mean of the phase voltage over a preset number of voltage cycles exceeds a preset rated threshold, it can be determined that the voltage midpoint is not reliably connected. This method does not require high measurement accuracy, makes it easier to detect phase voltage changes, and more accurately determines whether the voltage midpoint is reliably connected. It is simple to implement and has higher reliability. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the prior art and embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 A flowchart illustrating a method for detecting the midpoint of AC power grid voltage according to an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of a device for detecting the midpoint of AC power grid voltage according to an embodiment of the present invention;

[0037] Figure 3 A circuit diagram of a device for detecting the midpoint of AC grid voltage on a single discharge module, provided in an embodiment of the present invention;

[0038] Figure 4 A circuit diagram of a detection device for the midpoint of the AC power grid voltage on another single discharge module provided in an embodiment of the present invention;

[0039] Figure 5 A circuit diagram of a device for detecting the midpoint of the AC power grid voltage on the dual discharge module provided in an embodiment of the present invention;

[0040] Figure 6 A circuit diagram of a detection device for the midpoint of the AC power grid voltage on another dual discharge module provided in an embodiment of the present invention. Detailed Implementation

[0041] The core of this invention is to provide a method and related components for detecting the midpoint of AC power grid voltage. It does not require high measurement accuracy, makes it easier to detect changes in phase voltage, and can more accurately determine whether the voltage midpoint is reliably connected. It is simple to implement and has higher reliability.

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] Please refer to Figure 1 , Figure 1 This is a flowchart of a method for detecting the midpoint of AC grid voltage according to an embodiment of the present invention. The method is applied to an inverter, which includes a unidirectional first discharge module. A first terminal of the first discharge module is connected to the first live wire of the inverter, and a second terminal of the first discharge module is connected to the neutral (N) line of the inverter. The method is used to discharge the first phase voltage between the first live wire and the neutral (N) line when the connection between the neutral (N) line and the electrical load is disconnected and the inverter is forward-biased. The detection method includes:

[0044] S101: Obtain the first average value of the first phase voltage between the first live wire and the N wire. The first average value is the arithmetic average value of the first phase voltage over a preset number of voltage cycles.

[0045] S102: Determine whether the first average value is within the preset rated threshold range;

[0046] S103: If the first average value is not within the rated threshold range, it is determined that the voltage midpoint is not reliably connected.

[0047] This embodiment does not limit the specific type of AC power grid. For example, it can be a single-phase three-wire AC power grid, or a single-phase four-wire AC power grid, or other AC power grids with a voltage midpoint.

[0048] This embodiment does not limit the specific structure of the first discharge module. For example, it can be a diode, or other unidirectional conducting devices or circuit structures, as long as it can discharge the first phase voltage between the first live wire and the N wire when the connection between the N line and the electrical load is broken and the module itself is forward conducting. Specifically, when the first terminal of the first discharge module is the forward terminal and the second terminal is the reverse terminal, the forward conduction of the first discharge module means that the voltage passing through the first discharge module flows from the forward terminal to the reverse terminal, i.e., the connection between the N line and the electrical load is broken, so that the voltage that should supply power to the electrical load is applied across the first discharge module and flows from the forward terminal to the reverse terminal. It should be noted that the first terminal of the first discharge module being the forward terminal and the second terminal being the reverse terminal is only one case provided in this embodiment; it is also possible for the second terminal of the first discharge module to be the forward terminal and the first terminal to be the reverse terminal. This embodiment is applicable to performing safety checks on the inverter's grid connection process before and during grid connection operations to ensure that grid power supply can proceed normally. This embodiment can be applied to various inverter systems, especially photovoltaic (PV) inverter systems. The method in this embodiment is not directly related to the inverter topology or the grid topology. It can be a three-phase inverter circuit or a single-phase inverter circuit, or a half-bridge inverter circuit or a full-bridge inverter circuit, etc. The specific selection can be made according to the actual situation, and there are no restrictions here.

