CN116505739B - Inverter, working condition detection method and device - Google Patents

Inverter, working condition detection method and device Download PDF

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Publication number
CN116505739B
CN116505739B CN202310777924.1A CN202310777924A CN116505739B CN 116505739 B CN116505739 B CN 116505739B CN 202310777924 A CN202310777924 A CN 202310777924A CN 116505739 B CN116505739 B CN 116505739B
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working condition
preset
switching tube
relay
inverter
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CN116505739A (en
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王博
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New H3C Technologies Co Ltd
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New H3C Technologies Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/52—Testing for short-circuits, leakage current or ground faults
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/56—Testing of electric apparatus
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0009—Devices or circuits for detecting current in a converter
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0012—Control circuits using digital or numerical techniques
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H02M1/325—Means for protecting converters other than automatic disconnection with means for allowing continuous operation despite a fault, i.e. fault tolerant converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode

Abstract

The embodiment of the application provides an inverter, a working condition detection method and a device, wherein the inverter comprises the following components: the digital signal processor DSP, the switching tube, the relay and the direct current bus; the DSP controls the attraction of the switching tube and the relay; acquiring a first sampling signal of three-phase current output by a switching tube within a preset time period after the switching tube and a relay are attracted; if the first sampling signal meets the preset short-circuit working condition, after the output voltage of the switching tube is reduced, the switching tube and the relay are controlled to conduct first preset times of actuation, so that second sampling signals of the first preset times are rapidly obtained, and whether the inverter is in a short-circuit working condition or in a heavy-load working condition is judged according to the second sampling signals of the first preset times and the preset short-circuit working condition. By applying the technical scheme provided by the embodiment of the application, the problem of damage to an inverter device or a load caused by short circuit to ground can be avoided.

Description

Inverter, working condition detection method and device
Technical Field
The present application relates to the field of computer technologies, and in particular, to an inverter, a method and an apparatus for detecting a working condition.
Background
The off-grid inverter has the function of supplying power to the load, and a short circuit to ground may exist between the inverter and the load during off-grid operation. If a short circuit to ground occurs, the instantaneous current flowing through the inverter is very large at the moment when the relay of the inverter is engaged, which may cause damage to the switching tube of the inverter and even to the load.
Disclosure of Invention
The embodiment of the application aims to provide an inverter, a working condition detection method and a working condition detection device, so as to avoid the problem that an inverter device or a load is damaged due to a short circuit to ground. The specific technical scheme is as follows:
in a first aspect of an embodiment of the present application, there is provided an inverter including a DSP (Digital Signal Processor ), a switching tube, a relay, and a dc bus; the direct current bus is connected with the switch tube, the switch tube is connected with the relay, the relay is used for being connected with a load, and the DSP is connected with the switch tube and the relay;
the DSP is used for:
controlling the switching tube and the relay to be attracted; acquiring a first sampling signal of three-phase current output by the switching tube within a first preset duration after the switching tube and the relay are attracted; if the first sampling signal meets the preset short-circuit working condition, the switching tube and/or the relay are/is controlled to be turned off;
reducing the output voltage of the switching tube to a target voltage, wherein the ratio of the target voltage to the rated voltage of the inverter is a preset ratio; controlling the switching tube and the relay to be attracted for a first preset time according to the target voltage, wherein the attracting time of the switching tube and the relay each time is a first preset time; acquiring a second sampling signal of the three-phase current output by the switching tube within a first preset duration after each time of the switching tube and the relay are attracted; and determining the working condition of the inverter according to the second sampling signals of the first preset times and the preset short-circuit working condition, wherein the working condition is a short-circuit working condition or a heavy-load working condition.
In some embodiments, the DSP is specifically configured to: if the number of times of the second sampling signals meeting the preset short-circuit working condition in the second sampling signals of the first preset times is larger than or equal to the second preset times, determining that the working condition of the inverter is a short-circuit working condition; otherwise, determining the working condition of the inverter as a heavy load working condition.
In some embodiments, the DSP is further configured to: and under the condition that the working condition of the inverter is a heavy-load working condition, after waiting for a second preset time period, controlling the switching tube and the relay to be attracted.
In some embodiments, the DSP is further configured to: after waiting for the second preset time length to control the switching tube and the relay to be attracted, acquiring a third sampling signal of the three-phase current output by the switching tube; if the third sampling signal meets the preset heavy load working condition, the switching tube and/or the relay is/are controlled to be turned off, and first prompt information is output, wherein the first prompt information is used for prompting a user to relieve load.
In some embodiments, the DSP is further configured to: and under the condition that the working condition of the inverter is a short-circuit working condition, outputting second prompt information, wherein the second prompt information is used for prompting a user that the circuit is short-circuited.
In some embodiments, the preset short-circuit condition is that the sampling signal is greater than a first preset current value, the sampling signal is greater than a rated current value of a first preset multiple, and the current difference between at least one phase and the other phase is greater than a second preset current value.
In a second aspect of the embodiment of the application, a method for detecting a working condition is provided, which is applied to a DSP of an inverter, wherein the inverter comprises the DSP, a switching tube, a relay and a direct current bus; the direct current bus is connected with the switch tube, the switch tube is connected with the relay, the relay is used for being connected with a load, and the DSP is connected with the switch tube and the relay; the method comprises the following steps:
controlling the switching tube and the relay to be attracted;
acquiring a first sampling signal of three-phase current output by the switching tube within a first preset duration after the switching tube and the relay are attracted;
if the first sampling signal meets the preset short-circuit working condition, the switching tube and/or the relay are/is controlled to be turned off;
reducing the output voltage of the switching tube to a target voltage, wherein the ratio of the target voltage to the rated voltage of the inverter is a preset ratio;
Controlling the switching tube and the relay to be attracted for a first preset time according to the target voltage, wherein the attracting time of the switching tube and the relay each time is a first preset time;
acquiring a second sampling signal of the three-phase current output by the switching tube within a first preset duration after each time of the switching tube and the relay are attracted;
and determining the working condition of the inverter according to the second sampling signals of the first preset times and the preset short-circuit working condition, wherein the working condition is a short-circuit working condition or a heavy-load working condition.
