Power conversion device

Abstract

The invention provides power conversion equipment. The power conversion equipment comprises a power conversion circuit, a controller, a first capacitor, a first wire and a second wire, the first wire is connected in series with a first inductor; an alternating-current output end of a first bridge arm in the power conversion circuit is connected with a first wire, a first end of a first capacitor is connected with one side of a first inductor, and a second end of the first capacitor is connected with a direct-current end of the power conversion circuit and a second wire; wherein the first wire is a live wire, and the second wire comprises at least one of a zero wire and a ground wire; the controller injects a harmonic signal of a first target frequency into a first bridge arm in the power conversion circuit, and when the voltage amplitude of a voltage signal of the first target frequency generated between the first wire and the second wire is within a first target range, information of abnormal connection of the second wire is output. Whether the zero line or the ground line is connected abnormally can be detected, the stability and the safety of power supply are ensured, meanwhile, the method is suitable for various power grid systems and power supply scenes, and the reliability is high.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to a power conversion device. Background Art

[0002] The power conversion device can be connected to the AC load through three live wires and one neutral wire, that is, a three-phase four-wire system is used to supply power to the outside. Alternatively, the power conversion device can be connected to the AC load through three live wires, one neutral wire and one ground wire, that is, a three-phase five-wire system is used to supply power to the outside. The neutral wire of the power conversion device is used as a wire to provide a current loop to the AC load, which can ensure that the power conversion device and the AC load form a power supply loop. The ground wire of the power conversion device can lead the leakage current generated in the system into the ground to ensure the stability of the system and the AC load.

[0003] When the neutral line of the power conversion device is abnormally connected to the AC load, for example, when the neutral line is suspended, the working circuit between the power conversion device and the AC load is disconnected, and the AC load cannot be powered on normally, causing the AC load to work abnormally or even be damaged. At the same time, it may interfere with the AC load. In addition, when the ground line of the power conversion device is abnormally connected to the AC load, the ground line of the power conversion device is disconnected from the AC load, and the leakage current generated by the power conversion device will have an adverse effect on the AC load and affect the stability of the power supply. Therefore, how to avoid abnormal connection of the neutral line or ground line of the power conversion device when the power conversion device is connected is a technical problem that technicians in this field urgently need to solve. Summary of the invention

[0004] The present application provides a power conversion device that can detect whether the neutral line or the ground line is abnormally connected to ensure the stability and safety of power supply. It is also suitable for various power grid systems and power supply scenarios, has a simple structure, is easy to implement and has high reliability.

[0005] In the first aspect, the present application provides a power conversion device, including a power conversion circuit, a controller, at least one first capacitor, at least one first wire and at least one second wire; wherein, any first wire is connected in series with a first inductor; the power conversion circuit includes at least one first bridge arm, the AC output end of each first bridge arm is connected to a corresponding first wire, the first end of the first capacitor corresponding to each first bridge arm is connected to the side of the first inductor on the first wire away from the first bridge arm, and the second end of the first capacitor corresponding to each first bridge arm is connected to the DC end of the power conversion circuit and a corresponding second wire; wherein the first wire is a live wire, and at least one second wire includes at least one of a neutral wire and a ground wire; the controller is used to, after injecting a harmonic signal of a first target frequency into at least one first bridge arm in the power conversion circuit, when the voltage amplitude of the voltage signal of the first target frequency generated between the first wire and the second wire is within the first target range, output information that the second wire is abnormally connected. In the present application, the power conversion device injects a harmonic signal of a first target frequency into at least one first bridge arm set in the power conversion circuit through the controller, so that the AC output end of the first bridge arm can transmit a voltage signal carrying the first target frequency to the corresponding first wire. Further, when the second wire is abnormally connected, the voltage signal of the first target frequency transmitted on the first wire can flow to the DC end of the power conversion device through the first capacitor, so that a voltage signal of the first target frequency is generated between the first wire and the second wire, and the voltage amplitude of the voltage signal is within the first target range. Therefore, the power conversion device detects the voltage amplitude of the voltage signal of the first target frequency generated between the first wire and the second wire through the controller, and can determine whether the second wire is abnormally connected. It can be understood that in the case where the power conversion device includes a ground wire, the second wire can be the ground wire to be detected. In the case where the power conversion device includes a neutral wire and a ground wire, the second wire can be the neutral wire and the ground wire to be detected. It can be seen that the power conversion device provided in the embodiment of the present application can detect whether the neutral wire or the ground wire is abnormally connected, and can also detect whether the neutral wire and the ground wire are abnormally connected at the same time, to ensure the stability and safety of the power supply, and is suitable for various power grid systems and power supply scenarios, and has a simple structure and is easy to implement.

[0006] In one possible implementation, the first target range includes a voltage greater than a first voltage threshold, the first voltage threshold is positively correlated with the voltage amplitude of the harmonic signal of the first target frequency, the first voltage threshold is negatively correlated with the capacitance of the first capacitor, and the controller is also used to: when the voltage amplitude of the voltage signal of the first target frequency generated between the first wire and the second wire is greater than the first voltage threshold, output information that the second wire is abnormally connected. In the present application, the controller can obtain the first voltage threshold based on the voltage amplitude of the harmonic signal of the first target frequency and the capacitance of the first capacitor to obtain the first target range, which is more flexible.

[0007] In one possible implementation, the first target range includes a target interval greater than the second voltage threshold and less than the third voltage threshold, the second voltage threshold and the third voltage threshold are positively correlated with the voltage amplitude of the harmonic signal of the first target frequency, and the second voltage threshold and the third voltage threshold are negatively correlated with the capacitance of the first capacitor, and the controller is also used to: when the voltage amplitude of the voltage signal of the first target frequency generated between the first wire and the second wire is greater than the second voltage threshold and less than the third voltage threshold, output information that the second wire is abnormally connected. In the present application, the controller can obtain the second voltage threshold and the third voltage threshold based on the voltage amplitude of the harmonic signal of the first target frequency and the capacitance of the first capacitor to determine the size of the target interval, which is more flexible.

[0008] In a possible implementation, the voltage amplitude of the harmonic signal of the first target frequency is negatively correlated with the capacitance of the first capacitor. In the present application, the power conversion device can adjust the voltage amplitude of the harmonic signal of the first target frequency according to the capacitance of the first capacitor, or set the corresponding first capacitor according to the voltage amplitude of the harmonic signal of the first target frequency, which can meet the needs of different application scenarios and has high flexibility.

[0009] In a possible implementation, the power conversion device includes two second conductors, one of which is a neutral wire and the other is a ground wire. In the present application, when the power conversion device includes a neutral wire and a ground wire, the power conversion device injects a harmonic signal of the first target frequency into at least one first bridge arm through a controller, and can simultaneously detect whether the neutral wire or the ground wire is abnormally connected, and the detection efficiency is high and easy to implement.

[0010] In one possible implementation, the power conversion device includes a plurality of first capacitors and a plurality of first conductors, the power conversion circuit includes a plurality of first bridge arms, and the controller is used to: inject a harmonic signal of a first target frequency into a first target bridge arm in the power conversion circuit, and when the voltage amplitude of a voltage signal of a first target frequency generated between a first conductor corresponding to the first target bridge arm and a second conductor is within a first target range, output information of abnormal connection of the second conductor; wherein the first target bridge arm is any one of the plurality of first bridge arms of the power conversion circuit. In the present application, the power conversion device can detect whether the neutral line or the ground line is abnormally connected by injecting the harmonic signal of the first target frequency into a first bridge arm through the controller, and the steps are simple and easy to implement.

[0011] In one possible implementation, the power conversion device includes a plurality of first capacitors and a plurality of first conductors, the power conversion circuit includes a plurality of first bridge arms, and the controller is used to: inject harmonic signals of a first target frequency into the plurality of first bridge arms in the power conversion circuit, and when the voltage amplitude of the voltage signal of the first target frequency generated between the first conductor corresponding to the first target bridge arm and the second conductor is within the first target range, output information of abnormal connection of the second conductor; wherein the first target bridge arm is any one of the plurality of first bridge arms of the power conversion circuit. In the present application, the power conversion device symmetrically injects the harmonic signals of the first target frequency into the plurality of first bridge arms through the controller, and can detect whether the neutral line or the ground line is abnormally connected, and at the same time, the voltage signal of the first target frequency is symmetrically injected between each first conductor, so as to ensure that each first conductor transmits the signal stably.

[0012] In a possible implementation, the at least one second conductor includes a neutral line, the power conversion device further includes a second capacitor, and the second end of the at least one first capacitor is connected to the neutral line through the second capacitor. In the present application, the second end of the first capacitor is connected to the neutral line through the second capacitor, which can enhance the isolation and filtering effect between the first conductor and the second conductor.

