CN112924855B - Grid-connected relay circuit - Google Patents
Grid-connected relay circuit Download PDFInfo
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- CN112924855B CN112924855B CN201911244845.4A CN201911244845A CN112924855B CN 112924855 B CN112924855 B CN 112924855B CN 201911244845 A CN201911244845 A CN 201911244845A CN 112924855 B CN112924855 B CN 112924855B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/327—Testing of circuit interrupters, switches or circuit-breakers
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
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Abstract
The embodiment of the invention discloses a grid-connected relay circuit, which comprises: the system comprises a bus voltage circuit, a power grid voltage circuit, a sampling control circuit and a relay group; the sampling control circuit is respectively electrically connected with the bus voltage circuit and the power grid voltage circuit and is used for acquiring the bus voltage of the bus voltage circuit and the power grid voltage of the power grid voltage circuit and adjusting the bus voltage to enable the voltage of the output side of the bus voltage to be equal to the power grid voltage; the sampling control circuit is further respectively electrically connected with the relay group, the first node and the second node, in the detection stage, the sampling control circuit is used for controlling the on-off of each relay in the relay group, then collecting the output side voltage and the on-off voltage of the relay between the first node and the second node, and judging the working state of at least one relay according to the comparison result of the difference value between the output side voltage and the on-off voltage of the relay and the preset threshold value. According to the embodiment of the invention, the abnormity detection of each relay is realized.
Description
Technical Field
The embodiment of the invention relates to an inverter technology, in particular to a grid-connected relay circuit.
Background
At present, a distributed photovoltaic power generation system is widely applied to power generation markets at home and abroad, a photovoltaic grid-connected inverter is one of key components of the photovoltaic power generation system, and converts direct current in a solar photovoltaic module matrix into alternating current through electric power and feeds the alternating current back to a power grid to realize grid-connected power generation.
The photovoltaic grid-connected inverter is connected to the grid through the grid-connected relay, and when some abnormal conditions occur in the grid-connected process, the photovoltaic grid-connected inverter can be disconnected with a power grid through the grid-connected relay, and is disconnected from the grid at the first time, so that circuit protection is realized. Therefore, the grid-connected relay needs to be subjected to self-checking before grid connection, timely grid disconnection is ensured when an abnormality occurs, and equipment damage is avoided.
However, the conventional inverter circuit cannot detect an abnormality of each relay.
Disclosure of Invention
The embodiment of the invention provides a grid-connected relay circuit, which realizes the abnormity detection of each relay in the circuit.
The embodiment of the invention provides a grid-connected relay circuit, which comprises: the system comprises a bus voltage circuit, a power grid voltage circuit, a sampling control circuit and a relay group connected between the output side of the bus voltage circuit and the input side of the power grid voltage circuit;
the relay group comprises a first relay, a second relay, a third relay and a fourth relay, wherein the first end of the first relay is electrically connected with the output positive electrode of the bus voltage circuit, the first end of the second relay is electrically connected with the input positive electrode of the power grid voltage circuit, the second end of the first relay is electrically connected with the second end of the second relay and connected to a first node, the first end of the third relay is electrically connected with the output negative electrode of the bus voltage circuit, the first end of the fourth relay is electrically connected with the input negative electrode of the power grid voltage circuit, and the second end of the third relay is electrically connected with the second end of the fourth relay and connected to the second node;
the sampling control circuit is respectively electrically connected with the bus voltage circuit and the power grid voltage circuit and is used for acquiring the bus voltage of the bus voltage circuit and the power grid voltage of the power grid voltage circuit and regulating the bus voltage to enable the voltage of the output side of the bus voltage to be equal to the power grid voltage;
the sampling control circuit is further respectively electrically connected with the relay group, the first node and the second node, in a detection stage, the sampling control circuit is used for controlling the on-off of each relay in the relay group, collecting the output side voltage and the relay on-off voltage between the first node and the second node, and judging at least one working state of the relay according to a comparison result of a difference value between the output side voltage and the relay on-off voltage and a preset threshold value.
Further, the bus voltage circuit includes: the system comprises a bus voltage source and an inverter power circuit electrically connected with the bus voltage source;
the sampling control circuit is respectively electrically connected with the bus voltage source and the inversion power circuit and is used for collecting the bus voltage of the bus voltage source and driving the inversion power circuit so as to enable the output side voltage of the inversion power circuit to be equal to the power grid voltage.
