CN106932674B - Inverter output filter capacitor residual life prediction method and device and power generation system - Google Patents
Inverter output filter capacitor residual life prediction method and device and power generation system Download PDFInfo
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- CN106932674B CN106932674B CN201710233279.1A CN201710233279A CN106932674B CN 106932674 B CN106932674 B CN 106932674B CN 201710233279 A CN201710233279 A CN 201710233279A CN 106932674 B CN106932674 B CN 106932674B
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- G01—MEASURING; TESTING
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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Abstract
The application discloses a method and a device for predicting the residual life of an output filter capacitor of an inverter and a power generation system, wherein the method comprises the following steps: judging whether the inverter is in a running state or not; when the inverter is judged to be in the running state, controlling an internal power device of the inverter to be switched off, and controlling a grid-connected switch to keep a closed state; acquiring voltages at two ends of an output filter capacitor of the inverter and current passing through the output filter capacitor of the inverter; and calculating the capacitance value of the output filter capacitor of the inverter according to the acquired voltage and current. The method and the device realize prediction of the residual life of the output filter capacitor of the inverter.
Description
Technical Field
The invention relates to the technical field of power electronics, in particular to a method and a device for predicting the residual life of an output filter capacitor of an inverter and a power generation system.
Background
Fig. 1 shows a power generation system (including but not limited to photovoltaic power generation system, wind power generation system) having components such as an inverter, a filter, and a grid-connected switch S, wherein: after the grid-connected switch S is closed, the power generation system is in a grid-connected state, the inverter converts the input direct current into alternating current to be output, and the filter filters the alternating current output by the inverter and then sends the alternating current to a power grid.
At present, filters commonly used in a power generation system are an LCL filter, an LC filter and derivatives thereof, and a capacitor (also called an inverter output filter capacitor) in the filter is the most important component through which a high-frequency current passes, so that effective prediction of the remaining life of an individual capacitor has an important influence on the reliability level of the whole power generation system.
Disclosure of Invention
In view of this, the invention provides a method and a device for predicting the remaining life of an output filter capacitor of an inverter, and a power generation system, so as to predict the remaining life of the output filter capacitor of the inverter.
A method for predicting the residual life of an output filter capacitor of an inverter comprises the following steps:
judging whether the inverter is in a running state or not;
when the inverter is judged to be in the running state, controlling an internal power device of the inverter to be switched off, and controlling a grid-connected switch to keep a closed state;
acquiring voltages at two ends of an output filter capacitor of the inverter and current passing through the output filter capacitor of the inverter;
and calculating the capacitance value of the output filter capacitor of the inverter according to the acquired voltage and current.
A method for predicting the residual life of an output filter capacitor of an inverter comprises the following steps:
judging whether the inverter is in a non-running state;
when the inverter is in a non-operation state, judging whether the voltage of a direct-current bus of the inverter is lower than a preset value;
when the voltage of the inverter direct-current bus is lower than the preset value, raising the voltage of the inverter direct-current bus;
and when the voltage of the direct-current bus of the inverter is not lower than the preset value, controlling a grid-connected switch to be closed, acquiring the voltage at two ends of an output filter capacitor of the inverter and the current passing through the output filter capacitor of the inverter, and calculating the capacitance value of the output filter capacitor of the inverter according to the acquired voltage and current.
Wherein, raise inverter direct current bus voltage, include: and charging the DC bus capacitor of the inverter by using the buffer circuit so as to raise the DC bus voltage of the inverter.
An inverter output filter capacitor residual life prediction device, comprising:
the information acquisition unit is used for acquiring voltages at two ends of the inverter output filter capacitor and current passing through the inverter output filter capacitor;
the control unit is used for judging whether the inverter is in a running state or not; when the inverter is judged to be in the running state, controlling an internal power device of the inverter to be switched off, and controlling a grid-connected switch to keep a closed state; and then calculating the capacitance value of the output filter capacitor of the inverter according to the voltage and the current acquired by the information acquisition unit.
An inverter output filter capacitor residual life prediction device, comprising:
the information acquisition unit is used for acquiring voltages at two ends of the inverter output filter capacitor and current passing through the inverter output filter capacitor;
the control unit is used for judging whether the inverter is in a non-running state or not; when the inverter is in a non-operation state, judging whether the voltage of a direct-current bus of the inverter is lower than a preset value; when the voltage of the inverter direct-current bus is lower than the preset value, raising the voltage of the inverter direct-current bus; and when the voltage of the direct-current bus of the inverter is not lower than the preset value, controlling the grid-connected switch to be closed, and calculating the capacitance value of the output filter capacitor of the inverter according to the voltage and the current acquired by the information acquisition unit.