[0013] In one possible implementation, the AC output end of each first bridge arm of the power conversion circuit is used to connect an AC load through a corresponding first wire, and the controller is used to: when injecting a harmonic signal of a first target frequency into at least one first bridge arm in the power conversion circuit, transmit a fundamental signal to the AC load through the first wire corresponding to at least one first bridge arm. In the present application, when injecting the harmonic signal of the first target frequency into the first bridge arm, the controller can control the action of the first bridge arm so that the first bridge arm simultaneously transmits the fundamental signal to the power grid through the first wire, that is, the AC signal output by the first bridge arm can be obtained by superimposing the fundamental signal and the voltage signal of the first target frequency. In this way, when the first wire is connected to the power grid, power backflow will not occur, resulting in damage to the power conversion circuit.

[0014] In a possible implementation, a second conductor is included, the second conductor is a zero line, the power conversion device also includes a ground line and a third capacitor, the zero line is connected in series with a second inductor; the AC output end of the second bridge arm in the power conversion circuit is connected to the zero line, the first end of the third capacitor is connected to the side of the second inductor on the zero line away from the second bridge arm, the second end of the third capacitor is connected to the ground line and the DC end of the power conversion circuit, and the controller is also used to: inject a harmonic signal of the second target frequency into the second bridge arm in the power conversion circuit, and when the voltage amplitude of the voltage signal of the second target frequency generated between the zero line and the ground line is within the second target range, output the information of abnormal ground connection. In the present application, the power conversion device can inject a harmonic signal of the second target frequency into the second bridge arm, so that the AC output end of the second bridge arm can transmit a voltage signal carrying the second target frequency to the corresponding zero line. Further, when the ground line connection is abnormal, the voltage signal of the second target frequency transmitted on the zero line can flow to the DC end of the power conversion device through the third capacitor, so that a voltage signal of the second target frequency is generated between the zero line and the ground line, and the voltage amplitude of the voltage signal is within the second target range. Therefore, the power conversion device can determine whether the ground wire is abnormally connected by detecting the voltage amplitude of the voltage signal of the first target frequency generated between the neutral wire and the ground wire through the controller, thereby ensuring the stability and safety of the power supply. The structure is simple and easy to implement.

[0015] In a possible implementation, the power conversion device also includes a positive bus capacitor and a negative bus capacitor connected in series to the neutral point, the positive bus capacitor is connected to the positive DC bus, and the negative bus capacitor is connected to the negative DC bus: the power conversion circuit is connected in parallel between the positive DC bus and the negative DC bus and connected to the neutral point; the DC end of the power conversion circuit is any one of the neutral point, the positive DC bus or the negative DC bus. In the present application, the power conversion device can use any one of the above-mentioned neutral point, the positive DC bus or the negative DC bus as the DC end of the power conversion circuit, and when the second wire connection is abnormal, the voltage signal of the first target frequency can flow to the DC end of the power conversion circuit, and the structure is simple and easy to implement.

[0016] In a possible implementation, the power conversion device further includes at least one voltage divider device, the second end of the first capacitor is connected to the DC end of the power conversion circuit and is connected to the second wire through a voltage divider device; or, the second end of the first capacitor is connected to the second wire and is connected to the DC end of the power conversion circuit through a voltage divider device; or, the second end of the first capacitor is connected to the DC end of the power conversion circuit through a voltage divider device, and is connected to the second wire through another voltage divider device; wherein the voltage divider device is a capacitor or a resistor. In the present application, the voltage divider device is arranged between the second wire and the DC end of the power conversion circuit, and can isolate the second wire from the DC end of the power conversion circuit.

[0017] In a possible implementation, the power conversion device further includes at least one first switch unit, each first switch unit is arranged between a corresponding first inductor and an AC load; the controller is used to inject a harmonic signal of a first target frequency into at least one first bridge arm in the power conversion circuit, including: the controller is used to control at least one first switch unit to be turned on, and then inject a harmonic signal of the first target frequency into at least one first bridge arm corresponding to at least one first switch unit in the power conversion circuit. In the present application, the power conversion circuit controls the first switch unit to be turned on, so that the voltage signal of the first target frequency output by the power conversion circuit can be transmitted to the first capacitor or to the AC load through the turned-on first switch unit, and the structure is simple and easy to control.

[0018] In one possible implementation,

[0019] The power conversion device also includes a second switch unit, which is arranged between the DC end of the power conversion circuit and the second end of the first capacitor, and the second end of the first capacitor is also connected to a second wire; the controller is used to inject a harmonic signal of the first target frequency into at least one first bridge arm in the power conversion circuit, including: the controller is used to control the second switch unit and at least one first switch unit to be turned on, and then inject the harmonic signal of the first target frequency into at least one first bridge arm corresponding to at least one first switch unit in the power conversion circuit. In the present application, the power conversion circuit controls the second switch unit to be turned on, so that when the voltage signal of the first target frequency output by the power conversion circuit is transmitted to the first capacitor through the turned-on first switch unit, a voltage signal of the first target frequency is generated between the first wire and the second wire, and the structure is simple and easy to control. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of an application scenario of the power supply system provided in this application;

[0021] Figure 2 A schematic diagram of another application scenario of the power supply system provided in an embodiment of the present application;

[0022] Figure 3 A schematic diagram of a framework of a power conversion device provided in an embodiment of the present application;

[0023] Figure 4 Another schematic diagram of a power conversion device provided in an embodiment of the present application;

[0024] Figure 5 Another schematic diagram of a power conversion device provided in an embodiment of the present application;

[0025] Figure 6Another schematic diagram of a power conversion device provided in an embodiment of the present application;

[0026] Figure 7 Another schematic diagram of a power conversion device provided in an embodiment of the present application;

[0027] Figure 8 Another schematic diagram of a power conversion device provided in an embodiment of the present application;

[0028] Fig. 9 Another schematic diagram of a power conversion device provided in an embodiment of the present application;

[0029] Fig.10 Another schematic diagram of a power conversion device provided in an embodiment of the present application;

[0030] Fig.11 Another schematic diagram of a power conversion device provided in an embodiment of the present application;

[0031] Fig.12 Another schematic diagram of a power conversion device provided in an embodiment of the present application;

[0032] Fig.13 Another schematic diagram of a power conversion device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0033] See also Figure 1 , Figure 1 A schematic diagram of an application scenario of the power supply system provided by the present application. The power supply system provided by the present application may include a DC power supply and at least one power conversion device, wherein the DC power supply may specifically be an energy storage battery. Exemplarily, if the power supply system includes multiple power conversion devices, the DC end of each power conversion device may be connected to the energy storage battery, and the AC output ends of multiple power conversion devices may be connected in parallel to an AC load. The power conversion device may invert the DC power provided by the energy storage battery, and output the AC power obtained after the inversion conversion to the AC load for power supply, or the power conversion device may rectify the AC power provided by the AC load, and provide the DC power obtained after the rectification conversion to the DC power supply for charging. The above-mentioned AC load may be understood as a power grid. Among them, the power grid refers to an AC network composed of substations and transmission and distribution lines of various voltages, which can provide industrial frequency AC power to the load. The power grid may be a single-phase AC power grid or a three-phase AC power grid, and the embodiments of the present application do not specifically limit this. Alternatively, the above-mentioned AC load may be understood as a load, for example, it may be a battery, a communication base station, or an electrical device such as a household appliance. For ease of explanation, the following content is described by taking the AC load as a power grid as an example.

[0034] In some feasible implementations, the DC power supply in the power supply system may be a photovoltaic array. In this case, the structure diagram of the power supply system can be referred to in Figure 2 As shown, Figure 2 A schematic diagram of another application scenario of the power supply system provided in an embodiment of the present application. Figure 2 Among the multiple power conversion devices of the power supply system shown, the DC end of some power conversion devices can be connected to the corresponding photovoltaic array. The photovoltaic array is composed of one or more photovoltaic strings connected in parallel, and a photovoltaic string can be obtained by connecting one or more photovoltaic modules in series. The photovoltaic array can convert light energy into electrical energy, and transmit the generated electrical energy to the DC end of the power conversion device in the form of direct current, or transmit it to the energy storage battery for storage. It can be understood that the power conversion device connected to the photovoltaic array in the power supply system can be an inverter, and the power conversion device connected to the energy storage battery in the power supply system can be a converter.

[0035] exist Figure 1 or Figure 2 In the application scenario of the power supply system shown, the power conversion device can be connected to the AC load through three live wires and one neutral wire, that is, the three-phase four-wire system is used to supply power to the power grid. Alternatively, the power conversion device can be connected to the power grid through three live wires, one neutral wire and one ground wire, that is, the three-phase five-wire system is used to provide electrical energy to the power grid. Among them, the neutral wire of the power conversion device is used as a wire to provide a current loop to the power grid, which can ensure that the power conversion device and the power grid form a power supply loop, and the ground wire of the power conversion device can lead the leakage current generated in the system into the ground to ensure the stability of the system and the power grid. When the neutral wire of the power conversion device is abnormally connected to the AC load, for example, when the neutral wire is suspended, the working loop between the power conversion device and the power grid is disconnected, and the load of the power grid cannot be energized normally, resulting in abnormal operation or even damage of the load, and at the same time, it may interfere with the power grid. In addition, when the ground wire of the power conversion device is abnormally connected to the power grid, the ground wire of the power conversion device is disconnected from the power grid, and the leakage current generated by the power conversion device will have an adverse effect on the power grid and affect the stability of the power supply.