Further, the sampling control circuit includes: the sampling circuit and the drive control circuit are electrically connected with the sampling circuit;
the sampling circuit is electrically connected with the bus voltage circuit, the power grid voltage circuit and the first node and the second node respectively;
and the drive control circuit is respectively and electrically connected with the inverter power circuit and the relay group.
Furthermore, the driving control circuit comprises a sine pulse width modulation unit, and the sine pulse width modulation unit is electrically connected with the inverter power circuit and used for outputting a sine pulse width modulation signal to adjust the inverter power circuit so that the voltage of the output side of the inverter power circuit is equal to the voltage of the power grid.
Further, the detection phase comprises a first detection phase and a second detection phase;
in the first detection stage, the sampling control circuit is used for controlling the first relay to be switched on, then collecting the output side voltage and the on-off voltage of the relay, and determining a first comparison result;
in the second detection stage, the sampling control circuit is used for controlling the first relay and the third relay to be simultaneously conducted, collecting the output side voltage and the on-off voltage of the relay, and determining a second comparison result;
the sampling control circuit is used for detecting the third relay according to the first comparison result and the second comparison result.
Further, the detection phase comprises a second detection phase and a third detection phase;
in the second detection stage, the sampling control circuit is used for controlling the first relay and the third relay to be simultaneously switched on, then collecting the output side voltage and the on-off voltage of the relay, and determining a second comparison result;
in the third detection stage, the sampling control circuit is used for controlling the third relay to be switched on, then collecting the output side voltage and the on-off voltage of the relay, and determining a third comparison result;
the sampling control circuit is used for detecting the first relay according to the second comparison result and the third comparison result.
Further, the detection phase comprises a fourth detection phase and a fifth detection phase;
in the fourth detection stage, the sampling control circuit is used for controlling the second relay to be conducted, collecting the output side voltage and the relay on-off voltage, and determining a fourth comparison result;
in the fifth detection stage, the sampling control circuit is used for controlling the second relay and the fourth relay to be simultaneously switched on, collecting the voltage of the output side and the on-off voltage of the relay, and determining a fifth comparison result;
the sampling control circuit is used for detecting the fourth relay according to the fourth comparison result and the fifth comparison result.
Further, the detection phase comprises a fifth detection phase and a sixth detection phase;
in the fifth detection stage, the sampling control circuit is used for controlling the second relay and the fourth relay to be simultaneously switched on, then collecting the output side voltage and the on-off voltage of the relay, and determining a fifth comparison result;
in the sixth detection stage, the sampling control circuit is used for controlling the fourth relay to be switched on, collecting the output side voltage and the relay on-off voltage, and determining a sixth comparison result;
the sampling control circuit is used for detecting the second relay according to the fifth comparison result and the sixth comparison result.
In the embodiment of the invention, in the detection stage, the sampling control circuit controls the on-off of each relay in the relay group, then the output side voltage and the relay on-off voltage between the first node and the second node are collected, and the working state of at least one relay is judged according to the comparison result of the difference value between the output side voltage and the relay on-off voltage and the preset threshold value. In the embodiment of the invention, preset thresholds are set in different on-off states of the relays in the relay group, the difference between the output side voltage and the on-off voltage of the relays is calculated and compared with the corresponding preset threshold, and whether each relay is abnormal or not can be judged according to the comparison result. In the embodiment of the invention, when the abnormality is detected, the inverter can alarm and stop in time, and the relay is judged to be in fault according to the relay driving state at the moment, so that the detection is accurate, the action times of the relay are reduced, the detection efficiency is greatly improved, the loss is reduced, and the reliable guarantee is provided for the stable operation of the inverter.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, a brief description will be given below of the drawings required for the embodiments or the technical solutions in the prior art, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic diagram of a grid-connected relay circuit according to an embodiment of the present invention;
FIG. 2 is a control schematic of the sampling control circuit;
fig. 3 is a control schematic of the detection phase.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described through embodiments with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. 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 invention.
