CN115166508B

CN115166508B - Failure detection method and relay failure detection device for grid-connected inverter

Info

Publication number: CN115166508B
Application number: CN202211092920.1A
Authority: CN
Inventors: 伊晓光; 方湃盛
Original assignee: Shenzhen Yuntian Digital Energy Co ltd
Current assignee: Shenzhen Yuntian Digital Energy Co ltd
Priority date: 2022-09-08
Filing date: 2022-09-08
Publication date: 2022-11-22
Anticipated expiration: 2042-09-08
Also published as: CN115166508A

Abstract

The utility model discloses a failure detection method and relay failure detection device of grid-connected inverter, the method is applied to the relay failure detection circuit of single-phase and three-phase grid-connected inverter, the circuit includes contravariant module, relay group, electric wire netting, the first electric capacity, impedance element, the second electric capacity that the relay group connects in parallel in proper order in series, the main relay of relay group and slave relay are switched on or off by first drive signal and second drive signal control respectively. The method comprises the following steps: and simultaneously controlling the main relay and the auxiliary relay to be disconnected so as to judge whether the fault is the first fault reason or not by comparing the power grid side voltage and the inversion side voltage of the relay group, and if not, alternately controlling one of the main relay or the auxiliary relay to be switched on, so that when the voltage of the impedance element is greater than the preset voltage threshold, the phase directions of the voltage of the impedance element and the voltage of the second power grid side are compared, and the relay with the specific short-circuit fault is judged. The method and the device are favorable for improving the accuracy of relay fault detection.

Description

Failure detection method and relay failure detection device for grid-connected inverter

Technical Field

The application relates to the technical field of circuit detection, in particular to a failure detection method of a grid-connected inverter and a relay failure detection device.

Background

In an actual system, because grid-connected current is large, a relay adhesion short-circuit phenomenon (namely, a relay short-circuit phenomenon) caused by overcurrent easily occurs in a grid-connected inverter, and the short-circuit fault needs to be identified before the inverter is started. The grid-connected inverter in the related art only comprises an inverter module, a power grid, and a main relay and a slave relay which are connected with the inverter module and the power grid, and the conventional identification and detection method can only identify the short-circuit fault of all the main relays and/or the short-circuit fault of all the slave relays by controlling the on-off of the main relay and the slave relay in the grid-connected inverter, but cannot specifically identify the fault reason of the short circuit of a single main relay or a single slave relay.

Disclosure of Invention

The embodiment of the application provides a failure detection method and a relay failure detection device for a grid-connected inverter, so that the accuracy of fault detection of relays of a single-phase grid-connected inverter and a three-phase grid-connected inverter is improved.

In a first aspect, an embodiment of the present application provides a method for detecting a failure of a grid-connected inverter, where the method is applied to a relay failure detection circuit of a single-phase grid-connected inverter, where the relay failure detection circuit of the single-phase grid-connected inverter includes an inverter module, a switch module, and a drive module, the inverter module includes an input power source and two bridge arms connected in parallel with the input power source, and each of the bridge arms is connected in series with a first switching tube and a second switching tube; the switch module comprises a phase line branch, two ends of the phase line branch are respectively connected with the connecting ends of the first switch tube and the second switch tube in the two bridge arms, the phase line branch comprises two relay groups and a power grid which are arranged in series, and sub-branches which are respectively connected with one relay group in parallel, the relay groups comprise a main relay and a slave relay which are arranged in series, one end of the main relay, far away from the slave relay, is connected with the power grid, one end of the slave relay, far away from the main relay, is connected with the bridge arms, and the sub-branches comprise a first capacitor, an impedance element and a second capacitor which are sequentially connected in series; the driving module is used for controlling the main relay and the auxiliary relay to be switched on or off;

the method comprises the following steps:

under the initial state that a first driving signal for controlling the main relay and a second driving signal for controlling the auxiliary relay are both off signals, acquiring a first inversion side voltage and a first power grid side voltage of the phase line branch circuit; wherein the first drive signal and the second drive signal are from the drive module;

comparing the first inversion side voltage with the first power grid side voltage to obtain a first comparison result;

if the first comparison result is that the first inversion side voltage is equal to the first power grid side voltage, a first fault reason is obtained;

otherwise, alternately adjusting the first driving signal or the second driving signal to be a conducting signal;

acquiring a preset voltage threshold value of an impedance element, the voltage of the impedance element, and a second inversion side voltage and a second power grid side voltage of the phase line branch according to the adjusted first driving signal or second driving signal;

comparing the second inversion side voltage with a second power grid side voltage to obtain a second comparison result;

if the second comparison result is that the second inversion side voltage is equal to the second power grid side voltage, a second fault reason is obtained;

otherwise, comparing the voltage of the impedance element with the preset voltage threshold to obtain a third comparison result;

and if the third comparison result shows that the voltage of the impedance element is greater than the preset voltage threshold, comparing the voltage of the impedance element with the voltage of the second power grid side to obtain a third fault reason.

In a second aspect, an embodiment of the present application provides a method for detecting a failure of a grid-connected inverter, where the method is applied to a relay failure detection circuit of a three-phase grid-connected inverter, where the relay failure detection circuit of the three-phase grid-connected inverter includes an inverter module, a switch module, and a driving module, the inverter module includes an input power source and three bridge arms connected in parallel with the input power source, and each of the bridge arms is connected in series with a first switch tube and a second switch tube; the switch module comprises three phase line branches, wherein a first end of each phase line branch is connected with a connecting end of the first switch tube and the second switch tube in one bridge arm, a second end of each phase line branch is connected with each other, each phase line branch comprises a relay group and a power grid which are arranged in series, and sub-branches which are respectively connected with the relay groups in parallel, each relay group comprises a main relay and a slave relay which are arranged in series, one end of each main relay, far away from the corresponding slave relay, is connected with the power grid, one end of each slave relay, far away from the corresponding main relay, is connected with the corresponding bridge arm, and each sub-branch comprises a first capacitor, an impedance element and a second capacitor which are sequentially connected in series; the driving module is used for controlling the main relay and the auxiliary relay to be switched on or off;

the method comprises the following steps:

under the initial state that a first driving signal for controlling the main relay and a second driving signal for controlling the auxiliary relay are both off signals, acquiring a first inversion side voltage and a first power grid side voltage of each phase line branch circuit; wherein the first drive signal and the second drive signal are from the drive module;

comparing the first inversion side voltage of each phase line branch with the first power grid side voltage to obtain a first comparison result;

if the first comparison result is that the first inversion side voltage of the phase line branch is equal to the first power grid side voltage corresponding to the phase line branch, a first fault reason is obtained;

acquiring the voltage of an impedance element, a preset voltage threshold of the impedance element and the second power grid side voltage of each phase line branch according to the adjusted first driving signal or second driving signal;

comparing the voltage of the impedance element with the preset voltage threshold value to obtain a second comparison result;

and if the second comparison result shows that the voltage of the impedance element is greater than the preset voltage threshold, comparing the voltage of the impedance element with the voltage of a second power grid side corresponding to the phase line branch to obtain a second fault reason.

In a third aspect, an embodiment of the present application provides a relay failure detection device, which is applied to a relay failure detection circuit of a single-phase grid-connected inverter, where the relay failure detection circuit of the single-phase grid-connected inverter includes an inverter module, a switch module, and a driving module, the inverter module includes an input power source and two bridge arms connected in parallel with the input power source, and each of the bridge arms is connected in series with a first switching tube and a second switching tube; the switch module comprises a phase line branch, two ends of the phase line branch are respectively connected with the connecting ends of the first switch tube and the second switch tube in the two bridge arms, the phase line branch comprises two relay groups and a power grid which are arranged in series, and sub-branches which are respectively connected with one relay group in parallel, the relay groups comprise a main relay and a slave relay which are arranged in series, one end of the main relay, far away from the slave relay, is connected with the power grid, one end of the slave relay, far away from the main relay, is connected with the bridge arms, and the sub-branches comprise a first capacitor, an impedance element and a second capacitor which are sequentially connected in series; the driving module is used for controlling the main relay and the auxiliary relay to be switched on or off;

the device comprises:

the acquisition unit is used for acquiring a first inversion side voltage and a first power grid side voltage of the phase line branch circuit in an initial state that a first driving signal for controlling the main relay and a second driving signal for controlling the slave relay are both disconnection signals; and acquiring a preset voltage threshold value of the impedance element, the voltage of the impedance element, and the second inversion side voltage and the second power grid side voltage of the phase line branch circuit according to the adjusted first driving signal or second driving signal.

The processing unit is used for comparing the first inversion side voltage with the first power grid side voltage to obtain a first comparison result; if the first comparison result shows that the first inversion side voltage is equal to the first power grid side voltage, a first fault reason is obtained; otherwise, alternately adjusting the first driving signal or the second driving signal to be a conducting signal; comparing the second inversion side voltage with a second power grid side voltage to obtain a second comparison result; if the second comparison result is that the second inversion side voltage is equal to the second power grid side voltage, a second fault reason is obtained; otherwise, comparing the voltage of the impedance element with the preset voltage threshold value to obtain a third comparison result; and if the third comparison result shows that the voltage of the impedance element is greater than the preset voltage threshold, comparing the voltage of the impedance element with the voltage of the second power grid side to obtain a third fault reason.