[0036] To this end, an embodiment of the present application provides a power conversion device, which detects whether the neutral wire or the ground wire is abnormally connected when the power conversion device is connected to the power grid, avoids abnormal connection of the neutral wire or the ground wire of the power conversion device, and ensures the stability and safety of the power supply.

[0037] The power conversion device provided in the embodiment of the present application includes a power conversion circuit and at least one first wire, and the first wire can be specifically a live wire. A first bridge arm corresponding to each first wire is provided in the power conversion circuit, and the AC output end of each first bridge arm is connected to a corresponding first wire. The power conversion device can control the action of each first bridge arm through a controller to adjust the AC signal output by the AC output end of the first bridge arm. The power conversion device also includes at least one second wire, which is connected to the DC end of the above-mentioned power conversion circuit. In the case where the power conversion device includes a neutral wire, the second wire can be a neutral wire to be detected. In the case where the power conversion device includes a ground wire, the second wire can be a ground wire to be detected. In the case where the power conversion device includes a neutral wire and a ground wire, the power conversion device includes two second wires, one of which is a neutral wire to be detected, and the other second wire is a ground wire to be detected. At least one first capacitor is also provided in the power conversion device, and each first capacitor is arranged between a corresponding first wire and the DC end of the power conversion circuit. In order to detect whether the second wire is abnormally connected, the power conversion device can inject a harmonic signal of the first target frequency into at least one first bridge arm in the power conversion circuit through a controller, and detect the voltage amplitude of the voltage signal of the first target frequency generated between the first wire and the second wire. When the voltage amplitude of the voltage signal of the first target frequency generated between the first wire and the second wire is within the first target range, it indicates that the connection of the second wire is abnormal, and the controller can output information that the second wire is abnormally connected. On the contrary, when the voltage amplitude of the voltage signal of the first target frequency generated between the first wire and the second wire is outside the first target range, it can be characterized that there is no abnormality in the connection of the second wire, and the controller can output information that the second wire is connected normally, or no information is output, indicating that there is no abnormal connection. It can be seen that the power conversion device provided in the embodiment of the present application can detect whether the neutral line or the ground line is abnormally connected, and can also detect whether the neutral line and the ground line are abnormally connected at the same time, which is suitable for various power grid systems and power supply scenarios, ensuring the stability and safety of power supply, and has a simple structure and is easy to implement.

[0038] In some feasible implementations, when the power conversion device is connected to the power grid using a three-phase four-wire system, the power conversion device is connected to the power grid through three live wires and one neutral wire. At this time, the power conversion device includes three first wires, i.e., three live wires, and one second wire, i.e., the neutral wire. The power conversion device can detect whether the neutral wire is abnormally connected to ensure the stability and safety of the power supply. For details, please refer to Figure 3 , Figure 3 A schematic diagram of a framework of a power conversion device provided in an embodiment of the present application. Figure 3The power conversion device shown includes a power conversion circuit, which includes three first bridge arms: a first bridge arm a, a first bridge arm b and a first bridge arm c. Among them, the AC output end of the first bridge arm a can be connected to the live wire A, the AC output end of the first bridge arm b can be connected to the live wire B, and the AC output end of the first bridge arm c can be connected to the live wire C. The above-mentioned first bridge arms can be three-level or multi-level bridge arms. At the same time, each first bridge arm is connected between the positive bus BUS+ and the negative bus BUS-, and each first bridge arm is connected in parallel at both ends of the series-connected DC side capacitor Cd1 and the DC side capacitor Cd2. In some application scenarios, the DC side capacitor of the power conversion circuit can also be set to more than two, Figure 3 The DC side capacitor Cd1 and the DC side capacitor Cd2 shown are only examples and do not constitute a limitation on the embodiments of the present application. The DC end of the power conversion circuit can be connected to the neutral line N, and the DC end can refer to the positive bus BUS+, the negative bus BUS-, or the neutral point BUSN connected to the DC side capacitor Cd1 and the DC side capacitor Cd2. In addition, in some application scenarios, when the power conversion circuit includes more than two DC side capacitors, the connection point of any two DC side capacitors can be used as the neutral point BUSN.

[0039] For ease of explanation, Figure 3 Take the neutral point BUSN connected by the DC side capacitor Cd1 and the DC side capacitor Cd2 as the DC end of the power conversion circuit for illustration. During the operation of the power conversion device, the controller can control the action of each first bridge arm so that the AC output end outputs a fundamental signal, and injects the fundamental signal into the power grid through the connected live wire. The controller can control the fundamental signals output by the three first bridge arms to have different phases, that is, the corresponding live wires of the three first bridge arms can inject fundamental signals of different phases into the power grid to realize multi-phase power transmission to the power grid. It can be understood that multi-phase power transmission can achieve more efficient power transmission efficiency and save the setting of transmission lines.

[0040] In some feasible implementations, the power conversion device may include a first inductance group L1, a first capacitor group C11, a switch unit K, and a first inductance group L2. Among them, the first inductance group L1 includes three first inductors, each of which is connected in series to a corresponding live wire. The first capacitor group C11 includes three first capacitors, the first end of each first capacitor is connected to a corresponding live wire, and the second end is connected to the DC end of the power conversion circuit. It should be noted that the connection between the device and the port or between the device and the device, and the port and the port mentioned in the embodiment of the present application can be a direct connection or an indirect connection through other electronic components, which is not limited in the embodiment of the present application. The switch unit K includes three first switch units and one second switch unit, each of which is connected in series to a corresponding live wire, and the second switch unit is arranged between the neutral line and the DC end of the power conversion circuit. The first inductance group L2 includes three first inductors, each of which is connected in series to a corresponding live wire, and there is also a second inductor connected in series to the neutral line. The specific connection relationship between the above-mentioned electronic devices can be referred to. Figure 3 As shown, the embodiments of the present application are not described in detail here. It should be noted that the first inductor group L1 and the first capacitor group C11 can form an LC filter circuit to filter the AC signals transmitted on each wire to improve the power quality. Similarly, the first inductor group L2 can filter, stabilize the voltage or eliminate electromagnetic interference of the output AC signal.

[0041] In some possible implementations, in order to Figure 3 The power conversion device can detect whether the neutral line N is abnormally connected, and the power conversion device can inject a harmonic signal of the first target frequency into one of the first bridge arms through the controller, and output information about the abnormal connection of the neutral line N when it is detected that the voltage amplitude of the voltage signal of the first target frequency generated between the live wire and the neutral line N is within the first target range. Exemplarily, the controller injects a harmonic signal of the first target frequency into the first bridge arm a as an example. Figure 3As shown, the controller can control the second switch unit on the neutral line N and the first switch unit on the live line A to close, and inject a harmonic signal of the first target frequency into the first bridge arm a with the neutral point BUSN as the reference ground, so as to control the first bridge arm a to move and output an AC signal to the live line A, and the AC signal carries a voltage signal of the first target frequency. Among them, the first target frequency can be determined according to the power frequency of the power grid to which the power conversion device is connected, and the first target frequency can be greater than the power frequency of the power grid. For example, assuming that the power frequency of the power grid is 50Hz, the first target frequency can be three times the power frequency, that is, the first target frequency can be 150Hz. In addition, the voltage amplitude of the harmonic signal of the first target frequency is negatively correlated with the capacitance of the first capacitor corresponding to the live line A, that is, the larger the capacitance of the first capacitor corresponding to the live line A, the smaller the voltage amplitude of the harmonic signal of the first target frequency injected by the controller into the first bridge arm a, and vice versa. Specifically, the magnitude of the first target frequency and the magnitude of the voltage amplitude of the harmonic signal injected into the first bridge arm a can be adjusted according to the needs of the actual application scenario, and the embodiment of the present application is not limited to this.

[0042] In addition, it should be noted that when the controller injects the harmonic signal of the first target frequency into the first bridge arm a, it can control the action of the first bridge arm a so that the first bridge arm a transmits the fundamental wave signal to the power grid through the live wire A at the same time, that is, the AC signal output by the first bridge arm a can be obtained by superimposing the fundamental wave signal and the voltage signal of the first target frequency. In this way, when the live wire A is connected to the power grid, power backflow will not occur, resulting in damage to the power conversion circuit.

[0043] Furthermore, when the AC signal injected by the first bridge arm a into the live wire A carries a voltage signal of the first target frequency, if the neutral wire N is suspended, that is, the neutral wire N is not connected to the grid, the live wire A and the neutral wire N cannot form a current loop. Figure 3As shown, the AC signal output by the first bridge arm a will flow to the neutral point BUSN through the first capacitor corresponding to the live wire A in the first capacitor group C11, thereby charging the first capacitor, and then generating a voltage signal of the first target frequency between the live wire A and the neutral wire N, and the voltage amplitude of the voltage signal of the first target frequency is within the first target range. On the contrary, if the neutral wire N is normally connected to the power grid, the live wire A can inject the AC signal output by the first bridge arm a into the power grid, then the live wire A and the neutral wire N are clamped by the power grid voltage, and the first capacitor in the first capacitor group C11 is not charged. At this time, the voltage signal of the first target frequency will not be generated between the live wire A and the neutral wire N, or the voltage amplitude of the voltage signal of the first target frequency generated between the live wire A and the neutral wire N is not within the first target range. It can be seen from this that after the controller injects the harmonic signal of the first target frequency into the first bridge arm a, it can detect whether the voltage amplitude of the voltage signal of the first target frequency generated between the live wire A and the neutral wire N is within the first target range, and then it can be determined whether the neutral wire is abnormally connected.