In some embodiments, the step of determining the working condition of the inverter according to the second sampling signal of the first preset times and the preset short-circuit working condition includes:
if the number of times of the second sampling signals meeting the preset short-circuit working condition in the second sampling signals of the first preset times is larger than or equal to the second preset times, determining that the working condition of the inverter is a short-circuit working condition; otherwise, determining the working condition of the inverter as a heavy load working condition.
In some embodiments, the method further comprises:
and under the condition that the working condition of the inverter is a heavy-load working condition, after waiting for a second preset time period, controlling the switching tube and the relay to be attracted.
In some embodiments, the method further comprises:
after waiting for the second preset time length to control the switching tube and the relay to be attracted, acquiring a third sampling signal of the three-phase current output by the switching tube; if the third sampling signal meets the preset heavy load working condition, the switching tube and/or the relay is/are controlled to be turned off, and first prompt information is output, wherein the first prompt information is used for prompting a user to relieve load.
In some embodiments, the method further comprises:
and under the condition that the working condition of the inverter is a short-circuit working condition, outputting second prompt information, wherein the second prompt information is used for prompting a user that the circuit is short-circuited.
In some embodiments, the preset short-circuit condition is that the sampling signal is greater than a first preset current value, the sampling signal is greater than a rated current value of a first preset multiple, and the current difference between at least one phase and the other phase is greater than a second preset current value.
In a third aspect of the embodiment of the application, a working condition detection device is provided, and the working condition detection device is applied to a DSP of an inverter, wherein the inverter comprises the DSP, a switching tube, a relay and a direct current bus; the direct current bus is connected with the switch tube, the switch tube is connected with the relay, the relay is used for being connected with a load, and the DSP is connected with the switch tube and the relay; the device comprises:
The control module is used for controlling the switching tube and the relay to be attracted;
the acquisition module is used for acquiring a first sampling signal of the three-phase current output by the switching tube in a first preset duration after the switching tube and the relay are attracted;
the control module is further used for controlling the switching tube and/or the relay to be turned off if the first sampling signal meets a preset short-circuit working condition; reducing the output voltage of the switching tube to a target voltage, wherein the ratio of the target voltage to the rated voltage of the inverter is a preset ratio; controlling the switching tube and the relay to be attracted for a first preset time according to the target voltage, wherein the attracting time of the switching tube and the relay each time is a first preset time;
the acquisition module is also used for acquiring a second sampling signal of the three-phase current output by the switching tube in a first preset time length after the switching tube and the relay are attracted each time;
the control module is further used for determining the working condition of the inverter according to the second sampling signals of the first preset times and the preset short-circuit working condition, wherein the working condition is a short-circuit working condition or a heavy-load working condition.
In some embodiments, the control module is further to:
if the number of times of the second sampling signals meeting the preset short-circuit working condition in the second sampling signals of the first preset times is larger than or equal to the second preset times, determining that the working condition of the inverter is a short-circuit working condition; otherwise, determining the working condition of the inverter as a heavy load working condition.
In some embodiments, the control module is further to:
and under the condition that the working condition of the inverter is a heavy-load working condition, after waiting for a second preset time period, controlling the switching tube and the relay to be attracted.
In some embodiments, the acquisition module is further to:
after waiting for the second preset time length to control the switching tube and the relay to be attracted, acquiring a third sampling signal of the three-phase current output by the switching tube;
the control module is further configured to: if the third sampling signal meets the preset heavy load working condition, the switching tube and/or the relay is/are controlled to be turned off, and first prompt information is output, wherein the first prompt information is used for prompting a user to relieve load.
In some embodiments, the control module is further to:
and under the condition that the working condition of the inverter is a short-circuit working condition, outputting second prompt information, wherein the second prompt information is used for prompting a user that the circuit is short-circuited.
In some embodiments, the preset short-circuit condition is that the sampling signal is greater than a first preset current value, the sampling signal is greater than a rated current value of a first preset multiple, and the current difference between at least one phase and the other phase is greater than a second preset current value.
The embodiment of the application has the beneficial effects that:
according to the technical scheme provided by the embodiment of the application, the DSP in the inverter is used for acquiring the first sampling signal of the three-phase current output by the switching tube within the first preset time after the switching tube and the relay are attracted, if the first sampling signal meets the preset short-circuit working condition, the output voltage of the switching tube is reduced, then the switching tube and the relay are controlled to conduct attraction for a first preset number of times, so that the second sampling signal for the first preset number of times is rapidly acquired, and the inverter is judged to be in a short-circuit working condition or a heavy-load working condition according to the second sampling signal for the first preset number of times and the preset short-circuit working condition. By applying the technical scheme provided by the embodiment of the application, the short circuit or heavy load working condition of the inverter can be rapidly determined, the problem of misjudgment of the short circuit working condition by the inverter is solved, the unexpected shutdown or equipment failure of the inverter caused by misjudgment of the working condition is avoided, and the problem of damage to inverter devices or loads caused by short circuit to ground is avoided.
Of course, it is not necessary for any one product or method of practicing the application to achieve all of the advantages set forth above at the same time.
Drawings
In order to more clearly illustrate the embodiments of the application or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the application, and other embodiments may be obtained according to these drawings to those skilled in the art.
