CN115656795A - Switch abnormity detection method and device, photovoltaic direct-drive power system and photovoltaic air conditioner - Google Patents
Switch abnormity detection method and device, photovoltaic direct-drive power system and photovoltaic air conditioner Download PDFInfo
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Abstract
The invention discloses a method and a device for detecting abnormal switching, a photovoltaic direct-drive power system and a photovoltaic air conditioner. Wherein the method is applied to a photovoltaic direct drive power system having a photovoltaic cell and a DC/AC converter, a first switch is arranged between a negative terminal of the photovoltaic cell and a negative terminal of the DC/AC converter, and a second switch is arranged between a positive terminal of the photovoltaic cell and a positive terminal of the DC/AC converter, the method comprising: after the insulation impedance of the photovoltaic cell is detected to be abnormal, judging whether the first switch is abnormal or not according to the insulation impedance of the negative terminal of the DC/AC converter; and after the first switch detects no abnormality, judging whether the second switch has abnormality or not according to the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the voltage of the direct current bus. According to the invention, the abnormal switching in the photovoltaic direct-drive power system can be automatically and accurately realized, and the abnormal operation of the photovoltaic direct-drive power system caused by the abnormal switching is avoided.
Description
Technical Field
The invention relates to the technical field of electronic power, in particular to a method and a device for detecting abnormal switching, a photovoltaic direct-drive power system and a photovoltaic air conditioner.
Background
The modern society develops at a high speed, the energy consumption is huge, the environmental pollution is increasingly serious, clean and pollution-free solar energy becomes the key point of new energy development, and the photovoltaic power generation technology corresponding to the clean and pollution-free solar energy is deeply valued.
The photovoltaic power generation technology is to convert clean and pollution-free solar energy into electric energy by utilizing the photovoltaic effect of a semiconductor interface of a solar photovoltaic panel, and the generated direct current is converted into alternating current through a DC/AC converter so as to be consumed and utilized. Among them, the switch (e.g., contactor, relay) serves as a medium for connecting the photovoltaic cell to the DC/AC converter, and functions to switch the photovoltaic cell into and out of the DC/AC converter. Most inverters on the market at present use mechanical direct current isolating switches, and faults easily occur, if the photovoltaic cells cannot be switched into a power system in time due to switch faults, the photovoltaic cells can continuously charge the bus capacitor under the shutdown state of the electric equipment, and accordingly damage is caused. However, in the existing photovoltaic direct-drive power system, the existing switch fault detection method is generally manual detection, the detection process is complicated, automatic and accurate fault detection cannot be realized, and the switch fault cannot be found in time.
Aiming at the problems that in the prior art, the switch fault detection process of a photovoltaic direct-drive power system is complicated, the automatic and accurate fault detection cannot be realized, and the switch fault cannot be found in time, an effective solution is not provided at present.
Disclosure of Invention
The embodiment of the invention provides a method and a device for detecting switch abnormity, a photovoltaic direct-drive power system and a photovoltaic air conditioner, and aims to solve the problems that in the prior art, the switch fault detection process of the photovoltaic direct-drive power system is complicated, and the automatic and accurate fault detection cannot be realized, so that the switch fault cannot be found in time.
In order to solve the above technical problem, the present invention provides a method for detecting abnormal switch, which is applied to a photovoltaic direct drive power system having a photovoltaic cell and a DC/AC converter, wherein a first switch is arranged between a negative terminal of the photovoltaic cell and a negative terminal of the DC/AC converter, and a second switch is arranged between a positive terminal of the photovoltaic cell and a positive terminal of the DC/AC converter, the method comprising:
judging whether the first switch is abnormal or not according to the insulation resistance of the negative terminal of the DC/AC converter;
and after the first switch is judged to be detected to be abnormal, judging whether the second switch is abnormal or not according to the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the direct current bus voltage.
Further, determining whether there is an abnormality in the first switch based on the insulation resistance of the negative terminal of the DC/AC converter includes:
controlling the second switch to be opened, and then detecting the insulation resistance of the negative terminal of the DC/AC converter under the condition that the first switch is opened and closed respectively;
and judging whether the first switch is abnormal or not according to the insulation resistance of the negative terminal of the DC/AC converter.
Further, determining whether the first switch is abnormal or not according to the insulation resistance of the negative terminal of the DC/AC converter includes:
after the first switch is turned off, judging whether the deviation of the insulation resistance of the negative terminal of the DC/AC converter and the insulation resistance of the negative terminal of the photovoltaic cell is within a first preset range or not;
if yes, judging that the first switch is abnormal in disconnection;
if not, the first switch is judged to be normally disconnected.