In a fourth aspect, an embodiment of the present application provides a relay failure detection apparatus, where the apparatus is applied to a relay failure detection circuit of a three-phase grid-connected inverter, where the relay failure detection circuit of the three-phase grid-connected inverter includes an inverter module, a switch module, and a drive module, the inverter module includes an input power source and three bridge arms connected in parallel with the input power source, and each bridge arm is connected in series with a first switch tube and a second switch tube; the switching module comprises three phase line branches, wherein a first end of each phase line branch is connected with a connecting end of the first switching tube and the second switching tube in one bridge arm, a second end of each phase line branch is connected with each other, each phase line branch comprises a relay group and a power grid which are arranged in series, and sub-branches which are respectively connected with the relay groups in parallel, each relay group comprises a main relay and a slave relay which are arranged in series, one end of the main relay, far away from the slave relay, is connected with the power grid, one end of the slave relay, far away from the main relay, is connected with the bridge arm, and each sub-branch comprises a first capacitor, an impedance element and a second capacitor which are sequentially connected in series; the driving module is used for controlling the main relay and the auxiliary relay to be switched on or off;

the device comprises:

the acquisition unit is used for acquiring a first inversion side voltage and a first power grid side voltage of each phase line branch in an initial state that a first driving signal used for controlling the main relay and a second driving signal used for controlling the slave relay are both off signals; wherein the first drive signal and the second drive signal are from the drive module; the phase line branch circuit is used for adjusting a first driving signal or a second driving signal of the phase line branch circuit according to the first driving signal or the second driving signal;

the processing unit is used for comparing the first inversion side voltage of each phase line branch with the first power grid side voltage to obtain a first comparison result; if the first comparison result is that the first inversion side voltage of the phase line branch is equal to the first power grid side voltage corresponding to the phase line branch, a first fault reason is obtained; otherwise, alternately adjusting the first driving signal or the second driving signal to be a conducting signal; comparing the voltage of the impedance element with the preset voltage threshold value to obtain a second comparison result; and if the second comparison result shows that the voltage of the impedance element is greater than the preset voltage threshold, comparing the voltage of the impedance element with the voltage of a second power grid side corresponding to the phase line branch to obtain a second fault reason.

When the failure detection method and the failure detection circuit provided by the application are applied to the single-phase grid-connected relay, the first driving signal and the second driving signal can be set as disconnection signals firstly, so that whether the relay failure detection circuit of the single-phase grid-connected inverter has a fault of a first fault reason or not is judged by comparing whether the voltage of the first inversion side is equal to the voltage of the first power grid side or not; if not, the first driving signal or the second driving signal is adjusted to be a conducting signal, and therefore whether the fault of a second fault reason exists in a relay failure detection circuit of the single-phase grid-connected inverter is judged by comparing whether the adjusted second inversion side voltage is equal to the second power grid side voltage or not; and if the voltage of the impedance element is not greater than the preset voltage threshold, the voltage of the impedance element is compared with the phase direction of the voltage of the second power grid side, so that whether the fault of a third fault cause of the fault of the single main relay or the single slave relay exists in the relay failure detection circuit of the single-phase grid-connected inverter or not is judged, and the relay with the specific fault is identified. Therefore, the fault detection method and the fault detection device can detect the fault conditions of all the main relays and/or all the slave relays and also can detect the fault conditions of a single main relay or a single slave relay, thereby being beneficial to improving the fault detection accuracy of the relay of the grid-connected inverter and improving the use reliability of the grid-connected inverter.

When the failure detection method and the failure detection circuit provided by the application are applied to a three-phase grid-connected relay, the first driving signal and the second driving signal can be set as disconnection signals firstly, so that whether the failure detection circuit of the relay of the three-phase grid-connected inverter has a failure of a first failure reason or not is judged by comparing whether the first inversion side voltage of each phase line branch is equal to the first power grid side voltage or not; if not, the first driving signal or the second driving signal is adjusted to be a conducting signal, the voltage of the impedance element is compared with a preset voltage threshold value of the impedance element, if the voltage of the impedance element is larger than the preset voltage threshold value, the voltage of the impedance element is compared with the phase direction of the second power grid side voltage of each phase line branch circuit, and therefore whether the relay failure detection circuit of the three-phase grid-connected inverter has the fault of the second fault reason of the single main relay or the single slave relay fault is judged, and the relay with the specific fault is identified. Therefore, the condition of the simultaneous short-circuit fault of the main relay and the slave relay of each phase line branch can be detected, and the fault condition of a single main relay or a single slave relay in each phase line branch can also be detected, so that the accuracy of fault detection of the relay of the grid-connected inverter is improved, and the use reliability of the grid-connected inverter is improved.

Drawings

In order to more clearly illustrate the embodiments of the present application 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 some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic circuit diagram of a detection method for detecting a failure of a single-phase grid-connected inverter according to an embodiment of the present disclosure;

fig. 2 is a flowchart of a failure detection method of a single-phase grid-connected inverter according to an embodiment of the present disclosure;

fig. 3 is a schematic circuit diagram of a failure detection method of a three-phase grid-connected inverter according to an embodiment of the present disclosure;

fig. 4 is a flowchart of a failure detection method for a three-phase grid-connected inverter according to an embodiment of the present disclosure;

fig. 5 is a block diagram illustrating functional units of a relay failure detection apparatus applied to a single-phase grid-connected inverter according to an embodiment of the present disclosure;

fig. 6 is a functional unit composition block diagram of a relay failure detection device applied to a three-phase grid-connected inverter according to an embodiment of the present application.

Detailed Description

In order to make the technical solutions of the present application better understood by those skilled in the art, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The terms "first," "second," and the like in the description and claims of the present application and in the above-described drawings are used for distinguishing between different objects and not for describing a particular order. Furthermore, the terms "include" and "have," as well as any variations thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may alternatively include other steps or elements not listed, or inherent to such process, method, article, or apparatus.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein can be combined with other embodiments.

Referring to fig. 1, fig. 1 is a schematic circuit diagram of a detection method for detecting a failure of a single-phase grid-connected inverter according to an embodiment of the present disclosure.

The failure detection method of the grid-connected inverter is applied to a relay failure detection circuit of a single-phase grid-connected inverter, and the relay failure detection circuit of the single-phase grid-connected inverter comprises an inversion module, a switch module and a driving module. The inverter module comprises an input power Vin and two bridge arms connected in parallel with the input power Vin, wherein a first switching tube Q1 and a second switching tube Q2 are connected in series on one bridge arm, and a first switching tube Q3 and a second switching tube Q4 are connected in series on the other bridge arm. The switch module comprises a phase line branch, one end of the phase line branch is connected with the connecting end of the first switch tube Q1 and the second switch tube Q2, and the other end of the phase line branch is connected with the connecting end of the first switch tube Q3 and the second switch tube Q4. The phase line branch road is including two relay groups and electric wire netting Grid that establish ties and the sub-branch road with the parallelly connected setting of a relay group respectively, and a relay group is connected with electric wire netting Grid including the main relay K1 and the slave relay K2 that establish ties and set up, and main relay K1 keeps away from the one end of slave relay K2, and the one end that the slave relay K2 kept away from main relay K1 is connected with first switch tube Q1 and second switch tube Q2's link. Another relay group is connected with the link of second switch tube Q3 and first switch tube Q4 with the one end that main relay K3 kept away from auxiliary relay K4 including main relay K3 and the auxiliary relay K4 that establish ties and set up, main relay K3 is connected with electric wire netting Grid, and auxiliary relay K4 keeps away from main relay K3. Each sub-branch comprises a first capacitor, an impedance element and a second capacitor which are sequentially connected in series. The driving module is used for controlling the main relay and the auxiliary relay to be switched on or switched off.

The impedance element is a high-impedance circuit component, and for example, the impedance element may be a resistor, a capacitor, an inductor, or the like.

The relay failure detection circuit of the single-phase grid-connected inverter can further comprise two inductors L, and the slave relay K2 and the slave relay K4 are respectively connected with the bridge arm through one inductor L. Specifically, one end of an inductor L is connected to one end of the slave relay K2 away from the master relay K1, and the other end of the inductor L is connected to the connection end of the first switching tube Q1 and the second switching tube Q2. One end of another inductor L is connected with one end of the slave relay K4 far away from the master relay K3, and the other end of the inductor L is connected with the connecting end of the first switch tube Q3 and the second switch tube Q4.

It will be appreciated that the first and second capacitances of the two sub-branches may each be connected in series with a different impedance element. In this embodiment, in order to reduce the measurement parameters and improve the detection efficiency, the first capacitors and the second capacitors of the two sub-branches may be connected in series with the same impedance element.

When the single-phase grid-connected inverter works, the control module (not shown) controls the on/off of the first switch tube Q1, the second switch tube Q2, the first switch tube Q3 and the second switch tube Q4 in the inverter module to output voltage.