Fig. 1 is a schematic structural diagram of an inverter according to an embodiment of the present application;
FIG. 2 is a schematic diagram of an example of detecting a working condition of an inverter according to an embodiment of the present application;
FIG. 3 is a schematic flow chart of a method for detecting working conditions according to an embodiment of the present application;
fig. 4 is a schematic structural diagram of a working condition detecting device according to an embodiment of the present application.
Detailed Description
The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. Based on the embodiments of the present application, all other embodiments obtained by the person skilled in the art based on the present application are included in the scope of protection of the present application.
The words appearing in the embodiments of the application are explained below.
An inverter: an energy conversion device for converting direct current into alternating current of a power grid or a load. The inverter comprises a photovoltaic inverter, an energy storage inverter and the like.
Off-grid operation: the AC output of the inverter is not connected with a power grid, and is only connected with the running state of a local load.
And (3) heavy load: refers to an operating state in which the load at the output end of the inverter exceeds the rated load.
The off-grid inverter has the function of supplying power to the load, and a short circuit to ground may exist between the inverter and the load during off-grid operation. If the ac side of the inverter and the load connection are short-circuited to ground, the positive electrode or the negative electrode of the dc bus capacitor is short-circuited to ground at the moment of the relay actuation of the inverter, and the instant discharge of the dc bus capacitor can cause the instant current flowing through the inverter to be very large, which may cause the damage of the switching tube of the inverter and even the damage of the load.
In order to accurately identify the working condition of the inverter and thus make adaptive treatment and solve the problem of damage to inverter devices or loads caused by short circuit to ground, an embodiment of the present application provides an inverter, as shown in fig. 1, which includes a DSP 11, a switching tube 12, a relay 13 and a dc bus 14. The DC bus 14 is connected with the switch tube 12, the switch tube 12 is connected with the relay 13, the relay 13 is used for being connected with a load, and the DSP 11 is connected with the switch tube 12 and the relay 13.
DSP 11 for:
the switching tube 12 and the relay 13 are controlled to be attracted; acquiring a first sampling signal of three-phase current output by the switching tube 12 within a first preset duration after the switching tube 12 and the relay 13 are attracted; if the first sampling signal meets the preset short-circuit working condition, the switching tube 12 and/or the relay 13 are/is controlled to be turned off;
reducing the output voltage of the switching tube to a target voltage, wherein the ratio of the target voltage to the rated voltage of the inverter is a preset ratio; controlling the switching tube and the relay to be attracted for a first preset time according to the target voltage, wherein the attracting time of the switching tube and the relay each time is the first preset time; acquiring a second sampling signal of the three-phase current output by the switching tube within a first preset time length after each time of the switching tube and the relay are attracted; and determining the working condition of the inverter according to the second sampling signals of the first preset times and the preset short-circuit working condition, wherein the working condition is a short-circuit working condition or a heavy-load working condition.
According to the technical scheme provided by the embodiment of the application, the DSP in the inverter is used for acquiring the first sampling signal of the three-phase current output by the switching tube within the first preset time after the switching tube and the relay are attracted, if the first sampling signal meets the preset short-circuit working condition, the output voltage of the switching tube is reduced, then the switching tube and the relay are controlled to conduct attraction for a first preset number of times, so that the second sampling signal for the first preset number of times is rapidly acquired, and the inverter is judged to be in a short-circuit working condition or a heavy-load working condition according to the second sampling signal for the first preset number of times and the preset short-circuit working condition. By applying the technical scheme provided by the embodiment of the application, the short circuit or heavy load working condition of the inverter can be rapidly determined, the problem of misjudgment of the short circuit working condition by the inverter is solved, the unexpected shutdown or equipment failure of the inverter caused by misjudgment of the working condition is avoided, and the problem of damage to inverter devices or loads caused by short circuit to ground is avoided.
In the embodiment of the present application, the dc bus 14 is used for discharging the switch tube 12 and providing dc for the switch tube 12.
The switching tube 12 may also be referred to as an inverter circuit for receiving dc power from the dc bus 14 and converting the dc power to ac power, such as A, B, C three-phase current in fig. 1.
The relay 13 is connected to the switching tube 12, and is configured to receive the three-phase current input by the switching tube 12 and output the three-phase current to the load to supply power to the load.
The DSP 11 is responsible for controlling the on and off of the switching tube 12 and the relay 13. As shown in fig. 1, the DSP 11 may control the on and off of the relay 13 by a driving signal, and may control the on and off of the switching tube by a PWM (Pulse Width Modulation ) signal.
When the inverter is started, the DSP 11 controls the voltage of the switching tube 12 to be a rated voltage, and controls the switching tube 12 and the relay 13 to be attracted. At this time, the inverter is in electrical communication with the load, and the inverter can supply power to the load at a rated voltage. In the embodiment of the present application, as shown in fig. 1, the inverter may further include a sampling device 15, where the sampling device 15 is connected between the switching tube 12 and the relay 13, and the sampling device 15 samples the three-phase current within a first preset period after the switching tube 12 and the relay 13 are attracted to obtain a sampling signal of the three-phase current, that is, a first sampling signal, and inputs the first sampling signal into the DSP 11. Here, the sampling device 15 samples the current values of the three-phase currents, and the number of first sampling signals obtained by each sampling is 3, that is, each phase current corresponds to one first sampling signal, and one first sampling signal is the current value corresponding to one phase current. The sampling device 15 may sample the three-phase current one or more times within a first preset time period after the switching tube 12 and the relay 13 are engaged. The first preset time period can be set according to actual conditions, so long as the inverter or the load is guaranteed not to be damaged due to current impact under the condition of passing through the current for the first preset time period.
