CN114362115B - Main transformer excitation-free inrush current operation method based on flexible power electronic switch - Google Patents
Main transformer excitation-free inrush current operation method based on flexible power electronic switch Download PDFInfo
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- CN114362115B CN114362115B CN202111672591.3A CN202111672591A CN114362115B CN 114362115 B CN114362115 B CN 114362115B CN 202111672591 A CN202111672591 A CN 202111672591A CN 114362115 B CN114362115 B CN 114362115B
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- 238000000034 method Methods 0.000 title claims abstract description 15
- 238000011217 control strategy Methods 0.000 claims abstract description 33
- 230000009466 transformation Effects 0.000 claims description 9
- 230000001360 synchronised effect Effects 0.000 claims description 8
- 230000000087 stabilizing effect Effects 0.000 claims description 4
- 230000002457 bidirectional effect Effects 0.000 claims description 3
- 108700041286 delta Proteins 0.000 claims description 3
- 230000005389 magnetism Effects 0.000 abstract description 6
- 230000005284 excitation Effects 0.000 description 11
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000035772 mutation Effects 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011162 core material Substances 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 230000000452 restraining effect Effects 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Protection Of Transformers (AREA)
Abstract
The invention discloses a main transformer excitation-free surge current operation method based on a flexible power electronic switch, which adopts the flexible power electronic switch to connect an alternating current bus at the low-voltage side of the main transformer with another 10KV alternating current bus to form a flexible transformer substation; the control strategy of the flexible power electronic switch is utilized to realize the synchronization of the zero lifting voltage of the alternating current buses at the two sides of the main transformer and the buses at the two sides of the high-voltage side switch K2 of the main transformer, and the operation mode prevents the abrupt change of the voltages at the two sides of the main transformer from generating exciting surge; the technical problems that in the prior art, exciting current is restrained by mutual offset of residual magnetism and magnetic bias of a transformer through an exciting current suppressor, the exciting current is restrained, the generation of the exciting current is not directly stopped, and the like are solved.
Description
Technical Field
The invention relates to the technical field of relay protection of power systems, in particular to a main transformer excitation-free inrush current operation method based on a flexible power electronic switch.
Background
The power transformer is an extremely important electrical device in a power system, and plays a role in changing a low voltage into a high voltage, changing the high voltage into a low voltage or isolating an alternating current power supply, and whether the transformer can work normally is directly related to continuous and stable operation of the power system. When the transformer is in no-load input or voltage recovery after external fault removal, excitation surge current with a large value can be generated on one side of abrupt voltage change of the transformer due to the saturation of magnetic flux of the iron core and the nonlinear characteristic of the iron core material. The exciting current generally reaches 6 to 8 times of rated current of the transformer, relay protection misoperation of the transformer is extremely easy to be caused, the power grid and the electric energy quality are polluted, the induced and the stress current disturb the adjacent running transformer, the exciting current with a large value can cause the damage of the transformer and the circuit breaker due to overlarge point power, the damage of the electric equipment caused by the induced operation overvoltage, the sudden rise or the sudden drop of the power grid voltage and the influence on the normal work of other electric equipment, and the suppression of the exciting current is worth focusing and researching.
At present, more and more power supply systems adopt a magnetizing inrush current suppressor, and the basic principle of the magnetizing inrush current suppressor is to suppress the magnetizing inrush current by mutual cancellation of residual magnetism and bias magnetism of a transformer. From the practical application, the device can basically inhibit the excitation surge current of the transformer under the normal condition; however, the generation of the excitation surge current cannot be directly stopped by suppressing the excitation surge current.
Disclosure of Invention
The invention aims to solve the technical problems that: the main transformer excitation-free inrush current operation method based on the flexible power electronic switch is provided to solve the technical problems that in the prior art, excitation inrush current is restrained through mutual cancellation of residual magnetism and bias magnetism of a transformer by an excitation inrush current suppressor, and the generation of the excitation inrush current is not directly stopped by restraining the excitation inrush current.