According to the relay short-circuit failure judgment method, the point A and the point B are constructed by utilizing the first capacitor, the second capacitor and the impedance element, and the high-impedance element is connected between the point A and the point B, so that the relay short-circuit failure judgment is realized by sampling the voltage of the impedance element, the voltage of the inversion side of the main relay and the voltage of the inversion side of the auxiliary relay and the voltage of the power grid side, all short-circuit failure conditions of the relay can be identified, and the relay with specific failure can be identified.

Referring to fig. 2, fig. 2 is a flowchart of a failure detection method of a grid-connected inverter according to an embodiment of the present disclosure. The failure detection method of the grid-connected inverter is applied to a relay failure detection circuit of a single-phase grid-connected inverter and is implemented before grid connection. As shown in fig. 2, the method for detecting the failure of the grid-connected inverter includes:

s101, acquiring a first inversion side voltage Uva and a first power grid side voltage Usa of the phase line branch circuit in an initial state that a first driving signal drive1 for controlling the main relay and a second driving signal drive2 for controlling the auxiliary relay are both off signals.

The first inversion side voltage Uva and the first power grid side voltage Usa are effective values. The first driving signal drive1 and the second driving signal drive2 are signals which are sent to the relay group by the driving module to control the connection or disconnection of the main relay and the auxiliary relay, the first driving signal drive1 is used for controlling the connection or disconnection of the main relay K1 and the main relay K3, and the second driving signal drive2 is used for controlling the connection or disconnection of the auxiliary relay K2 and the auxiliary relay K4. In order to simplify the structure of the single-phase grid-connected inverter, all the main relays are controlled by the same first driving signal drive1, and all the auxiliary relays are controlled by the same second driving signal drive 2.

Specifically, the first driving signal drive1 and the second driving signal drive2 are both turn-off signals, that is, the first driving signal drive1 and the second driving signal drive2 are both at zero level, so as to respectively control the main relay and the slave relay to be turned off.

S102, comparing the first inversion side voltage Uva with the first power grid side voltage Usa to obtain a first comparison result.

Step S102 is an operation performed in an initial state where the first driving signal drive1 and the second driving signal drive2 are both driven by the off signal.

In a specific implementation, comparing the first inverter side voltage Uva with the first grid side voltage Usa means comparing the magnitude of the first inverter side voltage Uva with the magnitude of the first grid side voltage Usa. The first comparison results in two cases: one is that the first inverter-side voltage Uva is equal to the first grid-side voltage Usa, and the other is that the first inverter-side voltage Uva is not equal to the first grid-side voltage Usa. Because each circuit component of the relay failure detection circuit of the single-phase grid-connected inverter has certain impedance, if the difference value between the first inversion side voltage Uva and the first power grid side voltage Usa is within a first preset range, it can also be determined that the first inversion side voltage Uva is equal to the first power grid side voltage Usa. The first preset range may be a range value set according to historical experience of the detection personnel, and specific numerical values of the first preset range are not further limited herein. When the first comparison result indicates that the first inverter-side voltage Uva is equal to the first grid-side voltage Usa, the following step S103 is executed; if the first comparison result indicates that the first inverter-side voltage Uva is not equal to the first grid-side voltage Usa, the following step S104 is performed.

S103, if the first comparison result indicates that the first inverter-side voltage Uva is equal to the first grid-side voltage Usa, a first fault cause is obtained.

If the first comparison result is that the first inverter side voltage Uva is equal to the first grid side voltage Usa, it indicates that although the execution actions of the first driving signal drive1 and the second driving signal drive2 respectively given to all the main relays and all the slave relays are off, the current actual circuit condition is that the relay failure detection circuit of the single-phase grid-connected inverter is in a conducting state. Therefore, it is possible to determine that the specific content of the first failure cause is that all the master relays and all the slave relays are short-circuited at the same time.

In specific implementation, if the first fault reason exists in the current actual circuit, the grid-connected inverter can report the fault and stop working.

And S104, if the first comparison result shows that the first inversion side voltage Uva is not equal to the first power grid side voltage Usa, alternately adjusting the first driving signal drive1 or the second driving signal drive2 to be a conducting signal.

If the first comparison result is that the first inverter-side voltage Uva is not equal to the first grid-side voltage Usa, it indicates that the relay failure detection circuit of the single-phase grid-connected inverter does not have a fault corresponding to the first fault cause, and therefore, if it is necessary to further identify whether the circuit has other fault conditions, steps S104 to S110 need to be executed to identify and determine.

In a specific implementation, in step S104, the first driving signal drive1 may be adjusted to be an on signal, and the second driving signal drive2 is still an off signal. Executing steps S105 to S110 at this time can detect whether there is a short circuit from the relay. After the steps S105 to S110 are completed, the first driving signal drive1 needs to be adjusted again to be the off signal, the second driving signal drive2 needs to be the on signal, and the steps S105 to S110 are performed again to detect whether the main relay is short-circuited according to the first driving signal drive1 and the second driving signal drive 2. All possible short-circuit fault conditions of the relay failure detection circuit of the single-phase grid-connected inverter can be identified through detection of the main relay and the auxiliary relay after the first driving signal drive1 and the second driving signal drive2 are adjusted. Of course, in other embodiments, the step S104 may also adjust the second driving signal drive2 to be an on signal, the first driving signal drive1 is still an off signal, and the subsequent steps are referred to above and will not be further described herein.

In one possible example, the adjusting the first driving signal drive1 or the second driving signal drive2 to be a turn-on signal includes: the single-phase grid-connected inverter starts phase-locking and wave-transmitting; when the second inverter side voltage Uva is equal to the second grid side voltage Usa, adjusting the first driving signal drive1 or the second driving signal drive2 to be a conducting signal; and the single-phase grid-connected inverter stops phase-locking wave generation.

It can be understood that before the first drive signal drive1 or the second drive signal drive2 is adjusted, that is, before the on or off states of the main relay and the slave relay are adjusted, the grid-connected inverter is enabled to send waves to the phase lock, so that the main relay or the slave relay can be prevented from being suddenly switched on or off to generate impact current, and therefore, the protection of each circuit component in the grid-connected inverter can be realized.

And S105, acquiring a preset voltage threshold value Uset of the impedance element, an impedance element voltage UR, and a second inversion side voltage Uva and a second power grid side voltage Usa of the phase line branch according to the adjusted first driving signal drive1 or second driving signal drive 2.

The impedance element voltage UR is a voltage of the impedance element, and the impedance element voltage UR, the second inverter-side voltage Uva, and the second grid-side voltage Usa are effective values. The preset voltage threshold Uset of the impedance element may be set according to the experience of the detecting person. The second inversion side voltage Uva and the second grid side voltage Usa are voltages obtained after the first driving signal drive1 and the second driving signal drive2 are adjusted. For example, the second inverter-side voltage Uva and the second grid-side voltage Usa may be voltage values when the first drive signal drive1 is an on signal and the second drive signal drive2 is an off signal; alternatively, the second inverter-side voltage Uva and the second grid-side voltage Usa may be voltage values when the first drive signal drive1 is the off signal and the second drive signal drive2 is the on signal.

S106, comparing the second inversion side voltage Uva with the second power grid side voltage Usa to obtain a second comparison result.

In specific implementation, comparing the second inverter side voltage Uva with the second grid side voltage Usa means comparing the magnitude of the second inverter side voltage Uva with the magnitude of the second grid side voltage Usa. The second alignment results have two cases: one is that the second inverter side voltage Uva is equal to the second grid side voltage Usa, and the other is that the second inverter side voltage Uva is not equal to the second grid side voltage Usa. Because each device of the relay failure detection circuit of the single-phase grid-connected inverter has a certain impedance, if the difference value between the second inverter side voltage Uva and the second grid side voltage Usa is within a second preset range, it can also be determined that the second inverter side voltage Uva is equal to the second grid side voltage Usa. The second preset range may be a range value set according to historical experience of the detection personnel, and specific numerical values of the second preset range are not further limited herein.

When the second comparison result indicates that the first inverter-side voltage Uva is equal to the first grid-side voltage Usa, the following step S107 is executed; if the second comparison result is that the first inverter-side voltage Uva is not equal to the first grid-side voltage Usa, the following step S108 is executed.

And S107, if the second comparison result shows that the second inverter side voltage Uva is equal to the second grid side voltage Usa, a second fault reason is obtained.

If the second comparison result is that the second inverter side voltage Uva is equal to the second grid side voltage Usa, it indicates that although the first driving signal drive1 and the second driving signal drive2 provide the main relay and the slave relay, the execution actions are as follows: one of the main relay and the slave relay is disconnected, and the other is connected, but the current actual circuit condition is that the relay failure detection circuit of the single-phase grid-connected inverter is in a connected state. Therefore, it can be determined that the specific content of the second failure cause is that two main relays that should perform the opening operation are short-circuited at the same time; alternatively, the specific content of the second failure cause is that two slave relays that should perform the opening operation are short-circuited at the same time.

In specific implementation, if the second fault cause exists in the current actual circuit, the grid-connected inverter can report the fault and stop working.

And S108, if the second comparison result shows that the second inversion side voltage Uva is not equal to the second power grid side voltage Usa, comparing the impedance element voltage UR with the preset voltage threshold value Uset to obtain a third comparison result.

