CN112653229A - Control method of dual-power switching device for restraining magnetizing inrush current of load transformer - Google Patents
Control method of dual-power switching device for restraining magnetizing inrush current of load transformer Download PDFInfo
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- 230000000452 restraining effect Effects 0.000 title claims description 4
- 238000012544 monitoring process Methods 0.000 claims abstract description 3
- 230000004907 flux Effects 0.000 claims description 47
- 230000009977 dual effect Effects 0.000 claims description 10
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 6
- 230000005389 magnetism Effects 0.000 claims description 3
- 239000007983 Tris buffer Substances 0.000 claims description 2
- 230000002401 inhibitory effect Effects 0.000 abstract description 2
- 238000004146 energy storage Methods 0.000 description 7
- 238000004364 calculation method Methods 0.000 description 5
- 238000010586 diagram Methods 0.000 description 4
- 238000004088 simulation Methods 0.000 description 4
- 230000005284 excitation Effects 0.000 description 2
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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
- H02J9/00—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting
- H02J9/04—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source
- H02J9/06—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems
- H02J9/062—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems for AC powered loads
-
- 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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/007—Arrangements for selectively connecting the load or loads to one or several among a plurality of power lines or power sources
- H02J3/0073—Arrangements for selectively connecting the load or loads to one or several among a plurality of power lines or power sources for providing alternative feeding paths between load and source when the main path fails, e.g. transformers, busbars
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- Y—GENERAL 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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/30—Systems integrating technologies related to power network operation and communication or information technologies for improving the carbon footprint of the management of residential or tertiary loads, i.e. smart grids as climate change mitigation technology in the buildings sector, including also the last stages of power distribution and the control, monitoring or operating management systems at local level
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- Y—GENERAL 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
- Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S20/00—Management or operation of end-user stationary applications or the last stages of power distribution; Controlling, monitoring or operating thereof
- Y04S20/20—End-user application control systems
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Business, Economics & Management (AREA)
- Emergency Management (AREA)
- Stand-By Power Supply Arrangements (AREA)
Abstract
The invention discloses a control method of a dual-power switching device for inhibiting magnetizing inrush current of a load transformer, which is used for switching and controlling the dual-power switching device, and comprises the following steps: (1) monitoring the power grid power supply; (2) judging whether the power grid power supply fails or not; (3) if the power grid power supply fails, stopping a driving signal of the common power switch; (4) detecting whether a common power switch is turned off; (5) and when the common power switch is turned off, the standby power switch is turned on.
Description
Technical Field
The invention relates to the field of electronic circuits, in particular to a control method of a dual-power switching device for restraining magnetizing inrush current of a load transformer.
Background
With the wider application of the energy storage device in the power grid, the dual power supply switching device is not limited to adopt the power supply of the power grid as a standby power supply. The standby power supply adopts the energy storage device, so that the situation that two power grid power supplies are powered off at the same time and the load has to be powered off can be avoided, and the quality of electric energy generated by the energy storage device can be controlled, so that the load can be supplied with electric energy with higher quality.
When the standby power supply is an energy storage device and a load transformer exists on a load side, a serious magnetizing inrush current phenomenon can be generated in the switching process. In view of the above-mentioned phenomenon,
disclosure of Invention
The invention analyzes the magnetizing inrush current generation process of the load side transformer in the switching process. It is found that when the power grid power supply is used as a standby power supply, the voltage amplitude and the phase angle of the power grid power supply are fixed and unchanged, so that the excitation inrush current can be restrained only by adopting a split-phase closing strategy. The invention provides a control method for performing voltage compensation through a standby power supply to eliminate a magnetic flux direct-current component in a switching process based on the standby power supply as a dual-power supply system of an energy storage device, and performs simulation calculation verification.
