CN109462243B - Low-voltage three-phase load unbalance adjusting system and method - Google Patents
Low-voltage three-phase load unbalance adjusting system and method Download PDFInfo
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- CN109462243B CN109462243B CN201810280707.0A CN201810280707A CN109462243B CN 109462243 B CN109462243 B CN 109462243B CN 201810280707 A CN201810280707 A CN 201810280707A CN 109462243 B CN109462243 B CN 109462243B
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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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- H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase networks
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/50—Arrangements for eliminating or reducing asymmetry in polyphase networks
Abstract
The invention relates to the field of power systems, in particular to a low-voltage three-phase load unbalance adjusting methodA method and system. A low-voltage three-phase load unbalance adjusting method is characterized by comprising the following steps: A1) setting the adjusting time point, setting the threshold value betax(ii) a A2) Collecting three-phase current by the control terminal at an interval time T, recording load current connected with the remote phase change switch at the interval time T and sending the load current to the control terminal, and entering step A3 after the collection is completed for 24 hours; A3) calculating three-phase load unbalance
A4) If it is
The control terminal controls the action of the remote phase change switch to adjust the three-phase load distribution. The substantial effects of the invention are as follows: the method has high tolerance on short-time three-phase load unbalance, avoids frequent phase change of a user side caused by the short-time three-phase load unbalance, performs phase change action at the moment of minimum historical average load, and reduces the risk of phase change of the user side as much as possible.
Description
Technical Field
The invention relates to the field of power systems, in particular to a low-voltage three-phase load unbalance adjusting system and method.
Background
Most distribution transformers all adopt three-phase transformer in the present urban and rural distribution network, transformer export three-phase load should reach the symmetry in theory, but the user mostly is single-phase in low voltage distribution network, three-phase load is used in mixture, and there are a large amount of single-phase loads, along with rural economy rapid development, peasant's life generally improves, high-power domestic appliance (air conditioner, electric heater, electromagnetic cooker, microwave oven, electric water heater, single-phase water pump etc.) increases, the load difference between the user is drawn big, rural resident builds new house in a large number simultaneously, the load migration causes the load distribution of whole platform district to appear changing. The irregularity and the unpredictability of the unbalanced condition of the load of a user lead to the long-term unbalance of the three-phase load of the low-voltage distribution network, the additional heating and vibration of the rotating motor caused by the unbalanced three-phase load, the increase of the leakage flux of the transformer and the local overheating, the increase of the line loss of the power grid, the misoperation of various protection and automatic devices and the like, so that the unbalanced three-phase load becomes a more prominent problem in the operation and the maintenance of the low-voltage power grid. Along with the continuous improvement of the level of low-voltage distribution network construction, the reliability, quality and service requirements on the operation of a low-voltage power grid are also continuously increased, and the problem of three-phase unbalanced load directly influences the economic benefit and safe operation of the power grid, so that the treatment of the problem of three-phase unbalanced load becomes more important.
Chinese patent CN 102751733B, published 2012, 6-26, a method for online managing three-phase load imbalance in a low-voltage distribution network, comprising the steps of: the distribution transformer low-voltage side three-phase load monitoring unit monitors the size of a three-phase load and transmits monitoring data to the distribution transformer three-phase load unbalance degree monitoring unit; the distribution transformer three-phase load unbalance monitoring unit judges whether the three-phase load unbalance exceeds a standard value or not, and if the three-phase load unbalance exceeds the standard value, the signal is transmitted to the online load phase modulation control unit through the communication unit; the online load phase modulation control unit judges whether the three-phase load unbalance of the distribution transformer is caused by the three-phase load unbalance of the low-voltage main line, if so, the online load phase modulation strategy is customized according to monitoring data of each branch load monitoring unit of the three-phase of the low-voltage main line, and the online load phase modulation judgment control unit sends a control command to the online load phase modulation change-over switch combination unit to switch the branch loads of users respectively, so that the three-phase load unbalance is treated online.
