CN107797023B - Three-phase voltage unbalance source positioning method, device and system - Google Patents
Three-phase voltage unbalance source positioning method, device and system Download PDFInfo
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- CN107797023B CN107797023B CN201610719964.0A CN201610719964A CN107797023B CN 107797023 B CN107797023 B CN 107797023B CN 201610719964 A CN201610719964 A CN 201610719964A CN 107797023 B CN107797023 B CN 107797023B
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- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
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Abstract
The embodiment of the invention provides a three-phase voltage unbalance source positioning method, device and system. The three-phase voltage unbalance source positioning method comprises the following steps: acquiring the voltage unbalance degree caused by the negative sequence voltage of the common connection point; if the voltage unbalance exceeds the voltage unbalance limit value, acquiring the voltage unbalance caused by the negative sequence current of the common connection point; and positioning the three-phase voltage unbalance source according to the voltage unbalance degree caused by the negative sequence voltage and the voltage unbalance degree caused by the negative sequence current. By adopting the technical scheme of the embodiment of the invention, the three-phase voltage unbalance of the public connection point can be accurately judged, the unbalance source can be quickly positioned, the test difficulty of the three-phase voltage unbalance is reduced, the three-phase voltage unbalance can be quickly eliminated, and the stable operation of the power system can be ensured.
Description
Technical Field
The invention relates to the technical field of power grids, in particular to a three-phase voltage unbalance source positioning method, device and system.
Background
The three-phase imbalance means that three-phase voltages (or three-phase currents) in the power system have inconsistent amplitudes and the amplitudes exceed a specified range. The unbalanced three-phase voltage of the power system can cause the increase of the electric energy loss of a power transmission line and a distribution transformer, the safe operation of electric equipment is influenced, and hidden danger is brought to the safe and stable operation of the system.
The reasons why the power system may cause three-phase imbalance of the power system can be summarized as follows: a failing imbalance and a non-failing imbalance. The fault imbalance refers to a voltage imbalance caused by a fault of an element of the power system, for example, a three-phase voltage imbalance caused by a voltage drop caused by a single-phase or two-phase short circuit of a power transmission line. The non-fault imbalance influence factors comprise three-phase impedance imbalance, load imbalance, three-phase voltage imbalance at the power supply side, voltage waveform distortion and the like of the power transmission line. For example, a public connection point of a new energy power station (a wind power station or a photovoltaic power station, etc.) is mostly at the end of a power grid, a regional power grid of the new energy power station belongs to a weak power grid with poor voltage stability, the power quality of the public connection point is easily influenced after the new energy power station is connected to a power system, and particularly, three-phase voltage imbalance of the public connection point is easily generated at the early stage of grid-connected operation.
At present, in the prior art, a study on three-phase voltage unbalance mainly aims at how to protect an electric power system by using the characteristic of three-phase voltage unbalance, how to eliminate three-phase voltage unbalance and the like, and neglects how to effectively and quickly judge the direction of a three-phase voltage unbalance source. For the three-phase imbalance caused by faults, an imbalance source can be determined according to the operation state of each electrical device, and the three-phase imbalance is eliminated by removing the faults. However, for non-fault three-phase voltage imbalance, a worker can only perform a large number of tests, verifications and searches for reasons at different positions according to experience, but cannot timely judge the position of an imbalance source, and a large amount of manpower and material resources are consumed, and time is wasted, so that the system runs in an imbalance state for a long time, the quality of electric energy is reduced, the equipment safety of an electric power system is affected, and the stability and the safety and the reliability of the electric power system are damaged.
Disclosure of Invention
The embodiment of the invention provides a method, a device and a system for positioning a three-phase voltage unbalance source, which are used for quickly positioning the three-phase voltage unbalance source, are convenient for troubleshooting and eliminating the three-phase voltage unbalance and are beneficial to improving the stability of a power system.
In order to achieve the above object, an embodiment of the present invention provides a method for positioning a three-phase voltage imbalance source, including: acquiring the voltage unbalance degree caused by the negative sequence voltage of the common connection point; if the voltage unbalance exceeds the voltage unbalance limit value, acquiring the voltage unbalance caused by the negative sequence current of the common connection point; and positioning the three-phase voltage unbalance source according to the voltage unbalance degree caused by the negative sequence voltage and the voltage unbalance degree caused by the negative sequence current.
Optionally, the positioning the three-phase voltage unbalance source according to the voltage unbalance caused by the negative sequence voltage and the voltage unbalance caused by the negative sequence current comprises: acquiring the ratio of the voltage unbalance caused by the negative sequence current to the voltage unbalance caused by the negative sequence voltage; if the ratio is smaller than or equal to a preset value, determining that the three-phase voltage unbalance source is positioned at a power station side or a load side; and if the ratio is larger than a preset value, determining that the three-phase voltage unbalance source is positioned on the side of the power grid.
