CN108761319B - Relay failure detection method, device and system for photovoltaic grid-connected inverter - Google Patents
Relay failure detection method, device and system for photovoltaic grid-connected inverter Download PDFInfo
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- CN108761319B CN108761319B CN201810305928.9A CN201810305928A CN108761319B CN 108761319 B CN108761319 B CN 108761319B CN 201810305928 A CN201810305928 A CN 201810305928A CN 108761319 B CN108761319 B CN 108761319B
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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- G01R31/327—Testing of circuit interrupters, switches or circuit-breakers
- G01R31/3277—Testing of circuit interrupters, switches or circuit-breakers of low voltage devices, e.g. domestic or industrial devices, such as motor protections, relays, rotation switches
- G01R31/3278—Testing of circuit interrupters, switches or circuit-breakers of low voltage devices, e.g. domestic or industrial devices, such as motor protections, relays, rotation switches of relays, solenoids or reed switches
Abstract
The embodiment of the invention provides a method, a device and a system for detecting the failure of a relay of a photovoltaic grid-connected inverter. And then, acquiring a voltage value of the first capacitor in a preset time period, and determining a first target value according to the direct current value of the voltage value and the alternating current value of the voltage value. And when the first target value is less than or equal to the preset relay adhesion fault threshold value, determining that the first relay is not subjected to adhesion fault, and when the first target value is greater than the preset relay adhesion fault threshold value, determining that the first relay is subjected to adhesion fault. Therefore, the scheme determines whether the relay breaks down or not by detecting the voltage value of the first capacitor and then comparing the voltage value with the preset threshold value. Only one voltage needs to be collected, the cost of detection hardware and the resources of a digital processing chip can be saved, and the judgment result is reliable due to the obvious preset threshold characteristics, so that the detection accuracy is improved.
Description
Technical Field
The invention relates to the technical field of new energy power generation, in particular to a method, a device and a system for detecting failure of a relay of a photovoltaic grid-connected inverter.
Background
The PV grid-connected inverter is an electric energy conversion device connected between a PV photovoltaic panel and a power grid, and functions to convert direct current generated by the PV photovoltaic panel into alternating current. For safety reasons, it is desirable that the inverter be able to timely remove the inverter from the grid upon detection of some abnormal condition.
At present, mainstream photovoltaic grid-connected inverters (such as a group-series type photovoltaic grid-connected inverter and a distributed photovoltaic grid-connected inverter) are isolated at an inversion side and a power grid side through relays, and the inverters are disconnected when abnormal conditions are detected, so that the inverters are timely cut off from the power grid.
Specifically, as shown in fig. 1, a double relay is needed to isolate the inverter from the grid, such as S1 and S2, so as to achieve the purpose of safety redundancy, and meanwhile, the fault condition of the relay needs to be accurately detected before the inverter is grid-connected, which generally includes two conditions: the relay sticking fault (namely the relay can not be normally switched off) and the relay normally-off fault (namely the relay can not be normally switched on).
At present, a commonly used detection method is to collect the inverter voltage Vinv and the grid voltage Vac measured by the inverter through the inverter, and then detect the relay fault condition by comparing the relevant values of the inverter voltage Vinv and the grid voltage Vac, and the specific process is as follows:
(1) detecting the sticking fault of the relay: firstly, a suction relay S1 is connected, a relay S2 is disconnected, and an inverter acquires inversion voltage Vinv and grid voltage Vac; secondly, the numerical conditions of Vinv and Vac (such as an effective value of Vinv-Vac, which is recorded as RMS | Vinv-Vac |) are compared in real time through a digital processing chip (such as a DSP) in the inverter, if RMS | Vinv-Vac | < Δ V1(Δ V1 is a given threshold value for judging the sticking fault of the relay), S2 is considered to be the suction, that is, the sticking fault occurs in S2; if RMS | Vinv-Vac | > Δ V1, then S2 is considered normal; finally, similarly to S2, the disconnection S1 may detect S1 whether a sticky failure has occurred.
(2) Detecting the normally-off fault of the relay: firstly, simultaneously attracting and engaging relays S1 and S2, and collecting inversion voltage Vinv and grid voltage Vac by an inverter; secondly, the numerical conditions of Vinv and Vac are compared in real time through a digital processing chip (such as a DSP) in the inverter, if RMS | Vinv-Vac | < Δ V2(Δ V2 is a given threshold value for judging the normally-open fault of the relay), S1 and S2 are considered to be normally attracted, and if RMS | Vinv-Vac | > Δ V2, the normally-open fault of S1 or S2 is considered to occur.