[0044] Among them, the above-mentioned first target range can specifically be greater than the first voltage threshold, that is, when the controller detects that the voltage amplitude of the voltage signal of the first target frequency generated between the live wire A and the neutral wire N is greater than the first voltage threshold, the controller can output the information of the neutral wire connection abnormality. It should be noted that, since when the neutral wire N is suspended, the voltage amplitude of the voltage signal of the first target frequency generated between the live wire A and the neutral wire N is related to the equivalent impedance of the first capacitor, and the equivalent impedance of the first capacitor is positively correlated with the voltage amplitude of the harmonic signal injected by the controller into the first bridge arm a, and negatively correlated with the capacitance of the first capacitor itself. Specifically, when the capacitance of the first capacitor is smaller, the equivalent impedance of the first capacitor is larger, and the charging voltage amplitude that the first capacitor can generate is also larger, and the value of the above-mentioned first voltage threshold can also be larger. Therefore, the controller can determine the above-mentioned first voltage threshold based on the voltage amplitude of the harmonic signal injected into the first bridge arm a and the capacitance of the first capacitor itself.

[0045] Alternatively, the first target range may specifically be a target interval greater than the second voltage threshold and less than the third voltage threshold, that is, when the controller detects that the voltage amplitude of the voltage signal of the first target frequency generated between the live wire A and the neutral wire N is located in the above target interval, the controller may output information about the abnormal connection of the neutral wire. It can be seen from the above that when the neutral wire N is suspended, the voltage amplitude of the voltage signal of the first target frequency generated between the live wire A and the neutral wire N is positively correlated with the voltage amplitude of the harmonic signal injected by the controller into the first bridge arm a, and negatively correlated with the capacitance of the first capacitor itself. Therefore, the controller may determine a target voltage threshold based on the voltage amplitude of the harmonic signal injected into the first bridge arm a and the capacitance of the first capacitor itself, and determine the fluctuation range of the detection based on the target voltage threshold to obtain the above second voltage threshold and the third voltage threshold, and determine the corresponding target interval. Exemplarily, assuming that when the controller injects a harmonic signal of the first target frequency into the first bridge arm a, and when the neutral wire N is suspended, the harmonic voltage division generated after the first capacitor is charged is equal to 5V, then the controller may determine that the target voltage threshold is 5V. Meanwhile, assuming that the fluctuation range detected by the controller is 10%, the second voltage threshold may be equal to the product of 5V and 0.9, and the third voltage threshold may be equal to the product of 5V and 1.1. The above is only an example and does not constitute a limitation to the embodiments of the present application.

[0046] In some feasible implementations, when the capacitance of the first capacitor is extremely small, the equivalent impedance of the first capacitor will tend to infinity, and the first capacitor connected in series between the live wire and the neutral wire N can be regarded as an open circuit. At this time, if the neutral wire N is suspended, the voltage signal of the first target frequency transmitted on the live wire A is rarely transmitted to the DC end of the power conversion circuit through the first capacitor, but the controller can still detect that the voltage amplitude of the voltage signal of the first target frequency generated between the live wire A and the neutral wire N is within the above-mentioned first target range. Therefore, in the case where the first capacitor connected between the live wire A and the neutral wire N is open circuit, the controller provided in the embodiment of the present application can still detect whether the neutral wire is online, and the reliability is high.

[0047] In some feasible implementations, in order to determine whether the voltage amplitude of the voltage signal of the first target frequency generated between the live wire A and the neutral wire N is within the above-mentioned first target range, the controller may first sample and obtain the voltage signal with a frequency equal to the first target frequency on the live wire A and the neutral wire N, that is, filter out the voltage signals of other frequencies. If the controller does not extract the voltage signal with a frequency equal to the first target frequency on the live wire A and the neutral wire N, it indicates that the neutral wire N is normally connected to the power grid. When the controller extracts the voltage signal with a frequency equal to the first target frequency on the live wire A and the neutral wire N, the controller may further detect whether the voltage amplitude of the voltage signal of the first target frequency is within the above-mentioned first target range. If the voltage amplitude of the voltage signal of the first target frequency is within the above-mentioned first target range, it indicates that the neutral wire N is abnormally connected, otherwise it indicates that the neutral wire N is normally connected to the power grid. In some feasible implementations, in addition to injecting the harmonic signal of the above-mentioned first target frequency into the first bridge arm a, the controller may also inject the harmonic signal of the first target frequency into the above-mentioned first bridge arm b or the first bridge arm c to detect whether the neutral wire N is abnormally connected. It is understandable that the controller can inject a harmonic signal of the first target frequency into the first bridge arm b or the first bridge arm c, and control the first switch unit on the live wire B or the live wire C and the second switch unit on the neutral wire N to be closed, so as to detect whether the neutral wire N is abnormally connected. The specific implementation principle can be referred to in the above content, in which the controller injects a harmonic signal of the first target frequency into the first bridge arm a to detect whether the neutral wire N is abnormally connected, and the embodiments of the present application are not described in detail here.

[0048] In some feasible implementations, in addition to injecting the harmonic signal of the first target frequency into the first bridge arm a, the first bridge arm b or the first bridge arm c, the controller can also symmetrically inject the harmonic signal of the first target frequency into the first bridge arm a, the first bridge arm b and the first bridge arm c, and control the first switch unit on the live wire A, the live wire B and the live wire C and the second switch unit on the neutral wire N to close, so as to detect whether the neutral wire N is abnormally connected. It can be understood that at this time, if the neutral wire N is suspended, then Figure 3The voltage signals of the first target frequency on the three live wires shown will each flow to the neutral point BUSN through the corresponding first capacitor, thereby generating a voltage signal of the first target frequency between each live wire and the neutral wire N, and the voltage amplitude is within the first target range. Therefore, when the controller symmetrically injects the harmonic signal of the first target frequency into the first bridge arm a, the first bridge arm b and the first bridge arm c at the same time, the controller can detect whether the voltage amplitude of the voltage signal of the first target frequency generated between any live wire and the neutral wire N is within the first target range to determine whether the neutral wire N is abnormally connected. It can be understood that the controller injects the harmonic signal of the first target frequency into the above-mentioned first bridge arm a, the first bridge arm b and the first bridge arm c at the same time to detect whether the neutral wire N is abnormally connected. The specific implementation method of the controller injecting the harmonic signal of the first target frequency into the above-mentioned first bridge arm a to detect whether the neutral wire N is abnormally connected can be referred to in the above content, and the specific implementation method of the controller injecting the harmonic signal of the first target frequency into the above-mentioned first bridge arm a to detect whether the neutral wire N is abnormally connected is not repeated here in the embodiment of the present application.

[0049] In some feasible implementations, the specific structure of the power conversion device can also be as follows: Figure 4 As shown, Figure 4 Another schematic diagram of the framework of the power conversion device provided in an embodiment of the present application. Figure 4 In the power conversion device shown in the figure, the first bridge arm a, the first bridge arm b, the first bridge arm c, the positive bus BUS+, the negative bus BUS-, the neutral point BUSN connected to the DC side capacitor Cd1 and the DC side capacitor Cd2, and the first inductor group L1, the switch unit K and the first inductor group L2 of the power conversion circuit can refer to the above content and Figure 4 In addition, the power conversion device includes a resistor unit R11, which includes three first resistors, each of which has a first end connected to a corresponding live wire and a second end connected to the neutral wire N of the power conversion circuit and the DC end of the power conversion circuit. Figure 3 The power conversion device shown and Figure 4 The power conversion devices shown differ in that Figure 3 The first capacitor group C11 shown can be replaced by Figure 4 The resistor unit R11 is shown.

[0050] It should be noted that, similar to the first capacitor in the above-mentioned first capacitor group C11, each first resistor in the resistance unit R11 can transmit the voltage signal of the first target frequency transmitted on the live line to the DC end of the power conversion circuit when the neutral line N is suspended, so as to generate a voltage signal of the first target frequency between the live line and the neutral line N, and the voltage amplitude of the voltage signal is within the first target range.

[0051] It can be understood that the DC end of the power conversion circuit can be the positive bus BUS+, the negative bus BUS-, or the neutral point BUSN to which the DC side capacitor Cd1 and the DC side capacitor Cd2 are connected. Figure 4 The positive bus BUS+ is used as an example for illustration, which does not constitute a limitation on the embodiments of the present application. Figure 4 The specific implementation principle of the power conversion device shown in the figure to detect whether the neutral line N is abnormally connected through the controller, the power conversion circuit and the resistor unit R11 can be referred to the above Figure 3 The specific implementation method of the present application will not be described in detail here.