Referring to fig. 1, a schematic diagram of a grid-connected relay circuit according to an embodiment of the present invention is shown. The grid-connected relay circuit provided by the embodiment comprises: the system comprises a bus voltage circuit 1, a power grid voltage circuit 2, a sampling control circuit 3 and a relay group 4 connected between the output side of the bus voltage circuit 1 and the input side of the power grid voltage circuit 2; the relay group 4 comprises a first relay RLY1, a second relay RLY2, a third relay RLY3 and a fourth relay RLY4, wherein a first end of the first relay RLY1 is electrically connected with an output positive electrode of the bus voltage circuit 1, a first end of the second relay RLY2 is electrically connected with an input positive electrode of the grid voltage circuit 2, a second end of the first relay RLY1 and a second end of the second relay RLY2 are electrically connected and connected to a first node c, a first end of the third relay RLY3 is electrically connected with an output negative electrode of the bus voltage circuit 1, a first end of the fourth relay RLY4 is electrically connected with an input negative electrode of the grid voltage circuit 2, and a second end of the third relay RLY3 and a second end of the fourth relay RLY4 are electrically connected and connected to a second node d; the sampling control circuit 3 is respectively electrically connected with the bus voltage circuit 1 and the power grid voltage circuit 2, and is used for acquiring the bus voltage Vbus of the bus voltage circuit 1 and the power grid voltage Vg of the power grid voltage circuit 2, and regulating the bus voltage Vbus to make the output side voltage Vab equal to the power grid voltage Vg; the sampling control circuit 3 is further electrically connected with the relay group 4 and the first node c and the second node d respectively, in a detection stage, the sampling control circuit 3 is used for controlling the on-off of each relay in the relay group 4, then collecting the output side voltage Vab and the relay on-off voltage Vcd between the first node c and the second node d, and judging the working state of at least one relay according to the comparison result of the difference value between the output side voltage Vab and the relay on-off voltage Vcd and a preset threshold value.
In this embodiment, the bus voltage circuit 1 is located at the output side of the inverter, and is configured to provide a bus voltage VBus and output the bus voltage VBus as a grid voltage Vg. The grid voltage circuit 2 is connected to the input side of the grid, and is used for receiving the grid voltage Vg and supplying power. The sampling control circuit 3 is used for collecting the voltage in the circuit. The relay group 4 is connected between the output side of the bus voltage circuit 1 and the input side of the grid voltage circuit 2, the output side of the bus voltage circuit 1 being provided as nodes a and b. When the relay group 4 is switched on, the inverter is connected into the power grid and provides power grid voltage Vg for the power grid, and when the relay group 4 is switched off, the inverter is separated from the power grid, so that the disconnection can be realized when the grid connection is abnormal, and the equipment is protected.
In the present embodiment, the relay group 4 includes a first relay RLY1, a second relay RLY2, a third relay RLY3, and a fourth relay RLY4, a first terminal of the first relay RLY1 is electrically connected to the output positive electrode of the bus voltage circuit 1, a first terminal of the second relay RLY2 is electrically connected to the input positive electrode of the grid voltage circuit 2, a second terminal of the first relay RLY1 and a second terminal of the second relay RLY2 are electrically connected and connected to the first node c, a first terminal of the third relay RLY3 is electrically connected to the output negative electrode of the bus voltage circuit 1, a first terminal of the fourth relay RLY4 is electrically connected to the input negative electrode of the grid voltage circuit 2, and a second terminal of the third relay RLY3 and a second terminal of the fourth relay RLY4 are electrically connected and connected to the second node d. The relay group 4 is conducted, specifically, RLY 1-4 are conducted, and the inverter is connected to the power grid. The disconnection of the relay group 4 specifically means that when at least one of the RLYs 1 to 4 is disconnected, the inverter is disconnected from the power grid. The abnormal action of the relay may cause grid connection failure or grid disconnection failure, so the relay is detected in the embodiment.
In this embodiment, the sampling control circuit 3 is electrically connected to the bus voltage circuit 1 and the grid voltage circuit 2, respectively, and is configured to collect a bus voltage VBus of the bus voltage circuit 1 and a grid voltage Vg of the grid voltage circuit 2, and adjust the bus voltage VBus so that an output-side voltage Vab thereof is equal to the grid voltage Vg; the sampling control circuit 3 is also electrically connected to the relay group 4 and the first and second nodes c and d, respectively. The sampling control circuit 3 collects Vbus, vcd, and Vg, and is also electrically connected to the output side of the bus voltage circuit 1, for collecting the output side voltage Vab. Obviously, when the relay group 4 is turned on, the actual values of Vab and Vcd should be equal or the difference value is within the preset range, when the relay group 4 is abnormal, the actual value difference value of Vab and Vcd exceeds the preset range, and the sampling control circuit 3 may determine whether the relay action is abnormal according to the relationship of Vbus, vab, vcd and Vg.
If the output side of the inverter is incorporated into the power grid, the voltage at the output side of the inverter should be the grid voltage. The inverter has a bus voltage, so the sampling control circuit 3 has the effect of regulating the output side of the inverter to the grid voltage, and Vab should theoretically be equal to Vg after regulation, or the difference error between the two is very small.