However, the inventor has found that, for a three-phase inverter system, the above-mentioned inverter voltage Vinv and grid voltage Vac need to be collected, for example, when detecting a failure condition of two relays of the a-phase, the inverter voltage Vinv _ a of the a-phase and the grid voltage Vac _ a of the a-phase need to be collected at the same time, and then the above-mentioned determination logic is repeated. Similarly, when the relay fault of the B-phase and the C-phase is judged, the inverse voltage Vinv _ B, Vinv _ C of the B-phase and the C-phase and the grid voltage Vac _ B, Vac _ C of the B-phase and the C-phase need to be respectively acquired, so that three inverse voltage sampling circuits and three grid voltage sampling circuits are required in the inverter, and a digital processing chip (such as a DSP) in the inverter also needs a corresponding number of sampling ports, so that the hardware cost is increased and the resource of the digital processing chip is wasted.
Therefore, it is a great technical problem to be solved by those skilled in the art how to provide a method, an apparatus and a system for detecting a relay failure of a photovoltaic grid-connected inverter, which can reduce the cost of detection hardware and improve the accuracy of detection.
Disclosure of Invention
In view of this, embodiments of the present invention provide a method, an apparatus, and a system for detecting a relay failure of a photovoltaic grid-connected inverter, which can reduce the cost of detection hardware and improve the accuracy of detection.
In order to achieve the above purpose, the embodiments of the present invention provide the following technical solutions:
a relay failure detection method of a photovoltaic grid-connected inverter is applied to a photovoltaic grid-connected inverter system, the photovoltaic grid-connected inverter system comprises a bus capacitor, a first capacitor, an inversion unit, a first relay, a second relay and a filtering module, the bus capacitor is provided with a target midpoint, the photovoltaic grid-connected inverter system is provided with a power grid neutral point, and the relay failure detection method comprises the following steps:
controlling the first relay to be closed and controlling the second relay to be opened;
acquiring a voltage value of the first capacitor in a preset time period, wherein the preset time period comprises at least one power grid period;
determining a first target value according to the direct-current value of the voltage value and the alternating-current value of the voltage value;
and when the first target value is less than or equal to a preset relay sticking fault threshold value, determining that the first relay is not subjected to sticking fault, and when the first target value is greater than the preset relay sticking fault threshold value, determining that the first relay is subjected to sticking fault.
Optionally, the method further includes:
controlling the second relay to be closed and controlling the first relay to be opened;
acquiring a voltage value of the first capacitor in a preset time period, wherein the preset time period comprises at least one power grid period;
determining the first target value according to the direct-current value of the voltage value and the alternating-current value of the voltage value;
and when the first target value is less than or equal to a preset relay sticking fault threshold value, determining that the second relay does not have a sticking fault, and when the first target value is greater than the preset relay sticking fault threshold value, determining that the second relay has a sticking fault.
Optionally, the determining a first target value according to the dc value of the voltage value and the ac value of the voltage value includes:
determining the average value of the voltage values of the first capacitor as the direct current value;
and determining the periodic root mean square value of the difference value between the direct current value and the alternating current value of the first capacitor as the first target value.
Optionally, the preset relay adhesion fault threshold and the preset relay normally-off fault threshold are both greater than 0 and less than or equal to the periodic root mean square value of the grid voltage on the first capacitor.
A relay failure detection method of a photovoltaic grid-connected inverter is applied to a photovoltaic grid-connected inverter system, the photovoltaic grid-connected inverter system comprises a bus capacitor, a first capacitor, an inversion unit, a first relay, a second relay and a filtering module, the bus capacitor is provided with a target midpoint, the photovoltaic grid-connected inverter system is provided with a power grid neutral point, and the relay failure detection method comprises the following steps:
controlling both the first relay and the second relay to be closed;
acquiring a voltage value of the first capacitor in a preset time period, wherein the preset time period comprises at least one power grid period;
determining a second target value according to the direct-current value of the voltage value and the alternating-current value of the voltage value;
and when the second target value is less than or equal to a preset relay normally-off fault threshold value, determining that the first relay or the second relay has a normally-off fault, and when the second target value is greater than the preset relay normally-off fault threshold value, determining that the first relay and the second relay do not have a normally-off fault.
