CN106356878B - Interphase load transfer method based on waveform fitting - Google Patents

Interphase load transfer method based on waveform fitting Download PDF

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Publication number
CN106356878B
CN106356878B CN201610906279.9A CN201610906279A CN106356878B CN 106356878 B CN106356878 B CN 106356878B CN 201610906279 A CN201610906279 A CN 201610906279A CN 106356878 B CN106356878 B CN 106356878B
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CN
China
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circuit
current
phase
phase circuit
zero
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CN201610906279.9A
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Chinese (zh)
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CN106356878A (en
Inventor
刘凯
杨毅成
张洪兴
徐艳军
刘雪峰
杨正富
路桂林
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泰豪科技股份有限公司
中能华电(北京)电力技术研究院
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Priority to CN201610906279.9A priority Critical patent/CN106356878B/en
Publication of CN106356878A publication Critical patent/CN106356878A/en
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Publication of CN106356878B publication Critical patent/CN106356878B/en

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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00Circuit arrangements for ac mains or ac distribution networks
    • H02J3/26Arrangements for eliminating or reducing asymmetry in polyphase networks
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/50Arrangements for eliminating or reducing asymmetry in polyphase networks

Abstract

The invention provides a phase-to-phase load transfer method based on waveform fitting, which is applied to an alternating current circuit, wherein the alternating current circuit comprises a power supply side circuit, a switch circuit and a load side circuit which are sequentially connected, and the method comprises the following steps: receiving a commutation instruction for switching from a current phase circuit to a target phase circuit; detecting a current signal of the current phase circuit in the power supply side circuit, and when the detected current signal passes through zero, breaking the current phase circuit through the switch circuit; detecting a voltage signal of induced electromotive force generated in the load side circuit after the current phase circuit is disconnected; and when the detected voltage signal is equal to the voltage signal input by the target phase circuit, closing the target phase circuit through the switch circuit. The interphase load transfer method based on waveform fitting can avoid power failure of a user and reduce impact on a phase change device body and electric equipment.

Description

Interphase load transfer method based on waveform fitting
Technical Field
The invention relates to the technical field of low-voltage power distribution and energy conservation, in particular to an interphase load transfer method based on waveform fitting.
Background
The existing low-voltage line generally comprises an A-phase line, a B-phase line, a C-phase line and a zero line, if the load of the three-phase circuit is unbalanced, the electric energy loss of a distribution transformer and the low-voltage line is increased, a low-voltage problem may be caused, and even a single-phase winding of the transformer is burnt.
Currently, methods for automatically adjusting three-phase load imbalance include a power supply side interphase capacitance bridging method, a dynamic reactive power compensation method, a load side load transfer method and the like. The principle of the inter-phase bridging capacitor method is that capacitors are bridged on a low-voltage bus, and the three-phase current of a low-voltage outlet of a distribution transformer is basically balanced by the aid of the current which is distributed from a phase with a heavy load to a phase with a light load. The method has the advantages that the adjusting device is simple and convenient to install, and the defects that the unbalance of the three-phase current of the distribution transformer can be adjusted only and the unbalance of the three-phase current of the low-voltage line can not be adjusted. The dynamic powerless compensation method is a new method developed in recent years, the principle of the dynamic powerless compensation method is similar to that of an interphase bridging capacitor method, and the dynamic powerless compensation method has the advantages that the current imbalance and the voltage imbalance can be adjusted. The method has the advantages of complete functions, fine adjustment and high response speed, and has the defects of capability of only adjusting the unbalance of the three-phase current of the distribution transformer and incapability of adjusting the unbalance of the three-phase current of a low-voltage line, high power consumption of the device and high cost.
The principle of the load side load transfer method is that a plurality of automatic phase-changing terminals installed on a single-phase user branch line are adopted to automatically transfer part of the load of a user from a phase with a heavier load to a phase with a lighter load, so that basic balance of three-phase current of an outlet of a distribution transformer and the line is realized.
The current commonly used interphase load transfer method adopts a zero-crossing phase selection method, namely, in an ABC three-phase circuit, when the current waveform of the current phase with a heavier load crosses zero, the phase is disconnected, and when the waveform of the target phase voltage with a lighter load crosses zero, the phase is closed. The method has the problems that after the circuit is disconnected, induced electromotive force exists in a load side circuit, when target phase voltage crosses zero, the voltage of a closing point is not zero, and at the moment of closing the circuit, a relatively large current can be generated, so that relatively large impact is generated on electric equipment or electric appliances, or operation overvoltage is generated, the normal use of the electric equipment is influenced, or the quality of electric energy is reduced.