The control unit charges the inverter direct-current bus capacitor through the control buffer circuit to raise the voltage of the inverter direct-current bus.
A power generation system includes an inverter, a filter, and a grid-connected switch, wherein an output side of the inverter is connected to a grid through the filter and the grid-connected switch, and the power generation system further includes: any one of the inverter output filter capacitor remaining life prediction devices disclosed above.
The device for predicting the residual life of the output filter capacitor of the inverter is integrated in the inverter.
Wherein the power generation system is a single-phase system or a three-phase system.
When the grid side of the power generation system is connected with a load, the device for predicting the residual life of the output filter capacitor of the inverter works under the condition of cutting off the load.
According to the technical scheme, under the condition that the inverter does not output power, the power grid and the filter are utilized to form an electric loop, the capacitance value of the capacitor is calculated according to the sampling voltage and the current of the filter capacitor output by the inverter, the residual life of the capacitor is predicted, additional hardware does not need to be added, complex control does not need to be introduced, and the residual life of the filter capacitor output by the inverter is predicted simply and safely.
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 diagram of a power generation system disclosed in the prior art;
fig. 2 is a flowchart of a method for predicting the remaining life of an output filter capacitor of an inverter according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a power generation system employing an LCL filter;
fig. 4 is a flowchart of a method for predicting the remaining life of an output filter capacitor of an inverter according to another embodiment of the present invention;
fig. 5 is a schematic structural diagram of a device for predicting the remaining life of an output filter capacitor of an inverter 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.
Referring to fig. 2, an embodiment of the present invention discloses a method for predicting a remaining life of an output filter capacitor of an inverter, including:
step S01: judging whether the inverter is in a running state or not; when the inverter is judged to be in the running state, the step S02 is executed;
step S02: controlling an internal power device of the inverter to be turned off, and controlling a grid-connected switch to keep a closed state;
step S03: acquiring voltages at two ends of an output filter capacitor of the inverter and current passing through the output filter capacitor of the inverter;
step S04: and calculating the capacitance value of the output filter capacitor of the inverter according to the acquired voltage and current.
The following describes the technical solution shown in fig. 2 in detail, taking an example in which an LCL filter is used as a filter in the power generation system shown in fig. 1.
When the filter in the power generation system shown in fig. 1 is an LCL filter, the corresponding system structure diagram is shown in fig. 3, where the LCL filter includes: three-phase bridge arm side inductor Lm1、Lm2、Lm3Three-phase filter capacitors C1, C2 and C3, and three-phase network side inductor Lg1、Lg2、Lg3；Lm1C1 and Lg1To phase A, Lm2C2 and Lg2To phase B, Lm3C3 and Lg3Is connected to phase C.
After controlling the internal power device of the inverter to be turned off, the inverter stops power output, and at the moment, because the grid-connected switch S keeps a closed state, for any phase, the power grid of the phase, the filter capacitor and the grid-side inductor on the phase form an electric loop, specifically: phase A power grid and C1, Lg1Forming an electrical circuit, forming a current I1While forming a voltage U at C11(ii) a B-phase power grid and C2, Lg2Forming an electrical circuit, forming a current I2While forming a voltage U at C22(ii) a C-phase power grid and C3, Lg3Forming an electrical circuit, forming a current I3While forming a voltage U at C33。
According to the capacitance characteristics, for the A phase, the following conditions are satisfied
2*π*f*C1*U1＝I1
Is calculated to obtain
Wherein f is the grid frequency; c1 represents, on the one hand, a capacitive element and, on the other hand, the capacitance of this capacitive element; u shape1Is the effective value of the voltage on C1; i is1Is the effective value of the current passing through C1.
The same method can obtain the capacitance values of C2 and C3.
Since the attenuation degree of the capacitance value of the capacitor is basically proportional to the residual life of the capacitor, the residual life of C1, C2 and C3 can be predicted by calculating the current capacitance values of C1, C2 and C3.
As can be seen from the description of fig. 2 and fig. 3, in this embodiment, when the inverter has no power output, an electric loop is formed by using the power grid and the filter, and the capacitance value of the capacitor is calculated according to the sampling voltage and the current of the output filter capacitor of the inverter to predict the residual life of the capacitor, without adding extra hardware or introducing complex control, so that the residual life of the output filter capacitor of the inverter is predicted simply and safely.