The utility model provides a photovoltaic grid-connected inverter's relay failure detection device, is applied to photovoltaic grid-connected inverter system, photovoltaic grid-connected inverter system includes bus-bar capacitance, first electric capacity, contravariant unit, first relay, second relay and filtering module, bus-bar capacitance has the target midpoint, photovoltaic grid-connected inverter system has the electric wire netting neutral point, relay failure detection device includes:
the first control module is used for controlling the first relay to be closed and controlling the second relay to be opened;
the first acquisition module is used for acquiring the voltage value of the first capacitor within a preset time period, wherein the preset time period comprises at least one power grid period;
the first determining module is used for determining a first target value according to the direct-current value of the voltage value and the alternating-current value of the voltage value;
and the second determining module is used for determining that the first relay does not have the sticky fault when the first target value is less than or equal to a preset relay sticky fault threshold value, and determining that the first relay has the sticky fault when the first target value is greater than the preset relay sticky fault threshold value.
Optionally, the third determining module includes:
the first determining unit is used for determining that the average value of the voltage values of the first capacitor is the direct-current value;
a second determining unit, configured to determine a periodic root mean square value of a difference between the dc score and the ac score of the first capacitor as the first target value.
Optionally, the preset relay adhesion fault threshold and the preset relay normally-off fault threshold are both greater than 0 and less than or equal to the periodic root mean square value of the grid voltage on the first capacitor.
A relay failure detection device of a photovoltaic grid-connected inverter comprises:
the second control module is used for controlling the first relay and the second relay to be closed;
the second acquisition module is used for acquiring the voltage value of the first capacitor within a preset time period, wherein the preset time period comprises at least one power grid period;
the third determining module is used for determining a second target value according to the direct-current value of the voltage value and the alternating-current value of the voltage value;
and the fourth determining module is used for determining that the first relay or the second relay has the normally-off fault when the second target value is smaller than or equal to a preset relay normally-off fault threshold value, and determining that the first relay and the second relay do not have the normally-off fault when the second target value is larger than the preset relay normally-off fault threshold value.
A relay failure detection system of a photovoltaic grid-connected inverter comprises any one relay failure detection device.
Based on the technical scheme, the embodiment of the invention provides a relay failure detection method for a photovoltaic grid-connected inverter. And then acquiring the voltage value of the first capacitor in a preset time period, and determining a first target value according to the direct current value of the voltage value and the alternating current value of the voltage value. And when the first target value is less than or equal to a preset relay sticking fault threshold value, determining that the first relay is not subjected to sticking fault, and when the first target value is greater than the preset relay sticking fault threshold value, determining that the first relay is subjected to sticking fault. Therefore, the scheme determines whether the relay breaks down or not by detecting the voltage value of the first capacitor and then comparing the voltage value with the preset threshold value. Only one voltage needs to be collected, the cost of detection hardware and the resources of a digital processing chip can be saved, and the judgment result is reliable due to the obvious preset threshold characteristics, so that the detection accuracy is improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a photovoltaic grid-connected inverter in the prior art;
fig. 2 is a schematic structural diagram of a photovoltaic grid-connected inverter according to an embodiment of the present invention;
fig. 3 is a schematic flow chart of a method for detecting a relay failure of a photovoltaic grid-connected inverter according to an embodiment of the present invention;
fig. 4 is a schematic flowchart of a specific example of a method for detecting a relay failure of a photovoltaic grid-connected inverter according to an embodiment of the present invention;
fig. 5 is a schematic flow chart of a method for detecting a relay failure of a photovoltaic grid-connected inverter according to an embodiment of the present invention;
fig. 6 is another schematic flow chart of a specific example of a method for detecting a relay failure of a photovoltaic grid-connected inverter according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram of a relay failure detection device of a photovoltaic grid-connected inverter according to an embodiment of the present invention.
Detailed Description
Referring to fig. 2, fig. 2 is a schematic structural diagram of a pv grid-connected inverter system applied to a method for detecting a relay failure of a pv grid-connected inverter according to an embodiment of the present invention, where the pv grid-connected inverter system includes a bus capacitor (C1 and C2), a first capacitor CY, an inverter unit 201, a first relay S1, a second relay S2, and a filtering module.