[0052] In some feasible implementations, the specific structure of the power conversion device can also be as follows: Figure 5 As shown, Figure 5 Another schematic diagram of the framework of the power conversion device provided in an embodiment of the present application. Figure 5 In the power conversion device shown in the figure, the first bridge arm a, the first bridge arm b, the first bridge arm c, the positive bus BUS+, the negative bus BUS-, the neutral point BUSN connected to the DC side capacitor Cd1 and the DC side capacitor Cd2, and the first inductor group L1, the switch unit K and the first inductor group L2 of the power conversion circuit can refer to the above content and Figure 5 In addition, the first capacitor group C12 includes three first capacitors, each of which has a first end connected to a corresponding live wire and a second end connected to a neutral wire N of the power conversion circuit. Figure 3 The power conversion device shown and Figure 5 The difference between the power conversion devices shown is that the positions of the first capacitor groups are different.

[0053] It should be noted that the first capacitor group C12 is arranged between the live wire and the neutral wire N, and can filter out the differential mode signal in the AC power signal transmitted on each live wire, thereby improving the power quality.

[0054] Understandably, in order to Figure 5 The power conversion device can detect whether the neutral line N is abnormally connected, and the power conversion device can inject a harmonic signal of the first target frequency into one of the first bridge arms through the controller, and output information about the abnormal connection of the neutral line N when it is detected that the voltage amplitude of the voltage signal of the first target frequency generated between the live line and the neutral line N is within the first target range. For example, Figure 5As shown, the controller can control the second switch unit on the neutral line N and the first switch unit on the live line A to close, and with the neutral point BUSN as the reference ground, inject a harmonic signal of the first target frequency into the first bridge arm a to control the first bridge arm a to operate and output an AC signal to the live line A, and the AC signal carries a voltage signal of the first target frequency. Furthermore, it can be seen from the above content that when the AC signal injected by the first bridge arm a into the live line A carries a voltage signal of the first target frequency, if the neutral line N is suspended, that is, the neutral line N is not connected to the power grid, then the live line A and the neutral line N cannot form a current loop. At this time, Figure 5 As shown, the AC signal output by the first bridge arm a will flow to the neutral point BUSN through the first capacitor corresponding to the live wire A in the first capacitor group C12, thereby charging the first capacitor, and further generating a voltage signal of a first target frequency between the live wire A and the neutral wire N, and the voltage amplitude of the voltage signal of the first target frequency is within the first target range.

[0055] Alternatively, it can be known from the above content that the controller can control the first switch unit on the live wire B or the live wire C to close separately, and inject the harmonic signal of the first target frequency into the first bridge arm b or the first bridge arm c to detect whether the neutral wire N is abnormally connected. Figure 5 The three first bridge arms shown symmetrically inject harmonic signals of the first target frequency, and when the voltage amplitude of the voltage signal of the first target frequency generated between any live wire and the neutral wire N is detected to be within the first target range, the information of abnormal connection of the neutral wire N is output. It can be understood that the DC end of the above power conversion circuit can be the positive bus BUS+, the negative bus BUS-, or the neutral point BUSN where the DC side capacitor Cd1 and the DC side capacitor Cd2 are connected, Figure 5 The positive bus BUS+ is used as an example for illustration, which does not constitute a limitation on the embodiments of the present application. Figure 5 The specific implementation principle of the power conversion device shown in the figure to detect whether the neutral line N is abnormally connected through the controller, the power conversion circuit and the first capacitor group C12 can be referred to the above Figure 3 The specific implementation method of the present application will not be described in detail here.

[0056] In some feasible implementations, the specific structure of the power conversion device can also be as follows: Figure 6 As shown, Figure 6 Another schematic diagram of a power conversion device provided in an embodiment of the present application. Figure 6In the power conversion device shown in the figure, the first bridge arm a, the first bridge arm b, the first bridge arm c, the positive bus BUS+, the negative bus BUS-, the neutral point BUSN connected to the DC side capacitor Cd1 and the DC side capacitor Cd2, and the first inductor group L1, the switch unit K and the first inductor group L2 of the power conversion circuit can refer to the above content and Figure 6 In addition, the first capacitor group C13 includes three first capacitors and one second capacitor, the first end of each first capacitor is connected to a corresponding live wire, and the second end is connected to the neutral wire N of the power conversion circuit through the second capacitor. Figure 6 The power conversion device shown and Figure 5 The power conversion devices shown differ in that Figure 6 Each first capacitor in the first capacitor group C13 shown can be connected to the neutral line N through a second capacitor. It should be noted that the first capacitor group C13 is arranged between the live line and the neutral line N, and can filter the differential mode signal in the AC signal transmitted on each live line to improve the power quality.

[0057] It can be understood that the DC end of the power conversion circuit can be the positive bus BUS+, the negative bus BUS-, or the neutral point BUSN to which the DC side capacitor Cd1 and the DC side capacitor Cd2 are connected. Figure 6 The neutral point BUSN is used as an example for illustration, which does not constitute a limitation on the embodiments of the present application. Figure 6 The specific implementation principle of the power conversion device shown in the figure to detect whether the neutral line N is abnormally connected through the controller, the power conversion circuit and the first capacitor group C13 can be referred to the above Figure 3 The specific implementation method of the present application will not be described in detail here.

[0058] In some feasible implementations, the specific structure of the power conversion device can also be as follows: Figure 7 As shown, Figure 7 Another schematic diagram of a power conversion device provided in an embodiment of the present application. Figure 7 In the power conversion device shown in the figure, the first bridge arm a, the first bridge arm b, the first bridge arm c, the positive bus BUS+, the negative bus BUS-, the neutral point BUSN connected to the DC side capacitor Cd1 and the DC side capacitor Cd2, and the settings of the first inductor group L1, the switch unit K, the first inductor group L2 and the first capacitor group C12 of the power conversion circuit can refer to the above content and Figure 7 As shown, the embodiments of the present application are not described in detail here. Figure 7The first capacitor group C14 shown includes three first capacitors and a voltage divider, the first end of each first capacitor is connected to a corresponding live wire, the second end is connected to the DC end of the power conversion circuit, and is connected to the neutral line N of the power conversion circuit through the voltage divider. It can be seen that Figure 7 The first capacitor group C14 and Figure 3 The difference of the first capacitor group C11 shown is that Figure 7 The first capacitor group C14 shown is additionally provided with a voltage divider. Specifically, the voltage divider may be a resistor or a capacitor. For example, Figure 7 The first capacitor group C14 shown takes the voltage divider device as a capacitor as an example, which does not constitute a limitation on the embodiments of the present application. When the voltage divider device is a capacitor, the capacitor can isolate and filter the zero line N of the power conversion device and the DC end of the power conversion circuit. It should be noted that Figure 7 The first capacitor group C14 shown can also be replaced by Figure 3 The first capacitor group C11 shown, Figure 7 The first capacitor group C12 shown can also be replaced by Figure 6 The first capacitor group C13 shown, similarly, Figure 3 The first capacitor group C11 shown in the figure can also be replaced by the first capacitor group C14 or by Figure 4 The resistor unit R11 shown is not illustrated one by one in the embodiment of the present application.

[0059] Understandably, in order to Figure 7 The power conversion device can detect whether the neutral line N is abnormally connected, and the power conversion device can inject a harmonic signal of the first target frequency into any one of the first bridge arms through a controller, or symmetrically inject a harmonic signal of the first target frequency into each first bridge arm at the same time, and output information about the abnormal connection of the neutral line N when it is detected that the voltage amplitude of the voltage signal of the first target frequency generated between the live line and the neutral line N is within the first target range. For example, Figure 7 As shown, the controller uses the neutral point BUSN as the reference ground, injects a harmonic signal of the first target frequency into the first bridge arm a, so as to control the operation of the first bridge arm a and output an AC signal to the live wire A, and the AC signal carries a voltage signal of the first target frequency. Furthermore, it can be seen from the above content that when the AC signal injected by the first bridge arm a into the live wire A carries a voltage signal of the first target frequency, if the neutral wire N is suspended, that is, the neutral wire N is not connected to the power grid, then the live wire A and the neutral wire N cannot form a current loop. At this time, Figure 7As shown, the AC signal output by the first bridge arm a will flow to the neutral point BUSN through the first capacitor corresponding to the live wire A in the first capacitor group C12, and will flow to the neutral point BUSN through the first capacitor corresponding to the live wire A in the first capacitor group C14, thereby charging the first capacitors corresponding to the live wire A in the first capacitor group C12 and the first capacitor group C14, and then generating a voltage signal of a first target frequency between the live wire A and the neutral wire N, and the voltage amplitude of the voltage signal of the first target frequency is within the first target range.

