CN116995646B - Fault self-healing control method for flexible traction substation - Google Patents

Fault self-healing control method for flexible traction substation Download PDF

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CN116995646B
CN116995646B CN202310630751.0A CN202310630751A CN116995646B CN 116995646 B CN116995646 B CN 116995646B CN 202310630751 A CN202310630751 A CN 202310630751A CN 116995646 B CN116995646 B CN 116995646B
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voltage
phase
current
fault
control
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CN116995646A (en
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何晓琼
潘义松
支启莹
曾理
韩鹏程
王东
林静英
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Southwest Jiaotong University
Luoyang Institute of Science and Technology
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Southwest Jiaotong University
Luoyang Institute of Science and Technology
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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
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/001—Methods to deal with contingencies, e.g. abnormalities, faults or failures
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/22—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for distribution gear, e.g. bus-bar systems; for switching devices
    • 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
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • 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
    • H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase networks
    • 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
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • 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
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Control Of Electrical Variables (AREA)

Abstract

The invention provides a fault self-healing control method of a flexible traction substation, which belongs to the technical field of fault self-healing of traction substations, and comprises the steps of improving the structure of the substation on the basis of the existing traction substation; a bypass switch is arranged at the output position of each cascade converter module, and when the fault of the converter module is detected, the bypass switch is closed to cut off the output port of the converter module; after the fault converter module is cut off, the output of the cascade inverter in the converter is controlled by utilizing a carrier phase shifting mode; adding a direct-current voltage regulation strategy in rectifier control, and when a plurality of fault converter modules exist, improving the direct-current voltage class by using the direct-current voltage regulation strategy; the total voltage control outer loop is added in the cascade inverter control to control each phase of output voltage to be half of the total output voltage. The invention can ensure that the substation can continue to operate after the power electronic converter fails, thereby improving the reliability of the system.

Description

Fault self-healing control method for flexible traction substation
Technical Field
The invention belongs to the technical field of self-healing of faults of traction substation, and particularly relates to a fault self-healing control method of a flexible traction substation.
Background
Currently, current railway traction power supply systems in all countries of the world widely adopt a three-phase-two-phase power supply mode. The traction substation takes power from a three-phase power grid, and outputs the power by two power supply arms after the power is reduced by a traction transformer, so as to supply power for the traction grid. However, the voltage phase, amplitude and frequency between the two power supply arms and between the power substations are difficult to be completely consistent, so that the power supply arms and the power substations are required to be provided with electric phase splitting, and the power is supplied by adopting partition.
The zoned power supply itself presents a difficult parasitic problem and places serious constraints on the speed and load capacity of the electric locomotive. Under the system structure, a tight electromagnetic coupling relation exists between the traction power supply system and the traction network and between the traction loads, so that unbalance and impact of the traction loads can be fed back to the three-phase power network side through the traction substation, the electric energy quality of the three-phase power network is seriously influenced, and the electric energy quality of the three-phase power network is directly related to the normal operation of the traction power supply system and the traction loads. Along with the gradual maturation of power electronic devices, in order to solve the power quality problem of a traction power supply system, an electric phase splitting device is reduced or even cancelled, a flexible traction power supply system which takes a power electronic converter as core equipment can be adopted to realize through-type cross-region power supply, and the problems of negative sequence, reactive power, harmonic waves and the like of the existing power supply system are solved.
The flexible traction power supply system takes a power electronic device as a core, and comprises a large number of power electronic devices, and the converter is inevitably failed because the system has a severe running environment and works in high-voltage and high-power occasions for a long time. If the power substation is shut down due to the failure of the power electronic device, serious economic loss and serious potential safety hazard are caused. Therefore, high requirements are placed on the reliability of the flexible traction power supply system, and equipment is required to run for a long time, and even if part of power units or devices fail, the equipment cannot be stopped. This requires a faulty operation of the substation after the fault occurs, and thus a fault self-healing control strategy is required, which greatly improves the reliability of the system.