The filtering module may be an LCL filter, and includes an inductor L1, an inductor L2, and a capacitor Cf. The bus capacitor has a target midpoint O, and the photovoltaic grid-connected inverter system has a grid neutral point N.
The first capacitor CY may be disposed between the output negative electrode PV of the photovoltaic grid-connected inverter and ground, or may be disposed at another suitable position, such as between PV + and ground, where the suitable position may be selected according to actual design requirements.
Based on the inverter structure of fig. 2, the relay failure detection method provided by the embodiment of the invention, as shown in fig. 3, includes the steps of:
s31, controlling the first relay to be closed and controlling the second relay to be opened;
s32, acquiring a voltage value of the first capacitor in a preset time period, wherein the preset time period comprises at least one power grid period;
s33, determining a first target value according to the direct-current value of the voltage value and the alternating-current value of the voltage value;
s34, when the first target value is smaller than or equal to a preset relay sticking fault threshold value, determining that the first relay does not have sticking fault, and when the first target value is larger than the preset relay sticking fault threshold value, determining that the first relay has sticking fault.
The inventor considers that generally, in order to filter out interference and personal injury which may be brought by common-mode signals, the photovoltaic grid-connected inverter generally adds Y capacitors at key positions relatively to filter out harmful common-mode signals. Therefore, the embodiment detects the relay fault by collecting the alternating current signal on the Y capacitor and matching with the action of the relay self-checking switch.
In this embodiment, the first relay and the second relay may be the same relay, and the first relay and the second relay are distinguished by the first relay and the second relay in order to distinguish the installation positions of the relays. In this embodiment, a relay is controlled to be closed, and after other relays are opened, whether the closed relay breaks down or not is determined by obtaining preset parameters. Based on this principle, the method for detecting a failure of a relay provided by this embodiment may further include the steps of:
controlling the second relay to be closed and controlling the first relay to be opened;
acquiring a voltage value of the first capacitor in a preset time period, wherein the preset time period comprises at least one power grid period;
determining the first target value according to the direct-current value of the voltage value and the alternating-current value of the voltage value;
and when the first target value is less than or equal to a preset relay sticking fault threshold value, determining that the second relay does not have a sticking fault, and when the first target value is greater than the preset relay sticking fault threshold value, determining that the second relay has a sticking fault.
Schematically, with reference to fig. 4, the relay failure detection method provided in this embodiment is as follows:
(1) taking two relays of the A phase as an example, the relay of the A phase S1 is absorbed first, and the relay of the S2 is disconnected;
(2) after the relay completely responds to the action command, a digital processing chip (such as a DSP) samples the voltage of the CY capacitor in a fixed time period (such as DSP interruption time), and values of N power grid periods (N is an integer greater than or equal to 1) need to be collected, wherein the sampling value of the ith time is recorded as Vcy (i), and the total sampling times in the N power grid period time are recorded as N;
(3) calculating a direct current component in Vcy (i), namely calculating an average value of the acquired voltage of the CY capacitor;
(4) calculating the periodic root mean square value of an alternating current component in Vcy (i), namely calculating the periodic root mean square value of Vcy (i) -Vcy-ave, and marking the periodic root mean square value as RMS (Vcy (i) -Vcy-ave);
(5) and judging whether the sticking fault of the relay occurs according to the magnitude of the RMS (Vcy (i) -Vcy-ave). Because if relay S2 did not stick, then the voltage on CY capacitor would be PV negative to ground, a DC component, and RMS (Vcy (i) -Vcy-ave) would be a number close to 0; if the relay S2 is sticky, the phase a power grid is connected to the ground through a loop S1/S2- > Cf- > C2- > CY, where CY is a Y capacitor whose capacitance is much smaller than or equal to Cf and C2, so that the impedance of CY in this loop is much larger than that of Cf and C2, and according to the principle of impedance voltage division, the voltage of the phase a power grid is mostly divided across the CY capacitor, the voltage of CY capacitor is PV minus dc to ground + grid ac divided across the CY capacitor, and RMS (Vcy i) -Vcy _ ave is the periodic root mean square value of the grid voltage divided across the CY capacitor. According to the analysis, a threshold value delta V1 for judging the sticking fault of the relay can be set, and if RMS (Vcy (i) -Vcy _ ave) <deltaV 1, the fact that the sticking fault does not occur in S2 can be judged; if RMS (Vcy (i) -Vcy _ ave) >. DELTA.V 1, it may be determined that a sticky failure occurred at S2;
(6) by repeating the above steps (1) to (5), it can be determined whether or not the relay S1 has a sticky failure.