[0060] It should be noted that, from the above content, the first target range can specifically include a target range greater than the first voltage threshold, or a target range greater than the second voltage threshold and less than the third voltage threshold, and the first voltage threshold, the second voltage threshold and the third voltage threshold can be obtained by the voltage amplitude of the harmonic signal injected by the controller into each first bridge arm and the capacitance of the first capacitor itself. Figure 7 In the power conversion device shown, the first target range (i.e., the first voltage threshold, the second voltage threshold and the third voltage threshold mentioned above) can be obtained by the voltage amplitude of the harmonic signal injected by the controller into each first bridge arm, the first capacitor group C14 and the capacitance of the first capacitor in the first capacitor group C12.

[0061] It can be understood that the DC end of the power conversion circuit can be the positive bus BUS+, the negative bus BUS-, or the neutral point BUSN to which the DC side capacitor Cd1 and the DC side capacitor Cd2 are connected. Figure 7 The neutral point BUSN is used as an example for illustration, which does not constitute a limitation on the embodiments of the present application. Figure 7 The specific implementation principle of the power conversion device shown in the figure to detect whether the neutral line is abnormally connected through the controller, the power conversion circuit, and the first capacitor group C14 and the first capacitor group C12 can be referred to the above Figure 3 The specific implementation method of the present application will not be described in detail here.

[0062] In some feasible implementations, the specific structure of the power conversion device can also be as follows: Figure 8 As shown, Figure 8 Another schematic diagram of a power conversion device provided in an embodiment of the present application. Figure 8 In the power conversion device shown in the figure, the first bridge arm a, the first bridge arm b, the first bridge arm c, the positive bus BUS+, the negative bus BUS-, the neutral point BUSN connected to the DC side capacitor Cd1 and the DC side capacitor Cd2, and the settings of the first inductor group L1, the first capacitor group C12, the switch unit K and the first inductor group L2 of the power conversion circuit can refer to the above content and Figure 8 As shown, the embodiments of the present application are not described in detail here. Figure 8The first capacitor group C15 shown includes three first capacitors and two voltage dividers, the first end of each first capacitor is connected to a corresponding live wire, the second end is connected to the neutral wire N of the power conversion circuit through a voltage divider, and is connected to the DC end of the power conversion circuit through another voltage divider. Specifically, the voltage divider can be a resistor or a capacitor, for example, Figure 8 The first capacitor group C15 shown in the figure takes the voltage divider device as a capacitor as an example, which does not constitute a limitation on the embodiments of the present application. When the voltage divider device is a capacitor, Figure 8 The power conversion device shown and Figure 7 The power conversion devices shown differ in that Figure 8 The first capacitor group C15 shown is provided with two capacitors. Figure 8 The first capacitor group C12 shown can also be replaced by Figure 6 The first capacitor group C13 is shown, and the embodiments of the present application are not illustrated one by one here.

[0063] It can be understood that the DC end of the power conversion circuit can be the positive bus BUS+, the negative bus BUS-, or the neutral point BUSN to which the DC side capacitor Cd1 and the DC side capacitor Cd2 are connected. Figure 8 The neutral point BUSN is used as an example for illustration, which does not constitute a limitation on the embodiments of the present application. Figure 8 The specific implementation principle of the power conversion device shown in the figure to detect whether the neutral line N is abnormally connected through the controller, the first capacitor group C12 of the power conversion circuit and the first capacitor group C15 can be referred to the above Figure 3 The specific implementation method of the present application will not be described in detail here.

[0064] In some feasible implementations, the specific structure of the power conversion device can also be as follows: Fig. 9 As shown, Fig. 9 Another schematic diagram of a power conversion device provided in an embodiment of the present application. Fig. 9 In the power conversion device shown in the figure, the first bridge arm a, the first bridge arm b, the first bridge arm c, the positive bus BUS+, the negative bus BUS-, the neutral point BUSN connected to the DC side capacitor Cd1 and the DC side capacitor Cd2, and the first inductor group L1, the first capacitor group C14, the first capacitor group C12, the switch unit K and the first inductor group L2 of the power conversion circuit can refer to the above content and Fig. 9 As shown, the embodiments of the present application are not described in detail here. Fig. 9 The power conversion circuit shown also includes a second bridge arm, namely Fig. 9 The power conversion circuit shown includes four bridge arms. The AC output end of the second bridge arm is connected to the neutral line N, and the neutral line N may be connected in series with a first inductor. It should be noted that: Fig. 9The first capacitor group C12 shown can also be replaced by Figure 6 The first capacitor group C13 is shown. Fig. 9 The first capacitor group C14 shown can also be replaced by Figure 3 The first capacitor group C11 shown, or replaced by Figure 8 The first capacitor group C15 shown may be replaced by Figure 4 The resistor unit R11 shown is not illustrated one by one in the embodiment of the present application.

[0065] It can be understood that the DC end of the power conversion circuit can be the positive bus BUS+, the negative bus BUS-, or the neutral point BUSN to which the DC side capacitor Cd1 and the DC side capacitor Cd2 are connected. Fig. 9 The neutral point BUSN is used as an example for illustration, which does not constitute a limitation on the embodiments of the present application. Fig. 9 The specific implementation principle of the power conversion device shown in the figure to detect whether the neutral line is abnormally connected through the controller, the power conversion circuit, and the first capacitor group C11 and the first capacitor group C12 can be referred to the above Figure 3 The specific implementation method of the present application will not be described in detail here.

[0066] In some feasible implementations, when the power conversion device is connected to the power grid using a three-phase four-wire system, the power conversion device is connected to the power grid via three live wires and one ground wire. At this time, the power conversion device includes three first wires, i.e., three live wires, and one second wire, i.e., the above-mentioned ground wire. The power conversion device can detect whether the ground wire is abnormally connected to ensure the stability and safety of power supply.

[0067] For details, please refer to Fig.10 , Fig.10 Another schematic diagram of a power conversion device provided in an embodiment of the present application. Fig.10 In the power conversion device shown in the figure, the first bridge arm a, the first bridge arm b, the first bridge arm c, the positive bus BUS+, the negative bus BUS-, the neutral point BUSN connected to the DC side capacitor Cd1 and the DC side capacitor Cd2, and the settings of the first inductor group L1, the switch unit K, the first inductor group L2 and the first capacitor group C11 of the power conversion circuit can refer to the above content and Fig.10 As shown, the embodiments of the present application are not described in detail here. Fig.10 The first capacitor group C16 shown includes three first capacitors, each of which has a first end connected to a corresponding live wire and a second end connected to a ground wire of a power conversion circuit. The ground wire can also be connected to a DC terminal of the power conversion circuit via a voltage divider, which can be a capacitor or a resistor. For example, Fig.10The voltage divider device is taken as the fourth capacitor C4 as an example for description. The fourth capacitor C4 can isolate and filter the ground line PE and the DC end of the power conversion circuit.

[0068] Understandably, in order to Fig.10 The power conversion device can detect whether the ground wire PE is abnormally connected, and the power conversion device can inject a harmonic signal of the first target frequency into any one of the first bridge arms through a controller, or symmetrically inject a harmonic signal of the first target frequency into each first bridge arm at the same time, and output information about the abnormal connection of the ground wire PE when it is detected that the voltage amplitude of the voltage signal of the first target frequency generated between the live wire and the ground wire PE is within the first target range. For example, Fig.10 As shown, the controller uses the neutral point BUSN as the reference ground, injects a harmonic signal of the first target frequency into the first bridge arm a, so as to control the action of the first bridge arm a and output an AC signal to the live wire A, and the AC signal carries a voltage signal of the first target frequency. Furthermore, it can be seen from the above content that when the AC signal injected by the first bridge arm a into the live wire A carries a voltage signal of the first target frequency, if the ground wire PE is suspended, that is, the ground wire PE is not connected to the power grid, then the live wire A and the ground wire PE cannot form a current loop. At this time, Fig.10 As shown, the AC signal output by the first bridge arm a will flow to the neutral point BUSN through the first capacitor corresponding to the live wire A in the first capacitor group C16, thereby charging the first capacitor, and then generating a voltage signal of a first target frequency between the live wire A and the ground wire PE, and the voltage amplitude of the voltage signal of the first target frequency is within the first target range.

[0069] It can be understood that the DC end of the power conversion circuit can be the positive bus BUS+, the negative bus BUS-, or the neutral point BUSN to which the DC side capacitor Cd1 and the DC side capacitor Cd2 are connected. Fig.10 The neutral point BUSN is used as an example for illustration, which does not constitute a limitation on the embodiments of the present application. Fig.10 The first capacitor group C11 shown can be replaced by Figure 7 The first capacitor group C14 shown, or replaced by Figure 8 The first capacitor group C15 shown, or replaced by Figure 4 The resistor unit R11 shown is not illustrated one by one in the embodiment of the present application. Fig.10 The specific implementation principle of the power conversion device shown in the figure to detect whether the ground line PE is abnormally connected through the controller, the power conversion circuit, the first capacitor group C11 and the first capacitor group C16 can be referred to the above Figure 3 The specific implementation method of the present application will not be described in detail here.