Disclosure of Invention
Aiming at the defects in the prior art, the fault self-healing control method of the flexible traction substation provided by the invention provides a fault self-healing control strategy, so that the substation can continue to operate after the power electronic converter fails, and the reliability of the system is improved.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the scheme provides a fault self-healing control method of a flexible traction substation, which is characterized by comprising the following steps of:
s1, improving the structure of a substation on the basis of the existing traction substation, and converting three-phase electricity at a network side into controllable single-phase electricity;
s2, a bypass switch is arranged at the output position of the converter module, and when the fault of the converter module is detected, the bypass switch is closed to cut off the output port of the converter module;
s3, after the fault converter module is cut off, controlling the output of a cascade inverter in the converter in a carrier phase shifting mode, and changing a carrier phase shifting angle;
s4, adding a direct-current voltage regulation strategy in rectifier control after the fault converter modules are cut off, and improving the direct-current voltage level by using the direct-current voltage regulation strategy when a plurality of fault converter modules exist;
and S5, after the fault converter module is cut off, adding a total voltage control outer ring in the cascaded inverter control to control each phase of output voltage to be half of the total output voltage, and completing the control of fault self-healing.
The beneficial effects of the invention are as follows: the fault self-healing control strategy provided by the invention can maintain the stable output of the traction substation, and after the power electronic converter module fails, the flexible traction substation can reconstruct and isolate the failure module, so that the negative influence caused by most of faults is eliminated, the operation is kept under the condition of no need of shutdown maintenance or replacement, and the reliability and the stability of the system are greatly improved.
Further, the step S1 specifically includes:
on the basis of the existing traction substation, a matching transformer and a power electronic converter are added to convert three-phase electricity at the grid side into controllable single-phase electricity.
The beneficial effects of the above-mentioned further scheme are: according to the invention, the existing traction substation is transformed, so that the uncontrollable alternating current output by the matching transformer is converted into the single-phase alternating current with controllable phase, and the through flexible power supply is realized.
Still further, in the step S4, the dc voltage adjustment strategy is:
a1, determining a direct-current voltage instruction U according to the number of fault converter modules * dc ；
A2, direct current voltage command U * dc With the actual voltage U on the DC side dc After the difference is made, the difference is input into a PI controller to obtain an active current reference value i controlled by a current inner loop * sd ；
And A3, performing feedforward decoupling control on the d and q-axis current components to obtain a fundamental wave voltage control instruction so as to improve the direct current voltage level.
The beneficial effects of the above-mentioned further scheme are: by increasing the direct-current voltage output by the rectifier, the over-high modulation degree of the inverter connected after the rectifier can be avoided, the modulation degree is ensured to be within 1, and the waveform quality of the output voltage is improved.
Still further, the active current reference value i * sd The expression of (2) is as follows:
wherein K is zp2 And K zi2 Respectively representing the proportional coefficient and the integral coefficient of the rectifier voltage outer loop PI controller, s represents the laplace operator,indicating a DC voltage reference value, U dc Straight representationA current voltage.
The beneficial effects of the above-mentioned further scheme are: by coupling the voltage loop to the active current loop, the rectifier output dc voltage is controlled to stabilize while the power factor is controlled.
Still further, the expression of the fundamental voltage control instruction is as follows:
wherein u is zd And u zq Respectively represent a port voltage d-axis component and a port voltage q-axis component, K zp1 And K zi1 Respectively representing the proportional and integral coefficients of the PI controller in the rectifier current loop,and->Reference values, i, representing active and reactive currents, respectively sd And i sq Respectively representing a d-axis component of the network side current and a q-axis component of the network current, ω represents an angular frequency, L z Represents the inductance of the network side, u sd And u sd The d-axis component and q-axis component of the grid-side voltage are represented, respectively.
The beneficial effects of the above-mentioned further scheme are: the power factor of the network side can be controlled to be 1 through a dq decoupling voltage and current double closed loop control strategy, and three-phase balance is maintained.