Therefore, the scheme determines whether the relay breaks down or not by detecting the voltage value of the first capacitor and then comparing the voltage value with the preset threshold value. Only one voltage needs to be collected, the cost of detection hardware and the resources of a digital processing chip can be saved, and the judgment result is reliable due to the obvious preset threshold characteristics, so that the detection accuracy is improved.
On the basis of the foregoing embodiment, the method for detecting a relay failure provided in this embodiment can determine whether a normally-off fault occurs in the relay, as shown in fig. 5, and includes:
s51, controlling the first relay and the second relay to be closed;
s52, acquiring a voltage value of the first capacitor in a preset time period, wherein the preset time period comprises at least one power grid period;
s53, determining a second target value according to the direct-current value of the voltage value and the alternating-current value of the voltage value;
and S54, when the second target value is less than or equal to a preset relay normally-off fault threshold value, determining that the first relay or the second relay has a normally-off fault, and when the second target value is greater than the preset relay normally-off fault threshold value, determining that the first relay and the second relay do not have a normally-off fault.
In this embodiment, the determining the first target value according to the dc score of the voltage value and the ac score of the voltage value may specifically be: and determining the average value of the voltage values of the first capacitor as the direct current value, and then determining the periodic root mean square value of the difference value between the direct current value and the alternating current value of the first capacitor as the first target value.
And the preset relay adhesion fault threshold value and the preset relay normally-off fault threshold value are both larger than 0 and smaller than or equal to the periodic root mean square value of the grid voltage on the first capacitor.
Schematically, with reference to fig. 6, another relay failure detection method provided in this embodiment is as follows:
(1) taking A successive electric appliance as an example, issuing S1 and S2 attracting instructions;
(2) repeating the steps (2) to (4) in the relay sticking fault detection method to obtain RMS (Vcy (i) -Vcy _ ave);
(3) and judging whether the relay has the normally-off fault according to the magnitude of the RMS (Vcy (i) -Vcy-ave). According to the analysis in the step (5) of judging the sticking fault of the relay, the following steps are obtained: RMS (Vcy (i) -Vcy _ ave) is a value close to 0 if a normally-off failure occurs at S1 or S2; RMS (Vcy (i) -Vcy-ave) is the periodic RMS value of the grid voltage divided on the CY capacitor if the relay is normally attracted. According to the analysis, a normally-off fault threshold value delta V2 of the relay can be set, and if RMS (Vcy (i) -Vcy _ ave) <deltaV 2, the normally-off fault of S1 or S2 can be judged; if RMS (Vcy (i) -Vcy _ ave) >. DELTA.V 2, it can be determined that S1 and S2 have not experienced a normally-off fault.
By combining the specific embodiments, in the scheme, only one voltage on the CY capacitor needs to be acquired for judging two faults of the relay, the sampling circuit is few, the hardware cost and the digital processing chip resource can be saved, and meanwhile, the threshold values delta V1 and delta V2 for judging the faults of the relay are obvious in characteristics, better in setting and reliable in relay detection result.
On the basis of the foregoing embodiment, this embodiment further provides a device corresponding to the above relay failure detection method, where the device is applied to a photovoltaic grid-connected inverter system, where the photovoltaic grid-connected inverter system includes a bus capacitor, a first capacitor, an inverter unit, a first relay, a second relay, and an LCL filter module, the bus capacitor has a target midpoint, the photovoltaic grid-connected inverter system has a grid neutral point, and the first capacitor is disposed between an output negative electrode of the photovoltaic grid-connected inverter and ground. As shown in fig. 7, the relay failure detection apparatus includes:
the first control module 71 is used for controlling the first relay to be closed and controlling the second relay to be opened;
a first obtaining module 72, configured to obtain a voltage value of the first capacitor for a preset time period, where the preset time period includes at least one power grid period;
a first determining module 73, configured to determine a first target value according to the dc score of the voltage value and the ac score of the voltage value;
and a second determining module 74, configured to determine that the first relay does not have the sticky failure when the first target value is less than or equal to a preset relay sticky failure threshold, and determine that the first relay has the sticky failure when the first target value is greater than the preset relay sticky failure threshold.