Disclosure of Invention
The embodiment of the invention aims to provide an interphase load transfer method based on waveform fitting, which can quickly realize interphase load transfer in the phase change operation process and avoid power failure of a user; the instantaneous current of the break point and the closing point in the phase change operation tends to zero or equals to zero, so that the generation of large impact current is avoided, the stable transfer of the phase load is realized, and the impact on the phase change device body and the electric equipment is reduced. The purpose is through the three-phase unbalanced load of automatic adjustment distribution transformer and low voltage circuit, reduces the power consumption, less low-voltage problem, solves distribution transformer single-phase overload problem.
In order to achieve the above object, the present invention provides a method for transferring an interphase load based on waveform fitting, the method being applied to an ac circuit including a power supply side circuit, a switching circuit, and a load side circuit connected in sequence, the method including: receiving a commutation instruction for switching from a current phase circuit to a target phase circuit; detecting a current signal of the current phase circuit in the power supply side circuit, and when the detected current signal passes through zero, breaking the current phase circuit through the switch circuit; detecting a voltage signal of induced electromotive force generated in the load side circuit after the current phase circuit is disconnected; and when the detected voltage signal is equal to the voltage signal input by the target phase circuit, closing the target phase circuit through the switch circuit.
Further, when the detected current signal crosses zero, the step of breaking the current phase circuit by the switch circuit specifically includes: recording a first time point corresponding to a first preset zero crossing point of the detected current signal; calculating a first time interval between a first preset zero crossing point and a second preset zero crossing point of the current signal; and starting timing from the first time point, and when the timing duration reaches the first time interval, breaking the current phase circuit through the switch circuit.
Furthermore, the switch circuit has breaking/closing time delay when in breaking operation; accordingly, the method further comprises: starting timing from the first time point, and starting the breaking operation of the current phase circuit when the timing duration reaches a first preset duration, wherein the first preset duration is determined according to the following formula:
Tf1=Td1-Tr
wherein, Tf1Represents the first preset duration, Td1Representing said first time interval, Tr representing said opening/closing delay.
Further, when the detected current-phase voltage signal is equal to the voltage signal input by the target phase circuit, closing the target phase circuit through the switch circuit specifically includes: determining a second time interval between a time point when the current phase voltage signal is equal to the voltage signal input by the target phase circuit and a preset voltage zero-crossing time point in the voltage signal of the current phase circuit; and starting timing from the zero-crossing time point of the preset voltage, and closing the target phase circuit through the switch circuit when the timing duration reaches the determined second time interval.
Furthermore, the switch circuit has breaking delay when being closed; accordingly, the method further comprises: starting timing from the preset voltage zero-crossing time point, and starting the closing operation of the target phase circuit when the timing duration reaches a second preset duration, wherein the second preset duration is determined according to the following formula:
Tf2=Td2-Tr
wherein, Tf2Represents the second preset duration, Td2Representing said second time interval, Tr representing said opening/closing delay.
Furthermore, the switch circuit comprises a bidirectional thyristor and a magnetic latching relay which are respectively and correspondingly connected with each phase circuit in parallel; correspondingly, when the detected current signal crosses zero, the step of breaking the current phase circuit by the switch circuit specifically includes: at a first preset zero-crossing point of the current signal, the bidirectional controllable silicon corresponding to the current phase circuit is conducted and the magnetic latching relay corresponding to the current phase circuit is disconnected; and at a second preset zero-crossing point of the current signal, the bidirectional controllable silicon corresponding to the current phase circuit is cut off so as to break the current phase circuit.
Further, when the detected induced electromotive force voltage signal on the load side is equal to the voltage signal input by the target phase circuit, closing the target phase circuit through the switch circuit specifically includes: and when the voltage signal of the induced electromotive force generated by the load side circuit is equal to the voltage signal input by the target phase circuit, the bidirectional controllable silicon corresponding to the target phase circuit is conducted to close the target phase circuit.
Further, after the triac corresponding to the target phase circuit is turned on, the method further includes: and closing the magnetic latching relay corresponding to the target phase circuit, and stopping the bidirectional controllable silicon corresponding to the target phase circuit after the magnetic latching relay corresponding to the target phase circuit is closed.
