Alternating current power failure fault detection method, device, system and control unit

Abstract

The embodiment of the invention provides an alternating current power failure fault detection method, device and system and a control unit, and relates to the technical field of power electronics. The method comprises the following steps: acquiring an AC side fault state of AC-DC power conversion equipment; if the alternating current side fault state indicates that the alternating current-direct current power conversion equipment has the alternating current fault, controlling the alternating current-direct current power conversion equipment to shut down, and obtaining alternating current detection electrical parameters after shutdown; and performing AC power failure fault detection on the AC-DC power conversion equipment according to the AC detection electrical parameters to obtain an AC power failure fault detection result of the AC-DC power conversion equipment. According to the invention, based on the AC detection electrical parameters after shutdown, AC power failure fault detection is carried out on the AC-DC power conversion equipment, and then specific reasons for generating the AC power failure fault are accurately identified, so that the reliability of the AC power failure fault detection system and the AC-DC power conversion equipment is improved.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to an AC power failure detection method, device, system and control unit. Background Art

[0002] Since the AC / DC power conversion equipment in the AC power failure fault detection system is connected to the grid-connected switch, when the grid-connected switch is manually disconnected (such as suddenly switching off the switch), a series of faults will occur in the AC / DC power conversion equipment that is running on the grid, such as AC side (AC) over-voltage or under-voltage fault, DC side (DC) under-voltage fault, or AC side (AC) over-frequency or under-frequency fault, etc. However, the AC power failure fault detection system cannot accurately distinguish whether the AC power failure is caused by a sudden switch off or by a grid abnormality.

[0003] At present, AC power failures caused by power grid abnormalities can only be identified based on the detection electrical parameters of the AC / DC power conversion equipment. That is, the existing technology can identify normal AC failures, but cannot identify AC power failures caused by sudden power outages, that is, cannot identify abnormal AC failures, resulting in continuous occurrence of AC power failures, causing damage to the AC / DC power conversion equipment, thereby reducing the reliability of the AC power failure fault detection system. Summary of the invention

[0004] The purpose of the present application includes, for example, providing an AC power failure fault detection method, device, system and control unit, which can obtain the AC detection electrical parameters after shutdown according to the fault state of the AC side, so as to perform AC power failure fault detection on the AC-DC power conversion equipment according to the AC detection electrical parameters, and then accurately identify the specific cause of the AC power failure fault, and then identify abnormal AC faults (i.e., AC power failure faults), such as AC side overvoltage or abnormal DC bus state caused by power outage, thereby improving the reliability of the AC power failure fault detection system and the AC-DC power conversion equipment.

[0005] In order to achieve the above purpose, the technical solution adopted in the embodiment of the present application is as follows:

[0006] In a first aspect, an embodiment of the present application provides an AC power failure fault detection method, comprising:

[0007] Obtaining the AC side fault status of the AC / DC power conversion equipment;

[0008] If the AC side fault state indicates that the AC-DC power conversion device has an AC fault, the AC-DC power conversion device is controlled to shut down, and the AC detection electrical parameters after the shutdown are obtained;

[0009] An AC power failure fault detection is performed on the AC / DC power conversion device according to the AC detection electrical parameter to obtain an AC power failure fault detection result of the AC / DC power conversion device, wherein the AC power failure fault detection result is used to indicate whether the AC / DC power conversion device has an AC power failure fault.

[0010] Optionally, the method further comprises:

[0011] Determine the grid-connected operation mode of the AC / DC power conversion device; wherein the grid-connected operation mode is any one of a DC constant voltage mode and an AC / DC charging and discharging mode.

[0012] Optionally, if the grid-connected operation mode is a DC constant voltage mode, the acquiring of the AC side fault state of the AC / DC power conversion device includes:

[0013] Obtaining electrical parameters of a DC bus of the AC / DC power conversion device;

[0014] Determine whether the DC bus electrical parameter is continuously greater than a first preset threshold value within a first preset time;

[0015] If the DC bus electrical parameter is continuously greater than the first preset threshold value within the first preset time, determining that the AC side fault state is a first fault state to indicate that there is no AC fault in the AC / DC power conversion device;

[0016] If the DC bus electrical parameter is not continuously greater than the first preset threshold within the first preset time, the AC side fault state is determined to be a second fault state to indicate that an AC fault exists in the AC / DC power conversion device.

[0017] Optionally, determining whether the DC bus electrical parameter is continuously greater than a first preset threshold within a first preset time includes:

[0018] Determining a DC bus deviation parameter of the DC bus electrical parameter within the first preset time;

[0019] Determine whether the DC bus deviation parameter within the first preset time is continuously greater than a preset deviation threshold, where the first preset threshold is the preset deviation threshold.

[0020] Optionally, if the grid-connected operation mode is an AC / DC charging and discharging mode, the acquiring of the AC side fault state of the AC / DC power conversion device includes:

[0021] According to the AC detection electrical parameters, performing island detection on the AC / DC power conversion device to obtain an island detection result;

[0022] If the islanding detection result indicates that the AC-DC power conversion device is not in an islanding operation state, the AC side fault state is determined according to the AC detection electrical parameter.

[0023] Optionally, performing AC power failure fault detection on the AC / DC power conversion device according to the AC detection electrical parameter to obtain an AC power failure fault detection result of the AC / DC power conversion device includes:

[0024] Determining active electrical parameters according to the AC detection electrical parameters;

[0025] If the active electrical parameter is lower than a preset minimum electrical parameter, determining an active deviation parameter between the active electrical parameter and the preset minimum electrical parameter;

[0026] If the active power deviation parameter is continuously lower than the second preset threshold value within the second preset time, determining that the AC power failure fault detection result is a first detection result, so as to indicate that the AC / DC power conversion device has an AC power failure fault;

[0027] If the active deviation parameter is not continuously lower than the second preset threshold within the second preset time, the AC power failure fault detection result is determined to be a second detection result to indicate that there is no AC power failure in the AC / DC power conversion device.

[0028] Optionally, the method further comprises:

[0029] If the AC power failure fault detection result indicates that the AC-DC power conversion device has an AC power failure fault, reporting first fault indication information to indicate that the AC-DC power conversion device has an AC power failure fault;

[0030] If the AC power failure fault detection result indicates that the AC / DC power conversion device does not have an AC power failure fault, second fault indication information is reported to indicate that the AC / DC power conversion device has an AC fault.

[0031] In a second aspect, an embodiment of the present application provides an AC / DC power conversion device, the AC / DC power conversion device comprising: an AC / DC power conversion unit, a control unit, and a phase-locked loop;

[0032] The control unit is respectively connected to the input end of the AC / DC power conversion unit and the output end of the AC / DC power conversion unit; the output end of the AC / DC power conversion unit is also connected to the input end of the phase-locked loop; the output end of the phase-locked loop is connected to the control unit;

[0033] The control unit is used to execute the AC power failure fault detection method described in any one of the first aspects above.

[0034] In a third aspect, an embodiment of the present application provides an AC power failure fault detection system, the AC power failure fault detection system comprising: the AC / DC power conversion device, the grid-connected switch and the energy storage device described in the second aspect above;

[0035] The input end of the AC / DC power conversion device is connected to the energy storage device; the output end of the AC / DC power conversion device is connected to the grid-connected switch; and the grid-connected switch is connected to a preset power grid;

[0036] The AC / DC power conversion device is used to execute the AC power failure fault detection method described in any one of the first aspects above.

[0037] In a fourth aspect, an embodiment of the present application provides a control unit, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores a computer program executable by the at least one processor, and the computer program is executed by the at least one processor so that the at least one processor can execute the AC power failure fault detection method described in any one of the first aspects.