Still further, in step S5, the total voltage control outer loop is added to control the cascade inverter so that each phase of output voltage is half of the total output voltage, which specifically includes:
wherein,and->Respectively represent d-axis component reference values, K of M-phase and T-phase output voltages np3 And K ni3 Respectively representing the proportional coefficient and the integral coefficient of the PI controller of the voltage equalizing control loop of the inverter, s represents the Laplacian, U o Indicating the effective value of the total output voltage, U oM And U oT Representing the M-phase and T-phase output voltage effective values, respectively.
The beneficial effects of the above-mentioned further scheme are: the output voltage of the cascade inverter of the M phase and the T phase is controlled respectively, so that the total output voltage of the M phase and the T phase is equal, the equal power of the two phases is further ensured, and the problem of negative sequence of the network side is avoided.
Drawings
FIG. 1 is a flow chart of the method of the present invention.
Fig. 2 is a schematic structural diagram of a flexible traction substation according to the present invention.
FIG. 3 is a schematic diagram of a cut-out module in the self-healing reconstruction strategy of the present invention.
Fig. 4 is a schematic diagram of a carrier reconstruction portion in the self-healing reconstruction strategy according to the present invention.
FIG. 5 is a schematic diagram of a portion of a rectifier control in a self-healing reconstruction strategy according to the present invention.
Fig. 6 is a schematic diagram of a control portion of a cascaded inverter in a fault self-healing reconstruction strategy according to the present invention.
Detailed Description
The following description of the embodiments of the present invention is provided to facilitate understanding of the present invention by those skilled in the art, but it should be understood that the present invention is not limited to the scope of the embodiments, and all the inventions which make use of the inventive concept are protected by the spirit and scope of the present invention as defined and defined in the appended claims to those skilled in the art.
Examples
As shown in fig. 1, the invention provides a fault self-healing control method of a flexible traction substation, which comprises the following implementation steps:
s1, improving the structure of a substation on the basis of the existing traction substation, converting three-phase electricity at a network side into controllable single-phase electricity, wherein the method specifically comprises the following steps:
on the basis of the existing traction substation, a matching transformer and a power electronic converter are added to convert three-phase electricity at the grid side into controllable single-phase electricity.
In this embodiment, details of the flexible traction substation related to the present invention are as follows: on the basis of a traction transformer with a Vv wiring used by an existing traction substation, the structure of the substation is modified, three-phase electricity at the grid side is converted into controllable single-phase electricity by using power electronic equipment, and the controllable single-phase electricity is output to a traction grid, so that through power supply is realized. The structure of the flexible traction substation mainly comprises an existing traction transformer, a matching transformer and a power electronic converter. The existing traction transformer is in a Vv wiring mode, the primary side of the existing traction transformer is connected with a three-phase power grid, and the secondary side of the existing traction transformer is connected with a matching transformer to convert three-phase power into two-phase power. The matching transformer is composed of two single-phase multi-winding transformers, the primary sides of the matching transformers are respectively connected to two-phase outputs of the Vv traction transformer, and the secondary sides of the matching transformers are connected with the power electronic converter module, so that the functions of reducing voltage and isolating the electronic converter are realized. The power electronic converter consists of a single-phase NPC rectifier and a single-phase NPC inverter, the front end is connected with the matching transformer, the rear end is connected to the contact network after being output in cascade, the uncontrollable alternating current output by the matching transformer is converted into the single-phase alternating current with controllable phase, and the through flexible power supply is realized.
It should be noted that, in order to maintain the three-phase balance at the grid side, the rectifier in the converter module cannot work under the unit power factor, all the modules in the M phases need to work in an inductive state, and the T-phase module works in a capacitive state, so that the whole traction substation can be regarded as a load with three-phase balance for the three-phase grid after the traction transformation of Vv.
As shown in fig. 2, fig. 2 shows a flexible traction substation structure provided by the invention, and a matching transformer and a power electronic converter are added on the basis of the existing substation, so that three-phase electricity at a network side is converted into controllable single-phase electricity, and the controllable single-phase electricity is supplied to a contact network for train current taking.
