CN108896822B - Insulation impedance detection system and method for photovoltaic grid-connected inverter - Google Patents
Insulation impedance detection system and method for photovoltaic grid-connected inverter Download PDFInfo
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- CN108896822B CN108896822B CN201810795729.0A CN201810795729A CN108896822B CN 108896822 B CN108896822 B CN 108896822B CN 201810795729 A CN201810795729 A CN 201810795729A CN 108896822 B CN108896822 B CN 108896822B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/025—Measuring very high resistances, e.g. isolation resistances, i.e. megohm-meters
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/16—Measuring impedance of element or network through which a current is passing from another source, e.g. cable, power line
- G01R27/18—Measuring resistance to earth, i.e. line to ground
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/20—Measuring earth resistance; Measuring contact resistance, e.g. of earth connections, e.g. plates
Abstract
The application discloses an insulation impedance detection system and method of a photovoltaic grid-connected inverter, which aim to reduce the detection cost of simultaneously detecting insulation impedance of a plurality of inversion unit direct current sides to the ground. The system comprises a first insulation impedance detection circuit, a control unit and a direct current side switch which is independently arranged for each inversion unit; the direct current side switch corresponding to each inversion unit is connected between the direct current side of the inversion unit and the input end of the first insulation impedance detection circuit; the output end of the first insulation impedance detection circuit is connected to the input end of the control unit; the output end of the control unit is connected to the control end of each direct current side switch, and is used for controlling each direct current side switch to be alternately closed, receiving the sampling conditioning signal output by the first insulation impedance detection circuit, and then calculating the direct current side insulation impedance of each inversion unit according to the sampling conditioning signal output by the first insulation impedance detection circuit.
Description
Technical Field
The invention relates to the technical field of insulation impedance detection, in particular to an insulation impedance detection system and method of a photovoltaic grid-connected inverter.
Background
Fig. 1 shows a typical pv grid-connected inverter, which includes a plurality of inverter units, where the ac side of each inverter unit is connected to the grid through an independent grid-connected switch, and the dc side of each inverter unit is connected to an independent pv array.
Because the photovoltaic array is placed in the open air and is influenced by factors such as dust, rain, snow, fog and the like, the insulation impedance of the positive electrode and the negative electrode of the photovoltaic array to the ground can be changed, the safe operation of the photovoltaic grid-connected inverter is influenced, and the personal safety can be threatened. Therefore, before and after each inverter unit is connected to the grid, it is necessary to detect the dc-side insulation impedance of the inverter unit (i.e. the positive and negative electrode-to-ground insulation impedance of the photovoltaic array connected to the dc side of the inverter unit) in order to find and eliminate the potential safety hazard in time.
The existing insulation impedance detection product can only detect the insulation impedance of the direct current side of one path of inverter unit, and for a scene containing a plurality of inverter units in figure 1, a plurality of insulation impedance detection products need to be arranged at the same time, so that the cost is too high.
Disclosure of Invention
In view of the above, the present invention provides a system and a method for detecting insulation impedance of a photovoltaic grid-connected inverter, so as to reduce the detection cost for simultaneously detecting insulation impedance of a dc side to ground of a plurality of inverter units.
An insulation resistance detection system of a photovoltaic grid-connected inverter, the photovoltaic grid-connected inverter comprises a plurality of inversion units, an alternating current side of each inversion unit is connected into a power grid through an independent grid-connected switch, and a direct current side of each inversion unit is connected into an independent photovoltaic array, the insulation resistance detection system comprises:
the first insulation impedance detection circuit, the control unit and the direct current side switch which is independently arranged aiming at each inversion unit respectively;
the direct current side switch corresponding to each inversion unit is connected between the direct current side of the inversion unit and the input end of the first insulation impedance detection circuit;
the output end of the first insulation impedance detection circuit is connected to the input end of the control unit;
the output end of the control unit is connected to the control end of each direct current side switch, and is used for controlling each direct current side switch to be alternately closed, receiving the sampling conditioning signal output by the first insulation impedance detection circuit, and then calculating the direct current side insulation impedance of each inversion unit according to the sampling conditioning signal output by the first insulation impedance detection circuit.
Optionally, the insulation resistance detection system further includes:
the second insulation impedance detection circuit is connected between one line voltage output end of the grid-connected point and the input end of the control unit;
and a third insulation resistance detection circuit connected between the other line voltage output end of the grid-connected point and the input end of the control unit;
the control unit is further configured to receive the sampling conditioning signals output by the second insulation resistance detection circuit and the third insulation resistance detection circuit, and calculate three relative ground insulation resistances of the grid-connected point according to the sampling conditioning signals output by the second insulation resistance detection circuit and the third insulation resistance detection circuit.