Optionally, the obtaining the voltage unbalance caused by the negative-sequence current of the common connection point if the voltage unbalance exceeds the voltage unbalance limit value comprises: if the voltage unbalance exceeds a voltage unbalance limit value, acquiring the harmonic content of the public connection point; and if the harmonic content does not exceed the harmonic content threshold, acquiring the voltage unbalance degree caused by the negative sequence current of the common connection point.
Optionally, before the obtaining of the voltage imbalance caused by the negative sequence voltage of the common connection point, the method further comprises: acquiring a voltage value and a current value of the public connection point; and calculating the negative sequence voltage value of the common connection point according to the voltage value, and calculating the voltage unbalance degree caused by the negative sequence voltage according to the negative sequence voltage value.
Optionally, the calculating the voltage unbalance caused by the negative sequence voltage according to the negative sequence voltage value comprises: the voltage unbalance is calculated according to the following formulaU2，
Wherein, U2Is the negative sequence voltage value, U, of the point of common connectionLIs the root mean square value of the line voltage of the common connection point.
Optionally, the obtaining of the voltage imbalance caused by the negative-sequence current of the common connection point includes: and calculating a negative sequence current value of the public connection point according to the current value, and calculating the voltage unbalance degree caused by the negative sequence current according to the negative sequence current value.
Optionally, the calculating the voltage unbalance caused by the negative sequence current according to the negative sequence current value includes: the current imbalance is calculated according to the following formulaI2，
Wherein, I2Is the negative sequence current value of the point of common connection, ULIs the root mean square value, S, of the line voltage of the point of common connectiondThe three-phase short-circuit capacity of the common connection point.
Optionally, before the obtaining the voltage value and the current value of the common connection point, the method further comprises: and carrying out time synchronization on the voltage value and the current value.
Optionally, if the harmonic content does not exceed a harmonic content threshold, the method further comprises: and acquiring the duration that the voltage unbalance exceeds the voltage unbalance limit value, and carrying out corresponding three-phase voltage unbalance alarm according to the duration.
According to another aspect of the present invention, an embodiment of the present invention further provides a three-phase voltage unbalance source positioning device, including: the power quality monitoring module is used for acquiring the voltage unbalance degree caused by the negative sequence voltage of the public connection point; if the voltage unbalance exceeds the voltage unbalance limit value, acquiring the current unbalance caused by the negative sequence current of the common connection point; and the unbalanced source positioning module is used for positioning the three-phase voltage unbalanced source according to the voltage unbalance degree caused by the negative sequence voltage and the voltage unbalance degree caused by the negative sequence current.
Optionally, the imbalance source locating module comprises: the comparison unit is used for acquiring the ratio of the voltage unbalance caused by the negative sequence current to the voltage unbalance caused by the negative sequence voltage; the positioning unit is used for determining that the three-phase voltage unbalance source is positioned on the power station side or the load side if the ratio is smaller than or equal to a preset value; and if the ratio is larger than a preset value, determining that the three-phase voltage unbalance source is positioned on the side of the power grid.
Optionally, the power quality monitoring module comprises: the first obtaining unit is used for obtaining the harmonic content of the public connection point if the voltage unbalance exceeds a voltage unbalance limit value; if the harmonic content does not exceed the harmonic content threshold, acquiring the voltage unbalance degree caused by the negative sequence current of the public connection point
Optionally, the power quality monitoring module further includes: a second acquisition unit configured to acquire a voltage value and a current value of the common connection point; the calculating unit is used for calculating a negative sequence voltage value of the public connection point according to the voltage value and calculating a voltage unbalance degree caused by the negative sequence voltage according to the negative sequence voltage value; and/or calculating a negative sequence current value of the public connection point according to the current value, and calculating the current unbalance degree caused by the negative sequence current according to the negative sequence current value.
Optionally, the apparatus further comprises: and the time synchronization module is used for performing time synchronization on the voltage value and the current value.
Optionally, the apparatus further comprises: and the alarm module is used for acquiring the duration that the voltage unbalance exceeds the voltage unbalance limit value if the harmonic content does not exceed the harmonic content threshold, and carrying out corresponding three-phase voltage unbalance alarm according to the duration.
According to another aspect of the present invention, an embodiment of the present invention further provides a three-phase voltage unbalance source positioning system, including: a processor comprising a three-phase voltage imbalance source locating device as described in any one of the above; and the display is used for displaying the processing result of the processor.
Optionally, the system further comprises a data detection device for detecting the voltage value and the current value of the common connection point and sending the voltage value and the current value to the processor, so that the processor performs three-phase voltage unbalance source positioning.
According to the three-phase voltage unbalance source positioning method, device and system provided by the embodiment of the invention, whether the three-phase voltage unbalance occurs at the public connection point of the power system is judged according to the voltage unbalance degree caused by the negative sequence voltage of the public connection point, and when the three-phase voltage unbalance occurs at the public connection point, the asymmetrical impedance or load at the public connection point is analyzed according to the relation between the voltage unbalance degree caused by the negative sequence voltage and the voltage unbalance degree caused by the negative sequence current, and the direction of the unbalance source is further determined, so that the unbalance source can be quickly positioned, the three-phase voltage unbalance testing efficiency is effectively improved, the quick elimination of the three-phase voltage unbalance is facilitated, and the stable operation of the power system is ensured.