After the DSP 11 obtains the first sampling signal of the three-phase current, it is determined whether the first sampling signal of the three-phase current meets a preset short-circuit condition. If the first sampling signal meets the preset short-circuit working condition, namely, the inverter has a short-circuit or heavy-load working condition, the DSP 11 controls the switch tube 12 and/or the relay 13 to be turned off. Here, the DSP 11 may control the switching tube to be turned off to stop the power supply to the load, thereby avoiding the damage of the switching tube of the inverter; the relay can be controlled to be turned off so as to break the electrical connection between the inverter and the load, and damage to the load is avoided; the switching tube and the relay can be controlled to be turned off, so that the electric connection between the inverter and the load is thoroughly disconnected, namely, the electric connection between the strong current and the fault point is cut off, the damage of the switching tube of the inverter, even the damage of the load, is avoided, and the inverter or the load is prevented from being damaged due to current impact.
In the embodiment of the application, the preset short-circuit working condition is set according to the actual requirement.
For example, the preset short circuit condition may be that the sampling signal is greater than a first preset current value. The first preset current value may be set according to actual conditions. For example, the first preset current value may be set as a rated current value of the inverter. When the DSP 11 detects that the first sampling signal is less than or equal to the rated current value, it indicates that the current value of the inverter is normal, and the inverter can operate normally without performing other processing on the inverter. When the DSP 11 detects that the first sampling signal is greater than the rated current value, which indicates that the inverter is over-current, the DSP 11 may determine that the first sampling signal meets a preset short-circuit condition, and the inverter is in a short-circuit or heavy-load condition, so as to control the switching tube 12 and/or the relay 13 to be turned off, for example, to block the driving signal to turn off the relay, and turn off the switching tube 12 through the PWM signal.
For another example, the preset short-circuit condition may be that the sampling signal is greater than a first preset current value, the sampling signal is greater than a rated current value of a first preset multiple, and the current difference between at least one phase and the other phase is greater than a second preset current value. The first preset current value, the first preset multiple and the second preset current value can be set according to actual conditions. For example, the first preset current value may be set to a rated current value of the inverter, the first preset multiple may be set to 1.5 times, and the second preset current value may be set to 20A. When the DSP 11 detects that the first sampling signal is less than or equal to the rated current value, it indicates that the current value of the inverter is normal, and the inverter can operate normally without performing other processing on the inverter.
When the DSP 11 detects that the first sampling signal is larger than the rated current, the DSP 11 continuously detects whether the first sampling signal is larger than 1.5 times of the rated current value, and judges whether the current difference between phases is larger than 20A; if the first sampling signal is greater than 1.5 times of the rated current value and the current difference value between at least one phase and at least one phase is greater than 20A, the DSP 11 may determine that the inverter is over-current, control the switching tube 12 and/or the relay 13 to be turned off, and disconnect the electrical connection between the inverter and the load. If the first sampling signal is not satisfied, if the first sampling signal is smaller than or equal to 1.5 times of the rated current value, or the current difference value between all phases is smaller than or equal to 20A, the inverter can normally operate, and other processing is not needed.
After detecting that the first sampling signal meets the preset short-circuit working condition and controlling the switching tube and/or the relay to be turned off, the DSP 11 reduces the output voltage of the switching tube 12 to be a target voltage, wherein the ratio of the target voltage to the rated voltage of the inverter is a preset ratio; controlling the switching tube 12 and the relay 13 to be attracted for a first preset number of times according to the target voltage, wherein the attracting time of each switching tube and the relay is a first preset time; acquiring a second sampling signal of the three-phase current output by the switching tube 12 within a first preset time length after each time of the switching tube 12 and the relay 13 are attracted; and determining a short-circuit working condition or a heavy-load working condition of the inverter according to the second sampling signals of the first preset times and the preset short-circuit working condition.
In the embodiment of the present application, the sampling device 15 may generate the overcurrent hardware protection signal when the first sampling signal is greater than the first preset current value, and send the overcurrent hardware protection signal to the DSP 11. The DSP 11 may determine whether the sampling signal is greater than a first preset current value through the overcurrent hardware protection signal. For example, when the DSP 11 receives the overcurrent hardware protection signal, it determines that the sampling signal is greater than the first preset current value, otherwise, it determines that the sampling signal is less than or equal to the first preset current value.
In the embodiment of the application, the three-phase current output by the switching tube of the inverter is detected for multiple times through restarting the inverter for the first preset times, so that the heavy load or short circuit working condition of the inverter is accurately identified, the running reliability of the inverter is improved, the repeated overcurrent of the inverter caused by the heavy load or short circuit is prevented, the damage of key elements of the inverter is further caused, on the other hand, the safety of the inverter is improved, the damage to the human being caused by the short circuit is prevented, and meanwhile, the phenomenon that the normal running of the inverter is influenced by the heavy load or the short circuit is avoided.
In the embodiment of the application, after the inverter is started for the first time, when the DSP 11 detects that the first sampling signal meets the preset short-circuit working condition, the switch tube 12 and/or the relay 13 are controlled to be turned off. Because the condition of heavy load working condition caused by temporary load may exist when the power is started for the first time, the power can be started for the first preset times again after a period of time, and the duration of the suction of the switching tube and the relay each time is the first preset duration; to further identify the operating conditions of the inverter. When the first preset number of times of startup is performed, the DSP 11 may reduce the output voltage of the switching tube 12 to the target voltage, and control the switching tube 12 and the relay 13 to be engaged. The target voltage may be a rated voltage of the inverter with a preset proportion, for example, 15%, and may be specifically set according to actual situations. Then, the DSP 11 obtains a second sampling signal of the three-phase current output by the switching tube 12 within a first preset time period after the switching tube 12 and the relay 13 are attracted. After the switching tube 12 and the relay 13 are attracted for a first preset time period, the DSP 11 controls the switching tube 12 and/or the relay 13 to be turned off, and then the power-on is started again immediately, the DSP 11 re-executes the operation of reducing the output voltage of the switching tube 12 to the target voltage and controlling the switching tube 12 and the relay 13 to be attracted, so that the power-on is circularly executed for a first preset time, and the short-circuit working condition or the heavy-load working condition of the inverter is determined according to the second sampling signal of the first preset time and the preset short-circuit working condition.