According to the technical scheme provided by the embodiment of the invention, the embodiment of the invention can determine the zero-crossing time point of the current signal by detecting the current signal of the load side circuit. The zero-crossing time point of the current signal is used as the breaking point of the current phase, so that the instant current at the breaking point of the line tends to zero or is equal to zero, and larger current cannot be generated in the line. In addition, after the circuit is disconnected, the voltage signal in the target phase and the induced electromotive force signal in the load side circuit are detected, so that the time point when the voltage in the target phase circuit is equal to the voltage of the induced electromotive force on the load side can be determined, the time point is determined as the closing time point of the target phase, the instantaneous current at the closing point of the target phase circuit tends to be zero or equal to zero, larger current cannot be generated in the circuit, and the electric equipment can be protected.
Drawings
Fig. 1 is a graph of voltage waveforms after an ac circuit is disconnected in an embodiment of the present invention;
FIG. 2 is a waveform diagram illustrating a phase change process from phase A to phase B according to an embodiment of the present invention;
FIG. 3 is a waveform diagram illustrating a phase change process from phase A to phase C according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of an interphase load transfer terminal device based on waveform fitting in the embodiment of the present invention;
FIG. 5 is a schematic circuit diagram of an AC main circuit module according to an embodiment of the present invention;
fig. 6 is a circuit diagram of an ac main circuit module according to another embodiment of the present invention.
Detailed Description
In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution of the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, shall fall within the scope of the present invention.
The invention provides a phase-to-phase load transfer method based on waveform fitting, which is applied to an alternating current circuit, wherein the alternating current circuit comprises a power supply side circuit, a switch circuit and a load side circuit which are sequentially connected, and the method comprises the following steps: receiving a commutation instruction for switching from a current phase circuit to a target phase circuit; detecting a current signal of the current phase circuit, and when the detected current signal passes through zero, breaking the current phase circuit through the switch circuit; detecting a voltage signal of induced electromotive force generated in the load side circuit after the current phase circuit is disconnected; and when the detected voltage signal is equal to the voltage signal input by the target phase circuit, closing the target phase circuit through the switch circuit.
In this embodiment, when the detected current signal crosses zero, the step of disconnecting the current phase circuit by the switch circuit specifically includes: recording a first time point corresponding to a first preset zero crossing point of the detected current signal; calculating a first time interval between a first preset zero crossing point and a second preset zero crossing point of the current signal; and starting timing from the first time point, and when the timing duration reaches the first time interval, breaking the current phase circuit through the switch circuit.
In the embodiment, the switch circuit has an opening/closing delay when performing opening operation; accordingly, the method further comprises: starting timing from the first time point, and starting the breaking operation of the current phase circuit when the timing duration reaches a first preset duration, wherein the first preset duration is determined according to the following formula:
Tf1=Td1-Tr
wherein, Tf1Represents the first preset duration, Td1Representing said first time interval, Tr representing said opening/closing delay.
In this embodiment, when the detected present-phase voltage signal is equal to the voltage signal input to the target phase circuit, closing the target phase circuit by the switching circuit specifically includes: determining a second time interval between a time point when the current phase voltage signal is equal to the voltage signal input by the target phase circuit and a preset voltage zero-crossing time point in the voltage signal of the current phase circuit; and starting timing from the zero-crossing time point of the preset voltage, and closing the target phase circuit through the switch circuit when the timing duration reaches the determined second time interval.
In the present embodiment, the switch circuit has a closing delay time when performing a closing operation; accordingly, the method further comprises: starting timing from the preset voltage zero-crossing time point, and starting the closing operation of the target phase circuit when the timing duration reaches a second preset duration, wherein the second preset duration is determined according to the following formula:
Tf2=Td2-Tr
wherein, Tf2Indicating the second preset duration,Td2Representing said second time interval, Tr representing said opening/closing delay.
In the embodiment, the switching circuit comprises a bidirectional thyristor and a magnetic latching relay which are respectively connected in parallel and correspond to each phase circuit; correspondingly, when the detected current signal crosses zero, the step of breaking the current phase circuit by the switch circuit specifically includes: at a first preset zero-crossing point of the current signal, the bidirectional controllable silicon corresponding to the current phase circuit is conducted and the magnetic latching relay corresponding to the current phase circuit is disconnected; and at a second preset zero-crossing point of the current signal, the bidirectional controllable silicon corresponding to the current phase circuit is cut off so as to break the current phase circuit.
In this embodiment, when the detected induced electromotive force signal on the load side is equal to the voltage signal input to the target phase circuit, closing the target phase circuit by the switch circuit specifically includes: and when the voltage signal of the induced electromotive force generated by the load side circuit is equal to the voltage signal input by the target phase circuit, the bidirectional controllable silicon corresponding to the target phase circuit is conducted to close the target phase circuit.