Optionally, the relay failure detection apparatus provided in this embodiment may further include:
the second control module is used for controlling the first relay and the second relay to be closed;
the second acquisition module is used for acquiring the voltage value of the first capacitor within a preset time period, wherein the preset time period comprises at least one power grid period;
the third determining module is used for determining a second target value according to the direct-current value of the voltage value and the alternating-current value of the voltage value;
and the fourth determining module is used for determining that the first relay or the second relay has the normally-off fault when the second target value is smaller than or equal to a preset relay normally-off fault threshold value, and determining that the first relay and the second relay do not have the normally-off fault when the second target value is larger than the preset relay normally-off fault threshold value.
In addition, the third determining module may include:
the first determining unit is used for determining that the average value of the voltage values of the first capacitor is the direct-current value;
a second determining unit, configured to determine a periodic root mean square value of a difference between the dc score and the ac score of the first capacitor as the first target value.
And the preset relay adhesion fault threshold value and the preset relay normally-off fault threshold value are both greater than 0 and less than or equal to the periodic root mean square value of the grid voltage on the first capacitor.
The working principle of the device is described in the above embodiments of the method, and will not be described repeatedly.
On the basis of the above embodiment, the present embodiment further provides a relay failure detection system for a photovoltaic grid-connected inverter, including any one of the above relay failure detection devices.
In summary, the embodiment of the present invention provides a method for detecting a failure of a relay of a photovoltaic grid-connected inverter, which includes first controlling the first relay to be closed, and controlling the second relay to be opened. And then acquiring the voltage value of the first capacitor in a preset time period, and determining a first target value according to the direct current value of the voltage value and the alternating current value of the voltage value. And when the first target value is less than or equal to a preset relay sticking fault threshold value, determining that the first relay is not subjected to sticking fault, and when the first target value is greater than the preset relay sticking fault threshold value, determining that the first relay is subjected to sticking fault. Therefore, the scheme determines whether the relay breaks down or not by detecting the voltage value of the first capacitor and then comparing the voltage value with the preset threshold value. Only one voltage needs to be collected, the cost of detection hardware and the resources of a digital processing chip can be saved, and the judgment result is reliable due to the obvious preset threshold characteristics, so that the detection accuracy is improved.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.
Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative components and steps have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in Random Access Memory (RAM), memory, Read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. The method for detecting the relay failure of the photovoltaic grid-connected inverter is characterized by being applied to a photovoltaic grid-connected inverter system, wherein the photovoltaic grid-connected inverter system comprises a bus capacitor, a first capacitor, an inversion unit, a first relay, a second relay and a filtering module, the bus capacitor is provided with a target midpoint, the photovoltaic grid-connected inverter system is provided with a power grid neutral point, the first capacitor is arranged between an output negative pole of the photovoltaic grid-connected inverter and the ground or between an output positive pole of the photovoltaic grid-connected inverter and the ground, and the method for detecting the relay failure comprises the following steps:
controlling the first relay to be closed and controlling the second relay to be opened;
acquiring a voltage value of the first capacitor in a preset time period, wherein the preset time period comprises at least one power grid period;
determining a first target value according to the direct-current value of the voltage value and the alternating-current value of the voltage value;
and when the first target value is smaller than a preset relay sticking fault threshold value, determining that the second relay does not have a sticking fault, and when the first target value is larger than the preset relay sticking fault threshold value, determining that the second relay has a sticking fault.
2. The relay failure detection method of claim 1, further comprising:
controlling the second relay to be closed and controlling the first relay to be opened;
acquiring a voltage value of the first capacitor in a preset time period, wherein the preset time period comprises at least one power grid period;
determining the first target value according to the direct-current value of the voltage value and the alternating-current value of the voltage value;
and when the first target value is smaller than a preset relay sticking fault threshold value, determining that the first relay is not subjected to sticking fault, and when the first target value is larger than the preset relay sticking fault threshold value, determining that the first relay is subjected to sticking fault.