In this embodiment, in the detection stage, the sampling control circuit 3 is configured to control on/off of each relay in the relay group 4, collect the output side voltage and the relay on/off voltage Vcd between the first node and the second node, and determine the working state of at least one relay according to a comparison result between a difference between the output side voltage Vab and the relay on/off voltage Vcd and a preset threshold.
When one of the second relay and the fourth relay in the relay group 4 is in an off state, the theoretical value of Vcd should be 0, and the theoretical value of Vab on the output side of the bus voltage circuit 1 should be Vg, obviously, if the difference between the actual value of Vab and the actual value of Vcd actually acquired is large, it indicates that the relays are in a normal state, and if the difference between the actual value of Vab and the actual value of Vcd actually acquired is small, it indicates that at least one relay is in an abnormal state. When the relay group 4 is in a conducting state, the theoretical value of Vcd should be Vg, and the theoretical value of Vab on the output side of the bus voltage circuit 1 should be Vg, obviously, if the difference between the actual value of Vab and the actual value of Vcd collected actually is small, it indicates that the relay is in a normal state, and if the difference between the actual value of Vab and the actual value of Vcd collected actually is large, it indicates that at least one relay is in an abnormal state.
Knowing that the relay in the relay group 4 is in different switch states, the theoretical value of Vcd and the theoretical value of Vab can acquire the actual value of Vab and the actual value of Vcd, and then the detection of the relay is realized by judging the difference value between the actual value of Vab and the actual value of Vcd. The preset threshold is a critical value of the relay group 4, which is obtained in advance when the relays in the relay group 4 are in different on-off states. It can be understood that, when at least one relay in the relay set 4 is in the off state and the relay set 4 is in the on state, the corresponding preset thresholds may be different. Namely, each on-off state of the relay group corresponds to a preset threshold value.
In the detection stage, the sampling control circuit 3 controls 4 relays in the relay group 4 to realize different on-off states, and in the current on-off state, the theoretical value of Vcd and the theoretical value of Vab are both known, so that the difference value between the theoretical values of Vcd and Vab is also known, and the difference value between the theoretical values of Vcd and Vab is related to a preset threshold value. The sampling control circuit 3 collects an actual value of the output side voltage Vab and an actual value of the relay on-off voltage Vcd between the first node c and the second node d, and judges the working state of at least one relay according to a comparison result of a difference value between the actual value of Vab and the actual value of Vcd and a preset threshold value.
In this embodiment, in the detection stage, the sampling control circuit controls on/off of each relay in the relay group, collects the output side voltage and the relay on/off voltage between the first node and the second node, and determines the working state of at least one relay according to a comparison result between a difference between the output side voltage and the relay on/off voltage and a preset threshold. In this embodiment, preset thresholds are set in different on-off states of relays in the relay group, a difference between the output-side voltage and the on-off voltage of the relays is calculated and compared with the corresponding preset threshold, and whether each relay is abnormal or not can be determined according to a comparison result. In the embodiment, when the inverter is detected to be abnormal, the inverter can timely alarm and stop, and judge which relay breaks down according to the driving state of the relay at the moment, so that the detection is accurate, the action times of the relay is reduced, the detection efficiency is greatly improved, the loss is reduced, and the reliable guarantee is provided for the stable work of the inverter.
Illustratively, on the basis of the above technical solution, the optional bus voltage circuit 1 shown in fig. 1 includes: the system comprises a BUS voltage source BUS and an inverter power circuit 11 electrically connected with the BUS voltage source BUS; the sampling control circuit 3 is electrically connected with the BUS voltage source BUS and the inverter power circuit 11 respectively, and is used for collecting the BUS voltage Vbus of the BUS voltage source BUS and driving the inverter power circuit 11, so that the output side voltage Vab of the inverter power circuit 11 is equal to the grid voltage Vg.
In this embodiment, the sampling control circuit 3 is electrically connected to the BUS voltage source BUS for collecting the BUS voltage Vbus of the BUS voltage source BUS, and the sampling control circuit 3 is also electrically connected to the inverter power circuit 11 for driving the inverter power circuit 11 so that the output side voltage Vab of the inverter power circuit 11 is equal to the grid voltage Vg. The sampling control circuit 3 collects bus voltage Vbus and Vg in real time before detection so as to output certain PWM signals to drive the inverter power circuit 11, and the voltage Vab at the two ends of a and b is the same as the output Vg, so that the sampling control circuit can be used for detecting the relays RLY 1-RLY 4. The optional inverter power circuit 11 includes a power tube.