Referring to fig. 4, an embodiment of the present invention discloses another method for predicting a remaining life of an output filter capacitor of an inverter, including:
step S01: judging whether the inverter is in a non-running state; when the inverter is judged to be in the non-operation state, the step S02 is executed;
step S02: judging whether the voltage of the direct-current bus of the inverter is lower than a preset value or not; when the voltage of the direct-current bus of the inverter is judged to be lower than the preset value, the step S03 is carried out; when the voltage of the direct current bus of the inverter is judged to be not lower than the preset value, the step S04 is carried out;
step S03: raising the voltage of the direct current bus of the inverter, and returning to the step S02;
specifically, the buffer circuit can be used for charging the direct-current bus capacitor of the inverter to raise the direct-current bus voltage of the inverter;
step S04: controlling a grid-connected switch to be closed;
specifically, when the inverter is in a non-operating state, if the voltage of the dc bus of the inverter is too low, an impact current occurs at the moment of closing the grid-connected switch, so that the voltage of the dc bus of the inverter needs to be raised in advance;
step S05: and acquiring voltages at two ends of an output filter capacitor of the inverter and current passing through the output filter capacitor of the inverter, and calculating the capacitance value of the output filter capacitor of the inverter according to the acquired voltages and current.
The solution described in fig. 4 differs from that of fig. 2 in that: fig. 2 is a control pattern when the inverter is in an operating state, and fig. 4 is a control pattern when the inverter is in a non-operating state. However, both the two methods are finally carried out under the condition that the inverter does not have power output, an electric loop is formed by using a power grid and a filter, the capacitance value of the capacitor is calculated according to the sampling voltage and the current of the filter capacitor output by the inverter, and the residual life of the capacitor is predicted, and the method belongs to the same invention concept. In addition, the methods shown in fig. 2 and fig. 4 can be applied to a three-phase system, and can also be applied to a single-phase system, and the principles are the same, and are not described herein again. In practical applications, it is recommended to apply the methods shown in fig. 2 and fig. 4 together in the same system.
Referring to fig. 5, an embodiment of the present invention discloses a device for predicting a remaining life of an output filter capacitor of an inverter, including:
the information acquisition unit 100 is configured to acquire voltages at two ends of an output filter capacitor of the inverter and a current passing through the output filter capacitor of the inverter;
a control unit 200 for judging whether the inverter is in an operating state; when the inverter is judged to be in the running state, controlling an internal power device of the inverter to be switched off, and controlling a grid-connected switch to keep a closed state; and then, calculating the capacitance value of the output filter capacitor of the inverter according to the voltage and the current acquired by the information acquisition unit 100.
In addition, the embodiment of the invention also discloses a device for predicting the residual life of the output filter capacitor of the inverter, which comprises the following components:
the information acquisition unit is used for acquiring voltages at two ends of the inverter output filter capacitor and current passing through the inverter output filter capacitor;
the control unit is used for judging whether the inverter is in a non-running state or not; when the inverter is in a non-operation state, judging whether the voltage of a direct-current bus of the inverter is lower than a preset value; when the voltage of the inverter direct-current bus is lower than the preset value, raising the voltage of the inverter direct-current bus; and when the voltage of the direct-current bus of the inverter is not lower than the preset value, controlling the grid-connected switch to be closed, and calculating the capacitance value of the output filter capacitor of the inverter according to the voltage and the current acquired by the information acquisition unit.
Specifically, the control unit charges the inverter direct-current bus capacitor through controlling the buffer circuit to raise the inverter direct-current bus voltage.
The embodiment of the invention also discloses a power generation system, which comprises an inverter, a filter and a grid-connected switch, wherein the output side of the inverter is connected to a power grid through the filter and the grid-connected switch, and in addition, the power generation system also comprises: any one of the inverter output filter capacitor remaining life prediction devices disclosed above.
The device for predicting the residual life of the output filter capacitor of the inverter can exist as an independent device or can be integrated in the inverter. When the device is integrated in the inverter, the control unit of the device for predicting the residual service life of the output filter capacitor of the inverter and an inverter control system can share one control chip, so that the cost is saved.
The power generation system may be a single-phase system, or may be a three-phase system, but is not limited thereto. In addition, when a load (the load can be a pure load or an energy storage inverter) is connected to the grid side of the power generation system, the inverter output filter capacitor residual life prediction device works under the condition that the load is cut off.
In conclusion, under the condition that the inverter does not output power, the power grid and the filter are utilized to form an electric loop, the capacitance value of the capacitor is calculated according to the sampling voltage and the current of the output filter capacitor of the inverter, the residual life of the capacitor is predicted, extra hardware does not need to be added, complex control does not need to be introduced, and the residual life of the output filter capacitor of the inverter is predicted simply and safely.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.