However, when the three-phase load is unbalanced by adopting the method disclosed by the patent, the three-phase load monitoring unit monitors the size of the three-phase load in real time, then the three-phase load unbalance monitoring unit judges whether the three-phase load unbalance exceeds a set threshold value, if so, an online load phase modulation strategy is customized and executed by the online load phase modulation change-over switch combination unit, although the purpose of adjusting the three-phase load unbalance can be achieved, the tolerance degree of the short-time three-phase load unbalance is low, if the short-time three-phase load unbalance is unbalanced, after the reason for causing the short-time three-phase load unbalance is removed after adjustment is carried out according to short-time three-phase load unbalance data, the three-phase load is unbalanced again, and if more reasons for causing the short-time three-phase load unbalance exist in a platform area, the online load phase modulation change-over switch combination unit can frequently act. The currently disclosed hardware which can be used as an online load phase modulation change-over switch combination unit can not carry out load phase change without power failure, short-time power failure always exists in the load phase modulation process, and if the online load phase modulation change-over switch combination unit frequently acts, the accessed load can be frequently subjected to power failure, the normal operation of the load is influenced, and even the load is damaged.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the existing low-voltage three-phase load unbalance adjusting method has the technical problems of insufficient control on the phase change risk of a user side and low tolerance on short-time three-phase load unbalance. A method and apparatus for regulating the unbalance of three-phase low-voltage load features that the sampling is performed at intervals and the phase change is performed based on the sampling result of past 24 hr.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a low-voltage three-phase load unbalance adjusting method is suitable for a distribution transformer area provided with a remote phase change switch and a control terminal, wherein the control terminal is arranged at the output end of the distribution transformer, the control terminal respectively detects and stores the current of three phase lines, the remote phase change switch is connected with a one-phase or two-phase load, and the remote phase change switch detects and stores the load current thereof, and comprises the following steps: A1) setting a time of day t0Setting a threshold beta of the unbalance of the three-phase load for adjusting the time pointx(ii) a A2) The control terminal collects and stores the three-phase current at intervals of T, the remote phase change switch records the load current connected with the remote phase change switch at intervals of T and sends the load current to the control terminal, and the step A3 is carried out after the collection of the load current is completed for 24 hours; A3) respectively calculating the three-phase load unbalance degree of the ith acquisition
Then calculating the average value of all collected three-phase load unbalance degrees as the three-phase load unbalance degrees
A4) If it is
The control terminal controls the action of the remote phase change switch to adjust the three-phase load distribution. The low-voltage three-phase load unbalance adjusting method disclosed by the invention only carries out commutation adjustment once at the time t0 in one day, and the commutation adjustment strategy is obtained by calculating three-phase load current data acquired in the last 24 hours, so that the method has higher tolerance on short-time three-phase load unbalance and simultaneously reduces the commutation risk on the user side to the minimum.
Preferably, the method for adjusting the three-phase load distribution by controlling the remote phase-change switch action by the control terminal comprises the following steps: A41) respectively calculating the current average value I of three phase lines in 24 hoursA、IBAnd ICCalculating IA、IBAnd ICMean value of
A42) Calculating the average value I of the load current of each remote phase change switch in 24 hourskK belongs to K, and K is a set of all remote phase change switches; A43) the control terminal exhales remote phase change switch action combinations, and calculates the predicted three-phase load unbalance degree under each action combination
X belongs to X, X is the set of all remote commutation switch action combinations, and the lowest predicted three-phase load unbalance degree is selected
The corresponding action combination is used as an adjusting strategy to control the action of the remote phase change switch; predicting three-phase load imbalance of action combinations x
The calculation formula of (A) is as follows:
wherein x iskaIn order to influence the action of the remote phase change switch k on the phase A under the action combination x, if the phase A is rotated out, xkaIf phase A is transferred, x is-1ka1, otherwise xka＝0；xkbIn order to influence the action of the remote phase change switch k on the B phase under the action combination x, if the remote phase change switch k is rotated out from the B phase, xkbIf phase B is transferred to-1, xkb1, otherwise xkb＝0；xkcIn order to influence the action of the remote phase change switch k on the C phase under the action combination x, if the C phase is rotated out, xkcIf phase C is transferred to-1, xkc1, otherwise xkc＝0。
Preferably, the method for adjusting the three-phase load distribution by controlling the remote phase-change switch action by the control terminal comprises the following steps: a' 41) calculating the current average I of three phase lines in 24 hours respectivelyA、IBAnd ICCalculating IA、IBAnd ICMean value of
A' 42) calculating the average value I of the load current of each remote phase change switch in 24 hourskK belongs to K, and K is a set of all remote phase change switches; a' 43) distribution calculation of the current mean I of the three-phase lineA、IBAnd ICAnd
difference of (a) delta IA、△IBAnd Δ ICFind Delta IA、△IBAnd Δ ICThe phase with the maximum absolute value in the item is judged to be positive or negative, if the phase is positive, two I phases are selected from the phasekRespectively with the average value of the current of the other two phases
The absolute value of the difference value of (a) is closest to the remote commutation switch and the corresponding phase is switched in; if negative, selecting I from the other two phaseskAnd the respective current mean values and
the closest remote commutation switch and switches into that phase. By adopting the method of the step A '41-A' 43, the calculation of the three-phase load distribution regulation strategy can be simplified, the calculation amount of program operation is reduced, the power consumption is low, and the service life is prolonged.