Drawings
Fig. 1 is a flowchart of a three-phase voltage unbalance source positioning method according to a first embodiment of the present invention;
FIG. 2 is a flowchart of a three-phase imbalance source positioning method according to a second embodiment of the present invention;
fig. 3 is a schematic structural diagram of a common connection point provided by a three-phase voltage unbalance source positioning method according to a second embodiment of the present invention;
fig. 4 is a block diagram of a three-phase voltage unbalance source positioning device according to a third embodiment of the present invention;
fig. 5 is a block diagram of a three-phase voltage unbalance source positioning apparatus according to a fourth embodiment of the present invention;
fig. 6 is a block diagram of a three-phase voltage unbalance source positioning system according to a fifth embodiment of the present invention.
Detailed Description
The three-phase voltage imbalance source locating method, apparatus and system of embodiments of the present invention are described in detail below with reference to the drawings (like numbers represent like elements throughout the several views).
Example one
Fig. 1 is a flowchart of a three-phase voltage unbalance source positioning method according to a first embodiment of the present invention, which may be used to position a three-phase voltage unbalance source at a common connection point of an electric power system, so as to conveniently and quickly identify a position of the three-phase voltage unbalance source, thereby reducing difficulty in testing the three-phase voltage unbalance, facilitating quick elimination of the three-phase voltage unbalance, and ensuring stability of the electric power system. The three-phase voltage unbalance source positioning method provided by the embodiment of the invention mainly aims at detecting the non-fault three-phase voltage unbalance.
In this embodiment, the method for positioning the three-phase voltage unbalance source is performed by using an electric energy quality monitoring device of a common connection point as an example for description, but it should be understood by those skilled in the art that, in practical application, any other device having corresponding data acquisition and processing functions may refer to this embodiment to perform the method for positioning the three-phase voltage unbalance source of the present invention.
As shown in fig. 1, the method for positioning a three-phase voltage imbalance source of the present embodiment includes:
and S110, acquiring the voltage unbalance degree caused by the negative sequence voltage of the common connection point.
Because the three-phase voltage unbalance is an important index for measuring the quality of electric energy in the electric power system, and the negative sequence components of voltage and current in the electric power system are main reasons for causing the three-phase unbalance, the voltage unbalance caused by the negative sequence voltage of the common connection point in the electric power system can be obtained and can be used as a parameter for judging whether the three-phase voltage unbalance occurs in the electric power system.
In this embodiment, a booster station of a new energy power station (a wind power station, a photovoltaic power station, or the like) of an electric power system is used as a common connection point, and a voltage imbalance caused by a negative sequence voltage of the common connection point is detected and acquired. In other embodiments, other power stations connected to the power grid or the load side of the power grid output can be used as the common connection point.
And S120, if the voltage unbalance exceeds the voltage unbalance limit value, acquiring the voltage unbalance caused by the negative sequence current of the common connection point.
After the voltage unbalance degree caused by the negative sequence voltage of the public connection point is obtained, the voltage unbalance degree is compared with a voltage unbalance degree limit value, if the voltage unbalance degree caused by the negative sequence voltage exceeds the voltage unbalance degree limit value, the fact that the three-phase voltage unbalance occurs in the public connection point is determined, the voltage unbalance degree caused by the negative sequence current of the public connection point can be obtained, and the next detection is carried out.
The voltage unbalance limit value can be determined according to the national standard GB/T15543-2008. The national standard GB/T15543-2008 'electric energy quality three-phase voltage unbalance' makes the following regulations on the three-phase voltage unbalance:
4.1 the allowable value of the voltage unbalance degree of the common connection point of the power system is as follows: when the power grid normally operates, the negative sequence voltage unbalance degree is not more than 2%, and the negative sequence voltage unbalance degree is not more than 4% in short circuit.
4.2 each user connected to the point of common connection causes the negative sequence voltage unbalance tolerance of this point to be typically 1.3%, not exceeding 2.6% in the case of short circuit. The allowable value may vary appropriately depending on the load conditions at the connection point and the requirements for the adjacent generator, relay protection and safe operation of the automatic device, but must satisfy the 4.1 specification.
In this embodiment, the voltage imbalance limit is set to 1.3%. In other embodiments, the voltage imbalance limit may be adjusted based on the specifications of the point of common coupling to accurately detect whether a three-phase voltage imbalance is occurring at the point of common coupling.
And S130, positioning the three-phase voltage unbalance source according to the voltage unbalance degree caused by the negative sequence voltage and the voltage unbalance degree caused by the negative sequence current.