Further, determining whether the first switch is abnormal according to the insulation resistance of the negative terminal of the DC/AC converter, further includes:
after the first switch is closed, judging whether the deviation between the insulation resistance of the negative terminal of the DC/AC converter and the insulation resistance of the negative terminal of the photovoltaic cell is within a first preset range;
if yes, judging that the first switch is closed normally;
and if not, judging that the first switch is abnormally closed.
Further, after determining that there is no abnormality in the detection of the first switch, determining whether there is an abnormality in the second switch according to a voltage difference between a positive terminal and a negative terminal of the photovoltaic cell and a dc bus voltage, includes:
controlling the first switch to be switched off, and then acquiring a voltage difference between a positive terminal and a negative terminal of the photovoltaic cell and a direct-current bus voltage under the conditions that the second switch is switched on and off respectively;
and judging whether the second switch is abnormal or not according to the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the voltage of the direct-current bus.
Further, determining whether the second switch is abnormal according to the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the voltage of the direct current bus, includes:
after the second switch is closed, judging whether the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the deviation of the direct-current bus voltage are within a second preset range;
if yes, judging that the second switch is closed normally;
and if not, judging that the second switch is abnormally closed.
Further, whether the second switch is abnormal or not is judged according to the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the voltage of the direct current bus, and the method further comprises the following steps:
after the second switch is switched off, judging whether the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the deviation of the direct current bus voltage are within a second preset range or not;
if yes, judging that the second switch is abnormal in disconnection;
if not, the second switch is judged to be normally disconnected.
Further, before determining whether there is an abnormality in the first switch according to the insulation resistance of the negative terminal of the DC/AC converter, the method further includes:
judging whether the insulation resistance of the photovoltaic cell is in a normal range or not;
if yes, triggering to judge whether the first switch is abnormal according to the insulation resistance of the negative terminal of the DC/AC converter.
Further, after determining whether the second switch is abnormal according to the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the voltage of the direct current bus, the method further includes:
and if the second switch is not abnormal, controlling the photovoltaic cell to be switched into the photovoltaic direct-drive power system.
The invention also provides a switch abnormity detection device, which is used for realizing the switch abnormity detection method and comprises the following steps:
the first detection module is used for judging whether the first switch is abnormal or not according to the insulation impedance of the negative terminal of the DC/AC converter;
and the second detection module is used for judging whether the second switch is abnormal or not according to the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the voltage of the direct-current bus after judging that the first switch is detected to be abnormal.
The invention also provides a photovoltaic direct-drive power system which comprises the switch abnormity detection device.
The invention further provides a photovoltaic air conditioner which comprises the photovoltaic direct-drive power system.
The present invention also provides a computer-readable storage medium having stored thereon a computer program which, when executed by a processor, implements the above-described switch anomaly detection method.
By applying the technical scheme of the invention, whether a first switch between the negative terminal of the photovoltaic cell and the negative terminal of the DC/AC converter is abnormal or not is judged according to the insulation impedance of the negative terminal of the DC/AC converter, and after the first switch is judged to be detected to be abnormal or not, whether a second switch between the positive terminal of the photovoltaic cell and the positive terminal of the DC/AC converter is abnormal or not is judged according to the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the direct-current bus voltage.
Drawings
Fig. 1 is a block diagram of a photovoltaic direct drive power system according to an embodiment of the invention;
FIG. 2 is a flow chart of a switch anomaly detection method according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of insulation resistance detection according to an embodiment of the present invention;
fig. 4 is a binding diagram of a switching abnormality detection apparatus according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings. 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 terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the examples of the present invention and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise, and "a plurality" typically includes at least two.
It should be understood that the term "and/or" as used herein is merely one type of association that describes an associated object, meaning that three relationships may exist, e.g., a and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter associated objects are in an "or" relationship.
It should be understood that although the terms first, second, etc. may be used to describe the switches in embodiments of the present invention, the switches should not be limited to these terms. These terms are only used to distinguish between different switches. For example, a first switch may also be referred to as a second switch, and similarly, a second switch may also be referred to as a first switch, without departing from the scope of embodiments of the present invention.
The words "if", as used herein may be interpreted as "at \8230; \8230whenor" when 8230; \8230when or "in response to a determination" or "in response to a detection", depending on the context. Similarly, the phrases "if determined" or "if detected (a stated condition or event)" may be interpreted as "when determined" or "in response to a determination" or "when detected (a stated condition or event)" or "in response to a detection (a stated condition or event)", depending on the context.