When the converter module fails, the invention provides a fault self-healing control strategy, so that the substation continues to normally operate, the electric energy quality of the three-phase network side is ensured to be good, the stable output voltage is maintained, and the normal operation of the traction substation is ensured.
S2, a bypass switch is arranged at the output position of the converter module, and when the fault of the converter module is detected, the bypass switch is closed to cut off the output port of the converter module.
In this embodiment, after the fault occurs in the converter module, in order not to affect other modules, isolation of the fault converter module needs to be achieved first. When a fault of a certain converter module is detected, a bypass switch is closed to realize cutting, and then the system structure is re-constructed by using the rest normal modules, so that the system operates normally.
In this embodiment, when the power electronic converter module fails, in order to enable the substation to continue to operate without stopping, the failed converter module needs to be cut off to isolate the failure. The invention is realized by adding a short-circuit device as a bypass switch at the output port of the converter. The bypass switch is disconnected during normal operation, and the system output is not participated; when detecting that a fault occurs in a certain converter module, a bypass switch at the outlet of the module is closed, so that isolation is realized. As shown in fig. 3, a short-circuiting device is connected in parallel to the inverter output port of each converter module, and when the front-end rectification or the back-end inversion of the ith converter module needs to be cut off, a circuit breaker QF i Closing, and cutting off the fault module. All converter modules put into operation at this time are normal modules, and the remaining converter modules realize cascade output of a stable required voltage again through control.
And S3, after the fault converter module is cut off, controlling the output of the cascade inverter in the converter by using a carrier phase shifting mode, and changing the carrier phase shifting angle.
In this embodiment, after the fault current transformer module is removed, the system self-healing reconstruction strategy needs to keep the flexible traction substation capable of outputting normally and with good power quality. The output of the substation depends on a cascading inverter in the converter, the cascading inversion output is realized by adopting a carrier phase shifting mode, and the phase shifting angle is pi/2N under normal conditions. When one current transformer module is cut off, carrier reconstruction is required due to the reduction of the number of current transformer modules, and the phase shift angle between carriers becomes pi/(2N-1).
In this embodiment, when a plurality of converter modules are output in cascade, a carrier phase shift modulation strategy is adopted, and the number of modules in normal operation of M-phase and T-phase is set to be N, at this time, the maximum output voltage level number is 4 (2N) +1, that is, 8n+1, at this time, the phase shift angle of the phase difference between the carriers of each converter module is pi/2N, as shown in fig. 4 (a). When one converter module is cut off due to faults, the total number of the converter modules of the system is changed from 2N to 2N-1, and the maximum output voltage level number is 4 (2N-1) +1, namely 8N-3. If the cascade inverter still adopts the previous carrier wave, the voltage of the cascade system port is level-hopped to increase the harmonic content, and in order to ensure the electric energy quality of the cascade output voltage, the phase shift angle of the carrier wave needs to be changed into pi/(2N-1), as shown in fig. 4 (b).
S4, adding a direct-current voltage regulation strategy in rectifier control after the fault converter modules are cut off, and improving the direct-current voltage level by using the direct-current voltage regulation strategy when a plurality of fault converter modules exist;
the DC voltage regulation strategy is as follows:
a1, determining a direct-current voltage instruction U according to the number of fault converter modules * dc ；
A2, direct current voltage command U * dc With the actual voltage U on the DC side dc After the difference is made, the difference is input into a PI controller to obtain an active current reference value i controlled by a current inner loop * sd ；
And A3, performing feedforward decoupling control on the d and q-axis current components to obtain a fundamental wave voltage control instruction so as to improve the direct current voltage level.
In this embodiment, after one converter module is cut off, the number of converter modules is reduced, but the cascade output is guaranteed to be unchanged, which means that the output voltage of each converter module is higher than before, which leads to a higher modulation degree of the inversion part. In order to ensure that the inverter works in a linear interval, the modulation degree is still within 1, and the direct-current voltage can be improved, so that a direct-current voltage adjustment strategy is added in the control of the rectifier, and the direct-current voltage level is improved when the number of fault modules is excessive.