The main cause of non-fault three-phase voltage imbalance is three-phase impedance asymmetry or three-phase load asymmetry, which is mainly manifested as negative sequence voltage and negative sequence current damaging electrical components in the power system. On the basis, the three-phase impedance asymmetry or three-phase load asymmetry position in the public connection point is determined by utilizing the relation between the voltage unbalance of the negative sequence voltage and the voltage unbalance of the negative sequence current of the public connection point, and then a disturbance source causing the three-phase voltage unbalance is positioned.
The three-phase voltage unbalance source positioning method is suitable for detecting the non-fault three-phase voltage unbalance. Compared with the method for positioning the unbalanced source by multipoint testing in the prior art, the positioning method of the embodiment can quickly position the unbalanced source of the three-phase voltage when the three-phase voltage is unbalanced at the public connection point, reduces the testing difficulty of the unbalanced source of the three-phase voltage, is convenient to timely take treatment to eliminate the unbalanced source, can provide a basis for actively preventing the unbalanced source of the three-phase voltage, and ensures the stability and the safety and reliability of the power system.
According to the three-phase voltage unbalance source positioning method, whether three-phase voltage unbalance occurs at the public connection point is judged by obtaining the voltage unbalance degree caused by the negative sequence voltage of the public connection point of the power system, and when the public connection point is in a state of three-phase voltage unbalance, the direction of the unbalance source is further determined according to the relation between the voltage unbalance degree caused by the negative sequence voltage and the voltage unbalance degree caused by the negative sequence current, so that the test efficiency of the three-phase voltage unbalance is effectively improved, the three-phase voltage unbalance is favorably and quickly eliminated, and the stable operation of the power system is ensured.
Example two
Fig. 2 is a flowchart of a three-phase voltage unbalance source positioning method according to a second embodiment of the present invention, which is suitable for detecting a non-faulty three-phase voltage unbalance. As shown in fig. 2, the three-phase voltage unbalance source positioning method includes:
s210, acquiring a voltage value and a current value of the public connection point, calculating a negative sequence voltage value and a negative sequence current value of the public connection point, and calculating a voltage unbalance degree caused by a negative sequence voltage and a voltage unbalance degree caused by a negative sequence current.
In the embodiment, a booster station of a wind power plant connected to a power grid is selected as a public connection point, a voltage value and a current value are detected at a power station side, and the detected voltage value and the detected current value are respectively obtained and used as the voltage value and the current value of the public connection point. Of course, in other embodiments, the voltage value and the current value of the public connection point may also be detected on the grid side or the load side of the public connection point.
In an actual application scenario, as shown in fig. 3, two sides of a main substation transformer of a booster station are a 220kV high-voltage side and a 35kV low-voltage side, respectively, and a voltage transformer and a current transformer may be arranged on the 35kV low-voltage side or the 220kV high-voltage side to detect a voltage value and a current value of the booster station. And, preferably detect at 220kV high pressure side, because the position that 220kV generating line inserts the electric wire netting conveniently sets up voltage transformer and current transformer, avoided going on tedious work such as multiple spot detection and statistics calculation at 35kV low pressure side moreover.
The electric energy quality monitoring equipment of the booster station acquires the voltage and the current of a public connection point detected by a voltage transformer and a current transformer in real time and samples the voltage and the current, and in order to ensure the balance of sampling points of each cycle, software or a hardware module of a phase-locked loop principle is used in the electric energy quality monitoring equipment to track the system frequency, so that the reliability of the three-phase voltage unbalanced source positioning method of the embodiment is ensured.
Optionally, before the voltage value and the current value of the common connection point are obtained, the detected voltage value and the detected current value are paired, and the negative sequence voltage value and the negative sequence current value are respectively calculated by using the voltage value and the current value after time scale alignment, so as to improve the accuracy of the three-phase voltage unbalance test. Specifically, a module with a time synchronization function may be integrated in the power quality monitoring device, or a time synchronization device (e.g., a GPS time synchronization system) is communicatively connected to the voltage transformer and the current transformer to time the detected voltage value and current value.
After the power quality monitoring equipment acquires the voltage value and the current value of the public connection point, the negative sequence voltage value and the negative sequence current value of the public connection point are calculated according to the detected voltage value and current value respectively. Specifically, the detected voltage value and current value are discrete values, vector values of fundamental waves and each harmonic are obtained after discrete Fourier transform, a negative sequence component can be obtained by further applying a symmetric component, and the negative sequence voltage value and the negative sequence current value of the common connection point are calculated.
And after the negative sequence voltage value and the negative sequence current value of the public connection point are obtained, calculating the voltage unbalance degree caused by the negative sequence voltage and the voltage unbalance degree caused by the negative sequence current according to the negative sequence voltage value and the negative sequence current value respectively.