Specifically, the invention provides a control method of a dual power supply switching device for inhibiting the magnetizing inrush current of a load transformer, which is characterized in that the control method is used for switching and controlling the dual power supply switching device, the dual power supply switching device comprises a first branch and a second branch, the first branch is connected with a power grid power supply, the power grid power supply is connected to a common power switch, the power grid power supply is further switched and controlled by the common power switch, the second branch is connected with a standby power supply, the standby power supply comprises a storage battery and an inverter, the positive pole and the negative pole of the storage battery are respectively connected with the input end of the inverter, the inverter outputs three-phase alternating current, the output of the inverter is connected to the standby power switch, the standby power switch is used for switching and controlling, the common power switch and the standby power switch are connected to the input end of, the output of the load transformer is connected with a target load, and the method comprises the following steps:
(1) monitoring the power grid power supply;
(2) judging whether the power grid power supply fails or not;
(3) if the power grid power supply fails, stopping a driving signal of the common power switch to drive the common power switch to be turned off, otherwise, not operating;
(4) detecting whether a common power switch is turned off;
(5) when the common power switch is turned off, the standby power switch is turned on;
the method comprises the following steps:
(5.1) measuring the current respective phase and amplitude of the three-phase output of the standby power supply;
(5.2) determining respective equivalent expected voltage outputs based on the respective current phase and amplitude of the three-phase output of the backup power supply, and calculating expected voltage flux values corresponding to the voltage based on the expected voltage outputs
Wherein U isaltIs the amplitude of the standby supply voltage, thetaaltIs the standby supply voltage phase.
(5.3) measuring the amplitude and the phase angle of the output voltage of the three phases of the power grid power supply at the moment of the power grid power supply failure;
(5.4) calculating respective remanence of three-phase iron cores in the load transformer based on output voltages of the three phases of the grid power supply
Before the grid power supply is disconnected, the load transformer voltage is equal to the voltage of the grid power supply, so that
Utr sin(ωt+θtr)＝Upre sin(ωt+θpre)
Wherein U istrAnd thetatrIs the amplitude and phase angle, U, of the load transformer voltagepreAnd thetapreIs the amplitude and phase angle, t, of the voltage of the mains supplydisThe moment of disconnection of the power supply of the power grid;
(5.5) calculating the difference K between the expected voltage magnetic flux corresponding to the current output voltage of each phase of the standby power supply and the residual magnetism in the iron core of the corresponding phase in the load transformer,
(5.6) calculating the compensation voltage of each phase based on the difference between the remanence of each phase
(5.7) adjusting the output voltages of the three phases of the inverter so that the outputs of the three phases of the inverter are respectively superposed with respective compensation voltages.
Preferably, step (1) comprises measuring the effective value of the voltage of the grid power supply and comparing it with a predetermined upper or lower limit to determine if the grid power supply is faulty.
For example, the current respective phase and amplitude of the three phase outputs of the backup power supply may be measured by a Phase Locked Loop (PLL) and a valid value sample.
Technical effects
1. The invention can eliminate the magnetic flux direct current component generated in the load transformer in the switching process of the dual power supply switching device, thereby eliminating the excitation inrush current in the load transformer.
2. The invention can not increase the switching time and the power-off time of the load.
3. The three phases of the standby power supply are switched on simultaneously, so that the condition that the standby power supply is in phase failure for power supply is avoided.
4. The voltage compensation time of the invention is less than one period (the power frequency period is 0.02s), and the influence on the load is small.
Drawings
FIG. 1 is a schematic diagram of a dual power switching device with a transformer on the load side for use in the present invention;
FIG. 2 is a schematic diagram of a power switching process;
FIG. 3 is a schematic diagram of the connection of a three-phase core transformer;
FIG. 4 is a compensation relationship of compensation voltage and magnetic flux;
FIG. 5 is a voltage-flux diagram of a no voltage compensation strategy;
FIG. 6 is a voltage-flux plot after the compensation method of the present invention has been employed;
FIG. 7 is a flow chart of voltage compensation calculation;
FIG. 8 is a switching waveform without flux compensation control;
FIG. 9 is a switching waveform after the compensation method of the present invention is employed;
fig. 10 illustrates a case where a single backup power supply performs backup power supply for a plurality of power supply branches.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited thereto.