It is also noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that an article or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such article or apparatus. Without further limitation, an element defined by the phrases "comprising one of \8230;" does not exclude the presence of additional like elements in an article or device comprising the element.
An alternative embodiment of the present invention is described in detail below with reference to the drawings.
Example 1
The embodiment provides a method for detecting a switch abnormality, which is applied to a photovoltaic direct-drive power system having a photovoltaic cell and a DC/AC converter, and fig. 1 is a structural diagram of the photovoltaic direct-drive power system according to an embodiment of the present invention, as shown in fig. 1, a first switch KM1 is disposed between a negative terminal PV-of the photovoltaic cell and a negative terminal DC-of the DC/AC converter, and a second switch KM2 is disposed between a positive terminal PV + of the photovoltaic cell and a positive terminal DC + of the DC/AC converter, where the first switch may be a contactor or a relay.
Fig. 2 is a flowchart of a switch abnormality detection method according to an embodiment of the present invention, as shown in fig. 2, the method includes:
s101, judging whether the first switch KM1 is abnormal or not according to the insulation impedance of the negative terminal DC-of the DC/AC converter.
In the present embodiment, the insulation resistance of the negative terminal DC-of the DC/AC converter can be calculated from the voltage to ground of the negative terminal DC-of the DC/AC converter and the leakage current, and whether there is an abnormality in the first switch KM1 is determined from the change in the insulation resistance of the negative terminal DC-of the DC/AC converter before and after switching of the first switch KM1, and it is necessary to obtain the insulation resistance of the positive terminal PV + of the photovoltaic cell and the insulation resistance of the negative terminal PV-of the photovoltaic cell primarily first with the insulation resistance of the negative terminal PV + of the photovoltaic cell as a reference, and thus the voltage to ground of the positive terminal PV + of the photovoltaic cell, that is, the voltage to ground of detection point 1 in the figure, and the leakage current are detected, and the insulation resistance of the positive terminal PV + of the photovoltaic cell is calculated from the ratio of the voltage to ground of detection point 1 to the leakage current, and similarly, the voltage to ground of the negative terminal PV of the photovoltaic cell is calculated from the ratio of the voltage to ground of detection point 1 to ground to the leakage current to the detection point, that is, and the insulation resistance of the negative terminal PV of the photovoltaic cell is, that is calculated from the ratio of the detection point 2 to ground of the detection point to the leakage current.
In other embodiments of the present invention, the positive and negative insulation impedances of the photovoltaic cell or the negative terminal DC-of the DC/AC converter may be detected by the following methods:
fig. 3 is a schematic diagram of insulation resistance detection according to an embodiment of the present invention, as shown in fig. 3: the DSP is used for controlling the third switch KM3 and the fourth switch KM4 to be respectively connected to the positive terminals of the two paths of photovoltaic cells, the DSP is used for controlling the on and off of the switch K1 on the auxiliary branch to construct different circuit structures, the AD sampling module is used for collecting branch voltage Viso under different circuit structures to list two equations, and the DSP is used for calculating the positive terminal of the first path of photovoltaic cellInsulation resistance R of sub-PV 1+ x1 And the insulation resistance R of the positive terminal PV2+ of the second path of photovoltaic cell x2 And the insulation resistance R of the negative terminal PV-shared by two photovoltaic cells yn If the insulation resistance exceeds a specified limit, a fault is indicated and the device is inhibited from starting.
The insulation resistance detection principle of the positive terminal PV1+ of the first path of photovoltaic cells is the same as that of the positive terminal PV2+ of the second path of photovoltaic cells, and here, taking the insulation resistance detection of the positive terminal PV1 of the first path of photovoltaic cells as an example, when the switch K1 is turned off, the detected voltage is V iso_off In this case, the following equation is provided according to the circuit principle:
and Vpv1 is the voltage between the positive terminal PV1+ and the negative terminal PV < - > of the first path of photovoltaic cells.
With K1 closed, the voltage is detected, and then the following equation is given according to the circuit principle:
the insulating resistance of PV1+ and PV-to-ground can be respectively obtained by the equations of the joint type (1) and the joint type (2).
Briefly, the resistance to ground of PV1+ and PV-is two unknowns to be solved, and the resistance can be solved by switching in and switching out two equations of a resistance R1 column.
Similarly, the insulation resistance of PV2+ and PV-to-ground can be solved by switching in and out two equations of the resistor R3 column.