The inverter can be started for a first preset number of times, such as 3-5 times, so that the heavy load or short-circuit condition of the inverter can be more accurately judged. The determination of whether the second sampling signal meets the preset short-circuit condition may be referred to the determination that the first sampling signal meets the preset short-circuit condition, which is not described herein.
In the embodiment of the application, the second preset times can be configured, and the second preset times are smaller than or equal to the first preset times.
After restarting through the inverter with the first preset times, if the times of the second sampling signals meeting the preset short-circuit working condition in the second sampling signals with the first preset times are greater than or equal to the second preset times, determining the working condition of the inverter as a short-circuit working condition; otherwise, determining the working condition of the inverter as a heavy load working condition. For example, the first preset times are 5 times, the second preset times are 3 times, when the inverter is restarted for 5 times, if the second sampling signals with 3 times or more meet the preset short-circuit working condition, the working condition of the inverter is determined to be the short-circuit working condition; if only 0 times, 1 time or 2 times of second sampling signals exist to meet the preset short-circuit working condition, the working condition of the inverter is determined to be a heavy-load working condition.
Under the condition that the working condition of the inverter is a short-circuit working condition, the DSP 11 can output a second prompt message to prompt the user circuit to have a short circuit, wait for maintenance personnel to maintain, and not start the inverter any more so as to avoid irreversible damage to the inverter and the load.
Under the condition that the working condition of the inverter is the heavy-load working condition, after the DSP 11 waits for the second preset time period, the switching tube 12 and the relay 13 are controlled to be attracted.
In the embodiment of the present application, the second preset duration may be any duration, for example, 20 minutes, 30 minutes, or 1 hour, and may specifically be set according to actual situations, which is not limited herein. When the inverter is restarted for a first preset number of times, the sampling device 15 samples the three-phase current output by the switching tube 12 to obtain a second sampling signal, and if the working condition of the inverter is determined to be a heavy load working condition according to the obtained second sampling signal for the first preset number of times and a preset short-circuit working condition, the DSP 11 waits for a second preset duration, and then controls the switching tube and the relay to be attracted.
In the embodiment of the present application, after waiting for a second preset time period to control the switching tube 12 and the relay 13 to be engaged, the DSP 11 may obtain a third sampling signal of the three-phase current output by the switching tube 12; if the third sampling signal meets the preset heavy load working condition, the switching tube and/or the relay is/are controlled to be turned off, and first prompt information is output, wherein the first prompt information is used for prompting a user to relieve load. The preset heavy-load working condition can be the same as or different from the preset short-circuit working condition, and can be specifically set according to actual requirements. Here, because a temporary load may exist in the load, when the inverter restarts for the first preset times, a heavy load condition occurs in the inverter due to the temporary load; if the second preset duration is waited, the DSP 11 controls the switching tube and the relay to be attracted again, the third sampling signal obtained by the DSP 11 does not meet the preset heavy load working condition any more, the temporary load may not be hung up at this time, and the inverter can normally operate, and the inverter does not need to output the first prompt information to prompt the user to reduce the load. If the second preset duration is waited, the DSP 11 controls the switching tube and the relay to be attracted again, and the third sampling signal obtained by the DSP 11 still meets the preset heavy load working condition, which indicates that the heavy load is not caused by the temporary load or the temporary load is still hung up, the DSP 11 controls the switching tube and/or the relay to be turned off, outputs the first prompting information, prompts the user to reduce the load, and ensures the normal operation of the inverter and the load.
In order to describe the operation process of the inverter during the operation condition detection in detail, an inverter operation condition detection flow is described below with reference to an example shown in fig. 2. Wherein the first preset time length is 200 milliseconds (ms), the first preset multiple is 1.5, the second preset current value is 20A, the first preset times is 4, the second preset times is 3, the preset proportion is 15%, and the second preset time length is 30 minutes. The condition 1 is that the overcurrent hardware protection signal is triggered within 200ms after the switching tube and the relay are attracted, namely, the sampling signal (such as the first sampling signal and the second sampling signal) is larger than a first preset current value, the condition 2 is that the current instantaneous value is larger than 1.5 times of the rated current and the interphase current difference value is larger than 20A, namely, the sampling signal is larger than the rated current value of the first preset multiple, and the current difference value of at least one interphase is larger than a second preset current value. Here, the condition 1 and the condition 2 are both preset short-circuit working conditions and preset heavy-load working conditions.
Step S21, the DSP 11 detects whether the condition 1 is satisfied; if yes, triggering an overcurrent hardware protection signal within 200ms after the switching tube and the relay are attracted, executing the step S22, and if not, normally operating the inverter, and ending the flow.
Step S22, the DSP 11 detects whether the condition 2 is satisfied; if yes, i.e. the current instantaneous value is greater than 1.5 times of the rated current and the interphase current difference value is greater than 20A, step S23 is executed, if not, the inverter operates normally, and the flow is ended.
In step S23, the DSP 11 controls the output voltage of the switching tube to 15% of the rated voltage, and starts the machine 4 times continuously, and executes step S24.
In step S23, each time the power is restarted, the DSP 11 obtains the second sampling signal and the inter-phase current difference value within 200ms after the switching tube and the relay are closed. After 200ms of the switching tube and the relay are closed once, the DSP 11 controls the switching tube and/or the relay to be turned off, the switching tube and the relay are immediately controlled to be closed without waiting, and a second sampling signal and an inter-phase current difference value within 200ms of the switching tube and the relay are acquired after the switching tube and the relay are closed next time. The cycle is then continued until the inverter is turned on 4 times, and the DSP 11 obtains 4 second sampling signals and the inter-phase current difference.