In this embodiment, according to the formula:
to respectively calculate the negative sequence voltage U2Induced voltage unbalanceU2And a negative sequence current I2Induced voltage unbalanceI2. Wherein, the negative sequence voltage U2In kV, negative sequence current I2Has the unit of A, ULThe square mean root value of the line voltage of the public connection point is the unit of kV, and the value can be the average value of the effective values of the three detected line voltages; sdThe three-phase short circuit capacity, in MVA, for the common connection point can be obtained from related technologies such as related engineering design documents. Here, it is explained that the unit of each parameter described above is applied to the three-phase voltage unbalance source positioning performed at the booster station of the wind power plant in the present embodiment. In other embodiments, when three-phase voltage unbalance source positioning is performed on other types of common connection points, if the line voltage level and the short-circuit capacity level change, the unit of each parameter can be adjusted, and the two formulas are adjusted correspondingly.
In addition, the voltage value data detected by the voltage transformer, the current value data detected by the current transformer, and the negative sequence voltage value data, the negative sequence current value data and the voltage unbalance degree data calculated by the power quality monitoring equipment can be sent to the corresponding data storage for related processing or subsequent analysis.
It should be noted that, in the present embodiment, the method for calculating the voltage imbalance caused by the negative sequence voltage and the negative sequence current of the common node is not limited thereto, and any method that can calculate the voltage imbalance caused by the negative sequence voltage and the negative sequence current may be the three-phase voltage imbalance source positioning method of this embodiment, and is within the limited scope of the present application.
A variety of electrical protection devices (e.g., relay protection devices) are provided in an electric power system. The sampling frequency of the power quality monitoring equipment and the calculating frequency for calculating the voltage unbalance caused by the negative sequence voltage and the negative sequence current can be the same as or slightly lower than that of the electrical protection equipment, so that the large calculation amount caused by frequent detection of the voltage unbalance can be effectively avoided, and the CPU load of the power quality monitoring equipment is reduced.
And S220, acquiring the voltage unbalance degree caused by the negative sequence voltage of the common connection point.
In this embodiment, after the power quality monitoring device calculates the voltage unbalance degree caused by the negative sequence voltage, whether the three-phase voltage unbalance occurs at the common connection point can be accurately judged according to the voltage unbalance degree caused by the negative sequence voltage at the common connection point.
And S230, if the voltage unbalance exceeds the voltage unbalance limit value, acquiring the harmonic content of the public connection point.
And if the voltage unbalance caused by the acquired negative sequence voltage exceeds the voltage unbalance limit value, determining that the three-phase voltage unbalance occurs at the common connection point. At this time, harmonic content detection of the common connection point is performed for determining whether the three-phase voltage imbalance is caused by voltage waveform distortion due to harmonics.
And S240, if the harmonic content does not exceed the harmonic content threshold, acquiring the voltage unbalance degree caused by the negative sequence current of the common connection point.
For example, harmonic content data is obtained from harmonic detection equipment, if the harmonic content exceeds a harmonic content threshold value, it is determined that three-phase voltage unbalance generated at the public connection point is caused by harmonic, and an alarm can be given, so that a worker can eliminate the harmonic by timely processing. Wherein, the harmonic content threshold can be determined according to national standard GB/T14549 & 1993 electric energy quality public power grid harmonic.
If the harmonic content does not exceed the harmonic content threshold, determining that the three-phase voltage unbalance generated at the public connection point is not caused by the harmonic, and acquiring the voltage unbalance degree caused by the negative sequence current of the public connection point for next detection.
Preferably, under the condition that the harmonic content of the public connection point does not exceed the harmonic content threshold, the duration that the voltage unbalance exceeds the voltage unbalance limit value is obtained, and corresponding three-phase voltage unbalance alarm is carried out according to the duration. That is to say, after it is determined that the three-phase voltage imbalance is not caused by the harmonic wave, different levels of alarm are performed according to the duration time of the three-phase voltage imbalance, and the corresponding processing mode is conveniently adopted by the working personnel.
For example, four preset duration ranges are set: 0.5 to 30 cycles, 30 cycles to 3s, 3s to 1min, greater than 1min (wherein, the cycle may be determined according to specific parameters of the power system, for example, a 50Hz system corresponds to 20ms cycle). When the duration of the three-phase voltage unbalance is detected to be within the four preset duration ranges, an instant three-phase voltage unbalance alarm, a temporary three-phase voltage unbalance alarm, a short-time three-phase voltage unbalance alarm and a long-time three-phase voltage unbalance alarm are respectively carried out.
The three-phase voltage imbalance warning step described here may be executed before or after step S240, or may be executed in parallel with step S240.
And S250, positioning the three-phase voltage unbalance source according to the ratio of the voltage unbalance degree caused by the negative sequence current to the voltage unbalance degree caused by the negative sequence voltage.