Similarly, the insulation resistance of the negative terminal DC-of the DC/AC converter can also be obtained by the method described above, as long as the terminal PV-in fig. 3 is connected to the negative terminal DC-of the DC/AC converter.
And if the insulation impedance of the positive terminal PV + of the photovoltaic cell and the insulation impedance of the negative terminal PV-of the photovoltaic cell are both smaller than the grid-connected access allowable resistance value, judging whether the insulation impedance detection of the photovoltaic cell is abnormal, and judging whether the first switch KM1 is abnormal or not according to the insulation impedance of the negative terminal DC-of the DC/AC converter after judging that the insulation impedance detection of the photovoltaic cell is not abnormal.
S102, after the first switch KM1 detects no abnormality, determining whether the second switch KM2 is abnormal or not according to the voltage difference between the positive terminal PV + and the negative terminal of the photovoltaic cell and the dc bus voltage.
The DC bus voltage is a voltage between a positive terminal DC + of the DC/AC converter and a negative terminal DC-of the DC/AC converter.
According to the switch abnormity detection method, whether the first switch KM1 is abnormal or not is judged according to the insulation impedance of the negative terminal DC-of the DC/AC converter, and after the first switch KM1 is detected to be abnormal or not, whether the second switch KM2 is abnormal or not is judged according to the voltage difference between the positive terminal PV + and the negative terminal DC-of the photovoltaic battery and the direct-current bus voltage.
If the first switch KM1 is normally closed, the negative terminal PV-of the photovoltaic cell and the negative terminal DC-of the DC/AC converter after the first switch KM1 is closed are equivalently connected through a wire, so the insulation resistance of the negative terminal DC-of the DC/AC converter and the insulation resistance of the negative terminal PV-of the photovoltaic cell should be equal or close; if the first switch KM1 is normally opened, then the negative terminal PV-of the photovoltaic cell and the negative terminal DC-of the DC/AC converter are open after the first switch KM2 is opened, and therefore the insulation resistance of the negative terminal DC-of the DC/AC converter and the insulation resistance of the negative terminal PV-of the photovoltaic cell should be different from each other, and based on the above principle, after the detection of the insulation resistance of the photovoltaic cell is not abnormal, the determining whether the first switch KM1 is abnormal or not according to the insulation resistance of the negative terminal DC-of the DC/AC converter includes: controlling the second switch KM2 to be opened, and then calculating the insulation resistance of the negative terminal DC-of the DC/AC converter according to the insulation resistance of the negative terminal DC-of the DC/AC converter under the condition that the first switch KM1 is opened and closed respectively; whether the first switch KM1 is abnormal is judged according to the insulation resistance of the negative terminal DC-of the DC/AC converter. The insulation resistance of the negative terminal of the DC/AC converter is calculated from the voltage to ground of the negative terminal of the DC/AC converter, and is obtained by calculating the ratio of the voltage to ground of the negative terminal of the DC/AC converter and the leakage current of the negative terminal of the DC/AC converter.
Specifically, determining whether the first switch KM1 is abnormal or not according to the insulation resistance of the negative terminal DC-of the DC/AC converter includes: after the first switch KM1 is turned off, it is determined whether the deviation of the insulation resistance of the negative terminal DC-of the DC/AC converter from the insulation resistance of the negative terminal PV-of the photovoltaic cell is within a first preset range; if yes, judging that the first switch KM1 is disconnected abnormally; if not, judging that the first switch KM1 is normally disconnected; after the first switch KM1 is closed, whether the deviation of the insulation resistance of the negative terminal DC-of the DC/AC converter and the insulation resistance of the negative terminal PV-of the photovoltaic cell is within a first preset range or not is judged; if yes, judging that the first switch KM1 is normally closed; if not, the first switch KM1 is judged to be closed abnormally.