Preferably, an adjustment time t of the day is set0The method comprises the following steps: B1) reading the historical load data of the transformer area by big data, dividing one day into a plurality of time nodes, wherein the interval time between the time nodes is T, and sampling the historical load data of the transformer area at each time node; B2) calculating the average load of the distribution area of each time node; B3) selecting the time node with the minimum average load of the distribution area as the time t of the adjusting time point0. The load commutation is performed at the time when the average load is minimum in one day, and the risk of load commutation can be reduced to the greatest extent.
Preferably, the three-phase load unbalance degree threshold β isxThe value of (D) is 10%; the interval time T is 10 minutes. The method disclosed by the invention adjusts the three-phase load unbalance once at a fixed time point in one day, and the threshold value is necessarily adjusted to be low due to the reduction of the adjustment times, so that the threshold value beta of the three-phase load unbalance degree is adjusted according to practical experiencexWhen the value of (A) is set to 10%, the value is lower than 15% of the industry standard, and the good effect is achieved.
The short-time three-phase load unbalance with the duration shorter than (3T/10) can be skipped with high probability when the interval time is T, the tolerance capability to the short-time unbalanced load can be improved, the practice shows that the interval time is set to be 10 minutes, namely, the short-time load unbalance can be well tolerated, meanwhile, higher sensitivity can be kept, and the newly appeared load unbalance can be timely found and adjusted.
Preferably, the control terminal controlsThe method for controlling the action of the remote phase-change switch and adjusting the three-phase load distribution comprises the following steps: a' 41) calculating the average value I of the three-phase line current acquisition values in 24 hoursA、IBAnd ICThen calculate IA、IBAnd ICMean value of
A' 42) calculating the average value I of the collected values of the load current of each remote phase change switch within 24 hourskK belongs to K, and K is a set of all remote phase change switches; a' 43) the control terminal exhaustively exhausts the action combinations of the remote phase change switch, and calculates the predicted three-phase load unbalance degree under each action combination
X belongs to X, X is the set of all remote commutation switch action combinations, and the lowest predicted three-phase load unbalance degree is selected
The corresponding action combination is used as an adjusting strategy to control the action of the remote phase change switch; a' 44) calculating the standard deviation Q of the collected value of each remote phase change switch load current within 24 hourskK belongs to K, K is the set of all remote commutation switches, and if the standard deviation Q iskCounting N when the set threshold value is exceededkPlus 1, if NkIf the increment exceeds the threshold value, canceling the remote commutation switch, dividing all loads of the remote commutation switch into a plurality of sub-load areas, allocating a remote commutation switch for each sub-load area, and participating in three-phase load unbalance adjustment; predicting three-phase load imbalance of action combinations x
The calculation formula of (A) is as follows:
wherein x iskaTo be under action combination x, remotelyInfluence of the operation of phase-change switch k on phase A, x when phase A is shifted outkaIf phase A is transferred, x is-1ka1, otherwise xka＝0；xkbIn order to influence the action of the remote phase change switch k on the B phase under the action combination x, if the remote phase change switch k is rotated out from the B phase, xkbIf phase B is transferred to-1, xkb1, otherwise xkb＝0；xkcIn order to influence the action of the remote phase change switch k on the C phase under the action combination x, if the C phase is rotated out, xkcIf phase C is transferred to phase-1, xkc1 or xkc0 as an optional standard deviation QkIs set to
NkIs set to 12.
A low-voltage three-phase load unbalance adjusting system uses the low-voltage three-phase load unbalance adjusting method when low-voltage three-phase load unbalance adjustment is carried out, and comprises a control terminal and a plurality of remote phase-change switches, wherein the control terminal comprises a current collecting device, a microprocessor, a memory and a wireless communication device, the current collecting device respectively collects three-phase load currents at the output end of a distribution transformer, and the current collecting device, the memory and the wireless communication device are all connected with the microprocessor; the remote phase change switch comprises a current acquisition module, an MCU (microprogrammed control unit), a storage module, a wireless communication module and a phase change module, wherein the current acquisition module acquires load current of the remote phase change switch, and the current acquisition module, the storage module, the wireless communication module and the phase change module are all connected through the MCU.
The control terminal collects the current value of the three-phase line, the unbalance degree of the load current of the three-phase line is calculated according to the collected value, the control terminal is connected with the remote phase change switch through wireless communication, the remote phase change switch is connected with a certain load, and the load is changed according to the instruction of the control terminal so as to adjust the unbalance of the three-phase load.