[0049] In step S101, this embodiment does not limit the method for obtaining the first phase voltage between the first live wire and the neutral wire. For example, the first phase voltage can be obtained through electrical parameter acquisition elements installed in the inverter, such as various electrical sensors, or through a specific sampling circuit. Obtaining the first phase voltage includes obtaining its waveform, frequency, amplitude, phase, and phase sequence. Furthermore, this embodiment does not limit the method for obtaining the first average value of the first phase voltage between the first live wire and the neutral wire. For example, the first average value can be obtained through a sampling module, or the first average value can be obtained by obtaining the first phase voltage through a sampling module and then calculated by the control module. The specific method can be selected according to the actual situation and is not limited here.

[0050] This embodiment does not limit the specific value of the preset number of voltage cycles. In specific embodiments, one voltage cycle is usually used. Since the first phase voltage is AC and the first phase voltage is sinusoidal AC, the arithmetic average value of the first phase voltage within the preset number of voltage cycles is usually 0V. If the voltage midpoint is not reliably connected, that is, the connection between the N line and the electrical load is broken, after passing through the discharge module, the absolute value of the first average value of the first phase voltage is greater than 0V.

[0051] In step S102, the preset rated threshold range is a threshold range that reflects the normal fluctuation of the arithmetic mean of the phase voltage between the first live wire and the neutral wire when the voltage midpoint is reliably connected. The value and size of the preset rated threshold range are not specifically limited; they should be set by those skilled in the art based on actual conditions. When the first average value is within the rated threshold range, subsequent operations are not specifically limited. For example, the operation of continuing to execute step S102 to determine whether the first average value is within the preset rated threshold range can be performed, or the operation of executing step S102 to determine whether the first average value is within the preset rated threshold range can be performed after a specific time interval.

[0052] In step S103, when it is determined that there is no reliable connection at the voltage midpoint, the subsequent operation is not specifically limited. For example, it can be to control the inverter to disconnect from the electrical load, or to control the inverter to disconnect from the grid, or to control the inverter to power off, or to issue an abnormality reminder. The appropriate settings should be made by those skilled in the art based on the actual situation.

[0053] This invention provides a method for detecting the voltage midpoint of an AC power grid. A unidirectional discharge module is installed between the live wire and neutral (N) wire of the inverter. When the N wire is disconnected from the load, the first discharge module conducts forward. Since the first phase voltage between the live wire and the N wire is AC, only half a cycle of the phase voltage can pass through the unidirectional discharge module. This means the first discharge module discharges the phase voltage between the live wire and the N wire, causing a change in the arithmetic mean of the phase voltage over a preset number of voltage cycles. Therefore, when the arithmetic mean of the phase voltage over a preset number of voltage cycles exceeds a preset rated threshold, it can be determined that the voltage midpoint is not reliably connected. This method does not require high measurement accuracy, makes it easier to detect phase voltage changes, and more accurately determines whether the voltage midpoint is reliably connected. It is simple to implement and has higher reliability.

[0054] Based on the above embodiments:

[0055] Preferably, the preset number is 1.

[0056] In this embodiment, the number of voltage cycles of the first phase voltage is set to 1, that is, the first average value is the arithmetic average value of the first phase voltage within 1 voltage cycle. This shortens the time for collecting the first phase voltage and allows for more timely detection of the first phase voltage between the first live wire and the neutral wire. This makes the detection of whether the voltage midpoint is reliably connected more timely and improves the safety of the inverter grid connection.

[0057] Preferably, the inverter further includes a unidirectional second discharge module, the first end of which is connected to the second live wire of the inverter, and the second end of which is connected to the neutral wire of the inverter, for discharging the second phase voltage between the second live wire and the neutral wire when the connection between the neutral wire and the electrical load is disconnected and the inverter is forward-biased;

[0058] The detection methods also include:

[0059] Obtain the second average value of the second phase voltage between the second live wire and the N wire. The second average value is the arithmetic average of the second phase voltage over a preset number of voltage cycles.

[0060] S102 determines whether the first voltage value is within a preset rated threshold range; if the first average value is not within the rated threshold range, it determines that the voltage midpoint is not reliably connected, including:

[0061] Determine whether the first voltage value and the second voltage value are within the preset rated threshold range;

[0062] If either the first average voltage value or the second average voltage value is outside the rated threshold range, it is determined that the voltage midpoint is not reliably connected.