The technical scheme of the invention is as follows:
a main transformer excitation-free inrush current operation method based on a flexible power electronic switch is characterized in that a flexible power electronic switch is adopted to connect a main transformer low-voltage side alternating current bus with another 10KV alternating current bus to form a flexible transformer substation. The control strategy of the flexible power electronic switch is utilized to realize the synchronization of the zero lifting voltage of the alternating current buses at the two sides of the main transformer and the buses at the two sides of the high-voltage side switch K2 of the main transformer, and the operation mode prevents the abrupt change of the voltages at the two sides of the main transformer from generating exciting surge.
The operation method for forming the flexible transformer substation comprises the following steps: when the main transformer T1 is not put into operation, the main transformer low-voltage side switch K1 and the high-voltage side switch K2 are in an off state, and the alternating current buses on the two sides of the main transformer are not loaded. When the main transformer T1 is to be put into operation, the flexible power electronic switch is used for connecting the tail end of the alternating current bus at the low-voltage side of the main transformer with the tail end of another 10KV alternating current bus to form a flexible interconnection transformer substation.
The flexible power electronic switch is a bi-directional back-to-back inverter.
The control strategy of the flexible power electronic switch comprises the following steps: the VSC1 of the flexible power electronic switch is used for stabilizing the voltage of the direct current side of the flexible switch, the outer loop control of the control strategy adopts a constant direct current voltage Udc and a constant reactive power Q, the constant direct current voltage Udc and the constant reactive power Q respectively generate current reference values Idref and Iqref controlled by the inner loop of the current, the voltage amplitude command output by the inner loop of the current and the phase command output by the phase-locked loop are subjected to dq/abc coordinate transformation, and then the modulation waveform control VSC1 is obtained.
The control strategy of the flexible power electronic switch comprises the following steps: the VSC2 of the flexible power electronic switch realizes the zero lifting voltage of buses at two sides of the main transformer, and adopts a Uac/f control strategy, and the voltage reference value Uacref is a variable quantity which takes 1 minute to gradually rise from 0 to 10 KV; the outer loop control generates current reference values Idref and Iqref of the current inner loop control, a voltage amplitude command output by the current inner loop and a phase command output by the phase-locked loop are subjected to dq/abc coordinate transformation, and then a modulation waveform control VSC2 is obtained.
The voltage reference value Uacref change curve of the VSC2 zero-lifting voltage control strategy of the flexible power electronic switch.
The bus synchronous control method comprises the following steps: the VSC2 of the flexible power electronic switch realizes a synchronous control strategy, after the alternating current buses at two sides of the main transformer complete zero-rise boosting, after each voltage reaches rated voltage, the VSC2 is switched into a V/delta control strategy to realize that the voltage amplitude and the phase angle of the alternating current buses at two sides of the main transformer high-voltage side switch K2 are the same, voltage amplitudes V1 and V2 and phase angles delta 1 and delta 2 of the alternating current buses at two sides of the switch K2 are respectively collected through PT1 and PT2 to a voltage outer ring, the voltage outer ring is controlled to generate current reference values Idref and Iqref controlled by a current inner ring, and a voltage amplitude instruction output by the current inner ring and a phase instruction output by the phase-locked ring are subjected to dq/abc coordinate transformation, so that a modulation waveform control VSC2 is obtained.
The method specifically comprises the following steps:
step 1: starting the main transformer operation, and closing a switch K1;
step 2: accessing a flexible power electronic switch;
step 3: collecting information required by the flexible power electronic switch controller;
step 4: zero-starting boosting is completed by the buses at the two sides of the main transformer within 1 minute;
step 5: VSC2 is switched to V/delta control, so that buses at two sides of a switch K2 are synchronous;
step 6: and (5) closing the switch K2, and ending the operation of the main transformer excitation-free surge current.