Step S24, the DSP 11 detects whether more than 3 times of conditions 1 and 2 are met; if yes, triggering overcurrent hardware protection signals within 200ms after the switching tube and the relay are attracted for more than 3 times, wherein instantaneous values of currents for more than 3 times are all larger than 1.5 times of rated currents, and inter-phase current difference values for more than 3 times are all larger than 20A, and executing step S25; if not, step S26 is performed.
In step S25, the DSP 11 determines the inverter as a short-circuit condition, controls the switching tube and/or the relay to be turned off, outputs a second prompt message, and ends the process.
In step S26, the DSP 11 determines the inverter as a heavy load condition, and controls the switching tube and/or the relay to be turned off.
In step S27, after the DSP 11 waits for 30 minutes, the switching tube and the relay are controlled to be engaged.
Step S28, the DSP 11 detects whether the condition 1 and the condition 2 are satisfied; if yes, go to step S29; if not, the inverter operates normally, and the process is ended.
In step S29, the DSP 11 controls the switching tube and/or the relay to turn off, outputs the first prompt message, and ends the process.
In the technical scheme provided by the embodiment of the application, the heavy load or short-circuit working condition of the inverter can be accurately judged through the condition 1 and the condition 2, and after the short circuit is judged to occur between the inverter and the load, the inverter is not started any more, so that irreversible damage to the inverter caused by repeated start-up is prevented. Meanwhile, the DSP in the inverter outputs a second prompt message to report equipment faults and prompt a user or after-sales personnel to carry out field maintenance. After judging that the inverter has heavy load working conditions, starting the machine again after waiting for a second preset time period, judging whether the condition 1 and the condition 2 are met, and when the condition is still met, controlling a switching tube and/or a relay to be switched off by a DSP (digital signal processor) in the inverter, outputting first prompt information and prompting a user to carry out load shedding.
Based on the inverter, the embodiment of the application provides a working condition detection method, as shown in fig. 3, the application is applied to a DSP of the inverter, and the inverter comprises the DSP, a switching tube, a relay and a direct current bus; the direct current bus is connected with the switching tube, the switching tube is connected with the relay, the relay is used for being connected with a load, and the DSP is connected with the switching tube and the relay; the method comprises the following steps:
step S31, controlling the switching tube and the relay to be attracted;
step S32, acquiring a first sampling signal of three-phase current output by a switching tube in a first preset time period after the switching tube and a relay are attracted;
step S33, if the first sampling signal meets the preset short-circuit working condition, the switching tube and/or the relay are/is controlled to be turned off;
step S34, the output voltage of the switching tube is reduced to be a target voltage, and the ratio of the target voltage to the rated voltage of the inverter is a preset ratio;
step S35, controlling the switching tube and the relay to be attracted for a first preset time according to the target voltage, wherein the attracting time of the switching tube and the relay each time is the first preset time; acquiring a second sampling signal of the three-phase current output by the switching tube within a first preset time length after each time of the switching tube and the relay are attracted;
Step S36, determining the working condition of the inverter according to the second sampling signals of the first preset times and the preset short-circuit working condition, wherein the working condition is a short-circuit working condition or a heavy-load working condition.
According to the technical scheme provided by the embodiment of the application, the DSP in the inverter is used for acquiring the first sampling signal of the three-phase current output by the switching tube within the first preset time after the switching tube and the relay are attracted, if the first sampling signal meets the preset short-circuit working condition, the output voltage of the switching tube is reduced, then the switching tube and the relay are controlled to conduct attraction for a first preset number of times, so that the second sampling signal for the first preset number of times is rapidly acquired, and the inverter is judged to be in a short-circuit working condition or a heavy-load working condition according to the second sampling signal for the first preset number of times and the preset short-circuit working condition. By applying the technical scheme provided by the embodiment of the application, the short circuit or heavy load working condition of the inverter can be rapidly determined, the problem of misjudgment of the short circuit working condition by the inverter is solved, the unexpected shutdown or equipment failure of the inverter caused by misjudgment of the working condition is avoided, and the problem of damage to inverter devices or loads caused by short circuit to ground is avoided.
In some embodiments, the step of determining the working condition of the inverter according to the second sampling signal of the first preset times and the preset short-circuit working condition includes:
If the number of times of the second sampling signals meeting the preset short-circuit working condition in the second sampling signals of the first preset times is larger than or equal to the second preset times, determining the working condition of the inverter as a short-circuit working condition; otherwise, determining the working condition of the inverter as a heavy load working condition.
In some embodiments, the working condition detection method may further include the following steps: and under the condition that the working condition of the inverter is a heavy-load working condition, after waiting for a second preset time period, controlling the switching tube and the relay to be attracted.
In some embodiments, the working condition detection method may further include the following steps: after waiting for the second preset time length to control the switching tube and the relay to be attracted, acquiring a third sampling signal of the three-phase current output by the switching tube; if the third sampling signal meets the preset heavy load working condition, the switching tube and/or the relay is/are controlled to be turned off, and first prompt information is output, wherein the first prompt information is used for prompting a user to relieve load.
In some embodiments, the working condition detection method may further include the following steps: and under the condition that the working condition of the inverter is a short-circuit working condition, outputting second prompt information, wherein the second prompt information is used for prompting the user circuit to have a short circuit.
In some embodiments, the preset short-circuit condition is that the sampling signal is greater than a first preset current value, the sampling signal is greater than a rated current value of a first preset multiple, and the current difference between at least one phase and the other phase is greater than a second preset current value.