If the second comparison result corresponding to the execution result of the step S107 is that the second inverter side voltage Uva and the second grid side voltage Usa are not equal in size, it indicates that the relay failure detection circuit of the single-phase grid-connected inverter does not have a fault corresponding to the second fault cause, and therefore, if it is necessary to further identify whether other fault conditions exist in the circuit, the step S108 to the step S110 need to be executed, so as to further detect whether a fault condition of a single main relay and/or a single slave relay exists in the relay failure detection circuit of the single-phase grid-connected inverter, that is, specific conditions of the main relay K1, the main relay K3, the slave relay K2, and the slave relay K4 in the current actual circuit can be further detected.

The comparison of the impedance element voltage UR and the preset voltage threshold Uset refers to the comparison of the impedance element voltage UR and the preset voltage threshold Uset. The comparison between the impedance element voltage UR and the predetermined voltage threshold Uset is performed in a state where one of the first driving signal drive1 and the second driving signal drive2 is an on signal and the other is an off signal. Based on step S107, in this state, by comparing the impedance element voltage UR with the preset voltage threshold Uset, it can be determined whether there is a single short circuit between the two main relays or the two slave relays that should be in the off state, that is, whether there is a short circuit problem between each of the main relays and each of the slave relays in the actual circuit at present is identified.

Specifically, when there is no situation that two slave relays are simultaneously turned on, the master relay is controlled by the on signal, and the slave relays are controlled by the off signal, since the impedance of the impedance element is large, if any one of the two slave relays is turned on at this time, the voltage UR of the impedance element will be greater than the preset voltage threshold Uset, and thus it can be identified whether there is a short circuit of a single slave relay in the current actual circuit. Similarly, the above steps can be referred to identify whether a single main relay short circuit exists in the current actual circuit.

Specifically, the third alignment results have two cases: one is when the impedance element voltage UR is greater than the predetermined voltage threshold Uset, and the other is when the impedance element voltage UR is less than or equal to the predetermined voltage threshold Uset. When the impedance element voltage UR is greater than the preset voltage threshold Uset, step S109 is executed; when the impedance element voltage UR is less than or equal to the preset voltage threshold Uset, step S110 is performed.

And S109, if the third comparison result shows that the impedance element voltage UR is larger than the preset voltage threshold Uset, comparing the impedance element voltage UR with the second power grid side voltage Usa to obtain a third fault reason.

If the third comparison result shows that the impedance element voltage UR is greater than the preset voltage threshold Uset, it indicates that at least one of the main relays controlled by the off signal is short-circuited or that at least one of the slave relays controlled by the off signal is short-circuited. That is, there is a single short circuit condition in both main relays that should be in the off state; or there is a single short circuit condition in both slave relays that should be in the off state.

In a specific implementation, comparing the impedance element voltage UR with the second power grid side voltage Usa means comparing whether the phase direction of the impedance element voltage UR is the same as the phase direction of the second power grid side voltage Usa. If the phase directions of the impedance element voltage UR and the second grid side voltage Usa are the same, the third failure cause is: a main relay or a slave relay controlled by a disconnection signal in a relay group connected with the Grid anode of the power Grid is short-circuited; if the phase directions of the impedance element voltage UR and the grid-side voltage Usa are opposite, the third failure cause is: and a main relay or a slave relay controlled by a disconnection signal in a relay group connected with the Grid negative pole of the power Grid is in short circuit.

In specific implementation, if a third fault reason exists in the current actual circuit, the grid-connected inverter can report the fault and stop working.

S110, if the third comparison result indicates that the impedance element voltage UR is less than or equal to the preset voltage threshold Uset, then the detection result indicates that none of the main relays or all of the slave relays controlled by the turn-off signal is short-circuited.

When the failure detection method is applied to the single-phase grid-connected relay, the first driving signal drive1 and the second driving signal drive2 can be set as the disconnection signals, so that whether the relay failure detection circuit of the single-phase grid-connected inverter has the condition that all relays simultaneously fail is judged by comparing whether the first inversion side voltage Uva is equal to the first power grid side voltage Usa or not; if not, the first drive signal drive1 or the second drive signal drive2 is adjusted to be a conducting signal, and therefore whether the situation that all main relays or all auxiliary relays are simultaneously short-circuited is judged by comparing whether the adjusted second inverter side voltage Uva is equal to the second power grid side voltage Usa or not; if not, identifying whether a single main relay or a single slave relay is short-circuited by comparing the voltage UR of the impedance element with a preset voltage threshold Uset of the impedance element; and if the voltage UR of the impedance element is greater than the preset voltage threshold Uset, comparing the voltage UR of the impedance element with the phase direction of the voltage Usa at the side of the second power grid, and thus judging the relay which is in fault generation specifically in the relay failure detection circuit of the single-phase grid-connected inverter. Therefore, the fault detection method and the fault detection device can detect the fault conditions of all the main relays and/or all the slave relays and also can detect the fault conditions of a single main relay or a single slave relay, thereby being beneficial to improving the fault detection accuracy of the relay of the grid-connected inverter and improving the use reliability of the grid-connected inverter.

For example, based on the above failure detection method of the grid-connected inverter applied to the relay failure detection circuit of the single-phase grid-connected inverter, in step S104, the first driving signal drive1 is first adjusted to be the on signal, and the second driving signal drive2 is still the off signal, for example, as shown in fig. 1, the failure detection process of the grid-connected inverter includes:

step 1, acquiring a first inversion side voltage Uva and a first power grid side voltage Usa of a phase line branch circuit in an initial state that a first driving signal drive1 for controlling a main relay K1 and a main relay K3 and a second driving signal drive2 for controlling a slave relay K2 and a slave relay K4 are both off signals.

And 2, comparing the first inversion side voltage Uva with the first power grid side voltage Usa on the basis of the step 1 to obtain a first comparison result.

And 3, on the basis of the step 2, if the first comparison result shows that the first inversion side voltage Uva is equal to the first power grid side voltage Usa, it is determined that the main relay K1, the main relay K3, the slave relay K2 and the slave relay K4 are all in short circuit.

And 4, on the basis of the step 2, if the first comparison result shows that the first inversion side voltage Uva is not equal to the first power grid side voltage Usa, phase-locking the grid-connected inverter to send waves, so that after the inversion side voltage Uva is equal to the power grid side voltage Usa, the first driving signal drive1 is adjusted to be a conducting signal, and at the moment, the second driving signal drive2 is still a disconnecting signal.

And 5, on the basis of the step 4, acquiring a preset voltage threshold value Uset of the impedance element, an impedance element voltage UR, a second inverter side voltage Uva and a second power grid side voltage Usa according to the adjusted first driving signal drive1 and second driving signal drive 2.

And 6, comparing the second inverter side voltage Uva with the second power grid side voltage Usa on the basis of the step 5 to obtain a second comparison result.

And 7, on the basis of the step 6, if the second comparison result is that the second inverter side voltage Uva is equal to the second grid side voltage Usa, it is determined that the slave relay K2 and the slave relay K4 are short-circuited at the same time.

And 8, on the basis of the step 6, if the second comparison result is that the second inverter side voltage Uva is not equal to the second grid side voltage Usa, comparing the impedance element voltage UR with the preset voltage threshold value Uset to obtain a third comparison result.

Step 9, on the basis of step 8, if the third comparison result shows that the impedance element voltage UR is greater than the preset voltage threshold Uset, comparing the phase directions of the impedance element voltage UR and the second grid-side voltage usaa, and if the phase directions of the impedance element voltage UR and the second grid-side voltage usaa are the same, short-circuiting the slave relay K2; if the phase directions of the impedance element voltage UR and the second grid-side voltage Usa are opposite, the relay K4 is short-circuited.

Step 10, on the basis of step 8, if the third comparison result is that the impedance element voltage UR is less than or equal to the preset voltage threshold Uset, then the detection result is that neither the slave relay K2 nor the slave relay K4 is short-circuited under the control of the off signal.

Step 11, after the step 7, the step 9 or the step 10 is completed, referring to the step 4, performing phase-locked wave transmission on the grid-connected inverter, so that after the inversion-side voltage Uva is equal to the grid-side voltage Usa, the first driving signal drive1 is adjusted to be a turn-off signal, and the second driving signal drive2 is adjusted to be a turn-on signal. After the first driving signal drive1 and the second driving signal drive2 are adjusted, the detection of the main relay K1 and the main relay K3 is completed according to the adjusted first driving signal drive1 and the adjusted second driving signal drive2 with reference to steps 5 to 10, which will not be further described herein.

Referring to fig. 3, fig. 3 is a schematic circuit diagram of a failure detection method of a three-phase grid-connected inverter according to an embodiment of the present disclosure.