In this embodiment, after the triac corresponding to the target phase circuit is turned on, the method further includes: and closing the magnetic latching relay corresponding to the target phase circuit, and stopping the bidirectional controllable silicon corresponding to the target phase circuit after the magnetic latching relay corresponding to the target phase circuit is closed.
One embodiment of the invention provides a phase-to-phase load transfer terminal device based on waveform fitting. Referring to fig. 4 and 5, the terminal device includes an ac main circuit module 1, a sampling module 3, an instruction operation module 4, a main control module 6, and a communication interface module 8, where the main control module 6 is connected to the communication interface module 8, the sampling module 3, and the instruction operation module 4, respectively, and the sampling module 3 and the instruction operation module 4 are further connected to the ac main circuit module 1.
In this embodiment, the ac main circuit module 1 includes a power supply side circuit, a switch circuit, and a load side circuit, wherein the power supply side circuit includes a phase a circuit, a phase B circuit, and a phase C circuit that are connected in parallel, the switch circuit includes magnetic latching relays 014, 018, 0112 corresponding to each phase circuit, the load side circuit includes a current transformer 0113, a voltage transformer 0114, and a load side output terminal 0115, and the structures of the phase a circuit, the phase B circuit, and the phase C circuit are the same, and each of the phase a circuit, the phase B circuit, and the phase C circuit includes an input terminal 011, 015, 019, and a voltage transformer 013, 017, 0111.
Please refer to fig. 1. In the present embodiment, the voltage signals in each phase circuit are all sinusoidal in waveform. The phases of the voltage signals in the three-phase circuit are 120 ° apart. At the same time, only one phase circuit is in a closed state, and the other two phase circuits are in an open state. Assume that the current a-phase circuit is in a closed state, and the B-phase and C-phase circuits are in an open state. When the a-phase circuit is disconnected at a certain time, an induced electromotive force is generated on the load side, and the dotted line in fig. 1 is a waveform of the induced electromotive force. As can be seen from fig. 1, the induced electromotive force generated on the load side after the a-phase circuit is disconnected gradually decays to 0 with the passage of time. In the present embodiment, it can be assumed that, in the first period of the induced electromotive force generation, the waveform thereof can coincide with the voltage waveform in the a-phase circuit (that is, the decay value thereof with time is ignored). Thus, after the a-phase circuit is disconnected, a normal voltage waveform that lasts for one cycle is also applied to the load side.
Referring to fig. 2, the zero-crossing points of the current signal 200 of the a-phase circuit are T0 and T2, and the zero-crossing points of the voltage signal 100 of the a-phase circuit are T1. As can be seen from fig. 2, at time T1, when the voltage signal 100 crosses zero, the current signal 200 is not zero. Therefore, if the a-phase circuit is disconnected at time T1, a large current flows in the line, which may cause damage to the load-side electric equipment. In this embodiment, the a-phase circuit may be switched off at time T2, i.e., when the current signal 200 crosses zero, so that the instantaneous current at the switching point approaches zero or equals zero. And at this time, an induced electromotive force as shown by a dotted line in fig. 2 can also be generated in the load side circuit. In order that the voltage of the power source side circuit and the induced electromotive voltage of the load side circuit can be the same at the closing point of the B-phase circuit, the B-phase circuit can be closed at a time T3 shown in fig. 2, that is, when the voltage waveform of the induced electromotive voltage intersects with the voltage waveform 300 input from the B-phase circuit. Thus, when the B-phase circuit is closed, the voltage of the power supply side can be equal to the voltage of the load side, and the instantaneous current at the closing point tends to be zero or equal to zero. After the phase B circuit is closed, phase B current 500 may be generated in the circuit.
Similarly, referring to fig. 3, after the a-phase circuit is disconnected, the C-phase circuit may be closed at time T4, that is, when the voltage waveform of the induced electromotive force on the load side intersects the voltage waveform 400 input by the C-phase circuit, so that the instantaneous current at the closing point tends to zero or equal to zero.
Wherein T0 may be the first time point, and the position of the current signal corresponding to T0 may be the first preset zero-crossing point. The position of the current signal corresponding to T2 may be the second predetermined zero crossing point. T1 may be a time point corresponding to a zero crossing point of a preset voltage in the voltage signal of the current-phase circuit. After the C-phase circuit is closed, C-phase current 600 may be generated in the circuit.
Please refer to fig. 4 and 5 together. In this embodiment, the communication interface module 8 may be configured to receive a commutation instruction for switching from a current phase circuit to a target phase circuit, and send the commutation instruction to the main control module 6. For convenience of description, it is assumed that the current phase is phase a and the target phase is phase B. In this way, the main control module 6 can acquire the current signal of the current transformer 0113 in the load side circuit and the voltage signal of the voltage transformer 013 in the current phase circuit through the sampling module.