Preferably, the commutation module comprises three controllable main contact pairs, three secondary static contacts, a secondary moving contact and a commutation module output line, first ends of the three controllable main contact pairs are respectively connected with the phase A, the phase B and the phase C, second ends of the three controllable main contact pairs are respectively connected with the commutation module output line, control ends of the three controllable main contact pairs are respectively connected with the MCU, first ends of the three secondary static contacts are respectively connected with the phase A, the phase B and the phase C, the secondary moving contact comprises a contact body, an actuator and three controllable electronic switches, the three controllable electronic switches are arranged on the contact body side by side, first ends of the three controllable electronic switches are matched with the second ends of the three secondary static contacts, second ends of the three controllable electronic switches are respectively connected with the commutation module output line, control ends of the three controllable electronic switches are connected with the MCU, and the contact body is connected with the actuator, the actuator controls the contact body to be closed or separated from the three secondary fixed contacts, and the actuator is connected with the MCU. The working process of the phase commutation module is as follows:
F1) when a phase change instruction is not received, one controllable main contact pair of the three controllable main contact pairs is closed, the other two controllable main contact pairs are disconnected, the secondary moving contact is disconnected with the three secondary fixed contacts, and the three controllable electronic switches are all in an off state;
F2) when a phase change instruction is received, the secondary moving contact and the three secondary fixed contacts are closed, the first ends of the three controllable electronic switches are connected with the second ends of the three secondary fixed contacts, and then the state of the controllable electronic switch connected with the current position is changed into a connection state;
F3) the three controllable main contact pairs are switched off, and when the sinusoidal current of the currently switched-on controllable electronic switch is at a zero point, the controllable electronic switch is controlled to be switched off, and then the corresponding controllable electronic switch to be switched in is switched on;
F4) and the controllable main contact pair corresponding to the to-be-switched-in is switched on, the three controllable electronic switches are all switched off, and the secondary moving contact is controlled to be disconnected with the three secondary static contacts.
The controllable main contact pair can be composed of a first contact in insulation connection with the electric push rod and a second contact in connection with the three-phase line, the contact body is an insulator, three controllable electronic switches are arranged in the contact body side by side, the contact body is pushed forwards or retracted by the actuator, and the three controllable electronic switches are in good contact with the three secondary fixed contacts when the contact body is pushed forwards. The controllable main contact pair can be formed by other power devices, such as a pneumatic push rod, an electromagnetic switch, an electric steering engine or a linear motor and other power devices capable of engaging and disengaging the metal contacts. Similarly, the actuator of the secondary moving contact can be replaced by the power device.
The substantial effects of the invention are as follows: the method has high tolerance on short-time three-phase load unbalance, avoids frequent phase change of a user side caused by the short-time three-phase load unbalance, performs phase change action at the moment of minimum historical average load, and reduces the risk of phase change of the user side as much as possible.
Drawings
Fig. 1 is a flow chart of a low-voltage three-phase load imbalance adjusting method.
Fig. 2 is a block diagram of a method for setting an adjustment time point and a moment.
Fig. 3 is a view showing a structure of a commutation module.
The controllable three-phase contact device comprises a controllable main contact pair, an electric push rod, a phase change module output line, a controllable electronic switch, a controllable main contact pair, a controllable electric push rod, a phase change module output line, a controllable three-phase line, a controllable secondary contact, a controllable electronic switch, a controllable contact body, a controllable actuator and a controllable electronic switch, wherein the controllable main contact pair is 1, the electric push rod is 2, the phase change module output line is 3, the three-phase line is 4, the secondary contact is 5, the controllable electronic switch is 6, the controllable electronic switch is 7, the contact body is 8, and the actuator is provided.
Detailed Description
The following provides a more detailed description of the present invention, with reference to the accompanying drawings.
As shown in fig. 1, a flow chart of a method for adjusting a low-voltage three-phase load imbalance includes the following steps: A1) setting a time of day t0Setting a threshold beta of the unbalance of the three-phase load for adjusting the time pointx(ii) a A2) The control terminal collects and stores the three-phase current at intervals of T, the remote phase change switch records the load current connected with the remote phase change switch at intervals of T and sends the load current to the control terminal, and the step A3 is carried out after the collection of the load current is completed for 24 hours; A3) respectively calculating the three-phase load unbalance degree of the ith acquisition
Then calculating the average value of all collected three-phase load unbalance degrees as the three-phase load unbalance degrees
A4) If it is
The control terminal controls the action of the remote phase change switch to adjust the three-phase load distribution. The low-voltage three-phase load unbalance adjusting method disclosed by the invention only carries out commutation adjustment once at the time t0 in one day, and the commutation adjustment strategy is obtained by calculating three-phase load current data acquired in the last 24 hours, so that the method has higher tolerance on short-time three-phase load unbalance and simultaneously reduces the commutation risk on the user side to the minimum.