Optionally, the insulation resistance detection system further includes:
a fourth insulation resistance detection circuit connected to an input terminal of the control unit;
the alternating current side switch is connected between one line voltage output end of the grid-connected point and the input end of the fourth insulation impedance detection circuit;
and an alternating current side switch connected between the other line voltage output end of the grid-connected point and the input end of the fourth insulation resistance detection circuit;
the output end of the control unit is connected with the control ends of the two AC side switches;
the control unit is further configured to control the two ac side switches to be alternately turned on and off, receive the sampling conditioning signal output by the fourth insulation resistance detection circuit, and then calculate three phase-to-ground insulation resistances of the grid-connected point according to the sampling conditioning signal output by the fourth insulation resistance detection circuit.
Optionally, the insulation resistance detection system further includes:
the alternating current side switch is connected between one line voltage output end of the grid-connected point and the input end of the first insulation impedance detection circuit;
and an alternating current side switch connected between the other line voltage output end of the grid-connected point and the input end of the first insulation impedance detection circuit;
the output end of the control unit is connected with the control ends of the two AC side switches;
correspondingly, the control unit is specifically configured to control each switch in a switch group formed by each dc-side switch and each ac-side switch to be alternately closed, receive the sampled conditioning signal output by the first insulation impedance detection circuit, and then calculate three relative ground insulation impedances of the dc-side insulation impedance and the grid-connected point of each inverter unit according to the sampled conditioning signal output by the first insulation impedance detection circuit.
Optionally, the output end of the control unit is connected to the control end of each grid-connected switch.
Optionally, the first insulation impedance detection circuit includes a sampling circuit and a conditioning circuit;
the sampling circuit comprises a pulse power supply, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor and a sixth resistor, wherein:
a positive input terminal of the sampling circuit is grounded after sequentially passing through the first resistor, the second resistor and the fifth resistor;
the negative input terminal of the sampling circuit is grounded after sequentially passing through the fourth resistor, the third resistor and the fifth resistor; the pulse power supply is grounded through the sixth resistor;
and the common end of the first resistor and the second resistor is connected into the input end of the conditioning circuit.
The insulation impedance detection method of the photovoltaic grid-connected inverter comprises a plurality of inversion units, wherein the alternating current side of each inversion unit is connected into a power grid through an independent grid-connected switch, the direct current side of each inversion unit is connected into an independent photovoltaic array, and the insulation impedance detection method is applied to an insulation impedance detection system;
the insulation resistance detection system includes:
the first insulation impedance detection circuit, the control unit and the direct current side switch which is independently arranged aiming at each inversion unit respectively;
the direct current side switch corresponding to each inversion unit is connected between the direct current side of the inversion unit and the input end of the first insulation impedance detection circuit;
the output end of the first insulation impedance detection circuit is connected to the input end of the control unit;
the output end of the control unit is connected to the control end of each direct current side switch;
the insulation resistance detection method comprises the following steps:
the control unit controls the direct current side switches to be alternately closed;
receiving a sampling conditioning signal output by the first insulation impedance detection circuit;
and calculating the direct-current side insulation impedance of each inversion unit according to the sampling conditioning signal output by the first insulation impedance detection circuit.
Optionally, the insulation resistance detection system further includes:
the second insulation impedance detection circuit is connected between one line voltage output end of the grid-connected point and the input end of the control unit;
and a third insulation resistance detection circuit connected between the other line voltage output end of the grid-connected point and the input end of the control unit;
the insulation resistance detection method further includes:
receiving sampling conditioning signals output by the second insulation impedance detection circuit and the third insulation impedance detection circuit;
and calculating three relative ground insulation impedances of the grid-connected point according to the sampling conditioning signals output by the second insulation impedance detection circuit and the third insulation impedance detection circuit.
Optionally, the insulation resistance detection system further includes:
a fourth insulation resistance detection circuit connected to an input terminal of the control unit;
the alternating current side switch is connected between one line voltage output end of the grid-connected point and the input end of the fourth insulation impedance detection circuit;
and an alternating current side switch connected between the other line voltage output end of the grid-connected point and the input end of the fourth insulation resistance detection circuit;
the output end of the control unit is connected with the control ends of the two AC side switches;
the insulation resistance detection method further includes:
controlling the two switches on the alternating current side to be closed alternatively;
receiving a sampling conditioning signal output by the fourth insulation resistance detection circuit;
and calculating three relative ground insulation impedances of the grid-connected point according to the sampling conditioning signal output by the fourth insulation impedance detection circuit.