The invention has the beneficial effects that:
according to the invention, the flexible power electronic switch is used for forming a flexible interconnection transformer substation, the control strategy of the flexible power electronic switch is utilized to realize the synchronization of the zero lifting voltage of the alternating current buses at the two sides of the main transformer and the buses at the two sides of the high-voltage side switch K2 of the main transformer, and the excitation surge current generated by voltage mutation during the operation of the main transformer is effectively prevented.
The technical problems that in the prior art, exciting current is restrained by mutual offset of residual magnetism and magnetic bias of a transformer through an exciting current suppressor, the exciting current is restrained, the generation of the exciting current is not directly stopped, and the like are solved.
Drawings
FIG. 1 is a wiring mode of a flexible interconnection transformer substation during main transformer no-excitation inrush current operation in an embodiment of the invention;
FIG. 2 is a control strategy of the VSC1 according to an embodiment of the invention;
FIG. 3 illustrates a VSC2 zero lift control strategy according to an embodiment of the invention;
fig. 4 is a rising curve of a voltage reference value uaref in a control strategy of the VSC2 according to an embodiment of the present invention;
FIG. 5 illustrates a VSC2 synchronous control strategy according to an embodiment of the invention;
fig. 6 is a general control flow chart of main transformer excitation-free inrush current operation in an embodiment of the invention.
Detailed Description
As shown in FIG. 1, when the main transformer T1 is not put into operation, the main transformer low-voltage side switch K1 and the high-voltage side switch K2 are in an off state, and the alternating current buses at two sides are not loaded. When the main transformer is required to be put into operation, the low-voltage side switch K1 is closed firstly, and in order to prevent excitation surge current generated by voltage mutation on two sides of the main transformer from damaging the stable operation of a power system, a flexible power electronic switch is adopted to connect a 10KV alternating current bus on the low-voltage side of the main transformer with another 10KV alternating current bus to form a flexible interconnection transformer substation.
The flexible power electronic switch adopts a bidirectional back-to-back converter, the VSC1 of the bidirectional back-to-back converter is used for stabilizing the direct-current side voltage, a double closed-loop control strategy of the constant direct-current voltage is adopted, and a control block diagram is shown in figure 2. The VSC2 is configured to raise the main-low-voltage-side ac bus voltage from 0 to 10KV, and to raise the main-high-voltage-side ac bus voltage from 0 to 110KV as the low-voltage-side ac bus voltage increases. Thus, abrupt changes of voltages at two sides of the main transformer are avoided, and excitation surge current can be effectively prevented. Therefore, the VSC2 adopts a Uac/f control strategy, a control block diagram is shown in figure 3, and the voltage reference value Uacref of the alternating current bus at the low voltage side of the main transformer is gradually increased, so that the zero-starting voltage increase of the buses at the two sides of the main transformer is controlled within 1 minute, and the rising curve of the voltage reference value Uacref is shown in figure 4.
After the alternating current buses at the two sides of the main transformer are boosted by zero, the voltage of each alternating current bus reaches the rated voltage, the VSC2 is switched into a V/delta control strategy to realize that the voltage amplitude and the phase angle of the alternating current buses at the two sides of the main transformer high-voltage side switch K2 are the same, and the high-voltage side switch K2 is closed after synchronization is finished, so that the main transformer excitation-free inrush current operation is finished, and the control strategy is shown in figure 5.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
Fig. 1 is a wiring mode of a flexible interconnection transformer substation during main transformer no-excitation inrush current operation in an embodiment of the invention. When the main transformer T1 is not put into operation, the main transformer low-voltage side switch K1 and the high-voltage side switch K2 are in an off state, and the alternating current buses on the two sides of the main transformer are not loaded. When the main transformer T1 is to be put into operation, the flexible power electronic switch is used for connecting the tail end of the alternating current bus at the low-voltage side of the main transformer with the tail end of another 10KV alternating current bus to form a flexible interconnection transformer substation.