The method for controlling the remote phase change switch action by the control terminal and adjusting the three-phase load distribution comprises the following steps: A41) respectively calculating the current average value I of three phase lines in 24 hoursA、IBAnd ICCalculating IA、IBAnd ICMean value of
A42) Calculating the average value I of the load current of each remote phase change switch in 24 hourskK belongs to K, and K is a set of all remote phase change switches; A43) the control terminal exhales remote phase change switch action combinations, and calculates the predicted three-phase load unbalance degree under each action combination
X belongs to X, X is the set of all remote commutation switch action combinations, and the lowest predicted three-phase load unbalance degree is selected
The corresponding action combination is used as an adjusting strategy to control the action of the remote phase change switch; predicting three-phase load imbalance of action combinations x
The calculation formula of (A) is as follows:
wherein x iskaIn order to influence the action of the remote phase change switch k on the phase A under the action combination x, if the phase A is rotated out, xkaIf phase A is transferred, x is-1ka1, otherwise xka＝0；xkbIn order to influence the action of the remote phase change switch k on the B phase under the action combination x, if the remote phase change switch k is rotated out from the B phase, xkbIf phase B is transferred to-1, xkb1, otherwise xkb＝0；xkcIn order to influence the action of the remote phase change switch k on the C phase under the action combination x, if the C phase is rotated out, xkcIf phase C is transferred to-1, xkc1, otherwise xkc＝0。
The second embodiment of the method for regulating the three-phase load distribution by controlling the remote phase-change switch action by the control terminal comprises the following steps: a' 41) calculating the current average I of three phase lines in 24 hours respectivelyA、IBAnd ICCalculating IA、IBAnd ICMean value of
A' 42) calculating the average value I of the load current of each remote phase change switch in 24 hourskK belongs to K, and K is a set of all remote phase change switches; a' 43) distribution calculation of the current mean I of the three-phase lineA、IBAnd ICAnd
difference of (a) delta IA、△IBAnd Δ ICFind Delta IA、△IBAnd Δ ICThe phase with the maximum absolute value in the item is judged to be positive or negative, if the phase is positive, two I phases are selected from the phasekRespectively with the average value of the current of the other two phases
The absolute value of the difference value of (a) is closest to the remote commutation switch and the corresponding phase is switched in; if negative, selecting I from the other two phaseskAnd the respective current mean values and
the closest remote commutation switch and switches into that phase. By adopting the method of the step A '41-A' 43, the calculation of the three-phase load distribution regulation strategy can be simplified, the calculation amount of program operation is reduced, the power consumption is low, and the service life is prolonged.
The third embodiment of the method for controlling the remote phase change switch action and adjusting the three-phase load distribution by the control terminal comprises the following steps: a' 41) calculating the average value I of the three-phase line current acquisition values in 24 hoursA、IBAnd ICThen calculate IA、IBAnd ICMean value of
A' 42) calculating the average value I of the collected values of the load current of each remote phase change switch within 24 hourskK belongs to K, and K is a set of all remote phase change switches; a' 43) the control terminal exhaustively exhausts the action combinations of the remote phase change switch, and calculates the predicted three-phase load unbalance degree under each action combination
X belongs to X, X is the set of all remote commutation switch action combinations, and the lowest predicted three-phase load unbalance degree is selected
The corresponding action combination is used as an adjusting strategy to control the action of the remote phase change switch; a' 44) calculating the standard deviation Q of the collected value of each remote phase change switch load current within 24 hourskK belongs to K, K is the set of all remote commutation switches, and if the standard deviation Q iskCounting N when the set threshold value is exceededk Plus 1, if NkIf the increment exceeds the threshold value, canceling the remote commutation switch, dividing all loads of the remote commutation switch into a plurality of sub-load areas, allocating a remote commutation switch for each sub-load area, and participating in three-phase load unbalance adjustment; predicting three-phase load imbalance of action combinations x
The calculation formula of (A) is as follows:
wherein x iskaIn order to influence the action of the remote phase change switch k on the phase A under the action combination x, if the phase A is rotated out, xkaIf phase A is transferred, x is-1ka1, otherwise xka＝0；xbkIn order to influence the action of the remote phase change switch k on the B phase under the action combination x, if the remote phase change switch k is rotated out from the B phase, xkbIf phase B is transferred to-1, xkb1, otherwise xkb＝0；xkcIn order to influence the action of the remote phase change switch k on the C phase under the action combination x, if the C phase is rotated out, xkcIf phase C is transferred to-1, xkc1, otherwise xkc0. As an optional standard deviation QkIs set to
NkIs set to 12.
As shown in fig. 2, a flow chart of the method for setting the adjustment time point and the adjustment time point includes the following steps: B1) reading the historical load data of the transformer area by big data, dividing one day into a plurality of time nodes, wherein the interval time between the time nodes is T, and sampling the historical load data of the transformer area at each time node; B2) calculating the average load of the distribution area of each time node; B3) selecting the time node with the minimum average load of the distribution area as the time t of the adjusting time point0. The load commutation is performed at the time when the average load is minimum in one day, and the risk of load commutation can be reduced to the greatest extent.