The failure detection method of the grid-connected inverter is applied to a relay failure detection circuit of a three-phase grid-connected inverter, and the relay failure detection circuit of the single-phase grid-connected inverter comprises an inversion module, a switch module and a driving module. The inverter module comprises an input power source Vin and three bridge arms connected with the input power source Vin in parallel, wherein a first switch tube Q1 and a second switch tube Q2 are connected on one bridge arm in series, a first switch tube Q3 and a second switch tube Q4 are connected on the other bridge arm in series, and a first switch tube Q5 and a second switch tube Q6 are connected on the other bridge arm in series. The switch module comprises three phase line branches, and for convenience of description, the three phase line branches in fig. 3 are sequentially defined as a phase line branch a, a phase line branch B and a phase line branch C from top to bottom. One end of the phase line branch is connected with the connecting end of the first switch tube Q1 and the second switch tube Q2, one end of the phase line branch is connected with the connecting end of the first switch tube Q3 and the second switch tube Q4, one end of the phase line branch is connected with the connecting end of the first switch tube Q5 and the second switch tube Q6, and the other ends of the three phase line branches are connected with each other. Each phase line branch comprises a relay group and a power Grid which are arranged in series, and sub-branches which are respectively connected with the relay group in parallel. The relay group of A phase line branch road is connected with first electric wire netting Grid including the main relay K1 and the slave relay K2 that establish ties and set up, main relay K1 keep away from the one end of slave relay K2, and the one end that the slave relay K2 kept away from main relay K1 is connected with first switch tube Q1 and second switch tube Q2's link. The relay group of B phase line branch road is connected with second electric wire netting Grid including main relay K3 and the slave relay K4 that establishes ties and set up, main relay K3 keep away from the one end of slave relay K4, and the one end that the slave relay K4 kept away from main relay K3 is connected with first switch tube Q3 and second switch tube Q4's link. The relay group of C phase line branch road is connected with third electric wire netting Grid including main relay K5 and the slave relay K6 that establish ties and set up, main relay K5 keep away from the one end of slave relay K6, and the one end that the slave relay K6 kept away from main relay K5 is connected with first switch tube Q5 and second switch tube Q6's link. And one ends of Grid grids in the three phase line branches departing from the main relay are connected with each other. Each sub-branch comprises a first capacitor, an impedance element and a second capacitor which are sequentially connected in series. The driving module is used for controlling the main relay and the auxiliary relay to be switched on or switched off.

The relay failure detection circuit of the three-phase grid-connected inverter can further comprise three inductors L, and the slave relay K2, the slave relay K4 and the slave relay K6 are respectively connected with the bridge arm through one inductor L. Specifically, one end of one of the inductors L is connected to one end of the slave relay K2 away from the master relay K1, and the other end of the inductor L is connected to the connection end of the first switching tube Q1 and the second switching tube Q2. One end of another inductor L is connected with one end of the slave relay K4 far away from the main relay K3, and the other end of the inductor L is connected with the connecting end of the first switch tube Q3 and the second switch tube Q4. One end of another inductor L is connected with one end of the slave relay K6 far away from the main relay K5, and the other end of the inductor L is connected with the connecting end of the first switch tube Q5 and the second switch tube Q6.

It will be appreciated that the first and second capacitances of the three sub-branches may each be connected in series with a different impedance element. In this embodiment, in order to reduce the measurement parameters and improve the detection efficiency, the first capacitors and the second capacitors of the three sub-branches may be connected in series with the same impedance element.

When the three-phase grid-connected inverter works, the control module (not shown) controls the on/off of the first switch tube Q1, the second switch tube Q2, the first switch tube Q3, the second switch tube Q4, the first switch tube Q5 and the second switch tube Q6 in the inverter module, and voltage is output.

According to the relay short-circuit failure judgment method and device, the point A and the point B are constructed by utilizing the first capacitor, the second capacitor and the impedance element, and the high-impedance element is connected between the point A and the point B, so that the relay short-circuit failure judgment is realized by sampling the voltage of the impedance element and the voltage of the inversion side and the voltage of the power grid side of the relay group of each phase line branch circuit, all short-circuit failure conditions of the relay can be identified, and the relay with specific faults can be identified.

Referring to fig. 4, fig. 4 is a flowchart of a failure detection method of a grid-connected inverter according to an embodiment of the present application. The failure detection method of the grid-connected inverter is applied to a relay failure detection circuit of a three-phase grid-connected inverter. As shown in fig. 4, the method for detecting the failure of the grid-connected inverter includes:

s201, under the initial state that a first driving signal drive1 used for controlling the main relay and a second driving signal drive2 used for controlling the auxiliary relay are both off signals, obtaining a first inversion side voltage and a first power grid side voltage of each phase line branch.

And the voltage of the first inversion side corresponding to each phase line and the voltage of the first power grid side are effective values. The first driving signal drive1 and the second driving signal drive2 are signals which are sent to the relay group by the driving module to control the connection or disconnection of the main relay and the auxiliary relay, the first driving signal drive1 is used for controlling the connection or disconnection of the main relay K1, the main relay K3 and the main relay K5, and the second driving signal drive2 is used for controlling the connection or disconnection of the auxiliary relay K2, the auxiliary relay K4 and the auxiliary relay K6. In order to simplify the structure of the single-phase grid-connected inverter, all the main relays K1, K3 and K5 are controlled by the same first driving signal drive1, and the auxiliary relays K2, K4 and K6 are controlled by the same second driving signal drive 2.

S202, comparing the first inversion side voltage of each phase line branch with the first power grid side voltage to obtain a first comparison result.

Step S202 is an operation performed in an initial state where the first driving signal drive1 and the second driving signal drive2 are both driven by the off signal.

Specifically, comparing the first inverter side voltage and the first grid side voltage of each phase line branch refers to comparing whether the magnitude of the first inverter side voltage Uinv _ a of the phase line branch a is equal to the magnitude of the first grid side voltage Usa, comparing whether the magnitude of the first inverter side voltage Uinv _ B of the phase line branch B is equal to the magnitude of the first grid side voltage Usb, and comparing whether the magnitude of the first inverter side voltage Uinv _ C of the phase line branch C is equal to the magnitude of the first grid side voltage Usc. The relay failure detection circuit of the single-phase grid-connected inverter comprises a relay failure detection circuit, a phase line branch circuit and a phase line branch circuit, wherein each circuit component of the relay failure detection circuit of the single-phase grid-connected inverter has certain impedance, so that if the difference value of the first inversion side voltage of each phase line branch circuit and the first power grid side voltage is within a first preset range, the first inversion side voltage of the corresponding phase line branch circuit can be judged to be equal to the first power grid side voltage. The first preset range may be a range value set according to historical experience of the detection personnel, and specific numerical values of the first preset range are not further limited herein.

In the method, the following steps S203 to S207 may be performed corresponding to the first comparison result of each phase leg. If the first comparison result of each phase line branch indicates that the corresponding first inverter side voltage is equal to the first grid side voltage, the following step S203 is executed; if the first comparison result of at least one of the phase line branches indicates that the corresponding first inverter side voltage is different from the first grid side voltage, the following steps S204 to S207 are performed.

S203, if the first comparison result is that the first inversion side voltage of the phase line branch is equal to the first power grid side voltage corresponding to the phase line branch, a first fault reason is obtained.

Taking a phase line branch as an example, if the first inversion side voltage of the phase line branch is equal to the first grid side voltage corresponding to the phase line branch, it indicates that the first driving signal drive1 and the second driving signal drive2 respectively provide the disconnection for the execution actions of the main relay and the slave relay of the phase line branch, but the current actual circuit condition is that the phase line branch is in a conduction state. Therefore, the specific content of the first fault reason can be determined to be that the main relay and the slave relay of the phase line branch are simultaneously short-circuited.

Specifically, if the first inversion side voltage Uinv _ a of the phase line a branch is equal to the first grid side voltage Usa, the main relay K1 and the slave relay K2 of the phase line a branch are short-circuited at the same time. If the first inversion side voltage Uinv _ B of the phase line B branch is equal to the first grid side voltage Usb, the main relay K3 and the slave relay K4 of the phase line B branch are simultaneously short-circuited. If the first inversion side voltage Uinv _ C of the C-phase line branch is equal to the first grid side voltage Usc, the main relay K5 and the slave relay K6 of the C-phase line branch are simultaneously short-circuited. Therefore, the first fault cause can be that the main relay and the auxiliary relay of a single phase line branch are simultaneously short-circuited; or, the first failure cause may be that the main relay and the slave relay of any two phase line branches of the three phase line branches are short-circuited at the same time; alternatively, the first failure cause may be that all the main relays and all the slave relays of the three phase line branches are short-circuited at the same time.

In specific implementation, if the first fault cause exists in the current actual circuit, the grid-connected inverter can report the fault and stop working.

And S204, if the first comparison result shows that the first inversion side voltage is not equal to the first power grid side voltage, alternately adjusting the first driving signal or the second driving signal to be a conducting signal.

If the voltage of the first inversion side of a certain phase line branch is not equal to the voltage of the first power grid side, it is indicated that the main relay and the auxiliary relay of the phase line branch are not short-circuited at the same time. Therefore, if it is necessary to further identify whether there is a single short circuit in the main relay and the slave relay of the phase leg, step S205 to step S207 need to be executed on the basis of step S204.