[0063] It should be noted that in practical applications, the AC power grid typically has more than one live wire. For example, in a single-phase three-wire AC power grid, the grid includes a first live wire, a second live wire, and a neutral (N) wire. Correspondingly, the inverter also includes a first live wire, a second live wire, and a neutral (N) wire, thus achieving grid connection with the single-phase three-wire power grid. Furthermore, in addition to setting a first discharge module between the first live wire and the neutral (N) wire, a second discharge module can also be set between the second live wire and the neutral (N) wire to obtain the second average value of the second phase voltage between the second live wire and the neutral (N) wire. In this case, whether the first average voltage value is not within the rated threshold range or the second average value is not within the rated threshold range, it indicates that the voltage midpoint is not reliably connected.

[0064] This embodiment adds a second discharge module between the second live wire and the neutral wire, and obtains the second average value of the second phase voltage between the second live wire and the neutral wire. By determining whether the second average value is within the rated threshold range, it is also possible to determine whether the voltage midpoint is reliably connected, thereby improving the timeliness and accuracy of safety monitoring and reducing risks.

[0065] Preferably, before obtaining the first average value of the first phase voltage between the first live wire and the neutral wire in S101, the method further includes:

[0066] Determine whether the inverter's output voltage is the same as the grid voltage;

[0067] If they are the same, proceed to the step of obtaining the first average value of the first phase voltage between the first live wire and the N wire.

[0068] It should be noted that to determine whether the inverter's output voltage is the same as the grid voltage, it is necessary to compare various aspects of the inverter's output voltage and the grid voltage. For example, the waveform, frequency, amplitude, phase, and phase sequence of the inverter's output voltage can be compared with those of the grid voltage, but this is not the only limitation.

[0069] In this embodiment, when the inverter's output voltage differs from the grid voltage, the subsequent operations are not specifically limited. For example, the inverter can be disconnected from the grid, the inverter can be powered off, or an abnormality alert can be issued. Those skilled in the art should make the appropriate settings according to the actual situation.

[0070] Before obtaining the first average value of the first phase voltage between the first live wire and the N wire, this embodiment also needs to determine whether the output voltage of the inverter is the same as the grid voltage. If they are different, it indicates an abnormality, thus improving the safety of grid connection operation.

[0071] Preferably, it further includes:

[0072] If the inverter's output voltage is different from the grid voltage, the inverter's connection to the grid will be disconnected.

[0073] This embodiment controls the inverter to disconnect from the grid when the inverter's output voltage is different from the grid voltage, so as to facilitate timely debugging and repair, avoid grid connection failure, and prevent the inverter's components from burning out and failing to work properly or endangering personal safety, thus greatly improving the safety and reliability of the inverter's grid connection.

[0074] Please refer to Figure 2 , Figure 2 This invention provides a schematic diagram of a device for detecting the midpoint of AC grid voltage, applied to an inverter, comprising:

[0075] A unidirectional first discharge module 201, with its first end connected to the first live wire L1 of the inverter and its second end connected to the N line of the inverter, is used to discharge the first phase voltage between the first live wire L1 and the N line when the connection between the N line and the electrical load is disconnected and the forward conduction is enabled.

[0076] The control module 202 is used to execute the steps of the computer program to implement the AC power grid voltage midpoint detection method as described above.

[0077] This embodiment does not limit the specific structure of the first discharge module 201. For example, it can be a diode, or other unidirectional conducting devices or circuit structures, as long as it can discharge the first phase voltage between the first live wire L1 and the N wire when the connection between the N wire and the electrical load is broken and the module itself is forward conducting. The forward conduction of the first discharge module 201 means that the voltage passing through the first discharge module 201 flows from the first end of the first discharge module 201 to the second end of the first discharge module 201. That is, the connection between the N wire and the electrical load is broken, so that the voltage that should supply power to the electrical load is applied across the first discharge module 201 and flows from the first end of the first discharge module 201 to the second end of the first discharge module 201.