Threshold beta of three-phase load unbalancexThe value of (D) is 10%; the interval T is 10 minutes. The method disclosed by the invention adjusts the three-phase load unbalance once at a fixed time point in one day, and the adjustment times are reduced, so that the threshold value is necessarily adjusted to be low, and the three-phase load unbalance degree is adjusted according to practical experienceThreshold betaxWhen the value of (A) is set to 10%, the value is lower than 15% of the industry standard, and the good effect is achieved.
The short-time three-phase load unbalance with the duration shorter than (3T/10) can be skipped with high probability when the interval time is T, the tolerance capability to the short-time unbalanced load can be improved, the practice shows that the interval time is set to be 10 minutes, namely, the short-time load unbalance can be well tolerated, meanwhile, higher sensitivity can be kept, and the newly appeared load unbalance can be timely found and adjusted.
As shown in fig. 3, the system is a structure diagram of a commutation module, and includes a control terminal and a plurality of remote commutation switches, where the control terminal includes a current collection device, a microprocessor, a memory, and a wireless communication device, the current collection device collects three-phase load currents at an output end of a distribution transformer, and the current collection device, the memory, and the wireless communication device are all connected to the microprocessor; the remote phase change switch comprises a current acquisition module, an MCU, a storage module, a wireless communication module and a phase change module, wherein the current acquisition module acquires load current of the remote phase change switch, and the current acquisition module, the storage module, the wireless communication module and the phase change module are all connected through the MCU. The phase change module comprises three controllable main contact pairs 1, three secondary static contacts 5, a secondary moving contact 3 and a phase change module output line 3, wherein first ends of the three controllable main contact pairs 1 are respectively connected with an A-phase three-phase line, a B-phase three-phase line and a C-phase three-phase line 4, second ends of the three controllable main contact pairs 1 are respectively connected with the phase change module output line 3, second ends of the three controllable main contact pairs 1 are respectively driven by an electric push rod 2 independently, control ends of the three controllable main contact pairs 1 are all connected with an MCU, first ends of the three secondary static contacts 5 are respectively connected with the A-phase three-phase line, the secondary moving contact comprises a contact body 7, an actuator 8 and three controllable electronic switches 6, the three controllable electronic switches 6 are arranged on the contact body 7 in parallel, the first ends of the three controllable electronic switches 6 are matched with the second ends of the three secondary static contacts 5, the second ends of the three controllable electronic switches 6 are all connected with the phase change module output line 3, the control ends of the three controllable electronic switches 6 are connected with the MCU, the contact body 7 is connected with the actuator 8, the actuator 8 controls the contact body 7 to be closed or separated from the three secondary static contacts 5, and the actuator 8 is connected with the MCU.
The control terminal collects the current value of the three-phase line, the unbalance degree of the load current of the three-phase line is calculated according to the collected value, the control terminal is connected with the remote phase change switch through wireless communication, the remote phase change switch is connected with a certain load, and the load is changed according to the instruction of the control terminal so as to adjust the unbalance of the three-phase load.
The working process of the commutation module is as follows: F1) when a phase change instruction is not received, one controllable main contact pair 1 in the three controllable main contact pairs 1 is closed, the other two controllable main contact pairs 1 are disconnected, the secondary moving contact is disconnected with the three secondary static contacts 5, and the three controllable electronic switches 6 are all in an off state;
F2) when a phase change instruction is received, the secondary moving contact and the three secondary fixed contacts 5 are closed, at the moment, the first ends of the three controllable electronic switches 6 are connected with the second ends of the three secondary fixed contacts 5, and then the state of the controllable electronic switch 6 connected with the current position is changed into a connection state;
F3) the three controllable main contact 1 pairs are disconnected, when the sine current of the controllable electronic switch 6 which is switched on at present is at a zero point, the controllable electronic switch 6 is controlled to switch off the controllable electronic switch 6 which is switched on at present, and then the corresponding controllable electronic switch 6 which is to be switched in is switched on;
F4) the controllable main contact pair 1 corresponding to the to-be-switched-in is switched on, the three controllable electronic switches 6 are all switched off, and the secondary moving contact is controlled to be disconnected with the three secondary static contacts 5.
The controllable main contact pair 1 can be composed of a first contact which is in insulation connection with the electric push rod and a second contact which is respectively connected with the three-phase line. The contact body 7 is an insulator, the three controllable electronic switches 6 are arranged in the contact body 7 side by side, the contact body 7 is pushed forward or retracted by the actuator 8, and the three controllable electronic switches 6 are in good contact with the three secondary static contacts 5 when the contact body 7 is pushed forward. The controllable main contact pair 1 can be formed by other power devices, such as a pneumatic push rod, an electromagnetic switch, an electric steering engine or a linear motor and other power devices capable of engaging and disengaging the metal contacts. Likewise, the actuator 8 of the secondary moving contact can be replaced by the power device.