[0038] The beneficial effects of the embodiments of the present application include, for example:

[0039] The embodiments of the present application provide an AC power failure fault detection method, device, system and control unit. The method includes: by acquiring the AC side fault status of an AC / DC power conversion device, and when the AC side fault status indicates that the AC / DC power conversion device has an AC fault, controlling the AC / DC power conversion device to shut down, and acquiring AC detection electrical parameters after the shutdown, so as to perform AC power failure fault detection on the AC / DC power conversion device according to the AC detection electrical parameters, and obtain an AC power failure fault detection result of the AC / DC power conversion device, which is used to indicate whether the AC / DC power conversion device has an AC power failure fault, and then accurately identifying the specific cause of the AC power failure fault, and then identifying abnormal AC faults (i.e., AC power failure faults), such as AC side overvoltage or abnormal DC bus state caused by power outage, thereby improving the reliability of the AC power failure fault detection system and the AC / DC power conversion device. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0041] Figure 1A schematic diagram of the structure of an AC power failure detection system provided in an embodiment of the present application Figure 1 ;

[0042] Figure 2 A schematic diagram of the structure of an AC power failure detection system provided in an embodiment of the present application Figure 2 ;

[0043] Figure 3 A schematic diagram of the structure of an AC power failure detection system provided in an embodiment of the present application Figure 3 ;

[0044] Figure 4 A schematic diagram of the structure of a DC constant voltage ring provided in an embodiment of the present application;

[0045] Figure 5 A schematic diagram of the structure of a control unit provided in an embodiment of the present application;

[0046] Figure 6 A schematic diagram of a method for detecting AC power failure provided in an embodiment of the present application Figure 1 ;

[0047] Figure 7 A schematic diagram of a method for detecting AC power failure provided in an embodiment of the present application Figure 2 ;

[0048] Figure 8 A schematic diagram of a method for detecting AC power failure provided in an embodiment of the present application Figure 3 ;

[0049] Fig. 9 A schematic diagram of a method for detecting AC power failure provided in an embodiment of the present application Figure 4 ;

[0050] Fig.10 A schematic diagram of a method for detecting AC power failure provided in an embodiment of the present application Figure 5 ;

[0051] Fig.11 A schematic diagram of a method for detecting AC power failure provided in an embodiment of the present application Figure 6 ;

[0052] Fig.12 A schematic diagram of the structure of an AC power failure detection device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0054] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0055] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0056] In the description of the present application, it should be noted that if the terms "upper", "lower", "inside", "outside", etc. appear to indicate an orientation or position relationship, it is based on the orientation or position relationship shown in the drawings, or is the orientation or position relationship in which the product of the invention is usually placed when used. It is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0057] In addition, the terms “first”, “second”, etc., if used, are merely used to distinguish between the descriptions and should not be understood as indicating or implying relative importance.

[0058] It should be noted that, in the absence of conflict, the features in the embodiments of the present application may be combined with each other.

[0059] In order to clearly describe an AC power failure fault detection method, device, system and control unit provided in an embodiment of the present application, the AC power failure fault detection system is first described in detail with reference to the accompanying drawings. Figure 1 A schematic diagram of the structure of an AC power failure detection system provided in an embodiment of the present application Figure 1 .like Figure 1 As shown, the AC power failure fault detection system 200 may include: an energy storage device 210 , a grid-connected switch 220 and an AC / DC power conversion device 100 .

[0060] The input end of the AC / DC power conversion device 100 is connected to the energy storage device 210 to provide electrical parameters to the AC / DC power conversion device 100 through the energy storage device 210; the output end of the AC / DC power conversion device 100 is connected to the grid-connected switch 220, and the grid-connected switch 220 is connected to the preset power grid. If the grid-connected switch 220 is closed, it means that the AC power failure fault detection system 200 is in a grid-connected state, and the AC power parameters can be input into the preset power grid through the grid-connected switch 220; if the grid-connected switch 220 is disconnected, it means that the AC power failure fault detection system 200 is in a power failure and off-grid state. The preset power grid can be selected according to actual conditions. For example, the preset power grid can be selected as an external AC power grid (such as a municipal power grid).

[0061] The AC / DC power conversion device 100 is used to execute the AC power failure fault detection method. The AC / DC power conversion device 100 can be selected as a PCS.

[0062] The energy storage device 210 can be composed of a preset signal source and a capacitor Cdc in parallel; wherein the preset signal source can be selected according to actual conditions, for example, the preset signal source can be an energy storage unit (such as a battery), or a non-energy storage unit (such as a resistive load or a converter load), etc.

[0063] It should be noted that the grid-connected switch 220 may be provided in the AC power failure fault detection system 200 or in the AC / DC power conversion device 100, and no limitation is made here.

[0064] The AC power failure fault detection system provided in the embodiment of the present application provides electrical parameters to the input end of the AC / DC power conversion device through an energy storage unit, the output end of the AC / DC power conversion device is connected to a grid-connected switch, and the grid-connected switch is connected to a preset power grid, so that when the grid-connected switch is closed, the output electrical parameters of the AC / DC power conversion device are input into the preset power grid, and when the grid-connected switch is disconnected, power failure fault detection can be performed on the output electrical parameters of the AC / DC power conversion device, that is, whether a power failure occurs in the AC side of the AC power failure fault detection device according to the status information of the grid-connected switch, so as to improve the reliability and safety of the AC power failure fault detection system.

[0065] Furthermore, in order to clearly describe the AC power failure fault detection system 200 provided in the above embodiment, the present application also provides a structural schematic diagram of another AC power failure fault detection system. Figure 2 A schematic diagram of the structure of an AC power failure detection system provided in an embodiment of the present application Figure 2 .like Figure 2 As shown, the AC / DC power conversion device 100 may include: an AC / DC power conversion unit 110 , a control unit 120 and a phase-locked loop 130 .

[0066] Among them, the control unit 120 is respectively connected to the input end of the AC / DC power conversion device 110 and the output end of the AC / DC power conversion unit 110 to obtain the DC detection electrical parameters of the input end of the AC / DC power conversion device 110 and the AC detection electrical parameters of the output end of the AC / DC power conversion device 110; the output end of the AC / DC power conversion unit 110 is also connected to the input end of the phase-locked loop 130, and the output end of the phase-locked loop 130 is connected to the control unit 120 to process the output signal of the AC / DC power conversion unit 110 through the phase-locked loop 130, and transmit the processed signal to the control unit 120, so that the control unit 120 controls the input end of the AC / DC power conversion unit 110 according to the processed signal.

[0067] The AC / DC power conversion unit 110 can convert DC input electrical parameters into AC output electrical parameters. The AC / DC power conversion unit 110 can be selected according to actual conditions. For example, the AC / DC power conversion unit 110 can be selected as a grid-connected inverter.

[0068] It should be noted that the topology of the AC / DC power conversion unit 110 is not limited in this application, and the topology of the AC / DC power conversion unit 110 can be a two-level inverter or a three-level inverter. Figure 2 The topological structure of the AC / DC power conversion unit 110 is a two-level inverter, which is composed of three groups of switch tube units connected in parallel, wherein one group of switch tube units is composed of two switch tubes connected in series.

[0069] The control unit 120 is used to execute the AC power failure detection method.

[0070] The phase-locked loop 130 is used to process the received signal and extract the phase information of a clock signal therefrom. For example, the phase-locked loop 130 can output information of the preset power grid such as amplitude, phase ω and frequency θ through the three-phase voltage (such as VA, VB, VC) on the AC side of the input AC / DC power conversion device when the grid-connected switch 220 is closed. Among them, there are two amplitudes, such as the active component Vq and the reactive component Vd, and the amplitude depends on the transformation matrix formula of the phase-locked loop 130. Among them, the active component Vq can be an active component oriented on the preset power grid vector, and the reactive component Vd can be a reactive component at a vertical angle of 90 degrees. Then, when the three-phase voltage (such as VA, VB, VC) on the AC side of the AC / DC power conversion device is connected to the preset power grid through the grid-connected switch 220, that is, when the grid-connected switch 220 is closed, the active component Vq can be the phase voltage amplitude of the preset power grid, and the reactive component Vd is 0. When the three-phase voltage (such as VA, VB, VC) on the AC side of the AC / DC power conversion device is DC, that is, when the grid-connected switch 220 is disconnected, the active component Vq and the reactive component Vd are both sinusoidal waves with an average value of 0.