The optional grid voltage circuit 2 comprises a grid voltage source Vg and a capacitor, and a capacitor device in the circuit is charged in advance, so that the impact current of the inverter at the grid connection moment can be reduced.
In the embodiment, the inverter outputs the inverter voltage Vab in advance, so that once detection abnormality is found in the detection process, the inverter can alarm and stop in time, and the relay which fails is judged according to the relay driving state at the moment.
The optional sampling control circuit 3 shown in fig. 1 includes: a sampling circuit 31 and a drive control circuit 32 electrically connected to the sampling circuit 31; the sampling circuit 31 is electrically connected with the bus voltage circuit 1, the grid voltage circuit 2, the first node c and the second node d respectively; the drive control circuit 32 is electrically connected to the inverter power circuit 11 and the relay group 4, respectively.
Fig. 1 shows only the connection relationship of the sampling circuit 31 and a part of the structure. Essentially, the sampling circuit 31 is electrically connected to the BUS voltage source BUS of the BUS voltage circuit 1 to collect the BUS voltage Vbus; the sampling circuit 31 is also electrically connected with a power grid voltage source of the power grid voltage circuit 2 to collect power grid voltage Vg; the sampling circuit 31 is also electrically connected to the node a and the node b to collect the output side voltage Vab of the bus voltage circuit 1; the sampling circuit 31 is also electrically connected to the first node c and the second node d to collect the relay on-off voltage Vcd.
The drive control circuit 32 is electrically connected to the inverter power circuit 11, and is configured to output a PWM signal to adjust Vbus such that Vab is equal to Vg. The driving control circuit 32 is also electrically connected to the relay group 4 for controlling the on/off of each relay during the detection stage.
Optionally, as shown in fig. 2, the driving control circuit 32 includes a sinusoidal pulse width modulation unit SPWM, which is electrically connected to the inverter power circuit 11 and configured to output a sinusoidal pulse width modulation signal to adjust the voltage of the output side of the inverter power circuit 11 to be equal to the voltage of the power grid.
In this embodiment, before the relay detection starts, the sampling circuit 31 samples Vbus and the grid voltage Vg, and outputs a certain sinusoidal pulse width modulation Signal (SPWM) according to the inverter output voltage Vg and the bus voltage Vbus at this time, so as to drive the inverter power tube of the inverter power circuit 11, so that the voltages Vab and Vg at the two ends of a and b are the same.
Exemplarily, on the basis of the above technical solution, the selectable detection stages shown in fig. 3 include a first detection stage step1 and a second detection stage step2; in the first detection stage, the sampling control circuit is used for controlling the conduction of a first relay, then collecting the voltage of an output side and the on-off voltage of the relay and determining a first comparison result; in the second detection stage, the sampling control circuit is used for controlling the first relay and the third relay to be conducted simultaneously, then collecting the voltage of the output side and the on-off voltage of the relay, and determining a second comparison result; the sampling control circuit is used for detecting the third relay according to the first comparison result and the second comparison result.
In this embodiment, the selectable relay is turned on under the control of a high level signal and turned off under a low level signal. In the first detection stage, the sampling control circuit is used for controlling the first relay to be switched on, and then collecting the voltage of the output side and the on-off voltage of the relay to obtain a first comparison result. The absolute value of the difference between Vab and Vcd is obtained, the absolute value is compared with a preset threshold, the smaller relation or the smaller relation obtained by the comparison is a first comparison result, and the detection is determined to be normal or abnormal according to the comparison result of the absolute value of the difference between Vab and Vcd and the preset threshold.
Δ V1= | Vcd-Vab | is set, and Vset is the error threshold which is the preset threshold.
The first relay is closed. Theoretically, vab should be VG, vcd =0, and then Vab and Vcd, the difference between Vab and Vcd is compared with Vset, if the comparison result is greater than the threshold, the detection is normal, and if the comparison result is less than the threshold, the detection is abnormal. The actual values of Vab and Vcd are collected to obtain an actual difference value delta V1, wherein the detection is normal when delta V1 is larger than Vset, and the detection is abnormal when delta V1 is smaller than Vset. When the detection is normal, the state of the first relay cannot be determined, and therefore, further determination is required.
On the basis, further judgment is carried out, namely in the second detection stage, the sampling control circuit is used for controlling the first relay and the third relay to be simultaneously conducted, and then the voltage of the output side and the on-off voltage of the relay are collected to obtain a second comparison result.