In specific implementation, under the condition that insulation resistance detection of the photovoltaic cell is not abnormal, the voltage to ground and the leakage current of a sampling point 1 and a sampling point 3 can be respectively obtained, the insulation resistance of a negative terminal DC-of the DC/AC converter is calculated according to the voltage to ground and the leakage current of the sampling point 3, if the insulation resistance of the negative terminal DC-of the DC/AC converter is the same as the insulation resistance of a negative terminal PV-of the photovoltaic cell or the error is within a first preset range, the first switch KM1 is judged to be abnormal in disconnection, and the first switch KM1 is reported to be in fault; if the deviation of the two insulation impedances is not within a first preset range, judging that the first switch KM1 is normally disconnected; under the condition that the first switch KM1 is normally opened, controlling the first switch KM1 to be closed, calculating the insulation impedance of a positive terminal PV + and a negative terminal PV-of the photovoltaic cell according to the voltages to earth and the leakage currents of a sampling point 1 and a sampling point 2 respectively, calculating the insulation impedance of the positive terminal PV + of the photovoltaic cell and the negative terminal DC-of the DC/AC converter and the insulation impedance of the negative terminal DC-of the DC/AC converter according to the voltages to earth and the leakage currents of the sampling point 1 and a sampling point 3 respectively, and judging that the first switch KM1 is normally closed if the insulation impedance of the detected negative terminal DC-of the DC/AC converter is the same as the insulation impedance of the negative terminal PV-of the photovoltaic cell or the error is within a first preset range; if the error of the two insulation impedances is out of the first preset range, judging that the first switch KM1 is closed abnormally, and reporting the fault of the first switch KM 1.
If the second switch KM2 is normally closed, the positive terminal PV + of the photovoltaic cell and the positive terminal DC + of the converter are connected by a wire after the second switch KM2 is closed, so that the voltage Vov between the positive terminal PV + of the photovoltaic cell and the negative terminal PV-of the photovoltaic cell should be equal to or close to the DC bus voltage; if the second switch KM2 is normally turned off, then after the first switch is turned off, the positive terminal PV + of the photovoltaic cell and the positive terminal DC + of the converter are equivalent to open circuit, and therefore, the voltage Vov between the positive terminal PV + of the photovoltaic cell and the negative terminal PV-of the photovoltaic cell should be different from the DC bus voltage by a relatively large amount, based on the above principle, after the first switch KM1 detects no abnormality, whether the second switch KM2 has abnormality is determined according to the voltage difference between the positive terminal PV + and the negative terminal of the photovoltaic cell and the DC bus voltage, including: controlling the first switch KM1 to be opened, and then respectively acquiring the voltage difference between a positive terminal PV + and a negative terminal of the photovoltaic cell and the direct-current bus voltage under the condition that the second switch KM2 is opened and closed; and judging whether the second switch KM2 is abnormal or not according to the voltage difference between the positive terminal PV + and the negative terminal of the photovoltaic cell and the voltage of the direct-current bus.
Specifically, the step of judging whether the second switch KM2 is abnormal or not according to the voltage difference between the positive terminal PV + and the negative terminal of the photovoltaic cell and the dc bus voltage includes: after the second switch KM2 is closed, judging whether the voltage difference between the positive terminal PV + and the negative terminal of the photovoltaic cell and the deviation of the direct-current bus voltage are within a second preset range; if so, judging that the second switch KM2 is normally closed; if not, judging that the second switch KM2 is abnormally closed; after the second switch KM2 is switched off, judging whether the voltage difference between the positive terminal PV + and the negative terminal of the photovoltaic cell and the deviation of the direct-current bus voltage are within a second preset range; if yes, judging that the second switch KM2 is disconnected abnormally; if not, the second switch KM2 is judged to be normally disconnected.
In specific implementation, under the condition that the first switch KM1 is judged to be normal, the first switch KM1 is controlled to be opened, the second switch KM2 is controlled to be closed, at the same time, the voltage between the sampling point 1 and the sampling point 2, namely the output voltage Vpv of the photovoltaic cell is detected, according to the electrical characteristics of the photovoltaic panel, if the second switch KM2 is normally closed, the output voltage Vpv of the photovoltaic cell is reduced to the direct-current bus voltage Vdc from the open-circuit voltage Vov before the second switch KM2 is closed, namely, the Vov is close to Vdc, therefore, if the Vpv is the same as the bus voltage Vdc or fluctuates within a second preset range, the second switch KM2 is normally closed, otherwise, the second switch KM2 is judged to be abnormal in operation, and a fault of the second switch KM2 is reported; then, the second switch KM2 is controlled to be turned off, at this time, the voltage Vpv between the voltage sampling point 1 and the voltage sampling point 2 is detected, assuming that the open-circuit voltage Vov of the photovoltaic cell is 1000V, at this time, vpv = Vov =1000V, and under the condition that the photovoltaic cell is not switched in, the dc bus voltage is 600V, so if the difference value between the photovoltaic side voltage Vpv and the bus voltage Vdc exceeds a second preset range (the voltage difference is about 400V), it indicates that the second switch KM2 is normally turned off; at the moment, the second switch KM2 can be judged to work normally; otherwise, judging that the second switch KM2 works abnormally, and reporting the fault of the second switch KM 2.