Specifically, if the first inversion side voltage Uinv _ a of the phase line branch a is not equal to the first grid side voltage Usa, the main relay K1 and the auxiliary relay K2 of the phase line branch a are not short-circuited at the same time. If the first inversion side voltage Uinv _ B of the phase line B branch is not equal to the first grid side voltage Usb, the main relay K3 and the auxiliary relay K4 of the phase line B branch are not short-circuited at the same time. If the first inversion side voltage Uinv _ C of the C-phase line branch is not equal to the first grid side voltage Usc, the main relay K5 and the auxiliary relay K6 of the C-phase line branch are not short-circuited at the same time. Therefore, if the first comparison result indicates that the first inversion side voltage and the first grid side voltage are not equal, the first inversion side voltage and the first grid side voltage of one of the three phase line branches may be unequal, the first inversion side voltages and the first grid side voltages of any two phase line branches of the three phase line branches may be unequal, or the first inversion side voltages and the first grid side voltages of the three phase line branches may be unequal.

The first driving signal drive1 or the second driving signal drive2 is adjusted to be a conducting signal, that is, the first driving signal drive2 or the second driving signal drive2 is adjusted to be a high level, so as to respectively control the conduction of the main relay and the auxiliary relay.

In specific implementation, the first driving signal drive1 may be adjusted to be a conducting signal, the second driving signal drive1 is still a disconnecting signal, and steps S205 to S207 are performed on the basis, so as to identify whether the slave relay is short-circuited when the master relay and the slave relay of each phase line branch are not short-circuited at the same time. After step S205 to step S207 are completed, the first driving signal drive1 may be adjusted to be an off signal, the second driving signal drive2 is an on signal, and step S205 to step S207 are performed again, so as to identify whether the main relay is shorted when the main relay and the slave relay of each phase line branch are not shorted simultaneously. Of course, in other embodiments, step S204 may also be performed by first adjusting the second driving signal drive2 to be the on signal, and the first driving signal drive1 is still the off signal, and the subsequent steps are as described above, and will not be further described herein.

In one possible example, the adjusting the first driving signal drive1 or the second driving signal drive2 to be a turn-on signal includes: the three-phase grid-connected inverter starts phase-locking and wave-sending; when the second inversion side voltage is equal to the second power grid side voltage, adjusting the first driving signal drive1 or the second driving signal drive2 as a conducting signal; and the three-phase grid-connected inverter stops phase-locking wave generation.

It can be understood that before the first drive signal drive1 or the second drive signal drive2 is adjusted, that is, before the on or off states of the main relay and the slave relay are adjusted, the inverter phase-locked wave emission can avoid the sudden opening or closing of the main relay or the slave relay to generate an impact current, so that the protection of each component in the grid-connected inverter can be realized.

S205, acquiring the voltage UR of the impedance element, the preset voltage threshold Uset of the impedance element and the second power grid side voltage of each phase line branch according to the adjusted first driving signal drive1 or second driving signal drive 2.

The voltage UR of the impedance element is the voltage of the impedance element, and the voltage UR of the impedance element and the voltage of the second power grid side of each phase line branch are effective values. The preset voltage threshold Uset of the impedance element is set according to the experience of the detecting person. The impedance element voltage UR is a voltage of the impedance element. The second power grid side voltage of each phase line branch is the power grid side voltage corresponding to the phase line branch after the first driving signal drive1 and the second driving signal drive2 are adjusted.

S206, comparing the impedance element voltage UR with the preset voltage threshold value Uset to obtain a second comparison result.

Comparing the impedance element voltage UR with the preset voltage threshold Uset means comparing the impedance element voltage UR with the preset voltage threshold Uset. The comparison between the impedance element voltage UR and the predetermined voltage threshold Uset is performed in a state where one of the first driving signal drive1 and the second driving signal drive2 is an on signal and the other is an off signal. For example, based on step S204, if the first driving signal drive1 is an on signal and the second driving signal drive2 is an off signal, the impedance element voltage UR and the preset voltage threshold Uset are compared to determine whether there is a short circuit in the slave relay K2, the slave relay K4, or the slave relay K6 that should be in an off state in each phase line branch that is not short-circuited at the same time. Or, based on step S204, if the first driving signal drive1 is an off signal and the second driving signal drive2 is an on signal, comparing the impedance element voltage UR with the preset voltage threshold Uset, it can be determined whether there is a short circuit in the slave relay K1, the slave relay K3, or the slave relay K5 that should be in an off state in each phase line branch that is not short-circuited at the same time.

Specifically, when the main relay and the slave relay of the same phase line branch are not short-circuited at the same time, under the condition that the main relay is controlled by the on signal and the slave relay is controlled by the off signal, because the impedance of the impedance element is large, if any one of the three slave relays is on at this time, the voltage UR of the impedance element will be greater than the preset voltage threshold Uset, and at this time, step S207 may be executed to further determine the condition of each slave relay in the current actual circuit. Similarly, the above steps can be referred to identify whether the situation that each main relay in the current actual circuit has a short circuit of a single main relay.

Specifically, the second alignment result has two cases: one is when the impedance element voltage UR is greater than the predetermined voltage threshold Uset, and the other is when the impedance element voltage UR is less than or equal to the predetermined voltage threshold Uset. When the impedance element voltage UR is greater than the preset voltage threshold Uset, step S207 is executed; if the second comparison result shows that the impedance element voltage UR is less than or equal to the preset voltage threshold Uset, it indicates that all the main relays controlled by the turn-off signal are not short-circuited, or that all the slave relays controlled by the turn-off signal are not short-circuited.

And S207, if the second comparison result shows that the impedance element voltage UR is greater than the preset voltage threshold Uset, comparing the impedance element voltage UR with a second power grid side voltage corresponding to the phase line branch to obtain a second fault reason.

If the second comparison result is that the impedance element voltage UR is greater than the preset voltage threshold Uset, it indicates that at least one of the main relays controlled by the disconnection signal is short-circuited or that at least one of the slave relays is short-circuited. That is, a single short circuit or two short circuits exist in the main relays K1, K3, and K5 that should be in the off state; or there is a single short circuit or two short circuits in the slave relay K2, the slave relay K4 and the master relay K6 which should be in the off state, and will not be further described here.

In a specific implementation, comparing the impedance element voltage UR with the second grid side voltage means comparing whether the phase direction of the impedance element voltage UR is the same as the phase direction of the second grid side voltage of each phase line branch. If the phase of the impedance element voltage UR is the same as the phase of the second grid-side voltage, the second failure cause is: the main relay or the slave relay controlled by the disconnection signal in the phase line branch corresponding to the second system-side voltage for comparison with the impedance element voltage UR is short-circuited. Since the sum of the phases of the three phase line branches is zero, if the impedance element voltage UR is opposite to the phase of the grid-side voltage, the second failure cause is: all main relays or all slave relays controlled by the disconnection signal in all phase legs except the phase leg corresponding to the second grid-side voltage for comparison of the impedance element voltage UR are short-circuited at the same time. Therefore, by comparing whether the phase direction of the voltage UR of the impedance element is the same as the phase direction of the second power grid side voltage of each phase line branch, the situation that whether the main relay or the slave relay in the phase line branch corresponding to the second power grid side voltage for comparison is short-circuited can be quickly judged, and in addition, when the situation of the main relay of the phase line branch is identified, whether the two main relays of the other two phase line branches are short-circuited at the same time can be identified; or, when the situation of the phase line branch is identified from several points, whether the situation of simultaneous short circuit exists in two slave relays of the other two phase line branches is identified at the same time.

Specifically, when the first drive signal drive1 is an on signal and the second drive signal drive2 is an off signal: when the phase directions of the comparative impedance element voltage UR and the second power grid side voltage Usa of the phase line branch are the same, if the phase directions are the same, the slave relay K2 is short-circuited, and if the phase directions are opposite, the slave relay K4 and the slave relay K6 are short-circuited simultaneously; when the phase directions of the comparative impedance element voltage UR and the second power grid side voltage Usb of the B phase line branch are the same, if the phase directions are the same, the slave relay K4 is short-circuited, and if the phase directions are opposite, the slave relay K2 and the slave relay K6 are short-circuited simultaneously; and when the phase directions of the comparative impedance element voltage UR and the second grid side voltage Usc of the C phase line branch are the same, if the phase directions are the same, the slave relay K6 is short-circuited, and if the phase directions are opposite, the slave relay K2 and the slave relay K4 are short-circuited simultaneously. Similarly, when the first driving signal drive1 is an off signal and the second driving signal drive2 is an on signal: when the phase directions of the comparative impedance element voltage UR and the second power grid side voltage Usa of the phase line branch A are the same, if the phase directions are the same, the main relay K1 is in short circuit, and if the phase directions are opposite, the main relay K3 and the main relay K5 are in short circuit simultaneously; when the phase directions of the comparative impedance element voltage UR and the second power grid side voltage Usb of the B phase line branch are the same, if the phase directions are the same, the main relay K3 is in short circuit, and if the phase directions are opposite, the main relay K1 and the main relay K5 are in short circuit simultaneously; and when the phase directions of the comparative impedance element voltage UR and the second power grid side voltage Usc of the C phase line branch are the same, if so, the main relay K5 is in short circuit, and if not, the main relay K1 and the main relay K3 are in short circuit simultaneously.

In a specific implementation, the detecting personnel can selectively execute the above steps for each phase line branch according to an actual detection condition, and no further limitation is made herein.