[0070] In some feasible implementations, when the power conversion device is connected to the power grid using a three-phase five-wire system, the power conversion device is connected to the power grid through three live wires, one ground wire, and one neutral wire. At this time, the power conversion device includes three first wires, i.e., three live wires, and two second wires, i.e., the above-mentioned ground wire and neutral wire. The power conversion device can detect whether the ground wire and the neutral wire are abnormally connected to ensure the stability and safety of the power supply.

[0071] For details, please refer to Fig.11 , Fig.11 Another schematic diagram of a power conversion device provided in an embodiment of the present application. Fig.11 In the power conversion device shown in the figure, the first bridge arm a, the first bridge arm b, the first bridge arm c, the positive bus BUS+, the negative bus BUS-, the neutral point BUSN connected to the DC side capacitor Cd1 and the DC side capacitor Cd2, and the settings of the first inductor group L1, the switch unit K, the first inductor group L2 and the first capacitor group C14 of the power conversion circuit can refer to the above content and Fig.11 As shown, the embodiments of the present application are not described in detail here. Fig.11 The first inductor and the second switch unit are connected in series on the neutral line N shown in the figure. The neutral line N can be connected to the DC end of the power conversion circuit through a voltage divider. The voltage divider can be a capacitor or a resistor. For example, Fig.11 The voltage divider device is taken as the fourth capacitor C4 as an example for description. Fig.11 The power conversion device shown also includes a first capacitor group C17, a third capacitor in the first capacitor group C17 is arranged between the neutral line N and the ground line PE, and three first capacitors are arranged between a corresponding live line and the ground line PE. It should be noted that, Fig.11 The first capacitor group C14 shown can also be replaced by Fig.10 The first capacitor group C11 or Figure 8 The first capacitor group C15 shown or Figure 4 The resistor unit R11 and the first capacitor group C17 shown may also be replaced by the first capacitor group C16, which will not be illustrated one by one in the embodiments of the present application.

[0072] It can be understood that the DC end of the power conversion circuit can be the positive bus BUS+, the negative bus BUS-, or the neutral point BUSN to which the DC side capacitor Cd1 and the DC side capacitor Cd2 are connected. Fig.11 The neutral point BUSN is used as an example for illustration, which does not constitute a limitation on the embodiments of the present application. Fig.11 The power conversion device shown in the figure detects whether the ground line PE and the neutral line N are abnormally connected through the controller, the power conversion circuit, and the first capacitor group C14 and the first capacitor group C17. For the specific implementation principle, please refer to the above Figure 3The specific implementation method of the present application will not be described in detail here.

[0073] In some feasible implementations, the specific structure of the power conversion device can also be as follows: Fig.12 As shown, Fig.12 Another schematic diagram of a power conversion device provided in an embodiment of the present application. Fig.12 In the power conversion device shown in the figure, the first bridge arm a, the first bridge arm b, the first bridge arm c, the positive bus BUS+, the negative bus BUS-, the neutral point BUSN connected to the DC side capacitor Cd1 and the DC side capacitor Cd2 of the power conversion circuit, and the settings of the first inductor group L1, the switch unit K, the first inductor group L2, the first capacitor group C14 and the first capacitor group C17 can refer to the above content and Fig.12 As shown, the embodiments of the present application are not described in detail here. Fig.12 The power conversion circuit shown also includes a second bridge arm, namely Fig.12 The power conversion circuit shown includes four bridge arms. It should be noted that: Fig.12 The first capacitor group C14 shown can also be replaced by Fig.10 The first capacitor group C11 or Figure 8 The first capacitor group C15 shown or Figure 4 The resistor unit R11 and the first capacitor group C17 shown may also be replaced by the first capacitor group C16, which will not be illustrated one by one in the embodiments of the present application.

[0074] Understandably, Fig.12 The power conversion device shown detects whether the neutral line N is abnormally connected through the controller, the power conversion circuit and the first capacitor group C14, and at the same time detects whether the ground line PE is abnormally connected through the controller, the power conversion circuit and the first capacitor group C17. That is, Fig.12 The power conversion device shown can simultaneously detect the ground line PE and the neutral line N. Specifically, the power conversion device can inject a harmonic signal of the first target frequency into any one of the above-mentioned first bridge arms through a controller, or symmetrically inject a harmonic signal of the first target frequency into each first bridge arm at the same time, and when it is detected that the voltage amplitude of the voltage signal of the first target frequency generated between the live wire and the neutral line N is within the first target range, the power conversion device outputs information about abnormal connection of the neutral line N, and when it is detected that the voltage amplitude of the voltage signal of the first target frequency generated between the live wire and the ground line PE is within the first target range, the power conversion device outputs information about abnormal connection of the ground line PE. For example, please refer again to Fig.12, the controller uses the neutral point BUSN as the reference ground, injects a harmonic signal of the first target frequency into the first bridge arm a, so as to control the action of the first bridge arm a and output an AC signal to the live wire A, and the AC signal carries a voltage signal of the first target frequency. Further, it can be seen from the above content that when the AC signal injected by the first bridge arm a into the live wire A carries a voltage signal of the first target frequency, if the neutral wire N is suspended, that is, the neutral wire N is not connected to the power grid, then the live wire A and the neutral wire N cannot form a current loop. At this time, if Figure 7 As shown, the AC signal output by the first bridge arm a will flow to the neutral point BUSN through the first capacitor corresponding to the live wire A in the first capacitor group C14. At the same time, if the ground wire PE is suspended, that is, the ground wire PE is not connected to the power grid, the live wire A and the ground wire PE cannot form a current loop. At this time, the AC signal output by the first bridge arm a will flow to the neutral point BUSN through the first capacitor corresponding to the live wire A in the first capacitor group C17. As a result, the first capacitors corresponding to the live wire A in the first capacitor group C14 and the first capacitor group C17 will be charged, and then a voltage signal of the first target frequency will be generated between the live wire A and the neutral wire N, and the voltage amplitude of the voltage signal of the first target frequency is within the first target range, and a voltage signal of the first target frequency will be generated between the live wire A and the ground wire PE, and the voltage amplitude of the voltage signal of the first target frequency is within the first target range.

[0075] It can be seen that when injecting the harmonic signal of the first target frequency into any one of the first bridge arms or all of the first bridge arms, the controller can determine whether the neutral line N is abnormally connected by detecting the voltage amplitude of the voltage signal of the first target frequency generated between the live line A and the neutral line N. At the same time, it can determine whether the ground line PE is abnormally connected by detecting the voltage amplitude of the voltage signal of the first target frequency generated between the live line A and the ground line PE, thereby improving the detection efficiency. It can be understood that the DC end of the above-mentioned power conversion circuit can be the positive bus BUS+, the negative bus BUS-, or the neutral point BUSN connected to the DC side capacitor Cd1 and the DC side capacitor Cd2. Fig.12 The neutral point BUSN is used as an example for illustration, which does not constitute a limitation on the embodiments of the present application. Fig.12 The power conversion device shown in the figure detects whether the neutral line N is abnormally connected through the controller, the power conversion circuit and the first capacitor group C14, and detects whether the ground line PE is abnormally connected through the controller, the power conversion circuit and the first capacitor group C17. For the specific implementation principle, please refer to the above Figure 3 The specific implementation method of the present application will not be described in detail here.

[0076] In some possible implementations, Fig.12In the power conversion device shown, in addition to injecting a harmonic signal of the first target frequency into the first bridge arm to detect whether the ground line PE is abnormally connected, the controller can also inject a harmonic signal of the second target frequency into the second bridge arm, and when the voltage amplitude of the voltage signal of the second target frequency generated between the neutral line N and the ground line PE is within the second target range, output the information of the abnormal connection of the ground line PE. Specifically, when the controller injects the harmonic signal of the second target frequency into the second bridge arm, the AC signal injected by the second bridge arm into the neutral line N carries the voltage signal of the second target frequency. If the ground line PE is suspended, that is, the ground line PE is not connected to the power grid, the ground line PE and the neutral line N cannot form a current loop. The above-mentioned AC signal of the neutral line N will flow to the neutral point BUSN through the third capacitor in the first capacitor group C17, thereby charging the third capacitor, and then generating a voltage signal of the second target frequency between the ground line PE and the neutral line N, and the voltage amplitude of the voltage signal of the second target frequency is within the second target range. On the contrary, if the ground wire PE is normally connected to the power grid, the neutral wire N can inject the AC signal output by the second bridge arm into the power grid, then the ground wire PE and the neutral wire N are clamped by the power grid voltage, and the third capacitor in the first capacitor group C11 is not charged. At this time, the voltage signal of the second target frequency will not be generated between the ground wire PE and the neutral wire N, or the voltage amplitude of the voltage signal of the second target frequency generated between the ground wire PE and the neutral wire N is not within the second target range. It can be seen that after the controller injects the harmonic signal of the second target frequency into the second bridge arm, it can detect whether the voltage amplitude of the voltage signal of the second target frequency generated between the ground wire PE and the neutral wire N is within the second target range, and then determine whether the neutral wire is abnormally connected.