The above-described embodiments are only preferred embodiments of the present invention, and are not intended to limit the present invention in any way, and other variations and modifications may be made without departing from the spirit of the invention as set forth in the claims.
Claims (8)
1. A low-voltage three-phase load unbalance adjusting method is suitable for a distribution transformer area provided with a remote phase change switch and a control terminal, wherein the control terminal is arranged at the output end of the distribution transformer, the control terminal respectively detects and stores the current of three phase lines, the remote phase change switch is connected with a one-phase or two-phase load, the remote phase change switch detects and stores the load current, and the method is characterized in that,
the method comprises the following steps:
A1) setting a time of day t0Setting a threshold beta of the unbalance of the three-phase load for adjusting the time pointx；
A2) The control terminal collects and stores the three-phase current at intervals of T, the remote phase change switch records the load current connected with the remote phase change switch at intervals of T and sends the load current to the control terminal, and the step A3 is carried out after the collection of the load current is completed for 24 hours;
A3) respectively calculating the three-phase load unbalance degree of the ith acquisition
Then calculating the average value of all collected three-phase load unbalance degrees as the three-phase load unbalance degrees
A4) If it is
The control terminal controls the action of the remote phase change switch to adjust the three-phase load distribution;
the method for controlling the remote phase change switch action and adjusting the three-phase load distribution by the control terminal comprises the following steps:
A41) respectively calculating the current average value I of three phase lines in 24 hoursA、IBAnd ICCalculating IA、IBAnd ICMean value of
A42) Calculating the average value I of the load current of each remote phase change switch in 24 hourskK belongs to K, and K is a set of all remote phase change switches;
A43) the control terminal exhales remote phase change switch action combinations, and calculates the predicted three-phase load unbalance degree under each action combination
X belongs to X, X is the set of all remote commutation switch action combinations, and the lowest predicted three-phase load unbalance degree is selected
Corresponding action combination Xβ_min(xka，xkb，xkc) As an adjustment strategy, controlling the action of a remote phase change switch;
predicting three-phase load imbalance of action combinations x
The calculation formula of (A) is as follows:
wherein x iskaIn order to influence the action of the remote phase change switch k on the phase A under the action combination x, if the phase A is rotated out, xkaIf phase A is transferred, x is-1ka1, otherwise xka＝0；
xkbIn order to influence the action of the remote phase change switch k on the B phase under the action combination x, if the remote phase change switch k is rotated out from the B phase, xkbIf phase B is transferred to-1, xkb1, otherwise xkb＝0；
xkcIn order to influence the action of the remote phase change switch k on the C phase under the action combination x, if the C phase is rotated out, xkcIf phase C is transferred to-1, xkc1, otherwise xkc＝0。
2. The method of claim 1, wherein the method further comprises the step of,
the method for controlling the remote phase change switch action and adjusting the three-phase load distribution by the control terminal comprises the following steps:
a' 41) calculating the current average I of three phase lines in 24 hours respectivelyA、IBAnd ICCalculating IA、IBAnd ICMean value of
A' 42) calculating the average value I of the load current of each remote phase change switch in 24 hourskK belongs to K, and K is a set of all remote phase change switches;
a' 43) calculating the current mean I of the three phase linesA、IBAnd ICAnd
difference value Δ I ofA、ΔIBAnd Δ ICFinding Delta IA、ΔIBAnd Δ ICThe phase with the maximum absolute value in the item is judged to be positive or negative, if the phase is positive, two I phases are selected from the phasekRespectively with the average value of the current of the other two phases
The absolute value of the difference value of (a) is closest to the remote commutation switch and the corresponding phase is switched in; if negative, selecting I from the other two phaseskAnd the respective current mean values and
the closest remote commutation switch and switches into that phase.
3. The method of claim 1, wherein the method further comprises the step of,
setting an adjustment time t of the day0The method comprises the following steps:
B1) reading the historical load data of the transformer area by big data, dividing one day into a plurality of time nodes, wherein the interval time between the time nodes is T, and sampling the historical load data of the transformer area at each time node;
B2) calculating the average load of the distribution area of each time node;
B3) selecting the time node with the minimum average load of the distribution area as the time t of the adjusting time point0。
4. A low-voltage three-phase load unbalance adjustment method according to claim 2,
setting an adjustment time t of the day0The method comprises the following steps:
B1) reading the historical load data of the transformer area by big data, dividing one day into a plurality of time nodes, wherein the interval time between the time nodes is T, and sampling the historical load data of the transformer area at each time node;
B2) calculating the average load of the distribution area of each time node;
B3) selecting the time node with the minimum average load of the distribution area as the time t of the adjusting time point0。
5. The method of claim 1, wherein the method further comprises the step of,
the three-phase load unbalance thresholdValue of betaxThe value of (D) is 10%; the interval time T is 10 minutes.