[0078] This embodiment does not limit the specific form of the control module 202. For example, it can be a digital signal processor (DSP), but it is not limited thereto.

[0079] This invention provides a device for detecting the midpoint of AC grid voltage. By installing a unidirectional discharge module 201 between the live wire and neutral (N) wire of the inverter, when the connection between the N wire and the electrical load is broken, since the first phase voltage between the first live wire L1 and the N wire is AC, only a portion of the voltage can pass through the unidirectional discharge module 201. That is, the first discharge module 201 discharges the first phase voltage between the first live wire L1 and the N wire, causing a change in the arithmetic mean of the phase voltage between the first live wire L1 and the N wire over a preset number of voltage cycles. Therefore, when the arithmetic mean of the phase voltage over the preset number of voltage cycles is detected to exceed a preset rated threshold, it can be determined that the voltage midpoint is not reliably connected. This method does not require high measurement accuracy, makes it easier to detect changes in phase voltage, and more accurately determines whether the voltage midpoint is reliably connected. It is simple to implement and has higher reliability.

[0080] Preferably, it further includes:

[0081] The second discharge module has its first end connected to the second live wire of the inverter and its second end connected to the neutral (N) wire of the inverter. It is used to discharge the second phase voltage between the second live wire and the neutral wire when the connection between the neutral wire and the electrical load is disconnected and the neutral wire is forward-biased.

[0082] This embodiment does not limit the specific structure of the second discharge module. For example, it can be a diode, or other unidirectional devices or circuit structures, as long as it can discharge the second phase voltage between the second live wire and the N wire when the connection between the N line and the electrical load is broken and the module itself is forward-conducting. The forward conduction of the second discharge module means that the voltage passing through the second discharge module flows from the first end to the second end of the second discharge module. That is, the connection between the N line and the electrical load is broken, so that the voltage that should supply power to the electrical load is applied across the two ends of the second discharge module and flows from the first end to the second end of the second discharge module.

[0083] This embodiment adds a second discharge module between the second live wire and the neutral wire. By determining whether the second average value of the second phase voltage between the second live wire and the neutral wire is within the rated threshold range, it can also determine whether the voltage midpoint is reliably connected, thereby improving the timeliness and accuracy of safety monitoring and reducing risks.

[0084] Preferably, it further includes:

[0085] The first sampling module has a first terminal connected to the first terminal of the first discharge module 201 and the first live wire L1 of the inverter, and a second terminal connected to the second terminal of the first discharge module 201 and the N line of the inverter. The output terminal of the first sampling module is connected to the control module 202 and is used to obtain the first phase voltage between the first live wire L1 and the N line.

[0086] The second sampling module has its first terminal connected to the first terminal of the second discharge module and the second live wire of the inverter, and its second terminal connected to the second terminal of the second discharge module and the neutral (N) line of the inverter. The output terminal of the second sampling module is connected to the control module 202 and is used to obtain the second phase voltage between the second live wire and the neutral (N) line.

[0087] This embodiment does not limit the specific structure of the first sampling module and the second sampling module, as long as they can acquire the first phase voltage and the second phase voltage. Acquiring the first phase voltage through the first sampling module includes acquiring the waveform, frequency, amplitude, phase, and phase sequence of the first phase voltage. Acquiring the second phase voltage through the second sampling module includes acquiring the waveform, frequency, amplitude, phase, and phase sequence of the second phase voltage.

[0088] In this embodiment, the first phase voltage and the second phase voltage are obtained through a sampling module, which is highly flexible, easy to replace in case of failure, and extends the service life of the device.

[0089] Preferably, the first discharge module 201 includes:

[0090] The diode has its first end connected to the first live wire L1 of the inverter, and its second end connected to the first end of the resistor. It is used to discharge the first phase voltage between the first live wire L1 and the N line when the connection between the N line and the electrical load is disconnected and the N line is forward conducting.

[0091] The resistor's second end is connected to the inverter's neutral (N) line.

[0092] This embodiment does not specify the exact model and value of the diode and resistor. As long as it can achieve the following: when the connection between the N line and the electrical load is disconnected and the voltage between the first live wire L1 and the N line is applied across the diode and resistor, the diode will conduct in the forward direction and discharge the first phase voltage between the first live wire L1 and the N line.