[0071] It should be noted that, since the control unit 120 is connected to the input end of the AC / DC power conversion device 110, but since the input end of the AC / DC power conversion device 100 is connected to the energy storage device 210, the output end of the energy storage device 210 is the input end of the AC / DC power conversion device 110, that is, the control unit 120 is connected to the output end of the energy storage device 210, so that the control unit 120 can monitor the electrical parameters of the energy storage device 210. Similarly, since the control unit 120 is connected to the output end of the AC / DC power conversion device 110, but since the output end of the AC / DC power conversion device 100 is connected to the grid-connected switch 220, the input end of the grid-connected switch 220 is the output end of the AC / DC power conversion device 110, that is, the control unit 120 is connected to the input end of the grid-connected switch 220, so that the control unit 120 can monitor the input end of the grid-connected switch 220. In addition, it should be noted that since the control unit 120 is connected to the input end of the AC / DC power conversion device 110, the control unit 120 needs to also monitor the input end electrical parameters of the energy storage device 210 connected to the input end of the AC / DC power conversion device 110, so as to avoid changes in the electrical parameters of the input end of the AC / DC power conversion device 110 due to changes in the electrical parameters of the input end of the energy storage device 210.

[0072] Furthermore, in order to ensure the reliability of the data at the output end of the AC / DC power conversion unit 110 , the AC / DC power conversion device 100 may further include: a filtering module 140 .

[0073] Among them, the output end of the AC / DC power conversion unit 110 is connected to the grid-connected switch 22 through the filtering module 140, so that the DC power parameters at its input end are converted into AC power parameters through the AC / DC power conversion unit 110, and the AC power parameters at the output end of the AC / DC power conversion unit 110 are filtered through the filtering module 140 to improve the electromagnetic compatibility of the AC / DC power conversion device 100.

[0074] Among them, the filter module 140 is composed of three groups of filter units and one electromagnetic filter unit (EMC, ElectroMagnetic Compatibility), wherein one group of filter units can be composed of an inductor L; the filter module 140 is used to filter the AC power parameters output by the AC / DC power conversion device 110 to improve the electromagnetic compatibility of the AC / DC power conversion device 110.

[0075] In one possible implementation, the grid-connected operation structure corresponding to the AC power failure fault detection system is different according to the type of the preset signal source in the energy storage device 210. For example, if the preset signal source in the energy storage device 210 is a non-energy storage device (such as a resistive load or a converter load), then Figure 3 A schematic diagram of the structure of an AC power failure detection system provided in an embodiment of the present application Figure 3 .like Figure 3 As shown, the AC / DC power conversion device 100 may further include: a DC constant voltage ring 150 .

[0076] The first input end of the DC constant voltage loop 150 is the output end of the energy storage device 210; the second input end of the DC constant voltage loop 150 is the output end of the phase-locked loop 130; the output end of the DC constant voltage loop 150 is connected to the controller to control the input end of the AC / DC power conversion unit 110 according to the output signal of the DC constant voltage loop 150.

[0077] in, Figure 4 This is a schematic diagram of the structure of a DC constant voltage ring provided in an embodiment of the present application. Figure 4 As shown, the DC constant voltage loop 150 may include: a DC voltage loop 151 , an inductor current loop 152 and a wave generating unit 153 .

[0078] Among them, the DC voltage loop 151 is composed of an operation unit, a PI modulator and an inverse transformation unit, wherein the first input signal of the operation unit is a given setting value Vdc* (target DC bus electrical parameter) of the DC bus voltage, and the second input signal is the DC bus voltage Vdc. The two input signals are passed through the operation unit to obtain a DC bus deviation voltage ΔVdc, and the DC bus deviation voltage ΔVdc is input into the PI modulator to obtain a voltage regulation amount, and the voltage regulation amount is input into the inverse transformation unit to output a given setting value IL* (such as IL_a*, IL_b*, IL_c*) of the three-phase current.

[0079] Then, according to the given setting value IL* (such as IL_a*, IL_b*, IL_c*) of the three-phase current and the three-phase current IL, the inductor current loop 152 is input, and the wave generating unit 153 is controlled to generate waves according to the output of the inductor current loop 152, so as to control the input end of the power conversion device 110 according to the waveform generated by the wave generating unit 153. Among them, the wave generating unit 153 is composed of a three-phase PWM modulation unit (such as PWMA, PWMB, PWMC).

[0080] It should be noted that, in the DC constant voltage loop 150, the inductor current loop 152 can also be omitted, and the three-phase current IL output by the inverse conversion unit in the DC voltage loop 151 can be directly used to control the wave generating unit 153 for wave generating.

[0081] It can be seen that when the preset signal source is a non-energy storage device, the output end of the energy storage device 210 is mainly controlled according to the DC constant voltage loop 150 to achieve control of the input end of the AC / DC power conversion unit 110.

[0082] The AC / DC power conversion device provided in the embodiment of the present application comprises a control unit connected to the input end and the output end of the AC / DC power conversion unit, respectively, to monitor the input and output signals of the power conversion unit; the output end of the AC / DC power conversion unit is also connected to the input end of a phase-locked loop; the output end of the phase-locked loop is connected to the control unit; the control unit is used to execute an AC power failure fault detection method to collect the electrical signal at the output end of the AC / DC power conversion unit through the phase-locked loop, so as to judge whether a power failure fault occurs on the AC side of the AC / DC power conversion unit according to the output signal of the phase-locked loop, so as to improve the reliability and safety of the AC fault detection system.

[0083] Furthermore, in order to clearly describe the AC power failure fault detection system 200 provided in the above embodiment, the present application also provides a structural diagram of a control unit 120. Figure 5 This is a schematic diagram of the structure of a control unit provided in an embodiment of the present application. Figure 5 As shown, the control unit 120 may include: a processor 121 and a memory 122 .

[0084] The memory 122 stores machine executable instructions that can be executed by the processor 121, that is, when the control unit 120 is running, the above machine readable instructions are executed, and the processor 121 communicates with the memory 122 via a bus. The processor 121 can execute the machine executable instructions to implement the AC power failure detection method.

[0085] The memory 122, the processor 121 and the bus components are electrically connected to each other directly or indirectly to achieve data transmission or interaction. For example, these components can be electrically connected to each other through one or more communication buses or signal lines. The mobile storage device includes at least one software function module that can be stored in the memory 122 in the form of software or firmware or solidified in the operating system (OS) of the electronic device. The processor 121 is used to execute the executable module stored in the memory 122, such as the software function module and computer program included in the AC power failure detection method of the mobile storage medium.

[0086] Among them, the memory 122 can be, but is not limited to, random access memory (Random Access Memory, RAM), read only memory (Read Only Memory, ROM), programmable read-only memory (Programmable Read-Only Memory, PROM), erasable programmable read-only memory (Erasable Programmable Read-Only Memory, EPROM), electrically erasable read-only memory (Electric Erasable Programmable Read-Only Memory, EEPROM), etc.

[0087] The AC power failure fault detection method provided in the embodiment of the present application can be executed by the processor in the control unit 120. The AC power failure fault detection method provided in the above embodiment of the present application is explained and illustrated in detail in conjunction with the accompanying drawings. Figure 6 A schematic diagram of a method for detecting AC power failure provided in an embodiment of the present application Figure 1 .like Figure 6 As shown, the method may include:

[0088] S301. Acquire an AC side fault state of an AC / DC power conversion device.

[0089] In one possible implementation, reference Figure 2 According to the state parameters of the grid-connected switch collected by the control unit in the AC / DC power conversion device, the AC side fault state of the AC / DC power conversion device is determined. The AC side fault state can be selected according to the actual situation. For example, the AC side fault state can be an overvoltage of the power grid or an over-frequency or under-frequency of the power grid.

[0090] S302: If the AC side fault state indicates that the AC / DC power conversion device has an AC fault, the AC / DC power conversion device is controlled to shut down, and AC detection electrical parameters after the shutdown are obtained.

[0091] In one possible implementation, if the AC side fault status indicates that there is an AC fault in the AC / DC power conversion device, that is, there is an AC fault such as overvoltage, over-frequency or under-frequency on the AC side of the AC / DC power conversion device, then the AC power failure fault detection system needs to be shut down to ensure the safety of the AC power failure fault detection system. When the AC / DC power conversion device is shut down, the input end of the AC / DC power conversion device is in a blocked wave state, that is, the AC / DC power conversion device is no longer open-loop inverted, that is, the AC / DC power conversion device is not in an open-circuit operation state. At this time, the AC detection electrical parameters of the output end of the AC / DC power conversion device can be obtained. For example, the AC detection electrical parameters can be the three-phase voltage on the AC side of the AC / DC power conversion device (such as Figure 2VA, VB, VC).