In this embodiment, the main control module 6 includes a timer and a timer control unit for controlling the timer to be turned on or off, and the timer may be configured to record a change time of a current signal of a current transformer in the load side circuit and record a change time of a voltage signal of a voltage transformer in the current phase circuit in response to a control instruction of the timer control unit. Specifically, when detecting that the current waveform 200 shown in fig. 2 changes from positive to 0, i.e., at point T0, the main control module 6 may start the breaking timer procedure in the timer control unit. When detecting that the voltage waveform 100 in fig. 2 changes from negative to 0, i.e., at point T1, the main control module 6 may start a closing timer procedure in the timer control unit. Thus, the timer can time the breaking process and the closing process respectively, wherein the starting point for timing the breaking process is T0, and the starting point for timing the closing process is T1.
In this embodiment, the frequency of the voltage signal and the current signal in the line can be 50Hz, and the time span of the half period of the voltage signal and the current signal can be 10 ms. In this way, when the breaking time recorded in the timer is equal to 10-Tr, the main control module 6 can break the main contact S of the magnetic latching relay 014 corresponding to the a-phase circuit in advance by instructing the operation module 4. Wherein Tr is the breaking/closing time of the magnetic latching relay, that is, the breaking/closing delay, and the typical value is 5 milliseconds, that is, after a breaking or closing instruction is given to the magnetic latching relay, the main contact S will break or close the line after 5 milliseconds. Thus, after 5 milliseconds from T0, the main control module 6 can issue an opening command to the magnetic latching relay 014 through the command operation module 4, so that the a-phase circuit can be opened at point T2 in fig. 2.
In this embodiment, the timer in the main control module 6 may start timing the B-phase circuit closing process from time T1. Since the phase difference between the voltage signal of the a-phase circuit and the voltage signal of the B-phase circuit is 120 °, it can be calculated that the angle difference between the time T3 and the time T1 in fig. 2 is 150 °, and the time difference between T1 and T3 is (150/360) × 20 ═ 8.33 msec. In this way, when the counted time for the closing process in the timer is equal to 8.33-Tr, the main control module 6 may close the main contact S of the magnetic latching relay 018 corresponding to the B-phase circuit in advance through the instruction operation module 4, so that, from T1, after 3.33 milliseconds, the main control module 6 may issue a closing instruction to the magnetic latching relay 018 through the instruction operation module 4, so as to close the B-phase circuit at a point T3 in fig. 2.
In the present embodiment, the phase change process from the a-phase circuit to the C-phase circuit is also similar to the above process except that the time counted by the timer is different in the process of closing the C-phase circuit. Referring to fig. 3, when the breaking time recorded in the timer is equal to 10-Tr, the main control module 6 may instruct the operation module 4 to break the main contact S of the magnetic latching relay 014 corresponding to the a-phase circuit in advance. Wherein, Tr is the breaking/closing time of the magnetic latching relay, and the typical value is 5 milliseconds, that is, after the magnetic latching relay is given a breaking or closing instruction, the main contact S will break or close the line after 5 milliseconds. Thus, after 5 milliseconds from T0, the main control module 6 can issue an opening command to the magnetic latching relay 014 through the command operation module 4, so that the a-phase circuit can be opened at point T2 in fig. 2.
In this embodiment, the timer in the main control module 6 may start to count the C-phase circuit closing process from time T1. Since the phase difference between the voltage signal of the a-phase circuit and the voltage signal of the C-phase circuit is 240 °, it can be calculated that the angle difference between the time T4 and the time T1 in fig. 3 is 210 °, and the time difference between T1 and T4 is (210/360) × 20 ═ 11.67 msec. In this way, when the timing time for the closing process in the timer is equal to 11.67-Tr, the main control module 6 may close the main contact S of the magnetic latching relay 0112 corresponding to the C-phase circuit in advance by instructing the operation module 4. Thus, starting from T1, after 6.67 milliseconds, the main control module 6 can issue an open command to the magnetic latching relay 0112 through the command operation module 4, so that the C-phase circuit can be closed at point T4 in fig. 3.
In one embodiment of the present invention, the a-phase circuit, the B-phase circuit, and the C-phase circuit may further include fuses or air switches 12, 16, 110, which may limit the maximum current in each phase circuit, and when the current in the circuit exceeds the maximum limit value, the fuses may be blown or the air switches may be opened, so as to protect the electronic devices in the circuit from being damaged.