In this embodiment, when the system is operating normally, the dc side voltages of the converter modules are equal, and the modulation degrees of the inverters are equal, so the relationship between the total output voltage of the cascaded inverter and the dc side voltage is:
wherein n is the number of modules of the cascade converter, m is the modulation degree of the inverter, U dc For DC side voltage, U o Is the total output voltage of the cascaded inverter.
The formula (1) shows that the output voltage of the cascade inverter is in direct proportion to the number of cascade modules, the direct-current side voltage and the modulation degree, and when the converter module fails, the modulation degree of other normal modules can be improved to ensure that the total output voltage is unchanged. In general, in order to ensure continuous and stable output of the system, the cascade inverter is not allowed to operate within the maximum modulation range. In order to ensure that the inverter operates in the linear region, the modulation m should be less than 1. When the number of the fault current transformer modules is large, the modulation degree of the other normal modules is larger than 1, and the inversion modulation degree can be reduced by increasing the voltage of the direct current side, so that the fault self-healing reconstruction strategy of the power substation comprises a direct current voltage adjustment strategy in a rectifier control strategy.
In this embodiment, as shown in fig. 5, the present invention adds a portion for dynamically adjusting the dc side voltage in the rectifier control strategy, where the mathematical model of the three-phase rectifier under the dq coordinate system is:
wherein u is zd Representing the d-axis component of the port voltage, u zq Representing the q-axis component, i of the port voltage zd Representing the d-axis component, i of the net side voltage zd Representing the q-axis component of the net side voltage, L z Representing the inductance of the net side, i sd Representing the d-axis component, i of the net side current sd Representing the net side current q-axis component.
As can be seen from formula (2), u zd And u zq In the expression of (1), i sd And i sq Are coupled to each other, the grid voltage u sd 、u sq Disturbance of (2) and current coupling term omega.L z ·i sq And ω.L z ·i sd Will affect the controlled quantity i sd 、i sq . Therefore, feedforward decoupling control is required to be performed on d-axis current components and q-axis current components when a control strategy is designed, so that a fundamental wave voltage control command shown in a formula (3) is obtained:
wherein u is zd And u zq Respectively represent a port voltage d-axis component and a port voltage q-axis component, K zp1 And K zi1 Respectively representing the proportional coefficient and the integral coefficient of the PI controller in the current loop of the rectifier, s represents the laplace operator,and->Reference values, i, representing active and reactive currents, respectively sd And i sq Respectively representing a d-axis component of the network side current and a q-axis component of the network current, ω represents an angular frequency, L z Represents the inductance of the network side, u sd And u sq The net side voltage d-axis component and q-axis component are represented, respectively.
The rectifier needs to draw active power from the grid to maintain the dc side voltage stable, thus coupling the voltage loop to the active channel. Will beDC voltage command U * dc With the actual voltage U on the DC side dc After the difference is made, the difference is input into a PI controller to obtain an active current instruction i controlled by a current inner loop * sd 。
Wherein K is zp2 And K zi2 Respectively representing the proportional coefficient and the integral coefficient of the rectifier voltage outer loop PI controller, s represents the laplace operator,indicating the reference value of the direct current power supply, U dc Representing a dc voltage.
The dc voltage output by the rectifier needs to be dynamically adjusted according to the number of faulty converter modules, thus coupling the number of converter modules to the voltage command. Determining the direct-current voltage command U according to the number n of the fault converter modules * dc ：
And S5, after the fault converter module is cut off, adding a total voltage control outer ring in the cascaded inverter control to control each phase of output voltage to be half of the total output voltage, and completing the control of fault self-healing.
In this embodiment, the removal of the converter module after the fault brings two problems: firstly, the waveform quality of the output voltage of the cascade inverter is poor, secondly, the negative sequence problem is generated on the network side, the step S3 and the step S4 are used for reducing the waveform quality of the output voltage caused by faults, and the step S5 is used for eliminating the negative sequence problem on the network side caused by the faults.