[0092] S303 , performing AC power failure fault detection on the AC / DC power conversion device according to the AC detection electrical parameters, and obtaining an AC power failure fault detection result of the AC / DC power conversion device.

[0093] In a possible implementation, according to the AC detection electrical parameters obtained in step S203, an AC power failure fault detection is performed on the output end of the AC / DC power conversion device or the input end of the grid-connected switch to obtain an AC power failure fault detection result of the AC / DC power conversion device. The AC power failure fault detection result is used to indicate whether the AC / DC power conversion device has an AC power failure fault.

[0094] The embodiment of the present application provides a power failure fault detection method, which obtains the AC side fault status of an AC / DC power conversion device, and when the AC side fault status indicates that the AC / DC power conversion device has an AC fault, controls the AC / DC power conversion device to shut down, and obtains the AC detection electrical parameters after the shutdown, so as to perform AC power failure fault detection on the AC / DC power conversion device according to the AC detection electrical parameters, and obtain an AC power failure fault detection result of the AC / DC power conversion device, which is used to indicate whether the AC / DC power conversion device has an AC power failure fault, and then accurately identifies the specific cause of the AC power failure fault, and then identifies abnormal AC faults (i.e., AC power failure faults), such as AC side overvoltage or abnormal DC bus state caused by power outage, thereby improving the reliability of the AC power failure fault detection system and the AC / DC power conversion device.

[0095] Optionally, in a possible implementation example, the method may further include:

[0096] Determine the grid-connected operation mode of AC / DC power conversion equipment.

[0097] The grid-connected operation mode is any one of a DC constant voltage mode and an AC / DC charging and discharging mode.

[0098] In one possible implementation, before the AC / DC power failure detection system is powered on, the control unit needs to select the grid-connected operation mode of the AC / DC power conversion device corresponding to different preset working conditions according to the preset working conditions, that is, different grid-connected operation modes are set according to different preset working conditions to ensure that after the AC / DC power failure detection system is powered on, it can operate according to the selected grid-connected operation mode of the AC / DC power conversion device. Among them, the preset working condition can be selected according to the actual situation. For example, if the preset working condition is a distributed energy storage working condition, in the distributed energy storage working condition, it is necessary to Figure 2The energy storage device 210 shown in the figure performs charging and discharging operations, and the preset signal source in the energy storage device 210 is an energy storage unit (such as a battery); if the preset working condition is a DC bus stable working condition, under the DC bus stable working condition, it is necessary to Figure 2 The energy storage device 210 shown is set to a constant voltage state, and the preset signal source in the energy storage device 210 is a non-energy storage unit (such as a resistive load or a converter load).

[0099] In this application, if the preset operating condition is a distributed energy storage condition, the grid-connected operation mode corresponding to the distributed energy storage condition is an AC / DC charging and discharging mode; if the preset operating condition is a DC bus stable condition, the grid-connected operation mode corresponding to the DC bus stable condition is a DC constant voltage mode.

[0100] After being powered on, the AC / DC power-off fault detection system can execute the AC / DC power-off fault detection logic according to the determined grid-connected operation mode. Different grid-connected operation modes correspond to different AC / DC power-off fault detection logics. For example, if the grid-connected operation mode is the AC / DC charge-discharge mode, the AC / DC power-off fault detection system executes the charge-discharge operation power-off detection logic with battery; if the grid-connected operation mode is the DC constant voltage mode, the AC / DC power-off fault detection system can execute the DC constant voltage loop state detection and the AC / DC power-off fault detection logic of the AC side detection.

[0101] It should be noted that when the grid-connected operation mode of the control unit is determined, that is, the operation mode of the AC / DC power failure fault detection system after power-on is also determined. When the AC / DC power failure fault detection system is powered on, it can be executed according to the determined operation mode, and there is no situation of changing the grid-connected operation mode in the middle. In addition, it should be noted that when the AC / DC power failure fault detection system selects the grid-connected operation mode according to the preset working conditions, the selected grid-connected operation mode is sent to the control unit in the AC / DC power conversion device. The AC / DC power conversion device first checks and judges whether the currently selected grid-connected operation mode meets the operation requirements of the AC / DC power conversion device. If the currently selected grid-connected operation mode meets the operation requirements of the power conversion device, the AC / DC power failure fault detection system is powered on, and the corresponding AC / DC power failure fault detection logic is executed according to the grid-connected operation mode; if the currently selected grid-connected operation mode does not meet the operation requirements of the AC / DC power conversion device, the system is shut down and replaced with a new grid-connected operation mode to ensure that the selected grid-connected operation mode meets the operation requirements of the AC / DC power conversion device and improve the reliability and safety of the AC / DC power failure fault detection system.

[0102] The power failure fault detection method provided in the above embodiment of the present application is explained and illustrated in detail below in conjunction with the accompanying drawings. Figure 7 A schematic diagram of a method for detecting AC power failure provided in an embodiment of the present application Figure 2 .like Figure 7As shown, in the above method, if the grid-connected operation mode is a DC constant voltage mode, obtaining the AC side fault state of the AC / DC power conversion device may include:

[0103] S401. Obtain electrical parameters of a DC bus of an AC / DC power conversion device.

[0104] In a possible implementation, after the grid-connected operation mode of the AC / DC power conversion device is determined, that is, if the grid-connected operation mode is the DC constant voltage mode, the grid-connected switch in the DC constant voltage mode is suddenly powered off, causing the connection between the grid-connected switch and the preset power grid to be interrupted. The AC / DC power conversion device, which is in operation, suddenly loses the energy source of the preset power grid, resulting in the AC / DC power conversion device being unable to effectively support the DC bus electrical parameter Vdc, causing the DC bus electrical parameter Vdc to drop out of control. At the same time, in order to support the DC bus electrical parameter Vdc as much as possible, the AC / DC power conversion device saturates the modulation wave duty cycle of the wave generating unit, causing the switch tube in the AC / DC power conversion device to be abnormal in state, and then inverting the energy of the DC bus electrical parameter Vdc to the AC side. However, since the grid-connected switch on the AC side of the AC / DC power conversion device is powered off, the well network switch is in a no-load off-grid state, and then there is no load on the AC side of the AC / DC power conversion device to absorb the inverted energy, resulting in abnormal AC side electrical parameters.

[0105] Therefore, based on the above analysis, the DC bus electrical parameter Vdc at the input end of the AC / DC power conversion device can be obtained to detect power failure of the power conversion device according to the DC bus electrical parameter Vdc. The electrical parameter can be selected according to actual conditions, for example, the electrical parameter can be selected as voltage, current, etc.

[0106] It should be noted that in the present application, AC power-off detection in DC constant voltage mode can be achieved by using the DC bus electrical parameters of the AC / DC power conversion equipment, or obtaining the output value of the PI regulator, etc., which should not be understood as a limitation on the present application.

[0107] S402: Determine whether the DC bus electrical parameter is continuously greater than a first preset threshold within a first preset time.

[0108] The first preset threshold value may be selected according to actual conditions, for example, the first preset threshold value may be selected as 50V; the first preset time may also be selected according to actual conditions, for example, the first preset time may be selected as 10S.

[0109] In a possible implementation, it is determined whether the DC bus electrical parameter Vdc is continuously greater than a first preset threshold value (eg, 50V) within a first preset time (eg, 10S). If so, step S403 is executed; if not, step S404 is executed.

[0110] S403: If the DC bus electrical parameter is continuously greater than the first preset threshold value within the first preset time, determine that the AC side fault state is the first fault state to indicate that there is no AC fault in the AC / DC power conversion device.

[0111] In a possible implementation, if the DC bus electrical parameter Vdc is continuously greater than the first preset threshold value (such as 50V) within a first preset time (such as 10S), it means that in the AC power failure fault detection in the DC constant voltage mode of the grid-connected operation mode, the DC bus electrical parameter Vdc has not been able to be in a voltage-stabilizing state. At this time, it can be determined that the AC side fault state is the first fault state, indicating that there is no AC fault in the AC-DC power conversion device. It can be determined that the first fault state is an AC power failure caused by a power failure.

[0112] S404: If the DC bus electrical parameter is not continuously greater than the first preset threshold value within the first preset time, determine that the AC side fault state is a second fault state to indicate that an AC fault exists in the AC / DC power conversion device.