In order to avoid that the photovoltaic battery is switched into the photovoltaic direct-drive power system when the insulation impedance is abnormal and ensure the reliability of the power system, before judging whether the first switch is abnormal according to the insulation impedance of the negative terminal of the DC/AC converter, the method further comprises the following steps: judging whether the insulation resistance of the photovoltaic cell is in a normal range or not; if yes, triggering to judge whether the first switch is abnormal according to the insulation resistance of the negative terminal of the DC/AC converter.
In order to ensure the reliability of the power system, it is necessary to control the photovoltaic cell to be connected only after the insulation impedance of the photovoltaic cell is ensured to be normal and the first switch KM1 and the second switch KM2 of the photovoltaic direct-drive power system are not abnormal, so that after determining whether the second switch KM2 is abnormal according to the voltage difference between the positive terminal PV + and the negative terminal of the photovoltaic cell and the dc bus voltage, the method further includes: and if the second switch KM2 is not abnormal, controlling the photovoltaic cell to switch into the photovoltaic direct-drive power system.
In order to fully ensure the safety of the cut-in and cut-out of the photovoltaic cell, the switch detection process can be respectively executed once before the photovoltaic electromagnetic cut-in and after the photovoltaic cell is cut-out.
For a photovoltaic direct-drive power system, the installation capacity of a photovoltaic cell is determined by the capacity of electric equipment in the system, and the proportion is generally 1. In other words, after the capacity of the electric device is determined, the maximum capacity of the photovoltaic cell is also determined, and thus the maximum open-circuit voltage value Vov of the photovoltaic cell is also determined.
After the direct current bus voltage Vdc on the DC/AC converter side is established, the insulation impedance detection of the photovoltaic cell is carried out before the photovoltaic is switched on, the switch detection is carried out under the condition that the edge impedance detection of the photovoltaic cell is not abnormal, and the photovoltaic is switched on after all the detection is normal.
Example 2
This embodiment provides a switching abnormality detection apparatus for implementing the switching abnormality detection method of the above embodiment, and fig. 4 is a connection diagram of the switching abnormality detection apparatus according to the embodiment of the present invention, as shown in fig. 4, the apparatus includes: the first detection module 10 is configured to determine whether the first switch KM1 is abnormal according to the insulation resistance of the negative terminal DC-of the DC/AC converter.
In this embodiment, the specific method of detecting the insulation resistance of the photovoltaic cell may be to detect the voltage to ground of the positive terminal PV + of the photovoltaic cell, i.e., the voltage to ground of the detection point 1 in the figure, and the leakage current, calculate the insulation resistance of the positive terminal PV + of the photovoltaic cell based on the ratio of the voltage to ground of the detection point 1 to the leakage current, and similarly, detect the voltage to ground of the negative terminal PV-of the photovoltaic cell, i.e., the voltage to ground of the detection point 2 in the figure, and the leakage current, calculate the insulation resistance of the negative terminal PV-of the photovoltaic cell based on the ratio of the voltage to ground of the detection point 2 to the leakage current.
The second detecting module 20 is configured to, after the first switch KM1 detects no abnormality, determine whether the second switch KM2 is abnormal according to a voltage difference between the positive terminal PV + and the negative terminal of the photovoltaic cell and the dc bus voltage.
In the switch abnormality detection apparatus of the embodiment, the first detection module 10 determines whether the first switch KM1 is abnormal according to the insulation impedance of the negative terminal DC-of the DC/AC converter, and the second detection module 20 determines whether the second switch KM2 is abnormal according to the voltage difference between the positive terminal PV + and the negative terminal of the photovoltaic cell and the DC bus voltage after the first switch KM1 detects no abnormality. By the scheme, whether a first switch between the negative terminal PV & lt- & gt of the photovoltaic cell and the negative terminal DC & lt- & gt of the DC/AC converter and a second switch between the positive terminal PV & lt + & gt of the photovoltaic cell and the positive terminal DC & lt + & gt of the DC/AC converter are abnormal or not can be automatically and accurately realized, and abnormal operation of a photovoltaic direct-drive power system caused by the abnormal switches is avoided.
The first detection module 10 is specifically configured to: controlling the second switch to open and then calculating the insulation resistance of the negative terminal of the DC/AC converter from the voltage to ground of the negative terminal of the DC/AC converter with the first switch open and closed, respectively; whether the first switch is abnormal is judged according to the insulation resistance of the negative terminal of the DC/AC converter.