[0093] This embodiment uses a diode and a resistor to discharge the first phase voltage between the first live wire L1 and the N wire. The structure is simple, easy to implement, inexpensive, and economical.

[0094] This embodiment does not limit the conduction direction of the diode. When only the first discharge module 201 is connected to the inverter, please refer to... Figure 3 and Figure 4 ,in Figure 3 This is a circuit diagram of a device for detecting the midpoint of the AC power grid voltage on a single discharge module, provided in an embodiment of the present invention. Figure 4 This is a circuit diagram of another single-discharge module AC grid voltage midpoint detection device provided in an embodiment of the present invention; when both the first discharge module 201 and the second discharge module are connected to the inverter, please refer to... Figure 5 and Figure 6 ,in Figure 5 This is a circuit diagram of a device for detecting the midpoint of the AC power grid voltage on a dual discharge module, provided in an embodiment of the present invention. Figure 6 A circuit diagram of another AC-side grid voltage midpoint detection device for a dual-discharge module provided in an embodiment of the present invention:

[0095] The AC-side grid voltage midpoint detection device provided in this embodiment is connected to the AC-side grid via transformer Q5. A first discharge module consisting of a first diode Q1 and a first resistor R1 is added between the neutral (N) line and the first live wire L1, and a second discharge module consisting of a second diode Q2 and a second resistor R2 is added between the N line and the second live wire L2. The first phase voltage between the N line and the first live wire L1 is obtained through a first sampling module Q3, and the second phase voltage between the N line and the second live wire L2 is obtained through a second sampling module Q4. The first phase voltage between the N line and the first live wire L1 is equivalent to a first equivalent power supply Q6, and the second phase voltage between the N line and the second live wire L2 is equivalent to a second equivalent power supply Q7. Utilizing the voltage discharge principle, combined with the AC-side grid voltage midpoint detection method, reliable connection detection of the voltage midpoint can be achieved. The circuit is simple and reliable, and the software judgment method is simple, making it a low-cost and efficient detection method.

[0096] When the voltage midpoint is reliably connected, i.e., the neutral (N) line remains connected to the load, the voltage between the N line and the first live wire L1 and the second live wire L2 is not affected by the discharge module. The first average value of the first phase voltage between the N line and the first live wire L1, and the second average value of the second phase voltage between the N line and the second live wire L2, are both close to 0V, indicating normal operation. When the voltage midpoint is floating, i.e., the connection between the N line and the load is broken, the voltage between the N line and the first live wire L1 or the second live wire L2 is the voltage division of the filter capacitors and other components. The first and second phase voltages are sinusoidal AC signals with an initial arithmetic mean of 0V. After being discharged by the first and second discharge modules, the first and second average values ​​are biased, and their absolute values ​​are both greater than 0V. The bias formed by the discharge module is obvious and can be reliably identified, thus accurately determining whether the voltage midpoint is reliably connected.

[0097] When AC power is detected, meaning the inverter's output voltage matches the grid voltage, and the inverter is connected to the grid, the MCU (Microcontroller Unit) acts as the control module and begins detecting the first and second average values. If either the first or second average value exceeds a preset rated threshold range, grid connection is stopped.

[0098] The present invention also provides an inverter, including the voltage midpoint detection device as described above.

[0099] For a description of the inverter provided by this invention, please refer to the above embodiments; the invention itself will not be elaborated upon here.

[0100] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0101] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0102] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method of detecting the midpoint of an alternating current side grid voltage, characterized by, An inverter, comprising a unidirectional first discharge module, wherein a first terminal of the first discharge module is connected to a first live wire of the inverter, and a second terminal of the first discharge module is connected to the neutral (N) wire of the inverter, is used to discharge the first phase voltage between the first live wire and the N wire when the connection between the N wire and the electrical load is disconnected and the inverter is forward-biased, so as to change the arithmetic average value of the first phase voltage over a preset number of voltage cycles, wherein the detection method includes: Obtain the first average value of the first phase voltage between the first live wire and the N wire, wherein the first average value is the arithmetic average value of the first phase voltage over a preset number of voltage cycles; Determine whether the first average value is within a preset nominal threshold range; If the first average value is not within the rated threshold range, it is determined that the voltage midpoint is not reliably connected.