6. The method of claim 1, wherein the method further comprises the step of,
the method for controlling the remote phase change switch action and adjusting the three-phase load distribution by the control terminal comprises the following steps:
a' 41) calculating the average value I of the three-phase line current acquisition values in 24 hoursA、IBAnd ICThen calculate IA、IBAnd ICMean value of
A' 42) calculating the average value I of the collected values of the load current of each remote phase change switch within 24 hourskK belongs to K, and K is a set of all remote phase change switches;
a' 43) the control terminal exhaustively exhausts the action combinations of the remote phase change switch, and calculates the predicted three-phase load unbalance degree under each action combination
X belongs to X, X is the set of all remote commutation switch action combinations, and the lowest predicted three-phase load unbalance degree is selected
Corresponding action combination Xβ_min(xka，xkb，xkc) As an adjustment strategy, controlling the action of a remote phase change switch;
a' 44) calculating the standard deviation Q of the collected value of each remote phase change switch load current within 24 hourskK belongs to K, K is the set of all remote commutation switches, and if the standard deviation Q iskIf the number of the phase-change switches exceeds the set threshold, the number of the phase-change switches is counted, Nk is added with 1, if the number of the phase-change switches exceeds the threshold, the remote phase-change switches are cancelled, all loads of the remote phase-change switches are divided into a plurality of sub-load areas, each sub-load area is provided with one remote phase-change switch, and then the remote phase-change switches participate in three-phase load unbalance adjustmentSection;
predicting three-phase load imbalance of action combinations x
The calculation formula of (A) is as follows:
wherein x iskaIn order to influence the action of the remote phase change switch k on the phase A under the action combination x, if the phase A is rotated out, xkaIf phase A is transferred, x is-1ka1, otherwise xka＝0；
xkbIn order to influence the action of the remote phase change switch k on the B phase under the action combination x, if the remote phase change switch k is rotated out from the B phase, xkbIf phase B is transferred to-1, xkb1, otherwise xkb＝0；
xkcIn order to influence the action of the remote phase change switch k on the C phase under the action combination x, if the C phase is rotated out, xkcIf phase C is transferred to-1, xkc1, otherwise xkc＝0。
7. A low-voltage three-phase load unbalance adjustment system using the low-voltage three-phase load unbalance adjustment method according to claims 1 to 6, when performing low-voltage three-phase load unbalance adjustment,
the control terminal comprises a current acquisition device, a microprocessor, a memory and a wireless communication device, wherein the current acquisition device respectively acquires three-phase load current at the output end of the distribution transformer, and the current acquisition device, the memory and the wireless communication device are all connected with the microprocessor;
the remote phase change switch comprises a current acquisition module, an MCU (microprogrammed control unit), a storage module, a wireless communication module and a phase change module, wherein the current acquisition module acquires load current of the remote phase change switch, and the current acquisition module, the storage module, the wireless communication module and the phase change module are all connected through the MCU.
8. The low-voltage three-phase load unbalance adjustment system according to claim 7, wherein the commutation module comprises three controllable main contact pairs, three secondary stationary contacts, a secondary movable contact and a commutation module output line, first ends of the three controllable main contact pairs are respectively connected with the A phase, the B phase and the C phase, second ends of the three controllable main contact pairs are respectively connected with the commutation module output line, control ends of the three controllable main contact pairs are respectively connected with the MCU, first ends of the three secondary stationary contacts are respectively connected with the A phase, the B phase and the C phase, the secondary movable contact comprises a contact body, an actuator and three controllable electronic switches, the three controllable electronic switches are arranged on the contact body side by side, first ends of the three controllable electronic switches are matched with second ends of the three secondary stationary contacts, and second ends of the three controllable electronic switches are respectively connected with the commutation module output line, the three controllable electronic switch control ends are connected with the MCU, the contact body is connected with the actuator, the actuator controls the contact body to be closed or separated from the three secondary static contacts, and the actuator is connected with the MCU.
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| CN110927471A (en) * | 2019-12-16 | 2020-03-27 | 南方电网数字电网研究院有限公司 | Current three-phase unbalance monitoring method and device, computer equipment and storage medium |
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| CN116819191B (en) * | 2023-07-03 | 2023-12-05 | 连云港海连送变电工程有限公司 | Remote phase sequence checking method and system for fixed-point detection function of power grid |
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