The first detection module 10, when determining whether the first switch is abnormal according to the insulation resistance of the negative terminal of the DC/AC converter, specifically performs the following operations: after the first switch is turned off, judging whether the deviation of the insulation resistance of the negative terminal of the DC/AC converter and the insulation resistance of the negative terminal of the photovoltaic cell is within a first preset range or not; if yes, judging that the first switch is abnormal in disconnection; if not, judging that the first switch is normally disconnected; after the first switch is closed, judging whether the deviation of the insulation resistance of the negative terminal of the DC/AC converter and the insulation resistance of the negative terminal of the photovoltaic cell is within a first preset range or not; if yes, judging that the first switch is normally closed; and if not, judging that the first switch is abnormally closed.
The second detection module 20 is specifically configured to: controlling the first switch to be switched off, and then acquiring the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the direct-current bus voltage under the conditions that the second switch is switched on and off respectively; and judging whether the second switch is abnormal or not according to the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the voltage of the direct current bus.
When the second detection module 20 determines whether the second switch is abnormal according to the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the dc bus voltage, the specific operations are as follows: after the second switch is closed, judging whether the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the deviation of the direct-current bus voltage are within a second preset range or not; if yes, judging that the second switch is normally closed; if not, judging that the second switch is abnormally closed; after the second switch is switched off, judging whether the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the deviation of the direct current bus voltage are within a second preset range or not; if yes, judging that the second switch is abnormal in disconnection; if not, the second switch is judged to be normally disconnected.
In order to avoid the photovoltaic cell to cut into the photovoltaic direct-drive power system when the insulation impedance is abnormal and ensure the reliability of the power system, the first detection module is further used for: before judging whether the first switch is abnormal according to the insulation impedance of the negative electrode terminal of the DC/AC converter, judging whether the insulation impedance of the photovoltaic cell is in a normal range; if yes, triggering to judge whether the first switch is abnormal according to the insulation resistance of the negative terminal of the DC/AC converter.
In other embodiments of the present invention, when the insulation impedance of the photovoltaic cell, the first switch, and the second switch are not abnormal, the main control chip controls the photovoltaic cell to switch into the photovoltaic direct drive power system.
Example 3
The embodiment provides a photovoltaic direct-drive power system, which comprises the switch abnormality detection device, and is used for automatically and accurately detecting whether a first switch between a negative terminal PV & lt- & gt of a photovoltaic battery and a negative terminal DC & lt- & gt of a DC/AC converter exists or not, and a second switch between a positive terminal PV & lt + & gt of the photovoltaic battery and a positive terminal DC & lt + & gt of the DC/AC converter exists or not, so that abnormal operation of the power system caused by abnormal switch is avoided.
Example 4
The embodiment provides a photovoltaic air conditioner, which comprises the photovoltaic direct-drive power system, and is used for automatically and accurately judging whether a first switch between a negative terminal PV & lt- & gt of a photovoltaic battery and a negative terminal DC & lt- & gt of a DC/AC converter exists or not and a second switch between a positive terminal PV & lt + & gt of the photovoltaic battery and a positive terminal DC & lt + & gt of the DC/AC converter exists or not, so that the abnormal operation of the power system caused by the abnormal switch is avoided, and the operation reliability of the photovoltaic air conditioner is improved.
Example 5
The present embodiments provide a computer-readable storage medium having stored thereon a computer program which, when executed by a processor, implements the above-described method.
The above-described embodiments of the apparatus are merely illustrative, and the modules described as separate components may or may not be physically separate, and the components shown as modules may or may not be physical modules, may be located in one position, or may be distributed on multiple network elements. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.
Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware. With this understanding in mind, the above-described technical solutions may be embodied in the form of a software product, which can be stored in a computer-readable storage medium such as ROM/RAM, magnetic disk, optical disk, etc., and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the methods described in the embodiments or some parts of the embodiments.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (13)
1. A method of detecting a switching anomaly applied to a photovoltaic direct drive power system having a photovoltaic cell and a DC/AC converter, a first switch disposed between a negative terminal of the photovoltaic cell and a negative terminal of the DC/AC converter, and a second switch disposed between a positive terminal of the photovoltaic cell and a positive terminal of the DC/AC converter, the method comprising:
judging whether the first switch is abnormal or not according to the insulation impedance of the negative terminal of the DC/AC converter;
and after the first switch is judged to be detected to be abnormal, judging whether the second switch is abnormal or not according to the voltage difference between the positive electrode terminal and the negative electrode terminal of the photovoltaic cell and the direct-current bus voltage.