In this embodiment, after the fault is removed, the number of converter modules of the M phase and the T phase is no longer the same, which results in inconsistent power of the M phase and the T phase, and further results in an unbalanced phenomenon at the three-phase network side. In order to maintain the three-phase balance on the grid side, the control strategy needs to be changed after a fault has been cleared from one converter module. When one converter module is cut off due to the failure of the M phase, the M phase and the T phase are separately controlled, and the output voltage of the M phase and the T phase is respectively controlled to be half of the required cascade output voltage, so that the power consistency of the M phase and the T phase is kept, and the output voltage of each module of the M phase is higher than the output voltage of each module of the T phase.
In this embodiment, after one converter module is cut off, the problems of unbalanced three phases at the grid side and the like are brought. When the flexible traction substation normally operates, the M phase and the T phase of the matching transformer respectively supply power for N converter modules, and the converter modules are cascaded to supply power for the traction network. Let the output power of each converter module be P i And the power of each converter module is the same. The power of M phase and T phase of the matching transformer is the sum of N modules, namely NP i . When the converter module is cut off due to fault, the power of M phase or T phase required by the converter module becomes (N-1) P i The power of the M phase and T phase are no longer equal. The primary side voltages of the M phase and the T phase are the same, and are the output of the Vv traction transformer, and different power can lead to different currents of the two phases, namely different currents of the secondary side of the Vv traction transformer.
For a traction transformer with Vv, the M-phase and T-phase can be considered as two single phase loads. If two single-phase loads are to be arranged on the secondary side of the Vv transformer, the primary side is in a three-phase balanced state, the two single-phase loads are required to have the same power, the alpha phase resistance angle is 30 degrees, and the beta phase resistance angle is-30 degrees. In the substation designed by the invention, the current of the secondary side of the Vv traction transformer is different due to direct removal of the converter module, the power is also different, and serious network side three-phase imbalance phenomenon is caused.
In order to maintain the three-phase balance on the grid side, the current transformer needs to be controlled. Wherein the steady state operating strategy may be such that the alpha phase impedance angle is 30 degrees and the beta phase impedance angle is-30 degrees. When the current transformer cuts off the module due to failure, in order to maintain the balance of three phases at the network side, the power of M phase and T phase is required to be consistent through a new control strategy.
In order to maintain the balance of three phases at the network side, a control loop is added in the control of the cascade inverter, and the power of M phase and T phase is still equal after the reconstruction is controlled. When a fault of a phase converter module is removed, the output voltage of the other modules of the phase is raised, so that the overall output voltage level of all the modules of the phase reaches half of the overall output, and the power of the phase is half of the overall power. As shown in fig. 2, one of the M-phase converter modules fails, and is cut off by the bypass switch, at this time, the remaining N-1 converter modules of the M-phase are controlled, the output voltage after the N-1 converter modules are cascaded is controlled to be half of the total output voltage, the output voltage after the N converter modules of the T-phase are controlled to be half of the total output voltage, so that the M-phase and the T-phase still bear half of the output voltage respectively, that is, half of the output power is borne, and thus, the network side can keep three-phase balance.
In this embodiment, as shown in fig. 6, the present invention can achieve the purpose of maintaining the three-phase balance at the network side by adding the total voltage control outer loop to the control loop of the inverter. According to KVL and KCL laws, the inverter AC voltage equation set is:
wherein u is cd Representing the inverter output port voltage, u C Representing the capacitance voltage, L n Representing inductance, i L Represents the inductance current, r L Representing inductance parasitic resistance, i C Representing capacitive current, C n Representing capacitance, i o Represents the inverter output current, u o Representing the output voltage.