Specifically, the ratio of the voltage unbalance degree caused by the negative sequence current to the voltage unbalance degree caused by the negative sequence voltage is obtained, the ratio is compared with a preset value, and the position of the three-phase voltage unbalance source is determined according to the comparison result. The specific situation and engineering experience value of the preset value and the common connection point are determined, for example, in the embodiment, the booster station of the wind power plant is taken as the common connection point, and the preset value can be determined according to the operation parameters of each electrical device and line in the booster station. In this embodiment, the preset value is 0.65.
If the ratio is larger than a preset value, determining that the three-phase voltage unbalance source is positioned on the power grid side; and if the ratio is smaller than or equal to a preset value, determining that the three-phase voltage unbalance source is positioned on the power station side or the load side. The power station side is the input end of power grids such as a wind power station, a photovoltaic power station and the like which are accessed to a power grid, and the load side is the output end of the power grids such as an industrial area, a living area and the like which are accessed to the power grid.
When three-phase voltage unbalance occurs at the public connection point, the unbalance source can be positioned according to the ratio of the voltage unbalance caused by the negative sequence current to the voltage unbalance caused by the negative sequence voltage, the position of the three-phase voltage unbalance source can be determined in time without complex analysis, the three-phase voltage unbalance testing difficulty is reduced, and the testing efficiency is improved. For example, if it is determined that the unbalanced source is located on the load side, the impedance of the transmission line may be directly detected on the load side of the common connection point to determine the accurate position of the unbalanced source and perform timely processing.
The method for positioning the three-phase voltage unbalance source of the embodiment of the invention further shows a mode of acquiring a voltage value and a current value at the public connection point to calculate the voltage unbalance degree caused by the negative sequence voltage and the negative sequence current on the basis of the first embodiment, so that whether the public connection point has three-phase voltage unbalance can be more accurately determined; the method for determining the direction of the three-phase voltage unbalance source according to the ratio of the voltage unbalance degree caused by the negative sequence current to the voltage unbalance degree caused by the negative sequence voltage is further shown, so that the direction of the three-phase voltage unbalance source can be accurately distinguished, and the test difficulty of the three-phase voltage unbalance is reduced; and a mode of alarming according to the duration of the three-phase voltage unbalance is further added, so that different processing modes are conveniently adopted to eliminate the unbalance source, and the stability and the safety and the reliability of the power system are ensured.
EXAMPLE III
Fig. 4 is a block diagram of a three-phase voltage unbalance source positioning apparatus according to a third embodiment of the present invention, which is configured to perform the method steps of the first embodiment. As shown in fig. 4, the three-phase voltage unbalance source locating device includes a power quality monitoring module 410 and an unbalance source locating module 420.
Wherein: the power quality monitoring module 410 is used for acquiring the voltage unbalance degree caused by the negative sequence voltage of the common connection point; if the voltage unbalance exceeds the voltage unbalance limit value, acquiring the current unbalance caused by the negative sequence current of the common connection point; the unbalanced source positioning module 420 is configured to position the three-phase voltage unbalanced source according to the voltage unbalance caused by the negative sequence voltage and the voltage unbalance caused by the negative sequence current.
According to the three-phase voltage unbalance source positioning device, whether three-phase voltage unbalance occurs at the public connection point is judged according to the voltage unbalance degree caused by the negative sequence voltage of the public connection point, the public connection point is determined to be in a three-phase voltage unbalance state when the voltage unbalance degree exceeds the limit value, and the direction of the unbalance source is further determined according to the voltage unbalance degree caused by the negative sequence voltage and the voltage unbalance degree caused by the negative sequence current, so that the three-phase voltage unbalance testing efficiency is effectively improved, the three-phase voltage unbalance is favorably and quickly eliminated, and the stable operation of a power system is ensured.
Example four
Fig. 5 is a block diagram of a three-phase voltage unbalance source positioning apparatus according to a fourth embodiment of the present invention, which may be regarded as an optional implementation manner of the positioning apparatus according to the third embodiment, and may be used to execute the three-phase voltage unbalance source positioning method according to the second embodiment.
As shown in fig. 5, the unbalanced source positioning module 420 includes a comparing unit 421 and a positioning unit 422, where the comparing unit 421 is configured to obtain a ratio of a voltage unbalance caused by a negative-sequence current to a voltage unbalance caused by a negative-sequence voltage; the positioning unit 422 is used for determining that the three-phase voltage unbalance source is positioned at the power station side or the load side if the ratio is smaller than or equal to a preset value; and if the ratio is larger than the preset value, determining that the three-phase voltage unbalance source is positioned on the power grid side.
Optionally, the power quality monitoring module 410 includes a first obtaining unit 411, configured to obtain a harmonic content of the common node if the voltage imbalance exceeds the voltage imbalance limit; and if the harmonic content does not exceed the harmonic content threshold, acquiring the voltage unbalance degree caused by the negative sequence current of the common connection point.