When the failure detection method and the failure detection circuit provided by the application are applied to a three-phase grid-connected relay, the first driving signal drive1 and the second driving signal drive2 can be set as off signals, so that whether the main relay and the auxiliary relay of the same phase line branch of the relay failure detection circuit of the three-phase grid-connected inverter have the condition that the main relay and the auxiliary relay of the same phase line branch simultaneously fail is judged by comparing whether the first inversion side voltage of each phase line branch is equal to the first power grid side voltage; if not, the first driving signal drive1 or the second driving signal drive2 is adjusted to be a conducting signal, the voltage UR of the impedance element is compared with the preset voltage threshold value Uset of the impedance element, and if the voltage UR of the impedance element is larger than the preset voltage threshold value Uset, the condition that a single short circuit or two short circuits exist in all the main relays or all the slave relays controlled by the disconnecting signal is indicated. At the moment, the voltage UR of the impedance element is compared with the phase direction of the voltage of the second power grid side of each phase line branch, so that whether the single main relay or the single slave relay has a fault in the relay failure detection circuit of the three-phase grid-connected inverter is judged, and the specific faulty main relay and/or slave relay is identified. Therefore, the condition of the simultaneous short-circuit fault of the main relay and the slave relay of each phase line branch can be detected, and the fault condition of a single main relay or a single slave relay in each phase line branch can also be detected, so that the accuracy of fault detection of the relay of the grid-connected inverter is improved, and the use reliability of the grid-connected inverter is improved.

Referring to fig. 5, fig. 5 is a block diagram illustrating functional units of a relay failure detection apparatus 300 applied to a single-phase grid-connected inverter according to an embodiment of the present disclosure. The relay failure detection device 300 is applied to a relay failure detection circuit of a single-phase grid-connected inverter, the relay failure detection circuit of the single-phase grid-connected inverter comprises an inversion module, a switch module and a driving module, the inversion module comprises an input power supply and two bridge arms connected with the input power supply in parallel, and each bridge arm is connected with a first switch tube and a second switch tube in series; the switch module comprises a phase line branch, two ends of the phase line branch are respectively connected with the connecting ends of the first switch tube and the second switch tube in the two bridge arms, the phase line branch comprises two relay groups and a power grid which are arranged in series, and sub-branches which are respectively connected with one relay group in parallel, the relay groups comprise a main relay and a slave relay which are arranged in series, one end of the main relay, far away from the slave relay, is connected with the power grid, one end of the slave relay, far away from the main relay, is connected with the bridge arms, and the sub-branches comprise a first capacitor, an impedance element and a second capacitor which are sequentially connected in series; the driving module is used for controlling the main relay and the auxiliary relay to be switched on or off;

the relay failure detection device 300 includes:

an obtaining unit 301, configured to obtain a first inversion side voltage and a first grid side voltage of the phase line branch in an initial state where a first driving signal for controlling the main relay and a second driving signal for controlling the slave relay are both off signals; and for: acquiring a preset voltage threshold value of an impedance element, the voltage of the impedance element, and a second inversion side voltage and a second power grid side voltage of the phase line branch circuit according to the adjusted first driving signal or second driving signal;

the processing unit 303 is configured to compare the first inversion-side voltage with the first grid-side voltage to obtain a first comparison result; if the first comparison result shows that the first inversion side voltage is equal to the first power grid side voltage, a first fault reason is obtained; otherwise, alternately adjusting the first driving signal or the second driving signal to be a conducting signal; comparing the second inversion side voltage with a second power grid side voltage to obtain a second comparison result; if the second comparison result is that the second inversion side voltage is equal to the second power grid side voltage, a second fault reason is obtained; otherwise, comparing the voltage of the impedance element with the preset voltage threshold value to obtain a third comparison result; and if the third comparison result shows that the voltage of the impedance element is greater than the preset voltage threshold, comparing the voltage of the impedance element with the voltage of the second power grid side to obtain a third fault reason.

In one possible example, in terms of adjusting the first driving signal or the second driving signal to be an on signal, the processing unit 303 is further configured to: starting the single-phase grid-connected inverter to start phase-locking wave emission; when the second inversion side voltage is equal to the second power grid side voltage, adjusting the first driving signal or the second driving signal to be a conducting signal; and stopping the phase-locked wave sending of the single-phase grid-connected inverter.

Referring to fig. 6, fig. 6 is a block diagram illustrating functional units of a relay failure detection apparatus 400 applied to a three-phase grid-connected inverter according to an embodiment of the present disclosure. The relay failure detection device 400 is applied to a relay failure detection circuit of a three-phase grid-connected inverter, the relay failure detection circuit of the three-phase grid-connected inverter comprises an inversion module, a switch module and a driving module, the inversion module comprises an input power supply and three bridge arms connected with the input power supply in parallel, and each bridge arm is connected with a first switch tube and a second switch tube in series; the switch module comprises three phase line branches, wherein a first end of each phase line branch is connected with a connecting end of the first switch tube and the second switch tube in one bridge arm, a second end of each phase line branch is connected with each other, each phase line branch comprises a relay group and a power grid which are arranged in series, and sub-branches which are respectively connected with the relay groups in parallel, each relay group comprises a main relay and a slave relay which are arranged in series, one end of each main relay, far away from the corresponding slave relay, is connected with the power grid, one end of each slave relay, far away from the corresponding main relay, is connected with the corresponding bridge arm, and each sub-branch comprises a first capacitor, an impedance element and a second capacitor which are sequentially connected in series; the driving module is used for controlling the main relay and the auxiliary relay to be switched on or off;

the relay failure detection device 400 includes:

an obtaining unit 401, configured to obtain a first inversion side voltage and a first grid side voltage of each phase line branch in an initial state where a first driving signal for controlling the main relay and a second driving signal for controlling the slave relay are both disconnection signals; wherein the first drive signal and the second drive signal are from the drive module; the phase line branch circuit is used for adjusting a first driving signal or a second driving signal of the phase line branch circuit according to the first driving signal or the second driving signal;

the processing unit 403 is configured to compare a first inversion side voltage of each phase line branch with a first grid side voltage, so as to obtain a first comparison result; if the first comparison result is that the first inversion side voltage of the phase line branch is equal to the first power grid side voltage corresponding to the phase line branch, a first fault reason is obtained; otherwise, alternately adjusting the first driving signal or the second driving signal to be a conducting signal; comparing the voltage of the impedance element with the preset voltage threshold value to obtain a second comparison result; and if the second comparison result shows that the voltage of the impedance element is greater than the preset voltage threshold, comparing the voltage of the impedance element with the voltage of a second power grid side corresponding to the phase line branch to obtain a second fault reason.

In one possible example, in terms of adjusting the first driving signal or the second driving signal to be an on signal, the processing unit 403 is further configured to: starting the three-phase grid-connected inverter to carry out phase-locked wave generation; when the voltage of a second inversion side of the phase line branch is equal to the voltage of a second power grid side corresponding to the phase line branch, the first driving signal or the second driving signal is a conducting signal; and stopping the phase-locked wave generation of the three-phase grid-connected inverter.

It should be noted that the above is only a preferred embodiment of the present application, but the design concept of the invention is not limited thereto, and any insubstantial modifications made to the present application by using the design concept also fall within the scope of the present application.

Claims

1. The method is applied to a relay failure detection circuit of a single-phase grid-connected inverter, the relay failure detection circuit of the single-phase grid-connected inverter comprises an inversion module, a switch module and a driving module, the inversion module comprises an input power supply and two bridge arms connected with the input power supply in parallel, and each bridge arm is connected with a first switch tube and a second switch tube in series; the switching module comprises a phase line branch, two ends of the phase line branch are respectively connected with the connecting ends of the first switching tube and the second switching tube in the two bridge arms, the phase line branch comprises two relay groups and a power grid which are arranged in series, and sub-branches which are respectively connected with one relay group in parallel, the relay groups comprise a main relay and a slave relay which are arranged in series, one end of the main relay, far away from the slave relay, is connected with the power grid, one end of the slave relay, far away from the main relay, is connected with the bridge arms, and the sub-branches comprise a first capacitor, an impedance element and a second capacitor which are sequentially connected in series; the driving module is used for controlling the main relay and the auxiliary relay to be switched on or off;

the method comprises the following steps:

under the initial state that a first driving signal for controlling the main relay and a second driving signal for controlling the slave relay are both off signals, acquiring a first inversion side voltage and a first power grid side voltage of the phase line branch; wherein the first drive signal and the second drive signal are from the drive module;

acquiring a preset voltage threshold value of an impedance element, the voltage of the impedance element, and a second inversion side voltage and a second power grid side voltage of the phase line branch circuit according to the adjusted first driving signal or second driving signal;

otherwise, comparing the voltage of the impedance element with the preset voltage threshold value to obtain a third comparison result;

if the third comparison result is that the voltage of the impedance element is greater than the preset voltage threshold, comparing whether the phases of the voltage of the impedance element and the voltage of the second power grid side are the same or not to obtain a third fault reason; if the phase of the impedance element voltage is the same as the phase of the second grid side voltage, the third failure cause is: a main relay or a slave relay controlled by a disconnection signal in a relay group connected with the positive pole of the power grid is short-circuited; if the phases of the impedance element voltage and the grid-side voltage are opposite, the third failure cause is: and a main relay or a slave relay controlled by a disconnection signal in a relay group connected with the negative pole of the power grid is in short circuit.