The first relay and the third relay are closed. Theoretically, vab should be VG and Vcd should be VG, and then the difference between Vab and Vcd is compared with Vset, if the comparison result is smaller, the detection is normal, and if the comparison result is larger, the detection is abnormal. The actual values of Vab and Vcd are collected to obtain an actual difference value delta V1, wherein the detection is normal when delta V1 is smaller than Vset, and the detection is abnormal when delta V1 is larger than Vset.
In this embodiment, the sampling control circuit is configured to detect the third relay according to the first comparison result and the second comparison result. On the basis, the sampling control circuit judges that the first comparison result is normal and the second comparison result is abnormal, and then judges that the state of the relay group caused by the third relay is abnormal.
Exemplarily, on the basis of the above technical solution, the optional detection stages shown in fig. 3 include a second detection stage step2 and a third detection stage step3; in the second detection stage, the sampling control circuit is used for controlling the first relay and the third relay to be conducted simultaneously, then collecting the voltage of the output side and the on-off voltage of the relay, and determining a second comparison result; in a third detection stage, the sampling control circuit is used for controlling the conduction of a third relay, then collecting the voltage of the output side and the on-off voltage of the relay and determining a third comparison result; the sampling control circuit is used for detecting the first relay according to the second comparison result and the third comparison result.
In this embodiment, the selectable relay is turned on under the control of a high level signal and turned off under a low level signal. And in the second detection stage, the sampling control circuit is used for controlling the first relay and the third relay to be simultaneously switched on, and then collecting the voltage of the output side and the on-off voltage of the relay to obtain a second comparison result. The absolute value of the difference between the Vab and Vcd is obtained, the absolute value is compared with a preset threshold, the smaller relation or the smaller relation obtained by the comparison is a second comparison result, and the detection is determined to be normal or abnormal according to the comparison result of the absolute value of the difference between the Vab and Vcd and the preset threshold.
Δ V1= | Vcd-Vab | is set, and the preset threshold, i.e., the error threshold, is Vset.
The first relay and the third relay are closed. Theoretically, vab should be VG and Vcd should be VG, and then the difference between Vab and Vcd is compared with Vset, if the comparison result is smaller, the detection is normal, and if the comparison result is larger, the detection is abnormal. The actual values of Vab and Vcd are collected to obtain an actual difference value delta V1, wherein the detection is normal when delta V1 is smaller than Vset, and the detection is abnormal when delta V1 is larger than Vset.
On the basis, judgment is further carried out, namely in a third detection stage, the sampling control circuit is used for controlling the conduction of a third relay, and then the voltage of the output side and the on-off voltage of the relay are collected to obtain a third comparison result.
The third relay is closed. Theoretically, vab should be VG, vcd =0, and then Vab and Vcd, the difference between Vab and Vcd is compared with Vset, if the comparison result is greater than the threshold, the detection is normal, and if the comparison result is less than the threshold, the detection is abnormal. The actual values of Vab and Vcd are collected to obtain an actual difference value delta V1, wherein the detection is normal when delta V1 is larger than Vset, and the detection is abnormal when delta V1 is smaller than Vset.
In this embodiment, the sampling control circuit is configured to detect the first relay according to the second comparison result and the third comparison result. On the basis, the sampling control circuit judges that the second comparison result is abnormal and the third comparison result is normal, and then judges that the first relay causes the abnormal state of the relay group.
Exemplarily, on the basis of the above technical solution, the optional detection stages shown in fig. 3 include a fourth detection stage step4 and a fifth detection stage step5; in a fourth detection stage, the sampling control circuit is used for controlling the second relay to be conducted, then collecting the voltage of the output side and the on-off voltage of the relay, and determining a fourth comparison result; in a fifth detection stage, the sampling control circuit is used for controlling the second relay and the fourth relay to be simultaneously conducted, then collecting the voltage of the output side and the on-off voltage of the relay, and determining a fifth comparison result; and the sampling control circuit is used for detecting the fourth relay according to the fourth comparison result and the fifth comparison result.
In this embodiment, the selectable relay is turned on under the control of a high level signal and turned off under a low level signal. And in a fourth detection stage, the sampling control circuit is used for controlling the second relay to be switched on, and then acquiring the voltage of the output side and the on-off voltage of the relay to obtain a fourth comparison result. And obtaining the absolute value of the difference value of the Vg-Vcd, comparing the absolute value with a preset threshold, obtaining a fourth comparison result if the absolute value is smaller than the relation or the smaller than the relation, and judging whether the detection is normal or abnormal according to the comparison result of the absolute value of the difference value of the Vg-Vcd and the preset threshold.
Δ V2= | Vg-Vcd | is set, and the preset threshold, that is, the error threshold is Vset.