Optionally, the insulation resistance detection system further includes:
the alternating current side switch is connected between one line voltage output end of the grid-connected point and the input end of the first insulation impedance detection circuit;
and an alternating current side switch connected between the other line voltage output end of the grid-connected point and the input end of the first insulation impedance detection circuit;
the output end of the control unit is connected with the control ends of the two AC side switches;
correspondingly, the insulation resistance detection method comprises the following steps:
the control unit controls each switch in a switch group consisting of each direct current side switch and each alternating current side switch to be alternately closed;
receiving a sampling conditioning signal output by the first insulation impedance detection circuit;
and calculating the direct-current side insulation impedance of each inversion unit and the three relative ground insulation impedances of the grid-connected point according to the sampling conditioning signal output by the first insulation impedance detection circuit.
According to the technical scheme, the direct-current side switches are closed alternately, and the direct-current side voltages of the multiple inversion units are sent to the first insulation impedance detection circuit alternately, so that the direct-current side insulation impedance detection of the multiple inversion units shares one insulation impedance detection product, and the situation that one insulation impedance detection product is configured for the direct-current side insulation impedance detection of each inversion unit independently in the prior art is not needed, and therefore the cost is saved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a photovoltaic grid-connected inverter disclosed in the prior art;
fig. 2 is a schematic structural diagram of an insulation resistance detection system of a photovoltaic grid-connected inverter according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a first insulation resistance detection circuit according to an embodiment of the present invention;
FIG. 4 is a schematic structural diagram of another insulation resistance detection system according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of another insulation resistance detection system according to an embodiment of the present invention;
FIG. 6 is a schematic structural diagram of another insulation resistance detection system according to an embodiment of the present invention;
fig. 7 is a flowchart of an insulation resistance detection method for a photovoltaic grid-connected inverter according to an embodiment of the present invention;
FIG. 8 is a flowchart of another insulation resistance detection method according to an embodiment of the present invention;
FIG. 9 is a flowchart of another insulation resistance detection method according to an embodiment of the present invention;
fig. 10 is a flowchart of another insulation resistance detection method according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of 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 invention.
The embodiment of the invention discloses an insulation impedance detection system of a photovoltaic grid-connected inverter. As shown in fig. 1, the photovoltaic grid-connected inverter includes a plurality of inverter units, an ac side of each inverter unit is connected to a power grid through an independent grid-connected switch, and a dc side of each inverter unit is connected to an independent photovoltaic array. For convenience of description, in the following description, each inversion unit in fig. 1 is respectively identified as an inversion unit 1, an inversion unit 2, an inversion unit …, and an inversion unit N, where N is the total number of the inversion units, and N is greater than or equal to 2; the grid-connected switches corresponding to the inverter units i (i is 1, 2, 3, …, N) are identified as Ki, as shown in fig. 2.
Still referring to fig. 2, the insulation resistance detection system includes:
the first insulation impedance detection circuit 100, the control unit 200, and the dc side switches independently arranged for each inverter unit, for convenience of description, the dc side switch corresponding to the inverter unit i is identified as Si in the following;
the direct current side switch Si is connected between the direct current side of the inverter unit i and the input end of the first insulation impedance detection circuit 100;
the output end of the first insulation impedance detection circuit 100 is connected to the input end of the control unit 200;
the output end of the control unit 200 is connected to the control end of each dc-side switch, and is configured to control each dc-side switch to be alternately turned on and off, receive the sampling conditioning signal output by the first insulation impedance detection circuit 100, and calculate the dc-side insulation impedance of each inverter unit according to the sampling conditioning signal output by the first insulation impedance detection circuit 100.
The operation of the insulation resistance detection system shown in fig. 2 will be described in detail below.
In fig. 2, each dc-side switch is turned on alternately, and the dc-side voltages of the N inverter units are sent to the first insulation impedance detection circuit 100 alternately, so that the dc-side insulation impedance detection of the N inverter units shares one insulation impedance detection product, and it is not necessary to configure one insulation impedance detection product for each dc-side insulation impedance detection of each inverter unit separately, thereby saving the cost.
Specifically, in the initial condition, each dc-side switch is in an off state, and the on-off state of each grid-connected switch is not limited.
Next, the dc-side switch 1 is first closed, at this time, the output voltage of the photovoltaic array 1 is sent to the first insulation impedance detection circuit 100, the first insulation impedance detection circuit 100 outputs a corresponding sampling conditioning signal to the control unit 200, and the control unit 200 calculates the dc-side insulation impedance of the inverter unit 1 (optionally, the dc-side insulation impedance in multiple cycles can be continuously calculated for the inverter unit 1, so as to ensure the accuracy of the calculation result).