In an embodiment of the present invention, the terminal device further includes a power module 2, a data storage module 5, and a display keyboard circuit module 7, where the power module 2 is configured to supply power to each module in the terminal device, and the display keyboard circuit module 7 and the data storage module 5 are both connected to the main control module 6. The display keyboard circuit module 7 can be used as an interaction module between the main control module 6 and the outside, a user can send various instructions to the main control module 6 through the display keyboard circuit module 7, and the main control module 6 can also display various parameters of the current device to the user through the display keyboard circuit module 7. The data storage module 5 can store data generated during data processing of the terminal device.
In an embodiment of the present invention, the main control module 6 further includes a correction unit for correcting the open time or the close time of the magnetic latching relay. Specifically, as shown in fig. 2, the correction unit may control a timer to record the actual time ts from T0 until the current is zero. Since the theoretical time difference between the point T2 and the point T0 is 10 milliseconds, the correction time may be Toff equal to 10-ts during the separation process. Then, from the point T0, the time point at which the magnetic-hold relay 14 corresponding to the a-phase circuit performs the opening operation may be 10-Tr + Toff. The same method can be used for calculating the breaking correction time of the B-phase magnetic latching relay and the C-phase magnetic latching relay.
Likewise, for the closing correction time from the a phase to the B phase, as shown in fig. 2, the correction unit may control a timer to record a time ts1 from the start of T1 to the rise of the current signal from zero in the load-side current transformer. Since the theoretical time difference between the point T3 and the point T1 is 8.33 milliseconds, the closing correction time Ton of the magnetic latching relay corresponding to the B-phase circuit becomes 8.33-ts 1. Then the point in time at which the magnetic latching relay corresponding to the B-phase circuit performs the closing operation may be 8.33-Tr + Ton from the point T1. The closure correction times "from phase B to phase C" and "from phase C to phase a" can be calculated using the same method.
The closing correction time from phase a to phase C is also calculated in a similar manner to that described above for phase a to phase B. Referring to fig. 3, the correction unit may control a timer to record a time ts2 from T1 to a time when the current signal in the load-side current transformer rises from zero. Since the theoretical time difference between the point T4 and the point T1 is 11.67 milliseconds, the closing correction time of the magnetic latching relay corresponding to the C-phase circuit is Ton1, which is 11.67-ts 2. Then the point in time at which the magnetic latching relay corresponding to the C-phase circuit performs the closing operation may be 11.67-Tr + Ton from the point T1. The closure correction times "from phase C to phase B" and "from phase B to phase a" can be calculated using the same method.
Referring to fig. 6, in another embodiment of the present invention, the ac main circuit module 1 includes a power source side circuit, a switching circuit and a load side circuit, wherein the power source side circuit includes an a-phase circuit, a B-phase circuit and a C-phase circuit which are connected in parallel, the switching circuit includes triacs 14, 19 and 114 and magnetic latching relays 15, 110 and 115 which are connected in parallel and correspond to the respective phase circuits, each triac is connected to a control circuit thereof, and the control circuit is included in the command operation module 4 of fig. 4. The control circuit is used for applying a conduction trigger signal to the corresponding bidirectional controllable silicon so as to control the conduction or the cut-off of the bidirectional controllable silicon. The load side circuit comprises a current transformer 116, a voltage transformer 117 and a load side output terminal 118, and the A-phase circuit, the B-phase circuit and the C-phase circuit have the same structure and respectively comprise input terminals 11, 16 and 111 and voltage transformers 13, 18 and 113. In this embodiment, the control circuit of the triac has the characteristics of zero-crossing conduction and zero-crossing cutoff, and the associated triac has the characteristics of triggering conduction and zero-crossing cutoff.
Please refer to fig. 4 and fig. 6 together. In this embodiment, the communication interface module 8 may be configured to receive a commutation instruction for switching from a current phase circuit to a target phase circuit, and send the commutation instruction to the main control module 6. For convenience of description, it is assumed that the current phase is phase a and the target phase is phase B. In this way, the main control module 6 can acquire the current signal of the current transformer 116 in the load side circuit and the voltage signal of the voltage transformer 13 in the current phase circuit through the sampling module.