The output voltage u of the inverter can be obtained by a 1/4 period delay method o And output current i o Virtual voltage, current signal in two-phase stationary α - β coordinate system:
carrying out the formula (7) and the formula (8) into the formula (6), carrying out coordinate transformation by utilizing a transformation matrix from a two-phase static coordinate system to a two-phase rotating coordinate system, and ignoring the influence of inductance parasitic resistance, so that a mathematical model of the inverter under a d-q coordinate system is obtained as follows:
as can be seen from equation (9), the d-axis component u of the inverter output voltage od And q-axis component u oq Coupled to each other, the d-axis component i of the inductor current Ld And q-axis component i Lq Mutual coupling, the influence of the coupling amount is eliminated by adding corresponding voltage and current decoupling control respectively.
The feedforward decoupling of the output voltage and the load current of the single-phase inverter can be obtained by:
wherein K is np1 、K ni1 The specific column coefficient and the integral coefficient, i of the inverter current inner loop PI controller respectively * Ld 、i * Lq The set values of the active current and the reactive current are respectively given.
The output of the voltage outer loop is given value of active and reactive components of the current inner loop, and the following voltage control equation can be obtained according to a model equation (9) of the single-phase inverter in the dq coordinate system due to the adoption of the PI controller for the voltage outer loop:
wherein K is np2 、K ni2 The specific column coefficient and the integral coefficient of the inverter voltage outer loop PI controller are respectively, u * od 、u * oq Respectively the given values of the active voltage and the reactive voltage.
To control the M-phase and T-phase power to be consistent, it is necessary to control the two-phase output voltage to be consistent. Adding a total voltage control outer loop into the inverter control loop so that each phase of output voltage is half of the total output voltage:
wherein,and->Respectively represent d-axis component reference values, K of M-phase and T-phase output voltages np3 、K ni3 Proportional coefficient and integral coefficient of the PI controller of the voltage equalizing control loop of the inverter respectively, U o For the effective value of the total output voltage, the voltage is usually 27.5kV, U oM Is the effective value of the M-phase output voltage, U oT For the T-phase output voltage effective value, s represents the laplace operator.
The fault self-healing control method provided by the invention can maintain the stable output of the traction substation, after the power electronic converter module fails, the flexible traction substation can reconstruct and isolate the failure module, eliminate the negative influence caused by most of faults, keep working under the condition of no need of shutdown maintenance or replacement, and greatly improve the reliability and stability of the system.

Claims (3)

1. The fault self-healing control method of the flexible traction substation is characterized by comprising the following steps of:
s1, improving the structure of a substation on the basis of the existing traction substation, and converting three-phase electricity at a network side into controllable single-phase electricity;
s2, a bypass switch is arranged at the output position of the converter module, and when the fault of the converter module is detected, the bypass switch is closed to cut off the output port of the converter module;
s3, after the fault converter module is cut off, controlling the output of a cascade inverter in the converter in a carrier phase shifting mode, and changing a carrier phase shifting angle;
s4, adding a direct-current voltage regulation strategy in rectifier control after the fault converter modules are cut off, and improving the direct-current voltage level by using the direct-current voltage regulation strategy when a plurality of fault converter modules exist;
the dc voltage adjustment strategy in step S4 is as follows:
a1, determining a direct-current voltage instruction according to the number of fault converter modulesU * dc ；
A2, direct current voltage commandU * dc Actual voltage at DC sideU dc After the difference is made, the difference is input into a PI controller to obtain an active current reference value controlled by a current inner loopi * sd ；
A3, feedforward decoupling control is carried out on the d and q-axis current components to obtain a fundamental wave voltage control instruction so as to improve the direct current voltage level;
the active current reference valuei * sd The expression of (2) is as follows:
wherein,and->Respectively representing the proportional coefficient and the integral coefficient of the rectifier voltage outer loop PI controller,/>Representing the Laplace operator>Representing a direct voltage reference value,/->Representing a direct current voltage;
the expression of the fundamental voltage control instruction is as follows:
wherein,and->Represents the port voltage d-axis component and the port voltage q-axis component, respectively,/->And->Respectively representing the proportional coefficient and the integral coefficient of the PI controller in the current loop of the rectifier,/and>and->Reference values representing active current and reactive current, respectively,/->And->Represents the net side current d-axis component and net side current q-axis component, respectively, +.>Represents angular frequency +.>Representing the inductance of the net side>And->Respectively representing d-axis component and q-axis component of the grid-side voltage;
and S5, after the fault converter module is cut off, adding a total voltage control outer ring in the cascaded inverter control to control each phase of output voltage to be half of the total output voltage, and completing the control of fault self-healing.