Fig. 2 is a VSC1 control strategy for a flexible power electronic switch in accordance with the present invention. The VSC1 is mainly used for stabilizing the voltage of a direct current side of a flexible switch, so that the outer loop control of a control strategy adopts a constant direct current voltage Udc and a constant reactive power Q, current reference values Idref and Iqref controlled by a current inner loop are respectively generated, a voltage amplitude command output by the current inner loop and a phase command output by a phase-locked loop are subjected to dq/abc coordinate transformation, and then a modulation waveform control VSC1 is obtained.
Fig. 3 is a VSC2 zero-lift voltage control strategy for a flexible power electronic switch of the present invention. The VSC2 is required to realize the zero lifting voltage of buses at two sides of the main transformer, and a Uac/f control strategy is adopted, so that the voltage reference value Uacref is a variable quantity which takes 1 minute to gradually rise from 0 to 10KV. The outer loop control generates current reference values Idref and Iqref of the current inner loop control, a voltage amplitude command output by the current inner loop and a phase command output by the phase-locked loop are subjected to dq/abc coordinate transformation, and then a modulation waveform control VSC2 is obtained.
Fig. 4 is a change curve of a VSC2 zero-step-up voltage control strategy voltage reference value uaref of the flexible power electronic switch according to an embodiment of the present invention.
Fig. 5 is a VSC2 synchronization control strategy for a flexible power electronic switch in an embodiment of the present invention. After the alternating current buses at the two sides of the main transformer finish zero-rise boosting, after the voltage reaches rated voltage, the VSC2 is switched into a V/delta control strategy to realize that the voltage amplitude and the phase angle of the alternating current buses at the two sides of the main transformer high-voltage side switch K2 are the same, and voltage amplitude V1 and V2 and the phase angle delta 1 and delta 2 of the alternating current buses at the two sides of the switch K2 are respectively collected through PT1 and PT2 to supply voltage to a voltage outer ring. The voltage outer loop control generates current reference values Idref and Iqref of the current inner loop control, and the voltage amplitude command output by the current inner loop and the phase command output by the phase-locked loop are subjected to dq/abc coordinate transformation, so that a modulation waveform control VSC2 is obtained.
Fig. 6 is a general control flow of an embodiment of the present invention, including the following steps:
step 601: starting the main transformer operation, and closing a switch K1;
step 602: accessing a flexible power electronic switch;
step 603: collecting information required by the flexible power electronic switch controller;
step 604: zero-starting boosting is completed by the buses at the two sides of the main transformer within 1 minute;
step 605: VSC2 is switched to V/delta control, so that buses at two sides of a switch K2 are synchronous; step 606: and (5) closing the switch K2, and ending the operation of the main transformer excitation-free surge current.
Claims (2)
1. A main transformer excitation-free inrush current operation method based on a flexible power electronic switch is characterized by comprising the following steps of: a flexible power electronic switch is adopted to connect the alternating current bus at the low-voltage side of the main transformer with another 10KV alternating current bus to form a flexible transformer substation; the control strategy of the flexible power electronic switch is utilized to realize the synchronization of the zero lifting voltage of the alternating current buses at the two sides of the main transformer and the buses at the two sides of the high-voltage side switch K2 of the main transformer, and the operation mode prevents the abrupt change of the voltages at the two sides of the main transformer from generating exciting surge; the operation method for forming the flexible transformer substation comprises the following steps: when the main transformer T1 is not put into operation, the main transformer low-voltage side switch K1 and the high-voltage side switch K2 are in an off state, and the alternating current buses at the two sides of the main transformer are not loaded; when the main transformer T1 is about to be put into operation, a flexible power electronic switch is used for connecting the tail end of an alternating current bus at the low-voltage side of the main transformer with the tail end of another 10KV alternating current bus to form a flexible interconnection transformer substation; the flexible power electronic switch is a bidirectional back-to-back converter; the control strategy of the flexible power electronic switch comprises the following steps: the VSC1 