In this embodiment, when the a-phase circuit is disconnected, the sampling module 3 may collect a current signal of the current transformer 116 in the load-side circuit and a voltage signal of the voltage transformer 13 in the current-phase circuit. When it is detected that the current waveform 200 shown in fig. 2 changes from positive to 0 (i.e., at point T0 in fig. 2), because the control circuit of the triac 14 has the characteristic of zero-crossing conduction, when the current passes through 0, the control circuit thereof is conducted and the triac 14 is triggered to conduct. After the triac 14 is turned on, the main control module 6 can issue a breaking instruction to the magnetic latching relay 15 through the instruction operation module 4, so that the main contact S and the auxiliary node K of the magnetic latching relay 15 are broken. Thus, the a phase circuit is turned on by the triac 14.
In the present embodiment, when it is detected that the current waveform 200 in fig. 2 changes from negative to 0 (i.e., at point T2 in fig. 2), the main control module 6 can issue a turn-off command to the control circuit of the triac 14 through the command operation module 4. Thus, at the time when the current waveform 200 of fig. 2 crosses the zero point T2, the triac 14 and its control circuit may be turned off due to the zero-crossing and turn-off characteristics. Thus, the a-phase circuit can be switched off when the current waveform 200 crosses zero.
In this embodiment, when the B-phase circuit is closed, the main control module 6 must issue a conduction instruction to the control circuit of the triac 19 through the instruction operation module 4 when the magnetic latching relay 15 corresponding to the a-phase circuit is in an open state and the current of the load-side current transformer 116 is 0, because the control circuit of the triac 19 has the characteristic of zero-crossing conduction, at the time T3, when the voltage on the power supply side and the voltage on the induced electromotive force on the load side in the B-phase circuit are the same, the voltage applied to both ends of the control circuit of the triac 19 is the same, that is, the voltage on both ends is zero, and the control circuit of the triac 19 is conducted, so that the triac 19 is triggered to conduct. Thus, the B-phase circuit can be energized. Subsequently, the main control module 6 may issue a closing instruction to the magnetic latching relay 110 through the instruction operation module 4, so that the control circuit of the triac 19 may be switched off after the main contact S and the auxiliary node K of the magnetic latching relay 110 are closed, and thus, the triac 19 and the control circuit thereof are cut off at a zero crossing point. The B-phase circuit may be continuously energized by the magnetic latching relay 110.
The above-described process of the phase change operation from the A phase to the B phase is also applicable to the phase change operation in which the two phases of the "B phase to the C phase" and the "C phase to the A phase" are 120 ° out of phase.
For the phase-change operation with a phase difference of 240 ° between two phases "from a phase to C phase", "from C phase to B phase", and "from B phase to a phase", the dividing process may be consistent with the dividing process described above, and taking the example from a phase to C phase, the closing process may be as follows:
referring to fig. 3, when the magnetic latching relay 15 corresponding to the phase-a circuit is in a breaking state and the current of the load-side current transformer 116 is 0, the main control module 6 issues a conduction instruction to the control circuit of the triac 114 through the instruction operation module 4, and since the control circuit of the triac 114 has a characteristic of zero-crossing conduction, at the time T4, when the power-side voltage and the load-side induced electromotive voltage in the phase-C circuit are the same, the voltages applied to both ends of the control circuit of the triac 114 are the same, that is, the voltages at both ends are zero, and the control circuit of the triac 114 is conducted, so that the triac 114 is triggered to conduct. Thus, the C-phase circuit can be energized. Subsequently, the main control module 6 may issue a closing instruction to the magnetic latching relay 115 through the instruction operation module 4, so that the control circuit of the triac 114 may be switched off after the main contact S and the auxiliary node K of the magnetic latching relay 115 are closed, and thus, the triac 114 and the control circuit thereof are cut off at a zero crossing point. The C-phase circuit may be continuously energized by a magnetic latching relay 115.
According to the technical scheme provided by the embodiment of the invention, the embodiment of the invention can determine the zero-crossing time point of the current signal by detecting the current signal of the load side circuit. The time point of the zero crossing of the current signal is used as the breaking point of the current phase, so that large current cannot be generated in the circuit after the circuit is broken. In addition, after the circuit is disconnected, the voltage signal in the target phase and the induced electromotive force signal in the load side circuit are detected, so that the time point when the voltage in the target phase circuit is equal to the voltage of the induced electromotive force on the load side can be determined, the time point is determined as the closing time point of the target phase, the situation that large current cannot be generated in the circuit after the target phase circuit is closed can be guaranteed, and the electric equipment can be protected.
The foregoing description of various embodiments of the invention is provided to those skilled in the art for the purpose of illustration. Various alternatives and modifications of the invention will be apparent to those skilled in the art to which the invention pertains. Thus, while some alternative embodiments have been discussed in detail, other embodiments will be apparent or relatively easy to derive by those of ordinary skill in the art. The present invention is intended to embrace all such alternatives, modifications, and variances which have been discussed herein, and other embodiments which fall within the spirit and scope of the above application.