2. The fault self-healing control method of the flexible traction substation according to claim 1, wherein the step S1 is specifically:
on the basis of the existing traction substation, a matching transformer and a power electronic converter are added to convert three-phase electricity at the grid side into controllable single-phase electricity.
3. The fault self-healing control method of the flexible traction substation according to claim 1, wherein in the step S5, the total voltage control outer loop is added to control each phase output voltage to be half of the total output voltage, which specifically includes:
wherein,and->Representing d-axis component reference values of the output voltages of M phase and T phase respectively, < >>And->Respectively representing the proportional coefficient and the integral coefficient of the PI controller of the voltage equalizing control loop of the inverter,srepresenting the Laplace operator>Representing the total output voltage effective value, +.>And->Representing the M-phase and T-phase output voltage effective values, respectively.
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Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109067193A (en) * 2018-08-17 2018-12-21 燕山大学 A kind of cascade connection type electric power electric transformer and its imbalance compensation control method
CN112350326A (en) * 2020-10-23 2021-02-09 株洲中车时代电气股份有限公司 Rail transit traction power supply system, control method and system thereof, and related components
CN113114049A (en) * 2021-04-15 2021-07-13 湖南大学 Hybrid modular multilevel railway power regulator and control method and system thereof
CN114447972A (en) * 2021-12-21 2022-05-06 西南交通大学 Through flexible traction substation based on existing traction transformer and protection configuration method thereof
CN114498718A (en) * 2022-01-25 2022-05-13 西南交通大学 Flexible traction substation and control method thereof
CN114498577A (en) * 2021-12-21 2022-05-13 西南交通大学 Through flexible traction substation structure and protection configuration method thereof
CN114583973A (en) * 2022-03-28 2022-06-03 西南交通大学 Flexible traction substation structure and optimization control method thereof
CN115425674A (en) * 2022-11-08 2022-12-02 清华大学 Double-ring active disturbance rejection control method for bidirectional converter of flexible direct-current traction power supply system
CN115954877A (en) * 2023-01-18 2023-04-11 湖南大学 Control method and system for railway traction network and railway power supply and distribution network interconnection converter

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109067193A (en) * 2018-08-17 2018-12-21 燕山大学 A kind of cascade connection type electric power electric transformer and its imbalance compensation control method
CN112350326A (en) * 2020-10-23 2021-02-09 株洲中车时代电气股份有限公司 Rail transit traction power supply system, control method and system thereof, and related components
CN113114049A (en) * 2021-04-15 2021-07-13 湖南大学 Hybrid modular multilevel railway power regulator and control method and system thereof
CN114447972A (en) * 2021-12-21 2022-05-06 西南交通大学 Through flexible traction substation based on existing traction transformer and protection configuration method thereof
CN114498577A (en) * 2021-12-21 2022-05-13 西南交通大学 Through flexible traction substation structure and protection configuration method thereof
CN114498718A (en) * 2022-01-25 2022-05-13 西南交通大学 Flexible traction substation and control method thereof
CN114583973A (en) * 2022-03-28 2022-06-03 西南交通大学 Flexible traction substation structure and optimization control method thereof
CN115425674A (en) * 2022-11-08 2022-12-02 清华大学 Double-ring active disturbance rejection control method for bidirectional converter of flexible direct-current traction power supply system
CN115954877A (en) * 2023-01-18 2023-04-11 湖南大学 Control method and system for railway traction network and railway power supply and distribution network interconnection converter

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
"电气化铁路综合补偿器控制策略研究";何晓琼等;《铁道学报》;第42卷(第9期);74-84 *

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