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 (8)
1. A method for predicting the residual life of an output filter capacitor of an inverter is characterized by comprising the following steps:
judging whether the inverter is in a running state or not;
when the inverter is judged to be in the running state, controlling an internal power device of the inverter to be switched off, and controlling a grid-connected switch to keep a closed state, wherein the power grid and the filter form an electric loop; after the internal power device of the inverter is turned off, the inverter stops power output; acquiring voltages at two ends of an output filter capacitor of the inverter and current passing through the output filter capacitor of the inverter; calculating the capacitance value of an output filter capacitor of the inverter according to the acquired voltage and current, and predicting the residual life of the output filter capacitor of the inverter according to the capacitance value of the output filter capacitor of the inverter;
when the inverter is in a non-operation state, judging whether the voltage of a direct-current bus of the inverter is lower than a preset value; when the voltage of the inverter direct-current bus is lower than the preset value, raising the voltage of the inverter direct-current bus; when the DC bus voltage of the inverter is not lower than the preset value, the grid-connected switch is controlled to be closed, the power grid and the filter form an electric loop at the moment, the voltage at two ends of the output filter capacitor of the inverter and the current passing through the output filter capacitor of the inverter are obtained, the capacitance value of the output filter capacitor of the inverter is calculated according to the obtained voltage and current, and the residual life of the output filter capacitor of the inverter is predicted according to the capacitance value of the output filter capacitor of the inverter.
2. The method for predicting the residual life of the output filter capacitor of the inverter according to claim 1, wherein the raising the DC bus voltage of the inverter comprises:
and charging the DC bus capacitor of the inverter by using the buffer circuit so as to raise the DC bus voltage of the inverter.
3. An inverter output filter capacitor residual life prediction device, comprising:
the information acquisition unit is used for acquiring voltages at two ends of the inverter output filter capacitor and current passing through the inverter output filter capacitor;
the control unit is used for judging whether the inverter is in a running state or not; when the inverter is judged to be in the running state, controlling an internal power device of the inverter to be switched off, and controlling a grid-connected switch to keep a closed state, wherein the power grid and the filter form an electric loop; after the internal power device of the inverter is turned off, the inverter stops power output; then, the capacitance value of the output filter capacitor of the inverter is calculated according to the voltage and the current acquired by the information acquisition unit, and the residual life of the output filter capacitor of the inverter is predicted according to the capacitance value of the output filter capacitor of the inverter;
the control unit is also used for judging whether the inverter is in a non-running state; when the inverter is in a non-operation state, judging whether the voltage of a direct-current bus of the inverter is lower than a preset value; when the voltage of the inverter direct-current bus is lower than the preset value, raising the voltage of the inverter direct-current bus; and when the DC bus voltage of the inverter is not lower than the preset value, controlling a grid-connected switch to be closed, forming an electric loop by the power grid and the filter, calculating the capacitance value of the output filter capacitor of the inverter according to the voltage and the current acquired by the information acquisition unit, and predicting the residual life of the output filter capacitor of the inverter according to the capacitance value of the output filter capacitor of the inverter.
4. The apparatus of claim 3, wherein the control unit controls the buffer circuit to charge the inverter DC bus capacitor to increase the inverter DC bus voltage.
5. A power generation system comprises an inverter, a filter and a grid-connected switch, wherein the output side of the inverter is connected to a power grid through the filter and the grid-connected switch, and the power generation system is characterized by further comprising: the inverter output filter capacitor remaining life predicting device according to any one of claims 3 to 4.
6. The power generation system of claim 5, wherein the inverter output filter capacitor remaining life prediction device is integrated within the inverter.
7. The power generation system of claim 5, wherein the power generation system is a single phase system or a three phase system.
8. The power generation system of claim 5, wherein the inverter output filter capacitor remaining life prediction device operates with the load removed when a load is connected to the grid side of the power generation system.
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| CN109061314B (en) * | 2018-06-29 | 2021-05-11 | 华为技术有限公司 | Method and device for detecting capacitance value of filter capacitor of inverter |
| CN109596894A (en) * | 2019-01-02 | 2019-04-09 | 厦门科华恒盛股份有限公司 | Ac capacitor on-line monitoring method and device |
| CN113777429A (en) * | 2021-08-26 | 2021-12-10 | 上海核工程研究设计院有限公司 | Filter capacitor failure early warning method and control device |
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