The second relay is closed. Theoretically, vcd =0, then Vg and Vcd, the difference between them is compared with Vset, if the comparison result is greater than, the detection is normal, and if it is less than, the detection is abnormal. Acquiring actual values of Vg and Vcd to obtain an actual difference value delta V2, wherein the detection is normal when delta V2 is larger than Vset, and the detection is abnormal when delta V2 is smaller than Vset. In addition, when the detection is normal, the state of the second relay cannot be determined, and therefore, further determination is required.
On the basis, further judgment is carried out, namely in a fifth detection stage, the sampling control circuit is used for controlling the second relay and the fourth relay to be simultaneously conducted, and then the voltage of the output side and the on-off voltage of the relay are collected to obtain a fifth comparison result.
The second relay and the fourth relay are closed. Theoretically, vcd should be Vg, and then the difference between Vg and Vcd is compared with Vset, if the comparison result is smaller, the detection is normal, and if the comparison result is larger, the detection is abnormal. Acquiring actual values of Vg and Vcd to obtain an actual difference value delta V2, wherein the detection is normal when delta V2 is smaller than Vset, and the detection is abnormal when delta V2 is larger than Vset.
In this embodiment, the sampling control circuit is configured to detect the fourth relay according to the fourth comparison result and the fifth comparison result. On the basis, the sampling control circuit judges that the fourth comparison result is normal and the fifth comparison result is abnormal, and then judges that the state of the relay group caused by the fourth relay is abnormal.
Exemplarily, on the basis of the above technical solution, the optional detection stages shown in fig. 3 include a fifth detection stage and a sixth detection stage; in a fifth detection stage, the sampling control circuit is used for controlling the second relay and the fourth relay to be conducted simultaneously, then collecting the voltage of the output side and the on-off voltage of the relay, and determining a fifth comparison result; in a sixth detection stage, the sampling control circuit is used for controlling the conduction of a fourth relay, then collecting the voltage of the output side and the on-off voltage of the relay, and determining a sixth comparison result; and the sampling control circuit is used for detecting the second relay according to the fifth comparison result and the sixth comparison result.
In this embodiment, the selectable relay is turned on under the control of a high level signal and turned off under a low level signal. And in the fifth detection stage, the sampling control circuit is used for controlling the second relay and the fourth relay to be simultaneously switched on, and then acquiring the voltage of the output side and the on-off voltage of the relay to obtain a fifth comparison result. And obtaining the absolute value of the difference value of Vg-Vcd, comparing the absolute value with a preset threshold value, obtaining a second comparison result if the absolute value is smaller than the relation or the smaller than the relation, and judging whether the detection is normal or abnormal according to the comparison result of the absolute value of the difference value of Vg-Vcd and the preset threshold value.
Δ V2= | Vcd-Vg |, and the preset threshold, i.e., the error threshold, is set to be Vset.
The second relay and the fourth relay are closed. Theoretically, vcd should be Vg, and then the difference between Vg and Vcd is compared with Vset, if the comparison result is smaller, the detection is normal, and if the comparison result is larger, the detection is abnormal. Acquiring actual values of Vg and Vcd to obtain an actual difference value delta V2, wherein the detection is normal when delta V2 is smaller than Vset, and the detection is abnormal when delta V2 is larger than Vset.
On the basis, further judgment is carried out, namely in a sixth detection stage, the sampling control circuit is used for controlling the fourth relay to be conducted, then the output side voltage and the relay on-off voltage are collected, and a sixth comparison result is obtained.
The sixth relay is closed. Theoretically, vcd =0, then Vg and Vcd, the difference between them is compared with Vset, if the comparison result is greater than, the detection is normal, and if it is less than, the detection is abnormal. Acquiring actual values of Vg and Vcd to obtain an actual difference value delta V2, wherein the detection is normal when delta V2 is larger than Vset, and the detection is abnormal when delta V2 is smaller than Vset.
In this embodiment, the sampling control circuit is configured to detect the second relay according to the fifth comparison result and the sixth comparison result. On the basis, the sampling control circuit judges that the fifth comparison result is abnormal and the sixth comparison result is normal, and then judges that the state of the relay group caused by the second relay is abnormal.
It is to be noted that the foregoing description is only exemplary of the invention and that the principles of the technology may be employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious modifications, rearrangements, combinations and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.