Next, the dc-side switch 1 is turned off, the dc-side switch 2 is turned on, the output voltage of the photovoltaic array 2 is sent to the first insulation impedance detection circuit 100, the first insulation impedance detection circuit 100 outputs a corresponding sampling conditioning signal to the control unit 200, and the control unit 200 calculates the dc-side insulation impedance of the inverter unit 2.
By parity of reasoning, the direct current side switches 3-N are switched to be closed one by one, and the direct current side insulation impedances of the inversion units 3-N are calculated in sequence.
Aiming at the calculated direct-current side insulation impedance of the inverter unit i, if the direct-current side insulation impedance of the inverter unit i is abnormal, the grid-connected switch i needs to be disconnected and an alarm is sent to a maintainer; and if the direct-current side insulation impedance of the inverter unit i is in a normal value, closing the grid-connected switch i. These processing operations performed on whether the dc-side insulation impedance of the inverter unit i is normal or not may be executed by the control unit 200 (at this time, the output terminal of the control unit 200 is connected to the control terminal of each grid-connected switch), or may be processed by the upper management center, which is not limited.
Certainly, on the premise of ensuring that at most one dc-side switch is in a closed state at the same time, the specific manner of alternately closing each dc-side switch may be arbitrarily set according to actual needs, for example, if n is 3, the specific manner may be: closing the direct current side switch 1, then opening the direct current side switch 1, closing the direct current side switch 2, then opening the direct current side switch 2, and closing the direct current side switch 3; the method can also be as follows: closing the direct current side switch 1, then opening the direct current side switch 1, closing the direct current side switch 2, then opening the direct current side switch 2, then closing the direct current side switch 2, then opening the direct current side switch 2, and then closing the direct current side switch 3; the method can also be as follows: closing the DC side switch 1, then opening the DC side switch 1, closing the DC side switch 2, then opening the DC side switch 2, closing the DC side switch 3, then opening the DC side switch 3, and closing the DC side switch 2.
Alternatively, in the insulation resistance detection system disclosed above, the first insulation resistance detection circuit 100 may adopt a topology as shown in fig. 3, and includes two parts, i.e., a sampling circuit 101 and a conditioning circuit 102. The sampling circuit 101 specifically includes a pulse power supply, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, and a sixth resistor R6, where: the positive input terminal of the sampling circuit 101 is grounded after sequentially passing through R1, R2 and R5; the negative input terminal of the sampling circuit 101 is grounded after sequentially passing through R4, R3 and R5; the pulse power supply is grounded through R6; the common terminal of R1 and R2 is connected to the input terminal of the conditioning circuit 102.
When the direct current side switch i is closed, the input voltage of the sampling circuit 101 is the output voltage of the photovoltaic array i, the positive pole ground insulation resistance R + of the photovoltaic array i is connected between the positive input terminal of the sampling circuit 101 and the ground, the negative pole ground insulation resistance R-of the photovoltaic array i is connected between the negative input terminal of the sampling circuit 101 and the ground, the sampling circuit 101 samples internal relevant electrical parameters and outputs the internal relevant electrical parameters to the conditioning circuit 102, and the conditioning circuit 102 converts the sampling signals into digital signals which can be identified by the control unit 200.
It should be noted here that the topology of the first insulation resistance detection circuit 100 is not limited to fig. 3, and other existing topologies may be adopted, and the insulation resistance algorithm adopted by the control unit 200 needs to match the topology adopted by the first insulation resistance detection circuit 100.
Optionally, in the insulation resistance detection system disclosed above, each dc-side switch employs a relay, but the present invention is not limited to this, and for example, a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), an IGBT (Insulated Gate Bipolar Transistor), a triode, or the like may be employed. When the direct current side switch adopts the MOSFET, the control end of the direct current side switch refers to the grid electrode of the MOSFET; when the direct-current side switch adopts the IGBT, the control end of the direct-current side switch refers to the grid electrode of the IGBT; when the direct current side switch adopts a triode, the control end of the direct current side switch refers to the base electrode of the triode.
As shown in fig. 4, the embodiment of the present invention further discloses another insulation resistance detection system, which, compared with fig. 2, further includes:
a second insulation resistance detection circuit 300 connected between one line voltage output terminal of the grid-connected point and the input terminal of the control unit 200;
and a third insulation resistance detection circuit 400 connected between the other line voltage output terminal of the grid-connected point and the input terminal of the control unit 200;
the control unit 200 is further configured to receive the sampled and conditioned signals output by the second insulation resistance detection circuit 300 and the third insulation resistance detection circuit 400, and calculate three relative ground insulation resistances of the grid-connected point according to the sampled and conditioned signals output by the second insulation resistance detection circuit 300 and the third insulation resistance detection circuit 400.