[0113] In a possible implementation, if the DC bus electrical parameter Vdc is not continuously greater than the first preset threshold value (such as 50V) within the first preset time (such as 10S), it means that in the AC power failure fault detection when the grid-connected operation mode is the DC constant voltage mode, a voltage overvoltage or under-frequency fault is detected on the AC side of the AC-DC power conversion device. At this time, the AC side fault state can be determined to be the second fault state to indicate that the AC-DC power conversion device has an AC fault. That is, the second fault state can be determined to be an AC fault caused by a grid abnormality, such as an AC fault such as a grid voltage overvoltage or under-frequency fault.

[0114] The power failure fault detection method provided by the embodiment of the present application obtains the DC bus electrical parameters of the AC / DC power conversion device, and determines whether the DC bus electrical parameters are continuously greater than the first preset threshold value within a first preset time; if the DC bus electrical parameters are continuously greater than the first preset threshold value within the first preset time, the AC side fault state is determined to be the first fault state, indicating that there is no AC fault in the AC / DC power conversion device; if the DC bus electrical parameters are not continuously greater than the first preset threshold value within the first preset time, the AC side fault state is determined to be the second fault state, indicating that there is an AC fault in the AC / DC power conversion device, to determine that the grid-connected operation mode is the DC constant voltage mode, and according to the operation characteristics of the DC constant voltage mode, the AC power failure fault caused by the power outage is accurately identified, and according to the AC power failure fault detection logic in the DC constant voltage mode, that is, the loop state detection and the AC side power failure detection logic, it is avoided that the AC power failure fault detection system is in a fault state for a long time due to sudden power failure, thereby improving the reliability of the AC power failure fault detection system and the AC / DC power conversion device.

[0115] The power failure fault detection method provided in the above embodiment of the present application is explained and illustrated in detail below in conjunction with the accompanying drawings. Figure 8 A schematic diagram of a method for detecting AC power failure provided in an embodiment of the present application Figure 3 .like Figure 8 As shown, in the above method, determining whether the DC bus electrical parameter is continuously greater than the first preset threshold within the first preset time may include:

[0116] S501, determining a DC bus deviation parameter of a DC bus electrical parameter within a first preset time.

[0117] In one possible implementation, referring to the above Figure 4 , obtain the DC bus electrical parameter Vdc and the target DC bus electrical parameter Vdc*, wherein the DC bus electrical parameter Vdc is the actual operating electrical parameter of the DC bus, and the target DC bus electrical parameter Vdc* is the target electrical parameter set for the DC bus electrical parameter. Then, according to the operation unit in the DC voltage loop 151, determine the DC bus electrical parameter Vdc and the target DC bus electrical parameter Vdc*, and the DC bus deviation parameter ΔVdc within a first preset time (e.g., 10S).

[0118] For example, the DC bus deviation parameter ΔVdc may be calculated according to the following formula (1).

[0119] ΔVdc=(Vdc*)-Vdc Formula (1)

[0120] S502: Determine whether a DC bus deviation parameter within a first preset time period is continuously greater than a preset deviation threshold.

[0121] The first preset threshold is a preset deviation threshold, that is, the preset deviation threshold may change with the change of the first preset threshold, and if the first preset threshold is selected as 50V, the preset deviation threshold may be set to 50V.

[0122] In a possible implementation, it is determined whether the DC bus deviation parameter ΔVdc within a first preset time (such as 10S) is continuously greater than a preset deviation threshold (such as 50V). If so, the AC side fault state is determined to be a first fault state to indicate that there is no AC fault in the AC / DC power conversion device; if not, the AC side fault state is determined to be a second fault state to indicate that there is an AC fault in the AC / DC power conversion device.

[0123] It should be noted that if the preset power grid and the grid-connected switch are disconnected, that is, the power is suddenly disconnected, the AC side no longer provides energy, resulting in a decrease in the DC bus electrical parameters; the DC bus electrical parameters increase the DC bus deviation parameters, and the output of the PI modulator increases until the saturation output reaches the maximum duty cycle. However, due to the sudden disconnection of the AC side, the input end of the AC / DC power conversion device is in a no-load state, and the AC / DC power conversion device is a bidirectional topology. The large duty cycle also increases the electrical parameters of the DC bus electrical parameters Vdc that are inverted to the AC side. There is no load consumption in the off-grid no-load state, and the AC side will be in an overvoltage state for a long time. If the electrical parameters of the energy storage unit are very high, the inverter open-loop electrical parameters may also be very high. If the time is long, the AC / DC power conversion device may be damaged. The speed at which the electrical parameters of the energy storage unit decrease depends on the load size of the DC side of the AC / DC power conversion device. The most severe situation is no-load, and the DC bus electrical parameters decrease very slowly. If the inverter overvoltage shutdown is detected, it is impossible to distinguish whether it is an overvoltage caused by disconnection or a real overvoltage of the preset power grid. Furthermore, if the DC side electrical parameters of the AC / DC power conversion device are low and the switch is turned off, the overvoltage state may not be detected. The AC / DC power conversion device may not detect the power failure during long-term open-loop operation, which will reduce the reliability of the AC / DC power conversion device. Therefore, in the DC constant voltage mode, the DC side electrical parameters of the AC / DC power conversion device will inevitably decrease, and the DC bus deviation parameters will increase to above 0V. Therefore, the AC side fault state can be determined by determining the DC bus deviation parameters of the DC bus electrical parameters within the first preset time, and then the AC power failure fault detection result can be determined.

[0124] The power failure fault detection method provided by the embodiment of the present application determines the DC bus deviation parameters of the DC bus electrical parameters and the target DC bus electrical parameters within the first preset time through the DC bus electrical parameters and the target DC bus electrical parameters, and then determines whether the DC bus deviation parameters within the first preset time are continuously greater than the preset deviation threshold value. If so, the AC side fault state is determined to be the first fault state to indicate that there is no AC fault in the AC / DC power conversion device; if not, the AC side fault state is determined to be the second fault state to indicate that there is an AC fault in the AC / DC power conversion device. When determining that the grid-connected operation mode is the DC constant voltage mode, according to the operation characteristics of the DC constant voltage mode, the AC power failure fault caused by the power outage is accurately identified, and according to the AC power failure fault detection logic in the DC constant voltage mode, that is, the loop state detection and the AC side power failure detection logic, it is avoided that the AC power failure fault detection system is in a fault state for a long time due to sudden power failure, thereby improving the reliability of the AC power failure fault detection system and the AC / DC power conversion device.

[0125] The power failure fault detection method provided in the above embodiment of the present application is explained and illustrated in detail below in conjunction with the accompanying drawings. Fig. 9 A schematic diagram of a method for detecting AC power failure provided in an embodiment of the present application Figure 4 .like Fig. 9 As shown, in the above method, if the grid-connected operation mode is the AC / DC charging and discharging mode, obtaining the AC side fault state of the AC / DC power conversion device may include:

[0126] S601. Perform islanding detection on the AC / DC power conversion device according to the AC detection electrical parameters to obtain an islanding detection result.

[0127] In one possible implementation, since the grid-connected operation mode is an AC / DC charging and discharging mode, the preset signal source in the energy storage device may be an energy storage unit (such as a battery). When the voltage of the energy storage unit (such as a battery) remains unchanged, when the grid-connected switch on the AC side of the AC / DC power conversion device is disconnected, the AC side of the AC / DC power conversion device operates in open circuit saturation. Based on the AC detection electrical parameters, an island detection may be performed on the AC / DC power conversion device to obtain an island detection result.

[0128] S602: If the islanding detection result indicates that the AC / DC power conversion device is not in an islanding operation state, determine the AC side fault state according to the AC detection electrical parameters.

[0129] In a possible implementation, if the island detection result indicates that the AC / DC power conversion device is not in an island operation state, since the grid-connected switch is disconnected, the AC side of the general AC / DC power conversion device is in a no-load state, and when the voltage of the energy storage unit (such as a battery) remains constant, the AC side of the AC / DC power conversion device is in open circuit saturation operation, and the AC side fault state can be determined by detecting AC electrical parameters (such as the effective value of the AC side voltage and the phase-locked loop frequency θ). If the AC side fault state is the first fault state, it indicates that there is no AC fault in the AC / DC power conversion device, that is, an AC power-off fault; if the AC side fault state is the second fault state, it indicates that there is an AC fault in the AC / DC power conversion device.