2. The method of claim 1, wherein the adjusting the first driving signal or the second driving signal to be an on signal comprises:

the single-phase grid-connected inverter starts phase-locking and wave-transmitting;

when the second inversion side voltage is equal to the second power grid side voltage, adjusting the first driving signal or the second driving signal to be a conducting signal;

and the single-phase grid-connected inverter stops phase-locked wave sending.

3. The method of claim 1, wherein the third alignment comprises:

if the third comparison result is that the voltage of the impedance element is greater than the preset voltage threshold, at least one of the main relays or at least one of the auxiliary relays controlled by the disconnection signal is short-circuited;

if the third comparison result shows that the voltage of the impedance element is smaller than or equal to the preset voltage threshold, all the main relays or all the auxiliary relays controlled by the disconnection signal are not short-circuited.

4. The failure detection method of the grid-connected inverter is characterized by being applied to a relay failure detection circuit of a three-phase grid-connected inverter, wherein the relay failure detection circuit of the three-phase grid-connected inverter comprises an inversion module, a switch module and a driving module, the inversion module comprises an input power supply and three bridge arms connected with the input power supply in parallel, and each bridge arm is connected with a first switch tube and a second switch tube in series; the switch module comprises three phase line branches, wherein a first end of each phase line branch is connected with a connecting end of the first switch tube and the second switch tube in one bridge arm, a second end of each phase line branch is connected with each other, each phase line branch comprises a relay group and a power grid which are arranged in series, and sub-branches which are respectively connected with the relay groups in parallel, each relay group comprises a main relay and a slave relay which are arranged in series, one end of each main relay, far away from the corresponding slave relay, is connected with the power grid, one end of each slave relay, far away from the corresponding main relay, is connected with the corresponding bridge arm, and each sub-branch comprises a first capacitor, an impedance element and a second capacitor which are sequentially connected in series; the driving module is used for controlling the main relay and the auxiliary relay to be switched on or off;

the method comprises the following steps:

under the initial state that a first driving signal for controlling the main relay and a second driving signal for controlling the slave relay are both off signals, acquiring a first inversion side voltage and a first power grid side voltage of each phase line branch; wherein the first drive signal and the second drive signal are from the drive module;

if the second comparison result is that the voltage of the impedance element is greater than the preset voltage threshold, comparing whether the voltage of the impedance element is the same as the phase of the voltage of the second power grid side corresponding to the phase line branch or not to obtain a second fault reason; if the phase of the impedance element voltage is the same as the phase of the second grid side voltage, the second fault cause is: a main relay or a slave relay controlled by a disconnection signal in a phase line branch corresponding to the second power grid side voltage is short-circuited; if the phases of the impedance element voltage and the grid-side voltage are opposite, the second failure cause is: and all the main relays or all the slave relays controlled by the disconnection signals in all the phase line branches except the phase line branch corresponding to the second power grid side voltage are simultaneously short-circuited.

5. The method of claim 4, wherein the adjusting the first driving signal or the second driving signal to be an on signal comprises:

the three-phase grid-connected inverter starts phase-locking and wave-sending;

when the voltage of a second inversion side of the phase line branch is equal to the voltage of a second power grid side corresponding to the phase line branch, adjusting the first driving signal or the second driving signal to be a conducting signal;

and the three-phase grid-connected inverter stops phase-locked wave generation.

6. The method of claim 4, wherein the second alignment comprises:

if the second comparison result is that the voltage of the impedance element is greater than the preset voltage threshold, at least one of all the main relays or at least one of all the slave relays controlled by the disconnection signal is short-circuited;

if the second comparison result shows that the voltage of the impedance element is smaller than or equal to the preset voltage threshold, all the main relays or all the auxiliary relays controlled by the disconnection signal are not short-circuited.

7. The device is applied to a relay failure detection circuit of a single-phase grid-connected inverter, the relay failure detection circuit of the single-phase grid-connected inverter comprises an inversion module, a switch module and a driving module, the inversion module comprises an input power supply and two bridge arms connected with the input power supply in parallel, and each bridge arm is connected with a first switch tube and a second switch tube in series; the switch module comprises a phase line branch, two ends of the phase line branch are respectively connected with the connecting ends of the first switch tube and the second switch tube in the two bridge arms, the phase line branch comprises two relay groups and a power grid which are arranged in series, and sub-branches which are respectively connected with one relay group in parallel, the relay groups comprise a main relay and a slave relay which are arranged in series, one end of the main relay, far away from the slave relay, is connected with the power grid, one end of the slave relay, far away from the main relay, is connected with the bridge arms, and the sub-branches comprise a first capacitor, an impedance element and a second capacitor which are sequentially connected in series; the driving module is used for controlling the main relay and the auxiliary relay to be switched on or off;

the device comprises:

the acquisition unit is used for acquiring a first inversion side voltage and a first power grid side voltage of the phase line branch circuit in an initial state that a first driving signal used for controlling the main relay and a second driving signal used for controlling the slave relay are both off signals; acquiring a preset voltage threshold value of an impedance element, the voltage of the impedance element, and a second inversion side voltage and a second power grid side voltage of the phase line branch according to the adjusted first driving signal or second driving signal;

the processing unit is used for comparing the first inversion side voltage with the first power grid side voltage to obtain a first comparison result; if the first comparison result shows that the first inversion side voltage is equal to the first power grid side voltage, a first fault reason is obtained; otherwise, alternately adjusting the first driving signal or the second driving signal to be a conducting signal; comparing the second inversion side voltage with a second power grid side voltage to obtain a second comparison result; if the second comparison result is that the second inversion side voltage is equal to the second power grid side voltage, a second fault reason is obtained; otherwise, comparing the voltage of the impedance element with the preset voltage threshold value to obtain a third comparison result; if the third comparison result is that the voltage of the impedance element is greater than the preset voltage threshold, comparing whether the phases of the voltage of the impedance element and the voltage of the second power grid side are the same or not to obtain a third fault reason; if the phase of the impedance element voltage is the same as the phase of the second grid side voltage, the third failure cause is: a main relay or a slave relay controlled by a disconnection signal in a relay group connected with the positive pole of the power grid is short-circuited; if the phases of the impedance element voltage and the grid-side voltage are opposite, the third failure cause is: and a main relay or a slave relay controlled by a disconnection signal in a relay group connected with the negative pole of the power grid is in short circuit.

8. The device is applied to a relay failure detection circuit of a three-phase grid-connected inverter, the relay failure detection circuit of the three-phase grid-connected inverter comprises an inversion module, a switch module and a driving module, the inversion module comprises an input power supply and three bridge arms connected with the input power supply in parallel, and each bridge arm is connected with a first switch tube and a second switch tube in series; the switch module comprises three phase line branches, wherein a first end of each phase line branch is connected with a connecting end of the first switch tube and the second switch tube in one bridge arm, a second end of each phase line branch is connected with each other, each phase line branch comprises a relay group and a power grid which are arranged in series, and sub-branches which are respectively connected with the relay groups in parallel, each relay group comprises a main relay and a slave relay which are arranged in series, one end of each main relay, far away from the corresponding slave relay, is connected with the power grid, one end of each slave relay, far away from the corresponding main relay, is connected with the corresponding bridge arm, and each sub-branch comprises a first capacitor, an impedance element and a second capacitor which are sequentially connected in series; the driving module is used for controlling the main relay and the auxiliary relay to be switched on or off;

the device comprises:

the acquisition unit is used for acquiring a first inversion side voltage and a first power grid side voltage of each phase line branch circuit in an initial state that a first driving signal for controlling the main relay and a second driving signal for controlling the slave relay are both disconnection signals; wherein the first drive signal and the second drive signal are from the drive module; the phase line branch circuit is used for adjusting a first driving signal or a second driving signal of the phase line branch circuit according to the first driving signal or the second driving signal;

the processing unit is used for comparing the first inversion side voltage of each phase line branch with the first power grid side voltage to obtain a first comparison result; if the first comparison result is that the first inversion side voltage of the phase line branch is equal to the first power grid side voltage corresponding to the phase line branch, a first fault reason is obtained; otherwise, alternately adjusting the first driving signal or the second driving signal to be a conducting signal; comparing the voltage of the impedance element with the preset voltage threshold value to obtain a second comparison result; if the second comparison result is that the voltage of the impedance element is larger than the preset voltage threshold, comparing whether the voltage of the impedance element is the same as the phase of the voltage of a second power grid side corresponding to the phase line branch or not to obtain a second fault reason; if the phase of the impedance element voltage is the same as the phase of the second grid side voltage, the second fault cause is: a main relay or a slave relay controlled by a disconnection signal in a phase line branch corresponding to the second power grid side voltage is short-circuited; if the phases of the impedance element voltage and the grid-side voltage are opposite, the second failure cause is: and all the main relays or all the slave relays controlled by the disconnection signals in all the phase line branches except the phase line branch corresponding to the second power grid side voltage are simultaneously short-circuited.