Specifically, the abnormal insulation impedance on the ac side of the inverter unit also affects the safe operation of the photovoltaic grid-connected inverter, so it is very necessary to detect the insulation impedance on the ac side of the inverter unit. In FIG. 4, two additional insulation resistance detection circuits are added, and the input voltages are the voltages of the grid-connected point line UAB、UBC、UACOf the second insulation resistance detection circuit 300, e.g., the line voltage U applied to the input terminal of the second insulation resistance detection circuit 300ABThe third insulation resistance detection circuit 400 has a voltage U applied to the input terminalBCThen, the control unit 200 calculates a relative ground insulation impedance a and a relative ground insulation impedance B according to the sampled conditioning signal output by the second insulation impedance detection circuit 300, and calculates a relative ground insulation impedance B and a relative ground insulation impedance C according to the sampled conditioning signal output by the third insulation impedance detection circuit 400, so as to obtain three relative ground insulation impedances of the grid-connected point, that is, the ac side insulation impedance of any inverter unit.
The premise of grid-connected operation of the inverter unit i is that the insulation impedance of the direct current side and the insulation impedance of the alternating current side of the inverter unit i are both at normal values. Therefore, if the insulation impedance of the grid-connected point is abnormal or the insulation impedance of the direct current side of the inverter unit i is abnormal, the grid-connected switch i needs to be disconnected and an alarm is sent to a maintainer; and if the grid-connected point insulation impedance and the direct-current side insulation impedance of the inverter unit i are both in normal values, closing the grid-connected switch i. These processing operations performed on whether the insulation impedance is normal or not may be performed by the control unit 200 (at this time, the output terminal of the control unit 200 needs to be connected to the control terminal of each grid-connected switch), or may be processed by the report management center, which is not limited.
The first insulation resistance detection circuit 100, the second insulation resistance detection circuit 300, and the third insulation resistance detection circuit 400 may adopt the same topology, but are not limited thereto.
As shown in fig. 5, the embodiment of the present invention further discloses another insulation resistance detection system, which, compared with fig. 2, further includes:
a fourth insulation resistance detection circuit 500 connected to an input terminal of the control unit 200;
an ac side switch Q1 connected between one line voltage output terminal of the grid-connected point and the input terminal of the fourth insulation resistance detection circuit 500;
and an ac side switch Q2 connected between the further line voltage output terminal of the grid-connected point and the input terminal of the fourth insulation resistance detection circuit 500;
the output end of the control unit 200 is connected with the control ends of the two AC side switches;
the control unit 200 is further configured to control the two ac side switches to be alternately turned on and off, receive the sampled and conditioned signal output by the fourth insulation resistance detection circuit 500, and then calculate three phase-to-ground insulation resistances of the grid-connected point according to the sampled and conditioned signal output by the fourth insulation resistance detection circuit 500.
Compared with fig. 4, the scheme shown in fig. 5 has two ac side switches alternately closed, and two line voltages are alternately sent to the fourth insulation resistance detection circuit 500, instead of separately configuring an insulation resistance detection circuit for each line voltage, thereby saving cost.
As shown in fig. 6, the embodiment of the present invention further discloses another insulation resistance detection system, which, compared with fig. 2, further includes:
an ac side switch Q3 connected between one line voltage output terminal of the grid-connected point and the input terminal of the first insulation impedance detection circuit 100;
and an ac side switch Q4 connected between the further line voltage output terminal of the point-to-grid point and the input terminal of the first insulation impedance detection circuit 100;
the output end of the control unit 200 is connected with the control ends of the two AC side switches;
correspondingly, the control unit 200 is specifically configured to control each switch in a switch group formed by each dc-side switch and each ac-side switch to be alternately closed, receive the sampled conditioning signal output by the first insulation impedance detection circuit 100, and calculate three relative ground insulation impedances of the dc-side insulation impedance and the grid-connected point of each inverter unit according to the sampled conditioning signal output by the first insulation impedance detection circuit 100.
Compared with fig. 5, the scheme shown in fig. 6 allocates the task of detecting the three phase-to-ground insulation resistance of the grid-connected point to the first insulation resistance detection circuit 100 without additionally providing an insulation resistance detection circuit, thereby saving the cost.
In addition, the photovoltaic grid-connected inverter in the application may be an isolated photovoltaic grid-connected inverter, or may be a non-isolated photovoltaic grid-connected inverter. When the grid-connected inverter is a non-isolated photovoltaic grid-connected inverter, the three-phase-to-ground insulation impedance of the grid-connected point can reflect the dc-side insulation impedance of the grid-connected inverter unit, so that in fig. 4 to 6, the dc-side insulation impedance of the grid-connected inverter unit can be detected by detecting the three-phase-to-ground insulation impedance of the grid-connected point.