[0130] In a possible implementation manner, if the islanding detection result indicates that the AC / DC power conversion device is in an islanding operation state, then an islanding operation fault exists in the AC / DC power conversion device.

[0131] It should be noted that the detection of the island operation state can be obtained according to the existing technology, which will not be described in detail here. In addition, it should be noted that the island operation fault is a special AC power failure fault.

[0132] The power failure fault detection method provided by the embodiment of the present application can perform island detection on the AC / DC power conversion device according to the AC detection electrical parameters to obtain the island detection result; if the island detection result indicates that the AC / DC power conversion device is not in the island operation state, then the AC side fault state is determined according to the AC detection electrical parameters; if the island detection result indicates that the AC / DC power conversion device is in the island operation state, then the AC / DC power conversion device has an island operation fault. Therefore, the present application determines the real reason for the power failure on the AC side of the initial AC / DC power conversion device according to the island detection result, that is, it is possible to distinguish whether the AC side fault of the AC / DC power conversion device is a power failure caused by a power failure caused by a power outage or a fault caused by an abnormality in the power grid, thereby improving the reliability and safety of the fault detection of the AC fault detection system.

[0133] The power failure fault detection method provided in the above embodiment of the present application is explained and illustrated in detail below in conjunction with the accompanying drawings. Fig.10 A schematic diagram of a method for detecting AC power failure provided in an embodiment of the present application Figure 5 .like Fig.10 As shown, in the above method, performing AC power failure fault detection on the AC / DC power conversion device according to the AC detection electrical parameters to obtain the AC power failure fault detection result of the AC / DC power conversion device may include:

[0134] S701. Determine active electrical parameters according to AC detection electrical parameters.

[0135] In a possible implementation, if the fault on the AC side of the AC / DC power conversion device is an AC power failure, the cause of the fault is an AC power failure caused by a power failure. At this time, due to the disconnection of the grid-connected switch, the voltage on the AC side of the AC / DC power conversion device is approximately 0V, and the voltage amplitude can be judged, such as directly using the active component Vq value. And due to the no-load blocking, the AC side of the AC / DC power conversion device has no load consumption, and the three-phase voltage (such as Figure 2 VA, VB, VC) in the circuit will be converted into DC voltage and then decrease slowly. If the three-phase voltage (such as Figure 2 The amplitude detection of VA, VB, VC) in the circuit may have errors, so the active component Vq of the phase-locked loop can be used for detection.

[0136] And because the grid-connected switch is disconnected, the three-phase voltage (such as Figure 2VA, VB, VC in the active component Vq are all DC inputs, then the active component Vq is a sine wave with an average value of 0V, and the AC component in the active component Vq is filtered out by a preset filter to obtain active electrical parameters. Among them, the preset filter can be selected according to actual conditions, and the bandwidth of the preset filter can be set lower to facilitate filtering the AC component in the active component Vq. For example, the preset filter can be selected as a low-pass filter within 5Hz.

[0137] It should be noted that, in the above embodiment, the preset filter can also be cancelled, and the active component Vq of the phase-locked loop can be directly used as the active electrical parameter. In addition, it should be noted that the value of the active component Vq after passing through the preset filter, that is, the active electrical parameter is used as a complex judgment, which can avoid the residual voltage DC interference on the filter module after the wave is blocked.

[0138] S702: If the active electrical parameter is lower than a preset minimum electrical parameter, determine an active deviation parameter between the active electrical parameter and the preset minimum electrical parameter.

[0139] The preset minimum electrical parameter may be selected according to actual conditions. For example, the preset minimum electrical parameter may be selected as 0V.

[0140] In a possible implementation, if it is detected that the active electrical parameter Vq is lower than a preset minimum electrical parameter (such as 0V), an active deviation parameter between the active electrical parameter Vq and the preset minimum electrical parameter (such as 0V) may be determined.

[0141] S703: If the active power deviation parameter is continuously lower than the second preset threshold value within the second preset time, determine that the AC power failure fault detection result is a first detection result to indicate that an AC power failure fault exists in the AC / DC power conversion device.

[0142] The second preset threshold may represent a certain range of the low voltage undervoltage point (such as 0V). The second preset threshold may be selected according to the actual situation, for example, the second preset threshold may be selected as 311±20%V; the second preset time may be selected according to the actual situation, for example, the second preset time may be selected as 20S.

[0143] In a possible implementation, if the active deviation parameter Vq is continuously lower than the second preset threshold value (such as 311±20%V) within the second preset time (such as 20S), the AC side fault detection result can be determined as the first detection result to indicate that the AC / DC power conversion device has an AC power failure fault. Other faults except the AC power failure fault, such as AC faults (such as overvoltage or undervoltage faults, etc.), are cleared.

[0144] S704: If the active deviation parameter is not continuously lower than the second preset threshold value within the second preset time, determine that the AC power failure fault detection result is a second detection result to indicate that there is no AC power failure fault in the AC / DC power conversion device.

[0145] In one possible implementation, if the active deviation parameter Vq is not continuously lower than a second preset threshold value (such as 311±20% V) within a second preset time (such as 20S), the AC side fault detection result can be determined as the second detection result, indicating that there is no AC power failure fault in the AC / DC power conversion equipment, that is, there is an AC fault in the AC / DC power conversion equipment (such as overvoltage or undervoltage fault, etc.).

[0146] It should be noted that when the grid-connected operation mode is the AC / DC charging and discharging mode, the value of the active component Vq after passing through the preset filter, that is, the active power parameter, is used as a complex judgment to avoid residual voltage DC interference on the filter module after the wave blocking. Since the energy storage device discharges slowly, if the cause of the AC / DC power conversion device failure is judged according to the effective value of the AC side of the AC / DC power conversion device, an error in judgment may occur. If the instantaneous value of DC and AC is changed to judge, it takes a long time. Therefore, it is better to use the active power parameter Vq to judge in real time and more accurately.

[0147] The power failure fault detection method provided by the embodiment of the present application determines the active power parameter according to the AC detection power parameter; if the active power parameter is lower than the preset minimum power parameter, determines the active deviation parameter between the active power parameter and the preset minimum power parameter; if the active deviation parameter is continuously lower than the second preset threshold value during the second preset time, determines the AC power failure fault detection result as the first detection result, indicating that the AC-DC power conversion device has an AC power failure fault; if the active deviation parameter is not continuously lower than the second preset threshold value during the second preset time, determines the AC power failure fault detection result as the second detection result, indicating that the AC-DC power conversion device does not have an AC power failure fault. Therefore, the present application can determine the real cause of the power failure fault on the AC side of the AC-DC power conversion device according to the active power parameter under the premise that the AC-DC power conversion device has an AC fault, that is, it can distinguish whether the AC side fault of the AC-DC power conversion device is a power failure fault caused by a power failure caused by a power outage or a fault caused by an abnormality in the power grid, thereby improving the reliability and safety of the fault detection of the AC fault detection system.

[0148] Optionally, in a possible implementation example, the method may further include:

[0149] If the AC power failure fault detection result indicates that the AC-DC power conversion device has an AC power failure fault, first fault indication information is reported to indicate that the AC-DC power conversion device has an AC power failure fault.

[0150] In a possible implementation, if the AC power failure detection result indicates that the AC / DC power conversion device has an AC power failure, first fault indication information is reported to a host computer or other control device, where the first fault indication information indicates that the AC / DC power conversion device has an AC power failure.

[0151] It should be noted that if the AC / DC power conversion device has an AC power failure, it is necessary to exclude the situation where the AC / DC power conversion device has no other faults and report the first fault indication information. That is, when it is determined that the AC / DC power conversion device has an AC power failure, other faults such as AC faults (such as overvoltage or undervoltage faults, etc.) are cleared.

[0152] If the AC power failure fault detection result indicates that the AC / DC power conversion device does not have an AC power failure fault, second fault indication information is reported to indicate that the AC / DC power conversion device has an AC fault.

[0153] In a possible implementation, if the AC power failure detection result indicates that the AC / DC power conversion device does not have an AC power failure, second fault indication information is reported to a host computer or other control device, and the second fault indication information indicates that the AC / DC power conversion device has an AC failure.