3. The relay failure detection method according to claim 1 or 2, wherein the determining a first target value according to the dc score of the voltage value and the ac score of the voltage value includes:
determining the average value of the voltage values of the first capacitor as the direct current value;
and determining the periodic root mean square value of the difference value between the direct current value and the alternating current value of the first capacitor as the first target value.
4. The relay failure detection method according to claim 1 or 2, wherein the preset relay sticky fault threshold value and the preset relay normally-off fault threshold value are both greater than 0 and less than or equal to a periodic root mean square value of a grid voltage on the first capacitor.
5. The method for detecting the relay failure of the photovoltaic grid-connected inverter is characterized by being applied to a photovoltaic grid-connected inverter system, wherein the photovoltaic grid-connected inverter system comprises a bus capacitor, a first capacitor, an inversion unit, a first relay, a second relay and a filtering module, the bus capacitor is provided with a target midpoint, the photovoltaic grid-connected inverter system is provided with a power grid neutral point, the first capacitor is arranged between an output negative pole of the photovoltaic grid-connected inverter and the ground or between an output positive pole of the photovoltaic grid-connected inverter and the ground, and the method for detecting the relay failure comprises the following steps:
controlling both the first relay and the second relay to be closed;
acquiring a voltage value of the first capacitor in a preset time period, wherein the preset time period comprises at least one power grid period;
determining a second target value according to the direct-current value of the voltage value and the alternating-current value of the voltage value;
and when the second target value is larger than the preset relay normally-off fault threshold value, determining that the first relay and the second relay do not have normally-off faults.
6. The utility model provides a relay failure detection device of grid-connected PV inverter, its characterized in that is applied to grid-connected PV inverter system, grid-connected PV inverter system includes bus-bar capacitance, first electric capacity, contravariant unit, first relay, second relay and filtering module, bus-bar capacitance has the target midpoint, grid-connected PV inverter system has the electric wire netting neutral point, first electric capacity sets up between grid-connected PV inverter's output negative pole and ground or between grid-connected PV inverter's output positive pole and ground, relay failure detection device includes:
the first control module is used for controlling the first relay to be closed and controlling the second relay to be opened;
the first acquisition module is used for acquiring the voltage value of the first capacitor within a preset time period, wherein the preset time period comprises at least one power grid period;
the first determining module is used for determining a first target value according to the direct-current value of the voltage value and the alternating-current value of the voltage value;
and the second determining module is used for determining that the second relay does not have the sticky fault when the first target value is smaller than a preset relay sticky fault threshold value, and determining that the second relay has the sticky fault when the first target value is larger than the preset relay sticky fault threshold value.
7. The relay failure detection apparatus of claim 6, wherein the first determination module comprises:
the first determining unit is used for determining that the average value of the voltage values of the first capacitor is the direct-current value;
a second determining unit, configured to determine a periodic root mean square value of a difference between the dc score and the ac score of the first capacitor as the first target value.
8. The relay failure detection device of claim 6, wherein the predetermined relay sticky fault threshold and the predetermined relay normally-off fault threshold are both greater than 0 and less than or equal to a periodic root mean square value of the grid voltage across the first capacitor.
9. The utility model provides a relay failure detection device of grid-connected PV inverter, its characterized in that is applied to grid-connected PV inverter system, grid-connected PV inverter system includes bus-bar capacitance, first electric capacity, contravariant unit, first relay, second relay and filtering module, bus-bar capacitance has the target midpoint, grid-connected PV inverter system has the electric wire netting neutral point, first electric capacity sets up between grid-connected PV inverter's output negative pole and ground or between grid-connected PV inverter's output positive pole and ground, relay failure detection device includes:
the second control module is used for controlling the first relay and the second relay to be closed;
the second acquisition module is used for acquiring the voltage value of the first capacitor within a preset time period, wherein the preset time period comprises at least one power grid period;
the third determining module is used for determining a second target value according to the direct-current value of the voltage value and the alternating-current value of the voltage value;
and the fourth determining module is used for determining that the first relay or the second relay has the normally-off fault when the second target value is smaller than a preset relay normally-off fault threshold value, and determining that the first relay and the second relay do not have the normally-off fault when the second target value is larger than the preset relay normally-off fault threshold value.
10. A relay failure detection system of a photovoltaic grid-connected inverter, characterized by comprising a relay failure detection device according to any one of claims 6 to 9.
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