Fig. 1 shows a dual power supply circuit (or referred to as a switching device) applied in the present invention, which includes a first branch and a second branch, the first branch is connected to a power grid power supply, such as a three-phase 10kV power grid power supply, the power grid power supply is controlled by a common power switch, and the second branch is connected to a storage battery, an inverter and a backup power switch.
Under normal conditions, in order to save cost, each backup branch should provide backup power supply support for multiple branches that are normally powered, as shown in fig. 10, that is, the storage battery and the inverter should be connected in parallel with the independent power grid power supplies of different power supply branches through multiple backup power switches, respectively, so as to reduce cost, implement the power supply mode of single backup power supply and multiple power supply branches, in which case, the control method adopted when each power supply branch fails is the same as that shown in fig. 1. Only one power supply branch is shown in fig. 1, although the manner of supplying other power supply branches will be understood by those skilled in the art.
The power switch can adopt a common power thyristor and a standby power thyristor, and supplies power to the sensitive load after passing through the load transformer.
When a common power supply fails, it is necessary to determine the magnetic flux dc component of each phase in the three-phase coil in the load transformer when the failure occurs.
The reason why the magnetic flux direct current component is generated is analyzed below.
In the present embodiment, the analysis of the magnetic flux in the load transformer is performed based on a DELTA/Y core transformer widely used in the power grid. The manner in which the primary windings of the DELTA/Y core transformer are wired is depicted in fig. 3. As can be seen from fig. 3, the magnetic flux of each core leg is generated by the voltage of each line (each phase).
Each flux can be integrated from the line voltage as shown in equation (1):
in the formula uAB(t)、uBC(t)、uCA(t) is the instantaneous value of the three-phase line voltage at time t, #tr(t) is an instantaneous value of the magnetic flux in the core leg corresponding to each line voltage at time t.
During steady-state operation, the three-phase voltages of the load side transformer are symmetrical, and the sum of the instantaneous values of the three-phase voltages is zero. As shown in formula (2):
uAB,tr(t)+uBC,tr(t)+uCA,tr(t)＝0 (2)
since the magnetic flux is calculated by integrating the voltage, correspondingly, the sum of instantaneous values of the magnetic flux in the three core legs of the three-phase transformer on the load side is also zero, as shown in equation (3):
ψAB,tr(t)+ψBC,tr(t)+ψCA,tr(t)＝0 (3)
fig. 6 shows the transient state of the load-side line voltage and the core leg magnetic flux in the transformer during the switching process. Wherein, 1 is the power supply stage of the common power supply, 2 is the fault detection stage and the disconnection stage of the common power supply, 3 is the zero position stage, and 4 is the power supply stage of the standby power supply.
The switched values of the magnetic fluxes of the core legs of the phases can be calculated by the following formula (4):
firstly, the common power supply is normal, the common power supply supplies power to a load, the voltage of a load side line is equal to the voltage of a common power line and is a standard three-phase sine wave, and the magnetic flux in the corresponding iron core column is an integral value of the magnetic flux, so that the magnetic flux waveform is a standard sine wave lagging behind the line voltage waveform by 90 degrees.
In fig. 6, when the value of the normal power supply voltage drops to 0.5p.u., it can be seen that the voltage waveform abruptly changes at the time of the failure and is discontinuous before and after the failure, and the magnetic flux waveform is continuous before and after the failure because the magnetic flux has continuity. As can be seen from fig. 6, the normal power supply is in the zero phase before the standby power supply is turned on, and in the zero phase, the voltage on the side line of the load is 0, and accordingly the magnetic flux is maintained in this phase.
As shown in formula (5).
Equation (6) can be written as follows:
psi in the formulaalt(t) is the periodic component of the flux after the switching process generated by the standby supply voltage.
And the switched magnetic flux can be expressed as the sum of a periodic component (i.e., the magnetic flux generated by the backup power supply) and a dc component generated during the switching process, as shown in equation (8).
ψtr(t)＝ψalt(t)+K (8)
Therefore, the expression of the magnetic flux direct current component K can be obtained as shown in the formula (9):
as can be seen from the above equation, the dc component of the magnetic flux after switching is the difference between the two components. The first part
Is the residual magnetism in the core limb after the normal power supply is completely cut off, and the second part
The quasi-magnetic flux is formed in the iron core column at the instant of switching on the standby power supply.