2. The method of claim 1, wherein determining whether the first switch is abnormal according to the insulation resistance of the negative terminal of the DC/AC converter comprises:
controlling the second switch to open and then detecting the insulation resistance of the negative terminal of the DC/AC converter with the first switch open and closed, respectively;
and judging whether the first switch is abnormal or not according to the insulation resistance of the negative terminal of the DC/AC converter.
3. The method of claim 2, wherein determining whether the first switch is abnormal according to the insulation resistance of the negative terminal of the DC/AC converter comprises:
after the first switch is turned off, judging whether the deviation between the insulation resistance of the negative terminal of the DC/AC converter and the insulation resistance of the negative terminal of the photovoltaic cell is within a first preset range;
if yes, judging that the first switch is abnormal in disconnection;
if not, judging that the first switch is normally disconnected.
4. The method of claim 2, wherein determining whether the first switch is abnormal according to the insulation resistance of the negative terminal of the DC/AC converter further comprises:
after the first switch is closed, judging whether the deviation of the insulation resistance of the negative terminal of the DC/AC converter and the insulation resistance of the negative terminal of the photovoltaic cell is within a first preset range or not;
if yes, judging that the first switch is closed normally;
and if not, judging that the first switch is abnormally closed.
5. The method of claim 1, wherein after determining that the first switch detects no abnormality, determining whether the second switch has an abnormality based on a voltage difference between a positive terminal and a negative terminal of the photovoltaic cell and a dc bus voltage comprises:
controlling the first switch to be switched off, and then acquiring a voltage difference between a positive terminal and a negative terminal of the photovoltaic cell and a direct-current bus voltage under the conditions that the second switch is switched on and off respectively;
and judging whether the second switch is abnormal or not according to the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the voltage of the direct current bus.
6. The method of claim 5, wherein determining whether the second switch is abnormal according to the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the DC bus voltage comprises:
after the second switch is closed, judging whether the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the deviation of the direct-current bus voltage are within a second preset range;
if yes, judging that the second switch is closed normally;
and if not, judging that the second switch is abnormally closed.
7. The method of claim 5, wherein determining whether the second switch is abnormal according to a voltage difference between a positive terminal and a negative terminal of the photovoltaic cell and a DC bus voltage further comprises:
after the second switch is switched off, judging whether the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the deviation of the direct current bus voltage are within a second preset range or not;
if yes, judging that the second switch is abnormal in disconnection;
if not, the second switch is judged to be normally disconnected.
8. The method of claim 1, wherein before determining whether the first switch is abnormal based on the insulation resistance of the negative terminal of the DC/AC converter, the method further comprises:
judging whether the insulation resistance of the photovoltaic cell is in a normal range or not;
if yes, triggering to judge whether the first switch is abnormal or not according to the insulation resistance of the negative terminal of the DC/AC converter.
9. The method of claim 1, wherein after determining whether the second switch is abnormal based on a voltage difference between a positive terminal and a negative terminal of the photovoltaic cell and a dc bus voltage, the method further comprises:
and if the second switch is not abnormal, controlling the photovoltaic cell to be switched into the photovoltaic direct-drive power system.
10. A switching abnormality detection device for realizing the switching abnormality detection method according to any one of claims 1 to 9, characterized by comprising:
the first detection module is used for judging whether the first switch is abnormal or not according to the insulation impedance of the negative terminal of the DC/AC converter;
and the second detection module is used for judging whether the second switch is abnormal or not according to the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the voltage of the direct-current bus after judging that the first switch is detected to be abnormal.
11. A photovoltaic direct drive power system characterized by comprising the switching anomaly detection device of claim 10.
12. A photovoltaic air conditioner characterized by comprising the photovoltaic direct drive power system of claim 11.
13. A computer-readable storage medium, on which a computer program is stored, which program, when being executed by a processor, carries out the method according to any one of claims 1 to 9.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211261896.XA CN115656795A (en) | 2022-10-14 | 2022-10-14 | Switch abnormity detection method and device, photovoltaic direct-drive power system and photovoltaic air conditioner |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211261896.XA CN115656795A (en) | 2022-10-14 | 2022-10-14 | Switch abnormity detection method and device, photovoltaic direct-drive power system and photovoltaic air conditioner |
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| CN202211261896.XA Pending CN115656795A (en) | 2022-10-14 | 2022-10-14 | Switch abnormity detection method and device, photovoltaic direct-drive power system and photovoltaic air conditioner |
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| CN (1) | CN115656795A (en) |
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