Corresponding to the working condition detection method, the embodiment of the application also provides a working condition detection device, as shown in fig. 4, which is applied to a DSP of an inverter, wherein the inverter comprises the DSP, a switching tube, a relay and a direct current bus; the direct current bus is connected with the switching tube, the switching tube is connected with the relay, the relay is used for being connected with a load, and the DSP is connected with the switching tube and the relay; the device comprises:
the control module 41 is used for controlling the switching tube and the relay to be attracted;
the obtaining module 42 is configured to obtain a first sampling signal of the three-phase current output by the switching tube within a first preset duration after the switching tube and the relay are attracted;
the control module 41 is further configured to control the switching tube and/or the relay to be turned off if the first sampling signal meets a preset short-circuit condition; reducing the output voltage of the switching tube to a target voltage, wherein the ratio of the target voltage to the rated voltage of the inverter is a preset ratio; controlling the switching tube and the relay to be attracted for a first preset time according to the target voltage, wherein the attracting time of the switching tube and the relay each time is the first preset time;
the obtaining module 42 is further configured to obtain a second sampling signal of the three-phase current output by the switching tube within a first preset duration after each time of actuation of the switching tube and the relay;
The control module 41 is further configured to determine a working condition of the inverter according to the second sampling signal of the first preset number of times and a preset short-circuit working condition, where the working condition of the inverter is a short-circuit working condition or a heavy-load working condition.
According to the technical scheme provided by the embodiment of the application, the DSP in the inverter is used for acquiring the first sampling signal of the three-phase current output by the switching tube within the first preset time after the switching tube and the relay are attracted, if the first sampling signal meets the preset short-circuit working condition, the output voltage of the switching tube is reduced, then the switching tube and the relay are controlled to conduct attraction for a first preset number of times, so that the second sampling signal for the first preset number of times is rapidly acquired, and the inverter is judged to be in a short-circuit working condition or a heavy-load working condition according to the second sampling signal for the first preset number of times and the preset short-circuit working condition. By applying the technical scheme provided by the embodiment of the application, the short circuit or heavy load working condition of the inverter can be rapidly determined, the problem of misjudgment of the short circuit working condition by the inverter is solved, the unexpected shutdown or equipment failure of the inverter caused by misjudgment of the working condition is avoided, and the problem of damage to inverter devices or loads caused by short circuit to ground is avoided.
In some embodiments, the control module 41 may also be configured to: if the number of times of the second sampling signals meeting the preset short-circuit working condition in the second sampling signals of the first preset times is larger than or equal to the second preset times, determining the working condition of the inverter as a short-circuit working condition; otherwise, determining the working condition of the inverter as a heavy load working condition.
In some embodiments, the control module 41 described above may also be used to: and under the condition that the working condition of the inverter is a heavy-load working condition, after waiting for a second preset time period, controlling the switching tube and the relay to be attracted.
In some embodiments, the acquisition module 42 described above may also be used to: after waiting for the second preset time length to control the switching tube and the relay to be attracted, acquiring a third sampling signal of the three-phase current output by the switching tube;
the control module 41 described above may also be used to: if the third sampling signal meets the preset heavy load working condition, the switching tube and/or the relay is/are controlled to be turned off, and first prompt information is output, wherein the first prompt information is used for prompting a user to relieve load.
In some embodiments, the control module 41 described above may also be used to: and under the condition that the working condition of the inverter is a short-circuit working condition, outputting second prompt information, wherein the second prompt information is used for prompting the user circuit to have a short circuit.
In some embodiments, the preset short-circuit condition is that the sampling signal is greater than a first preset current value, the sampling signal is greater than a rated current value of a first preset multiple, and the current difference between at least one phase and the other phase is greater than a second preset current value.
In the above embodiments, it may be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented in software, may be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When loaded and executed on a computer, produces a flow or function in accordance with embodiments of the present application, in whole or in part. The computer may be a general purpose computer, a special purpose computer, a computer network, or other programmable apparatus. The computer instructions may be stored in or transmitted from one computer-readable storage medium to another, for example, by wired (e.g., coaxial cable, optical fiber, digital Subscriber Line (DSL)), or wireless (e.g., infrared, wireless, microwave, etc.). The computer readable storage medium may be any available medium that can be accessed by a computer or a data storage device such as a server, data center, etc. that contains an integration of one or more available media. The usable medium may be a magnetic medium (e.g., floppy Disk, hard Disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid State Disk (SSD)), etc.
It is noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
In this specification, each embodiment is described in a related manner, and identical and similar parts of each embodiment are all referred to each other, and each embodiment mainly describes differences from other embodiments. In particular, for the method and apparatus embodiments, the description is relatively simple, as it is substantially similar to the inverter embodiments, with reference to portions of the description of the inverter embodiments being relevant.
The foregoing description is only of the preferred embodiments of the present application and is not intended to limit the scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application are included in the protection scope of the present application.

Claims (11)

1. The inverter is characterized by comprising a digital signal processor DSP, a switching tube, a relay and a direct current bus; the direct current bus is connected with the switch tube, the switch tube is connected with the relay, the relay is used for being connected with a load, and the DSP is connected with the switch tube and the relay;
the DSP is used for:
controlling the switching tube and the relay to be attracted; acquiring a first sampling signal of three-phase current output by the switching tube within a first preset duration after the switching tube and the relay are attracted; if the first sampling signal meets the preset short-circuit working condition, the switching tube and/or the relay are/is controlled to be turned off;
reducing the output voltage of the switching tube to a target voltage, wherein the ratio of the target voltage to the rated voltage of the inverter is a preset ratio; controlling the switching tube and the relay to be attracted for a first preset time according to the target voltage, wherein the attracting time of the switching tube and the relay each time is a first preset time; acquiring a second sampling signal of the three-phase current output by the switching tube within a first preset duration after each time of the switching tube and the relay are attracted; determining the working condition of the inverter according to the second sampling signals of the first preset times and the preset short-circuit working condition, wherein the working condition is a short-circuit working condition or a heavy-load working condition;
The DSP is specifically used for:
if the number of times of the second sampling signals meeting the preset short-circuit working condition in the second sampling signals of the first preset times is larger than or equal to the second preset times, determining that the working condition of the inverter is a short-circuit working condition; otherwise, determining the working condition of the inverter as a heavy load working condition.