Corresponding to the above method embodiment, the embodiment of the present invention further discloses an insulation resistance detection method applied to the insulation resistance detection system shown in fig. 2, as shown in fig. 7, including:
step S01: the control unit 200 controls the direct current side switches to be closed alternately;
step S02: receiving a sampling conditioning signal output by the first insulation impedance detection circuit 100;
step S03: and calculating the direct-current side insulation impedance of each inverter unit according to the sampling conditioning signal output by the first insulation impedance detection circuit 100.
The embodiment of the invention also discloses an insulation resistance detection method applied to the insulation resistance detection system shown in fig. 4, as shown in fig. 8, the method comprises the following steps:
step S11: the control unit 200 receives the sampled and conditioned signals output by the second insulation resistance detection circuit 300 and the third insulation resistance detection circuit 400;
step S12: and calculating three relative ground insulation impedances of the grid-connected point according to the sampled conditioning signals output by the second insulation impedance detection circuit 300 and the third insulation impedance detection circuit 400.
Step S13: controlling each direct current side switch to be closed alternatively;
step S14: receiving a sampling conditioning signal output by the first insulation impedance detection circuit 100;
step S15: and calculating the direct-current side insulation impedance of each inverter unit according to the sampling conditioning signal output by the first insulation impedance detection circuit 100.
Of course, the steps S11 to S12 may be executed simultaneously with the steps S13 to S15, or after the step S15, without limitation.
The embodiment of the invention also discloses an insulation resistance detection method applied to the insulation resistance detection system shown in fig. 5, as shown in fig. 9, the method comprises the following steps:
step S21: the control unit 200 controls the two alternating-current side switches to be alternately closed;
step S22: receiving a sampling conditioning signal output by the fourth insulation resistance detection circuit 500;
step S23: calculating three relative ground insulation impedances of the grid-connected point according to the sampling conditioning signal output by the fourth insulation impedance detection circuit 500;
step S24: controlling each direct current side switch to be closed alternatively;
step S25: receiving a sampling conditioning signal output by the first insulation impedance detection circuit 100;
step S26: and calculating the direct-current side insulation impedance of each inverter unit according to the sampling conditioning signal output by the first insulation impedance detection circuit 100.
Of course, the steps S21 to S23 may be executed simultaneously with the steps S24 to S26, or after the step S15, without limitation.
The embodiment of the invention also discloses an insulation resistance detection method applied to the insulation resistance detection system shown in fig. 6, as shown in fig. 10, the method comprises the following steps:
step S31: the control unit 200 controls each switch in a switch group consisting of each dc-side switch and each ac-side switch to be alternately closed;
step S32: receiving a sampling conditioning signal output by the first insulation impedance detection circuit 100;
step S33: and calculating the direct-current side insulation impedance of each inverter unit and the three relative ground insulation impedances of the grid-connected point according to the sampling conditioning signal output by the first insulation impedance detection circuit 100.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The method disclosed by the embodiment corresponds to the system disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the system part for description.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the embodiments. Thus, the present embodiments are not intended to be limited to the embodiments shown herein but are to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. The utility model provides a photovoltaic grid-connected inverter's insulation impedance detecting system, photovoltaic grid-connected inverter includes a plurality of contravariant units, and the interchange side of every contravariant unit is incorporated into the electric wire netting through independent grid-connected switch, and the direct current side of every contravariant unit inserts independent photovoltaic array, its characterized in that, insulation impedance detecting system includes:
the first insulation impedance detection circuit, the control unit and the direct current side switch which is independently arranged aiming at each inversion unit respectively;
the direct current side switch corresponding to each inversion unit is connected between the direct current side of the inversion unit and the input end of the first insulation impedance detection circuit;
the output end of the first insulation impedance detection circuit is connected to the input end of the control unit;
the output end of the control unit is connected to the control end of each direct current side switch and is used for controlling each direct current side switch to be alternately closed, receiving a sampling conditioning signal output by a first insulation impedance detection circuit corresponding to the currently closed direct current side switch, and then calculating the direct current side insulation impedance of the inverter unit corresponding to the currently closed direct current side switch according to the sampling conditioning signal;
and if the insulation impedance of the direct current side of the inversion unit is abnormal, the grid-connected switch of the alternating current side of the inversion unit is switched off, and if the insulation impedance of the direct current side of the inversion unit is in a normal value, the grid-connected switch of the alternating current side of the inversion unit is switched on.