Therefore, the dc component of the magnetic flux of each phase of the switched load transformer is the difference between the expected magnetic flux value of the standby power voltage at the switching-on time and the residual magnetic value of the transformer, as shown in the following formula:
therefore, the invention provides a switching method for suppressing the direct current component of the magnetic flux by voltage compensation. According to the value of the magnetic flux direct current component generated at the switching moment, the voltage direct current component with the corresponding value is added into each phase voltage output by the standby power inverter and is maintained for a period of time, so that the magnetic flux direct current component in the switching process is eliminated in a short time.
The calculation formula of the constant voltage compensation is formula (11):
UT＝Δψ (11)
in the above equation, T is the compensation voltage time, Δ ψ is the compensated magnetic flux value, U is the voltage value of constant voltage compensation, U0The initial value of the voltage compensated for the linear decay voltage. Let Δ ψ be equal to K, which is an estimated value of the direct-current component of the magnetic flux, i.e., the difference between the expected magnetic flux value of the backup power supply voltage at the time of switching on and the transformer residual magnetic value. So that the dc component of the magnetic flux generated during switching can be eliminated.
It is known that voltage compensation by a line voltage effective value of one quarter of a cycle can cancel a flux peak, as shown in equation (12). Which can be used to conveniently calculate the compensation voltage.
As shown in fig. 7, the transformer voltage is integrated to obtain the magnetic flux value in the transformer, and the backup power is integrated to obtain the expected magnetic flux value for the backup power switch-on. At closing time ttransferThe difference between the two magnetic flux values is the dc component K of the magnetic flux to be generated. The compensation voltage U can be calculated by the magnetic flux DC componentcompAfter the three-phase compensation voltage is subjected to abc/dq conversion, the voltage compensation quantity U under dq axis coordinates can be obtainedd,compAnd Uq,comp. The compensation amount under the dq axis coordinate is compensated to a voltage output signal of the energy storage device inverter, so that the energy storage device inverter can output three-phase voltage superposed with compensation voltage.
The voltage compensation method is easy to control, and the initial value of the compensation voltage is small.
In order to verify the correctness of the control method, a simulation calculation is first performed to test the control method. The simulation calculations were performed in the MATLAB/Simulink platform. The corresponding parameters are as follows.
1) A transformer: 50kVA, 380V/220V, delta/Y connection mode and a nonlinear two-section line model;
2) a power grid power supply: line voltage 380V, 50 Hz;
3) loading: 16kW, 12 kVar;
4) electric power transmission line: l isline＝2mH，Rline＝0.1Ω。
The simulation results are shown in fig. 9.
The line voltage on which the dc component is superimposed can be output by controlling the output voltage of the inverter. After the line voltages are compensated for the dc voltage for 10ms, the dc component of the line voltages is removed. It can be seen that the magnetic fluxes of the phases of the transformer have no large dc component after switching, and it can be seen that the dc component of the magnetic flux of the AB phase is about 5%, and accordingly, the current on the load side has no inrush phenomenon after switching. The control strategy for suppressing the magnetizing inrush current through the voltage compensation can avoid the condition of phase-lack operation in the switching process caused by the method in the above chapter, and the power-off time of the load in the switching process cannot be increased. The compensated DC voltage value reaches about 30% at most, and no large impact is caused to the system.
While the principles of the invention have been described in detail in connection with the preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing embodiments are merely illustrative of exemplary implementations of the invention and are not limiting of the scope of the invention. The details of the embodiments are not to be interpreted as limiting the scope of the invention, and any obvious changes, such as equivalent alterations, simple substitutions and the like, based on the technical solution of the invention, can be interpreted without departing from the spirit and scope of the invention.