Claims (5)
1. A grid-tied relay circuit, comprising: the system comprises a bus voltage circuit, a power grid voltage circuit, a sampling control circuit and a relay group connected between the output side of the bus voltage circuit and the input side of the power grid voltage circuit;
the relay group comprises a first relay, a second relay, a third relay and a fourth relay, wherein a first end of the first relay is electrically connected with an output positive electrode of the bus voltage circuit, a first end of the second relay is electrically connected with an input positive electrode of the power grid voltage circuit, a second end of the first relay is electrically connected with a second end of the second relay and connected to a first node, a first end of the third relay is electrically connected with an output negative electrode of the bus voltage circuit, a first end of the fourth relay is electrically connected with an input negative electrode of the power grid voltage circuit, and a second end of the third relay is electrically connected with a second end of the fourth relay and connected to a second node;
the sampling control circuit is respectively connected with the bus voltage circuit and the power grid voltage circuit and is used for acquiring the bus voltage of the bus voltage circuit and the power grid voltage of the power grid voltage circuit and regulating the bus voltage to enable the voltage of the output side of the bus voltage to be equal to the power grid voltage;
the sampling control circuit is further electrically connected with the relay group and the first node and the second node respectively, in a detection stage, the sampling control circuit is used for controlling the on-off of each relay in the relay group, then collecting the output side voltage and the relay on-off voltage between the first node and the second node, and judging the working state of at least one relay according to the comparison result of the difference between the output side voltage and the relay on-off voltage and a preset threshold value;
the bus voltage circuit includes:
the system comprises a bus voltage source and an inverter power circuit electrically connected with the bus voltage source;
the sampling control circuit is respectively electrically connected with the bus voltage source and the inverter power circuit and is used for collecting the bus voltage of the bus voltage source and driving the inverter power circuit so as to enable the output side voltage of the inverter power circuit to be equal to the power grid voltage;
the sampling control circuit includes:
the sampling circuit and the drive control circuit are electrically connected with the sampling circuit;
the sampling circuit is electrically connected with the bus voltage circuit, the power grid voltage circuit and the first node and the second node respectively;
the driving control circuit is respectively and electrically connected with the inverter power circuit and the relay group;
the drive control circuit includes:
a sinusoidal pulse width modulation unit;
the sine pulse width modulation unit is electrically connected with the inverter power circuit and used for outputting a sine pulse width modulation signal to adjust the inverter power circuit to enable the voltage of the output side of the inverter power circuit to be equal to the voltage of the power grid.
2. The grid-connected relay circuit according to claim 1, wherein the detection phase comprises a first detection phase and a second detection phase;
in the first detection stage, the sampling control circuit is used for controlling the first relay to be switched on, then collecting the output side voltage and the on-off voltage of the relay, and determining a first comparison result;
in the second detection stage, the sampling control circuit is used for controlling the first relay and the third relay to be simultaneously conducted, collecting the output side voltage and the on-off voltage of the relay, and determining a second comparison result;
the sampling control circuit is used for detecting the third relay according to the first comparison result and the second comparison result.
3. The grid-connected relay circuit according to claim 1, wherein the detection phase includes a second detection phase and a third detection phase;
in the second detection stage, the sampling control circuit is used for controlling the first relay and the third relay to be simultaneously conducted, collecting the output side voltage and the on-off voltage of the relay, and determining a second comparison result;
in the third detection stage, the sampling control circuit is used for controlling the third relay to be switched on, then collecting the output side voltage and the on-off voltage of the relay, and determining a third comparison result;
the sampling control circuit is used for detecting the first relay according to the second comparison result and the third comparison result.
4. The grid-connected relay circuit according to claim 1, wherein the detection phase includes a fourth detection phase and a fifth detection phase;
in the fourth detection stage, the sampling control circuit is used for controlling the second relay to be conducted, collecting the output side voltage and the relay on-off voltage, and determining a fourth comparison result;
in the fifth detection stage, the sampling control circuit is used for controlling the second relay and the fourth relay to be simultaneously switched on, collecting the voltage of the output side and the on-off voltage of the relay, and determining a fifth comparison result;
the sampling control circuit is used for detecting the fourth relay according to the fourth comparison result and the fifth comparison result.
5. The grid-connected relay circuit according to claim 1, wherein the detection stages include a fifth detection stage and a sixth detection stage;
in the fifth detection stage, the sampling control circuit is used for controlling the second relay and the fourth relay to be simultaneously switched on, collecting the voltage of the output side and the on-off voltage of the relay, and determining a fifth comparison result;
in the sixth detection stage, the sampling control circuit is used for controlling the fourth relay to be switched on, collecting the output side voltage and the relay on-off voltage, and determining a sixth comparison result;
the sampling control circuit is used for detecting the second relay according to the fifth comparison result and the sixth comparison result.
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