2. The insulation resistance detection system of claim 1, further comprising:
the second insulation impedance detection circuit is connected between one line voltage output end of the grid-connected point and the input end of the control unit;
and a third insulation resistance detection circuit connected between the other line voltage output end of the grid-connected point and the input end of the control unit;
the control unit is further configured to receive the sampling conditioning signals output by the second insulation resistance detection circuit and the third insulation resistance detection circuit, and calculate three relative ground insulation resistances of the grid-connected point according to the sampling conditioning signals output by the second insulation resistance detection circuit and the third insulation resistance detection circuit.
3. The insulation resistance detection system of claim 1, further comprising:
a fourth insulation resistance detection circuit connected to an input terminal of the control unit;
the alternating current side switch is connected between one line voltage output end of the grid-connected point and the input end of the fourth insulation impedance detection circuit;
and an alternating current side switch connected between the other line voltage output end of the grid-connected point and the input end of the fourth insulation resistance detection circuit;
the output end of the control unit is connected with the control ends of the two AC side switches;
the control unit is further configured to control the two ac side switches to be alternately turned on and off, receive the sampling conditioning signal output by the fourth insulation resistance detection circuit, and then calculate three phase-to-ground insulation resistances of the grid-connected point according to the sampling conditioning signal output by the fourth insulation resistance detection circuit.
4. The insulation resistance detection system of claim 1, further comprising:
the alternating current side switch is connected between one line voltage output end of the grid-connected point and the input end of the first insulation impedance detection circuit;
and an alternating current side switch connected between the other line voltage output end of the grid-connected point and the input end of the first insulation impedance detection circuit;
the output end of the control unit is connected with the control ends of the two AC side switches;
correspondingly, the control unit is specifically configured to control each switch in a switch group formed by each dc-side switch and each ac-side switch to be alternately closed, receive the sampled conditioning signal output by the first insulation impedance detection circuit, and then calculate three relative ground insulation impedances of the dc-side insulation impedance and the grid-connected point of each inverter unit according to the sampled conditioning signal output by the first insulation impedance detection circuit.
5. The insulation resistance detection system according to any one of claims 1 to 4, wherein the output terminal of the control unit is connected to the control terminal of each grid-connected switch.
6. The insulation resistance detection system of any one of claims 1-4, wherein the first insulation resistance detection circuit comprises a sampling circuit and a conditioning circuit;
the sampling circuit comprises a pulse power supply, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor and a sixth resistor, wherein:
a positive input terminal of the sampling circuit is grounded after sequentially passing through the first resistor, the second resistor and the fifth resistor;
the negative input terminal of the sampling circuit is grounded after sequentially passing through the fourth resistor, the third resistor and the fifth resistor; the pulse power supply is grounded through the sixth resistor;
and the common end of the first resistor and the second resistor is connected into the input end of the conditioning circuit.
7. The insulation impedance detection method of the photovoltaic grid-connected inverter is characterized in that the insulation impedance detection method is applied to an insulation impedance detection system;
the insulation resistance detection system includes:
the first insulation impedance detection circuit, the control unit and the direct current side switch which is independently arranged aiming at each inversion unit respectively;
the direct current side switch corresponding to each inversion unit is connected between the direct current side of the inversion unit and the input end of the first insulation impedance detection circuit;
the output end of the first insulation impedance detection circuit is connected to the input end of the control unit;
the output end of the control unit is connected to the control end of each direct current side switch;
the insulation resistance detection method comprises the following steps:
the control unit controls the direct current side switches to be alternately closed;
receiving a sampling conditioning signal output by a first insulation impedance detection circuit corresponding to a currently closed direct current side switch;
calculating the direct-current side insulation impedance of the inversion unit corresponding to the currently closed direct-current side switch according to the sampling conditioning signal;
and if the insulation impedance of the direct current side of the inversion unit is abnormal, the grid-connected switch of the alternating current side of the inversion unit is switched off, and if the insulation impedance of the direct current side of the inversion unit is in a normal value, the grid-connected switch of the alternating current side of the inversion unit is switched on.
8. The insulation resistance detection method according to claim 7, wherein the insulation resistance detection system further comprises:
the second insulation impedance detection circuit is connected between one line voltage output end of the grid-connected point and the input end of the control unit;
and a third insulation resistance detection circuit connected between the other line voltage output end of the grid-connected point and the input end of the control unit;
the insulation resistance detection method further includes:
receiving sampling conditioning signals output by the second insulation impedance detection circuit and the third insulation impedance detection circuit;
and calculating three relative ground insulation impedances of the grid-connected point according to the sampling conditioning signals output by the second insulation impedance detection circuit and the third insulation impedance detection circuit.