Claims (2)
1. A control method of a dual power supply switching device for restraining the magnetizing inrush current of a load transformer is characterized in that the control method is used for carrying out switching control on the dual power supply switching device, the dual power supply switching device comprises a first branch and a second branch, the first branch is connected with a power grid power supply, the power grid power supply is connected to a common power supply switch, the power grid power supply is further subjected to switching control through the common power supply switch, the second branch is connected with a standby power supply, the standby power supply comprises a storage battery and an inverter, the positive pole and the negative pole of the storage battery are respectively connected with the input end of the inverter, the inverter outputs three-phase alternating current, the output of the inverter is connected to the standby power supply switch, the standby power supply switch is used for carrying out switching control, the common power supply switch and the standby power supply, the output of the load transformer is connected with a target load, and the method comprises the following steps:
(1) monitoring the power grid power supply;
(2) judging whether the power grid power supply fails or not;
(3) if the power grid power supply fails, stopping a driving signal of the common power switch to drive the common power switch to be turned off, otherwise, not operating;
(4) detecting whether a common power switch is turned off;
(5) when the common power switch is turned off, the standby power switch is turned on;
the method comprises the following steps:
(5.1) measuring the current respective phase and amplitude of the three-phase output of the standby power supply;
(5.2) determining respective equivalent expected voltage outputs based on the current respective phase and amplitude of the three phase output of the backup power supply, and based on the expectedThe voltage output calculates the expected voltage magnetic flux value corresponding to the voltage
Wherein U isaltIs the amplitude of the standby supply voltage, thetaaltIs the phase of the voltage of the backup power supply,
(5.3) measuring the amplitude and the phase angle of the output voltage of the three phases of the power grid power supply at the moment of the power grid power supply failure;
(5.4) calculating respective remanence of three-phase iron cores in the load transformer based on output voltages of the three phases of the grid power supply
Before the grid power supply is disconnected, the load transformer voltage is equal to the voltage of the grid power supply, so that
Utr sin(ωt+θtr)＝Upre sin(ωt+θpre)
Wherein U istrAnd thetatrIs the amplitude and phase angle, U, of the load transformer voltagepreAnd thetapreIs the amplitude and phase angle, t, of the voltage of the mains supplydisThe moment of disconnection of the power supply of the power grid;
(5.5) calculating the difference K between the expected voltage magnetic flux corresponding to the current output voltage of each phase of the standby power supply and the residual magnetism in the iron core of the corresponding phase in the load transformer,
(5.6) calculating the compensation voltage of each phase based on the difference between the remanence of each phase
(5.7) adjusting the output voltages of the three phases of the inverter so that the outputs of the three phases of the inverter are respectively superposed with respective compensation voltages.
2. The method of claim 1, wherein step (1) comprises measuring the effective value of the grid voltage and comparing it to a predetermined upper or lower limit to determine if the grid voltage is faulty.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP4231496A1 (en) * | 2022-02-16 | 2023-08-23 | Delta Electronics Inc. | Uninterruptible power apparatus and magnetic flux compensation method thereof |
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| CN109787347A (en) * | 2019-01-02 | 2019-05-21 | 中国船舶重工集团公司第七一九研究所 | A kind of double-power supply switching device and its switching method inhibiting transformer excitation flow |
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2020
- 2020-12-14 CN CN202011474241.1A patent/CN112653229A/en active Pending
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| JP2010158101A (en) * | 2008-12-26 | 2010-07-15 | Toshiba Corp | Power conversion apparatus |
| TW201112582A (en) * | 2009-09-21 | 2011-04-01 | Nat Univ Tsing Hua | Flux linkage compensator for uninterruptible power supply (UPS) |
| CN103814500A (en) * | 2011-09-13 | 2014-05-21 | 东芝三菱电机产业系统株式会社 | Power supply system |
| CN104393672A (en) * | 2014-12-08 | 2015-03-04 | 广东电网有限责任公司东莞供电局 | Motor seamless switching power supply method based on residual voltage estimation |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP4231496A1 (en) * | 2022-02-16 | 2023-08-23 | Delta Electronics Inc. | Uninterruptible power apparatus and magnetic flux compensation method thereof |
| US11936238B2 (en) | 2022-02-16 | 2024-03-19 | Delta Electronics, Inc. | Uninterruptible power apparatus and magnetic flux compensation method thereof |
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