2. The method for detecting the midpoint of AC power grid voltage as described in claim 1, characterized in that, The preset number is 1.

3. The method for detecting the midpoint of AC power grid voltage as described in claim 1, characterized in that, The inverter further includes a unidirectional second discharge module. The first end of the second discharge module is connected to the second live wire of the inverter, and the second end of the second discharge module is connected to the neutral wire of the inverter. It is used to discharge the second phase voltage between the second live wire and the neutral wire when the connection between the neutral wire and the electrical load is disconnected and the inverter is forward-biased. The detection method further includes: Obtain the second average value of the second phase voltage between the second live wire and the N wire, wherein the second average value is the arithmetic average value of the second phase voltage over a preset number of voltage cycles; Determine whether the first average value is within a preset rated threshold range; if the first average value is not within the rated threshold range, determine that the voltage midpoint is not reliably connected, including: Determine whether the first average value and the second average value are within the preset rated threshold range; If either the first average value or the second average value is outside the rated threshold range, then it is determined that the voltage midpoint is not reliably connected.

4. The method for detecting the midpoint of AC power grid voltage as described in any one of claims 1 to 3, characterized in that, Before obtaining the first average value of the first phase voltage between the first live wire and the N wire, the method further includes: Determine whether the output voltage of the inverter is the same as the grid voltage of the power grid; If they are the same, proceed to the step of obtaining the first average value of the first phase voltage between the first live wire and the N wire.

5. The method for detecting the midpoint of AC power grid voltage as described in claim 4, characterized in that, Also includes: If the output voltage of the inverter is different from the grid voltage of the power grid, the inverter is disconnected from the power grid.

6. A device for detecting the midpoint of AC power grid voltage, characterized in that, Applied to inverters, including: A unidirectional first discharge module, with a first end connected to the first live wire of the inverter and a second end connected to the neutral wire of the inverter, is used to discharge the first phase voltage between the first live wire and the neutral wire when the connection between the neutral wire and the electrical load is disconnected and forward conduction is enabled, so that the arithmetic average value of the first phase voltage changes within a preset number of voltage cycles. A control module is used to execute a computer program to implement the steps of the AC side grid voltage midpoint detection method as described in any one of claims 1 to 5.

7. The voltage midpoint detection device as described in claim 6, characterized in that, Also includes: The second discharge module has a first end connected to the second live wire of the inverter and a second end connected to the neutral (N) wire of the inverter. It is used to discharge the second phase voltage between the second live wire and the neutral (N) wire when the connection between the neutral (N) wire and the electrical load is disconnected and the neutral (N) wire is forward-biased.

8. The voltage midpoint detection device as described in claim 7, characterized in that, Also includes: A first sampling module, wherein a first terminal of the first sampling module is connected to a first terminal of the first discharge module and a first live wire of the inverter, a second terminal of the first sampling module is connected to a second terminal of the first discharge module and a neutral (N) wire of the inverter, and an output terminal of the first sampling module is connected to the control module, for obtaining the first phase voltage between the first live wire and the neutral (N) wire; The second sampling module has its first terminal connected to the first terminal of the second discharge module and the second live wire of the inverter, its second terminal connected to the second terminal of the second discharge module and the neutral (N) line of the inverter, and its output terminal connected to the control module, for obtaining the second phase voltage between the second live wire and the neutral (N) line.

9. The voltage midpoint detection device according to any one of claims 6 to 8, characterized in that, The first discharge module includes: A diode, wherein the first end of the diode is connected to the first live wire of the inverter, and the second end of the diode is connected to the first end of a resistor, for discharging the first phase voltage between the first live wire and the N wire when the connection between the N wire and the electrical load is disconnected and the N wire is forward conducting; The resistor, the second end of which is connected to the N line of the inverter.

10. An inverter, characterized in that, Includes the voltage midpoint detection device as described in any one of claims 6 to 9.

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