[0154] The power failure fault detection method provided by the embodiment of the present application, if the AC power failure fault detection result indicates that the AC-DC power conversion device has an AC power failure fault, then the first fault indication information is reported to indicate that the AC-DC power conversion device has an AC power failure fault; if the AC power failure fault detection result indicates that the AC-DC power conversion device does not have an AC power failure fault, then the second fault indication information is reported to indicate that the AC-DC power conversion device has an AC fault. Therefore, the present application can not only distinguish whether the fault is an AC power failure caused by a power failure or an AC fault caused by a power grid abnormality, thereby improving the reliability of fault detection, but also report the fault after determining the fault indication information, so as not to misreport the fault, which is beneficial to later maintenance.

[0155] To facilitate understanding of the above-mentioned AC power failure fault detection method, the embodiment of the present application further provides an example of a process of an AC power failure fault detection method, which is described below in conjunction with the accompanying drawings. Fig.11 A schematic diagram of a method for detecting AC power failure provided in an embodiment of the present application Figure 6 .

[0156] like Fig.11 As shown, the AC power failure detection method may include:

[0157] S801. Determine a grid-connected operation mode of an AC / DC power conversion device.

[0158] Specifically, before the AC / DC power failure detection system is powered on, the control unit needs to select the grid-connected operation mode of the AC / DC power conversion equipment corresponding to different preset working conditions according to the preset working conditions, that is, if the preset working condition is a distributed energy storage working condition, the grid-connected operation mode corresponding to the distributed energy storage working condition is the AC / DC charging and discharging mode; if the preset working condition is a DC bus stable working condition, the grid-connected operation mode corresponding to the DC bus stable working condition is the DC constant voltage mode. That is, different grid-connected operation modes are set according to different preset working conditions to ensure that after the AC / DC power failure detection system is powered on, it can operate according to the selected grid-connected operation mode of the AC / DC power conversion equipment.

[0159] S802: If the grid-connected operation mode is the DC constant voltage mode, perform AC power failure fault detection on the AC / DC power conversion device to obtain an AC power failure fault detection result of the AC / DC power conversion device.

[0160] Specifically, if the grid-connected operation mode is a DC constant voltage mode, if the DC bus deviation parameter ΔVdc lasts for a first preset time (such as 10S) and is greater than a first preset threshold (such as 50V), in the absence of other faults, it can be determined and reported that the AC / DC power conversion equipment has an AC power failure fault, and other AC faults (such as over-voltage, under-voltage, over-frequency, etc. of the preset power grid) can be cleared.

[0161] If only an AC fault is detected (such as over-voltage, under-voltage, over-frequency, etc. of the preset power grid), the machine will be shut down and the wave will be sealed first. The three-phase AC residual voltage of the AC / DC power conversion equipment is DC, and the filter value of the active electrical parameter Vq of the phase-locked loop (such as LC filtering within 5Hz) can be used for re-judgment. If the filter value of the active electrical parameter Vq is lower than the second preset threshold value (such as 311±20%V) close to the preset minimum electrical parameter (such as 0V) and meets the requirements of the second preset time (such as 20S), the AC fault can be cleared and no longer reported. If it is determined that the AC / DC power conversion equipment has an AC power failure, it will be reported. Otherwise, the AC fault (such as undervoltage or overvoltage, over-frequency, etc.) will continue to be reported normally.

[0162] S803: If the grid-connected operation mode is the AC / DC charging and discharging mode, perform AC power failure fault detection on the AC / DC power conversion device to obtain an AC power failure fault detection result of the AC / DC power conversion device.

[0163] Specifically, if the grid-connected operation mode is the AC / DC charging and discharging mode, the electrical parameters on the DC side of the AC / DC power conversion device remain constant. When the grid-connected switch is turned off, the AC side of the AC / DC power conversion device operates in an open circuit and saturated state, which may be an island operation problem. If the island detection result indicates that the AC / DC power conversion device is in an island operation state, the island operation state is directly reported; if the island detection result indicates that the AC / DC power conversion device is not in an island operation state, the AC side fault state is determined according to the AC detection electrical parameters. If the AC side fault state is the first fault state, it indicates that there is no AC fault in the AC / DC power conversion device; if the AC side fault state is the second fault state, it indicates that there is an AC fault in the AC / DC power conversion device. That is, if AC fault information is detected, the wave is first blocked and the machine is shut down, and the AC fault information is not reported, because the AC fault information may be caused by a true over-voltage or under-voltage fault, or it may be caused by an open circuit, and a secondary retest is required to determine. Therefore, when the AC fault information is detected and the machine is shut down, the AC side state of the AC / DC power conversion equipment is re-measured, and the filtering value of the active electrical parameter Vq (such as LC filtering within 5Hz) can be directly used for re-judgment. If the filtering value of the active electrical parameter Vq is lower than the second preset threshold value (such as 311±20%V) close to the preset minimum electrical parameter (such as 0V) and meets the second preset time (such as 20S), the AC fault can be cleared and no longer reported. If it is determined that the AC / DC power conversion equipment has an AC power failure, it will be reported; otherwise, the AC fault will continue to be reported normally (such as undervoltage or overvoltage, over-frequency, etc.).

[0164] It should be noted that the AC fault detection of the AC power failure fault detection system always exists, that is, the preset power grid is undervoltage, or the three-phase voltage is unbalanced, or the normal AC power failure (that is, the three-phase voltage is lower than the preset threshold), etc. This application is mainly used to solve the problem of abnormal AC power failure, such as the AC side overvoltage or abnormal DC bus status caused by power outage.

[0165] The AC power failure fault detection method provided by the embodiment of the present application determines the grid-connected operation mode of the AC / DC power conversion device. If the grid-connected operation mode is the DC constant voltage mode, the AC power failure fault detection is performed on the AC / DC power conversion device to obtain the AC power failure fault detection result of the AC / DC power conversion device; if the grid-connected operation mode is the AC / DC charging and discharging mode, the AC power failure fault detection is performed on the AC / DC power conversion device to obtain the AC power failure fault detection result of the AC / DC power conversion device. Therefore, the present application can use different AC power failure fault detection logics based on the AC / DC power conversion device running in different grid-connected operation modes to distinguish whether the fault is an AC power failure caused by power failure or an AC failure caused by power grid abnormality, thereby improving the fault detection reliability of the AC power failure fault detection system, preventing false fault reports, and facilitating later maintenance. At the same time, the specific cause of the AC power failure fault is accurately identified, thereby avoiding the AC power failure fault detection system from being in a fault state for a long time due to sudden power failure, thereby improving the reliability of the AC power failure fault detection system and the AC / DC power conversion device.

[0166] Based on the same inventive concept, an AC power failure fault detection device is also provided in the embodiment of the present application. Since the principle of solving the problem by the device in the embodiment of the present application is similar to the above-mentioned AC power failure fault detection method in the embodiment of the present application, the implementation of the device can refer to the implementation of the method, and the repeated parts will not be repeated.

[0167] Fig.12 The structure diagram of an AC power failure detection device provided in an embodiment of the present application is shown in FIG. Fig.12 As shown, the AC power failure detection device 90 may include:

[0168] An acquisition module 91 is used to acquire an AC side fault state of an AC / DC power conversion device;

[0169] A shutdown module 92, for controlling the AC / DC power conversion device to shut down if the AC side fault state indicates that the AC / DC power conversion device has an AC fault, and obtaining AC detection electrical parameters after the shutdown;

[0170] The detection module 93 is used to perform AC power failure detection on the AC / DC power conversion device according to the AC detection electrical parameters to obtain an AC power failure detection result of the AC / DC power conversion device. The AC power failure detection result is used to indicate whether the AC / DC power conversion device has an AC power failure fault.

[0171] In an optional implementation, the AC power failure detection device 90 is further used to: determine the grid-connected operation mode of the AC / DC power conversion device; wherein the grid-connected operation mode is: any one of the DC constant voltage mode and the AC / DC charging and discharging mode.