Claims (7)

1. An inter-phase load transfer method based on waveform fitting, which is applied to an alternating current circuit comprising a power supply side circuit, a switch circuit and a load side circuit which are connected in sequence, and is characterized by comprising the following steps:
receiving a commutation instruction for switching from a current phase circuit to a target phase circuit;
detecting a current signal of the current phase circuit in the power supply side circuit, and when the detected current signal passes through zero, breaking the current phase circuit through the switch circuit;
detecting a voltage signal of induced electromotive force generated in the load side circuit after the current phase circuit is disconnected;
closing the target phase circuit through the switching circuit when the detected voltage signal is equal to a voltage signal input by the target phase circuit;
when the detected current signal crosses zero, the step of breaking the current phase circuit through the switch circuit specifically comprises:
recording a first time point corresponding to a first preset zero crossing point of the detected current signal;
calculating a first time interval between a first preset zero crossing point and a second preset zero crossing point of the current signal;
and starting timing from the first time point, and when the timing duration reaches the first time interval, breaking the current phase circuit through the switch circuit.
2. The transfer method according to claim 1, wherein the switch circuit performs an opening/closing operation with an opening/closing delay; accordingly, the method further comprises:
starting timing from the first time point, and starting the breaking operation of the current phase circuit when the timing duration reaches a first preset duration, wherein the first preset duration is determined according to the following formula:
Tf1=Td1-Tr
wherein, Tf1Represents the first preset duration, Td1Representing said first time interval, Tr representing said opening/closing delay.
3. The transfer method according to claim 1, wherein closing the target phase circuit by the switching circuit when the detected present phase voltage signal is equal to the voltage signal input by the target phase circuit specifically comprises:
determining a second time interval between a time point when the current phase voltage signal is equal to the voltage signal input by the target phase circuit and a preset voltage zero-crossing time point in the voltage signal of the current phase circuit;
and starting timing from the zero-crossing time point of the preset voltage, and closing the target phase circuit through the switch circuit when the timing duration reaches the determined second time interval.
4. The transfer method according to claim 3, wherein the switch circuit is closed with a closing delay; accordingly, the method further comprises:
starting timing from the preset voltage zero-crossing time point, and starting the closing operation of the target phase circuit when the timing duration reaches a second preset duration, wherein the second preset duration is determined according to the following formula:
Tf2=Td2-Tr
wherein, Tf2Represents the second preset duration, Td2Representing said second time interval, Tr representing said opening/closing delay.
5. The transfer method according to claim 1, wherein the switching circuit comprises a triac and a magnetic latching relay connected in parallel and corresponding to each phase circuit; correspondingly, when the detected current signal crosses zero, the step of breaking the current phase circuit by the switch circuit specifically includes:
at a first preset zero-crossing point of the current signal, the bidirectional controllable silicon corresponding to the current phase circuit is conducted and the magnetic latching relay corresponding to the current phase circuit is disconnected;
and at a second preset zero-crossing point of the current signal, the bidirectional controllable silicon corresponding to the current phase circuit is cut off so as to break the current phase circuit.
6. The transfer method according to claim 5, wherein when the detected voltage signal of the induced electromotive force on the load side is equal to the voltage signal input by the target phase circuit, closing the target phase circuit by the switch circuit specifically includes:
and when the voltage signal of the induced electromotive force generated by the load side circuit is equal to the voltage signal input by the target phase circuit, the bidirectional controllable silicon corresponding to the target phase circuit is conducted to close the target phase circuit.
7. The transfer method of claim 6, wherein after the triac corresponding to the target phase circuit is turned on, the method further comprises:
and closing the magnetic latching relay corresponding to the target phase circuit, and stopping the bidirectional controllable silicon corresponding to the target phase circuit after the magnetic latching relay corresponding to the target phase circuit is closed.
CN201610906279.9A 2016-10-18 2016-10-18 Interphase load transfer method based on waveform fitting CN106356878B (en)

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CN107147113A (en) * 2017-06-05 2017-09-08 泰豪科技股份有限公司 A kind of phase change method and device without phase fault
CN107612003A (en) * 2017-09-14 2018-01-19 北京波粒智电科技有限公司 A kind of three-phase electricity commutation switching device and three-phase electricity commutation switching method
CN110429623A (en) * 2019-08-30 2019-11-08 北京同时开关技术有限公司 Phase change method, commutation device, electronic equipment and the readable storage medium storing program for executing of voltage

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