9. The insulation resistance detection method according to claim 7, wherein the insulation resistance detection system further comprises:
a fourth insulation resistance detection circuit connected to an input terminal of the control unit;
the alternating current side switch is connected between one line voltage output end of the grid-connected point and the input end of the fourth insulation impedance detection circuit;
and an alternating current side switch connected between the other line voltage output end of the grid-connected point and the input end of the fourth insulation resistance detection circuit;
the output end of the control unit is connected with the control ends of the two AC side switches;
the insulation resistance detection method further includes:
controlling the two switches on the alternating current side to be closed alternatively;
receiving a sampling conditioning signal output by the fourth insulation resistance detection circuit;
and calculating three relative ground insulation impedances of the grid-connected point according to the sampling conditioning signal output by the fourth insulation impedance detection circuit.
10. The insulation resistance detection method according to claim 7, wherein the insulation resistance detection system further comprises:
the alternating current side switch is connected between one line voltage output end of the grid-connected point and the input end of the first insulation impedance detection circuit;
and an alternating current side switch connected between the other line voltage output end of the grid-connected point and the input end of the first insulation impedance detection circuit;
the output end of the control unit is connected with the control ends of the two AC side switches;
correspondingly, the insulation resistance detection method comprises the following steps:
the control unit controls each switch in a switch group consisting of each direct current side switch and each alternating current side switch to be alternately closed;
receiving a sampling conditioning signal output by the first insulation impedance detection circuit;
and calculating the direct-current side insulation impedance of each inversion unit and the three relative ground insulation impedances of the grid-connected point according to the sampling conditioning signal output by the first insulation impedance detection circuit.
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| CN109725202B (en) * | 2018-12-27 | 2021-08-03 | 科华数据股份有限公司 | Multi-path MPPT insulation impedance detection device and method |
| CN109830985B (en) * | 2019-03-25 | 2021-11-02 | 阳光电源股份有限公司 | Multi-machine parallel system and power grid impedance detection method thereof |
| CN110456154B (en) * | 2019-07-26 | 2021-09-14 | 华为技术有限公司 | Insulation resistance detection circuit and method |
| CN111398852A (en) * | 2020-03-31 | 2020-07-10 | 厦门科灿信息技术有限公司 | Power output short circuit detection circuit and electronic equipment |
| CN111610411A (en) * | 2020-04-20 | 2020-09-01 | 华为技术有限公司 | Cable insulation impedance detection method and device |
| CN111766448B (en) * | 2020-08-07 | 2023-03-24 | 锦浪科技股份有限公司 | Control method for insulation detection module of photovoltaic energy storage system |
| CN112557754B (en) * | 2020-11-20 | 2021-11-16 | 珠海格力电器股份有限公司 | Insulation impedance detection method and device of photovoltaic inverter |
| CN114966205A (en) * | 2021-02-19 | 2022-08-30 | 华为数字能源技术有限公司 | Insulation impedance detection method, device and system |
| CN113252980A (en) | 2021-03-31 | 2021-08-13 | 华为技术有限公司 | Optical storage system and ground insulation impedance detection method |
| CN113504438B (en) * | 2021-06-08 | 2023-11-28 | 漳州科华电气技术有限公司 | Method and device for detecting insulation resistance of column head cabinet and column head cabinet |
| CN113328463A (en) * | 2021-07-09 | 2021-08-31 | 阳光电源股份有限公司 | Photovoltaic inverter system and insulation fault detection method thereof |
| CN115356540A (en) * | 2022-10-17 | 2022-11-18 | 阳光电源股份有限公司 | Alternating current-direct current ground insulation impedance monitoring device of inverter and self-checking method thereof |
| CN115327234A (en) * | 2022-10-17 | 2022-11-11 | 阳光电源股份有限公司 | Alternating current-direct current ground insulation impedance monitoring device and method of inverter |
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| CN202906494U (en) * | 2012-11-28 | 2013-04-24 | 东方日立(成都)电控设备有限公司 | Grid-connected photovoltaic power system capable of dynamically switching inversion units |
| CN203368361U (en) * | 2013-08-03 | 2013-12-25 | 阳光电源股份有限公司 | Photovoltaic inverter with multipath direct current input |
| CN204948018U (en) * | 2015-08-31 | 2016-01-06 | 上海正泰电源系统有限公司 | A kind of circuit of multi-machine parallel connection system prevention cell panel PID effect |
| CN107305224A (en) * | 2016-04-19 | 2017-10-31 | 台达电子企业管理（上海）有限公司 | Insulation resistance detection circuit, detection method and the photovoltaic DC-to-AC converter of photovoltaic DC-to-AC converter |
| CN106771834B (en) * | 2017-02-25 | 2019-07-12 | 华为技术有限公司 | A kind of more DC source input wires detection systems and photovoltaic string type inverter system |
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