[0172] In an optional embodiment, if the grid-connected operation mode is a DC constant voltage mode, the acquisition module 91 is specifically used to: obtain the DC bus electrical parameters of the AC / DC power conversion device; determine whether the DC bus electrical parameters are continuously greater than a first preset threshold value within a first preset time; if the DC bus electrical parameters are continuously greater than the first preset threshold value within the first preset time, determine that the AC side fault state is a first fault state, to indicate that there is no AC fault in the AC / DC power conversion device; if the DC bus electrical parameters are not continuously greater than the first preset threshold value within the first preset time, determine that the AC side fault state is a second fault state, to indicate that there is an AC fault in the AC / DC power conversion device.

[0173] In an optional embodiment, the acquisition module 91 is specifically used to: determine the DC bus deviation parameter of the DC bus electrical parameter within a first preset time; determine whether the DC bus deviation parameter within the first preset time is continuously greater than a preset deviation threshold, and the first preset threshold is a preset deviation threshold.

[0174] In an optional implementation, if the grid-connected operation mode is an AC / DC charging and discharging mode, the acquisition module 91 is specifically used to: perform island detection on the AC / DC power conversion equipment according to the AC detection electrical parameters to obtain the island detection result; if the island detection result indicates that the AC / DC power conversion equipment is not in an island operation state, then determine the AC side fault state according to the AC detection electrical parameters.

[0175] In an optional embodiment, the detection module 93 is specifically used to: determine the active electrical parameter based on the AC detection electrical parameter; if the active electrical parameter is lower than the preset minimum electrical parameter, determine the active deviation parameter between the active electrical parameter and the preset minimum electrical parameter; if the active deviation parameter is continuously lower than the second preset threshold value during the second preset time, determine that the AC power failure fault detection result is the first detection result, to indicate that the AC / DC power conversion device has an AC power failure fault; if the active deviation parameter is not continuously lower than the second preset threshold value during the second preset time, determine that the AC power failure fault detection result is the second detection result, to indicate that the AC / DC power conversion device does not have an AC power failure fault.

[0176] In an optional embodiment, the AC power failure fault detection device 90 is also used to: if the AC power failure fault detection result indicates that the AC / DC power conversion device has an AC power failure, then report first fault indication information to indicate that the AC / DC power conversion device has an AC power failure; if the AC power failure fault detection result indicates that the AC / DC power conversion device does not have an AC power failure, then report second fault indication information to indicate that the AC / DC power conversion device has an AC failure.

[0177] It should be noted that for details not disclosed in the AC power failure fault detection device in the embodiment of the present application, please refer to the details disclosed in the AC power failure fault detection method in the embodiment of the present application, and the details will not be repeated here.

[0178] The above modules may be one or more integrated circuits configured to implement the above methods, such as one or more application specific integrated circuits (ASICs), or one or more microprocessors, or one or more field programmable gate arrays (FPGAs). For another example, when a module is implemented in the form of a processing element scheduling program code, the processing element may be a general-purpose processor, such as a central processing unit (CPU) or other processor that can call program code. For another example, these modules may be integrated together and implemented in the form of a system-on-a-chip (SOC).

[0179] Optionally, the embodiment of the present application further provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the processor executes the steps of the AC power failure detection method for a mobile storage medium in the above embodiment. The specific implementation method and technical effect are similar and will not be repeated here.

[0180] In the several embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0181] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0182] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of hardware plus software functional units.

[0183] The above-mentioned integrated unit implemented in the form of a software functional unit can be stored in a computer-readable storage medium. The above-mentioned software functional unit is stored in a storage medium, including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) or a processor (English: processor) to perform some steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (English: Read-Only Memory, abbreviated: ROM), random access memory (English: Random Access Memory, abbreviated: RAM), disk or optical disk and other media that can store program codes.

[0184] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for detecting AC power failure, characterized in that: include: Obtaining the AC side fault status of the AC / DC power conversion equipment; If the AC side fault state indicates that the AC-DC power conversion device has an AC fault, the AC-DC power conversion device is controlled to shut down, and the AC detection electrical parameters after the shutdown are obtained; An AC power failure fault detection is performed on the AC / DC power conversion device according to the AC detection electrical parameter to obtain an AC power failure fault detection result of the AC / DC power conversion device, wherein the AC power failure fault detection result is used to indicate whether the AC / DC power conversion device has an AC power failure fault.

2. The AC power failure detection method according to claim 1, characterized in that: The method further comprises: Determine the grid-connected operation mode of the AC / DC power conversion device; wherein the grid-connected operation mode is any one of a DC constant voltage mode and an AC / DC charging and discharging mode.

3. The AC power failure detection method according to claim 2, characterized in that: If the grid-connected operation mode is a DC constant voltage mode, obtaining the AC side fault state of the AC / DC power conversion device includes: Obtaining electrical parameters of a DC bus of the AC / DC power conversion device; Determine whether the DC bus electrical parameter is continuously greater than a first preset threshold value within a first preset time; If the DC bus electrical parameter is continuously greater than the first preset threshold value within the first preset time, determining that the AC side fault state is a first fault state to indicate that there is no AC fault in the AC / DC power conversion device; If the DC bus electrical parameter is not continuously greater than the first preset threshold within the first preset time, the AC side fault state is determined to be a second fault state to indicate that an AC fault exists in the AC / DC power conversion device.

4. The AC power failure detection method according to claim 3, characterized in that: The step of determining whether the DC bus electrical parameter is continuously greater than a first preset threshold value within a first preset time includes: Determining a DC bus deviation parameter of the DC bus electrical parameter within the first preset time; Determine whether the DC bus deviation parameter within the first preset time is continuously greater than a preset deviation threshold, where the first preset threshold is the preset deviation threshold.

5. The AC power failure detection method according to claim 2, characterized in that: If the grid-connected operation mode is an AC / DC charging and discharging mode, the acquiring of the AC side fault state of the AC / DC power conversion device includes: According to the AC detection electrical parameters, performing island detection on the AC / DC power conversion device to obtain an island detection result; If the islanding detection result indicates that the AC-DC power conversion device is not in an islanding operation state, the AC side fault state is determined according to the AC detection electrical parameter.

6. The AC power failure detection method according to claim 1, characterized in that: The performing AC power failure fault detection on the AC / DC power conversion device according to the AC detection electrical parameter to obtain the AC power failure fault detection result of the AC / DC power conversion device includes: Determining active electrical parameters according to the AC detection electrical parameters; If the active electrical parameter is lower than a preset minimum electrical parameter, determining an active deviation parameter between the active electrical parameter and the preset minimum electrical parameter; If the active power deviation parameter is continuously lower than the second preset threshold value within the second preset time, determining that the AC power failure fault detection result is a first detection result, so as to indicate that the AC / DC power conversion device has an AC power failure fault; If the active deviation parameter is not continuously lower than the second preset threshold within the second preset time, the AC power failure fault detection result is determined to be a second detection result to indicate that there is no AC power failure in the AC / DC power conversion device.

7. The AC power failure detection method according to claim 1, characterized in that: The method further comprises: If the AC power failure fault detection result indicates that the AC-DC power conversion device has an AC power failure fault, reporting first fault indication information to indicate that the AC-DC power conversion device has an AC power failure fault; If the AC power failure fault detection result indicates that the AC / DC power conversion device does not have an AC power failure fault, second fault indication information is reported to indicate that the AC / DC power conversion device has an AC fault.

8. An AC / DC power conversion device, characterized in that: The AC / DC power conversion device comprises: an AC / DC power conversion unit, a control unit and a phase-locked loop; The control unit is respectively connected to the input end of the AC / DC power conversion unit and the output end of the AC / DC power conversion unit; the output end of the AC / DC power conversion unit is also connected to the input end of the phase-locked loop; the output end of the phase-locked loop is connected to the control unit; The control unit is used to execute the AC power failure fault detection method according to any one of claims 1 to 7.

9. An AC power failure detection system, characterized in that: The AC power failure detection system comprises: the AC / DC power conversion device, the grid-connected switch and the energy storage device as described in claim 8 above; The input end of the AC / DC power conversion device is connected to the energy storage device; the output end of the AC / DC power conversion device is connected to the grid-connected switch; and the grid-connected switch is connected to a preset power grid; The AC / DC power conversion device is used to execute the AC power failure fault detection method described in any one of claims 1 to 7.

10. A control unit, characterized in that: The control unit includes: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores a computer program executable by the at least one processor, and the computer program is executed by the at least one processor so that the at least one processor can execute the AC power failure fault detection method described in any one of claims 1-7.

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