Further, the power quality monitoring module 410 further includes a second obtaining unit 412 and a calculating unit 413, where the second obtaining unit 412 is configured to obtain a voltage value and a current value of the common connection point; the calculating unit 413 is configured to calculate a negative sequence voltage value of the common connection point according to the voltage value, and calculate a voltage imbalance caused by the negative sequence voltage according to the negative sequence voltage; and/or calculating the negative sequence current value of the common connection point according to the current value, and calculating the current unbalance degree caused by the negative sequence current according to the negative sequence current.
Further, the apparatus further includes a time comparing module 430, configured to time compare the voltage value and the current value.
Further, the device further comprises an alarm module 440, configured to obtain a duration that the harmonic content does not exceed the harmonic content threshold if the harmonic content does not exceed the harmonic content threshold, and perform a corresponding three-phase voltage imbalance alarm according to the duration.
According to the three-phase voltage unbalance source positioning device, the voltage value and the current value are collected at the public connection point to calculate the voltage unbalance degree caused by the negative sequence voltage and the negative sequence current, and whether the public connection point is unbalanced in three-phase voltage can be accurately determined; the position of the three-phase voltage unbalance source is determined according to the ratio of the voltage unbalance degree caused by the negative sequence current to the voltage unbalance degree caused by the negative sequence voltage, the position of the three-phase voltage unbalance source is accurately determined, and the testing difficulty of the three-phase voltage unbalance is reduced; and alarming is carried out according to the duration of the unbalance of the three-phase voltage, so that different processing modes are conveniently adopted to eliminate the unbalance source, and the stability, safety and reliability of the power system are ensured.
EXAMPLE five
Fig. 6 is a block diagram of a three-phase voltage unbalance source positioning system according to a fifth embodiment of the present invention. As shown in fig. 6, the three-phase unbalance source locating system includes a processor 610 and a display 620, wherein the processor 610 includes the three-phase voltage unbalance source locating device of the third embodiment or the fourth embodiment; and a display 620 for displaying the processing result of the processor 610.
In this embodiment, the system may further include a data detection device 630, a memory 640, a communication controller 650, or the like.
The data detection device 630 is used for detecting the three-phase voltage unbalance characteristic quantity of the common connection point and sending the three-phase voltage unbalance characteristic quantity to the processor, so that the processor can perform three-phase voltage unbalance source positioning. For example, the data detection device 630 may be a voltage transformer and a current transformer for detecting a voltage value and a current value of the common connection point in real time, respectively.
The memory 640 may be a database provided at the common connection point for storing data transmitted by the processor 610 and the data detecting device 630 during the three-phase voltage unbalance source locating process, for example, the voltage value and the current value of the common connection point detected by the data detecting device 630, or the negative sequence voltage value or the negative sequence current value of the common connection point calculated by the processor 610, and the voltage unbalance degree caused by the negative sequence voltage value or the negative sequence current value.
The communication controller 650 is used to transmit data between the devices, for example, to transmit the characteristic amount data detected by the data detection device 630 to the processor 610 or the memory 640, and to transmit the negative sequence voltage value data transmitted by the processor 640 to the memory 640, and the like.
Further, the system further comprises a time tick device 660, configured to receive the three-phase voltage imbalance characteristic quantity data of the common connection point detected by the data detection device 630 through the communication controller 650 for time tick when a module with a time tick function is not integrated in the memory 640, and transmit the three-phase voltage imbalance characteristic quantity data of the common connection point to the time tick through the communication controller 650 to the processor 610 for processing of three-phase voltage imbalance detection, or transmit the three-phase voltage imbalance characteristic quantity data to the memory 640 for storage. Specifically, the time tick device 660 can be a GPS time tick system.
The system can be used for executing the three-phase voltage unbalance source positioning method in the first embodiment or the second embodiment, when three-phase voltage unbalance occurs in the power system, the direction of the unbalance source is quickly determined, the three-phase voltage unbalance is conveniently eliminated, and the stability of the power system is improved.
It should be noted that, according to the implementation requirement, each component/step described in the present application can be divided into more components/steps, and two or more components/steps or partial operations of the components/steps can be combined into a new component/step to achieve the purpose of the present invention.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (15)
1. A three-phase voltage unbalance source positioning method is characterized by comprising the following steps:
acquiring the voltage unbalance degree caused by the negative sequence voltage of the common connection point;
if the voltage unbalance exceeds the voltage unbalance limit value, acquiring the voltage unbalance caused by the negative sequence current of the common connection point;
positioning a three-phase voltage unbalance source according to the voltage unbalance degree caused by the negative sequence voltage and the voltage unbalance degree caused by the negative sequence current,
wherein, the positioning the three-phase voltage unbalance source according to the voltage unbalance caused by the negative sequence voltage and the voltage unbalance caused by the negative sequence current comprises:
acquiring the ratio of the voltage unbalance caused by the negative sequence current to the voltage unbalance caused by the negative sequence voltage;
if the ratio is smaller than or equal to a preset value, determining that the three-phase voltage unbalance source is positioned at a power station side or a load side;
and if the ratio is larger than a preset value, determining that the three-phase voltage unbalance source is positioned on the side of the power grid.