[0077] It can be understood that the controller can determine the second target range based on the voltage amplitude of the harmonic signal injected into the second bridge arm and the capacitance of the third capacitor itself, and the second target frequency of the harmonic signal injected into the second bridge arm by the controller can be negatively correlated with the capacitance of the third capacitor. The specific implementation method can be referred to the above Figure 3 In addition, the first target frequency and the second target frequency may be the same or different, and the first target range and the second target range may be the same or different, which are not limited in the embodiment of the present application.

[0078] In some feasible implementations, the specific structure of the power conversion device can also be as follows: Fig.13 As shown, Fig.13 Another schematic diagram of a power conversion device provided in an embodiment of the present application. Fig.13In the power conversion device shown in the figure, the first bridge arm a, the first bridge arm b, the first bridge arm c, the second bridge arm, the positive bus BUS+, the negative bus BUS-, the neutral point BUSN connected to the DC side capacitor Cd1 and the DC side capacitor Cd2, and the first inductor group L1, the switch unit K, the first inductor group L2 and the inductor and capacitor group C5 of the power conversion circuit can refer to the above content and Fig.13 As shown, the embodiments of the present application are not described in detail here. Fig.13 The power conversion circuit shown further includes a third capacitor C3, which is arranged between the neutral line N and the ground line PE.

[0079] It can be understood that the DC end of the power conversion circuit can be the positive bus BUS+, the negative bus BUS-, or the neutral point BUSN to which the DC side capacitor Cd1 and the DC side capacitor Cd2 are connected. Fig.13 The neutral point BUSN is used as an example for illustration, which does not constitute a limitation on the embodiments of the present application. Fig.13 In the power conversion device shown in FIG. 1 , the control can be performed by injecting a harmonic signal of a second target frequency into the second bridge arm, and when the voltage amplitude of the voltage signal of the second target frequency generated between the neutral line N and the ground line PE is within the second target range, the information of abnormal connection of the ground line PE is output. The specific implementation method can refer to the above Figure 3 The specific implementation method of the present application will not be described in detail here.

[0080] In some possible implementations, Figures 10 to 13 The power conversion device shown may also be provided with Figure 6 The first capacitor group C12 shown, or, may be provided with Figure 7 The first capacitor group C13 is shown, and the embodiments of the present application are not illustrated one by one here.

[0081] In general, the power conversion device provided by the embodiment of the present application injects a harmonic signal of the first target frequency into at least one first bridge arm set in the power conversion circuit through a controller, so that the AC output end of the first bridge arm can transmit a voltage signal carrying the first target frequency to the corresponding first wire. Further, the power conversion device is provided with a corresponding first capacitor between each first wire and the DC end of the power conversion device. When the second wire is abnormally connected, the voltage signal of the first target frequency transmitted on the first wire can flow to the DC end of the power conversion device through the first capacitor. At the same time, since the DC end of the power conversion device is connected to the second wire, when the voltage signal of the first target frequency passes through the first capacitor, a voltage signal of the first target frequency will be generated between the first wire and the second wire, and the voltage amplitude of the voltage signal is within the first target range. Therefore, the power conversion device can detect the voltage amplitude of the voltage signal of the first target frequency generated between the first wire and the second wire at this time through the controller. When the voltage amplitude is within the first target range, it indicates that the connection of the second wire is abnormal, and the controller outputs information about the abnormal connection of the second wire. On the contrary, when the voltage amplitude of the voltage signal of the first target frequency generated between the first wire and the second wire is outside the first target range, it indicates that there is no abnormality in the connection of the second wire, and the controller can output information that the second wire is connected normally, or not output information, indicating that there is no abnormal connection. Specifically, in the case where the power conversion device includes a neutral wire, the second wire can be the neutral wire to be detected. In the case where the power conversion device includes a ground wire, the second wire can be the ground wire to be detected. In the case where the power conversion device includes a neutral wire and a ground wire, the second wire can be the neutral wire and the ground wire to be detected. It can be seen that the power conversion device provided in the embodiment of the present application can detect whether the neutral wire or the ground wire is abnormally connected, and can also detect whether the neutral wire and the ground wire are abnormally connected at the same time, to ensure the stability and safety of power supply, and is suitable for various power grid systems and power supply scenarios, and at the same time has a simple structure and is easy to implement.

Claims

1. A power conversion device, characterized in that: The invention comprises a power conversion circuit, a controller, at least one first capacitor, at least one first wire and at least one second wire; wherein any one of the first wires is connected in series with a first inductor; the power conversion circuit comprises at least one first bridge arm, the AC output end of each of the first bridge arms is connected to a corresponding one of the first wires, the first end of the first capacitor corresponding to each of the first bridge arms is connected to a side of the first inductor on the first wire away from the first bridge arm, and the second end of the first capacitor corresponding to each of the first bridge arms is connected to a DC end of the power conversion circuit and a corresponding one of the second wires; Wherein, the first conductor is a live wire, and the at least one second conductor includes at least one of a neutral wire and a ground wire; The controller is used to, after injecting a harmonic signal of a first target frequency into at least one of the first bridge arms in the power conversion circuit, output information about abnormal connection of the second wire when a voltage amplitude of a voltage signal of the first target frequency generated between the first wire and the second wire is within a first target range.

2. The power conversion device according to claim 1, characterized in that: The first target range includes a voltage greater than a first voltage threshold, the first voltage threshold is positively correlated with the voltage amplitude of the harmonic signal of the first target frequency, the first voltage threshold is negatively correlated with the capacitance of the first capacitor, and the controller is further used to: When the voltage amplitude of the voltage signal of the first target frequency generated between the first wire and the second wire is greater than the first voltage threshold, information that the second wire is abnormally connected is output.

3. The power conversion device according to claim 1, characterized in that: The first target range includes a target interval greater than a second voltage threshold and less than a third voltage threshold, the second voltage threshold and the third voltage threshold are positively correlated with the voltage amplitude of the harmonic signal of the first target frequency, and the second voltage threshold and the third voltage threshold are negatively correlated with the capacitance of the first capacitor, and the controller is further used to: When the voltage amplitude of the voltage signal of the first target frequency generated between the first wire and the second wire is greater than the second voltage threshold and less than the third voltage threshold, information that the second wire is abnormally connected is output.

4. The power conversion device according to any one of claims 1 to 3, characterized in that: The voltage amplitude of the harmonic signal of the first target frequency is negatively correlated with the capacitance of the first capacitor.

5. The power conversion device according to any one of claims 1 to 4, characterized in that: The AC output end of each first bridge arm of the power conversion circuit is used to connect an AC load through the corresponding first wire, and the controller is used to: When the harmonic signal of the first target frequency is injected into at least one of the first bridge arms in the power conversion circuit, the fundamental wave signal is transmitted to the AC load through the first wire corresponding to the at least one first bridge arm.

6. The power conversion device according to any one of claims 1 to 5, characterized in that: Two second conducting wires are included, one of which is the neutral wire and the other is the ground wire.

7. The power conversion device according to any one of claims 1 to 5, characterized in that: The invention comprises a second conductor, which is the neutral line. The power conversion device further comprises a ground line and a third capacitor, and the neutral line is connected in series with a second inductor. The AC output end of the second bridge arm in the power conversion circuit is connected to the neutral line, the first end of the third capacitor is connected to the side of the second inductor on the neutral line away from the second bridge arm, and the second end of the third capacitor is connected to the ground line and the DC end of the power conversion circuit. The controller is also used for: A harmonic signal of a second target frequency is injected into the second bridge arm in the power conversion circuit, and when the voltage amplitude of the voltage signal of the second target frequency generated between the neutral line and the ground line is within a second target range, information on abnormal ground line connection is output.

8. The power conversion device according to any one of claims 1 to 7, characterized in that: The power conversion device also includes a positive bus capacitor and a negative bus capacitor connected in series to a neutral point, the positive bus capacitor is connected to a positive DC bus, and the negative bus capacitor is connected to a negative DC bus: the power conversion circuit is connected in parallel between the positive DC bus and the negative DC bus and is connected to the neutral point; the DC end of the power conversion circuit is any one of the neutral point, the positive DC bus or the negative DC bus.

9. The power conversion device according to any one of claims 1 to 8, characterized in that: The power conversion device further comprises at least one first switch unit, each of the first switch units being arranged between a corresponding first inductor and an AC load; The controller is used to inject a harmonic signal of a first target frequency into at least one of the first bridge arms in the power conversion circuit, including: The controller is used for injecting a harmonic signal of the first target frequency into at least one first bridge arm corresponding to the at least one first switch unit in the power conversion circuit after controlling the at least one first switch unit to be turned on.

10. The power conversion device according to claim 9, characterized in that: The power conversion device further includes a second switch unit, which is arranged between a DC end of the power conversion circuit and a second end of the first capacitor, and the second end of the first capacitor is also connected to the second wire; The controller is used to inject a harmonic signal of a first target frequency into at least one of the first bridge arms in the power conversion circuit, including: The controller is used to inject a harmonic signal of the first target frequency into at least one of the first bridge arms corresponding to the at least one first switch unit in the power conversion circuit after controlling the second switch unit and the at least one first switch unit to be turned on.

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