2. The inverter of claim 1, wherein the DSP is further configured to:
and under the condition that the working condition of the inverter is a heavy-load working condition, after waiting for a second preset time period, controlling the switching tube and the relay to be attracted.
3. The inverter of claim 2, wherein the DSP is further configured to:
after waiting for the second preset time length to control the switching tube and the relay to be attracted, acquiring a third sampling signal of the three-phase current output by the switching tube; if the third sampling signal meets the preset heavy load working condition, the switching tube and/or the relay is/are controlled to be turned off, and first prompt information is output, wherein the first prompt information is used for prompting a user to relieve load.
4. The inverter of claim 1, wherein the DSP is further configured to:
and under the condition that the working condition of the inverter is a short-circuit working condition, outputting second prompt information, wherein the second prompt information is used for prompting a user that the circuit is short-circuited.
5. The inverter of any of claims 1-4, wherein the preset short circuit condition is a sampling signal greater than a first preset current value, the sampling signal greater than a rated current value of a first preset multiple, and a current difference between at least one phase and at least one phase is greater than a second preset current value.
6. The working condition detection method is characterized by being applied to a Digital Signal Processor (DSP) of an inverter, wherein the inverter comprises the DSP, a switching tube, a relay and a direct current bus; the direct current bus is connected with the switch tube, the switch tube is connected with the relay, the relay is used for being connected with a load, and the DSP is connected with the switch tube and the relay; the method comprises the following steps:
controlling the switching tube and the relay to be attracted;
acquiring a first sampling signal of three-phase current output by the switching tube within a first preset duration after the switching tube and the relay are attracted;
if the first sampling signal meets the preset short-circuit working condition, the switching tube and/or the relay are/is controlled to be turned off;
reducing the output voltage of the switching tube to a target voltage, wherein the ratio of the target voltage to the rated voltage of the inverter is a preset ratio;
Controlling the switching tube and the relay to be attracted for a first preset time according to the target voltage, wherein the attracting time of the switching tube and the relay each time is a first preset time;
acquiring a second sampling signal of the three-phase current output by the switching tube within a first preset duration after each time of the switching tube and the relay are attracted;
determining the working condition of the inverter according to the second sampling signals of the first preset times and the preset short-circuit working condition, wherein the working condition is a short-circuit working condition or a heavy-load working condition;
the step of determining the working condition of the inverter according to the second sampling signals of the first preset times and the preset short-circuit working condition comprises the following steps:
if the number of times of the second sampling signals meeting the preset short-circuit working condition in the second sampling signals of the first preset times is larger than or equal to the second preset times, determining that the working condition of the inverter is a short-circuit working condition; otherwise, determining the working condition of the inverter as a heavy load working condition.
7. The method of claim 6, wherein the method further comprises:
and under the condition that the working condition of the inverter is a heavy-load working condition, after waiting for a second preset time period, controlling the switching tube and the relay to be attracted.
8. The method of claim 7, wherein the method further comprises:
after waiting for the second preset time length to control the switching tube and the relay to be attracted, acquiring a third sampling signal of the three-phase current output by the switching tube; if the third sampling signal meets the preset heavy load working condition, the switching tube and/or the relay is/are controlled to be turned off, and first prompt information is output, wherein the first prompt information is used for prompting a user to relieve load.
9. The method of claim 6, wherein the method further comprises:
and under the condition that the working condition of the inverter is a short-circuit working condition, outputting second prompt information, wherein the second prompt information is used for prompting a user that the circuit is short-circuited.
10. The method of any of claims 6-9, wherein the predetermined short circuit condition is a sampling signal greater than a first predetermined current value, the sampling signal greater than a nominal current value of a first predetermined multiple, and a current difference between at least one phase and the other phase is greater than a second predetermined current value.
11. The working condition detection device is characterized by being applied to a Digital Signal Processor (DSP) of an inverter, wherein the inverter comprises the DSP, a switching tube, a relay and a direct current bus; the direct current bus is connected with the switch tube, the switch tube is connected with the relay, the relay is used for being connected with a load, and the DSP is connected with the switch tube and the relay; the device comprises:
The control module is used for controlling the switching tube and the relay to be attracted;
the acquisition module is used for acquiring a first sampling signal of the three-phase current output by the switching tube in a first preset duration after the switching tube and the relay are attracted;
the control module is further used for controlling the switching tube and/or the relay to be turned off if the first sampling signal meets a preset short-circuit working condition; reducing the output voltage of the switching tube to a target voltage, wherein the ratio of the target voltage to the rated voltage of the inverter is a preset ratio; controlling the switching tube and the relay to be attracted for a first preset time according to the target voltage, wherein the attracting time of the switching tube and the relay each time is a first preset time;
the acquisition module is also used for acquiring a second sampling signal of the three-phase current output by the switching tube in a first preset time length after the switching tube and the relay are attracted each time;
the control module is further used for determining the working condition of the inverter according to the second sampling signals of the first preset times and the preset short-circuit working condition, wherein the working condition is a short-circuit working condition or a heavy-load working condition;
The control module is specifically configured to: if the number of times of the second sampling signals meeting the preset short-circuit working condition in the second sampling signals of the first preset times is larger than or equal to the second preset times, determining that the working condition of the inverter is a short-circuit working condition; otherwise, determining the working condition of the inverter as a heavy load working condition.
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