2. The method of claim 1, wherein obtaining the voltage imbalance caused by the negative-sequence current of the common connection point if the voltage imbalance exceeds a voltage imbalance limit comprises:
if the voltage unbalance exceeds a voltage unbalance limit value, acquiring the harmonic content of the public connection point;
and if the harmonic content does not exceed the harmonic content threshold, acquiring the voltage unbalance degree caused by the negative sequence current of the common connection point.
3. The method of claim 1, wherein prior to said obtaining a negative sequence voltage induced voltage imbalance of a point of common connection, the method further comprises:
acquiring a voltage value and a current value of the public connection point;
and calculating the negative sequence voltage value of the common connection point according to the voltage value, and calculating the voltage unbalance degree caused by the negative sequence voltage according to the negative sequence voltage value.
4. The method of claim 3, wherein the calculating the negative sequence voltage induced voltage imbalance from the negative sequence voltage value comprises:
the voltage unbalance is calculated according to the following formulaU2，
Wherein U2 is the negative sequence voltage value of the common connection point, ULIs the root mean square value of the line voltage of the common connection point.
5. The method of claim 3, wherein obtaining the voltage imbalance caused by the negative-sequence current at the common connection point comprises:
and calculating a negative sequence current value of the public connection point according to the current value, and calculating the voltage unbalance degree caused by the negative sequence current according to the negative sequence current value.
6. The method of claim 5, wherein calculating the negative sequence current induced voltage imbalance from the negative sequence current values comprises:
the current imbalance is calculated according to the following formulaI2，
Wherein, I2Is the negative sequence current value of the point of common connection, ULIs the root mean square value, S, of the line voltage of the point of common connectiondThe three-phase short-circuit capacity of the common connection point.
7. The method of claim 2, wherein prior to said obtaining the voltage and current values of the point of common connection, the method further comprises:
and carrying out time synchronization on the voltage value and the current value.
8. The method of claim 2, wherein if the harmonic content does not exceed a harmonic content threshold, the method further comprises:
and acquiring the duration that the voltage unbalance exceeds the voltage unbalance limit value, and carrying out corresponding three-phase voltage unbalance alarm according to the duration.
9. A three-phase voltage imbalance source positioning device, comprising:
the power quality monitoring module is used for acquiring the voltage unbalance degree caused by the negative sequence voltage of the public connection point; if the voltage unbalance exceeds the voltage unbalance limit value, acquiring the current unbalance caused by the negative sequence current of the common connection point;
the unbalanced source positioning module is used for positioning the three-phase voltage unbalanced source according to the voltage unbalance degree caused by the negative sequence voltage and the voltage unbalance degree caused by the negative sequence current,
wherein the imbalance source locating module comprises:
the comparison unit is used for acquiring the ratio of the voltage unbalance caused by the negative sequence current to the voltage unbalance caused by the negative sequence voltage;
the positioning unit is used for determining that the three-phase voltage unbalance source is positioned on the power station side or the load side if the ratio is smaller than or equal to a preset value;
and if the ratio is larger than a preset value, determining that the three-phase voltage unbalance source is positioned on the side of the power grid.
10. The apparatus of claim 9, wherein the power quality monitoring module comprises:
the first obtaining unit is used for obtaining the harmonic content of the public connection point if the voltage unbalance exceeds a voltage unbalance limit value; and if the harmonic content does not exceed the harmonic content threshold, acquiring the voltage unbalance degree caused by the negative sequence current of the common connection point.
11. The apparatus of claim 10, wherein the power quality monitoring module further comprises:
a second acquisition unit configured to acquire a voltage value and a current value of the common connection point;
the calculating unit is used for calculating a negative sequence voltage value of the public connection point according to the voltage value and calculating a voltage unbalance degree caused by the negative sequence voltage according to the negative sequence voltage value; and/or calculating a negative sequence current value of the public connection point according to the current value, and calculating the current unbalance degree caused by the negative sequence current according to the negative sequence current value.
12. The apparatus of claim 10, further comprising:
and the time synchronization module is used for performing time synchronization on the voltage value and the current value.
13. The apparatus of claim 10, further comprising:
and the alarm module is used for acquiring the duration that the voltage unbalance exceeds the voltage unbalance limit value if the harmonic content does not exceed the harmonic content threshold, and carrying out corresponding three-phase voltage unbalance alarm according to the duration.
14. A three-phase voltage imbalance source locating system, comprising:
a processor performing the three-phase voltage imbalance source locating method of any one of claims 1 to 8;
and the display is used for displaying the processing result of the processor.
15. The system of claim 14, further comprising a data detection device for detecting and transmitting voltage and current values of the point of common connection to the processor for the processor to perform three-phase voltage imbalance source localization.
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| CN112485523B (en) * | 2020-11-25 | 2024-04-09 | 云南电网有限责任公司电力科学研究院 | Method for judging harmonic voltage measurement distortion |
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