of the flexible power electronic switch is used for stabilizing the voltage of the direct current side of the flexible switch, the outer loop control of the control strategy adopts a constant direct current voltage Udc and a constant reactive power Q, the constant direct current voltage Udc and the constant reactive power Q respectively generate current reference values Idref and Iqref controlled by the inner loop of the current, the voltage amplitude command output by the inner loop of the current and the phase command output by the phase-locked loop are subjected to dq/abc coordinate transformation, and then the modulation waveform control VSC1 is obtained; the control strategy of the flexible power electronic switch comprises the following steps: the VSC2 of the flexible power electronic switch realizes the zero lifting voltage of buses at two sides of the main transformer, and adopts a Uac/f control strategy, and the voltage reference value Uacref is a variable quantity which takes 1 minute to gradually rise from 0 to 10 KV; the outer loop control generates current reference values Idref and Iqref of the current inner loop control, a voltage amplitude command output by the current inner loop and a phase command output by the phase-locked loop are subjected to dq/abc coordinate transformation, and then a modulation waveform control VSC2 is obtained; a change curve of a voltage reference value Uacref of a VSC2 zero-lifting voltage control strategy of the flexible power electronic switch; the bus synchronous control method comprises the following steps: the VSC2 of the flexible power electronic switch realizes a synchronous control strategy, after the alternating current buses at two sides of the main transformer complete zero-rise boosting, after each voltage reaches rated voltage, the VSC2 is switched into a V/delta control strategy to realize that the voltage amplitude and the phase angle of the alternating current buses at two sides of the main transformer high-voltage side switch K2 are the same, voltage amplitudes V1 and V2 and phase angles delta 1 and delta 2 of the alternating current buses at two sides of the switch K2 are respectively collected through PT1 and PT2 to a voltage outer ring, the voltage outer ring is controlled to generate current reference values Idref and Iqref controlled by a current inner ring, and a voltage amplitude instruction output by the current inner ring and a phase instruction output by the phase-locked ring are subjected to dq/abc coordinate transformation, so that a modulation waveform control VSC2 is obtained.
2. The main transformer excitation-free inrush current commissioning method based on a flexible power electronic switch as claimed in claim 1, wherein the main transformer excitation-free inrush current commissioning method is characterized by comprising the following steps: the method specifically comprises the following steps:
step 1: starting the main transformer operation, and closing a switch K1;
step 2: accessing a flexible power electronic switch;
step 3: collecting information required by the flexible power electronic switch controller;
step 4: zero-starting boosting is completed by the buses at the two sides of the main transformer within 1 minute;
step 5: VSC2 is switched to V/delta control, so that buses at two sides of a switch K2 are synchronous;
step 6: and (5) closing the switch K2, and ending the operation of the main transformer excitation-free surge current.
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| CN202111672591.3A CN114362115B (en) | 2021-12-31 | 2021-12-31 | Main transformer excitation-free inrush current operation method based on flexible power electronic switch |
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| CN104283207A (en) * | 2014-10-13 | 2015-01-14 | 南方电网科学研究院有限责任公司 | Raising-voltage-from-zero starting method for wind farm to be connected to flexible direct-current power transmission system |
| CN106229945A (en) * | 2016-10-10 | 2016-12-14 | 山东中实易通集团有限公司 | A kind of excitation surge current eliminates system and method |
| CN110620372A (en) * | 2018-06-20 | 2019-12-27 | 聊城信源集团有限公司 | System for eliminating excitation inrush current of regional power grid |
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- 2021-12-31 CN CN202111672591.3A patent/CN114362115B/en active Active
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| CN104283207A (en) * | 2014-10-13 | 2015-01-14 | 南方电网科学研究院有限责任公司 | Raising-voltage-from-zero starting method for wind farm to be connected to flexible direct-current power transmission system |
| CN106229945A (en) * | 2016-10-10 | 2016-12-14 | 山东中实易通集团有限公司 | A kind of excitation surge current eliminates system and method |
| CN110620372A (en) * | 2018-06-20 | 2019-12-27 | 聊城信源集团有限公司 | System for eliminating excitation inrush current of regional power grid |
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| 基于PWM逆变器的船舶变压器励磁涌流消除方法;毕大强;郭瑞光;;船舶工程(01);全文 * |
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